Leaching of indium from end-of-life LCD panels via catalysis by synergistic microbial communities

Highlights: • Three types of pathways were used to extract indium from end-of-life LCD panels. • The S-mediated pathway was demonstrated to be a promising method for bioleaching indium due to the ideal efficiency attained. • The concept of combining S-mediated leaching of indium with existing pathways was reported. -- Abstract: Currently, a large amount of discarded liquid crystal displays (LCDs) are being produced, and the improper treatment of discarded LCDs causes serious environmental pollution problems. Indium is the most valuable metal in LCDs and is present in such devices at a concentration of over 0.025%. In this study, the bioleaching of indium from end-of-life LCD panels was comprehensively investigated through three methods: S-mediated pathway, Fe-mediated pathway and Mixed pathway of S- and Fe-mediated, which yielded maximum bioleaching efficiencies of approximately 100%, 0% and 78%, respectively. Microbial community analysis showed that the dominant functional bacteria under the S-mediated pathway were Acidithiobacillus. The Acidithiobacillus genus catalysed the leaching of indium, which was mainly achieved by indirect bioleaching. In addition, the microorganisms can secrete enzymes and extracellular polymeric substances, which also contributed to the leaching of indium. Therefore, this work provides an economical and efficient biological method for future research and practical applications in indium recovery from solid waste.