Metal recovery from spent refinery catalysts by means of biotechnological strategies.
A bioleaching study aimed at recovering metals from hazardous spent hydroprocessing catalysts was carried out. The exhaust catalyst was rich in nickel (4.5 mg/g), vanadium (9.4 mg/g) and molybdenum (4.4 mg/g). Involved microorganisms were iron/sulphur oxidizing bacteria. Investigated factors were elemental sulphur addition, ferrous iron addition and actions contrasting a possible metal toxicity (either adding powdered activated charcoal or simulating a cross current process by means of periodical filtration). Ferrous iron resulted to be essential for metal extraction: nickel and vanadium extraction yields were 83% and 90%, respectively, while about 50% with no iron. The observed values for molybdenum extraction yields were not as high as Ni and V ones (the highest values were around 30-40%). The investigated actions aimed at contrasting a possible metal toxicity resulted not to be effective; in contrast, sequential filtration of the liquor leach had a significant negative effect on metals extraction. Nickel and vanadium dissolution kinetics resulted to be significantly faster than molybdenum dissolution ones. Furthermore, a simple first order kinetic model was successfully fitted to experimental data. All the observed results supported the important role of the indirect mechanism in bioleaching of LC-Finer catalysts.
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Department of Marine Sciences, Polytechnic University of Marche, Via Brecce Bianche, 60131 Ancona, Italy. f.beolchini@univpm.it
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D042763:Acidithiobacillus / Q000737:chemistry / Q000378:metabolism; D013856:Acidithiobacillus thiooxidans / Q000737:chemistry / Q000378:metabolism; D000704:Analysis of Variance; D001709:Biotechnology / Q000379:methods*; D002384:Catalysis; D005296:Ferrous Compounds / Q000737:chemistry; D007202:Indicators and Reagents; D007220:Industrial Waste; D007700:Kinetics; D008670:Metals / Q000737:chemistry*; D008982:Molybdenum / Q000737:chemistry; D009532:Nickel / Q000737:chemistry; D010578:Petroleum; D013455:Sulfur / Q000737:chemistry; D014639:Vanadium / Q000737:chemistry; D014961:X-Ray Diffraction
D005296:Ferrous Compounds; D007202:Indicators and Reagents; D007220:Industrial Waste; D008670:Metals; D010578:Petroleum; D014639:Vanadium; D013455:Sulfur; D009532:Nickel; D008982:Molybdenum