Degradation of chloramphenicol by thermally activated persulfate in aqueous solution

• CAP can be efficiently decomposed by TAP technology.
• Sulfate radicals and hydroxyl radicals are responsible of CAP degradation.
• CAP decomposition was significantly influenced by operating conditions.
• TAP oxidation could be applied to wastewater or even concentrated wastewater treatment.
• Intermediate products during TAP oxidation were identified, and a primary reaction mechanism was proposed.

The feasibility of using thermally activated persulfate (TAP) to degrade chloramphenicol (CAP) in aqueous solution was evaluated. Results showed that CAP degradation followed a pseudo-first-order model under all conditions tested and the observed rate constants well fitted the Arrhenius equation. CAP degradation rate constants (kobs  ) increased with increased temperature and sodium persulfate (SPS) dosage. A lower pH resulted in a greater increase in CAP degradation and the highest degradation efficiency was obtained at pH 2.96. Scavenging tests suggested that sulfate radicals (SO4-) predominated under acidic conditions, whereas hydroxyl radicals (HO) gradually predominated under alkaline conditions. Coexisting Cl− ions slightly enhanced decomposition at an appropriate concentration ([Cl−]0/[SPS]0 = 1:1) but inhibited degradation at other levels. The effects of NO3-,H2PO4- and HPO42- on CAP degradation were negligible, whereas NO2-, HCO3-, and HA significantly inhibited CAP decomposition. The highest degradation rate was achieved with a single SPS injection. Considering that CAP oxidation in the multi-phases of wastewater matrices by TAP presented slower kinetics, 62.2–96.3% removal efficiencies were achieved within 160 min. The TOC removal ratios after 160 min TAP oxidation increased from 10.7% to 90.1% as the [SPS]0/[CAP]0 increased from 1:1 to 80:1, respectively. Overall, eleven intermediate products during TAP oxidation were identified, and a primary reaction mechanism was proposed.