Bioleaching of Metals from E-Waste Using Microorganisms: A Review

Abstract

The rapid and improper disposal of electronic waste (e-waste) has become an issue of great concern, resulting in serious threats to the environment and public health. In addition, e-waste is heterogenous in nature, consisting of a variety of valuable metals in large quantities, hence the need for the development of a promising technology to ameliorate environmental hazards associated with the indiscriminate dumping of e-waste, and for the recovery of metal components present in waste materials, thus promoting e-waste management and reuse. Various physico-chemical techniques including hydrometallurgy and pyrometallurgy have been employed in the past for the mobilization of metals from e-waste. However, these approaches have proven to be inept due to high operational costs linked to the consumption of huge amounts of chemicals and energy, together with high metal loss and the release of secondary byproducts. An alternative method to avert the above-mentioned limitations is the adoption of microorganisms (bioleaching) as an efficient, cost-effective, eco-friendly, and sustainable technology for the solubilization of metals from e-waste. Metal recovery from e-waste is influenced by microbiological, physico-chemical, and mineralogical parameters. This review, therefore, provides insights into strategies or pathways used by microorganisms for the recovery of metals from e-waste.

From E-Waste to High-Value Materials: Sustainable Synthesis of Metal, Metal Oxide, and MOF Nanoparticles from Waste Printed Circuit Boards

“…Redox is an approach that permits the conversion of insoluble metals into corresponding soluble metallic forms [ 65 ]. Next, the complexation mechanism, also referred to as the chelation mechanism, involves the formation of complexes between ligands and target metals within a solid matrix.…”

“…This leads to the creation of cyanides, organic acids, or siderophores, which play a crucial role in mobilizing metals from waste materials. Complexation typically follows acidolysis and is employed for extracting metals like silver, gold, iron, platinum, and palladium [ 8 , 65 , 66 ].…”

“…Conversely, low pulp density can impede productivity in large-scale applications. Optimal pulp densities of 0.5%, 1%, and 4% have been identified for the effective biorecovery of precious metals from e-waste [ 65 ].…”

“…Biosorption is a physicochemical process that involves interactions between biological surfaces or components and ions in a solution. It encompasses both living and nonliving biomass, as well as individual organic compounds, for the purpose of removing metals from e-waste through complexation, chelation, coordination, and ion exchange [ 65 , 72 ].…”

Editorial: Bioleaching and biorecovery of critical raw materials from secondary sources

“…Bioleaching has emerged as a sustainable and green technology for metal recovery and is an alternative to conventional extractive processes with a reduced effect on climate change (Mohan and Joseph, 2020 ). This approach has been used commercially for the extraction of metals from low-grade ores and attracts attention for applying innovative methods to mobilize critical metals from secondary sources (Castro et al, 2020 ; Danouche et al, 2024 ), such as e-wastes (Baniasadi et al, 2019 ; Adetunji et al, 2023 ), spent catalysts (Moosakazemi et al, 2023 ), fly ash, red mud (Hedrich and Schippers, 2021 ), and scraps (Ilyas et al, 2013 ), to contribute to the development of a circular economy.…”