Plasma-Facilitated Synthesis of Amidoxime/Carbon Nanofiber Hybrids for Effective Enrichment of ~(238)U(VI) and ~(241)Am(III)

摘要

Plasma- and chemical-grafted amidoxime/carbon nanofiber hybrids (p-AO/ CNFs and c-AO/CNFs) were utilized to remove ~(238)U(VI) and ~(241)Am(III) from aqueous solutions, seawater, and groundwater. Characteristic results indicated more nitrogen-containing groups in p-AO/CNFs compared to c-AO/CNFs. The maximum adsorption capacities of p-AO/CNFs at pH 3.5 and T = 293 K (588.24 mg of ~(238)U(Vl)/g and 40.79 mg of ~(241)Am(in)/g from aqueous solutions, respectively) were significantly higher than those of c-AO/CNFs (263.18 and 22.77 mg/g for ~(238)U(VI) and ~(241)Am(III), respectively), which indicated that plasma-grafting was a highly effective, low-cost, and environmentally friendly method. Adsorption of ~(238)U(VI) on AO/CNFs from aqueous solutions was significantly higher than that of ~(238)U(VI) from seawater and groundwater; moreover, AO/CNFs displayed the highest effective selectivity for ~(238)U(VI) compared to the other radionuclides. Adsorption of U(VI) onto AO/CNFs created inner-sphere complexes (e.g., U—C shells) as shown by X-ray absorption fine structure analysis, which was supported by surface complexation modeling. Three inner-sphere complexes gave excellent fits to pH-edge and isothermal adsorption of ~(238)U(VI) on the AO/CNFs. These observations are crucial for the utilization of plasma-grafted, AO-based composites in the preconcentration and immobilization of lanthanides and actinides in environmental remediation.