Zeta potential study of natural- and acid-activated sepiolites in electrolyte solutions

Abstract

Detailed characterisation of natural sepiolite from the Eskisehir region of Turkey was performed using X-ray diffraction, X-ray fluorescence, field emission scanning electron microscopy, specific surface area (BET method), Fourier transform infrared spectra, derivative thermogravimetry (DTG) and differential thermal analysis. Electrokinetic properties of natural- and acid-activated sepiolites were investigated as a function of the concentration of various electrolytes, such as NaCl, KCl, LiCl, CaCl2, MgCl2, NaNO3, Na2CO3, FeCl3 and Al(NO3)3. While mono and divalent cations and anions did not change the surface charge of natural- and acid-activated sepiolite, trivalent cations changed the surface charge from negative to positive. Acid-activated sepiolite samples shifted towards the positive region in nearly all electrolyte solutions when compared with the natural sepiolite