Current Research Trends of Microbiological Leaching for Metal Recovery from Industrial Wastes

The concept of microbiological leaching have played a greater role to recover valuable metals from various sulfide minerals or low grade ores during the middle era of twentieth century and that continued till the end of the century. Slowly, due to depletion of ore/minerals, and implementation of stricter environmental rules, microbiological leaching process has been shifted for its application to recover valuable metals from the different industrial wastes. Although there are conventional processes, physical and chemical methods, for treatment of industrial wastes, these technologies have certain limitation in practical applications. The microbial method is an efficient and cost!effective alternative to chemical and physical methods because of its low demand for energy, material and less generation of waste byproduct. There are several industrial wastes that possess toxic elements and thus when leached into atmosphere cause serious environmental problem. Among the wastes, spent petroleum catalysts, electronic scraps, lithium battery wastes, sewage sludge, fly ash etc. are some of the major industrially produced wastes. These solid wastes mostly contain Ni, V, Mo, Co, Cu, Pb, Zn, and Cr like heavy metals in it. The major microorganisms those play the significant role in recovery of heavy metals from such wastes belong to acidophilic group. These acidophilic groups thrive in acidic pH ranges (pH 2.0 – 4.0) and help in dissolving the metals from solid phase of wastes into the aqueous phase. Among the bacteria Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans, Leptospirillum ferrooxidans, and Sulfolobus sp., are well known consortia for the bioleaching activity while Penicillium, and Aspergillus niger are some fungi those help in metal leaching process. The current chapter will be thoroughly studied about the application of these acidophilic microorganisms for the metal recovery from different industrial wastes. The key microorganisms and their bioleaching mechanism have been focused here.