Treatment of Heavy Metals in Soil and Groundwater Using Iron and Reactive

Minerals 15 September – 2016

Today’s Webinar: Aims

Will examine the reduction, adsorption, and precipitation of heavy metals in groundwater by reagents based on elemental iron, iron sulphides and related reactive minerals.

Key topics include:

– Review of metals treatment terminology;

– Review of relevant chemistry;

– Performance data from independent testing & full scale results.

Today’s Webinar: Speakers

Alan Seech – a scientist with 25 years experience in soil chemistry, microbiology, and environmental remediation. His focus has been on development of technologies for treatment of soil, sediment, and groundwater containing hard to degrade organics, such as PAHs, pesticides, and organic explosive compounds.

Mike Mueller – PeroxyChem’s Business Development Manager in EMEA - responsible for their Soil & Groundwater Remediation technologies portfolio. Based in Austria, he has been working in this region for over 6 years, initially with Adventus (which was acquired by FMC Corporation), now known as PeroxyChem.

Chair – Ian Grant – Brownfield Briefing Managing Editor

Questions

Please submit questions during the webinar using your chat box.

If you have any unanswered questions please submit them to the Brownfield Briefing LinkedIn group, following the webinar.

http://brownfieldbriefing.com/li

Treatment of Heavy Metals in Soil & Groundwater

using Elemental Iron and Reactive Minerals

1. PeroxyChem Environmental Solutions 2. Alan Seech Ph.D., California USA

3. Mike Mueller MBA, Innsbruck Austria

Brownfield Briefing Webinar Series 15 S t b 2016

Presentation Outline

• Background: History, definitions, MetaFix® reagent composition, features, dosage, and application methods

• Chemistry: Solubility and stability of heavy metal hydroxides vs. heavy metal sulfides vs. heavy metal iron oxyhydroxides

• Removal mechanisms for major heavy metals

• A detailed look at Chromium

• Bench-scale Tests: some results from comparisons of MetaFix® and other reagents, mixed metals, and metals with cVOCs

• Case Studies: Soil and Groundwater Treatment

• Questions & Answers

ZVI Reduction of Inorganics: Some History Elemental Metals in Chemical Reduction Processes

More Recently for Organics

Use of Elemental Metals for Environmental Remediation

9

And then for Heavy Metals

• Treatment of heavy metals and other inorganic contaminants by reductive precipitation and adsorption

• Various materials including ZVI, pyrite, organic carbon, gypsum

10

MetaFix® Reagents

MetaFix® is a family of injectable reagents designed to treat heavy metals in soil and groundwater using chemical reduction, precipitation, and adsorption. Reagents do not rely on in situ biological sulfate reduction or carbon

metabolism -- so their performance is not inhibited by high toxicity (e.g., alkalinity, acidity, salts, high COI concentrations)

Composed of iron-bearing reducing agents

Treatment results in conversion of aqueous heavy metals to low solubility mineral precipitates with broad pH stability

Adsorption on iron corrosion products is also important

Custom formulations for unusual site conditions

11

Low Dosage Rates: 0.5% - 4.0% (w/w) for soil 0.1% - 1.0% (w/w) for groundwater

Application by soil mixing, trenching, or injection

(40% – 50% solids) aqueous suspension Low cost treatability testing (£1,800) to

determine dosage and enable bespoke formulation

MetaFix® Reagents

12

Metal

Precipitation as Metal

Hydroxides or Iron Metal

Oxyhydroxides

Precipitation as Metal

Sulfides/Iron Metal

Sulfides

Adsorption and Co-

precipitation with Iron Corrosion Products

Precipitation as Metal

Carbonates

Adsorption of organo-

metal species

As (III, V) ● ● ●

Cr(VI) ● ●

Pb, Cd, Ni ● ● ● ● ●

Cu, Zn ● ● ●

Se ● ● ●

Hg ● ● ●

MetaFix® Mechanisms

Fe0.75Cr0.25(OH)3

EPA 625/8-80-003, 1980; Banerjee et al., 2013. Veolia Water Inc. Environ. Sci. Technol. 1988, 22, 972-977

Aqueous Solubility & Stability of Heavy Metals as Hydroxides, Iron Oxyhdroxides, and Sulfides

14 EPA 625/8-80-003, 1980

Heavy Metal Precipitates: Sulfides, Carbonates, and Hydroxides

15

Chromium Reduction by FeS

16

Adsorption on Iron Corrosion Products

From Dick Brown, ERM Ewing NJ

17

Cr(VI) Reduction Sulfide vs. Sulfide + Iron Oxyhydroxide

Kim et al., 2007. Geochemical Journal. 41: 397-405.

Mechanism: Free sulfide ion reduced to elemental sulfur on goethite surface promotes formation of ferrous iron which reduces hexavalent chromium to precipitated trivalent form as shown in TEM image.

18

Iron-based Chromium Treatment

• Reduction of Cr+6 to Cr+3 by ZVI is followed by its precipitation as mixed Fe-Cr oxyhydroxides with a mineral structure similar to that of goethite (α-FeOOH), with some Cr+3 also deposited into a hematite-like structure (Fe2O3).1,2

• Solubility of Fe-Cr oxyhydroxides is <0.05 µg/L over a broad pH range (5.0 - 12.0)3

• The Fe-Cr oxide which has the form of hematite (Fe2O3) is primarily deposited on the surface of precipitates2

1. Blowes et al., 2000. J. Contam. Hydrol. 45: 123-137 2. Tratnyek et al., 2003. In: Tarr, M. Chemical Degradation Methods for Wastes and Pollutants 3. Eary and Rai. 1988. Env. Sci. Technol. 22:972-977.

19 Rai et al., 1989. Sci. Tot. Env. 86:15-23.

Solubility of Mixed Fe-Cr Oxyhydroxides

Reduction of Cr(VI) to Cr(III) by Fe+2 is rapid (minutes) and the main product is a mixed Fe-Cr oxyhydroxide. Precipitates with more Fe/less Cr have lower solubility but all are much less soluble than Cr(OH)3 and have solubility well below most remedial standards for groundwater. The free energy of formation for Fe-Cr oxyhydroxide is lower than that for Cr(OH)3, so it will be preferentially formed when free Fe+2 is available.

20 Independent Test Results from Professor D. Cassidy, WMU. , D. Gray AECOM. 2014

Performance of MetaFix® and calcium polysulfide in treatment of Cr and Ni in soil/groundwater slurry

79.3

31.9

13.4 12.1 11.4 6.4 4.1

8.4 3.3 2.1

0

10

20

30

40

50

60

70

80

90

Cr Ni

SPLP

Con

cent

ratio

ns, m

g/L

Reagent Dosing, wt/wt% and pH after 20 Days of Treatment

Control (20 day pH 6.4) CaPS 1.5% (20 day pH 8.2)MetaFix 1.0% (20 day pH 6.6) CaPS 7.3% (20 day pH 9.4)MetaFix 5.0% (20 day pH 6.5)

21 Batch study, 10.0 g soil + 200 mL groundwater, 7 days incubation,

Influence of EHC® Metals and MetaFix® on TCLP lead and arsenic (US Site)

22 Confidential Client, Independent Laboratory

Mixed Metal/cVOC Plumes

Table 1. Influence of control and treatment on heavy metal concentrations.

Biotic Control

MetaFix® I-6

23 Confidential Client, Independent Laboratory

Mixed Metal/cVOC Plumes

Table 1. Influence of control and treatment on VOC concentrations in microcosms.

Biotic Control

MetaFix® I-6

Case Study 1 Ex-situ treatment of Lead-impacted industrial process waste.

TCLP lead reduced from 11.7 mg/L to 0.22 mg/L.

• Direct soil mixing with excavator

• Reagent dosage at 6.0 % w/w

• Soil water content set to 80% of WHC (wet, not saturated)

• 7 day treatment time

• Earlier attempts at treatment with FeSO4 and fly ash at 40% w/w were ineffective

25

• Site: Manufacturing facility, Oregon USA

• Consultant: Maul, Foster and Alongi

• COCs: Mixed heavy metals including Al, As, Cd, Cr, Cu, Pb, Hg and Ni; High pH

• Treatment: Excavation of source area soil combined with 80 ft (25 m) long MetaFix PRB to prevent migration of any residual impacts into adjacent river

• Application: Reagent mixed into backfill to cover down-gradient wall of excavation

and form PRB

Case Study 2 PRB for Treatment of Mixed Heavy Metals

26

Influence of pH on Aluminium Solubility

Soluble species of Aluminium • Solubility sharply influenced by

aqueous pH

• At low pH a trivalent cationic form exists, but as pH moves toward neutral protons are lost, and charge falls from +3 to +2 to +1 and on to neutral

• As pH moves alkaline solubility of the neutral form Al(OH)3 increases

27

Phase I: Screening of three different MetaFix formulations at two dose rates of 4 and 8% by soil mass

Bench Scale Treatability Study: Phase I, Reagent Screening

28

• Phase II: MetaFix I-3F selected for further evaluation and tested at three lower dosages of 1, 2 and 3 % by soil mass to refine dosing requirements

• Results from the two studies indicate that a 4.0% (w/w) dosage was as effective as

the higher 8.0% dosage. In addition, based on the results of the 2nd study, concluded that dosage of 4.0% would be somewhat more effective than a 3.0% dose, and substantially more effective than either the 1.0% or 2.0% dosages.

Bench Scale Treatability Study: Phase II – Dosage Evaluation

29

• Impacted soil was excavated down to 18 ft (5.5 m) bgs and removed

• MetaFix PRB was installed along sheet piling at the downgradient wall of excavation, in conjunction with backfilling the excavation with clean soil

• PRB Dimensions: 80 ft long x 3 ft wide x 15 ft thick (from 5 to 20 ft bgs) • MetaFix Target Dosage in Soil: 6% by soil mass

• MetaFix Mass: 24,000 lbs (12 x 1 tonne supersacks)

PRB Design and Implementation

30

Site Map

31

MetaFix Blended into Soil using Backhoe

MetaFix applied in 1.25 ft (0.4 m) lifts with one supersack per lift, and then blended into soil using backhoe

32

Early Results

1

10

100

1000

10000

Tota

l met

als (

ug/L

)

MW-02

Al As Cu

• Post installation monitoring data available from ~3 and 4 months after PRB installation

• Small post installation increase presumably attributable to physical mobilisation of metals

pH Eh (mV)

DO (mg/L)

Cond. (µS/cm)

Baseline 10.24 -62 0.88 1,800 3 months 9.83 -47 0.09 6,360 4 months 9.8 9.6 0.91 7,061

PRB installation

33

Case Study 3 Mercury Treatment to Non-Detect Levels at

Former Industrial Site

• Mercuric chloride was used as a catalyst in chemical synthesis at this former chemical plant

• Soil Hg concentrations in the contaminated area ranged from 300 to 420 mg/kg.

• Remedial goal: stabilise the soil and then dispose treated material at an offsite landfill; the land will be developed for residential use.

34

• Results from the treatability study indicated the optimum MetaFix formation

could be applied at a dosage rate as low as 0.5% (w/w) to achieve the RG (<1.0

µg/L ) of SPLP Hg.

Mercury Treatment to 0.1 µg/L SPLP at a Former Industrial Site

Control MetaFix 0.5%

(wt/wt) MetaFix 1.0%

(wt/wt)

Moisture (%) 18.3 18.5 20.0

pH 8.6 8.0 7.9

Total Hg (mg/kg)

315 293 314

SPLP Hg (µg/L)

35.1 <1.0 <1.0

35

A pilot study was conducted in four treatment cells:

• MetaFix applied at 0.5,% 1.0,% and 2.0% (w/w)

~ 50 - 100 m3 batches

• Reagent spread on soil and mixed with an excavator

• Further mixing with a screening bucket

• Water added to adjust the moisture content close to the saturation level while the soil was mixed with an excavator bucket

• Final mixing was completed with the screening bucket to assure homogeneity

• Soil was covered to react anaerobically for 7 days

0.117 0.1308 0.0911 0.0732

0.0001

0.001

0.01

0.1

1

0.5% 0.5% 1% 2%Hg S

PLP

Conc

entr

atio

ns (µ

g/L)

MetaFix Dosage (w/w)

Baseline MetaFix

ND

ND

ND

ND

• Hg was treated to non-detect levels of <1.0 µg/L

Mercury Treatment to Non-Detect Levels at a Former Industrial Site

36

• The MetaFix dosage of 0.5% w/w selected for

the full scale treatment.

• Full scale implementation utilises an

integrated soil mixing system where soil

crushing/screening and reagent dosing/mixing

are completed in a single process.

• Treatment time is 7 days.

• Thousands of tonnes successfully treated

Mercury Treatment to Non-Detect Levels at a Former Industrial Site

37

Stability of MetaFix® Mineral Precipitates

Independent Laboratory Multiple Extraction Testing; Values (mg/L are 9.02, 0.02, 0.80, 0.06

38

Key Benefits Summary

1. Lower solubility of heavy metal precipitates based on iron and iron-sulfide chemistry provides high assurance of attaining remedial goals.

2. Not dependent on alkalinity for removal of metals. Broad pH range stability of metal precipitates based on iron and iron-sulfide chemistry reduces the danger of rebound.

3. Proven ability to address multiple heavy metals including: Al, As, Cd, Cr, Cu, Hg, Ni, Pb, Se, V, and Zn. Superior Cr(VI) treatment with the formation of more stable mixed (Cr, Fe) hydroxides.

4. Ability to treat heavy metals successfully at sites where the soil/groundwater has high acute toxicity.

5. Capable of treating comingled plumes. Simultaneous removal of soluble heavy metals, and dehalogenation of chlorinated solvents.

6. Longevity of treatment (micro-scale ZVI and FeS estimated > 10 years).

7. Low overall treatment costs based on lower reagent dosing rates, as low as 0.1% - 4% (wt/wt), versus other metals treatment technologies.

Technology that really Works

Treatment of Heavy Metals in Soil and Groundwater using Elemental Iron and Reactive Minerals

Alan Seech, Ph.D.

PeroxyChem Environmental Solutions Senior Manager – Technology Applications

3334 E. Coast Highway, Suite 114, Corona Del Mar, CA 92625 P: +1 949-388-7065 | M: +1 949-514-1068

Alan.Seech@PeroxyChem.com

Mike Mueller, B.Sc., MBA PeroxyChem Environmental Solutions

Business Development Manager, EMEA | Soil & Groundwater Remediation Franz-Plattner-Straβe 28F, 6170 Zirl, Tirol, Austria P: +43 (0)5238.53262 | M: +43 (0)664.180.3060

Mike.Mueller@peroxychem.com

www.PeroxyChem.com/Remediation

Questions?

Q&A Session

If you have any unanswered questions please submit them to the Brownfield Briefing LinkedIn group, following the webinar.

http://brownfieldbriefing.com/li

Upcoming events…

Free webinar: The National Quality Mark Scheme for Land Contamination Management: 13:00 BST, Tuesday 20 September

Brownfield Remediation 2016: London, Thursday 13 October

Brownfield Briefing Awards: London, Thursday 13 October

http://brownfieldbriefing.com/events

Today’s Webinar: Speakers

Alan Seech – a scientist with 25 years experience in soil chemistry, microbiology, and environmental remediation. His focus has been on development of technologies for treatment of soil, sediment, and groundwater containing hard to degrade organics, such as PAHs, pesticides, and organic explosive compounds.

Mike Mueller – PeroxyChem’s Business Development Manager in EMEA - responsible for their Soil & Groundwater Remediation technologies portfolio. Based in Austria, he has been working in this region for over 6 years, initially with Adventus (which was acquired by FMC Corporation), now known as PeroxyChem.

Chair – Ian Grant – Brownfield Briefing Managing Editor

Thank you for attending

A downloadable recording of this presentation (with slides) will be available shortly. If you have any questions, please contact Glen (glen@environment-analyst.com)