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Title: Electro-bioleaching of Spent Hydroprocessing Ni-Mo Catalysts
Authors: HO KOK YONG
Keywords: Spent catalysts, electrodialysis, electro-bioleaching, TCLP
Issue Date: 17-Jan-2011
Citation: HO KOK YONG (2011-01-17). Electro-bioleaching of Spent Hydroprocessing Ni-Mo Catalysts. ScholarBank@NUS Repository.
Abstract: The main focus of this study is the use of electrodialysis and bioleaching technologies to treat spent Ni-Mo hydroprocessing catalysts and to develop a novel ¿electro-bioleaching¿ technique to recover the heavy metals (Al, Ni and Mo) from the spent catalysts. A systematic characterization of both coked and decoked Ketjenfine KF840 catalyst was first carried out to allow a better understanding of the different leaching results of the catalysts. Electrodialysis was investigated with various assisting agents added to spent catalysts of two different states - coked and decoked. The assisting agents tested were (i) 0.1M citric acid, (ii) A. thiooxidans two-step culture medium (where the bacteria was first cultured in nutrient medium without catalyst for three days, after which the medium was added to the catalysts), and (iii) A. thiooxidans spent medium (where the bacteria was first cultured in nutrient medium without catalyst for seven days followed by filtration to remove cells, after which the medium was added to the catalysts). Control experiments were also run using deionized water. It was found that the A. thiooxidans spent medium gave the highest metal leaching efficiency in the electrodialytic cell, followed by citric acid. A. thiooxidans two-step culture medium fared much worse both in terms of metal leaching efficiency and metal transport. The best leaching efficiencies obtained for Al, Ni and Mo were 48.7%, 88.0% and 52.8% respectively. However, none of the assisting agents resulted in a reduction of the Ni concentration in the Toxicity Characteristic Leaching Procedure (TCLP) leachate of treated catalysts to a level below the regulatory limit.
Appears in Collections:Master's Theses (Open)

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