几种不同吸附氡性能活性炭的孔结构表征

Characterization of Pore Structure of Several Activated Carbons With Different Radon Adsorption Capabilities

在氡室内测定了4种椰壳基活性炭样品对氡的动态吸附系数,发现不同活性炭对氡的吸附能力有较大差别。为了分析活性炭降氡性能与孔结构的关系,采用氮吸附方法测定了4种样品在77.3K时对氮的吸附等温线,并计算了孔的比表面积、孔体积、平均孔径和孔径分布孔等参数。结果表明,比表面积为800m2/g时活性炭对氡有较强的吸附能力,比表面积相近时,微孔部分所占的百分比越高对氡的吸附能力越强。采用不同的理论方法对4种样品的孔径分布进行了表征。H-K方法计算的微孔分布表明微孔分布以超微孔为主,BJH方法的结果表明吸附氡性能较好的活性炭在中孔部分呈多峰分布,DFT全孔分布计算结果表明,微孔尺寸分布在0.7～2nm之间,中孔范围也有显著的多峰分布,但在孔径尺寸上与BJH方法得到的结果略有不同。

The radon dynamic adsorption coefficients（DAC） of four types of activated carbons measured in radon room are different from each other.The pore structures（specific surface area,pore size distribution,pore volume,etc.） influence the adsorption ability significantly.Physical adsorption of inert nitrogen was used for evaluation pore structures of those four activated carbon samples.The results show that activated carbon with specific surface area about 800 m2/g has the strong adsorption ability to radon and when the specific surface areas are close,the adsorption ability to radon increases with the micropore specific surface＇s percentage.Pore size distribution（PSD） was calculated by H-K,BJH and density function theory（DFT）.The micropore size distribution calculated by H-K method shows that pore with size between 0.7-2 nm plays the most important role for adsorption of radon.Mesopore size distribution calculated by BJH method and DFT method shows that mesopore distribution with discrete peaks is more useful to help radon adsorption on activated carbons.