Determination Of The Dependencies Between The Net Retention Volumes And The Parameters Characterizing The Properties Of Adsorbents
Determination of the Dependencies Between the Net Retention Volumes and the Parameters Characterizing the Properties of Adsorbents
H. Grajek, Z. Witkiewicz
1Military Technical Academy, Institute of Chemistry,
Kaliski st. 2, 00-908 Warsaw, Poland
Propane adsorption isotherms have been determined chromatographically on different samples of activated carbon for different volumes of adsorbate injected onto the column.
The dependencies between the pore volume filled with propane during chromatographic process, W, and molar differential work of adsorption, A, have been determined on the basis of the propane adsorption isotherms. The W=f(A) expressions have been differentiated with respect to the molar differential work of adsorption. The obtained asymmetrical distribution functions of pore volume with respect to molar differential work of adsorption have had the extremums coordinates which depended on the amount of adsorbate injected on a column. In each adsorption system the obtained pore volume distribution functions have been spread to the higher values of molar differential work of adsorption. It suggested, that the obtained distribution functions have been approximated to the real distribution of propane adsorption energy on the active carbon surface and asymmetrical chromatographic peak, which the adsorption isotherm of propane has been previously calculated from.
The extremum co-ordinates and shapes of the distribution functions have been shifted in the direction of higher values of adsorption energy. It corresponded to the behaviour of the peaks.
Taking into account all the observations it has been decided to check if the correlation between the extremes of dependency (dW/dA)T,F=g(A) exists for the constant temperature of column, T, and the constant volumetric flow rate of mixture carrier gas – propane, F, through the adsorbent bed in chromatographic column and the net retention volume, Vn. The obtained interdependences connecting the magnitudes calculated directly from
chromatographic measurements and the values characterizing the dynamic adsorption process occurring in a chromatographic column have been calculated by the Lavenberg-Marquardt method.
The interdependence between the retention time of propane peak maxima and its profile and the extremum of distribution function of pore volume with respect to molar differential work of adsorption does exist.
On the basis of the distribution functions it has not been possible to recognize if the chromatographic process has been ideal and non-linear or non-ideal and non-linear.
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