Preparation Of Ion-exchange Membrane Doped By Modifed TiO₂ And Their Application Performances For Electrodialysis

In order to address the increasing demand for fresh water due to accelerated social and economic growth in the world,water treatment technologies,such as desalination,have been rapidly developed in attempts to safeguard water security.Electromembrane desalination processes,such as electrodialysis?ED?,belong to a category of desalination technologies,which involve the removal of ions from ionic solutions with the use of electrically charged membranes termed ion exchange membranes?IEMs?.The challenges associated with IEMs had drawn the attention of many researchers,who had investigated various approaches to enhance their properties.The incorporation of nanomaterials is one of the popular approaches employed.Titanium dioxide?TiO₂?nanoparticle is one of the well-known nano materials which has gained a great deal of attention because of its high hydrophilicity,high adsorption capacity,stable chemical property,low cost and safety toward both humans and the environment.Therefore,it has great theoretical value and profound practical applications to blending TiO₂ with polymers to prepare membranes.The aim of this paper was to improve the performance of ion exchange membrane,functionalized TiO₂ and then blended it with polyvinyl chloride?PVC?and ion exchange resin powder to prepare IEMs.The main experimental procedure and results were as follows:?1?The performance of PVC based cation exchange membrane?CEM?was obviously enhanced by incorporating organophosphorylated titania nanoparticles?OPTi?.To fabricate this modified membrane,pristine TiO₂ were firstly phosphorylated by amino trimethylene phosphonic acid,then mixed with the powder of PVC.This modified titania nanoparticles was tested by XPS and FT-IR to ensure the formation of OPTi.The effects of the blending ratio of OPTi on membrane performance such as water uptake,ion exchange content,mechanical properties and membrane surface resistance were particularly investigated.Results showed that the addition of OPTi significantly improved the performance of CEM.Besides,this composite membrane exhibited a superior ED performance such as a reduction of 26.68%on energy consumption and an increase of 29.27%on current efficiency.?2?The performance of PVC based anion exchange membrane?AEM?was obviously enhanced by incorporating quaternized titania nanoparticles?Q-TiO₂?.To fabricate this modified membrane,the free radical copolymerization of allyl trimethylammonium chloride with 3-?iso-butenoyl?propyl trimethoxysilane was carried out,and then the reaction products loaded the quaternary ammonium groups onto TiO₂ by coupling reaction,then mixed with the powder of PVC.This modified titania nanoparticles was tested by XPS and FT-IR to ensure the formation of Q-TiO₂.The effects of the blending ratio of Q-TiO₂ on membrane performance such as water uptake,ion exchange content,mechanical properties and membrane surface resistance were particularly investigated.Results showed that the addition of Q-TiO₂ significantly increased the concentration of fixed ion on the membrane surface,which lowered the resistance and improved the permselectivity and mechanical properties.?3?The CEM-2 and AEM-0.5 with excellent properties were selected through the investigation of the properties of modified IEMs.The application of electrodialysis was studied with the optimized self-made IEMs,and the commercial heterogeneous IEMs were taken as reference.The experimental results showed that the self-made IEMs had high desalination efficiency,and with good electrodialysis performance,99.30%ion removal rate in the process of seawater desalination.So the self-made IEMs had great application potential in the field of electrodialysis technology in the treatment of brine desalination.