Selective removal of cesium ions from aqueous solution by different metal (Zn2+/Ni2+) hexacyanocobaltate

Radioactive ¹³⁷Cs removal and treatment have attracted widespread attention since the Chernobyl disaster and the Fukushima Daiichi nuclear plant accident. So far, Prussian blue analogs (PBAs) are recognized as the most effective Cs⁺ adsorbents possessing excellent sorption ability and radiation resistance. Here, two types of PBA-based Cs⁺ adsorbents, potassium zinc hexacyanocobaltate (Zn-Co PBA) and potassium nickel hexacyanocobaltate (Ni-Co PBA), were prepared by chemical precipitation method. Consequently, Zn-Co PBA and Ni-Co PBA had fast adsorption kinetics, and could remove 86.12% and 91.49% of Cs⁺ within 5 min, respectively. Zn-Co PBA and Ni-Co PBA were stable in a wide pH range, with Q_max of 96.53 and 77.52 mg/g for Cs⁺, respectively, both removing 98.5% of Cs⁺. In addition, Zn-Co PBA can eliminate 93.79% of Cs⁺ even in Cs⁺ spiked seawater containing high concentration of competitive cations. The adsorption mechanism indicates that the primary process involves ion exchange between K⁺ in the adsorbent and Cs⁺.