C60 Fullerol–enhanced Fenton-like activation of persulfate under visible light irradiation toward degradation of bisphenol X

Like other Fenton systems, the PDS-based Fenton system still faces the bottleneck of the rapid conversion of Fe(II) to Fe(III) in the system. Our previous researches have found that Fullerol could promote the Fe(III)/Fe(II) cycle in two ways: 1. Fullerol directly reduces Fe(III) into Fe(II); 2. Fullerol complexed with Fe(III) to generate Fullerol-Fe(III) complex with lower redox potential, thereby promoting the formation of Fe(II). This is undoubtedly a good way to solve the bottleneck of the PDS-based Fenton systems, while in recent years, new ideas have been put forward about the type of reactive oxidizing species (ROS) in the PDS-based Fenton systems: ferryl ion species (Fe(IV)) was formed, and played a role of pollutants degradation. In this study, we proved the formation of Fe(IV) during C60 Fullerol–enhanced Fenton-like activation of PDS with visible light irradiation. The experimental results showed that Fe(IV), SO4·− and OH were analyzed in the Fe(III)/PDS/Fullerol system by probes and EPR experiments. The yield of methyl phenyl sulfone (η(PMSO2)) and the results of p-CBA experiment indicated that both Fe(IV) and ·OH played an important role in the Fe(III)/PDS/Fullerol system. Combined with Fe(II) formation and PDS consumption results, it is indicated that with the addition of Fullerol, the Fe(II)/PDS molar ratio increased, and changed major oxidizing intermediate from ·OH to Fe(IV). Under visible light condition, the oxidation rates of BPS in the Fe(III)/PDS/Fullerol system were about 1.55 × 10–2 min−1, which was about five times that of the Fe(III)/PDS system at pH 3.0 (3.10 × 10–3 min−1). This study found that in the Fe(III)/PDS/Fullerol system, both Fe(IV) and ·OH play a role in the degradation of BPS.