title: Molecular Mechanisms of Ultrafiltration Membrane Fouling in Polymer-Flooding Wastewater Treatment: Role of Ions in Polymeric Fouling.
abstract: 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 (Fad,max) were closely correlated with the CPL resistance (Rp), 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 (Rg). Calcium ions (Ca(2+)) and sodium ions (Na(+)) caused more severe fouling. In the presence of Ca(2+), the large Rp corresponded to high foulant-foulant Fad,max, resulting in high flux loss. In addition, the Rg with Ca(2+) was minor, but the flux recovery rate after chemical cleaning was the lowest, indicating that Ca(2+) 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.
authors.affiliation: School of Environmental Science and Engineering; State Key Laboratory of Pollution Control and Resource Reuse, Tongji University , Shanghai, China , 200092.
authors.forename: Guicai
authors.initials: G
authors.lastname: Liu
authors.affiliation: School of Environmental Science and Engineering; State Key Laboratory of Pollution Control and Resource Reuse, Tongji University , Shanghai, China , 200092.
authors.forename: Shuili
authors.initials: S
authors.lastname: Yu
authors.affiliation: Key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences , PO Box 800-204, Shanghai 201800, P.R. China.
authors.forename: Haijun
authors.initials: H
authors.lastname: Yang
authors.affiliation: Key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences , PO Box 800-204, Shanghai 201800, P.R. China.
authors.forename: Jun
authors.initials: J
authors.lastname: Hu
authors.affiliation: Key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences , PO Box 800-204, Shanghai 201800, P.R. China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Shandong Academy of Environmental Science ; Jinan, China , 250013.
authors.forename: Bo
authors.initials: B
authors.lastname: He
authors.affiliation: School of Environmental Science and Engineering; State Key Laboratory of Pollution Control and Resource Reuse, Tongji University , Shanghai, China , 200092.
authors.forename: Lei
authors.initials: L
authors.lastname: Li
authors.affiliation: School of Environmental Science and Engineering; State Key Laboratory of Pollution Control and Resource Reuse, Tongji University , Shanghai, China , 200092.
authors.forename: Zhiyuan
authors.initials: Z
authors.lastname: Liu
mesh_terms: D007477:Ions; D008567:Membranes, Artificial; D018625:Microscopy, Atomic Force; D011108:Polymers / Q000737:chemistry*; D011145:Polyvinyls; D014462:Ultrafiltration / Q000379:methods*; D014865:Waste Disposal, Fluid / Q000379:methods*; D062065:Wastewater / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry; D005465:Fluorocarbon Polymers
chemical_list: D007477:Ions; D008567:Membranes, Artificial; D011108:Polymers; D011145:Polyvinyls; D062065:Wastewater; D014874:Water Pollutants, Chemical; C024865:polyvinylidene fluoride; D005465:Fluorocarbon Polymers