Adsorption characteristic of moisture by precipitated silica including kinetics and thermodynamics analysis

doi:10.16085/j.issn.1000-6613.2017.05.032

Abstract

Abstract: Precipitated silica is an important adsorption material. The ability of moisture adsorption of precipitated silica was tested under different temperatures (15℃,20℃,25℃ and 30℃) and various relative humidities (RH=11%,33%,43%,75%,85% and 98%). And the dynamics of moisture adsorption was analyzed. The isothermal adsorption heat of precipitated silica was calculated based on the principle of thermodynamics of porous media isothermal adsorption. The adsorption mechanism was analyzed by XRD,SEM,FTIR,and pore structure. The results showed that the precipitated silica had excellent performance on the moisture adsorption. The moisture content reached 23.71% under the condition of 30℃ and 98%RH after 48 hours. Precipitated silica performed better under lower temperatures and higher relative humidities when the relative humidity was between 11% and 85%,while moisture adsorption ability increased with the rise of temperature when the relative humidity was 98%. The adsorption reaction was consistent with the pseudo second order kinetics equation. It could be concluded that the moisture adsorption isotherms is S type physical adsorption of condensable vapor in porous material,and Van der Waals force and hydrogen bond are the main forces.

Key words: precipitated silica, moisture adsorption, kinetics, thermodynamics

摘要： 白炭黑是一种重要的吸附材料，以沉淀白炭黑为原料，研究了沉淀白炭黑在温度为15℃、20℃、25℃和30℃，相对湿度为11%、33%、43%、75%、85%和98%条件下的吸湿性能，并进行吸湿动力学分析。利用多孔介质等温吸附热力学原理，计算沉淀白炭黑的等温吸附热。结合XRD、SEM、FTIR和氮吸附法分析沉淀白炭黑的吸湿机理。结果表明：沉淀白炭黑具有良好的吸湿性能，在温度为30℃、相对湿度为98%时48h吸湿量达到23.71%。相对湿度在11%~85%范围内，温度越低、相对湿度越高，沉淀白炭黑的吸湿性能越强；相对湿度为98%时，温度越高，沉淀白炭黑的吸湿性能越强。沉淀白炭黑的吸湿动力学符合准二级动力学模型。等温吸湿曲线符合典型的可冷凝蒸汽在孔隙物质中物理吸附的S型曲线，水分子与沉淀白炭黑之间的作用力主要为范德华力和氢键作用。

关键词: 沉淀白炭黑, 吸湿, 动力学, 热力学

CLC Number:

TB321

HU Zhibo, ZHENG Shuilin, CHEN Yang, LIU Yangyu, SUN Zhiming. Adsorption characteristic of moisture by precipitated silica including kinetics and thermodynamics analysis[J]. Chemical Industry and Engineering Progress, 2017, 36(05): 1818-1824.

胡志波, 郑水林, 陈洋, 刘阳钰, 孙志明. 沉淀白炭黑吸湿特性及动力学、热力学分析[J]. 化工进展, 2017, 36(05): 1818-1824.

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