Pore-Scale Analysis of Calcium Carbonate Precipitation and Dissolution Kinetics in a Microfluidic Device

• Published in: Environmental science & technology Vol. 53; no. 24; pp. 14233 - 14242
• Main Authors: Yoon, Hongkyu, Chojnicki, Kirsten N, Martinez, Mario J
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 17-12-2019; American Chemical Society (ACS)
• Subjects: Calcium; Calcium Carbonate; Chemical Precipitation; Computational fluid dynamics; Confocal microscopy; Dissolution; Dynamic structural analysis; Effective precipitation; Evolution; Fluid dynamics; Fluid flow; Fluid mechanics; GEOSCIENCES; Hydrodynamics; Image analysis; Image processing; Inlets; Kinetics; Lab-On-A-Chip Devices; Microfluidic devices; Microfluidics; Minerals; Organic chemistry; Plumes; Precipitates; Reaction kinetics; Solubility; Temporal variations
• DOI: 10.1021/acs.est.9b01634
• EISSN: 1520-5851
• ISSN: 0013-936X

In this work, we have characterized the calcium carbonate (CaCO3) precipitates over time caused by reaction-driven precipitation and dissolution in a micromodel. Reactive solutions were continuously injected through two separate inlets, resulting in transverse-mixing induced precipitation during the precipitation phase. Subsequently, a dissolution phase was conducted by injecting clean water (pH = 4). The evolution of precipitates was imaged in two and three dimensions (2-, 3-D) at selected times using optical and confocal microscopy. With estimated reactive surface area, effective precipitation and dissolution rates can be quantitatively compared to results in the previous works. Our comparison indicates that we can evaluate the spatial and temporal variations of effective reactive areas more mechanistically in the microfluidic system only with the knowledge of local hydrodynamics, polymorphs, and comprehensive image analysis. Our analysis clearly highlights the feedback mechanisms between reactions and hydrodynamics. Pore-scale modeling results during the dissolution phase were used to account for experimental observations of dissolved CaCO3 plumes with dissolution of the unstable phase of CaCO3. Mineral precipitation and dissolution induce complex dynamic pore structures, thereby impacting pore-scale fluid dynamics. Pore-scale analysis of the evolution of precipitates can reveal the significance of chemical and pore structural controls on reaction and fluid migration.