A Greener Approach to Extract Copper from Fertilizer Industry Spent Catalyst

Large quantities of catalysts after their useful life are discarded as waste material from fertilizer industry. Disposal of spent catalyst is a problem as it falls under the category of hazardous industrial waste due to its heavy metals concentration. This investigation applied a novel approach to extract copper from spent low-temperature shift catalyst (CuO–ZnO–Al₂O₃) using chelation process. Ethylenediaminetetraacetic acid (EDTA) was used as the chelating agent. Optimum parameters to extract 95% copper were found as: EDTA concentration 0.5 M, reaction temperature 100 °C, solid-to-liquid ratio 1:25 (g/ml), particle size 120 µm and reaction time 4 h. A kinetic analysis of the experimental data was done by shrinking core model which revealed the rate-controlling step of the leaching process as product layer diffusion. The activation energy calculated was 10.58 kJ/mol which supports leaching process to be the product layer diffusion controlled. The process adopted is eco-friendly as the EDTA was recovered after the extraction of copper from the spent catalyst and reused again. The recycled EDTA obtained after the extraction was characterized by NMR and SEM. The activity of the recycled EDTA was found to be consistent with the fresh EDTA.