Effects of organic macromolecular conditioning on gypsum scaling of forward osmosis membranes

• Published in: Journal of membrane science Vol. 450; pp. 153 - 161
• Main Authors: Liu, Yaolin, Mi, Baoxia
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.01.2014; Elsevier
• Subjects: Alginate; Applied sciences; Carboxylate functional group; Chemistry; Colloidal state and disperse state; Conditioning; Crystals; Direct observation; Exact sciences and technology; Exchange resins and membranes; Flux; Forms of application and semi-finished materials; Forward osmosis; General and physical chemistry; Gypsum; Gypsum scaling; Macromolecules; Membranes; Microbalances; Organic conditioning; Polymer industry, paints, wood; Surface chemistry; Technology of polymers; Direct observation; Gypsum scaling; Carboxylate functional group; Alginate; Forward osmosis; Organic conditioning; Polymeric membrane; Osmosis; Alginates; Carboxylate; Membrane; Cellulose acetate; Functional group
• ISSN: 0376-7388; 1873-3123
• DOI: 10.1016/j.memsci.2013.09.001

This study analyzed the membrane surface conditioning due to the adsorption of different organic macromolecules and investigated how such conditioning affected the gypsum scaling behavior in forward osmosis (FO) membrane processes. A commercially available cellulose acetate FO membrane was used as the base membrane. The membrane surface was conditioned respectively by representative organic macromolecules, namely bovine serum albumin (BSA), Aldrich humic acid (AHA), and sodium alginate, prior to gypsum scaling experiments. Results of direct observation and flux decline experiments showed that the chemistry of organic macromolecules greatly influenced the gypsum scaling of an FO membrane thus conditioned. Specifically, the AHA and alginate conditioning increased gypsum crystal sizes, shortened the crystal nucleation time, and accelerated the flux decline. In contrast, the BSA conditioning noticeably hindered the formation of gypsum crystals and thus slowed down the flux decline caused by gypsum scaling. Further investigation of the conditioning layer properties by quartz crystal microbalance with dissipation and the scaling layer morphologies by SEM suggested that the conditioning layers of AHA and alginate, each containing a high density of carboxylate functional groups along their long chain structures, exhibited strong adsorption of calcium ions as well as accelerated surface or heterogeneous crystallization; in comparison, the conditioning layer of BSA, which has a low carboxylate density and a three-dimensional structure, showed a low level of calcium ion adsorption and a slowdown in gypsum crystallization. •We investigated the effects of organic conditioning on gypsum scaling.•Direct observation was used to characterize scaling layer formation.•Humic acid and alginate conditioning accelerates gypsum scaling.•BSA conditioning interrupts gypsum scaling.•Carboxylate groups of the organic macromolecules enhance surface crystallization.