Abstract
Kaolinite is a difficult-to-float clay existing in coal slurries which negatively impacts coal flotation. A better understanding of its adsorption behavior would improve coal-slurry processing. Carbon impurities in the kaolinite can affect this behavior. The appearance and elemental surface composition of the carbon impurities precipitated by kaolinite oxidative treatment were microscopically analyzed, and their chemical speciation and relative C and O contents were probed. The mechanisms of adsorption on the main kaolinite cleavage planes ((001) and (001) surfaces) for two carbon-impurity structural models, a phenolic hydroxyl unit (Ph–OH) and carbon hydroxyl unit (C–OH), were considered using density functional theory methods. The carbon impurities consisted mainly of C and O, with C present mostly as C–C, C–H, and C–O species, and O existing mainly in –OH and C–O structures. Both Ph–OH and C–OH units adsorbed stably on the kaolinite (001) and (001) surfaces through hydrogen bonding between the hydroxyl groups and surfaces. A strong electrostatic attraction occurred between the Ph–OH benzene ring and kaolinite surfaces, whereas the carbon ring in C–OH did not interact with either surface. Finally, for both units, adsorption on the kaolinite (001) surface was more stable than on the (001) surface.
Highlights
Coal-associated kaolinite is one of the major clay minerals in coal-water slurries [1]. It is fine-grained with high surface electronegativity, and strong hydration films readily form on the particle surfaces [2]
The hydration film can increase the viscosity of kaolinite particle–fluid suspensions [5], further reducing the efficiency of subsequent coal-slurry dewatering
The main method of regulation is to add surfactants, such as cationic amine salts or quaternary ammonium salts, which regulate the hydrophobicity of the kaolinite surfaces [7]
Summary
Coal-associated kaolinite is one of the major clay minerals in coal-water slurries [1]. It is fine-grained with high surface electronegativity, and strong hydration films readily form on the particle surfaces [2]. The surface hydration films strengthen the hydration repulsion as well as steric hindrance effects among the particles in the coal slurries. These effects, combined with the electrostatic repulsion caused by the large number of negative charges on the particle surfaces, help maintain the stability of fine kaolinites in coal slurries [3,4], which makes it difficult for the kaolinite to aggregate and settle, and seriously affects the sedimentation and clarification of coal-water slurries.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
