Advances in bioleaching of waste lithium batteries under metal ion stress

Abstract

In modern societies, the accumulation of vast amounts of waste Li-ion batteries (WLIBs) is a grave concern. Bioleaching has great potential for the economic recovery of valuable metals from various electronic wastes. It has been successfully applied in mining on commercial scales. Bioleaching of WLIBs can not only recover valuable metals but also prevent environmental pollution. Many acidophilic microorganisms (APM) have been used in bioleaching of natural ores and urban mines. However, the activities of the growth and metabolism of APM are seriously inhibited by the high concentrations of heavy metal ions released by the bio-solubilization process, which slows down bioleaching over time. Only when the response mechanism of APM to harsh conditions is well understood, effective strategies to address this critical operational hurdle can be obtained. In this review, a multi-scale approach is used to summarize studies on the characteristics of bioleaching processes under metal ion stress. The response mechanisms of bacteria, including the mRNA expression levels of intracellular genes related to heavy metal ion resistance, are also reviewed. Alleviation of metal ion stress via addition of chemicals, such as spermine and glutathione is discussed. Monitoring using electrochemical characteristics of APM biofilms under metal ion stress is explored. In conclusion, effective engineering strategies can be proposed based on a deep understanding of the response mechanisms of APM to metal ion stress, which have been used to improve bioleaching efficiency effectively in lab tests. It is very important to engineer new bioleaching strains with high resistance to metal ions using gene editing and synthetic biotechnology in the near future.

Keywords: Biofilm; Bioleaching; Electrochemistry; Metal ion stress; Waste lithium battery.

Fig. 1

Commercial-scale BIOX® bioleaching process in Barberton, South Africa (Kaksonen et al. 2014). [Image courtesy of Dr. Anna H Kaksonen, The Commonwealth Scientific and Industrial Research Organization, Australia]

Fig. 2

Examples of bioleaching applications

Fig. 3

A process flowsheet for bioleaching WLIB

Fig. 4

Bioleaching performance by contact and non-contact microbial cell

Fig. 5

Various detoxification mechanisms for microorganisms under metal

Fig. 6

SEM (left) and CLSM (right) images of A. caldus SM-1 biofilm on S32654 SASS steel coupon surface [Dong et al. 2018]

Fig. 7

Tafel polarization curves of pyrite working electrode with and without biofilm coverage 7 days after Li⁺/Co2⁺ addition to simulate metal ion stress in bioleaching [Liu et al. 2022]

Fig. 8

A putative mechanism model for S. thermosulfidooxidans adaptation to Ni2⁺ stress [Chen et al. 2022]