Degradation of atrazine in river sediment by dielectric barrier discharge plasma (DBDP) combined with a persulfate (PS) oxidation system: Response surface methodology, degradation mechanisms and pathways

Abstract

Abstract Single degradation systems based on dielectric barrier discharge plasma (DBDP) or persulfate (PS) oxidation cannot achieve the desired goals (high degradation efficiency, high mineralization rate and low product toxicity) of degrading atrazine (ATZ) in river sediment. In this study, DBDP was combined with a PS oxidation system (DBDP/PS synergistic system) to degrade ATZ in river sediment. A Box–Behnken design (BBD) design including five factors (discharge voltage, air flow, initial concentration, oxidizer dose and activator dose) and three levels (-1, 0 and 1) was established to test a mathematical model by response surface methodology (RSM). The results confirmed that the degradation efficiency of ATZ in river sediment was 96.5% in the DBDP/PS synergistic system after 10 min of degradation. The experimental total organic carbon (TOC) removal efficiency results proved that 85.3% of ATZ is mineralized into CO2, H2O and NH4+, which effectively reduces the possible biological toxicity of the intermediate products. Active species (sulfate (SO4•−), hydroxy (•OH) and superoxide (•O2−) radicals) were found to exert positive effects in the DBDP/PS synergistic system and illustrated the degradation mechanism of ATZ. The ATZ degradation pathway, composed of 7 main intermediates, was clarified by fourier transform infrared spectroscopy (FTIR) and gas chromatography-mass spectrometry (GC-MS). This study indicates that the DBDP/PS synergistic system is a highly efficient, environmentally friendly, novel method for the remediation of river sediment containing ATZ pollution.