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.

• Polyethylenimine-Magadiite Layered Silicate Sorbent for CO₂ Capture,
  Romulo B. Vieira, Heloise O. Pastore
  Environ. Sci. Technol. 2014.
  DOI: 10.1021/es404501e