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90 AZERBAIJAN CHEMICAL JOURNAL № 1 2023 ISSN 2522-1841 (Online)
ISSN 0005-2531 (Print)
UDC 669.292.3
STUDY OF CONDITIONS FOR THE ASSOCIATED EXTRACTION OF VANADIUM AND GALLIUM DURING ALKALINE LEACHING OF RAW ALUNITE ORE
A.A.Heydarov, A.Kh.Osmanova
M.Nagiyev Institute of Catalysis and Inorganic Chemistry, Ministry of Science and Education
of the Republic of Azerbaijan
arzuosmanova235@gmail.com
Received 01.06.2022 Accepted 24.09.2022
Alunite ore containing a significant amount of aluminum, iron oxide, titanium dioxide, and other valuable components (Ga - 0.003 wt%, V - 0.0315 wt.%) is the main raw material for the production of alumina and promising raw material for the production of gallium and vanadium. This paper studies the dynamics of the distribution of gallium and vanadium in the liquid phase during the dissolution of raw alunite in an alkaline solution are studied. The results have showed that alkali concentration, leaching temperature, liquid-to-solid ratio have a significant effect on the degree of extraction of these elements from solution. It has been found that when raw alunite ore is leached with a 5% NaOH solution (S:L=1:6) for 2 hours, the degree of extraction of Ga and V is, respectively, 50.2 and 59.23% of their total content in the rock.
Keywords: vanadium, gallium, alunite, alkaline leaching, recovery rate.
doi.org/10.32737/0005-2531-2023-1-90-96 Introduction
Gallium and vanadium are of significant value in engineering and can become profitable by-products [1]. Gallium is mainly produced worldwide as a by-product of the Bayer process [2, 3]; vanadium is also extracted from sludge during the production of alumina [4, 5]. Gallium is predominantly used in semiconductors as well as light emitting diodes [2], while vanadium is used in the steel industry [6-9].
Gallium and vanadium are closely related to aluminum and therefore occur predominantly in aluminum minerals. The proximity of the ionic radii of gallium, vanadium, and aluminum (0.62, 0.67, and 0.57A0, respectively) determines the possibility of their isomorphic substitution in rocks and minerals. The isovalent iso-
3+ 3+
morphism V ^Al is known, as well as its occurrence of more than 90% of the total vanadium content in the crystal lattices of alumino-silicate clay materials [10, 11]. In Dashkesan alunite ores, the gallium content varies within 0.0005-0.03%, and the vanadium content reaches up to 0.06% [12], in connection with which their extraction is planned along the way. The literature describes a large number of
various methods for processing alunitized rock [13, 14]. In almost all sources, crushed alunite rock is roasted and reduced in fluidized bed furnaces. Roasting of alunite, carried out at a temperature of 6200C for a duration of 1 hour, leads to the decomposition of alunite and kao-linite of waste rock with the release of water. The recovered ore is further processed by the Bayer hydro-chemical process into alumina.
The associated extraction of gallium and vanadium from reduced alunite was studied in the works of Acad. G.B. Shakhtakhtinsky [15, 16]. His works studied the extraction and concentration of gallium and vanadium from aluminate solutions obtained after the dissolution of reduced alunite. To reduce the economic costs associated with the consumption of significant energy and temperature, researchers found a new method for processing alunite [17].
It is known that in alunite rocks, alunite is easily dissolved in solutions of caustic potassium (sodium) above 600C, and at the same time, aluminum goes into the solution in the form of potassium (sodium) aluminate, as well as alkali metal sulfates. Quantitative characteristics of the alunite dissolution kinetics were studied in [18]. However, the extraction of gal-
lium and vanadium from raw alunite ore into solution has not been studied.
This paper considers the issue of studying the conditions for the extraction of vanadium and gallium during alkaline leaching of raw alunite ore without resorting to roasting. These are the first systematic studies on the extraction of gallium and vanadium from raw alunite.
Experimental part
The properties of the feedstock and processed products were studied by the following methods:
- phases were identified by XRD using an AXS 200 diffractometer (Bruker, Germany);
- the content of elements in solutions was determined by the ICP-AES method using an ICP-AES 8300 spectrometer (Perkin Elmer, Germany) and for comparison with KFK-2.
The diffraction pattern of the sample was identified by XRF using CuKa radiation. The morphology of the sample was examined using scanning electron microscopy (SEM/EDS, Hi-tachi-4800, Germany).
In the experiments, the pH of the solution was adjusted with the appropriate alkalis and acids with the HI2211 Munn Instrument.
The work used a sample of alunite from the Zaglik deposit of the composition, mass %: AhO3 - 24.09; SiO2 - 31.09; Fe2O3 - 4.14; TiO2 - 0.48; K2O - 5.15; Na2O - 0.23; SO3 - 27.11; V-0.0315; Ga - 0.003. According to X-ray phase analysis, the main minerals of the technological sample of alunite raw materials are alunite, kaolinite (dickite), hematite and quartz (Figure 1).
Aluminum in the ore is in the composition of alunite and dickite. Figure 2 shows SEMEDS images of a raw alunite sample. Gallium and vanadium containing minerals were not detected, probably due to their low content for the sensitivity of the device.
Alunite leaching was carried out by using a wide range of variable process parameters: NaOH concentration (2.5; 3.8; 5; 10, 20%), temperature (50; 60; 70; 80 and 900C), S: L = (1:2; 1:4; 1:6; 1:8; g/l), stirring time (0.5; 1; 1.5; 2 and 3 hours). Experiments on the extraction of Ga and V from alunite were carried out in a 150 ml container with continuous mechanical stirring. The technique for studying the capacity was to mix a sample of ore in a NaOH solution so that an excess of alkali was provided in all cases.
Fig. 1. X-ray diffraction pattern of the raw alunite ore of the Zaglik deposit.
Fig. 2 SEM and EDS analysis of the raw alunite ore.
A glass beaker with 100 ml of a solution of one of the indicated concentrations was placed in a thermostat, and when the solution reached a given temperature, alunite samples were added, after a certain time an aliquot sample was taken. The content of gallium and vanadium was determined by the photocolorimet-ric method [19].
Results and discussion
To select the optimal solvent for the extraction of vanadium from raw alunite ore, acids and alkali were used. To do this, 50 ml of concentrated acid and alkali were added to finely crushed alunite ore until a doughy mass was obtained, then 100 ml of water was added, boiled for 3 hours at a constant volume of water and filtered. After that, vanadium was determined in the aqueous and acid extracts and in
the undissolved residue. The results of the determinations are given in Table 1.
As can be seen from Table 1, vanadium is almost not extracted from raw alunite ore with water, hydrochloric and nitric acids. Sulfuric acid extracts vanadium partially, and alkali extracts completely. Therefore, further experiments were carried out by alkaline leaching of alunite.
The influence of various factors on the degree of extraction of vanadium, gallium and other indicators in the process of leaching from raw alunite was studied: alkali concentration, process temperature, intensity of pulp mixing, leaching duration, S:L ratio.
In the process of leaching, the degree of extraction of vanadium and gallium is determined by their amount, which passed into the mother liquor and washing water. Based on the analysis of solutions and leaching tailings, one
can judge the distribution of useful components between the liquid and solid phases.
Preliminary experiments have established that when the stirrer speed is more than 700 rpm, the rate of transition of aluminum, gallium and vanadium into the solution does not depend on the stirring speed. Therefore, in subsequent tests, the stirring speed was kept constant at 700 rpm.
The effect of NaOH concentration on the completeness of extraction of vanadium and gallium from raw alunite is shown in Table 2. The extraction of vanadium and gallium into solution is strongly affected by the concentration of NaOH.
Experimental conditions: alkali concentration varies from 2.5-20%, weight of alunite 25 g, temperature 500C, S:L=1:6; leaching time 2 hours. From the data in Table 2, it can be seen that the leaching efficiency is observed at an
initial alkali concentration of 5%. The degree of extraction of V and Ga at 5% leaching alkali concentrations is 32.95% and 42.6%, respectively. Despite the fact that with an increase in alkali concentration, the transition of gallium and vanadium into solution increases, however, from an economic point of view, 5% NaOH was chosen. It is appropriate to note that the optimal concentration of NaOH for leaching raw alunite is 5% [14].
To save the consumption of the leaching reagent for the extraction of Ga and V, the percentage concentration of alkali was chosen to be 5%. The effect of temperature on the extraction of vanadium and gallium during leaching was studied on a sample crushed to - 0.05 mm, with an experiment duration of 2 hours in the temperature range of 50-900C; S:L = 1:6. The results of the experiments are given in Table 3.
Table 1. Distribution of vanadium in alunite processing products
in solution in the insoluble residue
Acid and alkaline extracts
Water Acids and Vanadium Degree of vanadium Content Degree of vanadium ex-
alkali content, % extraction, % vanadium, % traction of, %
— HCl 0.003 9.53 0.0285 90.47
— HCl 0.0015 4.76 0.0300 95.23
— HNO3 0.002 6.35 0.0295 93.65
— HNO3 0.0015 4.76 0.0300 95.238
— H2SO4 0.0180 57.14 0.0135 42.86
— H2SO4 0.0158 50.16 0.0157 49.84
— NaOH 0.0310 98.41 0.0005 1.59
— NaOH 0.0310 95.23 0.0015 4.77
Table 2. Data on the effect of NaOH concentration on the completeness of extraction of vanadium and gallium from raw alunite
Experience number NaOH concentration,0/« Remaining, g Concentration in solution,mg/l Extraction degree, %
V Ga V Ga
One 2.5 15.35 5.07 0.71 9.965 14.2
2 3.8 13.9 12.48 1.32 23.77 26.4
3 five 13.0 17.3 2.43 32.95 48.6
4 10 12.7 23.4 2.96 44.57 59.2
five twenty 12.6 30.03 3.25 57.2 65
Table 3. Effect of temperature on the extraction of vanadium and gallium during leaching
Temperature 50 0 C 60 0 C 70 0 C 80 0 C 90 0 C
Ga content in solution mg/l 2.43 2.51 3.5 4.1 4.73
Degree of Ga extraction, % 48.6 50.2 70 82 94.6
V content in solution, mg/l 17.3 31.1 35.5 41.73 49.875
Degree of extraction V, % 32.95 59.23 67.62 79.5 95
From the data obtained, it can be seen that with an increase in the leaching temperature from 50-900C, the extraction of vanadium and gallium into the solution increases. It can be seen that temperature plays a decisive role in the leaching of vanadium and gallium. For example, operating at 700C, the extraction efficiency of vanadium and gallium reaches 70% and 75.5% respectively, further increasing the temperature to 900C, the extraction efficiency of vanadium and gallium reaches 90.6% and 94.5%, respectively. Thus, it can be concluded that the leaching temperature of 900C will be sufficient and is considered acceptable, optimal. However, because of the high energy consumption at such a temperature, a lower value of this factor - 700C should be taken as optimal, taking into account that the leaching of aluminum, as the main component of the process, completely goes into solution at 700C [20].
The influence of the ratio of liquid to solid on the extraction of vanadium and gallium into solution was studied at a ratio of 2:1; 3:1; 6:1; 10:1 and 7:1, subject to the leaching condi-
tions specified in Table 3. The results of the experiments are shown in Figure 3. It follows from the data obtained that a change in the S:L ratio within the limits used in practice has practically no effect on the extraction of rare metals into solution.
In order to obtain more concentrated solutions for vanadium and gallium, it is desirable to carry out leaching at a minimum S:L ratio.
Judging by the data in Figure 3, the best results, in terms of the maximum extraction of V and Ga into the mother liquor, were obtained with S: L = 1:10, however, the solutions are too dilute in V and Ga. Therefore, we came to the conclusion that S: L =1:6 is optimal.
The effect of leaching duration on the extraction of vanadium and gallium into solution was studied with ore weights of 25 g each. In these experiments, other leaching conditions remained unchanged, namely 5% NaOH, temperature -700C, S: L =1:6.
It follows from the results of the experiments that with an increase in the duration of leaching to 2 hours, the extraction of both vana-
dium and gallium increases somewhat. It is concluded that a leaching time of 120 min would be sufficient and could be considered optimal for the extraction of vanadium and gallium.
As can be seen from Table 3, the content of Ga and V in the solution can reach up to 4.53 mg/l for Ga and 42.68 mg/l for V. The concentration of Ga and V in the aluminate solution is very low. In order to concentrate Ga and V, the resulting mother liquors were recycled. In this case, the initial concentration of NaOH was stable (5%). After six-fold recirculation of the solution, the Ga concentration in the recycled solution increases by almost 6 times, and the vanadium concentration by 5.5 times.
In the resulting solution, the concentration of Ga reaches 27.18 mg/l, and vanadium 234.74 mg/l.
Conclusions
The conditions for the extraction of gallium and vanadium from raw alunitized rock with an alkali solution have been and it has been found that when it is leached with a 5% NaOH solution (S:L=1:6) for 2 hours, the degree of extraction of Ga and V is, respectively, 50.2 and 59.23 of their total content in the rock.
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ALUNÎT MiNERALININ QOLOVi iLO EMALI ZAMANI VANADiUM VO QALLiUMUN MOHLULA
ÇIXMASI §ORAiTiNiN TODQiQi
A.A.Heydarov, A.X.Osmanova
Alunit mineralinin tarkibinda çoxlu miqdarda aluminium, damir oksid, titan dioksid va digar qiymatli komponentlar (Ga - 0.003%, V - 0.0315%) vardir. Buna göra da, alunit filizi alminiumun oksidi, qallium va vanadiumun alinmasi ûçûn perspektivli xammal sayila bilar. Tadqiqat içinda xam alunit mineralinin qalavida qizdirilmaqla hall olmasi zamani qallium va vanadiumun mahlula çixim dinamikasi izlanilmiçdir. Müayyan olunmuçdur ki, qalavinin qatiligindan, temperaturdan va bark-maye faza nisbatindan asili olaraq qallium va vanadiumun mahlula çixim faizi dayiçir. Malum olmuçdur ki, 5%-li qalavi mahlulu NaOH (b:m=1:6 nisbatinda) 2 saat arzinda alunit süxurundan qalliumu 50.2%, vanadiumu isa 59.23% mahlula çixarir.
Açar sözlzr: vanadium, qallium, alunit, qalavi ila emal, çixim faizi.
ИССЛЕДОВАНИЕ УСЛОВИЙ ПОПУТНОГО ИЗВЛЕЧЕНИЯ ВАНАДИЯ И ГАЛЛИЯ ПРИ ЩЕЛОЧНОМ ВЫЩЕЛАЧИВАНИИ СЫРОЙ АЛУНИТОВОЙ РУДЫ
А.А.Гейдаров, А.Х.Османова
Алунитовая руда, содержащая значительное количество алюминия, оксида железа, диоксида титана и других ценных компонентов (Ga-0.003 мас. %, V-0.0315 мас. %) является основным сырьем для получения глинозема и перспективным сырьем для получения галлия и ванадия. В данной работе исследована динамика распределения галлия и ванадия в жидкой фазе при растворении сырого алунита в щелочном растворе. Результаты показали, что концентрация щелочи, температура выщелачивания, отношение жидких и твердых веществ, имеют значительное влияние на степень извлечения этих элементов из раствора. Установлено, что при выщелачивании сырой алунитовой руды 5%-ным раствором NaOH (Т:Ж=1:6) в течение 2 часов, степень извлечения Ga и V составляет соответственно, 50.2 и 59.23% от общего их содержания в породе
Ключевые слова: ванадий, галлий, алунит, щелочное выщелачивание, степень извлечения.
