A controllable reduction-oxidation coupling process for chloronitrobenzenes remediation: From lab to field trial

•ZVI/H2O2 delivers a controllable reduction-oxidation coupling process for CNBs remediation.•ZVI pre-reduction significantly accelerates CNBs mineralization rate by ·OH.•The performance of ZVI/H2O2 based reduction-oxidation process is controlled by the addition time of H2O2.•The efficiency of this controllable reduction-oxidation process has been validated in remediating real site contaminated by CNBs. Chloronitrobenzenes (CNBs) are typical refractory aromatic pollutants. The reduction products of CNBs often possess higher toxicity, and the electron-withdrawing substituent groups are detrimental to the ring-opening during the oxidation treatment, leading to ineffective removal of CNBs by either reduction or oxidation technology. Herein we demonstrate a controllable reduction-oxidation coupling (ROC) process composed of zero-valent iron (ZVI) and H2O2 for the effective removal of CNBs from both water and soil. In water, ZVI first reduced p-CNB into 4-chloronitrosobenzene and 4-chloroaniline intermediates, which were then suffered from the subsequent oxidative ring-opening by ·OH generated from the reaction between Fe(II) and H2O2. By controlling the addition time of H2O2, the final mineralization rate of p-CNB reached 6.6 × 10−1 h−1, about 74 times that of oxidation alone (9.0 × 10−3 h−1). More importantly, this controllable ROC process was also applicable for the site remediation of CNBs contaminated soil by either ex-situ treatment or in-situ injection, and, respectively decreased the concentrations of p-CNB, m-CNB, and o-CNB from 1105, 980, and 94 mg/kg to 3, 1, and < 1mg/kg, meeting the remediation goals (p-CNB: < 32.35 mg/kg, o-CNB and m-CNB: < 1.98 mg/kg). These laboratory and field trial results reveal that this controllable ROC strategy is very promising for the treatment of electron-withdrawing groups substituted aromatic contaminates. [Display omitted]