Degradation of Acyclovir by Zero-valent Iron Activated Persulfate Oxidation: Kinetics and Pathways Research

Acyclovir (ACV) is a commonly used antiviral drug; however, its poor bioavailability can lead to at least ng/L level residue in natural water. Sulfate radical, produced from persulfate (PS) by zero-valent iron (ZVI) activation, was demonstrated to effectively degrade ACV in this study. Influencing parameters, including ZVI dose, PS usage, initial ACV concentration, solution pH, and temperature, were evaluated to find the optimal degradation conditions. Intermediates were identified and main degradation pathways were proposed. Experiments showed that ACV degradation by ZVI/PS oxidation followed a pseudo zero-order reaction well (R² > 0.99). At pH ≦ 9, the optimal combination was 0.4 mM PS with 1.2 mM ZVI, in order to completely remove 10 μM ACV during 60-min reaction. Heat activation of PS would hinder the effect of ZVI if temperature was 45 °C or above. ACV could be oxidized to four major degradation products, including methoxyacetic acid (P1, C₃H₆O₃, m/z = 91), 1,1,2-trinitroethane (P2, C₂H₃N₃O₆, m/z = 165), trinitromethane (P3, CHN₃O₆, m/z = 151), and dinitromethane (P4, CH₂N₂O₄, m/z = 105). Though the mineralization rate was not high (about 24.0%), ZVI/PS oxidation was proved to be an available treatment method for ACV-induced water pollution.