A method for comprehensive recycling of titanium-containing blast furnace slag leachate

Abstract

This invention discloses a method for the comprehensive recycling of titanium-containing blast furnace slag leachate, comprising the following steps: S1, titanium-containing blast furnace slag is crushed, roasted, and acid-leached to obtain titanium-rich material and leachate; S2, the pH of the leachate is adjusted with ammonia to obtain aluminum hydroxide and filtrate 1; S3, filtrate 1 is reacted with an oxidant to obtain manganese dioxide and filtrate 2; S4, filtrate 2 is adjusted with sodium hydroxide, and then sodium carbonate is added to react to obtain calcium and magnesium precipitate and filtrate 3; S5, filtrate 3 is adjusted with nitric acid and then separated by a bipolar membrane to obtain sodium hydroxide and nitric acid; S6, the calcium and magnesium precipitate is stirred with water and then reacted with carbon dioxide to obtain filtrate 4 and light calcium carbonate; S7, filtrate 4 is decomposed by heating to obtain basic magnesium carbonate. This invention not only achieves high-value utilization of titanium, calcium, magnesium, aluminum, and other elements in titanium-containing blast furnace slag, but also recycles the nitric acid, sodium hydroxide, ammonia, and carbon dioxide used, resulting in low production costs and high added value of the prepared products.

Description

Technical Field

[0001] This invention belongs to the field of comprehensive recycling of titanium-containing resources, and specifically relates to a method for comprehensive recycling of titanium-containing blast furnace slag leachate. Background Technology

[0002] The blast furnace ironmaking process using vanadium-titanium magnetite produces titanium-containing blast furnace slag with a complex mineral composition and structure. The titanium in this slag cannot be further recovered, nor can it be utilized using traditional blast furnace slag processing methods; it can only be stockpiled in slag yards. Titanium-containing blast furnace slag is a valuable titanium resource, but due to the lack of efficient processing technology, its large-scale accumulation places enormous pressure on environmental pollution control.

[0003] With the increasing scarcity of titanium resources and the growing emphasis on environmental protection, the resource utilization of titanium-containing blast furnace slag has been a key focus of domestic research. Currently, various technical routes have been developed, including acid hydrolysis, alkali dissolution, chlorination separation, and electrochemical molten salt electrolysis. However, these methods generally suffer from high production costs, the generation of new untreated wastewater and waste residue, and stringent reaction conditions.

[0004] Besides titanium, titanium-containing blast furnace slag also contains a large amount of impurities such as calcium, magnesium, aluminum, and silicon. To achieve large-scale utilization of titanium-containing blast furnace slag, a comprehensive resource recycling approach is necessary. Acid hydrolysis is considered a potential technology for large-scale processing of titanium-containing blast furnace slag due to its advantages such as high recoverability of elements, large processing capacity, and strong adaptability to raw materials. Acid hydrolysis can be divided into one-step and two-step methods. The one-step method involves leaching titanium and other acid-soluble substances together into a solution for further separation; the two-step method involves first leaching the impurities from the titanium-containing blast furnace slag and then recovering titanium from the leaching residue. Regardless of the method, both involve significant acid consumption and the challenge of recovering impurities such as calcium, magnesium, and aluminum. Therefore, the main obstacles to the industrial application of acid hydrolysis are: ① reducing acid consumption and lowering production costs; ② comprehensive recycling of elements such as calcium, magnesium, and aluminum, avoiding environmental problems; ③ a large market capacity and high added value for the produced products, facilitating large-scale processing.

[0005] Light calcium carbonate is an inorganic functional material prepared by chemical precipitation. Depending on the precipitation method and reagents used, it can be formulated into products with specific crystal forms, morphologies, and sizes. Compared to heavy calcium carbonate (a naturally occurring type of calcium carbonate), it has a lower density, larger settling volume, and more uniform particle size and morphology, making it widely applicable in daily chemicals, rubber, plastics, papermaking, and biomedicine. In 2022, the market size of light calcium carbonate in my country exceeded 13 billion yuan, with a demand of over 15 million tons.

[0006] Basic magnesium carbonate is a widely used chemical product characterized by its light weight, loose structure, and low relative density. It can be used as an additive and modifier in various chemical products such as flame retardants, electronic materials, ceramics, and glass. It can also be used to produce a series of magnesium chemical products, including magnesium oxide and high-purity magnesium slag. Basic magnesium carbonate is a major intermediate raw material. In 2022, my country's primary magnesium market consumption reached 13.5 billion yuan, with a primary magnesium production capacity of 1.4 million tons, accounting for 80% of global capacity.

[0007] Patent CN 102312102A discloses a comprehensive utilization method for titanium-containing blast furnace slag. Using titanium-containing blast furnace slag as raw material, hydrochloric acid leaching is used to obtain titanium-rich material. At the same time, aluminum hydroxide, magnesium oxide and calcium chloride products are obtained by graded precipitation, realizing the comprehensive recycling of resources. However, a large amount of acid and alkali are consumed in the recycling process, resulting in high production costs and low economic benefits.

[0008] Patent CN 111498855 A discloses a comprehensive utilization method for water-quenched blast furnace slag. The invention uses high-titanium blast furnace slag as raw material, employs nitric acid for leaching, and then controls precipitation in steps to obtain titanium dioxide, calcium sulfate, aluminum hydroxide, magnesium carbonate, and sodium nitrate products. This prior art uses sodium sulfate precipitation to obtain calcium sulfate, but calcium sulfate is only slightly soluble, with a solubility of 0.25 g / 100 g water (at room temperature). Because the reaction system is acidic, the dissolution of calcium sulfate is further aggravated. Therefore, the precipitate will inevitably contain calcium ions and sulfate ions, leading to a decrease in the purity of the subsequent precipitated product and a lower added value for the calcium sulfate product. Furthermore, using nitric acid as the leaching agent is problematic because titanium-containing blast furnace slag is highly alkaline, and the leaching process consumes a large amount of acid. Without considering the recycling of the leaching agent and precipitant, production costs would increase significantly. Moreover, the annual production of sodium nitrate is only a few hundred thousand tons, indicating a limited market capacity, which is not conducive to the large-scale development and utilization of titanium-containing blast furnace slag. Summary of the Invention

[0009] To address the problems of low added value, small market capacity, high acid and alkali consumption, and potential environmental pollution associated with existing methods for the comprehensive recycling of titanium-containing blast furnace slag, this invention provides a method for the comprehensive recycling of titanium-containing blast furnace slag leachate. This method utilizes titanium, calcium, magnesium, aluminum, and other elements in the titanium-containing blast furnace slag to achieve high added value, while recycling the nitric acid, sodium hydroxide, ammonia, and carbon dioxide used. This process has low production costs and produces high-value-added products, opening up a new technical route for the comprehensive recycling of titanium-containing blast furnace slag and offering significant economic and social benefits.

[0010] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0011] A method for comprehensive recycling of titanium-containing blast furnace slag leachate, the method comprising the following steps:

[0012] S1. Titanium-containing blast furnace slag is crushed, activated, roasted, and leached with nitric acid to obtain titanium-rich material and leachate;

[0013] S2. The leachate obtained in step S1 is adjusted to pH 4.5-5.5 with ammonia water, and then the solid and liquid are separated to obtain aluminum hydroxide and filtrate 1.

[0014] S3. After adding an oxidant to the filtrate 1 obtained in step S2 and reacting, solid-liquid separation is performed to obtain manganese dioxide and filtrate 2.

[0015] S4. Add sodium hydroxide solution to the filtrate 2 obtained in step S3 to adjust the pH to 12-13, then add sodium carbonate and react to separate the solid and liquid, to obtain calcium and magnesium precipitate and filtrate 3.

[0016] S5. Add nitric acid to the filtrate 3 obtained in step S4 to adjust the pH to 6-8, and then separate it through a bipolar membrane to obtain sodium hydroxide and nitric acid.

[0017] S6. Add water to the calcium and magnesium precipitate obtained in step S4, stir, and then pass carbon dioxide through to react. Then separate the solid and liquid to obtain filtrate 4 and light calcium carbonate.

[0018] S7. After heating and decomposing the filtrate 4 obtained in S6, solid-liquid separation is performed to obtain basic magnesium carbonate.

[0019] Preferably, in step S1, the titanium-containing blast furnace slag is a solid waste generated during the iron smelting process of vanadium-titanium magnetite. The titanium-containing blast furnace slag, after crushing, has a fineness of 80%–90% -200 mesh, and is roasted at a temperature of 800℃–900℃ for 1–2 hours.

[0020] The roasting treatment has the following effects: 1) It can oxidize the reduced-valence iron in the blast furnace slag to trivalent iron, avoiding the redox reaction after the subsequent addition of nitric acid, thereby preventing the generation of nitrogen oxide gas. 2) It can cause secondary crystallization of titanium-containing blast furnace slag, transforming it from a blocky form into a granular aggregate, which is beneficial for the leaching of calcium, magnesium, and aluminum in the titanium-containing blast furnace slag, thereby increasing the titanium dioxide content in the titanium-rich material. 3) It can weaken or eliminate the vitrification phenomenon of titanium-containing blast furnace slag, which is beneficial for the leaching of calcium, magnesium, and aluminum in the titanium-containing blast furnace slag, thereby increasing the titanium dioxide content in the titanium-rich material. 4) It can increase the crystallinity of titanium-containing blast furnace slag, enhance its reactivity, and increase the leaching rate of calcium, magnesium, and aluminum in the titanium-containing blast furnace slag, thereby increasing the titanium dioxide content in the titanium-rich material.

[0021] Preferably, in step S1, the reaction conditions for nitric acid leaching are as follows: 60% nitric acid and water are added to the roasted clinker, and the mixture is stirred and reacted under normal pressure, followed by solid-liquid separation; the amount of 60% nitric acid used is 1.5 to 2.5 times the mass of the roasted clinker, the amount of water used is 1.5 to 2.5 times the mass of the roasted clinker, the reaction temperature is 80 to 100°C, and the reaction time is 4 to 6 hours.

[0022] Preferably, in step S1, the leachate is obtained by solid-liquid separation after leaching blast furnace slag, and its elemental content is as follows: Ca: 40-50 g / L, Mg: 15-20 g / L, Al: 20-25 g / L, Mn: 2-3 g / L, NO3 ... Mn: 2-3 g / L, NO3: 40-50 g / L, Mg: 15-20 g / L, Mn: 2-3 g / L, NO3: 40-5 - :180~250g / L, Fe<0.005g / L, pH=1.5~2.0.

[0023] Preferably, in step S2, the concentration of ammonia water is 10-20%, and the ammonia water and the leachate are added dropwise into the reaction vessel in parallel. The pH of the reaction system is controlled at 4.5-5.5, the reaction temperature at 50-70℃, and the reaction time at 1-2 hours. The resulting aluminum hydroxide is granular, and the solid-liquid separation speed is fast. The addition of ammonia water to adjust the pH value in this invention has the following advantages: First, ammonia water is a weak base, which helps to adjust the pH of the reaction system during the aluminum precipitation process, avoiding excessively high local concentrations in the reaction system, which would lead to an increase in the content of impurity elements in the aluminum precipitation product; second, ammonium ions can be recovered and recycled in the subsequent calcium and magnesium precipitation process. The reaction equation for step S2 is:

[0024] Al(NO3)3+3NH3·H2O=Al(OH)3↓+3NH3NO3

[0025] Preferably, in step S3, the oxidant converts manganese ions into manganese dioxide precipitate under oxidizing conditions, and is one of hydrogen peroxide, oxygen, ozone, or air. Oxygen, ozone, and air are gas-liquid reactions; the amount of oxidizing gas added is controlled by the aeration time, and the manganese content in the oxidized liquid is tested to be within acceptable limits. The amount of hydrogen peroxide added is 1.05 to 1.1 times the theoretical amount. Since manganese dioxide is more stable at pH 7 to 8, the pH is adjusted to 7 to 8 with a 5% sodium hydroxide solution before the reaction, and then the oxidant is added or introduced.

[0026] Preferably, in step S4, the concentration of the sodium hydroxide solution is 30%, the precipitation temperature is 80–95°C, the pH of the solution is adjusted to 12–13, the amount of sodium carbonate added is 10–20 g / L, and the stirring reaction time is 0.5–1 h. This step mainly converts the calcium and magnesium ions in filtrate 2 into precipitates. Alternatively, the sodium hydroxide solution and sodium carbonate can be added simultaneously. The reaction equation for step S4 is:

[0027] Ca(NO3)2+2NaOH=Ca(OH)2↓+2NaNO3

[0028] Mg(NO3)2+2NaOH=Mg(OH)2↓+2NaNO3

[0029] Ca(NO3)2+Na2CO3=CaCO3↓+2NaNO3

[0030] NH3NO3+NaOH=NaNO3+NH3↑+H2O

[0031] Preferably, in step S5, the mass concentration of nitric acid is 40%–50%, and the pH of the solution is adjusted to 6–8. Since bipolar membrane operation requires a specific pH value, adding nitric acid to adjust the pH to the above range yields the best separation effect. After adjustment, the total content of polyvalent cations such as calcium, magnesium, aluminum, manganese, and iron in the solution is less than 0.005 g / L.

[0032] Preferably, in step S6, the amount of calcium and magnesium precipitate added to the water is 40-50 g / L, the stirring reaction time is 1 hour, the mechanical stirring speed is 400-600 r / min, and carbon dioxide is introduced to react until the pH of the slurry is 7-7.5. The reaction equation for step S6 is:

[0033] Ca(OH)₂ + CO₂ = CaCO₃↓ + H₂O

[0034] Mg(OH)₂ + 2CO₂ = Mg(HCO₃)₂

[0035] MgCO3 + CO2 + H2O = Mg(HCO3)2

[0036] Preferably, in step S6, the light calcium carbonate is washed at 50-80°C for 1-2 hours.

[0037] Preferably, in step S7, the pyrolysis temperature is 95℃~100℃, and the pyrolysis time is 1~2h. The reaction equation for step S7 is:

[0038] Mg(HCO3)2=MgCO3↓+CO2↑+H2O (thermal decomposition)

[0039] This invention achieves comprehensive recovery and utilization of elements such as calcium, magnesium, aluminum, and titanium in titanium-containing blast furnace slag, and has the following advantages compared with existing technologies:

[0040] 1) The invention employs a roasting activation treatment to improve the leaching effect of impurity elements calcium, magnesium, and aluminum. The leaching rates of calcium, magnesium, and aluminum are all above 95%, achieving comprehensive recovery and utilization of various elements in the blast furnace slag leachate. The prepared light calcium carbonate, basic magnesium carbonate, and other products have high added value and a large market capacity, which is conducive to the large-scale development and utilization of titanium-containing blast furnace slag.

[0041] 2) The invention enables the recycling of nitric acid as a leaching agent and ammonia, sodium hydroxide, and carbon dioxide as precipitants. This results in low production costs and no emissions of polluting gases into the environment, making it a green circular economy process.

[0042] In summary, the invention not only realizes the high-value utilization of elements such as titanium, calcium, magnesium, and aluminum in titanium-containing blast furnace slag, but also recycles the nitric acid, sodium hydroxide, ammonia, and carbon dioxide used. The process has low production costs and high added value of the prepared products, opening up a new technical route for the comprehensive recycling and utilization of titanium-containing blast furnace slag, and has strong economic and social benefits. Attached Figure Description

[0043] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying 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.

[0044] Figure 1 This is a flowchart illustrating the comprehensive recycling and utilization of titanium-containing blast furnace slag leachate according to the present invention.

[0045] Figure 2 This is a scanning electron microscope image of titanium-containing blast furnace slag before roasting treatment.

[0046] Figure 3 This is a scanning electron microscope image of titanium-containing blast furnace slag after roasting treatment.

[0047] Figure 4 This is a comparison of XRD analysis results for titanium-containing blast furnace slag before and after roasting treatment. Detailed Implementation

[0048] The technical solutions and problems solved by the embodiments of the present invention will be described below with reference to the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them.

[0049] Comparative Example 1

[0050] A method for the comprehensive recycling of titanium-containing blast furnace slag leachate specifically includes the following steps:

[0051] S1. Take 100g of titanium-containing blast furnace slag (crushed to a fineness of -200 mesh, 90% content), 250g of 60% nitric acid, and 150g of water. React them in a water bath at 90℃ for 5 hours. Then, separate the solid and liquid components to obtain filtrate and filter residue. The main element contents in the filtrate are Ca: 20.5g / L, Mg: 2.0g / L, Al: 2.5g / L, Mn: 0.1g / L, and Fe: 0.2g / L. The calcium leaching rate is 61.2%, the magnesium leaching rate is 21.4%, and the aluminum leaching rate is 15.2%. Because the titanium-containing blast furnace slag was not roasted beforehand, the leaching effect of removing impurities was not ideal. At the same time, the reaction process was accompanied by the generation of yellow smoke (nitrogen oxides), and the experimental results were not satisfactory. Therefore, the next step of the experiment was not carried out.

[0052] Comparative Example 2

[0053] A method for the comprehensive recycling of titanium-containing blast furnace slag leachate specifically includes the following steps:

[0054] S1. Take 200g of titanium-containing blast furnace slag that has been crushed to a fineness of -200 mesh and has a content of 90%, and then roast it at 400℃ for 5 hours. After it cools naturally, the roasted clinker is obtained.

[0055] S2. Take 100g of roasted clinker, 250g of 60% nitric acid, and 150g of water, and react them in a water bath at 90℃ for 2 hours. Then, separate the solid and liquid components to obtain filtrate and filter residue. The main element contents in the filtrate are Ca: 30.2g / L, Mg: 6.0g / L, Al: 6.5g / L, Mn: 0.5g / L, and Fe: 0.2g / L. The leaching rate of calcium is 71.2%, the leaching rate of magnesium is 62.8%, and the leaching rate of aluminum is 48.7%. Due to the low roasting temperature, the leaching effect on removing impurities is not ideal, and further experiments were not conducted.

[0056] Comparative Example 3

[0057] A method for the comprehensive recycling of titanium-containing blast furnace slag leachate specifically includes the following steps:

[0058] S1. Take the crushed titanium-containing blast furnace slag and roast it at 900℃ for 1.5h. After it cools naturally, the roasted clinker is obtained. Take 100g of roasted clinker, 250g of 60% nitric acid and 150g of water and react them at 90℃ for 5h. Then, separate the solid and liquid to obtain a leachate with a calcium content of 48.3g / L, magnesium content of 16.5g / L, aluminum content of 17.5g / L, manganese content of 1.6g / L and iron content of 0.001g / L.

[0059] S2. Pour 200ml of the S1 leachate into a beaker, add 10% ammonia solution dropwise under a 50℃ water bath to adjust the pH of the solution to 4.0, and maintain the temperature for 1 hour. After the reaction, perform solid-liquid separation. Because the precipitant ammonia solution was not added in parallel with the leachate, aluminum did not precipitate sufficiently. The resulting aluminum hydroxide was a paste, making solid-liquid separation extremely difficult. After drying, the filter material weighed 14.5g, with an aluminum content of only 25.13% and a high content of impurity elements. The experiment was terminated.

[0060] Comparative Example 4

[0061] A method for the comprehensive recycling of titanium-containing blast furnace slag leachate specifically includes the following steps:

[0062] S1. Take the crushed titanium-containing blast furnace slag and roast it at 900℃ for 1.5h. After it cools naturally, the roasted clinker is obtained. Take 100g of roasted clinker, 250g of 60% nitric acid and 150g of water and react them at 90℃ for 5h. Then, separate the solid and liquid to obtain a leachate with a calcium content of 48.3g / L, magnesium content of 16.5g / L, aluminum content of 17.5g / L, manganese content of 1.6g / L and iron content of 0.001g / L.

[0063] S2. The leachate and a 10% ammonia solution were added concurrently in a water bath at 50℃, maintaining the pH of the reaction system at 5.0. The amount of leachate added was 200 ml. The reaction was maintained at this temperature for 1 hour. After the reaction, solid-liquid separation was performed. The resulting aluminum hydroxide was granular. The solid-liquid separation was rapid. The dried filter material weighed 10.9 g, with an aluminum content of 32.1%.

[0064] S3. Take 200ml of the aluminum-precipitated liquid from S2 and pour it into a beaker. Add 2ml of 30% hydrogen peroxide at room temperature and stir for 30 minutes. After the reaction, separate the solid and liquid to obtain manganese dioxide and the manganese-precipitated liquid. The manganese content in the manganese-precipitated liquid is 0.27g / L. Because sodium hydroxide was not used to adjust the pH before the reaction, the removal effect of manganese ions was not ideal, and the experiment was terminated.

[0065] Comparative Example 5

[0066] A method for the comprehensive recycling of titanium-containing blast furnace slag leachate specifically includes the following steps:

[0067] S1. Take the crushed titanium-containing blast furnace slag and roast it at 900℃ for 1.5h. After it cools naturally, the roasted clinker is obtained. Take 100g of roasted clinker, 250g of 60% nitric acid and 150g of water and react them at 90℃ for 5h. Then, separate the solid and liquid to obtain a leachate with a calcium content of 48.3g / L, magnesium content of 16.5g / L, aluminum content of 17.5g / L, manganese content of 1.6g / L and iron content of 0.001g / L.

[0068] S2. The leachate and a 10% ammonia solution were added concurrently in a water bath at 50℃, maintaining the pH of the reaction system at 5.0. The amount of leachate added was 200 ml. The reaction was maintained at this temperature for 1 hour. After the reaction, solid-liquid separation was performed. The resulting aluminum hydroxide was granular. The solid-liquid separation was rapid. The dried filter material weighed 10.9 g, with an aluminum content of 32.1%.

[0069] S3. Take 200ml of the aluminum-precipitated liquid from S2 and pour it into a beaker. Add 5% sodium hydroxide solution to adjust the pH of the aluminum-precipitated liquid to 8.0. Then add 2ml of 30% hydrogen peroxide at room temperature and stir for 30min. After the reaction is complete, solid and liquid are separated to obtain manganese dioxide and manganese-precipitated liquid. The manganese content in the manganese-precipitated liquid is reduced to 0.0002g / L.

[0070] S4. Take 150 ml of the manganese-precipitated solution from S3 and pour it into a three-necked flask. Connect the condenser and add sodium hydroxide solution under 90°C water bath conditions, maintaining the pH of the reaction solution at 12.5. Stir the reaction for 1 hour. The ammonia concentration collected by the condenser is 8.7%. After the reaction, solid-liquid separation yields calcium and magnesium precipitates and a filtrate. The filtrate contains 0.018 g / L of magnesium and 1.5 g / L of calcium. In step S4, sodium hydroxide was added but sodium carbonate was not added. Therefore, the calcium ions in the manganese-precipitated solution were only converted to calcium hydroxide and not calcium carbonate. Since the solubility of calcium hydroxide is 0.15–0.20 g / 100 g, while the solubility of calcium carbonate is 0.0005 g / 100 g, the calcium ions were not completely precipitated, and the removal effect of calcium and magnesium ions was not ideal. The experiment was terminated.

[0071] Comparative Example 6

[0072] A method for the comprehensive recycling of titanium-containing blast furnace slag leachate specifically includes the following steps:

[0073] S1. Take the crushed titanium-containing blast furnace slag and roast it at 900℃ for 1.5h. After it cools naturally, the roasted clinker is obtained. Take 100g of roasted clinker, 250g of 60% nitric acid and 150g of water and react them at 90℃ for 5h. Then, separate the solid and liquid to obtain a leachate with a calcium content of 48.3g / L, magnesium content of 16.5g / L, aluminum content of 17.5g / L, manganese content of 1.6g / L and iron content of 0.001g / L.

[0074] S2. The leachate and a 10% ammonia solution were added concurrently in a water bath at 50℃, maintaining the pH of the reaction system at 5.0. The amount of leachate added was 200 ml. The reaction was maintained at this temperature for 1 hour. After the reaction, solid-liquid separation was performed. The resulting aluminum hydroxide was granular. The solid-liquid separation was rapid. The dried filter material weighed 10.9 g, with an aluminum content of 32.1%.

[0075] S3. Take 200ml of the aluminum-precipitated liquid from S2 and pour it into a beaker. Add 5% sodium hydroxide solution to adjust the pH of the aluminum-precipitated liquid to 8.0. Then add 2ml of 30% hydrogen peroxide at room temperature and stir for 30min. After the reaction is complete, solid and liquid are separated to obtain manganese dioxide and manganese-precipitated liquid. The manganese content in the manganese-precipitated liquid is reduced to 0.0002g / L.

[0076] S4. Take 150 ml of the manganese-precipitated liquid from S3 and pour it into a three-necked flask. Connect the condenser and add sodium hydroxide solution under water bath temperature of 90℃ to maintain the pH of the reaction solution at 12.5. Stir the reaction for 1 h, then add 2.3 g of sodium carbonate solid and stir the reaction for 0.5 h. The ammonia concentration collected by the condenser is 7.5%. After the reaction is completed, solid and liquid separation is performed to obtain calcium and magnesium precipitate and filtrate. The magnesium content in the filtrate is 0.0003 g / L and the calcium content is 0.001 g / L.

[0077] S5. Repeat and scale up the above steps to prepare 2000ml of filtrate. Then add nitric acid solution to adjust the pH to 7.0 and put it into a bipolar membrane device for acid-base separation.

[0078] S6. Take 10g of the calcium and magnesium precipitate obtained in step S4, add 220ml of water, stir and react at room temperature for 1h at a stirring speed of 500r / min, then introduce carbon dioxide gas to react until the pH of the slurry is 7.2, and finally separate the solid and liquid. The obtained filter material is light calcium carbonate after washing. After drying, the calcium carbonate content is analyzed to be 97.5%.

[0079] S7. Take 500 ml of the filtrate obtained in step S7 and stir it in a water bath at 80℃ for 1 hour. After the reaction, separate the solid and liquid to obtain the filter material and filtrate. Wash and dry the filter material to obtain basic magnesium carbonate. After drying, the magnesium oxide content is 41.5%, and the magnesium content in the filtrate is 5.7 g / L. This indicates that the pyrolysis temperature was too low, and the pyrolysis of magnesium bicarbonate was incomplete.

[0080] Comparative Example 7

[0081] A method for the comprehensive recycling of titanium-containing blast furnace slag leachate specifically includes the following steps:

[0082] S1. Take the crushed titanium-containing blast furnace slag and roast it at 900℃ for 1.5h. After it cools naturally, the roasted clinker is obtained. Take 100g of roasted clinker, 250g of 60% nitric acid and 150g of water and react them at 90℃ for 5h. Then, separate the solid and liquid to obtain a leachate with a calcium content of 48.3g / L, magnesium content of 16.5g / L, aluminum content of 17.5g / L, manganese content of 1.6g / L and iron content of 0.001g / L.

[0083] S2. The leachate and a 10% sodium hydroxide solution were added concurrently in a water bath at 50℃, maintaining the pH of the reaction system at 5.0. 200 ml of leachate was added, and the reaction was maintained at this temperature for 1 hour. After the reaction, solid-liquid separation was performed. The resulting aluminum hydroxide was granular, and the solid-liquid separation was rapid. The dried filter material weighed 15.4 g, with an aluminum content of only 21.11%, a calcium content of 6.5%, and a magnesium content of 4.8%. Because sodium hydroxide solution was used instead of ammonia to adjust the pH, the local concentration in the reaction system was excessively high, resulting in a higher content of impurity elements in the precipitated aluminum product.

[0084] Example 1

[0085] A method for comprehensive recycling of titanium-containing blast furnace slag leachate, the flowchart of which is as follows: Figure 1 As shown, the specific steps include:

[0086] S1. Take the crushed titanium-containing blast furnace slag and roast it at 900℃ for 1.5h. After it cools naturally, the roasted clinker is obtained. Take 100g of roasted clinker, 250g of 60% nitric acid and 150g of water and react them at 90℃ for 5h. Then, separate the solid and liquid to obtain a leachate with a calcium content of 48.3g / L, magnesium content of 16.5g / L, aluminum content of 17.5g / L, manganese content of 1.6g / L and iron content of 0.001g / L.

[0087] Figure 2 The image shows a scanning electron microscope (SEM) image of titanium-containing blast furnace slag before roasting treatment. The cross-section of the titanium-containing blast furnace slag is smooth and continuous, exhibiting obvious vitrification characteristics. Figure 3 The image shows a scanning electron microscope (SEM) image of titanium-containing blast furnace slag after roasting treatment. It indicates that after roasting treatment, the titanium-containing blast furnace slag becomes a fine layered and granular aggregate, and the vitrification phenomenon is weakened or disappears. Figure 4 The XRD analysis results before and after roasting of titanium-containing blast furnace slag show that the number of crystal peaks in the blast furnace slag increased significantly and the crystallinity improved after roasting.

[0088] S2. The leachate and a 10% ammonia solution were added concurrently in a water bath at 50℃, maintaining the pH of the reaction system at 5.0. The amount of leachate added was 200 ml. The reaction was maintained at this temperature for 1 hour. After the reaction, solid-liquid separation was performed. The resulting aluminum hydroxide was granular. The solid-liquid separation was rapid. The dried filter material weighed 10.9 g, with an aluminum content of 32.1%.

[0089] S3. Take 200ml of the aluminum-precipitated liquid from S2 and pour it into a beaker. Add 5% sodium hydroxide solution to adjust the pH of the aluminum-precipitated liquid to 8.0. Then add 2ml of 30% hydrogen peroxide at room temperature and stir for 30min. After the reaction is complete, solid and liquid are separated to obtain manganese dioxide and manganese-precipitated liquid. The manganese content in the manganese-precipitated liquid is reduced to 0.0002g / L.

[0090] S4. Take 150 ml of the manganese-precipitated liquid from S3 and pour it into a three-necked flask. Connect the condenser and add sodium hydroxide solution under water bath temperature of 90℃ to maintain the pH of the reaction solution at 12.5. Stir the reaction for 1 h, then add 2.3 g of sodium carbonate solid and stir the reaction for 0.5 h. The ammonia concentration collected by the condenser is 7.5%. After the reaction is completed, solid and liquid separation is performed to obtain calcium and magnesium precipitate and filtrate. The magnesium content in the filtrate is 0.0003 g / L and the calcium content is 0.001 g / L.

[0091] S5. Repeat and scale up the above steps to prepare 2000ml of filtrate. Then add nitric acid solution to adjust the pH to 7.0 and put it into a bipolar membrane device for acid-base separation.

[0092] S6. Take 10g of the calcium and magnesium precipitate obtained in step S4, add 220ml of water, stir and react at room temperature for 1h at a stirring speed of 500r / min, then introduce carbon dioxide gas to react until the pH of the slurry is 7.2, and finally separate the solid and liquid. The obtained filter material is light calcium carbonate after washing. After drying, the calcium carbonate content is analyzed to be 97.5%.

[0093] S7. Take 500 ml of the filtrate obtained in step S7 and stir it in a water bath at 95°C for 1 hour. After the reaction, separate the solid and liquid to obtain the filter media and filtrate. Wash and dry the filter media to obtain basic magnesium carbonate. After drying, the magnesium oxide content is 41.6%, and the magnesium content in the filtrate is 0.6 g / L. The recovery rates of calcium, magnesium, aluminum, and manganese are all greater than 99%.

[0094] Example 2

[0095] A method for the comprehensive recycling of titanium-containing blast furnace slag leachate specifically includes the following steps:

[0096] S1. Take the crushed titanium-containing blast furnace slag and roast it at 900℃ for 1.5h. After it cools naturally, the roasted clinker is obtained. Take 100g of roasted clinker, 250g of 60% nitric acid and 150g of water and react them at 90℃ for 5h. Then, separate the solid and liquid to obtain a leachate with a calcium content of 48.5g / L, magnesium content of 14.8g / L, aluminum content of 19.7g / L, manganese content of 1.1g / L and iron content of 0.0005g / L.

[0097] S2. The leachate and a 10% ammonia solution were added concurrently in a water bath at 50℃, maintaining the pH of the reaction system at 5.5. The amount of leachate added was 200 ml. The reaction was maintained at this temperature for 1 hour. After the reaction, solid-liquid separation was performed. The resulting aluminum hydroxide was granular. The solid-liquid separation was rapid. The dried filter material weighed 12.4 g, with an aluminum content of 31.9%.

[0098] S3. Take 200ml of the aluminum-precipitated liquid from S2 and pour it into a beaker. Add 5% sodium hydroxide solution to adjust the pH of the aluminum-precipitated liquid to 8.0. Then, oxidize it with an ozone generator at room temperature for 1 hour. After the reaction is completed, solid and liquid are separated to obtain manganese dioxide and manganese-precipitated liquid. The manganese content in the manganese-precipitated liquid is reduced to 0.0004g / L.

[0099] S4. Take 150 ml of the manganese-precipitated liquid from S3 and pour it into a three-necked flask. Connect the condenser and add sodium hydroxide solution under water bath temperature of 90℃ to maintain the pH of the reaction solution at 12.5. Stir the reaction for 1 h, then add 3.5 g of sodium carbonate solid and stir the reaction for 0.5 h. The ammonia concentration collected by the condenser is 8.4%. After the reaction is completed, solid and liquid are separated to obtain calcium and magnesium precipitate and filtrate. The magnesium content in the filtrate is 0.0002 g / L and the calcium content is 0.0005 g / L.

[0100] S5. Repeat and scale up the above steps to prepare 2000ml of filtrate. Then add nitric acid solution to adjust the pH to 7.0 and put it into a bipolar membrane device for acid-base separation.

[0101] S6. Take 10g of the calcium and magnesium precipitate obtained in step S4, add 220ml of water, stir and react at room temperature for 1h at a stirring speed of 500r / min, then introduce carbon dioxide gas to react until the pH of the slurry is 7.5, and finally separate the solid and liquid. The obtained filter material is light calcium carbonate after washing. After drying, the calcium carbonate content is analyzed to be 98.1%.

[0102] S7. Take 500 ml of the filtrate obtained in step S7 and stir it in a water bath at 95℃ for 1 hour. After the reaction is complete, separate the solid and liquid to obtain the filter media and filtrate. Wash and dry the filter media to obtain basic magnesium carbonate. The magnesium oxide content after drying is 42.1%, and the magnesium content in the filtrate is 0.4 g / L. The recovery rates of calcium, magnesium, aluminum, and manganese are all greater than 99%.

[0103] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles 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 method for comprehensive recycling of titanium-containing blast furnace slag leachate, characterized in that, The method includes the following steps: S1. Titanium-containing blast furnace slag is crushed, activated, roasted, and leached with nitric acid to obtain titanium-rich material and leachate; S2. The leachate obtained in step S1 is adjusted to pH 4.5-5.5 with ammonia water, and then the solid and liquid are separated to obtain aluminum hydroxide and filtrate 1. S3. After adding oxidant to the filtrate 1 obtained in step S2 and reacting, solid-liquid separation is performed to obtain manganese dioxide and filtrate 2. S4. Add sodium hydroxide solution to the filtrate 2 obtained in step S3 to adjust the pH to 12~13, then add sodium carbonate and react to separate the solid and liquid to obtain calcium and magnesium precipitate and filtrate 3. S5. Add nitric acid to the filtrate 3 obtained in step S4 to adjust the pH to 6-8, and then separate it through a bipolar membrane to obtain sodium hydroxide and nitric acid. S6. Add water to the calcium and magnesium precipitate obtained in step S4, stir, and then pass carbon dioxide through to react. Then separate the solid and liquid to obtain filtrate 4 and light calcium carbonate. S7. After heating and decomposing the filtrate 4 obtained in S6, solid-liquid separation is performed to obtain basic magnesium carbonate.

2. The method for comprehensive recycling of titanium-containing blast furnace slag leachate according to claim 1, characterized in that, In step S1, the titanium-containing blast furnace slag is a solid waste generated during the ironmaking process of vanadium-titanium magnetite. After crushing, the titanium-containing blast furnace slag has a fineness of -200 mesh accounting for 80%~90%, and the roasting temperature is 800℃~900℃ and the roasting time is 1h~2h.

3. The method for comprehensive recycling of titanium-containing blast furnace slag leachate according to claim 1, characterized in that, In step S1, the reaction conditions for nitric acid leaching are as follows: 60% nitric acid and water are added to the roasted clinker, and the mixture is stirred and reacted under normal pressure, followed by solid-liquid separation; the amount of 60% nitric acid used is 1.5 to 2.5 times the mass of the roasted clinker, the amount of water used is 1.5 to 2.5 times the mass of the roasted clinker, the reaction temperature is 80 to 100°C, and the reaction time is 4 to 6 hours.

4. The method for comprehensive recycling of titanium-containing blast furnace slag leachate according to claim 1, characterized in that, In step S1, the leachate is obtained by solid-liquid separation after leaching blast furnace slag, and its elemental content is as follows: Ca: 40~50 g / L, Mg: 15~20 g / L, Al: 20~25 g / L, Mn: 2~3 g / L, NO3 ... Mn: 2~3 g / L, NO3: 40~50 g / L, Mn: 2~3 g / L, NO3: 40~50 g / L, Mn: 2~3 g / L, NO3: 40~50 g / L, Mn: 2~3 g / L, NO3: 40~50 g / L, Mn: 2~3 g / L, - :180~250g / L, Fe<0.005g / L, pH=1.5~2.

0.

5. The method for comprehensive recycling of titanium-containing blast furnace slag leachate according to claim 1, characterized in that, In step S2, the concentration of ammonia water is 10-20%, and ammonia water and leachate are dripped into the reaction vessel in parallel. The pH of the reaction system is controlled at 4.5-5.5, the reaction temperature at 50-70℃, and the reaction time at 1-2 hours. The resulting aluminum hydroxide is in granular form.

6. The method for comprehensive recycling of titanium-containing blast furnace slag leachate according to claim 1, characterized in that, In step S3, the oxidant is one of hydrogen peroxide, oxygen, ozone, or air. Before the reaction, the pH is adjusted to 7-8 with a 5% sodium hydroxide solution, and then the oxidant is added or introduced to react.

7. The method for comprehensive recycling of titanium-containing blast furnace slag leachate according to claim 1, characterized in that, In step S4, the concentration of the sodium hydroxide solution is 30%, the precipitation temperature is 80~95℃, the pH of the solution is adjusted to 12~13, the amount of sodium carbonate added is 10~20g / L, and the stirring reaction time is 0.5~1h.

8. The method for comprehensive recycling of titanium-containing blast furnace slag leachate according to claim 1, characterized in that, In step S5, the mass concentration of nitric acid is 40%~50%, the pH of the solution is adjusted to 6~8, and the total content of polyvalent cations of calcium, magnesium, aluminum, manganese and iron in the solution after adjustment is less than 0.005g / L.

9. The method for comprehensive recycling of titanium-containing blast furnace slag leachate according to claim 1, characterized in that, In step S6, the amount of calcium and magnesium precipitate added to water is 40-50 g / L, the stirring reaction time is 1 h, the mechanical stirring speed is 400-600 r / min, and carbon dioxide is introduced to react until the pH of the slurry is 7-7.5; the light calcium carbonate is washed at 50-80℃ for 1-2 h.

10. The method for comprehensive recycling of titanium-containing blast furnace slag leachate according to claim 1, characterized in that, In step S7, the heating decomposition temperature is 95℃~100℃, and the heating decomposition time is 1~2h.

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