Preparation Of Forward Osmosis Membranes Blend With Additives And Study Of Antifouling Ability

The lack of high performance membranes is the main factor of hindering the development of the forward osmosis technology.At present,the research of modified CA forward osmosis membranes is lack of systematic and comprehensive.This paper studied the effect of the 6 kinds of additives on the properties of CA membrane systematically.The main contents of this research includ: through phase inversion method,the cellulose acetate(CA)forward membranes were prepared using ZnCl2,lactic acid,and poly-vinylpyrrolidone(PVP)as additives.The effects of different additives on the membrane structure were investigated by contact angle measurement,scanning electron microscopy(SEM)and atomic force microscope(AFM);the effects of different additives on the separating property were investigated by water flux,salt rejection;the effects of different additives on antifouling ability were investigated by fouling experiment with BSA as typical foulant,and the micro forces between bovine serum albumin(BSA)and membrane.The results show that the following:(1)Lactic acid and ZnCl2 had no obvious effect on the CA membrane roughness;the roughness of CA membrane with PVP increased by 3 nm,but it wasn't affected by its content.When the content of nanoparticles additives fCNT,TiO2 and SiO2 are 1wt%,2wt% and 2wt%,respectively.The nanoparticles were found together.So the CA membrane roughness increased sharply.6 kinds of additives improved the surface hydrophilicity of CA membrane.And hydrophilic enhanced with the increase of additive content,the effect from good to bad is in turn: fCNT,ZnCl2,Ti O2 and SiO2,lactic acid,PVP.(2)The CA membranes structure were optimized by 6 kinds of additives.The additives increased the size of holes and the number of finger holes of CA membrane.The effect of the traditional additives ZnCl2 was best;CA membrane ZnCl2-2 internal hole was the largest,and the bending rate is smallest.Compared with ZnCl2,the number of finger holes were less of other 5 kinds of CA membranes.(3)In terms of improving the CA membrane water flux,the effect of ZnCl2 is best,the water flux is as high as 15.7 L/(m2?h),175% and 34% higher than the CA membrane without additives and commercial CTA membrane,respectively.The water fluxes of CA membranes with lactic acid and PVP are 14.6 and 10.8 L/(m2?h)respectively.The water flux of CA membrane with nanoparticles additives has improved,but the effect was inferior to ZnCl2 and lactic acid,its flux is about 9 L/(m2?h).In terms of reverse salt flux,all of additives reduced the reverse salt flux.The effect of ZnCl2 and nanoparticle additives were best,the minimum was 0.458 g/(m2?h).The second is the PVP,the worst is lactic acid.(4)In the aspect of reducing flux attenuation speed,the effect 3 kinds of nanoparticles were similar and best,followed by ZnCl2,finally the PVP and lactic acid.CA membrane with nanoparticles,flux recovery rate is over 96%,the flux recovery rate of CA membrane Zn Cl2-2 was 96.5%,lactic acid-5 and PVP-2 were 89.3%,85.5% respectively.The micro forces between BSA and CA membrane from strong to weak was followed by: CA membrane with nanoparticles,ZnCl2-2,lactic acid-5,PVP-2 and CA membrane without additive.In general,the effect of nanoparticles fCNT,TiO2 and SiO2 were superior to the traditional additives ZnCl2,lactic acid,PVP on antipollution of CA membrane.