HR: 1340h
AN: B33A-1015    [Abstracts]
TI: Predicting Serpentine Dissolution Rates: Implications for Mineral Sequestration of CO2
AU: * Thom, J G
EM: jthom@eos.ubc.ca
AF: Department of Earth and Ocean Sciences - University of British Columbia, 6339 Stores Road, Vancouver, BC V6T1Z4 Canada
AU: Dipple, G
EM: gdipple@eos.ubc.ca
AF: Department of Earth and Ocean Sciences - University of British Columbia, 6339 Stores Road, Vancouver, BC V6T1Z4 Canada
AB: Weathering of silicate minerals is one of the major processes controlling the long-term sink of atmospheric CO₂ in the natural global carbon cycle. Silicate mineral weathering in mine tailing environments or in CO₂ injected ultramafic aquifers can also play a significant role in strategies for mitigating the atmospheric accumulation of CO₂, however, on much shorter time-scales. The interaction of groundwater with mine tailings or injected CO₂ with deep aquifers containing Mg and Ca-rich silicates may result in the formation of secondary carbonate minerals. In-situ carbonate mineral precipitation within Mg and Ca-rich mine tailings represents a previously unrecognized and potentially significant CO₂ sink. To determine the significance of this CO₂ sink, dissolution experiments of serpentine group minerals were assessed for their Mg flux (the apparent rate limiting step in this accelerated form of mineral sequestration). Steady-state Mg and Si flux from chrysotile over a range of pH in the temperature range of 20C to 25C were determined experimentally using a single pass continuously stirred tank reactor with a time frame for observing the steady state condition of between 10 to 20 days. Steady state magnesium flux from chrysotile (mol_Mg/m²/s) behaves linearly between pH 2 and 8 F_Mg = -0.3pH - 9.5 This linear behavior is in agreement with previous pH static (7 to 8) batch experiments. This empirical rate law combined with the experimentally determined activation energy, 70 kJ mol^-1 (Thomassin et al., 1977) allows simulation of CO₂ sequestration in mine tailing environments and serpentine hosted aquifer injection systems.
DE: 1009 Geochemical modeling (3610, 8410)
DE: 1012 Reactions and phase equilibria (3612, 8412)
DE: 1030 Geochemical cycles (0330)
DE: 1039 Alteration and weathering processes (3617)
DE: 1886 Weathering (0790, 1625)
SC: Biogeosciences [B]
MN: Fall Meeting 2005