Coupled reaction and solvent extraction process to utilize distiller waste using N235-isoamylol system

Abstract

ABSTRACT Distiller waste produced from the Solvay Process, which mainly contains calcium chloride (CaCl2), is being discharged and has not yet been fully recycled. In this study, a coupled reaction and solvent extraction process was adopted to utilize distiller waste using the mixed organic solvent composed of N235 and isoamylol. High purity and good crystallinity calcite with an average of 40~50 μm were prepared in this process. The effect of operation conditions was firstly studied and the conversion rate of CaCl2 reached 83.40% in single-stage with the optimized conditions: reaction time of 3 h, N235/isoamylol volume ratio of 1, reaction temperature of 25°C, N235/CaCl2 molar ratio of 3, and the initial CaCl2 concentration of 1 mol·L−1. The enthalpy change of the overall reaction was −89.93 kJ·mol−1. Then, the phase equilibrium was measured and the theoretical extraction stage was predicted to be 3 with the target conversion rate of 90%. Three-stage counter-current extraction process showed that about 93.75% CaCl2 was mineralized into CaCO3 and the results had a good agreement with the McCabe-Thiele calculation. This indicated that multi-stage counter-current extraction can effectively improve the conversion rate of Ca2+ and related result was of great significance in treating distiller waste industrially.