CROSS-LINKED SMECTITES .2. FLOCCULATION AND MICROFABRIC CHARACTERISTICS OF HYDROXY-ALUMINUM-MONTMORILLONITE

Cross-linking of Li-montmorillonite by hydroxy-aluminum oligomers was performed in a specially constructed mixing apparatus. Observations on flocculation and solution composition were carried out during and after the crosslinking reaction; the dry product was studied by scanning electron microscopy. Flocculation was most pronounced at Al/montmorillonite ratios between 0. 98 and 2. 45 mM/g; below and above this range, flocculation was much less intensive. These observations can be explained by heterocoagulation and protecting colloid action. A complete neutralization of the montmorillonite charge was estimated at 1. 9 mM adsorbed Al per g clay, and in order to account for the electrical charge of the hydroxy-Al, polymers with an average charge of 0. 5 per Al atom must be assumed on the montmorillonite surface. Differences in the microfabric of dry Al-CLM as a function of Al/montmorillonite ratio can be explained along the lines of the interpretation of the flocculation studies. Refs.