Adsorption of Uranium (VI) From Aqueous Solution Using Melamine Formaldehyde Organo Clay Nanocomposite Foam as a Novel Adsorbent

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Uranium is a toxic radioactive element and is usually found in the environment in hexavalent form. It has become necessary to remove uranium, which can be released into the environment in excessive amounts through nuclear industrial activities, from access waters. Melamine formaldehyde/organo clay nano composite foam (MFCNCF) was prepared as a novel adsorbent by hardening with thermal treatment. Structural, crystallographic textural and surface morphological characterization of the prepared adsorbent was made by Fourier transform infrared spectrophotometry (FTIR), X-Ray diffraction (XRD), Scanning electron microscopy (SEM) and High-resolution transmission electron microscopy (HRTEM) analyses. This study aimed to investigate the adsorption of U(VI) from aqueous solutions by MFCNCF and its dependence on various variables, such as initial uranium concentration, adsorption time, adsorbent dosage, initial pH, and temperature. Additionally, its adsorption isotherm analysis and adsorption kinetics and thermodynamics were also examined. For this purpose, batch adsorption experiments were carried out and the equilibrium concentration of U(VI) in the aqueous solution was measured with a UV-Vis spectrophotometer at a wavelength of 433 nm, which corresponds to its maximum absorptivity. The results regarding adsorption kinetics showed that 30 min was sufficient to reach adsorption equilibrium and the data showed a high fit to the pseudo-second-order kinetic model. Isotherm analysis also revealed a high fit of the data to the Type III isotherm and the Halsey model. Based on these fits, an adsorption mechanism involving two regions (electrostatic and complex formation) is proposed for the current adsorption system. The adsorption isosteric enthalpy and entropy values for the first and second regions were found to be −5.35 and 2.02 kJ/mol and −16.98 and 6.40 J/mol, respectively. The experimental results showed that the prepared nanocomposite foam adsorbent is an effective and potential alternative for the effective removal of U(VI) from aqueous solutions.

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