The role of zinc(II) in the CO2 absorption by aqueous NH3 and in the CO2 desorption reaction at room temperature and pressure. A potentially cost-effective method for CO2 capture and recycle

The absorption of CO2 by aqueous NH3 solutions has been investigated at atmospheric pressure and 0 °C. The CO2 absorption is fast and occurs with high efficiency (88-99 %). The maximum CO2-removal efficiency increases slightly with the NH3 concentration. Addition of zinc(II) salts (as chloride, nitrate or sulfate) to the NH3 absorbent solution increases the overall CO2-absorption capacity without appreciably affecting the removal efficiency. Stripping of pure CO2 from HCO3-solutions is achieved by adding the calculated amount of ZnIIsalts, which under ambient conditions lead to rapid release of about 30-35 % of the initially captured CO2. At the same time, about 65-70 % of the captured CO2 is transformed into solid basic zinc carbonates. The recovery of these valuable solid products and the release of only 1/3 of free CO2 at room temperature and pressure reduces the cost of the overall process of CO2 capture, making it a potentially attractive method for CO2 capture on a larger scale.