ISSN 0040-5795, Theoretical Foundations of Chemical Engineering, 2009, Vol. 43, No. 4, pp. 464–467. © Pleiades Publishing, Ltd., 2009.Original Russian Text © L.G. Gerasimova, M.V. Maslova, E.S. Shchukina, 2008, published in Khimicheskaya Tekhnologiya, 2008, Vol. 9, No. 6, pp. 241–244.

464

One way of the sulfuric acid treatment of spheneconcentrate has been conceived to obtain titanium saltsas final products—ammonium titanyl sulfate(NH

4

)

2

TiO(SO

4

)

2

· H

2

O (ATS) and titanyl sulfateTiOSO

4

· H

2

O (TMS) [1]. In the process of the hydro-metallurgy treatment of titanium rare metal raw materi-als, their isolation by the selective crystallization frommulticomponent sulfate solutions has been well studied[2, 3]. Obtaining the salts by sphene concentrate treat-ment has been studied to a much lesser extent.

Titanium salts are crystalline substances, whoseseries of properties allow their wide use in the synthesisof various titanium-containing products. In particular,they are not prone to caking in storage and thus are eas-ily transported. By dissolving the salts in water, con-centrated titanium solutions with a minimum numberof defect elements can be obtained, which makes theirtransformation into sufficiently pure titanium dioxide,compositional shell pigments, precursors for sorbentssynthesis, catalysts, etc., easier. In addition, ATS exhib-its excellent tanning characteristics. For severaldecades, it was produced in one factory of the formerSoviet Union and was used as a tanning agent for bothhard and soft leathers in numerous tanneries [4, 5]. Inconnection with the phasing out of its production, con-sumers were devoid of this nontoxic and inexpensivestarting material.

Before the sulfuric acid treatment, the sphene con-centrate should be finely grinded (into particles of a sizeof <50

µ

m). This operation is conducted to acceleratethe heterogeneous chemical reactions proceedingbetween the liquid and crystal solid phases. The grind-ing breaks down the substance grains to the point of dis-rupting the crystal structure, which is accompanied by

the ionization of the particle surfaces, making themamorphous, and, as a consequence, increases the sub-stance reactivity. The product formation frequentlystarts directly on the surface of the solid phase particles.This phenomenon is of particular interest in the casewhen the solid phase represents a complex of compo-nents having a crystal structure.

The procedure of the sphene concentrate treatmentto extract titanium (IV) into the solution is as follows.Into a sulfuric acid solution (550–650 g/l H

2

SO

4

)heated to 80–90

°

C, a concentrate whose mass con-sumption in relation to the acid volume corresponded tothe ratio

T

:

V

l

= 1 : 3 was added. The suspension washeated and kept at a refluxed state for 10 h with stirringand returned the steam phase to the reaction zone. Afterthe elapsed time, the suspension was cooled and the liq-uid phase was separated from the reaction products andunopened concentrate particles. In the liquid phase, thecontent of titanium (IV) as TiO

2

and H

2

SO

4

was deter-mined. From the formula

R

=

cV

/

m

τ

,

where

c

, mol/l, is the concentration of TiO

2

in the solu-tion;

V

, l is the volume of the solution;

m

, g is the massof the concentrate; and

τ

, h is the duration of the pro-cess; the rate of the extraction process was calculated;the degree of titanium (IV) transfer from the spheneinto the solution was also determined.

The reaction of the grinding-activated sphene withsulfuric acid in the investigated range of its concentra-tions is described by the equation [6]

CaSiTiO

5

+ 2H

2

SO

4

= TiOSO

4

+

↓

CaSO

4

+

↓

SiO

2

·

x

H

2

O + H

2

O.

The Technology of Sphene Concentrate Treatment to Obtain Titanium Salts

L. G. Gerasimova, M. V. Maslova, and E. S. Shchukina

Tananaev Institute of Chemistry and Technology of Rare Elements and Mineral Raw Materials, Kola Scientific, Russian Academy of Sciences, Apatity, Russia

e-mail: gerasimova@chemy.kolasc.ru

Received February 28, 2007

Abstract

—The rate of titanium (IV) extraction from sphene concentrate by its treatment with sulfuric acidsolutions was determined. The sulfatization conditions to form stable titanium (IV) sulfate solutions suitablefor preparing crystal substances—titanyl sulfate and ammonium titanyl sulfate—were found. The kinetics ofthe crystallization was studied. The phase composition of the titanium salts was established, and the content ofimpurities was determined by using X-ray analysis. It was shown that the technology for producing titaniumsalts is simple, which makes it possible to prepare in a few operations the precursors for the synthesis of hard-to-get expensive titanium-containing materials.

DOI:

10.1134/S0040579509040186

TECHNOLOGY OF INORGANIC SUBSTANCESAND MATERIALS

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2009

THE TECHNOLOGY OF SPHENE CONCENTRATE TREATMENT 465

The transfer of Ti(IV) into the liquid phase and theformation of the solid products—calcium sulfate andamorphous SiO

2

·

x

H

2

O—take place. Titanium (IV),due to its high solubility under the aforementioned con-ditions, is concentrated in the liquid phase. Sincesphene dissolution is a heterogeneous process and pro-ceeds at the interface between the liquid (sulfuric acidsolution) and solid (sphene particles) phases, its ratecan be dependent not only on the sulfuric acid concen-tration and temperature, which initiate the crystaldestructions, but also on the surface area, i.e., the dis-persity of the particles. Firstly, the extraction of tita-nium (IV) from the sphene to the liquid phase proceedsquite intensively (step I—approximately over 3.5–4 h).An increase in the concentration of H

2

SO

4

, its con-sumption, and, correspondingly, the temperature, posi-tively influences the reaction rate. The process slowsdown as the amount of the solid reaction productsincreases [7]. The X-ray phase analysis of the solidphase shows that the reaction products (amorphousSiO

2

·

x

H

2

O and crystal CaSO

4

) are formed as individ-ual phases and probably generate a porous cover on thesurface of the sphene particles. The rate of the furtherTi(IV) extraction from the sphene is determined by therate of the reagent diffusion through the cover (step II—from 4 to 10 h). The dissolution mechanism for both of thesteps is the same. Only the process rate varies (Fig. 1).

The composition of sulfuric acid solutions contain-ing titanium and prepared by the extraction from thesphene concentrate (production solutions) is repre-sented in Table 1.

The solutions from experiments 2 and 4 were usedto investigate the preparation of titanium salts and tostudy their composition and properties.

Crystallization of ATS

The procedure for the crystallization of ammoniumtitanyl sulfate from its solution is as follows. Into a solu-tion prepared for obtaining ATS, crystal ammonium sul-fate was added in such an amount to reach the overall saltcontent—H

2

SO

4

+ (NH

4

)

2

SO

4

—within the range 550–600 g/l. Ammonium sulfate was added slowly over1.5–2 hwith a working stirrer. Next, the suspension was stirredfor another 2 h and kept for 2 h without stirring. The pre-cipitate was filtrated under a vacuum and washed on aBuchner funnel with a saturated ammonium sulfate solu-tion at the consumption S :

V

l

= 1 : 0.25.

The data represented in Table 1 show that the Ti(IV)extraction degree varies in the range from 90 to 96.3%.At that, the lowest value was obtained in the experimentwhere a part of the acid, before the addition of ammo-nium sulfate, was neutralized with an ammonia solution.The introduction of ammonia, firstly, provided adecrease in the concentration of Ti(IV) and, secondly, ledto a partial transformation of highly reactive Ti(IV) intothe colloid form, which did not participate in forming thecrystal precipitate and thus remained in the liquid phase.

The addition of water leads to a similar decrease in theconcentration of Ti(IV); as a result, the Ti(IV) extractiondegree decreases to 92.6%. The crystal optics analysis ofthe samples shows that they represent a single phase withthe refractive index

N

= 1.580 corresponding to the com-position (NH

4

)

2

TiO(SO

4

)

2

· H

2

O. And only in the samplefrom experiment 1 was the presence of another phasewith a considerably lesser refractive index detected. Itwas found that the aggregation degree of the particles isapproximately the same for all of the experiments, i.e.,each aggregate includes 5–8 particles; however, thehigher the concentration of the acid and titanium (IV) inthe starting solution, the smaller the size of these parti-cles is. Accordingly, the suspension filtration rate islower if more concentrated solutions are used. The saltbasicity index (

A

) is the determining parameter in usingATS as a leather tanning agent. The basicity was calcu-lated from the following formula

A

= (

X

–

X

1

· 0.407) · 100/

X

,

where

X

is a mass fraction of TiO

2

, %;

X

1

is a mass frac-tion of active sulfuric acid, %; and 0.407 is the conver-sion coefficient from H

2

SO

4

to TiO

2

.

To meet the technical conditions, the basicity valueshould be in the range 42–48 [8]. The amounts of impu-rities in the AST samples are listed below.

14

12

10

8

6

4500 550 600 650

95908580757065605550

L,

%

[H

2

SO

4

], g/l

R

tota

l

×

10

–4

, mol

/g h

12

Fig. 1.

Influence of the solution acidity on (

1

) the rate oftitanium extraction from sphene (

R

overall

) and (

2

) the degreeof titanium extraction into the liquid phase (

L

).

Table 1.

Composition of production solutions

Experi-ment

number

Concentration of H

2

SO

4

in the start-ing solutions, g/l

Concentrations in the production solutions, g/l

TiO

2

H

2

SO

4

H

2

SO

4free

1 500 100.2 438.0 315.0

2 550 112.6 470.0 331.5

3 600 125.6 523.9 369.4

4 650 128.7 558.1 375.1

466

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GERASIMOVA et al.

Crystallization of TMS

Titanyl sulfate as its monohydrate is isolated fromsulfuric acid titanium solutions where the concentrationof free sulfuric acid is not less than 800 g/l. To reachthis, the solution resulting from the sphene concentratetreatment was evaporated at 60

°

C under a vacuum,heated to refluxing, and powdered TMS was introducedinto the solution to form “crystallization germs” andthus shorten the breakdown time. The suspension waskept at refluxing for 5 h. Then, the resulted precipitate

was separated and washed on the filter with cold water(Table 3).

The dependence of the TMS crystallization rate(determined from the change of the TiO

2

content in theliquid phase) on the number of germs is represented inFig. 2. In the presence of germs, the crystallization pro-ceeds at a twofold rate.

By washing TMS on the filter with water, up to 2%of titanium (IV) goes into the mother liquid. As it hasbeen found by the crystal optic and X-ray phase analy-sis, the investigated samples contain only the phaseTiOSO

4

· H

2

O in which TMS monoparticles of the size1–1.5

µ

m are incorporated into aggregates. The contentof impurities in the titanium salts, which was determinedby X-ray fluorescence analysis with a MAKS-GV spec-troscope, is represented in Table 4.

Judging from the data provided, almost all of the nio-bium contained in the sphene concentrate is concentratedin TMS. This fact allows for the thinking of the possibil-ity of its extraction at one of the TMS treatment steps.

CONCLUSIONS

Thus, it has been shown that the treatment of spheneconcentrate with diluted sulfuric acid gives the solu-tions suitable for obtaining titanium salts which can beused as marketable products or can be worked into

Table 2.

Crystallization conditions and properties of ATS

Experiment number [TiO

2

], g/l [H

2

SO

4

], g/l [H

2

SO

4

+ (NH

4

)SO

4

]*, g/l

α

, %

A

, % Dilution

1 112.5 470.0 550 96.6 40.3 Without dilution

2 112.5 470.0 600 96.3 48.5 Without dilution

3 86.6 220.1 550 90.0 46.8 Addition of 25% ammonia

4 86.6 395.4 550 92.6 47.5 Addition of water

5 118.7 558.1 550 95.2 43.9 Without dilution

* Concentration of components in the free state.

Table 3. Crystallization conditions of TMS

Experiment number

Solution parameters before salting outConsumption of germs, %

Filter parametersExtraction of Ti4+, %

V, ml [TiO2], g/l [H2SO4], g/l V, ml [TiO2], g/l [H2SO4], g/l

1 200 173.2 919 not 115 12.9 1096 95.6

2 200 173.2 919 2 125 8.6 1025 97.0

3 200 173.2 919 5 130 8.4 1044 96.8

Time, h

20018016014012010080604020

0 1 2 3 4 5

1

23

[TiO

2], g

/l

Fig. 2. Influence of the presence of “germs,” %, on the crys-tallization of TMS (1) without germs, (2) 2, and (3) 5.

THEORETICAL FOUNDATIONS OF CHEMICAL ENGINEERING Vol. 43 No. 4 2009

THE TECHNOLOGY OF SPHENE CONCENTRATE TREATMENT 467

hard-to-get titanium products such as titanium dioxide,pearl pigment, and sorbents. The cost of such productswill be less than that of analogous materials isolated byusing traditional schemes.

REFERENCES

1. Gerasimova, L.G., Maslova, M.V., Lazareva, I.V., andMatveev, V.A., The Use of the Sphene Concentrate forPreparation of Sorbents, Obogashch. Rud, 2005, no. 4,pp. 31–34.

2. Nikolaev, A.I., Pererabotka netraditsionnogo titanovogosyr’ya Kol’skogo poluostrova (Processing of Non–Tradi-tional Titanium Raw Materials of Kola Peninsula), Apa-tity: Kol’skii Nauchnyi Tsentr, 1991.

3. Kalinnikov, V.T., Nikolaev, A.I., and Zakharov, V.I., Gid-grometallutgicheskaya kompleksnaya pererabotkanetraditsionnogo titano–redkometall’nogo i alyumosil-ikatnogo syr’ya (Hydrometallurgy Complex Processingof Non–Traditional Titanium–Rare-Metal and Alumino-silicate Raw Materials), Apatity: Kol’skii NauchnyiTsentr, 1999.

4. Godneva, M.M. and Motov, D.L., Khimiya podruppytitana. Sulfity i ikh rastvory (Chemistry of Titanium Sub-Group. Sulfates and Their Solutions), Leningrad: Nauka,1980.

5. Motov, D.L., Fiziko–khimiya i sul’fatnaya tekhnologiyatitano–redkometall’nogo syr’ya (Physical Chemistryand Sulfate Technology of Titanium–Rare-Metal RawMaterials), Apatity: Kol’skii Nauchnyi Tsentr, 2002,Parts 1, 2.

6. Lazareva, I.V., Gerasimova, L.G., Maslova, M.V., Okhri-menko, R.F., Treatment of Sphene with Sulfuric Acid Solu-tions, Zh. Prikl. Khim., 2006, vol. 79, no. 1, pp. 18–21.

7. Lazareva, I.V., The Development of Technology forPreparation of Composition Pigments from Waste Mate-rials of Apatite–Nepheline Ore Enrichment, Cand. Sci.(Eng.) Dissertation, Apatity: Kola Sci. Center, Russ.Acad. Sci., 2005.

8. Tekhnicheskie usloviya TU 095.290–79: Sul’fat titanila iammoniya (Specifications TU 095.290–79: TitanylAmmonium Sulfate).

Table 4. Impurity content of titanium salts

Experi-ment

number

Content, wt %with respect to TiO2

Fe2O3 CaO Nb2O3 CeO2 SiO2

ATS, the TiO2 content is 20–21%

1 0.14 0.08 0.10 0.14 0.06

2 0.09 0.04 0.06 0.13 –

3 0.10 0.03 0.05 0.12 0.02

4 0.09 0.06 0.09 0.14 0.03

5 0.15 0.06 0.08 0.13 0.03

TMS, the TiO2 content is 39.1–40.8%

1 1.98 0.08 1.14 0.11 0.01

2 1.89 0.02 0.89 0.12 0.04

3 1.98 0.04 0.93 0.10 0.10