physico-chemical properties of florida phosphatic...
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PHYSICO-CHEMICAL PROPERTIES
OF FLORIDA PHOSPHATIC CLAYS
FINAL REPORT
BROMWELL ENGINEERING, INC.202 Lake Miriam Drive
Lake land , F1orida 33803
P r i n c i p a l I n v e s t i g a t o r : LESLIE G. BROMWELL
Prepared f o r
FLORIDA INSTITUTE OF PHOSPHATE1855 West Main Street
Bartow, F l o r i d a 3 3 8 3 0
RESEARCH
Pro jec t Manager : Henry L. Barwood
June, 1982
PREPARED UNDER CONTRACT NO. 80-02-003
DISCLAIMER
The contents of this report are reproduced herein as receivedfrom the contractor.
The opinions, findings, and conclusions expressed herein arenot necessarily those of the Florida Institute of PhosphateResearch, nor does mention of company names or products con-stitute endorsement by the Florida Institute of PhosphateResearch.
I.
II.
III.
IV.
V.
TARLE OF CONTENTS
ABSTRACT
LIST OF TABLES
BACKGROUND
SCOPE OF STUDY
DESCRIPTION OF DATA BASE
SAMPLING LOCATIONS AND PROCEDURES
A. Settling Area Samples
B. Beneficiation Plant Samples
TEST PROCEDURES AND RESULTS
A. Solids Contents
1. Settling Area Samples
2. Fresh Slurry Samples
B. Physical Properties
1. Atterberg Limits
2. Particle Size Distribution
3. Specific Gravity
4. Compressibility and Permeability
5. Vane Shear Strength
C. Chemical Analyses
1. Supernatant Water
2. Composition of solids s
Page.
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5
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VI.
VII.
VIII.
TABLE OF CONTENTS
D. Mineralogy
1. Procedures
2. Reference Data
3. Results
a. General
b. Expandable Clay Phases
c. Illite
d. Palygorskite
e. Kaolinite
4. Estimates of Mineralogical Composition
5. Scanning Electron Microscopy
CORRELATION OF RESULTS
A. Sedimentation Behavior
B. Chemistry
C. Mineralogy
SUMMARY AND RECOMMENDATIONS
REFERENCES
LIST OF FIGURES
Page
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92
ABSTRACT
The chemical composition, mineralogy, and mechanical properties
of waste phosphatic clay samples from a variety of central Florida
sources have been determined by field sampling and laboratory testing.
Sample sources included 38 settling areas (clay slurry impoundments),
18 beneficiation plants, and 7 future mine sites. Laboratory tests
included solids content, grain size, liquid and plastic limits, specific
gravity, sedimentation and consolidation, permeability, shear strength,
chemical analyses, X-ray diffraction analysis and scanning electron
microscopy. The data have been assimilated into a computerized data
base (SYSTEM 2000) for storage, retrieval, and evaluation. The data
base is organized so that it can assimilate a continuously growing body
of in formation, including additional parameters that may be developed
during future studies of phosphatic clays.
This report describes the sampling program and laboratory testing
that were done and the data base that was developed. Significant test
results are presented in graphical and tabular form, and conclusions
are made based on evaluation of the results. Recommendations for
expanding and updating the data base are also provided.
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3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
Data Base Organization
Data Base Definition
Mine Master Numbers
Settling Area Sampling
Fresh Slurry Sampling
LIST OF TABLES
Record
Record
Weighted Average Solids Content
of Samples from Settling Areas
Comparison of Mineralogy and Soil
Classification Data - Washer Plant Samples
Comparison of Settling Behavior with
Mineralogy and Soil Classification Data
- Settling Area Samples
Vane Shear Test Results
Analyses of Supernatant Water
Summary of Chemical Analyses
Comparison of Average Mineral Values
Mineralogical Analysis Flow Chart
Reference Data Non-Clay Minerals
Clay Minerals Reference Data
Non-Clay Minerals XRD Data
Clay Minerals XRD Data
Key XRD Data for Interstratification on
Mixed Treatment Specimens
Key XRD Data for Magnesium Saturated
Glycerol Solvated Specimens Heated
Chemical Analysis by X-ray Fluorescence
Summary of Mineral Composition
Page
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9-16
17-18
20
22
27-31
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42-45
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50
53
54
59
60-61
65
68
71-72
73
i v
I. BACKGROUND
Phosphate mining and processing has been a major industry in
central Florida since the late 19th Century. The phosphate ore
(termed “matrix”) occurs as shallow deposits of gravel, sand, and clay
overlain by sandy overburden. These materials are easily excavated
by large walking draglines. The matrix is slurrified with water jets
and pumped to a processing plant for beneficiation. The phosphate
product, consisting of sand and gravel-sized particles of carbonate
fluorapatite (termed “Phosphate rock”), is primarily utilized to make
phosphoric acid feedstock for high-analysis fertilizers.
Rapid expansion of the Florida phosphate industry following
World War II, combined with improved technology for product
recovery, resulted in the production of large volumes of minus 150
mesh waste material (termed phosphatic clays or "slimes"). Typically,
one ton of clay waste (dry weight) is produced for each ton of
phosphate rock product,
Leaving the beneficiation plant as a dilute slurry (on the order
of 3% solids by weight), the clay slimes require the construction of
large above-ground impoundments to provide adequate volume and
retention time for sedimentation and water clarification. These
impoundments, or settling areas ar typically 400 to 800 acres in size,
surrounded by earth dams ranging from 20 to 60 feet in height. At
the present rate of mining approximately 150,000 acre-feet of new
storage volume must be provided annually for waste clay disposal. To
provide this volume, approximately 70% of the mined acreage is
designated for clay settling areas.
Disposal of the phosphatic clays has caused environmental
problems for the industry with regard to water consumption, potential
water pollution, and land reclamation. Between 1942 and 1971, twenty
earth dam failures were recorded that resulted in off-property releases
1
of semi-fluid clays into rivers and streams. Following the last dam
failure in December 1971, a comprehensive set of dam regulations was
adopted by the State of Florida (Chapter 17-9, Rules of the Department
of Environmental Regulation). These rules have proven to be very
effective. However, the threat of a dam failure, particularly from
older dams that remain in active service, is ever-present.
Reclamation of clay impoundments is mandated by State law
(Chapter 211.32) requiring restoration of all lands disturbed by phos-
phate mining after July 1, 1975. However, reclamation of clay
impoundments is an expensive and time-consuming operation, and the
practical re-use alternatives of the reclaimed land are generally limited
to improved pasture. Increased pressure is being exerted by
environmental groups and government agencies to require reclamation
of mined lands to pre-mining contours, as well as to restore natural
hydrological and ecological functions. These goals cannot be achieved
using the conventional settling ponds for waste clay disposal.
Beginning in
along with various
Mines, and several
phosphate slimes in
the late 1940’s, the phosphate mining companies,
research groups, including TVA, the Bureau of
universities, began to study the properties of
an effort to develop improved dewatering methods
to reduce or eliminate the need for above-grade storage (Davenport, et
al., 1953; Houston, et al., 1949; LaMer and Smellie, 1956-58; Specht,
1950; Vondrasek, 1962). Potential by-product uses were also studied
(Tyler and Waggaman, 1953; Gooch and Dobson, 1960; Poole, 1951;
Vasan, 1971; Whitaker, 1960).
Although the research conducted from 1940 to 1970 was extensive,
very little was accomplished in terms of either practical solutions to
the slimes dewatering problem or an understanding of the fundamental
physico-chemical properties of the clay wastes. To a large extent,
this was a result of very limited sampling and testing to ascertain the
2
variability of clay slimes and to relate observed behavior to funda-
mental properties. Since the clay wastes are now known to vary
greatly in composition and behavior from mine to mine, and even within
a given mine site, the lack of a comprehensive definition of clay pro-
perties makes the pre-1970 research results of relatively little value.
Beginning in 1972, the Florida phosphate industry and the U.S.
Bureau of Mines engaged in a cooperative research effort1 to develop
practicable methods for dewatering phosphatic clays. During six years
of research, extensive laboratory and field
ducted (Bromwell and Oxford, 1977; Lamont,
al., 1977; Martin, et al., 1977; Bromwell and
Feld, 1979).
investigations were con-
et al., 1975; Keshian, et
Raden, 1979; Smelley and
At the start of the Florida Phosphatic Clays Research Project,
samples of fresh plant slimes were collected from fifteen active mines.
These fifteen samples were tested extensively by the Bureau of Mines
(Lamont, et al., 1975) and served as a reference data base for the
project. This information was expanded during the mid-1970’s by data
obtained on samples taken during field testing projects, samples of
relatively pure reference clay minerals obtained at selected sites, and
various academic theses (Bromwell, 1974, 1975, 1976; Hawkins, 1973;
Roma, 1976; Chanchani, 1976; Keshian, 1976; Stevenson, 1976; Buie and
Fellers, 1977).
1Designated as the Florida Phosphatic Clays Research Project
(FPCRP), directed by Leslie G. Bromwell, an independent consultantrepresenting ten Florida phosphate mining companies.
3
These data, although extremely useful, are very limited in severalrespects, viz:
0 Samples were primarily taken during the time period 1972 to1975.
0 Samples were taken from active mining operations only.
In order to provide adequate information for future research
efforts , an updated and expanded data base is needed that includes
samples from older unreclaimed clay settling areas, active clay settling
areas, current mining operations, and proposed future mine sites.
Research studies on clay dewatering should utilize accurate char-
acterizations of the specific clay waste material being tested. Only in
this manner can the results of various research studies be correlated
and their applicability to various mining situations evaluated. There-
fore, this study was undertaken to survey the range of waste clay
properties in the central Florida phosphate district and to establish a
computerized data base. The data base will allow properties of the
clays to be be stored, retrieved, and manipulated in a manner so as to
facilitate future site-specific studies, as well as to assist in future
research efforts involving recovery of mineral values from clay wastes
and improved dewatering techniques.
II. SCOPE OF STUDY
During the period June 1989, through March 1981, 38 clay settling
areas of various ages were sampled by Bromwell Engineering and the
samples returned to the laboratory for testing. Also, fresh clay
slurry samples were taken at 18 beneficiation plants, and 7 clay
slurry samples were obtained during processing of prospect cores
taken from future mine sites.
4
Laboratory testing included classification tests such as percent
solids, particle size distribution, specific gravity, and plasticity
limits. Other physical properties determined for selected samples
included sedimentation behavior (thirty-day settling tests), slurry
consolidation testing to determine compressibility and permeability over
a range of solids contents, and shear strength determinations by
shear testing.
vane
Chemical analyses were made to identify principal elements in both
selected clay samples and in supernatant water after settling of the
clays. Mineral constituents were identified by X-ray diffraction, and
the size and shape of various mineral species were examined by scan-
ning electron microscopy (SEM) coupled with energy dispersive anal-
ysis by X-ray (EDAX). The X-ray analyses and SEM work were done
under the supervision of Dr. R. Torrence Martin at M.I.T.
The large amount of data generated from the sampling and testing
effort were entered into a computerized data base management system.
This data base, SYSTEM 2000, operating on the McAuto Cyber Service
(McDonnell Douglas Automation Company) through a time-sharing
terminal, allows easy storage, retrieval, and manipulation of desired
sub-sets of data according to key word identifiers. The data base is
organized so that it can assimilate a continuously growing body of
information, including additional parameters that may be developed
during future studies of phosphatic clays.
The data base, incorporating all of the pertinent results obtained
during this study, is being provided to the Florida Institute of Phos-
phate Research for use by other researchers and for future updating
as additional data are collected.
III. DESCRIPTION OF DATA BASE
The SYSTEM 2000 data base is used to provide storage and
5
retrieval capability for data characterizing waste phosphatic clays. The
data are of two distinct types: that which is representative of par-
ticular field conditions (solids content as a function of location in a
clay settling area being the most common example) and that which
represents a specific property of the clay (plasticity limits, for ex-
ample). The data base is organized in such a manner that it can
accumulate a continuously growing body of information. It is also able
to incorporate additional parameters as desired in the future.
The two basic components of SYSTEM 2000 are data elements and
repeating groups. Elements store data values in the form of a name, a
text, an integer, a decimal, a date, or other numerical unit. Re-
peating groups are employed when one or more elements may be used
to store more than one occurrence of data. Repetitive sampling of a
particular waste clay source or similar sampling of numerous sources
are applications for which the design of SYSTEM 2000 is well suited.
SYSTEM 2000 employs user-oriented language to perform query
and update functions, thus facilitating input and access. For example,
the command,
PRINT (Settling Area Designations)
WHERE (Settling Area Size) GT 400,
might be used to create a list of all settling areas sampled that were
greater than (GT) 400 acres in size. Further conditional commands
might be used to define, for instance, the time frame under
consideration.
Some data manipulation may be performed within the data base by
employing both system and user-defined functions. Computer manip-
ulation of the data may be implemented for statistical analysis,
graphing, or such other functions as may be programmed externally.
Establishment of the data base structure is accomplished by
organizing data elements and repeating groups in a manner that will
6
promote efficient access, utilizing a variety of data definition options
to optimize the use of computer storage space. Table 1 is a simplified
portrayal of the data base organization, showing examples of data
elements assigned at each data level. Table 2 presents a complete
definition of the data base.
It will be noted in Table 1 that repeating groups (RG) constitute
data sub-units, and as such they represent the links among the vari-
ous hierarchical levels. Generally, the clay properties data base is
organized to record times and locations for sampling within a given
mine, storing test data in various elements and repeating groups under
the heading “Sample Information”.
All waste clay samples are associated with a particular mine,
which is identified not only by name but by a master number (see
Table 3). The mine number provides the prefix digits for the indi-
vidual sample numbers, making the association clear for all samples.
Numerous sources of waste clay samples may have been utilized within
any given mine. Thus, "Information on Source of Sample” (settling
area, washer, met lab) is a repeating group for each mine.
The sample source is characterized by a name, e.g., the settling
area designation (Element 22), as well as other items listed in Table 2.
Each source may have been sampled on any number of occasions. For
a given source, such occasions are organized under the repeating
group "Sampling Event"” (Element 38).
Sampling events are identified by date. Conditions unique to the
sample source at that time, such as settling area status
(active/inactive), fluid elevation, etc., are also recorded The re-
peating group "Location Information" (Element 48) permits recording
further detail about samples obtained in a specific sampling event. In
the case of settling area samples, for instance, specific sites within
the settling area can be designated.
7
TABLE I
DATA BASE ORGANIZATION
123202138394648495556586885
150151152164165173174175
Mine Master NumberCompanyMine NameInformation on Source of Sample (RG)*Source NameSampling Event (RG in 20)Sample Acquisition DateSettling Area StatusLocation Information (RG in 38)Grid LocationSample Information (RG in 48)Sample NumberSample DepthSolids ContentChemical Analysis (RG in 55).
.Settling Tests and Slurry Consolidation (RG in 55)Test TypeTest HistoryStress Increment (RG in 150)LoadHeight vs. Time Readings (RG in 164)HeightTime
*Note: : (RG) indicates Repeating Groups
8
ElementCode
1
2
3
4
6
16
\D 17
Element TABLE 2 -DATA BASE DEFINITION-Page 1Title
Mine Master Number
Description
Arbitrary integer, ordinarily two digits, assigned to eachexisting or former mine
Company
Mine Name
Mine Location
Property Size
Nominal Production
Property owner associated with a particular mine master number
Accepted name of existing or former mine
Text listing county and township-range coordinates of mine
Total acreage associated with existing or former mine
Phosphate rock usual annual production (expressed in MMT/yr)by active beneficiation plant
Clay : Product Ratio Ratio of waste clay production to nominal production
18 Mine Startup, Shutdown Startup date and actual or anticipated shutdown date
20 Information on Source Repeating Group intended to identify and describe repeatedly used waste clay
21
22
23
29,30,33
of Sample
Source Name
Settling AreaD e s i g n a t i o n
Settling Area Size
Fill History
sample sources within a particular mine
Identification of the origin of a waste clay sample if otherthan a settling pond; usually this implies a “fresh” sample fromwasher or field pipeline
Name/number of pond serving as source of individual or compositewaste clay sample
Pond extent in acres
Dates of completion and/or beginning of pond fill with narrativeto indicate historical clay loading schedule
,,, ,/
Element ElementCode Title
34,35 Inlet
36,37
25
26
210,211
E212,213
Outlet
Dam Crest Elevation
Fill Depth Maximum
Plant Location
Settling Area Location
TABLE 2-Page 2 (continued)
Number of existing waste clay inlet points to pond with text toidentify location on the standard grid
Number of existing clear water outlets from pond with text iden-tifying location on the standard grid
Crest elevation (in feet, MSL) of embankment surrounding pond
Vertical distance (in feet) from nominal pond bottom to limitingfill elevation
Where the beneficiation plant is the sample source, its coordi-nates are expressed in Florida Plane Coordinate System (N and Ecoordinates in l000-foot units)
Where samples originate from a settling pond, its location isidentified by the coordinates of its A-l grid point on theFlorida Plane Coordinate System (N and E coordinates in lOOG-foot units)
38 Sampling Event RG intended to identify the time of a sampling event and de-scribe certain conditions unique to that time
39 Sample Acquisition Date of acquisition of pond, plant, or metlab sample
40 Matrix Acquisition Date of matrix acquisition where waste clay is generated from amatrix sample, ordinarily in a metlab
43 Settling Area FluidElevation
Elevation (in feet, MSL) of slurry in pond at time of sampling
46 Settling Area Status Identification of active/inactive status at time of sampling
,, ,,,,
ElementCode
48
49
490
50
=:51
52,53,535
491
ElementTitle
Location Information
Settling Area AreaLocation
Grid
Grid Location Detail
Prospect BoreholeLocation
Tap Location
Distance from Inlet,Outlet, Embankment
TABLE 2-Page 3 (continued)
RG intended to provide more detailed information regarding theorigin of a sample within a given source at a particular sam-pling time
Identification of grid point for settling pond samples
Specification of offset, in standard format, for settling pondsamples that originated more than about 50 feet from a desig-nated grid point
Text to indicate section, township, and range representing ori-gin of matrix for waste clay samples generated by a metlab
Text to indicate specifically the origin of a slurry samplehaving beneficiation plant or metlab as its general source(examples, primary cyclone overflow, secondary slime pipeline)
Lateral distance (in feet) of the sampling location from themain slurry inlet of the pond, from the main clear water outlet,and from the embankment
Weight for Averaging Component assigned to store an area 1 weighting factor tosettling area sampling locations for the purpose of estimatinga settling area average clay solids content (based on averagesat particular sampling
536 Weighted AverageSolids Content inLocation
Average value of claypling location
locations)
solids content (%) at a particular sam-
Element ElementCode
55TitleSample Information
56 Sample Number
h
PNV 57 Alternate Sample
Number
575 Proprietary SampleNumber
50 Sample Depth fromFluid Surface
64 Test AssignmentSummary
TABLE 2-Page-4 (continued)
RG intended to record all data associated with testing of asample that was acquired at a particular time from a certainlocation I source within a particular mine
Unique identification number for each sample described in thedata base; consists of six digits, the first two of which cor-respond to the mine master number; the four suffix digits willbe of the form OXXX, 06XX, 07XX, or 08XX; the 06XX series iden-tifies “fresh” slurry samples acquired from beneficiation plantsor metlabs; 07XX and 08XX are temporary numbers assigned toidentify sub-samples removed from the lab for processing else-where (specifically, for chemical and mineralogical determina-tions) -- the temporary numbers generally will not be recordedin the data base; all other individual composite samples areassigned numbers OXXX sequentially on acquisition
Alternate designation deemed useful in identification, e.g.,one assigned by the metlab or, occasionally, a temporary number
Data element reserved for storage of sample numbers assoc-ated with restricted data; for such samples, the number isrecorded here and the “Sample Number” (non-proprietary) is vacant,i . e . , it does not exist; thus, a general call-up of data, wherethe proviso “Sample Number must exist" will avoid inadvertent-ly retrieving restricted data
Vertical distance (in feet) from fluid (or solid) surface tothe sample location
List of test names for which results are avilable in the database for the particular sample
Element ElementCode Title
65 Total Solids Content
66
67
68
PW
69
73
74
77
78
79
80
81,82,83
Sand Fraction
Degree of Saturation
Clay Solids Content
Specific Gravity
Liquid Limit
Plastic Limit
Conductivity
pH
Grain SizeDistribution Test
Test Description
D60, D50, DlO
TABLE 2-Page 5 (continued)
Value of parameter; for individual settling pond samples thevalue is generally that which existed in the field; for pondcomposite samples it is typically the value measured shortlyafter composite preparation; the value is ordinarily notrecorded for “fresh” slurry samples
Weight proportion of +150 material in particular sample (indi-vidual or composite), dry weight basis; recorded as describedfor "Total Solids Content”
Value of parameter
Value of parameter; recorded as described for “Total SolidsContent”
Value of parameter
Value of parameter
Value of parameter
Value of parameter
Value of parameter
RG (in 55) intended to record waste clay grain size distributionand the values of certain derived parameters for a particularsample
Text describing method of grain size determination employed
Nominal particle size (in microns) defining commonly notedpoints on the grain size curve
ElementCode84
85 Chemical Analysis
86
87
88-968
P*
97
110
111
112
113
119 Vane Shear Test
ElementTitleGrain SizeDistribution
Component of
Handling andNotes
Sample
Testing
(Various ChemicalDeterminations)
Viscosity Test
X-ray Diffraction
System Data
Sample Processing1Jotes
Two Theta Increments
TABLE 2-Page 6 (continued)
RG (in 79) employed to record pairs of “Grain Size” and “PercentFiner” data
RG (in 55) intended to record the results of chemical determina-tions and describe certain qualifying factors
Text to describe the portion of the sample subjected to chemicalanalysis if it was not evaluated in bulk
Text to describe pre-treatment or special testing considerationsinvolved in chemical analysis of the particular sample
Value of parameter; data elements are currently assigned forU3O8, gross alpha,CEC , Fe203,
radium 226, CO2, carbon, insol,,K2O, TOC ,
Al2O3, CaO, SiO2, MgO, P2O5, crude H2O,, F, LOI
RG (in 55) intended to describe test conditions and resultsassociated with determinations made by rotary viscometerRG (in 55) intended to record X-ray diffractometer data and de-scribe system and sample conditions
Text to record diffractometer operating configuration existingduring evaluation of the sample under consideration
Text to describe sample pre-treatments, fractionation, or otherfactors preceding diffraction analysis
RG (in 110) intended to record the paired diffractogram valuesof two-theta and net peak amplitude, as well as to identify cer-tain mineral names and relative peak amplitudes
RG (in 55) intended to record the results of vane shear testingon waste clay samples in the field and the laboratory
ElementCode
129
140
150
151WWI
152,153
155
156
157
157
160-163
ElementTitle
TABLE 2-Page 7 (continued)
Triaxial Test
PermeabilityDetermination
Settling and SlurryConsolidation
Test Type
Test History
Initial Height
Maximum Stress Level
Initial Solids Content
Final Solids Content
A, B, C, D
RG (in 55) intended to record the results of triaxial tests con-ducted on waste clay samples
RG (in 55) intended to record the results of permeability testsin waste clay samples in the field and the laboratory (otherthan information derived from slurry consolidation tests)
RG (in 55) intended to record slurry consolidation test data ateach individual stress increment as well as results derived fromevaluation of stress increment data; free settling tests repre-sent a special case, i.e., the “self-weight” stress increment ofa consolidation test
Name (settling test; slurry consolidation test) employed to dis-tinguish between standard settling test (generally 2000 cc) andlarger scale lab consolidation tests that feature externalloading
Beginning and ending dates of the test
Slurry height on initiation of free settling test or self-weightincrement of consolidation test
Highest stress increment (in psf) employed in consolidation test
Slurry solids content on initiation of free settling test orself-weight increment of consolidation
Highest solids content reached in settling or consolidation test
Compressibility and permeability parameters defining therelationships : -B
e = Aa K - CeD
(16)
TABLE 5-Page 1
MasterNumber
001
002
003
004
005
006
007
008
009
010
011
012
013
014
015
016
017
018
019
021
022
023
024
Company
IMC
IMC
Royster
IMC
AMAX
IMC
CF Mining
Brewster
Agrico
Borden
Agrico
Agrico
USSAC
USSAC Rockland
W.R. Grace Hookers Prairie
Brewster Polk A
Gardinier Ft. Meade
ESTECH Watson
W.R. Grace Bonny Lake
IMC Homeland
Mobil Ft. Meade
ESTECH Silver City
Mobil Nichols
MINE (TRACT) MASTER NUMBERS
Tract Name- -
Achan
Noralyn
Mulberry
Clear Springs
Big Four
Kingsford
Hardee
Hills "B"
Saddle Creek
Tenoroc
Payne Creek
Ft. Green
Hancock
Rockland
17
TABLE 3-Page 2
Master
Number Company
025 IMC Phosphoria
049 Waste Mgt. Sydney
050 Am. Cyanamid Hills "C"
051 Agrico Boyette
053 Holloway Pauway
054 Am. Cyanamid Saddle Creek
055 USSAC Bartow
056 Noranda Hopewell
062 Agrico Palmetto
075 W.R. Grace Four Corners
077 USSAC So. Rockland
078 Gardinier Hardee
079 Mobil So. Ft. Meade
083 Beker Wingate Creek
085 Agrico So. Ft. Green
088 W.R. Grace NE Manatee
MINE (TRACT) MASTER NUMBERS
Tract Name
18
The repeating group “Sample Information” (Element 55) heads the
hierarchical level that records clay properties. The level includes data
elements for the various parameters listed in Table 2,
groups for recording multi-valued properties or those
more detailed data, e.g., consolidation characteristics.
The total depth of the data base below the initial
elements is seven hierarchical levels. The total number
and repeating
derived from
group of data
of components
is presently 144. Although not all components are currently employed,
any filled element at any level must be associated with at least one
filled element at every higher level in order to provide a continuous
chain of information up to the initial data groups. Simply stated, each
piece of waste clay test data on file must be associated with a unique
sample number obtained from a specific location on a given date.
IV. SAMPLING LOCATIONS AND PROCEDURES
A. Settling Area Samples
During the period June 1980, through March 1981, samples
were taken at 38 waste clay impoundments (“settling areas”) of various
ages. These sampling locations are listed in Table 4, and Figure 1
shows the general location of the settling areas.
Access for sampling was provided by a variety of methods
depending upon the surface condition of the settling area. Methods
used included airboat, tracked vehicle, and on foot, with or without
flotation pads.
Sampling was conducted using a piston-tube sampler attached
to extension rods to reach depths of 50 feet or more. A schematic
drawing of the sampler is shown in Figure 2. In most cases the
samples were taken at 5-foot intervals to the bottom of the pond. In
some of the older areas, however, either dense slimes or deposits of
coarse waste material were occasionally encountered that prevented
sampling to the bottom of the pond.
19
Sampling location control was maintained by establishing a
grid system for each settling area. Square grid elements were used,
oriented north-south and east-west, with a 500-foot repeat interval.
The north-south lines are labelled alphabetically with “A” westernmost.
The east-west lines are labelled numerically with “1” southernmost.
The grid is positioned with respect to the settling area by placing the
A-line tangent to the westernmost portion of the pond and the l-line
tangent to the southernmost portion. The A-l grid point is the origin
of the grid. For a rectangular settling area with north-south orien-
tation, the A-l point would represent the southwest corner. For a
pond of irregular configuration, the A-l point will generally be outside
the impoundment. Where sampling locations do not correspond to
designated grid points, the offsets are reported in a notation that
specifies distance, to the nearest 100 feet, and direction, relative to
the nearest grid point. Thus, G-4 (lS, 2W) represents a sampling
location 100 feet south and 200 feet west of grid point G-4.
B. Beneficiation Plant Samples
Fresh clay slurry samples were obtained from 18 operating
beneficiation plants, as indicated in Table 5. Seven additional sam-
ples, also listed in Table 5, representing future mining sites, were
obtained during metallurgical laboratory processing of prospect core
samples.
The fresh slurry samples were taken by compositing grab
samples into a plastic-lined 55-gallon drum over an extended time
period (minimum three days}. In the laboratory, these samples were
allowed to settle until at least 15 gallons of clear supernatant water
were present. Five gallons of supernatant water were then decanted
and saved, and the remaining contents of the drum were stirred to
obtain a uniform slurry. Sufficient material was then removed and
21
placed in 5-gallon plastic containers to conduct the required tests on
each sample.
V. TEST PROCEDURES AND RESULTS
A. Solids Contents
The total solids content was measured for all samples re-
turned to the laboratory. Approximately 50 grams of sample were
dried for 24 hours at 105°C for this test. Wet sieving was used to
determine the percentage passing a No. 140 mesh standard sieve, and
the clay solids content was then calculated as,
s= wcWe+ ww x 100
where WC
= weight of "clay" (minus 140 mesh material)
Ww = weight of water
The clay solids content reflects actual changes in the moisture regime
of the fine-grained fraction of the sample, whereas changes in total
solids content may reflect a change in the amount of coarse-grained
material in the sample with no change in clay consistency.
1. Settling Area Samples
The total solids content, percent larger than 140 mesh
(sand fraction), and calculated clay solids contents for all settling area
samples are listed by sample location in the SYSTEM 2000 data base.
The clay solids content data vs. depth can be grouped-into several typical patterns, as shown in Figure 3. The most
commonly observed pattern in an active settling area is shown by
curve 1, with solids contents low at the solids/water interface and
increasing gradually with depth as self-weight stresses cause increased
23
consolidation. Within a few feet of the bottom, an abrupt increase in
solids content occurs, reflecting the consolidation caused by drainage
and seepage forces across the deposit boundary. For above-ground
settling areas, the increase in solids content near the bottom is gen-
erally greater and extends over a greater depth, reflecting both better
drainage conditions and higher seepage forces. This reverse-S type
curve generally starts at solids contents on the order of 8% to 15%,
with values generally in the range of 15% to 25% in the dominant central
portion of the profile. Solids contents at the bottom are generally on
the order of 40% to 50%; with lower values down to 30% occasionally
encountered.
When waste clay impoundments are retired and the
surface begins to dry out, solids contents in the surface zone of
desiccation will exceed those in the central zone, which typically is
still consolidating under self-weight stresses. The resulting Curve 2
has a C-shape, as shown in Figure 3. The zone of obvious influence
of desiccation is generally on the order of 5 feet or less, with surface
solids contents generally 45% to 55%, decreasing to the order of 25%
within the central zone. Solids contents at the bottom are similar to
those measured in active settling areas.
Although the reverse " S ” curve and “C" curve are
typical of active and retired areas, respectively, deviations from these
norms are also very common. Among the older retired or abandoned
areas, several were found where consolidation and desiccation had led
to a reasonably uniform solids content with depth, as shown by
Curve #3 in Figure 3. These areas all were on natural ground and
generally on the order of 10 feet or less in thickness. Solids contents
for such areas were generally found to be in the 50% to 55% range.
At several locations, particularly in deep, old settling
areas, solids contents were found to be erratic with depth, exhibiting
intermediate layers of higher solids content than the material
24
immediately above and below. This type of profile is illustrated by
Curve 4 in Figure 3. In certain instances, groups of sampling
locations exhibited such layers at similar depths, strongly suggesting
wide lateral extent. In many other cases, however, no correlation was
identified among locations with respect to this sort of solids content
variation.
In younger settling areas (active
similar deviations from the S-curve standard form
cases , the "layering" is less distinct than in old
the general rise (and subsequent fall) in solids
or newly retired),
were seen. In such
impoundments , since
content may extend
over a 10 - to 15-foot depth span . It is discernible, though, since such
regions may be 5% to 10 % solids higher than adjacent zones. Moreover,
wide lateral extent is frequently observed.
Although the filling (and draining) histories of most of
the sampled ponds are not known, several that exhibit subsurface
“layers” are known to have had the surface water drained during past
periods of inactivation. Thus it is likely that the layering is related
to partial crust development by desiccation that occurred between
filling cycles.
Occasionally coarse material (larger than 140 mesh) was
found in the settled clays. In virtually every instance, the occur-
rence of such material was associated with higher values of clay solids
content than would be expected based on nearby samples where the
clay was not mixed
is similar to what
sand / clay mixing.
settling area inlet
with sand. Qualitatively, the solids content profile
would be predicted for consolidation promoted by
Locations exhibiting this behavior are typically near
regions where coarse materials in the waste slurry
stream are deposited.
A final pattern of solids content with respect to depth
was observed at some locations in younger ponds. It resembles the
S-curve of active areas, but is characterized by a central zone that is
25
nearly indistinguishable from the top and bottom portions. That is to
say, solids content increases at a fairly constant and relatively rapid
rate throughout the entire column, as shown by Curve 5 of Figure 3.
In those instances where the deposit is shallow (10 to 15 feet), the
phenomenon might be a result of bottom seepage. In deeper deposits,
profiles of this sort frequently have relatively high average solids
content and are probably indicative of very favorable clay consolidation
properties.
The average solids contents for the settling area sam-
ples are listed in Table 6 and plotted as a histogram
Approximately three-quarters of all the average values
range of 15% to 30% solids, with a median value of 24.1%.
2. Fresh Slurry Samples
Standard sedimentation tests using 2000 ml graduated
cylinders were run on the fresh slurry samples from beneficiation
in Figure 4.
were in the
plants (18 samples) and from metallurgical lab processing of prospect
ore samples (7 samples). The thirty-day solids contents are shown in
Table 7, along with a tabulation of other physical and mineralogical
data. Thirty-day solids contents ranged from 6.4% to 15.3%) with a
median value of 12.1%.
These results are similar to those obtained by the
Bureau of Mines (Lamont, et.al. , 1975) on 15 samples taken from
beneficiation plants in 1972. The BOM samples showed a range of 30
day settled solids from 5.7% to 15.9%, with a median value of 10.9%. It
is interesting to note on Table 7 that the samples from prospect cores,
representing proposed
solids. These samples
of 10.6%.
future mines, fell in the lower range of settled
ranged from 6.4% to 13.3%, with a median value
26
B. Physical Properties
Tests were conducted on a wide range of samples to deter-
mine plasticity, grain size, and specific gravity, as well as shear
strength, consolidation, and permeability parameters. The test
samples included both fresh clay slurry obtained from beneficiation
plants or metlabs and composites of numerous individual samples
acquired from individual settling areas, Various composites were made
in order to produce samples. that were representative of the entire
settling pond, or representative of a distinctive region (e.g., deep or
shallow zone ; area near-to/far-from inlet) or representative of a
particular
tabulation
provide a
feature (e.g., a high-sand zone).
The parameters measured are described below. A complete
of the data is available from the SYSTEM 2000 data base.
1. Atterberg Limits
Atterberg limits are simple classification tests that
measure of plasticity, Although the tests have no fund-
amental significance, they have been shown to correlate with clay
mineralogy and soil behavior (Casagrande, 1948; Carrier and Beckman,
1982). The test methods are described in ASTM D 423 and D 424.
The liquid limit (LL) is defined as the water content2 above which the
clay behaves essentially as a liquid, and below which it behaves as a
plastic material. The plastic limit (PL) is defined as the water content
2The water content, w, is defined by:
Ww= w
wS
x lOO%, where WW
= weight of water, and WS
= Weight ofSolids or
Water content and solids content, S, are related as follows:
w = (F -1) x 100%.
33
above which the clay is still plastic and below which it is a semi-solid.
The plasticity index (PI) is defined as the liquid limit minus the
plastic limit, and represents the water content range over which the
material exhibits plastic behavior. High values of liquid limit and
plasticity index reflect high percentages of active clay minerals, which
generally results in poor consolidation and strength properties.
Liquid limit and plasticity index are plotted on the
plasticity chart shown in Figure 5. Values obtained from previous
studies on phosphatic clays by Bromwell Engineering are also shown
for comparison. The phosphatic clays fall in the CH range of the
chart, indicating a highly plastic clay material.
The range of plasticity values for the clays is quite
large, with liquid limit values generally between 100 and 250, and PI
generally between 60 and 200. Samples falling below these ranges
generally have significant amounts of sand-size material, whereas
samples falling above this range represent unusual cases of extreme
colloidal behavior.
Figure 5 shows a wide range of plasticity values from
both settling areas and from fresh slurry samples. This is indicative
of the large variability in phosphatic clays produced in Central
Florida.
A "typical” phosphatic clay has a liquid limit of about
170, and a plasticity index of about 110. These values indicate that
the clay exhibits plastic behavior* over a wide range of water to solids
ratios, from about 0.6 to 1.7. Very few natural clay soils exhibit
such plasticity, Mexico City Clay and scattered deposits of pure
smectite minerals being notable exceptions.
*Plastic behavior means that it has a measurable shear resistance andundergoes changes of shape without rupturing.
34
At the liquid limit, typical phosphatic clay has a solids
content of about 35%. Hence, the vast majority of the clay in both
active and old settling areas is above the liquid limit. This means that
settled clays, if disturbed and remolded, would flow like fluids with
essentially zero shear strength.
The term “liquidity index ” (LI) is used to express the
consistency of soft clays having high water contents. It is calculated
as follows:
LI = w - WpPI
Wherew = Water Content
wP= Plastic limit
PI = Plasticity Index
The liquidity index for a typical phosphatic clay,
existing at a solids content of 25% in a settling area, is about 2.
Few natural clay deposits exhibit a liquidity index higher than 1.
Those that do are known as “sensitive" or “quick” clays, since they
essentially liquefy when remolded.
2. Particle Size Distribution
In addition to wet sieving all samples on a 140 mesh
screen to determine the percentages of tailings sand and slimes, hy-
drometer tests were run on selected samples. The hydrometer analysis
is a laboratory test used to measure the particle size distribution for
mineral grains too small to sieve. The technique is based on Stokes’
law for spheres falling through a fluid. The test method is described
in ASTM D 422. Of most interest is the weight proportion of the
slimes that is finer than a particle size of 2 micrometers (µm).
Particles smaller than 2 µm are clay-sized, and it is this fine-grained
fraction that causes poor sedimentation/consolidation behavior. Table 7
35
lists the percent smaller than 2 µm for the fresh slurry samples. The
range in values is from 28 to 87, with a median value of 67%. Table 8
shows values of minus 2µm for selected samples from settling areas.
The range for all settling area samples was from 25% to 91%, with a
median value of 74%.
3. Specific Gravity
The specific gravity of the solid particles is measured by
the method of ASTM D 854. Most of the components of the waste clay
slurry individually have specific gravities in the range 2.6 to 2.9,
except apatite (3.2) , wavellite (2.3) and palygorskite (2.1). The
median value of specific gravity for all of the samples was 2.77, with
the fresh slurry samples having a slightly lower median value (2.75)
than the samples from settling areas (2.79).
4. Compressibility and Permeability
The dewatering behavior of phosphatic clays, both
under self-weight and under imposed stresses, is controlled by the
compressibility and permeability of the material. Both of these par-
ameters vary with solids content of the material. Measurements of
permeability and compressibility are required in order to compare the
dewatering performance of clays from different locations, and also to
evaluate the effectiveness of proposed new methods for clay de-
watering. Methods that cause increases in permeability or decreases in
compressibility will result in improved clay consolidation performance
and improved soil strength at a given stress level.
Consolidation and permeability parameters were mea-
sured on fresh slurry samples using a slurry consolidation device
developed especially for such applications (Bromwell and Carrier,
1979). A schematic drawing of the device is shown in Figure 6. The
test involves placing about 5 gallons of slurry into the device and
36
measuring the volume change that occurs with time under increasing
increments of applied load. At each load level, the sample is allowed
to reach equilibrium (constant volume) before the next load is applied.
The results of slurry consolidation tests on fresh washer slimes are
shown in Figures 7 and 8. Figure 7 shows the void ratio or solids
content as a function of effective stress. The spread of values for a
given effective stress is quite large, but this variation has been
observed previously on phosphatic clay samples (Roma, 1976; Carrier,
et al., 1982).
At low effective stresses, on the order of 5 lb/ft2, the
solids contents ranged from about 15% to 20%. At stresses on the
order of 100 lb/ft2, which are typical of average self-weight stresses
in settling areas, the range of equilibrium solids contents was from
about 28% to 40%. This
samples from individual
tents and final reclaimed
Figure 8
illustrates the necessity to test representative
sites in order to estimate ultimate solids con-
heights of clay disposal areas.
shows the permeability values measured as a
function of void ration or solids content. Permeability decreases by
several orders of magnitude as the solids content increases. Con-
solidation rates are directly dependent upon permeability values, with
clays having low permeability requiring longer time to consolidate to an
equilibrium solids content.
At a given solids content, the range in permeability was
as much as a factor of 10 between the highest and lowest samples.
This means that a sample having low permeability could require ten
times as long to reach the same solids content as a sample with high
permeability. This clearly indicates the importance of measuring
permeability on representative samples from individual mine sites in
order to estimate rates of consolidation dewatering for various clay
disposal situations.
37
5. Vane Shear Strength
Undrained shear strength was measured on consolidated
clay samples using a laboratory vane shear device. Table 9 lists the
strength values measured on samples consolidated in the laboratory
from a slurry. Both peak (maximum) and residual (remolded)
strengths were measured. Solids contents of the samples ranged from
26% to 40%. Peak shear strength values ranged from 11 to 57 lb/ft2,
indicating a very soft and weak material. A shear strength of 50
lb/ft2 will only support a surface load on the order of 250 lb/ft22 An
average adult exerts a pressure on the order of 350 lb/ft2 when
standing on both feet.
Remolded shear strengths were very low, with typical
sensitivity values ranging from 2 to 5. The low remolded strength
indicates that the clays, once disturbed by shearing action, would
behave essentially as viscous fluids.
The ratio of peak undrained strength to maximum
consolidation pressure ranged from 0.21 to 0.31, which is within the
range of values previously reported for normally consolidated soft
clays (Bjerrum, 1972). Based on Bjerrum’s correlation, the expected
value of Su oc for the samples would be approximately 0.3 to 0.35.
C. Chemical Analyses
Chemical analyses were made on selected samples of slimes
solids and on samples of supernatant water removed from drum samples
of fresh- slimes. The chemical analyses were made primarily to assist
in evaluating the potential for recovery of additional mineral values
and to establish the variability of chemical constituents across the
mining district. The parameters measured included conductivity and
pH (using a 1:1l suspension for slimes samples); total dissolved solids;
loss on ignition (1,000 ° C ) ; cation exchange capacity (CEC); and the
38
elements P, Ca, Mg, Al, Fe, Si, K, C, S, Cl, F, N, U, and I Ra.
Gross CI radiation was also measured cn some samples, as were ‘Cr, Mn,
Rb, Sr, Ti, and Zn.
Results of the chemical analyses are tabulated in the
SYSTEM 2000 Data Base, and summarized in Tables 10 and 11. i
1. Supernatant Water
Table 10 summarizes the analyses made on supernatant
tvater samples. These samples were taken from three existing. bene-
ficiation plants and three future mine sites, as indicated on the table.
The results obtained in this sampling confirm earlier tests indicating
that the clay envirorlment is a calcium-magnesium-bicarbonate-sulfate
dominated system. The degree of correspondence between this 1981
sampling and the 19’72 sampling conducted for the U.S. Bureau of
Mines is remarkable, as indicated by the average values listed
for the major elements:
below
Average Concentration (mg/fI)
No. of Samples
Ca Mg Na HCO3 SO4 Cl Fl TDS ---_c_---
1981 Samples 6 53 21 13 141 96 19 1.8 327
a 1972 Samples* 15 57 22 18 112 144 17 2.0 344
’ From Lament , et cl. (1975)
The cation exchange capacity (CEC) and exchangeable
cation species were also measured on selected samples. CEC measures
the amount of positive cations required to neutralize the net negative
charge that exists on all clay particles. These cations are exchange-
able; that is, they may be replaced by cations of another type if the
composition of the pore fluid changes. The CEC is usually expressed
as milliequivalents per 100 grams of dry clay. Typical values of CEC
40
for natural clays are 3 to 15 for kaolinite and attapulgite, and 80 to
150 for montmorillonite.
The cation exchange capacity and principal exchange-
able species were measured by washing the samples three times with
1.0 normal sodium acetate, followed by a wash with ethanol, and then
extracting the adsorbed sodium by several washings with ammonium
acetate. The amount of extracted sodium was measured and expressed
as the CEC. The cations extracted by the initial washings with sodium
acetate were determined as well.
The results of these tests on 5 samples of phosphatic clay were as
follows :
Sample Ca Mg K CEC Cations
CEC
90600 8.1 11.8 1.3 37.0 .57
90036 12.2 12.9 1.3 45.0 .59
780600 22.1 10.7 1.8 44.1 .78
850600 11.2 12.9 1.3 30.2 .84
83-600 28.9 13.1 2.0 46.2 .95
Note : All values are in milliequivalents per 100 grams dry soil.
May (1975) measured the CEC of the 15 slurry samples
taken from active beneficiation plants for the Bureau of Mines in 1972.
He used barium instead of sodium as the exchange ion, and obtained
values of CEC ranging from 17 to 45. Since different procedures and
exchange ions have been shown to give differing values of CEC for the
same clay, May’s values appear to agree reasonably well with the range
of values found for the present samples.
46
It should be noted that the sum of the values of Ca +
Mg + K tabulated above do not equal the total cation exchange cap-
acity. Their sum ranges from 57% to 95% of the CEC. Other cations,
probably including H, Al, Fe, and Na, make up the difference.
2. Composition of Solids
Table 11 summarizes pertinent chemical data on selected
slimes samples. The data are grouped according to source, i.e. , old
settling areas, recent (young) settling areas, existing washer plants,
and metlab samples from future mines.
Although the variability in chemical composition from
site to site is quite large, the average values of major constituents
show little variability between old settling areas, recent settling areas,
and fresh slimes from existing plants. Average P205 values, for
example, were almost the same (12.2 +9.3%) from all three sources.
Furthermore, these values were essentially the same as determined on
fresh samples by the Bureau of Mines in 1972, as shown in Table 11.
The only major variation in chemistry was observed for
the seven samples from future mine sites, also shown in Tables 10
and 11. As Table 12 indicates, these samples had an average P205
content of only 8%, versus 12% for the other samples. Furthermore, Ca
and Mg values were much higher for the future mine sites, indicating
a much higher dolomite content in the slimes fraction. Uranium con-
centration was much lower in the samples from future mines, averaging
only 35 ug/g vs. values of 127 to 159 for the active and old sources. -
The data indicate that additional recovery of phosphate
and other mineral values from slimes produced during future mining
operations is likely to be much less attractive than would be the case
using the slimes from present and past mining operations.
No correlation was observed between chemical para-
meters and any physical property measured. In a rough sense,
47
I _., ,
TABLE 12
COMPARISON OF AVERAGE MINERAL VALUES
Old Settling Areas
Recent Settling Areas
1972 Beneficiation Plants* 15 12.0 16.2 2.9
1981 Beneficiation Plants 16 12.5 17.6 2.6
Future Mines 7 8.0 19.5 5.5
Number of
Samples
11
15
%
p205
% CaO
%
wo b/g)
U308
12.3 17.3 1.9 159
11.9 17.0 2.6 142
127
I 35
* From Lamont, et al., 1975.
48
variations in Mg might be expected to correlate with physical
properties affected by palygorskite content. However, the percentage
of Mg is so small, and probably dominated by dolomite content, that no
correlation between- Mg and physical properties was observed.
Similarly, pH and/or conductivity might be expected to
correlate with settling behavior. However, no such correlation was
found. This is most likely a result of divalent cation saturation and
excess bicarbonate in the system, which results in obliterating of
colloidal double-layer effects and buffering of potential pH effects. As
a consequence, physical behavior appears to be controlled primarily by
interactions between aggregated clay particles. These interactions are
most likely affected by changes in particle and aggregate size and
shape, and to a lesser extent, by chemical factors.
D. Mineralogy
1. Procedures
The mineralogy of 65 samples from 34 sites was ex-
amined by X-ray diffraction analysis with supporting scanning electron
microscopy (SEM) and chemical analyses (EDAX). The flow sheet,
Table 13, indicates the general analysis scheme. X-ray diffraction
(XRD) of the air dry powders listed on the left side of the analysis
scheme provided data for clay content of the different size fractions
and the relative amount of non-clay minerals, especially apatite.
Organic matter was determined by the Walkley-Black method (peech et
al., 1974) with sucrose as reference (100%).
The as-received slurry was mixed for two minutes in a
Waring blender at about 4 % solids before wet sieving, first through a
105pm sieve and then through a 44pm sieve. The only pretreatment
prior to Stokes’ law settling for -2pm fractionation was decantation of
the supernatant liquid to remove soluble salts until the electrolyte
49
Table 13. Mineralogical Analysis Flow Chart,
r
-[ -105+44pm Fract~di;~~~;,i;;tion
4---i -4411m Fraction
/
Air Dry 'Grind to -44~13
1 1 Air dry powder 1
I-2pm Fraction }T
r Clay slurry
I
Adjust to 3% Solid's ,, Homoionizo
'dandom powder
Organic X9D Natter (Bulk)
Mg or K Clay slurry 3%
0. A. 'I G to slurry
0. A.
0. A.= Oriented aggregate ‘G = Glycerol solvated
50
concentration was low enough that the suspension was visually dis-
persed. Quartz and dolomite were lower in the -2pm fraction but
apatite, which was the most abundant non-clay species, showed very
little reduction. To see if the apatite concentration could be reduced,
two samples were given a much .more severe treatment. Bulk slurry ’
free of soluble salt was adjusted to pH 9.5 using NaOH and then mixed
at maximum speed in a Waring Blender for 10 minutes. The -2pm
fraction from this additional chemical and mechanical work produced no
discernable difference in the XRD data. Homoionic clay was prepared
by three washes of the clay with the appropriate cation in a 1M chlo-
ride salt solution followed by distilled water washes until the elect-
rolyte concentration was about 10-3M as indicated by conductivity
measurement on the supernatant . Oriented aggregates were prepared
on glass slides from the homoionic clay using 3mk of 3% solids so that a
uniform clay film was achieved for all specimens. Glycerol solvation
was by the slurry method (Novich & Martin, 1981).
Peeling of air dry clay films from the glass slide was a
problem for many samples. The problem only occurred with K satu-
rated specimens. Samples where , the -2um K specimen peeled severely,
the -44pm Mg specimen showed no tendency to peel. Rapid filtration
onto a sintered steel plate or mixing glass fibers with the slurry
before filtration failed to prevent peeling. There was no consistent
pattern to the peeling during drying with any of the mineralogical
factors reported herein, For phosphatic waste clays where palygor-
skite is expected, a Mg saturated specimen may be advantageous over ’
a K specimen because the dry dOOl spacing for Mg smectite is less
than for K smectite, thus yielding a wider separation between dry
smectite and palygorskite peaks.
The x-ray diffraction, XRD, was done using Norelco
equipment. Radiation was CuK at 40 KV and 20 ma. Detection of the a
51
diffracted radiation was with a scintillation counter behind a graphite
crystal monochronometer. Goniometer speed was lo or 114’20 per
minute. Recorder speed was either 2’ or 4’2~1 per inch of chart
travel. Proper alignment for clay work was verified using chloresterol
and n-tetradecanol (dool = 39.63) where mean d eon. for
orders was 39.59 with. a coefficient of variation of (dool
= 33.6A)
the first eight
0.11%.
During X-ray examination all heated specimens were
kept dry by a small silica gel desiccator having a Mylar window for
passage of the X-ray beam. Specimens stored in position on the
goniometer for a week showed no change in XRD trace while removal of
the silica gel desiccator frequently produced a change in the XRD
trace within an hour.
Random powder mounts were prepared by chopping with
a razor blade. XRD data using a pole figure device consistently
indicated nearly ides1 random orientation for random powder mounts
carefully prepared.
To indicate relative change in a given mineral between
samples or between size fractions, the XRD data are reported as
relative peak amplitude, R. The relative peak amplitude is the ampli-
tude of a specific XRD peak divided by the peak amplitude for that
same XRD peak taken from the appropriate reference mineral data
given in Tables 14 and 15. The sample to be analyzed and the refer-
ence mineral data were all collected on specimens uniformly prepared so
that the R values reasonably reflect relative changes of a given’ min-
eral phase within the sample suite.
2. Reference Data
Table 14 gives peak amplitudes for specific XRD peaks
to be used as reference for the non-clay minerals (quartz, dolomite,
52
Table 14. Reference Data Non-Clay Minerals
Mineral
Quartz:' SiO2
Dolomite:2 c=WCO3)2
Apatite: 1
CagF(P0413, 42.2% P2O5
Wavellite.3 (AlOH)3(P04)2'5H7_0, 34.5% P2o5
Crandallite:4 C~.7Sr,_3~~13(PO~)z(OH)S Hz0 7.26%SrO, 33.1% P2O5
K Feldspar:5 KAlSi308, 16.9% K20
_----_--
d(A.1 A(c/s) (cmL/g)
4.26 745 3.35 3400 36.38 2.46 305
2.89 1310 48.83 2.19 330
2.66
2.85
2.79 2.69,
284 71.10 130
3.20
8.6 260 8.4 340 28.33 4.8 180
2.33
5.7 2.94
U 44.7‘
U.
2.9
3.24 900 SO.48 2.57
Mass
XRD Data Attenuation Coefficient
1. Average
2. Florida
3. Average
three Florida samples.
sample supplied by Ardaman & Associates.
two Florida samples supplied by R. Stevenson and by Ardaman & Associates.
4. Literature data for Florida sample, Blanchard (1972).
Specific Gravity
5. Average three samples M.I.T. collection.
53
apatite , wavellite, crandallite, and feldspar). The quartz and apatite
peak data are the average for three specimens from central Florida.
Three separate peaks were used for quartz because all the important
quartz peaks are superimposed on clay peaks making some uncertainty
in measuring net peak amplitude.
The two apatite peaks selected were distinct for apatite.
The coefficient was 10% for. each peak amplitude between the three
specimens that all came from the phosphate mining area of Florida.
The dolomite reference specimen from central Florida
contained 3% quartz and 8% apatite. Peak amplitudes for the two major
dolomite peaks given in Table 14 have been corrected for these im-
purities.
The wavellite amplitude data in Table 14 were based
upon very small samples that made analysis difficult. Three peaks are
given for wavellite because of the pronounced tendency for preferred
orientation. Averaging the data from three peaks tends to cancel any
orientation effect.
Information on crandallite was from literature sources
only, because no sample was available. Crandallite identification has
been deliberately biased toward the sample from Alachua, Florida,
described by Blanchard (1972)..- The data in Table 14 are for material
that is 70% ideal crandallite and 30% ideal goyazite. The potash
feldspar data were the average from two microcline samples and one
perthite sample available in the M. I. T. collection.
Chemical formulae for the non-clay minerals represent
ideal composition , which is believed to be justified based upon available
XRD data from phosphatic clay materials. The starting composition for
the clay minerals was the average composition for a given species as
given by Weaver and Pollard (1973), then biased to include 4 to 5%
Feg03 for species expected to contain iron.
55
Mass attenuation coefficients, p, for the reference
minerals were calculated using the composition as given in Tables 14
and 15 along with the elemental mass attenuation coefficients for CuK u
radiation taken from I. T. X. C. (1974). When reliable chemical data are
available, the calculated mass attenuation for a sample, p S’
is more
accurate than any ps deduced from direct XRD measurement.
Specific gravity, G, for non-clay minerals are mean
values taken from the literature on each ‘mineral. Clay mineral G
values were calculated from the composition as given and the crystal
dimensions of the unit cell:
Satisfactory
cult to obtain because of
clay mineral reference specimens are diffi-
the decided tendency for clay minerals to
exist as interstratifications of several phases. In other words, a
single phase clay mineral is&. a rarity. In natural occurring sedi-
mentary deposits, illite-smectite mixed layering is very common, and
mixed layered
Palygorskite-smectite
be expected to occur
kaolinite-smectite
mixed layering has
based upon crystal
has been reported.
not been reported but might
chemical considerations.
for naming a ‘clay mineral is One of the requirements
that the sequence of basal spacings give a rational series of peaks
whose coefficient of variation is less than 0.7%. For expandable min-
era1 phases such Bs smectites, this introduces the additional ex-
-perimental problem of defining a useable reproducible fully hydrated
condition. Novich and Martin (1981) have established an optimum level
of glycerol treatment to be used for routine analysis. Fortunately,
there exists a fairly wide range of glycerol treatment level that give
about the same XRD data.
A solids content of 3% was selected as slurry con-
centration for. preparation of
‘and on unknown samples.
oriented aggregates on reference clays
The 3% concentration, represents a
56
compromise between obtaining good orientation and the infinite thick
specimen desired for quantitative analysis.
A number of smectites were examined as possible refer-
ences. The data in Table 15 are average values, corrected for impur-
ities, from a ferruginous smectite and a Florida sample*.
No illite clay has been located in Florida, so two spec-
imens from the M.I. T. collection were examined in some detail. One
contained some expandable layers, making it unsuitable as a reference.
A specimen from Montana that contained no expandable layers had
about 2% chlorite as the only impurity, making it the best illite refer-
ence presently available.
Two of the three palygorskite specimens investigated
contained considerable smectite. The palygorskite data in Table 15
came from a specimen collected at Mobil Chemical’s Fort Meade mine,
and was free of any other detectable clay phase. The specimen did
contain 13% apatite and 1.5% quartz and the peak amplitude data have
been corrected for these impurities. The 10.5A palygorskite peak,
when present, as distinct from the 10A illite peak is a definitive
indication of palygorskite. The presence of a single peak between
10.5 and 10A suggests the presence of illite, palygorskite, or both but
does not provide definitive identification. Palygorskite has a strong
peak at 3.23A that becomes confused with the other clay peaks as well
as wavellite and feldspar. The 6.5 and 5.4A palygorskite peaks are
distinctive; unfortunately these two peaks are weak.
The kaolinite reference data in Table 15 came from a
South Carolina clay that contained 6% mica. This kaolinite is con-
sidered to be a valid reference for kaolin in the Florida phosphatic
Ferruginous smectite from Washington state, Clay Minerals Society, Source Clay #SWa-1, and Florida smectite collected by R.T. Martin at Mobil Chemical’s Nichols mine.
57
clays because a small specimen of kaolinite, collected in 1974 from
Occidental’s White Springs mine in North Florida, was indistinguishable
from the South Carolina kaolinite.
All clay minerals have an XRD peak at about 4.45A that
clearly shows in random powder mounts. For all the reference clay
specimens discussed above, the 4.45 peak gave an average amplitude
of 9Ocls with a coefficient of variation of 138. The amplitude of the
4.45A peak from a random powder mount is used as a measure of the
total clay mineral content of that sample with due allowance for vari-
ation in mass attenuation coefficients.
Based upon available information, the data in Tables 14
and 15 are consl_‘,ered reasonable reference data for phosphatic waste
clay materials.
3. Results
a. General -
Apatite, quartz and clay were ubiquitous in all
phosphatic clay samples examined. The mineral phases listed in Tables
16 and 17 completely account for all XRD peaks observed in the
samples. Apatite content ranged from a 1OOR of 9.7 to 62 with 28 of
the 65 samples having 100R for apatite greater than 40. The samples
lowest in apatite were generally high in dolomite. The high
dolomite-low apatite samples generally came from future mining sites.
Dolomite was found in 46 of the 65 samples and wavellite was present
in 45 of the samples. Crandallite was present in 30 samples. No
reference crandallite was available; therefore the number of x’s in
Table 15 were used to indicate relative amount.
Feldspar was found in 33 samples. Potash feldspar
was the feldspar, as clearly indicated from XRD data on +44um
fractions. The 1OOR value for feldspar in Table 15 actually represents
an upper bound because no allowance has been made for palygorskite.
58
Sample Quartz Dolomite Wave? Crand? Apatite
10033 12.1 5.2 6.4 10070 3.8 2.6 6.1 20052 4.8 1.7 6.8 20054 11.0 0.8 4.1 20053 8.9 1.6 4.7
60600 6.1 8.7 0 70600 4.9 0 4.5 70131 2.5 6.8 6.0 80600 6.6 0 6.6 80088 3.0 0 6.8
0 0 X
X
xx
0 X
0 0 0
0 xx
X
0 X
X
0 X
xx
X
xx
xx
0 0 0
0 0 X
X
XX
xxx
X
X
0
24.6 1.8 35.7 0 61.7 0.7 38.6 0.7 60.1 0
40600 2.8 1.7 0 40053 1.8 1.7 4.7 50057 5.3 3.3 7.4 50600 6.2 1.1 6.2 60051 3.2 5.3 3.8
42.7 54.5 40.8 28.7 30.9
18.4 25.4 32.8 24.3 24.3
90036 2.1 0 7.5 90600 3.9 2.6 0
110038 2.5 3.3 5.5 110600 1.5 0.6 4.2 12u;o25 2.7 2.1 7.0
60.0 42.7 45.7 34.6 41.7
120600 2.9- 7.2 130028 5.5 140030
_ 1.7 3.7 3;2-
140170 3 ..8 3.2 140171 3.3 2.9
3.5 5.2' 6.4 4.5 7.7
27.3 45.9 43.5 33.1 32.0
150600 5.0 .., 8.7 0 150031 4.2 4.0 0 160600 2.4 4.0 0 160033 3.0 4.9 5.6 170600 6.6 2.1 6.1
17.6 26.9 40.1 40.1 22.9
180600 ,2. 2 2.0 8.9 180082 1.8 1.5 6.8 180083 2.2 3.0 0 180030 3.7 2.3 6.5
36.6 50.8 58.7 47.1
Table 16. Non-Clay Minerals XRD Data
RELATIVE AMPLITUDE, 1OOR Feld- spar
0 1.1 1.1 2.2 1.1
0 1.3 0.7 0.7 0
0 2.2 0.7 0 0
0 0 0
1.1 1.1
0 0 0
0.7 0.7
1.1 1.1 n 0
1 Wave. = Wavellite
2 Crand. = Crandallite, number of x indicate relative amount.
Orgal Mw
3
O,* 1.1 1.1 0 .I 0 .I
0 .I
0 .I 0.1 1' .< 1.:
1'. ! 0 ’ 1:; 0
0 .I
0 .I 1 0:: 0.1 1.:
0.: 0.' 0.1 0.1 0.:
0.1 0.. 0' 0:; 0 .I
1.: 1.: 0.' 0.'
59
Sample Quartz Dolomite Wave! Crand? Apatite
190600 3.3 0 0 190054 3.0 0 3.7 190055 2.5 0 6.6 190086 6.3 0 0 250600 3.4 0 -0
39.4 51.6 56.4 46.0 20.2
210001 2.2 0 0 220045 542 2.1 5.4 220046 2.7 1.7 506 220092 2.0 0.6 220600
5.5 8.8 2.Q 4.0
52.4 39.7 41.7 49.4 33.5
220121 230600 230071 230038 230039
1.2 0 5 3.8 0.8 9.4 3.6 1.4 0 3.1 0 .3 4.2 0. 3
46.0 36.0‘ 35.0 23.2 23.9
240044 21.8 2.0 O- 240045 2.4 5.5 0 500078 2.2 0 3 500041 2.4 0 0 500042 9.6 0 3
35.4 34.7 38.7 42,l 40.0
510027 8.9 1.7 4.5 530021 3.3 0 2.1 550022 4.8 0 5.7 620001 4.1 4.9 4.1 750600 2.0 38.9 0
37.9 60,7 50.1 42.2 9.7
770600 7.6 3.3 0 780600 2.9 4.3 0 790600 2.6 28.5 4.8 830600 10.1 0 0 850600 3.3 16.7 3.0
26.5 19.9 21.6 20.3 21.8
880600 4.2 18.3 0
0 xx
X
X
0
0 X
0 xx
X
X
0 0 0 0
0. 0 X
X
X
0 0
xx 0 0
0 0 0 0 0
0. 11.4
Table 16. Non-Clay Minerals XRD Data
RELATIVE AMPLITUDE, 1OOR
1 Wave. = Wavellite
3
Feld- spar
0 0
0.7 0
0.7
0 0
1.1 0
1.1
0 1.8 0 0 0
5.3 0.9 0 -0 0
1.5 0 0
0.7 0
0 1.1 1.1 0
0.7
0
Organic Matter
(%I
1.1 1.1 2.6 5.4 1.0
0.6 0.7 0.9 1.0 1.7
1.4 2.3 0.5 0.3 0.6
0.3 0.6 0.5 0.5 0.8
0.9 0.7 0.5 0.5 1.9
0.4 0.5 0.3 6.6 0.1
2.8
'Crand. = Crandallite, number of x indicate relative amount.
59a
Table 17. Clay Minerals XRD Data
Sample Total Clay Smectite
10033 66.7 32.5 10070 78.9 20.0 20052 44.4 5.0 20054 46.7 4.0 20053 3&O 7.0
40600 37.8 21.5 40053 33.3 7.5 50057 66.7 27.5 50600 57.8 37.5 60051 72.2 27.5
60600 70600 70131 80600 80088
90036 50.0 90600 40.0
110038 61.1 110600 62.2 120025 73.3
120600 62.2 130028 44.4 140030 60.0 140170 48.9 140171 62.2
150600 150031 160600 160033 170600
180600 46.7 5.0 180082 42.2 a.5 180083 40.0 8.0 180030 31.1 5.5
RELATIVE AMPLITUDE, 1OOR -
57.8 64.4 46.7 57.8 62.2
60.0 71.1 44.4 62.2 57.8
22.0 28.0 14.5 33.0 22.5
6.0 22.5 20.0 14.0 18.0
20.5 _ 8.8 12.5 20.5. 29.5
32.5 28.5 10.0 16;5 21.5
r
60
Illite
20.0 12.5
20.5 21.3 18.8
12.5 12.0 8.8
15.0 10.6
1ilG 1o:o
10.6
11.0
9.4 9.4
13.1
13.1 13.1
10.0 15.8
6.3 7.5
Palygo: rskite Kaolin
0 10.4 6.4
11.4
1‘. 0 0.80 0.25 0.65 0.40
20.8 0.3 9.6 0.50
16.0 2.0 0 1.3
16.0 1.1
12.8 0
9.6
10.4
0 1.9 1.0 0.3 0.3
6.4 12.5 16.0 17.6 10.4
9.6 14.4 15.2 12.0 16.8
2.5 0.6 2.5 ; 0.1 >
: :
2
0 “,*I
: 1.0
14.4 0.9 12.0 1.5 14.4 0.6 12.8 1.0 17.6 0.3
8.0 3.2 15.2 0.40 16.0 0.85 12.0 0.4
RELATIVE AMPLITUDE, lOOR
Sample Total Clay Smectite Illite
190600 48.9 25.0 16.8 190054 46.7 6.5 5-6 190055 37.8 7.5 5.0 190086 46.7 12.5 9.5 250600 66.7 34.0 12.5
210001 44.4 12.5 220045 71.1 20.5 220046 55.6 17.5 220092 51.1 14.5 220600 40.0 22.5
10.0 11.9 13.8
11.3
220121 37.8 9.5 230600 48.9 15.0 230071 62.2 23.0 230038 68.9 31.5 230039 66.7 27.0
8.1 9.0
10.0 8.8
240044 35.6 12.5 240045 60.0 16.0 500078 48.9 10.0 500041 48.9 9.5 500042 44.4 10.5
8.8 10.0
510027 71.1 21.5 530021 46.7 10.0 550022 42.2 9.0 620001 75.6 13.8 750600 28.9 18.0
13.8 7.5
7.5 10.0
770600 53.3 10.0 780600 60.0 19.5 790600 33.3 18.0 830600 57.8 42.5 850600 51.1 12.0
15.0 9.9
37.5 6.3
880600 44.4 13.5 9.4
Table 17. Clay Minerals XRD Data
Palygo- rskite
0 7.2 7.2 8.0
4.6 0.75 0.88 1.7 1.3
14.4 0 17.6 0.35 18.4 0.45 15.2 0.50 13.6 0.4
8.8 10.4 9.6
8.0
0.5 1.2 0.85 0.6 0.5
8.8 0.45 0 0.45
12.8 0.75 14.4 0.90 16.0 0.90
11.2 0.60 9.6 1.6
13.6 0.75 9.6 0.35 8.0 1.5
35.2 2.0 19.2 0.2 16.8 0.3
0 1.9 9.6 0.6
0.2
Kaolin
61
Clay minerals were present in most of the +44pm
fractions obtained from wet sieving. Microscopic examination of these
coarse fractions universally revealed no distinct clay aggregates but
that all mineral grains were coated. The microscopic properties of the
coatings were consistent with clay. The grain coatings appeared to be
nearly as prevalent in samples where clay was not detected by XRD as
in coarse fractions where clay was abundant.
To investigate the kind of clay in the 105-44pm
fraction, two samples representing the extremes were severely
mechanically abraded to produce muddy water which after standing for
ten minutes was used as “fines” to make oriented aggregates for XRD.
These fines indicated that wavellite was preferentially coating the
coarse particles, with some smectite and palygorskite also present. ”
clay phase relative
and kaolinite was
abundant apatite
The data in Table 16 give the amplitude of a given
to the reference minerals. Smectite was ubiquitious
generally present as a minor clay phase. The
even in the -2pm or -1um fraction hindered
interpretation of the clay peak XRD data. The clay species were
dominately dioctahedral, although the possibility of some trioctahedral
clay cannot be excluded.
Representative samples that illustrate the range of
XRD behavior are shown in Figures 9, 10, 11 and 12. These XRD
traces also show the effect of various treatment conditions. Figure 9
shows the maximum R for smectite and illite which were found in the
sample of fresh plant slurry from Deker’s mine in Manatee County
(830600). Smectite indicated in the other figures in decreasing order
was 50057 > 770600 > 90036.
and 770600 where illite was
sequence for palygorskite in
770600 > 50057 > 90036. No
The order for illite R was 50057 > 90036
indicated by the peak about 18’28. The
the XRD data shown in Figs. 9 to 12 was
palygorskite was found in sample 830600.
62
F. values for kaolinite were small in all samples: however, the small
amount of kaolinite shows prominent peaks at 12.5 and 25’28. For
discussion purposes each clay phase will be considered separately.
b. Expandable Clay Phases
Superimposed W. Figs. 9 to 12 is 8 horizontal line
labeled S1 through S6 indicating the- 28 position for six orders of
smectite basal spacing with a mean value of. 18A. The 18A was a
somewhat arbitrary reference in order to provide a consistent
reference line for all the figures. An amplitude scale change occurs in
the figures about 10°2e. In Fig. 12 a section of amplitude scale
(involving kaolinite) was omitted in order to effectively show the
essential features of all peaks.
The quantitative measurement of the higher order
smectite peak position is hampered _by interference from other mineral
phases. The S2 peak commonly was a shoulder on the low angle side
of the illite peak, Diffraction peaks from wavellite and crandallite
interfere with the S 3 and S 6 peaks. The general clay prism peak
about 28 = 200, which for palygorskite does not decrease due to
orientation, coincides with the S4 peak. The effect of kaolinite
obscuring the S5 peak is obvious in the figures. In spite of the
interferences, higher order smectite peaks are qualitatively evident in
the figures.
The apparent variable position of higher order S
peaks relative to the ideal S positions and the very broad shape of
these peaks suggest possible interstratification of clay minerals.
Further evidence of interstratification was provided by satellite peaks
in the 20 range 5.2O to So28 that were not associated directly with
smectite or illite and whose position varied with hydration state.
63
Positive evidence for kaolin interstratification was not found in the
XRD data from any sample.
Satellite peaks suggestive of interstratification
were observed on 34 samples following magnesium saturation and gly-
cerol solvation treatment, MgG, and an additional 15 samples indicated
probable interstratification based upon XRD data during dehydration.
Thus, there was a second expandable clay phase indicated in 49 of the
65 samples in
peak positions
19. Somewhat
addition to the ubiquitious smectite phase. Key XRD
relative to interstratification are given in Tables 18 and
fortuitiously there were equal numbers of samples that
showed interstratification for MgG in the two different procedures used
for the dehydration sequence.
In Table 18, dehydration was on potassium sat-
urated heated specimens, K-heat. Seventeen samples showed evidence
of interstratification for MgG, however, for K-heat specimens inter-
stratification was confirmed on only 4 of the 17 with an additional 4
samples suggesting interstratification following K-heat. Sample 50057
in Fig. 10 was typical of samples in the MgG, K-heat group that
showed no interstratification. Figure 12 for sample 90036 was the
extreme indication of interstratification for the MgG, K-heat group.
Potassium saturated specimens were heated to higher temperatures but
the only change in XRD data related to the kaolin phase. Upon de-
hydration of potassium saturated specimens the phases smectite, illite,
and palygorskite all have a major peak between 8.5 and 8.8O2a which
makes any differentiation difficult. This fact, coupled with the results
in Table 18, and the peeling problem mentioned earlier, prompted the
search for an alternative procedure to evaluate interstratification.
Heating MgG specimens is a simple alternative that
from the results given in Table 19 appears useful, The heat treatment
of MgG specimens confirmed probable interstratification in all 17
64
Table 18. Key XRD Data for Interstratification on Mixed Treatment Specimens.
Treatment
SAMPLE MgG
NUMBER (d values)
10033 12.9 17.7 10070 11.6 18.4 20052 14,18.4 40053 12.1 18.4
90036 14,18 110038 12.3 18.4,. 120025 13.6,18.8- 130028 18 -*
140030 13.6,18.4 160033 14,18.4 180082 18 180083 19.2
190054 12.6 18 190055 13 18.4 190086 12.3 17.8 220045 12.6 18.8
230071 11 18.4 240944 18.8 240045 12.1 18.4 530021 11.8 18.8
620001 14,18
MqG = Magnesium saturated and glycerol solvated.
K,300 = Potassium saturated and heated 20 hr. @ 300°mC.
K, 3OOOC 20 HR
(d values)
9.8 10.6, 11.8
10.0 11.8
+-10.4+ 10.1-t
10.1 11.8 10.1 14
10.0 14 _ -.
10.2 11.8
65
THIS PAGE TO BE. LEFT BLANX
66
samples where RlgG had indicated inter.stratification and an additional
11 samples gave evidence of interstratification after heat treatment of
MgG specimens. The 16 hr. at 250°C produced a stable condition
because a batch of phosphatic clays heated an additional 16 to 24 hr.
at 250°C gave no detectable change in the XRD trace for the range 3
to 32O28. A reference sample of Mg montmorillonite, glycerol solvated
and heated 16 hr. at 250°C, gave a single peak at 13.3A that moved to
12.5A after heating to 45ooc.
generally produced
required to achieve
As shown in Table 19 increasing the temperature
measurable changes in the XRD trace. The time
phase stability at the various temperatures has not
been investigated in detail. Examples covering the range of behavior
during heat treatment are given in Figs. 13, 14 and 15. Figure 13
shows the change in a single major peak between 10 and 11A. This
type of behavior was observed for 11 of the samples. Figure 14 shows
the change in a single major peak between 11 and 13A. This behavior
was observed on three samples. Figure 15 shows the change that
occurred to two major peaks. This type of behavior was observed for
10 of the samples. Specimens KG heated, while showing the
interstratification, did not show the effect as clearly as the MgG
heated specimens. In fact, MgG heated specimens gave better
indications of interstratification than did KG heated specimens.
Vermiculite, if present, is a minor expandable phase because the 18A
smectite peak position and amplitude was the same for KG as for MgG
on all samples that were compared.
Clearly, the 1OOR for smectite in Table 17 does not
very accurately portray the total expandable material. However, the
above results at least provide useful differentiation between the
various clay samples and also suggest an approach for future research
to develop improved differentation procedures for phosphatic clays.
67
Table 19. Key XRD Data for Magnesium Saturated, Glycerol Solvated Specimens Heated.
d values
SAMPLE NUMBER 25“C 250°C, 16 Hr. 350°C, 4 Hr. 450°C, 4 Hr.
- A. NO INTERSTATIFICATION
40600 18.8 70600 18.0 80088 17.9 90600 18.0
150600 17.9 250600 18.0 230038 18.0 780600 18
10.4 13 13
12.6 -
12.6 13
12.6 10.6
B. INTERSTRATIFIED AFTER HEAT -
50600 18 9.8-tlO.3 80600 18 10 12.6
120600 18.4 10 14 180030 17.5 10.5 +13
190600 18 10.6-t 220600 17.9 10.6-t- 230039 17.8 12.8 750600 18.4 10.6 13.6
770600 18.8 10.5 790600 18.8 10.4 17 880600 17.8 11.8-t
10.4 9.7
10-t 10
9.9 t11.3-t
10-t 10
9.8 9.8 14 10 10 16
9.9,10.6,12,14 9.8 10.6 10.5 +-10.5-t 14
10 13.6,17 9.9
10-+11.8-t 10+12
10.5 10.2 12.3
9.9 11.8
C. INTERSTRATIFIED BEFORE HEAT -
60600 12.5,18 lOt10.5+11.8 9.9 14 70131 14,18 llt13.8+ lO-+
110600 14,18 10.5 13 10.2 140170 12.5,18 10.8t12.8 10 14
140171 12.5,18 +13.8+ 150031*
10,11.6,13.4 13,18 104-----+14 10-t
160600 14,18 10.4 170600
10.6,11.3,13.4 lO----tl8 +11.6-t 10.6-t
180600 lo-18 10.8 .15 10.5 220121 lo-18 +13.4+ 10.2 t14-t 230600 13,18 10.6 13.6 10.5,13.8
10.4 9.7 9.9
10
9.9 9.9 9.8
10
10 14 9.9 14 9.9 13.6
10 14
10 14 10
9.9
9.8,L1.8 9.8 12.3 14
10,10.8 10
9.9 14
9.9 14 10.6+11.8
-+lO 10.2t+13.8
9.9 14 500078 12,14,18 10.5 14 10.5,11.8,14 10.5 14
500041 14,18 10.4t12 10.4 16 tlO+ 13.6 500042 14,18 10.4 13.8 10.5 10.3 14 510027" 14,18 10-t 1 10+11
830600 12.6,18 9.8 11.8 9.8 11.8 14 9.8 14 850600 14,18 t10.5 10.4 lO.2 14
* Heated @ 300°C, 16 hr. and 400°C, 4 hr.
68
C. Illite
Illite was present in 48 samples as shown in Table
17. In fourteen additional samples, where the 10A illite peak was
indeterminant because of palygorskite, a 5A peak indicative of illite
was found. Therefore, only in three samples 02-802, 04-801, and
18-802 was the presence of illite doubtful based on the XRD data.
d. Palygorskite
Palygorskite peak ratio was based solely upon the
10.5A peak because the 6.5 and 5.4A peaks were so weak that the
error in calculating a peak ratio was excessive. The samples with
dashes in the palygorskite column of Table 17, indicating indeterminant
R for palygorskite, all showed detectable 6.5 and/or 5.4A peaks.
From palygorskite spiking of phosphatic clays it was determined that
less than 5% palygorskite could not be determined by XRD. There-
fore, the six samples listed as zero palygorskite in Table 5 really
means that these samples may contain up to 5% palygorskite.
e. Kaolinite
The detection level for kaolinite was much lower
than for the other clay minerals because of a) peak position, and b)
large peak amplitude for kaolinite. Although the kaolinite peaks were
sometimes large compared to other clay peaks, as shown in Fig. 12 for
example, the peak ratios always indicated kaolinite was a minor clay
phase. Heat stability of the kaolinite in the sample suite was variable.
Kaolinite was destroyed in some samples at 400°C while others required
55OoC to destroy the kaolin XRD peaks. There appeared to be no
relationship between kaolinite heat stability and the nature of the
interstratification as discussed above.
4. Estimates of Mineralogical Composition
To convert peak ratio, R, values into weight fraction,
x, requires the mass attenuation coefficient, lo s, for the sample; then
69
Table 20 gives the results of chemical analyses on 15
selected samples, and the calculated values of p S’
The chemical
analyses were made by X-ray fluorescence on fused samples. Table 21
gives the weight percent, 100x i, for the 15 samples. The crandallite
weight percent assumed all SrO was in the mineral crandallite and that
the composition was constant at 0.7 ideal crandallite and 0.3 goyazite.
The summation of non-clay minerals account for 30 to
81% of the sample with apatite the major non-clay species. There was
a very good correlation, r 2
= 0.95, between % P205 by chemical
analysis and weight percent of apatite from XRD that had a slope of
2.54 which is within 7% of the ideal slope one would expect using the
apatite composition in Table 14. The MgO content correlated rea-
sonably, r2 = 0.77, with dolomite content but was not correlated to
palygorskite content as determined by XRD. There was no significant
relation between K20 content and illite percentage determined from
XRD.
The sum of clay species ranged from 26 to 76 percent,
values that for the most part agreed reasonably with the total clay
content determined from the 4.45A XRD peak, also shown in Table 21.
5. Scanning Electron Microscopy
Scanning electron microscopy (SEW, coupled with
energy dispensive analysis by X-ray. (EDAX), provides a powerful
adjunct for making observations on fine grained materials such as
phosphatic clays. For example, the SEM-EDAX combination showed
that apatite grains smaller than lpm equivalent spherical diameter were
common and that palygorskite apparently was ubiquitous even though
XRD sometimes indicated no palygorskite.
A number of techniques for preparing phosphatic waste
clay specimens for SEM have been tried. The most satisfactory
70
) Ai203
: Fe203
‘<
TiO2
Cr203
Zn02
0.50 0.44 0.50 0.55 0.57 0.58 0.59 0.55
0.030 0.026 0.029 0.035 0.030 0.031 0.030 0.034
0.011 0.019 0.011 0.014 0.026 0.019 0.018 0.027
CaO 14.3 22.9 20.2 10.7 10.2 17.8 17.4 14.6
MgO 2.69 2.69 1.33 2.29 1.96 1.59 1.80 1.75
MnO 0.02 0.03 0.03 0.03 0.03 0.03 0.03 0.03
SrO 0.086 0.154 0.117 0.063 0.058 0.110 0.105 0.084
Na,O 0.40 0.49 0.52 0.35 0.40 0.40 0.40 0.37
0.91 0.58 0.54 0.96 1.09 0.57 0.57 0.50
0.007 0.005 0.004 0.008 0.007 0.005 0.004 0.003
G
K2°
Rb20
'2'5
U 0.005 0.013 0.008 0.005 0.003: 0.008 0.008 0.008
LO1 15.9 14.7 13.8 16.0 14.8 13.5 13.5 12.4
SUM 99.61 100.28 99.55 100.40 100.98 99.50 99.74 100.71
TABLE 20. Chemical Analyses by X-Ray Fluorescence (Cont'd)
WEIGHT PERCENT
140171 180030 220121 230038 230039 500078 500041 500042
35.8 26.9 26.5 40.4 44.1 30.6 31.4 42.4
15.5 12.1 14.8 15.8 14.9 15.7 15.4 12.8
4.08 3.23 5.56 6.55 6.37 5.16 5.88 4.75
9.37 16.0 15.6 6.64 6.44 13.4 12.6 10.4'
54.6 64.2 64.1 56.1 55.3 61.3 62.3 58.4
71
SiO2
A2203
Fe203
Ti02
Cr203
Zn02
CaO
MgO
MnO
SrO
Na20
K2°
a20
0.14 0.40 0.39 0.40 0.36 0.42 0.40
l.10 0.63 0.48 0.91 1.12 0.69 0.96
0.007 0.003 0.003 0.007 0.009 0.003 0.005
'2'5 9.46 18.8 18.6 9067 7.65 15.7 10.1 i
U 0.008
LO1
SUM
13.77
101.04
53.5
10.47 12.31 17.8
99.89 100.21
62.3 61.5
-100.91
55.5
TABLE 20. Chemical Analyses by X-Ray Fluorescence
WEIGHT PERCENT -
10070 20053
39.1 28.9
16.6 9.76
3.95 2.44
40053 70131
25.1 32.7
12.3 15.4
2.71 2.97
80088 130028 140170
39.2 32.8 37.0
16.9 13.5 14..0
4.45 3.73 3.94
0.48 0.43 0.41 0.46 0.56 .0,55 0.48
0.028 0.021 0.027 0.028 0.030 0.026 0.026
0.015 0.028 0.020 0.016 0.019 0.035 0.024
13.9 26.1 25.5 16.5 10.4 19.2 15.7
2.40 1.80 2.24 3.89 2.41 2.11 2.80
0.02 0.02 0.01 0.02 0.04 0.02 0.02
0.077 0.088 0.108 0.134 0.096 0.132 0.086
0.005
16.6
99.91
51.9
0,008 ’
11.85 15.2
100.77
58.3
100.75 :
57.4
72
Table 21. Summary of Mineral Composition.
10070
20053
40053
70131
80088
ptz l - Dol. Wave. Cran-. Apa. SUM.
6 3 12 1.0 27 49
15 2 10 1.2 53 81
3 2 10 1.5 47 64
4 8 12 1.9 26 52
4 0 13 1.3 18 36
130028 9
140170 6
140171 5
180030 7
220121 2
230038 5
230039 6
500078 4
500041 4
500042 15
Weight Percent
Non-Clay Species Clay Species
2
4
3
3
0
0
0
0
0
0
Smec... .&
26
10
11
19
28
11 108 38
9 108 27
15 102 25
15 2.1 43
11 1.6 42
62
48
49
70
57
12
29
38
8
15
6 0.9 18 30 42
6 008 19 32 36
7 1.5 33 46 15
0 1.4 37 42 14
6 101 33 55 15
13
10
11
11
14
11
10
Paly.. Kaol, SUM Total
0 1.4 40 77
17 0.8 28 26
14 1.0 26 33
13 1.8 44 46
13 005 52 62
20 1.9 34 43
17 1.9 59 47
22 1.8 76 60
19 0.8 28 25
14 1.0 30 35
11
19
22
23
1.1 54 69
009 58 67
105 35 49
1.8 38 52
1.7 40 42
73
procedure was the major one used herein. The specimens for SEM
were 0. 25cm3 of 4% slurry (-44um fraction) dried onto a cover glass
except as noted below.
General features observed during SEM examination of all
samples were apatite, nondescript clay lumps, cornflake texture attri-
buted to smectite, and palygorskite strings. During SEM an im-
pression of relative amount from four specific features 1) palygorskite,
2) wavellite, 3) gel, and 4) kaolin was noted. Estimation of the
amount of a constituent from SEM has many uncertainties; never-
theless, one does obtain an impression for the relative amount of a
particular feature present in samples within any suite examined.
Examples for all the features just mentioned are discussed in
conjunction with specific photomicrographs.
Fig. 16 shows photomicrographs from sample 10033, from
IMC’s Achan 9 settling area. Palygorskite strings were apparent in
Fig. 16 at a magnification of 2000X’. Fig. 16b and 16c were increased
magnification from the center of Fig. 16a, which clearly showed the
ball of string character of a palygorskite lump. Clay lumps also were
present that contained no palygorskite especially as shown by the clay
in the lower right corner of Fig. 16~. The mica shaped particles were
found to contain much more potassium than general clay lumps. The
small round particles generally had calcium and phosphorous
concentration in the same proportion found in apatite. Two of these
very small particles are shown in the upper left corner of Fig. 16~.
Figures- 17 and 18 are of sample 20052, from IMC’s
Noralyn N12A Settling Area. Figure 17b was typical for this sample,
generally characterized by cornflake texture particles as in the upper
right quadrant and the gel appearing fine material throughout the
photograph. A magnified view from the upper right quandrant of Fig.
16b shown in Fig. 17b reveals a few palygorskite strings. The
74
palygorskite lump in Fig. 17a was probably completely palygorskite
because all the edges of the lump were palygorskite. The photo in
Fig. 18a, taken in the lower left quadrant of Fig. 17a, showed a
typical palygorskite “ball of string” appearance. Treatment of this
sample with sodium hydroxide to raise the pH to 9 dispersed the clay
as shown by Fig. 17c relative to Fig. 17b. The crossed lath particles
just to the right of center if Fig. 17~ are wavellite particles. These
wavellite particles, visible at the right edge of Fig. 18~ have sharp
clean edges, no the wispy character of palygorskite common in the left
half of Fig. 18~.
Sample 50057, shown in Fig. 19, came from AMAX’s Big
Four mine. It contained some large wavellite particles as shown by the
40pm long laths above center in Fig. 19a. Wavellite laths dominate the
lower half of Fig. 19b while the upper half was primarily palygorskite.
Figure 19c shows very flexible palygorskite strings draped across
wavellite laths. Comparison of Fig. 20a wavellite with Fig. 2Oc
palygorskite clearly indicates the difference in appearance between
these two elongate particles commonly found in phosphatic waste clay.
Sample 50057 contained clay particles that had no palygorskite coating
as shown in the upper half of Fig. 20b.
Fig. 21 shows three photomicrographs of sample 60051,
taken from IMC’s Kingsford K2 area. In Fig. 21b, palygorskite
appeared to be forming from other clay material. The area of maximum
palygorskite observed in this sample, shown in Fig. 21~ also showed
other clay species. From Fig. 21c it would appear that smectite clay
might be coating a palygorskite lump. After dispersal at pH 9,
palygorskite appeared to be everywhere in this sample, as shown in
Fig. 22. The gel appearance of Fig. 21a became more pronounced in
Fig 22.
75
Fig. 23 shows photomicrographs of sample 90036, from
Agrico’s Saddle Creek No. 1 area. The fine particle material in sample
90036 did not produce a gel appearance in SEhl as shown in Fig. 23a.
Palygorskite in this sample appeared to be segregated. The clay lump
in Fig. 23b contained little evidence of palygorskite while Fig. 23C had
the ball of string palygorskite appearance. Palygorskite was not
common in either this sample or in sample 110038, shown in Fig. 24.
Sample 110038 was a composite sample from Agrico’s Payne Creek No. 6
area. The photo in Fig. 24a was taken to show clay particles with no
palygorskite coating and particles with palygorskite coating. Fig. 24b
and 24c show detail for the two extremes. The large palygorskite
lump in Fig. 24a was called a coated lump rather than a palygorskite
lump because there were places at the edge which were palygorskite
free. .
Kaolin was specifically observed only in samples 110038
and 90036. The thick book at the center of Fig. 25a was kaolin and
the thin particle running to the bottom edge of Fig. 25a was mica
Wlite). The fine material from sample 110038 produced a somewhat
gel-like appearance in SEM.
Sample 130028, -2pm fraction oriented aggregate film for
XRD, peeled from the slide during drying. Figure 25b and 25c were
photos from the top and bottom surfaces of the air-dried peeled film.
Any difference in material between top and bottom surfaces of the film
was very small. Palygorskite was prevalent.
Palygorskite was most abundant in. samples 20052 and
50057, where SEM showed no discernable difference. Samples 60051,
110038, 90036, 10033 followed in decreasing order for amount of
palygorskite in SEM. Comparison of SEM palygorskite observations
76
with XRD 1OOR values for palygorskite given in Table 17 produced the
following :
SEM 20052 = 50057 > 60051 > 110038 > 90036 > 10033
XRD (lOOR) 10 16 16 16 6 0
The agreement between the two data sets is not very good. In sample
10033 for example, where no XRD evidence for palygorskite was found,
SEM showed considerable palygorskite that had the same visual
appearance as palygorskite in samples 20052, and 50057.
Wavellite was very commonly observed in sample 50057
during SEM examination and was found in sample 20052 but not in any
of the other samples. From XRD data, wavellite in sample 90036 was
as abundant as in sample 50057, and sample 10033 contained as large
XRD wavellite peaks as in sample 26052. However, wavellite was
observed during SEM examination of samples 20052 or 90036.
not
XRD data indicated as much kaolin in samples 50057 and
60051 as in sample 110038, but SEM observations on samples 60057 and
60051 showed no kaolin. For sample 60051, one might attribute the
lack of SEM kaolin observation to the large amount of gel material;
however, sample 50057 had very little gel material, and still kaolin was
not found in SEM. Gel material was most prevalent in samples 20052
and 60051, and least abundant in samples 10033 and 50057. The use of
EDAX failed to reveal any difference in chemical
gel fine material and non-gel fine material.
composition was clay plus calcium and phosphorous
composition between
The fine material
(apatite).
VI. CORRELATION OF RESULTS
A. Sedimentation Behavior
Previous testing of phosphatic clays has indicated a
77
relationship between palygorskite (attapulgite) content and poor
settling behavior (Bromwell, 1974; Lamont, et. al., 1975). The results
shown in Table 7 for fresh slurry samples are plotted in Fig. 16 as 30
day settled solids content vs. palygorskite relative peak amplitude.
The correlation is seen to be rather poor, but a few general
observations can be made.
At the higher palygorskite contents, settling behavior is
poor. Conversely, none of the samples with very low palygorskite
contents showed poor settling behavior. Thus, it is possible to make
general predictions of settling behavior based on palygorskite content:
1. If the palygorskite content is high, settling behavior
will be poor.
2. If the palygorskite content is very low, settling
behavior will at least be average, and likely will be
good.
3. If the palygorskite content is neither very low or very
high, other factors will control settling behavior and no
prediction can be made.
Attempts were made to find other factors
settling behavior. A study of Table 7 reveals that
that influence
the following
parameters have no discernible influence on settling behavior:
0 Percent minus 2urn o Total clay (4.5A x-ray peak ratio) o Specific conductance o Other mineral species
A general inverse relationship between liquid limit and solids
content can
predictions of
If the liquid
poor.
be seen, as plotted in Figure 17. Again, rough
settling behavior could be made based on these results.
limit is high (>200), settling behavior is likely to be
78
Interestingly, smectite content appears to favorably influence
settling behavior, as shown in Fig. 18. Higher smectite contents
resulted in high settled solids. However, intermediate and low
smectite contents appeared to have little influence on settling behavior,
Clearly, the factors that influence sedimentation behavior are
not well known. Colloidal theory would predict that particle size, pH,
and conductance would have a major effect. However, bebause the
clay particles are naturally flocculated by the high divalent cation
concentration that exists in the Floridan aquifer water used for
processing, the factors controlling sedimentation behavior are
extremely complex.
B. Chemistry
No correlations ‘between the chemistry of either the
supernatant water or the mineral solids_ and any physical property
were found. The chemical analyses on supernatant water from
beneficiation plant and met lab samples agreed very well with those
obtained on samples tested by the Bureau of Mines in 1972, as
described in Section V.C.
The variability in chemical composition of the phosphatic clay
solids was quite large. However, the average value of P205 on all the
samples except future mine sites was essentially 12%, the same value as
found by the Bureau of Mines on the 1972 samples.
The average value of P205 for the 7 samples from future
mine sites was only 8%) with a high value of 9.2%.
Uranium content showed some correlation with P205 content
as shown in Figure 29. Again, the correlation is not particularly
good, and leads to the conclusions that low P205 content results in low
U308 content, and high P205 content generally results in high U308.
Figures 30 and 31 show the general distributions of P205
and U308 from the samples tested. Highest levels of P205 and of
79
U308 were found in the area bordering the
Bartow, and in the area between Mulberry and
of both elements were found in the mining
County.
Peace River north of
Bartow. Lowest levels
areas outside of Polk
_ as did the 42 composite samples from
settling areas (IO. 6%). The distribution of palygorskite from the
samples te-sted for this study is shown in Figure 32. Highest
concentrations were found generally along the Peace River, with some
high values further west in Polk and Hillsborough Counties.
The other major minerals present, smectite, illite, and
apatite, showed significant differences between fresh samples and
samples from settling areas:
Smectite
Average Relative Peak Amplitude (8) Plant Settling Area Slurry Samples
22 15
Illite 11 7
Apatite 27 42
Furthermore, the data indicate that these changes increase
with time. Comparing the five most recent settling areas with the five
80
oldest settling areas gave the following result:
Age of Settling Area Recent Old
(~10 yrs) (>25 yrs) Smectite 17 13 Illite 13 4 Apatite 33 45
In the case of the clay minerals, it appears likely that an
actual mineralogical alteration may be occurring. The SEM examination
may have detected changes in progress as described in Section V.D. 5,
and shown on Figure 21b.
Also, in this regard, it is interesting to note that only 8 of
the 25 fresh slurry samples from beneficiation plants and met labs
showed evidence of interstratification prior to heat treatment, whereas
26 of the 42 settling area samples showed interstratification
as-received. After heat treatment, 9 additional fresh slurry samples
showed evidence of interstratification.
Of the 8 samples that showed no inter&ratification even after
heat treatment, 6 of them were fresh slurry samples. Although the
evidence for mineralogical changes with time after placement into a
settling area is not very strong at this point, it would appear to be a
fruitful area for future research.
The higher apatite peak ratios observed in older samples,
however, do not indicate an actual increase of apatite content, but
merely an enhancement of the apatite peak. This
chemical analyses, which show the average P205
essentially the same for fresh plant slimes as for
samples (approximately 12%).
is confirmed by the
concentration to be
all the settling area
81
VII. SUMMARY AND RECOMMENDATIONS
1. Phosphatic clay samples were taken from a variety of
sources, including old .settling areas, active settling areas,
beneficiation plants, and future mine sites. These samples
were tested to determine mechanical properties, chemical
composition, and mineralogy. The data were assimilated into
a computerized data base (SYSTEM ‘2000) for storage, re-
trieval, and evaluation.
2. Samples were taken at 5-foot depth intervals at numerous
locations within 38 clay settling areas. The samples showed
a wide range of solids contents, with average values at
various sampling locations ranging from about 138 solids to
over 50% solids. The lower values occurred
areas still in the process of being filled.
isted at old areas that have been drained
and in some cases reclaimed to pasture. A
the weighted average solids contents showed
of 24.1%.
3. Fresh clay slurry samples were obtained
at newer, active
sigh values ex-
for many years
histogram of all
a median value
from eighteen
operating beneficiation plants and seven future mine sites.
The samples from future mining sites were obtained during
metallurgical laboratory processing of prospect core samples.
Standard settling tests were run on these samples, and the
solids content at thirty days showed some inverse correlation
with palygorskite (attapulgite) content and with liquid limit.
The correlation were not very good, however, and it appears
82
4.
5.
6.
that other physico-chemical factors must also influence
settling behavior.
Shear strength measurements on laboratory consolidated
samples of clay slurry showed peak vane strengths on the
order of 37 to 57 lb/ft2 at solids contents between 30% and
40%. These values of shear strength indicate an extremely
soft and unstable soil.
Slurry consolidation testing of fresh washer slimes provided
values of compressibility and permeability as a function of
solids contents. At stresses on the order of 100 lb/ft2,
which are typical of self-weigh-t stresses in settling areas,
the range of equilibrium solids contents was from about 28%
to 40%. Also, at a given solids content, the permeability
(which controls how fast a slurry will dewater) ranged by as
much as a factor of 10 between the highest and lowest sam-
ples. Also, permeability decreased by several Drders of
magnitude as the solids content increased. These data
indicate the necessity of measuring consolidation properties
on representative samples from individual mine sites in order
to estimate rates of dewatering for various clay disposal
situations.
Chemical analyses were made both on selected clay samples
and on supernatant water from settled clays. The superna-
tant water samples were in close agreement with tests made
in 1972 by the U.S. Bureau of Mines on samples collected
from active beneficiation plants. The test results show that
a3
the clay environment is a calcium-magnesium-bicarbonate-
sulfate dominated system. The existence of excess divalent
cations and bicarbonate apparently results in minimizing of
colloidal double-layer effects and buffering of potential pH
effects in the clay-water system. As a consequence, physi-
cal behavior appears to be controlled primarily by inter-
actions between aggregated clay particles, and not by
chemical effects.
7. Although the variability in chemical composition of the slimes
was quite large from site to site, the average values of major
constituents showed little variability between old settling
areas, recent settling areas, and fresh slimes from existing
plants . Average P205 _ values were almost the same (12.2 +
0.3%) from all three sources. Furthermore, these values
were essentially the same as the value of 12.0% determined by
the Bureau of Mines on fresh samples from fifteen plants in
1972.
8. The only major variations in chemistry were observed for the
samples from future mine sites. These samples had an
average P205 content of only 8%. Also, Ca and Mg values
were much higher for the future mine sites, and uranium
concentration was much lower. Based on these limited data,
future resource recovery from slimes at new mines would
appear to be less favorable than from older deposits.
9. The mineralogy of samples from 34 sites was examined by
X-ray diffraction analysis with supporting scanning electron
microscopy (SEM) and chemical analyses (EDAX). The
84
10.
12.
13.
amount of mineral species estimated by
X-ray peak to those on pure
minerals and the ratio a relative
amplitude, R.
species detected the waste were apatite,
, dolomite, crandallite, and
Apatite was dominant non-clay except for few
samples future mining high in Gener-
ally, was as in the fraction as
the bulk For samples both X-ray chemi-
cal were obtained, was a correlation between
amount of and Mg chemical analysis, apatite
and respectively, by
Clay mineral identified were illite, paly-
gorskite , dolomite, and interstratified material. Smectite
occurred in all samples and was the most abundant clay
species in 42 of the 65 samples.
Palygorskite was identified
However, SEM examination
ubiquitous, even though
palygorskite. By “spiking”
by X-ray in 54 of the samples.
indicated that palygorskite was
X-ray sometimes indicated no
samples with various amounts of
reference palygorskite, it was determined
by weight could not be detected by X-ray.
that less than 5%
The mineral species of primary interest from this study are
palygorskite, P205, and U308; palygorskite because of its
affect on physical properties (poor settling, high plasticity),
85
and P205 and U308 because of potential economic value for
future mineral recovery. The aerial distribution found for
these three mineral values is shown in Figure 33. The
highest values for all three generally occur in the Peace
River watershed, and particularly adjacent to the river in
the area north between Bartow and Ft. Meade. Occasional
high values of palygorskite were found at other locations in
Polk and Hillsborough Counties as well.
14. Significant differences in clay mineralogy were observed
between fresh slurry samples and samples taken from settling
areas of various ages. Older settling areas showed lower
values of smectite and illite, although the average pal-
ygorskite values were about the same from all sources.
Fresh slurry samples showed less evidence of inter-
stratification than samples from settling areas. Evidence
for the occurrence of actual mineralogical transformations
with time is not strong, but both X-ray and SEM gave
indications that this may be the case.
15. The variations in waste clay composition projected for new
mining sites should be investigated in more detail. Addi-
tional samples should be tested from future mine sites to
determine if, in fact, low values of P205, uranium and
palygorskite ; and high values of dolomite will occur.
Further definition of clay mineralogy and mechanical
properties for representative samples from future mining
sites would be useful to assist in projecting both future
waste disposal requirements and resource recovery potential.
86
16. More detailed investigation of clay mineralogy is needed in
order to evaluate the possible influences of mineralogy, and
changes in mineralogy with time, on observed clay behavior.
In particular, better methods to identify expandable inter-
stratified material, and to identify palygorskite, are needed.
Further study of subtle variations in the X-ray patterns may
also be helpful in determining to what extent variations in
mineralogy influence clay behavior.
17. The data base described herein provides an updated and
expanded source of information for use by other researchers
on waste clays. Future research should utilize accurate
characterizations of the specific clay waste material being
tested and the properties compared with the range presented
in the data base. Only in this manner can the results of
various research studies be correlated and their applicability
to various mining situations evaluated.
18. In order to provide adequate information for future research
efforts, and to evaluate changes in clay properties and
behavior as mining operations move into new areas, the data
base should be maintained and updated as new information
becomes available.
87
VII. REFERENCES
Bjerrum, L., “Embankments on Soft Ground,” Proc. ASCE Specialty Conference on Performance of Earth and Earth-Supported Structures, V. II, p. l-54, 1972.
Blanchard, F. N., (1972). Am. Miner. v, 57, p. 413-484.
Bromwell, L. G., “Annual Progress Report, I1 Florida Phosphatic Clays Research Project, Lakeland, Florida, 1974, 1975, 1976.
Bromwell, L. G., and Carrier, W. D. , III, “Consolidation of Fine-Grained Mining Wastes, ” Prepared for Sixth Pan American Conference on Soil Mechanics and Foundation Engineering, Lima, Peru, December, 1979.
Bromwell, L. G., Martin, R. T., and Sholine, J. H., “Field Tests of Phosphatic Clay Dewatering, ” Geotechnical Practice for Disposal of Solid Waste Materials, ASCE Geotechnical Division Specialty Conference, Ann Arbor, June, 1977.
Bromwell, L. G., and Oxford, T. P., “Waste Clay Dewatering and Dis- posal,” Geotechnical Practice for Disposal of Solid Waste Materials, ASCE Geotechnical Division Specialty Conference, Ann Arbor, June, 1977.
Bromwell, L. G., and Raden, D. J., “Disposal of Phosphate Mining Wastes ,” Current Geotechnical Practice in Mine Waste Disposal, ASCE Geotechnical Division Special Publication, 1979.
Buie, B. F., and Fellers, T . J. , “Electron Microscope Investigation of the Shape and Texture of Particles and Aggregates as a Factor in Their Flocculation and Settling in Phosphate Slimes,” Final Report, Prepared for the U.S. Department of the Interior, Bureau of Mines, Washington, D. C., July, 1977.
Carrier, W. D., III, and Beckman, J. D., - Paper submitted to Geotechnique, 1982.
Carrier, W. D., III, Bromwell, L. G., and Somogyi, F., “Design Storage Capacity of Slurried Mineral Waste Ponds,” ASCE, Journal of Geo-technical Engineering Division, May, 1983, pp. 699-716.
Casagrande , A. , “Classification and Identification of Soils, ” Trans. ASCE, V. 113, pp. 901-991, 1948.
88
Chanchani , R . , “The Effect of Deflocculants on the Rheological Behavior of Concentrated Phosphate Slimes ,‘I Masters Thesis, University of Florida, 1976.
Davenport, J. E., Kieffer, G. W., and Brown, E. II., +Disposal of Phos-phate Tailing, ++ Tennessee Valley Authority, Division of Chemical Development, Research Branch (Wilson Dam, Alabama), TVA Report 661, July, 1953, 125 pp.
Gooch, W. R., and ‘Dobson, E. E. (assigned to Florida Lightweight Products Company, Pembroke, Florida), “Phosphate Slimes Disposal, ++ U . S. Patent 2,947,418, August 2, 1960. Hawkins, W. H “Physical, Chemical, and Mineralogical Properties of Pl&,phatic Clay Slimes from the Bone Valley Formation,++ Masters Thesis, University of Florida, 1973.
Houston, E. C., Jones, V. C., and Powell, R. E., “Dewatering of Phosphate Tailings,” Transactions, AIME, 1949, Vol. 194, pp. 365-370.
I. T. X . C . (1974) “International Tables for- X-ray Crystallography”, 4.
Keshian, B . , Jr. , “Dewatering of Phosphatic Clay Waste, TV Masters Thesis, Department of Civil Engineering, M. I. T. , Cambridge, Massachusetts, 1976.
V.
Keshian, B., Jr., Ladd, C. C., and Olson, R. E., ttSedimentation- Consolidation Behavior of Phosphatic Clays ,” Geotechnical Practice for Disposal of Solid Waste Materials, ASCE Specialty Conference, Ann Arbor, June, 1977.
Lamont, W. E., McLendon, J. T., Clements, L. W., Jr., and Feld, I. L l , ++Characterization Studies of Florida Phosphate Slimes, ” U. S . Bureau of Mines Report of Investigations No. 8089, 1975.
LaMer, V. K., -and Smellie, R. H., Jr., ++Flocculation , Subsidence, and Filtration of Phosphate Slimes, I. General, ++ Journal of Colloid Science, 1956, Vol. 11, pp. 704-709 (also, subsequent articles in 1957, Vol. 12 and 1958, Vol. 13).
Martin, R. T., Bromwell, L. G., and Sholine, J. H. , “Field Tests of Phosphatic Clay Dewatering , +’ Geotechnical Practice for Disposal of Solid Waste Materials, ASCE Geotechnical Division Specialty Con- ference, Ann Arbor, June, 1977.
89
May, Alexander, “Electronphoretic Mobilities and Cation Exchange Capacities of Floriday Phosphate Slimes ,” Tuscaloosa Metallurgy Research Laboratory, U.S. Bureau of Mines, 1975.
Nov-ich, B . E. and R. T. Martin, (1981)) Quantitative Evaluation of Clay Solvation Methods, In Press: Clays & Clay Minerals.
Peech, M., L.A. Dean and J. Reed, (19471, U.S.D.A. Circular #‘757
Poole, M., “Lightweight Aggregate from Phosphate Slimes,” Engineering and Mining Journal, 1951, Vol. 52, No. 5, pp. 92-93.
Roma, J. R., “Geotechnical Properties of Phosphatic Clays, ” Masters Thesis, Department of Civil Engineering, M. I. T., Cambridge, Massachusetts, 1976.
Smelley, A. G., and Feld, I. L., “Flocculation Dewatering of Florida Phosphatic Clay Wastes, 11 U.S. Bureau of Mines Report of Investigations No. 8349, 1979.
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Tyler, P. M., and Waggaman, W. H., “Report on Possible Utilization of Phosphate Rock Slimes, ‘l National Research Council, Division of Engineering and Industrial Research, Minerals and Metals Advisory Board, Report #MMAB-45-C) June, 1953, 144 pp.
Vasan, S., “Utilization of Florida Phosphate Slimes, ” Proceedings, Third Symposium on Mineral Waste Utilization, Co-sponsored by Bureau of Mines and ITT Research Institute, Chicago, IlIinois, March 14-16, 1972, IIT Research Institute, Chicago, Illinois, 1972, pp. 171-177.
Vondrasek, A. F., “A Summary Evaluation of Slimes Disposal Techniques ,” International Min.erals and Chemical Corporation Internal Report, June, 1962, 67 pp.
Weaver, C. E. and L. D. Pollard, (19731, Vhe Chemistry of Clay
Minerals. I’
90
Whitaker, L. R., “Ceramic Bodies from Phosphate Wastes,” U.S. Patent 3,097,954, October 26, 1960.
91
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
LIST OF FIGURES
Sampling Locations
Piston Sampler
Typical Solids Content Profiles
Average Solids Contents from Settling Areas
Plasticity Chart for Phosphatic Clays
Slurry Consolidometer
Compressibility vs. Effective Stress -
Permeability vs. -
XRD Traces for
XRD Traces for
XRD Traces for
XRD Traces for
XRD Traces for
Peak lo-1lA
XRD Traces for
Peak 11-13A
XRD Traces for
Scanning Electron
Scanning Electron
Scanning Electron
Scanning Electron
Scanning Electron
Scanning Electron
Scanning Electron
Scanning Electron
Scanning Electron
Scanning Electron
and 130028
Void Ratio and Solids Content
Sample 830600
Sample 50057
Sample 770600
Sample 90036
MgG Heated Category with Single Major
MgG Heated Category with Single Major
MgG Heated Category with Two Major Peaks
Photomicrographs of Sample 10033
Photomicrographs of Sample 20052
Photomicrographs of Sample 20052
Photomicrographs of Sample 50057
Photomicrographs of Sample 50057
Photomicrographs of Sample 60051
Photomicrographs of Sample 60051 at pH9.
Photomicrographs of Sample 90036
Photomicrographs of Sample 110038
Photomicrographs of Samples 110038
92
LIST OF FIGURES CONT’D.
26.
27.
28.
29.
30.
31.
32.
33.
Settling Behavior vs. Palygorskite Content
Thirty Day Solids vs. Liquid Limit
Settling Behavior vs. Smectite Content
Uranium Content vs. Phosphate Content
P2 O5 Concentration
U3 06 Concentration
P2 O5 Concentration
Distribution of Palygorskites P2 05, and U3 08
93
. . .
CAM-LOCK
CONNECTOR
IO’ LENGTHS OF
3/4” ALUMINUM PIP
VENT HOLES
CLAMPS
3/8”0 THREADED ROD-
RUBBER PISTON
GUIDE
L ROPE
EYE BOLT
ROD GUIDE
8”X 2.5” I.D. THIN
ALL BRASS TUBING
3/8” FLAT WASHER AND
TNUT TOP AND BOTTOM
SCHEMATIC OF
PISTON TUBE SAMPLER
FIGURE 2
Typ.ical Solids Content Profiles
Surface
(Liquid/Solid Interface)
CLAY SOLIDS CONTENT t-b
@ typical active area reverse-S-curve
@ typical old area C-curve
@ uniform solids content in old above-ground area
@ active area exhibiting a layer or jog caused by stage filling
0 active area with indistinct depth zone?
FIGURE 3
DRAWING NUMBER .
D C CD
2 8
cn 0 -.
Q v)
WEIGHT TRANSFER APPARATUS
TABLE J I L-ii-1 I- ll
Schematic of Slurry Consolidometer
Figure 6
32 28 24 20 16 12 8 4
DECREES TWO THETA
,
?ig. 9. XRD Traces for Sample 830603, -44Pm Fraction: -MgG; n ----MgG 350- C;
A = Apatite, I = Illite, K = Kaolin, S = Smectite, Q = Quart?
32 28 24 20 16 12 8 4
DEGREES TWO THETA
Fig. 10. XRD Traces for Sample 50057, -44llm Fraction: +gG ----K300°C;
A = Apatite, I = Illite, K = Kaolin, P = Palygorskite, S = Smectite
1 I
I
’ \ 1’ ,
I I I
I I
I \ \
32 28 24 16 12 8 4.
DEGREES TWO THETA
Fig. 11. XRD Traces for Sample 770600, -44um Fraction: BgG
----MgG 350'C A = Apatite, D = Dolomite, I = Illite, K = Kaolin, P = Palygorskite, S = Smectite, Q = Quartz
. I i
K
1
Fig.
DEGREES TWO THETA
-2. XRD Traces for Sample 90036, -2pm Fraction: --ivlgG
----K300°C
A = Apatite, I = Illite, K = Kaolin, P = Palygorskite, S = Smectite, W = Wavellite
14 12 4 12 10
DEGREES TWO THETA (28)
Fig. 14. XRD Traces for MgG Heated Category with Single Major Peak ll-13A: 250°C for 20 hrs.;
----------350°C for 4 hrs.; --- 450°C for 4 hrs.
a) H 4w
b) ’ lum ’
Fig 22. Scanning Electron Photomicrographs of Sample 60051 at pH9.
Fresh Slurry Samples
30 DAY SETTLED SOLIDS CONTENT (%)
Palygorskite Vs. Settled Solids Content
FIGURE 2i
4 1
0
03
0
SMECTITE RELATIVE PEAK RATIO
. . .
.
.
. .
. I
. .
.
. .
.
. .
.
. .
.
cn CD
-c - -. 3 n
R20E R21E R22E
-J-/- p2 05 1 c--
CONCENTRATION 1{ ?-
\ R23E R24E R25E
L
4
O* SCALE IN MILES
FIGURE 30 I
R26E
I r- u3 08 -CONCENTRATION
FIGURE 3 1
R20E R21E R22E R23E R24E R25E R26E
R20E R21E R22E
I r PALYGORSKITE -CONCENTRATION
FIGURE 32 ! I I
I t I
R23E R24E R25E R26E
/ _j
ii,
ii 17 SCALE IN MILES
ii
14
c1
.-.- Hillsborough _.-.-. co. _.-.- Manatee
DISTRIBUTION OF - PALYGORSKITE
05, AND U,O, LEGEND
200
100
0
SCALE IN MILES
FIGURE 33
Pdygorskite ___ -
R22E R23E R24E R25E R26E R20E R21E