Composite Nanoarchitectonics: Alginate Beads Encapsulating Sepiolite/Magnetite/Prussian Blue for Removal of Cesium Ions from Water

Multicomponent sepiolite/magnetite/Prussian blue (PB) were prepared following the nanoarchitectonics approach by incorporating PB pigment to sepiolite fibers previously assembled with magnetite, being later encapsulated within in situ formed calcium alginate beads. These composites were characterized by diverse physicochemical techniques, showing homogeneous dispersion of the assembled nanoparticles (NP) on the surface of sepiolite fibers, the formed Ca-alginate beads exhibiting stability and superparamagnetic response. Based on the affinity of PB toward cesium ions, these beads were tested as selective adsorbent to remove Cs+ from water under different experimental conditions. The maximum adsorption capacity of the beads for Cs+ ions determined by Langmuir equation was around 130 mg/g. The resulting beads maintain a constant adsorption capacity over a large domain of pH, i.e. from 4 to 11. The mechanism of Cs+ removal could be mainly ascribed to the complexing ability of PB, although in minor extent also to cation-exchange properties of sepiolite as well as to interactions with residual carboxylic groups from the alginate biopolymer matrix. The resulting multicomponent composite can be considered as an efficient, economic, ecologic and easily recoverable adsorbent for the removal of Cs+ ions from solution, including radioactive 137Cs, and therefore contributing to environmental remediation of pollution caused in nuclear plants.