Utilization of Bipolar Membrane Electrodialysis for the Removal of Boron from Aqueous Solution

Bipolar membrane electrodialysis (BMED) was used to remove boron from aqueous solution. BMED was compared with conventional electrodialysis (ED) using aqueous solutions of sodium tetraborate containing 100 mg/L of boron. With use of BMED, more than 90% of the boron was removed under both acidic (pH 2.3) and basic (pH 9.1) conditions, whereas only 35−45% of the boron was removed using conventional ED. Over 90% of the boron was removed from the diluate solution over a wide range of initial pH from 2.3 to 12.0. A high initial pH reduces the current efficiency of boron removal because of the high mobility and high concentration of hydroxide ions compared with those of borate ions. The power requirement for boron removal increased as the initial pH and concentration of sodium chloride increased, but decreased as the applied voltage was increased. BMED is a promising option for removal of boron from aqueous solution.