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UDC 669.334.6
RESEARCH OF LEACHING CONDITIONS OF COBALT FROM HIGH-SILICA CONTAINED COBALT ORES WITH MINERAL ACIDS
A.A.Gaydarov, N.V.Yusifova
M.Nagiev Institute of Catalysis and Inorganic Chemistry NAS of Azerbaijan
naile.yusifova@inbox. ru Received 18.01.2016
In the article the results of studying the process of extracting cobalt out of Dashkesan high-siliceous cobalt ores are cited. The composition of cobalt ore was studied. It was shown that due to the presence of hard soluble minerals and silica compounds of cobalt in the composition of ore leaching of Co with solutions of hydrochloric acid (7 and 20%) and sulfuric acid (up to 2 N) is insufficiently effective. The method of processing ore that provides for its sulfatizing roasting with further leaching with water is suggested. It was observed that extraction of cobalt by sulfatization at 7000C made up 85.52%.
Keywords: Cobalt, ore, sulphatizing roasting, leaching, sintering, extraction.
Introduction
Cobalt and its compounds are widely used in various industries: metallurgical, chemical, radio-electronic. Alloying steel with cobalt increases its heat resistance and improves mechanical properties. From cobalt-containing alloys different tools - drill bits, cutters, etc are produced. To produce permanent magnets cobalt is used as high-performance positive electrode for the production of lithium batteries. Radioactive cobalt (Co60) is used in gamma-detection and in medicine. Cobalt is one of the vital microelements for organism. The daily human need for cobalt is 0.007-0.015 mg. On 28 January 2016 the price of cobalt on the world market, according to the data, In-fo.geo.ru, was about 22 $/kg.
Basically, minerals of cobalt are sulfides, arsenides and silicates. It often forms a compound with an impurity of iron, copper, manganese, lead and some other metals [1].
Ores from which cobalt is extracted, are very diverse in their chemical and mineralogical composition, the cobalt content in them varies widely - from tenths of a percent to a few percentages. But unoxidized ores (sulfides or arsenic ores), especially complex ones have industrial uses even at the concentration of cobalt 0.15% and less than it, as they enter to the enrichment process [2-7].
Dashkesan is the most important mining district in Azerbaijan. Dashkesen district is not only abundant with its iron ores but also with its cobalt and alunite ores. Azerbaijani scientists
G.Kh.Efendiev [7] and M.A.Kashkai [8] have installed characteristics of cobalt sulphoarsenic minerals for all Dashkesan metallogenic region. Basically, they are cobaltite (CoAsS), safflorite (Co,Fe,Ni)As2, glaucodot (Co,Fe)AsS, skutteru-dite CoAs3.
Cobaltite is the main ore mineral of sul-foarsenic complex and the main cobalt mineral of deposit of Dashkesan ore district [9]. Currently processing Dashkesan cobalt ores is not carried out in Azerbaijan.
For the processing of high-silica aluminum ores containing cobalt, appropriate to use acid methods, as these methods allow to selectively allocate silica contained ores already at the acid processing stage, which is a kind of chemical enrichment process of cobalt.
In the acidic methods of processing low-quality aluminum ores they usually use sulfuric and hydrochloric acids, which permit relatively easy to carry out a selective separation of silica and alumina already on the stage of acidic ore processing.
The aim of current work is maximum extraction of cobalt from high-silica-containing Dashkesan deposite ore by using acidic methods (hydrochloric and sulfuric acid), also by sintering-acidic methods.
Experimental part
Research objects. The studied cobalt ore of Dashkesan deposit is polymineral ore. According to the results of X-ray and miner-alogical analysis methods this ore contains the following minerals: cobaltite, erythrite, clino-
chlore, andradite, a-quartz, hematite, aluminum phosphide.
Under the microscope, the major rock-forming minerals - aluminosilicates (clino-chlore, andradite) are observed in the form of large and small grains of irregular shape.
Cobaltite in polished sections is characterized by its weak anisotropy effects, it is of a pinkish-brown color. Depending on its location it can be found in the cracks among garnet skarns, sometimes it is intergrown with saf-florite accompanied with pyrite.
From the results of mineralogical analysis it follows that investigated cobalt ore is also high siliceous aluminum raw material which contains: clinochlore - 44.2%, andradite - 23.3%, a-quartz
- 11.2%, aluminum phosphide - 2.2%.
Despite the low aluminum content (4.57.6%) the presence of other valuable components such as Mg, K, Ti, Mn, Cr has been revealed. Complexity of this type ore processing, whose enrichment process is difficult, is associated with presence of both sulfoarsenic and oxidized minerals and their intergermination and also presence of other metals-impurities. Dash-kesan cobalt ore has the following average of chemical composition (in count of oxides), mas.%: Na2O - 1.48, MgO - 5.65, A^ -14.29, SiO2 - 44.64, SO3 - 0.85, K2O - 1.32, CaO - 7.19, As2O3 - 5.20, Fe2O3 - 12.93, MnO
- 0.43, TiO2 - 0.54. Established that the CoO content in the ore is in the 3.58-5.48% range.
Research methods. While conducting research ore was pre-milled to a particle size 0.074 mm (200 mesh). Obtained material is close to monodisperse. A weighed sample of the ore or calcine (5-10 g) was placed in a flask in which water or acid leaching was held and stirred under heating with a magnetic stirrer. Leaching was carried out at temperatures of 293-363 K, in different concentrations of acid for 60-300 minutes. The sediment after processing reagent was filtered, washed with water and washing water was combined with the primary filtrate. The influence of parameters on the leaching extraction of components of the ore or calcine in the solution was determined by analyzing samples of the liquid and solid phases of the slurry. Determination of metals (Al, Mg,
Cu, Fe, Mn, Co, As) in solution was conducted with the X-ray fluorescence spectrometer "Bruker S2 PICOFOX" (Germany). Thermo-gravimetric analyses of initial ore and product of its sulfation are carried out on derivatograph Yupiter STA 449 F3 (Germany) in the range of 20-1000°C in an argon flow at speed temperature of rise at 100C/min. Mineralogical analysis of cobalt ore was performed using the Oxford EDS microscope. X-ray phase analyses of cobalt ore and products was made at AXS diffractometer of company "Bruker".
Results and Discussion
In the present work a study in has been made of the decomposition process of cobalt ore from Dashkesan deposit with solutions of sulfuric and hydrochloric acids, and sintering-acidic methods to selectively extract the raw components of raw material and finding the optimal conditions for its decomposition to ensure maximum extraction of valuable components in a solution depending on the different physical and chemical factors.
Preliminary experiments showed that while processing studied ore with water transition of cobalt to solution does not occur. It shows that, basically, cobalt in the ore is in hard uncovered form. pH magnitude of liquid phase does not change too, hydrolysis of compounds, within the ore does not occur. For comparative assessment of the interaction of ore creating elements with various liquid environment their solubility in various concentration of hydrochloric and sulfuric acids was studied.
Figure 1 shows data which describe the effects of initial concentration of sulfuric acid solution at the extraction degree of cobalt from ore. Constant factors are: processing temperature -200C, leaching duration - 60 minutes, and S:L=1:5. As is seen from the figure, the processing of raw materials with sulfuric acid, with the increasing acid concentration from 0.5 to 2 N extraction degree of cobalt increased from 7.3 to 35.17%. In conjunction with cobalt to the liquid phase there also move iron sulfates, potassium, calcium, manganese, zinc. Transition copper and aluminum is only 2 and 4% respectively.
Results of experiments (Table 1) show that while the leaching with the solution of 2 N H2SO4 concentration of cobalt in solution in-
creases with the increasing duration of the leach. However, with this the content of iron and arsenic impurities in solution significantly increases.
Initial concentration of H2SO4, N
Fig.1. The dependence of the cobalt content in the solution, from initial concentration of sulfuric acid at a temperature of 200C, at the ratio S:L =1:5.
Table 1. Dynamic content of elements in solution, depending on the concentration of H2SO4 acid (temperature
- 200C, the ratio S:L=1:5, duration of leaching - 1 hour)
и <и ■Л * 1 d Content of elements, mg/l
о о £ s $ а к 5 (и о ° K Ca Mn Fe Co Cu As
1 0.1 6.8 171.2 10.17 1.48 336.5 3.2 370.1
2 0.5 9.1 194 36.1 526 1320 21.2 1452
3 1 42.1 221 45.2 725 1450 24.7 1656
4 1.5 44.6 252 49.8 1056 1592 30.8 1908
5 2 47.2 328 58.9 1131 1618 33.20 1980
Increasing the ratio of S:L reduces extraction of Co(II, III) in solution. This may be due to the fact that an increase in water flow reduces the acidity of the solution and, consequently, degrades the leaching of cobalt compounds.
The nature of the curve (Figure 1) leads to the conclusion that increasing the initial concentration of 1N H2SO4 to 2 N exertes no substantial effect on the speed of dissolving of cobalt, which diminishes with time.
The dynamics of dissolving of cobalt, depending on the duration of leaching H2SO4-1N concentration, in a S:L=1:5 ratio, at 200C temperature has shown in Figure 2.
As is seen from Figure 2, the process is characterized with a high rate of cobalt leaching in the first hours, but after its deceleration was observed.
Fig.2. Depending extraction rates of Co and Fe while the duration of leaching ore with sulfuric acid (CH2so4 =1N, at 200C temperature, in S:L=1:5 ratio).
To determine the optimum temperature mode cobalt leaching from ore experiments to study the influence of the test temperature on the extraction of cobalt in solution were carried out. The data shows that increasing the temperature of the process from 20 to 800C promotes increasing extraction of cobalt to solution from 31.52 to 76.7%. One can draw a conclusion that the sulfuric acid leaching does not provide a sufficiently high extraction of cobalt to the liquid phase. For looking more effective ways to opening cobalt ores we have also studied the possibility of extracting cobalt with hydrochloric acid solutions.
Effect of hydrochloric acid concentration on the process of the initial ore decomposition was studied at two concentration 7 and 20 %, and established optimal conditions: the process temperature - 900 C, dosage of acid - 120% of the stoichiometry for chlorination of ore components, the duration of the process of acid digestion - 1 hour (Table 2). As is seen from Table 2, increasing the concentration of hydrochloric acid leads to increasing the concentration of cobalt associated elements such as Mg, Al, As, Fe, Ca, K, which dissolving significantly complicate the following purification steps of cobalt from other metals. Reducing acidity of the solutions leads to decrease in extraction degree of cobalt. X-ray phase analysis of filter cake, obtained after leaching, showed that the most minerals in raw material also remain in a filter cake leaching.
Table 2. The results of the initial sulfuric acid leaching cobalt ore. Conditions of experiments: temperature - 900C, leaching time - 1 hour, weighted ore -10 g, ratio S:L=1:5_
Expenditure of HCl, % Content, g/l Extraction degree, % Content of cake, % Weight of cake, g
Co Fe As Co Fe As Co Fe As 6.9
7 3.04 9.6 3.8 66.07 57.85 73.63 1.1 5.0 1.02 6.7
20 3.32 10.6 4.01 72.92 64.98 77.41 0.95 4.38 0.98 6.5
The result of sulfuric acid leaching cobalt from studied ores also indicate that it is not possible to achieve sufficiently high extraction into solution: the extraction degree of cobalt does not exceed 66.07-72.92% (Table 2). Thus, studies have shown that the processing of cobalt ores with solutions of sulfuric and hydrochloric acids do not provide sufficient full transition of cobalt in solution. In order to achieve high extraction of cobalt we have tested sulfatizated ore roasting and leaching of pre sulfatizated calcine.
One of the efficient methods of opening sulfo-arsenic material is its sulfatization of sulfuric acid concentration. Sample ore (10 g) was stirred with concentrated sulfuric acid (1.84
3 0
g/sm ) and sintered at 300 C. Weight of sample as a result of sulfatization on average increased by 1.5 times. Decisive impact on sulfatization completeness is provided by amount of acid and temperature. The obtained at various temperatures (r=400-700°C) sulfatizated ore mass leached with water at 800C, during 1 hour. Ratio S:L=1:5. Indices of sulfatization process of cobalt material with concentrated sulfuric acid has shown in Table 3. Sulfatization of cobalt in calcine with sulfuric acid intensively proceeds at 4000C (extraction degree of Co is 73.68%), extraction degree of solution is maximum at 7000C temperature (output 85.52%) after which extraction of cobalt increases with increasing temperature. At higher than 7000C the formation of cobalt ferrite starts. Maximum sul-fatization of iron was obtained at 400-500°C. With increasing temperature up to starts 5000C iron sulfatization decreases, while 7000C concentration of iron in solution is 0.245 g/l.
For the opening of mechanism of the sulfate formation process there were used a thermal and X-ray analysis techniques. In Figures 3 and 4 the thermogram of the original heating and sul-fated cobalt raw materials are presented.
Table 3. The results of water leaching sulfated product at different temperatures. Conditions of experiment: temperature - 900C, leaching time - 1 hour, weighted ore -10 g, ratio S:L=1:5
Data Temperature of sulfatization, 0C
400 600 700
Weight ore, g 10 10 10
Sulfated product, g 15.058 13.412 12.934
Output of cake, g 6.947 7.2 7.338
Contet of cake, g
Co 0.864 0.78 0.45
Fe 5.01 4.868 10.91
As 1.734 1.635 1.58
Concentration in the water solution, g/l
Co 3.36 3.43 3.9
Fe 9.3 9.25 0.245
As 2.77 2.827 2.86
Extraction to water, %
Co 73.68 75.2 85.52
Fe 57.195 26.94 1.506
As 53.47 54.57 55.2
On the curve of DTA thermogram heating a raw material shown in Figure 3 is registered in the range of endothermic effect at temperatures 151-2060C and exothermal effect at 692-7600C.
This effect at temperatures up to 2060C corresponds to a process of evaporation of crystallization water of minerals. The temperature range 692-7600C occurs oxidation process of minerals included into ore content, mainly alu-minosilicate components.
For comparison, in Figure 4 cited is the thermogram of obtained sulfatizated cobalt ores with 4500C, which shows that unlike the cobalt raw material were clearly expressed two en-doeffects were at the temperature 137-250 and 641-7830C. The second endoeffect corresponds to the process of thermal decomposition of sulfates, which proves the diffraction pattern of the initial and sulfatizated material.
TG, %
100
99
98
97
96
95
94
Mass loss 0.72%
Peak 721.10C
DTA, цУ/mg
2.0
1.5
1.0
0.5
0.0
100 200 300 400 500 600 700 800 900
Temperature, 0C
Fig.3. The thermogram of the initial heating of cobalt ore.
TG, %
DTA, цУ/mg
100
95
90
85
80
Peak 137.50С, 100.01%
Mass loss 2.22%
Peak 112.00C
Peak 165.60C
Peak 2190C
I—I—' 100
Peak 641.80C
Peak 853.10С , Peak 726.60С
'Peak 740.90С Peak 738.30С
Mass loss 15.33%
Peak 783.50С, 76.79% ^
Rest of mass 76.45% (948.40С)
200 300 400 500 600 700 Temperature, 0C
Fig.4. The thermogram of heating sulfatizated cobalt ore.
800 900
3.0
2.5
2.0
1.5
1.0
0.5 0.0
Figure 5 presents the diffractograms of the original ore (a), and the sulfatization products at 400 (b), 600 (c) and 7000C (d). In the diffraction pattern of initial ore there are clearly expressed lines of minerals: a-quartz, feldspar, clinochlore, andradite, cobaltite.
The diffractogram of the sample taken at 4000C (Figure 5) shows the presence in its composition of a divalent sulfate, ferric(III) and a-quartz. Sufficiently clear expressed cobaltite reflexes that testifies to that at this temperature
sulfuric acid does not degrade the crystalline structure of this mineral. In the diffractogram of the sample taken at 7000C, presented are mainly reflexes of a-quartz, hematite, iron ferrite, cobalt sulfate and undecomposed iron sulfate. An interesting fact is that the reflexes of andradite in all samples of sulfated material obtained at different temperatures (Figure 5 b-d), does not disappear. Comparison of the results shows that concentrated sulfuric acid mainly decomposes minerals of cobaltite and clinochlore.
5.0e+003 4.0e+003
3.0e+003 2.0e+000 1.0e+003
¿:8e«
8.0e+003
6.0e+003
4.0e+003
2.0e+000 1.0e+004 5.0e+003
6.0e+003 4.0e+003
2.0e+000 0.0e+000
7000C
10
20 30
4
40
50
10 20 30 40 50
7I7 a
5 A .. 3 5 1 400°C
10
30
40
50
. 5 . htiij iÀ
6
M
10
20
30
40
50
Fig.5. Original diffractogram cobalt ore (a) and sulfatizated products produced at 400 (b), 600 (c), 700 C (d). Conditional meanings: 1 - andradite, 2 - hematite, Fe2O3, 3 - silica, SiO2, 4 - cobalt sulfate, 5 - clinochlore (ferruginous), 6 - cobaltite, 7 - iron sulfate(III).
4
d
4
2
b
Based on the data obtained by X-ray and thermogravimetric analysis methods, it was established that in spite of incomplete decomposition of ore minerals, extraction of cobalt in solution at temperature ranging 650-7000C makes up 85.92%, that corresponds to the formation of cobalt sulfate.
The obtained experimental data permit to conclude that the investigated sulfatization cobalt ore with concentrated sulfuric acid under optimum conditions, enables to transfer water-soluble form of cobalt (~85.52%) with simultaneous minimal sulfatization iron (1.5%).
As follows from Table 3, in this method of the concentration of extraction degree of valuable components exceeds the previous (Table. 1) and makes up for a Co - 85.52%, for Fe -1.5%, for As - 55.2%.
Conclusion
It is established that while leaching the initial ore by water extraction of cobalt to the solution is not observed. It is expedient to use a sulfuric acid solution, which allows to selectively isolate the silica from the ore. However, the use of sulfuric acid to 2 N concentration does not permit completely to extract cobalt to solution. Processing method of ore with its sulfated calcine with next leaching calcine with water is offered. It is was found that extraction of cobalt from sulfatizated ore at 7000C is 85.52%.
Studies have showed that at the processing cobalt ores the use of sulfatization ore roasting and subsequent water leaching of calcine is expedient.
References
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YÜKSOKSiLiKATLI KOBALTLI FiLiZLORDON KOBALTIN MiNERAL TUR§ULARLA YUYULMASI
SORAITiNiN TODQiQi A.A.Heydarov, N.V.Yusifova
Da§kasan yataginin kobaltli filizinin mineroloji tarkibi öyrsnilmiijdir. Kobaltli filizin xlorid va sulfat tur§usu ila yuyulmasi tadqiq edilmi§dir. Göstarilir ki, filizin tarkibinda gatin hall olan kobaltin minerallarinin va silikatli birla§malarinin olmasi, kobaltin xlorid tur§usu ila (2 N-a qadar) yuyulmasi kifayat qadar effektiv üsul deyildir. Kobaltin xlorid tur§usu ila gixarilmasi 77.4 %, sulfat tur§usu ila isa 76.7 % ta§kil edir. Filizin emali ügün sulfatla§dinci bi§irma prosesi va daha sonra su ila yuma taklif edilmi§dir. A§kar olunmu§dur ki, Co gixanlmasi maksimum temperaturda 7000C-da 85.52% ta§kil edir. Agar sözlar: kobalt, filiz, sulfatia§dmci bi§irm3, yuyulma, biti§ma, cixartma.
ИССЛЕДОВАНИЕ УСЛОВИЙ ВЫЩЕЛАЧИВАНИЯ КОБАЛЬТА ИЗ ВЫСОКОКРЕМНИСТЫХ КОБАЛЬТОВЫХ РУД МИНЕРАЛЬНЫМИ КИСЛОТАМИ
А.А.Гейдаров, Н.В.Юсифова
Приведены результаты исследования процесса извлечения кобальта из высококремнистых кобальтовых руд Даш-кесанского месторождения. Изучен вещественный состав исследуемой руды. Установлено, что присутствие в составе руды труднорастворимых минералов кобальта и силикатных соединений является причиной недостаточно эффективного выщелачивания кобальта растворами серной (до 2 н) и соляной (7-20%) кислот. Предложен способ переработки руды, предусматривающий ее сульфатизирующий обжиг с дальнейшим выщелачиванием огарка водой. Найдено, что извлечение кобальта из просульфатизированной при 7000С руды составляет 85.52%.
Ключевые слова: кобальт, руда, сульфатизирующий обжиг, выщелачивание, спекание, извлечение.
