Abstract
Ferric hydroxide (Fe(OH)3) gel, prepared from FeCl3 and NaOH solutions, was aged at 100°C in the presence and absence of silicate ions to examine the effect of silicate ions on the conversion process of condensed Fe(OH)3 gel to iron oxides. The aged suspensions containing colloidal particles in each stage were separated into solid particles and supernatant solutions by centrifugation. X-ray diffraction measurements and transmission electron microscopic observations of the solid particles revealed that β-FeOOH was formed from the Fe(OH)3 gel and subsequently converted into α-Fe2O3, and the addition of silicate ions in the Fe(OH)3 gel decreased the conversion rate to β-FeOOH and α-Fe2O3 particles. IR measurements of the solid particles and inductively coupled plasma analyses of the supernatant solutions showed that the adsorption of silicate ions on specific plane of the solid particles was decisive factor for the suppression of the conversion process.
