Dolomite extraction

Solvent extraction foUowing roasting and leaching is a promising processing method for dolomitic shale from Nevada (9). 

Magnesium carbonate is extracted from dolomite rock, and after mixing with fiber reinforcement is slurry cast into appropriate molds. After drying, the products are machined to size. 

Figure 4.1. Removal of carbonate from Israeli arid soils as indicated by the X-ray diffractograms after extraction of the carbonate fraction by NaOAc-HOAc solutions at various pHs for 16 hours. C calcite d = 3.04 A, and D dolomite, d = 2.89 A. Number 1, 2, 3, 4, 5, and 6 indicate non-treated soil (No. 1), treatments (No. 2-6) with NaOAc-HOAc solutions at pH 7.0, 6.0, 5.5, 5.0 and 4.0, respectively (after Han and Banin, 1995. Reprinted from Commun Soil Sci Plant Anal, 26, Han and Banin A., Selective sequential dissolution techniques for trace metals in arid-zone soils The carbonate dissolution step, p 563, Copyright (1995), with permission from Taylor Francis US)...

The graph obtained by X-ray diffraction (Fig. 4.1) showed that the NaOAc-HOAc solution at pH 5.0 could not completely dissolve the trace quantities of dolomite from the soils during the first 16 hours of extraction. Tessier et al. (1979), however, reported that the peak generated by dolomite after extraction by the buffer at pH 5.0 disappeared from sediment. 

Dow seawater A process for extracting magnesium from seawater. Calcined dolomite (CaO-MgO, dololime), or calcined oyster shell, is added to seawater, precipitating magnesium hydroxide. This is flocculated, sedimented, and filtered off. For use as a refractory it is calcined for the manufacture of magnesium chloride for the manufacture of magnesium metal, it is dissolved in hydrochloric acid. Developed by the Dow Chemical Company and later operated by the Steetly Company in West Hartlepool, UK, and Sardinia. 

Ground calcium carbonate, extracted from the earth, is present in practically every country in the world in varying quantities in the form of limestone, marble, dolomite or chalk. Following the extraction, GCC needs to be ground. Dry grinding, the cheaper alternative, is often limited to a minimum particle size of 2- 3 microns. Wet grinding, more expensive, is used for fine and ultra fine material or when the final product must be a slurry (paper or paint application). Precipitated calcium carbonate is produced by chemical reaction between... 

The most common reagent for the extraction of trace metals from carbonate phases in soil is lmoll-1 sodium acetate acidified to pH 5 with acetic acid (Kunze, 1965). Carbonate phases effectively attacked include dolomite, but the presence of acetic acid also promotes the release of metals specifically sorbed on inorganic and organic substrates (Tessier et al., 1979). 

In the process used by Norsk Hydro, magnesium hydroxide extracted from seawater with the aid of calcined dolomite is mixed with charcoal and magnesium chloride brine and is heated to 1000-1200°C in the presence of chlorine produced during subsequent electrolysis of magnesium chloride. The main reactions are [266]... 

MAGRAM A process for extracting magnesium metal from dolomite. Similar to Magnetherm, but uses asbestos as the fluxing material and does not require the use of vacuum. Developed by an... 

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