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ISSN 2522-1841 (Online) AZERBAIJAN CHEMICAL JOURNAL № 2 2022 63
ISSN 0005-2531 (Print)
UDC 544.344.015.3: 546.57'23
PROCESSING OF THE VANADATE FRACTION IN AJINAUR TITANIUM-MAGNETIC
CONCENTRATES
U.N.Sharifova
M.Nagiev Institute of Catalysis and Inorganic Chemistry, NAS of Azerbaijan
demirtitan2015@gmail.com
Received 25.06.2021 Accepted 04.08.2021
The conditions for purification and waste-free utilization of the vanadate fraction of processing Ajinaur titanomagnetite concentrates in Azerbaijan by the carbonization method, including desiliconization, extraction of aluminum, regeneration of sodium carbonate and production of vanadium pentoxide, have been determined. It was found that TABAC (three alkylbenzylammonium chloride) is an effective ex-tractant for extracting vanadium from carbonate - vanadate solutions without destroying carbonate ions. A technological scheme for processing carbonate-alkaline vanadate solutions to obtain vanadium pent-oxide of reactive purity 99.7% corresponding in the quality to the analytical grade, y-Al2O3 and soda regeneration has been drawn up.
Keywords: titanomagnetite concentrates, vanadanate fraction, extraction, obtaining vanadium pentoxide.
doi.org/10.32737/0005-2531-2022-2-63-68
Introduction
There are a number of methods for processing titaiomagnetite concentrates, including the extraction of vanadium by pyrometallurgical and hydrometallurgical methods [1-5]. They are based on high-temperature smelting of concentrates to obtain vanadite cast irons and titanium slags, and then on the nonsemification of cast iron-steels and vanadium slags. The resulting slags are further processed by various chemical methods for the extraction of titanium and vanadium. The hydrometallurgical method developed in [6, 7] is based on the roasting-leaching processes and is characterized by a higher extraction of vanadium (80-90%), but it is used only for processing high-vanadium ores and concentrates (1% V2O5) with relatively small volumes of them extraction. The disadvantages of this method are large material flows associated with the extraction of vanadium, and the formation of a large volume of fine titanium-containing iron ore residues. The pyrometallurgical method developed in [8-12] includes the processes of producing pig iron by reducing the smelting of titano-magnetite ores or concentrates with flux additives in a blast furnace or ore-thermal electric furnaces and blowing it with oxygen in converters or special ladles to obtain a carbonaceous semi-product (pig iron) and vanadium slag. The carbonaceous semi-product is used for the pro-
duction of steel, and the slag is processed by the hydrometallurgical method to obtain V2O5.
According to the method proposed in [13], titanomagnetite concentrate containing 57.5% Fe, 0.66% V (in terms of V2O5 - 1.18%) and 16.6% TiO2 is subjected to reduction smelting in ore-thermal electric furnaces in presence of solid carbon. This produces a metal product containing up to 99% Fe, and a slag containing 9-35% FeO, 31-46% TiO2 and 1.2-1.6% V (2.14-2.9% V2O5). About 98% of titanium and vanadium remain in the slag phase. The slag is further processed to extract vanadium and titanium. A similar method for processing titanomagnetite concentrate is described in [14]. The concentrate containing 64% Fe, 7.6% TiO2 and 1.6% V2O5 is rounded, and the pellets with the addition of 26% carbon (by weight of the concentrate) are subjected to reduction melting in an electric furnace to obtain cast iron and vanadium-containing titanium slag. In this case, a large amount of vanadium, together with titanium, is concentrated in the slag. Under conditions of smelting reduction of the initial concentration, the rate of the iron metallization process in the liquid phase proceeds slowly, as a result of which the duration of the electric smelting process significantly increases. This leads to high energy consumption.
According to the method [15] of processing titanomagnetite concentrates, pellets of
titanomagnetite concentrate (55-64% Fe, 2.517% TiO2, 0.5-1.3% V2O5, 0.5-3% SiO2, 0.54% Al2O3, 0.1-1.05% Cr2O3, 0.5-3% MgO, 0.11.7% MnO) without flux additives are first subjected to preliminary metallization using a gas reducing agent, then metallized pellets are melted in ore-thermal electric furnaces with direct production of metallic iron, bypassing the smelting of pig iron, and complex titanium-vanadium slag. In this case, almost all or most of the vanadium is concentrated in the titanium slag. Depending on the composition of the concentrate used, the V2O5 content ranges from 2 to 7%, and the TiO2 content ranges from 24-60%. Subsequently, the metal is processed to obtain high-quality steel, and the slag is processed by a hydro-metallurgical method to extract vanadium and titanium. The main disadvantage of this method is the use for the separation of metallized iron and vanadium-containing titanium slag in an energy-intensive process - smelting in electric furnaces.
However, these processes which are complex and expensive, require a large consumption of fuel and energy resources, as well as they are multistage and are accompanied by the loss of target components. In works [16-24], in relation to the concentrates of placer titanomagnetites in the south-western coast of the Caspian Sea and the Ajinaur deposit of Azerbaijan, the processes of complex processing of titanomagnetite concentrates are developed using the non-blast method of direct reduction of pellets with natural gas at low temperatures in the solid phase with the extraction of valuable components. In the process of complex processing of titanomagnetite concentrates with a flux additive Na2CO3, which promotes the separation of iron from titanium and elements of the oxide phase, during reduction with natural gas, along with metallization of iron, vanadium (III) is oxidized to vanadium (IV and V) and during leaching of the reduced product, followed by obtaining iron powders and titanium dioxide, vanadium is completely converted into vanadate-carbonate solutions, in the form of NaVO3 and Na3VO4 [1619]. In [20-24], technological schemes of processing Ajinaur titanomagnetite concentrates are presented to obtain iron powder a-Fe (99%), anatase and rutile modifications of technical tita-
nium dioxide (99% TiO2), titanium (99% Ti) and the separation of the vanadate phase.
This work aims to determine the conditions for processing the vanadate fraction of the Ajinaur titanomagnetite concentrates to obtain vanadium pentoxide V2O5 of reactive purity.
Experimental methods and results
During the experiments, both classical and modern methods of physicochemical analysis were used. In particular, we used DSC brand NETZSCH STA 449F3 STA449F3A-0836-M, DTA (Netzsch 404 F1 Pegasus system) and XRF (powder diffractometer D8 Advance from Bruker, CuKa1-radiation), Automatic X-ray diffractometer DRON-3M; Thermo Scientific XRF spectrometer. Vanadium was determined by photocolorimetric method with vanadium extraction with bis (2-hydroxy, 5-octylbenzyl) amine in benzene. The object of research is the vanadate fraction of the Ajinaur titanomagnetite concentrates of Azerbaijan. For the purification and utilization of carbonate-alkaline vanadate solutions of the Ajinaur titanomagnetite concentrates, an experimental technique was used, which was used in the processing of titanomag-netite concentrates from the southwestern coast of the Caspian Sea [18]. Based on the experiments carried out, a technological scheme for processing the vanadate fraction was determined (Figure 1).
Desiliconization of vanadate solution
After water leaching of the reduced titan-omagnetites into the resulting vanadate-carbo-nate solutions, in addition to the fully recoverable vanadium, silicon, in the form of Na2SiO3, aluminum, in the form of Na[Al(OH)4] and residual amounts of carbonate and caustic alkali, are partially transferred. Therefore, it becomes necessary to utilize silicon, aluminum and further extract vanadium in the form of pentoxide with the regeneration of soda. The conditions for the de-siliconization of these solutions have been studied. When settling vanadate solutions, a white precipitate of aluminosilicates spontaneously separates from them, due to the binding of sodium silicate and aluminate:
Na2SiO3+Na[Al(OH)4]=NaAlSiO4-H2O|+2NaOH.
Precipitation is accelerated when the solution is heated. A single concentration of the solution at 90~1000C for 3 hours and the separation of precipitates achieve a degree of desili-conization of 98-99%, and the residual silicon content does not exceed 0.1 g /l.
Filtrate carbonation and aluminum recovery
After separation of precipitates of sodium hydroaluminosilicate in vanadate solutions, along with vanadium, caustic and carbonate alkalinity, contains more than 30 g/l of Al2O3. Therefore, we further studied the conditions for purifying vanadate solutions from aluminum by carbonization with carbon dioxide with the extraction of alumina. Aluminum orthohydroxide, Al(OH)3, is released from aluminate solutions when carbon dioxide is passed through. The reaction of precipitation of orthohydroxide is represented in the form: 2Na[Al(OH)4]+CO2 = 2Al(OH)3 j+Na2CO3+H2O and the alkali turns into sodium carbonate:
2NaOH + CO2 = Na2CO3 + H2O
The influence of various factors on the degree of extraction of Al2O3 was studied. The optimal conditions for carbonization of the van-adate-aluminate solution with carbon dioxide were established in a wide range of Al2O3 concentrations: temperature 70-600C, duration 7-10 min, CO2 feed rate - 1.2 l/min, which achieve a fairly complete degree of aluminum extraction -95%, as well as complete carbonization of caustic alkali by 100%. It was found that the carbonization of vanadate-aluminate solutions with CO2 is accompanied by a strong exothermal reaction, as well as a drop in the pH of the solution from 12.6 to 8.5. The obtained sediment was washed, dried at 110-1200C, and subjected to diffraction analysis. The precipitate of aluminum hydroxide compounds contains dawsonite -NaAlCO3(OH)2 and sodium aluminate of the composition NaAl5O8 in a 1:1 ratio, which decompose during firing to form A12O3 and Na2CO3. The Na+ cations contained in their composition prevent the passivation of y-alumina during burning at 8000C.
Soda regeneration
After desiliconization and extraction of y-Al2O3, the vanadate solution contains sodium
vanadate (4.5-5 g/l V2O5) and soda (up to I15 g/l). When the vanadate solution is carbonized, bicarbonate is gradually precipitated:
Na2CO3 + CO2 + H2O = NaHCO3|
The optimal conditions for the regeneration of soda and its separation from vanadium in the form of sodium bicarbonate by stepwise carbonation with carbon dioxide have been determined. At a temperature of 35-400C, with a gradual decrease to 180C, a CO2 supply rate of 0.5-1 l/min, after 3 stages carbonization, the total degree of extraction of soda reaches 95% with a purity of 96.7-99.5%. The concentration of V2O5 in the purified solution reaches 60 g/l.
Extraction of vanadium. Obtaining V2O5
For extraction, a solution of technical TABACh (three alkylbenzylammonium chloride) was used:
Cl
U n cH2R3N
here R is an alkyl radical: C7-C9.
0.45M solution of technical TABACh, allowed to extract vanadium directly from carbonate solutions. When extracting vanadium in a carbonate medium (V2O5 - 4.5 g / l, Na2CO3 - up to 120 g/l), during the processing of placer ti-tanomagnetites, the degree of extraction of vanadium even with a 20-fold excess of carbonate ions (VB:VO = 2:1, pH - 10.8-11) for 1 step was quite high - 60%, and for 5-6 steps it was almost complete. When extracting from car-bonate-vanadate solutions, the maximum vanadium saturation of the solution of the TABAC modified form was from 21 to 28.8 g/l.
A number of compounds were tested to study the conditions for the re-extraction of vanadium from the extractant. The most effective stripping agents were solutions of NH4Cl and (MH4)2CO3 salts. Studies have shown that during the stripping of vanadium with ammonium chloride at Vwater:Vorg = 2:1 and a contact time of 10 min, the maximum extraction of vanadium takes place at a concentration of NH4Cl and during the stripping with a solution of (NH4)2CO3 at a concentration of 20, 40% when
the degree of stripping is with a single treatment it reaches 90%. In the process of re-extraction, a precipitate of ammonium metavanadate NH4VO3 is formed, which was dried and calcined at 5500C to constant weight:
2NH4VO3= V2O3+2NH3+H2O.
The aqueous phase with residual vanadium was returned to the re-extraction process for reuse. After the decomposition of NH4VO3, vanadium pentoxide of reactive purity of 99.7% was obtained, corresponding in quality to the analytical grade.
It was found that, due to the presence of carbonate-alkaline vanadate solutions obtained during the leaching of reduced titanomagnetites, along with carbonate and caustic alkali, which significantly impairs the extraction of vanadium, it is more efficient to extract vanadium after carbonization of these solutions and separation of aluminum, then the degree of extraction of vanadium for 1 step it already reaches 70%, with C (V5+): C (CO3 ) = 1:15. In addition, after the utilization of aluminum and obtaining y-Al2O3, the extraction of vanadium from purified solutions without destroying carbonate ions contributes to the production of pure soda solutions during their recirculation into the head process of granulation of titanomagnetite concentrates, or for regeneration of soda. After the utilization of aluminum, the extraction of vanadium in 4-5 stages of extraction reaches 99.6% of its content in the original titanomagnetites and the original soda is regenerated.
The technological scheme for the processing of carbonate-alkaline vanadate solutions to obtain vanadium pentoxide of reactive purity 99.7%, corresponding in quality to the analytical grade, y-Al2O3 and the regeneration of soda with the combined use of titanomagnetite concentrates is shown in Figure 1.
Conclusion
Thus, modified trialkylbenzylammonium chloride is an effective extractant for extracting vanadium from carbonate-vanadate solutions without destroying carbonate ions. In general, an economical, waste-free and closed-circuit technology has been developed for the complex
processing of the Ajinaur titanomagnetite concentrates to obtain y-alumina and vanadium pentoxide V2O5 of high purity with the regeneration of the used sodium carbonate.
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ACINOHUR TiTANMAQNETiT KONSENTRATLARININ VANADAT FRAKSiYASININ i^LONMOSi
U.N.§arifova
Azarbaycanin Acinohur titanomaqnetit konsentratlanmn vanadat fraksiyasinin karbonla§dirma usulu ila tamizlanmasi va tullantisiz istifadasi §araiti, o cumladan silisiumsizla§dmlmasi, aluminium ayrilmasi, natrium karbonatin barpasi va vanadium pentoksidin alinmasi §araiti i§lanmi§dir. TABAX-in (ugalkilbenzilammonium xloridin) karbonat - vanadat mahlullarindan karbonat ionlarini pargalamadan vanadiyum gixarmaq ugun tasirli bir ekstragent oldugu a§kar edilmi§dir. Titanomaqnetit konsentratlarinin karbonat-qalavi vanadat mahlullarindan y-Al2O3, analitik tamizlik daracali - 99.7% li vanadium pentoksid reaktivinin alinmasi va sodanin barpasi proseslarinin texnoloji sxem tartib edilmi§dir.
Agar sozlar: titanmaqnetit konsentratlari, vanadat fraksiyasi, ekstraksiya, vanadium pentoksidin alinmasi.
ПЕРЕРАБОТКА ВАНАДАТНОЙ ФРАКЦИИ АДЖИНАУРСКИХ ТИТАНОМАГНЕТИТОВЫХ
КОНЦЕНТРАТОВ
У.Н.Шарифова
Определены условия очистки и безотходной утилизации ванадатной фракции переработки Аджинаурских титаномагнетитовых концентратов Азербайджана карбонизационным методом, включающие обескремнивание, извлечение алюминия, регенерацию карбоната натрия и получение пентаоксид ванадия. Выявлено, что триалкилбензиламмоний хлорид является эффективным экстрагентом для извлечения ванадия из карбонатно-ванадатных растворов без разрушения карбонат-ионов. Составлена технологическая схема переработки карбонатно-щелочных ванадатных растворов титаномагнетитовых концентратов с получением пентаоксида ванадия реактивной чистоты 99,7% соответствующий по качеству марки ч.д.а, y-Al2O3 и регенерацией соды.
Ключевые слова: титаномагнетитовые концентраты, ванаданатная фракция, экстракция, получение пентаоксида ванадия.
