The characterisation of microporous carbons by adsorption from liquid and vapour phases

Abstract

Two series of activated carbons were prepared from pure polyfurfuryl alcohol and polyvinylidene chloride by gasification with carbon dioxide at 850°C. Micro-pore volumes in these carbons were estimated by adsorption of carbon dioxide (273K) using Dubinin theory, by adsorption of nonane (273K) and by adsorption of nitrogen (77K) on carbons with and without pre-adsorbed nonane. Reasonable agreements are found. Adsorption on these carbons is reported, from aqueous solution, of p-nitrophenol, malonic, benzoic and oxalic acids, and of iodine from carbon tetrachloride solution. Transitional pore filling occurs by these adsorbates (with exception of malonic acid). Adsorption of p-nitrophenol, particularly at low C/C s values of about 1 × 10 −3, is extremely sensitive to microporous structure. Its adsorption over larger ranges of C/C s resembles closely adsorption of carbon dioxide (195K) and at higher C/C s values of nitrogen (77K). Other adsorbates adsorb little at C/C s values of 1 × 10 −3. Adsorption of p-nitrophenol is probably the most informative of adsorbates in solution, and the experimental procedures are convenient. The usual problem of giving significance to surface area values, using the BET equation, is encountered giving some limitations to interpretations of isotherms of p-nitrophenol from aqueous solution.