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.
Keywords: Chloronitrobenzenes; Environmental remediation; H(2)O(2); Reduction-oxidation coupling; Zero-valent iron.
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