title: X-ray-driven reaction front dynamics at calcite-water interfaces.
abstract: The interface between minerals and aqueous solutions hosts globally important biogeochemical processes such as the growth and dissolution of carbonate minerals. Understanding such processes requires spatially and temporally resolved observations and experimental controls that precisely manipulate the interfacial thermodynamic state. Using the intense radiation fields of a focused synchrotron x-ray beam, we drove dissolution at the calcite/water interface and simultaneously probed the dynamics of the propagating reaction fronts using surface x-ray microscopy. Evolving surface structures were controlled by the time-dependent solution composition, as characterized by a kinetic reaction model. At extreme disequilibria, we observed the onset of reaction front instabilities with velocities of > 30 nanometers per second. These instabilities serve as a signature of transport-limited dissolution of calcite under extreme disequilibrium.
authors.affiliation: Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, IL, USA. Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, USA. laanaitn@ornl.gov fenter@anl.gov.
authors.forename: Nouamane
authors.initials: N
authors.lastname: Laanait
authors.affiliation: Department of Earth and Environmental Sciences, University of Illinois at Chicago, Chicago, IL, USA.
authors.forename: Erika B R
authors.initials: EB
authors.lastname: Callagon
authors.affiliation: X-ray Science Division, Argonne National Laboratory, Argonne, IL, USA.
authors.forename: Zhan
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: Department of Geological Sciences, University of Delaware, Newark, DE, USA.
authors.forename: Neil C
authors.initials: NC
authors.lastname: Sturchio
authors.affiliation: Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, IL, USA.
authors.forename: Sang Soo
authors.initials: SS
authors.lastname: Lee
authors.affiliation: Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, IL, USA. laanaitn@ornl.gov fenter@anl.gov.
authors.forename: Paul
authors.initials: P
authors.lastname: Fenter