Dosanjh, Ardeep (2010)
M.Res. thesis, University of Birmingham.
The primary aim of this research was to investigate the redispersibility of the commercial calcite slurry product, Carbilux, after drying. Various dispersants and pH changes were made to improve the colloidal stability. The commercial product contained an unknown organic dispersant which was removed by washing and zeta potential results were measured. The rheological properties of the various samples were investigated and a sample selection was made to obtain powders from conventional oven drying, freeze drying and spray drying for redispersibility analysis. The powder properties were compared using laser diffraction for particle size analysis and zeta potentials, scanning electron microscopy, gas adsorption for surface area analysis, shear rate controlled rheology tests and compressive load tests to obtain agglomerate strengths. The particle size distributions and rheological properties are strongly correlated as an increased number of free fine particles increased the viscosity due to more interparticulate interactions. The removal of the organic dispersant produced unstable systems supported by rheological evidence of shear thickening at high shear rates. The agglomerate strengths weakened with the removal of the organic. The particle size distribution analysis supports this but the rheological evidence tends to be less conclusive due to changes of the colloidal chemistry in the washing and drying processes.
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