Olivine Dissolution Kinetics Research Articles

Aqueous carbonation of peridotites for carbon utilisation: a critical review.

Peridotite and serpentinites can be used to sequester CO2 emissions through mineral carbonation. Olivine dissolution rate is directly proportional with temperature, presence of CO2, surface area of mineral particles and presence of ligands and is inversely proportional to pH. Olivine dissolution is better under air flow and increases seven times when rock-inhibiting fungus (Knufia petricola) is used. Olivine dissolution retards as silica layers form during reaction. Sonication, acoustic and concurrent grinding using various grinding medias have been used to artificially break these silica layers and achieve high magnesium extraction. Wet grinding using 50 wt.% ethanol enhanced CO2 uptake of dunite 6.9 times and CO2 uptake of harzburgite by 4.5 times. The best economical process is single-stage concurrent grinding at 130 bar, 185 °C, 15 wt.% solids and 50 wt.% grinding media (zirconia) using 0.64 M NaHCO3. Ratio of grinding media to feed should not be less than 3:1. Yield increases with temperature, pressure, time of reaction, pH and rpm and using additives and grinding media and reducing particle size. This review aims to investigate the progress from 1970s to 2021 on aqueous mineral carbonation of olivine and its naturally available rocks (harzburgite and dunite). This paper comprehensively reviews all aspects of olivine carbonation including olivine dissolution kinetics, effects of grinding and concurrent grinding, thermal activation of olivine feedstock (dunites and harzburgites) as well as chemistry of olivine mineral carbonation. The effects of different reaction parameters on the carbonation yield, role of mineral carbonation accelerators and costs of mineral carbonation process are discussed.

Dynamics of coupled olivine dissolution and serpentine precipitation revealed by hydrothermal flow-through experiments at 260 °C–300 °C

Serpentinization is an important process that influences rock rheology, global fluid circulation, and microbiological activity in the deep sea, and is induced by hydrothermal fluid flow. Elemental olivine dissolution and serpentine precipitation govern the overall dynamics of serpentinization, and its prediction and modeling require an understanding of the reaction mechanism including the rate-limiting process. In this study, we examined the initial stage of coupled olivine dissolution and serpentine precipitation at 260 °C–300 °C and 50 MPa using a hydrothermal flow-through experimental apparatus. Saline water (0.5 m NaCl) was continuously injected into olivine powder at a constant flow rate (3.3 × 10−5 L s−1). Petrologic observation of solid products after experimental runs revealed that serpentine is produced from olivine. The hydration flux of serpentinization in this experiment is similar to estimates made using closed-system experiments, indicating that fluid flow does not affect the hydration rate at the flow rates adopted. Moreover, mass-balance calculations based on outlet fluid compositions during experiments suggest that both the overall serpentine precipitation and olivine dissolution rates decrease over time, and the serpentine precipitation rate is lower than the olivine dissolution rate during serpentinization. Although a comparison of speciated solutions observed in this experiment with results obtained by kinetic reaction modeling did not constrain the relationship between serpentine precipitation and olivine dissolution, a comparison with other experimental data and kinetic modeling results indicates that serpentine precipitation occurs more slowly than olivine dissolution at 170 °C. These results suggest that the relationship between serpentine precipitation and olivine dissolution kinetics varies with temperature and time, with such dynamic behavior governing serpentinization processes in the oceanic crust.

Whole rock basalt alteration from CO2-rich brine during flow-through experiments at 150 °C and 150 bar

Four flow-through experiments at 150°C were conducted on intact cores of basalt to assess alteration and mass transfer during reaction with CO2-rich fluid. Two experiments used a flow rate of 0.1ml/min, and two used a flow rate of 0.01ml/min. Permeability increased for both experiments at the higher flow rate, but decreased for the lower flow rate experiments. The experimental fluid (initial pH of 3.3) became enriched in Si, Mg, and Fe upon passing through the cores, primarily from olivine and titanomagnetite dissolution and possibly pyroxene dissolution. Secondary minerals enriched in Al and Si were present on post-experimental cores, and an Fe2O3-rich phase was identified on the downstream ends of the cores from the experiments at the lower flow rate. While we could not specifically identify if siderite (FeCO3) was present in the post-experimental basalt cores, siderite was generally saturated or supersaturated in outlet fluid samples, suggesting a thermodynamic drive for Fe carbonation from basalt-H2O-CO2 reaction. Reaction path models that employ dissolution kinetics of olivine, labradorite, and enstatite also suggest siderite formation at low pH. Furthermore, fluid-rock interaction caused a relatively high mobility of the alkali metals; up to 29% and 99% of the K and Cs present in the core, respectively, were preferentially dissolved from the cores, likely due to fractional crystallization effects that made alkali metals highly accessible. Together, these datasets illustrate changes in chemical parameters that arise due to fluid-basalt interaction in relatively low pH environments with elevated CO2.

Effect of the heterotrophic bacterium Pseudomonas reactans on olivine dissolution kinetics and implications for CO2 storage in basalts

This work is aimed at quantification of forsteritic olivine (Fo92) dissolution kinetics in batch and mixed-flow reactors in the presence of aerobic gram-negative bacteria (Pseudomonas reactans HK 31.3) isolated from an instrumented well located within a basaltic aquifer in Iceland. The release rate of mineral constituents was measured as a function of time in the presence of live and dead cells in constant-pH (4–9), bicarbonate-buffered (0.001–0.05M), nutrient-rich and nutrient-free media in batch reactors at 0–30atm of CO2 partial pressure (pCO2). In batch reactors at 30atm pCO2, 0.1M NaCl and 0.05M NaHCO3 the rates were weakly affected by the presence of bacteria. In nutrient media, the SEM observation of reacted grains revealed the presence of biofilm-like surface coverage that does not modify Mg and Si release rate at the earlier stages of reaction but significantly decreased the dissolution after prolonged exposure.Olivine dissolution rates measured in flow-through reactors are not affected by the presence of dead and live bacteria at pH ⩾9 in 0.01M NaHCO3 solutions. In circumneutral, CO2-free solutions at pH close to 6, both live and dead bacteria increase the dissolution rate, probably due to surface complexation of exudates and lysis products. In most studied conditions, the dissolution was stoichiometric with respect to Mg and Si release and no formation of secondary phases was evidenced by microscopic examination of post-reacted grains. Obtained results are consistent with known molecular mechanism of olivine dissolution and its surface chemistry. Overall, this work demonstrates negligible effect of P. reactans on olivine reactivity under conditions of CO2 storage in the wide range of aqueous fluid composition.

Dissolution of olivine in the presence of oxalate, citrate, and CO 2 at 90 °C and 120 °C

In this article, we report the results from a study of olivine dissolution kinetics under operating conditions suitable for ex situ aqueous mineral carbonation for CO 2 storage. We studied the effect of oxalate and citrate ions on the dissolution of gem-quality San Carlos olivine (Mg 1.82Fe 0.18SiO 4). Flow-through experiments were performed at 90 °C and 120 °C, at f CO 2 between 4 and 81 bar, with a solution containing either sodium oxalate or sodium citrate in a molality range between 10 −3 and 10 −1. The pH was varied between 2 and 7 by adding HCl, LiOH, and adjusting f CO 2 . At all investigated temperatures and for pH values in a broad range, both sodium oxalate and sodium citrate increased dissolution rate with the strongest effect up to one order of magnitude in presence of 0.1 m of oxalate, at 120 °C, and above pH 5. The enhancement effect was primarily ascribed to the oxalate or citrate ions that are the dominant species in this pH range. The overall dissolution process was described using the population balance equation (PBE) coupled with a mass balance equation to account for the evolution of the particle size distribution (PSD) of olivine. Far from equilibrium conditions for dissolution were established in all the experiments in order to achieve a surface-reaction controlled mechanism. We described the reaction with a surface complexation model, which assumes adsorption of a proton and of an oxalate (citrate) ions (proton and oxalate) on adjacent sites in order to enhance dissolution, and we derived a dissolution rate equation in presence of oxalate: r = r ⁎ 1 + K H a H n 1 + β K X a X 1 + K X a X , where r ⁎ is the specific dissolution rate commonly used in absence of organic compounds, and K H , K X , and β are thermodynamic and kinetic parameters. The values of these parameters have been estimated from the experimental data and the agreement between the model results and the experiments is very good.

The effect of [formula omitted] and salinity on olivine dissolution kinetics at [formula omitted

This paper reports the results of an experimental study on the dissolution kinetics of olivine ( Mg 1.82 Fe 0.18 SiO 4 ) at operating conditions relevant to the mineral carbonation process for the permanent storage of CO 2 . In particular, we investigated the effects of CO 2 fugacity ( f CO 2 ) and of salinity on the kinetics of olivine dissolution, which is assumed to be the rate-limiting step of the overall carbonation process. Dissolution experiments were carried out at 120 ∘ C in a stirred flow-through reactor. Different pH values (between 3 and 8) and solution compositions were investigated by varying f CO 2 and by dosing LiOH (for pH control), NaCl, and NaNO 3 . The specific dissolution rate values, r, were estimated from the experimental data using a population balance equation (PBE) model coupled with a mass balance equation. The logarithms of the obtained r values were regressed with a linear model as a function of pH and compared to the model reported earlier [Hänchen, M., Krevor, S., Mazzotti, M., Lackner, K.S., 2007. Validation of a population balance model for olivine dissolution. Chem. Eng. Sci. 62, 6412–6422] for experiments with neither CO 2 nor salts. Our results confirm that, at a given temperature, olivine dissolution kinetics depends on pH only, and that f CO 2 and the concentrations of NaCl and NaNO 3 affect it through their effect on pH.

Analysis of the effect of temperature, pH, CO2 pressure and salinity on the olivine dissolution kinetics

Abstract The dissolution kinetics of olivine has been extensively studied under several temperatures, CO2 pressures, and solution compositions. Dissolution is an important mechanism in the aqueous mineral carbonation process. The overall carbonation reaction consists of dissolution of mineral silicate, e.g. olivine, serpentine and wollastonite, followed by carbonate precipitation, thus fixing CO2 into naturally occurring stable solids, such as magnesite and calcite. The slowness of the dissolution kinetics hinders the overall carbonation reaction and in order to make the process technically and economically feasible, such a reaction should be sped up by finding the optimum operating conditions. Experiments were performed in a flow-through reactor at 90–120–150 ∘C. The pH was adjusted by adding either acids (e.g., HCl, citric acid) or LiOH, and by changing PCO2. The salinity was changed by adding NaCl and NaNO3. From the experimental data, the dissolution rate was estimated by using the population balance equation (PBE) model coupled with a mass balance, and the obtained values were regressed with a linear model log ( r ) = − n p H − B , where r is the specific dissolution rate (mol s−1 cm−2).

Mineral carbonation process for CO2 sequestration

Abstract The most promising route for mineral carbonation is the aqueous process using naturally occurring silicate minerals. The overall carbonation reaction consists of the dissolution of MgO- or CaO-bearing silicates such as olivine, serpentine, and wollastonite, followed by the precipitation of carbonates such as magnesite and calcite. In this paper, we report the experiments to investigate both the dissolution and the precipitation processes, separately. Olivine dissolution kinetics has been studied under several temperature and CO2 pressure, and by varying the solution composition. The experiments were performed in a flow-through reactor at 90–120–150 ∘C. The pH was adjusted using either acids (e.g., HCl, citric acid) or LiOH, and by changing the CO2 pressure while the salinity was varied by adding NaCl and NaNO3. To estimate the dissolution rate for each experiment, a population balance equation (PBE) model coupled with a mass balance was applied. The obtained values were regressed over a pH range from 2 to 8, using a linear model of the form log ( r ) = − n p H − B , where r is the specific dissolution rate (mol cm−2 s−1). The experiments to study the kinetics of magnesite precipitation were performed in batch using the H2O–CO2–Na2CO3–MgCl2 system at 90, 120, and 150 ∘C and at 100 bar of CO2 pressure. The solution composition and solid phases were monitored with insitu Raman spectroscopy. At the conditions applied, we observed two mechanisms: direct precipitation of magnesite and simultaneous precipitation of magnesite and hydromagnesite followed by the transformation of the latter into the former.

Kinetic model of olivine dissolution and extent of aqueous alteration on mars

If water was ever present on Mars, as suggested by geomorphological features, then much of the surface and subsurface may have experienced chemical weathering. Among those materials most readily altered is olivine, which has been identified on the Martian surface with IR spectroscopy and Mossbauer techniques and occurs in Martian meteorites. We use geochemical models of olivine dissolution kinetics to constrain the residence time of olivine on the surface of Mars in the presence of liquid water. From these models, we have calculated maximum dissolution rates and minimum residence times for olivine as a function of temperature, pH, Fe-composition, and particle size. In general, the most favorable conditions for olivine dissolution are fayalite-rich compositions, small particle sizes, high temperatures, and acidic solutions that are far from equilibrium. The least favorable conditions for olivine dissolution are forsterite-rich compositions, large particle sizes, ultra-low temperatures, and a neutral pH solution near equilibrium. By using kinetic models of olivine dissolution to bound dissolution rates and residence times, we can make inferences about the temporal extent of aqueous alteration on the surface of Mars. Under favorable conditions (pH 2, 5 °C, and far from equilibrium) a relatively large 0.1 cm (radius) particle of Fo 65 composition can completely dissolve in 370 years. Particles may last 10 2–10 4 times longer under less favorable conditions. However, residence times of a few million years or less are small compared to the age of most of the Martian surface. The survival of olivine on the surface of Mars, especially in older terrains, implies that contact with aqueous solutions has been limited and wet periods on Mars have been short-lived.

Oriented precipitate complexes in iron-rich olivines produced experimentally in aqueous oxidizing environment

Iron-rich olivines (Fa100∼Fa70Fo30) experimentally altered in alkaline and acidic aqueous oxidizing environment were examined in transmission electron microscope to determine the precipitate phases and their crystallographic relationships to the host. The planar zones consist of precipitates of laihunite and hematite in alkaline aqueous oxidizing environment while hematite and amorphous silica in acidic aqueous oxidizing environment. The directions of planar zones produced in alkaline aqueous oxidizing environment are parallel to (100)∼(001) of olivine dependent on the composition of the host olivines, while those produced in acidic aqueous oxidizing environment are always parallel to (001) of olivine independent from the composition of the host olivine. These differences are interpreted by the dissolution kinetics of olivine.

Olivine dissolution kinetics at near-surface conditions

Fluidized bed dissolution experiments have been conducted as a function of pH at 25°C with fayalitic olivine (Fo 6) in HCl solutions and with forsteritic olivine (Fo 91) in solutions containing the organic ligand potassium hydrogen phthalate (KHP). At 25°C the dissolution rate ( R) of fayalite as a function of pH is: R(mol cm −2s −))=1.1·10 −10a H+ 0.69 +3.2·10 −14+1.2·10 −16a H+ −0.31 where a H + is the activity of H + in solution. The dissolution rate at 25°C of Fo 6 at a given pH is a factor of 6 greater than that of forsteritic olivine. The assumption that the rates increase on a molar basis with Fe content allows calculation of dissolution rates of Fe-Mg solid solution olivines of intermediate compositions. Batch-type dissolution experiments were completed with Fo 91 at 65°C in solutions at pH 1.8, 6.0 and 9.8. The rate equation obtained from these experiments is: R (mol cm −2s −1)=3.5·10 −10a H+ 0.5+1.0·10 −13a H + 0.5 When combined with previously published data for Fo 91 at 25°C, the 65°C experiments indicate that the activation energy of the olivine dissolution reaction in acidic, organic-free solutions is ∼19 ± 2.5 kcal. mol −1. Dissolution experiments with forsteritic olivine in solutions containing KHP at 25°C demonstrate that the rate of dissolution is increased in these solutions relative to rates measured in KHP-absent HCl-H 2O solutions. Apparently, the increase in rate is caused by Mg complexation at the olivine surface. Ligand-promoted dissolution is thought to occur in parallel with proton-promoted dissolution. Therefore, the net rate, R net , is the sum of the two rates: R net (mol cm −2s −1)=0.8·10 −12[L P] 0.45+R H + where [ L P] denotes the concentration of KHP; and R H + denotes the proton-promoted dissolution rate.