RU2623974C1 - Method of processing titanium-containing mineral raw materials - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: method involves fluoridation of the ilmenite concentrate with a saturated aqueous solution of hydrobifluoride and/or ammonium fluoride (solid-to-liquid ratio=1:8-10) at boiling temperature for 40-60 minutes, followed by separation of the precipitate of fluoromammonium iron salts from a solution containing a fluorammonium titanium salt. The resulting solution is purified from manganese by adding metallic iron powder. The resulting precipitate is separated and the filtrate is purified from the iron by precipitation with a 30% hydrogen peroxide solution. The resulting precipitate is sent for further processing, and a 25% ammonia solution is added to the purified filtrate until complete precipitation at pH 9 of ammonium oxofluorotitanate (NH₄)₃TiOF₅, which is directed for the production of titanium dioxide by step-like pyrohydrolysis to 850-950°C.

EFFECT: increased degree of purification of titanium dioxide with increasing the completeness of its use.

3 cl, 2 ex

Description

The invention relates to the processing of titanium-containing mineral raw materials, mainly placer titanium ores hydrofluoride method, and can be used to obtain titanium dioxide, which is used as a pigment. It should be noted that Russia annually consumes about 50,000 tons of titanium pigment, currently mainly purchased abroad.

Processing ilmenite concentrate by the hydrofluoride method to produce pigment-grade titanium dioxide with a high whiteness index is often hampered by the presence of chromophore impurities, since in most cases placer titanium ores along with ilmenite contain its leukoxenized (oxidized to various degrees) forms.

A known method of processing titanium-containing mineral raw materials (RU 2058408, publ. 1996.04.20) to obtain fine titanium dioxide of high purity and iron oxide doped with impurities (Cr, V, Ni, Co, Ti), including sintering of raw materials with ammonium hydrodiforide in a ratio of 85 -117% of the stoichiometric temperature at a temperature of 50-180 ° С, heat treatment of the fluorinated mass and separation of fluorination products by sublimation with the release of titanium ammonium fluoride complex and its subsequent pyrohydrolysis to obtain titanium dioxide. The sludge remaining after sublimation of the titanium compound is hydrolyzed to obtain iron oxide. Obtained in a known manner, titanium dioxide is contaminated with iron due to the inability to prevent dust extraction of finely dispersed iron fluorides at the sublimation stage, in addition, ammonia released during the decomposition of fluorine complexes of iron and titanium during sublimation partially reduces Ti (IV) to Ti (III), which is a chromophore impurity and negatively affects the brightness of titanium dioxide, while the iron oxide obtained by pyrohydrolysis, in turn, is contaminated, in addition to the above impurities, with calcium and magnesium fluorides, which that at a temperature of 800-840 ° C do not undergo pyrohydrolysis.

A known method of processing titanium-containing raw materials (RU 2139249, publ. 1999.10.10) to obtain finely dispersed titanium and iron oxide pigments by alloying a titanium-containing concentrate with ammonium hydrodifluoride, followed by aqueous leaching of the melt, separating the ammonium fluoroferrates that have precipitated at pH 7-8, and crystallized ammonium hexafluorotitanate solution. The solubility of iron fluoro ammonium complexes in water is higher than in a solution of ammonium fluoride. In the case of water leaching of the melt, part of the iron goes into solution and crystallizes together with ammonium hexafluorotitanate, contaminating the final product, which does not allow to obtain a sufficiently pure titanium pigment without additional iron removal operations.

Closest to the claimed is a method for the separation of titanium and iron (RU 2182886, publ. 2002.05.27) in the processing of titanium-containing mineral raw materials by treatment with a saturated aqueous solution of ammonium fluoride with a ratio of T: W equal to (0.5-2): 1, and a temperature of 50-100 ° C to obtain a precipitate of insoluble ammonium fluoroferrates and its subsequent separation from a solution of ammonium fluorotitanate, after which the solution is purified from iron impurities by adding ammonia to pH 6.5-7.5, and then precipitated by raising its pH to 9 purified oxofluorotitanate a Monia, from which the titanium dioxide of high purity.

However, when processing in a known manner titaniferous minerals containing leykoksenizirovannye ilmenite and form a significant amount of Fe ^3+, removing the problem, in addition to iron (III), other chromophoric impurities - manganese. If in TiO _{2 the} amount of manganese in terms of MnO reaches 0.003%, then the titanium pigment acquires an unpleasant gray tint, which sharply reduces its color characteristics (Belenky E.F., Riskin I.V. Chemistry and technology of pigments // 4th Edition. “Chemistry.” 1974. S. 108).

The ilmenite manganese isomorphic replaces the divalent iron in the range from 0.5 to 2.5%, and in the processing of the classical forms of ilmenite with aqueous fluoride / ammonium bifluoride resulting salt NH ₄ MnF ₃ coprecipitated adequately isostructural with it ferrous salt NH ₄ FeF ₃ in the form of solid solutions.

The objective of the invention is to provide a highly efficient method for processing leukoxenized titanium-containing mineral raw materials with obtaining high-purity titanium dioxide.

The technical result of the proposed method is to increase the degree of purification of titanium dioxide obtained from leukoxenized titanium-containing mineral raw materials, while increasing the completeness of the use of the latter.

The specified technical result is achieved by a method of processing titanium-containing mineral raw materials, including fluorination of it with a saturated aqueous solution of hydrodifluoride and / or ammonium fluoride by heating, followed by separation of the insoluble precipitate containing iron fluoroammonium salts from the solution containing ammonium fluorotitanate, the resulting solution is purified from iron impurities and added to it a 25% ammonia solution to pH 9 for the complete precipitation of ammonium oxofluorotitanate used to produce titanium dioxide, in which rum, in contrast to the known one, fluorination is carried out at a ratio of T: L = 1: (8-10) at a boiling point of the reaction mixture for 40-60 minutes, while the solution containing ammonium fluorotitanate is further purified from iron to purify it from iron By adding metallic iron powder to the solution in an amount providing a mass ratio of Fe / Mn of at least 100, the reaction mixture is heated to boiling point and boiled for 15-20 minutes to obtain a precipitate containing fluorine-ammonium complex salts of iron (II, III) mixed withargantsa which after cooling is separated by filtration and sent to further processing.

Additional purification of the solution of ammonium fluorotitanate from iron is carried out using a 30% hydrogen peroxide solution at a molar ratio of H ₂ O ₂ : Ti = 1: 1.

In an optimal embodiment of the method, the iron-containing precipitate isolated at the stage of purifying the solution of ammonium fluorotitanate from iron is sent for further processing to obtain titanium dioxide with a purity of 97-98%.

The method is as follows.

An ilmenite concentrate containing oxidized forms of ilmenite in the form of leukoxene is placed in a reactor and subjected to fluorination with an aqueous solution of ammonium hydrodifluoride / fluoride T: W = 1: (8-10).

This ratio of fluorinating agent and mineral raw materials to a lesser extent impedes the process of occlusion of the feedstock with reaction products and provides a fairly complete opening, in contrast to the known method, where a large amount of unreacted residue is formed, which must be returned to the cycle, adding to the primary raw material. In process of accumulation in the processed raw materials of returned unreacted residues, its processing becomes more difficult.

The reaction mixture is heated to boiling point and boiled for 40-60 minutes with stirring, while its boiling point ranges from 105-108 ° C. The evolved ammonia is captured and discharged using a gas outlet pipe. The resulting solution containing a soluble fluoroammonium salt of titanium is filtered off from the precipitated gray precipitate, which, according to X-ray diffraction analysis, contains a ferric ammonium salt of ferric (NH ₄ ) ₃ FeF ₆ , a small amount of unreacted feedstock and an admixture of ammonium hexafluorotitanate .

For complete extraction of ammonium hexafluorotitanate, the precipitate is washed with a hot (60-70 ° C) solution of 10% ammonium fluoride and filtered. The filtrate obtained at this stage containing soluble fluorine complexes of titanium and silicon is combined with the main filtrate obtained after fluorination of the feedstock. And the precipitate is subject to further processing with obtaining Fe ₂ O ₃ as a commercial product.

The combined filtrate containing titanium fluoroammonium salts in a 15-18% solution of ammonium fluoride (Fe content at the level of tenths of mg / ml, Mn - hundredths of mg / ml) is subjected to additional purification from manganese compounds and then from iron compounds. For this purpose, after preliminary determination of the manganese content in it, metallic iron powder is added in an amount providing a mass ratio of Fe / Mn of at least 100, the resulting reaction mass is heated to boiling and boiled for 15-20 minutes. After cooling the solution by filtration, a precipitate of poorly soluble in the presence of ammonium fluoride complex salts of iron (II), (III) mixed with manganese is separated. The fluorotitanate solution is purified from manganese salts due to the coprecipitation of the manganese salt NH ₄ MnF3 with the complex salt NH ₄ FeF ₃ isostructural. Part of the iron is precipitated by oxidation to form the complex (NH _{4) 3} FeF _6.

In the known method, the purification of the filtrate from iron is carried out by partial hydrolysis with a solution of ammonia, which is added to the filtrate to pH values in the range of 6.5-7.5. However, when using an ammonia solution, a constant precise control of the pH change is necessary, since an increase in pH> 7.5 leads to an unjustified increase in the fluorotitanate precipitate and loss of titanium, not all iron precipitates at pH <6.5.

Such a need disappears when the filtrate is purified from iron using a solution of hydrogen peroxide.

In the proposed method, the purified compounds of manganese (Mn 6,9-7,5⋅10 ^-5 mg / ml) of the filtrate with content of Fe 0,30-0,35 mg / ml of purified iron from the addition of 30% hydrogen peroxide solution at a molar ratio of H ₂ O ₂ : Ti = 1: 1.

,

) (Бакеева Н.Г., Гордиенко П.С, Пашнина Е.В. // ЖОХ. 2008. Т. 78. Вып. 4. С. 544).At the moment of peroxolysis of the fluoro ammonium salt of titanium and the formation of the complex compound (NH ₄ ) ₃ TiO ₂ F ₅ , a heterovalent isomorphic substitution of a group of ions with close-sized ionic radii occurs (

,

) (Bakeeva N.G., Gordienko P.S., Pashnina E.V. // Zhokh. 2008.V. 78. Issue 4. P. 544).

As a result, due to the isostructurality of the salts (NH ₄ ) ₃ TiO ₂ F ₅ and (NH ₄ ) ₃ FeF ₆ , they co-precipitate. At pH values close to neutral, peroxolysis of the titanium salt occurs without the addition of an alkaline agent according to the reaction:

(NH ₄ ) ₂ TiF ₆ + NH ₄ F + H ₂ O ₂ → (NH ₄ ) ₃ TiO ₂ F ₅ + 2HF

Hydrofluoric acid formed as a result of the reaction lowers the pH of the solution, and the peroxolysis of the titanium salt does not pass completely, but only partially.

The precipitate of ammonium peroxopentafluorotitanate containing a chromophore impurity of a fluorocomplex compound of iron, which is formed as a result of partial peroxolysis, is sent to obtain titanium dioxide by step pyrohydrolysis to 850-950 ° C. In this case, titanium dioxide with a purity of 97-98% is obtained as a commercial product, which can be used as raw material for the production of metallic titanium.

The target product — titanium dioxide of pigment quality — is obtained in a known manner. After purification from iron (Fe content not exceeding 1.4⋅10 ^-4 mg / ml), the filtrate is hydrolyzed by adding a 25% ammonia solution to pH 9, which allows precipitation of up to 95% of the titanium compound contained in the filtrate. A further increase in the pH of the solution is undesirable, since it leads to contamination of the precipitate with silicon. The precipitated precipitate is subjected to stepwise pyrohydrolysis to 850-950 ° C. The titanium dioxide obtained as a result of pyrohydrolysis with a purity of 99.6-99.8% with a whiteness of 91-94 cu can be used in the production of white pigment.

Examples of specific implementation of the method

Processing was carried out on ilmenite concentrate (Tugan deposit, Tomsk region), containing, wt.%: TiO ₂ 59.7, FeO 1.7, Fe ₂ O ₃ 23.7, MnO 1.28, SiO ₂ 3.12, and other impurity elements (Zr, Al, Cr, Ca, Mg, REE).

The content of titanium, manganese and iron in the filtrate was determined by atomic emission spectroscopy with inductively coupled argon plasma on a Plasmoguant 110 instrument.

The whiteness (W) of TiO ₂ samples was calculated based on the reflection coefficients ρ _λ . Reflection coefficients were measured on a U 3010 spectrophotometer relative to the MgO standard (100%) on titanium dioxide samples pressed in the form of tablets with a diameter of 35 mm under a pressure of 1.5 MPa (Belenky E.F., Riskin I.V. Chemistry and technology of pigments // 4th edition. “Chemistry.” 1974. P. 108).

Example 1

A portion of a 10 g leukoxenized ilmenite concentrate was mixed with 24.4 g of ammonium hydrodifluoride dissolved in 70 ml of water (T: W = 1: 8). The reaction mixture was placed in a reactor lined with magnesium plates, heated to boiling point, and boiling was maintained for 40 minutes with stirring. Ammonia released during the reaction was captured and discharged through a vent pipe. The hot solution was separated from the precipitate formed. The precipitate was washed from soluble titanium salts with 50 ml of a hot 10% solution of NH ₄ F. The lighter complex salt of ferric iron (NH ₄ ) ₃ FeF ₆ (its weight was 7.1 g) was separated by decantation from the filter from the unreacted black mineral residue the mass of which was approximately 1.3 g, and the filtrate obtained after washing was combined with a common filtrate. The Ti content in the combined filtrate was 28 mg / ml, Fe 0.27 mg / ml, Mn 0.019 mg / ml. According to the results of the analysis, the unreacted residue contained, wt.%: Fe ₂ O ₃ 12.59, TiO ₂ 2.71, MnO 4.1, and other elements.

To purify the filtrate containing titanium fluoroammonium salts from manganese, iron powder of the reduced metal grade “chda” was added to the hot filtrate in an amount of 0.23 g (at the rate of 0.2 g per 100 ml of solution) and boiled for 15 minutes. The reaction was accompanied by the release of gaseous hydrogen. The precipitate of complex salts of iron (II, III) with an admixture of manganese (24.9% Fe 1.9% Mn) was separated by filtration. Mn content of the resultant filtrate 7,5⋅10 ^-5 mg / ml, Fe - 0,3 mg / ml. For additional purification from iron, 6.4 ml of 30% H ₂ O _{2 was} added to 116 ml of the filtrate. A lemon-colored precipitate (NH ₄ ) ₃ TiO ₂ F ₅ (4.8 g) was separated from the solution, which was subjected to stepwise pyrohydrolysis to obtain 1.52 g of titanium dioxide (98% purity). The purified filtrate containing Fe 1.4 содержанием10 ^-4 mg / ml, Mn 7.3⋅10 ^-5 mg / ml was hydrolyzed with 25% ammonia solution to pH 9 to precipitate ammonium oxofluorotitanate (NH ₄ ) ₃ TiOF ₅ , which was subjected to step pyrohydrolysis up to 850 ° C. The resulting titanium dioxide weighing 3.84 g (99.6% TiO ₂ , 0.23% SiO ₂ , <0.1% Nb, Zr, S and K) had a brightness of 94 cu The total yield of TiO ₂ was 89.8%.

Example 2

A portion of leukoxenized ilmenite concentrate weighing 10.1 g was treated according to example 1 with a concentrated solution of ammonium fluoride at T: W = 1: 10. The reaction mixture was boiled for 60 minutes. After separation and washing of the precipitate containing iron salts and unreacted residue, the filtrate was purified from manganese by adding 0.26 g of iron powder with boiling for 20 minutes. The Mn content in the filtrate obtained after removal of the precipitate was 6.9 × 10 ⁻⁵ mg / ml, Fe — 0.35 mg / ml. Further purification from iron was carried out by adding 6.6 ml of a 30% solution of Н ₂ О ₂ to the solution to isolate a precipitate of (NH ₄ ) ₃ TiO ₂ F ₅ , which was pyrohydrolyzed to 850 ° С to obtain titanium dioxide anatase modification weighing 1.64 g mixed with iron. The filtrate after removal of the precipitate (Fe content 1.1 × 10 ⁻⁴ mg / ml, Mn 6.4 × 10 ⁻⁵ mg / ml) was hydrolyzed according to Example 1 to obtain a precipitate of (NH ₄ ) ₃ TiOF ₅ , followed by pyrohydrolysis of the latter 3.91 g of titanium dioxide with a whiteness of 91 cu were isolated to 950 ° C. The total yield of TiO ₂ was 90.4%).

Claims (3)

1. A method of processing titanium-containing mineral raw materials, including its fluorination with a saturated aqueous solution of hydrodifluoride and / or ammonium fluoride when heated, followed by separation of the insoluble precipitate containing fluoroammonium salts of iron from a solution containing ammonium fluorotitanate, the resulting solution is purified from iron impurity and added to it 25% ammonia solution to pH 9 to completely precipitate ammonium oxofluorotitanate used to produce titanium dioxide, characterized in that the fluorination is carried out at wearing T: L = 1: (8-10) at the boiling point of the reaction mixture for 40-60 minutes, while the solution containing ammonium fluorotitanate is further purified from iron by purification of the Mn compounds by adding metallic iron powder in an amount that ensures the mass ratio of Fe / Mn is not less than 100, the reaction mixture is heated to boiling point and boiled for 15-20 minutes to obtain a precipitate containing fluoroammonium complex salts of iron (II, III) with an admixture of manganese, which after cooling is separated by filtration and sent for further processing. 2. The method according to p. 1, characterized in that the purification of the solution of ammonium fluorotitanate from iron is carried out using a 30% hydrogen peroxide solution in a molar ratio of H ₂ O ₂ : Ti = 1: 1. 3. The method according to p. 2, characterized in that the iron-containing precipitate isolated at the stage of purification of the solution of ammonium fluorotitanate from iron is sent for further processing to obtain titanium dioxide with a purity of 97-98%.