Metals bioleaching from electronic waste by Chromobacterium violaceum and Pseudomonads sp

Abstract

These days, electronic waste needs to be taken into consideration due to its materials content, but due to the heterogeneity of the metals present, reprocessing of electronic waste is quite limited. The bioleaching of metals from electronic waste was investigated by using cyanogenic bacterial strains (Chromobacterium violaceum, Pseudomonas aeruginosa and Pseudomonas fluorescens). A two-step bioleaching process was followed under cyanide-forming conditions for maximum metals mobilization. Both single and mixed cultures of cyanogenic bacteria were able to mobilize metals from electronic waste with different efficiencies. In all the flasks in which high metal mobilizations were observed, the consequent biomass productions were also high. Pseudomonas aeruginosa was applied in the bioleaching process for the first time and this achieved its bioleaching ability of mobilization of metals from electronic waste. Chromobacterium violaceum as a single culture and a mixture of C. violaceum and P. aeruginosa exhibited maximum metal mobilization. Chromobacterium violaceum was capable of leaching more than 79, 69, 46, 9 and 7% of Cu, Au, Zn, Fe and Ag, respectively at an electronic waste concentration of 1% w/v. Moreover, the mixture of C. violaceum and P. aeruginosa exhibited metals leaching of more than 83, 73, 49, 13 and 8% of total Cu, Au, Zn, Fe, and Ag, respectively. Precious metals were mobilized through bioleaching which might be considered as an industrial application for recycling of electronic waste in the near future.

Consideration of Influential Factors on Bioleaching of Gold Ore Using Iodide-Oxidizing Bacteria

“…In contrast, some microorganisms such as cyanogenic or amino acid-excreting microorganisms solubilize the elemental gold by the formation of gold-complexing metabolic products acting as biogenic lixiviants [13]. Bioleaching of gold by cyanogenic bacteria has been reported [17][18][19][20].…”

Phylogeny of Bacteria from Steelmaking Wastes and Their Acidic Enrichment Cultures

“…Previous studies reported bioleaching ability of Chromobacterium violaceum to mobilize diverse metals, including Zn, from solid and electronic materials [29] [30]. An unexpected result was the occurrence of a strong dominance of Escherichia in the TSC waste.…”

Gold biorecovery from e-waste: An improved strategy through spent medium leaching with pH modification

“…This observation corroborates a bioleaching study which showed an increase in pH (from 7 to 9) in two-step bioleaching at 1% w/v pulp density of ESM. (Pradhan and Kumar, 2012). In contrast to low pulp densities, pH gradually decreased to below 7 at higher pulp densities of 2% and 4%.…”

“…Faramarzi et al, 2004 obtained a maximum gold dissolution of 14.9% from shredded pieces of printed circuit board by C. violaceum in one-step bioleaching (where electronic scrap was added directly to the bacterial growth medium). Another study reported that C. violaceum leached 70% of gold from electronic scrap following a two-step bioleaching protocol (Pradhan and Kumar, 2012). A direct comparison of gold recoveries from bioleaching studies is difficult since the metal composition of ESM is heterogeneous and varies with age, origin, and manufacturer, and the acid digestion protocols used by different researchers are dissimilar.…”