A hybrid electrocoagulation–Solvay reactor for coupled CO2 mineralization and selective brine desalination via ion recovery and solid precipitation

This study presents the design and performance of a novel hybrid reactor that integrates electrocoagulation (EC) with Solvay-based chemical treatment to enable simultaneous carbon dioxide (CO 2 ) capture and hypersaline brine desalination. The system features a temperature-controlled vertical chamber where direct CO 2 gas injection into brine promotes carbonate formation and CO 2 mineralization. Uniform mixing is achieved via mechanical stirring, while vertically oriented aluminum electrodes (1–4 V) induce electrochemical coagulation and facilitate solid recovery. The reactor operates within a controlled temperature range (22–50°C) to optimize reaction kinetics. A combination of chemical additives calcium oxide (CaO), ammonium bicarbonate (NH 4 HCO 3 ), and ammonia solution (NH 4 OH) was tested for enhanced selective precipitation. Maximum efficiency was observed with all three additives, achieving ∼85% calcium, 100% potassium, 99% magnesium, and 61% sodium removal, along with ∼97.5% sulfate reduction. Solid-phase characterization confirmed the recovery of valuable precipitates, including sodium bicarbonate, calcium sulfate, calcium carbonate, and magnesium hydroxide. The integrated system demonstrated a high CO 2 uptake of ∼16.49 g CO 2 /L of treated brine, illustrating its dual capability for carbon capture and resource recovery. This reactor platform introduces a scalable and sustainable route for environmental remediation, brine valorization, and carbon management in saline waste streams.