Original scientific paper

Properties of the Mixed Polyethyleneglycoles-iodide Ions Adsorption Layers on a Mercury Electrode

Jadwiga Saba ; Faculty of Chemistry, M. Curie-Sklodowska University, 20031 Lublin, Poland
Grażyna Dalmata ; Faculty of Chemistry, M. Curie-Sklodowska University, 20031 Lublin, Poland
Jolanta Nieszporek ; Faculty of Chemistry, M. Curie-Sklodowska University, 20031 Lublin, Poland
Jan Szaran ; Faculty of Chemistry, M. Curie-Sklodowska University, 20031 Lublin, Poland

Abstract

Adsorption of a mixture of I- ions and polyethyleneglycoles of molecular weights 400 (PEG 400) and 10 000 (PEG 10 000) on a mercury electrode from NaClO₄ solution of constant ionic strength is described. Parallel courses of linear dependences of the potential of zero charge with the increase of I- ion concentration in the Solutions with PEG and without PEG indicate removal of water molecules by adsorption of I- ions and not PEG molecules. The standard Gibbs energy of adsorption Δ_adG° and parameter B obtained from the virial isotherm do not depend on PEG 10 000 concentration. This can be associated with the full coverage of the electrode surface with its molecules already at a concentration of 10-4 mol dm-3. For PEG 400, a dependence of adsorption parameters on its concentration was observed. Lower repulsive interaction between the adsorbed I- ion in PEG Solutions indicates a favourable effect of PEG molecules on I- ion adsorption compared with H₂O. The values of rate constants k_sapp of Zn2+ ion reduction as a piloting ion were determined. Acceleration of the processes inhibited by PEG 400 or PEG 10 000 by I- ions is based on formation of ion pairs Zn2+−I- on the mercury surface. Kinetic measurements con-firm stronger adsorption of PEG 10 000 compared with PEG 400.

Keywords

electrochemistry; adsorption of I^- ions; inhibition of Zn²⁺ reduction; coadsorption; mixed adsorption layers

Hrčak ID:

132007

URI

https://hrcak.srce.hr/132007

Publication date:

4.9.2000.

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