THE INFLUENCE OF ALUMINUM ON IRON OXIDES

The effect of clay minerals as aluminum sources on iron oxides synthesized from ferrihydrite at pH 5 and in 0.1 M KOH at 70 and 25°C was studied. Depending on type of clay mineral, temperature, and pH, aluminum released from these sources favors the formation of hematite over goethite, retards or inhibits crystallization, and enters the crystal lattice of goethite and hematite where it replaces iron. Silicate released at high pH forms Fe-O-Si bonds with the ferrihydrite and can also inhibit crystallization.