WO2019137543A1 - Method for preparing high-purity tio2 by selectively leaching from titanium concentrate with rich oxygen - Google Patents

Abstract

A method for preparing high-purity TiO2 by selectively leaching from titanium concentrate with rich oxygen, comprising the following steps: (1) crushing and activating titanium concentrate, placing the raw materials in an autoclave for alkali leaching using a sodium hydroxide solution; introducing oxygen into the autoclave before the alkali leaching, and then heating and stirring; (2) performing filtration and separation, and washing the alkali decomposition product with water to prepare an alkali decomposition residue; (3) performing acid leaching on the alkali decomposition residue and hydrolyzing same, adding seed crystal, and then the heating and stirring; (4) performing filtration and separation, washing the acid leaching residue with water, drying said residue and calcining same at 800-900°C so as to prepare rutile-type high-purity TiO2. According to the method, high-performance materials can be prepared easily; resource recycling can be achieved; the energy can be saved; and the emission can be reduced.

Description

Preparation of high purity TiO by oxygen-rich selective leaching of titanium concentrate       2 method      Technical field

The invention belongs to the technical field of non-ferrous metallurgy, and in particular relates to a method for preparing high-purity TiO ₂ by oxygen-rich selective leaching of titanium concentrate.

Background technique

Titanium content accounts for about 0.61% of the crustal mass. It is ranked as the fourth structural metal after aluminum, iron and magnesium according to the abundance of elements in the earth's crust. Its chemical nature is active, and there is no elemental state in nature. Compound forms such as acid salts are widely found in seawater, soil, rocks, animals and plants. Although there are many minerals containing titanium, the main applications in the industry are ilmenite, vanadium-titanium magnetite and rutile ore; the titanium-bearing minerals in the earth's crust are the most widely distributed, and the largest reserves are ilmenite. About 80% of the titanium ore resources are also the main raw materials for the preparation of titanium products. According to the degree of oxidation of ilmenite in the natural environment, it can be divided into primary ilmenite and weathered ilmenite; the original ilmenite structure is dense and complex, and the iron is mainly in the form of ferrous iron, and its molecular formula is FeTiO ₃ or FeO·TiO ₂ has a theoretical TiO ₂ content of 52.63%. The weathered ilmenite structure is relatively loose, and the grade of TiO _{2 is} relatively high. The iron is mainly in the form of ferric iron, and its molecular formula is Fe ₂ O ₃ ·TiO ₂ .

Most of China's ilmenite is used in the production of titanium dioxide raw materials by sulfuric acid process, only a small part of which is processed into titanium-rich material, which is used as a raw material for the production of titanium dioxide, titanium tetrachloride and titanium sponge by chlorination process, along with titanium sponge and titanium. Widely used in base alloys and titanium chloride white; the ilmenite content in China is generally not high, and the content and types of impurities are relatively high. It is difficult to purify. So far, no direct preparation of high-purity TiO ₂ from titanium concentrate has been realized. Industrial production; currently more than 90% of the world's titanium ore is used to produce titanium dioxide, about 4 to 5% of titanium ore is used to produce titanium, and the remaining ilmenite is used to make electrodes, alloys, carbides, ceramics, glass. And chemicals, etc.; titanium dioxide chemical name is titanium dioxide, is a white inorganic pigment, non-toxic, harmless, best opacity, best whiteness and brightness, is considered to be the best performance in the world. A white pigment widely used in coatings, plastics, paper, printing inks, chemical fiber, rubber, cosmetics and other industries.

At present, the methods for preparing pigment-grade titanium white mainly include sulfuric acid method, chlorination method, hydrochloric acid method and mixing method (potassium chlorotitanate method); the sulfuric acid method for producing titanium white process is characterized by long process, intermittent operation, many processes, and processes. Complex, titanium white grade is lower; at the same time, the biggest problem of sulfuric acid method is the by-product of a large amount of ferrous sulfate and dilute sulfuric acid waste, each production of 1 ton of titanium dioxide, the discharge of ferrous sulfate 3 to 4 tons and dilute sulfuric acid 8 to 10 Tons, these two by-products are narrow in sales, high in recycling cost, and extremely serious in environmental pollution, which has become a bottleneck in the development of titanium dioxide industry. The process of producing titanium dioxide by chlorination process is characterized by short process, large production capacity, high automation level and three wastes. Less and higher product grades; however, the source of chlorination raw materials is difficult, and the cost of raw materials is high. Although the emissions of the three wastes are small, the materials and products in production are mostly substances with certain toxicity and corrosiveness, such as Cl ₂ and TICl _{4 .} Other chlorides, the generated waste is more difficult to handle, the chlorination method is complicated, the production is difficult, the equipment material and automatic control level are very high, and the equipment investment cost is large, which makes it difficult to promote; The titanium white process reacts hydrochloric acid with ilmenite to separate insoluble residue, iron powder to reduce high-valent iron to low-cost iron, crystallizes ferrous chloride crystals, separates ferrous chloride crystals, and then contains titanium. The leachate is subjected to a first solvent extraction, the extract phase is a solution containing titanium and high iron, the raffinate phase is an aqueous solution containing ferrous iron, the return process is used to regenerate hydrochloric acid, and the process is returned to the leaching process; the titanium-containing extract phase is subjected to the second time. The extraction and extraction phases are aqueous solutions containing titanium, and the raffinate phase is a solution containing high iron, and is returned to the hydrochloric acid regeneration process; the titanium chloride solution after extraction and purification is hydrolyzed to obtain metatitanic acid, and the hydrochloric acid and water in the gas phase are returned to the hydrochloric acid regeneration system. The hydrolyzed metatitanic acid is calcined, wet-milled, inorganic coated, filtered, washed, dried, jet-pulverized and packaged, which is the finished titanium dioxide, which is lower in cost than the sulfuric acid method and the chlorination method; Industrial production has not yet been achieved. The potassium chlorotitanate method is a method in which a sulfuric acid method and a TiCl ₄ gas phase oxidation method are combined; the principle of the method is to add potassium chloride after freezing to remove ferrous sulfate in a titanyl sulfate solution obtained by a sulfuric acid method, and After the potassium chloride reaches a saturated concentration, hydrogen chloride gas is introduced, and the titanium oxysulfate is converted into potassium chlorotitanate. After deep freezing, the potassium chlorotitanate crystal is precipitated, filtered, washed and completely dried to form TICl ₄ and KCl. ;TICl ₄ as a raw material for oxidized rutile titanium dioxide, KCl can be recycled and reused; the process is complicated and not industrialized; the patent No. 201610504443.3 proposes that ilmenite and 98% sulfuric acid solution are mixed in a certain ratio, and at a certain volume About 20% of the waste acid is injected into the reactor and stayed for 25-40 minutes; the material is discharged from both ends of the reactor, passed into the first-stage dissolution tank, and then overflowed into the secondary dissolution tank; then enters the reduction tank (stirring and Add iron powder), add anion and cationic sedimentation agent to remove suspended impurities, and obtain clear titanium liquid; the method uses large concentration of sulfuric acid, there is a safety hazard in the production process, and the amount of precipitant is too large. The impurities react to form complex precipitates, which are difficult to be effectively separated and recycled, resulting in environmental pollution. The patent No. 201510118254.8 proposes that the rutile type is obtained by grinding, calcining, leaching, cooling and removing iron, and hydrolyzing and calcining titanium liquid. -90% titanium dioxide; adding a certain amount of potassium pyrosulfate during the calcination process reduces the calcination temperature, increases the extraction rate of titanium dioxide, and effectively utilizes the ammonia gas generated by the calcination process and the waste acid produced by the hydrolysis process to achieve Recycling; the method is long in process and complicated in process, the roasting process has to consume a large amount of energy, the equipment requirements are high, and the leaching of impurity products is incompletely separated; the application No. 200610007297.X refers to the production of titanium dioxide by ilmenite sub-molten salt method. The method comprises the steps of: reacting ilmenite in a liquid phase medium of a sub-molten salt KOH, and obtaining the pure titanium dioxide by hydrolysis, calcination and impurity removal, and the reaction temperature is 240-350 °C. The alkali consumption of the method is too large, the reaction temperature is high, the equipment requirements are high, and the alkalinity is too high, the water consumption of the washing process is greatly increased, the impurity separation is difficult, and the potassium content of the prepared titanium white is relatively high.

Summary of the invention

According to the above problems existing in the existing titanium white production process, the present invention provides a method for preparing high-purity TiO ₂ by oxygen-rich selective leaching of titanium concentrate, using industrial titanium concentrate as raw material and sodium hydroxide and hydrochloric acid as solvent. Using high-temperature oxygen-enriched alkali leaching and high-pressure hydrochloric acid acid leaching to prepare high-purity titanium-rich material and primary titanium dioxide by mechanical activation, oxygen enrichment, high pressure and other enhanced leaching methods, subsequent purification and crystal transformation High purity TiO _{2 was prepared} .

The method of the invention proceeds as follows:

(1) crushing the titanium concentrate to a particle size of ≤0.125mm, completing the activation treatment to obtain titanium concentrate powder; placing the titanium concentrate powder in an autoclave with alkali solution of sodium hydroxide solution, wherein the quality of the sodium hydroxide solution The concentration is 20-40%, the ratio of sodium hydroxide solution to titanium concentrate powder is (5-15):1; first, oxygen is introduced into the autoclave, then the temperature is raised to 180-300 ° C, stirring Under the conditions of 1 to 3 hours of heat preservation, alkali leaching;

(2) filtering and separating the material after alkali leaching to obtain an alkali decomposition product and an alkali immersion liquid; washing the alkali decomposition product to a neutral state to prepare an alkali decomposition slag;

(3) The alkali decomposition slag is placed in an autoclave and subjected to acid leaching hydrolysis by hydrochloric acid, wherein the mass concentration of hydrochloric acid is 14 to 20%, and the ratio of hydrochloric acid to alkali decomposition slag is liquid to solid ratio (4 to 10): 1 In the acid leaching hydrolysis process, the seed crystal is first added to facilitate the growth of the titanium oxide nucleation formed by the alkali decomposition slag during the hydrolysis of hydrochloric acid, and then the temperature is raised to 100-180 ° C, and the temperature is maintained for 1 to 3 hours under stirring to complete the acid. Immersion hydrolysis

(4) filtering and separating the material after acid leaching to obtain acid leaching slag and acid leaching solution; washing the acid leaching slag until the filtrate is neutral, drying and removing water, and finally calcining at 800-900 ° C for 30-60 min, Made of rutile high purity TiO ₂ with a purity of ≥98.5%.

In the above method, the alkali immersion liquid obtained in the step (2) removes SiO ₂ using CaO as a precipitating agent, and when the weight percentage of SiO ₂ is ≤0.05%, it is returned to the step (1) as a sodium hydroxide solution.

In the above method, after the obtained acid immersion liquid is heated and evaporated, excess hydrogen chloride is volatilized, and the hydrochloric acid prepared by absorption is concentrated to a mass concentration of 14 to 20%, and is returned to the step (3).

The above seed crystal is titanium dioxide and/or metatitanic acid in an amount of 0.2 to 0.5% by mass based on the total mass of the alkali decomposition slag.

The above titanium concentrate contains 45 to 46% by weight of TiO ₂ , 3 to 4% of SiO ₂ , 1 to 1.5% of CaO, 3 to 3.5% of MgO, 42 to 43% of TFe, 0.6 to 0.9% of MnO, and Al ₂ O. ₃ 1 to 1.1%.

The rutile-type high-purity TiO ₂ described above is used for the preparation of high-purity titanium dioxide.

In the above method, the material remaining after the acid immersion liquid is heated and evaporated is a metal chloride acid immersion liquid, and the impurity metal ions in the acid liquid are extracted to form a single metal salt solution; respectively, the single metal salt solution is placed in a filtered state. In the liquid electrolysis cell, the temperature and the cell voltage are adjusted, and the current density is controlled, so that the cathode region of the cell directly forms high-purity hydroxide precipitates with Fe ³⁺ , Mn ²⁺ , Mg ²⁺ , and Ca ²⁺ ; Since the concentration of Fe ³⁺ ions is high to prevent agglomeration of iron hydroxide, a small amount of iron red is added before iron removal, and the cathode region of the electrolytic cell is mechanically stirred, and the directional flow of the electrolyte and hydroxide in the cathode region is filtered through a filtering device to realize Solid-liquid separation, the filtrate is recycled back to the cathode region to produce ultra-fine high-purity iron red; according to the same principle, the impurity metal ions are removed separately, since the impurity metal ions contained in the leachate are located after H ⁺ , and the leachate is in the electrolysis process. Containing a large amount of Cl ^- , there will be hydrogen and chlorine gas between the two stages of the electrolysis cell; the anode and cathode gases are collected to obtain by-product hydrogen and chlorine. The filtered product is dried to obtain an impurity oxyhydroxide product or calcined to obtain an oxidized product thereof, and the purity is ≥95%.

The main reactions involved in the direct separation of the hydroxide precipitation by electroporation are as follows:

Anodic reaction: 2Cl ^- -2e = Cl ₂ ↑,

Cathodic reaction: 2H ⁺ +2e = H ₂ ↑,

Total reaction: MeCl ₂ +2H ₂ O=Me(OH) ₂ +H ₂ +Cl ₂ ,

Calcination reaction: Me(OH)=MeO+H ₂ O↑.

The principles and benefits of the present invention are:

(1) Oxygen is introduced during the leaching process to oxidize the low-priced titanium oxide in the titanium concentrate, destroying the stable hematite ore phase, and combining the impurity elements dispersed in the solid solution to form an acid. a base compound which is removed and removed in a subsequent wash filtration stage;

(2) to ensure the tightness of the system during the leaching process, as the oxygen is introduced or the temperature continues to rise, a large gas pressure is generated in the kettle, and the dynamic conditions of the leaching process are largely optimized to oxidize the titanium concentrate. The precipitation of impurities and the destruction of the mineral phase have a promoting effect. As a means of strengthening leaching, in the process of cooperating with other leaching process parameters, the temperature, pH, leaching time and other process conditions can be appropriately reduced to achieve environmental protection and energy saving. purpose;

(3) The alkali leaching of titanium concentrate firstly has a certain destructive effect on the surface of slag particles, which is beneficial to the precipitation of impurity phase and enhance the effect of subsequent acid leaching. At the same time, acid-base composite high pressure leaching is simpler than acid leaching, Si The impurity removal rate of oxides such as Al is greatly increased, the dedusting pressure of subsequent production processes is greatly reduced, and high-performance materials are easily prepared, and acid leaching will oxidize Fe ²⁺ in the leachate, which will improve electroforming in the later stage. Iron slag process efficiency;

(4) The alkali used is sodium hydroxide, and the waste lye produced in the alkali leaching process can be added with a small amount of CaO, so that the Si impurities can be effectively removed, and the concentrate can be used for alkali leaching of titanium concentrate; acid leaching process With hydrochloric acid, the waste acid produced is heated, and the HCl gas volatilized by heating is absorbed by water atomization, and the formed hydrochloric acid solution is concentrated and returned to the leaching process to realize recycling of resources, and almost no industrial waste water or waste residue is produced to realize green production. ;

(5) The impurity ions can be separated and electrically converted by using the extraction principle, and the obtained metal oxide or hydroxide has high purity, and ultra-fine high-purity oxide can be obtained by drying and calcining, and electrolysis can be produced. The valuable by-product hydrogen and chlorine gas can be recycled back to the process through the impurity-free acidic leachate to achieve green recycling and energy saving.

Detailed ways

In the embodiment of the present invention, after the SiO ₂ is removed by using CaO as a precipitating agent, the formed calcium silicate is used for preparing cement.

The autoclave for caustic soak used in the embodiment of the present invention is a ZRYK 1L stainless steel nickel-plated autoclave of Weihai Zhengwei Machinery Equipment Co., Ltd.

The autoclave for acid leaching used in the examples of the present invention is a KCFD1-10 type zirconium autoclave of Yantai Keli Chemical Equipment Co., Ltd.

The titanium concentrate crushing device in the embodiment of the present invention is a pulverisette 5/4 classic line planetary high energy ball mill of FRITSCH.

The liquid-solid ratio in the embodiment of the present invention is the weight ratio of the volume of the liquid material (sodium hydroxide solution or hydrochloric acid) to the solid material (vanadium-titanium magnetite powder or alkali-decomposed slag), and the unit is L/kg.

The titanium dioxide used in the examples of the present invention is a commercially available analytically pure reagent, and the metatitanic acid used is a commercially available chemically pure reagent.

In the embodiment of the present invention, the stirring speed in the alkali immersion is 300 to 600 r/min.

In the embodiment of the present invention, the stirring speed in the acid leaching hydrolysis is 200 to 500 r/min.

The titanium concentrate used in the examples of the present invention contains 45.64% by weight of TiO ₂ , 3.65% of SiO ₂ , 1.12% of CaO, 3.22% of MgO, 42.45% of TFe, 0.855% of MnO and 1.02% of Al ₂ O ₃ .

In the embodiment of the present invention, the material remaining after the acid immersion liquid is heated and evaporated is an acid liquid, and the impurity metal ions in the acid liquid are extracted and stripped to obtain a single metal salt solution; respectively, a single metal salt solution is placed therein. In the electrolytic cell of the filter solution (cationic membrane), the temperature and the cell voltage (temperature 20 ° C, cell voltage 20 V) are adjusted, and the current density is controlled so that the cathode region of the cell directly is combined with Fe ³⁺ , Mn ²⁺ , Mg ²⁺ , Ca ²⁺ generates high-purity hydroxide precipitation; in the case of Fe, the Fe ³⁺ ion concentration is high to prevent iron hydroxide agglomeration, a small amount of iron red is added before iron removal, and the cathode region of the electrolytic cell is mechanically stirred, and the cathode region is electrolyzed. The liquid and hydroxide directional flow is filtered through a filtering device to achieve solid-liquid separation, and the filtrate is recycled to the cathode region to obtain ultra-fine high-purity iron red; according to the same principle, the impurity metal ions are separately removed, and the impurities are contained in the leachate. after the metal ion is located in the activity ⁺ electrolysis the leachate contains a large amount of H Cl ^-, so there will be two hydrogen between the cell, chlorine gas generated; collecting anode and cathode gas, Hydrogen and chlorine by-products obtained. The filtered product is dried to obtain an impurity oxyhydroxide product or calcined to obtain an oxidized product thereof, and the purity is ≥95%.

The present invention will be further described in detail below with reference to the embodiments.

Example 1

The titanium concentrate is crushed to a particle size of ≤0.125 mm, and the activation treatment is completed to obtain titanium concentrate powder; the titanium concentrate powder is placed in an autoclave and alkali leached with a sodium hydroxide solution, wherein the concentration of the sodium hydroxide solution is 20 %, the ratio of sodium hydroxide solution to vanadium-titanium concentrate powder is 15:1 according to the liquid-solid ratio; firstly, oxygen is introduced into the autoclave, then the temperature is raised to 180 ° C, and the mixture is kept under stirring for 3 hours to complete the alkali leaching; The alkali leached material is separated by filtration to obtain an alkali decomposition product and an alkali immersion liquid; the alkali decomposition product is washed with water until the filtrate is neutral to prepare an alkali decomposition slag; the alkali immersion liquid uses CaO as a precipitant to remove SiO ₂ , and the liquid phase After the mass percentage of SiO ₂ is ≤0.05%, it is recycled as a sodium hydroxide solution;

The alkali decomposition slag is placed in an autoclave and subjected to acid leaching hydrolysis by hydrochloric acid, wherein the concentration of hydrochloric acid is 14%, the ratio of hydrochloric acid to alkali decomposition slag is 4:1, and the crystal is first added during acid hydrolysis. The titanium oxide nucleation formed during the hydrolysis of hydrochloric acid in the alkali decomposition slag is grown, and then the temperature is raised to 100 ° C, and the mixture is kept under stirring for 3 hours to complete the acid leaching hydrolysis; the seed crystal is metatitanic acid, and the amount is 0.5% of the total mass of the alkali decomposition slag;

The acid leached residue is filtered and separated to obtain acid leaching slag and acid leaching solution; the acid leaching residue is washed with water until the filtrate is neutral, and then dried to remove water, and finally calcined at 900 ° C for 30 min to prepare rutile high purity TiO. ₂ ; After the acid immersion liquid is heated and evaporated, the excess hydrogen chloride gas is atomized and absorbed by water, and the prepared hydrochloric acid is concentrated to a mass concentration of 14% and recycled; the rutile high-purity TiO ₂ contains TiO ₂ 98.58% by mass percentage, SiO ₂ 0.11%, CaO<0.05%, MgO<0.01%, Fe ₂ O ₃ 0.06%, Mn<0.05%, S 0.09%.

Example 2

The method is the same as that in Embodiment 1, except that:

(1) The weight concentration of the sodium hydroxide solution is 30%, the ratio of the sodium hydroxide solution to the vanadium-titanium magnetite powder is 10:1 according to the liquid-solid ratio; the alkali immersion temperature is 220 ° C, and the time is 2 hours;

(2) The concentration of hydrochloric acid is 18%, the ratio of hydrochloric acid to alkali decomposition slag is 8:1; the seed crystal is titanium dioxide, and the amount is 0.3% of the total weight of the alkali decomposition slag; acid hydrolysis temperature 150 ° C, time 2h;

(3) Hydrogen chloride gas is concentrated by water atomization absorption to a concentration of 18%; acid leaching residue is washed and dried at 850 ° C for 40 minutes; rutile high purity TiO ₂ contains TiO ₂ 99.17% by mass, SiO ₂ 0.08%, CaO<0.05%, MgO<0.01%, Fe ₂ O ₃ 0.02, Mn<0.05%, S<0.05%.

Example 3

The method is the same as that in Embodiment 1, except that:

(1) The weight concentration of the sodium hydroxide solution is 40%, the ratio of the sodium hydroxide solution to the vanadium-titanium magnetite powder is 5:1 according to the liquid-solid ratio; the alkali immersion temperature is 300 ° C, and the time is 1 h;

(2) The concentration of hydrochloric acid is 20%, the ratio of hydrochloric acid to alkali decomposition slag is 10:1; the seed crystal is a mass mixture of titanium dioxide and metatitanic acid, and the amount is the total weight of alkali decomposition slag. 0.2%; acid leaching hydrolysis temperature 180 ° C, time 1h;

(3) Hydrogen chloride gas is concentrated by water atomization absorption to a concentration of 20%; acid leaching residue is washed with water and calcined at 800 ° C for 60 min; rutile high purity TiO ₂ contains TiO ₂ 99.52 by mass percentage, SiO ₂ 0.05%, CaO<0.01%, MgO<0.01%, Fe ₂ O ₃ 0.01%, Mn<0.05%, S<0.05%.

Claims (5)

A method for preparing high-purity TiO ₂ by oxygen-rich selective leaching of titanium concentrate, which is characterized by the following steps: (1) crushing the titanium concentrate to a particle size of ≤0.125mm, completing the activation treatment to obtain titanium concentrate powder; placing the titanium concentrate powder in an autoclave with alkali solution of sodium hydroxide solution, wherein the quality of the sodium hydroxide solution The concentration is 20-40%, the ratio of sodium hydroxide solution to titanium concentrate powder is (5-15):1; oxygen is introduced into the autoclave, and the temperature is raised to 180-300 ° C under stirring conditions. Insulation for 1~3h, complete alkali leaching; (2) filtering and separating the alkali leached material to obtain alkali decomposition product and alkali immersion liquid; washing the alkali decomposition product to the filtrate to be neutral to prepare alkali decomposition slag; (3) The alkali decomposition slag is placed in an autoclave and subjected to acid leaching hydrolysis by hydrochloric acid, wherein the mass concentration of hydrochloric acid is 14 to 20%, and the ratio of hydrochloric acid to alkali decomposition slag is liquid to solid ratio (4 to 10): 1 In the acid leaching hydrolysis process, the seed crystal is first added to facilitate the growth of the titanium oxide nucleation formed by the alkali decomposition slag during the hydrolysis of hydrochloric acid, and then the temperature is raised to 100-180 ° C, and the temperature is maintained for 1 to 3 hours under stirring to complete the acid. Immersion hydrolysis (4) filtering and separating the material after acid leaching to obtain acid leaching slag and acid leaching solution; washing the acid leaching slag until the filtrate is neutral, drying and removing water, and finally calcining at 800-900 ° C for 30-60 min, Made of rutile high purity TiO ₂ with a purity of ≥98.5%. The method for preparing high-purity TiO ₂ by oxygen-rich selective leaching of titanium concentrate according to claim 1, characterized in that the alkali immersion liquid obtained in the step (2) uses CaO as a precipitating agent to remove SiO ₂ , in the liquid phase. After the mass percentage of SiO ₂ is ≤0.05%, it is returned to the step (1) as a sodium hydroxide solution. The method for preparing high-purity TiO ₂ by oxygen-rich selective leaching of titanium concentrate according to claim 1, characterized in that the acid immersion liquid obtained in the step (4) is heated and evaporated, and the excess hydrogen chloride is volatilized and absorbed. The formed hydrochloric acid is concentrated to a mass concentration of 14 to 20%, and is returned to the step (3). The method for preparing high-purity TiO ₂ by oxygen-rich selective leaching of titanium concentrate according to claim 1, wherein the seed crystal is titanium dioxide and/or metatitanic acid, and the amount of the alkali-decomposed slag is 0.2. ~0.5%. The method for preparing high-purity TiO ₂ by oxygen-rich selective leaching of titanium concentrate according to claim 3, wherein after the evaporation of the acid immersion liquid is completed, the residual chloride solution is separated and electrically charged by the extraction method. The metal oxide or hydroxide obtained by the conversion has a high purity and is calcined to obtain an ultrafine high-purity oxide.