the behavior of radium enriched barite in geochemically reducing conditions aids in understanding...
TRANSCRIPT
1 February 2014
The Behavior of Radium-Enriched Barite in Geochemically Reducing Conditions Aids in Understanding Radium Anomalies
Richard Murphy, Ph.D.Don CarpenterARCADIS U.S., Inc.
Society for Mining, Metallurgy, and Exploration2014 Meeting
2 February 2014
THIS PRESENTATION WILL SYSTEMATICALLY ADDRESS THE
FOLLOWING ITEMS:
Occurrence of Radium
Incorporation of Radium into Barite
Destabilizing Geochemical Conditions
Reprecipitation of Radium
Discussion of Findings
3 February 2014
Decay of Naturally Occurring Uranium and Thorium Generates Radioactive Progeny and NORM
Radium isotopes are produced within each decay chain
Comparatively short half-life of Radium-228 results in rapid natural attenuation
4 February 2014
Radium Occurs Naturally in Groundwater Systems Throughout US
5 February 2014
Precipitation of Alkaline Earth Sulfates can Co-Precipitate Radium Sulfate forming a NORM
Ba+2 + SO4-2 → BaSO4
Ba+2 + (Ra+2) + SO4-2 → Ba(Ra)SO4
Acid insoluble
Low (“insolubility”) of Barite causes Radium and decay products to be largely retained within crystalline structure
6 February 2014
Radium and Mining/Milling
NORM occurrence in copper ore
Uranium soluble at acid and alkaline pH
Acid leaching (sulfuric acid) will liberate uranium however high sulfate concentrationslimit radium dissolution
At alkaline pH, radium less soluble
Radium present naturally in groundwater systems at mines due to geochemically-reducing systems (where present)
7 February 2014
Typically Instability of Barite is the Least of the NORM-Related Problems its Presence May Engender
Millions of barrels of petroleum-related NORM awaiting disposal
150,000 barrels being generated per year
American Petroleum Institute in 1989 suggested that 1/3 of all producing U.S. oil and gas wells have elevated radiation
Present as dispersed ,potentially non-actionable material, at many sites:
Mines, Mills, Smelters, Tailings, Slag
8 February 2014
The Insolubility of Barite Under Geochemically Oxidizing Conditions Prevents its Chemical Removal
pH (oxidizing conditions)
Dissolved Barium (mg/L)
Dissolved Sulfate (mg/L)
4 0.32 5.17 0.30 5.19 0.30 5.1
9 February 2014
Precipitation of Alkaline Earth Sulfates can Co-Precipitate Radium Sulfate forming a NORM
Ba+2 + SO4-2 → BaSO4
Ba+2 + (Ra+2) + SO4-2 → Ba(Ra)SO4
Precipitation Reaction Documents:1) Importance of Barium ion activity2) Importance of Sulfate ion activity
10 February 2014
This Chemical Behavior is Leveraged for Removal of Both Dissolved Barium and Radium
Best Demonstrated Available Technology [BDAT]
1) Addition of Sodium Sulfate [Na2SO4]2) Addition of Barium Chloride [BaCl2]
BaSO4 readily passes Toxicity Characteristics Leaching Procedure (TCLP)
11 February 2014
Stability of Barite (and Radium) is a Function of Both Dissolved Barium and Sulfate Ion Activity
BaSO4 = Ba+2 + SO4-2
log_k -9.97
aBa+2 * aSO4-2 = 10-9.97
Note that any process that results in removal of one of these results in destabilization of the barite
Linear relationship (i. e., remove one, dissolve the other)
12 February 2014
Modeling Results Also Document Relationship Between Barium and Total Dissolved Solids
Empirical relationship has been noted between NORM formation and Total Dissolved Solids (and depth)
Barium solubility can be shown to be a function of chloride concentration (activity)
Barium (brine) Barium (chloride-free)05
1015202530354045
Barium Solubility (ppm) – 81° C
13 February 2014
Barite Solubility Increases at High Ionic Strength due to Thermodynamics
Rosenberg et al., 2011
14 February 2014
Sulfate Reducing Bacteria can Quantitatively Remove Sulfate in the Presence of Sufficient Organic Carbon
2CH2O + SO4-2 2HCO3
- + H2S
60.0 g CH2O + 96.1 g SO4-2 122.0 g HCO3
- + 34.1 g H2S
Consequently, any environment where solid phase metabolizable organic carbon as a ratio approaching 60% of the available dissolved phase sulfate can lead to depletion of the dissolved sulfate
Dissolution of previously solid phase sulfates (e. g., Barite) may occur
15 February 2014
Geochemically-Reducing Systems Liberate Radium
Szabo et al., 2012
16 February 2014
Radium Release from Dissolving Barite can Result in an Important Increase in Dissolved Radium Activity
500 mg of Barium per Kilogram of Soil
850 mg of Barite per Kilogram of Soil
5 pCi of Radium per Milligram of Barite
4,250 pCi of Radium per Kilogram of Soil
17 February 2014
Dissolution of only a Comparatively Small Amount of Radium-226 can Exceed the Drinking Water Standard
4,250 pCi/Kg of Soil of Radium
5 pCi/L is Drinking Water Standard
Consequently, Dissolution of Barite within 1 Kilogram of Soil can impact 850 Liters of Water
18 February 2014
Geochemical Leading to Reducing Conditions Can Result in Adverse and Unexpected Radium
Release of a bacteriological organic substrate (petroleum, biological wastes, etc.)
Elevated Radium typically found with predictable co-contaminants
Cr+3
As+3
Ba+2
H2S
Fe+2
19 February 2014
The Optimum Modes of Control, if Necessary, Relate Back to the Initial Dissolution Reaction
Ba+2 + SO4-2 = BaSO4
Oxygenate system (H2S → SO4-2)
Add a more readily soluble sulfate (Na2SO4, MgSO4)
Radium can re-incorporate intobarium, strontium, and calcium minerals through co-precipitation
Rosenberg et al., 2011
20 February 2014
Radium Co-precipitate with Calcium and Strontium
Ca+2 + SO4-2 + 2H2O → CaSO4 * 2H2O
Ca+2 + (Ra+2) + SO4-2 + 2H2O →
Ca(Ra)SO4 * 2H2O
Ca+2 + (Ra+2) + SO4-2 → Ca(Ra)SO4
Acid Soluble – HClLess adherence of the scaleMore readily removedPotential release of radium
21 February 2014
Instability of Radium-Enriched Barite
The Insolubility of Barite Under Geochemically Oxidizing Conditions Prevents its Chemical Removal
Precipitation of Alkaline Earth Sulfates can Co-Precipitate Radium Sulfate forming a NORM
Stability of Barite is a Function of Both Dissolved Barium and Sulfate Ion Activity
Sulfate Reducing Bacteria can Quantitatively Remove Sulfate in the Presence of Sufficient Organic Carbon
Dissolution of only a Comparatively Small Amount of Radium can Exceed the Drinking Water Standard
