Adsorption of Europium (III) on Amidoxime-Functionalized Ficus virens Aerial Root Hydrochar: Statistical Optimization, Equilibrium Isotherm, and Kinetic Analyses

The long-living radionuclides existing in nuclear wastes are a serious ecological threat. The present study delineates the application of amidoxime-functionalized Ficus virens aerial roots derived hydrochar (AO-f-ARHC) as a novel multifunctional absorbent material for retention of aqueous Eu3+ ions. The physicochemical characterization of AO-f-ARHC was accomplished utilizing X-ray diffraction (XRD), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX), transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FTIR) techniques. The adsorptive effectiveness of the synthesized adsorbent was estimated by using central composite design (CCD). Langmuir saturation capacity (Qm) was 166 mg/g at 313 K. The adsorption kinetics data complied with pseudo second order kinetic model. The process spontaneity and endothermic behavior were manifested by the negative ΔG° (= −5.10 kJ/mol) and positive ΔH° (= 21.26 kJ/mol), respectively, at 313 K. The mechanism of adsorption primarily included electrostatic interaction, metal-π interaction, and pore-filling. AO-f-ARHC's Eu3+ uptake efficacy in the presence of coexisting ions and real water samples along with the reusability potential confirmed its competence in wastewater treatment.