Ultrasound Promoted Adsorption Of Anionic Dyes On Modified Zirconium Pillared Bentonite

The treatment of azo dye wastewater has always been a difficult problem.Adsorption is a common way of removal,but the adsorption process is slow.Zirconium Pillar Bentonite（Zr-Bent）has good resistance to acid/base and is commonly used to adsorb anionic contaminants.However,it has the problems of long preparation time and high energy consumption.In this paper,the anionic azo dye Congo Red（CR）was used as the research object,and the adsorption performance of CR was improved by the modification of Zr-Bent for the advantage of ultrasonic cavitation effect.The results are as follows:（1）Compared with the adsorption of Zr-Bent alone,the adsorption rate and the removal rate were increased by 11 times and 10%with ultrasonic assistance;according to the electron microscope and BET analysis,ultrasound can change the structure of Zr-Bent to increase Zr-Bent specific surface area,pore volume and active sites,and improve adsorption performance.In the process of adsorption and mass transfer,ultrasound can speed up CR molecules to pass through the water film,occupy active sites,and promote chemical adsorption.Therefore,in the adsorption process with ultrasound can change the structure of Zr-Bent,meanwhile,the liquid-solid phase mass transfer process and the chemical adsorption rate could be promoted.（2）Four Zr-Bent preparation methods（hydrothermal synthesis,microwave,ultrasound,micro-wave combined ultrasound）were compared,and it was found that under microwave combined ultrasound conditions,Zr-Bent preparation time was the shortest（1.83h）,adsorption capacity and removal rate highest.According to the characterization,the Zr-Bent prepared under different p H conditions has different structures.As the p H increased from 2 to 10,interlayer spacing,specific surface area,pore volume increase and the number of active sites of the material increased with the increase in p H,which increases the probability of contact with CR.（3）According to the results of Box-Behnken response surface optimization experiment,in the modified Zr-Bent adsorption process of CR,the dosage has the most significant effect on the CR removal rate.The optimized reaction conditions are:p H=6,time is 10min,adsorbent dosage is 0.4g·L^-1,CR removal rate is 96.57%,adsorption capacity is 240mg·g^-1,which is close to the prediction model verification result(CR The removal rate is 98.7%,and the adsorption capacity is 246 mg·g^-1),indicating that the response surface model can better predict the results of Zr-Bent adsorption CR.According to the correlation coefficient R²,the Zr-Bent adsorption CR process is more in line with the quasi-second-order kinetic model and the Langmuir adsorption isotherm model,indicating that the adsorption process is a monolayer chemical adsorption,and its theoretical maximum adsorption capacity is 537.3mg·g^-1.Combined with the FT-IR spectrum,the hydroxyl functional group of Zr-Bent can perform ligand exchange and electrostatic adsorption with CR.Use 0.2mol·L^-1Na OH solution to regenerate Zr-Bent under ultrasonic conditions.After five cycles,the removal rate of CR dye still exceeds 80%,indicating that the adsorbent,Zr-Bent was stable and had strong regeneration ability,and could be used to adsorb anionic dye polluted water.