Preparation Of Hydrophilic Composite Nanofiltration Membrane Through Interfacial Polymerization And The Application Research In Rare Earth Recovery

In the paper, the hydrophilic composite NF membranes were developed for compounding the ultra-thin functional layers which were prepared by interfacial polymerization on polysulfone(PSF) supporting membranes, and applicated in the research of rare earth separation to explore the optimal operating conditions. And the research content includes the following three parts:Polysulfone ultrafiltration membrane was prepared by phase invertion process which was using PSF as membrane material, PEG-600, PVP K30 as additive and DMAc as solvent. The influence of the concentration of PSF, PEG-600 and PVP(K30) on the permeability fluxes and rejection rate of membranes were investigated, and the optimum process conditions of membrane manufacture were as followed: PSF concentration of 15%-17%, PEG-600 concentration of 1.5%-2.5%, PVP concentration of 4%-6%. The flux of permeate range from 247 L/m2·h to 372 L/m2·h, and the rejection of 1 g/L BSA ranged from 93.5% to 99.4% at 0.1 MPa.The hydrophilic composite nanofiltration membrane was prepared on the polysulfone support membrane, with PIP and TMC as reactants, by interfacial polymerization. The effects of different preparing conditions on the membrane performance were studied, including the concentration of PIP、TMC and sodium phosphate, reacting time, curing temperature and curing time. The optimal preparation conditions were given as follows: PIP of 1%-1.5%, sodium phosphate of 1%-2%, TMC of 0.25%-0.3%, reacting time about 60-70 s in water phase and 55-65 s in hexane, and curing temperature at 70-80℃ and curing time about 8-12 min. The permeate was about 36.78 L/m2·h and the rejection of 1g/L Mg SO4 was over 94% at 0.6MPa. The SEM phenograms, AFM phenograms and the contact angle test result showed that the addition of sodium phosphate increased the effective membrane area and had a good hydrophilicity. Separation performance order of the optimal membrane to different inorganic salts is as follows: Na2SO4(94.76%)≈Mg SO4(94.54%)> Mg Cl2(78.66%)>Na Cl(42.5%), and increasing the operating pressure appropriately will help to increase the membrane flux and the rejection rate.Finally, hydrophilic composite nanofiltration membranes were used in recycling rare earth ions in low concentration of rare earth leaching liquid for studying the application performance of hydrophilic composite nanofiltration membrane. The results presented that the rejection of rare earth ions kept about 93%, and the higher the feed temperature and operating pressure can increase the rejection rate and flux. After concentrating 0.33g/L rare earth leaching solution for 8h at 1MPa, concentrated solution of rare earth ion concentration was 3.48 times of the stock solution, the concentration of rare earth ions in permeate is 0.015 g / L.According to results above, hydrophilic composite nanofiltration membranes have good intercept performance to the rare earth ions, which will be prospected application in rare earth recovery.