Synthesis of Na Compounds from Sodium Concentrated Solution Using Carbonation and Cryo-crystallization

Carbonation (step I) and cryo-crystallization (crystallization at low temperature) (step II) were performed to synthesize Na compounds from sodium concentrated solution. In the step 1, the solubility and pH of carbon dioxide (95 wt.%) affecting carbonation could be changed by the variation of reaction temperature. The step II was performed at 2 °C after carbonation. The injection of carbon dioxide was carried out twice for the stable production and the saturated solubility of carbonate ions in solution. Firstly, we tried to inject CO2 for controlling the solubility of CO2 by changing the reaction temperature from 35 °C to 10 °C, and the second injection was aimed at 10 °C for inducing nucleation of Na compound through carbonation after NaCl solution addition. In the cryo-crystallization step, the crystal growth of Na compounds could be induced by slowing the carbonation rate through reaction temperature change from 10 °C to 2 °C. In this study, the effect on NaOH concentration was examined and the purity of Na compound was increased when 2M NaOH was used. In addition, the synthesized Na compounds were mostly rod-shaped and consisted of sodium carbonate or sodium carbonate with monohydrate.