Adsorption of uranium from aqueous solution using HDTMA+-pillared bentonite: isotherm, kinetic and thermodynamic aspects

Abstract

The ability of hexadecyltrimethylammonium cation pillared bentonite (HDTMA+-bentonite) has been explored for the removal and recovery of uranium from aqueous solutions. The adsorbent was characterized using small-angle X-ray diffraction, high resolution transmission electron microscopy, and Fourier transform infrared spectroscopy. The influences of different experimental parameters such as solution pH, initial uranium concentration, contact time, dosage and temperature on adsorption were investigated. The HDTMA+-bentonite exhibited the highest uranium sorption capacity at initial pH of 6.0 and at 80 min. Adsorption kinetics was better described by the pseudo-second-order model and adsorption process could be well defined by the Langmuir isotherm. The thermodynamic parameters, △G° (308 K), ΔH°, and ΔS° were determined to be −31.64, −83.84 kJ/mol, and −169.49 J/mol/K, respectively, which demonstrated the sorption process of HDTMA+-bentonite towards U(VI) was feasible, spontaneous, and exothermic in nature. The adsorption on HDTMA+-bentonite was more favor than Na-bentonite, in addition the saturated monolayer sorption capacity increased from 65.02 to 106.38 mg/g at 298 K after HDTMA+ pillaring. Complete removal (≈100%) of U(VI) from 1.0 L simulated nuclear industry wastewater containing 10.0 mg U(VI) ions was possible with 1.5 g HDTMA+-bentonite.