The molecular structures of polysaccharides affect their reverse osmosis membrane fouling behaviors

• Published in: Journal of membrane science Vol. 625; p. 118984
• Main Authors: Tong, Xin, Zhao, Xue-Hao, Wu, Yin-Hu, Bai, Yuan, Ikuno, Nozomu, Ishii, Kazuki, Hu, Hong-Ying
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.05.2021
• Subjects: Membrane fouling; Molecular structure; Polysaccharides; Reverse osmosis; XDLVO theory; Polysaccharides; Reverse osmosis; Molecular structure; Membrane fouling; XDLVO theory
• ISSN: 0376-7388; 1873-3123
• DOI: 10.1016/j.memsci.2020.118984

Polysaccharides were usually considered as important organic compounds causing organic fouling of reverse osmosis (RO) membranes. In this study, the RO membrane fouling behaviors and mechanisms of 9 polysaccharides with different molecular weights and structures were studied. It was found that not the molecular weight but the molecular structure mainly influenced the fouling behavior. Straight-chain polysaccharides tended to cause slight and slow membrane fouling (final flux decline < 30% in 100 h), while branched-chain polysaccharides led to severe fouling (final flux decline > 50% in 50 h) and formed thicker foulant layers on membrane surfaces. The presence of Ca2+ could double and even triple the flux decline of straight-chain acid polysaccharides, but showed barely effect on branched-chain polysaccharides as well as neutral polysaccharides. The extended Derjaguin-Laudau-Verwey-Overbeek (XDLVO) theory revealed that attractive energy dominated the interaction between branched-chain polysaccharides and membranes. The addition of Ca2+ turned the repulsive interaction between straght-chain acid polysaccharides and membranes into attractive interaction, but showed no significant effect on neutral polysaccharides. The viscosity of straight-chain polysaccharides didn't increase with the polysaccharide concentrations, while that of branched-chain polysaccharides showed a positive relationship with mass concentrations. Ca2+ also enhanced the viscosity of straight-chain acid polysaccharides. [Display omitted] •Polysaccharides with branched chains had high fouling potential with or without Ca2+.•Straight-chain polysaccharides showed slight fouling potential without Ca2+.•Ca2+ could aggravate membrane fouling of acidic straight-chain polysaccharides.•Studied the relationship between viscosity and fouling behaviors of polysaccharides.•Quantified and compared the fouling extent of representative polysaccharides.