Manganese Oxides Supported On A Novel Type Of Porous Silica Gel For Catalytic Degradation Of Tricyclazole With Ozone

With strong oxidizing property and no secondary pollution,the ozone oxidation of wastewater shows a wide application and development in potentials.But the ozone oxidation alone has selectivity to target pollutants and cannot completely degrade organic matter in a short time.Therefore,the treatment cost of wastewater is relatively high.The heterogeneous catalytic ozonation technology mainly combines the oxidizing property of ozone and catalytic performance of the catalyst to accelerate the decomposition of ozone to produce·OH which oxidizing is stronger than that of ozone.Moreover,the heterogeneous catalyst can be recycled and reduced in cost,and has a well prospect in the field of advanced wastewater treatment.In this paper,a novel type of porous Cu-Silica Gel?CuSG?was used as the catalyst carrier,MnO₂ was the active metal component,and the biodegradable tricyclazole was used as the target pollutant.The main content includes the preparation of the supported MnO₂ catalyst,the catalytic performance of the catalyst and the degradation mechanism of the catalytic oxidation of tricyclazole.Finally,the catalytic performance of the supported MnO₂ catalyst in practical engineering applications was investigated by simulating a fluidized bed reactor.MnO₂-CuSG was prepared by impregnation-calcination method.The catalyst was characterized by BET,SEM-EDS,and ICP.The results showed that CuSG has a high specific surface area of 478 cm²/g and a large pore volume of 0.8 cm³/g,and the amount of Mn metal that can be supported on the catalyst is as high as 3.7%,which is 3.4 times that of the general catalyst carrier.The catalytic activity was systematically assessed by monitoring the tricyclazole removal efficiencies at different operational parameters,such as different treatment processes,catalyst dosage,pH,and ozone concentration.The results showed that in the conditions of ozone concentration 15 mg/L,catalyst dosage 13 g/L and pH=7.0,the degradation efficiency of tricyclazole can reach 95.98%and the TOC removal efficiency reaches 76.13%after 60minutes.After five consecutive repeated experiments,the degradation efficiency of tricyclazole was maintained above 90%,which indicates that the stability of the catalyst was excellent.The catalyst was applied to the simulated fluidized bed reactor to degrade the tricyclazole.The optimum concentration of ozone was 20 mg/L,dosage of catalyst was 16g/L,and HRT was 2.5 h.Under the conditions,the degradation efficiency of tricyclazole in the system effluent was basically stabled at 95.75%.The experimental results showed that the catalyst has an ecellent practical application value in the catalytic ozonation of tricyclazole-containng wastewater.The addition of T-butanol?TBA?as hydroxyl radicals?·OH?scavengers caused that the degradation efficiency of tricyclazole decreased from 95.98%to 72.14%,which proved that the degradation mechanism of catalytic ozonation of tricyclazole was O₃ oxidation mainly,·OH oxidation is supplemented.Analysis of intermediate degradation products of tricyclazole by LC-MS,detection of5-methylbenzo[4,5]thiazolo[2,3-c][1,2,4]triazole-2-oxide,5-methylbenzo[4,5]thiazolo[2,3-c][1,2,4]trizole 1,2-dioxide,5-methylbenzo[4,5]thiazolo[2,3-c][1,2,4]trizole-2?3H?-ol.The possible mechanism to degrade TC in the O₃/MnO₂-CuSG system is that the molecular ozone attacks the tertiary amine to form N-oxides and hydroxyl radicals attacks the electron-rich 1,2,4-triazole ring to achieve hydroxylation.