Hydrophilic Modification Of PTFE Flat Sheet Membrane

Membrane separation is a physical separation method of environment friendly and low energy consumption.It is widely used in sewage treatment and air filtration.PTFE flat sheet membrane has the characteristics of high and low temperature resistance,acid and alkali resistance,and aging resistance.Because of the unique molecular chain structure of PTFE flat sheet membrane,PTFE membrane was used in various harsh environment.But due to the strong hydrophobic in the surface of PTFE flat sheet membrane,and the surface wettability is very poor,which limits its application in the field of water.So the hydrophilic modification of PTFE flat sheet membrane has received more and more attention.Being based on the existed modification methods of PTFE membrane,we studied the structure and properties of PTFE flat sheet membrane,and investigated a physical modification method without breaking the original nature of PTFE.The hydrophilic age nt was evenly coated on the membrane surface,and GA was used as cross- linking agent to enhance the fastness of hydrophilic agent and PTFE flat sheet membrane.The surface morphology,chemical structure,pore structure,and the hydrophilic ability were researched by SEM,FTIR,Mercury Injection Apparatus and Porous Analyzer.The filtration performance and resistance to protein were analysed by a cross-flow device.The main research contents are listed as follows:(1)PVAc was dissolved in anhydrous ethanol,and made PVAc alcoholysis by adjusting the pH of the solution.Using GA as a cross- linking agent to make hydrophilic agent firmly attached to the membrane.Further hydrolysis the ester group of not been alcoholysised to improve the hydrophilic performance of PTFE flat sheet membrane.The experiment results show that the unmodified membrane remains good membrane pore structure and a high porosity.After modification,the pore size of the membrane became smaller and a little some pores were blocked.The optimum conditions of the experiment:the concentration of PVAc alcohol solution is 45 g·L-1,the alcoholysis time is 30 min,the concentration of GA is 6 g·L-1,the concentration of PEG is 30 g·L-1 and the hydrolysis time is 150 min.It was showed that the hydrophilic group of-OHs were attached the surface of the modified membrane.The contact angle dropped from 135.65° to 58.7°,and the initial water flux was 272.1 kg·m-2·h-1.The hydrophilic persistence of the modified membrane is good,and the rejection of ceramic cutting waste water is 99.55%.Finally the hydrophilic membrane can effectively inhibit the pollution of protein adsorption.PMV was dissolved in anhydrous ethanol,and made PMV alcoholysis by adjusting the pH of the solution to 9.Using GA as a cross-linking agent to make hydrophilic agent firmly attached to the membrane.The experiment results show that the unmodified membrane remains “fibrillar-node” network structure,and the membrane pores distribute evenly.After modification,part of the fibrils became thicker,nodes become smaller,and porosity is a little bit down. The optimum conditions of the experiment:the concentration of PMV alcohol solution is 20 g·L-1,the alcoholysis time is 120 min,the concentration of GA is 9 g·L-1 and the concentration of PEG is 40 g·L-1.It was showed that the hydrophilic group of-OHs were attached the surface of the modified membrane;The contact angle dropped from 135.2° to 61.5°,and the initial water flux was 260 kg·m-2·h-1.The hydrophilic persistence of the modified membrane is good,and the rejection of ceramic cutting waste water is 98.53%.Finally the hydrophilic membrane can effectively inhibit the pollution of protein adsorption.