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Free radicals trapped in polysilazane (PSZ) induced by γ-ray irradiation in an Ar atmosphere at room temperature and their decay behaviors were investigated via electron spin resonance (ESR). The G value of the whole initial free radicals was calculated to be 1.8 radicals/100 eV. The free radicals trapped in PSZ were rather stable in Ar at room temperature, and their half-life was estimated to be 470 h according to the decay line. However, they decayed rapidly via reactions with oxygen when exposed to air, and their half-life decreased to 4 h. Interestingly, the free radicals could not be eliminated completely even though the temperature was increased up to 200 °C in an Ar atmosphere. Combing with ESR parameters calculation using DFT method, we found that Si-centered radicals were the main products of PSZ after irradiation in Ar at room temperature. Additionally, we proposed the probable conversion reactions of these radicals under different post-treatment conditions.

It is still a challenge that directly reducing the uranium concentration of wastewater or radioactive wastes by adsorption to or below the criterion (30 ppb), especially from the system of low uranium concentration due to weak affinity and bad collection. Herein we have successfully introduced hydroxypyridone (HOPO) groups onto polyethylene nonwoven fabric (PENWF) surface denoted as PENWF-HOPO by radiation graft technology and follow-up two-step chemical reactions to deeply remove uranium from low-concentration (500 ppb) aqueous solutions. The chemical structures, surface morphologies, and thermal stabilities of the original and modified PENWF were characterized in detail by FT-IR, XPS, SEM, and TGA, with the results indicating successful preparation and good thermal stability of the adsorption material used under ambient conditions. Batch adsorption results show that the adsorbent removes the uranium almost completely within 12 h in a wide pH (3–10) range, and the adsorption obeys the Langmuir isotherm. Desorption and regeneration confirms its excellent regeneration and reusability (5 cycles). Importantly, this adsorbent could efficiently remove uranium (more than 97% removal ratio) from diluted aqueous solution, in which contains a serial of competing metal ions (La3+, Cr3+, Ba2+, Mn2+, Pb2+, Ni2+, Co2+, Cu2+, Zn2+, Sr2+, Cs+) or high NaF, Na2SO4, and NaH2PO4 concentrations (40 g/L).