recovery of nickel from spent catalysts by hydrometallurgical method

there are no appreciable amounts of nickel resources in iran; therefore, secondary resources of this element are to be more considered in future. spent nickel catalysts that are used in various industrial processes are one of them. for example nickel catalyst that is used in hydrogenation of edible oil have large amounts of nickel and they are generally supported on porous materials like silica and alumina. thus, economically extraction of nickel from these materials is an important subject. hydrometallurgy is the common method for recovery of nickel by suitable leachant. in this work, different acids such as sulfuric, nitric and hydrochloric are used as the solvent for nickel recovery. the effect of some parameters on the recovery of nickel such as acid concentration, reaction time, temperature and oil existence were studied. the results obtained show that, by leaching spent nickel catalyst at high temperature with nitric acid, extraction of nickel is more than 90%. furthermore, elimination of oil from spent catalyst with organic solvent increases the nickel extraction. the results of the kinetic analysis of the leaching data for various experimental conditions indicated that the reaction is controlled by diffusion through the catalyst network.