Zinc(II) ions under diffusive regime controls the stability of vaterite: Derivation of pore scale chemical dynamics near CaCO3 clogging interface via coupled micro-XRF/XRD/XANES and SAXS imaging.

• DOI: 10.5194/egusphere-egu24-17340
• Publication Date: 2024-03-11T09:04:59Z
• Authors: Ashish Rajyaguru; Enzo Curti; Dario Ferreira Sa...; Christian Appel; Daniel Grolimund
• Keywords: Vaterite; Small-angle X-ray scattering; Clogging; XANES

Reactive transport of solutes in porous media involving dissolution/precipitation reactions may alter the physical properties intact rocks, such as porosity and permeability. Such processes are difficult to predict characterize due heterogeneity at pore scale, caused by intimate coupling chemical processes. So far, experimental studies have mainly focused either on aspects, using short time batch or microfluidic experiments, transport, a medium classical counter diffusion cells. The former approach offers large flexibility selecting modifying parameters like pH, ionic strength, element concentrations, thereby allows systematic derivation data mineral precipitation dissolution ex-situ conditions. latter studying changes (bulk) rock under realistic (in-situ) conditions over longer times, with limited knowledge scale parameters, which vary space time. Therefore, each these methods limits full characterization evolution chemistry medium, particularly near clogging zones that form precipitation. In this study, we present methodology reactive within microscopic (1-10 um). We datasets record, 300 mm tapered glass capillaries filled silica gel, CaCO3 polymorphs has been induced via Na2CO3 CaCl2 reservoir solutions. Two systems, one containing 1 mM ZnCl2 titrant, other without Zn, were prepared evolved for three years. Optical microscopy synchrotron-based techniques (micro XRF/XRT/XRD, micro XANES SAXS) used system selected times (1, 6, 12, 24, 36 months). both experiments several calcite and/or vaterite crystal aggregates collectively reduced gel formed central part capillary. obtained Zn-free show crystals calcium rich capillary (i.e., side titrant) remain stable entire duration experiment converting more calcite. Zn-doped system, year start dissolve afterwards. carbonate ions released did not lead formation new precipitates Ca-rich Instead, zinc hydroxy phase is formed. Through first zone an extended period truly undisturbed in-situ Our results small concentrations Zn2+ water strong effect precipitation/dissolution kinetics polymorphs, well their morphology.