Method for preparing mica iron oxide by using sulfate process titanium dioxide by-product

Abstract

The invention discloses a method for preparing mica iron oxide by using sulfate process titanium dioxide by-products, and particularly relates to the technical field of inorganic powder materials. The method comprises the following steps: dissolving for preliminary impurity removal, purifying for impurity removal, oxidizing, precipitating, aging and washing. Air is introduced through aeration, then hydrogen peroxide is added to oxidize the ferrous sulfate purification liquid, the usage amount of hydrogen peroxide can be reduced, and the cost is reduced; the mica iron oxide is prepared from the sulfate process titanium dioxide by-product ferrous sulfate heptahydrate, so that full utilization of resources is realized. According to the method, sodium carbonate is used for preparing the hydrated ferric hydroxide complex, when sodium carbonate reacts with ferric sulfate, alkalinity generated by hydrolysis of carbonate ions is relatively weak, the reaction process is relatively mild, and the hydrated ferric hydroxide complex with uniform particle size distribution and regular morphology can be formed.

Description

Technical Field

[0001] The present invention relates to the technical field of inorganic powder materials, and particularly relates to a method for preparing micaceous iron oxide using by-products of titanium white produced by the sulfuric acid method. Background Art

[0002] At present, the main method for producing titanium white in China is the sulfuric acid method for titanium white, which produces a large amount of by-product ferrous sulfate in industrial production. For every ton of titanium white produced by the sulfuric acid method for titanium white, 3-5 tons of ferrous sulfate heptahydrate are produced. The by-product ferrous sulfate contains a large amount of impurities, so its utilization rate is extremely low. Unreasonable treatment causes waste of iron resources, economic losses, and environmental pollution. Among inorganic pigments, iron-based pigments account for a very high proportion, and their production and sales volume ranks first. There are mainly iron red, iron yellow, iron black, etc. Using the by-product ferrous sulfate of titanium white as the production raw material for iron-based pigments can not only effectively utilize resources, reduce environmental pollution, but also reduce the production cost of iron oxide. At present, the demand for iron oxide in China is increasing continuously, with a very high growth rate. However, the research and production of micaceous iron oxide, which has a higher value in iron oxide pigment products, are very few. Micaceous iron oxide has good anti-aging, rust-proof, acid-resistant, alkali-resistant, salt-resistant, and strong adaptability to climate environment. Synthetic micaceous iron oxide exceeds natural micaceous iron oxide in terms of purity particle size distribution, crystal form, performance, etc.

[0003] Chinese Patent CN100390072C discloses a method for preparing micaceous iron oxide with controllable particle size and color by using by-product ferrous sulfate of titanium white as raw material through processes such as dissolution and purification, oxidation, precursor formation, hydrothermal reaction crystallization, and post-treatment. However, this method uses green vitriol as raw material and requires a large amount of oxidants (such as NaClO3, H2O2, etc.) to oxidize Fe 2+ According to the records in this patent, the addition amount of hydrogen peroxide is 6%-10% of ferrous sulfate in terms of hydrogen peroxide, which is more than 98% after conversion, so the raw material treatment cost is high; ② The hydrothermal reaction process requires an excessive amount of NaOH solution, resulting in a large alkali consumption and high production cost. Summary of the Invention

[0004] Therefore, the present invention provides a method for preparing micaceous iron oxide using by-products of titanium white produced by the sulfuric acid method to solve the problems in the prior art.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] According to a method for preparing micaceous iron oxide using by-products of titanium white produced by the sulfuric acid method provided by the present invention, the method includes:

[0007] Step 1, dissolution and preliminary impurity removal

[0008] The ferrous sulfate heptahydrate separated by the crystallization of titanium dioxide by sulfuric acid method is added to water under stirring at room temperature, and the temperature is gradually increased to 60-80 °C while stirring. After complete dissolution, it is filtered to obtain a ferrous sulfate heptahydrate solution with a concentration of 30-40% (w / w).

[0009] Step Two, purification and impurity removal

[0010] An alkaline solution is added to the ferrous sulfate heptahydrate solution, and the pH of the solution is adjusted step by step to 2.5-5. After heating and stirring for reaction, a flocculant is added for solid-liquid separation to obtain a purified ferrous sulfate solution.

[0011] Step Three, oxidation

[0012] The purified ferrous sulfate solution is taken, air is introduced and heated for reaction, and an oxidant is continuously added to fully oxidize ferrous sulfate to obtain a hydrated ferric sulfate slurry.

[0013] Step Four, precipitation

[0014] The hydrated ferric sulfate slurry is gradually added dropwise with sodium carbonate, and the reaction temperature and pH value are controlled for reaction. After forming a hydrated iron hydroxide complex, α-Fe2O3 seeds are added, and a mica iron oxide crystal slurry is obtained under hydrothermal reaction.

[0015] Step Five, aging and washing

[0016] The mica iron oxide crystal slurry obtained in Step Four is cooled and aged, and after aging, solid-liquid separation is carried out. The solid mica iron oxide is taken for washing, crushing, screening, drying, cooling, and packaging to obtain mica iron oxide.

[0017] Further, in Step One, the rate of gradual temperature increase is 3-5 °C / min; to avoid local supersaturation leading to impurity encapsulation and reduce the dissolution of heat-sensitive impurities.

[0018] In the present invention, the solution concentration is in the range of 30-40% (w / w, mass of ferrous sulfate heptahydrate / mass of ferrous sulfate solution). Excessively high may lead to an increase in viscosity in subsequent steps and difficulty in subsequent filtration; too low will affect the reaction efficiency and increase energy consumption; this step can be monitored in real time by a densitometer.

[0019] The stirring speed is controlled at 60-200 rpm / min; it is necessary to balance the dissolution efficiency and energy consumption. Excessively high may introduce bubbles or cause the solution to splash.

[0020] The filtration medium is preferably an acid-resistant filter cloth or a ceramic membrane to prevent corrosion of equipment under acidic conditions.

[0021] Further, in Step Two, the step-by-step adjustment of the solution pH is specifically to first adjust the solution pH to 2.5-3, and then continue to adjust the solution pH to 3-5; to avoid premature hydrolysis of ferrous ions.

[0022] Further, in the second step, the alkaline solution is 10 - 12% sodium hydroxide solution or ammonia water, and the total addition amount is 2% - 5% of the raw material mass.

[0023] Further, in the second step, the flocculant is precipitated using polyacrylamide flocculant, and the usage amount is 0.1 - 0.3% of the mass of the ferrous sulfate heptahydrate raw material; the precipitation time is 2 - 5 h, and the supernatant solution is taken.

[0024] In this step, the heating temperature is controlled at 70 - 80 °C to promote the aggregation of the colloid and accelerate precipitation.

[0025] Further, in the third step, air is introduced in an aeration manner, and the volume of air introduced is 10 - 50% of the volume of the ferrous sulfate solution per minute.

[0026] Further, in the third step, hydrogen peroxide is selected as the oxidant; the addition amount of the oxidant is 80% - 100% of the hydrogen peroxide required by the oxidation reaction chemical formula. H2O2 (without residue) is superior to chlorine-containing oxidants (which may introduce Cl- pollution).

[0027] In this step, the heating temperature is controlled at 70 - 90 °C to accelerate the reaction, but boiling causing the solution to splash should be avoided; after the reaction is complete, KSCN is used to detect Fe 2+ residue (no blue indicates complete oxidation).

[0028] Further, in the fourth step, the addition amount of α-Fe2O3 seeds is in the hydrated ferric sulfate. α-Fe2O3 nanoparticles (particle size < 100 nm) are used as seeds, and the addition amount is 0.1 - 0.3%, w / w, α-Fe2O3 seed mass / ferrous sulfate mass; it can significantly improve the crystal form consistency of the product.

[0029] Further, in the fourth step, the reaction temperature is controlled at 70 - 90 °C and treated in a high-pressure reactor for 0.5 - 2 hours; the pH value is controlled at 3 - 6 to convert hydrated ferric sulfate into iron hydroxide.

[0030] Further, in the fourth step, the conditions for the hydrothermal reaction are 180 - 220 °C and treated in a high-pressure reactor for 4 - 8 hours. The temperature needs to be strictly controlled. Too high may cause particle sintering, and too low may result in incomplete reaction.

[0031] In this step, the dropping rate of sodium carbonate is controlled (the rate is 0.5 - 1 mL / min) and the pH 3 - 6 is maintained to prevent the formation of amorphous Fe(OH)3 due to local over-alkalinity.

[0032] In the fifth step, the aging conditions: aging at 70 - 90 °C for 1 - 2 hours can promote Ostwald ripening and increase the grain size. Do not stir or reduce the stirring rate to 50 rpm to reduce crystal breakage.

[0033] Washing: Wash with deionized water multiple times until the conductivity < 50 μS / cm to remove Na + , SO4 2- .

[0034] Drying: Spray drying or vacuum drying (80 - 100 °C), avoiding crystal form transformation caused by high temperature.

[0035] Screening: Pass through a 200 - mesh sieve to ensure the particle size ≤ 75 μm, meeting the coating industry standard.

[0036] Advantages of the present invention:

[0037] In the present invention, air is introduced by aeration, and then hydrogen peroxide is added to oxidize the ferrous sulfate purification solution, which can reduce the usage amount of hydrogen peroxide and lower the cost; mica iron oxide is prepared from the by - product ferrous sulfate heptahydrate of titanium dioxide by the sulfuric acid method in the present invention, realizing the full utilization of resources.

[0038] In the present invention, sodium carbonate is used to prepare hydrated iron hydroxide complex. When sodium carbonate reacts with ferric sulfate, the alkalinity generated by the hydrolysis of carbonate ions is relatively weak and the reaction process is relatively mild, which is conducive to the formation of hydrated iron hydroxide complex with uniform particle size distribution and regular morphology. Sodium carbonate solution has a certain buffering capacity, which can make the pH change of the system relatively stable during the reaction process. Different from sodium hydroxide, it will not cause the pH of the solution to rise rapidly, making it easier to control the pH value of the reaction system and avoiding side reactions or changes in product properties caused by too high pH. The corrosiveness of sodium carbonate is much weaker than that of sodium hydroxide. During the operation process, the requirement for the corrosion resistance of equipment is relatively low, and it also reduces the risk of operators contacting strong corrosive substances, improving the safety of the production process. The price of sodium carbonate is usually cheaper than that of sodium hydroxide. Especially in large - scale production, using sodium carbonate can reduce the raw material cost. Description of the Drawings

[0039] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings described below are only exemplary. For those of ordinary skill in the art, without creative efforts, other implementation drawings can be obtained according to the provided drawings.

[0040] The structures, ratios, sizes, etc. illustrated in this specification are only used to cooperate with the content disclosed in the specification for those familiar with this technology to understand and read, and are not used to limit the limited conditions under which the present invention can be implemented. Therefore, they do not have technical essence. Any modification of the structure, change in the proportional relationship, or adjustment of the size, without affecting the effects that the present invention can produce and the purposes that can be achieved, should still fall within the scope that can be covered by the technical content disclosed in the present invention.

[0041] Figure 1 This is a purification flow chart of by - products of titanium white by sulfuric acid method provided in Embodiment 1 of the present invention;

[0042] Figure 2 This is a flow chart of obtaining hydrated ferric sulfate slurry by oxidizing ferrous sulfate solution provided in Embodiment 2 of the present invention;

[0043] Figure 3 This is a flow chart of generating precursor and hydrothermal reaction from hydrated ferric sulfate slurry provided in Embodiment 3 of the present invention;

[0044] Figure 4 This is a flow chart of a method for preparing micaceous iron oxide from by - products of titanium white by sulfuric acid method provided in Embodiment 4 of the present invention. Specific embodiments

[0045] The following specific embodiments illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of them. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

[0046] The standard for sufficient oxidation (qualified ferrous content) is that the ferrous content is lower than 0.5%. The detection method is carried out according to the national standard method for detecting ferrous sulfate (GBT14591 - 2016, detection method for ferrous (reducing substances) in polymeric ferric sulfate).

[0047] Judgment for stopping adding oxidant: Take the solution to detect the ferrous content (reducing substances). When it is lower than 0.5%, stop adding the oxidant.

[0048] Embodiment 1

[0049] This embodiment provides a method for preparing micaceous iron oxide using by - products of titanium white by sulfuric acid method. The flow chart is as Figure 1 shown:

[0050] S1: Dissolution tank: Add 500 g of by - product ferrous sulfate heptahydrate of titanium white by sulfuric acid method (raw material iron content 18%, converted to ferrous sulfate heptahydrate 89.3%) by weighing. Slowly add the raw material to a dissolution tank with a stirrer paddle and pre - added 700 ml of water, and start stirring. The stirring speed is 120 revolutions per minute. Heat it to 80°C at a gradient heating rate of 3°C / min, and keep stirring for 45 minutes to obtain a ferrous sulfate solution with a concentration of 37.4%;

[0051] S2: Purification tank: Add 10.1% sodium hydroxide solution, with a mass of 2% of the mass of the raw material ferrous sulfate heptahydrate. The pH of the ferrous sulfate solution is 2.24. Then continue to add 10.1% sodium hydroxide solution, with a mass of 1% of the mass of the raw material ferrous sulfate heptahydrate, to obtain a ferrous sulfate solution with a pH of 3.20. Heat the solution to a temperature of 80°C, with a stirring speed of 120 revolutions per minute, and keep stirring for 45 minutes. Add a polyacrylamide flocculant with a mass of 0.2% of the prepared raw materials. Let the solution precipitate for 4 hours, and take the supernatant to obtain a purified ferrous sulfate solution.

[0052] S3: Oxidation tank: Introduce air volume into the purified ferrous sulfate solution obtained in step S2 at a rate of 25% of the solution volume per minute. Heat and keep the solution temperature at 80°C for 45 minutes. Add 90% of the amount of hydrogen peroxide required for the reaction of oxidizing ferrous ions to ferric ions based on the total iron content of the solution. Keep stirring at 80°C for 3 hours to obtain a hydrated ferric sulfate slurry; (The specific process flow is as Figure 2 shown. If the ferrous content is qualified, directly proceed with the subsequent treatment of the hydrated ferric sulfate slurry. If it is unqualified, add an oxidant for oxidation. In this way, the introduction of air reduces the usage amount of the oxidant and lowers the cost; by detecting the ferrous content, accurately add the amount of oxidant to oxidize ferrous, reducing the cost)

[0053] S4: Reaction tank: After adding 0.2% of α-Fe2O3 seeds (particle size: Dv(10) = 0.043 μm, Dv(50) = 0.074 μm, Dv(90) = 0.102 μm) to the hydrated ferric sulfate slurry, gradually add sodium carbonate dropwise (at a speed of 0.5 mL / min), control the reaction temperature at 80°C and the pH value at 4.5 for the reaction. After generating a hydrated iron hydroxide complex, transfer the slurry to an autoclave, add mica powder, and carry out a hydrothermal reaction at 200°C for 5 hours to obtain a slurry of mica iron oxide crystals; (The specific process flow is as Figure 3 shown. By controlling the addition amount of the alkali solution and controlling the pH, the product quality and color are controlled)

[0054] S5: Synthesis kettle: Cool the slurry of mica iron oxide crystals obtained in step S4 to 82°C, age for 2 hours, wash it with deionized water multiple times until the conductivity < 50 μS / cm to remove Na + 、SO4 2- ; Dry it under vacuum at 80°C, then crush the crystalline crystals, pass through a 200-mesh sieve to ensure that the particle size ≤ 75 μm, dry it, and cool it for packaging.

[0055] The obtained product was tested. The purity of iron oxide was 96.1%, and the color was reddish-brown, meeting the requirements of the detection index of mica iron oxide. Through electron microscope detection, the product was in the form of mica flakes with uniform particles. The particle size of the product was measured by a particle size analyzer (Dv(10) = 25.925μm, Dv(50) = 49.054μm, Dv(90) = 59.932μm). The product quality was 111.4g, and the recovery rate was 96.9%.

[0056] Example 2

[0057] This example provides a method for preparing mica iron oxide using the by-product of titanium white by the sulfuric acid method:

[0058] S1: Weigh 500g of the by-product ferrous sulfate heptahydrate of titanium white by the sulfuric acid method, and slowly add the raw material to a dissolution tank with a stirring paddle that has been pre-added with 700ml of water and start stirring. The stirring speed is 200 revolutions per minute, and it is heated to 80°C at a gradient heating rate of 5°C / min and kept stirring for 45 minutes to obtain a ferrous sulfate solution with a concentration of 37.4%;

[0059] S2: Add a 10.1% sodium hydroxide solution with a mass of 2% of the mass of the raw material ferrous sulfate heptahydrate. The pH of the ferrous sulfate solution is 2.21. Then continue to add a 10.1% sodium hydroxide solution with a mass of 2% of the mass of the raw material ferrous sulfate heptahydrate to obtain a ferrous sulfate solution with a pH of 4.73. Heat the solution temperature to 80°C, stir at a speed of 65 revolutions per minute, keep stirring for 45 minutes, add a polyacrylamide flocculant with a mass of 0.2% of the prepared raw material, let the solution precipitate for 4h, and take the supernatant to obtain a purified ferrous sulfate solution;

[0060] S3: The purified ferrous sulfate solution obtained in step S2 is aerated with air at a rate of 50% of the solution volume per minute, heat is maintained to keep the solution temperature at 80°C for 30 minutes, add 85% of the amount of hydrogen peroxide required for the reaction of oxidizing ferrous ions to ferric ions based on the total iron content of the solution, and keep stirring at 80°C for 3h to obtain a hydrated ferric sulfate slurry;

[0061] S4: After adding 0.3% of α-Fe2O3 seeds (particle size: Dv(10) = 0.043μm, Dv(50) = 0.074μm, Dv(90) = 0.102μm) to the hydrated ferric sulfate slurry, gradually add sodium carbonate (at a rate of 0.5mL / min), control the reaction temperature at 80°C and pH value = 6 for the reaction. After forming a hydrated iron hydroxide complex, transfer the slurry to an autoclave, add mica powder, and carry out a hydrothermal reaction at 200°C for 5h to obtain a slurry of mica iron oxide crystals;

[0062] S5: Cool the slurry of the mica iron oxide crystals obtained in step S4 to 80 °C, age for 2 h, wash repeatedly with deionized water until the conductivity < 50 μS / cm to remove Na + , SO4 2- ; Dry in vacuum at 80 °C, then crush the crystalline crystals, pass through a 200-mesh sieve to ensure that the particle size ≤ 75 μm, dry, cool and package.

[0063] The obtained product was tested. The purity of iron oxide was 98.4%, the color was reddish-brown, meeting the requirements of the mica iron oxide detection index. The product was detected by an electron microscope as mica flakes with uniform particles. The particle size analyzer detected that the particle size of the product was (Dv(10) = 28.492 μm, Dv(50) = 52.523 μm, Dv(90) = 60.479 μm). The product quality was 101.8 g, and the recovery rate was 89.3%.

[0064] Example 3

[0065] This example provides a method for preparing mica iron oxide using the by-product of sulfuric acid process titanium white:

[0066] Before S3, add a process of pH detection. If pH < 3, add alkali solution to adjust pH > 3, add flocculant, and continue the subsequent operations. If pH > 3, directly add flocculant and carry out the subsequent operations. Others are exactly the same as in Example 1. The flow chart is as Figure 4 shown.

[0067] Example 4

[0068] This example provides a method for preparing mica iron oxide using the by-product of sulfuric acid process titanium white:

[0069] S1: Weigh 500 g of the by-product ferrous sulfate heptahydrate of sulfuric acid process titanium white (the raw material iron content is 18%, converted to ferrous sulfate heptahydrate is 89.3%), and slowly add the raw material to a dissolution tank with a stirring paddle and pre-added 700 ml of water, and start stirring. The stirring speed is 120 revolutions per minute. Heat to 80 °C at a gradient heating rate of 3 °C / min, and keep stirring for 45 minutes to obtain a ferrous sulfate solution with a concentration of 37.4%;

[0070] Add 10.1% sodium hydroxide solution, with a mass of 2% of the mass of the raw material ferrous sulfate heptahydrate. The pH of the ferrous sulfate solution is 2.20. Continue to add 10.1% sodium hydroxide solution, with a mass of 1% of the mass of the raw material ferrous sulfate heptahydrate, to obtain a ferrous sulfate solution with a pH of 3.17; Heat the solution temperature to 80 °C, with a stirring speed of 120 revolutions per minute, keep stirring for 45 minutes, add 0.2% mass of the prepared polyacrylamide flocculant of the raw material, let the solution precipitate for 4 h, and take the supernatant to obtain a purified ferrous sulfate solution;

[0071] S3: The purified ferrous sulfate solution obtained in step S2 is aerated with air at a rate of 25% of the solution volume per minute, heated to maintain the solution temperature at 80 °C for 45 minutes, and 90% of the amount of sodium peroxide required for the reaction of oxidizing ferrous ions to ferric ions based on the total iron content of the solution is added. Stir at 80 °C for 3 h to obtain a hydrated ferric sulfate slurry;

[0072] S4: After adding 0.2% of α-Fe2O3 seeds (particle size: Dv(10) = 0.043 μm, Dv(50) = 0.074 μm, Dv(90) = 0.102 μm) to the hydrated ferric sulfate slurry, sodium carbonate is gradually added dropwise (at a rate of 0.5 mL / min), and the reaction temperature is controlled at 80 °C and the pH value is 4.5 for the reaction. After forming a hydrated iron hydroxide complex, the slurry is transferred to an autoclave, mica powder is added, and hydrothermal reaction is carried out at 200 °C for 5 h to obtain a slurry of mica iron oxide crystals;

[0073] S5: The slurry of mica iron oxide crystals obtained in step S4 is cooled to 82 °C, aged for 2 h, washed repeatedly with deionized water until the conductivity < 50 μS / cm to remove Na + 、SO4 2- ; Vacuum dry at 80 °C, then crush the crystalline crystals, pass through a 200-mesh sieve to ensure that the particle size ≤ 75 μm, dry, and cool for packaging.

[0074] The obtained product is tested. The purity of iron oxide is 95.1%, the color is reddish-brown, meeting the requirements of the mica iron oxide detection index. By electron microscope detection, the product is in the form of mica flakes with uniform particles. The particle size of the product detected by a particle size analyzer is (Dv(10) = 25.114 μm, Dv(50) = 47.573 μm, Dv(90) = 59.159 μm), the product quality is 109.7 g, and the recovery rate is 95.4%.

[0075] Comparative Example 1

[0076] This comparative example provides a method for preparing mica iron oxide using by-products of titanium white by the sulfuric acid method:

[0077] In this comparative example, in Step 1, instead of using the gradient heating method, it was directly heated to 80 °C and kept warm with stirring for 45 minutes to obtain a ferrous sulfate solution with a concentration of 37.4%. Other conditions were exactly the same as those in Example 1. The obtained product was tested. The purity of iron oxide was 90.6%, the color was reddish-brown, meeting the detection index requirements of mica iron oxide. The product was detected by an electron microscope to be mica flakes with uniform particles. The particle size analyzer detected the particle size of the product as (Dv(10) = 13.672 μm, Dv(50) = 38.452 μm, Dv(90) = 47.468 μm). The product quality was 105.8 g, and the recovery rate was 92.0%. This shows that direct heating and temperature increase lead to local supersaturation of the solution, resulting in poor effect of ferrous oxidation precipitation and impurity removal.

[0078] Comparative Example 2

[0079] This comparative example provides a method for preparing mica iron oxide using by-products of titanium dioxide by sulfuric acid method:

[0080] In this comparative example, in Step 2, a 10.1% sodium hydroxide solution was directly used to adjust the pH to 4.53. Other conditions were exactly the same as those in Example 1. The obtained product was tested. The purity of iron oxide was 96.7%, the color was reddish-brown, meeting the detection index requirements of mica iron oxide. The product was detected by an electron microscope to be mica flakes with uniform particles. The particle size analyzer detected the particle size of the product as (Dv(10) = 24.892 μm, Dv(50) = 47.545 μm, Dv(90) = 58.715 μm). The product quality was 92.8 g, and the recovery rate was 80.7%. This shows that directly using an alkaline solution to adjust the pH easily adds an excessive amount and removes the effective component ferrous, resulting in a low yield.

[0081] Comparative Example 3

[0082] This comparative example provides a method for preparing mica iron oxide using by-products of titanium dioxide by sulfuric acid method:

[0083] In this comparative example, in Step 3, instead of introducing air, hydrogen peroxide was directly used, and the amount of hydrogen peroxide used for all oxidation was 120%. Other conditions were exactly the same as those in Example 1. The obtained product was tested. The purity of iron oxide was 95%, the color was reddish-brown, meeting the detection index requirements of mica iron oxide. The product was detected by an electron microscope to be mica flakes with uniform particles. The particle size analyzer detected the particle size of the product as (Dv(10)

[0084] = 25.478 μm, Dv(50) = 46.978 μm, Dv(90) = 59.246 μm). The product quality was 110 g, and the recovery rate was 95.6%. This shows that simply using hydrogen peroxide will far increase the amount of hydrogen peroxide used and increase the reaction cost.

[0085] Comparative Example 4

[0086] This comparative example provides a method for preparing micaceous iron oxide using the by - product of sulfuric acid process titanium white:

[0087] In this comparative example, in step four, instead of using sodium carbonate, sodium hydroxide is used. Specifically: the hydrated ferric sulfate slurry obtained in step S3 is added with 20.2% sodium hydroxide solution, the pH is controlled at 4.5, and stirred for 45 minutes to generate a hydrated ferric hydroxide complex slurry. The slurry is transferred to an autoclave, mica powder is added, and hydrothermal reaction is carried out at 200 °C for 5 h to obtain a slurry of micaceous iron oxide crystals. The rest is exactly the same as in Example 1. The obtained product is detected. The purity of iron oxide is 95.3%, the color is reddish - brown, meeting the requirements of the detection index of micaceous iron oxide. Through electron microscope detection, the product is in the form of evenly - sized mica flakes. The particle size analyzer detects that the particle size of the product is (Dv(10)=8.726 μm, Dv(50)=31.815 μm, Dv(90)=55.421 μm), the product quality is 109.7 g, and the recovery rate is 95.4%. It shows that when sodium carbonate reacts with ferric sulfate, the alkalinity generated by the hydrolysis of carbonate ions is relatively weak and the reaction process is relatively mild, which is conducive to the formation of a hydrated ferric hydroxide complex with a uniform particle size distribution and regular morphology. The sodium carbonate solution has a certain buffering capacity, which can make the pH change of the system relatively stable during the reaction process. Different from sodium hydroxide, it will not cause the pH of the solution to rise rapidly, making it easier to control the pH value of the reaction system and avoiding side reactions or changes in product properties caused by too high pH.

[0088] Comparative Example 5

[0089] This comparative example provides a method for preparing micaceous iron oxide using the by - product of sulfuric acid process titanium white:

[0090] In this comparative example, in step five, aging is not carried out. After cooling to 80 °C, solid - liquid separation is carried out immediately. The solid micaceous iron oxide is taken for washing, crushing, screening, drying, cooling, and packaging. The rest is exactly the same as in Example 1. The obtained product is detected. The purity of iron oxide is 95.2%, the color is reddish - brown, meeting the requirements of the detection index of micaceous iron oxide. Through electron microscope detection, the product is in the form of evenly - sized mica flakes. The particle size analyzer detects that the particle size of the product is (Dv(10)=11.0152 μm, Dv(50)=43.854 μm, Dv(90)=57.621 μm), the product quality is 106.9 g, and the recovery rate is 93.0%. It shows that carrying out aging enables the reaction to proceed fully to improve the yield, allows the precipitation crystals to grow and increases the crystal particle size with a uniform particle size distribution.

[0091] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made thereto based on the present invention, which will be obvious to those skilled in the art. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing micaceous iron oxide using by-products of titanium white by sulfuric acid process, characterized in that, The method includes the following steps: Step 1: Dissolution and preliminary impurity removal Using ferrous sulfate heptahydrate obtained from the crystallization and separation of titanium white by the sulfuric acid method, it is stirred and added to water at room temperature, and the temperature is gradually increased to 60 - 80 °C while stirring. After complete dissolution, it is filtered to obtain a ferrous sulfate heptahydrate solution with a concentration of 30 - 40% (w / w). Step 2: Purification and impurity removal An alkaline solution is added to the ferrous sulfate heptahydrate solution, and the pH of the solution is adjusted step by step to 2.5 - 5. After heating and stirring for reaction, a flocculant is added for solid-liquid separation to obtain a purified ferrous sulfate solution. Step 3: Oxidation Air is introduced into the purified ferrous sulfate solution and heated for reaction, and an oxidant is continuously added to fully oxidize ferrous sulfate to obtain a hydrated ferric sulfate slurry. Step 4: Precipitation Sodium carbonate is gradually added dropwise to the hydrated ferric sulfate slurry, and the reaction temperature and pH value are controlled for reaction. After forming a hydrated iron hydroxide complex, α-Fe2O3 seeds are added, and a mica iron oxide crystal slurry is obtained under hydrothermal reaction. Step 5: Aging and washing The mica iron oxide crystal slurry obtained in Step 4 is cooled and aged. After aging, solid-liquid separation is carried out. The solid mica iron oxide is taken for washing, crushing, screening, drying, cooling, and packaging to obtain mica iron oxide.

2. A method for preparing micaceous iron oxide using by-products of titanium white by sulfuric acid method according to claim 1, characterized in that, In Step 1, the rate of gradual temperature increase is 3 - 5 °C / min.

3. A method for preparing micaceous iron oxide using by-products of titanium white by sulfuric acid process according to claim 1, characterized in that, In Step 2, adjusting the pH of the solution step by step specifically means first adjusting the pH of the solution to 2.5 - 3, and then continuing to adjust the pH of the solution to 3 - 5.

4. A method for preparing micaceous iron oxide using by-products of titanium white by sulfuric acid process according to claim 1, characterized in that, In Step 2, the alkaline solution is a 10 - 12% sodium hydroxide solution or ammonia water, and the addition amount is 2% - 5% of the raw material mass.

5. A method for preparing micaceous iron oxide using by-products of titanium white by sulfuric acid process according to claim 1, characterized in that, In Step 2, a polyacrylamide flocculant is used for precipitation, and the usage amount is 0.1 - 0.3% of the mass of the ferrous sulfate heptahydrate raw material.

6. A method for preparing micaceous iron oxide using by-products of titanium white by sulfuric acid method according to claim 1, characterized in that, In Step 3, air is introduced in an aeration manner, and the volume of air introduced is 10 - 50% of the volume of the ferrous sulfate solution per minute.

7. A method for preparing micaceous iron oxide using by-products of titanium white by sulfuric acid process according to claim 1, characterized in that, In Step 3, hydrogen peroxide is selected as the oxidant; the addition amount of the oxidant is 80% - 100% of the hydrogen peroxide required by the oxidation reaction chemical formula.

8. A method for preparing micaceous iron oxide using by-products of titanium white by sulfuric acid process according to claim 1, characterized in that, In Step 4, the addition amount of α-Fe2O3 seeds is 0.1 - 0.3% w / w of the hydrated ferric sulfate.

9. A method for preparing micaceous iron oxide using by-products of titanium white by sulfuric acid method according to claim 1, characterized in that, In Step 4, the reaction temperature is controlled at 70 - 90 °C and treated in a high-pressure reaction kettle for 0.5 - 2 hours; the pH value is controlled at 3 - 6.

10. A method for preparing micaceous iron oxide using by-products of titanium white by sulfuric acid method according to claim 1, characterized in that, In Step 4, the conditions for the hydrothermal reaction are 180 - 220 °C and treated in a high-pressure reaction kettle for 4 - 8 hours.

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