Prussian Blue Analogues of A2[Fe(CN)6] (A: Cu2+, Co2+, and Ni2+) and Their Composition-Dependent Sorption Performances towards Cs+, Sr2+, and Co2

Investigation in radioactive contaminant removal from aqueous solutions has been considered essential upon unexpected nuclear accidents. In this report, we have successfully prepared Prussian blue analogues (PBAs) with different substituted cations (A2[Fe(CN)6] (A: Cu2+, Co2+, and Ni2+)). The synthesized PBAs were characterized and employed for the removal of Cs+, Sr2+, and Co2+ as sorption models, which are commonly found in radioactive waste. Sorption examinations reveal that Cu2[Fe(CN)6] has the highest sorption capacity towards Cs+, Sr2+, and Co2+ compared with those of Co2[Fe(CN)6] and Ni2[Fe(CN)6]. This is mainly attributed to the cation-exchange ability of substituted metal within the framework of PBAs. The sorption mechanism is qualitatively and quantitatively supported by infrared spectroscopy (IR) and total reflection X-ray fluorescence spectroscopy analysis (TXRF). In addition, it was found that Cs+ is adsorbed most effectively by PBAs due to the size matching between Cs+ ions and the channel windows of PBAs. These findings are important for the design of sorbents with suitable ion-exchange capacity and selectivity toward targeted radioactive wastes.