Method for producing high-purity iron red by using iron waste residue of rare earth smelting

Abstract

The application discloses a method for producing high-purity iron red by using iron waste slag in rare earth smelting, and relates to the field of rare earth smelting. According to the principle that iron hydroxide can be crystallized by heating in sodium hydroxide solution, and is converted into a crystal type of hydrated ferric oxide which is hardly soluble in acid by high-temperature pyrolysis, and the difference in solubility of the two in an acidic condition is used for selective leaching and separation, the iron waste slag produced in the rare earth wet smelting can be converted into a crystal type of hydrated ferric oxide by two-stage heating to different temperatures in sodium hydroxide solution, so that the solubility of iron and non-iron elements in an acidic condition is changed, and the dissolution and separation are facilitated. The process has low actual alkali consumption, and the residual alkali can be recycled, the obtained high-purity iron red meets the national standard in terms of color and impurity content, and the operation process is simple and meets the national green development concept.

Description

A method for producing high-purity iron oxide from iron slag produced by rare earth smelting Technical Field

[0001] This invention relates to the field of rare earth smelting, and more specifically to a method for producing high-purity iron oxide from iron waste slag from rare earth smelting. Background Technology

[0002] Fluorocarbonate cerium ore is the most widely distributed rare earth resource and one of the important raw materials for my country's rare earth industry. Currently, the mainstream process is oxidative roasting-hydrochloric acid leaching-alkali conversion-optimal dissolution. Because this ore contains approximately 1%-2% iron, a considerable amount of iron waste is generated during the rare earth hydrometallurgical process. This waste is mainly composed of ferric hydroxide with a rare earth content of 5%-10%, and contains various non-metallic impurities. Typically, there is no reasonable method for the resource utilization of this iron waste; it can only be temporarily stored and piled up, which occupies land and pollutes the environment. Summary of the Invention

[0003] To address the aforementioned shortcomings of existing technologies, this invention provides a method for producing high-purity iron oxide from iron slag produced by rare earth smelting.

[0004] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows:

[0005] A method for producing high-purity iron oxide red using iron waste from rare earth smelting is provided, comprising the following steps:

[0006] S1: Mix sodium hydroxide solution and iron waste residue evenly and then grind;

[0007] S2: Stir the ground mixture continuously at a speed of 170-190 r / min and heat it to 145-155℃ for 1.5 h; then raise the temperature to 165-175℃ and increase the stirring speed to no less than 240 r / min for 1.5 h.

[0008] S3: Let the well-reacted mixture stand for 2 hours to precipitate, and then separate the solid and liquid phases to obtain a solid mixed hydroxide.

[0009] S4: Mix the mixed hydroxides with water to form a slurry, and the solid-liquid ratio of the slurry is 1:1;

[0010] S5: Add hydrochloric acid to the slurry, control the hydrogen ion molar concentration to 0.6-0.8 mol / L, and stir continuously at 65-75℃ for 20-25 min;

[0011] S6: After the reaction is complete, add polyacrylamide solution and let stand for solid precipitation. After solid-liquid separation, calcine the precipitate at 825℃ for 1.5h to obtain high-purity iron red.

[0012] Furthermore, in step S1, the sodium hydroxide solution is 50% sodium hydroxide.

[0013] Furthermore, the volume ratio of 50% sodium hydroxide to iron slag is 3:1.

[0014] Furthermore, in step S1, the sodium hydroxide solution is mixed with the iron waste and then ground to a particle size of D98 = 38 μm.

[0015] Furthermore, in step S2, the heating rate is 200℃ / h.

[0016] Furthermore, the mixed hydroxide needs to be washed with plasma water before entering step S4 and before the precipitate in step S6 is calcined.

[0017] Furthermore, in step S6, when calcining the precipitate, the precipitate is turned over once every 15 minutes.

[0018] Furthermore, in step S3, before the well-reacted mixture is allowed to settle and precipitate, plasma water is added to the well-reacted mixture until the volume of the mixture before heating and reaction is reached.

[0019] The beneficial effects of this invention are as follows:

[0020] This invention is based on the principle that ferric hydroxide can crystallize upon heating in sodium hydroxide solution, and further heating decomposes it into a sparingly soluble crystalline hydrated ferric oxide through high-temperature pyrolysis. This process involves the conversion of rare earth elements into rare earth hydroxides. The difference in solubility of these two elements under acidic conditions is then utilized for selective leaching and separation. This allows the iron waste generated during rare earth hydrometallurgy to be heated in sodium hydroxide solution in two stages to different temperatures to obtain a crystalline hydrated ferric oxide, thereby altering the solubility of iron and non-ferrous elements under acidic conditions, facilitating dissolution and separation. This process has low actual alkali consumption, and residual alkali can be recycled. The resulting high-purity iron oxide red meets national standards in terms of both color and impurity content. Furthermore, the operation is simple and aligns with the national green development concept. Attached Figure Description

[0021] Figure 1 is a schematic diagram of the process for producing high-purity iron red from iron waste slag according to the present invention;

[0022] Figure 2 is a photograph of the iron oxide red prepared in Example 1. Detailed Implementation

[0023] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0024] Iron waste slag produced during the smelting process of fluorocarbon cerium ore was measured to have a specific gravity of 1.25; every 200g of iron waste slag contained 134.58g of ferric oxide and 16.8g of rare earth oxides.

[0025] Example 1

[0026] The preparation of iron oxide red according to the method shown in Figure 1 specifically includes:

[0027] S1: Take 200g of the above iron waste slag, add 480ml of 50% sodium hydroxide solution and mix, put it into a ball mill and grind it until the particle size D98 = 38μm, that is, the particle size D98 is 400 mesh;

[0028] S2: The ground mixture is continuously stirred using a thermostatic magnetic stirrer at a speed of 180 r / min. In practice, the stirring speed can also be selected as 170, 175, 185 or 190 r / min. The heating rate is 200℃ / h, and the mixture is heated to 150℃ for crystallization reaction for 1.5h. In practice, the crystallization reaction temperature can also be selected as 145, 147, 152 or 155℃. The temperature is then increased to 175℃. In practice, the high-temperature pyrolysis temperature can also be selected as 165, 167, 170 or 172℃. The stirring speed is increased to 240 r / min, and the high-temperature pyrolysis reaction is carried out for 1.5h.

[0029] S3: Add plasma water to the mixture after the reaction to the volume before the reaction, let the mixture stand for 2 hours to precipitate, and separate the solid and liquid phases to obtain a solid mixed hydroxide. In specific implementation, the liquid phase obtained from the solid-liquid separation is a sodium hydroxide solution. The sodium hydroxide solution is collected and can be used to re-prepare the sodium hydroxide solution in step S1 to achieve the recycling of sodium hydroxide.

[0030] S4: Mix the mixed hydroxides with water to form a slurry, and the solid-liquid ratio of the slurry is 1:1;

[0031] S5: Slowly add 15% dilute hydrochloric acid to the slurry and stir continuously at 65-75℃ for 20-25 minutes, controlling the residual acid hydrogen ion concentration to be 0.65mol / L;

[0032] S6: After the reaction is complete, add polyacrylamide solution and let stand to allow solid precipitation. After solid-liquid separation, calcine the precipitate in a muffle furnace at 825℃ for 1.5 h to obtain high-purity iron oxide red as shown in Figure 2. Its weight was measured to be 133.5 g, with a ferric oxide content of 99.25% and a rare earth content of 0.11%.

[0033] Example 2

[0034] Experimental group setup: In step S2, the ground mixture was continuously stirred at 180 r / min using a constant temperature magnetic stirrer, heated to 150°C for crystallization reaction for 1.5 h, then heated to 175°C, and the stirring speed was increased to 240 r / min for high-temperature pyrolysis reaction for 1.5 h. The remaining conditions were the same as in Example 1.

[0035] Set up control group 1: In step S2, the crystallization reaction was carried out by heating to 160℃ for 1.5h, and the other conditions were kept the same as those of the experimental group;

[0036] Set up control group 2: In step S2, the crystallization reaction was carried out by heating to 140℃ for 1.5h, and the other conditions were kept the same as those of the experimental group;

[0037] Set up control group 3: In step S2, the high-temperature pyrolysis reaction was carried out at 180℃ for 1.5h, and the other conditions were kept the same as those of the experimental group;

[0038] Set up control group 4: In step S2, the high-temperature pyrolysis reaction was carried out at 160℃ for 1.5h, and the other conditions were kept the same as those of the experimental group;

[0039] The obtained iron oxide was tested, and the test results are shown in Table 1.

[0040] Table 1

[0041]

[0042]

[0043] As shown in Table 1, the crystallization reaction temperature of control group 1 was too high, resulting in a lower mass of iron oxide red compared to the experimental group. This is because the excessively high crystallization reaction temperature caused the premature formation of a hydrated ferric oxide film on the surface of the material particles, which hindered the crystallization of internal ferric hydroxide and resulted in incomplete crystallization of the material, affecting the subsequent iron dissolution rate. On the other hand, the crystallization reaction temperature of control group 2 was too low, which caused the crystallization reaction to not proceed, resulting in a lower mass of iron oxide red compared to the experimental group.

[0044] In contrast, the high-temperature pyrolysis reaction temperature in Group 3 was too high, which led to a decrease in the iron dissolution rate. Although the decrease was not significant, the iron oxide produced showed agglomeration. Subsequent detection of the liquid phase revealed the presence of sodium ferrite. The formation of sodium ferrite was lost with the liquid phase, which was not conducive to recovery, greatly increasing energy consumption and causing resource waste.

[0045] The high-temperature pyrolysis reaction temperature of control group 4 was too low, which increased the amount of iron leaching compared to control group 3. However, this resulted in a small amount of impurities not being completely converted into soluble sodium salts. The impurities remained in the solid phase, affecting the purity of the final iron oxide red.

[0046] In summary, the method of this invention can separate iron elements from iron slag generated in rare earth hydrometallurgy to obtain high-purity iron oxide. The control of the temperature of the crystallization reaction and the high-temperature pyrolysis reaction affects the final dissolution rate and purity of iron oxide; too high or too low a temperature will lead to poor efficiency.

[0047] The entire process of producing high-purity iron oxide from iron waste slag has low alkali consumption, and the residual alkali can be recycled. The high-purity iron oxide obtained meets national standards in terms of both color and impurity content. Moreover, the operation process is simple and in line with the national green development concept.

Claims

1. A method for producing high-purity iron oxide red from iron slag produced by rare earth smelting, characterized in that, The process includes the following steps: S1: Mix sodium hydroxide solution and iron waste residue evenly and then grind them; the iron waste residue is iron-containing waste residue generated during the smelting of fluorocarbon cerium ore; S2: Stir the ground mixture continuously at a speed of 170-190 r / min and heat it to 145-155℃ for 1.5 h; then raise the temperature to 165-175℃ and increase the stirring speed to no less than 240 r / min, and react for 1.5 h; S3: Let the reacted mixture stand to precipitate for 2 h, and separate the solid and liquid phases to obtain a solid mixed hydroxide; S4: Add water to the mixed hydroxide to prepare a slurry, and the solid-liquid ratio of the slurry is 1:1; S5: Add hydrochloric acid to the slurry, control the hydrogen ion molar concentration to 0.6-0.8 mol / L, and stir continuously at 65-75℃ for 20-25 min; S6: After the reaction is complete, add polyacrylamide solution and let stand to allow solid precipitation. After solid-liquid separation, calcine the precipitate at 825℃ for 1.5h to obtain high-purity iron red. In step S1, the sodium hydroxide solution is 50% sodium hydroxide. The volume ratio of the 50% sodium hydroxide to the iron waste slag is 3:

1. In step S1, the sodium hydroxide solution and iron waste slag are mixed and ground to a particle size D98=38μm. In step S2, the heating rate is 200℃ / h. The mixed hydroxide needs to be washed with plasma water before entering step S4 and before calcining the precipitate in step S6. In step S6, when calcining the precipitate, the precipitate is turned over once every 15min. In step S3, before the reacted mixture is allowed to stand and precipitate, plasma water is added to the reacted mixture to the volume of the mixture before heating and reaction.

2. The method for producing high-purity iron oxide from iron slag produced by rare earth smelting according to claim 1, characterized in that, In step S2, the temperature is raised to 150°C and reacted for 1.5 hours, and then raised to 175°C and reacted for another 1.5 hours.

3. The method for producing high-purity iron oxide from iron slag produced by rare earth smelting according to claim 1, characterized in that, In step S5, the molar concentration of hydrogen ions in the system is controlled to be 0.65 mol / L.

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