The kinetic study indicated that HA adsorption followed the pseudofirst- order model. The maximum monolayer adsorption capacity qm of HA was found to be 54.80 mg g⁻¹ and 330.34 mg g⁻¹ for natural and HDTMA-bentonite, respectively. The adsorption efficiency of natural and HDTMA-bentonite was examined for humic acid (HA) removal by batch adsorption experiments under different operating conditions. The X-ray results indicated that the geometry of the interlayer space changes by the intercalation of HDTMA cations, resulting in an increase in the basal spacing from 1.34 to 1.96 nm. Natural and modified bentonites were characterized using thermogravimetric analysis (TGA), X-ray diffraction (XRD) and infrared spectroscopy (FTIR). In this study, the main objective is the preparation and the characterization of a modified Algerian bentonite based adsorbent by intercalation with hexadecyltrimethylammonium bromide (HDTMA). 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.
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. 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. Adsorption kinetics was better described by the pseudo-second-order model and adsorption process could be well defined by the Langmuir isotherm. The HDTMA+-bentonite exhibited the highest uranium sorption capacity at initial pH of 6.0 and at 80 min. The influences of different experimental parameters such as solution pH, initial uranium concentration, contact time, dosage and temperature on adsorption were investigated.
The adsorbent was characterized using small-angle X-ray diffraction, high resolution transmission electron microscopy, and Fourier transform infrared spectroscopy. The ability of hexadecyltrimethylammonium cation pillared bentonite (HDTMA+-bentonite) has been explored for the removal and recovery of uranium from aqueous solutions.
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