Effects of inorganic cations and organic polymers on the physicochemical properties and microfabrics of kaolinite suspensions

Abstract

The effects of inorganic cations and organic polymers on the physicochemical properties and microfabrics which including the floc size distributions of kaolinite suspensions were systematically investigated by batch sedimentation tests. Kaolinite surface charges, salt concentrations and polymer polarity as well as polymer dosage were found to be the key factors that affect the particle associations, floc sizes, zeta potential, and turbidity of a kaolinite suspension. The relationship between flocs sizes, turbidity, and zeta potential of kaolinite sediments were established and the significance of understanding the polymer induced flocculation and aggregation of suspended kaolinite sediments was discussed. Assisted by the zeta potential measurements, an increase of ionic strength was found to compress the electrical double layer (EDL) of kaolinite and result in imbalance of the interparticle forces, thus the particle associations and floc sizes varied significantly. The addition of polymers was found to facilitate flocculation of kaolinite through long-range polymer bridging and short-range ion-dipole interaction, including the hydrogen bonding and Colombian interactions, which in turn affected the flocs size, zeta potential, and turbidity of the suspensions. Test results also showed that the clay-polymer suspensions possessed a unimodal lognormal particle size distribution (PSD) which leading to a more quantitative understanding of floc sizes of suspended sediments.