University of Twente Student Theses


Multilayer polyelectrolyte coating of cation exchange membranes to increase monovalent selectivity in reverse electrodialysis

Schneider, Helen (2014) Multilayer polyelectrolyte coating of cation exchange membranes to increase monovalent selectivity in reverse electrodialysis.

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Abstract:The uphill transport of multivalent ions is one of the main obstacles for a high power generation, using river and sea water in reverse electrodialysis. This project deals with the reduction of multivalent ion transport across cation exchange membranes, making use of electrostatic repulsion. For this purpose Fuji V1 cation exchange membranes (CEMs) were coated via layer-by-layer assembly, using poly(allylamine hydrochloride) (PAH) and poly(styrene sulfonate) (PSS). Successful film growth on silicon wafers was detected by reflectometry measurements. Contact angle measurements were used to verify film growth on silicon wafers as well as on CEMs. The ionic strength during layer deposition on membranes was varied (0.05M, 0.5M, 2.5M NaCl), in order to investigate its influence on membrane performance. Modified membranes were compared by their performance in resistance and single-salt permselectivity measurements. The results show the highest resistance and lowest apparent permselectivity for membranes, coated under low ionic strength conditions and are thereby advocating their use for multivalent cation rejection. However, the results differ only slightly and one needs to be aware of possible error sources such as temperature fluctuation and bubbles in the measuring cell. In order to make confident statements, the measurement of permselectivity for mixed salt solutions was aspired. It was found that the measurement parameters were not optimized for getting significant results. However, valuable insight about the experimental set-up has been gained, more precisely the measurement should be performed over a longer time span (>2 hours) and with a lower applied current density (<10 mA).
Item Type:Essay (Bachelor)
Faculty:TNW: Science and Technology
Subject:50 technical science in general
Programme:Advanced Technology BSc (50002)
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