摘要：

In previous studies of adsorption on carbon, some adsorbents have displayed markedly larger adsorptive capacities than others, presumably due to differences in specific surface area as well as the nature of the carbon surface in each instance. This paper reports changes in adsorptive capacity of carbon adsorbents resulting from alteration of the carbon surface by chemical treatment, particularly with respect to formation and removal of acidic surface oxides. Increased concentration of surface oxides on carbon greatly reduces the amount of phenol and nitrobenzene that can be adsorbed from dilute aqueous solution of these compounds. In the case of phenol, adsorption from aqueous solutions of higher concentration does not appear to be strongly affected by the presence or absence of acidic chemisorbed oxygen on the surface of the carbon adsorbent. This is interpreted in terms of a two-step adsorption isotherm for phenol on carbon. Alteration of the carbon surface by oxidation and reduction appears to be reversible to a large extent, as evidenced by measurements of both surface acidity and adsorptive capacity. Possible explanations for this behavior are discussed.

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