Ammonia surface-functionalized graphene oxide for carbon dioxide capture

• Main Author: Baldovino, Fritzie Hannah B.
• Format: text
• Language: English
• Published: Animo Repository 2017
• Subjects: Carbon dioxide mitigation; Ammonia; Ammonia > Physiological effect; Chemical Engineering
• Online Access: https://animorepository.dlsu.edu.ph/etd_doctoral/590
• Institution: De La Salle University

Ammonia (NH3) was proven to be a promising solvent on the absorption of CO2, however, remained not commercialized due to its very high volatility. In this regard, this study aimed to synthesize a new material using aqueous ammonia grafted to graphene oxide (GO) and evaluate its physicochemical properties and CO2 adsorption performance. A novel way of functionalizing using supercritical technology was described in this study to chemically bond the N-groups to the carbon structure of the GO solving the volatility problem. An excellent material referred as nitrogen-functionalized graphene oxide (N-FGO) possessing very high thermal stability (~500áµ’C) and high N-content was produced (~11% N). Further, the new material was successfully utilized as an adsorbent for CO2 adsorption with capacities that can compete with the results of related pioneering studies. The new adsorbent has a better capacity than the unmodified GO, GO functionalized through impregnation, and N-groups functionalized in other carbon materials (i.e. graphite, graphite oxide, and carbon nanotubes). Optimized conditions for the adsorption process was found to be at 80áµ’C, 100 ml/min flow of CO2, and 8 mg of adsorbent. Kinetics of the adsorption reported a combination of physical and chemical adsorbent-adsorptive interactions forming the adsorbate. Heterogeneous multilayer adsorption occurred as indicated by the Freundlich isotherm. Further, thermodynamics study showed that the adsorption process has an optimum temperature at 80áµ’C. It implies that it can be exothermic, random, and spontaneous (20áµ’C to 80áµ’C), or the opposite (80áµ’C to 140áµ’C) depending on the range of temperatures used. An advantage can be seen in having a high optimum adsorption temperature over conventional sorbents as less energy is required to cooling down or pre-processing the post-combustion gases prior adsorption. Complete desorption of CO2 was possible at 200C in an N2 environment. Moreover, N-FGO exhibited high stability as can be regenerated and reused several times.