Abstract
X-ray diffraction, infrared spectroscopy, thermogravimetry and mass spectrometry were employed to study the behavior and distribution of fluorine in sulfuric acid treatment of the melt of beryl-bertrandite-phenakite-fluorite concentrates with alkali fluxes. It was established that fluorine in a solid phase is predominantly present in the form of sodium and calcium fluorosilicates and in a gaseous phase it is evolved in the form of silicon tetrafluoride and fluorosulfonic acid.
Highlights
At JSC Ulba Metallurgical Plant the production of beryllium constitutes the processing of complex beryllium raw materials consisting of beryl concentrates Be3Al2[Si6O18] and collective concentrates of bertrandite Be4[Si2O7](OH)2, phenakite Be2[SiO4] and fluorite СаF2
Infrared absorption spectrum showed that concentrate melting followed by water quenching leads to partial destruction of Si-O-Si bonds, as indicated by the shift of the maximum of Si-O bond in a silicon-oxygen tetrahedron towards low frequency range – 948.5 cm–1
The absorption bands in the 850-1150 cm–1 and 600-850 cm–1 regions indicate the violation of a distant order in the crystalline structure which is typical of amorphous solids
Summary
At JSC Ulba Metallurgical Plant the production of beryllium constitutes the processing of complex beryllium raw materials consisting of beryl concentrates Be3Al2[Si6O18] and collective concentrates of bertrandite Be4[Si2O7](OH), phenakite Be2[SiO4] and fluorite СаF2. Hydrometallurgical technology of their processing consists in preliminary melting with alkali fluxes (Na2CO3 and CaCO3) at 1400 °С, water melt granulation and subsequent sulfuric acid (60%) leaching of the baked melt (hereinafter referred to as the melt). To decompose complexes increasing pH up to 12 is required which causes conjoint precipitation of impurities and incomplete beryllium precipitation For these reasons, fluorine removal before the precipitation stage of Be(OH) is an urgent task
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