Aiming at the settlement problem of coal silme water derived from the washing of high ash and sulfur coal,a new type of Fe3 O4-chitosan/bentonite composite flocculant was synthesized by solvothermal method.Through focusing on the effect of the pH value of coal slurry water on the settlement process,combining with the physical and chemical properties of the flocculant,the flocculation precipitation mechanisms between slime water properties and flocculation were investigated.The results indicate that the flocculant containing —NH3+electropositive groups can effectively reduce the electronegativity of the slurry surface,the electrostatic effect between coal particles and the Van der Waals repulsive potential energy and significantly improve the effect of slurry particle hydrophobic aggregation at pH=5.The flocculant possesses certain reusability with the help of additional magnetic field.