Acid mine drainage concentration

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. 

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. 

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. 

The U.S. Department of Energy is funding research at the Idaho National Engineering Laboratory, Idaho Falls, Idaho, to determine if sawdust can be used exclusively to support a bioprocess for the remediation of acid mine drainage containing significant concentrations of cyanide and other ions. 

McKinley, J.P. Jenne, E.A. (1991) Experimental investigation and review of the solids concentration" effect in adsorption studies. Environ. Sci. Technol. 25 2082-2087 McKinnon, W. Choung, J.W. Xu, Z. Einch, J.A. (2000) Magnetic seed in ambient temperature ferrite process applied to acid mine drainage treatment. Environ. Sci. Techn. 34 2575-2581... 

HPT Research, Inc., has developed the ionic state modification (ISM) process for the treatment of acid mine drainage (AMD). ISM is an ex situ treatment technology that uses magnets, electricity, and proprietary chemical to precipitate heavy metals, remove sulfate ions, and neutralize acidity from AMD and industrial wastewaters. The end products of the process are a metal hydroxide sludge, a calcium sulfate sludge, and treated liquid effluent. The vendor claims that the metal hydroxide sludge may have some value as an ore, the calcium sulfate may be used as an agricultural additive to soils, and the liquid effluent is free of metal contamination and has low sulfate concentrations. 

The Met-Tech separation process is a liquid ion exchange process for the ex situ recovery, separation, and concentration of a wide range of heavy metals. The technology is commercially available and, according to the vendor, has been tested at the pilot scale. According to the vendor, future applications will be in soil remediation, acid mine drainage, and the recycling of spent nuclear waste. 

The Biocat II technology is an improvement of the Biocat process (U.S. Patent 5,076,927), which treats acid mine drainage and heap leach effluents. The improvements were made under a Phase I Small Business Innovation Research (SBIR) grant funded by the Defense Advanced Research Projects Agency, a component of the U.S. Department of Defense (D10362Y, p. 4). If adequate concentrations of sulfuric acid are not present, additional acid may be required to operate the process. 

Walker, Schreiber and Rimstidt (2006) list the oxidation rate of arsenopyrite in water as io 1014 0 03 mol m-2 s-1 at 25 °C, pH 6.3-6.7, and dissolved 02 concentrations of 0.3-17 mgL-1. Unexpectedly, the dissolved 02 concentrations had essentially no effect on the oxidation rate. However, in laboratory solutions simulating acid mine drainage (pH = 1.8), the oxidation rate of arsenopyrite was found to increase with increasing temperature (15-45 °C) and concentrations of chloride or Fe(III) sulfate (Fe2(S04)3) (Yu, Zhu and Gao, 2004). The oxidation of arsenopyrite primarily released As(III). The oxidation of As(III) to As(V) was slow, but also increased with increasing temperature and chloride or Fe(III) sulfate concentrations (Yu, Zhu and Gao, 2004). 

Allen SK, Allen JM, Lucas S. 1996. Dissolved metal concentrations in surface waters from west-central Indiana contaminated with acidic mine drainage. Bull Environ Contain Toxicol 56 240-243. 

Figure 8.10 Sorption constants for Cu, Zn and Cd on natural oxyhydroxides as a function of pH obtained from field measurements. The points were obtained in the Carnon River, UK (V, Johnson, 1986) in 40 sites in Canadian lakes representing a variety of geological settings, lake pH values, and trace element concentrations in the sediments and in the overlying waters (O, Tessier, 1992) and in streams affected by acid mine drainage (A, Chapman et at., 1983). Log= Fe-M / Fe-ox [Mz+] (adapted from Tessier, 1992).

Table 33 Water analysis of an acid mine drainage AMD (pH = 2,3) and of a groundwater GW (pH = 6,6) (concentrations in mg/L)...

The reactions in an aquifer shall be modeled in the presence of calcite and large concentrations of pyrite and organic matter for the acid mine drainage from the exercise in chapter 3.1.3.3. As no inorganic carbon is given in the analysis and calcite is to be used as kinetically reacting mineral in the model, the analysis has to be completed by e g. 1 mg/L carbon, formally. 

At a time Tl, an acid mine drainage of the following composition is added (concentration in mmol/L) ... 

TABLE 6.1. Concentrations of Environmentally Important Constituents (mg L 1) in Acid Mine Drainages in the United States and Canada. 

Aluminum is one of the most abundant elements in the earth s crust. Acid rain and acid mine drainage are two major causes of increased aluminum in freshwater systems. As acid water goes through soil, pH decreases and aluminum dissolves. The process may increase aluminum concentrations to toxic levels (>2 mg L-1). Aluminum is toxic to both humans and aquatic organisms, especially to humans undergoing dialysis. 

Table 13.10 gives some critical threshold values of NH3 in the environment. In-stream standards in many states allow a maximum concentration of 0.02 mg L-1 unionized ammonia in trout waters and 0.50 mg L 1 in all other waters. No limits are set in drinking water standards. Ammonia is often used to neutralize acid mine drainages (AMD) as well as other industrial acid- or metal-rich drainages (e.g., woodpulp and electronics). Many states have banned or discourage the use of ammonia for such purposes unless extensive monitoring is carried out. 

But not only mercury is released by mining. Mn ore mining activities taking place in the Brazilian Amazon basin as open pits (for instance in the Serra do Navio, Amapa State), represent a potential source of associated ferrous metals (such as Ni, Cr, Cu, As). Acid mine drainage contains dissolved and particulate metals in toxic concentrations, affects the pH of streams and mobilizes metals. Moreover, wind dispersal of material from unstable spoil heaps can result in local or regional atmospheric contamination. Despite the likely importance of this source in the environment, it is currently not possible to estimate the quantities of trace... 

Coal mining exposes suffides (primarily pyrite) in coal and associated rocks to oxygen and moisture. These oxidize the sulfides and form sulfuric acid. The resulting acidic waters (referred to as acid mine drainage (AMD)) adversely impact the biota in watersheds downstream from active and abandoned mines. Oxidation of the sulfides also releases chalcophyllic trace elements into the water. Many of these elements precipitate in oxygenated surface waters and are concentrated in stream sediments (Goldhaber et at, 2001). 

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