Abstract:

The active layer of cellulose triacetate (CTA) forward osmosis membrane was modified by surface coating. Firstly, a metal-polyphenol precursor layer was constructed by self-assembly of tannic acid (TA) and iron ions (Fe³⁺) on the membrane surface, and then the hydrophilic functional layer of tannic acid/diethylenetriamine (TA/DETA) was further coated. Finally, the Ag/polyvinylpyrrolidone (PVP) antibacterial functional layer was in-situ formed on the membrane surface by the reductive property of TA, and the TA/Fe³⁺-TA/DETA-Ag/PVP modified membrane was prepared. The change of membrane water flux during dynamic fouling experiment was investigated using a cross flow forward osmosis device. The surface morphology and the composition of the original membranes and fouled membranes were analyzed by scanning electron microscopy (SEM) and infrared spectroscopy (FTIR). The distribution of bacteria and pollutants on the fouled membrane surface was characterized by confocal laser scanning microscope (CLSM). And the cleaning efficiency of original CTA membrane and modified membrane was compared. The results showed that the water contact angle of TA/Fe³⁺-TA/DETA-Ag/PVP modified membrane decreased from 78.79° to 33.05°, and the hydrophilicity was significantly improved. After the 15 days dynamic fouling experiment, the flux of original CTA membrane and TA/Fe³⁺-TA/DETA-Ag/PVP modified membrane decreased to 52.14% and 72.81% of their initial flux, respectively. Compared with CTA membrane, the amount of live bacteria and organic contaminants on the surface of TA/Fe³⁺-TA/DETA-Ag/PVP modified membrane was substantially reduced. After hydraulic cleaning and osmotic backwashing, the flux recovery of TA/Fe³⁺-TA/DETA-Ag/PVP modified membrane was up to 80.37%, which was much higher than 49.88% of CTA membrane, and the TA/Fe³⁺-TA/DETA-Ag/PVP modified membrane exhibited a better antifouling performance.

Key words: membrane, forward osmosis, surface modification, tannic acid, wastewater treatment, antifouling

摘要：

采用表面涂覆的方法对三醋酸纤维素（CTA）正渗透膜的活性层进行改性，首先利用单宁酸（TA）与铁离子（Fe³⁺）在膜表面以自组装的形式构建金属-多酚前体层，在此基础上进一步涂覆单宁酸/二乙烯三胺（TA/DETA）亲水功能层，最后借助TA的还原性在膜表面原位形成Ag/聚乙烯吡咯烷酮（PVP）抗菌功能层，制备了TA/Fe³⁺-TA/DETA-Ag/PVP改性膜。利用错流式正渗透装置探究动态污染实验中膜通量的变化情况，通过扫描电子显微镜（SEM）和红外光谱（FTIR）分析膜污染前后表面形貌和组成，使用激光共聚焦显微镜（CLSM）对膜表面污染物微观分布进行表征，并对比CTA原膜和改性膜的清洗效能。结果表明：TA/Fe³⁺-TA/DETA-Ag/PVP改性膜的水接触角由78.79°下降至33.05°，亲水性显著提升。在15天的动态污染实验结束后，CTA膜和TA/Fe³⁺-TA/DETA-Ag/PVP改性膜的通量分别衰减为各自初始通量的52.14%和72.81%，且与CTA原膜相比，TA/Fe³⁺-TA/DETA-Ag/PVP改性膜表面的活细菌数量和有机污染物量大幅减少。经过水力清洗和渗透反洗后，TA/Fe³⁺-TA/DETA-Ag/PVP改性膜的通量恢复率可达80.37%，远高于CTA原膜的49.88%，具有较强的抗污染性。

关键词: 膜, 正渗透, 表面改性, 单宁酸, 污水处理, 抗污染