Moisture retention and drying kinetics in inhibitor-treated coal particles: the role of bidirectional salt migration

This study investigates the coupled transport of water and inhibitors under thermal gradients during the absorption and drying processes in porous coal particles treated with inhibitor solutions. A custom-built experimental system precisely controlled temperature (30–70 °C) and humidity (50–95% RH) while measuring the spatiotemporal evolution of moisture content and ion concentration. The results indicate that inhibitors enhance moisture uptake by up to 9.25 times, with kinetics strongly influenced by cation type, concentration, and temperature. During absorption, capillary forces induce distinct downward ion migration, leading to enrichment in the middle layers. Conversely, during drying, dissolved ions retard moisture loss by reducing surface tension. The downward movement of the evaporation front drives a reverse (upward) ion transport, resulting in surface crystallization and subsequent pore clogging. These findings provide fundamental insight into the interfacial transport mechanisms governing water-salt dynamics in porous media under thermal gradients.