Highly efficient lead removal from water by Nd_0.90Ho_0.10FeO₃ nanoparticles and studying their optical and magnetic...

Ho-doped NdFeO₃ was synthesized using the citrate method. The X-ray diffraction (XRD) illustrated that Nd_0.90Ho_0.10FeO₃ was crystalline at the nanoscale, with a crystallite size of 39.136 nm. The field emission scanning electron microscope (FESEM) illustrated the porous nature of Nd_0.90Ho_0.10FeO₃, which increases the active sites to absorb the heavy metals on the sample surface. Energy-dispersive X-ray (EDX) data assures the prepared sample has the chemical formula Nd_0.90Ho_0.10FeO₃. The magnetic properties of Nd_0.90Ho_0.10FeO₃ were determined using the magnetization hysteresis loop and Faraday's method. Many magnetic parameters of the sample have been discussed, such as the coercive field, the exchange bias (H_ex), and the switching field distribution (SFD). Ho-doped NdFeO₃ has an antiferromagnetic (AFM) character with an effective magnetic moment of 3.903 B.M. The UV-visible light absorbance of Nd_0.90Ho_0.10FeO₃ is due to the transfer of electrons from the oxygen 2p state to the iron 3d state. Nd_0.90Ho_0.10FeO₃ nanoparticles have an optical direct transition with an energy gap E_g = 1.106 eV. Ho-doped NdFeO₃ can adsorb many heavy metals (Co²⁺, Ni²⁺, Pb²⁺, Cr⁶⁺, and Cd²⁺) from water. The removal efficiency is high for Pb²⁺ ions, which equals 72.39%. The Langmuir isotherm mode is the best-fit model for adsorbing the Pb²⁺ ions from water.