Enhanced bioleaching efficiency of metals from E-wastes driven by biochar

Area of Science:

• Environmental Science and Engineering
• Biotechnology and Bio-based Materials

Background:

• Electronic wastes (e-wastes) contain valuable metals, necessitating efficient recycling methods.
• Bioleaching offers an eco-friendly and cost-effective approach for metal recovery from e-wastes.
• Conventional bioleaching can be slow and inefficient, requiring optimization.

Purpose of the Study:

• To investigate the use of redox-active biochar for enhancing metal bioleaching efficiency from printed circuit boards (PCBs).
• To elucidate the mechanisms by which biochar influences carbon-, sulfur-, and iron-mediated bioleaching pathways.
• To assess the impact of biochar on the microbial community and its role in metal recovery.

Main Methods:

• Experimental bioleaching of PCBs using different mediated pathways (C, S, Fe) with and without biochar.
• Monitoring of metal leaching kinetics, particularly copper (Cu) and iron (Fe) species (Fe(II)/Fe(III)).
• Analysis of microbial populations (Alicyclobacillus spp. and Sulfobacillus spp.) and their dynamics.

Main Results:

• Biochar significantly enhanced Fe-mediated bioleaching, reducing leaching time by one-third compared to biochar-free systems.
• Biochar facilitated the Fe(II)/Fe(III) redox cycle, promoting efficient copper leaching.
• Biochar regulated the ratio of key microbial species (Alicyclobacillus spp. and Sulfobacillus spp.), enhancing bioleaching efficiency.

Conclusions:

• Redox-active biochar is an effective additive for improving the efficiency of iron-mediated bioleaching of metals from e-wastes.
• Biochar acts as a solid redox mediator, accelerating the crucial iron redox cycle in the bioleaching process.
• This study presents a low-cost, sustainable method for enhancing metal recovery from electronic waste.