Comparison of the effect of metal oxide nanoparticles (copper, zinc, and iron) on the removal of cobalt by electrocoagulation processes from refinery wastewater

Cobalt is one of the heavy metals that can enter the environment via refinery wastewater due to its wide use. Various methods have been used to remove it. Recently, electrocoagulation has become one of the methods used in the treatment of wastewater. In this work, the best efficiency was achieved at a potential difference of 30 volts and a time of 60 minutes, with an efficiency of 52%. In the next steps, the experiments were carried out using copper, iron, and zinc nanoparticles, each of which was able to reduce the amount of cobalt by 87%, 73%, and 61%, respectively. The results showed that of the metal oxides used, iron oxide nanoparticles were able to remove the largest amount of cobalt from the wastewater, followed by copper and zinc. Using the statistical method of reaction surface, the optimal operating conditions for cobalt removal were determined and a second-order kinetic model was presented according to the laboratory parameters. The predictions of the statistical model resulting from the experimental design show good agreement with the laboratory data for the removal of cobalt in the present work.