Ca-alginate/carboxymethyl chitosan/Ni_0.2Zn_0.2Fe_2.6O₄ magnetic bionanocomposite: Synthesis, characterization and application for single adsorption of Nd⁺³, Tb⁺³, and Dy⁺³ rare earth elements from aqueous media

This study aims to research the adsorption of Nd⁺³, Tb⁺³, and Dy⁺³ from aqueous media onto the magnetic calcium alginate/carboxymethyl chitosan/Ni_0.2Zn_0.2Fe_2.6O₄ (CA/CMC/Ni_0.2Zn_0.2Fe_2.6O₄) bionanocomposite in a single system. FE-SEM, FT-IR, EDX, VSM, and TGA were applied to characterize the product. The VSM result showed the saturation magnetization values of 45.87 and 14.14 emu/g for the bare Ni_0.2Zn_0.2Fe_2.6O₄ nanoparticles and CA/CMC/Ni_0.2Zn_0.2Fe_2.6O₄, respectively. The adsorption results showed that at optimum conditions of contact time of 40 min, pH of 5.5, and 0.8 g/L, the adsorption efficiency of the adsorbent for Nd⁺³, Tb⁺³, and Dy⁺³ was 97.75, 96.83, and 97.85%, respectively. The ions adsorption kinetic onto the CA/CMC/Ni_0.2Zn_0.2Fe_2.6O₄ was in accordance with pseudo-second-order (PSO) model. The evaluation of equilibrium data was performed by the isotherm models of Langmuir and Freundlich. Fitting the experimental data of Tb⁺³ and Dy⁺³ was done better with Freunlich model than Langmuir model, while fitting tests for Nd⁺³ adsorption data showed better coverage using Langmuir model with a maximum adsorption capacity of 73.37 mg/g. The results of the parameters of thermodynamic showed the endothermic and spontaneous properties of the process. Additionally, the efficacy of the adsorbent was studied using 0.2 M HNO₃ in four adsorptions–desorption cycles. Overall, the obtained results demonstrated that the environmentally friendly magnetic bionanocomposite adsorbent can be applied effectively for Nd⁺³, Tb⁺³, and Dy⁺³ adsorption with favorable adsorption efficiency.