title: Sequential biological process for molybdenum extraction from hydrodesulphurization spent catalyst.
abstract: Spent catalyst bioleaching with Acidithiobacillus ferrooxidans has been widely studied and low Mo leaching has often been reported. This work describes an enhanced extraction of Mo via a two stage sequential process for the bioleaching of hydrodesulphurization spent catalyst containing Molybdenum, Nickel and, Aluminium. In the first stage, two-step bioleaching was performed using Acidithiobacillus ferrooxidans, and achieved 89.4% Ni, 20.9% Mo and 12.7% Al extraction in 15 days. To increase Mo extraction, the bioleached catalyst was subjected to a second stage bioleaching using Escherichia coli, during which 99% of the remaining Mo was extracted in 25 days. This sequential bioleaching strategy selectively extracted Ni in the first stage and Mo in the second stage, and is a more environmentally friendly alternative to sequential chemical leaching with alkaline reagents for improved Mo extraction. Kinetic modelling to establish the rate determining step in both stages of bioleaching showed that in the first stage, Mo extraction was chemical reaction controlled whereas in the subsequent stage, product layer diffusion model provided the best fit.
authors.affiliation: Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, Singapore 117585, Singapore.
authors.forename: Shruti
authors.initials: S
authors.lastname: Vyas
authors.affiliation: Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, Singapore 117585, Singapore. Electronic address: chetyp@nus.edu.sg.
authors.forename: Yen-Peng
authors.initials: YP
authors.lastname: Ting
mesh_terms: D042763:Acidithiobacillus / Q000378:metabolism*; D000535:Aluminum / Q000378:metabolism*; D001673:Biodegradation, Environmental; D002384:Catalysis; D004926:Escherichia coli / Q000378:metabolism*; D007700:Kinetics; D008982:Molybdenum / Q000378:metabolism*; D009532:Nickel / Q000378:metabolism*
chemical_list: D009532:Nickel; D008982:Molybdenum; D000535:Aluminum
keywords: Acidithiobacillus ferrooxidans; Escherichia coli; Kinetic modelling; Sequential bioleaching; Spent catalyst