Method for preparing high-purity iron oxide red by utilizing jarosite slag

Abstract

The invention discloses a method for preparing high-purity iron oxide red by utilizing jarosite slag, which comprises the following steps: mixing the jarosite slag with an oxalic acid solution, carrying out solid-liquid separation on a reaction product to obtain a zinc-powder-rich product, adding oxalic acid into an iron-rich complex ion Fe (C2O4) 33 <-> leaching solution to reduce iron powder so as to convert the iron powder into ferrous oxalate crystal precipitate, and carrying out solid-liquid separation on the iron-rich complex ion Fe (C2O4) 33 <-> leaching solution to obtain the high-purity iron oxide red. High-purity battery-grade ferrous oxalate powder is obtained through vacuum drying treatment, roasting is conducted under the inert atmosphere condition, a high-purity iron oxide red product with the purity larger than or equal to 98.5% and the particle size meeting the battery-grade use standard is finally obtained, and finally resource utilization and high-value utilization of the jarosite slag are achieved. The method provided by the invention not only overcomes the defects of long process flow, high energy consumption and high smelting cost of traditional jarosite slag treatment, but also solves the difficult problem of dangerous waste treatment for enterprises, generates various products with high added values, and has remarkable social benefits and economic benefits.

Description

Technical Field

[0001] The present invention belongs to the field of resource utilization of bulk hazardous / solid waste in nonferrous industry, and specifically relates to a method for high-value utilization of bulk hazardous waste jarosite slag in nonferrous industry and preparation of high-purity iron oxide red, which is particularly suitable for hazardous / solid resources where iron is mainly Fe 3+ The resource utilization of iron-containing dust and mud is carried out in the form of impurity elements such as CaO, MgO, Al2O3, SiO2, Cu, Pb, etc., and the content of impurities such as CaO, MgO, Al2O3, SiO2, Cu, and Pb is not higher than 15%, and the S content is 5~20%. It can be widely used in the resource utilization of large-scale solid waste in non-ferrous metal smelting, steel metallurgy and other industries. Background Art

[0002] Yellow jarosite slag, also known as jarosite slag (hereinafter referred to as jarosite slag), is the tailings produced by the jarosite method for removing iron when the non-ferrous industry conducts hydrometallurgical smelting of zinc, copper, nickel, cobalt, manganese and other valuable metals. The chemical formula of jarosite slag is AFe3(SO4)2(OH)6 (A is K + 、Na + , Pb 2+ 、H3O +), typically containing 25-40% Fe and 5-15% S. In addition, it also contains certain amounts of valuable metals such as Zn, Pb, Cu, and Ni, generally totaling 10-20%, primarily in the form of sulfates and oxides. For example, a hydrometallurgical zinc smelting plant with an annual output of 200,000 tons of electrolytic zinc generates nearly 60,000 tons of ferroalloy slag annually. By 2024, my country's cumulative zinc production will be approximately 8 million tons, with nearly 3 million tons of ferroalloy slag generated, making it a typical, bulk hazardous waste in the nonferrous metallurgy industry. Currently, treatment and disposal of ferroalloy slag primarily include pyrometallurgical, hydrometallurgical, and combined pyrometallurgical-hydrometallurgical processes. However, these treatment methods have the following drawbacks: Pyrometallurgical treatment of ferroalloy slag, due to its inherently high S content, produces high SO₂ concentrations in the flue gas after roasting, causing environmental pollution and significantly increasing environmental remediation costs. Furthermore, since metals such as Cu and Ag are difficult to volatilize, they are often directly incorporated into the reduced iron, resulting in low yields of valuable elements and significant resource waste. The wet process selectively enriches valuable elements from the leachate by adding reagents such as acids and alkalis, supplemented by high temperature, high pressure, and microbial methods, using extraction and ion precipitation. However, the complex process and the large amount of wastewater and waste residue generated still require further treatment, which is costly. The combined pyrometallurgical-wet process can more comprehensively recover valuable elements from iron alum residue, but this process is not only costly but also generates SO2 pollution in the flue gas, tailings, and tail liquid. Therefore, it has not yet been promoted and applied in actual production practice. The patent "A Wet Treatment Process for Ferrovanadium Slag in Wet Zinc Smelting" (CN 202110434643.7) proposes a method for reducing ferrovanadium slag with SO2, followed by oxidation of the solution, and ultimately producing hematite through solid-liquid separation and purification. This method overcomes the shortcomings of pyrometallurgical treatment, which involves high energy consumption and high pollution. However, the process is relatively demanding, and SO2 pollution during the reduction stage poses serious environmental problems. The patent "A Method for Preparing Autoclaved Bricks from Ferrovanadium Slag" (CN201810891593.3) proposes a method for preparing autoclaved bricks from ferrovanadium slag with a certain compressive strength, using ferrovanadium slag as a raw material and synergizing it with other types of solid waste (coarse aggregate, fine aggregate, iron tailings, etc.). However, this method does not fundamentally solve the treatment and disposal problems of ferrovanadium slag. Harmful components such as sulfur in the autoclaved bricks produced are easily leached, causing environmental pollution. Furthermore, the equipment investment cost is high, and the product added value is low, making it unsuitable for market promotion.

[0003] In view of this, and in response to the cost and environmental issues faced by the resource and high-value utilization of existing iron alum slag, the present invention proposes a method for preparing high-purity iron oxide red through the process of "selective leaching of oxalic acid to extract iron - hydrothermal reduction precipitation to prepare high-purity ferrous oxalate - solid-phase reaction to prepare high-purity iron oxide red". This method not only overcomes the shortcomings of traditional iron alum slag treatment and disposal processes, such as long process flow, high energy consumption, and high smelting costs, but also solves the difficult problem of hazardous waste disposal for enterprises. At the same time, the high-value-added products (battery-grade ferrous oxalate, high-purity iron oxide red) produced can also bring new economic growth points to enterprises, with significant social, economic and environmental benefits. Summary of the Invention

[0004] The purpose of the present invention is to overcome the problems of the existing jarosite slag disposal technology, such as long process flow, high energy consumption, large amount of unorganized emissions, and low product added value, and to provide a method for preparing high-purity red iron oxide using jarosite slag. The method uses jarosite slag as a raw material, utilizes the rich iron resources therein, and ultimately prepares high-purity red iron oxide, thereby achieving the purpose of completely converting hazardous waste resources into high-value-added products.

[0005] To achieve the above-mentioned object of the present invention, the present invention provides a method for preparing high-purity red iron oxide using jarosite slag, which uses jarosite slag actually produced by non-ferrous smelting enterprises as raw material. First, an organic acid solution (preferably oxalic acid) is used as a leaching agent, and iron powder is used as a reducing agent. The three are mixed in a certain proportion to form a slurry. The complex reaction between iron ions and organic acid radical ions (such as oxalate ions) is used to convert the rich iron resources in the electric furnace dust ash into a high-value-added product ferrous oxalate under low temperature and normal pressure experimental conditions; the slurry after the reaction is subjected to solid-liquid separation. At this time, the Zn content in the leached residue can be greatly increased, and it can be used as a zinc extraction raw material, which greatly reduces the direct zinc extraction raw material processing amount while obtaining a higher purity zinc product; the reaction tail liquid can be used as a solvent to continuously leach the jarosite slag, without external waste liquid discharge, and overall near-zero emission is achieved; in order to enrich the product variety, high-purity ferrous oxalate is used as a raw material, and the ferrous oxalate is finally converted into high-purity red iron oxide under an inert roasting atmosphere, thereby ultimately realizing the resource utilization and high-value utilization of the jarosite slag.

[0006] The present invention provides a method for preparing high-purity iron oxide red by utilizing jarosite slag, which is specifically implemented according to the following process and steps:

[0007] S1 Raw material pretreatment

[0008] Using jarosite slag, a bulk iron-rich hazardous waste from hydrometallurgical zinc smelting, as raw material, particle size analysis and moisture content analysis were performed. Based on the moisture content analysis results, the jarosite slag was first dehydrated and dried to obtain a dry jarosite slag material with a moisture content of ≤5.0%. Based on the particle size analysis results, the dry jarosite slag material was ground to obtain a fine-grained jarosite slag raw material with a -0.074mm particle size content of ≥85%.

[0009] S2 Oxalic Acid Selective Leaching

[0010] The fine-grained jarosite slag raw material obtained in step S1 is mixed with an oxalic acid solution with a mass fraction of 8-25%, and the oxalic acid solution is added according to a liquid-solid ratio of 10 / 1ml / g to 30 / 1ml / g of the jarosite slag. After sufficient stirring and mixing, the reaction device is placed in a constant temperature water bath at 50-90°C to allow the iron-containing components in the jarosite slag to undergo a hydrothermal complexation reaction with oxalate to generate soluble iron-containing complex ions Fe(C2O4)3 3- The product after the reaction is separated into solid and liquid, and the supernatant is filtered several times to remove the suspended impurities in the leachate to obtain the iron-rich complex ion Fe(C2O4)3 3- Leachate A; suspended impurities are filtered and dehydrated to obtain a zinc-rich powder product with a ZnO content greater than 33%;

[0011] S3 Preparation of Battery-Grade Ferrous Oxalate by Hydrothermal Reduction Precipitation

[0012] The iron-rich complex ion Fe(C2O4)3 obtained in step S2 3- Leaching solution A is used as raw material, oxalic acid and reduced iron powder are used as additives, and the reaction mixture is prepared according to the reaction of oxalic acid with Fe(C2O4)3 in leachating solution A. 3- The mass ratio of the substance is controlled at (0.6~2) / 1, the reduced iron powder and Fe(C2O4)3 in the leaching solution A 3- The mass ratio of the substances was controlled at (0.8~2.5) / 1 for addition, the stirring speed was regulated, the reaction temperature was controlled at 30~60℃, and the reaction time was 4~10 h. The redox reaction between iron ions of different valences was used to convert the high concentration of iron-rich complex ions Fe(C2O4)3 in the solution into 3- The ferrous oxalate crystalline precipitate is then filtered, washed, and dehydrated in a vacuum drying oven at a certain temperature. The vacuum drying temperature is controlled at 60-90°C, the vacuum degree is controlled at -0.2-0 MPa, and the drying time is 5-20 hours to obtain high-purity battery-grade ferrous oxalate powder. The filtered tail liquid B can be recycled as a solvent for subsequent leaching of jarosite residue.

[0013] S4 Preparation of High-Purity Iron Oxide Red by Solid-Phase Reaction

[0014] The high-purity battery-grade ferrous oxalate powder obtained in step S3 is used as raw material and calcined in an inert atmosphere at a temperature of 400-600 °C. The calcination time is controlled within 4-10 h, and finally a high-purity iron oxide red product with a purity of ≥99.0% and a particle size that meets battery-grade standards is obtained.

[0015] Furthermore, in step S1, the jarosite slag raw material is required to have Fe mainly in the form of Fe2O3, with a total iron content of ≥25%, of which Fe 3+ It is better to account for more than 80% of the total iron content; the moisture content of the fine-grained iron-rich material is preferably ≤1.0%, and the content of -0.074 mm particle size in the fine-grained raw material is ≥95%.

[0016] Furthermore, in step S2, the oxalic acid solution and the iron alum slag are preferably added according to a liquid-solid ratio of 15 / 1ml / g~20 / 1ml / g; the mass fraction of the oxalic acid solution is preferably controlled at 10~15%; the stirring speed is controlled at 200~300 r / min; the reaction temperature of the hydrothermal complex reaction is preferably controlled at 70~80°C, and the reaction time is generally 2~6h, with 3~4h being optimal.

[0017] Further, in step S3, according to the reaction between oxalic acid and Fe(C2O4)3 in leachate A, 3- The mass ratio of the substance is controlled at (1.0~1.5) / 1, the reduced iron powder and Fe(C2O4)3 in the leaching solution A 3- The mass ratio of the substances should be controlled at (1.25~1.75) / 1 for addition; the reaction temperature should be controlled at 40~50 ℃, the reaction time should be 6~8 h, and the stirring speed should be controlled at 200~300 r / min.

[0018] Preferably, in step S3, the vacuum drying temperature is controlled at 70-80°C, the vacuum degree is controlled at -0.2-0.1 MPa, and the drying time is 10-15 hours.

[0019] Preferably, in step S4, the calcination is carried out in an argon or nitrogen atmosphere, with the gas flow rate controlled at 200-400 sccm; the calcination temperature is 400-450° C.; and the calcination time is controlled at 6-7 h.

[0020] Compared with the prior art, the method of preparing high-purity iron oxide red by using jarosite slag of the present invention has the following innovations and beneficial effects:

[0021] (1) The present invention provides a method for treating iron alum residue through a wet process to prepare high-purity red iron oxide, ultimately achieving the harmless disposal and high-value utilization of this hazardous waste, iron alum residue, and is an original innovation. Compared with the traditional high-temperature pyrolysis roasting process, this process overcomes the shortcomings of high roasting temperatures and large emissions, effectively reducing the threat posed by hazardous waste to the environment while reducing the production cost of high-purity red iron oxide from the raw material side, resulting in significant economic advantages.

[0022] (2) The present invention provides a method for high-value utilization of typical hazardous waste iron alum slag in the nonferrous industry through the process of "hydrothermal complexation selective leaching - hydrothermal reduction precipitation to prepare high-purity ferrous oxalate - solid-phase reaction to prepare high-purity iron oxide red". Using hazardous waste as raw material, by adjusting the reaction conditions, iron oxide red powder with an average particle size of 4.056 μm is finally prepared. The particle size is fine and controllable; the product purity is greater than 98.5%, and can reach a maximum of more than 99%, which meets the quality requirements of downstream high-performance material manufacturers such as batteries, has high added value, and is more competitive in the market.

[0023] (3) The present invention provides a method for preparing high-purity red iron oxide using iron alum slag as raw material, through wet leaching, and cascade separation and extraction of the rich iron resources therein. Compared with conventional technologies, the final tail liquid in this method is not discharged, but is returned to the leaching process for recycling. Neutralization treatment of the tail liquid is not required, which significantly reduces emissions and reduces environmental protection management costs by more than 60%.

[0024] (4) The present invention provides a method for preparing a high-value-added product, red iron oxide, by using iron alum slag, a typical hazardous waste in the nonferrous industry, as a raw material for resource utilization and high-value-added utilization. From the perspective of the overall production process of red iron oxide, the method can reduce production costs by more than 50%, has high technical and economic value, and has greater industrialization prospects than traditional iron alum slag treatment and red iron oxide preparation processes. The reaction conditions are mild, some traditional production processes have been greatly simplified, the investment cost is low, and the direct economic benefits are significant. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a process flow chart of the principle of a method for preparing high-purity iron oxide red using jarosite slag according to the present invention;

[0026] Figure 2 The XRD diffraction pattern of the jarosite slag powder used in the method of the present invention is obtained by using a Cu-Kα target radiation, a diffraction angle 2θ of 10-90°, and an X-ray wavelength λ of 0.15416 nm;

[0027] Figure 3 This is a scanning electron microscope image of the jarosite slag powder used in the method of the present invention;

[0028] Figure 4 A graph showing the effect of temperature on the leaching rate of the iron component in jarosite slag when the jarosite slag is subjected to hydrothermal complex leaching by the method of the present invention;

[0029] Figure 5 A graph showing the influence of oxalic acid concentration on the leaching rate of iron components in jarosite slag when the hydrothermal complex jarosite leaching method of the present invention is performed;

[0030] Figure 6 A graph showing the influence of the liquid-to-solid ratio on the leaching rate of the iron component in the jarosite slag when the jarosite slag is leached by hydrothermal complexation according to the method of the present invention;

[0031] Figure 7 A graph showing the effect of reaction time on the leaching rate of iron components in jarosite slag when the method of the present invention is used to perform hydrothermal complex leaching of jarosite slag;

[0032] Figure 8 This is a particle size analysis diagram of the acid leaching product obtained by hydrothermal complexation of jarosite slag with oxalic acid according to the method of the present invention;

[0033] Figure 9 This is the XRD spectrum of the acid leaching product obtained by hydrothermal complexation of jarosite slag with oxalic acid according to the method of the present invention, using Cu-Kα target radiation, a diffraction angle 2θ of 10-90°, and an X-ray wavelength λ of 0.15416 nm;

[0034] Figure 10 This is a scanning electron microscope image of the acid leaching product obtained by hydrothermal complexation of jarosite residue with oxalic acid according to the method of the present invention;

[0035] Figure 11 A graph showing the effect of temperature on the purity and particle size of ferrous oxalate during the preparation of ferrous oxalate by hydrothermal reduction precipitation.

[0036] Figure 12 A graph showing the effect of the iron powder addition ratio on the purity and particle size of ferrous oxalate when preparing ferrous oxalate by hydrothermal reduction precipitation according to the method of the present invention;

[0037] Figure 13 This is the particle size distribution diagram of the ferrous oxalate product prepared by hydrothermal reduction precipitation according to the present invention;

[0038] Figure 14 The XRD diffraction pattern of ferrous oxalate product prepared by hydrothermal reduction precipitation was obtained using Cu-Kα target radiation with a diffraction angle 2θ of 10~90° and an X-ray wavelength of λ=0.15416 nm.

[0039] Figure 15 This is a scanning electron microscope image of ferrous oxalate prepared by hydrothermal reduction precipitation according to the method of the present invention;

[0040] Figure 16 The particle size analysis diagram of high-purity iron oxide red powder prepared by solid phase reaction according to the present invention (specific surface area is 1597 m 2 / kg). DETAILED DESCRIPTION

[0041] To further describe the present invention, a method for preparing high-purity iron oxide red by utilizing jarosite slag is described in further detail below with reference to the accompanying drawings and examples.

[0042] The experimental raw material in the embodiment is jarosite slag, a zinc smelting by-product produced in the production activities of a certain hydrometallurgical zinc smelting enterprise.

[0043] To understand the chemical composition of jarosite slag, a multi-element chemical analysis was conducted. The results are shown in Table 1. The Fe, Zn, and Pb contents in the jarosite slag were 27.80%, 6.34%, and 1.69%, respectively. The S content in the jarosite slag was high, at 13.48%. Other elements, such as CaO, MgO, Al₂O₃, and SiO₂, were 1.02%, 0.48%, 2.42%, and 7.68%, respectively. The basicity (CaO + MgO) / (SiO₂ + Al₂O₃) was 0.15, indicating a typical acidic slag.

[0044] Table 1 Chemical multi-element analysis of jarosite slag / wt%

[0045]

[0046] Depend on Figure 2 It can be seen that the phase composition of jarosite slag is relatively simple, and its phases mainly include: ammonium jarosite NH4Fe3(SO4)2(OH)6, lead jarosite Pb(Fe3(SO4)2(OH)6)2, and zinc ferrite ZnFe2O4. Among them, the valuable element iron mainly exists in the form of ammonium jarosite, lead jarosite, and zinc ferrite compounds, zinc mainly exists in the form of zinc ferrite, and sulfur mainly exists in ammonium jarosite and lead jarosite.

[0047] Figure 3 This is a scanning electron microscope image of the jarosite slag powder used in the method of the present invention. Figure 3 It can be seen that the particle size of jarosite slag is relatively small, and the interior mainly presents a state of existence of a large molecular structure of small particle agglomerates. The leaching of iron components in jarosite slag requires chemical forces to destroy the bonds between molecules. It is difficult to achieve the separation and recovery of valuable components using conventional physical sorting methods.

[0048] Experimental studies have shown that the zinc ferrite phase in jarosite slag will be destroyed after acid leaching, further releasing the iron component and further enriching the zinc component. At the same time, based on the complexation between Fe ions, Zn ions and oxalate ions, the clean extraction and cascade separation and recovery of valuable components can be achieved.

[0049] Depend on Figure 1 As shown in the process flow chart of the present invention, a method for preparing high-purity red iron oxide using jarosite slag is shown. In the embodiment, the method of the present invention is implemented by the following process steps:

[0050] S1 Raw material pretreatment

[0051] Jarrosite slag, a bulk iron-rich hazardous waste from hydrometallurgical zinc smelting enterprises, was used as raw material. The jarosite slag was first dehydrated and dried in a drying oven at 80 ℃ for 12 h to obtain a dry material with a moisture content of ≤0.5%. According to the results of particle size analysis, the initial particle size distribution of the jarosite slag was 72% with a particle size of -0.074 mm. The dry material was ball milled in a planetary ball mill for 6 h to obtain a fine-grained jarosite slag with a particle size of -0.074 mm and a content of 97.0% of fine-grained jarosite slag.

[0052] S2 Oxalic Acid Selective Leaching

[0053] The fine-grained jarosite slag obtained in step S1 is mixed with the oxalic acid solution in a set ratio, and after being fully stirred and mixed evenly, the reaction device is placed in a constant temperature water bath, and the reaction temperature, reaction time and other condition parameters are adjusted to allow the iron-containing components in the jarosite slag to undergo a hydrothermal complexation reaction with the oxalate ions to generate soluble iron-containing complex ions Fe(C2O4)3 3- The product after the reaction is separated into solid and liquid, and the supernatant is filtered several times to remove the suspended impurities in the leachate to obtain the iron-rich complex ion Fe(C2O4)3 3- Leachate A: The suspended impurities are filtered and dehydrated to obtain a zinc-rich powder product with a ZnO content greater than 33%.

[0054] Figure 4 A graph showing the effect of temperature on the leaching rate of the iron component in jarosite slag when the jarosite slag is subjected to hydrothermal complex leaching by the method of the present invention; Figure 5 A graph showing the influence of oxalic acid concentration on the leaching rate of iron components in jarosite slag when the hydrothermal complex jarosite leaching method of the present invention is performed; Figure 6 A graph showing the influence of the liquid-to-solid ratio on the leaching rate of the iron component in the jarosite slag when the jarosite slag is leached by hydrothermal complexation according to the method of the present invention; Figure 7 The present invention is a method for leaching jarosite slag by hydrothermal complexation, and the reaction time is used to determine the leaching rate of the iron component in the jarosite slag.

[0055] Depend on Figure 4-7 It can be seen that under the conditions of liquid-to-solid ratio of 20:1, oxalic acid solution concentration of 15% and reaction time of 2 h, the leaching rate of jarosite slag increases with increasing temperature. The leaching rate growth varies greatly at 30-40 °C and gradually stabilizes at 70-80 °C. With the increase of oxalic acid concentration, the leaching rate shows a higher level when the oxalic acid concentration is 10-15%. It is appropriate to further optimize the oxalic acid concentration to 12-15%. Under the premise of keeping the oxalic acid concentration unchanged, the oxalic acid content in the solution will increase with the increase of liquid-to-solid ratio. Considering the equipment investment cost and production cost, the optimal reaction conditions should be 15:1-20:1. The leaching efficiency increases with time, and the reaction time should be controlled at 3-4 h.

[0056] The above experimental conditions indicate that the optimal hydrothermal leaching conditions for jarosite slag are: reaction temperature of 80°C, oxalic acid concentration of 15%, liquid-to-solid ratio of 20:1, reaction time of 180 minutes, and stirring speed of 300 rpm. XRF analysis and characterization of the leached product are shown in Table 2.

[0057] Table 2 Chemical multi-element analysis of jarosite slag acid leaching products (wt%)

[0058]

[0059] As shown in Table 2, the suspended impurities were filtered and dehydrated to obtain a zinc-rich powder product with a ZnO content of 34.15%.

[0060] Figure 8 This is a particle size analysis diagram of the acid leaching product obtained by hydrothermal complexation of jarosite slag with oxalic acid according to the method of the present invention; Figure 9 This is the XRD spectrum of the acid leaching product obtained by hydrothermal complexation of jarosite slag with oxalic acid according to the method of the present invention, using Cu-Kα target radiation, a diffraction angle 2θ of 10-90°, and an X-ray wavelength λ of 0.15416 nm.

[0061] Depend on Figure 8 、 Figure 9 It can be seen that the particle size of the acid leaching product obtained in this experiment is D10=1.92 μm, D50=5.318 μm, and D90=21.45 μm. The leached residue was characterized using a D8 ADVANCE X-ray diffraction analyzer, and the results are as follows: Figure 9 As shown, the main components of the leached residue are zinc oxalate (ZnSO4·2H2O) and lead sulfate (PbSO4). This indicates that the acid chemical action destroys the molecular structure within the jarosite residue, releasing the valuable elements present therein. Scanning electron microscopy (SEM) was further used to examine the external morphology of the leached residue samples.

[0062] Depend on Figure 10 As shown in the scanning electron microscope image of the acid leaching product obtained by the oxalic acid hydrothermal complexation of jarosite slag by the method of the present invention, obvious erosion marks appear on the surface of the jarosite slag particles after acid leaching, and the surface becomes loose and rough, indicating that the acid-soluble phase of the jarosite slag is leached during the reaction process, and the particle structure is destroyed and becomes an irregular step shape.

[0063] S3 Preparation of Battery-Grade Ferrous Oxalate by Hydrothermal Reduction Precipitation

[0064] The iron-rich complex ion Fe(C2O4)3 obtained in step S2 3- Leaching solution A is used as raw material, oxalic acid and reduced iron powder are used as additives, and the oxalic acid and Fe(C2O4)3 in the leachating solution A are mixed according to the set 3- The mass ratio of the substance, the reduced iron powder and Fe(C2O4)3 in the leachate A 3- The mass ratio of the substances is added, the stirring speed is adjusted, the reaction temperature and reaction time are controlled, and the iron-rich complex ion Fe(C2O4)3 with a high concentration in the solution is converted to Fe(C2O4)3 by the redox reaction between iron ions of different valences. 3- The ferrous oxalate crystalline precipitate is converted into ferrous oxalate crystalline precipitate; the ferrous oxalate crystalline precipitate is filtered, washed, and dehydrated in a vacuum drying oven at a certain temperature and vacuum degree, and the drying time is controlled to obtain high-purity battery-grade ferrous oxalate powder; the filtered tail liquid B can be recycled as a solvent for subsequent cyclic leaching of jarosite slag.

[0065] Figure 11 A graph showing the effect of temperature on the purity and particle size of ferrous oxalate during the preparation of ferrous oxalate by hydrothermal reduction precipitation. Figure 12 The curve diagram of the influence of the iron powder addition ratio on the purity and particle size of ferrous oxalate when preparing ferrous oxalate by hydrothermal reduction precipitation according to the present invention is shown in the figure. The experimental results show that under the conditions of the molar mass ratio of iron powder to oxalic acid of 1.25:1 and the reaction time of 2h, the influence of reaction temperature on the purity and particle size of the product is investigated. Figure 11 As shown in the figure, the most suitable time for the formation of ferrous oxalate is 40~45℃. Under the conditions of reaction temperature of 40℃ and reaction time of 8h, the effect of the addition ratio of iron powder on the purity and particle size of the product was investigated. The results are shown in Figure 12 As shown in the figure, the appropriate iron powder addition ratio for ferrous oxalate generation is 1.25~1.5.

[0066] Figure 13 This is the particle size distribution diagram of the ferrous oxalate product prepared by hydrothermal reduction precipitation according to the present invention; Figure 14The XRD diffraction pattern of the ferrous oxalate product prepared by hydrothermal reduction precipitation was obtained using a Cu-Kα target radiation with a diffraction angle 2θ of 10-90° and an X-ray wavelength λ of 0.15416 nm. The ferrous oxalate product was analyzed using a Bettersize 2000 laser particle size analyzer. The results are as follows: Figure 13 The product was characterized using a D8 ADVANCE X-ray diffraction analyzer, and the results were as shown in Figure 14 It was found that the prepared ferrous oxalate corresponds to the ferrous oxalate standard card JCPDS NO.23-0293, and the detected peak intensity is large, proving that the product is well crystallized and has high crystallinity; no impurity peaks appear, further verifying that the product has high purity.

[0067] Figure 15 This is a scanning electron microscope image of ferrous oxalate prepared by hydrothermal reduction precipitation according to the present invention. Figure 5 It can be seen that the ferrous oxalate product is in the shape of a regular cuboid, has a small particle size, good reactivity, and excellent physical and chemical properties. It can be used as a raw material for preparing high-value-added iron oxide red.

[0068] S4 Preparation of High-Purity Iron Oxide Red by Solid-Phase Reaction

[0069] The high-purity battery-grade ferrous oxalate powder obtained in step S3 was used as raw material, and the reaction was carried out under Ar atmosphere and a calcination temperature of 450 °C for 6 h to finally obtain a high-purity iron oxide red product with a purity of ≥99.6% and a particle size that meets battery-grade standards.

[0070] Figure 16 The particle size analysis diagram of high-purity iron oxide red powder prepared by solid phase reaction according to the present invention (specific surface area is 1597 m 2 / kg). Figure 16 As can be seen, the iron oxide red powder prepared by the reaction has a relatively fine particle size, with D10 = 2.28 μm, D50 = 4.31 μm, and D90 = 8.28 μm. Table 3 shows the mass analysis results of the iron oxide red prepared in the experiment. As can be seen from Table 3, the iron oxide red prepared in this example has a high purity of up to 99.60%; the contents of major impurity components such as K, Na, Cu, Zn, Ni, sulfate, and chloride are relatively low, and the product is of good quality, meeting the requirements for battery-grade iron oxide red use and having a promising market prospect.

[0071] Table 3 Iron oxide red product quality analysis results

[0072]

Claims

1. A method for preparing high-purity iron oxide red using jarosite slag, characterized in that Use the following steps to implement: S1 Raw material pretreatment Using jarosite slag, a bulk iron-rich hazardous waste from hydrometallurgical zinc smelting, as raw material, particle size analysis and moisture content analysis were performed. Based on the moisture content analysis results, the jarosite slag was first dehydrated and dried to obtain a dry jarosite slag material with a moisture content of ≤5.0%. Based on the particle size analysis results, the dry jarosite slag material was ground to obtain a fine-grained jarosite slag raw material with a -0.074mm particle size content of ≥85%. S2 Oxalic Acid Selective Leaching The fine-grained jarosite slag raw material obtained in step S1 is mixed with an oxalic acid solution with a mass fraction of 8-25%, and the oxalic acid solution is added according to a liquid-solid ratio of 10 / 1ml / g to 30 / 1ml / g of the jarosite slag. After sufficient stirring and mixing, the reaction device is placed in a constant temperature water bath at 50-90°C to allow the iron-containing components in the jarosite slag to undergo a hydrothermal complexation reaction with oxalate to generate soluble iron-containing complex ions Fe(C2O4)3 3- The product after the reaction is separated into solid and liquid, and the supernatant is filtered several times to remove the suspended impurities in the leachate to obtain the iron-rich complex ion Fe(C2O4)3 3- Leachate A; suspended impurities are filtered and dehydrated to obtain a zinc-rich powder product with a ZnO content greater than 33%; S3 Preparation of Battery-Grade Ferrous Oxalate by Hydrothermal Reduction Precipitation The iron-rich complex ion Fe(C2O4)3 obtained in step S2 3- Leaching solution A is used as raw material, oxalic acid and reduced iron powder are used as additives, and the reaction mixture is prepared according to the reaction of oxalic acid with Fe(C2O4)3 in leachating solution A. 3- The mass ratio of the substance is controlled at (0.6~2) / 1, the reduced iron powder and Fe(C2O4)3 in the leaching solution A 3- The mass ratio of the substances was controlled at (0.8~2.5) / 1 for addition, the stirring speed was regulated, the reaction temperature was controlled at 30~60℃, and the reaction time was 4~10 h. The redox reaction between iron ions of different valences was used to convert the high concentration of iron-rich complex ions Fe(C2O4)3 in the solution into 3- The ferrous oxalate crystalline precipitate is then filtered, washed, and dehydrated in a vacuum drying oven at a certain temperature. The vacuum drying temperature is controlled at 60-90°C, the vacuum degree is controlled at -0.2-0 MPa, and the drying time is 5-20 hours to obtain high-purity battery-grade ferrous oxalate powder. The filtered tail liquid B can be recycled as a solvent for subsequent leaching of jarosite residue. S4 Preparation of High-Purity Iron Oxide Red by Solid-Phase Reaction The high-purity battery-grade ferrous oxalate powder obtained in step S3 is used as raw material and calcined in an inert atmosphere at a temperature of 400-600 °C. The calcination time is controlled within 4-10 h, and finally a high-purity iron oxide red product with a purity of ≥98.5% and a particle size that meets battery-grade standards is obtained.

2. The method for preparing high-purity iron oxide red by utilizing jarosite slag as claimed in claim 1, wherein: In step S1, the Fe in the jarosite slag raw material is mainly present in the form of Fe2O3, and the total iron content is ≥25%, of which Fe 3+ It accounts for more than 80% of the total iron content.

3. A method for preparing high-purity iron oxide red using jarosite slag as claimed in claim 1, characterized in that: In step S1, the moisture content of the fine-grained iron-rich material is ≤1.0%; the content of -0.074 mm particle size in the fine-grained raw material is ≥95%.

4. A method for preparing high-purity iron oxide red using jarosite slag as claimed in claim 1, characterized in that: In step S2, the oxalic acid solution and the iron alum slag are added according to a liquid-solid ratio of 15 / 1 ml / g to 20 / 1 ml / g; the mass fraction of the oxalic acid solution is controlled at 10-15%.

5. A method for preparing high-purity iron oxide red using jarosite slag as claimed in claim 4, characterized in that: In step S2, the stirring speed is controlled at 200-300 r / min; the reaction temperature of the hydrothermal complexation reaction is controlled at 70-80°C, and the reaction time is 2-6 hours.

6. A method for preparing high-purity iron oxide red using jarosite slag as claimed in claim 4, characterized in that: In step S2, the reaction time of the hydrothermal complexation reaction is 3 to 4 hours.

7. A method for preparing high-purity iron oxide red using jarosite slag as claimed in claim 1, 2, 3, 4 or 5, characterized in that: In step S3, the oxalic acid reacts with Fe(C2O4)3 in the leaching solution A. 3- The mass ratio of the substance is controlled at (1.0~1.5) / 1, the reduced iron powder and Fe(C2O4)3 in the leaching solution A 3- The mass ratio of the substances is controlled at (1.25~1.75) / 1 for addition.

8. A method for preparing high-purity iron oxide red using jarosite slag as claimed in claim 7, characterized in that: In step S3, the reaction temperature is controlled at 40-50°C; the reaction time is 6-8 h; and the stirring speed is controlled at 200-300 r / min.

9. A method for preparing high-purity iron oxide red using jarosite slag as claimed in claim 8, characterized in that: In step S3, the vacuum drying temperature is controlled at 70-80°C, the vacuum degree is controlled at -0.2-0.1 MPa, and the drying time is 10-15 h.

10. The method for preparing high-purity iron oxide red using jarosite slag according to claim 9, wherein: In step S4, calcination is performed under an argon or nitrogen atmosphere with a gas flow rate controlled at 200-400 sccm; a calcination temperature at 400-450°C; and a calcination time at 6-7 h.

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