Geochemical Modeling to Evaluate Remediation Options for Iron-Laden Mine Discharges

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1 Geochemical Modeling to Evaluate Remediation Options for Iron-Laden Mine Discharges Charles Chuck Cravotta III U.S. Geological Survey Pennsylvania Water Science Center

2 Summary Aqueous geochemical tools using PHREEQC have been developed by USGS for OSMRE s AMDTreat costanalysis software: ü Iron-oxidation kinetics model considers ph-dependent abiotic and biological rate laws plus effects of aeration rate on the ph and concentrations of CO 2 and O 2. ü Limestone kinetics model considers solution chemistry plus the effects of surface area of limestone fragments. ü Potential water quality from various treatments can be considered for feasibility and benefits/costs analysis.

3 TREATMENT OF COAL MINE DRAINAGE Al 3+ Passive Fe 2+ / Fe 3+ Mn 2+ Active Increase ph/oxidation with natural substrates & microbial activity Reactions slow Large area footprint Low maintenance Increase ph/oxidation with aeration &/or industrial chemicals Reactions fast, efficient Moderate area footprint High maintenance

4 ACTIVE TREATMENT 28 % aeration; no chemicals (Ponds) 21 % caustic soda (NaOH) used 40 % lime (CaO; Ca(OH) 2 ) used 6 % flocculent or oxidant used 4 % limestone (CaCO 3 ) used

5 PASSIVE TREATMENT

6 Vertical Flow Limestone Beds Bell Colliery Pine Forest ALD & Wetlands PASSIVE TREATMENT Limestone Dissolution, O 2 Ingassing, CO 2 Outgassing, Fe(II) Oxidation, & Fe(III) Accumulation Silver Creek Wetlands

7 Frequency in percent, N=99 Frequency in percent, N=41 BIMODAL ph FREQUENCY DISTRIBUTION Anthracite AMD A. Anthracite Mine Discharges Bituminous AMD B. Bituminous Mine Discharges ph decreases after oxidation of net acidic water (Fe oxidation and hydrolysis): Fe O H 2 O Fe(OH) H + ph, field ph, lab (aged) ph increases after oxidation of net alkaline water (CO 2 outgassing): HCO 3 - = CO 2 (gas) + OH - ph, field ph, lab (aged) ph

0+ is being recoded from FoxPro to C++ to facilitate its use on

8 PHREEQ-N-AMDTREAT AMDTreat AMDTreat is a computer application for estimating abatement costs for AMD (acidic or alkaline mine drainage). AMDTreat is maintained by OSMRE. The current version of AMDTreat 5.0+ is being recoded from FoxPro to C++ to facilitate its use on computer systems running Windows 10. The PHREEQC geochemical models described below will be incorporated to run with the recoded program.

9 AMDTREAT 5.0+ With the PHREEQC chemical titration tool, AMDTreat 5.0+ has capability to estimate: ü Quantity and cost of caustic chemicals to attain a target ph (without and with pre-aeration); ü Chemistry of treated effluent after reactions; and ü Volume of sludge produced as the sum of precipitated metal hydroxides plus unreacted chemicals.

10 AMDTREAT 5.0+ PHREEQ-N-AMDTreat chemical titration tool accurately relates caustic addition, ph, and metals solubility but ü assumes instantaneous, complete reactions without consideration of kinetics of gas exchange rates; and ü ignores effects of changing ph on iron oxidation rate.

11 AMDTreat 5.0+ Caustic Addition St. Michaels Discharge Escape PresentaBon

12 New PHREEQC Kinetics Models for AMDTreat 5.0+ ü FeII oxidation model that utilizes established rate equations for gas exchange and ph-dependent iron oxidation and that can be associated with commonly used aeration devices/steps (including decarbonation); ü Limestone dissolution model that utilizes established rate equation for calcite dissolution and that can be adjusted for surface area of commonly used aggregate particle sizes.

13 KINETICS OF IRON OXIDATION ph & GAS EXCHANGE EFFECTS

14 Iron Oxidation Kinetics are ph Dependent (abiotic and microbial processes can be involved) (1996) (Kirby et al., 1999) ** C bact is concentrabon of iron-oxidizing bacteria, in mg/l, expressed as dry weight of bacteria (2.8E-13 g/cell or 2.8E-10 mg/cell ). The AMDTreat FeII oxidabon kinebc model uses most probable number of iron-oxidizing bacteria per liter (MPNbact). C bact = 150 mg/l is equivalent to MPNbact = 5.3E11, where Cbact = MPNbact (2.8E-10).

15 Abiotic Homogeneous Fe(II) Oxidation Rate (model emphasizes ph) Hours Days Months Years Minutes Fe(OH) 1+ Between ph 5 and 8 the Fe(II) oxidation rate increases by 100x for each ph unit increase.* At a given ph, the rate increases by 10x for a 15 C increase. Using the activation energy of 23 kcal/mol with the Arrhenius equation, the rate can be adjusted for temperature. Fe(OH) 2 0 Fe 2+ log k T1 = log k T2 + Ea /(2.303 * R) (1/T 2-1/T 1 ) *Extrapolation of homogeneous rate law: -d[fe(ii)]/dt = k 1 [Fe(II)] [O 2 ] [H + ] -2 k 1 = 3 x mol/l/min At [O 2 ] = 0.26 mm (po 2 = 0.21 atm) and 25 C. Open circles (o) from Singer & Stumm (1970), and solid circles ( ) from Millero et al. (1987). Dashed lines are estimated rates for the various dissolved Fe(II) species.

16 Effects of O 2 Ingassing and CO 2 Outgassing on ph and Fe(II) Oxidation Rates Batch Aeration Tests at Oak Hill Boreholes (summer 2013) Control Not Aerated Aerated H 2 O 2 Addition

17 PHREEQC Coupled Kinetic Model of CO 2 Outgassing & Homogeneous Fe(II) Oxidation Oak Hill Boreholes ph FeII Dissolved CO 2 Dissolved O 2 k L,CO2 a = s -1 k L,O2 a = s -1 k L,O2 a = s -1 k L,CO2 a = s -1 k L,O2 a = s -1 k L,CO2 a = s -1 k L,O2 a = s -1 k L,CO2 a = s -1

18 CO 2 Outgassing is Proportional to O 2 Ingassing (model specifies first-order rates for out/in gassing) -d[c]/dt = k L, C a ([C] - [C] S ) exponenbal, asymptobc approach to steady state k L,CO2 a = s k L,CO2 a = s -1 k L,CO2 a = s -1 k L,CO2 a = s -1 Atmospheric equilibrium Atmospheric equilibrium Aerated Not Aerated 1st Order O 2 ingassing rate constant (1/s) y = 2.43x R² = kla [O2] vs. kla [CO2] st Order CO 2 outgassing rate constant (1/s)

19 New Iron Oxidation Rate Model for AMDTreat (combines abiotic and microbial oxidation kinetics) The homogeneous oxidation rate law (Stumm and Lee, 1961; Stumm and Morgan, 1996), expressed in terms of [O 2 ] and {H + } (=10 -ph ), describes the abiotic oxidation of dissolved Fe(II): -d[fe(ii)]/dt = k 1 [Fe(II)] [O 2 ] {H + } -2 The heterogeneous oxidation rate law describes the catalytic abiotic oxidation of sorbed Fe(II) on precipitated Fe(III) oxyhydroxide surfaces, where (Fe(III)) is the Fe(III) oxyhydroxide concentration expressed as Fe in mg/l (Dempsey et al., 2001; Dietz and Dempsey, 2002): -d[fe(ii)]/dt = k 2 (Fe(III)) [Fe(II)] [O 2 ] {H + } -1 The microbial oxidation rate law describes the catalytic biological oxidation of Fe(II) by acidophilic microbes, which become relevant at ph < 5 (Pesic et al., 1989; Kirby et al., 1999): -d[fe(ii)]/dt = k bio C bact [Fe(II)] [O 2 ] {H + } where k bio is the rate constant in L 3 /mg/mol 2 /s, C bact is the concentration of iron-oxidizing bacteria in mg/l (dry weight), [ ] indicates aqueous concentration in mol/l.

New Iron Oxidation Rate Model for AMDTreat PHREEQC Coupled Kinetic Models of CO 2 Outgassing & Fe(II) Oxidation Kinetic variables can be adjusted, including CO 2 outgassing and O 2 ingassing rates

20 New Iron Oxidation Rate Model for AMDTreat PHREEQC Coupled Kinetic Models of CO 2 Outgassing & Fe(II) Oxidation Kinetic variables can be adjusted, including CO 2 outgassing and O 2 ingassing rates plus abiotic and DuraBon of aerabon (Bme for reacbon) TimeSecs : is 8 hrs microbial FeII oxidation rates. Constants are temperature corrected. OpBon to specify FeIII recirculabon *mulbply Fe.mg by to get [H2O2] CO 2 outgassing rate in sec Adjustment CO 2 outgassing rate Aer3: k L,CO2 a = s -1 Adjustment O 2 ingassing rate (x klaco2) Aer2: k L,CO2 a = s -1 Adjustment abiobc homogeneous rate Aer1: k L,CO2 a = s -1 Adjustment abiobc heterogeneous rate Iron oxidizing bacteria, microbial rate Calcite saturabon limit Hydrogen peroxide added* Adjustment to H2O2 rate Aer0: k L,CO2 a = s -1 User may estimate Fe2 from Fe and ph plus TIC from alkalinity and ph. And specify H 2 O 2 or recirculation of FeIII. Output includes ph, solutes, net acidity, TDS, SC, and precipitated solids.

21 Estimated CO 2 Outgassing & O 2 Ingassing Rate Constants for Various Treatment Technologies Fast Slow Fast Slow kl,a_20 = (LN((C 1 -C S )/(C 2 -C S ))/t) / ( (TEMPC - 20) ), where C is CO 2 or O 2. Dissolved O 2, temperature, and ph were measured using submersible electrodes. Dissolved CO 2 was computed from alkalinity, ph, and temperature data.

Revised AMDTreat Chemical Cost Module Caustic Titration with Pre-Aeration (Decarbonation) PHREEQC Coupled Kinetic Models of CO 2 Outgassing & Fe(II) Oxidation Original option for no aeration, plus

22 Revised AMDTreat Chemical Cost Module Caustic Titration with Pre-Aeration (Decarbonation) PHREEQC Coupled Kinetic Models of CO 2 Outgassing & Fe(II) Oxidation Original option for no aeration, plus new option for kinetic pre-aeration (w/ wo hydrogen peroxide) that replaces original equilibrium aeration. Duration of pre-aeration in sec CO 2 outgassing rate constant in sec -1 Adjustment CO 2 outgassing rate (x klaco2) Adjustment O 2 ingassing rate (x klaco2) Hydrogen peroxide added* Adjustment to H 2 O 2 rate Calcite saturation limit Dropdown kla Allows selection and evaluation of key variables that affect chemical usage efficiency. *mulbply Fe.mg by to get [H2O2]

New Module For AMDTreat PHREEQC Coupled Kinetic Models of CO 2 Outgassing & Fe(II) Oxidation, with Caustic Pre-Treatment OpBon to adjust inibal ph with causbc CO 2 outgassing rate OpBon to specify

23 New Module For AMDTreat PHREEQC Coupled Kinetic Models of CO 2 Outgassing & Fe(II) Oxidation, with Caustic Pre-Treatment OpBon to adjust inibal ph with causbc CO 2 outgassing rate OpBon to specify FeIII recirculabon *mulbply Fe.mg by to get [H2O2] Adjustment CO 2 outgassing rate Adjustment O 2 ingassing rate (x klaco2) Adjustment abiobc homogeneous rate Adjustment abiobc heterogeneous rate Variable CO 2 outgassing and O 2 ingassing rates apply. Can choose to adjust initial ph with caustic. The required quantity of caustic is reported in units used by AMDTreat. Iron oxidizing bacteria Kinetic variables, including CO Calcite saturabon limit 2 Hydrogen peroxide added outgassing and O 2 ingassing rates plus Adjustment to H2O2 rate abiotic and microbial FeII oxidation rates, can be adjusted by user. In addition to caustic chemicals, hydrogen peroxide and recirculation of FeIII solids can be simulated.

24 KINETICS OF LIMESTONE DISSOLUTION ph, CO 2, and SURFACE AREA EFFECTS

25 Limestone Dissolution Rate Model for AMDTreat ( PWP model emphasizes ph and CO 2 ) r = (k 1 a H+ + k 2 a H2CO3* + k 3 a H2O ) According to Plummer, Wigley, and - k 4 a Ca2+ a HCO3- Parkhurst (1978), the rate of CaCO 3 dissolution is a function of three forward (dissolution) reactions: CaCO 3 + H + Ca HCO - 3 k 1 CaCO 3 + H 2 CO 3 * Ca HCO - 3 k 2 CaCO 3 + H 2 O Ca HCO OH - k 3 and the backward (precipitation) reaction: Ca HCO - 3 CaCO 3 + H + k 4 Although H +, H 2 CO 3 *, and H 2 O reaction with calcite occur simultaneously, the forward rate is dominated by a single species in the fields shown. More than one species contributes significantly to the forward rate in the gray stippled area. Along the lines labeled 1, 2, and 3, the forward rate attributable to one species balances that of the other two.

26 Limestone Dissolution Rate Model for AMDTreat (generalized expression corrects for surface area) Appelo and Postma (2005) give a generalized rate expression for calcite dissolution that considers physical characteristics of the system as well as solution chemistry: R = k ( A / V ) ( 1 Ω ) n where A is calcite surface area, V is volume of solution, Ω is saturation state (IAP/K = 10 SIcc ), and k and n are empirical coefficients that are obtained by fitting observed rates. For the PWP model applied to 1 liter solution, the overall rate becomes: R = (k 1 a H+ + k 2 a H2CO3* + k 3 a H2O ) ( A ) (1-10 (n SIcc) ) Plummer and others (1978) reported the forward rate constants as a function of temperature (T, in K), in millimoles calcite per centimeter squared per second (mmol/cm 2 /s): log k 1 = / T log k 2 = / T log k 3 = / T for T < 298; log k 3 = / T for T > 298

Limestone Dissolution Rate Model for AMDTreat (surface area correction for coarse aggregate) Plummer, Wigley, and Parkhurst (1978) reported unit surface area (SA) of 44.5 and 96.

27 Limestone Dissolution Rate Model for AMDTreat (surface area correction for coarse aggregate) Plummer, Wigley, and Parkhurst (1978) reported unit surface area (SA) of 44.5 and 96.5 cm 2 /g for coarse and fine par8cles, respec8vely, used for empirical tes8ng and development of PWP rate model. These SA values are 100 8mes larger than those for typical limestone aggregate. Mul3ply cm 2 /g by 100 g/mol to get surface area (A) units of cm 2 /mol used in AMDTreat rate model.

New Module For AMDTreat PHREEQC Kinetic Model of Limestone Dissolution TimeSecs : 7200 is 2 hrs Surface area, cm 2 /mol ** Equilibrium approach Mass available **MulBply surface area (SA) in cm 2 /g

28 New Module For AMDTreat PHREEQC Kinetic Model of Limestone Dissolution TimeSecs : 7200 is 2 hrs Surface area, cm 2 /mol ** Equilibrium approach Mass available **MulBply surface area (SA) in cm 2 /g by 100 to get SAcc in cm 2 /mol. Calcite dissolution rate model of Plummer, Wigley, and Parkhurst (PWP; 1978). Empirical testing and development of PWP rate model based on coarse and fine calcite particles with surface areas of 44.5 and 96.5 cm 2 /g, respectively. Surface area and exponential corrections permit application to larger particle sizes (0.45 to 1.44 cm 2 /g) used in treatment systems.

New Module For AMDTreat PHREEQC Coupled Kinetic Models of Limestone Dissolution & Fe(II) Oxidation Surface area Equilibrium approach Mass available CO 2 outgassing rate Adjustment CO 2 outgassing

29 New Module For AMDTreat PHREEQC Coupled Kinetic Models of Limestone Dissolution & Fe(II) Oxidation Surface area Equilibrium approach Mass available CO 2 outgassing rate Adjustment CO 2 outgassing rate Adjustment O 2 ingassing rate (x klaco2) Adjustment abiobc homogeneous rate Adjustment abiobc heterogeneous rate Iron oxidizing bacteria Calcite saturabon limit Hydrogen peroxide added Adjustment to H2O2 rate Rate models for calcite dissolution, CO 2 outgassing and O 2 ingassing, and FeII oxidation are combined to evaluate possible reactions in passive treatment systems. Can simulate limestone treatment followed by gas exchange and FeII oxidation in an aerobic pond or aerobic wetland, or the independent treatment steps (not in sequence).

PHREEQC Coupled Kinetic Models Sequential Steps Limestone Dissolution + Fe(II) Oxidation Pine Forest ALD + Aerobic Wetlands Sequential steps: Variable detention times, adjustable CO 2 outgassing

30 PHREEQC Coupled Kinetic Models Sequential Steps Limestone Dissolution + Fe(II) Oxidation Pine Forest ALD + Aerobic Wetlands Sequential steps: Variable detention times, adjustable CO 2 outgassing rates, limestone surface area, temperature, and FeIII. Next slide Can simulate passive treatment by anoxic or oxic limestone bed, open (limestone) channels or spillways, aerobic cascades, ponds, and wetlands.

PHREEQC Coupled Kinetic Models Sequential Steps Pine Forest ALD + Aerobic Wetlands 9 8 7 6 5 4 3 2

31 PHREEQC Coupled Kinetic Models Sequential Steps Pine Forest ALD + Aerobic Wetlands Step Treatment 1 ALD 2 Riprap 3 Pond 4 Cascade 5 Wetland 6 Cascade 7 Wetland 8 Cascade 9 Wetland 0

outgassing rates, limestone surface area, temperature, and FeIII.

32 PHREEQC Coupled Kinetic Models Sequential Steps Caustic + Limestone Dissolution + Fe(II) Oxidation Silver Creek Aerobic Wetlands Sequential steps: Pre-treatment with caustic and/or peroxide and, for each subsequent step, variable detention times, adjustable CO 2 outgassing rates, limestone surface area, temperature, and FeIII. Next slide Can simulate active treatment, including chemical addition or aeration, or passive treatment, including anoxic or oxic limestone bed, open (limestone) channels or spillways, aerobic cascades, ponds, and wetlands.

33 PHREEQC Coupled Kinetic Models Sequential Steps Silver Creek Aerobic Wetlands Step Treatment 1 Pond 2 Aeration 3 Pond 4 Aeration 5 Pond 6 Riprap 7 Wetland 8 Riprap 9 Wetland

34 Conclusions ü Geochemical kinetics tools using PHREEQC have been developed to evaluate mine effluent treatment options. ü Graphical and tabular output indicates the ph and solute concentrations in effluent. ü By adjusting kinetic variables or chemical dosing, various passive and/or active treatment strategies can be simulated. ü AMDTreat cost-analysis software can be used to evaluate the feasibility for installation and operation of treatments that produce the desired effluent quality.

35 Disclaimer / Release Plans Although this software program has been used by the U.S. Geological Survey (USGS), no warranty, expressed or implied, is made by the USGS or the U.S. Government as to the accuracy and functioning of the program and related program material nor shall the fact of distribution constitute any such warranty, and no responsibility is assumed by the USGS in connection therewith. ü FY2017 Development, beta testing and review. ü FY2018 Official USGS software release planned: ü ü FY2018 Incorporation of PHREEQC treatment simulations with AMDTreat to be released by OSMRE: ü

36 Questions? ü Are the current models capable of simulating manganese (MnII) oxidation kinetics? ü Can the models simulate the adsorption of cations by hydrous ferric oxides (HFO) as a kinetic process? ü Have you considered adsorption based rate models for the heterogeneous FeII and MnII oxidation kinetics? ü Does the limestone model consider changes in surface area of due to its dissolution or the accumulation of HFO coatings? ü Does the microbial FeII oxidation rate model consider oxidation by neutrophilic iron bacteria such as Gallionella or Leptothrix? ü What about the simulation of anaerobic processes in a BCR (Biochemical Reactor) and precipitation of metal sulfides?

37 References Burrows JE, Cravotta CA III, Peters SC (2017) Enhanced Al and Zn removal from coal-mine drainage during rapid oxidation and precipitation of Fe oxides at near-neutral ph: Applied Geochemistry 78, Cravotta CA III (2003) Size and performance of anoxic limestone drains to neutralize acidic mine drainage: Journal of Environmental Quality 32, Cravotta CA III (2015) Monitoring, field experiments, and geochemical modeling of Fe(II) oxidation kinetics in a stream dominated by netalkaline coal-mine drainage, Pennsylvania, U.S.A. Applied Geochemistry 62, Cravotta CA III, Means B, Arthur W, McKenzie R, Parkhurst DL (2015) AMDTreat 5.0+ with PHREEQC titration module to compute caustic chemical quantity, effluent quality, and sludge volume. Mine Water and the Environment 34, Davison W, Seed G (1983) The kinetics of the oxidation of ferrous iron in synthetic and natural waters. Geochimica et Cosmochimica Acta 47, Dempsey BA, Roscoe HC, Ames R, Hedin R, Byong-Hun J (2001) Ferrous oxidation chemistry in passive abiotic systems for the treatment of mine drainage. Geochemistry: Exploration, Environment, Analysis 1, Dietz JM, Dempsey BA (2002) Innovative treatment of alkaline mine drainage using recirculated iron oxides in a complete mix reactor. American Society of Mining and Reclamation 19th Annual Meeting, p Geroni JN, Cravotta CA III, Sapsford DJ (2012) Evolution of the chemistry of Fe bearing waters during CO 2 degassing. Applied Geochemistry 27, Kirby CS, Elder-Brady JA (1998) Field determination of Fe 2+ oxidation rates in acid mine drainage using a continuously-stirred tank reactor. Applied Geochemistry 13, Kirby CS, Thomas HM, Southam G, Donald R (1999) Relative contributions of abiotic and biological factors in Fe(II) oxidation in mine drainage. Applied Geochemistry 14, Kirby CS, Dennis A, Kahler A (2009) Aeration to degas CO 2, increase ph, and increase iron oxidation rates for efficient treatment of net alkaline mine drainage: Applied Geochemistry 24, Langmuir D (1997) Aqueous environmental geochemistry. Prentice Hall, New Jersey, USA, 600 p. (especially p ) Parkhurst DL, Appelo CAJ (2013) Description of input and examples for PHREEQC version 3 A computer program for speciation, batchreaction, one-dimensional transport, and inverse geochemical calculations. USGS Techniques Methods 6-A43, 497 p. Pesic B, Oliver DJ, Wichlacz P (1989) An electrochemical method of measuring the oxidation rate of ferrous to ferric iron with oxygen in the presence of Thiobacillus ferrooxidans. Biotechnology and Bioengineering 33, Plummer LN, Wigley ML, Parkhurst DL (1978) The kinetics of calcite dissolution in CO 2 -water systems at 5 o to 60 o C and 0.0 to 1.0 atm CO 2. American Journal of Science 278, Rathbun RE (1998) Transport, behavior, and fate of volatile organic compounds in streams: USGS Professional Paper 1589, 151 p. Singer PC, Stumm W (1970) Acidic mine drainage: the rate-determining step. Science 167, Stumm W, Lee G.F. (1961) Oxygenation of ferrous iron. Industrial and Engineering Chemistry 53, Stumm W, Morgan JJ (1996) Aquatic chemistry--chemical equilibria and rates in natural waters (3rd): New York, Wiley-Interscience, 1022 p. (especially p )

38 SOLUBILITY AND SORPTION CONTROL OF TRACE ELEMENTS

39 Concentration, Me TOT (mg/l) Solubilities of Metal Hydroxides Fe III Fe III & Mn IV ARE LEAST SOLUBLE; OXIDATION RATE IS LIMITING Al III Mn IV ph METALS HAVE LOW SOLUBLITY AT NEUTRAL TO ALKALINE ph Fe II Mn II Al(OH)3 Fe(OH)3 Fe(OH)2 MnO2 Mn(OH)2 Cu(OH)2 Pb(OH)2 Ni(OH)2 Zn(OH)2 Co(OH)2 Cd(OH)2 Mg(OH)2 Ca(OH)2

40 0 2 Fe Limited by Fe II -Carbonate and Fe III -Hydroxide and Sulfate Solubilities Dissolved Fe is predominantly Fe II Solid phase Fe II (OH) 2 -log [Fe T, Fe II & Fe III (mol/l)] Fe(OH)3 (amorph) Goethite FeOOH Schwertmannite, x=1.75 Siderite FeCO3 Fe(OH)2 AMD140 [FeTOT] ph Fe II CO 3 Fe III 8 O 8 (OH) 4.5 (SO 4 ) 1.75 Fe III OOH Fe III (OH) 3 Aqueous phase Temp = 25 o C pso 4 TOT = 2.3 pk + = 4.30 pco 2 = 2.0

41 SORPTION OF CATIONS ON HFO PERCENT DISSOLVED Pb+2 CrIII Cu+2 Zn+2 Cd+2 Co PERCENT ADSORBED 20 Ni+2 Mn Ba Sr ph

42 SORPTION OF ANIONS ON HFO PERCENT DISSOLVED SO4-2 AsO4-3 SeO3-2 CrO4-2 PO ph PERCENT ADSORBED

Priority Pollutants in Untreated and Treated Discharges from Coal Mines

Priority Pollutants in Untreated and Treated Discharges from Coal Mines Charles A. Cravotta III Research Hydrologist USGS Pennsylvania Water Science Center New Cumberland, PA Presented March, 28, 2012,