Experimental study on plagioclase dissolution rates at conditions relevant to mineral carbonation of seafloor basalts

Juan Carlos de Obeso, Adedapo N. Awolayo, Michael J. Nightingale, Chunyang Tan, Benjamin M. Tutolo

Research output: Contribution to journalArticlepeer-review

4 Scopus citations

Abstract

Over the last two decades, all scenarios projected to achieve the goals of the Paris climate agreements have required negative emissions of greenhouse gases. Mineral carbonation of basalt is a promising negative emission technology for long-term storage of carbon dioxide (CO2). During mineral carbonation, dissolved CO2 is converted into solid carbonate minerals through reaction with silicate minerals. Plagioclase feldspars are the most abundant primary silicate minerals in basalts readily available for water-rock interactions. Despite numerous recent laboratory studies, the rate at which plagioclase dissolution occurs under the required conditions for large-scale carbon storage remain poorly constrained. In this study, we present new flow-through experiments quantifying the apparent dissolution rates of plagioclase in sodium chloride solutions with elevated concentrations of dissolved CO2 at temperatures between 25 °C and 125 °C and pressure of 200 bars. The mildly acidic conditions produced by carbonic acid yield apparent rates that are slower than those previously reported for plagioclase under more acidic conditions and alkaline conditions. We used these apparent rates to develop new temperature-dependent rate equations for plagioclase dissolution in solutions buffered by carbonic acid: kCa=10−9.811±0.664exp[Formula presented]∙[Formula presented]−[Formula presented] kSi=10−10.334±0.445exp[Formula presented]∙[Formula presented]−[Formula presented] where k is the rate constant (mol m−2 s−1) at any temperature (T in K), R is the universal gas constant (8.3145 KJ/mol/K)and Tr is the reference temperature (298.15 K). Utilizing the new Ca rate equation into a geochemical model, we estimated that the reaction time to achieve carbonate saturation in a closed system with high CO2 ranges from a few days to a few years depending on water-to-mineral ratios. These results could have significant implications for required monitoring on projects or achieving gigaton-scale of carbon storage and mineralization annually, where planned injection rates of million(s) of tons of CO2 per well per year could overwhelm aquifer alkalinity, lower pH, and reduce the efficiency of carbon mineralization.

Original languageEnglish (US)
Article number121348
JournalChemical Geology
Volume620
DOIs
StatePublished - Mar 20 2023

Bibliographical note

Funding Information:
This research was undertaken thanks in part to funding from the Canada First Research Excellence Fund, the Pacific Institute for Climate Solutions , and the National Science and Engineering Research Council of Canada (NSERC) under Discovery Grant RGPIN-2018-03800 . A.N.A acknowledges financial support from an NSERC Postdoctoral Fellowship. We thank Andrew Luhmann for meaningful discussions that allowed us to simplify the experimental setup and Qin Zhang for discussions that improved the quality of this manuscript. We acknowledge editorial handling by Oleg Pokrovsky as well as critical comments by Oleg Pokrovsky, D. Wolff-Boenisch and two anonymous reviewers that helped us improve the manuscript.

Publisher Copyright:
© 2023 Elsevier B.V.

Keywords

  • Basalt alteration
  • Experimental Geochemistry
  • Kinetics
  • Plagioclase

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