Method for extracting scandium from by-product FeSO4H2O in sulfuric acid method titanium dioxide waste acid concentration process

Abstract

The invention discloses a method for extracting scandium from a byproduct FeSO4 # imgabs0 # H2O in a sulfuric acid process titanium dioxide waste acid concentration process, and belongs to the field of valuable resource recovery. The method comprises the following steps: mixing and dissolving FeSO4 # imgabs1 # H2O and water, filtering to obtain a ferrous sulfate solution, freezing, crystallizing and filtering to obtain a scandium-containing solution, and circulating for multiple times to increase the scandium concentration; then ferric iron in the solution is reduced, the pH is adjusted with barium hydroxide, scandium is precipitated, and a mixed solid of barium sulfate and scandium hydroxide is separated out; the method comprises the following steps: dissolving scandium hydroxide with acid, filtering and washing, precipitating scandium with oxalic acid or sodium oxalate, and finally roasting scandium oxalate at high temperature to prepare scandium oxide with Sc2O3 greater than or equal to 99.99% and Sc2O3 / REO greater than or equal to 99.9999%. The method has the advantages of being convenient to operate, simple in technological process, low in production cost and good in environmental protection benefit, industrialization is easy, the scandium element in the sulfuric acid process titanium dioxide waste acid concentration byproduct can be efficiently recycled, and efficient utilization of resources is achieved.

Description

Technical Field

[0001] The present invention belongs to the field of valuable resource recovery, and specifically relates to a method for recovering FeSO4, a by-product of the waste acid concentration process of titanium dioxide produced by sulfuric acid process. Method for extracting scandium from H2O. Background Art

[0002] Scandium, a rare earth element, boasts relatively abundant reserves worldwide. However, over 75% of scandium is associated with other minerals, making its extraction challenging. Complex extraction processes, low overall recovery rates, and high costs contribute to the high price of scandium products, making it one of the world's most expensive metals.

[0003] Scandium ore resources are primarily found in minerals such as bauxite, phosphate rock (including weathered and leached phosphate deposits), vanadium-titanium magnetite, tungsten ore, and rare earth ores. Currently, the raw materials for scandium extraction are mostly derived from secondary resources, such as wastewater or solid waste generated during the comprehensive utilization of associated minerals. Common secondary resources for scandium extraction include uranium byproducts, tungsten smelting slag, hydrolysis acidic wastewater from sulfuric acid production of titanium dioxide, chlorinated fumes from boiling titanium extraction, titanium-containing blast furnace slag, red mud, ion-adsorbed rare earth ores, and Bayan Obo tailings.

[0004] Since different scandium-containing raw materials have different physical and chemical properties, especially chemical composition and solubility in different leaching agents, the scandium extraction processes involved in different raw materials are also different.

[0005] The waste titanium dioxide acid produced in the sulfuric acid process will generate FeSO4 during evaporation and concentration. Currently, insufficient attention is being paid to the recovery of scandium from this byproduct, and an efficient, mature recovery process has yet to be established. Existing methods for extracting scandium suffer from complex processes, high costs, low recovery rates, and difficulty ensuring product purity, making them inadequate for large-scale industrial production. Summary of the Invention

[0006] Based on this, in view of the shortcomings of the above-mentioned prior art, the present invention provides a method for concentrating FeSO4, a by-product of the waste acid of titanium dioxide produced by sulfuric acid process. Method for extracting scandium from H2O, which can efficiently recover FeSO4 as a by-product during the evaporation and concentration of waste acid from sulfuric acid-based titanium dioxide The valuable element scandium in H2O can be extracted and high-purity scandium oxide can be obtained. It also has the advantages of easy operation, simple process flow, high efficiency, low production cost, good environmental benefits and easy industrialization.

[0007] In order to achieve the above objectives, the following technical solutions are adopted: The present invention provides a method for preparing FeSO4, a by-product of the waste acid concentration process of titanium dioxide produced by sulfuric acid process. The method for extracting scandium from H2O comprises the following steps: S1: FeSO4, a by-product of the sulfuric acid titanium dioxide waste acid concentration process Stir H2O and water thoroughly until FeSO4 The H2O is completely dissolved, and the insoluble matter is filtered off to obtain the first ferrous sulfate solution; S2: freeze crystallize the first ferrous sulfate solution obtained in step S1, and then filter to obtain FeSO4 7H2O crystals and scandium-containing solutions; S3: Convert FeSO4 H2O is added to the scandium-containing solution obtained in step S2 and stirred thoroughly until FeSO4 H2O is completely dissolved to obtain a second ferrous sulfate solution; the second ferrous sulfate solution is frozen and crystallized according to the same steps as step S2, and then filtered to obtain FeSO4 7H2O crystals and a scandium-containing solution; repeating the above process several times until the scandium concentration in the scandium-containing solution reaches a predetermined concentration; S4: using a reducing agent to fully reduce the trivalent iron formed by oxidation in the scandium-containing solution having a predetermined concentration obtained in step S3, and then filtering to obtain a filtrate; S5: adjusting the pH of the filtrate to a set value with a barium hydroxide solution, and filtering to obtain a mixed precipitate of barium sulfate precipitate and scandium hydroxide precipitate; S6: using an acid solution to fully dissolve the scandium hydroxide in the mixed precipitate of the barium sulfate precipitate and the scandium hydroxide precipitate, stirring is strengthened during the dissolution process, and after the scandium hydroxide is completely dissolved, the system is filtered and washed to obtain a scandium-containing filtrate; S7: precipitating the scandium in the scandium-containing filtrate obtained in step S6 with oxalic acid or sodium oxalate, filtering after complete precipitation to obtain the precipitate as scandium oxalate; after the scandium oxalate is calcined at high temperature, scandium oxide with Sc2O3≥99.99% and Sc2O3 / REO≥99.9999% is obtained.

[0008] In some embodiments, in step S1, FeSO4, a by-product of the sulfuric acid titanium dioxide waste acid concentration process, is used to H2O and water are mixed in a mass ratio of (5 - 7): 10 at 50℃-70℃ until FeSO4 H2O dissolves completely.

[0009] In some embodiments, in step S2, the temperature of the frozen crystallization is controlled at -5~10°C; the first ferrous sulfate solution obtained in step S1 is frozen and crystallized according to a three-stage temperature control system, the first stage is naturally cooled from 50°C~70°C or cooled to 30°C~40°C at a cooling rate of 1~20°C / min, the second stage is cooled from 30°C~40°C at a cooling rate of 1~5°C / min to 20°C~25°C, and the third stage is cooled from 20°C~25°C at a cooling rate of 0.02~1°C / min to -5°C~10°C, and the cooling process is synchronously stirred at a stirring frequency of 100~500rpm.

[0010] In some embodiments, in step S3, FeSO4 H2O and the scandium-containing solution obtained in step S2 are mixed at a mass ratio of (0.5-3):7 at 50-70°C until FeSO4 The H2O is completely dissolved to obtain a second ferrous sulfate solution; the predetermined concentration of the scandium element in the scandium-containing solution needs to be ≥0.01 g / L, and is usually selected from 0.04 g / L to 0.1 g / L. In some embodiments, in step S5, the concentration of barium hydroxide is ≥0.01 mol / L, and the pH value of the filtrate is 3.5-5.5; after filtering the filtrate, a ferrous sulfate solution is obtained, which is continuously circulated and used in steps S1-S3.

[0011] In some embodiments, in step S6, the acid solution is selected from sulfuric acid, hydrochloric acid, or nitric acid with a concentration of ≥0.1 mol / L; after the scandium hydroxide is completely dissolved, the system is filtered and washed to obtain barium sulfate, which is recovered after washing and filtration, and the obtained wash water is used to prepare the acid solution for dissolving the scandium hydroxide; In some embodiments, in step S7, the concentration of oxalic acid or sodium oxalate is ≥0.1 mol / L, the amount of oxalic acid or sodium oxalate used is 1-1.5 times the theoretical amount required for complete precipitation of scandium, and the pH value of the mixed solution at the scandium precipitation endpoint is controlled at 0-5.5.

[0012] In some embodiments, in step S5, the concentration of the barium hydroxide solution is 0.2-2 mol / L, the reaction temperature during the precipitation process is ≥0°C, and the barium hydroxide solution is added at a rate of 4-10 ml / min. 100ml of scandium solution).

[0013] In some embodiments, in step S6, the concentration of the acid solution is 1-3.5 mol / L, the reaction temperature of the dissolution process is controlled at 0-90°C, the liquid-to-solid ratio (ml:g) of the acid solution and the mixed precipitate is ≥1, and the washing process liquid-to-solid ratio (ml:g) is ≥1; countercurrent washing is performed, and the number of washing stages is 3-5.

[0014] In some embodiments, in step S7, the concentration of oxalic acid or sodium oxalate is 0.5-1.5 mol / L, the amount of oxalic acid or sodium oxalate used is 1-1.1 times the theoretical amount required for complete precipitation of scandium, the precipitation temperature is ≥10°C, the washing liquid-to-solid ratio (ml:g) is ≥1, countercurrent washing is performed, and the number of washing stages is 3-5.

[0015] In some embodiments, in step S4, the reducing agent is selected from reduced iron powder, sulfur dioxide, or sodium metabisulfite.

[0016] In some embodiments, in step S7, scandium in the scandium-containing filtrate obtained in step S6 is precipitated with oxalic acid or sodium oxalate, and filtered after complete precipitation. The obtained filtrate can be recycled for the above-mentioned oxalic acid or sodium oxalate precipitation process; the precipitate is countercurrently washed and filtered to obtain scandium oxalate and washing water, and the washing water can be recycled for the process of washing the precipitate to obtain scandium oxalate; the scandium oxalate is calcined at 600-900°C for 3-8h to finally obtain scandium oxide with Sc2O3≥99.99% and Sc2O3 / REO≥99.9999%.

[0017] The present invention has the following beneficial technical effects: 1. Simple and efficient process: The present invention realizes the recovery of FeSO4, a by-product of the waste acid concentration process of titanium dioxide from sulfuric acid process, through a series of orderly steps, including dissolution, freezing crystallization, reduction, precipitation, dissolution, reprecipitation and roasting. Scandium is efficiently extracted from H2O. The entire process is rationally designed. Through multiple cycles of dissolution and crystallization, the concentration of the scandium-containing solution is effectively increased, laying a good foundation for subsequent precipitation and purification. The operation steps are simple and clear, and easy to control.

[0018] 2. Low cost: In terms of raw materials, FeSO4, a by-product originally considered as waste during the concentration of waste acid from titanium dioxide produced by sulfuric acid method, is used. Using H2O as a raw material for scandium extraction transforms waste into valuable resources, reducing raw material costs. The reagents used, such as reduced iron powder, sulfur dioxide, sodium metabisulfite, barium hydroxide, oxalic acid, or sodium oxalate, are all common, relatively inexpensive chemical raw materials used in reasonable quantities. Furthermore, recycling features within the process, such as the recycle of ferrous sulfate solution and the reuse of wash water, further reduce production costs and improve resource utilization.

[0019] 3. High Product Purity: After treatment using the present method, the scandium oxide obtained is of exceptional purity, with Sc2O3 ≥ 99.99% and Sc2O3 / REO ≥ 99.9999%. This is due to precise control of reaction conditions in each step, such as temperature, pH, and reagent dosage, which effectively removes impurities and ensures a high-purity product, meeting the stringent purity requirements of high-end applications.

[0020] 4. Ease of industrialization: The method of the present invention is easy to operate and requires minimal equipment. The process parameters and operating conditions employed are easily implemented and controlled in industrial production. Reaction temperature, stirring speed, and reagent dosage can all be precisely adjusted using conventional industrial equipment and control systems, making it suitable for large-scale industrial production and providing a viable technical solution for the industrial recovery of scandium resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 The FeSO4 by-product of the sulfuric acid titanium dioxide waste acid concentration process of the present invention Flowchart of the method for extracting scandium from H2O. DETAILED DESCRIPTION

[0023] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the embodiments of the present invention are further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0024] It should be understood that the embodiments of the present invention shown in the exemplary embodiments are merely illustrative. Although only a few embodiments have been described in detail in the present invention, it is readily apparent to those skilled in the art that various modifications are feasible without departing substantially from the teachings of the subject matter of the present invention. Accordingly, all such modifications should be included within the scope of the present invention. Without departing from the gist of the present invention, other replacements, modifications, variations, and deletions may be made to the design, operating conditions, and parameters of the following exemplary embodiments.

[0025] Based on the above purpose, the first aspect of the embodiment of the present invention proposes a method for concentrating FeSO4, a by-product of the waste acid of sulfuric acid titanium dioxide, Method for extracting scandium from H2O. Figure 1 Shown is a schematic flow chart of the method.

[0026] like Figure 1 As shown in , the method may include the following steps: S1: FeSO4, a by-product of the sulfuric acid titanium dioxide waste acid concentration process Stir H2O and water thoroughly until FeSO4 The H2O is completely dissolved, and the insoluble matter is filtered off to obtain the first ferrous sulfate solution; S2: freeze crystallize the first ferrous sulfate solution obtained in step S1, and then filter to obtain FeSO4 7H2O crystals and scandium-containing solutions; S3: Convert FeSO4 H2O is added to the scandium-containing solution obtained in step S2 and stirred thoroughly until FeSO4 H2O is completely dissolved to obtain a second ferrous sulfate solution; the second ferrous sulfate solution is frozen and crystallized according to the same steps as step S2, and then filtered to obtain FeSO4 7H2O crystals and a scandium-containing solution; the above process is repeated several times until the scandium concentration in the scandium-containing solution reaches a predetermined concentration, which needs to be ≥0.01 g / L, usually 0.04 g / L-0.1 g / L; several times is defined as n times, n ≥ 0.

[0027] S4: using a reducing agent to fully reduce the trivalent iron formed by oxidation in the scandium-containing solution obtained in step S3 and reaching a predetermined concentration, and then filtering to obtain a filtrate; the reducing agent is selected from reduced iron powder, sulfur dioxide or sodium metabisulfite.

[0028] S5: adjusting the pH of the filtrate to 3.5-5.5 with a barium hydroxide solution, and filtering to obtain a mixed precipitate of barium sulfate and scandium hydroxide; the mixed precipitate of barium sulfate and scandium hydroxide is used for the next step of extracting scandium and recovering barium sulfate; S6: using an acid solution to fully dissolve the scandium hydroxide in the mixed precipitate of the barium sulfate precipitate and the scandium hydroxide precipitate, stirring is strengthened during the dissolution process, and after the scandium hydroxide is completely dissolved, the system is filtered and washed to obtain a scandium-containing filtrate; S7: precipitating the scandium in the scandium-containing filtrate obtained in step S6 with oxalic acid or sodium oxalate, filtering after complete precipitation to obtain the precipitate as scandium oxalate; after the scandium oxalate is calcined at high temperature, scandium oxide with Sc2O3≥99.99% and Sc2O3 / REO≥99.9999% is obtained.

[0029] The scandium in the scandium-containing filtrate obtained in step S6 is precipitated with oxalic acid or sodium oxalate, and after complete precipitation, the scandium is filtered. The obtained filtrate can be recycled for the above-mentioned oxalic acid or sodium oxalate precipitation process; the precipitate is washed and filtered to obtain scandium oxalate and washing water, and the washing water can be recycled to the process of washing the precipitate to obtain scandium oxalate; the scandium oxalate is calcined at 600-900℃ for 3-8h to finally obtain scandium oxide with Sc2O3≥99.99% and Sc2O3 / REO≥99.9999%.

[0030] In some embodiments, in step S1, FeSO4, a by-product of the sulfuric acid titanium dioxide waste acid concentration process, is used to H2O and water are mixed in a mass ratio of (5 - 7): 10 at 50℃-70℃ until FeSO4 H2O dissolves completely.

[0031] In some embodiments, in step S1, FeSO4 is produced as a by-product during the evaporation and concentration of waste acid from the sulfuric acid process. H2O is usually yellow, and its scandium content is ≥5g / t, and the common scandium content range is 30~60g / t. There is no specific requirement for the stirring intensity when mixing H2O and water. Mix H2O and water thoroughly until there is no solid deposition in the reactor, dissolve FeSO4 The water used for H2O can be tap water, distilled water or recycled water with a total ion concentration of less than 0.1% obtained through comprehensive treatment in the factory. The dissolution time depends on the time it takes to completely dissolve. The higher the concentration of scandium and ferrous sulfate in the solution obtained in this process, the better.

[0032] In some embodiments, in step S2, the temperature of the frozen crystallization is controlled at -5~10°C; the first ferrous sulfate solution obtained in step S1 is frozen and crystallized according to a three-stage temperature control system, the first stage is naturally cooled from 50℃~70℃ or cooled to 30℃~40℃ at a cooling rate of 1~20℃ / min, the second stage is cooled from 30℃~40℃ at a cooling rate of 1~5℃ / min to 20℃~25℃, and the third stage is cooled from 20℃~25℃ at a cooling rate of 0.02~1℃ / min to -5℃~10℃. The cooling process is stirred synchronously with a stirring frequency of 100~500rpm. The purpose of this process is to convert the ferrous sulfate in the solution into FeSO4 7H2O crystallization, to control the cooling gradient and cooling rate to increase FeSO4 7H2O crystallization efficiency and reduce FeSO4 Loss of scandium in solution caused by the precipitation of 7H2O crystals.

[0033] In some embodiments, in step S3, FeSO4 H2O and the scandium-containing solution obtained in step S2 are mixed at a mass ratio of (0.5-3):7 at 50-70°C until FeSO4 H2O is completely dissolved to obtain the second ferrous sulfate solution. There is no specific requirement for the stirring intensity. As long as FeSO4 The H2O and scandium-containing solution are fully mixed to achieve no solid deposition in the reactor. The freezing crystallization temperature can be controlled at -5~10℃. The temperature control system is as follows: there are three stages of temperature control. The first stage is natural cooling from 50~70℃ or cooling to 30℃~40℃ at a cooling rate of 1~20℃ / min. The second stage is cooling from 30℃~40℃ at a cooling rate of 1~5℃ / min to 20℃~25℃. The third stage is cooling from 20℃~25℃ at a cooling rate of 0.02~1℃ / min to -5~10℃. The cooling process requires simultaneous stirring at a stirring frequency of 100~500rpm. The purpose of this process is to convert ferrous sulfate in the solution into FeSO4 7H2O crystallizes and filtrates to obtain FeSO4 7H2O crystals and scandium solution; continue to repeat the above "FeSO4 The process of "mixing H2O and scandium-containing solution to dissolve", "freezing crystallization and filtering of ferrous sulfate solution" is repeated n times, n≥0, until the scandium concentration in the scandium-containing solution n reaches a predetermined concentration, i.e. ≥0.01g / L, usually 0.04~0.1g / L. The purpose of this process is to increase the scandium concentration in the scandium-containing solution n as the raw material for subsequent scandium precipitation, but the scandium concentration should not be too high, as too high a scandium concentration will easily lead to the freezing crystallization of scandium sulfate and FeSO4 7H2O eutectic or FeSO4 The inclusion of scandium sulfate in 7H2O crystals leads to the loss of scandium in the scandium-containing solution.

[0034] In some embodiments, in step S5, the concentration of barium hydroxide is ≥0.01 mol / L, and the stirring is strengthened during the precipitation process to ensure that no solid is deposited at the bottom of the reactor; the reaction time depends on the endpoint pH, and the precipitation endpoint pH is preferably controlled at 3.5~5.5; after filtering the filtrate, a ferrous sulfate solution is obtained, and the ferrous sulfate solution is continuously circulated and used in steps S1-S3.

[0035] In some embodiments, in step S6, the acid solution is selected from sulfuric acid, hydrochloric acid, or nitric acid with a concentration of ≥0.1 mol / L; after the scandium hydroxide is completely dissolved, the system is filtered and washed to obtain barium sulfate, which is recovered after washing and filtration, and the obtained washing water is used to prepare the acid solution for dissolving the scandium hydroxide.

[0036] In some embodiments, in step S7, the concentration of oxalic acid or sodium oxalate is ≥0.1 mol / L, and the amount of oxalic acid or sodium oxalate used is 1-1.5 times the theoretical amount required for complete precipitation of scandium; the pH value of the scandium precipitation endpoint mixed solution is controlled at 0-5.5, preferably the pH value of the scandium precipitation endpoint mixed solution is controlled at 2.5~3.5.

[0037] In some embodiments, in step S5, the concentration of the barium hydroxide solution is 0.2-2 mol / L, the reaction temperature of the precipitation process is ≥0°C, preferably 30-60°C; the barium hydroxide solution is added at a rate of 4-10 ml / (min 100ml of scandium-containing solution), the scandium-containing solution in this "100ml of scandium-containing solution" refers to the filtrate adjusted with the barium hydroxide solution in step S5. This filtrate is obtained after filtering the scandium-containing solution in step S4, and is therefore also a scandium-containing solution.

[0038] In some embodiments, in step S6, the concentration of the acid solution is preferably 1-3.5 mol / L, and the stirring is strengthened during the dissolution process to ensure that no solids are deposited at the bottom of the reactor; the reaction temperature during the dissolution process is controlled at 0-90°C, preferably 20-40°C; the liquid-to-solid ratio (ml:g) of the acid solution and the mixed precipitate is ≥1, and preferably the liquid-to-solid ratio (ml:g) of the acid solution and the mixed precipitate is 5-10; the washing liquid-to-solid ratio (ml:g) of the washing process is ≥1, and preferably the liquid-to-solid ratio (ml:g) of the acid solution and the mixed precipitate is 3-5; countercurrent washing is performed, and the number of washing stages is 3-5.

[0039] In some embodiments, in step S7, the concentration of oxalic acid or sodium oxalate is 0.5-1.5 mol / L, the amount of oxalic acid or sodium oxalate used is 1-1.1 times the theoretical amount required for complete precipitation of scandium, the precipitation temperature is ≥10°C, the washing liquid-to-solid ratio (ml:g) is ≥1, countercurrent washing is performed, and the number of washing stages is 3-5.

[0040] In some embodiments, in step S4, the amount of reduced iron powder, sulfur dioxide, and sodium metabisulfite added depends on the concentration of ferric iron in the scandium-containing solution n, as long as all the ferric iron in the scandium-containing solution n is reduced to ferrous iron.

[0041] The present invention concentrates the by-product FeSO4 in the process of sulfuric acid titanium dioxide waste acid concentration. H2O is fully dissolved and the leachate is frozen and crystallized to remove FeSO4 7H2O, and then freeze the crystallization filtrate to fully dissolve FeSO4 H2O, and then freeze crystallize the filtrate to remove FeSO4 7H2O, thereby circulating FeSO4 Dissolution of H2O and FeSO4 7H2O is crystallized and removed to obtain a solution with a high scandium concentration as a raw material for precipitating scandium, and then the trivalent iron in the solution is reduced with a reducing agent, and then scandium is precipitated with barium hydroxide to obtain a mixture of barium sulfate and scandium hydroxide, and the scandium hydroxide in the mixture is dissolved with acid to obtain a scandium-containing solution, and then the scandium ions in the solution are precipitated with oxalic acid or sodium oxalate, and scandium oxalate is obtained after filtration and washing. After the scandium oxalate is roasted, scandium oxide with Sc2O3≥99.99% and Sc2O3 / REO≥99.9999% is obtained. The method of the present invention is easy to operate, simple in process flow, low in production cost, good in environmental protection benefits, easy to industrialize, and can efficiently recover FeSO4, a by-product of the sulfuric acid process titanium dioxide waste acid concentration process. There is a valuable element scandium in H2O.

[0042] This method prioritizes environmental protection throughout the scandium extraction process. Wastewater and residue generated in each step are properly treated and recycled, reducing waste emissions. For example, the recycling of barium sulfate precipitate and the reuse of wash water not only reduce environmental pollution but also maximize resource utilization, in line with the concept of sustainable development.

[0043] The present invention is further illustrated by the following examples.

[0044] Example 1 Step S1: Take FeSO4, a by-product of the sulfuric acid titanium dioxide waste acid concentration process H2O, the scandium content of which is 40g / t, weigh 500g of FeSO4 H2O, add 1000g distilled water, stir and mix at 60℃, stirring speed is 200rpm, until FeSO4 The H2O is completely dissolved and then filtered to obtain a high concentration ferrous sulfate solution 1.

[0045] Step S2: Transfer the ferrous sulfate solution 1 to a freeze crystallization device and perform freeze crystallization according to the temperature control system. First, naturally cool from 60°C to 30°C, then cool from 30°C to 20°C at a cooling rate of 3°C / min, and finally cool from 20°C to 0°C at a cooling rate of 0.05°C / min. During the entire cooling process, the stirring frequency is maintained at 300 rpm. After the freeze crystallization is completed, filter and obtain FeSO4 7H2O crystals and scandium-containing solution 1.

[0046] Step S3: Weigh 150g FeSO4 Add H2O to the scandium solution 1 and stir at 60℃ with a stirring speed of 200rpm to make FeSO4 H2O is completely dissolved to obtain a high concentration of ferrous sulfate solution 2. The ferrous sulfate solution 2 is subjected to freeze crystallization, and the freeze crystallization conditions are the same as those in step S2. After filtration, FeSO4 is obtained. 7H2O crystals and scandium solution 3. Repeat the process of "FeSO4 The process of mixing and dissolving H2O and the scandium-containing solution, freezing and crystallizing the high-concentration ferrous sulfate solution, and filtering was repeated three times to finally obtain scandium-containing solution 4. After testing, the scandium concentration in scandium-containing solution 4 was 0.035 g / L.

[0047] Step S4: Add an appropriate amount of reduced iron powder to the scandium-containing solution 4. The amount of reduced iron powder to be added is calculated based on the concentration of ferric iron in the solution (an excess amount of iron powder can also be used for reduction). Stir the mixture thoroughly to reduce all the ferric iron to ferrous iron. Filter the mixture to obtain a filtrate.

[0048] Step S5: Prepare a 0.5 mol / L barium hydroxide solution, slowly add the barium hydroxide solution to the filtrate while stirring, and control the addition rate to 6 ml / min. 100ml of scandium solution), the reaction temperature is controlled at 40℃. The solution pH is adjusted to 4.0, and after the pH stabilizes, it is filtered to obtain a mixed precipitate solid of ferrous sulfate solution, barium sulfate precipitate and scandium hydroxide precipitate. The ferrous sulfate solution is collected and used for the subsequent dissolution of FeSO4 H2O.

[0049] Step S6: 2 mol / L sulfuric acid is used to dissolve the mixed precipitate of barium sulfate and scandium hydroxide. The mixture is stirred and dissolved at 30°C, with a liquid-to-solid ratio of 8:1. After the scandium hydroxide is completely dissolved, the mixture is filtered and washed with distilled water at a liquid-to-solid ratio of 4:1. This is followed by three stages of countercurrent flow. This produces a scandium-containing filtrate and barium sulfate. The barium sulfate is then washed, filtered, and recovered, and the wash water is used to prepare the sulfuric acid for dissolving the scandium hydroxide.

[0050] Step S7: Prepare a 1 mol / L oxalic acid solution and add it to the scandium-containing filtrate. The amount of oxalic acid solution used is 1.1 times the theoretical amount required for complete scandium precipitation. The precipitation reaction is carried out at 40°C, with the pH at the scandium precipitation endpoint controlled at 3.0. After precipitation is complete, the solution is filtered, and the filtrate is reused in the scandium precipitation process. The solid is washed and filtered to obtain scandium oxalate. The washing liquid:solid ratio is 4:1, and the solution is washed three times. The scandium oxalate is calcined in a muffle furnace at 700°C for 5 hours to obtain scandium oxide with a Sc2O3 content of 99.99% and a Sc2O3 / REO ratio of 99.9999%.

[0051] Example 2 Step S1: Select FeSO4, a by-product of the sulfuric acid titanium dioxide waste acid concentration process H2O, the scandium content of which is 85g / t, weigh 600g of FeSO4 H2O, add 1200g of water with a total ion concentration of <0.1%, stir and mix at 55℃ with a stirring speed of 250rpm until FeSO4 The H2O is completely dissolved. After filtration, a high concentration of ferrous sulfate solution 1 is obtained.

[0052] Step S2: Place ferrous sulfate solution 1 into a freeze crystallization apparatus and perform freeze crystallization according to the temperature control system. Cool the solution from 55°C to 30°C at a rate of 10°C / min, then from 30°C to 20°C at a rate of 2°C / min, and finally from 20°C to -2°C at a rate of 0.03°C / min. Maintain the stirring frequency at 350 rpm. After the freeze crystallization is complete, filter and obtain FeSO4. 7H2O crystals and scandium-containing solution1.

[0053] Step S3: Weigh 200g FeSO4 Add H2O to the scandium solution 1 and stir at 55℃ with a stirring speed of 250rpm to make FeSO4 H2O is completely dissolved to obtain a high concentration of ferrous sulfate solution 2. The ferrous sulfate solution 2 is subjected to freeze crystallization, and the freeze crystallization conditions are the same as those in step S2. After filtration, FeSO4 is obtained. 7H2O crystals and scandium solution 3. Repeat "FeSO4 The process of "mixing and dissolving H2O and the scandium-containing solution, freezing and crystallizing the high-concentration ferrous sulfate solution, and filtering" was repeated three times to obtain a scandium-containing solution 4. The scandium concentration in the scandium-containing solution 4 was 0.081 g / L.

[0054] Step S4: introducing an appropriate amount of sulfur dioxide gas into the scandium-containing solution 4, wherein the amount of sulfur dioxide introduced is determined according to the concentration of ferric iron in the solution, and the ferric iron is fully reacted to reduce the ferric iron to ferrous iron, and then filtering is performed to obtain a filtrate.

[0055] Step S5: Prepare a 0.3 mol / L barium hydroxide solution and slowly add the barium hydroxide solution to the filtrate while stirring. The addition rate is controlled at 5 ml / min. 100ml of scandium solution) and the reaction temperature was maintained at 35°C. The solution pH was adjusted to 4.2 and filtered after the pH stabilized to obtain a mixed solid of ferrous sulfate solution, barium sulfate precipitate, and scandium hydroxide precipitate. The ferrous sulfate solution was collected and used for the subsequent dissolution of FeSO4 H2O.

[0056] Step S6: Dissolve the solid mixture of barium sulfate and scandium hydroxide in 1.5 mol / L hydrochloric acid, stirring at 25°C. The acid-to-solid ratio is 7:1. After the scandium hydroxide is completely dissolved, filter and wash with deionized water at a liquid-to-solid ratio of 3:1, then perform four countercurrent washes. This produces a scandium-containing filtrate and barium sulfate. The barium sulfate is washed, filtered, and recovered. The wash water is used to prepare the hydrochloric acid for dissolving the scandium hydroxide.

[0057] Step S7: Prepare a sodium oxalate solution with a concentration of 0.8 mol / L and add it to the scandium-containing filtrate. The amount of sodium oxalate solution used is 1.05 times the theoretical amount required for complete scandium precipitation. The precipitation reaction is carried out at 35°C, with the pH of the scandium precipitation endpoint controlled at 2.8. After precipitation is complete, the solution is filtered, and the filtrate is reused in the scandium precipitation process. The solid is washed and filtered to obtain scandium oxalate. The washing liquid:solid ratio is 3:1, and the solution is washed four times. The scandium oxalate is placed in a muffle furnace and calcined at 650°C for 6 hours to obtain scandium oxide with a Sc2O3 content of 99.99% and a Sc2O3 / REO ratio of 99.9999%.

[0058] Example 3 Step S1: Take FeSO4, a by-product of the sulfuric acid titanium dioxide waste acid concentration process H2O, the scandium content of which is 50g / t, weigh 700g of this FeSO4 H2O, add 1400g tap water, stir and mix at 70℃, stirring speed is 300rpm, until FeSO4 The H2O is completely dissolved. After filtration, a high concentration of ferrous sulfate solution 1 is obtained.

[0059] Step S2: Transfer the ferrous sulfate solution 1 to a freeze crystallization device and perform freeze crystallization according to the temperature control system. Cool the solution from 70°C to 30°C at a cooling rate of 15°C / min, then from 30°C to 20°C at a cooling rate of 4°C / min, and finally from 20°C to 5°C at a cooling rate of 0.08°C / min. The stirring frequency is maintained at 400 rpm. After the freeze crystallization is completed, filter and obtain FeSO4 7H2O crystals and scandium-containing solution 1.

[0060] Step S3: Weigh 250g FeSO4 H2O was added to the scandium solution 1 and stirred at 70℃ with a stirring speed of 300rpm to make FeSO4 H2O is completely dissolved to obtain a high concentration of ferrous sulfate solution 2. The ferrous sulfate solution 2 is subjected to freeze crystallization, and the freeze crystallization conditions are the same as those in step S2. After filtration, FeSO4 7H2O crystals and scandium solution 3. Repeat "FeSO4 The process of "mixing and dissolving H2O and the scandium-containing solution, freezing and crystallizing the high-concentration ferrous sulfate solution, and filtering" was repeated five times to obtain scandium-containing solution 6. After testing, the scandium concentration in scandium-containing solution 6 was 0.066 g / L.

[0061] Step S4: Add an appropriate amount of sodium metabisulfite to the scandium-containing solution 6, the amount of sodium metabisulfite to be added being calculated based on the concentration of ferric iron in the solution, and stir the mixture thoroughly to reduce the ferric iron to ferrous iron. After the reaction is complete, filter the mixture to obtain a filtrate.

[0062] Step S5: Prepare a 1 mol / L barium hydroxide solution, slowly add the barium hydroxide solution to the filtrate, and control the addition rate to 8 ml / min while stirring. 100ml of scandium solution) and the reaction temperature was controlled at 50°C. The pH of the solution was adjusted to 4.5 and filtered after the pH stabilized to obtain a mixed solid of ferrous sulfate solution, barium sulfate precipitate and scandium hydroxide precipitate. The ferrous sulfate solution was used to dissolve FeSO4 in the subsequent reaction. H2O.

[0063] Step S6: Dissolve the solid mixture of barium sulfate and scandium hydroxide in 3 mol / L nitric acid, stirring at 35°C. The solution is dissolved at a liquid-to-solid ratio of 9:1. After the scandium hydroxide is completely dissolved, filter and wash the mixture three times with distilled water at a liquid-to-solid ratio of 5:1. This produces a scandium-containing filtrate and barium sulfate. The barium sulfate is then washed, filtered, and recovered. The wash water is used to prepare the nitric acid for dissolving the scandium hydroxide.

[0064] Step S7: Prepare an oxalic acid solution with a concentration of 1.2 mol / L and add it to the scandium-containing filtrate. The amount of oxalic acid solution used is 1.1 times the theoretical amount required for complete scandium precipitation. The precipitation reaction is carried out at 50°C, with the endpoint pH of the scandium precipitation controlled to 3.2. After precipitation is complete, the solution is filtered, and the filtrate is reused in the scandium precipitation process. The solid is washed and filtered to obtain scandium oxalate. The washing liquid:solid ratio is 5:1, and the solution undergoes three stages of countercurrent washing. The scandium oxalate is calcined in a muffle furnace at 800°C for 4 hours to obtain scandium oxide with a Sc2O3 content of 99.99% and a Sc2O3 / REO ratio of 99.9999%.

[0065] The above are exemplary embodiments disclosed in the present invention, but it should be noted that various changes and modifications may be made without departing from the scope of the embodiments disclosed in the claims. Although the elements disclosed in the embodiments of the present invention may be described or required in individual form, they may also be understood as plural unless expressly limited to the singular.

[0066] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to limit the scope of the disclosure of the present invention (including the claims) to these examples. Within the spirit of the present invention, the technical features of the above embodiments or different embodiments may be combined, and many other variations exist in different aspects of the above embodiments, which are not provided in detail for the sake of clarity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for concentrating FeSO4, a by-product of the waste acid from sulfuric acid titanium dioxide The method for extracting scandium from H2O is characterized by: The following steps are involved: S1: FeSO4, a by-product of the sulfuric acid titanium dioxide waste acid concentration process Stir H2O and water thoroughly until FeSO4 H2O is completely dissolved, and the insoluble matter is filtered out to obtain the first ferrous sulfate solution; S2: freeze crystallize the first ferrous sulfate solution obtained in step S1, and then filter to obtain FeSO4 7H2O crystals and scandium-containing solutions; S3: Convert FeSO4 H2O is added to the scandium-containing solution obtained in step S2 and stirred thoroughly until FeSO4 H2O is completely dissolved to obtain a second ferrous sulfate solution; the second ferrous sulfate solution is frozen and crystallized according to the same steps as step S2, and then filtered to obtain FeSO4 7H2O crystals and a scandium-containing solution; repeating the above process several times until the scandium concentration in the scandium-containing solution reaches a predetermined concentration; S4: using a reducing agent to fully reduce the trivalent iron formed by oxidation in the scandium-containing solution having a predetermined concentration obtained in step S3, and then filtering to obtain a filtrate; S5: adjusting the pH of the filtrate to 3.5-5.5 with a barium hydroxide solution, and filtering to obtain a mixed precipitate of barium sulfate precipitate and scandium hydroxide precipitate; S6: using an acid solution to fully dissolve the scandium hydroxide in the mixed precipitate of the barium sulfate precipitate and the scandium hydroxide precipitate, stirring is strengthened during the dissolution process, and after the scandium hydroxide is completely dissolved, the system is filtered and washed to obtain a scandium-containing filtrate; S7: Precipitate the scandium in the scandium-containing filtrate obtained in step S6 with oxalic acid or sodium oxalate. After complete precipitation, filter and wash to obtain the precipitate as scandium oxalate; after high-temperature roasting, the scandium oxalate is obtained to obtain scandium oxide with Sc2O3≥99.99% and Sc2O3 / REO≥99.9999%.

2. FeSO4, a by-product of the waste acid concentration process of titanium dioxide from sulfuric acid process according to claim 1 The method for extracting scandium from H2O is characterized by: In step S1, FeSO4, a by-product of the sulfuric acid titanium dioxide waste acid concentration process, is used to H2O and water are mixed in a mass ratio of (5-7):10 at 50℃-70℃ until FeSO4 H2O dissolves completely.

3. FeSO4, a by-product of the waste acid concentration process of titanium dioxide from sulfuric acid process according to claim 1 The method for extracting scandium from H2O is characterized by: In step S2, the temperature of the freeze crystallization is controlled at -5°C to 10°C; the first ferrous sulfate solution obtained in step S1 is freeze crystallized according to a three-stage temperature control system, wherein the first stage is naturally cooled from 50°C to 70°C or cooled to 30°C to 40°C at a cooling rate of 1°C / min to 20°C to 25°C at a cooling rate of 1°C / min to 5°C / min, and the third stage is cooled from 20°C to 25°C to -5°C to 10°C at a cooling rate of 0.02°C / min to 1°C. The cooling process is synchronously stirred at a stirring frequency of 100-500 rpm.

4. The FeSO4 by-product from the sulfuric acid process titanium dioxide waste acid concentration process according to claim 1 The method for extracting scandium from H2O is characterized by: In step S3, FeSO4 H2O and the scandium-containing solution obtained in step S2 are mixed at a mass ratio of (0.5-3):7 at 50-70°C until FeSO4 The H2O is completely dissolved to obtain a second ferrous sulfate solution; the predetermined concentration of the scandium element in the scandium-containing solution must be ≥0.01 g / L.

5. The FeSO4 by-product from the sulfuric acid titanium dioxide waste acid concentration process according to claim 1 The method for extracting scandium from H2O is characterized by: In step S5, the concentration of barium hydroxide is ≥0.01 mol / L; after filtering the filtrate, a ferrous sulfate solution is obtained, which is continuously circulated and used in steps S1-S3.

6. FeSO4, a by-product of the waste acid concentration process of titanium dioxide from sulfuric acid process according to claim 1 The method for extracting scandium from H2O is characterized by: In step S6, the acid solution is selected from sulfuric acid, hydrochloric acid or nitric acid with a concentration of ≥0.1 mol / L; after the scandium hydroxide is completely dissolved, the system is filtered and washed to obtain barium sulfate, which is recovered after washing and filtration, and the obtained washing water is used to prepare the acid solution for dissolving the scandium hydroxide.

7. The FeSO4 by-product from the waste acid concentration process of titanium dioxide produced by sulfuric acid process according to claim 1 The method for extracting scandium from H2O is characterized by: In step S7, the concentration of oxalic acid or sodium oxalate is ≥0.1 mol / L, the amount of oxalic acid or sodium oxalate used is 1-1.5 times the theoretical amount required for complete precipitation of scandium, and the pH value of the mixed solution at the scandium precipitation endpoint is controlled at 0-5.

5.

8. FeSO4, a by-product of the waste acid concentration process of titanium dioxide from sulfuric acid process according to claim 4 The method for extracting scandium from H2O is characterized by: In step S5, the concentration of the barium hydroxide solution is 0.2-2 mol / L, the reaction temperature during the precipitation process is ≥0°C, and the barium hydroxide solution is added at a rate of 4-10 ml / min. 100ml of scandium solution).

9. FeSO4, a by-product of the waste acid concentration process of titanium dioxide produced by sulfuric acid process according to claim 5 The method for extracting scandium from H2O is characterized by: In step S6, the concentration of the acid solution is 1-3.5 mol / L, the reaction temperature during the dissolution process is controlled at 0-90°C, the liquid-to-solid ratio (ml:g) of the acid solution and the mixed precipitate is ≥1, and the washing process liquid-to-solid ratio (ml:g) is ≥1; countercurrent washing is performed, and the number of washing stages is 3-5.

10. The FeSO4 by-product from the sulfuric acid process titanium dioxide waste acid concentration process according to claim 6 The method for extracting scandium from H2O is characterized by: In step S7, the concentration of oxalic acid or sodium oxalate is 0.5-1.5 mol / L, the amount of oxalic acid or sodium oxalate used is 1-1.1 times the theoretical amount required for complete precipitation of scandium, the precipitation temperature is ≥10°C, the washing liquid-solid ratio (ml:g) is ≥1, countercurrent washing is performed, and the number of washing stages is 3-5.

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