Inverse gas chromatography study of synthetic hydroxyapatite surface by hexane adsorption at finite surface coverage

Abstract

The sorption of both organic and inorganic substances on synthetic hydroxyapatite (HAP) was studied intensively in the last decade, due to HAP application in diverse fields of science and technology. In this paper, HAP was synthesized by neutralisation method. The obtained powder was pure, stoichiometric HAP, with specific surface area of 21 m2 /g, determined by N2 adsorption. The chromatographic column was filled with the synthesized HAP powder and the adsorption of n-hexane was studied, at finite surface coverage. Different volumes of adsorbate were injected (1-6 μl) in the temperature range 433-463 K. Sorption isotherms were determined, using BET model. From the linear BET equation, monolayer coverages (αm) and BET constans (C) were calculated, for each working temperature. The velues of αm were used to estimate the specific surface area. Isosteric heat of adsorption (qst) was calculated and discussed, as well as the adsorption energy distribution function (χ).