Efficient Removal of [UO2]2+, Cs+, and Sr2+ Ions by Radiation-Resistant Gallium Thioantimonates

Efficient Removal of Cs+ and Sr2+ Ions by Granulous (Me2NH2)4/3(Me3NH)2/3Sn3S7·1.25H2O/Polyacrylonitrile Composite

The need to effectively and selectively remove radioactive ¹³⁷Cs and ⁹⁰Sr from nuclear waste solutions persists to mitigate their environmental mobility and high radiotoxicity. Because it is difficult to effectively remove them from acidic environments that degrade most sorbents, new sorbent materials are highly desirable. Here, efficient removal of Cs⁺ and Sr²⁺ is achieved by the composite of layered tin sulfide (Me₂NH₂)_4/3(Me₃NH)_2/3Sn₃S₇·1.25H₂O (FJSM-SnS) and polyacrylonitrile (PAN) (FJSM-SnS/PAN). The granulous composite possesses regular particle morphology and good mechanical strength as an engineered form. It shows excellent acid-base and γ-irradiation resistance, high maximum adsorption capacities (q_m) of 296.12 and 62.88 mg/g for Cs⁺ and Sr²⁺ ions, respectively, and high selectivity even in the presence of excess Na⁺ ions or using lake water. Impressively, q_m^Cs of FJSM-SnS/PAN reaches 89.29 mg/g under even acidic conditions (pH = 2.5). The column loaded with FJSM-SnS/PAN granules exhibits high removal rates (R) toward low-concentration Cs⁺ and Sr²⁺ ions under both neutral and acidic conditions. Moreover, the composite can be recycled and reused with high R^Cs and R^Sr. This work highlights the great potential of metal sulfide ion-exchangers in engineered form for the efficient removal of Cs⁺ or Sr²⁺ ions, especially under acidic conditions, for radionuclide remediation.

Efficient Photocatalytic Extraction of Uranium over Ethylenediamine Capped Cadmium Sulfide Telluride Nanobelts

The photocatalysts for hexavalent uranium (U(VI)) reduction suffered from the low uranium uptake capacity and weak long-wavelength light absorption. Herein, we synthesized the CdS_xTe_1-x nanobelts capped by ethylenediamine (EDA), which provided amino groups as the adsorption sites. With the increase of the Te content, the amino groups on the CdS_xTe_1-x nanobelts decreased because of the variation of the electron density of Cd²⁺, whereas the light adsorption was enhanced due to the narrowed bandgap. In photocatalytic reduction of U(VI), the CdS_0.95Te_0.05-EDA nanobelts exhibited a considerable U(VI) removal ratio of 97.4% with a remarkable equilibrium U(VI) extraction amount on per weight unit of the adsorbent (q_e) of 836 mg/g. The bandgap structure and Fourier transform infrared spectroscopy (FT-IR) spectra analysis revealed that the optimum photocatalytic activity of CdS_xTe_1-x nanobelts was achieved at a 5% of Te^2- doping, which balanced the factors of amino groups and bandgap. This adsorption-photoreduction process offers an ultrahigh uranium extraction capacity over wide uranium concentrations.

Facile syntheses of silver thioantimonates exhibiting second-harmonic generation responses and large birefringence

Two chalcogenide crystalline compounds, [enH2][Ag4Sb2S6] (en = ethylenediamine) and [enH][Ag2SbS3], have been successfully synthesized by mild ionothermal and solvothermal means. [enH][Ag2SbS3] crystallizes in the noncentrosymmetric (NCS) and polar space group Pc, and its linear and nonlinear optical (NLO) properties have been investigated for the first time. Second harmonic generation (SHG) measurements revealed that [enH][Ag2SbS3] affords powder SHG performance values of 2.5 × KDP @1064 nm and 0.2 × AgGaS2 @2100 nm. Additional particle size vs. SHG efficiency measurements indicate that [enH][Ag2SbS3] is phase-matchable. The calculated birefringence Δn is 0.177 at 1064 nm, which is sufficiently large (the largest value among NCS thioantimonates) to achieve phase matching. [enH2][Ag4Sb2S6] crystallizes in the centrosymmetric space group P21/c and its structure features a double-layered variant honeycomb-like anionic network parallel to the ac plane separated by [enH2]2+ cations. The optical band gaps of [enH2][Ag4Sb2S6] and [enH][Ag2SbS3] are found to be 2.37 and 2.53 eV, respectively. Theoretical studies using density functional theory have been implemented to further elucidate the relationship between the band structure and NLO properties in [enH][Ag2SbS3].

Highly efficient capture of uranium from seawater by layered double hydroxide composite with benzamidoxime

Through swelling/restoration reaction, benzamidoxime (BAO) is introduced into MgAl-LDH interlayers to assemble a new composite of MgAl-BAO-LDH (abbr. BAO-LDH). Wet samples of the BAO-LDH obtained by washing with diverse solvents are present in colloidal state, which facilitates the fabrication of thin film adsorbents convenient for actual application. After drying, the assembled sample exhibits floral morphology composed of thin nanosheets, much different from hexagonal morphology of NO₃^- intercalated MgAl-LDH precursor (NO₃-LDH), demonstrating a phenomenon rarely found in swelling/restoration. The BAO-LDH depicts an extremely large maximum sorption capacity (q_m^U) of 327 mg·g^-1 and ultra-high selectivity for U. At low U concentrations (5-10 ppm), nearly complete capture (~100%) is achieved in a wide pH range of 3-11, while at high U concentrations (110 ppm), quite high U removals (≥93.0%) are obtained at pH = 6-8, meaning perfect suitability for trapping U from seawater. For natural seawater containing trace amounts of U (3.93 ppb) coexisting with high concentration of competitive ions, the BAO-LDH displays significantly high U removal (87%). Complexation between interlayer BAO (N and O as ligands) with UO₂²⁺ and synergistic interactions of LDH layer hydroxyls with UO₂²⁺ contribute to the highly effective uranium capture. All results demonstrate the BAO-LDH is a promising adsorbent applied in seawater uranium extraction and nuclear wastewater disposal.

4-Mercaptobenzoic acid as a MALDI matrix for highly sensitive analysis of metals

4-Mercaptobenzoic acid (MBA) is introduced as a matrix for laser desorption/ionization time-of-flight mass spectrometry (MS) analysis of metals, exhibiting matrix-interference-free background, greatly enhanced MS signal intensity, and excellent reproducibility. The developed method was successfully extended for the rapid screening and sensitive determination of ultratrace metals in fine particulate matter (PM_2.5).

Layered Thiostannates with Distinct Arrangements of Mixed Cations for the Selective Capture of Cs+, Sr2+, and Eu3+ Ions

The selective capture of radioactive cesium, strontium, and lanthanides from liquid nuclear waste is of great significance to environmental remediation and human health. Herein, the rapid and selective removal of Cs⁺, Sr²⁺, and Eu³⁺ ions is achieved by two metal sulfides (FJSM-SnS-2 and FJSM-SnS-3). Both structures feature [Sn₃S₇]_n^2n- layers with the mixed cations of [CH₃NH₃]⁺ and [Bmmim]⁺ (1-butyl-2,3-dimethylimidazolium) as templates. However, the ratios and arrangements of mixed cations in the interlayered spaces are distinct. It is unprecedented that [CH₃NH₃]⁺ and [Bmmim]⁺ in FJSM-SnS-2 are alternatingly arranged in different interlayered spaces, whereas they in FJSM-SnS-3 are located in the same interlayered spaces. It is the first time that the ionic liquid cation and protonated organic amine have been simultaneously incorporated into metal sulfides. Both compounds show high capacities, rapid kinetics, and a wide pH active range for Cs⁺, Sr²⁺, and Eu³⁺. Even under excess Na⁺ ions, both show excellent selectivity in capturing trace Sr²⁺ and Eu³⁺ ions. FJSM-SnS-3 presents the highest K_d^Eu to date. They still retain high removal efficiency even after intense β and γ radiation. Moreover, it is first confirmed by the in situ tracking method of mass spectrometry that the large-sized [Bmmim]⁺ ions are exchangeable. It is found that the arrangement of cations between interlayered spaces is a crucial factor affecting ion exchange performance. This work will likely change the consensus that large-sized organic cations are difficult to be exchanged and thus further highlight the great potential of metal sulfide ion exchangers for radionuclide remediation.

Dual Ion-Imprinted Mesoporous Silica for Selective Adsorption of U(VI) and Cs(I) through Multiple Interactions

Separation of uranium and cesium from low-level radioactive effluents (LLRE) is of great significance for sustainable development of the nuclear industry and for the environment. However, high salinity and massive coexisting ions of LLRE are giant challenges for the separation. To address the challenges, we report a strategy for efficient and simultaneous separation of uranium and cesium from a high-salt environment by dual ion-imprinted mesoporous silica based on multiple interactions. The as-prepared adsorbents can reach equilibrium for uranium and cesium within 1 h with a maximum capacity of 221.7 mg U g^-1 and 34.5 mg Cs g^-1. The sorption mechanism demonstrates that the highly active phenolic hydroxyl groups of imprinted cavities can extract uranium and cesium effectively through multiple interactions, including coulomb attraction, redox, ion exchange, and complexation. The synergism of multiple interactions and imprinted cavity endows the sorbent with good selectivity for uranium and cesium over other cations and with excellent salt tolerance. This work demonstrates a new strategy of selective extraction of nuclides by multifunction adsorbent through multiple interactions.

Robust and Flexible Thioantimonate Materials for Cs+ Remediation with Distinctive Structural Transformation: A Clear Insight into the Ion-Exchange Mechanism

It is imperative yet challenging to efficiently sequester the ¹³⁷Cs⁺ ion from aqueous solutions because of its highly environmental mobility and extremely high radiotoxicity. The systematical clarification for underlying mechanism of Cs⁺ removal and elution at the molecular level is rare. Here, efficient Cs⁺ capture is achieved by a thioantimonate [MeNH₃]₃Sb₉S₁₅ (FJSM-SbS) with high capacity, fast kinetics, wide pH durability, excellent β and γ radiation resistances, and facile elution. The Cs⁺ removal is not significantly impacted by coexisting Na⁺, K⁺, Ca²⁺, Mg²⁺, and Sr²⁺ ions which is beneficial to the remediation of Cs⁺-contaminated real waters. Importantly, the mechanism is directly illuminated by revealing an unprecedented single-crystal to single-crystal structural transformation upon Cs⁺ uptake and elution processes. The superior Cs⁺ removal results from an unusual synergy from strong affinity of soft S^2- with Cs⁺, easily exchangeable [MeNH₃]⁺ cations, and the flexible and robust framework of FJSM-SbS with open windows as trappers.

Charge-Enhanced Separation of Organic Pollutants in Water by Anionic Covalent Organic Frameworks

The effective removal of organic pollutants in wastewater is a key environmental challenge. In this work, an anionic covalent organic framework (named TpPa-SO₃Na) was synthesized through a green two-in-one synthesis strategy with autocatalytic imine formation. The slowly generated acetic acid as a catalyst is favorable to sustain the reversibility of the covalent organic framework (COF) formation reaction and improve the crystallinity of TpPa-SO₃Na. TpPa-SO₃Na consists of a homogeneous distribution of sulfonate groups to produce negatively charged regular channels. The strong electrostatic and hydrogen-bonding interactions between the sulfonate groups anchored in the nanochannels and the amine groups in organic pollutants improve the adsorption selectivity and capacity. These structures allow a high degree of control over adsorption processes to boost the adsorption kinetics and improve selective separation. TpPa-SO₃Na exhibits ultrafast adsorption (<1 min) of cationic antibiotics and dyes (average over 95%). Furthermore, TpPa-SO₃Na exhibits high selectivity for the uptake of dye molecules on the basis of the differences in charge and molecular size. This work explored functional designs and green manufacturing of anionic COFs for removal of hydrophilic organic pollutants.

Two new layered metal chalcogenide frameworks as photocatalysts for highly efficient and selective dye degradation

Dye photodegradation is an important research topic, and great efforts have been made to target the photocatalysts with highly efficient and selective performance. Reported here are two layered anion chalcogenide frameworks with semiconducting properties combined with highly open interlayer spaces, which are used as efficient photocatalysts to show excellent size and charge selectivity towards organic dye molecules. In addition, the organic templates inside the chalcogenide frameworks are exchanged via an ion-exchange process, and the resulting host frameworks with much looser internal spaces play significant roles in improving the photocatalytic activity.

Removal of Sr2+ Ions by a High-Capacity Indium Sulfide Exchanger Containing Permeable Layers with Large Pores

An ethylammonium-templated indium sulfide, [CH₃CH₂NH₃]₆In₈S₁₅ (InS-2), featuring anionic layers perforated with large, 24-membered rings that facilitate the accommodation of hydrated Sr²⁺ ions is reported. InS-2 exhibits an excellent adsorption performance toward Sr²⁺ with a top-ranked capacity (q_m = 143.29 mg g^-1), rapid kinetics, wide pH durability (3-14), β- and γ-radiation resistances, and a facile elution.

Combined use of tannic acid-type organic composite adsorbents and ozone for simultaneous removal of various kinds of radionuclides in river water

Tannic acid-type organic composite adsorbents (PA316TAS, AR-01TAS, PYRTAS, WA10TAS, WA20TAS, and WA30TAS), combined with hydrolyzed and sulfonated tannic acid (TAS) and porous-type strongly basic anion-exchange resin (PA316), benzimidazole-type anion-exchange resin embedded in high-porous silica beads (AR-01), pyridine-type anion-exchange resin (PYR), acrylic-type weakly basic anion-exchange resin (WA10), or styrene-type weakly basic anion-exchange resins (WA20 and WA30) for simultaneous removal of various kinds of radionuclides in river water were successfully synthesized. The adsorption behavior of twelve kinds of simulated radionuclides (Mn, Co, Sr, Y, Ru, Rh, Sb, Te, Cs, Ba, Eu, and I (I^- and IO₃^-)) on these composite adsorbents has been studied in real river water at room temperature. PA316TAS adsorbents showed much higher distribution coefficients (K_d) for all metal ions. TAS structure has more selective adsorption ability for Mn, Co, Sr, Y, Cs, Ba, Eu, and IO₃^-. On the other hand, Y, Ru, Rh, Sb, Te, Eu, I (I^- and IO₃^-) were adsorbed on both PA316 and TAS structures. To evaluate the validity of these mechanistic expectations, the respective chemical adsorption behaviors of Mn, Co, Sr, etc. and PA316TAS adsorbent were examined in river water ranging in temperature from 278 to 333 K. As was expected, one adsorption mechanism for Mn, Co, Sr, Cs, and Ba systems and two types of adsorption mechanisms for Y, Ru, Rh, Sb, Te, Eu, I (I^- and IO₃^-) systems were observed. On the other hand, the precipitation of Mn, Co, Y, Ru, Rh, Te, and Eu was formed by ozonation for river water, that is, ozone can transform Mn, Co, Y, Ru, Rh, Te, and Eu ions into the insoluble precipitates. Hence, one straight line for Sr, Cs, Ba systems and two types of straight lines for Sb, I (I^- and IO₃^-) systems were obtained in river water treated with ozone. The chromatography experiments of Cs, Sr, I (I^- and IO₃^-) were carried out to calculate their maximum adsorption capacities. The obtained maximum adsorption capacities of Cs, Sr, and I^- mixed with IO₃^- were 1.7 × 10^-4 (Cs), 1.8 × 10^-3 (Cs/O₃), 7.8 × 10^-5 (Sr), 5.6 × 10^-4 (Sr/O₃), 5.4 × 10^-2 (I^- and IO₃^-), 3.1 × 10^-2 (I^- and IO₃^-/O₃) mol/g - PA316TAS. It was discovered that the maximum adsorption capacities of I^- and IO₃^- for the composite adsorbent is unprecedented high and the capacity become much greater than an order of magnitude, compared with those of previous reports. This phenomenon suggests the formation of electron-donor-acceptor (EDA) complexes or pseudo EDA complex. Based on these results, it was concluded that the combined use of tannic acid-type organic composite adsorbents and ozone made it possible to remove simultaneously and effectively various kinds of radionuclides in river water in the wide pH and temperature ranges.

Syntheses, structures, and photocatalytic properties of open-framework Ag-Sn-S compounds

Four open-framework Ag-Sn-S compounds K2Ag2Sn2S6 (1); K2Ag2SnS4 (2); Rb2Ag2SnS4 (3); and Cs2Ag2SnS4 (4) have been synthesized using a solvothermal method. Compound 1 possesses a unique three-dimensional (3D) structure in which Ag+ ions are two-coordinated. Compounds 2-4 have the same layered structure in which Ag+ ions are tetrahedrally coordinated. Photocatalytic degradation properties of methylene blue have been investigated and compound 1 displays excellent photodegradation activities. The photoelectric response properties, optical properties, and theoretical calculations of these compounds have also been studied.

Efficient Cs+-Sr2+ Separation over a Microporous Silver Selenidostannate Synthesized in Deep Eutectic Solvent

Efficient Cs⁺-Sr²⁺ separation, highly desirable for radionuclide recovery in medical and industrial applications, was achieved by the ion exchange technique over a novel microporous silver selenidostannate, [NH₃CH₃]_0.5[NH₂(CH₃)₂]_0.25Ag_1.25SnSe₃ (AgSnSe-1). This material was synthesized in deep eutectic solvent (DES), where the alkylammonium cations play significant structure-directing roles in the construction of micropores that allow for selective ion exchange toward Cs⁺ against Sr²⁺. The much greater K_d^Cs (1.06 × 10⁴ mL g^-1) over K_d^Sr (87.7 mL g^-1) contributes to an outstanding separation factor SF_Cs/Sr of ∼121.4 that is top-ranked among inorganic materials. An ion exchange column filled with AgSnSe-1 exhibits a remarkable separation effect for 10 000 bed volumes of continuous flow, with removal rates of ∼99.9% and ∼0 ± 5.5% for Cs⁺ and Sr²⁺, respectively. AgSnSe-1 exhibits excellent β and γ radiation resistances and a chemical stability over a broad pH range of 1-12. The Se leaching level below the safe guideline value for drinking water highlights the environmental-friendly nature of AgSnSe-1. The high Cs⁺ exchange performance is almost unaffected by Na⁺, Mg²⁺, and Ca²⁺ cations. The Cs⁺-laden product AgSnSe-1Cs can be facilely eluted for recycling use, highlighting the great potential of open framework metal selenides in nuclear waste treatment and renewable energy utilization.

Effective removal of cesium from wastewater via adsorptive filtration with potassium copper hexacyanoferrate-immobilized and polyethyleneimine-grafted graphene oxide

As an attractive alternative to radioactive cesium removal, we introduced an adsorptive filtration method using a composite membrane consisting of potassium copper hexacyanoferrate (KCuHCF) and graphene-based support. Polyethyleneimine-grafted reduced graphene oxide (PEI-rGO), used as an immobilizing matrix, was effective not only in distributing KCuHCF inside the composite with the aid of abundant amino-functionality, but also in achieving high water flux by increasing the interlayer spacing of the laminar membrane structure. Due to the rapid and selective cesium adsorption properties of KCuHCF, the fabricated membrane was found to be effective in achieving complete removal of cesium ions under a high flux (over 500 L m^-2 h^-1), which is difficult in a conventional membrane utilizing the molecular sieving effect. This approach offers strong potential in the field of elimination of radionuclides that require rapid and complete decontamination.

The Uptake of Hazardous Metal Ions into a High-Nuclearity Cluster-Based Compound with Structural Transformation and Proton Conduction

The discovery of novel high-nuclearity oxo-clusters considerably promotes the development of cluster science. We report a high-nuclearity oxo-cluster-based compound with acid/alkali-resistance and radiation stabilities, namely, (H₃O)₇[Cd₇Sb₂₄O₂₄(l-tta)₉(l-Htta)₃(H₂O)₆]·29H₂O (FJSM-CA; l-H₄tta = l-tartaric acid), which features a two-dimensionally anionic layer based on the largest Sb-oxo-clusters with 28-metal-ion-core [Cd₄Sb₂₄O₂₄]. It is challenging to efficiently capture Sr²⁺, Ba²⁺ (analogue of ²²⁶Ra), and [UO₂]²⁺ ions from aqueous solutions due to their high water solubility and environmental mobility, while it is unprecedented that a novel Sb-oxo-cluster-based framework material FJSM-CA can efficiently remove these hazardous ions accompanied with intriguing structural transformations. Especially, it shows fast ion-exchange abilities for Sr²⁺, Ba²⁺, and [UO₂]²⁺ (reaches equilibrium within 2, 10, and 20 min, respectively) and high exchange capacity (121.91 mg/g), removal rate R (96%), and distribution coefficient K_d^U (2.46 × 10⁴ mL/g) for uranium. Moreover, the underlying mechanism is clearly revealed, which is attributed to strong electrostatic interactions between exchanged cations and highly negative-charged frameworks and the strong affinity of (COO)^- groups for these cations. Proton conduction of the pristine and Sr²⁺, Ba²⁺, [UO₂]²⁺-loaded products was investigated. This work highlights the design of new oxo-cluster-based materials for radionuclide remediation and proton conduction performance.

Facile Synthesis of Porous Polymer Using Biomass Polyphenol Source for Highly Efficient Separation of Cs+ from Aqueous Solution

In this work, a series of polyphenol porous polymers were derived from biomass polyphenols via a facile azo-coupling method. The structure and morphologies of the polymer were characterized by BET, TEM, SEM, XRD, TGA and FT-IR techniques. Batch experiments demonstrated their potentialities for adsorptive separation of Cs⁺ from aqueous solution. Among them, porous polymers prepared with gallic acid as starting material (GAPP) could adsorb Cs⁺ at wide pH value range effectively, and the optimal adsorption capacity was up to 163.6 mg/g, placing it at top material for Cs⁺ adsorption. GAPP exhibited significantly high adsorption performance toward Cs⁺ compared to Na⁺ and K⁺, making it possible in selective removal of Cs⁺ from ground water in presence of co-existing competitive ions. Moreover, the Cs-laden GAPP could be facilely eluted and reused in consecutive adsorption-desorption processes. As a result, we hope this work could provide ideas about the potential utilization of biomass polyphenol in environmental remediation.

Proton Conduction of an Acid-Resistant Open-Framework Chalcogenidometalate Hybrid in Anhydrous versus Humid Environments

Solid proton conductors are broadly applicable to various electrochemical devices; therefore, it is highly desirable to develop robust materials with high proton conductivity under both anhydrous and humid environments within a wide temperature range. In this work, we investigated the proton conducting properties of a 3D open-framework chalcogenidometalate hybrid, [CH₃NH₃]₂[H₃O]Ag₅Sn₄Se₁₂·C₂H₅OH (1), which exhibited both anhydrous and water-assisted proton conduction. Importantly, the excellent thermal and chemical stabilities of hybrid 1 are superior to many MOF-based proton conducting materials. This present study proved to be a considerable advance based on open-framework chalcogenidometalates in the design of robust solid proton conducting materials that are capable of operating under humid and anhydrous environments in a wide temperature range.

Synthesizing Crystalline Chalcogenidoarsenates in Thiol-Amine Solvent Mixtures

Thiol-amine solvent mixtures have been widely applied in the solution processing of binary chalcogenide thin films due to their excellent ability to dissolve various bulk binary chalcogenides. However, application of this solvent system in preparing new crystalline chalcogenidometalates has not been explored. In this work, by using a thiol-amine solvent mixture of n-butylamine (BA) and 1,2-ethanedithiol (EDT) as the reaction medium and protonated piperazine (pip) cation as the template, we synthesized a series of new chalcogenidoarsenates with structures ranging from discrete clusters to two-dimensional layers, namely, [pipH₂][pipH][AsS₄] (1), [pipH₂][pipH][As(Se_0.4S_0.6)₄] (2), [pipH₂]₂[pipH]₂[In₂As^III₂As^V₂S_13.3(S₂)_0.7] (3), [pipH₂]₂[pipH]₂[In₂As^III₂As^V₂S_10.2Se_3.1(Se₂)_0.7] (4), [pipH₂]_0.5[AsS(S₂)] (5), [pipH₂]_0.5[AsS₂] (6), [pipH]₂[AgAsS₄] (7), [pipH₂]_1.5[GaAs^IIIAs^VS₇] (8), and Cs₂[pipH]₂[InAs₆S₁₂]Cl (9). Particularly, compounds 3, 4, and 8 contain mixed-valent As^III and As^V ions in their discrete clusters and one-dimensional chain. In addition, compound 5 could thermodynamically transform to compound 6 with increasing reaction temperature, which may be attributed to the thermodynamically unstable S-S species in the chains of 5. The BA-EDT solvent mixture was crucial to the synthesis of these compounds, since no title crystals can be prepared by replacing the BA-EDT solvent mixture with other conventional solvents or removing one component of the BA-EDT solvent mixture from the reaction system. Our research demonstrates that thiol-amine solvent systems could be promising reaction media for growing novel crystalline chalcogenidometalates.

Nearly Identical but Not Isotypic: Influence of Lanthanide Contraction on Cs2NaLn(PS4)2 (Ln = La-Nd, Sm, and Gd-Ho)

The effect of lanthanide contraction often results in topological and symmetry changes in compounds with the same compositions as a function of lanthanide cation size. Here we report on the first example of a lanthanide thiophosphate exhibiting a change in the lanthanide cation environment without any topological or symmetry change. A series of new lanthanide thiophosphates with mixed alkali cations were obtained via a flux crystal growth technique using a CsI flux. The obtained compounds Cs₂NaLn(PS₄)₂ (Ln = La-Nd, Sm, and Gd-Ho) were grown as large single crystals (∼0.1-1 mm³) and characterized using single-crystal X-ray diffraction and magnetic susceptibility measurements. As we moved across the series, the structural studies revealed a change in the lanthanide coordination environment depending on the identity of the lanthanide. Although all compounds in the Cs₂NaLn(PS₄)₂ series crystallize in the same space group and have the same Wyckoff atom positions, a slight change in size between Sm³⁺ and Gd³⁺ causes a subtle change in coordination number from 9 (for Ln = La-Sm) to 8 (for Ln = Gd-Ho), resulting in two distinct but virtually identical structure types. Ab initio calculations were performed, and the observed experimental trend was corroborated computationally. Magnetic measurements performed on the Cs₂NaLn(PS₄)₂ (Ln = Ce, Pr, Nd, Gd, and Tb) compounds revealed paramagnetic behavior.

Microwave irradiation assisted sodium hexametaphosphate modification on the alkali-activated blast furnace slag for enhancing immobilization of strontium

An inadvertent leakage of ⁹⁰Sr into the environment can induce an easy accumulation in biosphere and cause a continuous radiation to the surrounding ecosystem. In this study, sodium hexametaphosphate (Na₆O₁₈P₆) was employed to modify the blast furnace slags (BFS) to enhance the chemical stabilization of Sr²⁺ ions in the BFS-based cementitious materials. Microwave irradiation (MW) was used to further increase the binder activity of BFS samples and strengthened the mechanical strengths and durability of BFS-based blocks. A combination of experimental factors including the mass ratio of Na₆O₁₈P₆ to BFS-Sr_0.1 of 15%, the ratio of solid to liquid of 1:4 mg/L, the output power of 650 W, and the activation time of 3 min was most conductive to achieving an optimal microwave-irradiation process. Four extraction solutions were sorted by their leaching abilities following as MgSO₄ solution > H₂SO₄ solution > CH₃OOH solution > deionized (DI) water based on their leaching results. Compared with microwave irradiation, an addition of Na₆O₁₈P₆ to BFS samples obtained a better compressive strength for BFS-based blocks. However, a microwave-irradiation treatment was more effective in improving the resistances of blocks to gamma irradiation and thermal-thaw changes. Exposing to gamma irradiation over 6 months and enduring to thermal-thaw tests over 15 cycles, the microwave-treated blocks only lost 3.29% and 2.23% of leaching removal efficiencies in deionized water, respectively. Microwave irradiation increased the mechanical strengths of BFS-based blocks and inhibited leaching of Sr²⁺ ions from matrices mainly by strengthening hydration reactions and Sr²⁺ encapsulation.

Grafting functional groups in metal–organic frameworks for U(vi) sorption from aqueous solutions

Recent highlights of the organic groups-functionalized MOFs for uranium extraction from aqueous solution are discussed.

Di-lacunary [In6S15]12− cluster: the building block of a highly negatively charged framework for superior Sr2+ adsorption capacities

Reported is the construction of a highly negatively charged layered material [CH₃CH₂NH₃]₆In₆S₁₂ (InS-1) by introducing a lacunary cluster as the building block. InS-1 exhibits an effective adsorption for Sr²⁺ ion with a high q_m of 105.35 mg g⁻¹.

A thio-functionalized zinc phosphite with a large-channel framework and enhanced removal ability of mercury ion from aqueous solutions

New thio-functionalized zinc phosphite (NTOU-2S) exhibited the different structural properties and removal ability of Hg²⁺ cation from the sulfur-free NTOU-2.

Fast and Selective Removal of Aqueous Uranium by a K+-Activated Robust Zeolitic Sulfide with Wide pH Resistance

For the nuclear industry, uranium is not only an important strategic resource but also a serious global contaminant with radiotoxicity and high chemotoxicity. It is very important to efficiently capture uranium from complex aqueous solutions for further treatment and disposal of nuclear wastes. Herein, we first demonstrate the suitability of a three-dimensional (3D) water-stable K⁺-exchanged zeolitic sulfide, namely K@GaSnS-1, for the remediation of radioactive and toxic uranium by ion exchange. In comparison to the pristine compound GaSnS-1, the K⁺-activated porous sulfide K@GaSnS-1 exhibits faster [UO₂]²⁺ ion uptake kinetics, following the pseudo-second-order adsorption model. Further studies indicate that K@GaSnS-1 shows high exchange capacity (q_m^U = 147.6 mg/g) and wide pH resistance (pH 2.75-10.87). In particular, it can efficiently capture [UO₂]²⁺ ion even when excessive amounts of Na⁺, K⁺, Mg²⁺, and Ca²⁺ ions are present. The highest distribution coefficient value K_d, signifying the affinity and selectivity for [UO₂]²⁺ ion, reaches as high as 1.24 × 10⁴ mL/g. More importantly, the uranium in corresponding exchanged samples can be facilely and effectively eluted by a low-cost and eco-friendly method. These merits of K@GaSnS-1 make it promising for the effective and selective removal of uranium from complex contaminated water.

Ammoniating Covalent Organic Framework (COF) for High-Performance and Selective Extraction of Toxic and Radioactive Uranium Ions

An ideal porous adsorbent toward uranium with not only large adsorption capacity and high selectivity but also broad applicability even under rigorous conditions is highly desirable but still extremely scarce. In this work, a porous adsorbent, namely [NH4]+[COF-SO3 -], prepared by ammoniating a SO3H-decorated covalent organic framework (COF) enables remarkable performance for uranium extraction. Relative to the pristine SO3H-decorated COF (COF-SO3H) with uranium adsorption capacity of 360 mg g-1, the ammoniated counterpart of [NH4]+[COF-SO3 -] affords ultrahigh uranium uptake up to 851 mg g-1, creating a 2.4-fold enhancement. Such a value is the highest among all reported porous adsorbents for uranium. Most importantly, a large distribution coefficient, K d U, up to 9.8 × 106 mL g-1 is observed, implying extremely strong affinity toward uranium. Consequently, [NH4]+[COF-SO3 -] affords highly selective adsorption of uranium over a broad range of metal ions such as SU/Cs = 821, SU/Na = 277, and SU/Sr = 124, making it as effective uranium adsorbent from seawater, resulting in amazing uranium adsorption capacity of 17.8 mg g-1. Moreover, its excellent chemostability also make it an effective uranium adsorbent even under rigorous conditions (pH = 1, 8, and 3 m acidity).

Intensive study on structure transformation of muscovite single crystal under high-dose γ-ray irradiation and mechanism speculation

Intensive study on structure transformation of muscovite single crystal under high-dose γ-ray irradiation is essential for its use in irradiation detection and also beneficial for mechanism cognition on defect formation within a matrix of clay used in the disposal of high-level radioactive waste (HLRW). In this work, muscovite single crystal was irradiated with Co-60 γ ray in air at a dose rate of 54 Gy min-1 with doses of 0-1000 kGy. Then, structure transformation and mechanism were explored by Raman spectrum, Fourier-transform infrared spectrum, X-ray diffraction, thermogravimetric analysis, CA, scanning electron microscope and atomic force microscopy. The main results show that variations in the chemical/crystalline structure are dose-dependent. Low-dose irradiation sufficiently destroyed the structure, removing Si-OH, thus declining hydrophilicity. With dose increase up to 100 kGy, CA increased from 20° to 40°. Except for hydrophilicity variation, shrink occurred in the (004) lattice plane which later recovered; the variation range at 500 kGy irradiation was 0.5% close to 0.02 Å. The main mechanisms involved were framework break and H2O radiolysis. Framework break results in Si-OH removal and H2O radiolysis results in extra OH introduction. The extra introduced OH probably results in Si-OH bond regeneration, lattice plane shrink and recovered surface hydrophilicity. The importance of framework break and H2O radiolysis on structure transformation is dose-dependence. At low doses, framework break seems more important while at high doses H2O radiolysis is important. Generally, variations in the chemical structure and surface property are nonlinear and less at high doses. This indicates using the chemical structure or surface property variation to describe irradiation is correct at low doses but not at high doses. This finding is meaningful for realizing whether muscovite is suitable for detecting high-dose irradiation or not, and mechanism exploration is efficient for identifying the procedure for defect formation within the matrix of clay used in disposal HLRW in practice.

Deep eutectic solvothermal synthesis of an open framework copper selenidogermanate with pH-resistant Cs+ ion exchange properties

Reported here is the deep eutectic solvothermal synthesis of an open framework copper selenidogermanate [NH₃CH₃]_0.75Cu_1.25GeSe₃ (CuGeSe-1), which shows a pH-resistant Cs⁺ ion exchange performance (q_m = 225.3 mg g⁻¹).