Radionickel ion (⁶³Ni²⁺) remediation is critical for public health and the environment, but selectively capturing of Ni²⁺ from complex environments like seawater presents a challenge. Metal sulfide ion exchangers (MSIEs) are emerging as efficient adsorbents for radionuclides; however, the study of MSIEs for selectively removing Ni²⁺ is still in its infancy. Herein, the layered metal sulfide K₂Cu₂Sn₂S₆ (CTS-1) with a unique sandwich-like anionic framework was synthesized by the hydrothermal method for the first time, representing a novel approach in the selective capture of Ni²⁺ from complex environments. Single-crystal structural analysis confirmed the sandwich-like framework, in which a [Cu-S] sublayer is sandwiched by two [Sn-S] sublayers with parallel grooves. The charge-balancing K⁺ ions are located within these grooves. Due to its special structure, CTS-1 exhibits remarkable adsorption capacities for Ni²⁺ with rapid kinetics (a high rate constant k₂ of 7.26×10⁻² g/(mg·min)), broad pH durability (removal rates >97% at pH 3–12), and high selectivity (separation factors for Ni²⁺ >700 against various cations). Impressively, it can efficiently remove Ni²⁺ from multiple complex environments, achieving a 90.28% removal rate even in seawater (C₀^Ni ~5 mg/L). CTS-1 is environmentally friendly and suitable for use in fixed-bed columns for the practical application. Moreover, Ni²⁺ ions are captured through ion exchange with K⁺, and the high selectivity stems from the strong affinity of S²⁻ for Ni²⁺ and the trapping effect of the grooves within the structure. In summary, this pioneering study demonstrates the highly selective capture of Ni²⁺ by a sandwich-like layered MSIE, potentially inspiring the development of efficient scavengers for radionuclides.

中文翻译：

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通过夹层状金属硫化物离子交换器从复杂环境中高选择性捕获 Ni2+


放射性镍离子 （⁶³Ni²⁺） 修复对公共卫生和环境至关重要，但从海水等复杂环境中选择性捕获 Ni²⁺ 是一项挑战。金属硫化物离子交换剂 （MSIE） 正在成为放射性核素的高效吸附剂;然而，MSIE 选择性去除 Ni²⁺ 的研究仍处于起步阶段。在此，首次通过水热法合成了具有独特三明治状阴离子框架的层状金属硫化物 K₂Cu₂Sn₂S₆ （CTS-1），代表了一种从复杂环境中选择性捕获 Ni²⁺ 的新方法。单晶结构分析证实了三明治状框架，其中 [Cu-S] 子层被两个具有平行凹槽的 [Sn-S] 子层夹在中间。电荷平衡 K⁺ 离子位于这些凹槽内。由于其特殊的结构，CTS-1 对 Ni²⁺ 表现出显著的吸附能力，具有快速动力学（7.26×10-2 g/（mg·min） 的高速率常数 k₂）、广泛的 pH 耐久性（pH 3-12 时的去除率 >97%）和高选择性（Ni²⁺ >700 对各种阳离子的分离因子）。令人印象深刻的是，它可以从多种复杂环境中高效去除 Ni²⁺，即使在海水中也能达到 90.28% 的去除率 （C₀^Ni ~5mg/L）。CTS-1 环保，适用于实际应用的固定床塔。 此外，Ni²⁺ 离子通过与 K⁺ 的离子交换而被捕获，高选择性源于 S²⁻ 对 Ni²⁺ 的强亲和力以及结构内凹槽的捕获作用。总之，这项开创性研究证明了夹心状层状 MSIE 对 Ni²⁺ 的高度选择性捕获，这可能会激发放射性核素高效清除剂的开发。