Degradation of methyl orange by pyrite activated persulfate oxidation: mechanism, pathway and influences of water substrates
Hui Liu, Fenwu Liu, Jian Zhang, Jiaxing Zhou, Wenlong Bi, Junmei Qin, Qingjie Hou, Yue Ni, Shaozu Xu, Chen Yang
Abstract
Abstract Degradation mechanism of methyl orange (MO), a typical azo dye, with pyrite (FeS2) activated persulfate (PS) was explored. The results showed that when the initial concentration of MO was 0.1 mM, FeS2 was 1.6 g/L and PS was 1.0 mM, the removal rate of MO could reach 92.9% in 150 min, and the removal rate of total organic carbon could reach 14.1%. In addition, both pH ≤ 2 and pH ≥ 10 could have an inhibitory effect in the FeS2/PS system. Furthermore, Cl− and low concentrations of had little effect on the degradation of MO with FeS2/PS. However, and high concentrations of could inhibit the degradation of MO in the system. Besides, MO in river water and tap water were not degraded in FeS2/PS system, but acidification (pH = 4) would greatly promote the degradation. In addition, the removal rate of MO with FeS2/PS could still reach about 90% after five cycles of FeS2. Furthermore, the intermediates and possible degradation pathways were speculated by LC-MS, and the degradation mechanism of MO by FeS2/PS was that the cycle of Fe(III)/Fe(II) could continuously activate persulfate to produce . The results could provide technical support for azo dye degradation in the FeS2/PS system.