Layered Silicates for CO2 Capture

Layered Silicates for CO2 Capture

Author: Veronika Belusa

Romulo B. Vieira and Heloise O. Pastore, University of Campinas, Sao Paulo, Brazil, prepared a Layered Silicate Sorbent (LSS) for CO2 capture. The solid sorbent was synthesized of the layered silicate magadiite and organo-magadiite modified through an ion exchange procedure with hexadecyltrimethylammonium bromide (CTAB) and impregnation with polyethylenimine (PEI). The sorbents were named MAG-PEI-x and 25CTA-MAG-PEI-x, where x represents the loading of PEI as weight percentage in the sample. The final material was obtained as a white solid, which agglomerated with increasing concentration of PEI.
Two kinds of PEI are present in the sorbent: an exposed PEI layer with external sites and a bulky PEI with internal sites. The first is responsible for higher CO2 adsorption whereas the second is capable only of low CO2 adsorption. Higher concentrations of the ion exchange surfactant CTA+ decreased the total adsorption capacity due to the difficulty for CO2 to access the inner PEI sites. However, it improved the access of CO2 to the exposed PEI layer.

MAG-PEI25 showed maximum adsorption capacities of 6.11 mmolg−1 at 75 °C. The sorbents displayed high thermal stability and fast kinetics of desorption and may be submitted to adsorption/desorption cycles. The Avrami model proved to be a good kinetic model to describe the interaction of CO2 with PEI impregnated in layered silicates.


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