Direct Conversion of Bromine-Rich Fluid into High-Value Calcium Bromide via Continuous Electrodialysis Metathesis

Bromine-rich fluid, which can be generated during the bromine extraction from seawater by the air blow-out method, is usually acidized to produce liquid bromine. Liquid bromine will be further used in the synthesis of bromides. This traditional method for the treatment of bromine-rich fluid and the production of bromides is relatively complex and can produce a large amount of bromine-containing wastewater. The objective of this work is to develop a highly efficient and eco-friendly method for treating bromine-rich fluid and then producing bromides. In this work, a continuous electrodialysis metathesis was designed to directly convert the bromine-rich fluid, which mainly contains sodium bromide and sodium bromate, into high-value calcium bromide and the byproduct calcium bromate. This method realizes the direct conversion of bromine-rich fluid into CaBr2 for the first time, eliminating the intermediate step─preparation of Br2 in the conventional methods. The comprehensive parametric study showed that the concentrations of calcium bromide and calcium bromate can reach up to 1.31 and 0.195 mol/L in the product solution, respectively. Based on the analysis of the phase diagrams and the determined solubility, the evaporation followed by the solid–liquid extraction was proposed to purify CaBr2 and Ca(BrO3)2. The purity of calcium bromide can be increased to 93.27%, with a yield of 91.15%. This work provides a new method for the efficient utilization of bromine-rich fluid and the clean production of calcium bromide, and it can also be easily expanded to the recovery of other bromide resources.