Preparation,Hydrophilic Modification And Properties Of Polyethersulfone Membrane By RTIPS Method

Currently,membrane technology has been widely used in petrochemical,environmental,energy,metallurgy,textile,food,aerospace and electronics.Polyether sulfone(PES)is a membrane material with excellent properties.At present,the main preparation method of PES membrane is non-solvent induced phase separation(NIPS)method.In this paper,polyethersulfone(PES)was used as membrane material,N,Ndimethylacetamide(DMAc)was good solvent,diethylene glycol(DEG),polyethylene glycol 200(PEG200)and polyethylamine Alcohol 300(PEG300)were poor solvents,cellulose acetate(CA),inorganic titanium dioxide sol(TiO2 sol)and A polybiphenyl phenol sulfate(BPA-PS)were hydrophilic additives,respectively.Polyethersulfone flat-sheet and hollow fiber microporous membranes were prepared by non-solventinduced phase separation(NIPS)and reverse thermal-induced phase separation(RTIPS)methods.Scanning electron microscopes(SEM),pure water flux,BSA rejection rate,mechanical properties,atomic force microscopy(AFM),energy dispersive X-ray spectroscopy(EDX),X-ray photoelectron spectroscopy(XPS),and pure water contact angles were used to characterize the elemental composition,structure and properties of membranes.The effects of different solvent non-solvent ratios,polymer concentration,types of non-solvent,additive content and water bath temperature on the membrane structure and properties were investigated.Firstly,Four membrane-forming systems were studied,namely PES/N,Ndimethylacetamide(DMAc)/diethylene glycol(DEG),PES/DMAc/polyethylene glycol 200(PEG200),PES/DMAc/PEG300 and PES/DMAc/PEG400.The effects of PES molecular weights,PES concentrations,PEG molecular weights and ratios of nonsolvent/solvent on phase separation temperature are investigated,and the influence of different membrane formation mechanisms(RTIPS or NIPS)on the properties and structure of the membrane was explored.The molecular weight of PES has little effect on the cloud point.With the increase of PES content,the cloud point of the prepared solution was decreased while the viscosity increased.As the PEG molecular weight increases,both the cloud point and the viscosity of the casting solution increased.Membranes prepared by the DEG/DMAc mixed solvent,showed higher tensile strength and elongation at break than for membranes produced by a PEG200/DMAc or PEG300/DMAc mixed solvent.When the membrane formation mechanism was the RTIPS process,tensile strength,the elongation at break and the Young's modulus were higher than for the corresponding membranes prepared by the NIPS process.It is concluded that the advantage of the RTIPS process is the easy preparation of membranes with symmetrical bi-continuous morphology resulting in good mechanical properties.Subsequently,a novel antifouling polyethersulfone(PES)hollow fiber membrane was modified by the addition of bisphenol sulfuric acid(BPA-PS)using reverse thermally induced phase separation(RTIPS)process.BPA-PS was synthesized by click chemistry and was blended to improve the hydrophilicity of PES hollow fiber membranes.The performance of PES/BPA-PS hollow fiber membranes,which were changed with the contents of BPA-PS and the temperatures of coagulation water bath,was characterized by scanning electron microscopy(SEM),pure water flux(JW),BSA rejection rate(R),atomic force microscope(AFM),x-ray photoelectron spectroscopy(XPS),fourier transform infrared spectroscopy(FTIR)and water contact angle.The cloud point,which was used to explore the temperature of the phase separation,changed a little bit with the addition of BPA-PS.Nevertheless,the water contact angle displayed the decreasing trend from 92.6° to 61.6° with the addition of BPA-PS.The flux of pure water(JW)and BSA rejection rate(R)of the membranes increased first and then decreased with the increased BPA-PS.And the optimal pure water flux(739 L/(m2h)and BSA rejection rate(79.2%)were obtained from the membrane with 1 wt.%BPAPS.The mechanism of membrane formation transformed NIPS to RTIPS when the temperature of coagulation water bath increased to the cloud point.In the meantime,the finger-like cross sections changed into sponge-like structures.As for the membranes prepared by RTIPS,the pure water flux and BSA rejection rate were both higher than the membranes achieved from NIPS.This phenomenon confirmed that the membrane produced by RTIPS had better performance than that via NIPS process.This study provides a method for combining reverse heat-induced phase separation(RTIPS)with click chemistry to produce PES/BPA-PS.Hollow fiber membrane new process method.Finally,a new attempt to prepare polyethersulfone(PES)-Titania(TiO2)organicinorganic hollow fiber hybrid membranes were investigated by sol-gel process assisted reverse thermally induced phase separation(RTIPS)method.The membrane formation mechanism underwent NIPS(coagulation temperature lower than cloud point)or RTIPS(coagulation temperature higher than cloud point)process.Properties of hollow fiber hybrid membranes,which varied with TiO2 sol addition and coagulation temperature,were investigated by SEM,EDX,AFM,TGA,XPS and contact angle.SEM results showed that the dense skin layer was produced in the hybrid membranes via NIPS process,while porous skin layer and sponge-like structures emerged in the hybrid membranes via RTIPS process.As a result,pure water flux,BSA rejection,mechanical properties of hybrid membranes by RTIPS were higher than that via NIPS.With the increase of TiO2 sol content,the cloud point temperature increased,the water contact angle decreased from 98.2° to 56.2°,and the pure water flux(Jw)and BSA rejection(R)of the hybrid membrane first increased and then decreased.The organicinorganic hybrid membranes prepared with 1 wt.%TiO2 sol content by RTIPS method exhibited decent performance,which reached maximum pure water flux of 1046 L/(m2h)and BSA rejection of 75%.In general,the PES-TiO2 hollow fiber hybrid membrane prepared by sol-gel process assisted reverse thermally induced phase separation(RTIPS)method showed excellent pure water flux,BSA rejection,mechanical properties and anti-pollution performance.This study provides a new process for the preparation of organic-inorganic hybrid membranes.