Monovalent-ion-selective membranes for reverse electrodialysis

• Published in: Journal of membrane science 2014-04, Vol.455, p.254-270
• Main Authors: Güler, Enver, van Baak, Willem, Saakes, Michel, Nijmeijer, Kitty
• Format: Article
• Language: English
• Subjects: Antifouling; Chemistry; Coating; Colloidal state and disperse state; Electrodialysis; Exact sciences and technology; Freshwater; General and physical chemistry; Ion exchangers; Membrane characterization; Membranes; Monovalent-ion selectivity; Reverse electrodialysis; Rivers; Salinity gradient energy; Selectivity; Sulfates
• ISSN: 0376-7388; 1873-3123
• DOI: 10.1016/j.memsci.2013.12.054

Reverse electrodialysis (RED) is a process that can be used to generate energy from salinity gradients. Since its application in practice requires the use of natural seawater and river water, the presence of multivalent ions is inevitable, but this currently limits RED performance. Membranes with selectivity for monovalent ions may overcome this limitation. Standard ion exchange membranes have low monovalent-ion selectivity. We used a relatively fast method to coat a standard commercial anion exchange membrane to improve its monovalent-ion selectivity. The coating layer was formed by copolymerization of 2-acryloylamido-2-methylpropanesulfonic acid (AMPS) as the active polymer and N,N-methylenebis(acrylamide) (MBA) as the crosslinker, using UV irradiation. The monovalent ion selectivity of the resulting membranes was comparable to that of commercial monovalent-selective membranes. Furthermore, the modified membranes with their negatively charged coating showed increased hydrophilicity and exhibited sufficient antifouling potential against organic foulants. When they were tested in an RED stack, their performance was found to depend especially on the proportion of the divalent ions (sulfate) in the river water stream. However, the use of the currently available monovalent selective membranes was not found to be very effective for obtaining higher gross power densities in RED. Mechanism of monovalent ion selectivity by integration of an anion exchange membrane with a cation exchange layer. [Display omitted] •Design of monovalent ion selective membranes for RED.•Developed membranes showed monovalent selectivity comparable to commercial ones.•The developed membrane combines antifouling tendency and monovalent ion selectivity.•RED performance was dependent on multivalent ion concentration in the river water.