Enhancement of gold and silver recovery from discarded computer printed circuit boards by Pseudomonas balearica SAE1 using response surface methodology (RSM)

Abstract

Two-step bioleaching was applied using a cyanogenic bacterium SAE1 to recover gold (Au) and silver (Ag) from the computer printed circuit boards (CPCBs) via central composite design of a response surface methodology (CCD-RSM). To enhance Au and Ag recovery, factors like pH level, pulp density, temperature and glycine concentration were optimized and their interactions were studied. CCD-RSM optimization resulted in 73.9 and 41.6% dissolution of Au and Ag, respectively, at initial pH 8.6, pulp density 5 g/L, temperature 31.2 °C, and glycine concentration 6.8 g/L, respectively. Two quadratic models were proposed by RSM which can be utilized as an efficient tool to predict Au and Ag recovery through bioleaching. The experimental results are in line with the predicted results, indicating reliability of RSM model in enhancing the Au and Ag recovery from CPCBs. The increased bioleaching yield of Au and Ag from discarded CPCBs has its importance in industrial e-waste recycling and safe disposal.

Microbial biominers: Sequential bioleaching and biouptake of metals from electronic scraps

“…In this study, we observed the leaching of small amounts of Au on day 7, in contrast with other acidophilic bacteria bioleaching studies (Marra et al, 2018 ). Gold mobilization from e‐scraps and waste electrical and electronic equipment (WEEE) has been mainly performed via complexolysis, a mechanism mediated by heterotrophic cyanogenic microorganisms (Arshadi et al, 2016 ; Kumar et al, 2018 ; Pradhan & Kumar, 2012 ).…”

“…Higher e-scraps concentrations (5%-20% w/v) have been assessed to increase the yield, however, they also observed toxic effects on non-adapted cultures and unwashed e-scraps (Natarajan & Ramanathan, 2015;Shaikh Shafikh et al, 2018) observed the leaching of small amounts of Au on day 7, in contrast with other acidophilic bacteria bioleaching studies (Marra et al, 2018). Gold mobilization from e-scraps and waste electrical and electronic equipment (WEEE) has been mainly performed via complexolysis, a mechanism mediated by heterotrophic cyanogenic microorganisms (Arshadi et al, 2016;Kumar et al, 2018;Pradhan & Kumar, 2012).…”

Neural network prediction of bioleaching of metals from waste computer printed circuit boards using Levenberg‐Marquardt algorithm

“…The influence of the change of process parameters on bioleaching of metals from e-waste has been widely explored by several authors using acidophilic and mesophilic bacteria. 14,39,40 The effect of pH, pulp density, and inoculum volume was observed to have a significant effect on the extraction rates of metals from CPCBs. 31,41 Hence, optimization of the operational conditions to enhance the extraction rate of Cu, Ag, Figure 11 shows training, validation, and test mean squared error and the linear regression analysis between measured (T) and predicted (Y) values for extraction rates of Cu, Ag, and Au.…”

Exploring bioleaching potential of indigenous Bacillus sporothermodurans ISO1 for metals recovery from PCBs through sequential leaching process

“…Considering previous studies, incubation temperature, pH, e-waste amount (i.e. pulp density), glycine concentration and time are the major factors which affect the bioleaching process of bacterial strains (Kumar et al 2018b); therefore, these factors were optimized in the present study for maximum recovery of metals via OFAT method. The optimization was initiated at 37 °C with 4% (v/v) inoculum, 130 rpm for 48 hours incubation period.…”

“…Biohydrometallurgy is an alternative method which has been explored in the past few years to mobilize metals from their mine sources as well as e-waste. Biohydrometallurgy is a microbe-mediated method, known as 'bioleaching' that encompasses benefits like less energy consumption, economic, eco-friendly, easy in operation, etc., and therefore considered as green technology for treating mine wastes and e-waste (de Andrade et al 2019;Marra et al 2018;Kumar et al 2018aKumar et al , 2018b. The sulphur-reducing and cynogenic microorganisms such as Acidithiobacillus ferrooxidans and Chromo bacterium violaceum are the foremost microorganisms exploited for metals extraction from numerous mineral sulphide ores and oxidic wastes (Arshadi et al 2019).…”