Bioleaching of Al from spent fluid catalytic cracking catalyst using Aspergillus species

Bioleaching uses biodegradable organic acids, thereby making the process environmental friendly as compared to chemical leaching. In this work, bioleaching of aluminium (Al) metal from spent catalyst was investigated by using three Aspergillus strains (A. niger, A. foetidus, and A. carbonarius). Bioleaching was performed in batch culture mode at different loading densities of spent catalyst (i.e., 0.4%, 0.8% and 1.2% (w/v)). The highest Al leaching efficiency of 88.43% was obtained at 0.8% ((w/v)) catalyst loading using A. foetidus, further increase in the catalyst loading decreased the efficiency. In addition to this, molasses was used as a carbon source (low-cost) at various concentrations for bioleaching of spent catalyst and the results were found to be significant at 40 g/L sugar concertation with 60% bioleaching efficiency. Overall, this study indicates that A. foetidus have the potential for leaching of Al from spent catalysts. Therefore, present research findings suggested that, instead of using mineral acids, organic acids (biodegradable) usage for metal leaching process is highly reliable and eco-friendly as well.