Kinetic and Mechanistic Insights into the Oxidative Transformation of Atrazine by Aqueous Fe(IV): Comparison with Hydroxyl and Sulfate Radicals

This study explored the oxidative transformation of atrazine(ATZ)by an aqueous iron(IV)-oxo complex (Fe(IV)) formed throughozonation of Fe(II) and compared it to ATZ oxidation by (OH)-O-& BULL; and SO4 (& BULL;-) generated by ultraviolet(UV) irradiation of H2O2 and peroxydisulfate(PDS), respectively. The second-order rate constant between Fe(IV)and ATZ was estimated to be greater than (5.18 & PLUSMN; 0.3) x10(5) M-1 s(-1) at pH 3,which was markedly higher than the reactivity of Fe(IV) toward variouswater matrices. Consequently, Fe(IV) achieved the most effective selectiveabatement of ATZ, compared with (OH)-O-& BULL;- and SO4 (& BULL;-)-mediated processes. Moreover,in the Fe(II)/O-3 system, we identified six products ofATZ and grouped them into three types: dealkylation (desethyl-atrazine[DEA] and desisopropyl-atrazine), alkylic-oxidation (atrazine amide[CDIT] and 2-hydroxy-4-(2-hydroxy-ethylamino)-6-isopropylamino-s-triazine), and dechlorination-hydroxylation (N-(4-hydroxy-6-(isopropylamino)-1,3,5-triazin-2-yl) acetamide anddeethylhydroxyatrazine) products. These products also constitutedthe primary outcomes of ATZ in the UV/H2O2 andUV/PDS systems. Mechanism analysis revealed that Fe(IV) and SO4 (& BULL;-) triggered the dealkylation ofATZ by electron transfer, whereas (OH)-O-& BULL; initiateddealkylation by H-atom abstraction, which resulted in the reactiveoxidant nature-dependent distribution of specific ATZ oxidation products.Specifically, the [CDIT]/[DEA] ratio was quantified as 0.2, 0.7, and2.3 in Fe(IV)-, (OH)-O-& BULL;-, and SO4 (& BULL;-)-mediated oxidation processes, respectively. Accordingly, this ratiowas developed as a sensitive internal probe for evaluating the relativecontribution of Fe(IV) and (OH)-O-& BULL;/SO4 (& BULL;-) during ATZ oxidative abatement.