Bioleaching of nickel from spent petroleum catalyst using Acidithiobacillus thiooxidans

摘要

Bioleaching of metals from hazardous spent hydro-processing catalysts was attempted in thesecond stage after growing the bacteria with sulfur in the first stage. The first stage involvedtransformation of elemental sulfur particles to sulfuric acid through an oxidation process byacidophilic bacteria. In the second stage, the acidic medium was utilized for the leaching process.Nickel, vanadium and molybdenum contained within spent catalyst were leached from the solidmaterials to liquid medium by the action of sulfuric acid that was produced by acidophilic leachingbacteria. Experiments were conducted varying the reaction time, amount of spent catalysts,amount of elemental sulfur and temperature. At 50 g/L spent catalyst concentration and 20 g/Lelemental sulfur, 94.3% Ni, after 7 days. Chemical leaching with commercial sulfuric acid of thesimilar amount that produced by bacteria was compared. Various leaching parameters such ascontact time, pH, pulp densities, particle size, and temperature were studied in detail. Bioleachresidues were characterized by SEM.