Research On The Degradation Of Printing And Dyeing Wastewater With The Bi₂WO₆/IO₄^- System Combined With Ultrasound

Water shortage and water pollution are urgently needed to be solved in the 21st century.The large amount of printing and dyeing wastewater has brought catastrophic effects to the environment.The numerous dyes on the market are gradually developing towards anti-oxidation,anti-photolysis and anti-biochemistry.Therefore,the degradation of printing and dyeing wastewater,which is complicated in composition,high in concentration,large in color,and toxic or tri-performance(carcinogenic,teratogenic,mutagenic),is unprecedentedly difficult.Therefore,the conventional treatment method seems to be ineffective for today's printing and dyeing wastewater.It is necessary to study a new type of wastewater pretreatment method to achieve the goal of comprehensive treatment after the treated water quality reaches the discharge standard.Ultrasonic degradation technology is a hotspot in the field of wastewater treatment in the 21st century.It uses pyrolysis,free radical oxidation and supercritical water oxidation,which are widely used in wastewater treatment.Its combined application with other degradation technologies will be Potential trends in the future of antifouling.This paper will study the degradation of printing and dyeing wastewater by Bi2WO6/IO4-system under ultrasonic irradiation.(1)A novel layered high specific surface area Bi2WO6 micron particle was prepared by hydrothermal method using Na2WOa·2H2O and Bi(NO3)3·5H2O as raw materials and composite binder PVP,respectively,using XRD,SEM,UV-Vis/DRS and N2 adsorption were used to characterize and analyze the crystal structure,morphology and optical properties of the catalyst.The results show that the prepared Bi2WO6 particles have a stratified flower-like morphology and a large specific surface area.(2)The ultrasonic catalytic activity of Bi2WO6 was evaluated by using methylene blue(MB)as a model pollutant.The degradation efficiency of degradation of MB by Bi2WO6 adsorption,ultrasonic irradiation and Bi2WO6 acoustic catalysis was studied:Bi2WO6 adsorption<ultrasonic<Bi2WO6acoustic catalysis,which indicates that Bi2WO6 microspheres have good ultrasonic catalytic activity.In addition,the effects of ultrasonic power,ultrasonic duty cycle,Bi2WO6 concentration and pH on ultrasonic catalytic efficiency were also investigated.Under the optimal conditions of ultrasonic power of 400 W,duty ratio of 9:1,catalyst mass concentration of 1.5 g/L and pH=11,the optimum degradation rate was 93.5%after 80 min.The active substances that may be produced in the process of ultrasonic degradation combined with Bi2WO6 mainly include·OH,1O2,HO2·,H2O2,which are the core substances in the degradation reaction.The optical energy provided by sonic cavitation exceeds the band gap energy of barium tungstate,which can excite Bi2WO6 as a photocatalyst and then generate photogenerated electron-hole pairs.The photogenerated holes(h+)can directly degrade MB,or The reaction of-OH in the solution produces more ·OH,which greatly increases the degradation rate of MB.(3)Taking MB as the research object,based on the experimental design of Box-Behken design combined with response surface analysis,the factors affecting the reaction of ultrasonic and sodium periodate combined with degradation of MB were optimized,and the mathematics of MB degradation reaction was established.model.Under the optimized experimental conditions determined by the model,the theoretical prediction value of MB degradation rate is 96.9%,while the experimentally verified MB degradation rate is 93.6,and the deviation between the two is only 3.3%.The model is highly significant,and the predicted value is in good agreement with the experimental value.The model can be applied to predict the degradation rate in the MB degradation reaction.From the response surface and contour plot analysis of the model:ultrasonic power,IO4-substance concentration,solution PH three factors on the degradation of MB is not a simple linear relationship,there is a certain interaction between the two.(4)The degradation efficiencies of MB degradation by ultrasound,IO4-oxidation and ultrasound and IO4-combination were studied:IO4-oxidation<ultrasonic<ultrasound IO4-combination,indicating that ultrasound and IO4-have good ultrasonic oxidation active.In addition,the optimum conditions of ultrasonic power of 400W,IO4-substance concentration of 20mmol/L and PH=7 were obtained through experiments.The degradation rate reached 93.8%after 80 min,which was compared with the previous response surface methodology.The optimization conditions are basically the same,achieving a good fit between theory and experiment.Finally,the degradation efficiency of MB combined with ultrasound,Bi2WO6,ultrasound and IO4-combination,ultrasound and Bi2WO6/IO4-combination was compared.It was found that the combined effect of ultrasound and Bi2WO6/IO4-can be completely degraded in 40 minutes.Therefore,it can be concluded that degradation of MB by Bi2WO6/IO4-system under ultrasonic irradiation can greatly shorten the drop.