Ammonium Hydrodifluoride Research Articles

Decomposition of Mineral Raw Materials Using a Mixture of Ammonium Hydrodifluoride and Sulfate

Decomposition of Mineral Raw Materials Using a Mixture of Ammonium Hydrodifluoride and Sulfate

Low-temperature method for desiliconization of polymetallic slags by ammonium bifluoride solution.

Throughout the period of operation of non-ferrous metal deposits, a significant amount of waste has been accumulated. The accumulated waste contains valuable metals in concentrations that allow considering them as valuable raw materials. However, it is worth noticing the presence of problems that previously did not allow for more complete extraction of the target components. Such problems include the presence of significant amounts of silicon dioxide in the form of a silicate matrix, the removal of which will allow the extraction of valuable components with the elimination of industrial waste areas. The paper considers a method for removing silicon from the polymetallic slags. According to the results of the work, it was found that silicon passes into solution in the form of ammonium hexafluorosilicate. Iron, aluminum, and a number of other components react with ammonium hydrofluoride, but do not leach into the solution due to their low solubility in the resulting system. After removing silicon, the solid residue was subjected to pyrohydrolysis to obtain a product that can be subjected to magnetic separation to obtain a magnetic iron concentrate and a non-ferrous metal concentrate. The formed concentrate can later be used to extract zinc, lead, silver, etc. The productive solution was directed to the deposition of silicon with the subsequent production of silicon dioxide. The resulting solution can be directed to evaporation in order to regenerate and reuse ammonium hydrodifluoride.

Development of approaches to the creation of technology for extracting "invisible" gold from the ores of the Sukhoe deposit (Primorye)

In the south of the Far East, a large deposit of Sukhoe gold has been identified, where the noble metal is in a dispersed form, being present in the form of microscopic particles, or entering the structure of sulfide minerals. It was found out that the «invisible» (nano) form of finding gold is mainly associated with pyrite and arsenopyrite. To develop a technology for extracting a useful component, the completeness and convenience of opening the stone material with the transfer of all components into a solution is crucial. The article presents the results of a study of the possibility of preparing samples of mineral raw materials for the analytical determination of the elemental composition by thermal treatment of samples with a mixture of ammonium hydrodifluoride NH4HF2 and ammonium sulfate (NH4)2SO4. Based on a comparative analysis, it was shown that when using a mixture of ammonium hydrodifluoride with ammonium sulfate, it is possible to more fully open the mineral raw materials compared to using only ammonium hydrodifluoride. A mixture of NH4HF2 with (NH4)2SO4 is recommended as a new promising reagent for the decomposition of ores with "invisible" gold.

DEVELOPMENT OF A LOW-TEMPERATURE DESILICONIZATION METHOD FORTHE POLYMETALLIC SLAGS WITH A SOLUTION OF AMMONIUM HYDROGEN FLUORIDE

This paper considers a method for removingsilicon dioxide from the polymetallic slags of the Nerchinsk silver smelters, which operated from the 17th to the 19th centuries. The main com-ponents are presented both in the oxygen-containing form (iron, silicon, etc.) and in the form of sulfides (lead,zinc). It was found that during the process, silicon passes into solution in the form of ammonium hexafluorosilicate. Iron, aluminum and a number of other components react with NH4HF2, but stay in the solid phase due to their low solubility in the resulting system. After remov-ing silicon, the solid residue is subjected to pyrohydrolysis to obtain a product that can be subjected to magnetic separation to obtain a magnetic iron concentrate and a non-ferrous metal concentrate, which can later be used to extract zinc, lead, silver, etc. Fluorine is removed from the cycle with the pyrohydrolysis product in the form of calcium fluoride. Productive solution is directed to the silicon dioxide production. The final solution of ammonium fluoride is used for ammonium hydrodifluo-ride by means of the water evaporation. In the process of evaporation of the ammonium fluoride solution, the ammonia molecule is split off with the formation of ammonium hydrodifluoride. The whole process of desiliconization is shown in the technological scheme. Main stages of the method demand typical equipment, so it allows us to speak about the applicability of this method in industry for both mineral and artificial raw materials with a high content of silicon dioxide or silicates of various compositions.

Studying Conditions for Purifying Natural Graphite with Ammonium Hydrodifluoride

Studying Conditions for Purifying Natural Graphite with Ammonium Hydrodifluoride

PHASE FORMATION PROCESSES AT LOW-TEMPERATURE FLUORINATION OF ZIRCONIUM SILICATE

Zirconium silicate ceramics is widely used in different fields of engineering. One of the most actual problem of zircon ceramics is the requiring of high temperatures for its sintering. Perspective method for activation of silicate materials with the aim of intensification of synthesis and sintering processes is the low-temperature fluoridation with the ammonium hydrofluoride. In accordance with that, processes occurring during the interaction of plasma dissociated zircon and natural zircon with ammonium hydrodifluoride were studied. It was established that plasma dissociated zircon actively interacts with ammonium hydrofluoride in the solid phase. Natural zircon because of its chemical inertness reacts with ammonium hydrofluoride only when latter melts. The main product of fluorinating is ammonium hexafluorosilicate. By-products are ammonium hexafluorozirconate and ammonium heptafluorozirconate. Their quantity increases with the content of ammonium hydrofluoride in mixtures. Kinetic equation of reaction between zircon and ammonium hydrofluoride is k×τ = 1-(1-α)1/n. Activation energy of plasma dissociated zircon and natural zircon fluorinating reactions are 13.9 and 32.7 kJ/mol, respectively. Order of reactions (n) are 2.0 and 1.5, respectively. Thermal treatment of fluorinated materials at 400 °C leads to ammonium hexafluorosilicate sublimation and thermal dissociation of ammonium fluorozirconates to zirconium fluoride and fluorozirconate intermediates. It was established that low-temperature fluoridation of zircon makes possible to regulate chemical composition of minerals. Materials obtained by ammonium hydrofluoride treatment of plasma dissociated and natural zircon can be potentialy used in the functional zircon and zirconia-zircon ceramics technology.

Fluorammonium method of titanium slag processing

Titanium dioxide is the most common titanium-containing product on the world market, and the demand for it is increasing. The global consumption of TiO2 is 7 – 7.5 million tons annually. Titanium dioxide is mainly obtained from ilmenite and rutile concentrates. The largest producers are China, USA, Germany, UK, Mexico, and Saudi Arabia. In addition to the natural resources of titan, there are man-made sources. This type of resource includes titanium-containing slags obtained as a result of pyrometallurgical processing of ores and concentrates containing titanium dioxide. These slags, in addition to titanium dioxide, contain silicon in the form of dioxide, silicates or aluminosilicates, whose chemical processing is difficult due to their high melting point (more than 2000 °C) and the chemical stability of these compounds in mineral acids (sulfuric, nitric, hydrochloric). Processing of such raw materials is carried out by “classical” chlorine and sulfuric acid methods. The use of fluorides in industry is realized in the production of aluminum, zirconium, uranium, beryllium, niobium, etc., which indicates the possibility of using fluoride methods for titanium slags processing. The article discusses a method for producing titanium dioxide based on the use of ammonium hydrodifluoride NH4HF2 , which has a high reactivity to a number of chemically resistant oxides (oxides of silicon, titanium, aluminum, etc.). The fluoroammonium method for processing titanium slag using NH4HF2 involves slag decomposition of in NH4HF2 melt followed by silicon admixture sublimation. Cleaning from iron, aluminum and other impurities is carried out using a solution of NH4HF2. Further precipitation of titanium with treatment of the precipitate by AlCl3 and ZnCl2 solutions followed by calcination allows to obtain a rutile modification of titanium dioxide.

Phase formation processes in natural magnesium silicates of various structures by their ammonium fluoride treatment

The processes of forsterite, enstatite and talc treatment by ammonium fluoride have been studied. The phaseformation processes occurring during firing of fluorinated minerals were studied. It was established that structural silica of minerals reacts with ammonium hydrodifluoride with the formation of ammonium hexafluorosilicate. The sublimation of ammonium hexafluorosilicate leads to remove structural silica from minerals with partial destruction of their structure. The firing of fluorinated minerals leads to their structural transformation with the formation of magnesium nesosilicates and fluoronesosilicates.

Studies on the opportunities of producing superpure graphite from the high-carbone rocks of the Jiamusi-Hankaiskaya province

The results of the research of the conditions of the purification of the natural graphite with the usage of the processes of the hydrodifluoride technology are given. The interaction of the major impurity elements of the concentrate with NH4HF2 resulting in the formation of the complex fluorine ammonium salts and simple fluorides is established to occur during processing of the graphite concentrate with ammonium hydrodifluoride. Conducting the fluoridization with usage of 20% of surplus of NH4HF2 has been found to allow reaching the complete fluoridization of the impurity components which are present in the graphite. The complex fluorine ammonium salts and the fluorides of alkaline metals have appeared to be removed from fluoridated concentrate by means of the water leaching.

Development of physicochemical foundations of the technology of extraction of low-ash graphite from high-carbone rocks of the Jiamusi-Hankaiskaya province

The majority of high technologies which are indicators of the level of development of the industrial production in the advanced countries are inconceivable without graphite use. The bulk of graphite is imported into Russia from abroad. Enormous resources of crystal graphite are concentrated in ore deposits of the Jiamusi-Hankaiskaya province with submeridional strike towards the adjacent territories of the South of the Far East of Russia and the northeast of China. There are features of Dalnerechensk group (with Filinskoye being the largest of them), deposits of of Lesozavodsk group (Tamginskoye, Turgenevskoye) and graphite-ore giant of Liumao Mashan group of the Heilongjian province in the Northern, central and Southern sides of this province respectively. A characteristic feature of the graphite ores of these objects is the abundance of inclusions of quartz, native metals, intermetallic compounds. Using the deposits of the Lesozavodsk group as an example, the possibilities of extracting high-purity graphite from them were investigated. The results of the research of the conditions of the purification of the natural graphite with the usage of the processes of the hydrodifluoride technology are given. The interaction of the major impurity elements of the concentrate with NH4HF2 resulting in the formation of the complex fluorine ammonium salts and simple fluorides is established to occur during processing of the graphite concentrate with ammonium hydrodifluoride. Conducting the fluoridization with usage of 20 percents of surplus of NH4HF2 has been found to allow reaching the complete fluoridization of the impurity components which are present in the graphite. The complex fluorine ammonium salts and the fluorides of alkaline metals have appeared to be removed from fluoridated concentrate by means of the water leaching. As a result of the experiments, the foundations for the introduction of promising industrial hydrofluoride technology for the purification of natural graphite from impurities have been created. The application of the developed basic scheme for the production of high-purity graphite opens up wide prospects for the deep processing of graphite ores in the deposits of Primorye

Complex processing of titanium-rare metal raw material

The paper is devoted to investigation of the complex processing of titanium-rare metal raw materials with ammonium hydrodifluoride. It is stated that fluorination of the main components of the mineral raw materials with ammonium hydrodifluoride proceeds with formation of complex ammonium fluorometallates and simple fluorides. It is showed that in the process of aqueous leaching of the fluorinated mineral raw material niobium and tantalum completely pass into solution together with titanium, iron, and silicon fluoroammonium salts while all the rare-earth elements stay in the insoluble residue as complex fluorosodium salts together with CaF2. The method of separation of the fluoroammonium salts with obtaining marketable products and isolation of the rare-earth elements from the insoluble residue is offered.

Processing of perovskite concentrate by ammonium hydrodifluoride

The results of studies of the hydrodifluoride leaching of the perovskite concentrate have been presented. It has been shown that processing the perovskite concentrate using fluoride technology enables one to transform niobium and tantalum into a solution, along with fluoroammonium salts of titanium, iron, and silicon, and to isolate rare-earth elements in the form of complex fluoroammonium salts mixed with CaF2 within a few stages.

Interaction of loparite concentrate with ammonium hydrodifluoride

Results obtained in a study of the interaction between the loparite concentrate and ammonium hydrodifluoride are reported. It was found that the reactions of the main components of the concentrate with NH4HF2 yield complex ammonium fluorometallates. It was shown that water leaching of the fluorinated product makes it possible to transfer niobium and tantalum into solution together with fluoroammonium salts of titanium and silicon and to concentrate rare-earth elements in the insoluble residue in the form of complex salts of general formula NaLnF4.

Physico-Chemical Features of the Synthesis of Mullite in Mixtures of Quartz-Pyrophyllite Rock with a Fluoride-Forming Component

It is established that the use of an ammonium fluoride treatment on quartz-pyrophyllite rock (45% pyrophyllite and 53% quartz) at 650°C changes the traditional mechanism by which mullite is synthesized; it is formed not from metapyrophyllite but from fluoridated pyrophyllite, with the formation of aluminum trifluoride and topaz being intermediate stages of the synthesis process. The optimum ratio of quartzpyrophyllite rock to ammonium hydrodifluoride is 1:1.6, which at 1300°C increases the yield of acicular mullite (with particles 20 – 30 μm long and 3 – 5 μm in cross section) from 12 to 68 wt.%. The content of residual quartz in the mullite is no greater than 15 – 18 wt.%.

Study of fluoride processing of kyanite concentrates

Specific features of the physicochemical processes occurring in the interaction of kyanite concentrates with ammonium hydrodifluoride, sublimation of ammonium hexafluorosilicate, recovery of alumina and aluminum fluoride, synthesis of amorphous silica particles, and reduction of additional reagents were studied. The thermodynamic parameters, rate constants, and activation energies of the occurring chemical reactions were determined. The optimal conditions of the fluoride processing of kyanite concentrates with integrated recovery of various useful components were found.

Method of increasing yield of fluoropolymer powders in thermal destruction of polytetrafluoroethylene waste

A method was proposed that enables the development of an industrial technology for processing polytetrafluoroethylene by distilling it in NH3-HF medium with a solid-phase product yield of more than 60%. The effect of the amount of ammonium hydrodifluoride introduced on the rate of the thermal destruction of polytetrafluoroethylene and the yield of fluororganic powder was studied.

Extraction of boron and silicon in hydrodifluoride processing of a datolite concentrate

The composition of volatile products upon heating of a datolite concentrate that was fluorinated with ammonium hydrodifluoride were studied; the temperature parameters of the transition of the boron and silicon compounds to the gaseous phase were determined and it was established that the difference of the volatilities of the boron and silicon fluoroammoium salts allows selective extraction of these products. A closed technical scheme for processing datolite concentrate by ammonium hydrodifluoride to produce commercial products, viz., ammonium fluoborate, boric acid, amorphous silica, and fluorite, was proposed.

Comprehensive utilization of silica raw material of the upper and Mid-Amur River basins

The analysis of physical-chemical processing of silica-containing raw material has revealed optimal conditions for production of amorphous silica, ammonium hexafluorosilicate, mullite-siliceous refractory, and other commercial products. Using ammonium hydrodifluoride, the authors have developed efficient technologies for complex extraction of valuable components from silica-containing raw material.

Physicochemical processes of the fluoride processing of aluminum ores

The physicochemical processes of the fluoride processing of aluminum ores with ammonium hydrodifluoride were studied theoretically and experimentally. The kinetics of the sintering of raw materials, the sublimation of ammonium hexafluorosilicate, and the formation of aluminum fluoride and alumina are described. The rate constants and activation energies of the chemical reactions were determined. As a result of the investigations, a rational chemical and metallurgical method for alumina production from different aluminum ores with the complex extraction of other useful components has been developed.

Interaction of datolite concentrate with ammonium hydrodifluoride

The interaction of datolite concentrate with ammonium hydrodifluoride were studied. Under heating, ammonium hydrodifluoride fluorinates datolite to form complex fluoroammonium salts of boron, silicon, and impurity metals. The activation energy and rate constants were calculated for the reaction of datolite concentrate with ammonium hydrodifluoride in the range 100–150°C. The composition of the volatiles formed upon the heating of the fluorinated concentrate was studied, the temperature parameters of the evolution of boron and silicon to the gas phase were determined, and a process for separating these elements was proposed.