Zero-valent iron (ZVI) activation of persulfate (PS) for oxidation of bentazon in water

Bentazon (BTZ) in water, a broadly used herbicide in agriculture, is toxic to human beings and has a negative impact on ecosystem. In this study, zero-valent iron (ZVI) activation of persulfate (PS) for the oxidation of BTZ was investigated. More active sulfate radicals produced from the system were principally responsible for the BTZ degradation. The BTZ removal well followed a pseudo-first-order (PFO) kinetics pattern. Key factors affecting the treatment were tested, including ZVI concentration, PS dose, initial BTZ concentration, initial solution pH, temperature and common coexisting ions in water. Under the optimal ZVI (4.477. mM) and PS (0.262. mM) concentrations, 0.021. mM BTZ was totally removed at an initial pH. ≤. 7.Generally, lower BTZ concentration, lower pH and higher temperature favored the treatment. Different coexisting ions exhibited different effects. Al³⁺, Cl^- and NO₃^- improved the treatment; NH₄⁺, Ca²⁺, and Mg²⁺ did not significantly influence the BTZ removal; and, Mn²⁺, Cu²⁺, CO₃^2-, HCO₃^-, PO₄^3-, HPO₄^2- and H₂PO₄^- inhibited the BTZ degradation. Most of BTZ were not mineralized, and instead degraded into three major degradation products including 2,1,3-benzothiadiazin-4(3H)-one-2,2-dioxide (P1, C₇H₆N₂O₃S), 2-aminobenzoic acid (anthranilic acid) (P3, C₇H₇NO₂), and 2-amino-2-sulfobenzoic acid (P5, C₇H₇NO₅S). This study demonstrates that ZVI/PS is a viable alternative for controlling BTZ-induced water pollution.