A novel separation process for the bromide and carbonate from the air blow-out alkali absorbed liquid and its phase equilibrium

Abstract

Efficiently separating bromide/carbonate-enriched liquids obtained from air-blown alkali absorption systems through sustainable and clean methods remains a persistent engineering challenge. In this paper, to realize the utilization of the absorbed liquid, the equilibria data about the absorbed liquid of the ternary system (NaBr - Na2CO3 - H2O) at 328.15, 338.15 and 368.15K and 101.325 kPa were determined with the isothermal dissolution equilibrium and the wet-residue solid phase method. Also, the phase diagrams of the ternary system (NaBr - Na2CO3 - H2O) at various temperatures were compared, and the variation rules involving the crystallization region and solubility were analyzed. Furthermore, this work proposes a novel method of separation and recovering Na2CO3·H2O and NaBr·2H2O with high purity from the absorbed liquid. The separation route has been proven to be feasible through the separation experiment of one-way process, and the product Na2CO3·H2O and NaBr·2H2O with purity of 99.10% and 99.50% have been obtained, where the recovery rate of Na2CO3 and NaBr are 100% finally. Moreover, the energy consumption and economic viability of the proposed separation process are analyzed and provided. The novel separation process plays a vital role in the utilization of the absorbed liquid and can be applied to wastewater treatment containing sodium bromide and sodium carbonate.