Activation of peroxymonosulfate by modified coagulation sludge for bisphenol A degradation

This study used coagulation sludge from a landfill leachate treatment to prepare a modified coagulation sludge (MCS) catalyst by the limited oxygen pyrolysis method, and the adsorption, degradation efficiency, and reaction mechanism of bisphenol A (BPA) in the MCS activated peroxymonosulfate (MCS/PMS) process were investigated. The pyrolysis temperature determined the adsorption capacity and the activation ability of MCS. At a pyrolysis temperature of 300 °C for 2 h, the MCS300-2 test material had the best adsorption capacity for BPA, while MCS450-2 prepared at a pyrolysis temperature of 450 °C for 2 h had a better catalytic performance towards PMS. In the MCS/PMS process, BPA (20 mg/L) could be completely degraded at 120 min under room temperature when the initial pH = 7, PMS dosage = 3 g/L, and MCS dosage = 0.3 g/L. Radical quenching experiments indicated that both hydroxyl radical (·OH) and sulfate radical (SO₄^-·) existed in the MCS/PMS process, and ·OH played a major role in BPA degradation. The changes in morphology, functional groups, components, and surface element valence state of MCS catalysts before and after the reaction were investigated. It was found that the BPA degradation reaction was a coupled adsorption and oxidation process, in which homogenous in situ and heterogeneous effects were included in the reactions. In addition, the stability of the MCS/PMS process was verified in different environmental scenarios, including ultrapure water, tap water, and municipal wastewater. Furthermore, the degradation intermediates (such as p-hydroxyl phenol and p-hydroxybenzoic acid) of BPA were determined by ultra-performance liquid chromatography-quadrupole time-of-flight mass spectrometry, and the reaction mechanisms in the MCS/PMS process were investigated.