Study of ground and unground leached vermiculite II. Thermal behaviour of ground acid-treated vermiculite

►Synthesis of amorphous silica and akaganeite by leaching of ground vermiculite. ►Heating up 800 °C produced an amorphous Fe2O3 attributed to the role of the silica. ►At 1050 °C appeared composite of separated grains of Fe2O3 embedded into SiO2 matrix. ►The crystalline Fe2O3 grains obtained consisted of α-Fe2O3 and ε-Fe2O3. ►TiO2 was associated to Fe2O3 grains.