The comparative adsorption of aromatics on mercury from water and ethyleneglycol

Abstract

The interfacial behaviour of benzaldehyde and p-methyl phenyl acetic acid in ethyleneglycol (EG), as well as that of o-dimethyltoluidine in water, has been investigated to obtain a number of adsorption parameters necessary to discuss the reliability, on a quantitative ground, of the “intrinsic” value of Gibbs adsorption energy, Δ G int°, relating, for a group of aromatic derivatives adsorbed on mercury, to the process: A pure+Hg⇌Hg(A adsorbed). It has been shown that this quantity does not depend on the solvent in use, so that it is really “intrinsic” and can be usefully related to structural molecular parameters of the adsorbate alone, allowing the interfacial behaviour to be foreseen a priori. As a consequence the solvation in the adsorption state of the interfacial active species, either in EG and in water, can be considered to contribute little to the whole adsorption Gibbs energy. Eventually, EG itself shows an interfacial activity almost the double of that of water, ∼−50 and ∼−21 kJ mol −1, respectively. So that, within this view the adsorption of aromatics from EG on mercury can be fully rationalized with respect their behaviour on Hg from water.