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

Unconventional ion exchangers can achieve efficient removal of [UO2]2+, Cs+, and Sr2+ ions from complex aqueous solutions and are of great interest for environmental remediation. We report two new gallium thioantimonates, [Me2NH2]2[Ga2Sb2S7]·H2O (FJSM-GAS-1) and [Et2NH2]2[Ga2Sb2S7]·H2O (FJSM-GAS-2), which present excellent ion exchange properties for [UO2]2+, Cs+, and Sr2+ ions. They exhibit high ion exchange capacities for [UO2]2+, Cs+, and Sr2+ ions ( qmU = 196 mg/g, qmCs = 164 mg/g, and qmSr = 80 mg/g for FJSM-GAS-1, qmU = 144 mg/g for FJSM-GAS-2) and short equilibrium times for [UO2]2+ ion exchange (5 min for FJSM-GAS-1 and 15 min for FJSM-GAS-2, respectively). Both compounds display active ion exchange with [UO2]2+ in the pH range of 2.9-10.5. Moreover, the sulfide compounds could maintain high distribution coefficients KdU even in the presence of excess Na+, Ca2+, and HCO3-. The distribution coefficient KdU of 6.06 × 106 mL/g exhibited by FJSM-GAS-1 is the highest among the reported U adsorbents. The [UO2]2+-laden products can be recycled by conveniently eluting the uranium with a low-cost method. These advantages combined with facile synthesis, as well as ß and γ radiation resistance, make FJSM-GAS-1 and FJSM-GAS-2 promising for selective separations in nuclear waste remediation.

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.

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]n2n- 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 KdEu to date. They still retain high removal efficiency even after intense ß 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.

[CH3 NH3 ]4 Ga4 SbS9 S0.28 O0.72 H: A Three-Dimensionally Open-Framework Heterometallic Chalcogenidoantimonate Exhibiting Ni2+ Ion-Exchange Property.

An open-framework chalcogenidoantimonate, namely, [CH3 NH3 ]4 Ga4 SbS9 S0.28 O0.72 H (1), has been solvothermally synthesized and structurally characterized. Interestingly, 1 showed Ni2+ ion-exchange properties and wide pH resistance, with a maximum exchange capacity of 76.9 mg g-1 . To the best of our knowledge, this is the first example of amine-directed three-dimensional (3D) heterometallic chalcogenidometalates for highly selective Ni2+ ion capture with a high distribution coefficient (Kd =1.65×105  mL g-1 ).