Boron Removal from Aqueous Solution by Bipolar Electrodialysis Hiroki Nagasawa a, * , Atsushi Iizuka a , Akihiro Yamasaki b and Yukio Yanagisawa a a Department of Environment Systems, Institute of Environmental Studies, School of Frontier Sciences, The University of Tokyo, Chiba, Japan b Department of Materials and Life Science, Seikei University, Tokyo, Japan Abstract Boron removal process using electrodialysis method combined with bipolar membrane water splitting reaction was investigated. By using bipolar membrane electrodialysis, pH value of boron contained solution will immediately increase and the dissociation reaction of boric acid into borate ions was enhanced. Therefore, boron can be effectively removed from boron contained solution. Experimental results confirm that bipolar membrane electrodialysis has an advantage over existing electrodialysis. Effect of initial concentration was investigated. It was confirmed that energy requirement for boron removal increase when the initial boron concentration increase. Keywords: Boron; Electrodialysis, Bipolar membrane; Water Introduction Boron compounds in water at high concentration are known to be toxic to humans and plants. The World Health Organization (WHO) has limited boron concentration in drinking water to less than 0.5 mg-B/L. Because of the increased use of desalinated seawater and underground water for drinking water and large amount of boron emissions via wastewater from the manufacturing process, the removal of boron from aqueous solutions has been an important issue in recent years. In aqueous solutions, boron is mainly present in the form of boric acid. According to the dissociation reaction, boric acid will form into borate ion at alkaline condition. H 3 BO 3 + OH - ↔ B(OH) - pKa = 9.1 (1) There are several methods investigated for removing boron from aqueous solutions, such as precipitation [1] , adsorption [2] , solvent extraction [3] and ion-exchange [4] . However, the precipitation and the adsorption methods are efficient only under high boron concentration. In the case of the solvent extraction and the ion-exchange, post regeneration process causes cost increases. Electrodialysis is one of the considerable options for boron removal from aqueous solution [5] . Using electrodialysis, borate ion will be efficiently removed from aqueous solution. However, borate ion only exist at alkaline condition, existing electrodialysis method cannot be utilized to acidic solutions. * Corresponding author. E-mail: hiroki_nagasawa@yy.k.u-tokyo.ac.jp 1