Dry Capture of Low-level CO2 from Public Indoor Spaces using Chemically Modified Carbonaceous Adsorbents - A Review

Although CO2 is prominent as the most important greenhouse gas, responsible for 64% of anthropogenic global warming, it is also a viable indicator for indoor air quality (IAQ). Due to the incessant increase in the human population and residence time indoors, the need to control indoor CO2 levels has become exigent. To this effect, dryphase removal technology via adsorption with zeolites, activated carbons (AC) and activated carbon fibers (ACFs) had sufficed. Chemically modified AC and ACF surfaces through alkali impregnation have been used to improve their selectivity toward CO2 at room temperature. Here we appraise the various methods in the literature and carry out performance evaluation based on the physical and chemical modification induced by the chemical agents and experimental conditions. This study reviews the improved adsorption of low concentration (0.3%) via surface reformation of commercial carbon-based adsorbents, and the highest adsorption capacity was 2.2 mmol/g CO2 at the indoor level, which was achieved by AC pellets doped with ammine functionalities.