Aluminium ions at polyelectrolyte interfaces. III. Role in polyacrylic acid/aluminium oxide and humic acid/kaolinite aggregate cohesion

Understanding the formation and breakup of humic acids and clays agglomerates is a difficult challenge owing to their complex nature. Thus, to progress in the study of the stability of such systems, attempts were made to replace the humic acid/kaolinite natural system by the polyacrylic acid/aluminium oxide synthetic system. Since the present investigation was dedicated to determine some characteristics of acidic soils which contain traces of aluminium ions, these ions were added to the adsorbent/polyacid systems as trace constituents. Initial and short-term phenomena related to the adsorption of humic and polyacrylic acids on aluminium oxide and kaolinite clay have been presented elsewhere. Here we present long-term phenomena regarding the formation and cohesion of oxide and clay aggregates formed in the presence of polyacrylic and humic acids, respectively. The results: of electrophoretic mobility measurements demonstrated the amphipathic character of polymeric layers adsorbed on aluminium oxide and the amphoteric character of humic acid layers adsorbed on kaolinite. The long-term stability of the two colloidal systems was determined to evolve similarly despite the existence of the these typical characteristics.