Preparation Of Ozone Catalytic Oxidation Catalyst And Its Application In Advanced Treatment Of Wastewater

In recent years,China's printing and dyeing and weaving industry has developed rapidly,and a large number of new dyes and auxiliaries have been put into use.This leads to the increasing emission of printing and dyeing wastewater and the complexity of the composition.The traditional biochemical method is difficult to make it meet the increasingly stringent emission standards.For this reason,people begin to pay attention to the depth treatment technology of printing and dyeing wastewater,and the heterogeneous ozonation technology is considered as an effective method for deep treatment of printing and dyeing wastewater because of its strong oxidation,no two pollution,and benefit recovery.In this paper,the catalytic oxidation system of the internal circulating fluidized bed was used to study preparation conditions of the catalyst,reaction operation parameters and degradation mechanism.This provides a theoretical basis for the industrialization of printing and dyeing wastewater.Coconut shell granular activated carbon?GAC?was used as the carrier,Mn and Mg as active components,Mg-Mn/GAC catalyst was prepared by the impregnation sol-gel method.The Cationic Red X-GRL simulated wastewater was used as the research object,and the effects of KMnO₄ content,calcination temperature,calcination time,concentration of soaking solution and oxidation method on the catalytic activity were investigated.The structure of the catalyst was analyzed by means of SEM,EDS,BET,XRD and XPS,and the stability of the catalyst was also studied.The experimental results showed that the activity of the catalyst was better when the addition of KMnO₄ was 80%of the theoretical value,the calcination temperature was 450?,the calcination time was 3 h,the impregnation solution was 0.5 mol/L.The active components were mainly in the form of MgMn₂O₄ and Mn₃O₄.When the reaction was 60 min,the removal rate of COD in the Cationic Red X-GRL wastewater was 74.51%and the chromaticity decreased from 338.5 to 7.8.After the catalyst was reused for 16 times,the removal rate of COD remained at about 65.00%,and it has good prospects for development.The two grade effluent was treated by catalytic ozonation in the form of continuous flow and the effects of catalyst dosage,O₃ concentration,initial pH value and hydraulic retention time?HRT?on the treatment effect were investigated.The results showed that the optimum operating conditions were as follows:the inlet flow rate was 1 L/min,the O₃ concentration was 40 mg/L,the dosage of Mg-Mn/GAC catalyst was 2 g/L,the HRT was 35 min,and the initial pH value was8.Under these conditions,after 60 min of the continuous reaction,the effluent quality basically reached a stable state,the COD was about 40 mg/L,the chromaticity decreased to less than 10,and the pH value was stable between 7.6-7.8,which reached the direct emission standard of the water pollutant discharge standard?GB4287-2012?of textile dyeing and finishing industry.Through the degradation experiments of cationic red X-GRL in different systems,the free radical inhibition experiment and the previous characterization experiments,the possible degradation mechanism of the Mg-Mn/GAC catalyst for the treatment of cationic red X-GRL was analyzed.Some organic compounds and O₃ were adsorbed on the surface of the catalyst,and a part of O₃ was directly ozonation with organic pollutants,some of which were decomposed to·OH by active sites,and indirect ozonation with organic compounds.The organic pollutants in the solution also have the above two reactions.The overall reaction mechanism is based on the hydroxyl radical mechanism,and the ozone is directly oxidized as the auxiliary.