Liquid-Liquid Extraction of Molybdenum (VI) from Nitric

Journal of MMIJ Vol.124 (2008) No.6,7

1. Introduction

The extraction of molybdenum from aqueous solutions has

been examined by a number of solvent extraction systems1). We

have also investigated the extraction of molybdenum (VI) from

aqueous acid and alkaline solutions by TBP (tributyl phosphate),

DEHPA, EHEHPA (2-ethylhexyl 2-ethylhexyl phosphonic acid),

TOPO (trioctyl phosphine oxide), TOA (trioctylamine) and

TOMAC (trioctylmethylammonium chloride)2,3). However,

since the molybdenum (VI) species in aqueous solutions are not

always elucidated, there only a few limited literatures on the

stoichiometry in solvent extraction of molybdenum (VI).

Accordingly the results for the solvent extraction of

molybdenum (VI) from hydrochloric acid solutions by DEHPA

have been reported in a previous paper 2).

As the molybdenum (IV) is found as the earth's crust in

the form of molybdenite (MoS2), the extraction system from

sulphuric acid solutions by DEHPA has relations with the

preparation of molybdenum (VI) from ore. The concentration

of molybdenum in the ore is general about 0.2 - 0.6 % by

weight, and the ore is usually concentrated to 60 - 90 % MoS2

by weight. Then molybdenum concentrates are converted to

sodium molybdate by fusion at 700 - 950 ℃, in an oxidizing

atmosphere with at least 15 % in excess of the amount of

Na2CO3 required to convert the molybdenum and sulphide

present in the concentrates to water-soluble molybdenum and

sulphur compounds. Afterwards the sodium molybdate solution

in sulphuric acid obtained by leaching the fusion mass with

water is supplied for the solvent extraction system4). Therefore

the present paper extends the work to the extraction of

molybdenum (VI) from nitric and / or sulphuric acids solutions

and the obtained results are compared with the extraction system

of molybdenum (VI) from hydrochloric acid solutions by

DEHPA.

2. Experimental

　2・1　ReagentsThe DEHPA (Daihachi Chemical Co. Ltd.) was purified by

washing several times successively with 10 % sodium carbonate

solution, 6 mol dm-3 HCl and-water. The resulting material was

diluted with purified kerosene or benzene (with hexane for

infrared (IR) spectrophotometry). The stock solution of

molybdenum (VI) was prepared by dissolving sodium molybdate (Na2MoO4・2H2O) in nitric or sulphuric acid of required

concentration. The aqueous solutions containing sodium

molybdate in 1 g dm-3 were in general used except loading test.

All chemicals were analytical grade.

　2・2　Extraction and analytical procedures Equal volumes (15 cm3 each) of DEHPA and aqueous

molybdenum solutions were shaken with a mechanical shaker at

340 r.p.m. for the required time at 20℃, except the experimentals

Journal of MMIJ Vol.124 p.467 − 472 (2008)

©2008 The Mining and Materials Processing Institute of Japan

467 〈51〉

Liquid-Liquid Extraction of Molybdenum (VI) fromNitric and Sulphuric Acids Solutions

by Di-(2-Ethylhexyl)-Phosphoric Acid*

The extraction of molybdenum (VI) from nitric and sulphuric acids solutions by di-(2-ethylhexyl)-phosphoric acid (DEHPA, HX) in benzene has been investigated under different conditions. The infrared and electronic absorption spectra measurements were made of the organic extracts. From the results, it is found that the extraction of molybdenum (VI) at low aqueous acidities ([HNO3] ≤ 3 mol dm-3 or [H2SO4] ≤ 3 mol dm-3) is governed by a cation-exchange reaction and at higher acidities ([HNO3] ≥ 3 mol dm-3 or [H2SO4] ≥ 3 mol dm-3) by solvating reaction: from HNO3 or H2SO4 solns. at low acidity, MoO2

2+ (aq) + 2(HX)2(org) MoO2X4H2(org) + 2H+(aq); from HNO3 or H2SO4 solns. at higher acidity, MoO2

2+ (aq) + 2NO-3(aq) + (HX)2(org) MoO2 (NO3)2・

2HX(org) or MoO22+ (aq) + SO4

2+(aq) + (HX)2(org) MoO2-SO4・2HX (org), respectively. When the extraction systems for molybdeenum (VI) from nitric and sulphuric acids solutions are compared with that from hydrochloric acid solutions, it is inferred that the extraction efficiencies are in the orders HNO3 H2SO4 HCl at low aqueous acidity and HNO3 ＞ H2SO4 HCl at higher aquous acidity. It is seen that the complexes MoO2X4H2 and MoO2 (NO3)2 ・ 2HX or MoO2 SO4・2HX, indicating the coordination number of six for molybdenum as the octahedral structure, are formed in the extraction from aqueous nitric and sulphuric acids solutions at low and higher acidities, similar to the extraction system in hydrochloric acid solutions.KEY WORDS : Liquid-Liquid Extraction, Molybdenum (VI), Di-(2-Ethylhexyl)-Phosphoric Acid (DEHPA),

Nitric and Sulphuric Acids Solutions

by Taichi SATO1, Hiroki SUZUKI2 and Keiichi SATO3

*Received 11 July, 2007: accepted for publication 17 March, 20081. Honorary Professor, Dr.Sc., Dr.Eng., Faculty of Engineering, Shizuoka University,

Hamamatsu, 432-8011 Japan ; Visiting Professor, Department of Materials and Metallurgical Engineering, Queen's University, Kingston, Ontario K7L 3N6, Canada

2. Research Fellow, Faculty of Engineering, Shizuoka University, (at present, K.I.Chem. Syn. Co., Ltd.)

3. Research Fellow, Faculty of Engineering, Shizuoka University, (at present, Toyo Ink Mfg. Co., Ltd.)

[For Correspondence] FAX: +81-3-3422-3114 (3-14-1, Daita, Setagaya-ku, Tokyo, 155-0033 Japan)


Taichi SATO, Hiroki SUZUKI and Keiichi SATO

on the effect of temperature. The equilibrations were complete

in 10 min for the extraction from nitric or sulphuric acid

solutions. The mixture was separated by centrifuge, and then the

concentration of molybdenum in both the aqueous and organic

phases was determined to obtain the distribution coefficient (Eoa,

the ratio of equilibrated concentration of molybdenum in organic

phase to that in aqueous phase). Molybdenum in organic phase

was stripped with 0.5 mol dm-3 sodium hydroxide solution in

initial two or three times and then 1 mol dm-3 nitric acid

solution. The concentration of molybdenum in aqueous solution

was determined by adding excess of Cy-DTA and back titrating

with zinc sulphate solution using xylenol orange (XO) as

indicator. The water content of the organic phase was

determined by the use of Karl Fisher titration.

Furthermore as the concentration of electrolyte has relation

with the activity of solute, the change in the activity of solute

must be considered in comparison of the extraction constants

examined at different ionic strengthes. Since the present

examination in acid concentration has been carried out in the

wide range at nearly 0.1 - 10 mol dm-3, the ionic strength of

solution intended to keep at constant by addition of sodium

perchlorate, NaClO4・H2O 5). In this case, however, it has been

seen that there is not so different between the values for the

extraction constants determined by using the concentration of

solute and taken by fixing the ionic strength of electrolyte.

Hence the extraction constant by the concentration for

electrolyte is usually treated in the present study.

　2・3　Electronin and IR spectral measurements The electronic absorption spectra for the organic extracts

were recorded on a Hitachi model 340 spectrophotometer using

matched 1.0 x 1.0 cm fused silica cells. The IR spectra of

samples, prepared by evaporating the organic solution from the

extraction with DEHPA in hexane, were determined of JASCO

models IRA-1 (4000 - 650 cm-1) and IR-F (700 - 200 cm-1)

using a capillary f ilm between thallium halide plates or

polyethylene films.

3. Results and Discussion

　3・1　Extraction isotherm in nitric acid systems The extraction of molybdenum (VI) from nitric acid

solutions at various concentrations containing 1 g dm-3 sodium

molybdate was carried out with DEHPA in benzene at 20 ℃ .

The results showed that the distribution coefficients decreased

with increasing aqueous acidity below about 3 mol dm-3 and

rose with above this concentration (Fig. 1). However, since the

shape of the distribution curve for the extraction of molybdenum (VI) from nitric acid solutions resembles that in the extraction

system from hydrochloric acid solutions in which the

distribution coefficients decrease and increase at below and

above about 2 mol dm-3, respectively2). Accordingly the

variation of the distribution coeff icients by DEHPA is

interpreted as follows: at low aqueous acidity molybdenum (VI)

is extracted by a cation-exchange reaction in which hydrogen is

liberated, and at higher aqueous acidity by solvating reaction

with non-ionic reagent like TBP (tributyl phosphate)6,7).

As the extraction of MoO22+ is generally considered to be

the prevailing species in dilute solutions of molybdenum salt,

the initial decrease in the distribution coefficient at low aqueous

acidity is inferred to be governed by the ion-exchange reaction

similar to the extraction of UO22+ by DEHPA 6):

　MoO22+ (a) + 2 (HX)2(o) MoO2X4H2(o) + 2H+ (a) … (1)

where (HX)2 referes to the dimeric reagent, and (a) and (o)

denote aqueous and organic phases, respectively. This leads

　log 4 Eoa = log K + 2 log (CS - 4CMo) / CH ……………… (2)

in which K is equilibrium constant, CS the total extractant

concentration, CMo molybdenum concentration in the organic

phase, and CH aqueous acidity. Log-log plots of Eoa vs. (CS - 4

CMo) / CH at low acidities (for pH 1, and 0.5 and 1 mol dm-3

HNO3) show that Eq. (2) is satisfied at [HNO3]init aq ≤ 3 mol

dm-3 (Fig. 2(a)), giving the straight line with the slope of ～ 2.

Thus the equilibrium equation (1) is given for the equation of

molybdenum (VI) from nitric acid solutions below 3 mol dm-3

with DEHPA.

At higher aqueous acidities, if the extraction involves the

conbination of n molecules of the DEHPA dimer, which is

bonded as monomer 2HX, with molybdenum species by a

reaction similar to that for TBP

　MoO22+ (a) + 2NO-

3 (a) + n (HX)2(o)

　　　　　　 MoO2 (NO3)2・2nHX(o), …………… (3)

we have

　log 2 n Eoa = log K1 + n log (CS - 2 n CMo) ……………… (4)

where K1 is constant. Log-log plots of Eoa vs. (CS - 2 n CMo) at

[NO-3] init aq ≥ 3mol dm-3 give the straight lines with a slope of

～ 2 for n = 1 (for 7 and 10 mol dm-3 acids), although those

468 〈52〉 469 〈53〉

Fig.1 Extraction of molybdenum (VI) from nitric acid solutions with DEHPA in benzene (numerals on curves are DEHPA concns., mol dm-3 ; numbers on the axis of abscissa denote the initial pH value and acid concns., mol dm-3, for nitric acid solns, respectively).


Liquid-Liquid Extraction of Molybdenum (VI) from Nitric and Sulphuric Acids Solutions by Di-(2-Ethylhexyl)-Phosphoric Acid

slopes should give unity (Fig.2(b)). However, since the reaction (1) will also occur to some extent at higher acidities, the

observed values of the distribution coefficient are probably

higher than if the extraction showed a nitrate dependency due to

Eq. (3) alone. This phenomenon resembles the case of

molybdenum (VI) extraction from hydrochloric acid solutions

by DEHPA2). Accordingly, since the slope of the line using n =

1 may be greater than unity, we assume that n = 1 (for the

bonded ratio [HX] / [Mo] org = 2) in Eq. (3), i.e.

　MoO22+ (a) + 2 NO-

3 (a) + (HX)2(o)

　　　　　　 MoO2 (NO3)2・2HX(o) ……………… (5)

In addition, the complex MoO2 (NO3)2・2HX at higher

acidities corresponds to the coordination number of six for

molybdenum in the complex MoO2X4H2 at low acitities,

although they have no coordination water.

Further when the molar ratios of [HX]init to [Mo] in the

organic phase as a function of [Mo] init aq in the extraction of

molybdenum (VI) from nitric acid solutions at pH1 were

determined with 0.05 mol dm-3 DEHPA in hexane at 20℃ , the

value of [HX] init and [H2O] org to [Mo] org approached the

limiting ones of 4 : 0 (Fig.3). This suggests that the complex

MoO2X4H2 is formed in the extraction from nitric acid solutions

at low aqueous acidity.

　3・2　Extraction isotherm in sulphuric acid system In the same manner, the extraction of molybdenum (VI)

from sulphuric acid solutions at various concentrations

containing 1 g dm-3 sodium molybdate with DEHPA in benzene

at 20℃ gave the results shown in Fig. 4: the distribution curve

468 〈52〉 469 〈53〉

Fig.2 (a) and (b), Dependence of distribution coefficient on DEHPA concentration in the extraction of molybdenum (VI) from nitric acid solutions at low (a) and higher (b) acidities with DEHPA (numerals on broken and continuous lines denote the initial pH value and acid concn., mol dm-3, for nitric acid solns., respectively). In Fig.2(b) the values are plotted out for n = 1.

Fig.3 Loading test for the extraction of molybdenum (VI) from nitric acid solut1ons containing sodium molybdate with 0.05 mol dm-3 DEHPA in hexane (at pH1,○ and △ denote the molar ratios of [HX]init and [H2O]org to [Mo]org ,respectively).

Fig.4 Extraction of molybdenum (VI) from sulphuric acid solutions with DEHPA in benzene (numerals on curves are DEHPA concns., mol dm-3; numbers on the axis of abscissa denote the initial pH value and acid concn., nolmality and / or mol dm-3 in parenses, for sulphuric acid solns., respectively).



for molybdenum (VI) resembled that in the extraction system

from nitric or hydrochloric acid solutions; the distribution

coefficients decreased with increasing aqueous acidity below

about 3 mol dm-3 and rised with above this concentration.

Accordingly it is inferred that the extraction of molybdenum (VI) from sulphuric acid solutions at low and higher acidities

progresses in the cation-exchange reaction and solvating one,

respectively, as well as the extraction systems from hydrochloric

and nitric acids solutions.

Therefore i t i s presumed that the extract ion of

molybdenum (VI) from sulphuric acid solutions at low aqueous

acidities follows Eqs. (1) and (2). However, the extraction at

higher aqeous acidities is considered as satisf ied by the

following equilibrium:

　MoO22+ (a) + 2 SO4

2-(a) + m(HX)2(o)

　　　　　　　 MoO2 SO4・2mHX(o), …………… (6)

and　log 2 m Eoa = log K2 + m log (CS - 2 m CMo) ……… (7)

where K2 is constant. Log-log plots of Eoa vs. (CS - 2 m CMo) at

[H2SO4] init aq ≤ 3 mol dm-3 (for pH 1 , 0.5 and 1 mol dm-3

H2SO4) show that Eq. (2) is satisfied at low acidities (Fig. 5(a)), giving the straight lines with the slope of ～ 2 for m = 2. Thus

the equilibrium equation (1) is given for the extraction of

molybdenum (VI) from sulphuric acid solutions below 3 mol

dm-3 with DEHPA. Otherwise, log -log plots of Eoa vs. (CS - 2

m CMo) at [H2SO4] init aq ≥ 3 mol dm-3 give the straight lines

with a slope of ～ 1 for m = 1 (for 3, 4.5 and 5 mol dm-3) (Fig. 5(b)). As this phenomenon is different from the cases of

molybdenum (VI) extraction from hydrochloric and nitric acid

solutions by DEHPA, it is seen that the influence of the reaction (1) is little for the extraction of molybdenum (VI) from

sulphuric acid solutions at higher acidities.

Furthermore, for this extraction system, the variation in

the molar ratios of [HX] init and [H2O] org as a function of

[Mo] init aq was similar to Fig. 3, suggesting the formation of the

complex MoO2・X4H2 at low aqueous acidity.

　3・3　Electronic spectra The absorption spectra of the aqueous solutions containing

0.02 g dm-3 sodium molybdate in sulphuric acid at 0.05 - 5 mol

dm-3 are shown in Fig. 6. The spectra of sodium molybdate

solutions in sulphuric acid at 2 - 5 mol dm-3 show an absorption

at 218 nm, and its absorption shifts to lower wavelength at

470 〈54〉 471 〈55〉

Fig.5 (a) and (b), Dependence of distribution coefficient on DEHPA concentration in the extraction of molybdenum (VI) from sulphuric acid solutions at low (a) and higher (b) acidities with DEHPA (numerals on lines denote the acid concns., mol dm-3 for surphuric acid solns., except for pH value in a broken line). In Fig. 5(b) the values are plotted out for m = 1.

Fig.6 Absorption spectra of sulphuric acid solutions containing 0.02 g dm-3

sodium molybdate (numerals on curves denote sulphuric acid concn., mol dm-3).


Liquid-Liquid Extraction of Molybdenum (VI) from Nitric and Sulphuric Acids Solutions by Di-(2-Ethylhexyl)-Phosphoric Acid

[H2SO4] < 2 mol dm-3 with decreasing acid concentration, and

then the absorption at 218 nm appears again at 0.05 - 0.25 mol

dm-3. Accordingly it is presumed that the species without

sulphate ion is dominated at the low acidity region. Additionally

the organic extracts from sulphuric acid solutions at low

acidities showed the similar spectra to the organic extracts from

hydrochloric acid solutions at low acidities2), and those from

aqueous solutions at higher acidities showed the absorption at

below 210 nm.

On the one hand, as the absorbance of nitric acid radical is

too large, the spectra of sodium molybdate in nitric acid could

not measure. However, the organic extracts from nitric acid

solutions at low acidities showed the spectra similar to the

organic extracts from hydrochloric acid, while those at higher

acidities showed the absorption at 213 nm.

Therefore the results for the absorption in the extraction

systems of molybdenum (VI) from sulphuric and nitric acids

solutions resemble that for the absorption spectra in the

extraction systems from hydrochloric acid solutions2).

Consequently, although the species of the molybdenum (VI) in

aqueous solutions are complicated, it is presumed that the main

species in sulphuric and nitric acid solutions might be regarded

as MoO22+ and MoO2SO4 and / or MoO2 (NO3)2 at low and

higher acidities, respectively.

　3・4　IR spectra The organic extracts from aqueous solutions containing

sodium molybdate 10 g dm-3 in hydrochloric, sulphuric and

nitric acids at low (pH 1) and higher acidities (10, 5 and 10 mol

dm-3 for HCl, H2SO4 and HNO3, respectively) with 0.1 mol

dm-3 DEHPA in hexane at 20℃ were examined by IR

spectroscopy. The IR spectrum of DEHPA exhibits the

following characteristic patterns in addition to the absorptions

of alkyl groups: a P - O stretching absorption band at 1230 cm-1

; OH stretching bands at 2680 and 2350 cm-1 and OH bending

band at 1690 cm-1 ,arising from the hydrogen bond in the

formation of dimer ; a (P - O) - C stretching band at 1030 cm-1 ;

a broad band at 605, 515, 480 and 370 cm-1, assigned to the (P -

O) bending vibration probably associated with other modes (Fig.7, 8). In the spectra of the organic extracts, as the

concentration of metal increases, the intensities of the OH bands

decrease, while the original P - O absorption shifts toward lower

frequency in the extraction of aqueous acid solutions containing

sodium molybdate at low and higher acidities, respectively.

For the organic extracts from aqueous acids solutions (HCl, H2SO4, HNO3) at low acidities, however, their spectra

resemble each other (Figs. 9, 10) : the P - O absorption splits

into two bands due to the POO- asymmetric stretching vibrations

at 1230 and 1190 cm-1, respectively. Simultaneously, the OH

absorption bands disappear in accordance with the data for the

water contents of the complexes, indicating that the complexes

do not contain water. The (O - P - O) bending absorptions

around 600 and 450 cm-1 also split into three bands at 600, 510

and 475 cm-1 , and the MoO2 symmetric and asymmetric

stretching absorptions and bending vibration appear at 950, 920

and 400 cm-1, respectively6,7). Hence the IR results confirm

that the metal extracted into DEHPA by cation exchange is

bonded to the phosphoryl oxygen atom.

On the other hand, the organic extracts from sulphuric and

nitric acids solutions at higher acidities exhibit the absorptions

similar to the spectra of the organic extracts from aqueous acids

solutions at low acidities. However, since the respective organic

extracts are formed by the solvating reaction containing each

anion, they show the characteristic absorption bands due to the

anion in each acid solution (for chloride, 335 cm-1 8,9); for

sulphate, 1060 cm-1 10) ; for nitrate, 1630, 1390, 1298 and 680

cm-1 11).

4. Conclusion

The extraction of molybdenum (VI) from nitric and

sulphuric acids solutions has been examined by DEHPA (HX).

470 〈54〉 471 〈55〉

Fig.7 Infrared spectra of the organic extracts from hydrochloric, sulphuric and nitric acids solutions containing sodium molybdate (D, E and F denote the organic extrcts from HCl, H2SO4 and HNO3 solns. at 10, 5 and 10 mol dm-3, respectively).

Fig.8 Far-infrared spectra of the organic extracts from hydrochloric, sulphuric and nitric acids solutions containing sodium molybdate (D, E and F denote the organic extracts from HCl, H2SO4 and HNO3 solns. at 10, 5 and 10 mol dm-3, respectively).



ジ−2 −エチルへキシル−リン酸による硝酸および硫酸溶液からのモリブデン (VI)の液−液抽出

佐藤太一 1　　鈴木裕紀 2　　佐藤馨一 2

　硝酸および硫酸溶液からのモリブデン (VI) の抽出が DEHPA

( ジ－ 2 －エチルへキシル－リン酸，HX) のベンゼン溶液により

種々の条件で検討された。有桟相への抽出物が赤外線および電子

スペクトルの測定により調べられた。その結果低酸濃度 ([HNO3]

≤ 3 mol dm-3 または [H2SO4] ≤ 3 mol dm-3) 溶液からのモリブデ

ン (VI) の抽出は陽イオン交換反応 MoO22+ (aq) + 2 (HX)2(org)

MoO2X4H2 (org) + 2H+ (aq) により，また高酸濃度 ([HNO3] ≥ 3 mol

dm-3 または [H2SO4] ≥ 3 mol dm-3) 溶液からの抽出では溶媒和反

応 MoO2 (NO3)2(aq) + (HX) 2 (org) MoO2 (NO3) 2・2HX または

MoO2 SO4 (aq) + (HX)2(org) MoO2 SO4・2HX (org) によりそれ

ぞれ支配されることが判った。そして硝酸および硫酸溶液から

のモリブデン (VI) の抽出系が塩酸溶液の抽出系と比較された時，

モリブデンの抽出効果は低酸濃度では HNO3 H2SO4 HCl で高

1. 普通会員　理博・工博　静岡大学名誉教授　工学部，

Visiting Professor, Department of Materials and Metallurgical

Engineering, Queen's University, Canada

2. 静岡大学　工学部　研究生

キーワード：液－液抽出，モリブデン (VI)，ジ－ 2 －エチ

ルヘキシル－リン酸 (DEHPA)，硝酸および硫

酸溶液

酸濃度では HNO3 ＞ H2SO4 HCl であることが判った。従って

八面体構造の配位数 6 のモリブデン単量体錯体 MoO2 X4H2 およ

び MoO2 (NO3) 2・2HX または MoO2 SO4・2HX がそれぞれ低酸

濃度および高酸濃度溶液から抽出生成される。それ故これらの抽

出状態は塩酸溶液からのモリブデン (VI) のそれと類似している

ことが明らかになった。

Consequently it is seen that the extraction of molybdenum (VI)

at low aqueous aciddities [HNO3] ≤ 3 mol dm-3 or [H2SO4]≤ 3

mol dm-3 proceeds due to an ion-exchange reaction

　MoO22+ (a) + 2 (HX)2(o)2 Mo O2X4H2(o) + 2H+ (a),

and at higher acidities [HNO3] ≥ 3 mol dm-3 or [H2SO4] ≥ 3

mol-3 due to a solvating reaction

　MoO22+ (a) + 2 NO-

3 (a) + (HX)2(o) MoO2 (NO3)2・2HX(o)

or MoO22+ (a) + SO4

2- (a) + (HX)2(o) MoO2 SO4 ・ 2HX(o).

Accordingly, monomeric complexes MoO2X4H2 and

MoO2(NO3)2・2HX or MoO2SO4・2HX, indicating the

coordination number of six for molybdenum (VI) as the

octahedral structure, are formed from aqueous nitric or sulphuric

acid solutions at low and higher acidities, respectively, similar to

the extraction system in hydrochloric acid solutions 2).

References 1) e.g., A. M. Al-Ani and T. M. Masoda : Hydrometallurgy, 9(1982), 211-214 ; S. Kikuchi, H.

Hattori and T. Hosaka : Journal of MMIJ, 105(1989), 245-248 ; M. H. H. Mahnaoud, S. Nakamura and K. Akiba : Sep. Sci. Technol., 31(1996), 2768-2774 ; N. I. Gerhardt and A. A. Palant : Hydrometallurgy, 55(2000), 1-18 ; and references cited therein.

2) T. Sato, H. Suzuki and M.Ueda : Journal of MMIJ, 123(2007), 39 - 44. 3) T. Sato, H. Watanabe and M. Suzuki : Solvent Extr. Ion Exch., (1986), 987-998 ;

Hydrometallurgy, 23 (1990), 297-308 ; T. Sato, T. Takeuchi and K. Sato : Proc. ISEC'86, Vol.2 (1986), pp.153 - 157 ; T. Sato : Journal of MMIJ, 111(1995), 119-124 ; T. Sato, H. Suzuki and K.Sato : Solvent Extr. Res. Devel. J., 14(2007), 31 - 42.

4) M. B. MacInnis and T. K. Kim : Handbook of Solvent Extraction edited by T. C. Lo, M. H. I. Baird and C. Hanson, (John Wiley & Sons., Inc., N.Y., 1983), p.693.

5) G. H. Morrison and H. Freiser : Solvent Extraction in Analytical Chemistry (John Wiley & Sons., Inc., N.Y., 1957), p.143.

6) T. Sato : J. Inorg. Nucl. Chem., 24(1962), 699-706. 7) T. Sato : J. Appl. Chem., 16(1966), 53-57. 8) J. R. Ferraro : Low-Frequency Vibrations of Inorganic and Coordination Compounds, (Plenum

Press, N.Y., 1971), p.101. 9) J. H. Canterford and R. Colton : Halides of the Secondes and Third Raw Transition Metals,

(Wiley Interscience, N.Y., 1968), p.225. 10) K. Nakamoto : Infrared and Raman Sectra of Inoranic and Coordination Compounds, 3rd

Ed., (Wiley Interscience, N.Y., 1968), p.239. 11) Ref. 10), p.244.

Fig.10 Far-infrared spectra of the organic extracts from hydrochloric, sulphuric and nitric acids solutions containing sodium molybdate (A, B and C denote the organic extracts from HCl, H2SO4 and HNO3 solns. at pH 1, respectively).

472 〈56〉 PB 〈00〉

Fig.9 Infrared spectra of the organic extracts from hydrochloric, sulphuric and nitric acids solutions containing sodium molybdate (A, B and C denate the organic extracts from HCl, H2SO4 and HNO3 solns. at pH 1, respectively).

Documents

Liquid-Liquid Extraction of Molybdenum (VI) from Nitric