Possibility for CO2 Sequestration Using Sea Water

In view of the abundant calcium and magnesium ions in sea water, an approach to CO₂ capture and sequestration is put forward through enhancing the alkalinity of sea water and increasing the partial pressure of CO₂. The purpose of these measures is to increase the concentration of carbonate ion and then accelerate the formation of carbonate precipitation, such as CaCO₃ and MgCO₃. With the increase of pH, some non-target product, e.g. Mg(OH)₂, may emerge and precipitate from sea water system, so there is a top limit which is found to be pH=9.25 in order to avoid this problem. Considering that it takes a long time for surface ocean water to absorb atmospheric CO₂, the engineered process may accelerate the natural kinetics to industrial rates if sea water is applied to scrub flue gas. Through calculation, it is found that applying alkalinity-enhanced sea water to accelerate the formation of carbonate precipitation is a potential and promising method to capture and sequester CO₂. In actual application, condensed sea water from desalination plant or high concentration brine can be introduced to react with waste CO₂. Additionally, if these carbonate precipitation could be separated, the natural carbonate resources, such as limestone, would be saved to some degree.