Kinetics and mechanisms of chloramphenicol degradation in aqueous solutions using heat-assisted nZVI activation of persulfate

Abstract

The reaction rate of chloramphenicol (CAP) using persulfate (PS) activated by nanoscale zero-valent iron (nZVI), heat and nZVI-heat were evaluated in this study. The results indicated that the nZVI-heat-PS system has a significant synergetic effect on CAP removal. The CAP degradation process can be divided into two stages based on the pseudo-first-order kinetic model. The pseudo-first-order kinetic constants (kobs) for the first and second stages were 0.267 ± 0.032 (R2 = 0.971) and 0.042 ± 0.003 min−1 (R2 = 0.988), respectively. The presence of aeration, humic acid (HA), NO3−, HCO3− and H2PO4− presented negative effects on CAP removal in nZVI-heat-PS treatment. Cl− exhibited dual effects (both stimulation or inhibition) on CAP degradation with different Cl− concentrations in the nZVI-heat-PS system. Scavenging experiments revealed that HO was the predominant radical for CAP degradation at pH 3 and both HO and SO4− contributed to the CAP degradation in the system. Six intermediate products were detected in the system and their possible degradation pathways were proposed. The study could provide a reference for PS-based advanced oxidation research.