Composition and extraction of tungsten(VI) complexes with 2-hydroxy-5-bromtiphenol and aminophenols Текст научной статьи по специальности «Химические науки»

50

CHEMICAL PROBLEMS 2019 no. 1 (17) ISSN 2221-8688

UDC 543. 42. 062: 546. 77

COMPOSITION AND EXTRACTION OF TUNGSTEN(VI) COMPLEXES WITH 2-HYDROXY-5-BROMTIPHENOL AND AMINOPHENOLS

A.Z. Zalov, K.A. Kuliev, N.A. Akberov, U.B. Abasgulieva, U.Sh. Bakhsieva

Azerbaijani State Pedagogical University Uz. Hadjibekov str., 68, AZ1000 Baku, e-mail: zalov1966@,mail. ru

Received 05.01.2019

The interaction of tungsten(VI) with 2-hydroxy-5-bromothiophenol (HBTP) in the presence of aminophenols (APs)was studied as follows:(N,N-diethylaminomethylthio)-4-methoxyphenol (APi), 2-(N,N-dibuthylaminomethylthio) -4-methoxyphenol (AP2), 2,6-bis-(N,N-dimethylaminomethyl)-4-methylphenol (AP3), 2,6-bis-(N,N- dimethylaminomethyl)-4-chloro-phenol (AP4), 2-(N,N-dimethylaminomethyl)-4-methylphenol (AP5), 2-(N,N-diethylaminomet-hyl)-4-bromophenol (AP6) and 4-chloro-2-(N,N- dimethylaminomethyl)-6-thio-phenylmethylphenol (AP7).The obtained ternary complexes have a composition of 1:2:2 (W:HBTP:AP) or 1:2:1 (AP3 and AP4). The optimum conditions for their formation and subsequent solvent extraction were found: organic solvent (chloroform), pH (4.1-5.6), concentration of reagents and extraction time. Degrees of extraction made up 98.1-98.6%. The complexes have absorption maximum at 470-482 nm and molar absorptivity coefficients ranged between (2.6-3.9)x104. The Beer's law is observed in the range of concentrations of tungsten 0.2-16 fig/ml.

Keywords: tungsten (V), solvent extraction, 2-hydroxy-5-bromothiophenol, ternary complex,

determination methods

Doi.org/10.32737/2221-8688-2019-1-50-57

INTRODUCTION

Alloys containing tungsten have valuable properties, including high temperature strength, corrosion resistance, hardness and wear resistance. The tungsten is used in argon-welding electrodes, light bulbs and X-ray tubes.

Methods for determining tungsten based on color reactions with organic reagents are numerous, but only some of them are used in analytical practice [1-3]. 2-hydroxy-5-chlorothiophenol [4,5], nitro catechol [6,7], 2,3-dihydroxynaphthalene [7] as well as various ion-binding reagents [8-9] are used for the determination of tungsten. It is known that the hydroxythiophenolate complexes of tungsten are not soluble in chloroform whereas the mixed ligand complexes with hydrophobic amines and aminophenols are well dissolved in various organic solvents. In that respect, a prospective reagent comprising a -OH and -SH

group in its molecule is 2-hydroxy-5-bromothiophenol (HBTP, H2R). The present work deals with the interaction of tungsten with HBTP in the presence of aminophenols (AP). The following APs were used: 2-(N,N-diethylaminomethylthio)-4-methoxyphenol (AP1), 2-(N,N-dibuthylaminomethylthio) -4-methoxyphenol (AP2), 2,6-bis-(N,N-dimethylaminomethyl)-4-methylphenol (AP3), 2,6-bis-(N,N- dimethylaminomethyl)-4-

chlorophenol (AP4), 2-(N,N-dimethylamino-methyl)-4-methylphenol (AP5), 2-(N,N-diethylaminomethyl)-4-bromophenol (AP6) and 4-chloro-2-(N,N-dimethylaminomethyl)-6-thiophenylmethylphenol (AP7). On the basis of the results obtained, new selective and sensitive procedures for the extraction and photometric determination of tungsten microscopes in steel were developed.

MATERIALS AND METHODS

Reagents. The W(VI) stock solution was prepared by dissolving Na2WO4 x 2H2O in water. Its exact concentration is established gravimetrically - precipitation of tungsten in the form of acid and weighing of the obtained WO3 [10]. Working solutions at a concentration of 0.1 mg / mL are obtained by diluting the stock solution. Chloroform solutions of HBTF and AF were used at a concentration of 0.01 mol/l. HBTP and AP were synthesized according to known methods: [11] and [12], respectively. Their purity was checked by paper chromatography and melting temperature determination. Chloroform is distilled before use.

Apparatus. The absorption of the extracts was read using a photocolorimeter KFK-2 and a spectrophotometer SF-26. For pH determination a I-120.2 ionometer was used with a glass electrode.

Procedure. In the graduated tubes equipped with ground stoppers, there are a W (VI) solution (0.1 to 0.8 mL, 0.1 mL interval), a solution of HBTP (2.4 ml) and AP solution (2.2-2.3 mL). The necessary acidity is created by adding solutions of NaOH or HCl at a concentration of 0.1 mol/l. The volume of the organic phase is brought to 5 ml with chloroform and the aqueous phase to 25 mL (with water). Suffice it to shake for extraction

(15 min) and after complete phase separation, the organic layer is separated and its absorption measured in 0.5 cm (490 nm) (KFK-2) wavelength cuvettes.

Procedure for dissolving steels. A weighted amount of steel (depending on the concentration of tungsten in it) is dissolved in HCl (1:1). A few drops of conc. HNO3. 60 ml of hot water and 5 ml of HCl (1:1) were added. It is refluxed for 5 minutes. The resulting yellowish precipitate of tungstic acids was removed by filtration through a blue band filter. The residue was thoroughly washed with 100 ml. water and dissolved in a solution of 0.5 mol/l NaOH. After cooling, the solution is transferred to a 50 ml volumetric flask. Water is added to the brand.

Experiments related to the reduction of tungsten. It is known that W (V) forms a dithiol colored compound, and W (VI) is reduced to W (V) by the reagent itself [3]. To fortify the conclusion, we conducted two series of experiments: 1) interaction between HBTP and W (V) obtained by reduction with SnCl2 and KI in the hydrochloric acid medium; 2) interaction between HBTP and W (V) in the absence of additional reducers. The products of both reactions were characterized by a maximum at X = 470 nm.

RESULTS AND DISCUSSION

In a weak acid and neutral medium (pH 2.0-6.8) the W (V) forms a water-soluble orange compound with HBTP. As the reagent concentration and the pH rises, the intensity of the coloration increases as well, and with the addition of various AF and organic solvents under certain conditions, well-extractable triple complexes are obtained.

Choice of solvent. We experimented with various organic solvents - chloroform, carbon tetrachloride, benzene, toluene, xylene, isobutanol, isopentanol, dichloroethane and

chlorobenzene. The extractability of the complexes was assessed by the distribution coefficient and the extraction rate. The chloroform, dichloroethane and chlorobenzene solvents were most suitable. All further studies were performed with chloroform.

The content of tungsten in the organic phase was determined photometrically by toluene-3,4-dithiol after reextraction, and the tungsten content in the aqueous phase by difference [5].

Table 1. Characteristics on the ternary complex with different AP

AP Composition pHopt

(W: nm

HBTP:AP)

AP1 1 2:2 4.2-5.2 470

AP2 1 2:2 4.7-5.4 480

AP3 1 2:1 4.3-5.3 482

AP4 1 2:1 4.5-5.5 475

AP5 1 2:2 4.5-5.4 473

AP6 1 2:2 4.1-5.4 479

AP7 1 2:2 4.2-5.6 477

We have found that the essence of the AF practically does not affect the extent of the tungsten extraction. As for single extraction in chloroform, it is in the range of 98.1-98.6%.

Effect of pH on the aqueous phase. Tungsten interacts with HBTP at pH> 1.5. For

£~10-4, lg p lg KeK Adherence

to Beer's

_law, qg/mL

3.7 6.3 9.14 0.2-13.0

3.9 6.9 10.1 0.2-16.0

2.8 5.3 8.20 0.2-13.0

2.7 5.6 7.35 0.2-13.0

2.6 5.5 7.12 0.2-15.0

3.0 6.2 8.92 0.2-14.0

3.3 6.5 9.01 0.2-16.0

the formation and extraction of the various triple complexes, the optimal pH values are taken in the range of 4.1-5.6 (Table 1). At pH above, the 7-8 extraction is not practically carried out due to the decrease in the protonation rate of aminophenols.

ÀA, nm

200 210 212 205 203 209 207

Fig. 1. The absorption spectra of the spectra of W(V)-HBTP-AP under optimal extraction conditions are as follows:

1-W(V)-HBTP-AP1; 2-W(V)-HBTP-AP2; 3-W(V)-HBTP-AP3; 4-W(V)-HBTP-AP4; 5-W(V)-HBTP-AP5; 6- W(V)-HBTP-AP6; 7-W(V)-HBTP-AP7

CW(VI)= 1.09X10-5 M; CHBTP=(9.2-9.6)x10-4 M; CAP= (8.8-9.3)x10-4 M; SF-26; X=490 nM; £=1.0 cm.

Electronic Spectra. Chloroform extracts of in [4, 5, 8, 9, 13,16]. Table 1 shows that the the various complexes have absorption complexes with AP1 and AP2 involved have maximum in the range of 470-482 nm. The the best characteristics. Their spectra are molar absorbances s are in the range of (2.7 - presented in Fig. 1. 3.9)x 104. They are higher than those reported

Effect of reagent concentration. For

the formation and extraction of triple complexes, the concentration of HBTP in the aqueous phase should be in the range (9.2-9.6)x10-4 mol/l, and that of AP - (8.8-9.3)x10-4 mol/l. When using chloroform solutions of HBTP, AP1 and AP2 (at a concentration of 0.01 mol/l), the optimal volumes are 2.4, 2.2 and 2.3 ml respectively. It is not recommended to use larger amounts of aminophenols.

The law of Bern is observed in a wide range of concentrations (Table 1) which allows the use of ternary complexes for the determination of tungsten. The detection limits of the AP1 and AP2 complexes are 0.06 g/ml and 0.05 g/ml respectively.

Resistance to dyeing and extraction time. Unlike the double complex of W (V)

with HBTP, the ternary complexes are resistant to both aqueous and organic solvents. We found that after extraction in chloroform, the staining was stabilized for about a month. To achieve an extraction equilibrium, shake it for approximately for 15 minutes.

Molar relations, elemental analysis and complexation equations. The molar interaction was established by the Asmus method and the equilibrium displacement method [14] (Fig. 2). The results obtained make it possible to conclude that when using AP1, AP2, AP5, AP6 and AP7 the molar ratios are 1:2:2 (w: HBTP: AP). When using the bis-aminophenols AP3 and AP4, which may form cations of the H2AP2+ type, the molar ratios are 1:2:1 (W: HBTP:AP).

Fig. 2. Determination of the complexes composition by the Asmus method. 1 -W; 2 - AP. a) W(V)-R-AP1; for R and for AP1 tga «2; b) W(V)-R-AP3; for R tga «2; for AP3 tga «1;. Cw(v)= 1.09x10-5 M; SF-26; X=490 nM; £=1.0 CM.

When adjusted for the molar ratios obtained and the fact that W(VI) is reduced to W (V) by HBTP (H2R) (and W(V) at pH 3-7 exist mainly in the form of [WO(OH) and

2+

[WO(OH)r [1]), we assume that the complex formation proceeds according to the following equations:

[WO(OH)]2+ + 2H2R ^ [WO(OH)R2]2- +4H+ (1 )

[WO(OH)R2]2- + 2HAP1+ ^ (HAP1+)2[WO(OH)R2] (2')

[WO(OH)R2]2- + H2AP32+ ^ (H2AP32+)[WO(OH)R2] (2")

Equation 2' represents the association of [WO(OH)R2]2- with the HAP + (AP1, AP2, To confirm the relationship between the components in the triple complexes with AP1 and AP2, they were isolated in solid state and assayed by elemental analysis:

AP5, AP6 and AP7) cations, and (AP3 and AP4) equation 2".

(HAP1)2[WO(OH)R2] - {Calculated,%: 19.19 W, 16.68 Br, 6.67 S, 2.92 N; Found,%: 19.43 W, 16.37 Br, 6.63 S, 2.76 N} and (HAP2)2[WO(OH)R2] - {Calculated,%: 14.72

W, 12.80 Br, 5.12 S, 2.24 N; Found,%: Equilibrium and extraction constants.

14.62 W, 12.74 Br, 5.09 S, 2.11 N}. On the basis of equation (2'), the following

equilibrium constants can be written:

The distribution coefficient (D) is equal to

^ _{(HAPMWO(OH)R,]}B

therefore

When logging, we get

lg p= lg D - 2lg [HAP1+] (3')

and in the case of AP3 and AP4 (equation 2)

lg p= lg D - lg [H2AP32 ] (3")

We calculated the extraction constants according to the equations

lg ReK = lg D - 2lg [HBTP2] - 2lg[HAP1+] (4')

lg KeK = lg D - 2lg [HBTP2 ] - lg[H2AP32+] (4")

The results of the calculations are presented in Table 1.

To determine the degree of aggregation equation set out in [15]. Calculations show that of the complexes in the organic phase, we all complexes are in monomeric form (y = 0.9-calculated the degree of polymerization by 1.2).

Table 2. Comparative characterization of tungsten determination procedures

Reagent(s) pH Solvent nm s-10-4, Linear interval, |jg/ml W [Ref.]

Toluene-3,4-dithiol 1.5-2.0 chloroform 640 1.92 - [2]

8-Mercaptoquinoline 0.5-3.0 isobutanol 412 0.367 <4 [1]

8-Hydroxyquinoline 4.4 chloroform 363 0.64 - [1]

4-nitrocatehol 1.2-3.6 chloroform 415 2.8 0.9-8.8 [13]

3-hydroxy-2- (2'-thienyl) -4-oxo-4H- 1 - 0.2 M HCl dichloromethane 415 6.45 0-2.8 [16]

benzopyran

HBTP + APi 2.0-5.8 chloroform 470 3.7 0.2-13.0 This work

HBTP + AP2 2.2-5.9 chloroform 480 3.9 0.2-16.0

Table 3. Results of tungsten determination in steel 339 (W - 0.183%, n = 5, P = 95%)

Method XX, % RSD, %

^ w , J . HBTP + AP1 Our Methods* HBTP + ap2 Toluene-3,4-dithiol [2] 0.180±0.011 5 0.182±0.007 3 0.185±0.009 4

- In the presence of 2 mL thioglycolic acid at a concentration of 0,01 mol/L

Effect of foreign ions and masking reagents. To assess the applicability of ternary complexes for the determination of tungsten in real objects, the influence of side ions was studied. It should be noted that a large amount of alkaline, alkaline- and rare-earth ions F-, Cl, Br-, SO32-, SO42- and C2O42- does not affect the definition. The inhibitory effect of Fe (III) was removed by means of thioglycolic acid (0.01 mol/l, 2 ml); Ti(IV) - ascorbic acid Cu(II) by means of thiourea Mo(VI) with oxalate. When using EDTA, the definition does not interfere with Ti (IV), V (IV), Nb (V), Ta (V), Mo (VI) and Fe (III).

Comparative characteristics of the procedures for determining W. Table 2 includes data that compare the analytical characteristics of the procedures developed by us with those of the already known procedures [1, 2, 13, 16].

Table 3 shows the results of the real object analysis - steel 339 (W content -0.183%). It can be concluded that the proposed procedures based on the use of HBTP and aminophenols AP1 AP2 are not inferior to those described in the literature. They allow reasonable, selective, accurate, cheap and reliable determination of tungsten in real objects.

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VOLFRAMIN (VI) 2-HÍDROKSÍ-5-BROMTÍOFENOL Vd AMÍNOFENOLLARLA KOMPLEKSLSRÍNÍN TdRKiBi Vd EKSTRAKSÍYASI

S.Z. Zalov, K.d. Quliyev, Nd. dkbarov, Ü.B. Aba§quliyeva, Ü.§. Bax§iyeva

Azsrbaycan Dövlst Pedaqoji Universiteti Uz. Hacibsyov 68, AZ1000 Baki; e-mail: [email protected]

Volframin (VI) 2-hidroksi-5-bromtiofenol(HBTF) vs aminofenollarla - 2-(N, N-dietilaminometiltio) -4-metoksifenol (AF1), 2- (N,N-dibutilaminometil)-4-metoksifenol (AF2), 2,6-bis- (N,N-dimetilaminometil)-4-metilfenol (AF3), 2,6-bis- (N,N-dimetilaminometil)-4-xlorofenol (AF4), 2-(N,N-dimetilaminometil) -4-metilfenol (AF5), 2- (N,N-dietilaminometil) -4-bromofenol (AF6) vs 4-xlor -2- (N,N-dimetilaminometil) -6-tiofenilmetilfenol (AF7) qarqiliqli tssiri tsdqiq edilmi^dir. Alinan müxtslifliqandli komplekslsri 1:2:2 (W:HBTF:AF) vs ya 1:2:1 (AF3 vs AF4) tsrkibins malikdir. Onlarin smslsgslmssi vs ekstraksiyasi ügün optimal §srait - üzvi hslledici - xloroform, pHop (4.1-5.6), reagentlsrin qatiligi vs ekstraksiya müddsti müsyysn edilmi^dir. Ekstraksiya dsrscssi 98.1-98.6% intervalinda dsyi^ir. Komplekslsr 470-482 nm-ds maksimum i§iqudmaya malikdir. Molyar udma smsali (2.6-3.9)*104 ts§kil edir. Ber qanununa tabe olma 0.2-16 ¡Ág/ml W qatiliginda mü^ahids olunur.

Agar sözlw. volfram (V), hslledici ils ekstraksiya, 2-hidroksi-5-bromotiofenol, üglü kompleks, tsyin metodikasi

СОСТАВ И ЭКСТРАКЦИЯ КОМПЛЕКСОВ ВОЛЬФРАМА (VI) С 2-ГИДРОКСИ-5-БРОМТИФЕНОЛОМ И АМИНОФЕНОЛАМИ

А.З. Залов, К.А. Кулиев, Н.А. Акперов, Ул.Б. Абаскулиева, Ул. Ш. Бахшиева

Азербайджанский государственный педагогический университет AZ1000 Баку, ул. У. Гаджибекова, 68; e-mail: [email protected]

Изучено взаимодействие вольфрама (VI) с 2-гидрокси-5-бромтиофенолом (ГБTФ) в присутствии аминофенолов (AФ^): 2- (N, N-диэтиламинометилтио) -4-метоксифенола (AФ1), 2-(Ы,Ы-дибутиламинометил)-4-метоксифенола ^Ф2), 2,6-бис-(Ы,Ы-диметиламинометил) 4-метилфенола ^Ф3), 2,6-бис- (N, N-диметиламинометил) -4-хлорфенола (AФ4), 2-(NN-диметиламинометил)-4-метилфенола (AФ5), 2-(N,N-диэтиламинометил)-4-бромфенола (AФ6) и 4-хлор-2-^,^диметиламинометил)-6-тиофенилметилфенола ^Ф7). Полученные тройные комплексы имеют состав 1:2:2 (W:ГБTФ:AФ) или 1:2:1 ^Ф3 и AФ4). Найдены оптимальные условия их образования и последующей экстракции: органический растворитель - хлороформ, рНоп (4.1-5.6), концентрация реагентов и время экстракции. Степень экстракции составляет 98.198.6%. Комплексы имеют максимумы поглощения при 470-482 нм. Молярные коэффициенты поглощения составляют (2.6-3.9)*104. Закон Бера наблюдается в диапазонах концентрации вольфрама 0.2 0.2-16.0 мкг/мл.

Ключевые слова: вольфрам (VI), экстракция растворителем, 2-гидрокси-5-бромтиофенол, тройной комплекс, методика определения