Steady-state and pulse radiolysis experiments have been performed to gain insight into the mechanism of Thiamphenicol (THA) and Florfenicol (FLO) degradation in aqueous solutions. Redox reactions of aqueous THA and FLO solutions with •OH, , and •H were studied by using pulse radiolysis techniques. The results indicated that the reaction pathway between THA/FLO and •OH was dominated by the initial solution pH value. In neutral condition, the addition reaction happened between •OH and benzene ring. The rate constants for the reactions of •OH with THA and FLO were found to be 1.09×10⁸ L•mol^－1• s^－1 and 3.14×10⁸ L•mol^－1•s^－1 respectively. But in alkaline condition, the organic bond OH^－ was removed by •OH. The dechlorination of THA and FLO was caused by attacking. The •H added on the benzene ring forming relative stable products, and the rate constants for the reactions of •OH with THA and FLO were 3.52×10⁷ L•mol^－1•s^－1 and 2.43×10⁸ L•mol^－1•s^－1, respectively. The reaction in alkaline solution was also discussed. The radiolysis degradation by-products were identified by GC/MS analysis and their degradation pathway were also conducted.

Key words: thiamphenicol, florfenicol, pulse radiolysis, degradation mechanism