Direct synthesis of bacteria-derived carbonaceous nanofibers as a highly efficient material for radionuclides elimination

Bacteria-derived carbonaceous nanofibers (CNFs) can be directly synthesized by the pyrolysis of bacterial cellulose pellicles under N₂ atmosphere. The batch adsorption experiments showed that the bacteria-derived CNFs displayed the excellent adsorption performance for radionuclides. The maximum adsorption capacities of the CNFs calculated from the Langmuir model at pH 4.5 and 293 K were 67.11 mg/g for Sr(II) and 57.47 mg/g for Cs(I). The adsorption of Cs(I) and Sr(II) on the CNFs decreased with increasing ionic strength at pH < 5.0, whereas no effect of ionic strength was observed at pH > 6.0, indicating that the outer-sphere surface complexation dominated the radionuclide adsorption at pH < 5.0 whereas the adsorption was attributed to inner-sphere surface complexation at pH > 6.0. The further evidence of surface complexation modeling indicated that Sr(II) and Cs(I) adsorption on the CNFs can be satisfactorily fitted by a double diffuse layer model with an outer-sphere (SOHSr²⁺/SOHCs⁺) and an inner-sphere complexes (SOSr⁺/SOCs). The X-ray photoelectron spectroscopy analyses demonstrated that the adsorption of Sr(II) and Cs(I) on the CNFs were ascribed to the combination of the oxygenated functional groups of the CNFs. These observations indicated that the CNFs, as inexpensive and available carbon-based nanomaterials, can be regarded as a promising adsorbent for the removal of radionuclides from aqueous solutions in environmental pollution cleanup.