Tailor-designed carbon-based novel fluorescent architecture for nanomolar detection of radioactive elements U(VI) and Th(IV) in pH ± 5.0

Highly stable nitrogen-doped Graphene Quantum Dots (N-GQD) functionalized with Pamoic Acid (PA@N-GQD) are utilized for nanomolar detection of radioactive elements, Uranium (VI) and Thorium (IV), in pH ± 5.0. The absorption, fluorescence, crystalline nature, elemental composition, functional groups, and morphological state of as-prepared PA@N-GQD are evaluated by UV-visible absorption, photoluminescence, XRD, XPS, FTIR, HRTEM, FESEM, and AFM characterizations. The aqueous solution of PA@N-GQD is characterized by its spherical morphology, averaging 6.5 nm in size. PA@N-GQD exhibits a gradual decrease in fluorescence intensity at 438 nm (λex 344 nm) upon the addition of Uranium (VI) and Thorium (IV) ions. The selectivity, sensitivity, competitivity, pH, time effect, and reversibility studies of PA@N-GQDs have been carried out using the photoluminescence technique. The attained fluorescence Limit of Detection (LoD) of PA@N-GQD for Uranium (VI) and Thorium (IV) ions are 2.009 × 10-9 and 1.351 × 10-9 M, respectively. From the fluorescence titration studies of U(VI) and Th(IV), the binding constant, Stern-Volmer constant, Modified Stern-Volmer constant, association constant, and dissociation constants have been calculated separately. These aforementioned results indicate that the PA@N-GQD has a higher binding affinity towards Th(IV) than U(VI) in aqueous medium. This current research represents the development of advanced materials for environmental and analytical applications, specifically focusing on the precise detection and quantification of radioactive elements.

The Study of Amidoxime-Functionalized Cellulose Separate Th(IV) from Aqueous Solution

Selective extraction of low-concentration thorium (Th(IV)) from wastewater is a very important research topic. In this paper, amidoxime cellulose was synthesized, and its composition and structure were characterized by FT-IR, SEM, XPS, and elemental analysis. The adsorption experiment results showed that the adsorption reaction was a spontaneous exothermic process. When the solid–liquid ratio was 0.12 g/L and the pH value was 3.5, the adsorption percentage of the Th(IV) in water onto amidoxime-functionalized cellulose (AO-CELL) could reach over 80%. The maximum adsorption capacity can reach to 450 mg/g. At the same time, the adsorption selectivity, desorption process and reusability of the material were also studied. The results showed that the AO-CELL had a good selectivity for Th(IV) in the system with Sr²⁺, Cu²⁺, Mg²⁺, Zn²⁺, Pb²⁺, Ni²⁺, and Co²⁺ as co-ions. In the nitric acid concentration of 0.06 mol/L system, the AO-CELL desorption rate of Th(IV) can reach 95%, and the adsorption rate of Th(IV) in aqueous solution of AO-CELL is still above 60% when the AO-CELL is reused four times. The above results show that the amidoxime cellulose adsorption material synthesized by our research group has good selective adsorption performance for Th(IV) of a low concentration in an aqueous solution and has a good practical application value.

Separation of thorium(IV) from aquatic media using magnetic ferrite nanoparticles

The separation and recovery of thorium from monazite is critical to the sustainable development of the nuclear industry as well as to environmental safety. Also, the removal of radionuclides from polluted sources is a critical issue in environmental control. Magnetic ferrite nanoparticles (MCMF-NP, Co0.5Mn0.5Fe2O4) were synthesized (4–22 nm in size) and characterized. MCMF-NP was investigated for Th(IV) separation from their aqueous medium under various test conditions of acidity, time, and Th(IV) concentration, in line with the uptake capacity. The amount of thorium adsorbed is improved when pH, time, and initial concentration are increased. The maximum uptake of Th(IV) by MCMF-NP was observed at pH 3.5–4 and a contact time of 180 min. A favorable adsorption mechanism was shown in the pseudo-second-order rate. Isotherm analysis shows an adequate process described by the Langmuir isotherm. MCMF-NP is an adsorbent capable of successful disposal of Th(IV) from waste solutions with a high uptake of 81.3 mg of Th(IV)/g of MCMF-NP. The possibility of re-using the MCMF-NP, adding value to this content as a way of compensating for the disposal costs, was studied and disused. MCMF-NP shows a good separation of thorium(IV) from monazite leach liquor as well as from wastewater samples.