Microbiological leaching of metals and its recovery from waste electrical and electronic equipment: a review
01 Apr 2019-World Review of Science, Technology and Sustainable Development (Inderscience Publishers)-Vol. 15, Iss: 1, pp 1-16
TL;DR: In this article, the authors mainly focused on e-waste generation, mechanisms of bio-leaching and various microorganisms employed for the extraction of metals from the electronic waste.
Abstract: Electronic waste or waste electrical and electronic equipment (WEEEs) is an emerging and fast-growing waste stream with complex characteristics. As per United Nations 'Global E-waste Monitor report, 2015' (Balde et al., 2014), the global quantity of total e-waste generated in 2014 was around 41.8 million metric tonnes (MT). The presence of metals like copper, aluminium, iron and various precious metals like gold, silver, palladium, platinum, etc., in high concentrations, made e-waste an 'urban mine'. Bioleaching is one of the successful bio-hydrometallurgical method, which can be employed for metal recovery from different WEEEs. Recovery of precious metals like copper, gold and silver is possible at high concentrations from WEEEs using acidophilic mesophiles and thermophiles and some fungal species. The current paper mainly aims to reflect on e-waste generation, mechanisms of bioleaching and various microorganisms employed for the extraction of metals from the electronic waste.
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TL;DR: In this article, the acidithiobacillus ferrooxidans was used to extract copper from printed circuit boards at laboratory scale using shake flasks and the effect of initial pH, amount and size of printed circuit board, and volume of inoculum on copper dissolution rates were evaluated.
Abstract: Computer circuit boards are a major electronic waste containing higher concentrations of copper, gold and silver. These metals may be recovered by bioleaching, an eco-friendly process to recover metals from natural ores. However, the application of the bioleaching to electronic waste is still in the infancy stage. Here, the bioleaching capability of Acidithiobacillus ferrooxidans to extract copper from printed circuit boards was investigated at laboratory scale using shake flasks. The effect of initial pH, amount and size of printed circuit boards, and volume of inoculum on copper dissolution rates were evaluated. Results show that the highest dissolution rate of 32.44% was achieved after 7 days of leaching at initial pH 2.0, 10 g/L of waste printed circuit board, 40% v/v of inoculum for 1 mm size of circuit board. The smallest size of 1 mm induces the higher dissolution rates, which is explained by higher surface area and thus better bacterial adhesion. Also, the copper dissolution rates increase with the inoculum volume. Overall, bioleaching of copper from waste printed circuit boards using Acidithiobacillus ferrooxidans is achievable.
18 citations
Cites background from "Microbiological leaching of metals ..."
...Personal computers with a usual lifespan of 5–8 years constitute for the larger amount of wastes in this category (Gurumurthy and Annamalai 2019)....
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...Personal computers with a usual lifespan of 5–8 years constitute for the larger amount of wastes in this category (Gurumurthy and Annamalai 2019)....
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TL;DR: Results from the study indicated that MPCBs can serve as an excellent secondary source for various metals and as an efficient alternative fuel.
Abstract: Globally, waste electrical and electronic equipment is one of the fastest-growing waste sectors. Mobile phones constitute the major portion of the telecommunication e-waste category. Over the years...
13 citations
Cites background from "Microbiological leaching of metals ..."
...…of metal content among different size MPCB fractions is investigated to suggest the best MPCB fraction size for metal recovery through different recovery techniques including pyrometallurgy, hydrometallurgy, and biohydrometallurgy (Annamalai and Gurumurthy 2019; Gurumurthy and Annamalai 2019)....
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22 Feb 2020
TL;DR: The predicted data showed that there is a great capability of using ANN for the prediction of Cu, Ag, and Au extraction from CPCB through bioleaching process, and the ANN model can be used to control the operational conditions for improved metals extraction throughBioleaching.
Abstract: The applicability of artificial neural network (ANN) to predict the bioleaching of metals using from computer printed circuit boards (CPCB) and the influence of process parameters were studied. The influence of process parameters initial pH (1.6‐2.4), pulp density (2%‐13%), and the initial volume of Inoculum (5%‐25%) were investigated on the rate of bioleaching of metals from CPCB. Network inputs were fed as initial pH, pulp density, and inoculum volume and with the extraction of Cu, Ag, and Au as output. The ANN was developed using the Levenberg‐Marquardt algorithm and trained for modeling and prediction. The most fitting architectures for Cu, Ag, and Au were [4‐5‐5‐2‐1], [4‐7‐5‐2‐1], [4‐7‐1‐1‐1] trained with Levenberg‐Marquardt algorithm, respectively. The R values were observed to be 0.996, 0.997, and 0.993 for Cu, Ag, and Au extraction predictions, respectively. The genetic algorithm model defined by ANN was used to achieve maximum extraction rates for Cu, Au, and Ag. The predicted data showed that there is a great capability of using ANN for the prediction of Cu, Ag, and Au extraction from CPCB through bioleaching process. Hence, the ANN model can be used to control the operational conditions for improved metals extraction through bioleaching.
4 citations
Cites background from "Microbiological leaching of metals ..."
...While in Equations (2), (3), (4), Y Cu, Y Ag, and Y Au are the fitness values of GA equivalent to Cu, Ag, and Au, respectively, while dCu, dAg, and dAu represent the extraction rates for Cu, Ag, and Au, respectively....
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TL;DR: In this article , the authors reviewed the mechanisms involved in the process of bio-leaching, the microorganisms employed, methods used and various developments as well as limitations along with recent advances and future prospects of the process bioleaching of metals from WEEE.
Abstract: Abstract: After the computer and mobile revolution, electric and electronic waste had become a serious threat to urban and rural communities equally. Prevention of the hazardous exposure and proper management are challenging in developing nations. One way to turn the crisis to opportunity is to extract metals from this Waste Electronic and Electric Equipment (WEEE) is making waste into a source of metal ores. The involvement of microbes in this technology could increase the boons by being an eco-friendly technique for reducing the hazardous nature. This article reviews the mechanisms involved in the process of bioleaching, the microorganisms employed, methods used and various developments as well as limitations along with recent advances and future prospects of the process of bioleaching of metals from WEEE.