Electronic grade titanium dioxide and method for preparing the same

Abstract

The application discloses electronic-grade titanium dioxide and a preparation method thereof, and relates to the field of titanium dioxide production; the electronic-grade titanium dioxide comprises the following components: TiO2 is greater than or equal to 99.5%, Fe2O3 is less than or equal to 0.004%, SiO2 is less than or equal to 0.1%, S is less than or equal to 0.01%, P is less than or equal to 0.02%, MgO is less than or equal to 0.01%, CaO is less than or equal to 0.01%, K2O+Na2O is less than or equal to 0.01%, Nb2O5 is less than or equal to 0.01%, Zn is less than or equal to 0.001%, Sb is less than or equal to 0.001%, a sieve residue is less than or equal to 0.05%, a rutile crystal content is 60-80%, volatile matter is less than or equal to 0.05%, and the whiteness of dry powder is greater than or equal to 95%. The application adopts a sulfuric acid method full-process technology, avoids the risk of metal impurities introduced by high-temperature scouring of stainless steel pipelines in a chlorination method process, and effectively controls the metal impurity content of the product through raw material selection and process parameter collaborative control, so that the requirement of electronic-grade titanium dioxide on high purity is met.

Description

Technical Field

[0001] This invention relates to the field of titanium dioxide production, and more particularly to an electronic-grade titanium dioxide and its preparation method. Background Technology

[0002] Titanium dioxide (TiO2) is currently the world's best-performing white pigment, widely used in coatings, plastics, papermaking, inks, and chemical fibers.

[0003] Electronic-grade titanium dioxide has extremely stringent purity requirements, requiring a TiO2 content of ≥99.5%, and strict limits on various impurity elements such as Fe, Si, S, P, Mg, Ca, K, and Na.

[0004] Existing methods for preparing electronic-grade titanium dioxide mainly have the following problems:

[0005] The chlorination process (Chinese Patent Publication No. CN107758738A) uses Incom nickel alloy stainless steel pipes in the oxidation process, and the high-temperature rinsing can easily introduce metal impurities, affecting product purity.

[0006] The hydrolysis parameters of the traditional sulfuric acid process (Chinese patent publication number CN120440946A) are not precisely controlled, resulting in uneven particle size distribution and unstable rutile crystal content in the product.

[0007] Therefore, there is an urgent need to develop a method that can stably prepare high-purity electronic-grade titanium dioxide to meet the stringent quality requirements of high-end electronic components.

[0008] Therefore, this invention proposes an electronic-grade titanium dioxide and its preparation method. Summary of the Invention

[0009] The purpose of this invention is to address the shortcomings of existing technologies by proposing an electronic-grade titanium dioxide and its preparation method.

[0010] To achieve the above objectives, the present invention adopts the following technical solution:

[0011] An electronic-grade titanium dioxide comprises the following components: TiO2 ≥ 99.5%, Fe2O3 ≤ 0.004%, SiO2 ≤ 0.1%, S ≤ 0.01%, P ≤ 0.02%, MgO ≤ 0.01%, CaO ≤ 0.01%, K2O + Na2O ≤ 0.01%, Nb2O5 ≤ 0.01%, Zn ≤ 0.001%, Sb ≤ 0.001%, sieve residue ≤ 0.05%, specific surface area of ​​6~10 m2 / g, loss on ignition ≤ 0.2%, rutile crystal content of 60~80%, volatile matter ≤ 0.05%, dry powder whiteness ≥ 95%, average particle size D50 of 0.5~1.0 μm, and bulk density of 0.6~0.8×1000 kg / m3.

[0012] Preferably, the electronic-grade titanium dioxide has a TiO2 content ≥ 99.5%, an Fe2O3 content ≤ 0.003%, a P content ≤ 0.050%, and a total iron content (calculated as elemental iron) ≤ 30 ppm.

[0013] A method for preparing electronic-grade titanium dioxide includes the following steps:

[0014] S01: Acid hydrolysis: Using low-phosphorus titanium concentrate with a P content <0.01wt% as raw material, the titanium concentrate is mixed with concentrated sulfuric acid at a mass ratio of 1:1.5~1:1.8 for acid hydrolysis reaction. The reaction temperature is 110~130℃, and the acid hydrolysis time is 2~4 hours to obtain titanium liquid. The total titanium concentration (equivalent to TiO2) in the titanium liquid is 125~135g / L, the F value is 1.85~1.95, the trivalent titanium concentration is 0.8~1.8g / L, the stability is ≥350mL / mL, and the acid hydrolysis rate is ≥96%.

[0015] S02: Sedimentation: The obtained titanium liquid is separated by gravity sedimentation, and the stability of the titanium liquid after sedimentation is controlled to be ≥350mL / mL.

[0016] S03: Controlled filtration: The settled titanium liquid is filtered in a controlled manner, and the residue in the filtered titanium liquid is ≤20mg / L, and the concentration of trivalent titanium is 0.8~1.8g / L;

[0017] S04: Disc filtration: The controlled titanium liquid is filtered by disc filtration. The total titanium concentration (TiO2 equivalent) of the filtered titanium liquid is 155~165g / L and the iron-titanium ratio is 0.28~0.35.

[0018] S05: Concentration: Vacuum concentration is performed on the titanium liquid after disc filtration. The total titanium concentration (TiO2 equivalent) of the concentrated titanium liquid is 175~185g / L, the F value is 1.85~1.95, the iron-titanium ratio is 0.28~0.35, the trivalent titanium concentration is 0.8~1.8g / L, the stability is ≥450mL / mL, and the residue is ≤20mg / L.

[0019] S06: Seed preparation: Hydrolyzed seed crystals were prepared by alkaline solution method, with an alkaline solution concentration of 8.4~8.6wt%, a seed crystal F value of 1.65~1.75, and a total titanium concentration (equivalent to TiO2) of 150~160g / L.

[0020] S07: Hydrolysis: The concentrated titanium liquid is mixed with seed crystals and subjected to a hydrolysis reaction. The hydrolysis temperature is 95~105℃, the hydrolysis time is 3~5 hours, the total titanium concentration (TiO2 equivalent) of the hydrolyzed titanium liquid is 150~165g / L, the trivalent titanium concentration is ≥0.5g / L, the hydrolyzed particle size is 2~2.6μm, the settling height is 60~150mm, the filtration time is 60~150s, and the hydrolysis rate is ≥95.5%.

[0021] S08: Primary water washing: The hydrolysis products are subjected to primary water washing, and the Fe2O3 content after washing is ≤500ppm;

[0022] S09: Preparation of trivalent titanium: Trivalent titanium solution is prepared by aluminum powder reduction using a portion of diwashed metatitanic acid as raw material. The concentration of trivalent titanium is 60~90g / L and the reduction rate is ≥90%.

[0023] S10: Bleaching: The material after primary water washing is bleached with trivalent titanium solution. The free acid concentration in the bleaching system is 30~50g / L, and the trivalent titanium concentration is ≥0.05g / L.

[0024] S11: Secondary water washing: The bleached material is subjected to secondary water washing, and the Fe2O3 content after washing is ≤20ppm;

[0025] S12: Calcination: The material after secondary water washing is fed into a rotary kiln for calcination at a temperature of 850~1000℃ for 4~8 hours to obtain the calcined product. The dry powder of the calcined product has a whiteness ≥95%, total iron (Fe2O3) ≤30ppm, rutile crystal form conversion rate of 60~80%, and sulfur content ≤0.01%.

[0026] S13: Pulverization: The calcined product is pulverized using an ultrafine airflow pulverizer. The residue on a 325-mesh sieve is ≤0.05%, and the total iron (Fe2O3) is ≤40ppm, to obtain electronic-grade titanium dioxide finished product.

[0027] Preferably, in step S01, the raw material composition of the low-phosphorus titanium concentrate, by mass percentage, includes: TiO2 ≥ 46%, Fe2O3 ≤ 8%, SiO2 ≤ 3.5%, P ≤ 0.01%, S ≤ 0.2%, MgO ≤ 0.5%, CaO ≤ 0.3%, Al2O3 ≤ 1.5%; the concentrated sulfuric acid is concentrated sulfuric acid produced by the sulfur-based acid production process, with an H2SO4 concentration ≥ 98 wt%, and wherein the Fe content ≤ 10 ppm, the Pb content ≤ 5 ppm, and the As content ≤ 2 ppm.

[0028] Preferably, in step S06, the alkaline solution is a sodium hydroxide solution with a NaOH concentration of 8.4~8.6wt%, and the Na2CO2 content is ≤0.5wt% and the NaCl content is ≤0.1wt%. During seed crystal preparation, the alkaline solution is added to the titanium solution at a rate of 5~10L / min, while stirring at a speed of 200~300r / min. The reaction temperature is 60~80℃, and the reaction time is 30~60 minutes.

[0029] Preferably, in step S07, hydrolysis is carried out in an intermittent hydrolysis vessel, the amount of seed crystal added is 8-15% of the volume of concentrated titanium liquid, the hydrolysis heating rate is 1-3℃ / min, and a crystal form promoter is added 30 minutes before the end of hydrolysis. The crystal form promoter is a composite system of K2O and P2O5, wherein the amount of K2O added is 0.1-0.3% of the mass of TiO2, and the amount of P2O5 added is 0.05-0.15% of the mass of TiO2.

[0030] Preferably, in step S08, the first-stage water washing uses deionized water for countercurrent washing, the washing water temperature is 60~80℃, the liquid-solid ratio is 5:1~10:1, and the number of washing cycles is 2~3.

[0031] In step S11, the secondary water wash uses deionized water with a conductivity ≤5μS / cm, a washing water temperature of 50~70℃, a liquid-to-solid ratio of 3:1~6:1, and 3~5 washes.

[0032] Preferably, in step S09, the preparation step of trivalent titanium is as follows: take a portion of the concentrated titanium liquid, add zinc powder to carry out a reduction reaction, the amount of zinc powder added is 1.05~1.15 times the theoretical amount, the reaction temperature is controlled at 50~70℃, the reaction time is 1~2 hours, and the reduction reaction is carried out under the protection of an inert gas, the inert gas is nitrogen or argon, and the gas purity is ≥99.99%.

[0033] Preferably, in step S12, the calcination is carried out using a rotary kiln fueled by natural gas, with a kiln head temperature of 900~1000℃ and a kiln tail temperature of 400~500℃. The material residence time in the kiln is 4~8 hours. During the calcination process, the atmosphere inside the kiln is a weakly oxidizing atmosphere with an oxygen content of 5~10 vol%. After cooling, the conversion rate of the calcined material is controlled to be 60~80%.

[0034] Preferably, in step S13, the pulverization is carried out using an ultrafine airflow pulverizer with a pulverization pressure of 0.6~0.8MPa, a classifying wheel speed of 2000~3500r / min, and a feeding speed of 200~500kg / h. The pulverized product is collected by a bag collector with a collection efficiency of ≥99.5%. The environmental cleanliness during the pulverization process meets the ISO14644-1 Class 8 standard.

[0035] The beneficial effects of this invention are as follows:

[0036] 1. This invention adopts a complete sulfuric acid process, which avoids the risk of introducing metal impurities by high-temperature rinsing of stainless steel pipes in the chloride process. Through the coordinated control of raw material selection and process parameters, the metal impurity content of the product is effectively controlled, meeting the high purity requirements of electronic-grade titanium dioxide.

[0037] 2. This invention uses low-phosphorus titanium concentrate and sulfuric acid production as raw materials, which reduces the introduction of phosphorus and other trace impurities from the source. It eliminates the need for additional deep purification of raw materials, reduces production costs, and ensures product quality stability.

[0038] 3. This invention, by optimizing the parameter coordination of acid hydrolysis, sedimentation, controlled filtration, disc filtration and concentration processes, enables the entire process of electronic-grade titanium dioxide production to be completed on a single production line, eliminating the need for separate treatment of titanium liquid and reducing equipment investment and operating costs.

[0039] 4. This invention employs a two-stage water washing process, with a trivalent titanium preparation and bleaching step between the first and second washes. By controlling the washing water quality, temperature, liquid-solid ratio, and number of washes, the iron content is effectively reduced, which is beneficial to improving the insulation and dielectric properties of the product. Attached Figure Description

[0040] Figure 1 This is a flowchart of a method for preparing electronic-grade titanium dioxide proposed in this invention. Detailed Implementation

[0041] The technical solution of the present invention will be further described in detail below with reference to specific embodiments.

[0042] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "setting" should be interpreted broadly. For example, they can refer to a fixed connection or setting, a detachable connection or setting, or an integral connection or setting. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0043] Example 1

[0044] An electronic-grade titanium dioxide, by mass percentage, comprises the following components: TiO2 ≥ 99.5%, Fe2O3 ≤ 0.004%, SiO2 ≤ 0.1%, S ≤ 0.01%, P ≤ 0.02%, MgO ≤ 0.01%, CaO ≤ 0.01%, K2O + Na2O ≤ 0.01%, Nb2O5 ≤ 0.01%, Zn ≤ 0.001%, Sb ≤ 0.001%, sieve residue ≤ 0.05%, specific surface area of ​​6~10 m2 / g, loss on ignition ≤ 0.2%, rutile crystal content of 60~80%, volatile matter ≤ 0.05%, dry powder whiteness ≥ 95%, average particle size D50 of 0.5~1.0 μm, and bulk density of 0.6~0.8 × 1000 kg / m3.

[0045] Example 2:

[0046] An electronic-grade titanium dioxide, by mass percentage, comprises the following components: TiO2 ≥ 99.5%, Fe2O3 ≤ 0.004%, SiO2 ≤ 0.1%, S ≤ 0.01%, P ≤ 0.02%, MgO ≤ 0.01%, CaO ≤ 0.01%, K2O + Na2O ≤ 0.01%, Nb2O5 ≤ 0.01%, Zn ≤ 0.001%, Sb ≤ 0.001%, sieve residue ≤ 0.05%, specific surface area of ​​6~10 m2 / g, loss on ignition ≤ 0.2%, rutile crystal content of 60~80%, volatile matter ≤ 0.05%, dry powder whiteness ≥ 95%, average particle size D50 of 0.5~1.0 μm, and bulk density of 0.6~0.8 × 1000 kg / m3.

[0047] The electronic-grade titanium dioxide has a TiO2 content ≥99.5%, an Fe2O3 content ≤0.003%, a P content ≤0.050%, and a total iron content (calculated as elemental iron) ≤30ppm.

[0048] Example 3:

[0049] This embodiment provides a method for preparing electronic-grade titanium dioxide, the steps of which are as follows:

[0050] (1) Raw material preparation

[0051] Low-phosphorus titanium concentrate with a phosphorus content of 0.008% was selected; sulfuric acid was produced using sulfur, with a sulfuric acid concentration of 98.5%.

[0052] (2) Acid hydrolysis

[0053] Titanium concentrate and sulfuric acid were mixed at a mass ratio of 1:1.6, and the reaction temperature was controlled at 140℃ for 2 hours. After acidolysis, the total titanium (TiO2 equivalent) in the titanium solution was adjusted to 130 g / L, the F value was 1.90, the trivalent titanium concentration was 1.2 g / L, the stability was ≥350 mL / mL, and the acidolysis rate was ≥96%.

[0054] (3) Settlement

[0055] Add flocculant polyacrylamide at a rate of 0.03% of the titanium solution mass, allow the sedimentation time to 4 hours, and test the stability of the supernatant to be ≥350 mL / mL.

[0056] (4) Control

[0057] The settled titanium liquid was filtered under controlled conditions to ensure that the residue was ≤20mg / L and the trivalent titanium was maintained at 1.2g / L.

[0058] (5) Disc filtration

[0059] The filtrate was filtered using a disc filter to control the total titanium (TiO2 equivalent) in the filtrate to be 160 g / L and the iron-to-titanium ratio to be 0.32.

[0060] (6) Concentration

[0061] The filtrate was concentrated under vacuum to control the total titanium (TiO2 equivalent) of the concentrated titanium solution to be 180 g / L, the F value to be 1.90, the iron-to-titanium ratio to be 0.32, the trivalent titanium to be 1.2 g / L, the stability to be ≥450 mL / mL, and the residue to be ≤20 mg / L.

[0062] (7) Seed preparation

[0063] Prepare an alkali solution with a concentration of 8.5%, mix the concentrated titanium solution with the alkali solution, control the F value to be 1.70, the total titanium (equivalent to TiO2) to be 155 g / L, the stirring speed to be 120 rpm, the reaction temperature to be 40℃, and the reaction time to be 30 minutes.

[0064] (8) Hydrolysis

[0065] Concentrated titanium solution was added to the seed crystals at a rate of 8% of the total titanium solution volume. The heating rate was 1.5℃ / min, the hydrolysis temperature was 105℃, the hydrolysis time was 4 hours, the hydrolysis particle size was controlled at 2.3μm, the settling height was 100mm, the filtration time was 100s, and the hydrolysis rate was ≥95.5%. Simultaneously, K₂O and P₂O₅ composite crystal form promoters were added at amounts of 0.08% and 0.04% of the titanium solution mass, respectively.

[0066] (9) One wash

[0067] The hydrolysis products were washed with deionized water (conductivity ≤5μS / cm) at 80℃, with a liquid-to-solid ratio of 3:1, and the washing was repeated 3 times. After washing, the Fe2O3 content was measured to be 450PPM.

[0068] (10) Preparation of trivalent titanium

[0069] Add zinc powder to the washed metatitanic acid. The amount of zinc powder added is 0.5% of the mass of metatitanic acid. The reaction temperature is 60℃, the reaction time is 45 minutes, nitrogen gas is introduced for protection, the concentration of trivalent titanium is controlled at 75g / L, and the reduction rate is ≥90%.

[0070] (11) Bleaching

[0071] Add sulfuric acid to the trivalent titanium solution to adjust the free acid to 40 g / L, control the trivalent titanium to ≥0.05 g / L, and bleach for 1 hour.

[0072] (12) Second wash

[0073] The bleached product was washed twice with deionized water (conductivity ≤5μS / cm) at a temperature of 80℃, a liquid-to-solid ratio of 3:1, and three times. The Fe2O3 content was 15PPM after washing.

[0074] (13) Calcination

[0075] Natural gas is used as fuel. The kiln head temperature is 950℃, the kiln tail temperature is 650℃, the material residence time is 8 hours, and an oxidizing atmosphere is maintained inside the kiln with an oxygen content of 5%. After calcination, the dry powder has a whiteness of ≥95%, total iron (Fe2O3) ≤30PPM, a conversion rate of 75%, and a sulfur content ≤0.01%.

[0076] (14) Crushing

[0077] The air jet mill (model: ALPINE AFG-630) imported from Germany was used for air jet milling, with a milling pressure of 0.6MPa, a classifying wheel speed of 4000rpm, and the residue on the 325 mesh sieve was controlled to be ≤0.05%, and the total iron (Fe2O3) was ≤40PPM.

[0078] Example 4

[0079] A method for preparing electronic-grade titanium dioxide. The difference between this embodiment and Embodiment 1 is that the F value in the acid hydrolysis step is adjusted to 1.85, and the F value in the seed preparation step is adjusted to 1.65; the other steps are the same as in Embodiment 3.

[0080] Example 5

[0081] A method for preparing electronic-grade titanium dioxide. The difference between this embodiment and Embodiment 1 is that the F value in the acid hydrolysis step is adjusted to 1.95, and the F value in the seed preparation step is adjusted to 1.75; the other steps are the same as in Embodiment 3.

[0082] Example 6

[0083] A method for preparing electronic-grade titanium dioxide. The difference between this embodiment and Embodiment 1 is that the kiln head temperature is adjusted to 900℃ and the kiln tail temperature is adjusted to 600℃ in the calcination step; the other steps are the same as in Embodiment 3.

[0084] Example 7

[0085] A method for preparing electronic-grade titanium dioxide. The difference between this embodiment and Embodiment 1 is that the number of washing steps in the first washing step is increased to 4, and the number of washing steps in the second washing step is increased to 5; the other steps are the same as in Embodiment 3.

[0086] Product performance comparison experiment

[0087] Experimental methods

[0088] 1. Whole component analysis method

[0089] X-ray fluorescence spectrometry (XRF, model: PANalytical Axios) was used for full elemental quantitative analysis of the product. Detection conditions: voltage 60kV, current 50mA, scanning range 2θ=10°~80°. Sample pretreatment: 5g of product powder was dried at 105℃ for 2 hours and then pressed into a tablet for measurement.

[0090] 2. Physical performance testing methods

[0091] Specific surface area: BET method was used (instrument model: Micromeritics TriStar II 3020), degassing temperature 200℃, degassing time 2 hours.

[0092] Average particle size D50: A laser particle size analyzer (instrument model: Malvern Mastersizer 3000) was used, and the dispersion medium was deionized water. The particles were ultrasonically dispersed for 5 minutes.

[0093] Dry powder whiteness: A whiteness meter (instrument model: HunterLab UltraScan VIS) was used, with a measurement wavelength of 457nm, and calibrated using a MgO standard white plate.

[0094] Bulk density: Weigh 100g of sample and place it in a 250mL graduated cylinder. After natural stacking, read the volume and calculate the bulk density.

[0095] Rutile crystal content: The rutile content was calculated by RIR method using an X-ray diffractometer (XRD, model: Bruker D8 Advance), Cu target Kα radiation, scanning range 2θ=20°~60°.

[0096] 3. Comparison Experiment of Impurity Iron Content

[0097] Three portions of each of the embodiments and commercially available samples, each weighing 10g, were taken. The iron content was determined using an inductively coupled plasma optical emission spectrometer (ICP-OES, model: PerkinElmer Avio 220 Max) at a detection wavelength of 238.204nm. The samples were digested using a nitric acid-hydrofluoric acid system via microwave digestion.

[0098] Table 1. Results of full component analysis of products in each embodiment.

[0099]

[0100] Table 2. Test results of physical performance of products in each embodiment.

[0101]

[0102] Experimental Results Analysis

[0103] From Table 1 and Table 2, we can see that:

[0104] Example 3 shows that all indicators meet the quality requirements of electronic-grade titanium dioxide, with TiO2 content of 99.72%, Fe2O2 content of only 0.0028%, and whiteness of 96.2%. Its overall performance is comparable to or even slightly better than commercially available products.

[0105] Example 4 (low F value) product has a larger particle size (D50=0.71μm), lower rutile content (63%), and slightly lower whiteness (95.4%), indicating that an excessively low F value is not conducive to crystal transformation and fineness control.

[0106] Example 5 (high F value) product has a finer particle size (D50=0.56μm), a higher rutile content (77%), but an increased specific surface area of ​​8.8m². 2 / g may affect downstream dispersibility.

[0107] In Example 6 (low-temperature calcination), the rutile content of the product was only 61%, the whiteness dropped to 94.8%, and the particle size increased to 0.82 μm, indicating that insufficient calcination temperature led to incomplete crystal transformation.

[0108] Example 7 (enhanced water washing) had the lowest iron content (Fe2O4=0.0022%), the highest whiteness (96.5%), and the overall impurity content was better than other examples, proving that increasing the number of two-stage water washings is beneficial to reducing the content of metal impurities.

[0109] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. An electronic-grade titanium dioxide, characterized in that, The product contains the following components by weight percentage: TiO2 ≥ 99.5%, Fe2O3 ≤ 0.004%, SiO2 ≤ 0.1%, S ≤ 0.01%, P ≤ 0.02%, MgO ≤ 0.01%, CaO ≤ 0.01%, K2O + Na2O ≤ 0.01%, Nb2O5 ≤ 0.01%, Zn ≤ 0.001%, Sb ≤ 0.001%, sieve residue ≤ 0.05%, specific surface area 6~10 m2 / g, loss on ignition ≤ 0.2%, rutile crystal content 60~80%, volatile matter ≤ 0.05%, dry powder whiteness ≥ 95%, average particle size D50 0.5~1.0 μm, bulk density 0.6~0.8×1000 kg / m3.

2. The electronic-grade titanium dioxide according to claim 1, characterized in that, The electronic-grade titanium dioxide has a TiO2 content ≥99.5%, an Fe2O3 content ≤0.003%, a P content ≤0.050%, and a total iron content (calculated as elemental iron) ≤30ppm.

3. A method for preparing electronic-grade titanium dioxide, used to prepare the electronic-grade titanium dioxide according to claim 1 or 2, characterized in that, Includes the following steps: S01: Acid hydrolysis: Using low-phosphorus titanium concentrate with a P content of <0.01wt% as raw material, the titanium concentrate is mixed with concentrated sulfuric acid at a mass ratio of 1:1.5~1:1.8 to carry out acid hydrolysis reaction to obtain titanium liquid; S02: Sedimentation: The obtained titanium liquid is separated by gravity sedimentation; S03: Controlled filtration: The settled titanium liquid is filtered in a controlled manner; S04: Disc filtration: The controlled titanium liquid is filtered through a disc filter; S05: Concentration: Vacuum concentration is performed on the titanium liquid after disc filtration; S06: Seed preparation: Hydrolyzed seed crystals were prepared by alkaline solution method, with an alkaline solution concentration of 8.4~8.6wt%, a seed crystal F value of 1.65~1.75, and a total titanium concentration of 150~160g / L; S07: Hydrolysis: The concentrated titanium liquid is mixed with seed crystals to carry out a hydrolysis reaction. The hydrolysis temperature is 95~105℃ and the hydrolysis time is 3~5 hours. S08: Primary water washing: The hydrolysis products are subjected to primary water washing, and the Fe2O3 content after washing is ≤500ppm; S09: Preparation of trivalent titanium: Trivalent titanium solution is prepared by aluminum powder reduction using a portion of diwashed metatitanic acid as raw material; S10: Bleaching: The material after primary water washing is bleached with trivalent titanium solution. The free acid concentration in the bleaching system is 30~50g / L, and the trivalent titanium concentration is ≥0.05g / L. S11: Secondary water washing: The bleached material is subjected to secondary water washing, and the Fe2O3 content after washing is ≤20ppm; S12: Calcination: The material after secondary water washing is sent into a rotary kiln for calcination; S13: Pulverization: The calcined product is pulverized using an ultrafine airflow pulverizer to obtain electronic-grade titanium dioxide.

4. The method for preparing electronic-grade titanium dioxide according to claim 3, characterized in that, In step S01, the raw material composition of the low-phosphorus titanium concentrate, by mass percentage, includes: TiO2 ≥ 46%, Fe2O3 ≤ 8%, SiO2 ≤ 3.5%, P ≤ 0.01%, S ≤ 0.2%, MgO ≤ 0.5%, CaO ≤ 0.3%, Al2O3 ≤ 1.5%; the concentrated sulfuric acid is concentrated sulfuric acid produced by the sulfur-based acid production process, with an H2SO4 concentration ≥ 98 wt%, and wherein the Fe content ≤ 10 ppm, the Pb content ≤ 5 ppm, and the As content ≤ 2 ppm.

5. The method for preparing electronic-grade titanium dioxide according to claim 3, characterized in that, In step S06, the alkaline solution is a sodium hydroxide solution with a NaOH concentration of 8.4~8.6wt%, and the Na2CO2 content is ≤0.5wt% and the NaCl content is ≤0.1wt%. During seed crystal preparation, the alkaline solution is added to the titanium solution at a rate of 5~10L / min, while stirring at a speed of 200~300r / min. The reaction temperature is 60~80℃, and the reaction time is 30~60 minutes.

6. The method for preparing electronic-grade titanium dioxide according to claim 3, characterized in that, In step S07, hydrolysis is carried out in an intermittent hydrolysis vessel. The amount of seed crystal added is 8-15% of the volume of concentrated titanium liquid, the hydrolysis heating rate is 1-3℃ / min, and a crystal form promoter is added 30 minutes before the end of hydrolysis. The crystal form promoter is a composite system of K2O and P2O5, wherein the amount of K2O added is 0.1-0.3% of the mass of TiO2, and the amount of P2O5 added is 0.05-0.15% of the mass of TiO2.

7. The method for preparing electronic-grade titanium dioxide according to claim 3, characterized in that, In step S08, the first-stage water wash uses deionized water for countercurrent washing, the washing water temperature is 60~80℃, the liquid-solid ratio is 5:1~10:1, and the number of washes is 2~3. In step S11, the secondary water wash uses deionized water with a conductivity ≤5μS / cm, a washing water temperature of 50~70℃, a liquid-to-solid ratio of 3:1~6:1, and 3~5 washes.

8. The method for preparing electronic-grade titanium dioxide according to claim 3, characterized in that, In step S09, the preparation step of trivalent titanium is as follows: take a portion of the concentrated titanium liquid, add zinc powder to carry out a reduction reaction, the amount of zinc powder added is 1.05 to 1.15 times the theoretical amount, the reaction temperature is controlled at 50 to 70°C, the reaction time is 1 to 2 hours, and the reduction reaction is carried out under the protection of an inert gas, which is nitrogen or argon, with a gas purity ≥ 99.99%.

9. The method for preparing electronic-grade titanium dioxide according to claim 3, characterized in that, In step S12, the calcination is carried out in a rotary kiln fueled by natural gas. The kiln head temperature is 900~1000℃ and the kiln tail temperature is 400~500℃. The material residence time in the kiln is 4~8 hours. The atmosphere in the kiln during the calcination process is a weak oxidizing atmosphere with an oxygen content of 5~10 vol%. After cooling, the conversion rate of the calcined material is controlled at 60~80%.

10. The method for preparing electronic-grade titanium dioxide according to claim 3, characterized in that, In step S13, the pulverization is carried out using an ultrafine airflow pulverizer with a pulverization pressure of 0.6~0.8MPa, a classifying wheel speed of 2000~3500r / min, and a feeding speed of 200~500kg / h.

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