Investigating the drying behaviour of clay-containing slurries

Abstract

Managing clay-containing slurries during drying process remains a persistent challenge in various industries. Despite challenges of drying clay-containing-slurries, limited information is available. The aim of this study is to explore the drying performance of slurries containing kaolin and bentonite and gain insights into the underlying drying mechanisms. The research presented integrates drying experiments, rheology measurements, settling experiments, zeta potential measurements, FTIR, TGA/DTA, and SEM analysis. Bentonite-containing slurries retained more moisture due to their high-water adsorption capacity, with higher bentonite percentages extending drying times. The addition of Ca²⁺ ions reduced moisture content by replacing Na⁺ ions with smaller Ca²⁺ ions, making the slurries less viscous. The addition of Ca²⁺ disrupted the gel-like structure of bentonite as confirmed by SEM and FTIR. In contrast, kaolin-containing slurries maintain lower moisture levels owing to the non-swelling structure of kaolinite. SEM showed the formation of agglomerates for kaolin when Ca²⁺ was added The addition of Ca²⁺ ions had a subtle impact on drying rates, despite a slight increase in slurry viscosity probably due to the agglomeration of kaolinite particles. Both slurries exhibited three drying phases: rapid drying due to high moisture, a moderate phase with reduced rates, and a final phase of slowed drying as tightly bound moisture was harder to remove. This paper demonstrated the significance of understanding the drying processes of clay-containing slurries to enhance the overall drying efficiency.