Properties of the Mixed Polyethyleneglycoles-iodide Ions Adsorption Layers on a Mercury ElectrodeReport as inadecuate

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Croatica Chemica Acta, Vol.73 No.3 September 2000. -

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 ΔadG° 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 ksapp 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.

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

Author: Jadwiga Saba - ; Faculty of Chemistry, M. Curie-Sklodowska University, 20031 Lublin, Poland Grażyna Dalmata - ; Faculty of Chemi



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