SURFACE TITRATIONS OF PERLITE SUSPENSIONS

The surface charge behaviour of unexpanded and expanded perlite sample s in KNO3 and NaCl solutions were investigated as a function of pH and ionic strength. The solutions of KNO3 and NaCl ranging from 10(-3) to 1.0 M were used. The potentiometric titration method was used to dete rmine the surface charge of perlite samples. It was confirmed that the perlite samples had no the point of zero charge and was negatively ch arged in the pH range of 3-10. The double extrapolation method was use d for determining the intrinsic equilibrium constants for simple ioniz ation and complex ionization reactions. The values obtained are pK(a2) (int) = 2.5 and pK-K+(int) = 2.3 in KNO3 solutions and pK(a2)(int) = 3.0 and pK-Na+(int) = 2.4 in NaCl solutions for unexpanded perlite, a nd pK(a2)(int) = 2.6 and pK-K+(int) = 2.4 in KNO3 solutions and pK(a2 )(int) = 2.7 and pK(Na+)(int) = 2.4 in NaCl solutions for expanded per lite. (C) 1998 Academic Press.