Hydro-adsorption and Textural Properties Study of Microporous Zeolites by Dynamic Laser Speckle Technique

Adsorption phenomena have various technological applications such as desiccants, catalysts and gas separation. Its uses depend on the textural properties of the solid adsorbent and the type of liquid or gas adsorbed. Therefore, it is important to find simple tools to measure these properties. The most common measurement methods are physicochemical based on N2 adsorption to determine the specific surface area and pore size distribution. However, these methods have certain limitations for microporous materials.

This chapter shows the use of the Dynamic Laser Speckle (DLS) technique to measure and compare the hydro-adsorption capacity of a microporous natural zeolite and its acidic, basic and calcinated forms. According to the water adsorption process of the samples, the DLS experimental results show the temporal evolution of the speckle patterns. The optical results obtained from the speckle patterns are adjusted using an improved Peleg´s equation. This new approach by the adsorption of water from solids allows a correlation with its specific surface areas where parameters obtained from DLS results are calibrated with those calculated by different conventional isotherms using the N2 adsorption-desorption method.