Electrodialysis process for carbon dioxide capture coupled with salinity reduction: A statistical and quantitative investigation

Rejected brine and CO2 are the two most common pollutants associated with the desalination process. The current study focuses on the sustainable and efficient handling of these emissions. Herein, a method is presented that can effectively manages waste fractions and results in value-added products. A multi-chamber electrodialysis was studied to remove salt from the water and capture CO2 to produce hydrochloric acid, carbonates/bicarbonate salt mixture, and irrigation standard water. The effects of process variables (sodium chloride concentration, voltage/area, and CO2 flow rate on CO2 uptake, current efficiency, % salt removal, waste-to-product ratio, and energy consumption were optimized using a central composite design. It was found that high voltage and high CO2 flow rate were beneficial for high CO2 uptake. Current efficiency for salt removal improved with low voltage and high salt concentration. In contrast, increasing voltage and reducing salt concentration reduced the waste-to-product ratio and improved % salt removal. A salt concentration of 0.76 M, a voltage/area of 2344 V/m2, and a CO2 flow rate of 1.3 l/min were optimum parameters, resulting in a CO2 uptake of 11 g/M NaCl, a current efficiency of 87 %, a salt removal percentage of 28 %, a waste-to-product ratio of 2.2, and energy consumption of 123 Wh/M NaCl. Under optimum conditions, the process was analyzed over time to determine the variations within the system caused by ion transfer. The sodium carbonate and bicarbonate liquid mixture was freeze-dried and quantified using Fourier transform infrared spectroscopy (FTIR).