| With the continuous development of society,human beings are facing many environmental problems,such as water shortage and water pollution problems.The core of solving such problems is to increase the reuse of water resources.Compared with traditional water separation technology,membrane separation technology,as an emerging water treatment technology,has many advantages,such as low energy consumption,safe and pollution-free,high separation efficiency and simple operation.However,the membrane structure of conventional materials can be easily damaged under some harsh conditions.Polyacrylonitrile(PAN)is a material with excellent solvent resistance and chemical stability,and its membranes can be prepared for use under extreme conditions.But PAN membranes are poorly hydrophilic,and long-term operation can cause serious membrane contamination,which in turn shortens the membrane life.Therefore,in this paper,PAN will be modified to strengthen its hydrophilicity and improve its anti-pollution performance to meet water treatment requirements.Firstly,PAN was subjected to click chemistry reaction with sodium azide.This process synthesizes different ratios of 1,2,3,4-tetrazole polyacrylonitrile(PAN-N).It enhances the hydrophilicity of PAN membranes.The PAN-N ultrafiltration membranes with different grafting degrees were prepared by phase transformation method,and their structures and morphologies were characterized by FTIR,~1H-NMR,XRD,SEM,TGA and contact angle.Then the effects of different 1,2,3,4-tetrazole grafting degree,PAN-N concentration and porogenic agent polyethylene glycol(PEG-600)content on the membrane performance were systematically investigated.The results showed that when the grafting degree was 10%(PAN-N-10),PAN-N concentration was 16 wt%and PEG-600 concentration was 10 wt%,the membrane had a flux of 125.2L/(m~2·h·bar),a retention rate of 82.5%and a contact angle of 57.3°,which was better than the original PAN membrane(flux of 95.7 L/(m~2·h·bar),retention rate of 69.8%and contact angle of 69.1°).In addition,the irreversible contamination index of the membrane was reduced from 33.5%to 17.2%of the original membrane,and the flux recovery rate of the membrane after three cycles was increased from 48.1%to 70.9%of the original membrane,showing higher resistance to contamination and recovery performance.The membrane formation kinetics was also studied,which showed that the membrane had a higher diffusion coefficient and better pore formation under the optimal conditions.Secondly,In order to further enhances the hydrophilic modification of PAN-N-10,the optimal PAN-N polymer(PAN-N-10)prepared in the previous step was reacted with iodoethane(EI),2-iodoethanol(IH),and iodoacetic acid(IA)to further enhance the hydrophilic properties respectively.The PAN-N-EI,PAN-N-IH and PAN-N-IA ultrafiltration membranes grafted with different functional groups were prepared by the phase transformation method to investigate the effects of modifying different functional groups on the membrane structure and properties.The membranes were tested for performance.The results showed that the comprehensive performance of the membranes was PAN-N-IA>PAN-N-IH>PAN-N-EI.And it was also found that the higher the hydrophilicity of the introduced groups,the better the hydrophilicity and the comprehensive performance of the membranes.More specifically,the pure water flux of PAN-N-IA membrane reached 180 L/(m~2·h·bar),which was 1.44times higher than that of PAN-N-10 membrane.The retention rate increased from 82.5%to 94.9%.The contact angle decreased from 63.2°to 45.1°.The total contamination index of the membrane decreased from 61.3%to 58.1%.The total flux recovery rate increased by 10.8%after three cycles.The overall performance of the membrane was better than that of PAN-N-10 membrane.Besides,the membrane diffusion in the coagulation bath was found to follow Fick’s law,indicating that the better the apparent diffusion coefficient of the membrane,the better the membrane porosity. |
PDF Full Text Request