Reduced product lifecycle and increasing demand for electronic devices have resulted in the generation of huge volumes of electronic waste (e-waste). E-wastes contain high concentrations of toxic heavy metals, which have detrimental effects on health and the environment. However, e-wastes also contain significant concentrations of precious metals such as gold, silver and palladium, which can be a major driving force for recycling of urban waste. Cyanogenic bacteria such as Chromobacterium violaceum generate cyanide as a secondary metabolite which mobilizes gold into solution via a soluble gold-cyanide complex. However, compared to conventional technology for metal recovery, this approach is not effective, owing largely to the low concentration of lixiviants produced by the bacteria. To overcome the challenges of bioleaching of gold from e-waste, several strategies were adopted to enhance gold recovery rates. These included (i) pretreatment of e-waste to remove competing metal ions, (ii) mutation to adapt the bacteria to high pH environment, (iii) metabolic engineering to produce higher cyanide lixiviant, and (iv) spent medium leaching with adjusted initial pH. Compared to 7.1 % recovery by the wild type bacteria, these strategies achieved gold recoveries of 11.3%, 22.5%, 30% and 30% respectively at 0.5% w/v pulp density respectively. Bioleached gold was finally mineralized and precipitated as gold nanoparticles using the bacterium Delftia acidovorans. This study demonstrates the potential for enhancement of biocyanide production and gold recovery from electronic waste through different strategies, and extraction of solid gold from bioleached leachate.
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20 January 2017
PROCEEDINGS OF THE 1ST INTERNATIONAL PROCESS METALLURGY CONFERENCE (IPMC 2016)
10–11 November 2016
West Java, Indonesia
Research Article|
January 20 2017
Bio-extraction of precious metals from urban solid waste
Subhabrata Das;
Subhabrata Das
Department of Chemical and Biochemical Engineering, Faculty of Engineering,
National University of Singapore
, 4 Engineering Drive 4, Singapore
117585
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Gayathri Natarajan;
Gayathri Natarajan
Department of Chemical and Biochemical Engineering, Faculty of Engineering,
National University of Singapore
, 4 Engineering Drive 4, Singapore
117585
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Yen-Peng Ting
Yen-Peng Ting
*
Department of Chemical and Biochemical Engineering, Faculty of Engineering,
National University of Singapore
, 4 Engineering Drive 4, Singapore
117585
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*
Corresponding author: [email protected]
AIP Conf. Proc. 1805, 020004 (2017)
Citation
Subhabrata Das, Gayathri Natarajan, Yen-Peng Ting; Bio-extraction of precious metals from urban solid waste. AIP Conf. Proc. 20 January 2017; 1805 (1): 020004. https://doi.org/10.1063/1.4974410
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