Analytical Expressions for Thermo‐Osmotic Permeability of Clays.

Abstract: In this study, a new formulation for the thermo‐osmotic permeability of natural pore solutions containing monovalent and divalent cations is proposed. The mathematical formulation proposed here is based on the theoretical framework supporting thermo‐osmosis which relies on water structure alteration in the pore space of surface‐charged materials caused by solid‐fluid electrochemical interactions. The ionic content balancing the surface charge of clay minerals causes a disruption in the hydrogen bond network when more structured water is present at the clay surface. Analytical expressions based on our heuristic model are proposed and compared to the available data for NaCl solutions. It is shown that the introduction of divalent cations reduces the thermo‐osmotic permeability by one third compared to the monovalent case. The analytical expressions provided here can be used to advantage for safety calculations in deep underground nuclear waste repositories. [ABSTRACT FROM AUTHOR]