BIOLEACHING OF METALS FROM A SPENT DIESEL HYDRODESULFURIZATION CATALYST EMPLOYING Acidithiobacillus thiooxidans FG-01

This study evaluates the recovery of heavy metals employing a spent catalyst from the hydrodesulfurization (HDS) of diesel, with no chemical, thermal or physical pretreatment, using the bacterial strain Acidithiobacillus thiooxidans FG-01. Direct and indirect bioleaching tests were carried out in Erlenmeyer flasks (500 mL). The influence of the pulp density and supplementation with elemental sulfur on the bioleaching were also investigated. The spent catalyst contained organochlorines, petroleum hydrocarbons and heavy metals in its composition. The best recovery results (26% Al, 26% V and 39% Mo) were achieved in the two-stage (indirect) bioprocess, with a pulp density of 50 g/L. It was not possible to recover Co, Cu and Ni (< 5%) under any of the conditions tested. The bacterial strain A. thiooxidans FG-01 was found to be a promising candidate for the recovery of Al, V and Mo using the crude spent HDS catalyst.