Effect of acid-base solutions used in acid-base compartments for simultaneous recovery of lithium and boron from aqueous solution using bipolar membrane electrodialysis (BMED)

Abstract

Application of bipolar membrane electrodialysis (BMED) for simultaneous separation and recovery of lithium and boron from aqueous solution was investigated using Astom Acilyzer EX3B model ED device. In the laboratory scale experiments performed, effects of acid and base solutions types and their concentrations employed in acid and base compartments, electrical potential applied on process efficiency were investigated. The results showed that separations and recoveries of both boron and lithium were effective when 0.05 M HCl and 0.05 M NaOH solutions have been used in acid and base compartments, respectively. The percent separations of boron and lithium were 86.9% and 94.7%, respectively, while their respective recoveries were 50% and 62% at 30 V. The maximum separation and recovery values for boron and lithium were obtained when a 30 V of electrical potential was applied. With optimal initial acid and base concentrations (0.05 M) used in acid and base compartments, the specific power consumption (SPC) was calculated as 7.9 kWh/m3 at 30 V.While higher initial acid and base concentrations showed higher boron and lithium separation efficiencies, relatively lower concentrations of acid and base solutions employed in acid and base compartments improved the recoveries of boron and lithium. Acid and base solutions generating a moderate conductive medium in acid and base compartments improved separations along with recoveries of boron and lithium from solution. When the solutions of 0.1 M HCl and 0.1 M NaOH were used in acid and base compartments, recoveries of boron and lithium were 27% and 33%, respectively. On the other hand, the recoveries of boron and lithium were 62% and 56%, respectively when 0.1 M H3BO3 and 0.1 M LiOH solutions were employed in acid and base compartments.