Gold leaching from ores using biogenic lixiviants – A review

Abstract

• The extraction of gold from ores by biosynthesized reagents is discussed. • The use of cyanogenic bacteria for extracting gold is reviewed and discussed. • The ability of iodide-oxidizing bacteria (IOB) on the solubilization of gold is examined. • The capability of organic compounds of microbial origin on the dissolution of gold is reviewed. • The benefits and drawbacks of microbial gold leaching over traditional cyanide-based gold leaching are discussed. The recovery of gold from different sources, such as ores and concentrates, commonly is carried out in industry using cyanidation because it has the advantage of high selectivity of gold over other elements. However, cyanidation has some technical, economic, and environmental limitations. Therefore, investigations have been conducted of new hydrometallurgical approaches for recovering gold from gold-bearing ores by using cheap, non-toxic, and effective reagents, such as biogenic lixiviants. In this paper, we summarize the research that has been conducted on applying biogenic reagents, such as biogenic cyanide, iodine, and triiodide, and organic compounds, such as amino acids, for the extraction of gold from ores. The use of cyanogenic bacteria, such as Chromobacterium violaceum ( C. violaceum ), Pseudomonas aeruginosa ( P. aeruginosa ), Bacillus megaterium ( B. megaterium ), and Micrococcus species ( sp.) , for extracting gold is reviewed and discussed. Also, this work reviews the ability of iodide-oxidizing bacteria (IOB), such as Roseovarius tolerans , on oxidizing iodide (I − ) to iodine (I 2 ) and triiodide (I 3 − ) and the solubilization of gold as gold diiodide and gold tetraiodide. The capabilities of organic compounds of microbial origin, such as amino acids, on the dissolution of gold also are reviewed and discussed. The advantages, disadvantages, and limitations of microbial leaching of gold over traditional cyanide-based gold leaching are presented. Recommendations for further studies are provided.