A study on the preparation and characterization of pigment quality from mill scale steel wastes

Abstract

Mill scale is an abundant solid waste from steel production. This material is a very valuable industrial waste due to its richness in iron (about 72 % Fe), chemical stability and variable usage in multiple fields which implies that it can bring social and environmental benefits. This work aims to recover Mill scale and reuse it to synthesize three iron oxide pigments ; Hematite (α-Fe2O3, red color), Magnetite (Fe3O4, black color) and Maghemite (γ-Fe2O3, brown color).To achieve this objective, Mill scale needs to be refined and granted to react with sulfuric acid to obtain ferrous sulfate FeSO4.xH2O which is used to produce Hematite by calcination between 600 and 900°C, then, Magnetite by reduction of hematite using a reducing agent at 400°C and Maghemite from a thermal treatment of magnetite at 200°C.It was shown within the experiments that the mill scale contains between 75% and 86.66% of Fe and a uniform distribution of particles size with a low Span. That gave red particles size (0.18 -0.193 µm) and specific surface area SSA: 6.12 m 2 /g, black particles sizes (0.2 -0.3 µm) and SSA 4.92 m 2 /g, brown particles size (0.18 -0.189 µm) and SSA 6.32 m 2 /g. The results revealed that the mill scale was successfully converted into pigments with good qualities.