Exploring carbon dioxide sequestration in desalination reject brine via NaOH reaction: A kinetics study
Nafis Mahmud, Ahmed Refaat Khodary, Daniel V. Esposito, Muftah H. El‐Naas
Abstract
• The kinetics associated with the reaction of desalination reject brine with CO2 in the presence of NaOH were evaluated. • The effect of various operating parameters on the kinetics of CO 2 -Brine-NaOH system were investigated. • Calcite and Hydromagnesite were the wo major solid products obtained the reactions. • A reaction rate model representing the CO 2 -Brine-NaOH system has been developed based on the obtained kinetics data. Seawater desalination is one of the most sustainable means of water supply in arid and semi-arid regions. Despite its undeniable potential to meet the global water demands, there are several environmental impacts associated with its operation, including the generation of reject brine and the emission of considerable amounts of CO 2 . Recently, the mineralization of carbon dioxide using desalination reject brine has emerged as a potential solution for simultaneous brine management and CO 2 sequestration. In this study, the reaction kinetics of desalination reject brine with CO 2 in the presence of NaOH are evaluated. The effect of various operating parameters, such as the temperature, CO 2 concentration, NaOH dosage, brine salinity, CO 2 flowrates and inert particles volume percent were investigated by varying them within the range of 15–55 °C, 3–20 %, 6–16 g/L, 5–72 g/L, 1–5 L/min and 0–20 %, respectively. The experimental data showed that the overall rate of CO 2 conversion is equal to the sum of the rates observed for Ca 2+ and Mg 2+ carbonation reactions and increases proportionally with the increase in CO 2 concentration. The addition of NaOH improved the Ca 2+ carbonation reaction rate but had no effect on Mg 2+ carbonation reactions within the investigated reaction conditions. Interestingly, increasing brine salinity had a negative effect on the reaction rate, while the change in temperature and inert particles had minimal effect on the overall reaction rate. Analysis of the solid products showed that Hydromagnesite and Calcite were the two major products obtained. Finally, experimental data were used to develop a rate model representing the CO 2 -Brine-NaOH system. The developed model will assist in successfully predicting the performance of the process and pave the way for efficient brine management and CO 2 sequestration.