An in-situ Pore-Size Distribution Determination Technique Based on the Capillary Phase Separation in Liquid Phase

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We developed a technique for the determination of pore-size distribution of immersed porous solids, which may swell in liquid, as it shows in the immersed state. The capillary phase separation, or a phase separation within fine pores even at a lower concentration than the saturated concentration, was utilized in the technique. We can calculate an in-situ pore size distribution from a measured liquid-phase adsorption isotherm of a suitable solute, or a probe molecule. Through the research, the following was concluded.1.Liquid-phase adsorption isotherms of some aromatic compounds from aqueous solution onto some porous solids were measured. Nitrogen isotherms of the solids were also measured to obtain their surface areas and pore size distributions. 2.Nonporous solids which have the same chemical composition as those of porous solids were employed to obtain the amount of surface adsorption in liquid phase onto these solids. Nitrogen adsorption isotherms were also measured. 3.From the data mentioned above, pore size distributions were calculated both from liquid phase adsorption data and from nitrogen adsorption data. The two distributions agreed well to prove the validity of the present technique. 4.Some studies have been carried out to brush up this technique for the application to swelling/shrinking materials. We have found the so-called Modelless Method can find pore size characteristics reasonably even if no data of surface adsorption is available. 5.Further, suitable probe molecules were found to be cyclic alkanes, especially cyclopentane. 6.Other than aqueous systems, this technique has been proven to be effective in some systems with non-aqueous solvents.Summarizing, a technique to measure in-situ pore size distribution of porous solids in liquid, which could never been detectable by conventional methods such as nitrogen adsorption and mercury porosimetry, has been established through this research project.