多孔介质中有效孔扩散系数的试验测量

提出了通过实时测量扩散过程中多孔介质浮重变化,直接测定有效扩散系数的方法.首先建立了联系有效扩散系数和试件浮重变化的数学模型,并求出了该模型的解析解;利用非线性超定方程组优化求解的方法,结合问题的解析解和实测数据,反求出模型中的参数,有效扩散系数和边界层传质系数.用上述参数预测的试件浮重变化与实测浮重变化相差很小.表明该方法的实用性和可靠性.

酸改性活性炭对甲苯、甲醇的吸附性能

分别用1mol.L-1硝酸、1mol.L-1盐酸、1mol.L-1硫酸对商业活性炭进行浸渍改性。采用比表面积及孔径分析仪、Boehm滴定、傅里叶转换红外光谱(FTIR)对活性炭的物化性质进行表征。以甲苯、甲醇为吸附质,在283K下进行了固定床吸附实验。研究表明:酸改性能去除表面碱性基团,显著增加表面酸性含氧官能团的含量;酸改性活性炭的吸附量与其比表面积、总孔容、微孔孔容、表面总酸性官能团呈现出良好的线性关系;Langmuir方程比Freundlich方程更加适合描述甲苯、甲醇在活性炭上的吸附;甲醇在活性炭上为物理吸附,甲苯在活性炭上以物理吸附为主,与表面官能团之间的化学键作用能增强甲苯吸附量;甲苯、甲醇在活性炭上的微孔有效扩散系数的大小顺序为:AC-N>AC-1>AC-S>AC-C;并且甲醇的微孔有效扩散系数大于甲苯。

THEORETICAL EFFECTS OF MOLECULAR DIMENSION AND CONFIGURATION ON EFFECTIVE DIFFUSION COEFFICIENT OF MACROMOLECULES IN MICROPOROUS MEMBRANES

This paper presents a theoretical method for predicting the effective diffusion coefficient of macromolecules in the microporous membrfines in view of the effects of molecular dimension and configuration. On the basis of the hindered diffusion theory of spherical neutral macromolecules in a micropore of a long cylinder, the effects of molecular dimension and configuration are studied by defining two molecular dimensions:the mean projected radius to predict the concentration partition and the ' hydrodynamically equivalent sphere' radius to evaluate the hydrodynamic reverse drag force. The quantitative comparison shows that the effective diffusion coefficients for different macromolecules predicted by the present method are more consistent with the available published experimental data.