不同种类金属离子改性椰壳活性炭吸附分离CO2/CH4的研究

摘要

Different kinds of metal ions, including alkali metal (K), alkaline-earth metals (Ca and Mg) and heavy metals (Fe, Cu and Ag), were utilized to modify the coconut shell activated carbon (AC).The physical and chemical characteristics of raw AC and metal ions modified AC were analyzed, and their performance for adsorption and separation of CO2/CH4 mixing gas was compared.The results showed that the specific surface area, total pore volume and micropore volume of the metal ions modified AC were decreased, whereas the mesopore volume was increased.The main functional groups of the raw AC and the modified AC were almost the same.The crystal phase structure of the samples changed little except the one modified by Ag+ showing diffraction peak of Ag.The adsorbed amount of CO2 on the metal ions modified AC was increased, which was closely related to the increasing surface polarity resulted from the loaded metal.However, the adsorbed amount of CH4 on these modified AC was lower than that on the raw AC.The separating effect of CO2/CH4 mixture gas on the modified AC, especially the K+ modified AC, was superior to that on the unmodified one.The performance CO2 adsorption capacity and CO2/CH4 separation effect followed the order of:alkali metal modified AC>alkaline-earth metals modified AC> heavy metals modified AC.%分别用碱金属 (K) 、碱土金属 (Ca、Mg) 和重金属 (Fe、Cu、Ag) 对椰壳活性炭 (AC) 进行改性, 对改性前后AC的理化性质及其对CO2/CH4的吸附分离效果进行了综合对比分析.结果表明, 经金属离子改性后AC的比表面积、总孔体积和微孔体积下降, 中孔体积变大;AC改性前后主要官能团基本相同, 除Ag+改性AC中出现了Ag的衍射峰外, 其余的物相结构基本没有改变.经金属离子改性后, AC对CO2的吸附量增大, 这与负载的金属增加了AC的表面极性密切相关;而对CH4的吸附则大体低于原AC.改性AC对CO2/CH4混合气的分离效果均优于原AC, 其中以K+改性效果最优.金属离子改性AC对CO2吸附能力和对CO2/CH4混合气分离效果的优劣程度大体为:碱金属改性AC>碱土金属改性AC>重金属改性AC.