Boric acid recovery in dilute during the desalination process in BMED system

Abstract

Bipolar membrane electrodialysis (BMED) system allows the simultaneous desalination and acid and base production. Boric acid (H3BO3) and sodium chloride (NaCl) forms during dissolution of sodium tetraborate-decahydrate (Na2B4O7.10H2O) in hydrochloric acid (HCl). The study presents that BMED process provides H3BO3 purification in dilute during the desalination process. In this study, desalination ratio, H3BO3 purification efficiency, acid and base production, specific energy consumption, and current efficiency were defined as performance indicators. The effects of initial H3BO3 concentration and flow rates of solutions on performance indicators were investigated under acidic condition. Additionally, two acidic conditions were evaluated with respect to desalination ratio and H3BO3 concentration in dilute. The results of the experiments indicated that the presence of H3BO3 does not affect the desalination process. The more H3BO3 concentration allows the more decrease in purification efficiency and current efficiency based on proton ions. The varying feed flow rate was found not effective on desalination, while purification efficiency increased with increasing flow rate. Initial H3BO3 concentration was determined as less effective on acid and base conversion than that of flow rate. In addition to simultaneous salt removal, acid and base recovery, the most important output of BMED will be H3BO3 recovery in high purity.