Adsorption Of Water And Organics
Adsorption of Water and Organics
on Microporous Carbons
R. Leboda1, V.M. Gun\’ko2, J. Skubiszewska-Zięba1,
D. Palijczuk3, S. Ziętek3, W.Tomaszewski3
1Faculty of Chemistry, Maria Curie-Sklodowska University, Maria Curie-Sklodowska sq. 3, 20-031 Lublin, Poland
2Institute of Surface Chemistry, Ukrainian National Academy of Sciences, General Naumov st. 17, 03164 Kiev, Ukraine
3Military Institute of Chemistry and Radiometry, 00-910 Warsaw, Poland
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Activated carbons are widely used as technical (for solvent recovery, gas separation, catalysis, etc.) and medicinal adsorbents. Their textural and adsorptive features depend on the carbon origin and treatment (activation) conditions changing not only the pore size distribution (PSD) but also the concentrations of different active surface sites responsible for specific adsorption of polar (electron-donor, electron-acceptor, proton-donor, proton-acceptor) compounds. The micro-, meso- and transport pore distributions and the nature of surfaces of carbons strongly impact the adsorptive characteristics in respect to kinetics and dynamics of adsorption of both polar and nonpolar compounds. Changes in carbon morphology and concentration of surface groups containing oxygen atoms; i.e., alterations in adsorptive capacity, can be elucidated on adsorption of nitrogen (practically pure nonspecific dispersion interaction with carbons to study the PSDs), water (specific interaction with the surface groups containing oxygen atoms) and nonpolar organics (e.g. benzene derivatives) bonded through nonspecific dispersion and specific p-p-electron interaction with carbon surfaces. A variety of initial and treated (oxidized and reduced) microporous carbons (prepared from plum stones and coconut shells) were characterized using adsorption-desorption of nitrogen at 77.4K, adsorption of water (Fig. 1) and tert-butylbenzene (TBB) without and with the presence of water vapor. The adsorption dynamics of TBB changes due to filling of pores by water depending on the PSD.
Fig. 1. Changes in the free energy on water adsorption on initial microporous carbon (EG0), oxidized with H2O2 (30 wt.%) and H2O in an autoclave 623K for 6 h (EG8), and reduced with hydrogen at 1073K for 8 h (EGH)
Acknowledgment
This research was supported by NATO (grant No. EST.CLG.976890), the Polish State Committee for Scientific Research and Ministry of High Education and Science of Ukraine (grant No. 2М/303-99).
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