Mine, acid drainage

Acid mine drainage (AMD) from abandoned coal and metal mining is a serious environmental problem that has affected thousands of miles of streams and waterways. AMD is created via the oxidation of sulfide minerals, such as pyrite see reactions (10.13) and (10.14)  

This process is greatly enhanced by the presence of ferric ion, which occurs by both bacterial and air oxidation of ferrous ion. Bacteria such as 

This section touches on aspects of acid mine drainage, tailings, and especially cyanide. Other gold mining wastes include arseihc (Chapter 2) and mercury (Chapter 19). 

Underground gold mines puncture ore bodies with adits, mine tunnels, and shafts that allow air and water to enter and react with sulfide materials that are exposed inside the mine. AMD can leach from underground mine openings into streams and aquifers. In open pit mines, sulfide minerals on the exposed sides of the pit excavation are moistened by 

Gold miners had a number of arsenic-associated health problems including excess mortality from cancer of the lung, stomach, and respiratory tract. Miners and schoolchildren in the vicinity of gold mining activities had elevated urine arsenic of 25.7 p,g/L (range 2.2-106.0 p-g/L). Of the total population at this location, 20% showed elevated urine arsenic concentrations associated with future adverse health effects arsenic-contaminated drinking water is the probable causative factor of elevated arsenic in urine. 

The significance of these elevated values is discussed in detail in Chapter 2. 

Reaction kinetics are an interesting aspect of iron chemistry in addition to the redox and precipitation reactions discussed in the previous section. The consideration of kinetics is very important in problems of water-quality significance such as acid mine drainage and the removal of iron from water. At pH values of greater than 5.5 the rate law for the oxygenation of ferrous iron is ° 

From this equation we can see that the rate of ferrous iron oxidation is first order with respect to oxygen and Fe and second order with respect to OH-, 

Stumm and J. J. Morgan, Aquatic Chemistry, Wiley-Interscience, New York, 

The classical stoichiometric picture of acid mine drainage is 

TABLE 7-7 Water Quality from Roaring Creek-Grassy Run Watershed of Elkins, W.Va. 

While the oxidation reaction is a natural one (see Section 4.4.2), the mining activities increase the scale and rate of the reaction (see eqn. 4.4). The resulting 

H2S04 makes drainage from abandoned mines strongly acidic (pH as low as 1 or 2). This acidity increases the solubility of aluminium and other metals, causing toxicity in aquatic ecosystems. Microorganisms are closely involved in sulphide oxidation, which can be modelled by a series of reactions  

Oxidation happens very slowly at the low pH values found in acid mine waters. However, below pH 3.5 iron oxidation is catalysed (see Box 4.4) by the iron bacterium Thiobacillus thiooxidans. At pH 3.5-4.5 oxidation is catalysed by Metallogenium. Ferric iron may react further with pyrite  

At pH values much above 3 the iron(III) precipitates as the common iron(III) oxide, goethite (FeOOH)  

The precipitated goethite coats stream beds and brickwork as a distinctive yellow-orange crust (Plate 5.2, facingp. 138), a very visible manifestation of the problem. 

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Because gravity is too weak to be used for removal of cakes in a gravity side filter (2), continuously operated gravity side filters are not practicable but an intermittent flow system is feasible in this arrangement the cake is first formed in a conventional way and the feed is then stopped to allow gravity removal of the cake. A system of pressure filtration of particles from 2.5 to 5 p.m in size, in neutralized acid mine drainage water, has been described (21). The filtration was in vertical permeable hoses, and a pressure shock associated with relaxing the hose pressure was used to aid the cake removal. 

PermeOx is also used to improve the bioremediation of soils contaminated with creosote or kerosene (see Bioremediation (Supplement)), to deodori2e sewage sludges and wastewater (see Odormodification), and to dechloriaate wastewater and effluents. A special formulation of calcium peroxide, made by FMC and sold ia the United States under the trademark Trap2ene, is used for removing metal ions from acidic waste streams such as coal ash leachate and acid mine drainage (see Wastes, industrial). 

Self-Test L.3B Many abandoned mines have exposed nearby communities to the problem of acid mine drainage. Certain minerals, such as pyrite (FeS,), decompose when exposed to air, forming solutions of sulfuric acid. The acidic mine water then drains into lakes and creeks, killing fish and other animals. At a mine in Colorado, a 16.45-mL sample of mine water was completely neutralized with 25.00 mL of 0.255 M KOH(aq). What is the molar concentration of H2S04 in the water ... 

As we saw in Section L, titration involves the addition of a solution, called the titrant, from a buret to a flask containing the sample, called the analyte. For example, if an environmental chemist is monitoring acid mine drainage and needs to know the concentration of acid in the water, a sample of the effluent from the mine would be the analyte and a solution of base of known concentration would be the titrant. At the stoichiometric point, the amount of OH " (or 11,0 ) added as titrant is equal to the amount of H30+ (or OH-) initially present in the analyte. The success of the technique depends on our ability to detect this point. We use the techniques in this chapter to identify the roles of different species in determining the pH and to select the appropriate indicator for a titration. 

Nyquist, J. and Greger, M., A field study of constructed wetlands for preventing and treating acid mine drainage, Ecological Engineering, 35 (5), 630-642, 2009. 

Turner, A., Rawling, M.C. (2002) Sorption of benzo[a]pyrene to sediment contaminated by acid mine drainage contrasting particle concentration-dependencies in river water and seawater. Water Res. 36, 2011-2019. 

There are, fortunately, some instances in which measured Eh values can be interpreted in a quantitative sense. Nordstrom et al. (1979), for example, showed that Eh measurements in acid mine drainage accurately reflect the aFe+++/aFe++ ratio. They further noted a number of other studies establishing agreement between measured and Nernst Eh values for various couples. Nonetheless, it is clearly... 

Sorption can significantly diminish the mobility of certain dissolved components in solution, especially those present in minor amounts. Sorption, for example, may retard the spread of radionuclides near a radioactive waste repository or the migration of contaminants away from a polluting landfill (see Chapters 21 and 32). In acid mine drainages, ferric oxide sorbs heavy metals from surface water, helping limit their downstream movement (see Chapter 31). A geochemical model useful in investigating such cases must provide an accurate assessment of the effects of surface reactions. 

The above reaction represents, in a simplified way, the origin of acid mine drainage. Streambeds in areas of acid drainage characteristically become coated with an orange layer of ferric precipitate. We can write a reaction representing the overall process by swapping ferric hydroxide in place of the ferrous ion ... 

Chapman, B. M., D. R. Jones and R. F. Jung, 1983, Processes controlling metal ion attenuation in acid mine drainage streams. Geochimica et Cosmochimica Acta 47,1957-1973. 

Davis, A., R. L. Olsen and D.R. Walker, 1991, Distribution of metals between water and entrained sediment in streams impacted by acid mine drainage, Clear Creek, Colorado, U.S.A. Applied Geochemistry 6, 333-348. 

Johnson, C. A., 1986, The regulation of trace element concentrations in river and estuarine waters with acid mine drainage, the adsorption of Cu and Zn on amorphous Fe oxyhydroxides. Geochimica et Cosmochimica Acta 50, 2433-2438. 

Mayo, A. L., P. J. Nielsen, M. Loucks and W. H. Brimhall, 1992, The use of solute and isotopic chemistry to identify flow patterns and factors which limit acid mine drainage in the Wasatch Range, Utah. Ground Water 30, 243-249. 

Taylor, B.E., M. C. Wheeler and D.K. Nordstrom, 1984, Isotope composition of sulphate in acid mine drainage as measure of bacterial oxidation. Nature 308, 538-541. 

Estimation and prediction as to whether waste rock and tailings will produce acid mine drainage (AMD) are precursory to environmental certification, and therefore are a critical step in mine development. Kinetic tests are carried out using a cell or column that are operated over a period of typically 1 year, whereas static tests are a onetime measurement to determine the acid producing potential (AP) and... 

Conference, West Virginia University. Neculita, C-M, Zagury, G, Bussiere, Bruno 2007. Passive Treatment of Acid Mine Drainage in Bioreactors, using Sulphate Reducing Bacteria Critical Review and Research Needs. Journal of Environmental Quality, 36, 1-16... 

Geomicrobiology Journal, 14, 41-49. http //www.dep.state.pa.us/deD/deputate/minre s/bamr/amd/science of amd.htm Tsukamoto T.K., Killion, H.A., Miller, G.C. 2004. Column experiments for microbiological treatment of acid mine drainage low-temperature, low-pH and matrix investigations, Water Research, 38, 1405-1418. 

KEYWORDS acid-mine drainage, trace elements, geochemical modeling... 

Kimball, B.A. 1997. Use of tracer injections and synoptic sampling to measure metal loading from acid mine drainage. U.S. Geological Survey Fact Sheet FS-245-96. 

Kimball, B.A., Broshears, R.E., Bencala, K.E., McKnight, D.M. 1994. Coupling of hydrologic transport and chemical reaction in a stream affected by acid mine drainage. Environmental Science Technology, 28, 2065-2073. 

Runkel, R.L. Kimball, B.A. 2002. Evaluating remedial alternatives for an acid mine drainage system - application of a reactive transport model. Environmental Science Technology, 36, 1093-1101. 

KEYWORDS Tailings, Acid mine drainage, Static and kinetic tests, quantitative mineralogy,... 

Fig. 3. Extrapolated oxidation-neutralization curve for the long-term prediction of acid mine drainage of the tree samples (Benzaazoua Al 2001)...

Paktunc, A.D. 1999. Characterization of mine wastes for prediction of acid mine Drainage. In Environmental impacts of mining activities, emphasis on mitigation and remedial measures, Springer Verlag, Berlin, Hidelberg, New York, Azcue, J.M., 19-40. 

KEYWORDS ground water, tailings, sulfate, pit lake, acid mine drainage... 

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