Dr. Jenna Poonoosamy

Biography

Jenna Poonoosamy is a physico-chemist and radiochemist and Head of the Reactive Transport Team at Forschungszentrum Jülich (IFN-2). Her research focuses on coupled hydro-geochemical processes in porous media, with particular emphasis on water-mineral interactions controlling the mobility of contaminants and radionuclides in the subsurface.
She studied Molecular Physical Chemistry at Université Paris-Saclay / ENS Paris-Saclay and holds a joint master’s degree in Nuclear Energy with a specialization in radiochemistry. She carried out her PhD research at the Paul Scherrer Institut and obtained her doctoral degree in Earth Sciences from the University of Bern in 2016. Her work is relevant to nuclear waste disposal, CO₂ sequestration, hydrogen storage, and geothermal systems. She received an ERC Starting Grant in 2022 for the project GENIES and the 2024 Nuclear Chemistry Division Award of the German Chemical Society (GDCh).

Introduction of the Lecture

Mineralization on the surface of growing gas bubbles: Coupling Reactive Transport , Gas Exsolution and Interfacial Instability

Coupled mineral dissolution and precipitation with gas exsolution are relevant subsurface processes occurring during CO2 sequestration, hydrogen storage, and radioactive waste disposal. While gas exsolution during mineral dissolution has been studied, its interaction with concurrent mineral precipitation remains unclear. In this work, we use a microfluidic reactor with real-time optical and 3D Raman imaging to study witherite dissolution in sulfate-rich acidic solutions, leading to barite precipitation and CO2 exsolution. “Cauliflower-like” structures are observed, in which barite encrusts gas bubbles, forming mineral-coated structures, a phenomenon that can be explained by the electric double layer of gas bubbles that causes local increase in saturation with respect to barite, favoring precipitation. Raman imaging reveals water droplets, cloud-like dispersions, trapped inside the mineral-encrusted bubbles. In addition to the cauliflower-like structures that trap gas bubbles, we identified conditions under which the system transitions to a multiphase flow regime, i.e., gas transport along with the liquid flow. Geochemical modeling shows that such processes are heavily coupled with the exsolution of CO2 and controlled by the acidity. The cauliflower-like structures only occur when the precipitation rate is faster than dissolution – a competition between the rate of gas production from witherite dissolution and the barite growth rate. Focused ion beam – scanning electron microscopy (FIB-SEM) was used to resolve the three-dimensional morphologies and intrinsic porosities of the mineral-encrusted bubbles. Analysis of these structures suggests that barite mineralization on growing bubbles may be governed by a Mullins-Sekerka instability but that the inherent diffusivity and crystal growth rate causes the system to deviate from Mullins-Sekerka. These cauliflower-like structures can reduce mineral dissolution, potentially slowing down the corrosion of waste canisters, but also impeding CO2 storage and hydrogen recovery by clogging pore spaces.