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

Phosphination of amino-modified mesoporous silica for the selective separation of strontium

Radioactive strontium (90Sr) is considered as one of the most dangerous radionuclides due to its high biochemical toxicity. For the efficient and selective separation of Sr from acidic environments, a novel functional adsorbent CEPA@SBA-15-APTES was prepared in this work through the phosphorylation of amino-modified mesoporous silica with organic content of approximately 20 wt%. CEPA@SBA-15-APTES was characterized by TEM, SEM, EDS, TG-DSC, BET, FTIR, and XPS techniques, revealing its characteristics of an ordered hexagonal lattice-like structure and rich functional groups. The experimental results demonstrated that the adsorbent exhibited good adsorption capacity for Sr over a wide acidity range (i.e., from 10-10 M to 4 M HNO3). The adsorption equilibriums of Sr by CEPA@SBA-15-APTES in 10-6 M and 3 M HNO3 solutions were reached within 30 and 5 min, respectively, and the adsorption capacities at 318 K were 112.6 and 71.8 mg/g, respectively. Furthermore, by combining the experimental and characterization results, we found that the adsorption mechanism consisted of ion exchange between Sr(II) and H+ (in P-OH) in the 10-6 M HNO3 solution and coordination between the Sr(II) and oxygen-containing (CO and P = O) functional groups in the 3 M HNO3 solution.

Layered metal sulfides with MaSbc- framework (M = Sb, In, Sn) as ion exchangers for the removal of Cs(Ⅰ) and Sr(Ⅱ) from radioactive effluents: a review

Nuclear power has emerged as a pivotal contributor to the global electricity supply owing to its high efficiency and low-carbon characteristics. However, the rapid expansion of the nuclear industry has resulted in the production of a significant amount of hazardous effluents that contain various radionuclides, such as 137Cs and 90Sr. Effectively removing 137Cs and 90Sr from radioactive effluents prior to discharge is a critical challenge. Layered metal sulfides exhibit significant potential as ion exchangers for the efficient uptake of Cs+ and Sr2+ from aqueous solutions owing to their open and exchangeable frameworks and the distinctive properties of their soft S2- ligands. This review provides a detailed account of layered metal sulfides with MaSb c- frameworks (M = Sb, In, Sn), including their synthesis methods, structural characteristics, and Cs+ and Sr2+ removal efficiencies. Furthermore, we highlight the advantages of layered metal sulfides, such as their relatively high ion exchange capacities, broad active pH ranges, and structural stability against acid and radiation, through a comparative evaluation with other conventional ion exchangers. Finally, we discuss the challenges regarding the practical application of layered metal sulfides in radionuclide scavenging.

Tailoring Hybrid Aluminoborate Frameworks by Incorporating Multicomponent Cadmium-Amine Complexes with Various Conformations

Inorganic-organic hybrid aluminoborates represent a subclass of porous materials, which rely on effective construction method and structure-directing agents. Herein, we prepared a series of hybrid aluminoborates through covalent decoration of unsaturated Cd²⁺ complexes, whose formation take advantage of chelating amine and long-chain diamine as mixed ligands. These isolated compounds, that is, [Cd(en)(1,4-dab)_0.5][AlB₅O₁₀] (1a; its analogue with discrete complex [Cd(en)(dien)H₂O][AlB₅O₁₀] is denoted as 1b), [Cd(1,2-dap)_1.5(1,4-dabH)_0.5]{Al[B₅O₈(OH)₂](B₅O₁₀)_0.5} (2), and [Cd(en)(1,3-dap)][AlB₅O₁₀] (3) feature open frameworks (1a, 1b, and 3) or a sandwich-like porous layer (2) that are constructed by AlO₄ tetrahedra and [B₅O₁₀]^5-/[B₅O₈(OH)₂]^3- clusters. However, they exhibit different structural features in interconnection, channel environment, and topology as a result of diversified interactions between unsaturated complexes and aluminoborate frameworks, that is, through forming two Cd-O bonds with (i) a pair of neighboring BO₃ and AlO₄, (ii) the same AlO₄, or (iii) the same BO₃. The variation in connection mode exerts essential influence on binding effects and steric hindrance that are reflected by changes in interatomic distance, bond angle, window configuration, and interlinkage of units. In addition, the incorporation of unsaturated Cd²⁺ complexes endows these aluminoborate materials with photoluminescence function. Compound 3 with a noncentrosymmetric structure exhibits second harmonic generation (SHG) response approximately 0.7 times that of KDP. The preparation strategy for hybrid aluminoborates proposed here combines well molecular design with templating assembly, whose synergistic effect would be crucial for drawing a rational pathway for inorganic synthesis, especially with focus on structural and functional innovation.

Efficient removal of Ba2+, Co2+ and Ni2+ by an ethylammonium-templated indium sulfide ion exchanger

Removal of radioactive ¹³³Ba, ⁶⁰Co and ⁶³Ni and their nonradioactive isotopes through ion exchange method would be highly beneficial for the safe disposal of liquid industrial waste, and it also bears importance for the emergency response to nuclear accident. Herein, we report the employment of an indium sulfide [CH₃CH₂NH₃]₆In₈S₁₅ (InS-2) with exchangeable ethylammonium cations for efficient and selective uptake of Ba²⁺, Co²⁺ and Ni²⁺. The corner-sharing linkage of P1-{In₈S₁₇} clusters in InS-2 endow the layered structure with nanoscale windows, which facilitates both transfer and accommodation of the large hydrated divalent metal ions. This results in ultrafast exchange kinetics (10-20 min) and top-level exchange capacities of 211.73 mg g^-1 for Ba²⁺, 103.57 mg g^-1 for Co²⁺, and 111.78 mg g^-1 for Ni²⁺. Particularly, InS-2 achieves ultrahigh K_d values of 2.3 × 10⁵ mL g^-1 for Ba²⁺, 2.0 × 10⁵ mL g^-1 for Co²⁺ and 1.6 × 10⁵ mL g^-1 for Ni²⁺, corresponding to remarkable removal efficiencies larger than 99.4% (C₀ ~ 6 ppm). InS-2 shows high β and γ irradiation resistance, wide pH durability (pH 3-13 for Ba²⁺, pH 3-11 for Co²⁺ and Ni²⁺), and outstanding selectivity against competitor ions (e.g. Na⁺, K⁺, Mg²⁺, Ca²⁺). The InS-2-filled ion exchange column exhibits a fantastic removal effect (R > 99%) for mixed Ba²⁺, Co²⁺, Ni²⁺, as well as Sr²⁺. The ultralong column-treatment on 20000 BVs of flow reveals an affinity order of Co²⁺ > Ni²⁺ > Ba²⁺ > Sr²⁺ for InS-2, which gives deep insights into the adsorption process and interaction between competitor ions. This excellent uptake of Ba²⁺ (Ra by analogy), Co²⁺ and Ni²⁺ ions by InS-2 highlights the great potential of metal chalcogenides as a type of promising materials for minimizing contamination in complex wastewater.

Highly selective cesium(I) capture under acidic conditions by a layered sulfide

Radiocesium remediation is desirable for ecological protection, human health and sustainable development of nuclear energy. Effective capture of Cs⁺ from acidic solutions is still challenging, mainly due to the low stability of the adsorbing materials and the competitive adsorption of protons. Herein, the rapid and highly selective capture of Cs⁺ from strongly acidic solutions is achieved by a robust K⁺-directed layered metal sulfide KInSnS₄ (InSnS-1) that exhibits excellent acid and radiation resistance. InSnS-1 possesses high adsorption capacity for Cs⁺ and can serve as the stationary phase in ion exchange columns to effectively remove Cs⁺ from neutral and acidic solutions. The adsorption of Cs⁺ and H₃O⁺ is monitored by single-crystal structure analysis, and thus the underlying mechanism of selective Cs⁺ capture from acidic solutions is elucidated at the molecular level.

The removal of radiocesium from acidic solutions is challenging. Here, the authors report the rapid and highly selective capture of cesium(I) from strongly acidic solutions by a robust layered metal sulfide.

Structural Investigation on the Efficient Capture of Cs+ and Sr2+ by a Microporous Cd-Sn-Se Ion Exchanger Constructed from Mono-Lacunary Supertetrahedral Clusters

Visualization of the ion exchange mechanism for 137Cs and 90Sr decontamination bears significance for safe radioactive liquid waste reprocessing and emergency response enhancement to nuclear accident. Here, the remediation of...

Mixed Solvothermal Synthesis of Tn Cluster-Based Indium and Gallium Sulfides Using Versatile Ammonia or Amine Structure-Directing Agents

Metal chalcogenide supertetrahedral Tn clusters are of current interest for their unique compositions and structures, which rely highly on the structure-directing agents. Herein, we report four novel Tn cluster-based indium and gallium sulfides, namely, [NH(CH₃)₃]₄In₄S₁₀H₄ (1), (NH₃)₄Ga₄S₆ (2), [NH₃CH₂CH₃]₅(NH₂CH₂CH₃)₂Ga₁₁S₁₉ (3), and [NH₃CH₂CH₂OH]₆Ga₁₀S₁₈·2NH₂CH₂CH₂OH (4). All four compounds were solvothermally synthesized in mixed amine-ethanol solutions or deep eutectic solvent (DES), where ammonia/amine molecules play significant structure-directing roles in the speciation and crystal growth. (1) Being protonated, the trimethylamine and ethanolamine molecules surround the T2-[In₄S₁₀H₄]^4- clusters (for 1) and [Ga₁₀S₁₈]_n^6n- open framework (for 4), respectively, compensating for the negative charge of the inorganic moieties. (2) With the lone pair of electrons, the ammonia molecules in 2 coordinate directly to corner Ga³⁺ ions of the {Ga₄S₆} cage to give a neutral T2-(NH₃)₄Ga₄S₆ cluster. (3) For compound 3, part of the ethylamine molecules act as terminating ligands for the T1 and T3 units in the [Ga₁₁S₁₉(NH₂CH₂CH₃)₂]_n^5n- layer, while the rest act as interlamellar countercations upon protonation. Theoretical studies reveal the contributions of N, C, and H to the density of states (DOS) for 2 and 3 because of their hybrid structures that combine the ammonia/amine ligands with sulfide moieties together.

Remarkable damage in talc caused by electron beam irradiation with a dose of up to 1000 kGy: lattice shrinkage in the Z- and Y-axis and corresponding intrinsic microstructural transformation process speculation

To reduce the polluted areas caused by the migration of radioactive or toxic matter, a clear understanding of soil matrix stability, especially the lattice, is essential under irradiation conditions like those of β-ray irradiation. In reality, the matrix of soil or clay is silicate, with talc being one of the most simple species with a similar structure to that matter, exhibiting “2 : 1” stacking and a complete crystal. Therefore, in this work, it was irradiated by an electron beam in air with dose up to 1000 kGy. Then, variations in lattice and the intrinsic microstructural transformation process, especially in terms of defect formation and transformation, were explored. The main results show that irradiation led to talc lattice plane shrinkage and amorphization. Shrinkage and amorphization levels in the Z-axis were more serious than those in the Y-axis. For a 1000 kGy-irradiated sample, the shrinkage level of the (002) lattice plane was close to 2% near 0.2 Å and that of (020) was close to 1.3% near 0.06 Å. Variation in the (002) lattice plane was more obvious than that of (020). The main mechanisms involve the cleavage of tetrahedral Si–O and linkage of tetrahedra and octahedra. Tetrahedral Si–O cleavage was visible, leading to serious amorphization. Nevertheless, lattice plane shrinkage, especially in the Z-axis, was mainly caused by linkage cleavage in this direction. In addition to linkage cleavage, dehydroxylation and H₂O volatilization occurred, coupled with H₂O radiolysis. Nevertheless, those factors are secondary to lattice variation.

Upon irradiation, tetrahedral Si–O and the links of tetrahedron and octahedron sheets are cleaved, leading to shrinkage and amorphization. That in the Z-axis is more pronounced than in the Y-axis.