Characterization of different types of petroleum refinery spent catalyst followed by microbial mediated leaching of metal values

The present study aims for characterization and classification of five different spent petroleum refinery catalysts followed by metal recovery via bioleaching. The nomenclature given to the different spent catalyst (SC) is SC1, SC2, SC3, SC4 and SC5 collected from an Indian petroleum refinery. All spent catalysts were crushed and ground prior to their characterization by X-Ray Fluorescence for chemical composition followed by X-Ray Diffraction and Scanning Electron Microscopy-Energy Dispersive X-Ray Spectroscopy for their mineralogy. Further, all five spent catalysts were classified based upon their chemical composition and mineralogy. Metal recovery from the spent catalysts was carried out by bioleaching by a mixed microbial consortium of iron and Sulphur oxidizing microorganisms. Most of the spent catalysts showed very significant metal recovery with respect to Ni, Cu, Cr, Mo, Zn, Sr and Ti. The study provides a possible metal recovery route via bioleaching for further testing and scaling up.