Removal of thorium from aqueous solution by adsorption with Cu3(BTC)2

Investigation of kinetic, isotherm and adsorption efficacy of thorium by orange peel immobilized on calcium alginate

In this research work the thorium uptake on immobilized protonated orange peel was studied in a batch system. The effects of effective parameters such as biosorbent dosage, initial metal ion concentration, and contact time on the biosorption of thorium were analyzed. The biosorption capacity of the immobilized orange peel for thorium at optimal conditions of initial pH 3.8, biosorbent dosage 8 g/L, and initial thorium concentration 170 mg/L was found to be 18.65 mg/g. According to the results of contact time, the biosorption process reached equilibrium after around 10 h of contact. Investigation of the kinetics showed that the biosorption of thorium onto immobilized orange peel follows the pseudo-second-order model. The Langmuir and Freundlich isotherms were used to model the experimental equilibrium data. The results showed better agreement by the Langmuir isotherm. The maximum absorption capacity of immobilized protonated orange peel for thorium adsorption was predicted by the Langmuir isotherm at 29.58 mg/g.

γ-Resistant Microporous CAU-1 MOF for Selective Remediation of Thorium

A simple solvothermal method was used to synthesize a metal-organic framework (MOF) with an Al metal entity, viz., CAU-1 NH₂. The synthesized MOF was characterized using different techniques like X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy (SEM), field emission SEM (FE-SEM), transmission electron microscopy, small-angle X-ray scattering, positron annihilation lifetime spectroscopy, and X-ray photoelectron spectroscopy. The radiation stability was evaluated by irradiating the material up to a cumulative dose of 2 MGy using ⁶⁰Co for the first time. The studies showed a remarkable gamma irradiation stability of the material up to 1 MGy. The porosity and surface area of the synthesized MOF were determined by Brunauer-Emmett-Teller, which showed a high specific surface area of 550 m²/g. The pH dependence study of Th uptake from an aqueous solution was performed from pH 2-8, followed by adsorption isotherm and adsorption kinetics studies. These results revealed that the Langmuir and pseudo-second-order kinetic models can be well adapted for understanding the Th uptake and kinetics, respectively. The synthesized MOF exhibited an ∼404 mg/g thorium adsorption capacity. Selectivity studies of adsorption of Th w.r.t. to U and different metal ions such as Cu, Co, Ni, and Fe showed that Th gets adsorbed preferentially as compared to other metal ions. In addition, the MOF could be used multiple times without much deterioration.

Intensification of thorium biosorption onto protonated orange peel using the response surface methodology

In this research work, intensifying the possibility of protonated orange peel to uptake thorium (IV) ions from aqueous solutions in a batch system was investigated and optimized using the response surface methodology. The effect of three independent process variables including thorium initial concentration, pH, and biosorbent dosage was assessed based on the central composite design. The validity of the quadratic model was verified by the coefficient of determination. The optimization results showed that the rate of thorium (IV) uptake under optimal conditions is 183.95 mg/g. The modeling results showed that the experimental data of thorium biosorption kinetics are fitted well by the pseudo-second-order model. According to the results, the biosorption process reached equilibrium after around 4 h of contact. The Langmuir isotherm describes the experimental biosorption equilibrium data well. The maximum absorption capacity of protonated orange peel for thorium adsorption was estimated by the Langmuir isotherm at 236.97 mg/g. Thermodynamic studies show that thorium adsorption on protonated orange peel is thermodynamically feasible, spontaneous, and endothermic.

Mineralogical Properties of a Refractory Tantalum-Niobium Slag and the Effect of Roasting on the Leaching of Uranium-Thorium

In order to realize sustainable development, it is beneficial to explore an appropriate process to recover the radionuclides contained in tantalum-niobium slag. By micro-mineralogical analysis and roasting experiments, the effect of uranium-thorium leaching from a refractory tantalum-niobium slag is investigated. The uranium and thorium content in the slag is 2.26 × 10³ mg/kg and 7.84 × 10³ mg/kg, which have large recovery value. As the surface area and pore size of the slag are very small, the leaching agent cannot fully penetrate the particles. Various methods of characterization are used to analyze the mineralogical properties of roasted slag at different temperatures. The leaching ratio of U-Th is 90.84% and 96.62% at the optimum roasting temperature of 500 °C, which are about 39% and 27% higher than original samples. The oxidants Fe³⁺, O₂ and Mn can also promote the conversion of insoluble U(IV) to soluble U(VI). Roasting reduces the content of organic C and S, thereby preventing reduction of U(VI), and increasing pore size as well as specific surface area also promote radionuclide leaching. Thus, the roasting method at 500 °C can destroy the surface wrapping structure of radionuclides, reduce the internal density of minerals, and improve uranium-thorium leaching ratio significantly. It is of great practical significance to reduce the radioactive hazard of waste tantalum-niobium slag and to strengthen the sustainable utilization of resources by suitable process improvement techniques.

A comparative investigation of uranium and thorium adsorption behavior on amidoximated copolymeric hydrogel

This work focuses on investigating the feasibility of using a crosslinked amidoximated copolymeric hydrogel as a potential adsorbent to recover uranium and thorium ions from aqueous media. The hydrogel was synthesized via gamma-irradiation copolymerization and characterized through FTIR, TGA, and SEM. The medium acidity notably affected the adsorption capacity of both ions. The adsorption data was in line with the pseudo-1st-order equation and the Freundlich isothermal model. The thermodynamics analysis showed that the temperature rise promoted the adsorption capacity. The reusability studies highlighted the good performance of the hydrogel up to five regeneration rounds.