Effect of Grinding on Sulfuric Acid Leaching Efficiency of Nickel and Aluminum from Oxidative Roasted Alkaline Leaching Residue of Spent Hydrodesulphurization Catalysts

Spent hydrodesulphurization (HDS) catalysts are treated with hydrometallurgical leaching processes such as caustic leaching and acid leaching with roasting as a pre-treatment step. In the alkaline leaching processes such as sodium carbonate roasting followed by water leaching, most of the molybdenum and vanadium are selectively leached and most of nickel is left in the residue after the alkaline leaching of spent HDS catalysts. Therefore, it is important to recover nickel from the alkaline leaching residue. The main form of nickel in the alkaline leaching residue is spinel, therefore, it is difficult to extract nickel from the residue using mineral acids. In the present study, the effect of grinding conditions on the leaching efficiency of nickel and aluminum from the oxidative roasted alkaline leaching residue was investigated. The dry and wet grinding, grinding speed, grinding time and the amount of roasted product in grinding significantly affected the leaching efficiency of nickel and aluminum. The leaching efficiency of nickel and aluminum from dry ground roasted product was high compared with wet ground roasted product. And also, the leaching efficiency of nickel and aluminum was low in the low amount of the roasted product fed in dry grinding and high grinding speed, because the particles were aggregated again.