Review and Perspectives of Anionic Dispersants for Coal–Water Slurry

Dispersants are chemical moieties that modify interfacial characteristics by adsorption at the solid–liquid interface, and they have been widely used in modern industrial production. This review focuses on the research and perspectives of anionic dispersants for coal–water slurry (CWS). Various common anionic dispersants are briefly summarized, including natural and synthetic species. The interactions between coal particles in the CWS suspension, including van der Waals attraction and electrostatic repulsion, are described by the DLVO (Derjaguin–Landau–Verwey–Overbeek) theory. Due to the hydrophobic interaction and the steric effect resulting from the adsorption of polymer dispersants, the extended DLVO theory is introduced to elucidate the various interactions in the CWS system. Based on the interactions between the coal particles, the adsorption behaviors at the coal–water interface, and the interactions between coal and water, the dispersion and stabilization mechanisms are systematically and theoretically discussed. According to the variations of interaction energies between the coal particles, the use of anionic polymer dispersants can weaken the hydrophobic attraction and enhance the steric hindrance and electrostatic repulsion. Also, the rheological behaviors of CWSs are outlined, with emphasis on the pipeline transportation of CWS and the three-parameter Herschel–Bulkley model. Additionally, the properties of anionic dispersants for CWS can be improved by adjusting their chemical structures such as molecular weight, side chain length, rigidity and flexibility of the molecular chain, and variety, quantity, position, and proportion of hydrophobic and hydrophilic groups. In view of the relationships between the structure and property, a direction on the selection and preparation of dispersant for CWS is suggested. Finally, the current challenges and future perspectives of dispersants for CWS are put forward.