Design And Preparation Of High-efficiency Anti-pollution Composite Membrane Based On The Synergy Of CNT And Electric Field

The main idea of this subject is the design and preparation of highly effective anti-fouling composite membranes based on the synergy of carbon nanotubes?CNTs?and electric field.The CNTs and external electric field act synergistically on the surface hydrophilicity,surface charge characteristics and surface roughness of the membrane to obtain polymer composite membranes with efficient separation performance and antifouling performance.In order to meet the requirements of chemical durability and improve membrane separation performance,CNTs as a promising low-dimensional nanomaterial are embedded in membranes to obtain better performance.Unfortunately,due to the inertness and hydrophobicity of the original CNTs,the dispersion in aqueous solution is unsatisfactory and the bonding with the organic substrate is poor.Therefore,CNTs are modified using physical or chemical methods to obtain better operability.In this project,polyvinylidene fluoride?PVDF?mixed matrix membranes containing polyethylene glycol?PEG?grafted CNT?PMWCNTs?was first prepared by phase inversion method.Compared with pristine PVDF membranes,PMWCNT/PVDF mixed matrix membranes significantly increase the water flux and stabilize the rejection rate of bovine serum albumin?BSA?because of the better hydrophilicity and antifouling properties.The mixed matrix membrane has satisfactory anti-protein fouling and anti-blood fouling performance?more than 90.0%of FRR?,and the membrane pollution can be further reduced under the action of a weak electric field(direct current,about 2V cm^-1).However,because CNTs are embedded under the polymer,they cannot directly contact the liquid to be treated,so the modification effect is limited.In this subject,?SLS-CNTs?,SLS-CNTs?non-covalently functionalized CNTs with sodium lignin sulfonate?SLS??directly modified the interfacial polymerization composite layer on the polyethersulfone?PES?substrates under the effect of an external electric field to obtain a nanofiltration composite membrane.Nanofiltration composite membrane has significantly improved water flux and stable salt rejection,and the membrane has improved resistance to chlorination and protein pollution.Excessive affinity between hydrophilic CNTs and water molecules will block the passage of water molecules.In order to modify the substrates and the interfacial polymerization layer of the nanofiltration composite membrane at the same time,the interfacial polymerization layer was prepared on the PES substrates containing the CNTs aligned by an external electric field to obtain the nanofiltration composite membranes.Aligned CNTs penetrate the substrates and the interfacial polymerization layer,resulting in a significant change in the structural morphology and permeability of the membrane.Nanofiltration composite membrane has greatly improved water flux(29.7 L·m^-2·h^-1·bar^-1)and stable salt rejection,and has excellent resistance to chlorination and protein pollution.