Molecular Mechanisms of Ultrafiltration Membrane Fouling in Polymer-Flooding Wastewater Treatment: Role of Ions in Polymeric Fouling

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• 作者：Guicai Liu ; Shuili Yu ; Haijun Yang ; Jun Hu ; Yi Zhang ; Bo He ; Lei Li ; Zhiyuan Liu
• 刊名：Environmental Science & Technology
• 出版年：2016
• 出版时间：February 2, 2016
• 年：2016
• 卷：50
• 期：3
• 页码：1393-1402
• 全文大小：551K
• ISSN：1520-5851

文摘

Polymer (i.e., anionic polyacrylamide (APAM)) fouling of polyvinylidene fluoride (PVDF) ultrafiltration (UF) membranes and its relationships to intermolecular interactions were investigated using atomic force microscopy (AFM). Distinct relations were obtained between the AFM force spectroscopy measurements and calculated fouling resistance over the concentration polarization layer (CPL) and gel layer (GL). The measured maximum adhesion forces (F_ad,max) were closely correlated with the CPL resistance (R_p), and the proposed molecular packing property (largely based on the shape of AFM force spectroscopy curve) of the APAM chains was related to the GL resistance (R_g). Calcium ions (Ca²⁺) and sodium ions (Na⁺) caused more severe fouling. In the presence of Ca²⁺, the large R_p corresponded to high foulant–foulant F_ad,max, resulting in high flux loss. In addition, the R_g with Ca²⁺ was minor, but the flux recovery rate after chemical cleaning was the lowest, indicating that Ca²⁺ created more challenges in GL cleaning. With Na⁺, the fouling behavior was complicated and concentration-dependent. The GL structures with Na⁺, which might correspond to the proposed molecular packing states among APAM chains, played essential roles in membrane fouling and GL cleaning.