(427a) Metal Recovery From Spent Catalyst By Means of Biotechnological Strategies to Scale-Up Studies

A bioleaching study aimed at recovering metals from hazardous spent hydro processing catalyst was carried out. The exhaust catalyst was rich in nickel (25%) vanadium (2.3%) and molybdenum (30%). Involved microorganisms were iron/sulfur oxidizing bacteria. Investigated factors were elemental sulphur addition, ferrous iron addition. Ferrous iron resulted to be essential for metal extraction. A mixed culture of two strains of Fe/S oxidizing bacteria (A. Ferrooxidans,A.thiooxidans)This culture was cultivated under acidic conditions (pH 2), in the ideal liquid growth media 9K : Two solution were prepared separately and blended only after their sterilization by autoclave. The first solution was obtained dissolving the following reagents in 1000 mL (NH₄)SO₄ 2.og, KCl 0.1g,H₂PO₄ 0.5g, MgSO₄.7H2O 0.5g and Ca (NO₃) 0.01g. and Sulfur as energy source.The second one was an energetic solution of 49.1g FeSO₄, dissolved in 300ml of distilled water. Sulfuric acid 4M was used to a adjust pH to 2, before serlization of the solutions. scale-up (from 50 to 500ml) of mixed cultures of Acidithiobacillus thiooxidans and Acidithiobacillus ferrooxidans was done for bioleaching. The experiments were carried out in Erlenmeyer flasks with media containing both sulfur powder and ferrous sulfate as substrates, at pH 2.0. The pH decreased to 0.93 in 4 days for 50ml , 0.66 in 7 days for 100ml and 0.98 in 18 days  500ml batch respectively. The media was centrifuged to get the filtrate and filtrate was used for leaching experiments, Nickel (92%), V (95%), Mo (4%) was achieved by the 0.9pH supernatant from the spent catalyst procured from petroleum refinery. Pellets were used for further scale-up studies. The biomass was checked using Folin-Lowry protein estimation method and Barium chloride method was used for sulfate ion estimation.