Reduction-Induced Highly Selective Uptake of Cesium Ions by an Ionic Crystal Based on Silicododecamolybdate

Cation adsorption and exchange has been an important topic in both basic and applied chemistry relevant to materials synthesis and chemical conversion, as well as purification and separation. Selective Cs+ uptake from aqueous solutions is especially important because Cs+ is expensive and is contained in radioactive wastes. However, the reported adsorbents incorporate Rb+ as well as Cs+, and an adsorbent with high selectivity toward Cs+ has not yet been reported. Highly selective uptake of Cs+ by an ionic crystal (etpyH)(2)[Cr3O(OOCH)(6)(etpy)(3)](2)[-SiMo12O40]3H(2)O (etpy =4-ethylpyridine) is described. The compound incorporated up to 3.8mol(Cs+)mol(s)(-1) (where s=solid) by cation-exchange with etpyH(+) and reduction of silicododecamolybdate with ascorbic acid. The amount of Cs+ uptake was comparable to that of Prussian blue, which is widely recognized as a good Cs+ adsorbent. Moreover, other alkali-metal and alkaline-earth-metal cations were almost completely excluded (<0.2molmol(s)(-1)).