Enhancement of NH3 and water adsorption by introducing electron-withdrawing groups with maintenance of pore structures

• Published in: Adsorption : journal of the International Adsorption Society 2019-01, Vol.25 (1), p.87-94
• Main Authors: Miyauchi, Masato, Ohba, Tomonori
• Format: Article
• Language: English
• Subjects: Acetaldehyde; Activated carbon; Adsorbed water; Adsorption; Ammonia; Chemistry; Chemistry and Materials Science; Electrons; Engineering Thermodynamics; Functional groups; Heat and Mass Transfer; Industrial Chemistry/Chemical Engineering; Isoprene; Oxides; Porosity; Separation; Surface chemistry; Surfaces and Interfaces; Thin Films; Water chemistry
• ISSN: 0929-5607; 1572-8757
• DOI: 10.1007/s10450-018-9995-5

Activated carbons have been well-used for separation, removal, and storage for various gases. Pore width and surface functional groups are primal factors of interactions with adsorbed molecules. Surface functional groups especially influence adsorptions of acidic and basic molecules, although all molecules are considerably influenced by pore width. Controlling optimal pore width and surface functional group is however very difficult, because both factors of pore width and surface functional groups are simultaneously changed in preparation process. We here attempted to prepare oxygen-introduced activated carbon with different surface oxides into activated carbons and with the similar pore structure. NH 3 , CO 2 , acetaldehyde, isoprene, and water were used for evaluating the influence of surface oxides in carbon pores. As the surface oxides increased, NH 3 adsorbed amounts were considerably increased accompanying an irreversible adsorption and a threshold pressure of water adsorption was shifted to lower relative pressure, while adsorption isotherms of the other molecules were rarely changed. A comparison of interaction between any surface oxides and adsorbed molecules indicated that NH 3 and water molecules having the electron donor were strongly adsorbed on the acid surface oxides. The oxygen-introduced activated carbons without any destruction of the pore structure exhibited a considerable adsorption potential for molecules having the electron donor, and maintained an adsorption potential for molecules having the nonpolar and electron acceptor, proposing effective removal and separation with high adsorption capacity.