Capture of radioactive cations from water using niobate nanomaterials with layered and tunnel structures

Niobates with one-dimensional (1D) morphology, layered KNb3O8 nanorods and tunnel structured Na2Nb2O6 center dot H2O nanofibers, are fabricated readily by a reaction between niobium oxide and alkali hydroxides under hydrothermal conditions. They exhibit ideal properties for removal of radioactive cations such as Sr2+, Ba2+ (as simulant for Ra-226(2+)) and Cs+ ions from wastewater through an ion exchange process. Compared with the Na2Nb2O6 center dot H2O nanofibers, the KNb3O8 nanorods displayed better performance for the irreversible entrapment of the toxic cations, particularly Ba2+ cations, due to the deformation of the layer structure. Besides, these 1D niobates are acid resistant with selective uptake of the radioactive cations in the presence of a large excess of K+ or Na+ ions.