P-cresol degradation through Fe(III)-EDDS/HO Fenton-like reaction enhanced by manganese ion: Effect of pH and reaction mechanism.

P-cresol is a highly toxic phenolic pollutant in coal chemical wastewater. The effective removal of p-cresol is of great significance to the ecological environment. In this study, the degradation of p-cresol by the Fe(III)-EDDS/HO Fenton-like reaction modified by Mn was investigated. The results showed that the removal rate of p-cresol could be significantly increased by the addition of Mn under neutral and weakly alkaline conditions (pH 6.5-8.5). Acidic conditions (pH 3.5) were not conducive to the Fenton-like reaction. This is because a neutral or weakly alkaline environment is conducive to Mn-EDDS complex formation, which can produce O to accelerate the reduction of Fe(III), and the efficiency of p-cresol degradation through a Fenton-like reaction catalyzed by the Fe(III)-EDDS complex is significantly improved. In addition, the degradation of EDDS through ·OH was reduced by O, which maintained and stabilized the Mn-EDDS complex and Fe(III)-EDDS complex. Under neutral conditions, the optimal dosage of Fe(III) is 0.7 mM, and the optimal molar ratios are EDDS/Fe(III) = 1: 1, Mn/Fe(III) = 1: 1, and HO/Fe(III) = 15: 1. The addition of free radical clearance isopropanol and CHCl proved that ·OH was the main active substance in the p-cresol degradation process.