Effect of component ratio of binary organic solvent on sorption of phenols by silica

摘要

Chromatography is employed to measure the adsorption constants of hydroxybenzenes on SiO_2 in a low-concentration region at varied compositions of a binary organic solvent (n-hexane-ethyl acetate). It is shown that the Henry constants vary depending on the polar-to-nonpolar component ratio in the binary solvent and the number and position of hydroxyl groups in phenol molecules. It is found that the absolute values of changes Δ(ΔG) in the free energy considerably increase as the content of ethyl acetate in the mixtures diminishes, with the ratios between the Δ(ΔG) values of ortho-, meta-, and para-isomers remaining practically unchanged. The data obtained can be used to optimize the processes of the adsorption separation of mixed polyphenols and the isolation of natural phenolic compounds on a preparative scale.