GEOCHEMICAL MODELING OF HARD-ROCK MINE DRAINAGE AND MINE-IMPACTED WATERS

Geochemical modeling of precipitation reactions in the complex matrix of acid mine drainage is fundamental to understanding natural attenuation, lime treatment, and treatment procedures that separate constituents for potential reuse or recycling. The three main dissolved constituents in acid mine drainage are iron, aluminum, and sulfate. During the neutralization of acid mine drainage (AMD) by mixing with clean tributaries or by titration with a base such as sodium hydroxide or slaked lime, Ca(OH)2, iron precipitates at pH values of 2–3 if oxidized and aluminum precipitates at pH values of 4–5 and both processes buffer the pH during precipitation. Mixing processes were simulated using the ion-association model in the PHREEQC code. The results are sensitive to the solubility product constant (Ksp) used for the precipitating phases. A field example with data on discharge and water composition of AMD before and after mixing along with massive precipitation of an aluminum phase is simulated and shows that there is an optimal Ksp to give the best fit to the measured data. Best fit is defined when the predicted water composition after mixing and precipitation matches most closely the measured water chemistry. Slight adjustment to the proportion of stream discharges does not give a better fit.

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Monitoring, field experiments, and geochemical modeling of Fe(II) oxidation kinetics in a stream dominated by net-alkaline coal-mine drainage, Pennsylvania, USA

Applied Geochemistry ◽

10.1016/j.apgeochem.2015.02.009 ◽

2015 ◽

Vol 62 ◽

pp. 96-107 ◽

Cited By ~ 10

Author(s):

C.A. Cravotta

Keyword(s):

Coal Mine ◽

Oxidation Kinetics ◽

Field Experiments ◽

Mine Drainage ◽

Geochemical Modeling ◽

Coal Mine Drainage

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Precipitation of heavy metals from acid mine drainage and their geochemical modeling

Selected Scientific Papers - Journal of Civil Engineering ◽

10.2478/sspjce-2014-0009 ◽

2014 ◽

Vol 9 (1) ◽

pp. 79-86 ◽

Cited By ~ 1

Author(s):

Aneta Petrilakova ◽

Magdalena Balintova ◽

Marian Holub

Keyword(s):

Acid Mine Drainage ◽

Mine Drainage ◽

Geochemical Modeling ◽

Vital Role ◽

Dissolved Metals ◽

Environmental Preservation ◽

Surface Water Hydrology ◽

Acid Mine ◽

Modeling Software ◽

High Concentrations

Abstract Geochemical modeling plays an increasingly vital role in a number of areas of geoscience, ranging from groundwater and surface water hydrology to environmental preservation and remediation. Geochemical modeling is also used to model the interaction processes at the water - sediment interface in acid mine drainage (AMD). AMD contains high concentrations of sulfate and dissolved metals and it is a serious environmental problem in eastern Slovakia. The paper is focused on comparing the results of laboratory precipitation of metal ions from AMD (the Smolnik creek, Slovakia) with the results obtained by geochemical modeling software Visual Minteq 3.0.

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ANC–BNC Titrations and Geochemical Modeling for Characterizing Calcareous and Siliceous Mining Waste

Minerals ◽

10.3390/min11030257 ◽

2021 ◽

Vol 11 (3) ◽

pp. 257

Author(s):

Clémentine Drapeau ◽

Cécile Delolme ◽

Clément Vézin ◽

Denise Blanc ◽

Thomas Baumgartl ◽

...

Keyword(s):

Mine Drainage ◽

Geochemical Modeling ◽

Mining Waste ◽

Main Element ◽

Liquid Phases ◽

Neutralizing Capacity ◽

Mineral Assemblages ◽

Ph Range ◽

Neutral Conditions

Pyrite and calcite are mineral phases that play a major role in acid and neutral mine drainage processes. However, the prediction of acid mine drainage (AMD) or contaminated neutral drainage (CND) requires knowledge of the mineral composition of mining waste and the related potential for element release. This paper studies the combination of acid–base neutralizing capacity (ANC–BNC) with geochemical modeling for the characterization of mining waste and prediction of AMD and CND. The proposed approach is validated with three synthetic mineral assemblages: (1) siliceous sand with pyrite only, representing mining waste responsible for AMD, (2) siliceous sand with calcite and pyrite, representing calcareous waste responsible for CND, and (3) siliceous sand with calcite only, simulating calcareous matrices without any pyrite. The geochemical modeling approach using PHREEQC software was used to model pH evolution and main element release as a function of the added amount of acid or base over the entire pH range: 1 < pH < 13. For calcareous matrices (sand with calcite), the results are typical of a carbonated environment, the geochemistry of which is well known. For matrices containing pyrite, the results identify different pH values favoring the dissolution of pyrite: pH = 2 in a pyrite-only environment and pH = 6 where pyrite coexists with calcite. The neutral conditions can be explained by the buffering capacity of calcite, which allows iron oxyhydroxide precipitation. Major element release is then related to the dissolution and precipitation of the mineral assemblages. The geochemical modeling allows the prediction of element speciation in the solid and liquid phases. Our findings clearly prove the potential of combined ANC–BNC experiments along with geochemical modeling for the characterization of mining waste and the assessment of risk of AMD and CND.

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Long Term Zinc Contamination and Transport at the Abandoned Ore Chimney Mine

Canadian Geotechnical Journal ◽

10.1139/cgj-2020-0270 ◽

2020 ◽

Author(s):

Colleen Harper ◽

Carling Ruth Walsh ◽

Carrie Fong ◽

Paul Gammon ◽

Richard T Amos

Keyword(s):

Natural Attenuation ◽

Mine Drainage ◽

Mine Waste ◽

Geochemical Modeling ◽

Waste Rock ◽

Ph Buffering ◽

Mine Waste Rock ◽

Site Water ◽

Waste Rock Piles ◽

Co Precipitation

Mine waste-rock piles can release low quality drainage that is harmful to the surrounding environment. Many studies have investigated recently placed waste rock, but fewer have examined geochemical processes within, and downgradient of, old waste rock, even though these processes may be expected to persist for many decades. The Ore Chimney property was the site of gold exploration activities that produced a small waste-rock pile; it was abandoned in 1934. Elevated concentrations of Zn are restricted to within 50 m of the waste rock, and pH remains neutral across the site. Water and sediment analyses and geochemical modeling indicate that several processes are involved in pH buffering and contaminant control. Water samples taken at the edge of the waste rock were not acidic, indicating that mechanisms within the waste rock, including carbonate buffering and preferential oxidation of sphalerite over pyrite, are preventing Acid Mine Drainage (AMD). Natural attenuation mechanisms are operating within wetlands at Ore Chimney with the most likely controls for Zn transport in ground and surface water being carbonate mineral precipitation, co-precipitation with Fe and Mn oxides and oxyhydroxide minerals and Al sulphate minerals, and adsorption onto calcite and organic matter. This investigation shows that, after long time frames, natural attenuation mechanisms may act to effectively immobilize metal contaminants.

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