The effects of void geometry and contact angle on the absorption of liquids into porous calcium carbonate structures

The absorption (permeation) of alcohols into porous blocks of calcium carbo nate has been studied experimentally and with a computer model, The experim ental measurement was of change in apparent weight of a block with time aft er contact with liquid. The modeling used the previously developed 'Pore-Co r' model, based on unit cells of 1000 cubic pores connected by cylindrical throats. To gain some insight into absorption into voids of complex geometr y, and to provide a representation of heterogeneities in surface interactio n energy, the cylindrical throats were converted to double cones. Relative to cylinders, such geometries caused hold-ups of the percolation of nonwett ing fluids with respect to increasing applied pressure, and a change in the rate of absorption of wetting fluids. Both the measured absorption of the alcohols and the simulated absorption of the alcohols and of water showed s ignificant deviations from that predicted by an effective hydraulic radius approximation. The simulation demonstrated the development of a highly hete rogeneous wetting front, and of preferred wetting pathways that were pertur bed by inertial retardation. The findings are useful in the design of high- performance, low-waste pigments for paper coatings, and environmentally fri endly printing inks, as well as in wider industrial, environmental, and geo logical contexts. (C) 2001 academic Press.