Feldspar dissolution at 25 degrees C and low pH

Brantley, Susan L.; Stillings, Lisa L.

doi:10.2475/ajs.296.2.101

Cited by 102 publications

(52 citation statements)

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“…doi: 10.1016/j.gca.2010.04.012 1984; Velbel, 1990;Brantley, 1992;Blum and Stillings, 1995;Drever and Clow, 1995). These hypotheses include the possible armoring effects of the secondary minerals that coat the feldspar grain surfaces (Correns and Von Engelhardt, 1938;Correns, 1940;Helgeson, 1971Helgeson, , 1972Luce et al, 1972;Paces, 1973;Busenberg and Clemency, 1976;Chou and Wollast, 1984;Nugent et al, 1998), the possible effects of the leached layer (Luce et al, 1972;Busenberg and Clemency, 1976;Chou and Wollast, 1984;Hellmann et al, 1990;Brantley and Stillings, 1996;Hellmann, 1997;Nesbitt and Skinner, 2001;Oelkers, 2001), the approach to saturation with respect to feldspars (Burch et al, 1993;Gautier et al, 1994;Oelkers et al, 1994;Oelkers, 2001;Beig and Lü ttge, 2006;Hellmann and Tisserand, 2006), unknown biological effects, and inhibition by adsorbed Al 3+ on feldspar surfaces (Chou and Wollast, 1985;Gautier et al, 1994;Oelkers et al, 1994;Oelkers, 2001).…”

Section: Introductionmentioning

confidence: 99%

Coupled alkali feldspar dissolution and secondary mineral precipitation in batch systems: 4. Numerical modeling of kinetic reaction paths

Zhu

Lü

Zheng

et al. 2010

Geochimica et Cosmochimica Acta

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This paper explores how dissolution and precipitation reactions are coupled in batch reactor experimental systems at elevated temperatures. This is the fourth paper in our series of "Coupled Alkali Feldspar Dissolution and Secondary Mineral Precipitation in Batch Systems". In our third paper, we demonstrated via speciation-solubility modeling that partial equilibrium between secondary minerals and aqueous solutions was not attained in feldspar hydrolysis batch reactors at 90-300°C and that a strong coupling between dissolution and precipitation reactions follows as a consequence of the slower precipitation of secondary minerals ). Here, we develop this concept further by using numerical reaction path models to elucidate how the dissolution and precipitation reactions are coupled. Modeling results show that a quasi-steady state was reached. At the quasi-steady state, dissolution reactions proceeded at rates that are orders of magnitude slower than the rates measured at far from equilibrium. The quasi-steady state is determined by the relative rate constants, and strongly influenced by the function of Gibbs free energy of reaction (DG r ) in the rate laws.To explore the potential effects of fluid flow rates on the coupling of reactions, we extrapolate a batch system (Ganor et al., 2007) to open systems and simulated one-dimensional reactive mass transport for oligoclase dissolution and kaolinite precipitation in homogeneous porous media. Different steady states were achieved at different locations along the one-dimensional domain. The time-space distribution and saturation indices (SI) at the steady states were a function of flow rates for a given kinetic model. Regardless of the differences in SI, the ratio between oligoclase dissolution rates and kaolinite precipitation rates remained 1.626, as in the batch system case (Ganor et al., 2007). Therefore, our simulation results demonstrated coupling among dissolution, precipitation, and flow rates.Results reported in this communication lend support to our hypothesis that slow secondary mineral precipitation explains part of the well-known apparent discrepancy between lab measured and field estimated feldspar dissolution rates (Zhu et al., 2004). Here we show how the slow secondary mineral precipitation provides a regulator to explain why the systems are held close to equilibrium and show how the most often-quoted "near equilibrium" explanation for an apparent field-lab discrepancy can work quantitatively. The substantiated hypothesis now offers the promise of reconciling part of the apparent fieldlab discrepancy.

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Section: Introductionmentioning

confidence: 99%

Coupled alkali feldspar dissolution and secondary mineral precipitation in batch systems: 4. Numerical modeling of kinetic reaction paths

Zhu

Lü

Zheng

et al. 2010

Geochimica et Cosmochimica Acta

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“…According to this solution-precipitation hypothesis, reprecipitation reactions occur well below solubility limits for secondary phases. In either case, the hydrolysis of bridging oxygens generally reduces the connectedness of network atoms before the atom is released into solution (Hellmann et al 1990;Brantley and Stillings 1997;Hamilton et al 2001;Tsomaia et al 2003). A distribution of tetrahedral or Q i sites (where i= 4, 3, 2, or 1 bridging oxygen) must characterize the gel layer regardless of whether it forms by solution-precipitation or by leaching.…”

Section: Determination Of Reaction Mechanismsmentioning

confidence: 99%

Nuclear Energy Advanced Modeling and Simulation (NEAMS) Waste Integrated Performance and Safety Codes (IPSC) : FY10 development and integration.

Criscenti¹,

Sassani²,

Argüello³

et al. 2011

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This report describes the progress in fiscal year 2010 in developing the Waste Integrated Performance and Safety Codes (IPSC) in support of the U.S. Department of Energy (DOE) Office of Nuclear Energy Advanced Modeling and Simulation (NEAMS) Campaign. The goal of the Waste IPSC is to develop an integrated suite of computational modeling and simulation capabilities to quantitatively assess the long-term performance of waste forms in the engineered and geologic environments of a radioactive waste storage or disposal system. The Waste IPSC will provide this simulation capability (1) for a range of disposal concepts, waste form types, engineered repository designs, and geologic settings, (2) for a range of time scales and distances, (3) with appropriate consideration of the inherent uncertainties, and (4) in accordance with robust verification, validation, and software quality requirements.Waste IPSC activities in fiscal year 2010 focused on specifying a challenge problem to demonstrate proof of concept, developing a verification and validation plan, and performing an initial gap analyses to identify candidate codes and tools to support the development and integration of the Waste IPSC. The current Waste IPSC strategy is to acquire and integrate the necessary Waste IPSC capabilities wherever feasible, and develop only those capabilities that cannot be acquired or suitably integrated, verified, or validated. This year-end progress report documents the FY10 status of acquisition, development, and integration of thermal-hydrologicchemical-mechanical (THCM) code capabilities, frameworks, and enabling tools and infrastructure.iv ACKNOWLEDGEMENTS

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“…(2)式からも明らかなように，DG r は系が平衡のときゼロとなり，過飽和では正，未飽和では負の値を示す。いずれの場合も，平衡から離れるに従い DG r の絶対値が大きくなる。これまでにも多くの研究により，長石の溶解速度に対する，pH や温度 (Chou and Wollast, 1985;Holdren, Jr. and Speyer, 1985a;Knauss and Wolery, 1986;Hellmann, 1994;1995;Chen and Brantley, 1997;Welch and Ullman, 2000)，反応表面積 Speyer, 1985b, 1987;Hodson, 2006)，各種溶液組成 (Amrhein and Suarez, 1988;Stillings and Brantley, 1995;Blake and Walter, 1999)，あるいはこれらの組み合わせ (Oelkers and Schott, 1995;Brantley and Stillings, 1996;Welch and Ullman, 1996;Stillings et al, 1996) …”

Section: Co 2 地中貯留における灰長石溶解プロセスの速度論的考察unclassified