三乙烯二胺改性活性炭纤维对气态甲基碘吸附研究

Adsorptive Removal of Gaseous Methyl Iodide by Triethylenediamine Modified Activated Carbon Fiber

气态甲基碘是核设施运行过程中难以处理的放射性气态产物之一。本文通过水热法制备了三乙烯二胺(TEDA)改性高比表面积粘胶基活性炭纤维材料,并开展了改性材料气态甲基碘吸附研究,通过BET、SEM-EDS、FT-IR、TGA、放射性测试方法对材料进行了表征和吸附性能分析。静态气态碘吸附结果表明,水热改性材料对单质碘吸附量提高了36%,达到1.84 g/g,甲基碘吸附量达到400 mg/g。甲基碘动态吸附实验表明,改性材料具有较高的吸附效率;随着温度和湿度的增加,吸附效率略有降低;环境湿度对气态甲基碘的吸附性能影响较大。温度30℃、相对湿度95%条件下的穿透测试表明,材料在12 h内未出现穿透,改性材料展现出优异的甲基碘吸附性能。放射性甲基碘吸附实验显示,水热改性材料吸附效率接近95%,超过未改性材料的3倍;TEDA改性活性炭纤维明显提高了对气态甲基碘的化学吸附能力。水热法TEDA改性粘胶基活性炭纤维材料表现出优异气态甲基碘吸附性能。

The rapid growth of the nuclear industry poses a great challenge for radioactive waste treatment.Volatile radioactive isotopes generated from uranium fission,especially gaseous iodine,attracted great attention due to their environment and health hazards.The widespread species of radioactive iodine are gaseous elemental iodine(I 2)and methyl iodide(CH 3I).It is difficult to trap the methyl iodide in high humid condition.Activated carbon and derivative materials are widely used as adsorbents to remove volatile iodine.Triethylenediamine(TEDA)is proposed as impregnation via isotope exchange mechanism.In this study,activated carbon fiber(ACF)with high surface area,heat resistant and chemically stable was used as substrate,TEDA-modified viscose-based activated carbon fiber was prepared by hydrothermal reaction.For fiber hydrothermal modified with 5%(mass fraction)TEDA,the surface area and pore volume decrease about 20%.Compared with conventional impregnation,more TEDA impregnation enters into the microporous structure of activated carbon fibers under hydrothermal environment.The gaseous iodine adsorption properties of modified activated carbon fiber were investigated.Static adsorption experiments of elemental iodine and methyl iodide were performed.The adsorption capacity of elemental iodine and methyl iodide increases by 36% and 50% respectively.Methyl iodide adsorption capacity of hydrothermal modified-ACF is 400 mg/g.The dynamic adsorption experiments show that the adsorption performance of modified activated carbon fiber for methyl iodine decreases with the increase of temperature and humidity.The adsorption performance of activated carbon fiber for methyl iodine is greatly affected by environmental humidity.Breakthrough experiment with 5 ppm of gaseous methyl iodide was conducted under high humid conditions(30℃,RH 95%),the feed gas flow rate was fixed at 15 L/min for 12 h.Breakthrough curve indicates that hydrothermal modified-ACF has good adsorption performance with respect to methyl iodide.The radioactive CH 3131 I adsorption experiments under severe conditions were carried out.The removal efficiency of hydrothermal modified-ACF increases from 29.11% to 94.85%.The affinity of methyl iodide is improved by TEDA-modified.The hydrothermal modified-ACF exhibits the high adsorption efficiency of gaseous iodine.