Preparation Of Mn/Mg/Ce Ternary Ozone Catalyst And Research On Degradation Of Printing And Dyeing Wastewater

Printing and dyeing wastewater often has the characteristics of high toxicity,high chromaticity,many organic pollutants,difficult to degrade and so on.High chromaticity affects the transmission of light in the water,and the dissolved oxygen in the water is consumed by organic pollutants,causing damage to the water and affecting the living environment of aquatic organisms.The treatment of printing and dyeing wastewater is difficult,and the conventional physical and chemical treatment is difficult to achieve a better treatment effect.The excellent performance of advanced oxidation process,especially the heterogeneous catalytic ozonation process in the removal of refractory organic compounds,has aroused great interest in the past few decades.Heterogeneous ozonation is a free radical reaction in the aqueous solution of various organic and inorganic compounds through the direct reaction of ozone molecules or the hydroxyl radical produced by the decomposition of ozone in water,which greatly improves the removal rate of pollutants.Catalytic ozonation has been widely studied because of its high efficiency and low negative effects.Due to the limitation of the physical and chemical properties of ozone,the development of a new type of ozone catalyst and the use of ozone catalytic oxidation technology to remove organic pollutants has become the focus of the current research.In view of the problems in the application of ozone catalysts and ozone catalytic oxidation technology,combined with the actual needs of printing and dyeing wastewater treatment,we have researched and developed new supported ozone catalysts with different compositions and structures,and prepared four Mn/Mg/Ce ternary catalysts with different carriers by impregnation method.It is applied to the degradation of methyl orange wastewater and red powder wastewater.In this study,attapulgite soil,silica gel,molecular sieve,alumina are called ATP,SG,MS and Al₂O₃ respectively.The corresponding catalysts are referred to as Mn/Mg/Ce@ATP,Mn/Mg/Ce@SG,Mn/Mg/Ce@MS,Mn/Mg/Ce@Al₂O₃.The specific work is as follows:(1)Mn/Mg/Ce type ternary catalysts(Mn/Mg/Ce@ATP,Mn/Mg/Ce@SG,Mn/Mg/Ce@MS,Mn/Mg/Ce@Al₂O₃)with four different supports were prepared by impregnation method.X-ray diffraction(XRD),BET,Fourier transform infrared spectroscopy(FT-IR),scanning electron microscopy(SEM)and other characterization techniques were used to analyze the differences in the degradation properties of the catalysts in the microscopic morphology characteristics,and the specific surface area of Mn/Mg/Ce@ATP was the largest,reaching 1836.143 m~2/g.The specific surface area of the other three catalysts decreased after the impregnation calcination,which may be because the micropores on the catalyst surface collapsed due to the high temperature of calcination or the supported metal oxides blocked the surface micropores.(2)The degradation ability of the catalyst to methyl orange wastewater under different reaction conditions was investigated.The optimal experimental conditions were selected by changing the p H of the reaction,the amount of catalyst,the composition of the impregnation solution and the material of the carrier.The catalyst was Mn/Mg/Ce@ATP,the amount of ozone was 36 PPM,p H=11,and the amount of catalyst was 5g/L.Under the best experimental conditions,the removal rate of methyl orange reached 96%when the reaction time was 120 min.(3)The degradation performance of four catalysts on COD(1556 mg/L)of red powder wastewater was investigated.When p H=11,catalyst dosage 5 g/L,reaction time 120 min,The degradation rates of Mn/Mg/Ce@ATP,Mn/Mg/Ce@SG,Mn/Mg/Ce@MS and Mn/Mg/Ce@Al₂O₃ on the COD of red powder wastewater are 48.7%,32.5%,39.6%and 37.1%,respectively.The treatment effect of methyl orange wastewater and red powder wastewater is the best.The experimental results show that the catalyst prepared in this study not only has a strong degradation effect on methyl orange single dye,but also has a good degradation effect on red powder wastewater with complex composition.(4)The mechanism of ozone catalytic oxidation and the degradation path of pollutants were studied by calculating the activation energy of four kinds of supported catalysts and free radical quenching experiment.It is concluded that hydroxyl radical plays a leading role in the degradation of pollutants in ozone catalytic oxidation system.