复合氧化改性活性炭的物性及其对甲苯的吸附性能

Characteristics of activated carbon modified by composite oxidation and its adsorption capacity for toluene

利用4种化学试剂(HNO3溶液、NH3溶液、H2O2溶液与Fe(NO3)3溶液)对商业活性炭进行化学氧化改性。在含5%氧气和95%氮气的混合气体中,对改性活性炭进行热复合氧化改性。采用热重分析仪、孔隙分析仪、傅里叶红外分析(FTIR)与Boehm滴定对活性炭结构与表面基团进行测试,并利用改性活性炭对甲苯进行等温吸附实验。研究结果表明:强氧化剂预处理活性炭有助于热复合氧化改性中活性炭微孔孔容的增大;活性炭表面含氧基团由化学氧化改性和热复合氧化改性共同作用产生,热改性温度较低时,其主要由化学氧化改性生成,温度较高时,酸性基团主要来源于氧气与活性炭表面的氧化反应;酸性基团的存在能够促进活性炭吸附甲苯;控制合理的热复合氧化改性条件,既可以增加活性炭表面酸性基团,又可扩充微孔孔容,从而综合提升活性炭对甲苯的吸附能力。

A commercial activated carbon was modified using four different aqueous solutions（HNO3, NH3, H2O2, and Fe（NO3）3）. Then, the treated adsorbents were further oxidized with 5% oxygen and 95% nitrogen. The chemical and physical properties of the modified samples were characterized by thermogravimetry（TG）, surface area analysis, Fourier transform infrared spectroscopy, and Boehm titration. The adsorption capacity of the prepared adsorbents for toluene was evaluated on a fix bed reactor. The results show that the micro-pore volume of the samples pre-modified by the strong oxidant can be increased as the composite oxidation modification. The oxygen groups existing on the activated carbon surface are produced by both chemical oxidation modification and thermal oxidation modification. At low temperatures, most oxygen groups are generated from chemical oxidation modification, while reactions between oxygen and activated carbon result in most oxygen groups at high temperatures. The acidic groups promote toluene adsorption on activated carbon. Through controlling modification conditions, the toluene adsorption capacity can be advanced, since multiple modification methods can expand the micropore volume of activated carbon and increase the amount of acidic group on its surface.