Study On Catalytic Supercritical Water Oxidation Of Aniline Wastewater

Aniline, as a harmful pollutant which seriously affected on human health, has attracted a lot of concerns. The traditional methods are not efficient in the treatment of aniline wastewater. Therefore, a new processing technology for the treatment of aniline wastewater is demanded.Supercritical Water Oxidation (SCWO) is a highly effective technology for the decomposition of hazardous compounds. The addition of catalysts could not only reduce the reaction temperature and pressure but also increase the reaction rate.In this thesis, MnOx/CeO2 catalysts were employed for the aniline oxidation in SCWO and the preparation of catalyst was also studied. Different preparation process of MnOx/CeO2 catalysts was dicussed through the characterization of TG-MS, XRD and catalytic activity tests. Co-precipitation was chosen as the optimized method for catalysts preparation. n(Mn): n(Ce) proportion and catalysts calcination temperature were discussed, the best ratio of Mn/Ce was 7/3, and catalysts calcination temperature was 550℃. The comparison of aniline decomposition in SCWO between non-catalyst, MnO2 catalysts and MnOx/CeO2 catalysts indicated that the addition of catalysts significantly improved the removal efficiency. MnOx/CeO2 catalysts behaved better performance than MnO2 catalysts.The effects of temperature, pressure, residence time and the ratio of excess oxygen on the decomposition of aniline were investigated. It was showed that these parameters could considerably affect the aniline decomposition. Under the optimum conditions of 420℃, 28MPa, the oxygen excess degree 20 and residence time more than 7s, the concentration of aniline could be below 1mg/L and TOC value less than 30mg/L, both of which met the discharge demands of regulation GB8978-1996.Macro-kinetics of catalytic supercritical water oxidation of aniline wastewater was also investigated. The resulting power-law rate expression is:The catalytic decomposition mechanism was investigated by analyzing the intermediate products. According to the experiment of catalytic mechanism, it was shown that ceria could support and supply crystal lattice oxygen for the oxidation reaction.