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

Abstract

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]0.25Ag1.25SnSe3 (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.

pH‐Controlled Switch over Coadsorption and Separation for Mixed Cs+ and Sr2+ by an Acid‐Resistant Potassium Thioantimonate

“…Thus the separation effect of SbS‐1K for mixed Cs + and Sr 2+ is outstanding and even better than those of titanium trisilicate K 1.26 H 0.74 TiSi 3 O 9 ·2H 2 O ( SF Cs/Sr = 149) [ 39 ] and metal chalcogenide AgSnSe‐1 ( SF Cs/Sr = 121.4). [ 40 ] As shown in Figure 7b, the adsorption kinetics for mixed Cs + and Sr 2+ ( C 0 ≈ 6 ppm for each) at pH 6 exhibits to be similar with the case of each individual ion, featuring an ultrafast and efficient (≈98–99%) capture with equilibrium time of 40 min. Once switched to pH 2, however, the capture of Sr 2+ was significantly inhibited with a great loss in R to ≈10% at equilibrium, while the Cs + adsorption keeps almost unaffected (Figure 7c).…”

“…Further increase of the HCl concentration leads to a partial decomposition (C e Sb = 45.79 ppm in 4 m HCl, 208.94 ppm in 5 m HCl) until the total collapse of the crystalline product occurs at a concentration of 5.5 m (C e Sb = 388.26 ppm, Figure 6f,g). The stability of SbS-1K over such a wide range from alkaline (pH 11) to extremely acidic (3 m HCl) conditions is impressive, which overperforms most of the pH-resistant metal chalcogenide adsorbents represented by (NH 4 ) 4 In 12 Se 20 (2.4 m HCl), [59] KMS-1 (pH 0.7-12), [30] FJSM-SnS (pH 0.7-12.7), [33] CuGeSe-1 (pH 1-12) [60] and AgSnSe-1 (1-12), [40] etc. In addition, SbS-1K shows superior R Cs values of 90.60%, 65.79% and 35.17% at pH 1, pH 0 (1 m HCl) or even in 2 m HCl solution (Figure 6h, Tables S14 and S15, Supporting Information), respectively, even higher than KMS-1 (≈43% pH 0.8) [30] and FJSM-SnS (≈47% at pH 0.7) [33] that tested under similar conditions.…”

“…[37] Titanosilicates like Na 2 Ti 2 O 3 (SiO 4 )•2H 2 O [38] and K 0.3 H 1.7 TiSi 3 O 9 •2.4H 2 O [39] were also well documented for selective adsorption of Cs + ions owing to their ideal tunnel size, and their performances would be effected by the crystallinity and/or protonation degree of materials as well. Very recently, the alkylammonium-directed metal selenide AgSnSe-1 [40] was emplored for extracting Cs + from Sr 2+ , with an excellent separtion factor SF Cs/Sr large than 120. Conversely, selective ion exchange for Sr 2+ against Cs + has also been achieved by inorganic materials such as MOFs (e.g., SZ-4, [21] MOF-808-SO 4 , [41] and MOF-808-C 2 O 4 [41] ) and metal sulfides (e.g., ZnSnS [42][43][44] and InS [45][46][47] series) as a result of collaborative coordination by the host network and/or particular ion-trapping interactions.…”

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

“…The above results demonstrate that InSnS-1 can effectively achieve Cs-Sr (or Cs-La) separation in acidic solutions even though the concentration of Sr 2+ (or La 3+ ) is much higher than that of Cs + . Sulfide ion exchanger AgSnSe-1 can achieve Cs-Sr separation ( SF Cs/Sr = 121.4) in neutral solutions with low concentration of Cs + and Sr 2+ (both around 6 mg/L) 51 . However, to the best of our knowledge, no example of SF Cs/Sr (or SF Cs/La ) value that exceeds 100 in strongly acidic solution has been reported, where the Sr 2+ (or La 3+ ) ion concentration is much higher than the Cs + ion concentration.…”

Conversion of Organically Directed Selenidostannate into Porous SnO2 Exhibiting Effective Electrochemical Reduction of CO2 to C1 Products

“…27,28 This contributes to a more efficient and faster synthesis for selenidostannate within hours compared to those conducted in neutral, volatile organic solvents (e.g., ethanol and dimethylformamide, DMF). 29,30 Besides, the choline component of DES acts as significant templates and counter cations that account for the construction of honeycomb-like [Sn 3 Se 7 ] n 2n− layers, whose parallel stacking gives the final hybrid of Ch-Sn 3 Se 7 (Figure 2). In the crystal lattice, all of the choline templates exhibit the same activation energy for release/decomposition in response to external thermal stimuli, implying that they can be precisely removed upon heating to a certain temperature.…”