Paper Title
Feasibility of Bioleaching and Acid Leaching in Recovery of Metals from Raw Spent Petroleum Refinery Catalyst

Abstract
Spent petroleum refinery catalysts have been designated as hazardous by the USEPA. In the recent years, microorganism-based leaching (bioleaching) has gained acceptance as an efficient, eco-friendly, and cost-effective method for recovery of metals form spent petroleum catalyst. In the current work, batch studies of bioleaching of metals (Al, Ni and Mo) from raw petroleum spent catalyst were conducted using chemoautotrophic Acidithiobacillus ferrooxidans. In addition, acid leaching using sulfuric acid was also conducted. The raw spent catalyst used in the current study was found to contain significant concentrations of Al (90.7 mg/g), Ni (14.4 mg/g), and Mo (82.5 mg/g). A scanning electron microscope (SEM) also confirmed the presence of these metals. Shake flasks bioleaching experiments using Acidithiobacillus ferrooxidans were conducted in 0K media (initial pH 1.8) having 4 g/L ferrous as an energy source and 1% (w/v) spent catalyst. An acid leaching test using sulfuric acid was also conducted under similar experimental conditions. All the experiments were conducted for 14 days and changes in pH and bioleaching yields were monitored. The results of the current study suggested that both bioleaching and acid leaching led to the complete removal of Ni (100%)within 48 h of the start of the experiment. On the contrary, the leaching of Mo and Al was slow and only 32% Mo and 19% Alwas leached in the first 48 h which gradually increased to 46% and 26%, respectively. The results suggested that bioleaching successfully leached heavy metals from spent catalyst. Keywords - Biohydrometallurgy, Bioleaching, Chemical Leaching, Heavy Metals, Spent Catalyst.