Comparative study of antipyrine degradation by UV and UV/persulfate system

The degradation of antipyrine (AP) in UV and UV/persulfate system was evaluated with several influencing factors including original AP dosage, persulfate (PS) dosage, pH, UV irradiance and humic acid dosage discussed. The results show that AP degradation fits the first-order kinetics well (R2>0.95). The degradation rates decrease in two systems when the AP dosage increases. The persudo-first-order-constant (kobs) in UV/PS system is higher than that in UV system. Degradation can be accelerated by enhancing oxidant persulfate, raising pH and increasing UV light intensity. PS dosage causes kobs to increase from 2.46×10-2 min-1 ([PS]0=0 mmol/L) to 2.76×10-2 min-1 ([PS]0=0.52 mmol/L). When pH=11.5, AP degradation (76.0% (UV) and 85.7% (UV/PS)) reaches the maximum. kobs decreases from 2.43×10-2 min-1 to 5.42×10-3 min-1 (UV) and from 2.64×10-2 min-1 to 5.2×10-3 min-1 (UV/PS) when light intensity reduces from 414 mJ/cm2 to 69 mJ/cm2. In UV system, kobs reaches the top of 2.53×10-2 min-1 with 7.5 mg/L HA (UV) and 3.28×10-2 min-1 with 2.5 mg/L HA (UV/PS). Excessive HA addition has a suppression effect because of the competitive reactions with radicals. kobs decreases to 2.01×10-2 min-1 (UV) and 2.80×10-2 min-1 (UV/PS).