  Freezing in charged porous media can induce significant pressure and cause
damage to tissues and functional materials. We formulate a thermodynamically
consistent theory to model freezing phenomena inside charged heterogeneous
porous space. Two regimes are distinguished: free ions in open pore space lead
to negligible effects of freezing point depression and pressure. On the other
hand, if nano-fluidic salt trapping happens, subsequent ice formation is
suppressed due to the high concentration of ions in the electrolyte. In this
case, our theory predicts that freezing starts at a significantly lower
temperature compared to pure water. In 1D, as the temperature goes even lower,
ice continuously grows, until the salt concentration reaches saturation, all
ions precipitate to form salt crystals, and freezing completes. Enormous
pressure can be generated if initial salt concentration is high before salt
entrapment. We show modifications to the classical nucleation theory, due to
the trapped salt ions. Interestingly, although the freezing process is
enormously changed by trapped salts, our analysis shows that the Gibbs-Thompson
equation on confined melting point shift is not affected by the presence of the
electrolyte.
