Combined process of CO2 capture by potassium carbonate and production of basic zinc(II) carbonates:: CO2 release from bicarbonate solutions at room temperature and pressure

The absorption of CO2 in aqueous solutions of K2CO3 has been investigated at six different temperatures in the range 10-60 degrees C and at atmospheric pressure. The CO2 absorption is fast and occurs with high efficiency without any added catalytic activator. The CO2 capture ranges between 83 and 99% expressed as the percentage of absorbed CO2 with respect to the neat CO2 flowing through the absorbent solution. The efficiency of CO2 removal increases with the temperature, which contrasts with the exoenthalpic nature of the reaction between CO2 and CO32- and the diminished solubility of CO2 at high temperature. Our finding indicates that the increase of the CO2/CO32- reaction rate with the temperature prevails over the opposite effect on the equilibrium due to the temperature increase. The stripping of pure CO2 from the HCO3- solutions has been achieved by adding a zinc(II) salt to the absorbed solutions which releases the captured CO2 rapidly and completely at room temperature and pressure with the simultaneous separation of solid compounds identified as mixtures of commercially valuable basic zinc carbonates. Although the exact evaluation of the overall merits of the proposed CO2 capturing technology would require a complete analysis of the energy profile of the process, it is obvious that any improvement of the CO2 capture process resulting in the associated synthesis of a valuable product without additional energy burdening reduces the Cost of CO2 capture and maximizes the neat balance CO2(captured)-CO2(emitted) where CO2(emitted) represents the total energy bill (electrical, thermal, mechanical) required to sustain the entire Cycle of CO2 abatement.