氧化硅纳米多孔材料表面的水蒸气吸附动力学研究

Experimental Study on Kinetics of Water-Vapor Sorption on Surface of Silica Nano-Porous Materials

采用称重法对氧化硅纳米多孔材料在温湿环境中的水蒸气吸附规律进行了实验研究.在25℃分别测定了不同孔隙率的材料在水蒸气相对蒸汽压为0.3～0.9范围内的吸附动力学曲线.分别采用不同的多层吸附等温式对材料的吸附等温线进行拟合,提出了一种双指数衰减动力学吸附模型方程,并和准一/二级动力学吸附模型一起对实验结果进行了拟合.结果表明:Redlich-Peterson、Fritz-Schlünder吸附等温式和BET多层吸附模型的拟合相关系数较大;BET多层吸附模型的拟合参数可给出单层饱和吸附量和吸附层数,吸附等温线由单层到多层存在临界点,具有明显的物理意义;氧化硅纳米多孔材料对湿空气中水蒸气的动态吸附过程可由双指数衰减模型来描述,与实验数据的相关系数在0.99以上,在整个吸附过程中均与实验数据拟合良好.

The thermal gravimetrical method was adopted to measure the water-vapor sorption of silica nano-porous materials in the thermal and moisture environment. The water-vapor sorption kinetics was experimentally investigated at environmental temperature 25 ℃ and different relative pressure of vapor from 0. 3 to 0. 9. The sorption equilibrium data were fitted with different equations. An exponential decay-2 model was proposed based on the experimental data and was compared with the pseudo-first-order and the pseudo-second-order equations. The results show that the correlation coefficients of the Redlich-Peterson equation, the Fritz-Sehliinder equation and the BET finite layer equation are higher than those of the other models the BET model is more reasonable because it can present the monolayer saturation sorption capacity and the sorption layer number, and the sorption equilibrium curve of materials exists an inflection point from monolayer sorption to multilayer sorption. In addition, the kinetics of water-vapor sorption on the surface of silica nano-porous materials can be described by the decay-2 model with correlation coefficients above 0.99, and the decay-2 model fits well with the experimental values in the whole sorption process.