Mine water

Fig. 10. An idealized view of an HDR heat mine. Water circulating ia a closed loop is heated as it passes through fractures ia the hot rock. The energy is...

In Situ Leaching. Copper and uranium ores are sometimes leached ia place by circulatiag acidified mine water through the underground deposit. This process is known as solution mining. 

Air or biological oxidation of pyrite leads to sulfate formation and dilute sulfuric acid in the mine drainage. This pollutes streams and the water supphes into which the mine water is drained. Means of controlling this problem are under study. 

Hydrometallurigcal Processes. In hydrometaHurgical processes, metal values and by-products are recovered from aqueous solution by chemical or electrolytic processes. Values are solubilized by treating waste, ore, or concentrates. Leaching of copper ores in place by rain or natural streams and the subsequent recovery of copper from mnoff mine water as impure cement copper have been practiced since Roman times. Most hydrometaHurgical treatments have been appHed to ores or overburden in which the copper was present as oxide, mixed oxide—sulfide, or native copper. PyrometaHurgical and hydrometaHurgical processes are compared in Reference 34. 

The foHowing factors are important in dump leaching (/) the role of bacteria (2) the appHcation of acid to prevent or delay precipitation of hydrated ferric sulfate (J) oxidation to remove excess iron from mine water in settling pools, as shown in equations 38 and 39 (4) optimization of dump configuration for good solution distribution and (5) avaHabHity of oxygen. 

Fe Fe"+ Fe"+ + e- acidic coal mine waters fixed-bed fiow-through anode 130... 

A Frasch mine can produce as much as 2.5 million tonnes of sulfur per annum- Such massive operations clearly require huge quantities of mining water (up To 5 million gallons daily) and abundant pou er supplies for tlie drilling, pumping and superheating operations. 

Waters of pH less than 6 may be expected to be corrosive, but, because any weak acids present in the solution may not be fully ionised, it does not follow that water of pH greater than 7 will not be corrosive. Mine waters are particularly corrosive to cast iron, often to such an extent as to preclude its use with them, because of their relatively high acid content, derived from the hydrolysis of ferric salts of the strong acids, mainly sulphate, and because the ferric ion can act as a powerful cathodic depolariser. 

Those salts which hydrolyse to give an acid solution, e.g. the strong acid salts of aluminium, iron and, to a lesser extent, calcium, give solutions which may be very corrosive to cast iron, particularly if they are well aerated. When oxidising salts are also present in these acid solutions, a particularly dangerous system may be created. It is owing to this combination of oxidising and acidic character that mine waters are so corrosive. 

Ferric chloride solutions are particularly aggressive to high-chromium irons. Rates of attack greater than 12 mm/y have been recorded for a 25% solution at 20°C. The useful resistance of the alloys to mine waters which contain this salt is probably because the concentration involved is very much lower than this. 

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 ... 

Vapor-liquid equilibrium data and calculated values for the dietlnia-mine-water system. Calculations were done using parameters from unconstrained LS estimation [reprinted from Computers < Chemical Engineering with permission from Elsevier Science /. 

P.L. Younger, S.A. Banwart and R.S. Hedin Mine Water Hydrology, Pollution,... 

The sol-gel-entrapped microbial cells have shown excellent tolerance to different alcohols [99], The immobilized E. coli cells followed the Michaelis-Menten equation when quantified with the (3-glucosidase activity via the hydrolysis of 4-nitrophenyl-(3-D-galactopyranosdie [142], The sol-gel matrices doped with gelatin prevented the cell lysis, which usually occurs during the initial gelation process [143], Microorganisms are now widely used in the biosorption of different pollutants and toxicants. Bacillus sphaericus JG-A12 isolated from uranium mining water has been entrapped in aqueous silica nanosol for the accumulation of copper and uranium [144], Premkumar et al. [145] immobilized recombinant luminous bacteria into TEOS sol-gel to study the effect of sol-gel conditions on the cell response (luminescence). The entrapped and free cells showed almost the same intensity of luminescence (little lower), but the entrapped cells were more stable than the free cells (4 weeks at 4°C). This kind of stable cell could be employed in biosensors in the near future. 

Nordstrom, D. K., E. A. Jenne and J. W. Ball, 1979, Redox equilibria of iron in acid mine waters. In E. A. Jenne (ed.), Chemical Modeling in Aqueous Systems, American Chemical Society, Washington DC, pp. 51-79. 

Sources of arsenic contamination and remediation of mine water at the historical Glen Wills mining area in Northeast Victoria, Australia... 

KEYWORDS arsenic, mine water, tailings, Glen Wills, Australia... 

The majority of the As in mine water from the internal shaft occurs as As3+, with only a minor component of As5+ (Fig. 5). Iron and As are predominantly in solution in these waters. Water from the internal shaft oxidises as it flows from the sump to the storage dam, and the amount of Fe and As in solution drops sharply as As is absorbed onto precipitating ferrihydrite (Fig. 6). The dominant As species in the sump and dam is As5+. Natural attenuation through passive oxidation removes 98% of the As in solution from the mine waters. 

Fig. 5. Variation in As species during oxidation of mine waters from the internal shaft, Maude Mine. Measured values are indicated. From Nelson (2008).

Fig. 6. Scholler plot showing variation in dissolved metals during oxidation of Maude Mine water.

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