Integrated fluoride processing of kyanite concentrates

Rimkevich, V. S.; Пушкин, А. А.; Girenko, I. V.; Eranskaya, T. Yu.

doi:10.3103/s1067821214040142

Cited by 14 publications

(3 citation statements)

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“…(3) (NH4)3SiF7 → (NH4)2SiF6 + HF↑ + NH3↑ (4) Solid-phase sintering of ilmenites, scheelite, wolframite, non-bauxite ores (kaolins, high-alumina shales, anorthosites, alkaline aluminosilicates etc.) with NH4HF2 or NH4F revealed that the fluorating agent is in molten state [12][13][14][15][16]. We also found that mixing and grinding at room temperature lead to intensive wetting of the reaction mixture due to the formation of ammonia and water.…”

Section: Results and Dscussionmentioning

confidence: 73%

“…The separation of tailing components during hydrochemical interaction with ammonium bifluoride in solution is based on the formation of fluorine-containing compounds having various physicochemical properties. The thermodynamic simulation showed that fluorination reactions of silicon-containing oxide phases and most of minerals begin at temperatures below 200 °С and are accompanied by heat release [12][13][14]. The interaction of NH4HF2 with the basic mineral pyroxene CaMgSi2O6 to form poorly soluble and highly soluble simple and complex fluorides is possible under standard conditions according to eq.…”

Section: Results and Dscussionmentioning

confidence: 99%

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Hydrofluoride Processing of Tailings From Wet Magnetic Separation of Titanomagnetite to Obtain Amorphous Silicon Dioxide

2023

Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.

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A method for the opening of silicon-containing technogenic feedstock using an aqueous solution of ammonium bifluoride (NH4HF2) with subsequent production of amorphous silica has been developed. In this work we examined wet magnetic separation tailings (WMST) – iron titanium-magnetite ore enrichment rejects that are formed in huge quantities and stored in sludge depositories at concentrating plants. The main rock-forming minerals of WMST are resistant silicates – pyroxene, amphibole, plagioclase and olivine with the total SiO2 content of about 50%. It was established that fluorination of silicon-containing minerals begins during mechanical dispersion of a dry reaction mixture at room temperature. The thermodynamic calculations confirm active interaction of components in the composition of mineral complexes already at 25 ℃, some of the processes being exothermic with entropy reserve. When the temperature increases to 90 ℃ and the duration of leaching to 5 h, the extraction of silicon in the form of soluble ammonium fluorosilicate grows. Insoluble calcium and magnesium fluorides and sparingly soluble under leaching conditions ammonium fluorometallates, as well as a part of unreacted rock are formed in the insoluble residue. Under the most effective desilication conditions (20% NH4HF2 solution, L:S=4:1, 2 h), the residual content of SiO2 decreases to 1–2%. The synthesis of finely dispersed amorphous silica (SiO2) was performed by hydrolytic deposition when the value of рН of clarified ammonium fluorosilicate solution was reduced by adding ammonia. It was shown that gradual introduction of hydrous ammonia (5 ml/h) into diluted fluorosilicate solution with a concentration of less than 5 g/l Si while constant stirring leads to the formation of spherical silica nanoparticles. The degree of silica extraction from tailings in the process of hydrofluorination of 20% NH4HF2 solution at 90 ℃ for 2 h was 98%, and the content of impurities in amorphous silica did not exceed 1–2%. Separation of finely dispersed suspension of insoluble fluorides and hydroxide impurities formed during stepwise hydrolysis of fluorosilicate solution to рН value less than 5 is a necessary condition for producing pure silica SiO2. The final product, similar to “white soot” in properties, is characterized by predominant particle size in the interval of 2-20 nm, a large surface area 230-360 m2/g and a low pycnometric density 1.62 g/cm3. For citation: Medyankina I.S., Pasechnik L.A. Hydrofluoride processing of tailings from wet magnetic separation of titanomagnetite to obtain amorphous silicon dioxide. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2023. V. 66. N 2. P. 70-77. DOI: 10.6060/ivkkt.20236602.6706.

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Section: Results and Dscussionmentioning

confidence: 73%

Section: Results and Dscussionmentioning

confidence: 99%

Hydrofluoride Processing of Tailings From Wet Magnetic Separation of Titanomagnetite to Obtain Amorphous Silicon Dioxide

2023

Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.

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“…Inorganic chemical reactions involving aluminium-fluoride interactions are of high relevance to a variety of geochemical, 2 environmental 3,4 as well as technological [5][6][7][8][9] processes. Aluminium fluoride (AF) catalysts are of notable technological interest, and the chemistry of their related aluminium hydroxo fluoride (AHF) [5][6][7][8][9] phases have received particular attention given their predispositions at forming in the presence of atmospheric and liquid water.…”

Section: Introductionmentioning

confidence: 99%

Bifluoride ([HF₂]⁻) formation at the fluoridated aluminium hydroxide/water interface

et al. 2016

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This study uncovers bifluoride-type (difluorohydrogenate(i); [HF2](-)) species formed at mineral/water interfaces. Bifluoride forms at [triple bond, length as m-dash]Al-F surface sites resulting from the partial fluoridation of gibbsite (γ-Al(OH3)) and bayerite (α-Al(OH3)) particles exposed to aqueous solutions of 50 mM NaF. Fluoride removal from these solutions is proton-promoted and results in a strongly self-buffered suspensions at circumneutral pH, proceeds at a F : H consumption ratio of 2 : 1, and with recorded losses of up to 17 mM fluoride (58 F nm(-2)). These loadings exceed crystallographic site densities by a factor of 3-4, yet the reactions have no resolvable impact on particle size, shape and mineralogy. X-ray photoelectron spectroscopy (XPS) of frozen (-155 °C) wet mineral pastes revealed coexisting surface F(-) and HF(0) species. Electron energy loss features pointed to multilayer distribution of these species at the mineral/water interface. XPS also uncovered a distinct form of Na(+) involved in binding fluoride-bearing species. XPS and solid state magic angle spinning (19)F nuclear magnetic resonance measurements showed that these fluoride species were highly comparable to a sodium-bifluoride (NaHF2) reference. First layer surface species are represented as [triple bond, length as m-dash]Al-F-H-F-Al[triple bond, length as m-dash] and [triple bond, length as m-dash]Al-F-Na-F-Al[triple bond, length as m-dash], and may form multi-layered species into the mineral/water interface. These results consequently point to a potentially overlooked inorganic fluorine species in a technologically relevant mineral/water interfacial systems.

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New insights into the thermal behavior and stability of ammonium bifluoride: non-isothermal thermokinetic analysis

Resentera

Esquivel

Rodríguez

2023

J Therm Anal Calorim

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Integrated fluoride processing of kyanite concentrates

Cited by 14 publications

References 1 publication

Hydrofluoride Processing of Tailings From Wet Magnetic Separation of Titanomagnetite to Obtain Amorphous Silicon Dioxide

Hydrofluoride Processing of Tailings From Wet Magnetic Separation of Titanomagnetite to Obtain Amorphous Silicon Dioxide

Bifluoride ([HF₂]⁻) formation at the fluoridated aluminium hydroxide/water interface

New insights into the thermal behavior and stability of ammonium bifluoride: non-isothermal thermokinetic analysis

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Integrated fluoride processing of kyanite concentrates

Cited by 14 publications

References 1 publication

Hydrofluoride Processing of Tailings From Wet Magnetic Separation of Titanomagnetite to Obtain Amorphous Silicon Dioxide

Hydrofluoride Processing of Tailings From Wet Magnetic Separation of Titanomagnetite to Obtain Amorphous Silicon Dioxide

Bifluoride ([HF2]−) formation at the fluoridated aluminium hydroxide/water interface

New insights into the thermal behavior and stability of ammonium bifluoride: non-isothermal thermokinetic analysis

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Bifluoride ([HF₂]⁻) formation at the fluoridated aluminium hydroxide/water interface