Potassium carbonate is a highly hygroscopic
salt, and this aspect
becomes important for CO2 capture from ambient air. Moreover,
CO2 capture from ambient air requires adsorbents with a
very low pressure drop. In the present work an activated carbon honeycomb
monolith was coated with K2CO3, and it was treated
with moist N2 to hydrate it. Its CO2 capture
capacity was studied as a function of the temperature, the water content
of the air, and the air flow rate, following a factorial design of
experiments. It was found that the water vapor content in the air
had the largest influence on the CO2 adsorption capacity.
Moreover, the deliquescent character of K2CO3 led to the formation of an aqueous solution in the pores of the
carrier, which regulated the temperature of the CO2 adsorption.
The transition between the anhydrous and the hydrated forms of potassium
carbonate was studied by means of FT-IR spectroscopy. It can be concluded
that hydrated potassium carbonate is a promising and cheap alternative
for CO2 capture from ambient air for the production of
CO2-enriched air or for the synthesis of solar fuels, such
as methanol.