POTENTIOMETRIC TITRATION OF ALUMINUM BENTONITE IN PRESENCE OF ALUMINUM HYDROUS OXIDE GEL

During the aging of Al-gel/Al-bentonite complexes, the influence of different quantities of amorphous or crystalline hydrous oxide in evaluating the total titratable acidity, the exchange acidity, and the (Equation presented) ions and basic aluminum polymers present on clay surfaces was studied. Al-bentonite in the presence of crystalline Al(OH)3showed no significant variations in the total titratable acidity values. On the contrary, it was found that the more Al-gel added and the older the complexes, the smaller the value of the titratable acidity and the content of (Equation presented) ions. A reaction between the aluminum bentonite and aluminum hydrous oxide, starting immediately after preparation of complexes, could increase the content of basic aluminum polymers. Since, in forming complexes, large amounts of Al-hydrous oxide interstratify, it is possible to envisage conditions unfavorable to complete titration of the polymers and aluminum ions fixed between the structural layers. The possibility that, in the presence of KCl, cationic and anionic exchange reactions occur leads to strictly defining the quantity of electrolyte required for exact determinations of the total titratable acidity. © 1978 The Williams & Wilkins Co.