A novel electro-Fenton process coupled with sulfite: Enhanced Fe3+ reduction and TOC removal.

Abstract To promote the reduction of Fe3+ and improve the mineralization of organic pollutants, a novel electro-Fenton coupled with sulfite (Fe3+-EF/sulfite) process was constructed, which was superior to Fe3+-EF process in terms of carbamazepine (CBZ) degradation and mineralization with 5.99 times enhancement in degradation rate constant and 15.7 times enhancement on TOC removal. The complexation of Fe3+ and sulfite prevented the precipitation of Fe3+, reduced Fe3+ to Fe2+, and accelerated the iron cycle, so that H2O2 utilization efficiency (0.051 mgTOC mgH2O2−1) was greatly improved and electric energy consumption was greatly reduced (0.081 kWh g−1 TOC). The quenching experiments and EPR test confirmed that the reactive species, such as SO3•-, SO4•-, •OH, O2•- and 1O2 were responsible for the degradation of CBZ. This process also expanded the pH application range from 3 to 9 with satisfactory CBZ removal efficiency. This work verified the suitability of the Fe3+-EF/sulfite process for different sulfites (sulfite and bisulfite), typical pollutants (atrazine, sulfamethazine, rhodamine B) and real wastewater with 2.1–18.7 folds enhancement in degradation rate. The Fe3+-EF/sulfite process can achieve deep mineralization with low cost and simple operation, which has a broad and cost-effective application prospect in removal of refractory organic pollutants.