Selective oxidation of histamine H₂-Receptor antagonists by peracetic Acid: Kinetics and mechanism

Peracetic acid (PAA) is an emerging substitutive oxidant to chlorine disinfectants owing to the low generation of harmful by-products. Herein, we report PAA-induced oxidation of histamine H₂-receptor antagonists (HRAs) via non-radical participation for the first time. Results showed that PAA can selectively oxidize HRAs with high reactivity to ranitidine (RNTD), nizatidine (NZTD), cimetidine (CMTD), and famotidine (FMTD), but low reactivity to roxatidine (RXTD). PAA-induced HRAs oxidation followed the second-order kinetic reaction, the apparent second-order reaction rate constants (k_{2, app}) of RNTD, FMTD, CMTD and NZTD were 18.78 ± (2.4), 37.22 ± (6.1), 36.53 ± (7.8), 30.04 ± (2.4) M⁻¹•s⁻¹, respectively. The value of k_{2, app} decreased as pH increased. Scavenging experiments indicated that PAA-induced HRAs oxidation proceeded via a non-radical process. The theoretical calculation and product analysis further reveal that the reaction involves the double-electron transfer from thioether sulfur in HRAs to peroxide bond. HRAs oxidation by PAA was not affected by water matrices (Cl^-, HCO₃^–, HA), which has good applicability in surface water (SW) and wastewater (WW). Toxicity assessment indicated ecotoxicity of oxidation products was much lower than that of HRAs. This work provided a facile and emerging technology to eliminate the HRAs and their toxicity in the wastewater.