RESUMO
In this study, we evaluated solid sorbents for their ability to passively control indoor CO2 concentration in buildings or rooms with cyclic occupancy (eg, offices, bedrooms). Silica supported amines were identified as suitable candidates and systematically evaluated in the removal of CO2 from indoor air by equilibrium and dynamic techniques. In particular, sorbents with various amine loadings were synthesized using tetraethylenepentamine (TEPA), poly(ethyleneimine) (PEI) and a silane coupling agent 3-aminopropyltriethoxysilane (APS). TGA analysis indicates that TEPA impregnated silica not only displays a relatively high adsorption capacity when exposed to ppm level CO2 concentrations, but also is capable of desorbing the majority of CO2 by air flow (eg, by concentration gradient). In 10 L flow-through chamber experiments, TEPA-based sorbents reduced outlet CO2 by up to 5% at 50% RH and up to 93% of CO2 adsorbed over 8 hours was desorbed within 16 hours. In 8 m3 flow-through chamber experiments, 18 g of the sorbent powder spread over a 2 m2 area removed approximately 8% of CO2 injected. By extrapolating these results to real buildings, we estimate that meaningful reductions in the CO2 can be achieved, which may help reduce energy requirements for ventilation and/or improve air quality.