The separation of radioactive cesium from high-level liquid waste (HLLW) requires effective adsorbents. In this study, a novel granular composite adsorbent (AMP/SPS) was synthesized by confining ammonium phosphomolybdate (AMP) within the macropores of sulfonated polystyrene (SPS) resin via an in-situ crystallization strategy. This approach effectively transforms the powder of AMP into robust, millimeter-sized beads suitable for column operations. The resulting AMP/SPS composite exhibited exceptional performance for Cs+ sequestration under simulated HLLW conditions, achieving a maximum sorption capacity of 266.26 mg/g at 298 K and 0.1 mol/L HNO3, which is significantly higher than that of most reported bead-type adsorbents. This enhanced performance originates from the synergistic integration of the SPS matrix, which provides high ion-exchange capacity, with the active AMP phase, which possesses strong intrinsic affinity for Cs+. The material demonstrated superior selectivity for Cs+ in simulated HLLW matrices with separation factors (SFCs/M) exceeding 10, alongside remarkable irradiation resistance, maintaining structural integrity and performance even after exposure to a gamma dose of 1200 kGy. Fixed-bed column tests further confirmed its practical applicability with a maximum dynamic sorption capacity of 199.7 mg/g. Density functional theory (DFT) calculations revealed that Cs+ forms a stable hexacoordinated complex with oxygen atoms from both the SPS sulfonic groups and the AMP structure. This configuration, stabilized by electrostatic and van der Waals interactions, explains the high affinity of the composite. These findings indicate that the AMP/SPS composite is a highly promising, efficient, and stable candidate for the advanced treatment of acidic nuclear waste. Furthermore, this strategy of combining active adsorbents with ion-exchangeable porous resins provides a valuable reference for the preparation of efficient radionuclide adsorbents.

Matrix diffusion is an essential process that controls radionuclide migration in the context of nuclear waste disposal in granite formations. Spiral ramps in underground nuclear repositories are vital for connecting the disposal zone with the surface environment, rendering radionuclide diffusion in the surrounding rock essential for safety evaluation. The excavation process can impact the diffusivity and permeability of granite rock, however, few investigations have been reported on the matrix diffusion of 137Cs+ and 99TcO4- in the granite surrounding rock at wall of TBM-created tunnels. To address this gap, this study investigated the diffusion of 137Cs+, 99TcO4-, Br-, and HTO in two samples (SR-70 and SR-200) collected from the spiral ramp of Beishan underground laboratory. The results indicated that the effective diffusion coefficients (De) for these radioactive substances in the granite samples were similar to those measured in the intact granite. The variability in biotite content and the presence of microfractures significantly influence the diffusion of charged species, such as 137Cs+, 99TcO4- and Br-. SR-70 is characterized by the presence of microfractures and a biotite content of 2.2%, resulting in minimal electrostatic influence on the diffusion of charged species. In contrast, SR-200 lacks microfractures and contains a higher biotite content of 8.2%, which leads to a pronounced cation excess diffusion for Cs+ and an anion exclusion effect for Br- and 99TcO4-. This study clarifies the diffusion behavior of 137Cs+, 99TcO4-, Br- and HTO within the granite surrounding rock of TBM-created tunnels, providing essential data and theoretical insights necessary for evaluating the safety and long-term stability of nuclear waste repositories situated in granite formations.

The migration of actinides (An) in deep geological repositories is significantly influenced by colloid-facilitated transport, particularly via the formation of An-silicate colloids. This study investigates the transport and release behaviors of Eu(III)-silicate colloids (used as an analog for trivalent actinides) in a simulated water-saturated granite fracture system. Transport experiments were conducted in a laboratory-scale fracture flow system to evaluate the effects of pH (7.3-8.5), ionic strength (1-400 mM), and fulvic acid (FA, 2.0-10.0 mg/L) on colloid mobility, while retention-release experiments were performed to assess their remobilization potential. Mechanisms were elucidated using size-fractionated analysis, with consideration of colloidal heterogeneity, and DLVO theory. The results indicate that Eu(III)-silicate colloids exhibit high mobility under conditions of high pH (8.5) and low ionic strength (1 mM), achieving a recovery rate of 97.9%. This enhanced transport is driven by strong electrostatic repulsion and minimized hydrodynamic size. The presence of FA further promotes mobility through steric stabilization and the formation of soluble Eu(III)-FA complexes. The transport mechanism transitions from Langmuirian blocking to ripening when Eu(III)-silicate colloids become unstable and aggregate under elevated ionic strength (e.g., >200 mM NaCl at pH 8.5). Colloidal fractions with higher Si/Eu ratios demonstrated superior transport capability due to their smaller size and stronger surface charge, indicating that the heterogeneity of Eu(III)-silicate colloids plays an important role in their transport behavior. Furthermore, retained colloids at pH 8.0 and 300 mM NaCl can be remobilized by perturbations such as decreasing ionic strength, increasing pH, or increasing flow velocity. This release process is governed by a dual mechanism involving both direct detachment from the fracture surface and the disaggregation of larger aggregates. However, prolonged retention times were found to inhibit remobilization due to the aging effect, which strengthens adhesion and leads to a transition towards more stable attachment. These findings provide critical insights into the environmental fate of An (III)-silicate colloids and emphasize the potential risks associated with their remobilization in fractured granite environments.

Colloid-facilitated radionuclide transport is a critical issue in the long-term safety assessment of repositories for high-level radioactive waste (HLW) in granitic formations. In this study, silica (Si30) and goethite (Gt) colloids were selected as analogues of corrosion products derived from HLW glass and iron-based canisters, respectively. Single, binary, and ternary transport experiments involving Eu(III), Si30, and Gt were conducted in water-saturated quartz sand columns under a range of disposal-relevant conditions to investigate effects of heteroaggregation between Si30 and Gt colloids on Eu(III) transport. The results showed that Si30 colloids can serve as effective carriers for Eu(III) transport at pH 8.3, whereas Gt impeded its transport. In the ternary systems, heteroaggregation of oppositely charged Si30 and Gt colloids inhibited the transport of both Si30 and Eu(III), with the extent of inhibition dependent strongly on Gt concentration. Elevated ionic strength (I) promoted Eu(III) desorption from both individual Si30 and Si30/Gt composite colloids. Classic DLVO calculations failed to predict colloidal interactions in systems with large disparities in particle size, while zone-of-interaction-normalized calculations showed better agreement with the experimental observations. These findings suggest that heteroaggregation of corrosion-derived colloids in HLW repositories significantly influences An(III) transport, and colloid-colloid and colloid-porous media interactions can be effectively described by DLVO calculations that account for surface heterogeneity and zone-of-interaction normalization.

Understanding the transport behavior of uranium (U) in granitic formations is crucial for the safety assessment of high-level radioactive waste (HLW) repository. Iron (oxyhydr)oxides and organic matter are abundant in such environments, readily forming composite colloids that influence radionuclide mobility. This study investigated the co-transport of U(VI) with goethite-humic acid (Gt-HA) colloids in water-saturated granite particle media. In the absence of colloids, U(VI) transport was governed by sorption onto the granite matrix. When Gt-HA colloids were present, U(VI) mobility was facilitated through associations with the colloids. In addition to pH and ionic strength, U(VI) concentration and the HA/Gt ratio significantly influenced the facilitation of U(VI) transport. At low U(VI) concentrations (0.2 and 2.0 mu M), Gt-HA colloids enhanced U(VI) transport. However, at higher concentrations (20.0 mu M), increased U(VI) sorption reduced colloid stability, hindering U(VI) mobility. Low HA/Gt ratios (<1/32) promoted the retention of Gt-HA colloids, impeding the transport of both colloids and associated U(VI). In contrast, HA/Gt ratios >= 2/32 stabilized the colloids by reversing the surface charge, promoting co-transport of Gt-HA colloids and U(VI). The transport and retention of Gt-HA composite colloids, with or without U(VI), followed colloidal size exclusion effect, and were well described by Derjaguin-Landau-Verwey-Overbeek (DLVO) theory and colloid filtration theory (CFT). These findings highlight the dual role of Gt-HA colloids in U(VI) mobility and provide valuable insights for HLW repository safety assessment in granitic formations.

The excavation disturbed zone (EDZ) in high-level radioactive waste geological repositories is a key channel for radionuclide migration, yet how its pore/microfracture structures affect the diffusion of charged radionuclide species remains inadequately studied. Here, we explored the critical impacts of such structures on the diffusion of HTO, Br-, 99TcO4-, and 137Cs+ in two typical EDZ granite cores from the Beishan underground research laboratory (URL), at depths of -70 m (EDZ-70) and -200 m (EDZ-200). While the total porosity and HTO effective diffusion coefficients of slices from both cores were generally comparable, diffusion behaviors of charged species differed significantly: EDZ-70 slices exhibited minimal electrostatic effect for Br- and 137Cs+, while the diffusion in slices of EDZ-200 demonstrated a pronounced anion exclusion effect for Br- and 99TcO4- and significant cation excess diffusion for 137Cs+ at low ionic strength. X-ray computed tomography and polarizing microscopy confirmed EDZ-70 was dominated by microfractures, while EDZ-200 featured dispersed fine pores. Such structural differences explaining the contrasting electrostatic interactions. Overall, the findings demonstrate that both the number and size of pores/microfractures codetermine the diffusion of charged radionuclide species in granite EDZ, highlighting the importance of detailed structural characterization for the long-term safety assessment of geological repositories.

With the continuous growth of global energy demand and the non-renewability of traditional fossil fuels, nuclear energy plays an important role in establishing a low-carbon emission and efficient energy system. Uranium, as an important raw material for nuclear energy, has great application value in the industrial and energy fields. The concentration of uranyl ions in uranium-containing wastewater typically ranges from several to tens of mg·L−1. In contrast, the concentration of uranyl ions in seawater is remarkably low, averaging approximately 3.3 μg·L−1. This paper provides a comprehensive review of the research progress and chemical foundations of uranyl ion-imprinted materials. It details their preparation processes, classification systems, and experimental characterization methods. Due to their high selectivity and efficient adsorption performance, these materials show significant advantages in extracting and separating uranyl ions from complex environments. Different types of uranyl ion-imprinted materials, such as amorphous porous uranyl ion-imprinted materials, crystalline porous uranyl ion-imprinted material, biobased uranyl ion-imprinted materials and surface uranyl ion-imprinted materials have shown broad application prospects. However, high-performance materials often rely on expensive monomers or complex synthesis, limiting large-scale preparation. The processes of elution and adsorption may potentially cause damage to the imprinted sites, thereby adversely affecting the service life. Future research endeavors should prioritize the development of cost-effective monomers alongside streamlined synthesis processes. Furthermore, increased efforts should be directed toward promoting material testing within complex systems, while concurrently establishing standardized protocols for unified performance evaluation. Through ongoing research and technological breakthroughs, these materials are poised to assume an increasingly pivotal role in the nuclear industry.

The separation of trivalent americium from lanthanides poses a significant challenge for nuclear waste management. In this study, we present a series of novel asymmetric tetradentate ligands PO-PzPhen, i.e., diethyl (9-(1H-pyrazol-1-yl)-1,10-phenanthrolin-2-yl)phosphonate (L1), dibutyl (9-(1H-pyrazol-1-yl)-1,10-phenanthrolin-2-yl)phosphonate (L2), bis(2-ethylhexyl) (9-(1H-pyrazol-1-yl)-1,10-phenanthrolin-2-yl)phosphonate (L3), diphenyl (9-(1H-pyrazol-1-yl)-1,10-phenanthrolin-2-yl)phosphonate (L4), and diethyl (9-(4-methyl-1H-pyrazol-1-yl)-1,10-phenanthrolin-2-yl)phosphonate (L5), which integrate lateral phosphonate and pyrazolyl groups on a phenanthroline core. By introducing hard/soft donor synergy, L1-L5 demonstrated robust extraction capabilities, high selectivity for Am(III) (SFAm/Eu reaching 49 for L3), and rapid extraction (equilibrium achieved within 10 min) under conditions of high acidity and favorable solubility in common diluents as well. The compositions of the extracted complexes, i.e., [ML(NO3)3] (M = Am(III) or Eu(III); L = L1-L5), were characterized using slope analysis, high-resolution mass spectrometry, and time-resolved fluorescence spectroscopy. X-ray crystallographic analysis established the precise 1:1 (M:L) coordination geometry, demonstrating that all N- and O-donors are involved in the metal-ligand interaction. On the basis of these structural insights, DFT calculations were employed to further elucidate the mechanisms for the Am(III) selectivity and relatively rapid extraction kinetics, highlighting the lower rotation energy and enhanced intrinsic binding affinity toward actinides. This study demonstrates that the asymmetric ligands with multiple functional groups can synergistically optimize solvent extraction performance, providing an efficient framework for the advanced partitioning of trivalent minor actinides from high-level radioactive wastes.

The removal of radioactive cesium isotopes, such as 137Cs and 135Cs, from high-level liquid waste (HLLW) is of great significance to nuclear industry. In this study, four new calix[4]arene-2,4-crown-6 ethers (C[4]C-6) with benzyl substituents, 25,27-bis(benzyloxy)calix[4]arene-crown-6 (Bn-C[4]C-6), 25,27-bis(4-methyl-benzyloxy) calix[4]arene-crown-6 (C1-Bn-C[4]C-6), 25,27-bis(4-butyl-benzyloxy)calix[4]arene-crown-6 (C4-Bn-C[4]C-6) and 25,27-bis(4-tert-butyl-benzyloxy)calix[4]arene-crown-6 (tBu-Bn-C[4]C-6), were synthesized and screened as extractants for Cs+ separation from HLLW. The ligands showed better extraction performance and higher Cs selectivity in comparison with their homologue with alkyl substituent. The higher Cs selectivity of the new ligands was in consistent with the larger stability constants of Cs complexes measured from UV-vis titrations. A multistage counter-current extraction process using the ligands as extractants resulted in a Cs removal of 99.9 % from the simulated HLLW. The ligands are promising for application because they also exhibit good tolerance to HNO3 and satisfactory irradiation stability. Moreover, the coordination mechanism of the ligands with Cs+ and the crystal structures of [Cs(Bn-C[4]C-6)(NO3)]& sdot;EtOAc and Cs(tBu-Bn-C[4]C-6)(NO3)(H2O) were investigated. The results confirmed that Cs+ coordinates with 6 oxygen donor atoms of the crown ether moiety and interacts with two rotated phenyl rings via cation-It interaction. Nitrate anion takes part in the coordination either in a bidentate mode or in a mono dentate mode along with a water molecule, which ensures a coordination number of 8 for Cs+. This study implies that benzyl and its derivatives are alternative options of the substituent groups to the 1,3-alternate calix[4]arene-2,4-crown-6 ligands besides traditional alkyls with variant lengths, regarding to Cs+ separation from HLLW.

Colloid interactions are usually interpreted using the classic Derjaguin-Landau-Verwey-Overbeek (DLVO) theory and its variants. However, the repulsive interaction energy given in some DLVO predictions was sometimes inconsistent with the observed aggregation in heterogeneous colloidal systems containing different types of colloids. To address this issue, we studied the heteroaggregation of silica and goethite colloids, two oppositely charged colloids commonly found in the environment, as functions of colloid mass ratio, pH and ionic strength. We found that the discrepancies between experimental observations and DLVO predictions can be attributed to the heterogeneous surface charge distributions of the primary aggregates, contradicting the DLVO assumption of homogeneously charged primary aggregates. Consequently, a new method considering the effect of heterogeneity, was developed to quantitatively evaluate the interaction energies between primary heteroaggregates based on the electrostatic and van der Waals interactions (Hetero-DLVO). The interaction energies, evaluated by considering all pairwise interactions among the component colloids of the two primary aggregates (i.e., silica-silica, goethite-goethite, and silica-goethite), showed good agreement with experimental observations under various conditions. This study contributes to a better understanding of heteroaggregation mechanisms, improved DLVO-based prediction strategies for heterogeneous colloidal systems, and facilitates accurate predictions of colloidal particle behavior in aquatic systems.

The relationship between the pore structure characteristics and methane adsorption behavior evolution during coalification is vital for elucidating coalbed methane (CBM) storage and the impact on gas production. The middle-high rank coals collected from the Western Guizhou were analyzed by the full-scale pore structure characterization and methane adsorption isotherms. The evolution of pore, including pore type, structure, and fractal dimension, and gas adsorption behavior were established. Based on the quantitative characterization of coal samples' desorption, diffusion, and permeability capabilities, the impact of the gas storage mechanism on the gas production at the microscale and the geology-adapted technologies for gas recovery was elucidated. The results show that as the coal rank increases, the methane adsorption spaces and sites within coal undergo a substantial expansion primarily due to the enhanced development of micropores. During this process, the quantity of mesopores remains low, but their proportion increases while macropores gradually diminish. Coal petrographic and quality parameters related to the pore structure parameter exhibit a strong correlation with saturated adsorption capacity (SAC), with micropores playing a dominant role in controlling methane molecule adsorption. Coalification, on the one hand, increases the methane adsorption site, coupled with an increase in gas-solid interaction due to the condensation of macromolecular structures, leading to an increase in SAC. On the other hand, it results in a reduction in the micropore diameter and an intensification of monolayer molecular adsorption, causing a significant decrease in average adsorbed molecular layers (AAML). Therefore, the increase in SAC accompanies a decrease in AAML. Although high-rank coals exhibit higher methane desorption volume, desorption efficiency, and diffusion capacity, their low permeability characteristics hinder fluid seepage. To facilitate efficient development of high-rank CBM, it is imperative to implement geological compatibility techniques aimed at reducing solid-gas interactions within coal reservoirs and enhancing the connectivity of the pore network.

Tetravalent actinides, An(IV), could become mobile in the subsurface if they occur in the colloidal form. B2O3 is one of the major components of high-level radioactive waste (HLW) glass, and the erosion of glass may lead to the leakage of An(IV) and borate, forming An(IV)-borate intrinsic colloid. However, the colloidal properties and transport behavior of such colloids are unknown so far. In this study, Ce(IV) was used as the analogue of An(IV), and the effect of Ce(IV)-borate colloid formation on Ce(IV) transport was studied as a function of Ce(IV) concentration, ionic strength (I), pH and humic acid (HA). It was found that Ce(IV)-borate colloid resulted from polycrystalline Ce(IV)-borate complexes, and its transport behavior was completely different to that of individual Ce(IV). The transport of Ce(IV)-borate colloid was favored at pH 8.9, suggesting that An(IV) could be mobile in the geological disposal system if forming An(IV)-borate colloid. At pH 5.0, Ce(IV)-borate colloid transport was facilitated with high HA concentration (10-25 mg/L), whereas it was relatively impeded with low HA concentration (0.1-1.0 mg/L). These findings emphasize the potential role of An(IV)-borate colloid formation in altering An(IV) transport behaviors, and provide important references for assessing An(IV) transport in the geological disposal system.

Tetravalent actinides (An(IV)), could be released from high-level radioactive waste (HLW) glass in the form of An(IV)-borate intrinsic colloid. In this study, Ce(IV) was selected as the analogue of An(IV), and the stability of Ce(IV)-borate colloid was studied as a function of pH, electrolytes, gibbsite colloid, and humic acid (HA) colloid by aggregation kinetics experiments. The isoelectric point (pHIEP) of Ce(IV)-borate colloid was determined to be 7.8, and aggregation of the colloid was increased progressively with the pH approaching this value. The critical coagulation concentrations (CCC) were followed the order that NaCl > KCl > MgCl2 > NaNO3 > CaCl2 > Na2SO4. The positively charged gibbsite colloid inhibited the aggregation of Ce(IV)-borate colloid due to enhanced electrostatic repulsion. In contrast, the effect of negatively charged HA on the stability of Ce(IV)-borate colloid was dependent on HA concentration. The presence of low concentrations of HA (0.1-1.0 mg/L) reduced the surface charge of Ce(IV)-borate colloids, resulting in lower CCC, whereas the higher HA concentrations (2.5-25 mg/L) enhanced the colloidal stability of Ce(IV)-borate particles. The Hamaker constant of Ce(IV)-borate colloid was calculated to be 1.29 × 10-20 J. The interaction energy calculated with Derjaguin-Landau-Verwey-Overbeek (DLVO) theory and its variants can well describe the changes of colloidal stability. These results provide comprehensive understanding of Ce(IV)-borate colloid properties and offer valuable insights for assessing the fate and transport of An(IV) in real subsurface environments.

The disposal of radioactive waste is one of the major factors constraining the sustainable development of nuclear energy in China. Although different types of radioactive waste correspond to different disposal methods, safety assessment for disposal in all cases must be carried out through research on radionuclide migration. Sorption is a key process governing the migration behavior of radionuclides within the disposal system, and consequently forms a core research topic for evaluating disposal safety of radioactive waste. This paper first outlines the key barrier materials in repositories, research methodologies for sorption, sorption mechanisms, and approaches to adsorption modeling. It then reviews and evaluates the research achievements made by domestic scholars over the past two decades, focusing on progress in sorption experiments and adsorption modeling. Finally, prospects and suggestions are proposed for future sorption research in the context of radioactive waste disposal in China.

Environmental radiochemistry is a basic and applicative science, which was born with the combination of radiochemistry and environmental sciences, and she was coming to be a branch of sciences with the human’s concerns of the health effects of environmental radioactivity at around 1950th. At that time, the major nuclear weapon production countries conducted a large amount of weapon related experiments and tests, and a considerable amount of radioactive materials were released into the environment. When these radioactive materials(radionuclides) coming into the environment, they will react with the environmental medium, and finally, through the channels of breath or food chain, coming into the human bodies, resulting in direct or potential health risks. This paper briefly introduces and discusses the concept and the source of environmental radiochemistry, she’s development in China, the main research areas in environmental radiochemistry, the important communication platforms with which the research works in environmental radiochemistry are published, presented and discussed, the hot spots of environmental radiochemistry research work and it’s up-to-data state in China, the role of environmental radiochemistry in the healthy and sustainable development of nuclear energy in China, the main developments in environmental radiochemistry, and finally, the major challenges for China’s environmental radiochemistry.

This study addresses two persistent challenges in uranium fluoride chemistry: resolving decades-long spectral assignment conflicts across UF2, UF3, and UF4 species, and conclusively settling the symmetry controversy of UF4. By the cryogenic matrix isolation IR spectroscopy technique in combination with relativistic quantum chemical calculations, we experimentally tracked the stepwise formation of UF to UF6 in neon and argon matrices. Theoretical validation has led to a reassignment of the infrared absorption bands for UF2, UF3, and UF4, defining their molecular geometries. While UF2 exhibits a V-shaped C2v structure and UF3 has a pyramidal C3v configuration, UF4 adopts a D2d geometry rather than a Td symmetry, arising from the Jahn-Teller distortion, which was verified by complete active space second-order perturbation theory (CASPT2) calculations incorporating spin-orbit coupling, supporting predictions from relativistic density functional theory and BW-MRCCSD calculations by Johnson et al. Moreover, weak van der Waals interactions between UFn (n = 2-4) and argon atoms induced vibrational redshift. Bonding analyses revealed that U-F bonds in UFn (n = 1-6) possess dual ionic-covalent character, with ionic contributions of 78-88%. The covalent enhancement in fluorides arises from the overlap of U 5f/6d orbitals with F 2p orbitals and their near-degeneracy. These findings reconcile historical discrepancies, establish definitive benchmarks, and advance uranium fluoride chemistry for nuclear fuel applications.

The separation of trivalent actinides (An(III)) from lanthanides (Ln(III)) is a critical challenge in nuclear waste management, as it enables the reduction of long-term radiotoxicity and supports advanced fuel cycle strategies. Herein, we report a series of tetradentate N-donor ligands (L1-L4) derived from a straightforward C-N coupling reaction between 2,9-dichloro-1,10-phenanthroline (Phen) and pyrazole (Pz) derivatives, i.e., 2,9-bis(1H-pyrazol-1-yl)-1,10-phenanthroline (L1), 2,9-bis(4-ethyl-1H-pyrazol-1-yl)-1,10-phenanthroline (L2), 2,9-bis(4-butyl-1H-pyrazol-1-yl)-1,10-phenanthroline (L3), and 2,9-bis(3-butyl-1H-pyrazol-1-yl)-1,10-phenanthroline (L4). These ligands exhibit exceptional Am(III) extraction efficiency and selectivity, achieving separation factors (SFAm/Eu) exceeding 220 in highly acidic HNO3 media. Slope analysis and electrospray ionization mass spectrometry (ESI-MS) confirmed a 1:1 M/L stoichiometry for the extracted species. Systematic UV-vis titration and single-crystal X-ray diffraction studies revealed an analogous 1:1 coordination structure in solution and solid states. The stability constants for Eu(III) followed the trend of L3 (5.92 ± 0.08) > L2 (5.75 ± 0.11) > L1 (5.56 ± 0.06) > L4 (5.31 ± 0.02), reflecting the interplay of inductive effects and steric hindrance imposed by alkyl substituents on the pyrazole moieties of the ligands. This work highlights the potential of C-N-coupled bis(pyrazole)phenanthroline ligands as highly selective extractants for An(III)/Ln(III) separation under acidic conditions.

Prussian blue (PB) is an economical material with exceptional sorption capacity and strong selectivity for radiocesium removal, making it a highly promising candidate for wastewater treatment. However, its microcrystalline structure and fine powder form pose challenges to its industrial application. While alginate-based granulation offers a viable method for preparing inorganic ion exchangers, the beads often suffer from insufficient mechanical strength. To overcome this limitation, this study developed novel millimeter-sized composite particles (SA-PB beads) by encapsulating PB within a silica-alginate hybrid matrix, and assessed their cesium removal efficiency through both batch and column experiments. The characterization results revealed that the incorporation of silica significantly enhanced the mechanical strength of the composite material, as compared to adsorbents without silica. Notably, the SA-PB beads containing 25 wt% PB exhibited both excellent mechanical strength and high Cs+ sorption capacity. The uptake of Cs+ on the fabricated beads followed both pseudo-secondorder kinetic model and the Langmuir isotherm. The maximum sorption capacity of the SA-PB beads was determined to be 22.8 mg/g at 25 degrees C, higher than that of most PB-based composites in bead, sponge, or filter forms. Thermodynamic analysis revealed that Cs+ sorption is a spontaneous and endothermic process, while selectivity tests showed strong Cs+ uptake even in the presence of competing ions, with separation factor values exceeding 8.0. Mechanistic studies identified Cs+ binding to cyano groups and immobilization within the lattice spaces of PB crystals. Column studies further demonstrated the practical applicability of the SA-PB beads as a stationary phase for Cs+ removal. This study not only highlights the SA-PB beads as a highly efficient composite for Cs+ uptake, but also provides valuable insights for designing granulated composite materials with high mechanical strength and sorption efficiency.

Tuning the extraction performance of phenanthroline-derived ligands for Am 3+ by combining different functional groups.