The Investigation Of The Modified Polyethersulfone Anion Exchange Membrane Towards Phosphate

The diethylenetriamine anion exchange group was grafted to the surface ofpolyethersulfone (PES) membrane via the covalent interactions of acylation and amination,then the prepared parameters of the PES anion exchange membrane were optimized. Themembrane was characterized by SEM and FTIR techniques. The adsorption properties ofthe modified PES anion exchange membrane towards phosphate were investigated,considering the presence of SO42-. The thermodynamic and kinetic characteristics of theanion exchange membrane with and without the coexistance of SO42-anion, were alsoconsidered. The reused performance of the anion exchange membrane was evaluated. Inaddition, the through curve of the membrane towards phosphate were also evaluated usingthe BDST (the bed depth service time) model, with and without the coexistence of SO42-.The experimental results show that the modified polyethersulfone exhibits anexcellent adsorption property towards phosphate. The optimal pH for the adsorptionprocess is3, and the adsorption equilibrium time is3hours. The batch adsorption resultsshow that the sorption kinetics fit well to second-order equation and the isotherms can bewell described by Langmuir model. D-R plots indicate the adsorption process is an ionexchange reaction. Thermodynamic parameters is ΔG0<0, ΔH0>0, ΔS0>0, indicating thespontaneous endothermic reaction. In the study of dynamic breakthrough curve, the masstransfer rate Kaand the bed sorption capacity N0obtained by the BDST model areconsistent with the results of the static adsorption processes. The adsorption/desorptionexperiment indicates that this anion exchange membrane possesses an excellent propertyof reuse.The theoretical calculation of the adsorption property of the membrane towardsphosphate were also studied through the density functional theory. The results showed thatthe phosphate and the diethylenetriamine functional group showed the nucleophilicity andthe electrophilicity in the adsorption process respectively. The adsorption energy of thePES anion exchange membrane towards phosphate was-41.416kJ/mol and the Gibbs freeenergy was-29.95kJ/mol. The results indicated that though the electrostatic interaction,the diethylenetriamine functional group of the PES anion exchange membrane showed asignificant adsorption of phosphate and the adsorption process was spontaneous.