Electrokinetic Properties of Vermiculite and Expanded Vermiculite: Effects of pH, Clay Concentration and Mono- and Multivalent Electrolytes

In this study, the zeta potential values of vermiculite and expanded vermiculite were measured to determine the effect of pH, clay concentration, and various mono- and multivalent electrolytes including NaCl, KCl, NH4Cl, NaNO3, NaClO4, Na2SO4, Na2CO3, Na3PO4 center dot 12H(2)O, MgCl2 center dot 6H(2)O, CaCl2 center dot 2H(2)O, BaCl2, SrCl2 center dot 6H(2)O, CuCl2 center dot 2H(2)O, CoCl2 center dot 6H(2)O, NiCl2, AlCl3, and CrCl3 center dot 6H(2)O on the electrokinetic properties of vermiculite samples. It was found that generally the measured zeta potential values of expanded vermiculite for the studied systems were slightly more negative than that of vermiculite. The pH profiles of vermiculite and expanded vermiculite at acidic, natural, and basic pH values were obtained to determine the effect of time on the pH values of clay suspensions. The zeta potential measurements showed that the surface charge of clay particles was negative in water. The isoelectric point of vermiculite and expanded vermiculite were determined as pH 2.30 and 2.57, respectively. Divalent cations (Mg2+, Ca2+, Sr2+, and Ba2+), heavy metal ions (Cu2+, Ni2+, and Co2+) and trivalent cations (Al3+ and Cr3+) were potential determining ions for vermiculite and expanded vermiculite particles. Moreover, divalent and trivalent cations caused the change of surface charge from negative to positive. On the other hand, monovalent cations (Na+, K+ and NH4+), monovalent anions (Cl-, NO3-, and ClO4-) and multivalent anions (SO42-, CO32-, and PO43-) acted as indifferent ions for these clay particles.