Photo-assisted electrochemical process is a promising technology for a clean ecosystem. It is largely utilized for recovering metals and oxidizing recalcitrant organic compounds. This paper aims to discuss the performance of the photo-oxidation and reduction by applying semiconductor photo-catalysis as the anode and graphite as the cathode for treating rainwater in Tehran, Iran. Organic pollutants and different metals were investigated to study the probable roles of the anodic potential, the gap between electrodes, and the concentration of electrolytes in the possible mechanisms. The laboratory experiments which lasted for 120 min exhibited that the best performance for organic, iron, manganese, and lead removal was at the anodic potential of 10 V and gap of 6 cm. But, for zinc and cadmium, the best performance occurred at the anodic potential of 5.5 V and sodium chloride of 0.65 g/L. The presented reactions and mechanisms demonstrated incidents using the treatment process. They were identical to the presented dendrogram and Pourbaix diagrams. The results of the diagrams showed iron, manganese, and lead were removed by oxidation at the photo-anode. Zinc and cadmium were mainly removed by precipitation. Chemical oxygen demand, iron, manganese, and lead were significantly related and behaved similarly in the treatment process. Their removal was controlled by all the analyzed parameters. This paper may present a cost-effective approach for removing organic and metallic pollutants by photo-assisted electrochemical process. It can be suggested for future evolution of photo-assisted electrochemical on the treatment applications of rainwater.

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