Abstract
Currently, with a large amount of fossil fuel consumption throughout the world, most of which are required for industry and transportation, the carbon dioxide (CO2) concentration of the atmosphere has been increasing to harmful levels, resulting in devastating global warming. Thus, the key to mitigating the acceleration of global warming is to reduce CO2 emission to atmosphere. Currently, the most common way to decrease the emission of CO2 is using adsorbents to capture CO2, thus separating it from other gases. Owing to the simple separation process that costs moderate energy, solid adsorbents are the most practical choice among a variety of adsorbents. Many current researches focus on silica materials, synthesized with surfactant and template such as SBA-15, MCM-41, etc., which possess high specific surface areas as their common advantage. These materials can serve as effective CO2 adsorbents after amine treatment. In our lab, we have successfully synthesized silica aerogels through sol-gel methods, featuring high specific surface areas and large pore volumes. To the best of our knowledge, research efforts have not yet been made on the utilization of silica aerogels for CO2 capture. Hence, we use silica aerogels as the basic material and transform it into a recyclable solid CO2 adsorbent through either amine-impregnation or amine-modification process. From our results, amine-impregnated silica aerogels were ineffective in CO2-capture, but the CO2 capture efficiency improved significantly for amine-modified silica aerogels. Hence, we focus on the amine-modification process for silica aerogels in our work, with the understanding that the possible application of this material is in an environment of gas mixtures. Therefore, in measuring the CO2 capacity, we set the environment as 5% CO2 (v/v). The highest CO2 capacity obtained was 64 mg-CO2/g-sorbent at 25℃ for none-water-treated samples and 61.6 mg-CO2/g-sorbent at 25℃ for water treated samples. Besides, we observed that this material showed a high rate of CO2 capture and a great stability in the adsorption-desorption cycle manifested with an excellent CO2 capacity even at the 6th cycle. In other words, this material has a great potential for CO2 capture. Meanwhile, many researches on CO2 adsorbents focus on carbon-based materials such as carbon nano-tubes, which are known for their high specific surface areas. We also tried to turn carbon aerogels with high specific surface areas into CO2 adsorbents with the amine-impregnation or amine-modification process. However, the CO2 capacity of this type of adsorbent becomes worse in gas mixture environments. It is essential to improve the CO2 selectivity of this adsorbent so that it may prove suitable for applications in gas mixture environments.