Behavior of Aqueous Electrolytes in Steam Cycles - The Final Report on the Solubility and Volatility of copper(I) and Copper(II) Oxides

Measurements were completed on the solubility of cupric and cuprous oxides in liquid water and steam at controlled pH conditions from 25 to 400 C (77 to 752 F). The results of this study have been combined with those reported from this laboratory in two previous EPRI reports to provide a complete description of the solubility of these oxides and the speciation of copper dissolved in liquid water and steam as a function of oxidation state, temperature, pH, and in the case of steam, pressure. These constitute the first set of reliable data for cuprous oxide solubility over this range of conditions. For the more intensively studied CuO case, agreement was found between our results and those of previous studies of its solubility in steam, whereas only partial agreement was evident for its solubility in liquid water. For both oxides this disagreement often amounted to orders of magnitude. The solubility of cuprous oxide is somewhat lower than that of CuO at ambient conditions, except as very high pH. However, by 350 C (662 F), Cu{sub 2}O is the more soluble phase. At 100 C (212 F) and above, the logarithm of the solubility of both phases decreases linearly with increasing pH to a minimum value then sharply increases linearly with pH. In other words, above 100 C the solubility of both oxides become highly pH dependent. In fact at constant pH during startup, very high copper concentrations can be reached in the boiler water, more than an order of magnitude above those at ambient or operating temperatures. The enhancing effect of added ammonia on the solubility of both oxides is most significant at low temperatures and is much greater for cuprous oxide. Consequently, the mobility of copper is affected significantly under AVT startup conditions. The oxidation of copper metal and presumably cuprous oxide by addition of air-saturated makeup water can lead to much higher copper concentrations than equilibrium with cupric oxide would allow, but the presence of both copper metal and cuprous oxide provides an effective scavenger for oxygen, even at room temperature, with copper levels consistent with those in equilibrium with cuprous oxide. The solubilities of Cu{sub 2}O and CuO in steam are quite similar and are virtually temperature independent at the 1 to 2 ppb level, respectively, although at supercritical conditions, both solubilities increase with increasing pressure and temperature. The species that partition to the vapor are believed to be the neutrally charged molecules, Cu(OH){sup 0} and Cu(OH){sub 2}{sup 0}, for the reduced and oxidized forms, respectively, and their concentrations in the vapor are therefore independent of the pH of the liquid water phase from which they originate

Modélisation expérimentale de la précipitation des minéraux carbonatés lors de l'activité bactérienne

TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

Co2 Mineralization in Mafic Rocks: From Laboratory Experiments to Pilot Sites

To date, one of the safest long-term CO2 storage solutions is through carbon mineralization in mafic (or ultramafic) rocks containing high proportions of Mg, Ca, and Fe, which can react with dissolved CO2 to form carbonate-bearing minerals, ensuring its stability over time. The challenges still to be faced by this approach include i) the scalability to a worldwide scenario; ii) the adaptability to local geological contexts; and iii) the standardization of its application at industrial levels. A number of experimental and theoretical studies have been carried out to face these challenges, especially in relation to high temperature scenarios, but few have developed to date a consistent experimental procedure able to determine the in situ carbon mineralization potential in low-temperature geological settings that would, if effective, enhance industrial confidence in CCS/CCUS technologies, and possibly in its future applications. Within this context, we provide an overview of the experimental studies that have been conducted over the last 20 years, with an emphasis on the ongoing research aimed at improving the knowledge of the conditions and elementary processes that control the sequestration potential of mafic and ultramafic reservoirs. The results of these studies should direct the advancement of experimental and analytical protocols and will help the development and successful application of future CCUS actions

The aqueous chemistry of aluminum: A new approach to high temperature solubility measurements

The solubility of boehmite, AlO(OH), has been measured as a function of pH (2 - 10, depending on ionic strength), temperature (100 - 250&deg;C) and ionic strength (0.03 - 1 molal, NaCl) in a hydrogen-electrode concentration cell, HECC, which provided in situ measurement of hydrogen ion molality. Samples of the solution were withdrawn after the pH reading stabilized for analysis of total aluminum content by ion chromatography. Acidic or basic titrant could then be metered into the cell to affect a change in the pH of the solution. The direction of approach to the equilibrium saturated state could be readily varied to ensure that the system was reversible thermodynamically. This represents our second application of direct pH measurement to high temperature solubility studies. The results at low ionic strength are compared with those from two recently-reported high-temperature studies of boehmite solubility, which relied on the conventional batch technique. Comparisons are also made with the low temperature (<90&deg;C) hydrolysis constants for aluminum garnered from solubility measurements with gibbsite as the stable phase. Based on these preliminary results, it is possible to draw some general conclusions concerning the relative importance of the aluminum species in solution and to reduce significantly the number of experiments needed to define this complex system in a thermodynamic sense

A systematic study of altered basalt reactivity as a function of the degree of alteration

The subsurface carbonation of basaltic rocks may be a favorable carbon storage option in a number of parts of the world. One great advantage of subsurface carbonation is that it provides safe, long-term storage with no risk of CO2 leakage back to the surface. In addition, subsurface mineral carbonation could be applied in areas where more conventional storage, such as in saline aquifers, is not possible. Examples include large flood basalt provinces, and the oceanic crust.This study is motivated to assess the carbonation potential of altered basaltic rocks, which are far more common than fresh basalts. Towards this goal, dissolution experiments were performed in batch reactors at 27 °C and element release rates were measured on a suite of altered basalts ranging from young surface basalt to basalts hydrothermally altered to the epidote facies. Our results suggest that altered basalts dissolve 0.5 to 2 orders of magnitude slower than basaltic glass and fresh crystalline basalt. Ca and Mg were preferentially released both at the beginning of the reaction and at steady state. Results suggest that altered basalts are suitable for subsurface carbonation but targeting reservoirs having temperatures of ~100 °C or greater would compensate for their slower reactivity compared to fresh basalts

Experimental Modeling of Carbonate Mineral Precipitation in the Presence of Cyanobacteria

International audienceCarbonate mineral precipitation in the presence of cyanobacteria is at the forefront of scientific research due to its importance for understanding paleo-environments of mineral formation and for optimizing conditions of mineralogical CO2 sequestration via biological pathway. Stromatolites are amongst the oldest known biological formations, and they provide insight into early Earth environments and climates. It is therefore essential to understand the processes governing their formation. Numerous field studies were carried out to characterize these bio-formed rocks and their way of formation showing that various parameters could be involved in the processes of formation of carbonate rocks. Thus, reproducing natural environments under laboratory-controlled conditions is an efficient approach to better understand the role of each parameter. The present chapter aims to present some results of these laboratory studies on the biomineralization of Ca, Ca-Mg and Mg carbonates, via analyzing and discussing mechanisms of mineral formation, providing examples of several case studies, assessing, based on available information, the stoichiometry of inorganic carbon removal in the form of carbonate minerals and organic carbon sequestered in the form of bacterial biomass, and finally recommending future research directions in this actively developing field of science

Experimental approach of CO2 biomineralization in deep saline aquifers

International audienceWe describe an experimental system including monitoring of temperature, pressure, pH, oxidation reduction potential and optical density at 600 nm, designed for studying the role of microorganisms on the geological sequestration Of CO2 and its transformation into solid carbonate phases. Measurements were performed in an artificial ground water (AGW) supplemented with urea (2 g.l(-1)) and equilibrated at controlled temperatures with a gaseous phase before bacterial inoculation. We used the ureolytic strain Bacillus pasteurii as a model carbonate precipitating bacteria and showed that it can successfully promote strong pH increases by ureolysis in the AGW equilibrated with CO2 pressures of up to I bar. Increasing salinities (5.8,13.5 and 35.0 g.l(-1)) have a positive effect on the rate of pH increase, whereas the effect of increasing temperatures (30,35 and 38 degrees C) is less important. Calcium is also shown to have a specific positive influence on the rate of ureolysis. The number of viable cells present in solution decreases greatly during the carbonate precipitation event but the population partially recovers once precipitation is over

Magnesium isotope fractionation during hydrous magnesium carbonate precipitation with and without cyanobacteria

The hydrous magnesium carbonates, nesquehonite (MgCO3·3H2O) and dypingite (Mg5(CO3)4(OH)2·5(H2O)), were precipitated at 25 °C in batch reactors from aqueous solutions containing 0.05 M NaHCO3 and 0.025 M MgCl2 and in the presence and absence of live photosynthesizing Gloeocapsa sp. cyanobacteria. Experiments were performed under a variety of conditions; the reactive fluid/bacteria/mineral suspensions were continuously stirred, and/or air bubbled in most experiments, and exposed to various durations of light exposure. Bulk precipitation rates are not affected by the presence of bacteria although the solution pH and the degree of fluid supersaturation with respect to magnesium carbonates increase due to photosynthesis. Lighter Mg isotopes are preferentially incorporated into the precipitated solids in all experiments. Mg isotope fractionation between the mineral and fluid in the abiotic experiments is identical, within uncertainty, to that measured in cyanobacteria-bearing experiments; measured ?26Mg ranges from ?1.54‰ to ?1.16‰ in all experiments. Mg isotope fractionation is also found to be independent of reactive solution pH and Mg, CO32?, and biomass concentrations. Taken together, these observations suggest that Gloeocapsa sp. cyanobacterium does not appreciably affect magnesium isotope fractionation between aqueous fluid and hydrous magnesium carbonate

In Situ CO2 Mineralization in Mantle-Derived Ultramafic Basements: Insights from Laboratory Experiments and Field Studies (Oman Ophiolite)

Carbon trapping in ultramafic (UM) and basaltic basements is one of the options explored to mitigate industrial CO2 emissions in the Earth’s atmosphere. UM rocks and basalts comprise silicates rich in divalent cations (Mg, Ca, Fe) that are dissolved to form carbonates when in contact with CO2-rich fluids, thus trapping CO2 over geological time scales. UM rocks have the highest concentrations in divalent cations and thus they have the highest potential for carbon trapping by CO2-mineralization. Nevertheless, because of their low permeability, UM basements have been overlooked for possible in situ CO2 storage in favor of basaltic basements. Recent research shows that CO2-mineralization is active and efficient in UM basements, and that it is associated to potential benefits, such as the production of H2. However, the hydrodynamic, physical and chemical mechanisms driving CO2-mineralization whilst sustaining fluid flow are still poorly understood and numerous scientific and technological challenges remain before implementing industrial CO2 geological storage in UM basements. Here we present an overview of our recent results on CO2-mineralization in UM rocks combining (i) laboratory experiments, and (ii) field studies of carbonated UM basements with a focus on the Semail ophiolite (Sultanate of Oman), in relation to the recently completed ICDP (International Continental Scientific Program) Oman Drilling Projec

Dissolved organic matter biodegradation along a hydrological continuum in permafrost peatlands

International audienc