Barite impurity

Calcareous minerals such as gypsum [13397-24-5] when added in stoichiometric amounts relative to the barite impurities, reduce acid-soluble barium losses (16). 

The fused product contains about 60—85% barium sulfide, unreacted barium sulfate, and impurities present in barite and ash. The soluble barium sulfide is extracted from the mixture with water and separated from the insoluble impurities by filtration. 

Recently attention has focused on the heavy metal impurities in barite. Proposed U.S. regulations would exclude many sources of barite ore. European and other countries are contemplating regulations of their own. 

Soft crystalline solid rhombic crystal pure salt is white but color may vary the color of the mineral barite may vary among red, yellow, gray or green depending on impurities density 4.50 g/cm refractive index 1.64 melts around 1,580°C decomposes above 1,600°C hardness 4.3 to 4.6 Mohs insoluble in water (285 mg/L at 30°C) and alcohol Ksp 1.1 x 10-i° soluble in concentrated sulfuric acid. 

Natural barium sulfate or barite is widely distributed in nature. It also contains silica, ferric oxide and fluoride impurities. Silica is the prime impurity which may be removed as sodium fluorosilicate by treatment with hydrofluoric acid followed by caustic soda. 

Barium sulfide occurs in the form of hlack ash, which is a gray to hlack impure product obtained from high temperature carbonaceous reduction of barite. It is the starting material in the manufacture of most barium compounds including barium chloride and barium carbonate. It is used in luminous paints for dehairing hides as a flame retardant and for generating H2S. 

The product, black ash, is a gray or black powder containing carbonaceous impurities and unreacted barite. Barium sulfide is separated from impurities by extraction with hot water and filtration. It is obtained as an aqueous solution of 15 to 30% strength. The commercial product is 80% to 90% BaS. 

The natural barite in our study consisted of twenty-five samples of different origin. Concentrations of potential luminescence impurities in several samples are presented in Table 4.11. For the correct interpretation of the luminescent bands, artificial barite standards have been investigated, as nominally pure, and activated. The laser-induced time-resolved technique enables us to detect Ag+, Bi +, Bi, Eu, Ce +, Nd +, (U02) and several still not identified emission centers (Figs. 4.29-4.31). 

Manganese impurities are always found in barite samples and Mn participation in barite luminescence was considered as possible. In order to check this we studied synthetic BaS04 artificially activated by Mn +. Relatively weak green luminescence was foimd (Fig. 5.47a) with a very long decay time of several ms, but such emission has not been found yet in natural barite. 

The possibility of Cr emission may be excluded because octahedral coordination is absent in barite structure. Luminescence of Fe is crystallographi-cally possible because tetrahedral surrounding presents in barite structure but Fe -S substitution is very difficult to suppose. The iron presence in ICP data is evidently connected with micro-impurities of iron minerals, which is usual for natural barite. Other ions, such as Ti and Ni with possible red luminescence, have ionic radii of 81 and 83 pm, respectively, which are small compared to the 156 ppm of Ba " ". ICP data confirm the absence of Ni in barite, while the minor quantities of Ti maybe connected to Ti" ". ... 

In order to check the possibility of ci -ions luminescence in the barite lattice, activation by Ag was accomplished (Gaft et al. 2001 a). The main reason was that in all natural barite samples the Ag and Cu impurities have been determined by ICP analysis (Table 4.11). Besides that, weak orange luminescence on the tail of the strong UV band was detected in BaS04 Ag under X-ray excitation (Prokic 1979). 

At 77 K the relative intensity of the band at 605 nm with an even longer decay time of 25 ms is much stronger. Such bands are usually connected with Mn +, but Mn " " in barite has different luminescence. Mn " in anhydrite CaS04 is characterized by a narrow band peaking at 505 nm. Thus such a band in barite may be connected with Ca impurity and anhydrite type local structure. 

The manufacture of soluble barium salts involves treatment of the mineral (usually barite) with the relevant acid, filtration to remove insoluble impurities, and crystallization of the salt. 

Barium sulfate, BaS04, occurs in the mineral barite (a). Calcium fluoride, Cap2, occurs in the mineral fluorite (b). Both are clear, colorless crystals. Minerals are often discolored by impurities. 

Barite is frequently contaminated with alkaline-soluble carbonate and sulfide minerals that cause serious drilling fluid problems. Therefore, small concentrations of impurities in barite can lead to significant contamination of the drilling fluid. ... 

Triboadhesive enrichment or beneficiation can be used successfully in two types of applications size classification of powdered materials and the separation of mineral particles from impurities. In the first category we may mention the classification of powders such as quartz, barite, magnetite, hematite, pyrite, feldspar, coal, asbestos, graphite, periclase (crystalline magnesium oxide), pegmatite, and iron ore. As an illustration of an application in the second category we may mention the separation of asbestos fiber ( falling product) from mineral dust that adheres to the drum surface ( retained product) [327]. 

A narrow band with a main shoulder at 302 nm with a very short decay time of 25 ns, and another with shoulders at 330 and 360 nm with a longer decay of 75 ns (Fig. 4.74c, d) in time-resolved spectra have spectral-kinetic parameters suitable for Ce " ". It is known that narrow bands near 300 nm are especially strong in (Ba,Sr)S04 (baritocelestine), while in barite they are situated at a longer wavelength (Gaft et al. 1985). The ionic radius of Ce + is 128 pm and a possible accommodation is isomorphic substitution for Ba (156 pm) or Sr " " (140 pm). Thus, two types of Ce " " centers may be connected with Sr impurity, the presence of which in barite samples is confirmed by ICP analysis (450-720 ppm). Luminescence of Ce in anhydrite is seen under excitation at 266 nm (Fig. 4.30b) and it is... 

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