Preparation And Application Of Polymetaphenylene Isophthalamide Hollow Fiber Membrane And Composite Membrane

The application of membrane separation technology in dye wastewater treatment has the advantages of low energy consumption,no secondary pollution,high treatment efficiency and reusable dyes.However,due to the general membrane materials are not resistant to high temperature and acid,it is necessary to neutralize the dyes before treatment,which increases the cost of treatment.While,in the application of dyes,nanofiltration membrane has a high rejection rate for dyes and salts,which is not conducive to the desalination of dyes.In order to solve the above problems,a high-performance polymer,poly(m-phenylene isophthalamide)(PMIA),was selected as the membrane material in this paper.It has high thermal stability,good purchasing chemistry and high mechanical properties.Firstly,PMIA hollow fiber ultrafiltration membranes were prepared by traditional dry-wet method.The rheological properties of spinning fluid and the special morphology of PMIA membranes were analyzed.The effects of polymer,LiCl,PVP-k15 and TiO2 content on the structure and properties of PMIA membranes were systematically analyzed.The separation performance of tight PMIA/TiO2 hollow fiber membranes for dyes and salts was tested.The retjection rates for four inorganic salts(Na2SOa,MgSO4,MgCl2,NaCl)were less than 5%,for Congo red and Reactive black 5 were 99.56%and 98.75%,respectively.Therefore,it is suitable for desalination and purification of anionic dyes with large molecular weight.Secondly,the self-made PMIA hollow fiber ultrafiltration membrane was used as substrate,and a composite nanofiltration membrane with pH-and ion-responsivity was prepared by interfacial polymerization of L-lysine and trimesoyl chloride(TMC).The effect of monomer concentration on film properties was explored.The composite membrane were characterized by Fourier transform infrared spectroscopy(FTIR),field emission scanning electron microscopy(FESEM),X-ray photoelectron spectroscopy(XPS),Zeta potentiometer and contact angle goniometer.Then the effects of salt concentration(ionic strength)and pH on the performance of the composite membrane were explored.The ion-responsivity was used to test the separation performance of salts and dyes before and after film swelling.The results show that the surface of the composite membrane contains a large number of carboxyl groups,which makes the membrane more hydrophilic and negatively charged;both responses can swell the surface of the composite membrane.After swelling,the salt and dye rejection rate of the membrane decreased;and the water flux increased more than three times.However,the rejection of Bright blue G with larger molecular weight still maintains 99.65%.Moreover,after swelling the composite film,Methyl orange and Bright blue G can be completely separated.Also,the composite membrane has higher anti-pollution and thermal stability,and with a flux recovery ratio of 94.23%.