Zeta Potentials of Suspended Humus in Multivalent Cationic Saline Solution and Its Effect on Electro-Osomosis Behavior

Abstract

The surface electrical charge was measured for laboratory grade organic soil colloidal particles by varying pH between 2 and 11 and at 0.001, 0.01, 0.1, and 1.0 mol/L of cationic saline solution (CaCl2, Na2Sio3, Al2(SO4)3, MgCl2, and Na2CO3) concentrations. The zeta (ζ) potential values showed low sensitivity to pH in salt solutions. The ζ potential of pure organic soils varied from +7.5 mV at pH 2.8 to −28.5 mV at pH 11.3. The ζ potential calculation of humus particles in distilled water showed an increase in ζ potential value beyond pH > 3.3, which could be due to charge development at the humic substances by direct transfer of H+ from organic soil to water. The surface electrical charge was almost zero at pH 3.25. Colloidal charge reversal was observed at several stages according to the electrolyte concentrations and chemical reagents. It was also found that using high molarities of multivalent saline solution (e.g., CaCl2, Na2Sio3, Na2CO3, and MgCl2) as electrolytes led to very high ζ potential values and consequently high electro-osmotic conductivity (Ke). On the basis of the results of this research, it is recommended that the ζ potential of the soils be determined before any application of electrokinetic (EK) treatment.