The comparative adsorption of aromatics on mercury from water and ethyleneglycol

The interfacial behaviour of benzaldehyde and p-methyl phenyl acetic acid i n 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" valu e of Gibbs adsorption energy; Delta G(int)degrees, relating, for a group of aromatic derivatives adsorbed on mercury, to the process: A(pure) + Hg rev ersible arrow Hg(A(adsorbed)). It has been shown that this quantity does no t 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 conseque nce 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 a ctivity almost the double of that of water, similar to - 50 and similar to - 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 b ehaviour on Hg from water. (C) 1998 Elsevier Science Ltd. All rights reserv ed.