Optimization Study of Nickel Leaching from Used Catalysts and Investigation of Nickel Separation by Precipitation

Nickel-based catalysts are used in refining and petrochemical processes. After being regenerated and reused several times, these catalysts are released as used catalysts in nature, which, in addition to environmental risks, are not economically viable due to the presence of the precious metal nickel. Hydrometallurgical methods are commonly used to extract nickel, which is difficult and expensive. Due to the significant shortage of nickel mines, the use of these secondary resources is quite important. In this study, the possibility of nickel recovery from used catalysts has been investigated. Initially, the cokes were removed, and then the effects of three different acids on nickel leaching were investigated. Various parameters such as temperature, mixing speed, liquid to solid ratio, particle size, and acid concentration were investigated. After the complete leaching of nickel, nickel purification was performed by selective nickel hydroxide precipitation.