Preparation And Performance Study Of Functionalized Carbon Nanotube/polyethersulfone Separation Membrane

Polymer membranes made with polyethersulfone（PES）as raw materials have been widely used in the field of wastewater treatment,but these membranes have a strong hydrophobic surface,which can easily cause membrane fouling during separation,which makes the membrane performance and service life are severely affected,so the appropriate modification of the membrane to enhance membrane performance is one of the focuses of membrane separation technology research in recent years.Carbon nanotubes（CNTs）are one-dimensional nanomaterials with a special tubular structure.They have high specific surface area and mechanical strength,and can provide additional water transport channels.They have become ideal nanomaterials in membrane separation technology.In this paper,the PES membranes were modified by surface coating and mixed matrix modification by using two functional CNTs respectively,and the modified membranes were characterized and tested for performance.First,the PES base membrane was prepared by the method of immersion precipitation phase inversion,sodium lignosulfonate（SLS）was used to modify multi-walled carbon nanotubes（MWCNTs）by non-covalent grafting to obtain S-MWCNTs.Then,a thin film composite（TFC）membrane was prepared by polymerizing a polypyrrole（PPy）film layer on the surface of the PES membrane.After that,S-MWCNTs was successfully mixed in the PPy layer to prepare a thin film nanocomposite（TFN）membrane.Systematic characterization and basic performance testing of PES,TFC,and TFN membranes were carried out.The results show that the TFN membrane maintains a high dye rejection rate（above 95.8%）,but also has a higher water flux(53.9 L·m^-2·h^-1).Due to good hydrophilicity and charge repulsion,TFN membrane also has high anti-fouling performance,maintaining a high flux recovery rate FRR（87.9%and 84.9%）during the two pollution cycles.The TFN membrane also has the ability to separate salts and dyes.In the 8 h test time,the rejection rate of the test dye is above 98.4%,and the rejection rate of Na Cl is below7.9%.Tannic acid（TA）was also modified by non-covalent grafting to modify MWCNTs to obtain T-MWCNTs,which was blended with PES and then phase inverted to prepare PES membrane and T-MWCNT/PES mixed matrix membrane.Basic characterization,separation,and filtration tests were performed on the membranes.The results show that,compared with PES membrane,the surface pores of the mixed matrix membrane become more and larger,and the finger-like pore structure becomes more obvious.Its pure water flux reached 325.9 L·m^-2·h^-1,which was increased by nearly 2.5 times,and the rejection rate of bovine serum albumin（BSA）remained above 91%,at the same time,the mechanical properties and anti-fouling properties of the membrane have also been improved.