Acid-Base Properties and Heavy and Alkaline Earth Metal Adsorption on the Oxide-Solution Interface: Non-Electrostatic Model.
A new approach was applied to the description of acid-base properties and heavy and alkaline earth metal adsorption on the oxide-solution interface. The acid-base properties of hematite have been determined at different temperatures. The adsorption of protons and hydroxyl ions on the hematite surface has a temperature independent character. The proton and hydroxyl ion adsorption in NaCl media was explained by the reactions. &tbond;H2O + H3O+ + Cl- = &tbond;H2OHCl + H2O &tbond;OH2 + OH- + Na+ = &tbond;OHNa + H2O. The modified equation of the Frumkin-Fouler-Guggenheim isotherm was used to simulate the experimental data (theta, relative adsorption): log[thetaHCl/(1 - thetaHCl)] - log[H+] - log[Cl-] = log KoHCl + log BH[NthetaHCl/(1 + (N - 1)thetaHCl)]; log[thetaNaOH/(1 - thetaNaOH)] - log[Na+] - log[OH-] = logKoNaOH + logBOH[NthetaNaOH/(1 + (N - 1)thetaNaOH)]. The model parameters were log BH = -4.92 +/- 0.1, log BOH = -2.61 +/- 0.05, N = 3.25 +/- 0.2. The site density of the hematite surface was determined to be 3.8 +/- 0.1 µ moles/m2. The values of the constants were log KoHCl (25-100 degreesC) = 9.50 +/- 0.1; log KoNaOH (25-100 degreesC) = 5.93 +/- 0.1. Copyright 1998 Academic Press.
Institute of Experimental Mineralogy, Russian Academy of Sciences, 142432 Chernogolovka, Moscow district, Russia
S
Pivovarov