Method for preparing iron oxide red from acidic ferrous wastewater

Abstract

The invention discloses a method for preparing iron oxide red by using acidic ferrous wastewater, and belongs to the technical field of iron oxide pigments. The method comprises the following steps: by taking acidic ferrous wastewater generated by an iron oxide red factory as a raw material, adjusting the pH value, adding iron powder and phosphate to remove impurities, and carrying out solid-liquid separation to obtain a high-purity ferrous sulfate solution; and concentrating and crystallizing the obtained ferrous sulfate solution, dehydrating and drying, crushing and grinding, calcining at high temperature, and crushing to obtain the high-purity iron oxide red. According to the method, the high-purity iron oxide red pigment is obtained by firstly adjusting the pH value, then adding the iron powder and the phosphate to remove impurities, then separating out FeSO4. 7H2O by utilizing a crystallization technology, dehydrating, drying and then carrying out high-temperature calcination, the process is reasonable, the preparation method is simple and feasible, and the method is suitable for industrial production. Iron oxide red production wastewater can be comprehensively utilized, and the product quality is equivalent to or partially superior to that of precipitated iron oxide red.

Description

Technical Field

[0001] The invention belongs to the technical field of iron oxide pigments, and more specifically, relates to a method for preparing red iron oxide by utilizing acidic ferrous wastewater. Background Art

[0002] With the development and progress of social production, people have higher and higher demands on the quality and quantity of red iron oxide. At the same time, since artificially synthesized red iron oxide can control its particle size, content and hue and other indicators, it has gradually replaced the low-quality natural red iron oxide. There are many process routes for artificially synthesizing red iron oxide pigments. The commonly used red iron oxide production processes mainly include dry process and wet process. Since the wet process produces fine particle size of red iron oxide and high product purity, the wet process is currently widely used.

[0003] In the wet process production process, a large amount of acidic wastewater containing ferrous ions will be generated. Generally, for every ton of red iron oxide produced, about 15-20 tons of acidic wastewater containing ferrous ions will be discharged. The main source is the aqueous solution of the finished red iron oxide separated from the reaction barrel and the wastewater discharged after washing the red iron oxide product. The average content of iron ions in this type of wastewater is between 0.05% and 0.35%, the pH value is about 3-5, it is acidic, the chromaticity of the wastewater is more than 400 times, and the concentration of ammonia nitrogen is high. It not only brings serious pollution to the surrounding environment, but also causes the loss of a large amount of secondary iron resources. Therefore, it is particularly important to reasonably treat and dispose of the wastewater from the red iron oxide plant and recycle the iron resources in the wastewater.

[0004] Chinese patent CN104445430A discloses a method for preparing red iron oxide seed crystals from wastewater from a red iron oxide plant. The specific preparation process is as follows: taking acidic ferrous salt wastewater into a reaction device, adding industrial caustic soda and aerating, adjusting the pH to 6-9; collecting iron-containing sludge at the bottom, continuing to add industrial caustic soda, adjusting the pH to 11-13, passing compressed air for oxidation reaction, and obtaining red iron oxide seed crystals; placing the seed crystals and water in a certain ratio in a reaction device, adding a sufficient amount of iron sheet, heating to 75-85°C, and passing air into the reaction system at a certain flow rate, fully stirring the seed crystals in the system, and after the reaction, dehydrating, washing, and drying the red iron oxide slurry to obtain red α-Fe 2 O 3 Pigment particles. However, this method uses industrial caustic soda as a raw material to adjust the pH of the solution, introduces salt impurities, requires a large amount of alkaline reagents, and increases the processing cost; Fe 2+ The precipitation speed is slow, the time consumption is long, and the reaction efficiency is low. Summary of the invention

[0005] In view of the above problems existing in the prior art, the technical problem to be solved by the present invention is to provide a method for preparing red iron oxide using acidic ferrous wastewater. The method is low-cost, can comprehensively utilize the wastewater produced by red iron oxide, and the product quality is equivalent to or partially better than that of red iron oxide produced by precipitation method.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing red iron oxide by using acidic ferrous wastewater, which takes the acidic ferrous wastewater produced by a red iron oxide plant as a raw material, adjusts the pH value, adds iron powder and phosphate to remove impurities, and obtains a high-purity ferrous sulfate solution after solid-liquid separation; the obtained ferrous sulfate solution is concentrated and crystallized, dehydrated and dried, crushed and ground, calcined at high temperature, and crushed to obtain high-purity red iron oxide.

[0008] Preferably, the specific process of adjusting the pH value is: adjusting the pH value of the acidic ferrous wastewater to 0.1-0.5 by adding concentrated sulfuric acid.

[0009] Preferably, the mass ratio of the iron powder to the phosphate is 1:0.5-2.5.

[0010] Preferably, the impurity removal time is 15 to 30 minutes, and the reaction temperature during impurity removal is 25°C.

[0011] Preferably, the specific process of the concentrated crystallization is: adding concentrated sulfuric acid to the obtained ferrous sulfate solution so that the mass fraction of sulfuric acid in the ferrous sulfate solution is 20-25%, cooling to -5--3°C for cooling crystallization, and obtaining FeSO 4 7H 2 O.

[0012] Preferably, the specific process of dehydration and drying is: the FeSO obtained by concentrating and crystallizing the ferrous sulfate solution at 260-290°C 4 7H 2 O dehydrates to FeSO 4 ·H 2 O.

[0013] As a preferred embodiment, the specific process of the pulverizing and grinding is as follows: the FeSO obtained after dehydration is 4 ·H 2 O is ground to a particle size no greater than 0.5 μm.

[0014] Preferably, the calcination temperature of the high-temperature calcination is 750-850° C., and the calcination time is 10-20 min.

[0015] Preferably, the calcination atmosphere during the high-temperature calcination is under the protection of an inert gas, and after the calcination is completed, the calcination is naturally cooled to room temperature.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] 1) The present invention removes impurities such as nickel ions and chromium ions by first adjusting the pH value and then adding iron powder and phosphate to remove impurities, and can increase the content of ferrous sulfate in the acidic ferrous wastewater produced by the iron oxide red plant, and then precipitate FeSO by crystallization technology. 4 7H 2 O, dehydrated and dried, and then calcined at high temperature to obtain high-purity iron oxide red pigment. The process is reasonable, the preparation method is simple and easy, the utilization rate of valuable components is high, and the resources are fully utilized;

[0018] 2) The preparation process of the present invention is simple, and the FeSO 4 ·H 2 O, post-calcination, reduce the particle size of raw materials, increase the reaction area, make the materials fully react, high calcination output, short calcination time, more energy saving and electricity saving. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described below in conjunction with specific embodiments. In the following embodiments, unless otherwise specified, the technical means used are conventional means well known to those skilled in the art.

[0020] The acidic ferrous wastewater in the following examples is the acidic ferrous wastewater (pH 3-4, Fe 2+ Concentration 600~800mg / L). The mass fraction of concentrated sulfuric acid is 98%.

[0021] Example 1

[0022] A method for preparing red iron oxide using acidic ferrous wastewater comprises the following steps:

[0023] 1) Using concentrated sulfuric acid to adjust the pH value of the acidic ferrous wastewater produced by the iron oxide red plant to 0.1, then adding 20g / L iron powder and 50g / L phosphate to remove impurities, reacting at 25°C for 15min, stirring at a speed of 1000r / min, and after the reaction, precipitating the impurity elements, filtering, and separating to obtain a high-purity ferrous sulfate solution;

[0024] 2) Add concentrated sulfuric acid to the ferrous sulfate solution obtained in step 1) so that the mass fraction of sulfuric acid in the ferrous sulfate solution is 25%, cool to -3°C for cooling and crystallization, and obtain FeSO 4 7H 2 O;

[0025] 3) The FeSO obtained after crystallization in step 2) 4 7H2 O is dehydrated and dried at 260 °C to obtain FeSO 4 ·H 2 O; FeSO 4 ·H 2 O is put into the ball mill of the material processing device and ground to a particle size of 0.5 μm;

[0026] 4) The ground material is put into a rotary kiln for calcination. Under the protection of inert gas, the reaction is carried out at a calcination temperature of 800° C. for 20 minutes. After the reaction is completed, it is naturally cooled to room temperature; the calcined product is crushed to obtain iron oxide red pigment.

[0027] Example 2

[0028] A method for preparing red iron oxide using acidic ferrous wastewater comprises the following steps:

[0029] 1) Using concentrated sulfuric acid to adjust the pH value of the acidic ferrous wastewater produced by the iron oxide red plant to 1.2, then adding 20g / L iron powder and 10g / L phosphate to remove impurities, reacting at 25°C for 30min, stirring at a speed of 1000r / min, and after the reaction, precipitating the impurity elements, filtering, and separating to obtain a high-purity ferrous sulfate solution;

[0030] 2) Add concentrated sulfuric acid to the ferrous sulfate solution obtained in step 1) so that the mass fraction of sulfuric acid in the ferrous sulfate solution is 20%, cool to -5°C for cooling and crystallization, and obtain FeSO 4 7H 2 O;

[0031] 3) The FeSO obtained after crystallization in step 2) 4 7H 2 O is dehydrated and dried at 260 °C to obtain FeSO 4 ·H 2 O; FeSO 4 ·H 2 O is put into the ball mill of the material processing device and ground to a particle size of 0.5 μm;

[0032] 4) The ground material is put into a rotary kiln for calcination. Under the protection of inert gas, the calcination temperature is 800° C. and the reaction is carried out for 15 minutes. After the reaction is completed, it is naturally cooled to room temperature; the calcined product is crushed to obtain iron oxide red pigment.

[0033] Example 3

[0034] A method for preparing red iron oxide using acidic ferrous wastewater comprises the following steps:

[0035] 1) Using concentrated sulfuric acid to adjust the pH value of the acidic ferrous wastewater produced by the iron oxide red plant to 0.1, then adding 20g / L iron powder and 50g / L phosphate to remove impurities, reacting at 25°C for 15min, stirring at a speed of 1000r / min, and after the reaction, precipitating the impurity elements, filtering, and separating to obtain a high-purity ferrous sulfate solution;

[0036] 2) Add concentrated sulfuric acid to the ferrous sulfate solution obtained in step 1) so that the mass fraction of sulfuric acid in the ferrous sulfate solution is 25%, cool to -5°C for cooling and crystallization, and obtain FeSO 4 7H 2 O;

[0037] 3) The FeSO obtained after crystallization in step 2) 4 7H 2 O is dehydrated and dried at 260 °C to obtain FeSO 4 ·H 2 O; FeSO 4 ·H 2 O is put into the ball mill of the material processing device and ground to a particle size of 0.5 μm;

[0038] 4) The ground material is put into a rotary kiln for calcination. Under the protection of inert gas, the reaction is carried out at a calcination temperature of 850° C. for 10 minutes. After the reaction is completed, it is naturally cooled to room temperature; the calcined product is crushed to obtain iron oxide red pigment.

[0039] Example 4

[0040] A method for preparing red iron oxide using acidic ferrous wastewater comprises the following steps:

[0041] 1) Using concentrated sulfuric acid to adjust the pH value of the acidic ferrous wastewater produced by the iron oxide red plant to 1.2, then adding 20g / L iron powder and 50g / L phosphate to remove impurities, reacting at 25°C for 15min, stirring at a speed of 1000r / min, and after the reaction, precipitating the impurity elements, filtering, and separating to obtain a high-purity ferrous sulfate solution;

[0042] 2) Add concentrated sulfuric acid to the ferrous sulfate solution obtained in step 1) so that the mass fraction of sulfuric acid in the ferrous sulfate solution is 25%, cool to -3°C for cooling and crystallization, and obtain FeSO 4 7H 2 O;

[0043] 3) The FeSO obtained after crystallization in step 2) 4 7H 2 O is dehydrated and dried at 280 °C to obtain FeSO 4 ·H 2 O; FeSO4 ·H 2 O is put into the ball mill of the material processing device and ground to a particle size of 0.5 μm;

[0044] 4) The ground material is put into a rotary kiln for calcination. Under the protection of inert gas, the calcination temperature is 750° C. and the reaction is carried out for 20 minutes. After the reaction is completed, it is naturally cooled to room temperature; the calcined product is crushed to obtain iron oxide red pigment.

[0045] Comparative Example 1

[0046] When preparing the iron oxide red pigment, iron powder and phosphate are directly added to the acidic ferrous wastewater produced by the iron oxide red factory to remove impurities. The rest of the preparation method is the same as that of Example 1.

[0047] Comparative Example 2

[0048] When preparing the iron oxide red pigment, 20 g / L iron powder and 10 g / L phosphate are directly added to the acidic ferrous wastewater produced by the iron oxide red factory to remove impurities. The rest of the preparation method is the same as that of Example 1.

[0049] Comparative Example 3

[0050] When preparing the iron oxide red pigment, only the pH value of the acidic ferrous wastewater produced by the iron oxide red factory is adjusted to 0.1, and the rest of the preparation method is the same as that of Example 1.

[0051] Comparative Example 4

[0052] When preparing the iron oxide red pigment, iron powder and phosphate are directly added to the acidic ferrous wastewater produced by the iron oxide red factory to remove impurities. The rest of the preparation method is the same as that of Example 2.

[0053] Comparative Example 5

[0054] When preparing the iron oxide red pigment, only 20 g / L iron powder was added for impurity removal, and the rest of the preparation method was the same as in Example 1.

[0055] Comparative Example 6

[0056] When preparing the iron oxide red pigment, only 50 g / L phosphate was added for impurity removal, and the rest of the preparation method was the same as in Example 1.

[0057] The red iron oxide prepared in Examples 1-4 and Comparative Examples 1-6 was tested for performance, and the test results are shown in Tables 1 and 2 below.

[0058] Table 1: Performance analysis data of iron oxide red products prepared in Examples 1-4

[0059]

[0060] Table 2: Performance analysis data of red iron oxide products prepared in Comparative Examples 1-6

[0061]

[0062] The high temperature resistance test of the iron oxide red pigment prepared in Examples 1-4 and Comparative Examples 1-6 was performed to obtain the following test data, which are shown in Table 3.

[0063] Temperature resistance test: The above samples were tested for their temperature resistance according to the national standard HG / T 3853-2006 Pigment Dry Powder Heat Resistance Test Method, and the test temperature was set to 700°C. Specific operation: The oven temperature was raised to 700°C, and after the oven temperature stabilized, a crucible containing 2.5g of the sample powder to be tested was placed in the oven, and the timing was started when the oven temperature rose to 700°C. After 30 minutes, the sample was taken out, and after the sample cooled, the color difference ΔE of the pigment before and after baking was measured.

[0064] Table 3: High temperature resistance test data of pigments prepared in Examples 1-4 and Comparative Examples 1-6

[0065]

[0066] As can be seen from Table 3, the iron oxide red pigment prepared by the present invention has very good high temperature resistance, can reach a high temperature resistance of 700° C., and can be widely used in some high temperature resistant fields.

[0067] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for preparing red iron oxide using acidic ferrous wastewater, characterized in that: The acidic ferrous wastewater produced by the red iron oxide plant is used as raw material, the pH value is adjusted, iron powder and phosphate are added to remove impurities, and a high-purity ferrous sulfate solution is obtained after solid-liquid separation; the obtained ferrous sulfate solution is concentrated and crystallized, dehydrated and dried, crushed and ground, high-temperature calcined, and crushed to obtain high-purity red iron oxide.

2. The method for preparing red iron oxide by using acidic ferrous wastewater according to claim 1, characterized in that: The specific process of adjusting the pH value is: adjusting the pH value of the acidic ferrous wastewater to 0.1-0.5 by adding concentrated sulfuric acid.

3. The method for preparing red iron oxide by using acidic ferrous wastewater according to claim 1, characterized in that: The mass ratio of the iron powder to the phosphate is 1:0.5-2.

5.

4. The method for preparing red iron oxide by using acidic ferrous wastewater according to claim 1, characterized in that: The impurity removal time is 15 to 30 minutes, and the reaction temperature during impurity removal is 25°C.

5. The method for preparing red iron oxide by using acidic ferrous wastewater according to claim 1, characterized in that: The specific process of the concentrated crystallization is: adding concentrated sulfuric acid to the obtained ferrous sulfate solution so that the mass fraction of sulfuric acid in the ferrous sulfate solution is 20-25%, cooling to -5--3°C for cooling crystallization to obtain FeSO4·7H2O.

6. The method for preparing red iron oxide by using acidic ferrous wastewater according to claim 1, characterized in that: The specific process of the dehydration and drying is: the FeSO4·7H2O obtained by concentrating and crystallizing the ferrous sulfate solution at 260-290° C. is dehydrated to FeSO4·H2O.

7. The method for preparing red iron oxide by using acidic ferrous wastewater according to claim 1, characterized in that: The specific process of the crushing and grinding is: grinding the FeSO4·H2O obtained after dehydration to a particle size not greater than 0.5 μm.

8. The method for preparing red iron oxide using acidic ferrous wastewater according to claim 1, characterized in that: The calcination temperature of the high-temperature calcination is 750-850° C., and the calcination time is 10-20 minutes.

9. The method for preparing red iron oxide by using acidic ferrous wastewater according to claim 1, characterized in that: The calcination atmosphere of the high-temperature calcination is under the protection of inert gas, and after the calcination is completed, it is naturally cooled to room temperature.

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