层层自组装PDADMAC/PSS纳滤膜的制备

以荷负电的聚砜超滤膜为基膜,采用静态层层自组装技术,制备了PDADMAC/PSS多层聚电解质纳滤膜.考察了支撑盐的种类、浓度、自组装层数对膜的分离性能、荷电性能、亲水性等的影响.研究结果表明,以NaCl为支撑电解质制得的膜具有较高的性能,聚合电解质溶液中支撑电解质的浓度以0.5mol/L为宜;在较优的条件下所制备的(PDADMAC/PSS)5对2g/L Na2SO4的截留率可达93%,通量在1.0MPa下接近60L/(m2.h),对NaCl的截留率仅为9%～13%,通量可达80L/(m2.h).膜表面的荷电量和接触角的变化均反映了聚电解质的交替自组装.以PSS为最外层的膜表面具有很好的负电性和很低的接触角.随着双层数的增加,膜表面的负电荷量的绝对值先逐渐增大,达到一个极大值后又逐渐减少,说明层数并非越多越好;以PSS作为最外层的膜具有很好的亲水性.

Preparation of PDADMAC/PSS nanofiltration membrane by layer-by-layer self-assembly technology

Using negatively charged PS ultrafiltration membrane as substrate,multilayer PDADMAC/PSS polyelectrolytes nanofiltration membranes were prepared by layer-by-layer self-assembly technology.The membrane surface morphology,charging property,as well as the effect of concentration and types of the support electrolyte on the membrane performance were investigated.The results indicated that the prepared NF membrane surface was uniform and with no defect;the values of negative charge on membrane surface first gradually increase with the bi-layer number,and then gradually decrease with the bi-layer number,which demonstrate that there should be an optimal concentration of the support electrolyte.In addition,the performance of the(PDADMAC/PSS)5 NF membranes prepared in optimal conditions was evaluated.The results showed that under 1.0 MPa,the Na2SO4(2 g/L) rejection was 93%,and the corresponding flux was up to 60 L/(m2·h);the NaCl rejection was only 9%~13%,while the flux could reach 80 L/(m2·h).The prepared NF membrane could be completely used for the separation of univalent and bivalent salt solution system.The variation of contact angles reflects the alternative self-assembly of the polyelectrylytes.The prepared NF membranes with PSS as surface layer have excellent hydrophilic property.