Adsorption on colloids and flocculation: The influence of salt

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Abstract
The stability of colloidal silica particles in a mixture of water and 2,6-lutidine is investigated in the presence of salt. Close to the demixing temperature of the solvent, a reversible flocculation occurs, coupled with lutidine adsorption on the colloid surface. Addition of Mg(NO3)2 is shown to suppress the lutidine adsorption and to reverse it into water adsorption. The flocculation disappears at the same time. This behavior is interpreted as a modification of the properties of the colloid surface by the salt and is in accord with current wetting theory.