Micro-structural Explanation for Differences in Gelation Properties of Kaolinites from Birdwood (S. Australia) and Georgia (U.S.A.)

Abstract

SEM observation of the aqueous suspension of kaolinite from Birdwood (South Australia) and Georgia (USA) show noticeable differences in microstructure. Birdwood kaolinite dispersion gels at very low solid loadings in comparison with Georgia KGa-1 kaolinite dispersion which remains fluid at higher solids loading. To explain this behaviour, particle interactions in the colloidal size fraction of Birdwood kaolinite have been proposed. These interactions may be brought about by the presence of nano-bubbles on clay crystal edges and may force clay particles to aggregate by bubble coalescence. This may explain the predominance of edge-edge (EE) contacts in suspension of Birdwood kaolinite. Such mostly EE linked particles build long strings that form a spacious cell structure. Hydrocarbon contamination of colloidal kaolinite particles and poor crystallisation are discussed as possible explanation of the unusual behaviour of Birdwood kaolinite. In Georgia KGa-1 kaolinite dispersions instead of EE contact between platelets displayed in Birdwood kaolinite, most particles have edge to face (EF) contacts building cardhouse structure. Such an arrangement is much less voluminous in comparison with the Birdwood kaolinite cellular honeycomb structure observed before in smectite aqueous suspensions. Such structural characteristics of KGa-1 kaolinite particles enables higher solid volume fractions pulps to form before significantly networked gel consistency is attained.