Abstract
The acid-base dissociation behaviour of the surface of β-FeOOH in aqueous suspension has been investigated by potentiometric titration. The zero point of charge of the electrical double layer of the oxide/solution interface (pH = 7·6 ± 0·1 in KNO3, NaNO3 and LiNO3 electrolytes) coincides with the pH of the isoelectric point, determined by the solid addition method. Chloride and sulphate anions are strongly adsorbed on the β-FeOOH surface and thus modify the balance of positive and negative groups on the surface. The sequence of interaction of monovalent cations with the surface is K+ = ≤ Na+ ≤ Li+. β-FeOOH appears to behave essentially in the same manner as found previously for α-FeOOH.
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