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AZ9RBAYCAN KIMYA JURNALI № 2 2016
55
UDC 546:542.61; 54-386:542.61
EXTRACTION OF URANILE-IONS OUT OF WATER SOLUTIONS BY THE CHLORINATED NAPHTHENIC ACIDS
S.R.Mamedova
M.Nagiev Institute of Catalysis and Inorganic Chemistry NAS of Azerbaijan
nuriyeva.1963@mail.ru Received 29.01.2016
The extraction of the small quantities of uranile-ions out of water solutions has been studied. It is established that chlorinated naphthenic acids are effective extragents of uranium from water solutions containing great quantities of salts of alkaline metals. pH1/2 extraction considerably shifts into acid (in the presence of chlorides) or alkaline sphere (in the presence of sulphates) depending on ammonic composition of salts and their concentration that permits to increase choiceness of extracting uranium. Effec-tivity of extracting uranium is considerably improved in the presence of minimum quantities of aniline or that of other amines. High effectiveness of extraction of uranium in the presence of aniline and under relative constancy of extraction in a wide interval of acidity of water phase served as foundation for working out the method of determining small quantities of uranium chlorinated by naphthenic acids.
Keywords: extraction, uranile-ions, organic reagents, water phase, alkaline metals.
Extraction of uranium by the organic reagents or solvents in order to extract it out of water solutions of different composition, its separation from other elements and purification got the wide application both in technological processes and in analytical practice.
At present a great deal of well-known papers are devoted to extraction of uranium out of acidic, neutral solutions [1-5] by the al-kylphosphorous acids, oxygen-containing organic solvents (ethers, ketones, aldehydes etc.), as well as by highmolecular amines [6]. That's why the old twels are taken and sent to the retirement: they are dissolved in the acid or alkali and by the method of extraction the uranium is extracted out of the solvent. The uranium easily creates extractional complexes and transfers into organic phase; the mixtures, which are necessary to escape, drop out in the water solution. The uranium is extracted from organic phase practically by the sahie methods as those while obtaining it from the ore [6, 7].
In this paper there have been presented the results of investigation on creation of the conditions for extraction of the small quantities of uranium out of strongly concentrated solutions of chlorides and sulphates, alkaline and alkalinearth elements. As an extragent for the first time there were used chlorinated naph-thenic acids (CNA). These are optimum condi-
tions of extraction, concentration, separation of uranium from the number of attendant elements.
The uranium determination in the corresponding phases after their arrangement in layers has been made by the colorimetric method [8].
As an extragent there has been used 1.0 M solution of CNA (average molecular weght is 232) in kerosene.
In the separate experiments as a diluent we have taken pure hydrocarbons - heptene, benzol and tetrachloromethane.
We have studied the extraction of uranile-ions 1.0 M by the solutions of naph-thenic acids (NA) and CNA in order to compare them in the identical conditions The results have been presented in Figure 1.
As is seen in Figure 1, the extraction of uranile-ions 1.0 M by CNA solution starts at pH=1.8, and at pH=4-6 they completely transfer into organic phase. Under the same conditions the extraction of uranile-ions NA starts only when pH=3.4 and their optimuml extraction is observed at pH=5.2. It should be mentioned that in the same conditions the curve of uranile-ions extraction by NA is shifted to one unit of pH into the alkaline field. The further pH increase in the water solution leads to consequent decrease in the coefficient of distribution, the emulsion appears on the boundary of the phases, in consequence the border between the phases loses its sharpness.
s,% 100
80 60
40 20
e,%
2 3 4 5 6 pH Fig.1. Dependence of uranile-ions extraction by chlorinated naphtenic acids (1) and by naphthenic acids (2) on pH sphere.
When pH>7 the phases get shifted, besides, the created emulsion strongly blocks the division of phases, and thus reduces the coefficient of distribution. The emulsion is easily de-structed while adding the minimum quantity of higher alcohols into the organic phase. The division of phases is much improved when using the solution of caustic kali, as well as the demanded significance of pH water solution is created.
The influence of (NaCl, Na2SO4) salts concentration on extraction of uranile-ions from the solutions of chloride and sulphuric acid sodium of different concentrations, dependent on pH is shown in Figures 2 and 3. s,%
100
80
60
40
20
2 3 4 5 6 pH Fig.2. Dependence of uranile-ions extraction by chlorinated naphthenic acids on pH sphere in the presenc of chlorine-ions:
1 - 2, 2 - 1, 3 - 0.5 N NaCl.
100 80 60 40 20
2 3 4 5 6 pH Fig.3. Dependence of uranile-ions extraction by chlorinated naphthenic acids on pH sphere in the presence of sulphate-ions: 1 - 2, 2 - 1, 3 - 0.5 N Na2SO4.
As it is seen (in Figure 2) while uranile-ions extraction out of such solutions, as distinct from the cases when the mentioned above salts are absent in the solution with a very little change of pH, the coefficient of distribution grows quickly, and the optimal extraction is noticeably shifted to acidic field. With the rise of chloride sodium concentration, the shifting becomes more noticeable and the optimal extraction takes place at pH of the balanced water solution < 2. Thus, if without chloride sodium, when pH of balanced water phase is 2.8 the uranil-ions extraction is just 45%, with its presence (2, 1, and 0.5 N NaCl) at the corresponding value of water solution pH, it achieves more than 98%.
A noticeable increase of uranile-ions extraction is observed in case of existance of sulphuric-acid sodium in the water solution. Depending on the concentration of the latter in solution, the curve of the extraction as distinct from the chloric sodium solutions, is shifted to more alkaline field (Figure 3). For example, among the other equal conditions, the significance of pH in balanced water solution, where 50% of uranile-ions are extracted, compiles:
2.5 +
NaCl
Na2SO4
>4.2.
-3.6-
Another important factor which influences the uranile-ions extraction is the concen-
S.R.MAMEDOVA
57
tration of the CNA in the organic phase, because, as it is supposed, the uranile-ions are extracted from the solution in the type of the uranile-chlor naphthenate.
As it is evident in Figure 4, where dependence of uranile-ions extraction on the ratio CNA/UO2+ is displayed, the optimal extraction of uranile-ions takes place at the ratio
CNA/UO2+ >6. The further increase in this most of naphthenates (UO2+, Co^ Ni" Cu"
In fact, the uranile-chlornaphthenate obtained by the preparative way (deposited from «-heptene solution) is very little dissolved in the ordinary diluters. The addition of chlornaph-thenic acids into the organic solvent leads to the sharp increase in solubility of chlor-naphthenate uranile. Apparently, such scheme of creation the soluble salt is typical for the
T;2+
2+
ratio nearly doesn't influence the rise of the distribution coefficient.
s.% 100 80 60
40 20
2.0
3.0
4.0
5.0 pH
Fig.4. Dependence of uranile-ions extraction on pH sphere at the different concentrations of the chlorinated naphthenic acids: 1 -1.0, 2 - 0.5, 3 - 0.25 M CNA.
Proceeding from this fact we can suppose that the extraction is the result of a secondary reaction between the salt (that is obtained during the interaction of uranile-ion with CAN) and free CNA. Thus, one of the basic factors, providing the effectiveness of the extractional process is a surplus quantity of the chloric naphthenic acids.
While studying the distribution of the chlorinated naphthenic acids between the different organic solvents and water, it has been found out the existance of dimer form of these acids in the inert diluters.
In accordance with it, the reaction of uranile-ions extraction by the chlorinated naph-thenic acids can be expressed as follows:
UO2+ = 4/2[(CNA)2]^(UO2R2-2(CNA)4+2H+.
2+
Fe etc.) the solubility of which after deposition from the organic phase by the corresponding precipitators is sharply reduced.
There also have been carried out the experiments on extraction of the uranium by the chlornaphthenic acids in the presence of aniline and other low-molecular amines. Besides, the equilibrium is established at once, the phases are separated exactly, and in the wide interval of pH in water phase the coefficient of distribution sharply rises, achieving 104-105.
Such a high effectiveness of extraction in the presence of aniline at the relative constancy of these data in the wide interval of the water phase acidity permits us to suppose the creation of a new extracted product - aminate complex of uranile, that is interacting with the chlorinated naphthenic acids and its transfer into the organic phase.
The additional information about the character and composition of the product extracted in the indicated conditions has been obtained with the heft of spectrum of absorpbing the extracts which were taken at spectropho-tometer SPh-5 in the field of 350-560 m^ (Figure 5).
The taken spectrum has been compared with the spectrum of absorption of the nitric acid uranile in the water solution. The stripes of absorption, typical for uranile in extractions have been shifted on 10-12 m^ to the longwaving field.
As for extraction obtained in the presence of aniline, there aren't any typical stripes in the visible part, and the swamped maximum is strongly shifted to a more hot wiring field.
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ЭКСТРАКЦИЯ УРАНИЛ-ИОНОВ ИЗ ВОДНЫХ РАСТВОРОВ ХЛОРИРОВАННЫМИ
НАФТЕНОВЫМИ КИСЛОТАМИ
С.Р.Мамедова
Изучено экстракционное извлечение небольших количеств уранил-ионов из водных растворов. Установлено, что хлорированные нафтеновые кислоты являются эффективными экстрагентами урана из водных растворов, содержащих большие количества солей щелочных металлов; рНу2 экстракции в зависимости от анионного состава солей и их концентрации значительно смещается в кислую (в присутствии хлоридов) или щелочную (в присутствии сульфатов) области, что позволяет повысить избирательность экстракции уранил-ионов. Эффективность экстракции уранил-ионов значительно улучшается в присутствии в органической фазе минимальных количеств анилина или других низших аминов. Высокая эффективность экстракции уранил-ионов в присутствии анилина при относительном постоянстве извлечения в широком интервале кислотности водной фазы послужила основанием для разработки метода определения малых количеств урана хлорированными нафтеновыми кислотами.
Ключевые слова: экстракция, уранил-ионы, органические реагенты, водная фаза, щелочные металлы.
URANiL-iONLARININ SULU MOHLULLARDAN XLORLA§DIRILMI§ NAFTEN TUR§ULARI iLO EKSTRAKSiYASI
S.RMammadova
Az miqdarda olan uranil-ionlann sulu mahlullardan ekstraksiya yolu ila gixarilmasi 6yranilmi§dir. Muayyan edilmi§dir ki, xlorla§dirilmi§ naften tur§ulari sulu mahlullardan uranin gixarilmasi ugun effektiv ekstragentdir. Qalavi metal duzlarinin i§tirakinda uranil-ionlarimn ekstraksiyasi, goturulmu;? duzun anion tarkibindan va onlarin qatiligindan asililigi 6yranilmi§dir. рН1/2 az miqdarda tur§ va ya qalavi muhita yerini dayi§ir, bu da uranil-ionlarinin segici olaraq ekstraksiyasina imkan verir. Uzvi fazaya az miqdarda kigik malekulali amin alava edilmasi uranin ekstraksiyasinin az miqdarda yax§ila§dirir. Lakin uranil-ionlarinin ekstraksiyasinin yuksak effektivliyi anilin i§tirakinda olur. Su fazasinin tur§ulugunun nisbatan geni§ intervalda xlorla§dirilmi§ naften tur§ulari ila uranil-ionlarinin gixarilmasi imkan verir ki, uranin mahlullarda az miqdarini tayin metodikasi i§lanib hazirlansin.
Agar sozlar: ekstraksiya, uranil-ionlari, uzvi reagentlar, su fazasi, qalavi metallar.
a
Fig.5. Spectrum of absorption of the aminate complex of uranile chlornaphthenate: I - water solution UO2(NO3)2, II - solution of uranile chlornaphthenate in kerosene, III - solution of uranile chlornaphthenate in benzol, IV - aminate complex of uranile chlornaphthenate.
References
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2. Пяртман А.К., Копырин А.А., Пузиков Е.А. Экс-
