A process for selectively extracting titanium from red mud

Abstract

This invention belongs to the field of hydrometallurgical technology and discloses a process for selectively extracting titanium from red mud. The process involves leaching gibbsite and / or boehmite-type bauxite using the Bayer process. The resulting red mud is washed and then activated with a dilute acid or ammonium salt solution to obtain highly active red mud. Ammonium salt and / or ammonia solution, along with hydrogen peroxide, are added to the highly active red mud to prepare a slurry. The pH of the slurry is controlled at 8-14. After a period of reaction, liquid-solid separation is performed to obtain a titanium-rich solution and the titanium-extracted red mud. The titanium-rich solution can be further processed to obtain titanium dioxide or titanium dioxide fiber materials, increasing the added value of the red mud. This invention selectively leaches titanium from red mud in a weakly alkaline system, achieving high-value recovery and utilization of titanium in red mud. The red mud after titanium extraction has a low alkali content and a significantly reduced titanium content, reducing the difficulty of using high-iron red mud as a raw material for blast furnace ironmaking.

Description

Technical Field

[0001] This invention belongs to the field of hydrometallurgical technology, specifically relating to a method for selectively extracting titanium from red mud. Background Technology

[0002] In 2021, global alumina production reached 138 million tons, an increase of 5.04 million tons compared to 2020, representing a year-on-year growth of 3.79%. my country's alumina production was 75.097 million tons, accounting for 54.40% of global alumina production, with more than half of this coming from high-iron gibbsite-type bauxite. Typically, producing 1 ton of alumina generates 0.7 to 2 tons of red mud, thus estimating annual red mud emissions to be between 97 and 276 million tons. Red mud has a complex composition and high alkali content; its storage not only occupies land and wastes resources but also easily causes environmental pollution and safety hazards.

[0003] In 2021, the global total titanium ore production was 8.27 million tons (equivalent to TiO2, the same below), while my country's titanium ore production was 2.857 million tons. my country's dependence on imported titanium raw materials is high, at approximately 40%, and the supply of high-quality titanium raw materials is heavily reliant on the international market.

[0004] Currently, red mud is used as a raw material for titanium extraction, and a great deal of research has been conducted on the process of extracting titanium from red mud:

[0005] (1) Reduction roasting-magnetic separation-sulfuric acid leaching: Red mud is mixed with coal powder, lime, and soda ash, and reduced roasted at 800~1000℃. The clinker is leached in water to obtain sodium aluminate solution, which is then desiliconized and used for alumina production. Most of the iron in the water-leached residue is separated by magnetic separation, and the non-magnetic portion is leached with sulfuric acid to obtain TiOSO4 solution, which is then hydrolyzed to prepare metatitanic acid. This method can obtain titanium-rich material with a purity of about 96%, which is used for titanium dioxide production by the chlorination process. The disadvantage is that CaTiO3 is generated during the reduction roasting process, which is difficult to process.

[0006] (2) Two-step acid leaching method: In the first step, under the conditions of pH=3, temperature of 25℃ and reaction time of 60min, hydrochloric acid is used to leach elements such as Na, Al, Si, and Ca from the red mud, while iron and titanium do not react. In the second step, sulfuric acid with a concentration of 80g / L is used for leaching. Under the conditions of temperature of 50℃, liquid-solid ratio of 20:1 and reaction time of 90min, most of the iron reacts while titanium does not react much, resulting in titanium slag with a TiO2 content of nearly 50%.

[0007] (3) Organic acid / hydrogen peroxide assisted leaching method: Organic acids such as citric acid or hydrogen peroxide can promote the reaction of titanium minerals. Under the conditions of 2.5M H2SO4, 75°C, liquid-solid ratio of 10:1, and reaction time of 120 min, adding organic acids such as citric acid that can coordinate with titanium to improve the leaching rate of titanium. However, there are problems such as large acid consumption, weak selectivity for the leaching of valuable elements, and difficulty in suppressing the leaching of iron when recovering high-value metal elements such as scandium and titanium.

[0008] (4) Hydrochloric acid-oxalic acid leaching-sulfation roasting method: This method can achieve the recovery of multiple elements from red mud. In the first step, Ca, Si, and Al are leached in a 1M hydrochloric acid solution at 40°C; in the second step, V and Fe are leached in a 2M oxalic acid solution at 95°C; in the third step, sulfation roasting is carried out at 150 - 400°C, and the product is leached with 0.5M sulfuric acid at 65°C to recover scandium and titanium. This method produces a large amount of acidic wastewater and is difficult to apply technically.

[0009] The patent document with the application number CN201510360507.2 proposes to first react red mud in a 1 - 3mol / L citric acid solution at 60 - 95°C for 60 min, wash the acid leaching residue with water, then roast it with NaOH at 750 - 850°C for 60 min, and then acidify the washed residue with H2SO4 and CaF2. The titanium-containing solution is hydrolyzed and then roasted to obtain high-purity TiO2. This method requires neutralizing the acid / alkali in the previous step, with a large amount of consumption, strong reaction conditions, and poor economy.

[0010] The patent document with the application number CN201510678319.4 proposes that for red mud with TiO2 > 8% and 0 < Fe2O3 < 42%, acid leaching-precipitation combined flotation is used to recover titanium and iron from red mud. First, red mud and concentrated sulfuric acid are prepared into a slurry according to a mass ratio of (20 - 50):100, and the reaction is carried out at 80 - 120°C for 120 minutes, and then the titanium-iron leaching solution is obtained by filtration; using bis(trifluoromethylsulfonyl)imide as the iron precipitant, butyl xanthate as the collector, and terpineol as the foaming agent, bis(trifluoromethylsulfonyl)imide, butyl xanthate, and terpineol are sequentially added to the titanium-iron leaching solution, stirred evenly and then froth flotation is carried out; the residual solution after froth flotation is the titanium-rich liquid product; the foam product is obtained as the iron-rich liquid product by hydrochloric acid extraction. The problems existing in this method are that a large amount of red mud dissolves, causing difficult treatment of waste acid; in addition, the titanium-rich liquid has a high impurity content and the iron-rich liquid is difficult to utilize.

[0011] The patent document with the application number CN200710015762.9 proposes to carry out reduction smelting on red mud to recover iron, the smelting slag is water-quenched and then part of aluminum, silicon, and sodium are leached, and then the water-quenched slag is acidified, and titanium is enriched in the slag. This method has high energy consumption, and the obtained titanium slag still contains较多 impurities and needs further treatment.

[0012] Patent application CN201310085601.2 utilizes waste acid from titanium dioxide production to leach red mud, and the leachate is used to recover scandium through extraction; the back-extraction solution is boiled and hydrolyzed, and the hydrolysis product is roasted to obtain titanium yellow powder; the acid leaching residue can be used to recover iron concentrate through strong magnetic separation. This method utilizes waste acid from titanium dioxide production for resource recovery, but a large amount of iron, silicon, and aluminum minerals are dissolved, resulting in a low titanium resource recovery rate. Summary of the Invention

[0013] In view of the problems existing in the prior art, the purpose of this invention is to provide a novel process for extracting titanium from red mud.

[0014] To achieve the above objectives, the present invention adopts the following specific technical solutions.

[0015] The titanium extraction process from red mud of this invention is compatible with the existing Bayer process for alumina production. The red mud produced during the process is washed, activated with dilute acid or dilute ammonium salt solution, and then slurried with ammonium salt solution and / or ammonia solution, as well as hydrogen peroxide. Titanium is selectively leached in a weakly alkaline system to obtain a titanium-rich solution and titanium-reduced red mud. The titanium-rich solution, after boiling, calcination, and acid washing, can yield titanium dioxide of acceptable composition, or nano-titanium dioxide can be synthesized in one step via a hydrothermal method. The titanium-reduced red mud can be used as a blending agent in blast furnace smelting.

[0016] Specifically, the process for selectively extracting titanium from red mud includes the following steps:

[0017] (1) The red mud obtained by dissolving gibbsite and / or boehmite type bauxite by Bayer process is washed and then activated with dilute acid or ammonium salt solution to obtain highly active red mud.

[0018] (2) Add ammonium salt or ammonia solution and hydrogen peroxide to highly active red mud to prepare slurry. Control the pH value of the slurry to 8~14. After reacting for a period of time, separate the liquid and solid to obtain titanium-rich solution and titanium-extracted red mud.

[0019] Furthermore, in some preferred embodiments of the present invention, the Bayer dissolution temperature is 140~260°C.

[0020] Furthermore, in some preferred embodiments of the present invention, the concentration of the dilute acid or ammonium salt is 5~20 g / L.

[0021] Furthermore, in some preferred embodiments of the present invention, the activation temperature is 10~70°C, and the activation time is 0.5~2h.

[0022] Furthermore, in some preferred embodiments of the present invention, the liquid-to-solid ratio of the activation is 3:1 to 10:1.

[0023] Furthermore, in some preferred embodiments of the present invention, the activation time is 10-120 min.

[0024] Furthermore, in some preferred embodiments of the present invention, the liquid-to-solid ratio of the slurry is 1:1 to 20:1; the concentration of hydrogen peroxide in the slurry is 1 to 20 wt%, and the concentration of NH4 is... + The concentration is 0.05~0.20 mol / L.

[0025] Furthermore, in some preferred embodiments of the present invention, the reaction temperature is 5~45°C and the reaction time is 5~70 min.

[0026] Furthermore, in some preferred embodiments of the present invention, the following steps are also included: boiling the titanium-rich solution, calcining the precipitated metatitanic acid at 450~750°C to obtain anatase titanium dioxide with TiO2 > 90%.

[0027] Furthermore, in some preferred embodiments of the present invention, the following step is also included: a titanium-rich solution is subjected to a hydrothermal reaction at 170~240°C to synthesize nano-TiO2.

[0028] Compared with the prior art, the present invention has the following significant advantages:

[0029] (1) This invention is compatible with the Bayer process for producing alumina, and follows the red mud washing process. Titanium is selectively leached in a weakly alkaline system, and other elements do not participate in the reaction.

[0030] (2) The process of extracting titanium from red mud is short, the reaction conditions are mild, the price of leaching agent is low, there is no wastewater discharge, some of the leaching agent can be recycled, and the requirements for process equipment are low.

[0031] (3) Titanium-rich solutions are also used to prepare titanium dioxide or nano-titanium dioxide photocatalysts, realizing the high-value utilization of red mud;

[0032] (4) After titanium extraction, the alkali content in the red mud is low and the titanium content is significantly reduced, which reduces the difficulty of using high-iron red mud as a raw material for blast furnace ironmaking. Attached Figure Description

[0033] Figure 1 This is a process route diagram used in an embodiment of the present invention. Detailed Implementation

[0034] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0035] Unless otherwise defined, all technical terms used hereinafter have the same meanings as those generally understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0036] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0037] This invention provides a process for extracting titanium from red mud, comprising the following steps:

[0038] (1) The red mud obtained by dissolving gibbsite and / or boehmite in Bayer process is washed and then activated with dilute acid or ammonium salt solution to obtain highly active red mud.

[0039] (2) Add ammonium salt and / or ammonia water and hydrogen peroxide to highly active red mud to prepare slurry, control the pH value of the slurry to 8~14, and after a period of reaction, separate the liquid and solid to obtain titanium-rich solution and titanium-extracted red mud.

[0040] In a specific embodiment, bauxite and circulating mother liquor are used to prepare a slurry, which is then subjected to a leaching reaction at 140-260°C. After the reaction, the slurry is diluted and separated by sedimentation to obtain a sodium aluminate solution and red mud. The red mud is washed multiple times, with the wash water returned to the slurry dilution process, while the underflow is unwashed red mud, which is used for titanium extraction.

[0041] During the leaching reaction, titanium-bearing minerals (anatase, rutile, ilmenite) in the ore react with alkaline solution to mainly generate different forms of titanates (primarily Na₂Ti₃O₇, Na₂TiO₃, CaTiO₃, etc.). Due to the low solubility of titanates in alkaline solution, they are easily precipitated, resulting in titanates adsorbing onto the surfaces of various minerals, exhibiting a large specific surface area and high activity.

[0042] During the activation process of sodium titanate in dilute acid or ammonium salt solutions, the Na-O bonds and some Ti-O bonds are converted by H+ in the solution. + or NH4 + Damage, causing Na-H + / NH4 + Replace, generate Na x H 2-x TiO3. When the Na / H ratio in sodium titanate is small, efficient and selective leaching of titanates can be achieved. Na-H + / NH4 + The substitution reaction equation is as follows:

[0043] Na2TiO3+xH + =Na 2-x H x TiO3+xNa+

[0044] Na₂TiO₃ + xNH₄ + =Na 2-x H x TiO3+xNa + +xNH3↑

[0045] In a specific embodiment, the concentration of the dilute acid or ammonium salt solution is 5~20 g / L, preferably 10~15 g / L.

[0046] In a specific embodiment, the activation temperature is 10~70℃, preferably 30~70℃; the activation time is 0.5~2h, preferably 1~2h.

[0047] In a specific embodiment, the concentration of hydrogen peroxide in the slurry is 1~20wt%, preferably 5~15wt%; the amount of ammonium salt added is 1~20g / L of slurry, preferably 10~20g / L of slurry.

[0048] In a specific embodiment, the reaction temperature is 5~45℃ and the reaction time is 5~70min.

[0049] In a specific embodiment, the ammonium salt mentioned in step (2) is selected from one or more of ammonium carbonate, ammonium bicarbonate, and urea.

[0050] In a specific embodiment, the following steps are also included: boiling the titanium-rich solution and calcining the precipitated metatitanic acid at 450~750℃ to obtain anatase titanium dioxide with TiO2 > 90%; or, subjecting the titanium-rich solution to a hydrothermal reaction at 170~240℃ to synthesize nano-TiO2.

[0051] Ammonia gas volatilized during boiling or hydrothermal reaction of titanium-rich solution is recovered; the solution obtained after solid-liquid separation of metatitanic acid precipitated from titanium-rich solution, and the solution obtained after solid-liquid separation of titanium-rich solution after hydrothermal reaction are used as washing liquid for red mud.

[0052] After titanium extraction, the alkali and titanium content of the red mud decreases significantly, making it suitable as an admixture for blast furnace smelting and enabling large-scale utilization of red mud.

[0053] The following is passed Figure 1 The process flow diagram and specific embodiments shown provide a further detailed explanation of the technical solution of the present invention.

[0054] Example 1:

[0055] Bauxite A: Al2O3 49.31%, Fe2O3 18.12%, SiO2 1.58%, TiO2 2.06%, A / S (aluminum-silicon ratio) is 31.28.

[0056] Circulating mother liquor A: Na2O k 250g / L, α k 3.11 (α) k (This represents the molar ratio of sodium oxide to aluminum oxide).

[0057] 500g of bauxite A and 1.51 L of circulating mother liquor A were added to a 5 L high-pressure reactor. After sealing, stirring was started, and the mixture was reacted at 250℃ for 1 hour. After cooling, the red mud sedimentation separation and washing were completed. 57.7g of red mud was taken and 5g / L of dilute sulfuric acid was added. The mixture was stirred at 50℃ for 30 minutes, with a liquid-to-solid ratio of 3:1.

[0058] After liquid-solid separation, hydrogen peroxide and ammonia were added to control the liquid-solid ratio at 5:1, preparing a solution containing 6wt% H2O2 and NH4+. + A slurry with a concentration of 0.10 mol / L was prepared, and the pH value of the slurry was controlled at 10 ± 0.2. The reaction was carried out at a reaction temperature of 35℃ and a stirring speed of 300 r / min for 35 min. After liquid-solid separation, a titanium-rich solution and titanium-extracted red mud were obtained.

[0059] Comparative analysis showed that the TiO2 content in red mud (i.e., red mud washed after Bayer process leaching) and red mud after titanium extraction decreased from 7.20% to 1.82%.

[0060] The solid phase precipitated after boiling the titanium-rich solution was calcined at 450℃ for 4 hours. The product was washed with 20 g / L dilute hydrochloric acid to obtain anatase TiO2 with a TiO2 content of 93.2%.

[0061] Example 2:

[0062] Bauxite B: Al₂O₃ 48.12%, Fe₂O₃ 19.04%, SiO₂ 1.47%, TiO₂ 2.14%, A / S (aluminum-silicon ratio) 32.63

[0063] Mother liquor B: Na2O k 230g / L, α k 3.11

[0064] Add 500g of bauxite B and 1.65 L of circulating mother liquor B to a 5 L high-pressure reactor. After sealing, start stirring and react at 250℃ for 1 hour. After cooling, complete the red mud sedimentation separation and washing. Take 50.6g of red mud, add 10g / L dilute sulfuric acid, and stir at 70℃ for 20 minutes, with a liquid-to-solid ratio of 5:1.

[0065] Add hydrogen peroxide and ammonium bicarbonate, controlling the liquid-to-solid ratio at 10:1, to prepare a solution containing 6wt% H2O2 and NH4+. +A slurry with a concentration of 0.05 mol / L was prepared, and the pH value of the slurry was controlled at 11±0.2. The reaction was carried out at a reaction temperature of 35℃ and a stirring speed of 300 r / min for 35 min. After liquid-solid separation, a titanium-rich solution and titanium-extracted red mud were obtained.

[0066] Comparative analysis showed that the TiO2 content in red mud (i.e., red mud washed after Bayer process leaching) and red mud after titanium extraction decreased from 7.29% to 4.62%.

[0067] The solid phase precipitated after boiling the titanium-rich solution was calcined at 550℃ for 4 hours. The product was washed with 10 g / L dilute hydrochloric acid to obtain anatase TiO2 with a TiO2 content of 91.5%.

[0068] Example 3:

[0069] Bauxite A: Al₂O₃ 49.31%, Fe₂O₃ 18.12%, SiO₂ 1.58%, TiO₂ 2.06%, A / S (aluminum-silicon ratio) 31.28

[0070] Mother liquor B: Na2O k 230g / L, α k 3.11

[0071] 500g of bauxite A and 1.64 L of circulating mother liquor B were added to a 5 L high-pressure reactor. After sealing, stirring was started, and the mixture was reacted at 250℃ for 1 hour. After cooling, the red mud sedimentation and washing were completed. 54.3g of red mud was taken and added to a 10g / L ammonium carbonate solution. The mixture was stirred at 70℃ for 20 minutes, with a liquid-to-solid ratio of 5:1.

[0072] Add hydrogen peroxide and ammonium carbonate solution, controlling the liquid-to-solid ratio at 20:1, to prepare a solution containing 10wt% H2O2 and NH4+. + A slurry with a concentration of 0.15 mol / L was prepared, and the pH value of the slurry was controlled at 10 ± 0.2. The reaction was carried out at a reaction temperature of 35℃ and a stirring speed of 300 r / min for 35 min. After liquid-solid separation, a titanium-rich solution and titanium-extracted red mud were obtained.

[0073] Comparative analysis showed that the TiO2 content in red mud (i.e., red mud washed after Bayer process leaching) and red mud after titanium extraction decreased from 7.03% to 2.38%.

[0074] The solid phase precipitated after boiling the titanium-rich solution was calcined at 650℃ for 8 hours. The product was washed with 15 g / L dilute hydrochloric acid to obtain anatase TiO2 with a TiO2 content of 92.2%.

[0075] Example 4:

[0076] Bauxite B: Al2O3 48.12%, Fe2O3 19.04%, SiO2 1.47%, TiO2 2.14%, A / S (aluminum-silicon ratio) is 32.63.

[0077] Mother liquor B: Na2O k 230g / L, α k 3.11

[0078] 500g of bauxite B and 1.62 L of circulating mother liquor B were added to a 5 L high-pressure reactor. After sealing, stirring was started, and the mixture was reacted at 250℃ for 1 hour. After cooling, the red mud sedimentation and washing were completed. 68.7g of red mud was taken and added to 15g / L dilute sulfuric acid. The mixture was stirred at 70℃ for 10 minutes, with a liquid-to-solid ratio of 3:1.

[0079] Add hydrogen peroxide and ammonia, controlling the liquid-to-solid ratio at 10:1, to prepare a solution containing 6wt% H2O2 and NH4+. + A slurry with a concentration of 0.10 mol / L was prepared, and the pH value of the slurry was controlled at 10 ± 0.2. The reaction was carried out at a reaction temperature of 35℃ and a stirring speed of 300 r / min for 35 min. After liquid-solid separation, a titanium-rich solution and titanium-extracted red mud were obtained.

[0080] Comparative analysis showed that the TiO2 content in red mud (i.e., red mud washed after Bayer process leaching) and red mud after titanium extraction decreased from 7.18% to 2.41%.

[0081] A titanium-rich solution was placed in a homogeneous reactor and reacted at 180°C for 24 hours to obtain TiO2 fibers with a length greater than 10 μm and a width less than 500 nm.

[0082] Example 5:

[0083] Bauxite B: Al2O3 48.12%, Fe2O3 19.04%, SiO2 1.47%, TiO2 2.14%, A / S (aluminum-silicon ratio) is 32.63.

[0084] Mother liquor B: Na2O k 230g / L, α k 3.11.

[0085] 500g of bauxite B and 1.65L of circulating mother liquor B were added to a 5L high-pressure reactor. After sealing, stirring was started, and the mixture was reacted at 250℃ for 1 hour. After cooling, the red mud sedimentation and washing were completed. 65.2g of red mud was taken and added to 10g / L dilute sulfuric acid. The mixture was stirred at 60℃ for 15 minutes, with a liquid-to-solid ratio of 3:1.

[0086] Add hydrogen peroxide and urea, controlling the liquid-to-solid ratio at 20:1, to prepare a solution containing 6wt% H2O2 and NH4+. + A slurry with a concentration of 0.15 mol / L was prepared, and the pH value of the slurry was controlled at 10 ± 0.2. The reaction was carried out at a reaction temperature of 35℃ and a stirring speed of 300 r / min for 20 min. After liquid-solid separation, a titanium-rich solution and titanium-extracted red mud were obtained.

[0087] Comparative analysis showed that the TiO2 content in red mud (i.e., red mud washed after Bayer process leaching) and red mud after titanium extraction decreased from 7.22% to 3.41%.

[0088] The leachate was placed in a homogeneous reaction vessel and reacted at 170°C for 18 hours to obtain TiO2 fibers with a length greater than 15 μm and a width less than 500 nm.

[0089] Example 6:

[0090] Bauxite B: Al2O3 48.12%, Fe2O3 19.04%, SiO2 1.47%, TiO2 2.14%, A / S (aluminum-silicon ratio) is 32.63.

[0091] Mother liquor B: Na2O k 230g / L, α k 3.11.

[0092] 500g of bauxite B and 1.65L of circulating mother liquor B were added to a 5L high-pressure reactor. After sealing, stirring was started, and the mixture was reacted at 250℃ for 1 hour. After cooling, the red mud sedimentation separation and washing were completed. 64.1g of red mud was taken and added to 10g / L dilute sulfuric acid. The mixture was stirred at 40℃ for 20 minutes, with a liquid-to-solid ratio of 5:1.

[0093] Add hydrogen peroxide and ammonia, controlling the liquid-to-solid ratio at 20:1, to prepare a solution containing 10wt% H2O2 and NH4+. + A slurry with a concentration of 0.05 mol / L was prepared, and the pH value of the slurry was controlled at 10 ± 0.2. The reaction was carried out at a reaction temperature of 35℃ and a stirring speed of 300 r / min for 20 min. After liquid-solid separation, a titanium-rich solution and titanium-extracted red mud were obtained.

[0094] Comparative analysis was conducted on the TiO2 content in red mud (i.e., red mud washed after Bayer process leaching) and red mud after titanium extraction. The analysis showed that the TiO2 content in the red mud decreased from 6.99% to 2.51%. The solid phase precipitated after boiling the leachate was calcined at 550℃ for 8 hours, and the product was washed with 15 g / L dilute hydrochloric acid to obtain anatase TiO2 with a TiO2 content of 94.7%.

[0095] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A process for selectively extracting titanium from red mud, characterized in that, Includes the following steps: (1) The red mud obtained by dissolving gibbsite and / or boehmite type bauxite by Bayer process is washed and then activated with dilute acid or ammonium salt solution to obtain highly active red mud; the concentration of the dilute acid or ammonium salt is 5~20 g / L. (2) Add ammonium salt and / or ammonia solution and hydrogen peroxide to highly active red mud to prepare slurry. Control the pH of the slurry to 8~14. After reacting for a period of time, separate the liquid and solid to obtain titanium-rich solution and titanium-extracted red mud.

2. The process for selectively extracting titanium from red mud as described in claim 1, characterized in that, The Bayer process is used to dissolve substances at temperatures ranging from 140 to 260°C.

3. The process for selectively extracting titanium from red mud as described in claim 1, characterized in that, The activation temperature is 10~70℃, and the activation time is 0.5~2h.

4. The process for selectively extracting titanium from red mud as described in claim 3, characterized in that, The liquid-to-solid ratio for activation is 3:1 to 10:

1.

5. The process for selectively extracting titanium from red mud as described in claim 1, characterized in that, The ammonium salt is selected from one or more of ammonium carbonate, ammonium bicarbonate, and urea.

6. The process for selectively extracting titanium from red mud as described in claim 1, characterized in that, The liquid-to-solid ratio of the slurry is 1:1 to 20:1; the concentration of hydrogen peroxide in the slurry is 1 to 20 wt%, and the concentration of NH4 is... + The concentration is 0.05~0.20 mol / L.

7. The process for selectively extracting titanium from red mud as described in claim 1, characterized in that, The reaction temperature is 5~45℃, and the reaction time is 5~70min.

8. The process for extracting titanium from red mud as described in claim 1, characterized in that, It also includes the following steps: The titanium-rich solution was boiled, and the precipitated metatitanic acid was calcined at 450~750℃ to obtain anatase titanium dioxide with TiO2 > 90%.

9. The process for extracting titanium from red mud as described in claim 1, characterized in that, It also includes the following steps: Nano-TiO2 was synthesized by hydrothermal reaction of titanium-rich solution at 170~240℃.

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