Obtaining a hematite pigment by thermal transformation of the surface oxide of reinforcing steel bars

Abstract

In this investigation work, the valuation of the surface oxide waste from reinforcing steel bars through to its thermal transformation into a pigment composed mainly of hematite (ɑ-Fe2O3) is reported. X-ray Fluorescence (XRF) and X-ray Diffraction (XRD) were used to determine the elemental content of the processed waste and identify the iron oxides involved in the calcination, respectively. The steelmaking waste powder is mainly composed by Fe2O3 (87.92 %), SiO2 (6.13 %), CaO (1.88 %), Al2O3 (1.30 %) and MnO (0.77 %). The total iron content corresponds to the following iron oxides: magnetite, maghemite, wustite, lepidocrocite, hematite and goethite. The thermal treatment of the residue at temperatures of 750-850 °C and holding times of 0.5-1.50 h, showed a high conversion of precursor iron oxides into hematite, with percentages of this phase ranging between 86.4 and 94.6%. The highest hematite obtaining was achieved at a condition of 850 °C and 1.00 h.

Keywords

• ɑ-Fe2O3
• iron oxide
• pigment characterization
• calcination
• crystalline phases