Natural mackinawite catalytic ozonation for N, N-dimethylacetamide (DMAC) degradation in aqueous solution: Kinetic, performance, biotoxicity and mechanism.

To enhance the degradation of N, N-dimethylacetamide (DMAC) in aqueous solution, the natural mackinawite (NM) is introduced for catalytic ozonation in this study as it is an environmentally friendly catalyst with low cost and easy availability. The properties of the NM were initially characterized via scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), Fourier Transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Then, impact factors including NM dosage, ozone gas concentration and initial pH were investigated and the optimal conditions (i.e., NM dosage = 3.5 g/L, ozone gas concentration = 300 L/min, initial pH = 6.8) were obtained in NM/O3 process. Besides, the superiority of the NM/O process was confirmed by the experiments that the degradation efficiency of DMAC in the NM/O process (i.e., 95.4%) was much higher than that in the zero-valent iron (ZVI)/O process (i.e., 46.1%) and the synthetic FeS/O process (i.e., 68.6%). Furthermore, the intermediate and possible degradation pathway of DMAC were proposed, and the biological toxicity of the intermediate was subsequently evaluated by the activated sludge. Finally, the mechanism of the NM/O3 process was proposed in this study based on control experiment and radical scavenging experiment. The extraordinary efficiency for DMAC degradation was found to be mainly caused by HO of the reactive oxygen species (ROS) (i.e., HO, O and HO) generated in the NM/O process. Therefore, this study confirmed that NM was a high efficient catalyst for degradation the toxic and refractory pollutants in catalytic ozonation system.