Bio-Hydrometallurgy of Electronic Waste: Extraction of Precious Metals by Cyanogenic Microorganisms and Influencing Factors

Extracting of precious metals from electronic waste (e-waste), such as waste printed circuit boards (WPCBs), contributes toenvironmental sustainability while offering high recovery rates and significant profitability. If improperly disposed of, Ewaste contains heavy and toxic metals that can leach into groundwater and rainwater, eventually entering the human foodchain. On the other hand, e-waste is also a rich source of precious metals, particularly gold (Au). One of the most effectivemethods for recovery from e-waste is bio-hydrometallurgy, which utilizes microorganisms to enhance recovery efficiency,ensure environmental compatibility, and reduce energy consumption. The indirect bioleaching method is employed in thecase of precious metal extraction from e-waste. This process requires bacteria or fungi capable of producing cyanogeniccompounds, including bacterial species such as Chromo-bacteriu-mviolaceum, Bacillus megaterium, Pseudomonasfluorescens, and Pseudomonas plecoglossicida, as well as fungal species such as Marasmiusoreades, Clitocybe sp., andPolysporus sp. Several factors influence bioleaching efficiency by cyanogenic microorganisms, including pulp density, pH,waste particle size, temperature, dissolved oxygen (DO), cyanide concentration, and production rate. Among these, pulpdensity, pH, DO, and cyanide content are more critical than waste particle size and temperature.

کلیدواژه ها:

E-Waste Recycling ، Precious Metal Extraction ، Bio-Hydrometallurgy ، Bioleaching