Probing the nano- and micro-scales of reverse osmosis membranes - A comprehensive characterization of physiochemical properties of uncoated and coated membranes by XPS, TEM, ATR-FTIR, and streaming potential measurements
Probing the nano- and micro-scales of reverse osmosis membranes - A comprehensive characterization of physiochemical properties of uncoated and coated membranes by XPS, TEM, ATR-FTIR, and streaming potential measurements
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DOI：
10.1016/j.memsci.2006.10.038
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发表时间：
2007-01-05
影响因子：
9.5
通讯作者：
Leckie, James O.
中科院分区：
文献类型：
--
作者：
Tang, Chuyang Y.;Kwon, Young-Nam;Leckie, James O.
聚酰胺（PA）复合反渗透（RO）膜的性能主要由几百纳米厚的致密皮层决定。对这一关键薄层的进一步理解将可能促进我们对膜污染和痕量有机物截留的理解和控制。不幸的是，生产RO膜的工艺和确切的化学成分是专有的。在这项研究中，使用XPS、ATR-FTIR、TEM显微镜和流动电位分析来表征商业全芳香族聚酰胺反渗透膜。通过以系统的方式一起使用这些技术，对于一些商业Ro膜，证实了富含-COH基团的脂肪族涂层的存在。虽然未涂覆的RO膜具有非常接近基于均苯三甲酰氯和1，3-苯二胺（在苯二胺中）的经典界面聚合化学的聚酰胺的预测值的表面元素组成（通过XPS测量），但涂覆的膜显示出更高的氧含量和更低的氮含量。典型的层状结构（聚砜层顶部的聚酰胺层）和粗糙的脊和谷特征在TEM显微照片中清晰可见。对于涂覆的膜，浅色涂层（缺乏电子密度）是可见的，特别是当存在染色的腐殖酸污垢层以增加涂层和背景之间的对比度时。在ATR-FTIR光谱中观察到涂层膜的强烈OH伸缩峰以及新的脂肪族C-H伸缩峰，其中未涂层膜通常存在的芳香族=C-H伸缩峰被淹没。对碳Is峰的高分辨率XPS扫描证实了涂层中醇-COH基团的存在，其中除了未涂覆的膜存在的两个峰之外，还鉴定了具有1.5eV的结合能位移的另外的峰：284.6eV（脂肪族和芳香族碳原子）和类似于287.8eV（羧基和酰胺键碳原子）。经涂覆的膜的测得的ζ电位值比未经涂覆的膜的测得的ζ电位值负性显著更小，这表明涂层可能是中性的。(c)2006年爱思唯尔B. V.保留所有战斗。
The performance of polyamide (PA) composite reverse osmosis (RO) membranes is essentially determined by a dense skin layer several hundred nanometers thick. Improved understanding of this critical thin layer will likely advance our understanding and control of membrane fouling and trace organics rejection. Unfortunately, the processes and exact chemistries for producing RO membranes are proprietary. In this study, XPS, ATR-FTIR, TEM microscopy, and streaming potential analysis were used to characterize commercial fully aromatic polyamide RO membranes. By using these techniques together in a systematic way, the presence of an aliphatic coating layer rich in -COH groups was confirmed for some commercial Ro membranes. While the uncoated RO membranes had surface elemental compositions (measured by XPS) very close to the predicted values for polyamides based on the classical interfacial polymerization chemistry of trimesoyl chloride and 1,3-benzenediamine (in-phenylene-diamine), the coated membranes showed higher oxygen and lower nitrogen content. The typical layered structures (a polyamide layer on top of a polysulfone layer) and the rough ridge-and-valley features were clearly visible in TEM micrographs. For a coated membrane, a light-colored coating layer (lack of electron density) was visible, especially when a stained humic acid foulant layer was present to increase the contrast between the coating and the background. An intense OH stretching peak in conjunction with new aliphatic C-H stretching peaks were observed in ATR-FTIR spectra for coated membranes, where the aromatic =C-H stretching peak normally present for uncoated membranes was overwhelmed. High-resolution XPS scans on carbon Is peaks confirmed the presence of alcoholic -COH groups in the coating layer, where an additional peak with a binding energy shift of 1.5 eV was identified in addition to the two peaks present for uncoated membranes: 284.6 eV (aliphatic and aromatic carbon atoms) and similar to 287.8 eV (carboxylic and amide bond carbon atoms). The measured zeta potential values of the coated membranes were significantly less negative than those of the uncoated ones, suggesting that the coating layer is likely neutral. (c) 2006 Elsevier B.V. All fights reserved.