聚酰胺复合膜的改性及其选择渗透性

非对称性的反渗透(RO)聚酰胺(PA)复合膜可以通过溶剂处理方法改性成为渗透汽化(PV)分离有机物水溶液的均相膜．实验选用了PA良溶剂(甲酸、乙酸、磷酸、盐酸、苯酚)作为PA膜的改性剂．溶剂改性条件(改性剂类型、浓度和处理时问)对改性膜的吸着性有明显影响．用质量分数8％的乙酸处理1h的PA膜，较之未改性膜，优先吸水性增强，对水的溶胀率SW增大，对异丙醇的溶胀率SIPA减小．乙酸处理的PA膜的SW与SIPA差值在所有溶剂处理的膜中最大，相应地PV分离IPA水溶液时，膜的分离因子和渗透通量也最大，处理过程溶剂分子与PA高分子链的接触和PA膜中微囊内高分子链段向外运行，是PA膜结构改变的主要因素．溶剂处理改变了膜的结构的机理能很好地解释非对称性RO膜的改性．

Modification and permselectivity of polyamide composite membrane

Asymmetric reverse osmosis (RO) polyamide (PA) composite membrane may be modified by means of solvent processing technique into pervaporation (PV) membrane for separating organic aqueous solution.Better solvents formic acid,acetic acid,phosphoric acid,hydrochloric acid and phenol etc.for PA were selected as the modifying agent in this study.The effect of the modifying conditions (type and concentration of the modifying agent,processing time of membrane in liquid medium) on the sorption of modified membrane was marked.After PA composite membrane was treated with mass fraction 8% acetic acid for 1 h,the swelling rate, S W, of water increased while that, S IPA of isopropanol decreased,as compared with the non-modified membrane.The difference between S W and S IPA of the membrane treated with acetic acid was the greatest among those with other modifying agents.The separation factor and flux of the modified membrane were correspondingly maximum when it was used in separating isopropanol aqueous solution by PV.The contact of solvent molecules in liquid medium with polymer chains in PA membrane, and the intra-nodular chains in PA membrane tending to diffuse by reptation towards the solvent molecules were the principal cause leading to change of structure of asymmetric PA composite membrane.The mechanism of changing membrane structure by means of the solvent processing technique may better interpret the modification of PA composite RO membrane.