Maximizing CO2 mineralization for a concurrent treatment and resource recovery system of seawater reverse osmosis desalination waste brine through electrochemical generation of alkali.

CO2 mineralization offers a potential long-term carbon storage solution to locations with no or limited access to underground carbon sequestration geologies. Recently, there has been a concerted effort to develop a brine utilization technology for mineralization integrating electrochemical alkali generation. In this work, exploration of alternative CO2 mineralization pathways with desalination brine to maximize carbon capture and mineralization efficiency in conjunction with the brine electrolysis was studied. Simulation and experimental verification of CO2 mineralization on the varying concentrations of alkali solution and CO2 gas, denoted as alkali-extended carbonate equilibria, yielded a variety of products, namely, Mg(OH)2 (94.1 ± 1.3 wt% Mg) and CaCO3 (97.1 ± 0.9 wt% Ca), hydromagnesite and aragonite. Systems mixing NaOH, Na2CO3 and NaHCO3 solutions with desalination brine for mineralization were optimized based on products purity, mineralization capacity and brine softening capability. The output of the study shows that CO2 capture (78 %), and mineralization (64 %) efficiencies are the highest for the Na2CO3-brine system. Concurrently, these results elucidate carbon capture and mineralization inefficiencies for process configurations studied, enabling potential system improvements for a more environmentally friendly process.