Effect of aluminium sulphate on interactions between silica surfaces studied by atomic force microscopy.

Surface interaction forces between different types of silica surfaces (pure silica beads, borosilicate glass beads, polished silicon wafers and fused silica slides) were measured by atomic force microscopy (AFM) in solutions of aluminium sulphate (alum) in order to understand the role of hydrated aluminium species on the coagulation of negatively charged oxide colloids in drinking water treatment. The alum coagulant concentration used in this study was 150 microM aluminium. The alum solutions were prepared from analytical grade Al2(SO4)3.

The effect of molecular weight of nonadsorbing polymer on the structure of depletion-induced flocs.

This work explores the structural compactness of depletion-induced particle flocs with respect to the molecular weight of nonadsorbing polymer flocculants. Small-angle static light scattering was used to monitor the structural characteristics of the flocs, which were formed by the addition of nonadsorbing poly(acrylic acids) to a stable colloidal polystyrene latex dispersion. It was found that the floc mass fractal dimension, considered to be a measure of structural compactness, was dependent upon both the molecular weight and the concentration of the polyacid.