Preparation of calcium carbonate and hydrogen chloride from distiller waste based on reactive extraction–crystallization process

• A novel route was proposed based on a reactive extraction–crystallization process.
• Calcite and HCl gas were produced with CO2 fixed in this process integration.
• The atom utilization is 100% and the transformation efficiency of DW is high.
• The multiphase process was studied and optimal reaction conditions and the mechanism were given.

The distiller waste containing mainly calcium chloride (CaCl2) is being discharged in the Solvay process, and it has not been recycled comprehensively. In this study, a novel route for the treatment of the distiller waste was developed, in which CaCl2 solution was transformed into calcium carbonate and hydrogen chloride based on a reactive extraction–crystallization process using N235–isoamyl alcohol as the extraction system. Experimental results showed that the optimum conditions were 240 min as reaction time, 20 °C as the best temperature, 1.0 mol L−1 as initial concentration of CaCl2, 50% volume fraction of N235, 2:1 as the best phase ratio, and one-time feeding pattern. The conversion rate of CaCl2 was up to 75% under the optimized conditions; moreover, the concentration of H+ in organic phase was 0.70 mol L−1 and rhomibic calcite of high purity could be obtained. The products were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and thermogravimetry/differential scanning calorimetry. The extraction mechanism involved the ion-pair formation and the extraction complex R3N·HCl was determined by saturation method. The enthalpy change of the overall reaction ΔH was −36.47 kJ mol−1, indicating that it was an exothermic reaction with the possibility of getting hindered at high temperature.