Fouling Behavior of Negatively Charged Natural Organic Matters to Anion Exchange Membranes in Reverse Electrodialysis

Abstract

Reverse electrodialysis (RED) represents an energy conversion technology from the salinity difference of concentrated salt solutions (e.g., sea water) and diluted salt solutions (e.g., river water). The RED stack is comprised of an alternating arrangement of cation- and anion-exchange membranes between two electrodes that selectively transfer anions and cations. However, the river water used for the RED may contain natural organic matters (i.e., humic acid and fulvic acid). Thus, electrostatic characteristics of organic matter may lead to membrane surface fouling. The membrane fouling cause increase electrical resistance and the increase of maintenance cost, and a significant decrease in operating performance. In this study, the influence of membrane fouling in RED by commercially available humic acid was investigated experimentally, and adsorption tests, open circuit voltage, stack resistance, and power density were measured at different operation conditions. As a result, it was confirmed that the adsorption of humic acid onto the surface of anion-exchange membranes occurred even though the direction of the electromigration of negatively charged humic acid was toward cation-exchange membranes. The fouling of anion exchange membranes by humic acid was highly influenced by the roughness of the surface of anion-exchange membranes. It was confirmed by isothermal curves (i.e., Frendlich isotherm). Acknowledgements This work was supported by the New and Renewable Energy of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) granted financial resource from the Ministry of Trade, Industry & Energy, and Republic of Korea (No. 20143030071240).