Wentao Wang

The effective management of High-Level Liquid Waste (HLLW) is critical for environmental and human health protection. The presence of platinum group metals (PGMs) in HLLW, particularly their refractory nature due to their high melting points, complicates vitrification processes. This study presents a targeted adsorption strategy using COF-42 for Pd²⁺ sequestration in HLLW systems. The comprehensive characterization of COF-42 and its Pd-loaded counterpart (Pd@COF-42) via PXRD, FT-IR, TGA, XPS, and SEM confirms structural robustness and successful Pd²⁺ incorporation. Kinetic and thermodynamic analyses reveal pseudo-second-order adsorption behavior with a maximum capacity of 170.6 mg/g, highlighting the exceptional Pd²⁺ affinity. Systematic optimization identifies HNO₃ concentration (≤3 M) and adsorbent dosage (≤30 mg) as critical parameters governing adsorption efficiency through protonation–deprotonation equilibria. Furthermore, COF-42 exhibits superior selectivity for Pd²⁺ over 13 competing metal ions and maintains ~80% adsorption efficiency after four regeneration cycles. These performance metrics originate from the synergistic interplay of (1) framework flexibility enabling adaptive Pd²⁺ coordination, (2) hierarchical porosity facilitating ion diffusion, and (3) dense –NH/–NH₂ groups acting as electron-rich chelation sites.

The separation of palladium from radioactive waste streams represents a critical aspect of the secure handling and disposal of such hazardous materials. Palladium, in addition to its radioactive nature, holds intrinsic value as a resource. Despite the urgency, prevailing adsorbents fall short in their ability to effectively separate palladium under highly acidic environments. To surmount this challenge, our research has pioneered the development of 1,3,5-tris(4-aminophenyl)benzene-2,5-Bis(methylthio)terephthalaldehyde COF (TAPB-BMTTPA-COF), a novel material distinguished by its remarkable stability and an abundance of sulfur-containing functional groups. Leveraging the pronounced affinity of the soft ligands’ nitrogen and sulfur within its molecular architecture, TAPB-BMTTPA-COF demonstrates an exceptional capability for the selective adsorption of palladium. Empirical evidence underscores the material’s swift adsorption kinetics, with equilibrium achieved in as little as ten minutes, and its broad tolerance to varying acidity levels ranging from 0.1 to 3 M HNO₃. Furthermore, TAPB-BMTTPA-COF boasts an impressive adsorption capacity, peaking at 343.6 mg/g, coupled with high selectivity in 13 interfering ions’ environment and the ability to be regenerated, making it a sustainable solution. Comprehensive analyses, including Fourier Transform Infrared Spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS), alongside Density Functional Theory (DFT) calculations, have corroborated the pivotal role played by densely packed nitrogen and sulfur active sites within the framework. These sites exhibit a robust affinity for Pd(II), which is the cornerstone of the material’s outstanding adsorption efficacy. The outcomes of this research underscore the immense potential of COFs endowed with resilient linkers and precisely engineered functional groups. Such COFs can adeptly capture metal ions with high selectivity, even in the face of severe environmental conditions, thereby paving the way for the more effective and environmentally responsible management of radioactive waste.

Developing a new efficient separation ligand based on the “CHON” principle to address the limitations of phosphorus containing extractants in nuclear fuel reprocessing can help further simplify the process flow and reduce the amount of secondary waste. Building upon this critical need, a novel ligand was developed through a strategic application of the Hard and Soft Acids and Bases (HSAB) theory, integrating a soft donor nitrogen atom into the linear architecture of bis-diglycolamide. This groundbreaking ligand, named N,N′-bis[2-(2-(N,N-dioctylcarbamoyl)ethoxy)ethylacetamido]-N″-diethylenetriamine (TOMDEA-BisDGA), has demonstrated remarkable potential in the extraction of Pu(IV). The study unveils that the ligand demonstrates remarkable selectivity and separation efficiency towards Pu(IV) ions while maintaining an exceptionally low extraction capacity for U(VI) across a wide acidity spectrum of 0.1~6 mol/L. To explain the structure properties of complex formed by the ligand and Pu(IV), a systematic analysis was performed, including slope analysis, proton nuclear magnetic resonance (NMR) titration, and Fourier-transform infrared (FT-IR) spectroscopy. This study explores the coordination and separation behavior of diglycolamide ligands with actinide. This work is expected to provide important information and theoretical bases upon which advanced design and optimization of ligands for high-performance processes for the separation of plutonium might be carried out. Such findings will contribute to the understanding of actinide chemistry and further the design of improved separation methods for nuclear applications.

The proper management of High-Level Liquid Waste (HLLW) is essential for safeguarding the environment and human health. The presence of platinum group metals (PGMs) in HLLW can impact its disposal due to their high melting points. Therefore, it is vital to eliminate PGMs during the initial treatment phase. Thus, this research introduces an adsorption method using COF-42 as an adsorbent to target palladium (Pd). The molecular structure, integrity, and morphology of COF-42 and Pd@COF-42 are thoroughly assessed using various techniques such as PXRD, FT-IR, TGA, XPS, and SEM. The study further investigates the adsorption kinetics and thermodynamics of Pd by COF-42, revealing that the adsorption process follows a Freundlich model. The maximum adsorption capacity of COF-42 is 170.6mg/g, demonstrating a superb adsorption capacity for palladium. Additionally, the study also explores the impact of adjusting HNO3 concentration, and COF-42 dosage on the adsorption performance, highlighting the influence of acidity levels on the final outcome. Lastly, the selectivity of COF-42 towards Pd in the presence of different metal ions and its ability to be reused underscore its effectiveness in Pd(II) adsorption, attributed to the synergistic effects of its flexible ligand, framework porosity, and concentrated –NH/–NH2 groups with a strong affinity for Pd2+.

In order to realize the effective separation of palladium from high-level liquid waste (HLLW), a ligand-supported adsorbent (NTAamide(C8)/SiO₂-P) was prepared by the impregnation method in a vacuum. The SiO₂-P carrier was synthesized by in situ polymerization of divinylbenzene and styrene monomers on a macroporous silica skeleton. The NTAamide(C8)/SiO₂-P adsorbent was fabricated by impregnating an NTAamide(C8) ligand into the pore of a SiO₂-P carrier under a vacuum condition. The adsorption performance of NTAamide(C8)/SiO₂-P in nitric acid medium has been systematically studied. In a solution of 0.2 M HNO₃, the distribution coefficient of Pd on NTAamide(C8)/SiO₂-P was 1848 mL/g with an adsorption percentage of 90.24%. With the concentration of nitric acid increasing, the adsorption capacity of NTAamide(C8)/SiO₂-P decreases. Compared to the other 10 potential interfering ions in fission products, NTAamide(C8)/SiO₂-P exhibited excellent adsorption selectivity for Pd(II). The separation factor (SF_{Pd/other metals} > 77.8) is significantly higher than that of similar materials. The interference of NaNO₃ had a negligible effect on the adsorption performance of NTAamide(C8)/SiO₂-P, which maintained above 90%. The adsorption kinetics of Pd(II) adsorption on NTAamide(C8)/SiO₂-P fits well with the pseudo-second order model. The Sips model is more suitable than the Langmuir and Freundlich model for describing the adsorption behavior. Thermodynamic analysis showed that the adsorption of Pd(II) on NTAamide(C8)/SiO₂-P was a spontaneous, endothermic, and rapid process. NTAamide(C8)/SiO₂-P also demonstrated good reusability and economic feasibility.

In this study, a novel organic–inorganic hybrid material IIGK@MnO₂ (2-naphthalenemethyl-isoleucine-isoleucine-glycine-lysine@manganese dioxide) was designed as a novel adsorbent for the removal of strontium ions (Sr²⁺). The morphology and structure of IIGK@MnO₂ were characterized using TEM, AFM, XRD, and XPS. The results indicate that the large specific surface area and abundant negative surface charges of IIGK@MnO₂ make its surface rich in active adsorption sites for Sr²⁺ adsorption. As expected, IIGK@MnO₂ exhibited excellent adsorbing performance for Sr²⁺. According to the adsorption results, the interaction between Sr²⁺ and IIGK@MnO₂ can be fitted with the Langmuir isotherm and pseudo-second-order equation. Moreover, leaching and desorption experiments were conducted to assess the recycling capacity, demonstrating significant reusability of IIGK@MnO₂.