Surface modification of reverse osmosis membrane by electrostatic deposition of polyelectrolyte for performance improvement

doi:10.11949/j.issn.0438-1157.20171021

Abstract

Abstract:

The commercial reverse osmosis (RO) membrane surface was chlorinated with the sodium hypochlorite solution. Then the chitosan as a polycation electrolyte was deposited on the chlorinated RO membrane surface with the help of electrostatic adsorption. With the aim of preparing high flux and high salt rejection RO membrane, the effects of solution pH, chlorination time, sodium hypochlorite concentration, chitosan concentration and deposition time on membrane performance were systematically studied. The water flux and the salt rejection were measured at 1.55 MPa and (298±1) K for a feed NaCl concentration of 2000 μg·g^-1. The results showed that, compared to the original RO membrane, the water flux of the chlorinated membrane increased by 19.89% when the chlorination solution pH=9, the chlorination time was 30 min and the chlorination concentration was 1000 mg·L^-1. A slightly increase of the salt rejection was also observed. Further modification of chitosan deposition on the chlorinated membrane surface showed that the membrane surface hydrophilicity was enhanced. When the chitosan concentration was 0.1%(mass) and the deposition time was 30 min, the water contact angle of the membrane surface was 34.88° and the salt rejection improved to 99.56%. The water flux of the deposition modified membrane reached 60.55 L·m^-2·h^-1, which was nearly maintained the same as the chlorinated RO membrane above. These results indicated that both the water flux and the salt rejection of the modified commercial RO membrane improved after the surface modification through chlorination and chitosan deposition.

Key words: membrane, desalination, permeation, chlorination, polyelectrolyte, chitosan, electrostatic deposition

摘要：

利用次氯酸钠溶液对商品反渗透膜表面进行氯化处理，然后将聚阳离子电解质壳聚糖通过静电吸附作用沉积在RO膜的表面，系统地研究了氯化过程的pH、氯化时间、次氯酸钠浓度、壳聚糖浓度及其沉积时间对膜性能的影响，以制备出高通量、高截留率的RO膜。在压力1.55 MPa、原料液温度（298±1）K的条件下，测定RO膜处理2000 μg·g^-1氯化钠溶液的水通量和截留率。结果表明，当pH=9、氯化时间为30 min、次氯酸钠浓度为1000 mg·L^-1时，水通量较原膜提高了约19.89%，截留率略有提高；当壳聚糖浓度为0.1%（质量分数）、沉积时间为30 min时，改性膜的接触角降低到34.88°，亲水性提高，水通量较氯化后的RO膜几乎保持不变，为60.55 L·m^-2·h^-1，截留率达到了99.56%。经过氯化和沉积改性后的RO膜水通量和截留率均得到了提高。

关键词: 膜, 脱盐, 渗透, 氯化, 聚电解质, 壳聚糖, 静电沉积

CLC Number:

TQ028.8

LIU Meiling, LIU Jun, WANG Qin, TAN Yong, LI Bao'an. Surface modification of reverse osmosis membrane by electrostatic deposition of polyelectrolyte for performance improvement[J]. CIESC Journal, 2018, 69(2): 830-839.

刘美玲, 刘军, 王琴, 谈勇, 李保安. 聚电解质静电沉积改性制备高性能反渗透膜[J]. 化工学报, 2018, 69(2): 830-839.

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