Efficient Co-Adsorption and Highly Selective Separation of Cs and Sr with a K -Activated Niobium Germanate by the pH Control.

Cs and Sr are hazardous to ecological environment and human health due to their strong radioactivity, long half-life, and high mobility. However, effective adsorption and separation of Cs and Sr from acidic radioactive wastewater is challenging due to stability issues of material and the strong competition of protons. Herein, a K -activated niobium germanate (K-NGH-1) presents efficient Cs /Sr coadsorption and highly selective Cs /Sr separation, respectively, under different acidity conditions. In neutral solution, K-NGH-1 exhibits ultrafast adsorption kinetics and high adsorption capacity for both Cs and Sr (q  = 182.91 mg g ; q  = 41.62 mg g ). In 1 M HNO solution, K-NGH-1 still possesses q of 91.40 mg g for Cs but almost no adsorption for Sr . Moreover, K-NGH-1 can effectively separate Cs from 1 M HNO solutions with excess competing Sr and M (M  = Na , Ca , Mg ) ions. Thus, efficient separation of Cs and Sr is realized under acidic conditions. Besides, K-NGH-1 shows excellent acid and radiation resistance and recyclability. All the merits above endow K-NGH-1 with the first example of niobium germanates for radionuclides remediation. This work highlights the facile pH control approach towards bifunctional ion exchangers for efficient Cs /Sr coadsorption and selective separation.