EFFECT OF PH CONDITIONS ON GOETHITE BEHAVIOR IN THE PRESENCE/ABSENCE OF DIFFERENT DISPERSANTS

Abstract

Dispersion and settling behavior of goethite has been studied and effect of pH values on surface properties of goethite particles with /without dispersants has been discussed. A prerequisite for the successful flocculation is the stabilization of the system which is achieved by the good dispersion of particles. The effect of pH, sodium silicate (Na2SiO3), sodium hexametaphosphate (Na6P6O18) and sodium pyrophosphate (Na4P2O7), on the surface charges of goethite was studied. The IEP of natural goethite was found by measuring zeta potential at pH value of 6.6. With the use of sodium silicate the IEP of goethite moves to pH 4.95. An IEP could not be detected when the poly-phosphates were used and the surface charge is negative from pH 2 to pH 12. The relatively high zeta potential values indicate a fairly stable dispersion, especially when the sodium hexametaphosphate were used as dispersant.
Keywords: goethite, dispersion, pH value, zeta potential, IEP.