Physicochemical Problems of Mineral Processing, 39 (2005), 47-65 Fizykochemiczne Problemy Mineralurgii, 39 (2005), 47-65 Trong Dang-Vu * , Jan HUPKA ∗ CHARACTERIZATION OF POROUS MATERIALS BY CAPILLARY RISE METHOD Received March 15, 2005; reviewed; accepted May 15, 2005 Capillary rise method is widely used for contact angle determination using Washburn equation. Penetration kinetics of porous media comprised from particles of varying size distribution was investigated. It was found that the penetration kinetics and the validation of Washburn’s theory depend not only on the particle size but also on the pore size distribution. The effect of particle size on contact angles was not observed. In case of bed consisting of wide size distribution particles, the smallest fraction plays a significant role creating the smallest capillaries and allowing for more even porous bed penetration. This increases precision of contact angle measurement. A difference of time between fluid flow through a porous bed and its complete saturation (∆t sf ) was proposed as a new parameter describing capillary size distribution in porous media. It allows for fast estimation of both capillary size distribution in a porous bed and precision of contact angle determination. Key words: capillary rise, penetration kinetics, Washburn’s equation, porous media. INTRODUCTION Capillary rise is a fundamental phenomenon existing in many natural processes and human activities [1]. Knowledge of capillarity laws is important in chemical, metallurgy, and ceramic industry, in oil recovery and civil engineering, in dyeing of textile fabrics, ink printing, and a variety of other fields. This explains the continuous interest in the subject from the side of industry and fundamental science. Experimental method based on capillary rise is widely used for porous media characterization (i.e. pore radius, contact angle, free surface energy). Among them measurement of height penetration and mass gain of wetting liquids in time are most commonly employed. In both approaches Washburn’s equation is a basic instrument for analysis of obtained results. For along time of using this equation, many modifications have been applied and although critics, Washburn’s equation presents useful model for evaluation of porous media observed in industrial practice. ∗ Department of Chemical Technology, Gdansk University of Technology, 80-952 Gdansk, Poland, jhupka@chem.pg.gda.pl