Activation of peroxymonosulfate by WTRs-based iron-carbon composites for atrazine removal: Performance evaluation, mechanism insight and byproduct analysis

Abstract

Water treatment residuals (WTRs), inevitable waste generated from drinking water production, are potential iron resource and can be used for pollution control. In this study, iron-rich WTRs bonded with powder activated carbon (PAC) were calcinated to synthesize iron‑carbon (Fe C) composites, which were then applied to activate peroxymonosulfate (PMS) for the elimination of herbicide atrazine (ATZ). Characterization results showed that Fe 0 and Fe 3 C coexisted in these Fe C composites, among which Fe-15%C exhibited the highest degradation efficiency (91.6%) in 120 min under the condition of 0.25 mM PMS, 0.06 g L −1 Fe-15%C and initial pH 3.58. The effects of Fe-15%C dose, PMS concentration, initial pH and humic acid were systematically investigated. In addition to sulfate radical (SO 4 − ) and hydroxyl radical ( OH), singlet oxygen ( 1 O 2 ) and superoxide radical (O 2 − ) were also involved in the Fe-15%C/PMS system. The iron species and carbon structure jointly contributed to PMS activation, and the conversion of Fe(III) to Fe(II) was enhanced by the addition of p -benzoquinone (BQ). LC-MS technique was used to detect the degradation intermediates of ATZ, which were mainly generated through dechlorination-hydroxylation and dealkylation processes. Cl − had a dual effect (inhibitory and accelerating effect) on the degradation of ATZ, and could influence the yield of chlorinated byproducts desethyl-atrazine (DEA) and desisopropyl-atrazine (DIA), i.e., DEA was hardly affected, but DIA was increased to varying degrees. Ultimately, Fe-15%C had potential to be a viable activator for the removal of ATZ as well as protein- and humic-like substances in natural water. • Fe C composites derived from bonded WTRs and PAC were applied in PMS activation. • SO 4 − , OH, 1 O 2 and O 2 − simultaneously existed in the Fe-15%C/PMS system. • Activation mechanism was proposed and degradation intermediates were identified. • Cl − showed a dual effect on ATZ removal while influencing chlorinated byproducts. • The conversion of Fe(III) to Fe(II) was accelerated by the addition of BQ.