A heterogeneous Fenton reaction system of N-doped TiO2 anchored on sepiolite activates peroxymonosulfate under visible light irradiation

Completely decomposing low concentrations of organic pollutants in neutral wastewater under sunlight irradiation poses an important challenge for water treatment systems. A combination of photocatalysis and Fenton techniques is expected to solve this problem. Herein, a novel heterogeneous Fenton reaction system with good photocatalytic performance was developed by activating peroxymonosulfate (PMS) via nitrogen-doped TiO 2 (N-TiO 2 ) and acid-activated sepiolite (ASep) nanocomposites (N-TiO 2 /ASep). The N-TiO 2 /ASep nanocomposites were prepared by anchoring the N-TiO 2 onto ASep. The electronic structure of the Ti 3+ self-doped N-doped TiO 2 was regulated by calcining N-TiO 2 /ASep nanocomposites under different atmospheres. Methyl orange degradation, influencing factors, and reaction mechanisms under visible light irradiation were investigated in detail. The results indicated that, under visible light irradiation, N-TiO 2 /ASep alone had almost no photocatalytic activity, and PMS alone exhibited only 20% photocatalytic activity. However, the N-TiO 2 /ASep(N 2 )/PMS system degraded about 95% of the methyl orange within 60 min. By contrast, the reaction rate constant of N-TiO 2 /ASep(N 2 )/PMS was nearly 5.44 times higher than that of TiO 2 /PMS . This excellent performance was attributed to the synergy among N-TiO 2 , ASep, and PMS. Moreover, the calculated carrier density and photocurrent density of N-TiO 2 /ASep (N 2 ) was nearly 3.75 and 2.80 times that of N-TiO 2 /ASep (Air), suggesting that N-TiO 2 /ASep(N 2 ) had a greater carrier separation efficiency because more Ti 3+ species were provided. Furthermore, radical scavenger experiments and electron spin resonance testing demonstrated that h + , O 2 − , SO 4 − and OH were the important radicals. More importantly, photocatalytic performance was optimal at pH 7 in the presence of various ions. The results of this study expanded the applications of PMS and advanced oxidation processes. This work provides the necessary scientific basis for further studies of organic pollutant remediation.