Intellectual Merit: Geologic CO₂ sequestration (GCS) is considered one of the most effective and promising mitigation strategies for mitigating anthropogenic CO₂. The project aimed at providing the underpinnings for understanding long-term sustainability of geologic CO₂ sequestration strategies, with a focus on nanoscale interfacial geochemical processes. Nanoscale reactions at fluid-mineral interfaces strongly influence the mechanisms and kinetics of important environmental processes, and these reactions can also be crucial in understanding processes in GCS systems. The project provides the basis for resolving discrepancies in reaction kinetics among data on different scales (from nanoscale to macroscale), and among laboratory and field site data in geologic CO₂ injection systems. This project focused on acquiring new and more accurate information on reaction pathways and rates, including identification of critical nanoscale-mesoscale processes not previously detected. It used a range of methods matched to the scale of the reaction space in porous media: complementary aquatic geochemistry, the unique and powerful tools of in situ time-resolved synchrotron-based x-ray techniques, and atomic force microscopy. The project integrated molecular-scale fluid chemistry and solid and interfacial chemistry with macroscale geophysical aspects, and it has provided clear quantitative and qualitative information on the reactive interplay of chemical reactions of caprocks, formation rocks, and wellbore cements with injected supercritical CO₂ (scCO₂) and brine. Furthermore, the PI’s team has investigated the effects of important environmental factors—such as salinity, different cations in brine, temperature, the extent of water, and the presence of organic compounds and oxyanions—on the interactions of scCO₂, water, and caprocks and formation rocks (or wellbore cement). One of the most striking new findings is that under GCS conditions nanoscale amorphous silica can form by the dissolution of clay minerals and subsequent precipitation after only 5 hours. The reactions can also accompany the formation of fibrous illite within only several hours of reaction, which can significantly increase flow-path tortuosity, extend deep into pores, and possibly cause a large permeability reduction for a given bulk volume. Although currently some data are available, the different scales of data for geologic CO₂ injection systems have not been linked. In establishing linkages between different scales, we utilized reactive transport modeling which combines experimental and computationally-simulated data from multiple scales. The project will help us design new, secure, and sustainable CO₂ sequestration. The findings also improve the academic and public understanding of climate change and geologic CO₂ sequestration.

From this project, the PI’s team has published 17 manuscripts, submitted three papers, and will submit one paper in December 2016, for a total of 21 manuscripts. The PI’s team disseminated their research outcomes through 38 invited presentations and 39 contributed presentations at national and international conferences, universities, laboratories, and industries. Five doctoral dissertations will result from the project. Three dissertations have been published, and two will be completed by spring/summer 2017.

Over the years of this CAREER project, the PI successfully strengthened her main research expertise and established herself as a rising leader in geochemistry. The PI served as the lead guest editor of a Special Issue of Environmental Science & Technology (January 2013). This special issue provided a panorama of current research on environmental and geochemical aspects of geologic carbon sequestration. The PI was named as a 2015 Kavli Fellow by the U.S. National Academy of Sciences and a 2016 Frontier of Engineering Fellow by the U.S. National Academy of Engineering. Currently, Professor Jun serves as the American Chemical Society’s Geochemistry Division Chair and was recently elected to serve on ACS’s Committee on Science to facilitate the advance of the science of chemistry and the formulation of science policy.

Broader Impacts: By integrating recruiting, training, and outreach programs, the research and education plans reached a diverse audience and broadened the participation of underrepresented minority groups in environmental science and engineering. The project has expanded the infrastructure for research and education by developing, in collaboration with K-12 teachers, research-based educational kits and related teaching modules devoted to energy and environmental issues for local K-12 schools. It has encouraged direct involvement of high school and undergraduate students. The project has enhanced graduate education by including international collaborative research activities through the McDonnell Academy Global Energy and Environment Partnership (MAGEEP) at Washington University. Finally, it has conducted outreach activities, including public lectures and hands-on demonstrations, to increase public awareness of the energy-environment nexus and greenhouse mitigation strategies.

Since 2011, 17 participants have been involved in this project, and 10 of them were from underrepresented groups. Seven doctoral students, eight undergraduate students, and one high school student participated in this project, enhancing their career perspectives. Altogether, they have received 20 honors and awards. Our developed educational teaching modules were presented at the National Science Teachers Association (NSTA) Annual Conference.

Last Modified: 12/09/2016
Modified by: Young-Shin Jun