Investigation of grafted sulfonated alkali lignin polymer as dispersant in coal-water slurry

The three-dimensional molecular structure of GSAL with long side chains well improves the hydrophily and electronegativity interaction (mainly is π–πconjugated adsorption) with coal surface and increases the adsorption capacity on coal surface. The steric hindrance effect of GSAL with higher molecular weight and longer hydrophilic side chains results in a rather thicker adsorbed film, and the adsorption behavior can help to decrease the solid liquid interfacial free energy so as to improve the wettability to coal particle. FDN adsorbs on coal particle by the lying form mainly by means of the electrostatic interactions between the sulfonic groups of FDN and the coal surface, the thickness of adsorbed film is thinner, that is difficult to form larger steric hindrance despite FDN has more adsorption mass. •GSAL with hydrophilic side chain and different molecular weights used as dispersants for coal-water slurry.•The adsorption isotherm of GSAL on coal surface belongs to Langmuir model.•The π–π interaction was the dominant driving force of GSAL absorbed on coal surface.•GSAL offered steric electrostatic repulsion and dramatic wettability.•The adsorption amount of GSAL on coal surface decreased and the adsorption forces between GSAL and coal surface increased with the increase of molecular weight.•GSAL was superior to FDN dispersant in reducing the viscosities of CWS. A novel grafted sulfonated alkali lignin polymers (GSAL) with hydrophilic side chain and different molecular weights prepared were used as dispersants for coal-water slurry (CWS). The viscosity reduction for CWS had been attributed primarily to the diminution of coal particles (adsorbed GSAL) interaction of steric electrostatic repulsion and dramatic wettability. The adsorption amount of GSAL-3 can reach to 1.58mg/g, and the isotherm of GSAL on coal surface belongs to the Langmuir model, the electrostatic self-assembly result indicated the dominant driving force of GSAL absorbed on coal surface was the π–π interaction. GSAL was superior in reducing the viscosities of CWS.