分子质量对天然水体有机物正渗透膜分离的影响

Effect of Molecular Weight on Forward Osmosis Membrane for Separation of Organic Matters in Natural Water

利用大分子质量海藻酸钠、中分子质量单宁酸等目标有机物及天然有机物系统研究分子质量对正渗透膜分离的影响。结果显示,相比于大分子质量海藻酸钠和小分子质量黄腐酸,中分子质量单宁酸及牛血清白蛋白产生的膜污染较重,单宁酸、牛血清白蛋白、黄腐酸、海藻酸钠的通量损失依次为54.72%、49.91%、29.64%、16.52%;当水样中天然有机物以大、中、小分子质量分布特征为主时,通量损失分别为46.5%、54.8%、50.5%,中分子质量天然有机物引起的膜污染较重;此外,大分子质量天然有机物的含量越多,膜污染越轻,正渗透膜对各分子质量天然有机物的截留率均在89%以上。结合XDLVO理论测定污染物与膜之间的界面能垒,以大分子质量有机物为主的水样具有较大的界面能垒(海藻酸钠ΔE_(b)=5.71×10^(−20)J,滤池反冲洗水ΔE_(b)=9.32×10^(−21)J),表明污染物与正渗透膜之间的排斥作用较大,膜污染较轻。

This paper investigated the effect of molecular weight on the performance of forward osmosis membrane for separation of the target organic matters such as macromolecular weight sodium alginate(SA)and medium molecular weight tannic acid(TA)and natural organic matters(NOM).Compared with macromolecular weight SA and small molecular weight fulvic acid(FA),the fouling of membrane for separating medium molecular weight TA and bovine serum albumin(BSA)was more serious,and the flux loss of the membrane for separating TA,BSA,FA and SA was 54.72%,49.91%,29.64%and 16.52%,respectively.When the NOM in water samples were mainly distributed in large,medium and small molecular weight,the flux loss was 46.5%,54.8%and 50.5%,respectively,and the membrane fouling caused by NOMs with medium molecular weight was more serious.In addition,the higher content of macromolecular weight NOM would reduce the membrane fouling,and the rejection rate of NOM with different molecular weights was always more than 89%.The interfacial energy barrier between the foulants and membrane was determined according to XDLVO theory.The water samples mainly composed of macromolecular organic matters had large interfacial energy barriers(ΔE_(b)=5.71×10^(-20)J for SA andΔE_(b)=9.32×10^(-21)J for filter backwash water),indicating that the repulsion between foulants and the membrane was large and the membrane fouling was not serious.