ADSORPTION OF FLUORIDE ON GOETHITE SURFACES-IMPLICATIONS ON DENTAL EPIDEMIOLOGY

Fluoride ion interaction with synthetically prepared goethite has been investigated over a range of pH values (4-9) and F- concentrations (1 0(-3)-10(-5) M). The amount of F- retained by goethite suspensions was found to be a function of pH, media ionic strength, F- concentration, and goethite concentration. The lowest ionic strength (0.001 M KNO3) gave the highest adsorption medium. Uptake was minimal at pH > 7 and i ncreased with decreasing pH. Thermodynamic properties for fluoride ads orption at 298 K and 323 K were investigated. The isosteric heat of ad sorption (DELTAH(r)) was calculated and the heterogeneity and homogene ity of the surface examined for goethite. In view of the importance of fluoride in dental health, the interaction of fluoride on goethite in the physical environment has important implications on dental epidemi ology.