Degradation of chloramphenicol by electron beam irradiation in aqueous solution

Electron beam irradiation-induced degradation of chloramphenicol (CAP) under different conditions was investigated. The results show that CAP can be effectively removed by electron beam irradiation. The degradation efficiencies of low initial concentration CAP can be remarkably improved in an acidic condition, and CAP removal followed the pseudo-first-order reaction kinetics. Results of Scavenging tests suggest that the degradation of CAP might be mainly ascribed to HO· oxidation and the direct decay of CAP molecules induced by irradiation. The removal efficiency of CAP was influenced by the additives (such as inorganic anions and HA) of aqueous solution, in the order of NO₂^- > I^- > Br^- > HA > CO₃^2-/HCO₃^- > NO₃^- > Cl^- > SO₄^2-, largely due to their competition with CAP for the reactive radicals generated, especially HO·. The degradation rate of CAP in deionized water was the highest among different water matrices. Up to 89.1% and 81.7% of CAP were removed from the filtrate and retentate phase of wastewater at an absorbed dose of 4 kGy, respectively. Six intermediates were identified by using GC-MS during CAP degradation, and some anions (Cl^-, NO₃^- and NO₂^-) were detected with IC. The CAP degradation pathway was proposed according to the intermediates.