Preparation, characterization and magnetic properties of Sm${}_{0.95}$Ho${}_{0.05}$FeO${}_3$ nanoparticles and their application in the purification of water

Sm${}_{0.95}$Ho${}_{0.05}$FeO${}_3$ was successfully prepared in a single phase using the citrate combustion method. The investigated sample was characterized using X-ray diffraction (XRD), a high-resolution transmission electron microscope (HRTEM) and X-ray photoemission spectroscopy (XPS). XRD confirmed that the sample was synthesized in an orthorhombic phase with an average crystallite size of 12 nm. HRTEM indicated that the sample was prepared in the nanoscale with an average particle size of 18 nm. XPS was used to identify the chemical bonds, binding energies and core levels of Sm${}_{0.95}$Ho${}_{0.05}$FeO${}_3$. The magnetic properties were studied using a vibrating sample magnetometer and DC magnetic susceptibility using Faraday's method. The sample has an antiferromagnetic behavior with weak ferromagnetic components. The presence of magnetic Ho${}^{3+}$ ions in the SmFeO${}_3$ sample causes the magnetic exchange interaction between the 2p orbital of Fe${}^{3+}$ and the 4d sub-shell of Ho${}^{3+}$ ions. The dependence of pH value on the removal efficiency of Pb${}^{2+}$ from water was studied. The maximum Pb${}^{2+}$ removal efficiency of the Ho-doped SmFeO${}_3$ nano perovskite is 26% at pH = 5 and 99% at pH = 8. The Freundlich, Langmuir and Temkin isotherms were studied to understand the adsorption mechanism. The Temkin adsorption isotherm best fitted with the experimental data.