The Designation,Synthesis And Adsorption Of Ion Exchange Resins For Aromatic Acids

Aromatic acids are important chemical raw materials and synthetic intermediates.A large amout of wastewaters containing aromatic acids can cause a variety of discharge problems due to their high concentrations,strong inorganic salt contents,high toxicity and low biodegradability.This kind of wastewaters can hardly meet the requirements of the discharge standard using common treatment techniques.Ion exchange method has a good effect on the removal of aromatic acids from wastewaters.However,the selection of functional groups on ion exchange resins has been based on the traditional experience in the process of resin synthesis owing to the lack of support and guidance of necessary theories over a long period of time.In this paper,Gaussian 09 software was used to simulate the interaction between macroporous anion exchange resins with different functional groups and benzene sulfonic acid,benzoic acid as well as phenol.The energy of the complex and the transfer tendency of NBO charge were calculated to discuss the interaction between them.The results were used as the basis for synthetic resins and the effects of pH value,temperature,salt content and time on the adsorption of the resins were studied.The results of software calculation showed that the LC-WPBE method in 6.3 1g(d,p)group was the closest to the measured results of the structure of the aromatic acids.For the structural optimization and calculation of NBO charge of aromatic acids and resin monomers,it could be seen that the adsorption of the resins on these acids are 1:1 combination.The binding energy of the same resin monomer to benzene sulfonic,benzoic acid and phenol were down in turn,and of the different resins to the same aromatic acid could be different.This difference would be verified in subsequent experiments.The binding energy of sulfate ion and resin monomer was higher than that of the three aromatic acids,so in the process of competitive adsorption,sulfate ion interference might be large.The results of static adsorption showed that the optimum adsorption pH of benzene sulfonic acid and benzoic acid is 2-4,and the adsorption capacity of phenol when the pH is less than 9 is stable and high.The adsorption process of benzene sulfonic acid,benzoic acid and phenol were in accordance with the Langmuir adsorption model and were spontaneous exothermic process.The coexistence of high concentration of SO42-had negative effects on the adsorption of benzene sulfonic acid,benzoic acid and phenol which were down in turn.Single chain amine resins had stronger salt resistance than double chain amine resins.The pseudo-second-order kinetic model was suitable for describing the process of adsorption of three aromatic acids,and the rate of phenol was higher than that of benzene sulfonic acid and benzoic acid.In benzene sulfonic acid/benzoic acid system,benzene sulfonic acid occupied the dominant position of adsorption with the adsorption coefficient between 20 and 100;in benzene sulfonic acid/phenol system,benzene sulfonic acid adsorption was dominant,and the adsorption coefficient is between 20 and 30;in benzoic acid/phenol system,the adsorption of benzoic acid was dominant and the adsorption of phenol was nearly stopped,so the adsorption coefficient was up to 2000.The results of static desorption experiments showed that when desorbed with NaCl aqueous solution the desorption rate of benzene sulfonic acid>benzoic acid>phenol,when desorption with ethanol the rate of phenol>benzoic acid>benzene sulfonic acid,which further confirmed the adsorption mechanism of the three aromatic acids were different.The dynamic adsorption experiments showed that the Bohart-Adams model had a good fitting effect on the dynamic adsorption experiment data,and the effluent concentration reached half of the original concentration in about 550-600 minutes.It is helpful to guide the selection of functionalized reagents and the mechanism of adsorption action in the synthesis of ion exchange resins,which can provide an effective way for the design and synthesis of selective separation of aromatic acids in waste water by computer aided simulation.