Effects of inorganic sulfates on the microstructure and properties of ion-exchange treated palygorskite clay

Palygorskite was modified with inorganic sulfates, including Na2SO4, ZnSO4, Al2(SO4)3, and Zr(SO4)2, using the high-pressure homogenization technology. The effects of type and concentration of sulfates on the morphology, micro-structure, surface potential, shear modulus and viscosity of palygorskite were investigated by scanning electron microscopy (SEM), nitrogen adsorption–desorption isotherms (BET), zeta potential and rheological measurements, respectively. The modification of palygorskite with ZnSO4 increased its specific surface area and micropore volume, but the largest pore size was obtained for the palygorskite modified with Al2(SO4)3. Zeta potential results suggested that the multivalent Al3+ and Zr4+ ions were more efficient in reducing the negative charge of palygorskite. The colloidal properties of the suspension were dependent on the type and concentration of sulfates, and the introduction of ZnSO4 simultaneously enhanced the dispersibility and colloidal properties of palygorskite.