Iodine-enhanced ultrasound degradation of sulfamethazine in water

This study investigated sulfamethazine (SMT) ultrasound degradation, enhanced by iodine radicals, generated by potassium iodide (KI) and hydrogen peroxide (H₂O₂) in situ. The results showed that the ultrasound/H₂O₂/KI (US/H₂O₂/KI) combination treatment achieved an 85.10 ± 0.45% SMT removal (%) in 60 min under the following conditions: pH = 3.2, ultrasound power of 195 W, initial SMT concentration of 0.04 mmol·L^-1, H₂O₂ concentration of 120 mmol·L^-1, and KI concentration of 2.4 mmol·L^-1. UV-Vis spectrophotometric monitoring of molecular iodine (I₂) and triiodide (I₃^-) revealed a correlation between the SMT degradation and the iodine change in the solution. Quenching experiments using methanol, t-butanol and thiamazole as radical scavengers indicated that iodine radicals, such as I and I₂^-, were more important than hydroxyl radicals (HO) for SMT degradation. SMT degradation under the US/H₂O₂/KI treatment followed pseudo-first order reaction kinetics. The activation energy (E_a) of SMT degradation was 7.75 ± 0.61 kJ·mol^-1, which suggested the reaction was controlled by the diffusion step. Moreover, TOC removal was monitored, and the obtained results revealed that it was not as effective as SMT degradation under the US/H₂O₂/KI system.