Aluminium ions at polyelectrolyte interfaces. I. Mechanism of polyacrylic acid/aluminium oxide and humic acid/kaolinite complex formation

Understanding adsorption phenomena involving humic acids and clays is a difficult challenge owing to their complex nature. Thus, to progress in the study of such systems, attempts were made to replace natural systems by polyacids and oxides of simpler chemical and morphological structure. 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. Phenomena related to the interactions of humic or polyacrylic acid with aluminium oxide and kaolinite clay have been investigated and the well-differentiated interfacial behaviour of the oxide and kaolinite was determined and discussed. The results of electrophoretic mobility measurements demonstrated the huge time-dependent effect of polymeric layers adsorbed on oxides and modified clays. Received: 24 July 2000 Accepted: 20 December 2000