Study On The Removal Characteristics And Mechanism Of Azo Dyes From Water By MIEX Resin

Congolese Red(Congo red,CR)and methyl orange(Methyl orange,MO)are representative substances of azo dyes.Because of its strong water solubility,small molecular weight and so on,it is difficult to be effectively removed by the traditional drinking water process.In recent years,the frequent accidents of azo dye wastewater,represented by Congolese red and methyl orange,have a great impact on the water environment and seriously threaten the safety of drinking water.Therefore,it is of great significance to seek a simple and efficient method to remove Congo red and methyl orange from water pollution to ensure the safety of drinking water.In this study,MIEX resin was used as adsorbent and Congo red and methyl orange as pollutants.By means of stirring adsorption,the adsorption process parameters,adsorption kinetics,adsorption thermodynamics,adsorption balance at different temperatures,characterization of MIEX resin before and after adsorption,and MIEX resin regeneration were studied,and the adsorption characteristics and mechanism of Congo red and methyl orange were revealed by MIEX resin removal of azo dyes in water bodies.Using the response surface,two polynomial regression model equations including four factors,such as the increase of MIEX resin,the initial concentration of Congo red and methyl orange,the pH value of solution and stirring time,were established,and the optimum process parameters for pollutant removal were optimized.The response surface diagram and contour graph are plotted,and the influence of the interaction between the factors on the removal effect of pollutants is analyzed,and the results show that the interaction between pH and MIEX resin dosage significantly affects the removal of Congolese red or methyl orange.The adsorption kinetics results show that the proposed two-stage kinetic model and the Ilovich kinetic model can better describe the adsorption kinetics of the azo dye Congo red or methyl orange on the MIEX resin,in which the fitting effect of the Ilovich model is better.The Boyd model shows that the adsorption rate of Congo red and methyl orange in MIEX resin is mainly controlled by liquid membrane.The adsorption equilibrium results at different temperatures showed that the adsorption amount of azo dyes Congo red and methyl orange on MIEX resin increased with the increase of temperature.Redridge-Peterson(Redlich-Peterson)model can better fit the adsorption equilibrium law of Congo red or methyl orange on MIEX resin.Thermodynamic results show that the adsorption of Congo red and methyl orange on MIEX resin is a spontaneous heat absorption process,and the increase of temperature is beneficial to adsorption.The results of MIEX resin regeneration show that NaCl solution with mass concentration of 0.7% and 0.3% can effectively regenerate the saturated resin of Congo red and methyl orange respectively,and MIEX resin still maintains good removal efficiency for pollutants after 8 adsorption-analytic cycle.Electron microscope scanning shows that the surface of MIEX resin has many voids and aperture,which is beneficial to the adsorption and removal of azo dyes pollutants.Infrared results analysis can be concluded that MIEX resin contains hydroxyl group,ether bond and other functional groups,and in the adsorption process is not only chemical action,but also van der Waals,hydrogen bond and other physical effects.In summary,MIEX resin can effectively remove the azo dyes Congo red and methyl orange from sudden water pollution,and provide theoretical and technical support for drinking water safety.