Powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and chemical analyses were used for characterizing the effect of sulfate ions on the conversion rate of condensed Fe(OH)3 gel, prepared from FeCl 3 and NaOH solution, to β-FeOOH and α-Fe2O 3 particles by aging at 100°C. Fine particles and supernatant solution were sampled from the aged suspensions containing colloidal particles. XRD profiles and TEM observation showed that β-FeOOH was formed from the gel and subsequently converted into α-Fe2O3. It was revealed that the addition of sulfate ions accelerated the β-FeOOH formation from the gel, but delayed the conversion from β-FeOOH to α-Fe2O3. The concentration changes of sulfate and chloride ions in the supernatant solution phases were in agreement with the conversion from Fe(OH)3 gel to β-FeOOH and α-Fe 2O3 particles.
- Ferric oxyhydroxide
- Fine particle