Sergi Molins

Learn More
The scale-dependence of geochemical reaction rates hinders their use in continuum scale models intended for the interpretation and prediction of chemical fate and transport in subsurface environments such as those considered for geologic sequestration of CO2. Processes that take place at the pore scale, especially those involving mass transport limitations(More)
Stable isotope fractionations of sulfur are reported for three consecutive years of acetate-enabled uranium bioremediation at the US Department of Energy's Rifle Integrated Field Research Challenge (IFRC) site. The data show a previously undocumented decrease in the time between acetate addition and the onset of sulfate reducing conditions over subsequent(More)
Understanding fracture alteration resulting from geochemical reactions is critical in predicting fluid migration in the subsurface and is relevant to multiple environmental challenges. Here, we present a novel 2.5D continuum reactive transport model that captures and predicts the spatial pattern of fracture aperture change and the development of an altered(More)
A combination of experimental, imaging, and modeling techniques were applied to investigate the pore-scale transport and surface reaction controls on calcite dissolution under elevated pCO2 conditions. The laboratory experiment consisted of the injection of a solution at 4 bar pCO2 into a capillary tube packed with crushed calcite. A high resolution(More)
New investigative tools, combined with experiments and computational methods, are being developed to build a next-generation understanding of molecular-to-pore-scale processes in fluid-rock systems and to demonstrate the ability to control critical aspects of flow and transport in porous rock media, in particular, as applied to geologic sequestration of(More)
The injection of CO2 into the Earth’s subsurface drives the fluid-rock system into “farfrom-equilibrium” conditions, which means that the fluxes that return the system to equilibrium are nonlinearly related to the generalized driving forces (e.g., chemical affinities and gradients in the fluid pressures and chemical potentials). The nonlinear response(More)
Field applications such as carbon sequestration drive the geochemistry of porous media far from equilibrium in relatively short time scales. In these short time frames, feedback processes between flow and geochemical reactions (e.g., mineral dissolution-precipitation) that take place at the pore scale are key to understanding the discrepancy between(More)
In this study of reductive chromium immobilization, we found that flow-through columns constructed with homogenized aquifer sediment and continuously infused with lactate, chromate, and various native electron acceptors diverged to have very different Cr(VI)-reducing biogeochemical regimes characterized by either denitrifying or fermentative conditions (as(More)
A novel reactive transport model has been developed to examine the processes that affect fracture evolution in a carbonate-rich shale. An in situ synchrotron X-ray microtomography experiment, flowing CO2 saturated water through a single fracture mini-core of Niobrara Shale provided the experimental observations for the development and testing of the model.(More)
Hexavalent chromium, Cr(VI), is a widespread and toxic groundwater contaminant. Reductive immobilization to Cr(III) is a treatment option, but its success depends on the long-term potential for reduced chromium precipitates to remain immobilized under oxidizing conditions. In this unique long-term study, aquifer sediments subjected to reductive Cr(VI)(More)