Method for comprehensive utilization of titanium dioxide waste residue

Abstract

Disclosed is a method for the comprehensive utilization of titanium dioxide waste residue. The method comprises: mixing titanium dioxide waste residue with water, adding a reducing agent to obtain a first solid-liquid mixture, and separating same to obtain a first solid and a first filtrate; adjusting the pH of the first filtrate to 5.0-6.0 to obtain a second solid-liquid mixture, and separating same to obtain a second solid and a second filtrate; subjecting the second solid to washing and an alkali solution treatment to obtain a sodium metaaluminate solution and a crude titanium solid, subjecting the sodium metaaluminate solution to concentration and crystallization to obtain a sodium metaaluminate solid, and subjecting the crude titanium solid to washing and purification to obtain a high-purity titanium product and a rare earth metal; adding a sodium sulfide solution to the second filtrate to obtain a third solid-liquid mixture, and separating same to obtain a third solid and a third filtrate; adjusting the pH of the third filtrate to 5.0-6.0 to obtain a fourth solid-liquid mixture, and separating same to obtain a fourth solid and a fourth filtrate; and using the fourth filtrate to prepare iron phosphate, iron oxalate and / or ferrous sulfate. In the method, a series of high-purity basic chemical raw materials can be obtained by subjecting titanium dioxide waste residue to a classification treatment.

Description

A method for comprehensive utilization of titanium dioxide waste Technical Field

[0001] This invention relates to the field of solid waste recycling technology, and in particular to a method for the comprehensive utilization of titanium dioxide waste residue. Background Technology

[0002] In the production of titanium dioxide using the sulfuric acid process, a series of byproducts are generated. After acidolysis, ilmenite reacts with concentrated sulfuric acid to produce ferrous sulfate, sulfur dioxide, titanium sulfate, and water. These substances undergo flocculation and sedimentation to yield titanium oxysulfate and acid-hydrolyzed titanium solution. The ferrous sulfate content in the titanium solution affects the particle size and distribution of the subsequently hydrolyzed metatitanic acid, as well as the slurry filtration and washing effects. Therefore, it needs to be removed during the crystallization of the titanium solution to effectively control the ferrous sulfate content.

[0003] Ferrous sulfate obtained from titanium dioxide solution through a single crystallization process has high purity and can be directly used to produce high-value-added products such as ferric phosphate, polyferric sulfate, and iron oxide red. After titanium extraction, the remaining mother liquor mainly contains sulfuric acid, residual titanium sulfate, ferrous sulfate, and various soluble and insoluble impurities. This mother liquor is concentrated by evaporation, followed by solid-liquid separation to obtain concentrated sulfuric acid and titanium dioxide waste residue. The titanium dioxide waste residue has a high impurity content and is typically disposed of as solid waste.

[0004] In related technologies, titanium dioxide waste residue is typically handed over to sulfuric acid plants for sulfuric acid production, and after decomposition, it is separately fed into sulfuric acid slag and sulfuric acid. Systematic analysis revealed that titanium dioxide waste residue contains a large amount of iron compounds and a small amount of unreacted titanium compounds, as well as trace amounts of rare earth metals, such as germanium and gallium, and trace amounts of precious metals. If companies hand over titanium dioxide waste residue to sulfuric acid plants for treatment, they usually incur additional disposal costs, increasing their expenses and resulting in low utilization rates of valuable elements within the waste residue. Summary of the Invention

[0005] This invention discloses a method for the comprehensive utilization of titanium dioxide waste residue, in order to solve the technical problem in related technologies where titanium dioxide waste residue is used to produce sulfuric acid, resulting in low utilization of valuable elements in the titanium dioxide waste residue.

[0006] To solve the above problems, the present invention adopts the following technical solution:

[0007] The present invention provides a method for comprehensively utilizing titanium dioxide waste residue, comprising the following steps:

[0008] Step 100: Mix titanium dioxide waste residue with water to obtain solid waste liquid. Add a reducing agent to the solid waste liquid to reduce ferric ions in the solution to ferrous ions and reduce tetravalent titanium ions in the solution to ferric ions, thereby obtaining a first solid-liquid mixture. Separate the first solid-liquid mixture to obtain a first solid and a first filtrate.

[0009] The reducing agent is iron powder, and the amount of iron powder added is 1 to 10% of the weight of titanium dioxide waste residue. After the iron powder is added, the pH value of the solid waste liquid is maintained at 1 to 2.

[0010] Step 200: Adjust the pH of the first filtrate to 5.0~6.0 to obtain a second solid-liquid mixture. Separate the second solid-liquid mixture to obtain a second solid and a second filtrate.

[0011] Step 300: The second solid is washed and treated with alkaline solution to obtain sodium aluminate solution and crude titanium solid. The sodium aluminate solution is concentrated and crystallized to obtain sodium aluminate solid, and the crude titanium solid is washed and purified to obtain high-purity titanium product and rare earth metal.

[0012] Step 400: Add sodium sulfide solution to the second filtrate to obtain a third solid-liquid mixture. Separate the third solid-liquid mixture to obtain a third solid and a third filtrate; wherein the third solid is a metal ion precipitate.

[0013] Step 500: Adjust the pH of the third filtrate to 5.0~6.0 to obtain a fourth solid-liquid mixture. Separate the fourth solid-liquid mixture to obtain a fourth solid and a fourth filtrate; wherein the fourth solid is a precipitate containing calcium and magnesium.

[0014] Step 600: The fourth filtrate is a ferric sulfate solution, which is used to prepare ferric phosphate, ferric oxalate and / or ferrous sulfate.

[0015] The technical solution adopted in this invention can achieve the following beneficial effects:

[0016] Firstly, this invention provides a method for comprehensively utilizing titanium dioxide waste residue. By classifying the waste residue, multiple elements can be extracted, yielding a series of high-purity basic chemical raw materials. This significantly improves the economic value of the waste residue and solves the technical problem of low utilization rate of valuable elements in the waste residue when used for sulfuric acid production. Furthermore, this method achieves the graded extraction of multiple elements simply by selecting appropriate precipitants and / or adjusting the pH of the solution. It requires minimal equipment investment, produces no harmful emissions, and allows for the recycling of added reagents, making it a green, efficient, and low-cost method for treating titanium dioxide waste residue.

[0017] Secondly, this invention utilizes a method for treating titanium dioxide waste residue. Adding iron powder to the solid waste liquid reduces ferric ions to ferrous ions, and simultaneously reduces tetravalent titanium ions to ferric ions. Ferrous ions and ferric titanium ions can form precipitates under different pH conditions, facilitating selective precipitation and separation of the two ions by adjusting the pH of the solution. Furthermore, the addition of iron powder can consume some of the acid in the solid waste liquid, maintaining the pH of the solid waste liquid at 1-2. When adjusting the pH of the first filtrate in step 200, the amount of alkali solution added can be reduced, further lowering the treatment cost.

[0018] Thirdly, this invention comprehensively utilizes the method of titanium dioxide waste residue. After adding iron powder, the pH value of the solid waste liquid is maintained at 1-2. Under this pH condition, neither ferrous nor titanium ions will precipitate, thereby reducing the metal element content in the first solid obtained from the separation of the first solid-liquid mixture, allowing the metal elements to be preserved in the solution primarily as ions. Specifically, the first solid obtained from the separation of the first solid-liquid mixture mainly contains clay, sand, and gravel, which can be used in brick factories for brick making. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 is a process flow diagram of the comprehensive utilization of titanium dioxide waste residue in an embodiment of this application. Detailed Implementation

[0021] In related technologies, titanium dioxide waste residue is typically handed over to sulfuric acid plants for sulfuric acid production. After the titanium dioxide waste residue is decomposed through combustion, the sulfur-containing components are recovered, while the remaining elements all enter the sulfuric acid slag. Furthermore, the sulfuric acid slag can also be used for iron smelting, and the remaining elements in the titanium dioxide ultimately enter the iron smelting waste residue. This method has a low utilization rate of valuable elements in the titanium dioxide waste residue, with most of them entering the waste residue and ultimately being discarded.

[0022] This application presents a method for comprehensively utilizing titanium dioxide waste residue. By classifying and processing the titanium dioxide waste residue, a series of high-purity basic chemical raw materials can be obtained, which greatly improves the economic value of titanium dioxide waste residue.

[0023] As shown in Figure 1, the method for comprehensively utilizing titanium dioxide waste residue in this application includes the following steps:

[0024] Step 100: Mix the titanium dioxide waste residue with water to obtain a solid-liquid mixture. For example, the solid-liquid ratio of the titanium dioxide waste residue to water is 1:2 to 5, and the water is hot water at 60 to 80°C. Using hot water to dissolve the titanium dioxide waste residue helps to accelerate its dissolution. Preferably, the solid-liquid ratio of the titanium dioxide waste residue to water is 1:2, or 1:3, or 1:4, or 1:5.

[0025] A reducing agent is added to the solid-containing waste liquid to reduce ferric ions to ferrous ions and tetravalent titanium ions to ferric ions, resulting in a first solid-liquid mixture. This mixture is then subjected to solid-liquid separation to obtain a first solid and a first filtrate. The first solid mainly contains clay and sand, and can be used in brick factories.

[0026] Preferably, the reducing agent is iron powder, and the amount of iron powder added is 1-10% of the weight of the titanium dioxide waste residue, and the addition of iron powder maintains the pH value of the solid waste liquid at 1-2. Preferably, the addition of iron powder maintains the pH value of the solid waste liquid at 1.5.

[0027] Ferric and tetravalent titanium ions readily co-precipitate at pH 2-3, making their separation difficult. This application addresses this issue by adding iron powder, which reduces ferric ions to ferrous ions and simultaneously reduces tetravalent titanium ions to ferric ions. Ferric and tetravalent titanium ions can then precipitate separately under different pH conditions, facilitating selective precipitation separation by adjusting the pH of the solution.

[0028] On the other hand, by adding iron powder, the iron powder can also consume some of the acid in the solid waste liquid, so that the pH value of the solid waste liquid is maintained at 1~2. When adjusting the pH value of the first filtrate in step 200, the amount of alkali added can be reduced, further reducing the treatment cost.

[0029] The addition of iron powder in this application maintains the pH value of the solid waste liquid at 1-2. Under this pH condition, neither ferrous nor titanium ions will precipitate, thereby reducing the metal element content in the first solid obtained from the separation of the first solid-liquid mixture, allowing the metal elements to be preserved in the solution primarily as ions. Specifically, the first solid obtained from the separation of the first solid-liquid mixture mainly contains clay, sand, and gravel, and can be used in brick factories for brick making.

[0030] Step 200: Adjust the pH of the first filtrate to 5.0~6.0 to obtain a second solid-liquid mixture. Separate the second solid-liquid mixture to obtain a second solid and a second filtrate.

[0031] Preferably, the substance used to adjust the pH is one or more of ammonia, sodium hydroxide, potassium hydroxide, and sodium carbonate. More preferably, the pH of the first filtrate is adjusted to 5.5. When the pH of the first filtrate is adjusted to 5.0-6.0, flocculent precipitate begins to appear in the first filtrate. At this time, trivalent titanium ions, aluminum ions, and rare earth ions in the first filtrate form precipitates.

[0032] When the pH rises to 4.5, oxygen in the air easily oxidizes ferrous ions to ferric ions. Therefore, in this step, both the pH adjustment and solid-liquid separation operations are performed under nitrogen protection to avoid the problem of oxygen in the air easily oxidizing ferrous ions to ferric ions.

[0033] Step 300: The second solid is washed and treated with alkaline solution to obtain sodium aluminate solution and crude titanium solid. The sodium aluminate solution is concentrated and crystallized to obtain sodium aluminate solid, and the crude titanium solid is washed and purified to obtain high-purity titanium product and rare earth metal.

[0034] Preferably, after the second solid is washed, the added alkaline solution is sodium hydroxide and / or potassium hydroxide, and the pH value of the mixture obtained after mixing the second solid and the alkaline solution is 12. After adding the alkaline solution, aluminum ions dissolve in the alkaline solution to form a sodium aluminate solution; the remaining solid is crude titanium solid containing rare earth ions.

[0035] More preferably, sodium aluminate solution can be concentrated and crystallized to obtain solid sodium aluminate. The concentration and crystallization conditions of sodium aluminate solution can be existing technology and will not be described in detail here. The obtained solid sodium aluminate can be used as a flocculant for water treatment, can be used in the preparation of aluminate cement for building materials, and can also be used as an aluminum source for various aluminum compounds (such as aluminum sulfate, supported alumina catalysts, aluminum hydroxide, etc.).

[0036] In addition to titanium, the crude titanium solid also contains rare earth ions. Further separation of the crude titanium solid is required. Preferably, dilute acid is added to the crude titanium solid for washing to obtain a fifth solid-liquid mixture. This fifth solid-liquid mixture is then subjected to solid-liquid separation to obtain a fifth solid and a fifth filtrate. The fifth solid is high-purity titanium, and the fifth filtrate is used to extract and purify rare earth elements.

[0037] Since the remaining elements have been separated, the fifth solid obtained is high-purity titanium with a purity of up to 99.85%. High-purity titanium can be applied in high-value-added fields such as semiconductors, biomedicine, new energy, and precision manufacturing.

[0038] For example, various rare earth elements can be separated using existing methods such as solvent extraction, fractional crystallization, precipitation, and ion exchange chromatography. The separated and recovered rare earth elements can be used in multiple fields such as permanent magnet materials, luminescent materials, catalysts, and biomedicine.

[0039] Alternatively, the dilute acid can be one or more of dilute sulfuric acid, dilute phosphoric acid, and dilute hydrochloric acid, with a concentration of 3-10% and a solid-liquid ratio of crude titanium solid to dilute acid of 1:2-4.

[0040] Step 400: Add sodium sulfide solution to the second filtrate to obtain a third solid-liquid mixture. Perform solid-liquid separation on the third solid-liquid mixture to obtain a third solid and a third filtrate. The third solid is a metal ion precipitate.

[0041] The second filtrate mainly contains ferrous ions, vanadium ions, aluminum ions, copper ions, zinc ions, magnesium ions, and calcium ions, as well as trace amounts of lead ions and arsenic ions. By adding sodium sulfide solution to the second filtrate, vanadium ions, aluminum ions, copper ions, zinc ions, lead ions, and arsenic ions can be precipitated and separated.

[0042] Since the second filtrate contains ferrous ions, all operations in this step are carried out under nitrogen protection to avoid the problem that oxygen in the air can easily oxidize ferrous ions to ferric ions.

[0043] Preferably, before adding sodium sulfide solution to the second filtrate, the method further includes a step of detecting the content of vanadium ions, aluminum ions, copper ions, zinc ions, lead ions, and arsenic ions in the second filtrate. For example, the content of vanadium ions, aluminum ions, copper ions, zinc ions, lead ions, and arsenic ions in the second filtrate can be detected by inductively coupled plasma mass spectrometry (ICP-MS).

[0044] The amount of sodium sulfide to be added can be determined based on the content of vanadium, aluminum, copper, zinc, lead, and arsenic ions in the second filtrate. Preferably, the amount of sodium sulfide added is the theoretically required amount for complete precipitation of vanadium, aluminum, copper, zinc, lead, and arsenic ions. It is also known that an excess of sodium sulfide may be added appropriately.

[0045] Preferably, a dilute acid is added to the third solid, and hydrogen sulfide is absorbed with an alkaline solution to obtain sodium sulfide. The obtained sodium sulfide is recycled back to step 400 to precipitate vanadium ions, aluminum ions, copper ions, zinc ions, lead ions, and arsenic ions. The dilute acid added to the third solid is one or more of dilute sulfuric acid, dilute phosphoric acid, and dilute hydrochloric acid, and the concentration of the dilute acid is 15-30%.

[0046] For example, the alkaline solution used to absorb hydrogen sulfide is sodium hydroxide. The resulting solution containing vanadium ions, aluminum ions, copper ions, zinc ions, lead ions, and arsenic ions can be further separated and purified through multi-step enrichment to obtain copper salts, zinc salts, lead salts, and arsenic salts that can be used in high-value-added fields.

[0047] Step 500: Adjust the pH of the third filtrate to 5.0-6.0 to obtain a fourth solid-liquid mixture. Perform solid-liquid separation on the fourth solid-liquid mixture to obtain a fourth solid and a fourth filtrate. The fourth solid is a precipitate containing calcium and magnesium.

[0048] The third filtrate mainly contains ferrous, calcium, and magnesium ions. To avoid the problem of oxygen in the air oxidizing ferrous ions to ferric ions, all operations are performed under nitrogen protection.

[0049] Preferably, hydrofluoric acid and / or ammonia are added to the third filtrate, and the pH of the third filtrate is adjusted to 5. Under this pH condition, calcium and magnesium ions can be precipitated to obtain calcium fluoride and magnesium fluoride.

[0050] Preferably, dilute acid is added to the fourth solid to obtain hydrofluoric acid, and the obtained hydrofluoric acid is recycled back to step 500 to precipitate calcium and magnesium ions. The dilute acid added to the third solid is one or more of dilute sulfuric acid, dilute phosphoric acid, and dilute hydrochloric acid, and the concentration of the dilute acid is 15-30%.

[0051] The resulting solution containing calcium and magnesium ions can be further separated and purified through multi-step enrichment to obtain calcium and magnesium salts that can be used in high-value-added fields.

[0052] Step 600: The fourth filtrate is a ferric sulfate solution, which is used to prepare ferric phosphate, ferric oxalate and / or ferrous sulfate.

[0053] The fourth filtrate mainly contains ferrous sulfate and trace impurities. This liquid can be used to prepare iron salts such as ferric phosphate and ferric oxalate, and it can also be recrystallized to obtain high-purity ferrous sulfate. For example, ferric phosphate can be used to prepare lithium iron phosphate cathode materials, ferric oxalate can be used to prepare magnetic materials, and high-purity ferrous sulfate can be used in water treatment, semiconductors, agriculture, and other fields.

[0054] The method for comprehensive utilization of titanium dioxide waste provided in this application will be described in detail below with reference to specific embodiments and application scenarios.

[0055] Analysis of titanium dioxide waste residue shows that it contains: 58% ferrous sulfate, 6% unreacted titanium compounds (TiO2, TiOSO4, etc.), 5% other metal sulfates (Al2(SO4)3, MnSO4, MgSO4, CaSO4, etc.), 3% free sulfuric acid and acidic wastewater, 6% silicates and insoluble impurities (SiO2, Al2O3, etc.), and 22% moisture. Example 1

[0056] This embodiment of the method for comprehensively utilizing titanium dioxide waste includes the following steps:

[0057] Step 100: Mix the above-mentioned titanium dioxide waste residue with hot water at 80℃, with a solid-liquid ratio of 1:2. After stirring evenly, add iron powder to the solid waste liquid, the amount of iron powder added being 6% of the weight of the titanium dioxide waste residue, and maintaining the pH value of the solid waste liquid at 1.5 after the addition of iron powder. After reacting for 60 minutes under stirring conditions, the iron powder reduces the ferric ions in the solution to ferrous ions, and simultaneously reduces the tetravalent titanium ions in the solution to trivalent titanium ions, obtaining a first solid-liquid mixture. Separate the first solid-liquid mixture to obtain a first solid and a first filtrate. The first solid mainly contains clay and sand, which is used in brick factories.

[0058] Step 200: Under a nitrogen atmosphere, ammonia water is added to the first filtrate, and the pH of the first filtrate is adjusted to 5.5. After stirring and reacting at room temperature for 30 minutes, a second solid-liquid mixture is obtained. Under a nitrogen atmosphere, the second solid-liquid mixture is subjected to solid-liquid separation to obtain a second solid and a second filtrate.

[0059] Step 300: After washing the second solid with water, sodium hydroxide solution is added to the second solid. The pH of the mixture obtained after mixing the second solid with the alkaline solution is 12. After stirring and reacting at room temperature for 30 minutes, sodium aluminate solution and crude titanium solid are obtained. Sodium aluminate solid is obtained after concentrating and crystallizing the sodium aluminate solution.

[0060] A 5% dilute sulfuric acid solution was added to crude titanium solid, with a solid-liquid ratio of 1:3. After stirring and reacting at room temperature for 30 minutes, a rare earth metal solution and a high-purity titanium product were obtained. ICP analysis showed that the purity of the high-purity titanium product was 99.15%.

[0061] Step 400: The contents of vanadium, aluminum, copper, zinc, lead, and arsenic ions in the second filtrate were determined by ICP-MS to be 62 ppm, 307 ppm, 0.5 ppm, 24 ppm, 2.6 ppm, and 0.2 ppm, respectively. Under a nitrogen atmosphere, sodium sulfide solution was added to the second filtrate. The amount of sodium sulfide added was the theoretical amount required to completely precipitate vanadium, aluminum, copper, zinc, lead, and arsenic ions. After stirring and reacting at room temperature for 30 min, a third solid-liquid mixture was obtained. Under a nitrogen atmosphere, the third solid-liquid mixture was subjected to solid-liquid separation to obtain a third solid and a third filtrate.

[0062] The contents of vanadium, aluminum, copper, zinc, lead, and arsenic ions in the third filtrate were determined by ICP-MS to be 0.3 ppm, 2.3 ppm, 0 ppm, 3.1 ppm, 1.8 ppm, and 0 ppm, respectively.

[0063] The third solid is a precipitate containing vanadium, aluminum, copper, zinc, lead, and arsenic ions. 20% dilute sulfuric acid is added to the third solid, with a solid-liquid ratio of 1:2 between the third solid and the dilute sulfuric acid. Sodium hydroxide is used to absorb the overflowing hydrogen sulfide and obtain sodium sulfide. The obtained sodium sulfide can be added again to step 400 to precipitate vanadium, aluminum, copper, zinc, lead, and arsenic ions. After multiple enrichment, vanadium, aluminum, copper, zinc, lead, and arsenic ions are used for further separation and purification.

[0064] Step 500: Under a nitrogen atmosphere, hydrofluoric acid is added to the third filtrate, and the pH of the third filtrate is adjusted to 5.0. After standing at room temperature for 60 minutes, a fourth solid-liquid mixture is obtained. Under a nitrogen atmosphere, the fourth solid-liquid mixture is subjected to solid-liquid separation to obtain a fourth solid and a fourth filtrate.

[0065] Add 20% dilute sulfuric acid to the fourth solid, with a solid-liquid ratio of 1:2 to obtain hydrofluoric acid. The obtained hydrofluoric acid is recycled back to step 500 to precipitate calcium and magnesium ions.

[0066] Step 600: Under a nitrogen atmosphere, recrystallize the fourth filtrate to obtain high-purity ferrous sulfate. The purity of the ferrous sulfate was determined to be 99.91% by potassium dichromate titration. Example 2

[0067] This embodiment of the method for comprehensively utilizing titanium dioxide waste includes the following steps:

[0068] Step 100: Mix the above-mentioned titanium dioxide waste residue with hot water at 80℃, with a solid-liquid ratio of 1:2. After stirring evenly, add iron powder to the solid waste liquid, the amount of iron powder added being 10% of the weight of the titanium dioxide waste residue, and maintaining the pH value of the solid waste liquid at 2 after the addition of iron powder. After reacting for 60 minutes under stirring conditions, the iron powder reduces the ferric ions in the solution to ferrous ions, and simultaneously reduces the tetravalent titanium ions in the solution to trivalent titanium ions, obtaining a first solid-liquid mixture. Separate the first solid-liquid mixture to obtain a first solid and a first filtrate. The first solid mainly contains clay and sand, which is used in brick factories.

[0069] Step 200: Under a nitrogen atmosphere, ammonia water is added to the first filtrate, and the pH of the first filtrate is adjusted to 5. After stirring and reacting at room temperature for 30 minutes, a second solid-liquid mixture is obtained. Under a nitrogen atmosphere, the second solid-liquid mixture is subjected to solid-liquid separation to obtain a second solid and a second filtrate.

[0070] Step 300: After washing the second solid with water, sodium hydroxide solution is added to the second solid. The pH of the mixture obtained after mixing the second solid with the alkaline solution is 12. After stirring and reacting at room temperature for 30 minutes, sodium aluminate solution and crude titanium solid are obtained. Sodium aluminate solid is obtained after concentrating and crystallizing the sodium aluminate solution.

[0071] A 5% dilute sulfuric acid solution was added to crude titanium solid, with a solid-liquid ratio of 1:3. After stirring and reacting at room temperature for 30 minutes, a rare earth metal solution and a high-purity titanium product were obtained. ICP analysis showed that the purity of the high-purity titanium product was 98.5%.

[0072] Step 400: The contents of vanadium, aluminum, copper, zinc, lead, and arsenic ions in the second filtrate were determined to be 80 ppm, 399 ppm, 0.7 ppm, 52 ppm, 5.5 ppm, and 2.2 ppm, respectively. Under a nitrogen atmosphere, sodium sulfide solution was added to the second filtrate. The amount of sodium sulfide added was the theoretical amount required to completely precipitate vanadium, aluminum, copper, zinc, lead, and arsenic ions. After stirring and reacting at room temperature for 30 minutes, a third solid-liquid mixture was obtained. Under a nitrogen atmosphere, the third solid-liquid mixture was subjected to solid-liquid separation to obtain a third solid and a third filtrate.

[0073] The concentrations of vanadium, aluminum, copper, zinc, lead, and arsenic ions in the third filtrate were determined by ICP-MS to be 0.4 ppm, 5.3 ppm, 0.1 ppm, 4.0 ppm, 1.9 ppm, and 0 ppm, respectively.

[0074] The third solid is a precipitate containing vanadium, aluminum, copper, zinc, lead, and arsenic ions. 20% dilute sulfuric acid is added to the third solid, with a solid-liquid ratio of 1:2 between the third solid and the dilute sulfuric acid. Sodium hydroxide is used to absorb the overflowing hydrogen sulfide and obtain sodium sulfide. The obtained sodium sulfide can be added again to step 400 to precipitate vanadium, aluminum, copper, zinc, lead, and arsenic ions. After multiple enrichment, vanadium, aluminum, copper, zinc, lead, and arsenic ions are used for further separation and purification.

[0075] Step 500: Under a nitrogen atmosphere, hydrofluoric acid is added to the third filtrate, and the pH of the third filtrate is adjusted to 5.5. After standing at room temperature for 60 minutes, a fourth solid-liquid mixture is obtained. Under a nitrogen atmosphere, the fourth solid-liquid mixture is subjected to solid-liquid separation to obtain a fourth solid and a fourth filtrate.

[0076] Add 20% dilute sulfuric acid to the fourth solid, with a solid-liquid ratio of 1:2 to obtain hydrofluoric acid. The obtained hydrofluoric acid is recycled back to step 500 to precipitate calcium and magnesium ions.

[0077] Step 600: Under a nitrogen atmosphere, recrystallize the fourth filtrate to obtain high-purity ferrous sulfate. The purity of the ferrous sulfate was determined to be 99.95% by potassium dichromate titration. Example 3

[0078] This embodiment of the method for comprehensively utilizing titanium dioxide waste includes the following steps:

[0079] Step 100: Mix the above-mentioned titanium dioxide waste residue with hot water at 80℃, with a solid-liquid ratio of 1:2. After stirring evenly, add iron powder to the solid waste liquid, the amount of iron powder added being 1% of the weight of the titanium dioxide waste residue, and maintaining the pH value of the solid waste liquid at 1 after the addition of iron powder. After reacting for 60 minutes under stirring conditions, the iron powder reduces the ferric ions in the solution to ferrous ions, and simultaneously reduces the tetravalent titanium ions in the solution to trivalent titanium ions, obtaining a first solid-liquid mixture. Separate the first solid-liquid mixture to obtain a first solid and a first filtrate. The first solid mainly contains clay and sand, which is used in brick factories.

[0080] Step 200: Under a nitrogen atmosphere, ammonia water is added to the first filtrate, and the pH of the first filtrate is adjusted to 6. After stirring and reacting at room temperature for 30 minutes, a second solid-liquid mixture is obtained. Under a nitrogen atmosphere, the second solid-liquid mixture is subjected to solid-liquid separation to obtain a second solid and a second filtrate.

[0081] Step 300: After washing the second solid with water, sodium hydroxide solution is added to the second solid. The pH of the mixture obtained after mixing the second solid with the alkaline solution is 12. After stirring and reacting at room temperature for 30 minutes, sodium aluminate solution and crude titanium solid are obtained. Sodium aluminate solid is obtained after concentrating and crystallizing the sodium aluminate solution.

[0082] A 5% dilute sulfuric acid solution was added to crude titanium solid, with a solid-liquid ratio of 1:3. After stirring and reacting at room temperature for 30 minutes, a rare earth metal solution and a high-purity titanium product were obtained. ICP analysis showed that the purity of the high-purity titanium product was 99.85%.

[0083] Step 400: The contents of vanadium ions, aluminum ions, copper ions, zinc ions, lead ions, and arsenic ions in the second filtrate were determined to be 58 ppm, 298 ppm, 0.3 ppm, 19 ppm, 1.1 ppm, and 0.1 ppm, respectively. Under a nitrogen atmosphere, sodium sulfide solution was added to the second filtrate. The amount of sodium sulfide added was the theoretical amount required to completely precipitate vanadium ions, aluminum ions, copper ions, zinc ions, lead ions, and arsenic ions. After stirring and reacting at room temperature for 30 minutes, a third solid-liquid mixture was obtained. Under a nitrogen atmosphere, the third solid-liquid mixture was subjected to solid-liquid separation to obtain a third solid and a third filtrate.

[0084] The contents of vanadium, aluminum, copper, zinc, lead, and arsenic ions in the third filtrate were determined by ICP-MS to be 0.2 ppm, 2.0 ppm, 0 ppm, 2.1 ppm, 1.2 ppm, and 0 ppm, respectively.

[0085] The third solid is a precipitate containing vanadium, aluminum, copper, zinc, lead, and arsenic ions. 20% dilute sulfuric acid is added to the third solid, with a solid-liquid ratio of 1:2 between the third solid and the dilute sulfuric acid. Sodium hydroxide is used to absorb the overflowing hydrogen sulfide and obtain sodium sulfide. The obtained sodium sulfide can be added again to step 400 to precipitate vanadium, aluminum, copper, zinc, lead, and arsenic ions. After multiple enrichment, vanadium, aluminum, copper, zinc, lead, and arsenic ions are used for further separation and purification.

[0086] Step 500: Under a nitrogen atmosphere, hydrofluoric acid is added to the third filtrate, and the pH of the third filtrate is adjusted to 6.0. After standing at room temperature for 60 minutes, a fourth solid-liquid mixture is obtained. Under a nitrogen atmosphere, the fourth solid-liquid mixture is subjected to solid-liquid separation to obtain a fourth solid and a fourth filtrate.

[0087] Add 20% dilute sulfuric acid to the fourth solid, with a solid-liquid ratio of 1:2 to obtain hydrofluoric acid. The obtained hydrofluoric acid is recycled back to step 500 to precipitate calcium and magnesium ions.

[0088] Step 600: Under a nitrogen atmosphere, recrystallize the fourth filtrate to obtain high-purity ferrous sulfate. The purity of the ferrous sulfate was determined to be 99.98% by potassium dichromate titration.

Claims

1. A method for comprehensively utilizing titanium dioxide waste residue, characterized in that, Includes the following steps: Step 100: Mix titanium dioxide waste residue with water to obtain solid waste liquid. Add a reducing agent to the solid waste liquid to reduce ferric ions in the solution to ferrous ions and reduce tetravalent titanium ions in the solution to ferric ions, thereby obtaining a first solid-liquid mixture. Separate the first solid-liquid mixture to obtain a first solid and a first filtrate. The reducing agent is iron powder, and the amount of iron powder added is 1 to 10% of the weight of titanium dioxide waste residue. After the iron powder is added, the pH value of the solid waste liquid is maintained at 1 to 2. Step 200: Adjust the pH of the first filtrate to 5.0~6.0 to obtain a second solid-liquid mixture. Separate the second solid-liquid mixture to obtain a second solid and a second filtrate. Step 300: The second solid is washed and treated with alkaline solution to obtain sodium aluminate solution and crude titanium solid. The sodium aluminate solution is concentrated and crystallized to obtain sodium aluminate solid, and the crude titanium solid is washed and purified to obtain high-purity titanium product and rare earth metal. Step 400: Add sodium sulfide solution to the second filtrate to obtain a third solid-liquid mixture. Separate the third solid-liquid mixture to obtain a third solid and a third filtrate; wherein the third solid is a metal ion precipitate. Step 500: Adjust the pH of the third filtrate to 5.0~6.0 to obtain a fourth solid-liquid mixture. Separate the fourth solid-liquid mixture to obtain a fourth solid and a fourth filtrate; wherein the fourth solid is a precipitate containing calcium and magnesium. Step 600: The fourth filtrate is a ferric sulfate solution, which is used to prepare ferric phosphate, ferric oxalate and / or ferrous sulfate.

2. The method for comprehensive utilization of titanium dioxide waste residue according to claim 1, characterized in that, Step 100: The solid-liquid ratio of titanium dioxide waste residue to water is 1:2~5, and the water is hot water at 60~80℃; And / or the first solid obtained in step 100 is used in a brick factory to make bricks.

3. The method for comprehensive utilization of titanium dioxide waste residue according to claim 1, characterized in that, Step 200 is carried out under nitrogen protection, and the substance used to adjust the pH is one or more of ammonia, sodium hydroxide, potassium hydroxide, and sodium carbonate.

4. The method for comprehensive utilization of titanium dioxide waste residue according to claim 1, characterized in that, In step 300, after the second solid is washed, the added alkaline solution is sodium hydroxide and / or potassium hydroxide, and the pH value of the mixture obtained after mixing the second solid with the alkaline solution is 12. The mixture obtained after mixing the second solid with the alkaline solution is sodium aluminate solution and crude titanium solid.

5. The method for comprehensive utilization of titanium dioxide waste residue according to claim 4, characterized in that, A fifth solid-liquid mixture is obtained by washing crude titanium solid with dilute acid. The fifth solid-liquid mixture is then subjected to solid-liquid separation to obtain a fifth solid and a fifth filtrate. The fifth solid is high-purity titanium, and the fifth filtrate is used to extract and purify rare earth elements. The dilute acid is one or more of dilute sulfuric acid, dilute phosphoric acid, and dilute hydrochloric acid, with a concentration of 3-10%. The solid-liquid ratio of crude titanium solid to dilute acid is 1:2-4.

6. The method for comprehensive utilization of titanium dioxide waste residue according to claim 1, characterized in that, Step 400 is performed under nitrogen protection and also includes the step of detecting the content of vanadium ions, aluminum ions, copper ions, zinc ions, lead ions and arsenic ions in the second filtrate.

7. The method for comprehensive utilization of titanium dioxide waste residue according to claim 6, characterized in that, In step 400, the amount of sodium sulfide added satisfies the theoretical amount required for precipitating vanadium ions, aluminum ions, copper ions, zinc ions, lead ions, and arsenic ions.

8. The method for comprehensive utilization of titanium dioxide waste residue according to claim 7, characterized in that, Step 400 also includes the following process: adding dilute acid to the third solid and absorbing hydrogen sulfide with alkaline solution to obtain sodium sulfide. The obtained sodium sulfide is recycled back to step 400 to precipitate vanadium ions, aluminum ions, copper ions, zinc ions, lead ions and arsenic ions. The dilute acid added to the third solid is one or more of dilute sulfuric acid, dilute phosphoric acid, and dilute hydrochloric acid, and the concentration of the dilute acid is 15-30%.

9. The method for comprehensive utilization of titanium dioxide waste residue according to claim 1, characterized in that, Step 500 is carried out under nitrogen protection, and the substance used to adjust the pH is hydrofluoric acid and / or ammonia.

10. The method for comprehensive utilization of titanium dioxide waste residue according to claim 9, characterized in that, Adding dilute acid to the fourth solid yields hydrofluoric acid, which is then recycled back to step 500 to precipitate calcium and magnesium ions. The dilute acid added to the third solid is one or more of dilute sulfuric acid, dilute phosphoric acid, and dilute hydrochloric acid, and the concentration of the dilute acid is 15-30%.

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