CO2 naturally dissolves in water to form carbonic acid. Under typical conditions the concentration of dissolved CO2 is low (~30 mM) so water is not suitable as a solvent for capture. If a base is added to raise the pH, the dissolved carbonic acid can react with the base, increasing the amount of CO2 captured through the following types of reactions:
CO2 + H2O + CO3-2 --> 2 HCO3-
Depending on the pressure of CO2 and temperature of the solution, up to one mole of CO2 can be capture per mole of added carbonate. There are some practical limits to the capture and that is the solubility limit of the bicarbonate ions; if the solubility limit is exceeded the ions can precipitate out of solution.
One downside of aqueous carbonate solutions is the slow rate of CO2 absorption, resulting in large scrubbing towers. In this work we are investigating the use of surfactants to accelerate the absorption of CO2 by aqueous carbonate solutions.
The more rapid decrease in pH of the catalyzed experiment indicates faster absorption of CO2 than in the uncatalyzed experiment.