title: Optimization of two-step bioleaching of spent petroleum refinery catalyst by Acidithiobacillus thiooxidans using response surface methodology.
abstract: A central composite design (CCD) combined with response surface methodology (RSM) was employed for maximizing bioleaching yields of metals (Al, Mo, Ni, and V) from as-received spent refinery catalyst using Acidithiobacillus thiooxidans. Three independent variables, namely initial pH, sulfur concentration, and pulp density were investigated. The pH was found to be the most influential parameter with leaching yields of metals varying inversely with pH. Analysis of variance (ANOVA) of the quadratic model indicated that the predicted values were in good agreement with experimental data. Under optimized conditions of 1.0% pulp density, 1.5% sulfur and pH 1.5, about 93% Ni, 44% Al, 34% Mo, and 94% V was leached from the spent refinery catalyst. Among all the metals, V had the highest maximum rate of leaching (Vmax) according to the Michaelis-Menten equation. The results of the study suggested that two-step bioleaching is efficient in leaching of metals from spent refinery catalyst. Moreover, the process can be conducted with as received spent refinery catalyst, thus making the process cost effective for large-scale applications.
authors.affiliation: a Mineral Resources Research Division, Korea Institute of Geoscience and Mineral Resources (KIGAM), Yuseong-gu , Daejeon , South Korea.
authors.forename: Haragobinda
authors.initials: H
authors.lastname: Srichandan
authors.forename: Ashish
authors.initials: A
authors.lastname: Pathak
authors.forename: Dong Jin
authors.initials: DJ
authors.lastname: Kim
authors.forename: Seoung-Won
authors.initials: SW
authors.lastname: Lee
mesh_terms: D013856:Acidithiobacillus thiooxidans / Q000378:metabolism*; D001673:Biodegradation, Environmental; D052918:Environmental Restoration and Remediation / Q000379:methods*; D006863:Hydrogen-Ion Concentration; D007220:Industrial Waste / Q000032:analysis*; D008670:Metals / Q000737:chemistry; D010578:Petroleum / Q000032:analysis*; D013455:Sulfur / Q000032:analysis
chemical_list: D007220:Industrial Waste; D008670:Metals; D010578:Petroleum; D013455:Sulfur
keywords: Acidithiobacilli; bioleaching; response surface methodology; spent refinery catalyst