新型聚酰胺正渗透膜去除地表水中全氟化合物的性能及机理研究

Perfluorinated compounds (PFCs) are widely present in surface water, which are characterized by persistence, pollution, bioaccumulation and refractibility. Nanofihration and reverse osmosis membrane separation technology has advantages including easy process and high efficiency, but there exists shortcomings such as high energy consumption and membrane pollution. Forward osmosis separation technology shows great potential at the removal of PFCs from surface water due to its advantages of high efficiency, low energy consumption and low pollution. However, the practical effect and mechanism of PFCs removal through forward osmosis membrane are still unclear..In this study, combined modification process of doping-blending and surface mineralization will be conducted to synthesize novel chitosan/polysulfone-silver chloride/polyamide thin film composite forward osmosis membranes. Then the morphology structure and element composition performance of the synthesized forward osmosis membranes will be characterized. Meanwhile, the forward osmosis performance including water flux and salt rejection will be determined. The removal effects of PFCs from practical and simulative surface water by the synthesized forward osmosis membranes will be comparatively studied and the influence of forward osmosis experiment conditions on PFCs removal will be also analyzed. The interaction mechanism between forward osmosis membrane and PFCs from surface water will be explored through analysis of influence of surface hydrophilcity and electric charge of forward osmosis membrane and co-existing materials including inorganic salt and other organics in water on PFCs removal. Finally the removal mechanism of the forward osmosis membranes for PFCs from surface water is revealed. This study is supposed to provide theoretical and experimental basis for removal of PFCs from water by forward osmosis membrane separation technology. In addition, this study could promote the development and application of removal technology for PFCs in surface water.

全氟化合物（PFCs）在地表水中广泛存在，具有持久性、污染性、生物积累性和难降解性等特点。纳滤和反渗透膜去除水中PFCs效率高，过程简单，但存在能耗高、膜污染等缺点。正渗透膜具有高效率、低能耗和低污染等特点，对去除地表水中PFCs具有较大潜力，然而实际去除作用和去除机理尚不清晰。.本项目拟通过共混掺杂和表面矿化改性制备具有大水通量和高选择性的新型壳聚糖/聚砜-氯化银/聚酰胺薄层复合正渗透膜，表征其结构形貌和元素组成，并测试其水通量和截留率；对比研究正渗透膜对实际地表水体和模拟水体中PFCs的去除作用，分析汲取液浓度和流速对去除PFCs效果的影响；研究正渗透膜表面亲水性和表面电荷，以及水中共存无机盐和其他有机物对PFCs去除效果的影响，揭示正渗透膜去除地表水中PFCs的机理。项目的研究成果可为正渗透膜去除地表水中PFCs提供理论和实验依据，同时也可促进地表水中PFCs去除技术的开发应用。

全氟化合物（PFCs）是一类普遍存在于地表水中的难降解有机污染物，有效去除PFCs 的工艺已成为目前环境友好处理技术领域的研究新热点。正渗透膜分离技术具有高效率、低能耗、低污染等特点，在去除地表水中全氟化合物领域表现出巨大潜力，然而传统的正渗透膜由于内浓差极化存在水通量低、选择性差等缺点。本项目通过氯化银表面矿化改性制备了新型的聚酰胺薄层复合正渗透膜，有效提高了膜的水通量和选择性研究了改性正渗透膜对地表水中全氟化合物的去除作用并探讨其机理，项目研究成果可为正渗透膜分离技术去除地表水中全氟化合物的实际应用提供实验基础和技术支撑。项目的研究结论如下：.（1）成功制备出氯化银表面矿化改性聚酰胺TFC正渗透膜，改性膜中氯化银粒子均匀分布在膜表面；氯化银表面矿化改性膜具有更强的表面亲水性，膜表面带的负电荷也更多；氯化银表面矿化改性膜具出更好的正渗透性能：更高的水通量和更高的盐截留率；改性膜中氯化银沉积量过多时，会在膜表面发生团聚，降低膜的正渗透性能和抗污染性能。.（2）建立了水中PFOA和PFOS的LC-MS分析方法，可实现PFOA和PFOS的有效分离；氯化银矿化改性膜具有更高的水通量和PFCs截留率，对PFOA和PFOS的去除率分别为96.2%和95.7%，同时也具有最大的水通量26.2 L/m2·h。未改性的正渗透膜虽然也具备较高的PFCs截留能力，但水通量太低，处理能力较差；氯化银表面矿化改性膜在去除PFCs过程中具有更低的水通量下降，而且在经过而且在经过反向冲洗后具有更高的水通量恢复率。氯化银能稳定存在于改性膜表面。改性膜具有良好的抗污染性能和稳定性。.（3）正渗透膜与PFCs的相互作用方式主要为疏水作用和静电相互作用。改性正渗透膜主要通过降低与PFCs的疏水作用以及增强与PFCs的静电排斥作用，实现对PFCs的高效截留。随着改性膜矿化度的增加，膜表面亲水性随之增强，膜表面多带负电荷随之增加，对PFCs的截留性能也随之加强；水中不同物质共存会对正渗透膜与PFCs的之间疏水作用及静电排斥作用产生影响，从而影响膜对PFCs的截留性能。