Kinetic oxidation of antipyrine in heat-activated persulfate

The kinetic oxidation of antipyrine by activated persulfate oxidation was investigated. The reaction kinetic rates under different temperature (T, 40–70°C), initial persulfate concentration ([PS]₀), and initial antipyrine concentration ([AP]₀) were examined in batch experiments. The results show that higher temperature, higher persulfate concentration, and lower initial antipyrine favored antipyrine degradation. A deep investigation into the reaction order obtained a more accurate kinetics rate equation (−d[AP]/dt = 0.34 [PS]₀ [AP]) with the limits of the experimental conditions applied here. The removal of antipyrine in 120 min was 54.3% at pH 4.5, and antipyrine degradation at different pH followed the order: pH 4.5 > pH 11.0 > pH 7.0 > pH 9.5. The persulfate disappearance fits pseudo-first-order kinetics well, the calculated disappearance rate of persulfate (k_obs-PS) was 2.33 ± 0.23 × 10⁻⁴ min⁻¹ at 60°C. Although 71.4% of initial antipyrine was degraded at 60°C, only 12.5% of initial antipyrine was mineralized. At last, norantipyrine and 5-pyrazolidinone-3-methyl-1-phenyl were identified to be the degradation products of antipyrine in heat activated persulfate system for the first time, and the degradation pathway of antipyrine was also tentatively proposed.