Influence of Anions on the Electrokinetic and Colloidal Properties of Palygorskite Clay via High-Pressure Homogenization

A series of palygorskite samples modified with electrolytes including KCl, KBr, KI, KH 2 PO 4 , KHSO 4 , K 2 HPO 4 , K 2 SO 4 , and K 3 PO 4 were prepared with the aid of high pressure homogenization. The changes of electrokinetic and rheological properties, as well as suspension stability of obtained palygorskite, were investigated through measurement of the zeta potential, flow curve, and sedimentation volume. The influences of charge, concentration, and type of anions on surface charge density of palygorskite were compared. The correlation among the surface charge, the rheological behavior, and suspension stability of palygorskite was discussed. The homogenization process could favor the migration of anions onto palygorskite. It was found that the structure maker anions (H 2 PO 4 − , HSO 4 − , HPO 4 2 − , SO 4 2 − , and PO 4 3 − ) made the surface of palygorskite more negatively charged. The flow curve measurements demonstrated that the association capacity of rods depended on the surface potential of palygorskite. A stable suspension was obtained when palygorskite was dispersed in K 2 SO 4 solutions and homogenized at 30 MPa.