The effect of organic vapor adsorption on the paramagnetic properties of activated carbons with different concentrations of surface oxides

✍ Scribed by M. Rozwadowski; H. Güsten

• Publisher: Elsevier Science
• Year: 1976
• Tongue: English
• Weight: 499 KB
• Volume: 14
• Category: Article
• ISSN: 0008-6223
• DOI: 10.1016/0008-6223(76)90098-1

✦ Synopsis

The effect of adsorption and desorption of organic vapors (methanol, n-butanol, cyclohexane) on the free spin concentration of an activated carbon with selectively modified surface oxides has been measured by electron spin resonance at 25°C. While equilibrated cyclohexane showed no effect on the paramagnetic properties of the activated carbons, methanol and n-butanol caused a decrease by 30-40% in free spin concentration in those carbons (G2, G, and G.,) whose surfaces had been oxidized by H,O,, KMnO, and (NHJ,S,O,, respectively. However, in carbon G, modified by HNO,, the free spin concentration increased upon adsorption of methanol and II-butanol. The number of chemisorbed alcohol molecules per lost or gained unpaired electron was calculated from the determined amount of irreversible adsorption and the loss/gain of free spin concentration after desorption at 25°C. It was concluded that the type of oxidized surface functional groups is decisive for its spin behaviour on surface complex formation. In the case of the carbon G,, unknown reactive chemical groups at the edge carbon atoms, which are not present in the other carbons investigated, induce an increase in the free spin concentration upon adsorption of alcohols.