The acid-base dissociation behaviour of the surface of γ-FeOOH is investigated by potentiometric acid-base titrations of the oxide suspensions in aqueous solutions. The zero point of charge (p.z.c.) of the electrical double layer of the reversible oxide solution interface is determined: in KNO3 titrations at various ionic strenghts cross over at pH = 7.6; by coincidence with the pH of the isoelectric point, determined by microelectrophoresis, the cross over of titrations in KNO3 is identified as the point of zero charge of the surface. Specific effects regarding monovalent anions (Cl-, ClO4-) are found to be absent, while SO4-- strongly adsorbs on the γ-FeOOH surface, thus modifying the balance of the positive and negative groups on the surface. The sequence of interaction of monovalent cations with the surface is reported: K+ < Na+ < Li+. Surprising and of particular interest are the strong adsorption of Na+, which has always been reported to interact only electrostatically with oxide surfaces, and the absence of specific interactions with Cl- ions. © 1982.

Surface behaviour of γ-FeOOH : Point of zero charge and specific ionic interactions / S. Ardizzone, L.G. Formaro, E. Pizzotti. - In: MATERIALS CHEMISTRY. - ISSN 0390-6035. - 7:5(1982), pp. 639-648.

Surface behaviour of γ-FeOOH : Point of zero charge and specific ionic interactions

S. Ardizzone
Primo
;
L.G. Formaro
Secondo
;
1982

Abstract

The acid-base dissociation behaviour of the surface of γ-FeOOH is investigated by potentiometric acid-base titrations of the oxide suspensions in aqueous solutions. The zero point of charge (p.z.c.) of the electrical double layer of the reversible oxide solution interface is determined: in KNO3 titrations at various ionic strenghts cross over at pH = 7.6; by coincidence with the pH of the isoelectric point, determined by microelectrophoresis, the cross over of titrations in KNO3 is identified as the point of zero charge of the surface. Specific effects regarding monovalent anions (Cl-, ClO4-) are found to be absent, while SO4-- strongly adsorbs on the γ-FeOOH surface, thus modifying the balance of the positive and negative groups on the surface. The sequence of interaction of monovalent cations with the surface is reported: K+ < Na+ < Li+. Surprising and of particular interest are the strong adsorption of Na+, which has always been reported to interact only electrostatically with oxide surfaces, and the absence of specific interactions with Cl- ions. © 1982.
Settore CHIM/02 - Chimica Fisica
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/2434/186940
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