Shear flocculation of celestite with anionic surfactants and effects of some inorganic dispersants

Shear flocculation characteristics of celestite (SrSO4) mineral have been investigated using sodium dodecyl sulfate (SDS) and Aero 845 as anionic surfactants. The celestite suspension could be flocculated by SDS and Aero 845 in the broad pH range. However, these surfactants were slightly more effective on the celestite suspension at a pH of 7. The shear flocculation of celestite with SDS and Aero 845 increased rapidly with increasing surfactant concentration. However, it decreased at SDS concentrations higher than 45 mg/dm3, and eventually stabilization of the suspension took place at concentration values above approximately 80 mg/dm3. From the experiments carried out to determine the effects of stirring speed and flocculation time on the shear flocculation of celestite suspension, it was found that a stirring speed of 500 rpm and a flocculation time of 3 min were required to achieve the maximum aggregation degree of celestite particles. The effects of sodium silicate, sodium phosphate and sodium polyphosphate used as inorganic dispersants on the shear flocculation of celestite were also studied. Sodium silicate strongly prevented the shear flocculation of celestite with SDS. However, the dispersive effect of sodium silicate was low in the presence of Aero 845. In the case of sodium polyphosphate, a dispersive effect on the celestite suspension was not observed for both surfactants. On the contrary, the shear flocculation power values increased slowly in the presence of sodium polyphosphate. In addition, the similar phenomenon also took place for sodium phosphate in the presence of SDS.