Comparative structural characterization of α-Fe2O3 obtained under different synthesis conditions for water remediation applications

Abstract

Hematite (α-Fe2O3) exhibits structural and surface properties of interest for the development for materials intended for the removal of inorganic contaminants from aqueous systems. In this work, a comparative structural evaluation by X-ray diffraction (DRX) was carried out on a commercial hematite sample (Fe2O3-COM) and two materials obtained by chemical precipitation under alkaline conditions using nitrate (Fe2O3-CP-N) and sulfate (Fe2O3-CP-S) iron precursors, as a preliminary step toward their evaluation for arsenic removal from water. The experimental diffraction patterns were compared with crystallographic reference data to identify the crystalline phases present. Intense and well-resolved reflections were fitted using Voigt functions to determine the full width at half maximum (FWHM) and crystallite size was estimated using the Scherrer equation with Cu Kα radiation. All three samples exhibited characteristic reflections of α-Fe2O3 with a rhombohedral structure and R-3c space group. Considering three selected reflections for each sample, the average crystallite sizes were 39.10 ± 1.16 nm for Fe2O3-COM, 19.10 ± 3.17 nm for Fe2O3-CP-N and 15.34 ± 6.91 nm for Fe2O3-CP-S. The synthesized materials therefore exhibited smaller average crystallite sizes than the commercial hematite, indicating the influence of the precursor and preparation conditions on their microstructural characteristics. Additionally, samples obtained by hydrothermal synthesis using nitrate (Fe2O3-HT-N) and sulfate (Fe2O3-HT-S) precursors are currently being processed. Their results will be incorporated into the comparative analysis. This study will support the selection of suitable synthesis conditions for subsequent arsenic adsorption experiments.

Keywords: hematite; X-ray diffraction; water remediation