Bioleaching of metals from spent catalysts for metal removal/recovery

Abstract

The objective of the project is to apply a microbial leaching process (a??bioleachinga??) for the mobilization and recovery of metals from spent catalysts. In this work, bioleaching of spent fluid catalytic cracking (FCC) catalyst using Aspergillus niger and spent hydroprocessing catalyst using the heterotrophic fungi; Aspergillus niger, Penicillium simplicissimum and autotrophic bacteria; Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans were investigated. Chemical leaching using citric, oxalic, gluconic, and sulphuric acid, and ferric chloride at concentrations equal to the acids produced in the bioleaching processes were also carried out and compared with bioleaching. It was shown that bioleaching realised higher metal extraction than chemical leaching. Extraction efficiency generally decreased with increased pulp density. Compared with abiotic controls, bioleaching gave rise to higher metal extractions than leaching using fresh medium and cell-free spent medium.