Accelerated Carbonation of Brucite in Mine Tailings for Carbon Sequestration

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• 作者：Anna L. Harrison ; Ian M. Power ; Gregory M. Dipple
• 刊名：Environmental Science & Technology (ES&T)
• 出版年：2013
• 出版时间：January 2, 2013
• 年：2013
• 卷：47
• 期：1
• 页码：126-134
• 全文大小：467K
• 年卷期：v.47,no.1(January 2, 2013)
• ISSN：1520-5851

文摘

Atmospheric CO₂ is sequestered within ultramafic mine tailings via carbonation of Mg-bearing minerals. The rate of carbon sequestration at some mine sites appears to be limited by the rate of CO₂ supply. If carbonation of bulk tailings were accelerated, large mines may have the capacity to sequester millions of tonnes of CO₂ annually, offsetting mine emissions. The effect of supplying elevated partial pressures of CO₂ (pCO₂) at 1 atm total pressure, on the carbonation rate of brucite [Mg(OH)₂], a tailings mineral, was investigated experimentally with conditions emulating those at Mount Keith Nickel Mine (MKM), Western Australia. Brucite was carbonated to form nesquehonite [MgCO₃路3H₂O] at a rate that increased linearly with pCO₂. Geochemical modeling indicated that HCO₃^{鈥?/sup> promoted dissolution accelerated brucite carbonation. Isotopic and aqueous chemistry data indicated that equilibrium between CO₂ in the gas and aqueous phases was not attained during carbonation, yet nesquehonite precipitation occurred at equilibrium. This implies CO₂ uptake into solution remains rate-limiting for brucite carbonation at elevated pCO₂, providing potential for further acceleration. Accelerated brucite carbonation at MKM offers the potential to offset annual mine emissions by 22鈥?7%. Recognition of mechanisms for brucite carbonation will guide ongoing work to accelerate Mg-silicate carbonation in tailings.}