Removal of cesium and strontium for radioactive wastewater by Prussian blue nanorods

In this work, novel Prussian blue tetragonal nanorods were prepared by template-free solvothermal methods to remove radionuclide Cs and Sr. The as-prepared Prussian blue nanorods were identified and characterized by scanning electron microscopy, transmission electron microscope, Fourier transform infrared spectroscopic, thermogravimetric analysis, zeta potential, and surface analysis, and its sorption performance was tested by batch experiments. Our results suggest that Prussian blue nanorods exhibited better adsorption performance than co-precipitation PB or Prussian blue analogue composites. Thermodynamic analysis implied that the adsorption process was spontaneous and endothermic which was described well with the Langmuir isotherm and pseudo-second-order equation. The maximum adsorption capacity of PB nanorod was estimated to be 194.26 mg g^-1 and 256.62 mg g^-1 for Cs⁺ and Sr²⁺(adsorbate concentration at 500 mg L^-1, the temperature at 298 k, pH at 7.0). Moreover, the experimental results showed that the Prussian blue nanorods have high crystallinity, few crystal defects, and good stability under alkaline conditions. The adsorption mechanism of Cs⁺ and Sr²⁺ was studied by X-ray photoelectron spectroscopy, X-ray diffraction, and ⁵⁷Fe Mössbauer spectroscopy. The results revealed that Cs⁺ entered the PB crystal to generate a new phase, and most of Sr²⁺ was trapped in the internal crystal and the other exchanged Fe²⁺. Furthermore, the effect of co-existing ions and pH on PB adsorption process was also investigated. The results suggest that PB nanorods were an outstanding candidate for removing Cs⁺ and Sr²⁺ from radioactive wastewater.