Adsorption Of Low Concentration U(Ⅵ) Onto Raw Sodium Feldspar And Activated Sodium Feldspar

In this study, raw sodium feldspar (RSF), sulfuric acid activated sodiumfeldspar (AASF) and conventional thermal activated sodium feldspar (TASF) wereselective as adsorbent. AASF was prepared with different concentration of sulfuricacid treatment and TASF was prepared with different calcination temperature heat.And the effect of pH, adsorption reaction time, adsorbent dosage, initial uraniumconcentration and ambient temperature on the adsorption of low concentrationuranium from the aqueous solution was investigated in a batch adsorptionexperiment. Meanwhile, selective adsorption experiment was conducted to comparethe selectivity of three adsorbent for uranium. Scanning electron microscopy (SEM)and Fourier transform infrared spectroscopy (FTIR) characterization were used toanalyses samples before and after the adsorption. Experiment data were fitted byLangmuir and Freundlich isotherm model to study the adsorption equilibrium.Pseudo-first-order model, pseudo-second-order model and intra-diffusion kineticsmodel were used to analyze adsorption process of uranium to material. Moreover,thermodynamic parameters Gibbs free energy (ΔGθ), enthalpy change (ΔHθ) andentropy (ΔSθ) were used to analyze the adsorption behavior of the adsorbent.The results showed that the uranium adsorption process by adsorbents from lowconcentration aqueous solutions was significantly influenced by the solution pH, andthe best acidity is pH6.0. It was found that the absorption rate is relatively slow andthe process reaches equilibrium in10h. The results also showed thatpseudo-second-order model is better than pseudo-first-order model and intra-diffusion kinetics model to describe the adsorption process, indicating thatadsorption of uranium is mainly controlled by the chemical reaction process andacid activation and thermal activation treatment helps to enhance the adsorption rateand adsorption capacity. Meanwhile, the equilibrium data is more in line with theLangmuir isotherm model, indicating that the uranium adsorption onto the materialis mainly in the form of monolayer coverage. And maximum adsorption capacitycalculated is0.27mg/g for RSF,0.35mg/g for AASF and0.51mg/g for TASF,respectively. The calculated ΔGθ, ΔHθand ΔSθshowed that the uranium adsorptionprocess onto adsorbents is an endothermic and spontaneous reaction. Selectivitycoefficients obtained indicated that the adsorbents for uranium have a goodselectivity and acid activation and thermal activation process greatly increases theselectivity of uranium.SEM results show that the acid activation and thermal activation of rawfeldspar can change the morphology. FTIR results showed that the adsorptionprocess, hydroxyl (-OH) in the sample play an important role in form ofU(VI)-bonding. These suggest that sodium feldspar and activated with acid and heattreatment have a good removal capability for low concentration of uraniumadsorption.