Understanding the dynamic pore wetting by 1H LF NMR characterization. Part 2: Effect of liquid surface tension

The first paper (Part 1) of this study fully described the effect of the dynamic viscosity of liquids on dynamic pore wetting of porous materials. The surface tension, as an important physical properties of liquids may also play a vital role in the pore wetting process. However, the quantitative characterization of dynamic pore wetting is difficult. Thus, this paper (Part 2) investigated the effect of liquid surface tension (mixture of 1-propanol and pure water in different proportions) on dynamic wetting of pores of different sizes in hydrophilic and hydrophobic active carbon by a 1H low-field nuclear magnetic resonance (1H LF NMR), and the quantitative model between surface tension and pore wetting percentage was built. The Crispation number of liquids in the pores of different sizes was calculated. For the hydrophilic samples, the wetting processes of pores of different sizes (except for mesopores) were not changed with the surface tension. For the hydrophobic sample, the liquid with lower surface tension achieved a higher pore wetting percentage and the order of pore wetting rate was: micropores > transition pores > mesoproes. The 60-min wetting percentages in pores of different sizes showed a linear decrease relationship with the surface tension. As the Crispation number increased, the 60-min wetting percentages in different pore sizes had a first-order linear increase trend. This paper not only provides a novel method for characterizing the dynamic pore wetting of porous materials, but also have a significance for regulating pore wetting process.

Automated summary

This study investigates the impact of liquid surface tension on dynamic pore wetting of porous materials through experiments and quantitative models. The results indicate that lower surface tension leads to higher pore wetting percentage in hydrophobic materials, and there is a certain pattern in the wetting processes of pores of different sizes.