Correlating pore size and surface chemistry during absorption into a dispersed calcium carbonate network structure

The mechanism of liquid absorption into coating pigment structures has been previously investigated (Gane et al. 2000), where it was shown that, despite the presence of big pores, associated with highly porous paper surfaces, liquid is absorbed observably slower than when fine pores are also present, despite an often lower porosity and permeability associated with the finer pores. This cannot be explained using the Washburn equation (Washburn 1921) alone but requires the inclusion of a pore differentiating mechanism (Gane et al. 2000), (Schoelkopf et al. 2000a). This can be achieved in different ways, one of which is by including inertial wetting terms (Bosanquet 1923). The effect of pore differentiation is that at short time-scales within the network structure, the finer pores dictate the initial absorption rate and the overall absorption capillarity. By comparing the rate of absorption over time for liquids of differing surface tension, it is possible to determine any effective potential surface chemistry differences between the fine pores and the larger pores within the network structure. In this study, the absorption dynamics of water and hexadecane into compressed samples of dispersed fine ground calcium carbonates are investigated. The absorption dynamic of pure liquids at both short and longer time-scale, water (polar) and hexadecane (non-polar) in this instance, differentiates the surface chemistry properties of the pigments as well as illustrating the impact of pore structure on the rate of absorption.