Carbonates dissolution

The spent salt from MSE is currently sent to an aqueous dissolution/carbonate precipitation process to recover plutonium and americium. Efforts to recover plutonium and americium from spent NaCl-KCl-MgCl2 MSE salts using pyrochemistry have been partially successful (3). Metallothermic reductions using Al-Mg and Zn-Mg alloys have been used in the past to recover plutonium and americium, and produce salts which meet plant discard limits. Attempts at direct reductions of MSE salts using... 

Reductive dissolution carbonate leaching of arsenic from sulfides... 

The presence of the complex carbohydrates provides the environment with a viscous hydrogel structure water removal gradually yields a mass of bacteria bound by undigested carbohydrates (celluloses) to form the stool. The presence of a hydrogel softens the mass and also provides water for dissolution. Carbon dioxide release is also a fermentation product, and if the redox potential is sufficiently low, bacteria can produce methane and hydrogen that can be detected in the breath particularly after the ingestion of pulses. In the upright position, the gas will rise to the transverse colon It is estimated that an adult produces approximately 2-3 L per day on 20 g fermentable fibre (most of which is eliminated in the breath). ... 

R.A. Berner, Crist. Deform., Dissolution Carbonates, Reun., (1980) 33. 

Further conversion of mixed-fay-er clays towards illite authigenesis. Authigenic kaolinite precipitation. Authigenic chlorite development. Mixed-layer s ordering corrensite,allevardite. Feldspar dissolution.Significant quartz overgrowths development, chert dissolution. Carbonate cement dissolution/predpi-tation. Some secondary porosity development. 

Precipitation/Dissolution, Carbonate and Acid-Based Chemistry... 

Dissolution and replacement. Some minerals, in particular carbonates, are not chemically stable over a range of pressures, temperatures and pH. Therefore there will be a tendency over geologic time to change to a more stable variety as shown in Figure 5.12. 

The dissolution of carbonates can create spectacular features like those found in many caves. The process is termed karstification. Some reservoirs are related to Karst. Examples are the Bohai Bay Field in China or the Nang Nuan oil field in the Gulf of Thailand. These reservoirs are characterised by high initial production from the large open pore system. However, since the Karst features are connected downdip to the waterleg this is usually followed by rapid and substantial water breakthrough. ... 

Carbonate reservoirs are usually affeoted to varying degree by diagenesis. However the process of dissolution and replacement is not limited to carbonates. Feldspar for instance is another family of minerals prone to early alterations. 

Compounds which dissolve in concentrated sulphuric acid may be further subdivided into those which are soluble in syrupy phosphoric acid (A) and those which are insoluble in this solvent (B) in general, dissolution takes place without the production of appreciable heat or colour. Those in class A include alcohols, esters, aldehydes, methyl ketones and cyclic ketones provided that they contain less than nine carbon atoms. The solubility limit is somewhat lower than this for ethers thus re-propyl ether dissolves in 85 per cent, phosphoric acid but re-butyl ether and anisole do not. Ethyl benzoate and ethyl malonate are insoluble. 

Neste patented an industrial route to a cellulose carbamate pulp (90) which was stable enough to be shipped into rayon plants for dissolution as if it were xanthate. The carbamate solution could be spun into sulfuric acid or sodium carbonate solutions, to give fibers which when completely regenerated had similar properties to viscose rayon. When incompletely regenerated they were sufficientiy self-bonding for use in papermaking. The process was said to be cheaper than the viscose route and to have a lower environmental impact (91). It has not been commercialized, so no confirmation of its potential is yet available. 

Sucralfate. Sucralfate [54182-58-0] (Carafate) (6) is a white amorphous powder soluble in dilute hydrochloric acid and sodium hydroxide. It is practically insoluble in water, ethanol, and carbon tetrachloride. Dissolution of aluminum occurs at pH <3. It may be prepared by the method described in Reference 7. 

The dissolution of carbon in molten iron in the lower part of the furnace, leads to the reduction of manganese oxide (eq. 15) and some sihea (eq. 14), both in the slag, whereby the subsequent dissolution of these metals occurs in the molten iron. 

The analytical chemistry of titanium has been reviewed (179—181). Titanium ores can be dissolved by fusion with potassium pyrosulfate, followed by dissolution of the cooled melt in dilute sulfuric acid. For some ores, even if all of the titanium is dissolved, a small amount of residue may still remain. If a hiU analysis is required, the residue may be treated by moistening with sulfuric and hydrofluoric acids and evaporating, to remove siUca, and then fused in a sodium carbonate—borate mixture. Alternatively, fusion in sodium carbonate—borate mixture can be used for ores and a boiling mixture of concentrated sulfuric acid and ammonium sulfate for titanium dioxide pigments. For trace-element deterrninations, the preferred method is dissolution in a mixture of hydrofluoric and hydrochloric acids. 

In most ores, sufficient Fe is already present. For some ores, it is necessary to add metallic iron. In practice, the oxidation potential of the solution can be monitored and controlled using the Fe /Fe ratio. Very high leaching efficiencies with H2SO ate common, eg, 95—98% dissolution yield of uranium (39). If acid consumption exceeds 68 kg/1 of ore treated, alkaline leaching is preferred. The comparative costs of acid, sodium hydroxide, and sodium carbonate differ widely in different areas and are the determining factor. 

Australian Vanadium—Uranium Ore. A calcareous camotite ore at YeeHrrie, AustraHa, is iU-suited for salt roasting and acid leaching. Dissolution of vanadium and uranium by leaching in sodium carbonate solution at elevated temperature and pressure has been tested on a pilot-plant scale... 

The efficiency of the weathering of rocks in using carbonic acid produced in the carbon cycle is affected by various hydrologic, environmental, and cultural controls. The fact that the principal anion in fresh surface water worldwide almost always is bicarbonate attests to the overriding importance of this process. Exceptions are systems in which evaporite minerals are available for dissolution by groundwater or where human activities are major sources of sulfate or chloride inflow. 

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