Auto-combustion Synthesis and Characterization of Iron Oxide Nanoparticles (α-Fe2O3) for Removal of Lead Ions from Aqueous Solution

Abstract

In this work, iron oxide nanoparticles (hematite; α-Fe2O3) were fabricated by using an auto-combustion technique with fuels: hexamine, urea and a mixture of them with the molar ratio as the following: (Fe:H:U = 1:2.5:0, 1:0:0.42 and 1:1.25:0.21) according to the rule of the combustion method. The as-fabricated iron oxide nanoparticles calcined at 500 °C for 30 min. the obtained iron oxide nanoparticles were characterized by using various tools such as X-ray diffraction (XRD), transmission electron microscopy (TEM) and Fourier-Transform Infrared Spectroscopy (FTIR). The results of XRD confirmed that the formation of the rhombohedral crystal structure of the synthesized iron oxide in the form of hematite (α-Fe2O3) after calcination. The extracted data from XRD and TEM techniques showed that the average particles and crystallite sizes of the fabricated hematite nanoparticles (FHU5 sample) was estimated to be about 35.43 nm and 36 nm, respectively. According to the FTIR spectra of the calcined FU5, FH5 and FHU5 samples, the bands at 439 cm−1 and 545 cm−1 are related to the vibration modes of Fe-O inside Fe2O3 lattice. The adsorption capacity of the calcined iron oxide nano-adsorbent (α-Fe2O3; FH5 sample) was examined at different parameters for the removal Pb2+ from aqueous media and the optimum conditions were determined. The extracted data showed that the removal of lead ions increased with the rise of pH value (4–6). The optimum conditions were found: pH 5.5, 120 min and 50 mg of the fabricated α-Fe2O3 at 25 °C. The models of adsorption isotherm and adsorption kinetics are used for the description of the removal leads ions over the calcined α-Fe2O3 nanoparticles. The thermodynamics factors are investigated for the removal of the lead ions over the fabricated hematite nanoparticles (α-Fe2O3).