Biosorption and Bioleaching of Heavy Metals from Electronic Waste Varied with Microbial Genera

Abstract

Industrialization and technological advancements have led to the exploitation of natural resources and the production of hazardous wastes, including electronic waste (E-waste). The traditional physical and chemical techniques used to combat E-waste accumulation have inherent drawbacks, such as the production of harmful gases and toxic by-products. These limitations may be prudently addressed by employing green biological methods, such as biosorption and bioleaching. Therefore, this study was aimed at evaluating the biosorption and bioleaching potential of seven microbial cultures using E-waste (printed circuit board (PCB)) as a substrate under submerged culture conditions. The cut pieces of PCB were incubated with seven microbial cultures in liquid broth conditions in three replicates. Atomic absorption spectroscopy (AAS) analysis of the culture biomass and culture filtrates was performed to evaluate and screen the better-performing microbial cultures for biosorption and bioleaching potentials. The best four cultures were further evaluated through SEM, energy-dispersive X-ray spectroscopy (EDX), and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) studies to identify the possible culture that can be utilized for the biological decontamination of E-waste. The study revealed the highest and differential ability of Pleurotus florida and Pseudomonas spp. for biosorption and bioleaching of copper and iron. This can be attributed to bio-catalysis by the laccase enzyme. For both P. florida and Pseudomonas spp. on the 20th day of incubation, laccase exhibited higher specific activity (6.98 U/mg and 5.98 U/mg, respectively) than other microbial cultures. The biomass loaded with Cu2+ and Fe2+ ions after biosorption was used for the desorption process for recovery. The test cultures exhibited variable copper recovery efficiencies varying between 10.5 and 18.0%. Protein characterization through SDS-PAGE of four promising microbial cultures exhibited a higher number of bands in E-waste as compared with microbial cultures without E-waste. The surface topography studies of the E-waste substrate showed etching, as well as deposition of vegetative and spore cells on the surfaces of PCB cards. The EDX studies of the E-waste showed decreases in metal element content (% wt/% atom basis) on microbial treatment from the respective initial concentrations present in non-treated samples, which established the bioleaching phenomenon. Therefore, these microbial cultures can be utilized to develop a biological remediation method to manage E-waste.

Extraction of Metals from Polluted Soils by Bioleaching in Relation to Environmental Risk Assessment

“…The same can be observed for Cu (39–72%), and when using Acidithiobacillus , Sulfobacillus and Ferroplasma , where Cu amounts to 27% [ 69 ], Pleurotus florida (18%) and Pseudomonas spp. (16.6%) [ 70 ].…”

Characterization and Optimization of Polymeric Bispicolamine Chelating Resin: Performance Evaluation via RSM Using Copper in Acid Liquors as a Model Substrate through Ion Exchange Method

“…There have been many studies investigating the use of different physicochemical methods in removal, reuse and recovery of copper from electronic waste, such as adsorption [ 13 , 14 , 15 , 16 ], incineration [ 17 ], landfill dumping [ 18 ], advanced/chemical oxidation [ 19 ] and precipitation [ 20 ]. Although such approaches could minimize the effect of electronics waste, they nonetheless have limitations [ 21 ] and lack cost-effectiveness. On the other hand, Igiri et al [ 22 ] reported bioleaching that is an eco-friendly technology as a circular economy for extracting valuable divalent metals such as Cu(II) ions from electronic waste [ 23 , 24 , 25 ].…”

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

“…It is an emerging physico-chemical adsorption technique that utilizes certain types of inactive, dead, or viable microbial biomass for the removal of metals from e-waste through complexation, chelation, coordination, and ion-exchange between the metals [12,39]. The microbial cell wall consists of many functional groups, including a carbonyl, phosphodiester, sulfonate, and phosphate group, that are needed for sequestering metals present in e-waste [106,107]. Biomass of several fungal, bacterial, and algal species has been used as a biosorbent for the recovery of heavy metals, precious metals, and rare earth metals from e-waste [12].…”