(425d) 3D Printing of Reactive Porous Media: Impact of Surface Functionalization on Mineral Growth Kinetics

There is a growing need to reduce the level of carbon dioxide (CO₂) in the atmosphere as the increasing atmospheric CO₂ has led to increases in global temperatures and other climate change impacts. Geological carbon sequestration aims to store captured CO₂ in deep geological formations. Therefore, understanding the rates and mechanisms of geochemical reactions is vital in these subsurface systems when exposed to CO2 is critical. As natural samples are heterogeneous and non-duplicative, we investigate methods for fabricating synthetic replicates of reactive rock samples using 3D printing to assess the impact of mineral dissolution and precipitation on porosity and permeability. X-ray Micro CT images of natural samples was used to generate 3D models for fused filament fabrication 3D printing of high impact polystyrene. Surface functionalization was applied to sulfonate the 3D printed surfaces, where the sulphonic acid moieties will subsequently seed calcite growth. FTIR spectroscopy was employed to confirm the surface presence of sulfonic acid groups. Precipitation of calcite crystals on 2D reactive HIPS films was evaluated gravimetrically, by X-ray Micro-CT and by XRD analysis. Weight based precipitation experiments show gradual increase in the calcite deposition on the 2D films over time. To analyze the effect of surface functionalization, the 2D films were surface functionalized over time and calcite deposition flow experiments were performed and confirmed that increase in surface functionalization facilitates improved deposition of calcite on 2D films. This approach is extended to 3D printed core samples and batch experiment showed internal precipitation of calcite as confirmed by XRD. Overall, this study helps to evaluate the reactive rock sample replicate’s mineral reaction and precipitation within the porous structures using 3D printing, mimicking geochemical reactions from geochemical systems, and facilitating the understanding of geological reactions caused by CO₂ storage in sub-surface systems.