Influence of carbon-oxygen surface groups on the adsorption of phenol by activated carbons

Abstract

<span style="font-size:14.0pt;font-family:" times="" new="" roman";color:black;mso-bidi-font-weight:="" bold"="" lang="EN-IN">Adsorption isotherms of phenol from its aqueous solutions on four samples of activated carbons having different surface areas and associated with varying amounts of carbon-oxygen surface groups have been determined in the concentration range 20-1000 mg/L. The adsorption of phenol does not depend upon surface area alone but is also influenced by the presence of carbon-oxygen surface groups. The amount of these surface groups was enhanced by oxidation with nitric acid, ammonium persulphate and hydrogen peroxide and was decreased by degassing the activated carbons at gradually increasing temperatures of 400, 650° and 950°C. The oxidation of the carbons decreases the adsorption of phenol, the extent of decrease depending upon the nature of the oxidative treatment. The adsorption increases on degassing of the carbon samples, the increase depending upon the nature of the carbon oxygen surface groups being eliminated at that temperature on degassing. The results indicate that while the presence of acidic carbon-oxygen surface groups which are evolved as CO₂ suppresses the adsorption of phenol, the presence of non-acidic surface groups which are evolved as CO tends to enhance the adsorption of phenol.

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