title: A novel process to treat spent petroleum catalyst using sulfur-oxidizing lithotrophs.
abstract: A novel process was developed using sulfur-oxidizing bacteria to extract metal values like Ni, V and Mo from spent petroleum catalyst. Bacteria were grown in elemental sulfur media for five day and after filtering, the filtrate was used for leaching purpose. Effect of different parameters such as contact time, particle size, pulp density and lixiviant composition were studied to find out the extent of metal leaching during the leaching process. XRD analysis proved the existence of V in oxide form, Ni in sulfide form, Mo both in oxide as well as sulfide forms, and sulfur in elemental state only. In all the cases studied Ni and V showed higher leaching efficiency compared to Mo. The low Mo leaching rate may be either due to formation of impervious sulfur layer or refractoriness of sulfides or both. Leaching kinetics followed dual rate, initial faster followed by slower. Dissolution mechanism was explained on the basis of both surface and pore diffusion rate. The leaching kinetics followed 1st order reaction rate. Finally, multiple linear regression analysis was carried out to compare the observed and calculated leaching percentage values for three metals.
authors.affiliation: Minerals and Material Processing Division, Korea Institute of Geoscience and Mineral Resources, Daejeon, South Korea.
authors.forename: Dong J
authors.initials: DJ
authors.lastname: Kim
authors.forename: Debaraj
authors.initials: D
authors.lastname: Mishra
authors.forename: Jong G
authors.initials: JG
authors.lastname: Ahn
authors.forename: Gautam R
authors.initials: GR
authors.lastname: Chaudhury
authors.forename: David E
authors.initials: DE
authors.lastname: Ralph
mesh_terms: D013856:Acidithiobacillus thiooxidans / Q000378:metabolism*; D002617:Chemical Industry; D004787:Environmental Pollution / Q000517:prevention & control*; D007700:Kinetics; D007723:Korea; D016014:Linear Models; D019216:Metals, Heavy / Q000737:chemistry / Q000302:isolation & purification*; D010084:Oxidation-Reduction; D010578:Petroleum / Q000032:analysis*; D013455:Sulfur / Q000378:metabolism; D014866:Waste Products / Q000032:analysis*; D014961:X-Ray Diffraction
chemical_list: D019216:Metals, Heavy; D010578:Petroleum; D014866:Waste Products; D013455:Sulfur