Chloride recovery and simultaneous CO₂ mineralization from rare earths high salinity wastewater by the Reaction-extraction-crystallization process

A novel route for recovery chloride from rare earths high salinity wastewater has proposed, which is based on a reaction-extraction-crystallization process using Trioctylamine (TOA)-isooctanol as the extraction system when CO₂ is mineralized concurrently. Under the optimum conditions, 91.04 % chloride can be transferred to the organic phase with the formation of calcium carbonate which can be used in saponification. Extraction mechanism is analyzed by saturated method and Fourier transform infrared spectrometer (FT-IR), and indicates that the ratio of stoichiometric coefficients between TOA and HCl is affirmed as 1, in accordance with the results by Density Functional Theory (DFT) analysis. Further, the loaded organic phase is stripped with 1 mol/L NaOH solution under the phase ratio (O/A) of 4:1, and the chloride in the stripping solution is concentrated to 100 g/L by five times accumulation, which is conductive to form NaCl crystal by salting-out. The process provides a low-energy-consuming, green, environmentally friendly way for high salinity wastewater treatment and carbon capture, utilization, and storage (CCUS).