Emergence of Bio-hydrometallurgy to Achieve Sustainable Process Development Goals in Extractive Metallurgy

The stringent environmental regulations and growing awareness of the low-carbon economy are presenting immense challenges to metallurgical operations, one of the major sectors with high emissions. Hydrometallurgy has been identified as a lower-emission technology in comparison to the high-temperature smelting and melt-refining processes. The close monitoring of traditional hydrometallurgical operations, however, does not fulfil the criteria for a sustainable, low-emission process. Recently, biotechnology has emerged as a green alternative within the hydrometallurgical domain, albeit significantly different from the basics involved in the process. Although the application of microbial activity has been successfully established in chalcopyrite leaching and bio-oxidation of gold-bearing minerals, the acceptability of bio-hydrometallurgy for other minerals and materials is still limited due to a wide research gap to connect solution chemistry, microbial activity, and extractive metallurgy. In general, a large portion of the total chemical consumption occurs in pre-treatment and/or leaching operations; hence, the primary application of microorganisms at the forefront can significantly minimize the overall consumption. Demonstrated applications in waste printed circuit boards and spent automobile catalysts have curtailed excessive acid usage, while the energy-intensive baking/roasting of monazite is successfully altered by microbial processing. Furthermore, the remarkable reduction in carbon footprints by the green biotechnology application in hydrometallurgy has been evaluated, which indicates sustainability in process metallurgy.