[Ln6O8] Cluster-Encapsulating Polyplumbites as New Polyoxometalate Members and Record Inorganic Anion-Exchange Materials for ReO4 - Sequestration

Synthesis and Evaluation of the Extraction Efficiency of Pristine Zeolite Na-A to Remove ReO4- Ions (Surrogate of 99TcO4-) from a Simulated Low-Level Waste Solution

Zeolite Na-A was synthesized through hydrothermal, alkali-fusion, and sonochemical methods, using kaolin as an economically viable precursor. The synthesized zeolite Na-A samples were characterized using XRD, FT-IR, SEM, and Raman spectroscopy. Specific surface area and pore size distribution analyses (by BJH and DFT models) were conducted using a BET surface area analyzer. Additionally, thermal degradation studies were performed by TG-DTA to check the thermal stability of zeolite Na-A at high temperatures. Furthermore, kaolin-derived zeolite Na-A was employed for the extraction of perrhenate ions (ReO4-), which are a nonradioactive surrogate for pertechnetate ions (99TcO4-) without any postsynthetic modifications (using toxic surfactants, etc.) utilizing in situ modification of the solution medium for the first time. The sonochemically synthesized zeolite Na-A demonstrated superior sorption performance for the solid-phase extraction of ReO4- ions from the simulated low-level waste solution. The adsorption process was found to follow pseudo-second-order kinetics. The Langmuir isotherm model fit perfectly with the experimental data (R2 = 0.997) and exhibited a maximum sorption capacity of 926.8 mg/g at pH ∼11, showing superior sorption capacities compared to those of the numerous materials reported earlier. XPS confirmed the speciation of extracted rhenium as NH4Re(VII)O4, providing critical insights into the adsorption mechanisms and validating the suitability of the sonochemically synthesized zeolites toward ReO4- sorption. Furthermore, Raman studies of ReO4- adsorbed zeolite Na-A reflect the absence of characteristic breathing bands, indicating the closure of the pore openings due to the occupancy of adsorbate moieties within the pores. This study not only highlights the utilization of sonochemically synthesized zeolite Na-A as an efficient, benign, and cost-effective adsorbent for 99TcO4- removal from nuclear waste but also emphasizes its potential sustainable applications in various other industrial processes such as wastewater treatment, catalysis, gas separation, pollution control, and resource recovery from industrial effluents and in the pharmaceutical industry for selective ion removal.

Post-Modification of a Robust Covalent Organic Framework for Efficient Sequestration of 99 TcO4 - /ReO4. Chemistry 2023;29:e202302168. [PMID: 37534580 DOI: 10.1002/chem.202302168] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Nuclear industry spent fuel reprocessing and some radioactive contamination sites often involve high acidity and salinity environments. Currently developed and reported sorbents in 99 TcO4 - sequestration from the nuclear waste are unstable and show low adsorption efficiency in harsh conditions. To address this issue, we developed a post-synthetic modification strategy by grafting imidazole-based ionic liquids (ILs) onto the backbone of covalent organic framework (COF) via vinyl polymerization. The resultant COF-polyILs sorbent exhibits fast adsorption kinetics (<5 min) and good sorption capacity (388 mg g-1 ) for ReO4 - (a nonradioactive surrogate of 99 TcO4 - ). Outstandingly, COF-polyILs composite shows superior ReO4 - removal even under highly acidic conditions and in the presence of excess competing ions of Hanford low-level radioactive waste stream, benefiting from the stable covalent bonds between the COF and polyILs, mass of imidazole rings, and hydrophobic pores in COF.

Achieving colour tuneable and white-light luminescence in a large family of dual-emission lanthanide coordination polymers

Expanding the family of lanthanide terpyridine coordination polymers has yielded eighteen new complexes with two different phases, Ln(TPC)₂(HCOO)(H₂O) (Ln-1) and Ln(TPC)(HCOO)₂ (Ln-2) (Ln = Sm-Lu, except Tm). Both structures are composed of lanthanide cations interconnected by 2,2':6',2''-terpyridine-4'-carboxylate ligands to yield one-dimensional chain topologies. However, the incorporation of an additional crystallographically unique decorative TPC ligand into Ln-1 gives rises to a distinct phase. The encapsulation of both metal- and ligand-based phosphors within single coordination polymers leads to dual-emission of the afforded materials. Furthermore, judicious lanthanide doping in heterometallic Ln-1 and Ln-2 allows for fine-tuning the photoluminescent colours over a wide range of gamut. Such a combination showcases the capability to fine-tune the emission colours from deep green, to red, and to blue. In addition, direct white-light emission upon UV excitation can be achieved in the Sm_xGd_1-x-1 system.

Task-Specific Tailored Cationic Polymeric Network with High Base-Resistance for Unprecedented 99TcO4 - Cleanup from Alkaline Nuclear Waste

Direct removal of 99TcO4 - from alkaline nuclear waste is desirable because of the nuclear waste management and environmental protection relevant to nuclear energy but is yet to be achieved given that combined features of decent base-resistance and high uptake selectivity toward anions with low charge density have not been integrated into a single anion-exchange material. Herein, we proposed a strategy overcoming these challenges by rationally modifying the imidazolium unit of a cationic polymeric network (SCU-CPN-4) with bulky alkyl groups avoiding its ring-opening reaction induced by OH- because of the steric hindrance effect. This significantly improves not only the base-resistance but also the affinity toward TcO4 - as a result of enhanced hydrophobicity, compared to other existing anion-exchange materials. More importantly, SCU-CPN-4 exhibits record high uptake selectivity, fast sorption kinetics, sufficient robustness, and promising reusability for removing 99TcO4 - from the simulated high-level waste stream at the U.S. Savannah River Site, a typical alkaline nuclear waste, in both batch experiment and dynamic column separation test for the first time.

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.

Structural Complexity and Magnetic Orderings in a Large Family of 3d-4f Heterobimetallic Sulfates

The synthesis of a large family of heterobimetallic lanthanide copper sulfates was realized via stoichiometric hydrothermal reactions among Ln₂O₃, CuO, and H₂SO₄, giving rise to four distinct phases, namely Ln₂Cu(SO₄)₂(OH)₄ (Ln = Sm-Ho) (LnCuSO₄-1), Ln₄Cu(SO₄)₂(OH)₁₀ (Ln = Tm-Lu) (LnCuSO₄-2), LnCu(SO₄)(OH)₃ (Ln = Nd-Gd, except Pm) (LnCuSO₄-3), and LnCu(SO₄)(OH)₃ (Ln = Dy-Lu) (LnCuSO₄-4), with completely different topologies. The passage from LnCuSO₄-1 and LnCuSO₄-3 to LnCuSO₄-2 and LnCuSO₄-4 across the 4f series, respectively, can be ascribed to the effect of lanthanide contraction, which progressively induces shrinking of the Ln-O distance, reduction in the Ln coordination number, and eventually structural transitions. The incorporation of identical 3d-4f metal ions into different spin-lattices, in conjunction with substitution of diverse Ln³⁺ cations within the same spin-lattice, gives rise to tunable magnetic properties varying from ferromagnetic ordering in GdCuSO₄-3 and HoCuSO₄-4 to antiferromagnetic ordering in YbCuSO₄-4, and to paramagnetic correlations found in GdCuSO₄-1 and YbCuSO₄-2.