Electrical Ultrafiltration Membrane: Construction,Separation And Antifouling Performance

Membrane separation technology can achieve selective interception of pollutants based on differences in component size or charge.It has the characteristics of simple operation,easy modularization,wide application range and low energy consumption,and is widely used in sewage treatment and water reuse.However,the trade-off effect between permeation flux and rejection rate and membrane fouling limited its further development.The conductive membrane has the dual characteristics of electrochemical activity and membrane separation,which has obvious advantages in synchronous improvement of osmotic selectivity and anti-pollution effect,and can achieve efficient and short process removal of pollutants.In this paper,two construction strategies of conductive separation membranes were proposed to improve the interception efficiency of target pollutants and alleviated membrane pollution based on the synergistic effect of electrochemistry and membrane separation.The specific research contents and conclusions are as follows:（1）Preparation and antifouling performance of metal particle coating composite conductive ultrafiltration membrane.Carbon nanotube（CNT）and Tannic acid（TA）were introduced into the membrane of polyvinylidene fluoride（PVDF）,using the reduction and fixation of silver ions by TA,Ag nanoparticle（Ag NPs）was formed in situ on the membrane matrix.The introduction of Ag NPs significantly improved the conductivity of the membrane,the resistance value decreased from 78.9Ω（PVDF/TA）to 58.2Ω（PVDF/TA-Ag）,and the pure water flux was 223.7 L/（m~2 h）at-2 V under the action of electric field,the interception rate of humic acid can reach 97%.Meanwhile,in the anti-pollution experiment,the flux recovery rate of PVDF/TA-Ag membrane reached 86.9%,which was 20%higher than that of PVDF/TA membrane without electric field.In addition,PVDF/TA-Ag membrane has excellent antibacterial effect under the action of electric field coupling,which can effectively solve the problem of biological contamination during operation.The above results showed that the introduction of Ag NPs coating improves the conductivity,retention effect and antifouling performance of polymer ultrafiltration membrane.（2）Construction and properties study of CNT ultrafiltration membrane with conductive level holes.Polyethylenimine（PEI）was crosslinked by CNT of different radial ratios,CNT ultrafiltration membranes with pore distribution were constructed.And CNT@TA-PEI ultrafiltration membranes were crosslinked by PEI and TA.By regulating the pore size and crosslinking degree of CNT layer,the local microelectric field environment on the membrane surface and around the pore was constructed.The flux of CNT@TA-PEI membrane was 120.8 L/（m~2 h）,and the interception effect of bovine serum protein was 96.6%.The dye rejection rate of CNT@TA-PEI membrane increased from less than 10%to more than 90%under electric field.Antifouling test showed that flux recovery rate of CNT@TA-PEI membrane reached 81.0%after circulating filtration.At the same time,the electric field also accelerated the adsorption of Sb on CNT@TA-PEI membrane,which broke through the limitation of slow mass transfer in the traditional adsorption process.The experimental results showed that the removal efficiency of Sb increases from 78%at 0 V to 99%at 3 V.In addition,in the face of the combined contamination of dye and metal ions,the CNT@TA-PEI membrane under the applied electric field showed a bifunctional force of electric repulsion and electric adsorption.The above results indicated that CNT@TA-PEI membrane can effectively overcome the trade-off problem of permeability flux/selectivity under the synergistic effect of pore size regulation and auxiliary electric field.In conclusion,in this paper,by constructing conductive ultrafiltration membrane and coupling electrochemical and membrane separation characteristics,the limitation of"trade-off"effect between permeation flux and rejection rate of traditional membrane body was broken,and the antifouling performance of membrane was effectively improved,which was expected to provide technical reference for the preparation and modification of conductive membrane.