CC BY
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ISSN 2522-1841 (Online) ISSN 0005-2531 (Print)
UDC 669.054.8
SOLVENT EXTRACTION OF COBALT FROM LEACHING SOLUTIONS
OF COBALT ORES
N.V.Yusifova, A.M.Pashajanov, N.I.Ismailov, T.M.Ismailov*
M.Nagiyev Institute of Catalysis and Inorganic Chemistry, Ministry of Science and Education
of the Republic of Azerbaijan *Azerbaijan Medical University
naile.yusifova@inbox.ru
Received 12.10.2022 Accepted 01.02.2023
The extraction of cobalt with amines has been studied in the most detail. The article presents experimental data obtained in the study of cobalt extraction from leaching solutions of cobalt ores with a mixture of tributylamine (TBA) in toluene and hexane. The dependence of the extraction degree and distribution coefficient of cobalt on pH, time, and the ratio of aqueous and organic phases have been studied. It has been shown that cobalt is maximally extracted with TBA in toluene in the pH range of 35 for no more than 5-10 minutes; in this case, 98% of cobalt extraction is achieved. The developed method of cobalt extraction with organic extractants can be widely used in non-ferrous metallurgy.
Keywords: cobalt, extraction, toluene, hexane, distribution coefficient, extraction degree, tributylamine.
doi.org/10.32737/0005-2531-2023-2-178-185
Introduction
Cobalt is applied to various fields of technology; however, it is mainly used in the manufacture of catalysts, battery electrodes and heat-, corrosion and wear-resistant alloys, which are used in the production of gas turbine engines [1]. Every year its consumption increases and production decreases. The main feedstock in the production of cobalt are sulfide cobalt ores [2]. Secondary raw materials, which have a complex and heterogeneous composition, are also an important source in the production of cobalt. These are mainly accumulated wastes from hydrometallurgical productions of the mining and processing industry. Thus, with an increase in the growth of accumulated waste from hydrometallurgical industries and the complexity of mining and processing low-grade ores, there is a need of search of alternative technologies for ores processing.
The extraction technology, as an affordable method for separating, concentrating and isolating metals is of particular importance. Many foreign enterprises over the world use the method of solvent extraction to obtain cobalt and its salts [3]. Extraction methods have recently become a promising direction in the
technology of processing leach solutions of non-ferrous metals due to ease of use, high degree of extraction, and process continuity.
The use of extraction method in hydrometallurgy is cost-effective if the resulting metal has a high cost. The development of extraction processes is conducted mainly in relation to clarified solutions. In addition, new extractants are being developed and researched.
Extraction of cobalt with organic solvents is one of the most common methods. The high efficiency and selectivity of this method provide rapid application and use in industry
Experimental part
Tributylamine of the "technical" brand made in company "Basf SE", D-67056 Ludwigshafen, Carl-Bosch-Strasse 38, Germany has been used as an extractant. The product purified by vacuum distillation contained at least 97% tributylamine. Physicochemical and technical indicators of (C4H9)3N: density 0.7782 (200C, g/cm3); molecular weight -185.3, boiling point 216-2170C, melting point -700C. It was a clear or light yellow liquid. The initial aqueous solutions of Co were prepared from cobalt ores according to the procedure [2]. For this purpose,
a sample of the ore was dissolved in water by heating, and then the solution was acidified to the required pH value.
IR spectra were recorded on a NICOLETIS 10 spectrometer (thermoscientific USA) 400-4000 sm-1.
The content of cobalt in the organic and aqueous phases was determined on a Bruker S2 Picofox X-ray fluorescence spectrometer (Germany).
The electronic conductivity of Co was determined by UV-visible Shumadzu 1800 190-800 nm.
The pH values of aqueous solutions were monitored using a universal ionometer of "Operation manual laboratory benchtop pH meters" company.
The extraction experiments were carried out in separating funnels by contacting the cobalt aqueous solution with the extractant solution at a ratio (1:1). The light absorption of the colored extract was measured with a KFK-2 photocolorimeter.
The extraction was carried out in the temperature-controlled separation funnels using a mechanical shaker for stirring. The contact time was at least 5-10 minutes and the temperature was 20±10C. For this purpose, 10 ml of cobalt solution and 5 ml of 1.0 M solution of tributylamine in toluene were added to a 150 ml separation funnel and the mixture was vigorously shaken for 5 minutes until a complete equilibrium in the system was obtained. After stirring, the phases were settled, separated and analyzed. After phase separation, the pH of the aqueous solution was measured and the initial and equilibrium aqueous solutions were determined and analyzed. Based on the results obtained, the recovery factor of cobalt was calculated according to the accepted rules. The extraction efficiency was characterized by the value of the distribution coefficient D and the extraction degree s. The extraction results were evaluated by the equilibrium concentration of the metal in the aqueous phase. The distribution coefficient D was calculated by the formula:
D=Corg/Caq
At the end of the process, the pH of aqueous phase was measured. Tributylamine in toluene and hexane was used as an extractant.
When extracting cobalt with tributylamine, it has been found that the dependence of the logarithm of the distribution coefficient lgDCo on the logarithm of the extractant concentration is straightforward. This fact indicates the formation of a complex of constant composition. The extraction of cobalt with amines has been studied in the most detail.
MeAmaq+nAMHHorg^[Me(AMHH)nAm]org and accordingly, the distribution coefficient
D
Me=
_[Me(ÂMHH)nAm]org [MeAmjaq
Results and discussion
The extraction was carried out in a temperature-controlled separation funnels using a mechanical shaker for stirring. The ratio of organic and aqueous phase was 1:1. Contact time was at least 5-10 minutes and temperature was 20±10C. For this purpose, 10 ml of cobalt solution and 5 ml of 1.0 M solution of tributylamine in toluene were added to a 150 ml separation funnel and the mixture was vigorously shaken for 5 minutes until a complete equilibrium in the system was obtained. After stirring, the phases were settled, separated and analyzed. After phase separation, the pH of the aqueous solution was measured and the initial and equilibrium aqueous solutions were determined and analyzed. Based on the results obtained, the recovery factor of cobalt has been calculated according to the accepted rules. The extraction efficiency is characterized by the value of the distribution coefficient D and extraction degree s. The extraction results were evaluated by equilibrium concentration of the metal in the aqueous phase. The distribution coefficient D was calculated by the formula: D=Corg/Caq
At the end of the process, the pH of aqueous phase was measured. Tributylamine in toluene and hexane was used as an extractant.
One of the decisive factors affecting the extraction of metals is the concentration of
extractant in the organic mixture. It is known in the literature that amines are widely used in the extraction of cobalt. The study of cobalt extraction was carried out in accordance with a common methodology, depending on the influence of a number of main factors, such as a change in the pH of the medium, changes in the concentration of cobalt, extractant, phase contact time, etc.
Extraction is carried out at pH 2-6 for no more than 5-10 min, depending on the cation concentration and extraction conditions. Based on the experimental data, the graphs of the dependence of extraction degree E and distribution coefficient D on the pH of the multicomponent solution were plotted (Table 1). During the extraction of cobalt with TBA in toluene, the degree of extraction increases with a change in pH from 2 to 5, in hexane at pH = 3.0 96.6% is extracted, in toluene at pH = 5.45 this value is 98.5% (Figure 1). With a decrease in pH to 2, the extraction of cobalt drops to 7075%, and the maximum extraction of all components reaches at pH=5.45 and is 98.5%. Tributylamine is readily soluble in aromatic solvents such as toluene and hexane. The cobalt extraction depending on the pH of the solutions, the concentration of the extractant and the presence of solvating reagents was studied. For comparison, cobalt(II) chloride hexahydrates of CoCl2^6H2O were prepared from model solutions. The extraction was carried out with stirring and regulation of a constant pH value, NaOH and H2SO4 solutions were used as neutralizers. The experiments were carried out at room temperature. The extraction rate when using salts of tertiary amines, proceeding by the anion exchange mechanism, is usually quite high.
The acidity of the aqueous medium has the greatest effect on the degree of cobalt extraction with tributylamine [4-6]. The data
obtained, show that the extraction of cobalt ion by extractant solutions from slightly acidic chloride media begins at pH = 0.77 and at pH = 5.67 cobalt is maximally transferred to the organic phase. The maximum extraction of cobalt (98.6%) reaches at pH=5. The extraction of cobalt proceeds stably in the whole investigated range of pH from 3 to 5.
The results of the experiments are shown in table 1 and in the form of curves for the cobalt extraction depending on the nature of the solvents. During phase separation, the luminosity of the colored extract was measured on a photocalorimeter [7, 8]. The experiments were carried out in cobalt solutions prepared from the Dashkesan cobalt ore which has the composition (wt%) shown in the Table.
The choice of organic solvents is known to be one of the main factors affecting the distribution coefficient of elements in extraction processes. Diluents contribute to the dissociation of extractant, increase its active concentration and increase the distribution coefficient of metal between the phases. [9, 10].
As can be seen from the figure (1), both investigated solvents are very effective. It is shown that the extraction of Co proceeds rapidly and significantly depends on the initial pH and the ratio of phase volumes Vorg:Vaq. Effective extraction of Co occurs at Vorg:Vaq= 1:1, pH=5 and T=200C. At the same time, 98% of Co is extracted into the organic phase in one stage for 5 minutes.
As can be assumed, the dissociation of extractant and formation of cationic cobalt complex in aqueous solution occur, which contributes to the formation of extractable compound and its extraction [11-13]. The data obtained show that the cobalt extraction proceeds completely in the range of pH=1.67-5.45.
Results of experiments on the study of solvent extraction of cobalt
% Mass Co Zn As Se Cd Fe Pb Cr Mn
Cobalt ore 4,58 0,096 39,906 0,014 0,005 18,79 0,605 0,029 4,085
Solution after ore leaching 4,50 0,092 38,894 0,013 0,004 15,375 0,480 0,025 4,065
Solution after extraction 4,41 0,002 34,608 0,013 0,003 9,608 0,307 0,023 3,698
8,%
100 90 80 70
60 50 40 30 20 10
6
0 1 2 3 4 5 6 PH
Fig. 1. Dependence of cobalt extraction on the nature of the solvent and pH:
-h§xane
• -toluene ;
100
ТЗ &
o
о
t+ч
o n o
a
о
"R w
80
60 -
40 20
0
2 4 6 8 10
The dependence of the extraction of cobalt with a tertiary amine on
a)
100
T3 80
is о
t+4 60
o n o
•a 40
л
w
20
C, mol/l
Dependence of cobalt extraction on the concentration of tertiary amine.
b)
Fig. 2. Cobalt extraction with tributylamine as a function of time (a) and concentration (c).
Determination of the composition of extractable compound
The composition of the extractable compound was studied by the equilibrium shift method [14]. It has been found that the extraction of cobalt is characterized by a rapid reaction with the formation of a complex
Co2+ (aq) + 2(HA)2(org)^C0A2(HA)2org+2H+aq
The effect of solvents on the cobalt extraction has been studied. The extractability decreases in the following order: toluene>hexane>kerosene, which is associated with an increase in the interaction strength of solvents with tributyl-amine and, accordingly, this leads to a decrease in the activity of extractant. This extractant is able for the extraction of non-ferrous metals from leaching solutions of cobalt ore.
T
Элемент Вес % Атомный %
NaK 1,38 1,57
MgK 1,86 2,00
AlK 0,37 0,35
SiK 1,34 1,24
SK 8,92 7,27
KK 0,21 0,14
CaK 33,69 21,97
FeK 15,96 7,47
CoK 4,08 3,28
ZnK 1,04 0,41
O 35,23 57,56
Fig. 3. Results of the analysis of EDC sample after Co extraction.
Analysis of the studied process by IR spectroscopy
During the extraction, to determine the Co-N bond, the infrared spectra of the extracted organic phase were recorded [15]. A comparative analysis of the extract obtained when it maximally saturated with cobalt and tributylamine in toluene was carried out. IR spectra were recorded in the frequency range of 400-4000 cm-1.
Analysis of the IR spectra of the extract of cobalt(II) shows (a) that the band is in the region 2797, 3086 in the IR spectrum of the
extract of the TBA solution in toluene. The IR spectra of cobalt extracts (b) have additional peaks in the region of 418, 411 cm-1, which can be attributed to the stretching vibrations of the Co-N bond. The comparative cobalt-containing extract (c) has additional peaks in the region of 419 cm-1. Comparative analysis of the IR spectrum of the studied extract of Co(II) with the IR spectra of Co containing extracts obtained in the extraction of TBA, available in the literature, enables to express an opinion about the formation of donor-acceptor bonds of cobalt-nitrogen [16].
Wave number, cm-1
Fig. 4. IR spectra of tributylamine in toluene (a) and cobalt-containing extract (b), comparative cobalt-containing extract from cobalt chloride hexahydrate (c).
Conclusions
Tributylamine is effective for the extraction of cobalt (II) ions. The maximum extraction of cobalt with TBA in toluene in the pH range of 3-5 for no more than 5-10 minutes reaches 98%. The results obtained during the cobalt extraction with TBA in toluene can be used in the processing of technical solutions.
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KOBALTLI FiLiZLORiN YUYULMU§ MOHLULLARINDAN MAYE EKSTRAKSiYA YOLU iLO
KOBALTIN ALINMASI
N.V.Yusifova, A.M.Pa$acanov, N.i.ismayilov, T.M.Ismayilov
Maqalada toluol va heksanda tributilamin qan§igi ila yuyulma mahlullarindan kobaltin gixanlmasinin tadqiqi zamani alda edilmi§ eksperimental malumatlar taqdim olunur. Kobaltin ekstraksiya daracasinin va paylanma amsallarinin sulu fazanin pH-dan asililiqlan alinmüjdir. Göstarilmiijdir ki, kobalt TBA ila toluolda pH 3-5 diapazonunda maksimum 5-10 daqiqa arzinda ekstraksiya edilir, bu zaman kobaltin giximi 98% gatir. Kobaltin üzvi ekstragentlarla gixarilmasi üsulu alvan metallurgiyada tatbiq oluna bilar. Kobaltin aminlarla gixarilmasi atrafli §akilda öyrsnilmi§dir.
Agar sözlar: ekstraksiya, toluol, heksan, paylanma amsali, gixarilmasi daracasi, tributilamin.
ИЗВЛЕЧЕНИЕ КОБАЛЬТА ИЗ РАСТВОРОВ ВЫЩЕЛАЧИВАНИЯ КОБАЛЬТОВЫХ РУД
ЖИДКОСТНОЙ ЭКСТРАКЦИЕЙ
Н.В.Юсифова, А.М. Пашаджанов, Н.И.Исмаилов, Т.М.Исмаилов
Наиболее подробно исследовано извлечение кобальта аминами. В статье приводятся экспериментальные данные, полученные при изучении экстракции кобальта из выщелачивающихся растворов кобальтовых руд смесью трибутиламина (ТБА) в толуоле и гексане. Изучена зависимость степени извлечения и коэффиценты распределения кобальта от рН, времени и концентрации водной органической фаз. Показано, что кобальт максимально экстрагируется ТБА в толуоле в диапазоне рН 3-5 в течении не более 5-10 минут, при этом достигается 98% извлечение кобальта. Способ извлечения кобальта органическими экстрагентами широко используется в цветной металлургии.
Ключевые слова: кобальт, экстракция, толуол, гексан, коэффициент распределения, степень извлечения, трибутиламин.
