Enhanced degradation of 2,4-DCP in a bicarbonate-modified Fenton with EDTA under near-neutral conditions

Abstract

To address the issues of low pH requirements and low active iron content in the traditional Fenton system, bicarbonate in this study was presented in Fenton system to form HCO4− through reaction with hydrogen peroxide (HCO3––H2O2, BAP) and activated by FeⅡ-EDTA to enhance the degradation of 2,4-DCP under near-neutral conditions. 2,4-DCP can be totally degraded after 60 min of reaction at pH of approximately 6.4 under the optimal concentrations of Fe2+, NaHCO3 and EDTA-2Na of 4 mmol·L−1, 10 mmol·L−1 and 2 mmol·L−1, respectively. In addition to serving as a reactant in the reaction between bicarbonate and hydrogen peroxide to form the intermediate HCO4−, bicarbonate also functions as a pH buffer to bring the solution’s pH closer to neutral. The introduction of EDTA-2Na can effectively inhibit iron precipitation to promote maintaining the existence of Fe in dissolved form, improving the catalytic capacity of the system and reduce the dosage of Fe2+. The primary involvement of ·OH in the reaction process was validated by free radical quenching studies and EPR testing; the contributions of 1O2 and O2·− were very small.