Catechol derivatives and anion adsorption onto alumina surfaces in aqueous media: influence on the electrokinetic properties

A high state of dispersion of alumina particles can be achieved by using molecules derived from Catechol 1,2(OH)2C6H4, such as Tiron (OH)2C6H2(SO3Na)2 which allows to obtain stable alumina suspensions. In the field of understanding the dispersion mechanism of Tiron and the contribution of each functional group grafted onto the benzene ring of the Tiron molecule, adsorption experiments and surface charge measurements were conducted by using several compounds, containing a benzene ring, and by varying the nature and the number of substituents. The influence of the size and of the charge of the counter ion, electrostatically attracted by a positive charged alumina surface, onto the suspension stability was also studied. Electrokinetic properties of the suspensions versus pH appear to be very useful to characterize the ion adsorption sequence for an oxide surface. With a high immersion heat, an alumina surface better adsorbs ions with a high structuring power for water molecules. This influences the charge developed onto the oxide surface.