Niobate nanofibers for simultaneous adsorptive removal of radioactive strontium and iodine from aqueous solution

Abstract

Radioisotopes pose a potential mass threat to public heath if accidently released into the environment. To mitigate the consequences, effective methods must be developed for removal of radioactive ions from the environment. In this study, we show that nanofibers of sodium niobate with negatively charged layers and readily exchangeable sodium ions between the layers can efficiently remove radioactive Sr2+. The exchange of Sr2+ ions with the interlayer Na+ ions can cause structural deformation of layers, trapping the Sr2+ in the nanofibers. Furthermore, silver oxide (Ag2O) nanocrystals can be firmly anchored on the surface of niobate nanofibers via coherent interfaces between Ag2O and niobate phases. I− anions in fluids can easily access the Ag2O nanocrystals and be efficiently trapped by forming an AgI precipitate that firmly attaches to the adsorbent. This bi-functional absorbent can be arranged to remove Sr2+ and I− ions simultaneously by optimizing the Ag2O loading and Na+ content of the niobate nanofibers. It can provide high adsorption capacity for both ions in basic media, unlike other adsorbents that can be used in acid or neutral media. The maximum adsorption capacities of Sr2+ and I− for Ag2O anchored sodium niobate nanofibers were found to be 148.92 and 296 m2 g−1 respectively. Furthermore, the niobate adsorbents can be readily dispersed in liquids and easily separated after purification due to their fibril morphology, which significantly enhances their adsorption efficiency and reduces separation costs. This study demonstrates that Ag2O anchored sodium niobate nanofibers with fibril morphology, negatively charged thin layers and readily exchangers are potential sorbent for the simultaneous uptake of cations and anions.