Enhanced heterogeneous catalytic oxidation of 2,4-dichlorophenoxyacetic acid in aqueous solution by nanoscale zero-valent iron particle@suparticlelfur/nitrogen dual-doped r-GO (nZVIPs@SN-G) composites

Abstract

Herein, we reported the synthesis of nanoscale zero-valent iron particles stabilized by sulfur/nitrogen dual-doped r-GO (nZVIPs@SN-G) and their applications as the heterogeneous catalysts to the degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) by combining H2O2 under varying pHs, temperatures, catalyst dosages and H2O2 concentrations, as well as in the presence of radical scavengers. The experimental results showed that this heterogeneous Fenton-like catalytic system remained effective up to 90 min of reaction time, and could reach at least 98% degradation efficiency at the optimal conditions, especially when the initial pH values were below 4.5. And the scavenging experiments revealed that 2,4-D was mainly decomposed by the attack of surface-bounded hydroxyl radicals (OH). The structure and properties of the nZVIPs@SN-G catalyst was characterized by X-ray diffraction (XRD), scanning elctron microscopy (SEM), surface area analysis (BET), Raman spectroscopy (Raman) and X-ray photoelectron spectroscopy (XPS). The SEM images indicated that nanoscale zero-valent iron particles (nZVIPs) with size of about 10–50 nm were uniformly stabilized on the surface of sulfur/nitrogen dual-doped r-GO (SN-G), and had good combination with the multilayer matrix. Additionally, the catalyst at the optimum pH could maintain effective degradation even after five cycles, and achieved 91% degradation efficiency of 2,4-D, which was indicative of a good stability. More importantly, the possible reaction mechanism and dechlorination pathway of 2,4-D by the nZVIPs@SN-G/H2O2 heterogeneous catalytic system was also illustrated in this study.