Studies on the recovery of metal ions from spent catalyst

Abstract

Bearing in mind the growing demand of valuable metals and the continuous depletion of their high grade ores, the recovery of metals from secondary sources has become a topic of interest. Secondary sources are basically those waste materials which contain valuable metals such as spent catalysts, electronic wastes (printed circuit board), spent batteries (Ni-Cd nd Li-ion batteries) and fly ash. Undoubtedly, the spent catalysts contribute the largest amount of industrial waste generated worldwide and contain a remarkable amount of valuable metals. newlineAs per economical as well as environmental point of view, the present research work deals with a detailed study of the recovery of metals (Zn and Cu) from spent fertilizer low temperature shift (LTS) catalyst. Since the LTS catalyst contains significant amounts of zinc and copper, therefore it can be considered as a good alternative for the recovery of these valuable metals. newlineTo meet the above purpose, firstly, the leaching study of metals from the solid spent catalyst was investigated using chelation and hydrometallurgical approaches. The effect of various parameters such as leaching agent concentration, leaching time, solid to liquid ratio, particle size, stirring speed and temperature were investigated. It was observed that the leaching efficiency of metal increases with rapid increase in acid concentration, time, solid to liquid ratio and temperature, while it decreases with increases in particle size. The comparative evaluation of the acid leaching process with chelate assisted leaching suggests that the leaching efficiency was found higher with HCl than that of EDTA. However, the order of leaching efficiency with other leaching agents was obtained as HClgtEDTAgtHNO3gtH2SO4. Additionally, kinetic analysis of the acid (HCl) leaching process was studied using shrinking core model (SCM) in order to find out the rate controlling step. The optimization study of chelation and the acid leaching processes were performed using Box behnken design and Taguchi orthogonal design