Ironoxide pigmenting powders produced by thermal treatment of iron solid wastesfrom steel mill pickling lines

Phase changes of iron containing solid wastes from steel mill pickling lines after thermal treatments were investigated aiming the determination of the appropriate conditions for its transformation to be useful for industrial raw materials. Above 275°C, the thermally treated wastes contain a mixture of α-Fe₂O₃ (hematite) and γ-Fe₂O₃ (maghemite) in different proportions, depending on the maximum heating temperature of the thermal treatment. Increasing the maximum temperature the maghemite participation is decreased through its transformation to hematite. Above 850°C hematite is the main constituent, suggesting that thermal treatment of the wastes in this temperature will give a product that could be used as red iron pigment.