Sr(II) coordination chemistry and precipitation under confinement

Understanding the factors that control nucleation and growth of solid phases in porous media, and how they differ from the bulk, is of fundamental importance given the large reactive surface areas of nanopores in subsurface and soil environments. Previous studies have shown that fluids in nanopores can hold higher supersaturations than bulk fluids, due to the existence of a so-called ‘crystallization pressure’ which is inversely proportional to the size of the nanopore. Moreover, coordination chemistry of confined complexes differs from that of bulk solutions, with some ions adopting different symmetries, which has an impact on nucleation and growth processes. Here, we aim to further explore these effects by (i) determining the symmetry of Sr(II) ions and neutral SrSO40 ion-pair species adsorbed in silica gel nanopores, and (ii) by performing SrSO4 precipitation experiments in mesoporous silica gels and following the changes in short-range order using Sr K-edge EXAFS experiments.