Biotechnological valorisation of Spent Automotive Catalytic Converters: Marine microorganisms in PGE leaching and recovery

The recovery of Platinum Group Elements (PGE) from secondary sources, such as Spent Automotive Catalytic Converters (SACC), is crucial for sustainable resource management and reducing environmental impact. Marine microorganisms offer many promising biotechnological applications, but their use in PGE bioleaching and biorecovery has been poorly explored. This study investigates the potential of SACC-tolerant marine microorganisms for platinum (Pt), palladium (Pd), and rhodium (Rh) bioleaching and their ability to recover Pt(II) from a synthetic solution containing its chloride salt. SACC media enrichments led to the isolation of 21 strains from marine coastal sediments. Screening for pH and Pt tolerance identified two acid-tolerant strains and a Maximum Tolerance Concentration (MTC) of 800 mg/l to K2PtCl4. The best-performing strains, belonging to the Microbacterium genus, could solubilise 27.3 % Pt, 8 % Pd, and 6.6 % Rh at circumneutral pH (7.0). The same microorganisms were able to bio-recover up to 92 % of the available Pt(II). These findings provide new insights into exploiting marine microorganisms in mining applications for eco-friendly and efficient SACC management and recovery.