Journal qf’ Chromatography , 556 (1991) 44 l-456 Elsevier Science Publishers B.V.. Amsterdam CHROM. 23 288 Chromatographic determination of the physico-chemical parameters of adsorption on active carbons ZYGFRYD WITKIEWICZ*, HENRYK GRAJEK and JERZY CHOMA Institute zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA of Chemistry. Military Terhnicul Accrdrmy, 01-489 W ar.raw 49 (Polandj ABSTRACT The adsorption isotherms of several polar and non-polar compounds on active carbons with mod- ilied surfaces wcrc determined chromatographically at dilTerent temperatures. The results were compared with those obtained by the static method. The entropies and heats of adsorption were calculated from the adsorption isotherms and compared with the values obtained from calorimetric measurements. The results were closest for adsorbems with a weakly developed microporous structure. The effect of the carrier gas flow-rate through the adsorbent bed in the column on the shape of the chromatographically determined adsorption isotherm was tested. The linear forms of equations corresponding to the BET, Hiittig. Kiselev and Hill physical adsorption models were used. The adsorption isotherms of aliphatic alcohols chroma- tographically were best dsscribcd in terms of the Hill model. INTRODUCTION In recent years, a good knowledge of the processes taking place on the phase boundary has become very important. The most important of these processes include, for both practical and theoretical reasons, primarily adsorption and heterogeneous catalysis [l]. The explanation of processes proceeding on the surfaces of adsorbents and catalysts requires the determination of their surface area and porous structure, in addition to the adsorption isotherms and thermodynamic functions. For this purpose common and widely used static methods are applied. These methods are fairly accu- rate but time consuming. A more rapid method of testing adsorbents and catalysts is afforded by ad- sorption gas chromatography [2,3]. The possibility of applying it in physico-chemical investigations follows from the fact that chromatographic separation is related to the properties and physico-chemical interactions of the column filling (e.g.. adsorbent or catalyst) with the chromatographed substances. The carrier gas also has some influen- ce, but its effect is minor so in practice the course of the chromatographic process depends predominantly on the properties of the adsorbent and the chromatographed substance (adsorbate). The properties of the adsorbate-absorbent system can be characterized by adsorption isotherms. The latter can be determined chromatograph- ically and from them the basic physico-chemical quantities characterizing the ad- sorbent can be found. The chromatographic method supplements the static proce- 0021-9673/91,‘%03.50 I$:, 1991 Elsevier Science Publishers B.V.