| Forward osmosis（FO）as a sustainable membrane technology has attracted more and more attention.The forward osmosis membrane has the advantages of low energy consumption,low pollution tendency and mild operating conditions,but the defects of low water flux,high reverse solute flux and effect of internal concentration polarization make it difficult for the forward osmotic membrane to be widely used in industry.As the supporting layer of thin film composite-forward osmosis（TFC-FO）membrane,the substrate often determines the performance of the TFC-FO membrane.Precisely for that reason,improving the structure of the base membrane is the most effective way to improve the performance of TFC-FO membrane.The way of achieving smaller structural parameters（improving the structure porosity and reducing the pore bending factor）and higher hydrophilicity to offset the negative effects of internal concentration polarization（ICP）effect and surface fouling is the key of control the structure characteristics of the substrates.In this paper,the effects of different contents of hydrophilic polymer polyvinyl butyral（PVB）on the structure characteristics of cellulose acetate butyrate（CAB）substrates and the properties of TFC-FO membrane were studied.Firstly,CAB/PVB blend membrane was prepared via nonsolvent induce phase separation（NIPS）method.PVB and polyethylene glycol 400（PEG400）were used as additives and N,N-dimethyl acetamide（DMAc）was used as solvent.The performance of the substrates was improved by changing the PVB concentration.The results showed that when the PVB concentration was 2wt%,the finger-like pores were formed inside the CAB/PVB membrane and the porosity were large.For this reason,the pure water flux of the substrate M2 reached 1265L·m-2·h-1.After interface polymerization on the surface of substrates to form TFC-FO membranes,TFC-M2 showed promising structural parameters:the pure water permeability coefficient(A,1.08 L·m-2·h-1·bar-1)and the structural parameter（S,363.5μm）,indicating that TFC-M2 had the smallest concentration polarization effect.The evaluation of the TFC-FO membranes showed that the water flux of the TFC-M2 was up to 27.5 L·m-2·h-1 at 1M Na Cl draw concentration and active-layer facing draw solution（AL-DS）mode.The TFC-M2 also has low specific salt flux Js/Jw（0.35 g/L）.Secondly,the CAB/PVB blend substrates were prepared by NTIPS method with caprolactam（CPL）used as diluent.The effect of PVB concentration on the structure characteristics of substrates was investigated,and the results showed that the substrate N2 had the best connectivity and hydrophilicity.After interface polymerization,TFC-N2 showed good permeability,and low reverse salt flux in AL-DS and AL-FS（active-layer facing draw solution）modes(1.56 g·m-2·h-1and 1.47 g·m-2·h-1).Finally,the fouling research of TFC-FO membranes which was prepared by the above two fabricating membrane methods was studied.Using BSA as the model pollutant,the membrane fouling behavior in AL-DS and AL-FS was studied,and the membrane fouling resistance was analyzed.The results showed that compared with the AL-DS mode,the membrane in the AL-FS mode was less susceptible to fouling and easier to clean off to get good recovery flux performance.Overall,TFC-M2 showed the excellent fouling performance. |
