基于膜特征参数变化的蛋白质超滤过程膜污染研究

为进一步研究多种蛋白质体系超滤过程的膜污染机制,采用切割相对分子质量为50×103的聚醚砜(polyethersulfone,PES)超滤膜,对溶菌酶(lysozyme,LYS)、牛血清蛋白(bovine serum albumin,BSA)、LYS+BSA等3种不同蛋白质溶液的超滤过程进行了研究.运用接触角仪、场发射扫描电镜(field emission scanning electron microscope,FESEM)、原子力显微镜(atomic force microscope,AFM)测定了不同污染阶段膜特征参数的变化.结果表明,超滤膜通量变化明显呈现3个阶段:初期(约0~5min)衰减迅速、中期(约5~60 min)衰减缓慢、后期(约60~120 min)趋于稳定;整个超滤过程中,LYS污染膜的通量衰减幅度最大,LYS+BSA次之,BSA最小.膜特征参数变化表明:LYS对膜的初期污染主要以膜孔窄化为主,中期污染由膜孔堵塞和膜孔窄化共同控制;BSA初期膜污染以膜孔堵塞为主,中期污染以膜孔窄化为主;滤饼层过滤是BSA、LYS后期膜污染的主要机制.LYS+BSA二元混合溶液中的LYS对膜污染的产生起主导作用.

Membrane Fouling Based on Change of Membrane Characteristic Parameters During Ultrafiltration of Protein

In order to further understand membrane fouling mechanism of various protein systems during ultrafiltration, polyethersulfone (PES) ultrafiltration membrane with relative molecular weight cut off of 50×10³ was used, the ultrafiltration processes of three kinds of protein solution were investigated: lysozyme (LYS), bovine serum albumin (BSA), and LYS+BSA. Contact angle meter, field emission scanning electron microscope (FESEM) and atomic force microscope (AFM) were adopted to determine the change of membrane characteristic parameters at different fouling stages. The results indicated that the changes of ultrafiltration membrane flux obviously exhibited three stages: sharp flux decline in the initial stage (approximately between 0-5 min), slow flux decline during the transition stage (approximately between 5-60 min), and stable flux in the late stage (approximately between 60-120 min). During the whole ultrafiltration process, the LYS-fouled membrane had the largest flux decline, followed by the LYS+BSA-fouled membrane, and the BSA-fouled membrane had the least decline. The changes of membrane characteristic parameters clearly indicated that the initial filtration stage of LYS was controlled by pore constriction, while pore blocking and pore constriction were the main fouling mechanism at the transition stage. Pore blocking was the main fouling mechanism of BSA in the initial fouling stage, while the transition stage was controlled by pore constriction. Cake filtration was the main fouling mechanism of LYS and BSA in the late stage. The membrane fouling of binary mixtures LYS+BSA appeared to be dominated by LYS.