Mercury penetration method: pore characterization

The evaluation of the commercial potential of ceramic porous membranes requires improved characterization of the membrane microstructure and a better understanding of the relationship between the microstructural characteristics of the membranes and the mechanisms of separation. To this end, a combination of characterization techniques should be used to obtain the best possible assessment of the pore structure and provide an input for the development of reliable models predicting the optimum conditions for maximum permeability and selectivity. The most established methods of obtaining structural information are based on the interaction of the porous material with fluids, in the static mode (vapor sorption, mercury penetration) or the dynamic mode (fluid flow measurements through the porous membrane). 

Mercury porosimetry is a method currently used to characterize the texture of porous materials. It enables determining pore volume, specific surface area and also distributions of pore volume and surface area versus pore size. It can be applied to powders, as weU as to monolithic porous materials. The basic hypothesis usually accepted is that mercury penetrates into narrower and narrower cavities or pores as pressure increases. Data analysis is performed using the intrusion equation proposed by Washburn (1921) ... 

Mercury porosimetry is featured in many of the contributions to this volume. Indeed, it is now one of the most popular methods available for the characterization of a wide range of porous materials and the derived pore sizes are often quoted in the patent and technical literature. The method is based on the non-wetting nature of mercury and the application of the Washburn equation. The volume of mercury penetrating into a porous solid is determined as a function of the applied pressure, which is assumed to be directly related to the pore width. 

Physico-chemical techniques are widely used for characterization of catalysts and porous materials in general. Well-known methods based on physical adsorption of inert gases (N2 and CO2) and penetration of mercury at elevated pressures provide information on the total surface area, pore volume, and pore size distribution (PSD) of the sample [1,2]. Gas adsorption and mercury porosimetry are often compared since they generate data of similar nature in the pore size range 4 - 100 nm. 

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