Syntheses and evaluations of three sulfonated polycondensate dispersants for coal–water slurries

Three sulfonated polycondensate dispersants—sulfonated acetone-formaldehyde (SAF), sulfonated phenol-formaldehyde (SPF) and sulfonated 2-naphthol-formaldehyde (SNF), were synthesized and applied as the dispersants for the coal–water slurries (CWSs) prepared from Chinese Shenfu coal. The CWS application performance investigations show that SNF can most effectively reduce CWS viscosity, but SAF has the best ability in stabilizing CWS. The physicochemical property investigations of the three dispersants show that the adsorption amount of SAF at coal–water interface is greater than those of SPF and SNF, and SAF has the greatest capacity in charging coal surface with electronegativity, but SNF has better wetting property than SPF and SAF on coal surface. It is indicated that the capabilities of the tested dispersants depend not only on the hydrophobic group character but also on the molecular flexibility. Based on the above, the principle of stabilization of the CWSs prepared from the three dispersants is presented.