An evaluation of two techniques for the removal of ultraviolet-absorbing contaminants from clays

Abstract

Elution of clays with buffer solutions was compared with the more destructive technique of peroxide oxidation to remove ultraviolet-absorbing contaminants from kaolinite and montmorillonite. Repetitive elution of kaolinite at pH 7.0 and of montmorillonite at pH 8.4 removed significant amounts, but the level of contamination after this treatment was still unacceptably high. Oxidation with hydrogen peroxide was considerably more effective, but X-ray diffraction data on the oxidized clays provided evidence of the breakdown of aggregates in the 2-5 µm size range. It was concluded that the contaminants were organic and that oxidation removed bonding groups from clay domains.