Mechanistic Insight into the Heterogeneous Electro-Fenton/Sulfite Process for Ultraefficient Degradation of Pollutants over a Wide pH Range

Electro-Fenton (EF) has received widespread attention in terms of water decontamination in advanced oxidation processes but still has the bottlenecks of a narrow pH (similar to 3) application range and a slow rate of reduction of the iron ion to sustain high treatment efficiency. Herein, an iron-carbon catalyst was synthesized to develop a heterogeneous EF/sulfite (hetero-EF/sulfite) process, which expanded the pH application range to 7 and increased the rate constant of carbamazepine (CBZ) degradation 10.74 times compared with that of the hetero-EF process. The catalyst was systematically characterized; important process factors such as the applied current, initial pH, and CBZ, catalyst, and sulfite dosage were investigated, and a possible degradation mechanism and a possible pathway were proposed. The quenching experiments and electron paramagnetic resonance test revealed the existence of active species such as (OH)-O-center dot, SO4 center dot-, O-2(center dot-), O-1(2), and their mutual transformation, in which (OH)-O-center dot and O-2(center dot-) were dominant. This work also verified the suitability of the hetero-EF/sulfite for different pollutants, and its universal enhancement for different heterogeneous and homogeneous catalysts. This modified EF process expands the pH application range and enables the co-generation and transformation of free radicals, which has broad prospects for application in the effective degradation of organic pollutants for water purification.

Automated summary

The study synthesized an iron-carbon catalyst to expand the pH application range to 7 in the EF/sulfite process, significantly increasing the rate constant for carbamazepine degradation. Results demonstrated the applicability of the process to different pollutants and its enhancement of various catalysts.