Abstract
In recent years, the demand for lithium-ion batteries (LIBs) has been increasing rapidly. Conventional recycling strategies (based on pyro- and hydrometallurgy) are damaging for the environment and more sustainable methods need to be developed. Bioleaching is a promising environmentally friendly approach that uses microorganisms to solubilize metals. However, a bioleaching-based technology has not yet been applied to recover valuable metals from waste LIBs on an industrial scale. A series of experiments was performed to improve metal recovery rates from an active cathode material (LiCoO2; LCO). (i) Direct bioleaching of ≤0.5 % LCO with two prokaryotic acidophilic consortia achieved >80 % Co and 90 % Li extraction. Significantly lower metal recovery rates were obtained at 30 °C than at 45 °C. (ii) In contrast, during direct bioleaching of 3 % LCO with consortia adapted to elevated LCO levels, the 30 °C consortium performed significantly better than the 45 °C consortium, solubilizing 73 and 93 % of the Co and Li, respectively, during one-step bioleaching, and 83 and 99 % of the Co and Li, respectively, during a two-step process. (iii) The adapted 30°C consortium was used for indirect leaching in a low-waste closed-loop system (with 10 % LCO). The process involved generation of sulfuric acid in an acid-generating bioreactor (AGB), 2-3 week leaching of LCO with the biogenic acid (pH 0.9), selective precipitation of Co as hydroxide, and recirculation of the metal-free liquor back into the AGB. In total, 58.2 % Co and 100 % Li were solubilized in seven phases, and >99.9 % of the dissolved Co was recovered after each phase as a high-purity Co hydroxide. Additionally, Co nanoparticles were generated from the obtained Co-rich leachates, using Desulfovibrio alaskensis, and Co electrowinning was optimized as an alternative recovery technique, yielding high recovery rates (91.1 and 73.6% on carbon felt and roughened steel, respectively) from bioleachates that contained significantly lower Co concentrations than industrial hydrometallurgical liquors. The closed-loop system was highly dominated by the mixotrophic archaeon Ferroplasma and sulfur-oxidizing bacteria Acidithiobacillus caldus and Acidithiobacillus thiooxidans. The developed system achieved high metal recovery rates and provided high-purity solid products suitable for a battery supply chain, while minimizing waste production and the inhibitory effects of elevated concentrations of dissolved metals on the leaching prokaryotes. The system is suitable for scale-up applications and has the potential to be adapted to different battery chemistries.
Original language | English |
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Number of pages | 18 |
Journal | Microbiology |
Volume | 170 |
Issue number | 7 |
DOIs | |
Publication status | Published - 17 Jul 2024 |
Bibliographical note
This is an open- access article distributed under the terms of the Creative Commons Attribution License. This article was made open access via a Publish and Read agreement between the Microbiology Society and the corresponding author’s institution. CC BYFunder
Illumina sequencing was performed within the Centre of Environmental Biotechnology Project [Bangor University (BU), UK] funded by the European Regional Development Fund (ERDF) through the Welsh Government; we particularly acknowledge the assistance provided by Marco Distaso, Rafael Bargiela, Gwion Williams, and Constance Tulloch (all BU). We would also like to thank Steve Mitchell (BioSem) for assistance with TEM (Welcome Trust Multi User Equipment Grant Nu. WT104915MA), Fraser Laidlaw for STEM image acquisition (the Zeiss Crossbeam Cryo FIB/SEM used was provided by the EPSRC grant no. EP/P030564/1), and Lorna Eades for ICP-OES analysis (all University of Edinburgh, UK). This research was supported by the Faraday Institution ReLiB project (grant codes FIRG005, FIRG027 and FIRG057) and an EPSRC fellowship (EP/N026519/1).Keywords
- bioleaching
- closed-loop metal recycling
- cobalt electrowinning
- lithium-ion batteries
- nanoparticles
ASJC Scopus subject areas
- Microbiology