Metal extraction, using bacteria

II, Metal Extraction Using Bacteria The Basic Principles... 

The pK of Ca2+aq (204), 12.6 at zero ionic strength, rising to over 13 as ionic strength increases, means that concentrations of CaOH+aq will be negligible in body fluids (lpolluted waters, and under all conditions of biological relevance, from the very low pHs of 0.5 (Thiobacillus thiooxidans) to 1.5 at which bacteria used for oxidative metal extraction operate (205), through acid soils and acid rain (pH 3 to 6), streams, rivers, and oceans (pH 6 to 8), soda lakes (pH 10), up to the pHs of 11 or more in Jamaican Red Mud slurry ponds (206) (cf. Section II.C.l below). 

The Extraction of Metals from Ores Using Bacteria... 

THE EXTRACTION OF METALS FROM ORES USING BACTERIA... 

Ewart, D. K., and Hughes, M. N. (1991). The extraction of metals from ores using bacteria. Adv. Inorg. Chem. 36, 103-135. 

After crude ores are mined, they are crushed and then the metals are extracted by chemical treatment or by heating to high temperatures. Another way to extract metals from ore is to use bacteria to do part of the job. This method is less damaging to the environment, costs less in terms of energy input, and offers a way to use low-grade ores productively. Today, 24 percent of the copper produced is the result of bioprocessing by bacteria. 

Metals associated with organic materials, inert compounds, or iron oxides may not be recovered during the extraction phase of the technology. Complexed hexavalent uranium has been shown to inhibit the growth of one strain of bacteria used for remediation. The effect becomes more pronounced at higher concentrations of uranium. 

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