Recovery of metal values from spent petroleum catalyst using leaching-solvent extraction technique

Leaching-solvent extraction process was developed to recover metal values from spent petroleum catalyst containing mainly Ni, V and Mo. The acid leaching studies using acetone-washed spent petroleum catalyst showed good metal recovery except for Mo. The low Mo recovery was due to formation of an impervious sulfur layer over the Mo matrix. The acid leaching efficiency improved using acetone–carbon disulfide (CS2) washed spent petroleum catalyst. More than 90% of Mo–Ni–V was recovered using 1 M H2SO4 followed by (NH4)2CO3 washing. The acidic leach liquor was processed through solvent extraction technique using LIX-84I. Mo and V in the leach liquor were separated by carrying out the solvent extraction studies at different pHs. A tentative process flow-sheet was developed.