Physical and chemical characteristics of hematite nanoparticles prepared using microwave-assisted synthesis and its application as adsorbent for Cu, Ni, Co, Cd and Pb from aqueous solution

Abstract

Hematite nanoparticles were synthesized using the microwave-assisted hydrothermal technique and from aqueous solution. The structure of the prepared material was characterized using x-ray fluorescence (XRF), X-ray diffraction (XRD), electron spin resonance (ESR), transmission electron microscopy (TEM), and electron diffraction (ED). The average particle size was found to be 18 nm while the XRD and ESR results confirmed the formation of hydrogenated hematite phase. XRD matched the hexagonal phase of Fe1.9H0.06O3 in which two ESR absorptions at Landé g-factor of 2.022 and 2.424 are attributed electron splitting at Fe3＋ and H+ sites, respectively. Radial distribution function (RDF) showed that the lattice parameters equal to a=5.82 Å and c=13.7 Å. Inductively coupled plasma optical emission spectroscopy (ICP-OES) was used to determine the ability of the material to adsorb Cu, Ni, Co, Cd and Pb ions from their aqueous solution. The effect of hydrogen concentration (pH)and the kinetic analysis showed that pseudo-second-order model of adsorption is suitable for rate-limiting processes around the particles surface that may involve chemisorption and physicochemical interactions between ionic species. Sorption isotherm study showed that the Langmuir isotherm model for single mono-layer sorption was more suitable and the maximum sorption capacity attained by the prepared hematite nanoparticle was around 100 mg/g and independent on the ion.