Magnesium carbonate dissolution

Calcium/magnesium carbonate/hydroxide and calcium phosphate can be removed by using 5 to 15% hydrochloric acid at 140 to 150 °F, by recirculating tetrasodium EDTA at 200 to 300 °F, or by 7 to 10% sulfamic acid at 140 to 150 °F. The temperature may need to be a little higher to start the dissolution process. 

ABSTRACT Atmospheric carbon dioxide is trapped within magnesium carbonate minerals during mining and processing of ultramafic-hosted ore. The extent of mineral-fluid reaction is consistent with laboratory experiments on the rates of mineral dissolution. Incorporation of new serpentine dissolution kinetic rate laws into geochemical models for carbon storage in ultramafic-hosted aquifers may therefore improve predictions of the rates of carbon mineralization in the subsurface. 

The impact of water hardness due to calcium or magnesium ions on detergents was explained in Section 7.3.1 The source of most Ca2+ and Mg2+ in hard water is the dissolution of limestone (CaCOs) or dolomite [CaMg(COs)2]. Magnesium carbonate is fairly soluble (1.26 mmol L 1 at ambient temperature), but CaCOs is much less so (0.153 mmol L 1). However, if the water contains dissolved CO2 (as indeed it will if it is exposed to the air see Exercise 14.9), the relatively freely soluble Ca(HCOs)2 forms, and the limestone slowly dissolves away ... 

The dominance of carbonate hydrolysis, carbo-nation, and sulfide oxidation in subglacial weathering reactions on aluminosilicate/silicate bedrock is also found on carbonate bedrock. However, the balance between carbonate dissolution and sulfide oxidation depends on the spatial distribution of sulfides in the bedrock and basal debris (Fairchild et al., 1999). Noncongruent dissolution of strontium and magnesium from carbonate is also observed in high rock water weathering environments, such as the distributed drainage systems, in which water flow is also low (Fairchild et al., 1999). 

Hypothesis 3, Diffusion of DIC together with DOC, sulfate, and cations from confining bed pore waters to the Black Creek aquifer provides sources of electron donor (organic carbon) and electron acceptor (sulfate) for microbial metabolism and additional inorganic carbon to drive low-magnesium calcite precipitation. The combination of magnesium-calcite dissolution from shell material driven by microbially produced carbon dioxide, and the precipitation of more thermodynamically stable low-magnesium calcite cement in the aquifer, can explain major ion and carbon isotope composition of Black Creek aquifer water. 

In deeper systems dominated by calcium-rich saline fluids, it has been shown that both solubility constraints and silicate reactions act to further remove bicarbonate ions as precipitated calcium and magnesium carbonates, often adjusting pH to levels greater than 9 (Barnes and O Neil, 1971 Fritz et al., 1987a Clauer et al., 1989). For example, during closed-system dissolution of magnesium olivine (forsterite), a major component of many ultramafic rocks, as the silicate water reaction proceeds water breaks down, H" " ions are consumed, carbonates precipitate, and hydroxyl ions force the pH to rise (Barnes and O Neil, 1971 Drever, 1988). 

The dissolution of dolomite, calcium magnesium carbonate, in hydrochloric acid is a reataion of particular importance in the acid stimulation of dolomite oil teseivoirsd The oil is contained in pore space of the carbonate material and must flow through the small pores to reach the well bore. In matrix stimulation, HCl is injected into a well bore to dissolve the porous carbonate matrix. By dissolving the solid carbonate the pores will increase in size, and die oil and gas will be able to flow out at faster rates, thereby increasing the productivity of tbe well. The dissolution reaction is... 

Incompatible with phenobarbital sodium, diazepam solution at a pH 5, ° some binary powder mixtures, lansoprazole, and formaldehyde. Acids will dissolve magnesium carbonate, with the liberation of carbon dioxide. Slight alkalinity is imparted to water. Magnesium carbonate was also found to increase the dissolution of acetazolamide formulations at a pH of 1.12 however, dissolution was retarded at a pH of 7.4. ... 

Magnesite is the most common magnesium carbonate mineral in geological environments. In spite of this fact, it is rarely observed precipitating from natural waters. Further, its low-temperature solubility has been extremely difficult to measure because of its very slow rate of dissolution in the laboratory (cf. Langmuir 1965). The - log of 4.9 for magnesite given in Table 6.1 is consistent... 

Soap scum is an insoluble precipitate that forms between the cations of minerals typically present in hard water and the anions of soaps and detergents. Divalent cations of calcium (Ca2+) and magnesium (Mg2+) from calcium carbonate and magnesium carbonate minerals are the primary components of hard water. Divalent cations of iron (Fe2+), manganese (Mn2+), and strontium (Sr2+) are also often present. An example of the dissolution (dissolving) process that releases calcium ions from calcium-containing minerals in contact with water with high acid levels is... 

Temperature has a great influence on the initial reaction rate. Under conditions of low slurry density, where the concentration of magnesium bicarbonate does not reach its solubility limit, the rate of dissolution of MgO increases with increasing temperature. However, under conditions where the concentration of magnesium bicarbonate reaches its metastable limit, the maximum solution of Mg(OH)2 is reached at about 15°C, after which magnesium carbonate starts to precipitate. 

Hypothetical reaction pathways chosen to model the L2 leachate-Uinta Sandstone system are illustrated in Figure 5. As a first approximation, dissolution/precipitation reactions affecting the mass balance of Na, K, Mo, SO4, and Cl were not considered. Instead, based upon the solubility controls discussed in the previous sections of this paper, the working hypothesis for the simulations is that the recarbonation of L2 leachate drives the reactions toward equilibrium. Along the path toward equilibrium, recarbonation is accompanied by the precipitation and dissolution of sepiolite, calcite, and an inferred hydrated magnesium carbonate mineral such as hydromagnesite. 

Initially (Fig. 7.11 (a)), the anodic dissolution occurs at the location where electrolyte droplets are present on the surface and where the Cl content is high. CO2 diffuses through the water droplets, and reacts with the Mg(OH>2 formed by the anodic dissolution of Mg. This results in rapid formation of magnesium carbonate magnesite. As long as sufhcient oxygen is present at the reaction sites on the surface, the cathodic reaction is probably to a large... 

The addition of trichloro- ortetrachloroethylene to aluminium components in dry cleaning equipments is responsible for many accidents. The effect of the carbon tetrachloride/methanol mixture in the 1/9 proportion of aluminium, magnesium or zinc causes the dissolution of these metals, whose exothermicity makes the interaction dangerous. There is a period of induction with zinc, which is cancelled out when copper dichloride, mercury dichloride or chromium tribromide is present. 

The rapid autocatalytic dissolution of aluminium, magnesium or zinc in 9 1 methanol-carbon tetrachloride mixtures is sufficiently vigorous to be rated as potentially hazardous. Dissolution of zinc powder is subject to an induction period of 2 h, which is eliminated by traces of copper(II) chloride, mercury(II) chloride or chromium(III) bromide. 

Figure 29.2 shows the mineralogic results of the calculation. Dolomite dissolves, since it is quite undersaturated in the waste fluid. The dissolution adds calcium, magnesium, and carbonate to solution. Calcite and brucite precipitate from these components, as observations from the wells indicated. The fluid reaches equilibrium with dolomite after about 11.6 cm3 of dolomite have dissolved per kg water. About 11 cm3 of calcite and brucite form during the reaction. Since calculation... 

To a flame-dried, three-neck, 1-1 flask were added, in order, p-xylene (107 g, 1.0 mol), phosphorus trichloride (412 g, 3.0 mol), and anhydrous aluminum chloride (160 g, 1.2 mol). The reaction mixture was slowly heated to reflux with stirring. After 2.5 h at reflux, the reaction was allowed to cool to room temperature and the volatile components distilled at reduced pressure. The residual oil was slowly added to cold water (1 1) with stirring, and a white solid formed. The solid was removed by filtration, washed with water, and air dried. The solid was suspended in water (1 1) to which was added 50% sodium hydroxide solution (90 ml) to cause dissolution. The solution was saturated with carbon dioxide and filtered through Celite . The basic solution was washed with methylene chloride (200 ml) and acidified with concentrated hydrochloric acid (200 ml). The white solid that separated was isolated by extraction with methylene chloride (3 x 250 ml). The extracts were dried over magnesium sulfate, filtered, and evaporated under reduced pressure to give the pure 2,5-dimethylbenzenephosphinic acid (99 g, 60%) as an oil, which slowly crystallized to a solid of mp 77-79°C. 

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