Iron oxide orange and its preparation method and use

Abstract

The present invention provides iron oxide orange, a preparation method thereof, and uses thereof. The preparation method comprises the following steps: providing an alkaline divalent iron salt aqueous solution as a feed liquid; providing oxygen to perform a first oxidation on the feed liquid to form an oxide material, and adjusting the pH of the reaction system to be not less than 11 during the first oxidation process; adjusting the pH of the oxide material to be acidic; then adding the divalent iron salt aqueous solution to form a reaction mass; and providing oxygen and elemental iron to perform a second oxidation on the reaction mass until the target hue is reached, thereby obtaining an iron oxide orange pigment of the corresponding color system. When the iron oxide orange particles formed by the method of the present application are used as a pigment, the resulting pigment has high color saturation and high tinting strength.

Description

Technical Field

[0001] The present invention relates to the field of chemical preparation, in particular to a new preparation method of iron oxide orange. Background Art

[0002] Iron Oxide Orange is a colorful iron oxide pigment with bright colors, high color saturation and high tinting strength. It has all the advantages of conventional iron oxide pigments.

[0003] The main production process of existing iron oxide orange pigment is dry mixing.

[0004] The dry mixing process is a physical mixing process, which is to put the finished pigment iron yellow and iron red dry powder into a mixing mixer in a certain proportion and mix them evenly.

[0005] The dry-blending process generates a large amount of dust, posing significant risks to both the environment and personnel. Because the iron orange pigment obtained from dry-blending is a mixture of two pigments with different crystal forms, it results in a wide particle size distribution and different specific gravities, which can lead to easy separation of the pigment in the dispersant.

[0006] Therefore, the research and development of chemically synthesized iron oxide orange is of great significance. Summary of the Invention

[0007] In view of the above-mentioned shortcomings of the prior art, the object of the present invention is to provide a new preparation method of iron oxide orange, which is used to solve the problems of poor dispersibility and serious environmental pollution of iron oxide orange in the prior art.

[0008] To achieve the above-mentioned purpose and other related purposes, the present invention is implemented by including the following technical solutions.

[0009] A first aspect of the present invention provides a method for preparing iron oxide orange, comprising the following steps:

[0010] 1) providing an alkaline divalent iron salt aqueous solution as a feed solution;

[0011] 2) providing oxygen to perform a first oxidation on the feed liquid to form an oxidized material, and adjusting the pH of the reaction system to be not less than 11 during the first oxidation process;

[0012] 3) adjusting the pH of the oxide material to be acidic;

[0013] 4) adding an aqueous solution of a divalent iron salt to form a reaction mass;

[0014] 5) providing oxygen and iron to carry out a second oxidation on the reaction material, and obtaining an iron oxide orange pigment of the corresponding color system when the target color is reached.

[0015] The feed solution in the present application can be obtained by mixing liquid alkali and divalent iron salt solution.

[0016] In the technical solution of this application, divalent iron salt and liquid alkali are used as the main initial reaction raw materials. A certain concentration of divalent iron salt solution and liquid alkali are neutralized and subjected to the first oxidation to generate seed crystals. Taking ferrous sulfate as an example, the chemical reaction is as follows:

[0017] FeSO4+2NaOH→Fe(OH)2↓+Na2SO4

[0018] 4Fe(OH)2+O2+2H2O→2Fe(OH)3

[0019] It should be noted that in the above process, the ferrous hydroxide colloid is not directly oxidized to form ferric hydroxide. Ferrous hydroxide is extremely unstable and easily generates different substances as the reaction conditions (especially pH, air flow, and temperature change) change. The applicant has particularly noted in practice that: when pH < 6, iron yellow FeOOH seeds are mainly formed; when pH is 7-10, iron black Fe3O4 is mainly formed; when pH is 11-13, Fe2O3·yH2O amorphous seeds are mainly formed, and when pH> 13, iron yellow FeOOH seeds are mainly formed. In the absence of external intervention, the oxidation process will reduce the pH of the system and change continuously, so a series of transition colors, brown-yellow, brown-black, and even iron-black, are often obtained during the oxidation process. As a result, the above-mentioned different seeds are added to the reactor containing iron sheet to finally obtain different products under high-temperature oxidation.

[0020] Preferably, in step 1), the pH of the feeding solution is 11-13.

[0021] In addition, the applicant found that pH control is very important for the present invention. In the first oxidation process, as Fe 2+ Oxidation will produce a large amount of H + , lowering the pH of the reaction system. As the pH decreases, the reaction easily enters the generation cycle of different crystal seeds, resulting in the generation of disordered miscellaneous crystals, which affects the color of the product after the second oxidation. Thus, the applicant maintains the pH in the range of not less than 11 during the first oxidation process through external intervention, and obtains macroscopic reddish-brown crystal seeds (Fe2O3·yH2O). The value of y determines the different forms of the crystal seeds, and different y values ​​can be dehydrated into iron yellow or iron red. Therefore, the applicant obtains iron oxide yellow (FeOOH) and iron oxide red (Fe2O3) simultaneously in the two oxidation processes by adjusting and controlling the pH to control the generation of miscellaneous crystals, thereby finally obtaining iron oxide orange. More preferably, in step 2), the pH of the reaction system is adjusted to 11 to 13 during the first oxidation process.

[0022] Preferably, in step 2), during the first oxidation process, the reaction temperature is less than or equal to 30° C. When the temperature is greater than 30° C., the color of the seed crystal has turned into brown.

[0023] It is important to note that ferrous hydroxide colloid does not directly oxidize to form ferric hydroxide. Ferrous hydroxide is extremely unstable and easily forms FeO·xFe2O3·yH2O when exposed to air. This substance changes with reaction conditions and time, and its ultimate development direction is different. As time goes by, the proportion of trivalent iron increases, and when oxygen is insufficient, it is easy to form iron black or other impurity crystals.

[0024] Preferably, in step 2), the first oxidation is stopped when the pH no longer changes.

[0025] Preferably, in step 2), the pH value and temperature of the system are regulated and sufficient oxygen is provided to form amorphous reddish-brown seed crystals.

[0026] After the seed crystals are prepared, the seed crystal solution is alkaline. According to the requirements of subsequent oxidation, the pH of the seed crystal solution needs to be adjusted to acidic, and then ferrous ions are added for the second oxidation.

[0027] A low ferrous iron concentration is not conducive to the second oxidation process, while a high ferrous iron concentration will cause the color to change too quickly, which is not conducive to controlling the color process. Preferably, in step 4), the concentration of divalent iron ions in the reaction material is 0.2 wt% to 1 wt%.

[0028] Due to the particularity of ferrous ions, the lower the pH, the more stable the ferrous ions are, and the higher the pH, the easier it is to hydrolyze or form a precipitate. When the pH is greater than 4, the ferrous sulfate solution is easily hydrolyzed to produce yellow flocs. When the pH is greater than 5, the ferrous solution immediately produces blue precipitate suspended particles. Therefore, the pH of the oxide material, i.e., the seed solution, is ≤4. Preferably, in step 3), the pH of the oxide material is adjusted to 2-4.

[0029] Preferably, in step 3), sulfuric acid is used to adjust the pH. Using hydrochloric acid or nitric acid is toxic and volatile. Furthermore, these acids have a strong ability to dissolve seed crystals, which can destroy the lattice of the seed crystals formed by the first oxidation. Furthermore, nitric acid contains nitrogen, and large-scale production requires subsequent treatment of ammonia nitrogen wastewater for discharge, which increases costs.

[0030] In practice, the applicant has found that temperature plays a crucial role in the second oxidation process. If the second oxidation temperature is too low, the oxidation rate slows, seed crystal dehydration becomes difficult, and the resulting pigment lacks a reddish hue. If the second oxidation temperature is too high, the reaction rate accelerates, seed crystal dehydration occurs too quickly, and the resulting pigment has a relatively high red hue but a low yellow hue. Therefore, strict temperature control is necessary to produce qualified iron oxide orange pigments.

[0031] Preferably, the temperature of the second oxidation is 80-90°C.

[0032] Iron participates in the reaction. Preferably, in step 5), the source of the iron can be low-carbon iron, such as iron with a carbon content of no more than 5 wt%. Carbon in high-carbon iron will subsequently precipitate and exist in the final product, thereby affecting the color of the final product.

[0033] Preferably, the divalent iron salt is selected from one or more of ferrous sulfate or its hydrate, ferrous chloride or its hydrate, and ferrous nitrate or its hydrate.

[0034] The present invention provides iron oxide orange obtained by the above-mentioned preparation method.

[0035] The present invention also provides the use of the iron oxide orange as a pigment in paints, printing inks, papermaking and building materials.

[0036] Compared with the prior art, the present invention has the following beneficial technical effects:

[0037] The iron oxide orange synthesis process of the present invention is a direct preparation method, which uses wet oxidation synthesis to produce a pigment with high color saturation and high tinting strength. Moreover, the reaction of the present invention is easy to control, and a range of iron oxide orange colors can be obtained. Because the iron oxide orange pigment is generated by a second oxidation after the first oxidation, the particle size is uniform compared to traditional mixing, and it is not easy to stratify in the coating dispersant. DETAILED DESCRIPTION

[0038] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention.

[0039] It should be noted that the process equipment or devices not specifically specified in the following embodiments are all conventional equipment or devices in the art.

[0040] Furthermore, it should be understood that the reference to one or more method steps in the present invention does not exclude the presence of other method steps before or after the combination of steps, or the insertion of other method steps between the explicitly referenced steps, unless otherwise specified. Furthermore, unless otherwise specified, the numbering of each method step is merely a convenient tool for identifying the method steps, and is not intended to limit the order of the method steps or the scope of the present invention. Changes or adjustments to the relative relationships between the method steps, without substantially altering the technical content, should also be considered within the scope of the present invention.

[0041] Iron Oxide Orange S960 is a type of iron oxide pigment with excellent lightfastness, weathering resistance, and acid and alkali resistance. It is widely used in industries such as building materials, coatings, and papermaking, and is a product with high market demand. It is characterized by a high red shade and strong tinting strength. To compare the performance of the iron oxide orange pigment produced by the technical solution of this application, this application uses Iron Oxide Orange S960 for comparison to illustrate the performance of the iron oxide orange pigment prepared by the method of this application.

[0042] Among them, the closer the strength is to 100%, the closer DL, DA and DB are to 0, and the closer the product is to the standard sample Iron Orange S960.

[0043] Use datecolor600 colorimeter to obtain LAB+ intensity.

[0044] Example 1

[0045] This embodiment is a specific synthesis of an iron oxide orange pigment:

[0046] 8750 ml of water was taken and 1000 ml of 30 g / 100 ml ferrous sulfate (heptahydrate) solution and 90.4 g of NaOH aqueous solution were added simultaneously under stirring at 150 r / min. The pH was then about 12.3.

[0047] Air intake 2.4m 3 / h, the pH dropped rapidly in the early stage of the reaction, and the liquid alkali was continuously added to maintain the pH in the range of 11-12. After about 30 minutes of reaction, the pH almost stopped decreasing, and the pH of the reaction system was finally controlled at 11.96, and the oxidation was completed to obtain a reddish-brown seed solution.

[0048] The pH of the seed solution was adjusted to 3 with sulfuric acid, and ferrous sulfate solution was added so that the content of ferrous sulfate heptahydrate in the reaction mass was 3 g / 100 ml (corresponding to a ferrous ion content of 0.5-0.6 wt %).

[0049] The prepared seed crystals were placed in a low carbon iron oxidation kettle at 85°C and air (6 L / min) was introduced to start the second oxidation. Samples were taken at regular intervals during the reaction for analysis.

[0050] Color changes during the oxidation reaction in Example 1: (See Table 1 with iron oxide orange S960 as the standard)

[0051] Table 1 Oxidation data of Example 1

[0052]

[0053] The color development shows that as oxidation progresses, the tinting strength becomes higher and higher, and after 36 hours of oxidation, it reaches the S960 product standard.

[0054] Example 2

[0055] This embodiment provides a specific method for synthesizing iron oxide orange:

[0056] Take 25L of water and add 3000ml of 30g / 100ml ferrous sulfate solution (heptahydrate) and 271g of sodium hydroxide solution at the same time under stirring (150r / min). The pH after mixing is about 12.07. Let air in for 6m 3 / h, the pH value dropped rapidly in the initial stage of the reaction, and the sodium hydroxide aqueous solution was continuously added dropwise to maintain the pH value in the range of 11-12. After about 45 minutes of reaction, the pH value hardly dropped any more, and the reaction was finally controlled at 11.32, and the oxidation was completed to obtain a reddish-brown seed solution.

[0057] The pH of the seed crystal solution was adjusted to 3 with sulfuric acid, and ferrous sulfate solution was added so that the content of ferrous sulfate heptahydrate in the seed crystals was 3 g / 100 ml.

[0058] The prepared reaction mass was placed in an oxidation kettle containing low carbon iron at 85°C and air (6 L / min) was introduced to initiate oxidation. Samples were taken and analyzed at regular intervals during the reaction.

[0059] Example 2 Color changes during oxidation reaction: (Assuming iron orange S960 as the standard, see Table 2)

[0060] Table 1 Oxidation data of Example 2

[0061]

[0062] The color development shows that as oxidation progresses, the tinting strength becomes higher and higher, and after 48 hours of oxidation, it reaches the S960 product standard.

[0063] Example 3

[0064] This embodiment provides a specific method for synthesizing iron oxide orange:

[0065] 43.75 L of water was taken and 5000 ml of 30 g / 100 ml ferrous sulfate (heptahydrate) solution and 452 g of sodium hydroxide solution were added simultaneously under stirring (150 r / min). The pH was about 12.19.

[0066] Air intake 12m 3 / h, the pH value dropped rapidly in the initial stage of the reaction, and the liquid alkali was continuously added to maintain the pH value in the range of 11-12. After about 70 minutes of reaction, the pH value hardly dropped any more, and the reaction was finally controlled at 11.76, and the oxidation was completed to obtain a brown-red seed solution.

[0067] The pH of the seed crystal solution was adjusted to 3 with sulfuric acid, and ferrous sulfate solution was added so that the content of ferrous sulfate heptahydrate in the seed crystals was 3 g / 100 ml.

[0068] The prepared reaction mixture was placed in an oxidation kettle containing low carbon iron and oxidized by introducing air (20 L / min) at 85°C. Samples were taken and analyzed at regular intervals during the reaction.

[0069] Example 3 Color changes during oxidation reaction: (Assuming iron orange S960 as the standard, see Table 3)

[0070] Table 3 Oxidation data of Example 3

[0071]

[0072] The color development shows that after 40 hours of oxidation, it reaches the S960 product standard and has a relatively full red color.

[0073] Example 4

[0074] This embodiment provides a specific method for synthesizing iron oxide orange:

[0075] Take 8000ml of water and add 2000ml of ferrous sulfate solution (heptahydrate) with a concentration of 22.5g / 100ml and 130g of sodium hydroxide aqueous solution at the same time under stirring (150r / min). The pH after mixing is about 11.07. Let 2m of air in. 3 / h, the pH value dropped rapidly in the initial stage of the reaction, and the pH value was maintained in the range of 11-12 by continuous addition of liquid alkali. After about 40 minutes of reaction, the pH value hardly dropped any more, and the reaction was finally controlled at 11.02, and the oxidation was completed to obtain a reddish-brown seed solution.

[0076] The pH of the seed crystal solution was adjusted to 3 with sulfuric acid, and ferrous sulfate solution was added so that the content of ferrous sulfate heptahydrate in the seed crystals was 3 g / 100 ml.

[0077] The prepared reaction mass was placed in an oxidation kettle containing elemental iron and oxidized by introducing air (6 L / min) at 85°C. Samples were taken and analyzed at regular intervals during the reaction.

[0078] Example 4 Color changes during oxidation reaction: (Assuming iron orange S960 as the standard, see Table 4)

[0079] Table 4 Oxidation data of Example 4

[0080]

[0081] The color development shows that as the oxidation progresses, the tinting strength becomes higher and higher, and after 30h of oxidation, it reaches the S960 product standard.

[0082] Example 5

[0083] This embodiment is a specific synthesis of an iron oxide orange pigment:

[0084] The difference between Example 5 and Example 1 is that the pH range of the first oxidation is controlled at 12-13, the final pH of the reaction is controlled at 12.32, and samples are taken and analyzed at regular intervals during the reaction.

[0085] Example 5 Color changes during oxidation reaction: (Assuming iron orange S960 as the standard, see Table 5)

[0086] Table 5 Oxidation data of Example 5

[0087]

[0088] Oxidation data showed that the color reached the S960 color standard after 24 hours.

[0089] Example 6

[0090] This embodiment is a specific synthesis of an iron oxide orange pigment:

[0091] The basic difference between Example 6 and Example 4 is that the pH of the first oxidation is controlled at 12-13, the final pH of the reaction is controlled at 12.72, and samples are taken and analyzed at regular intervals during the reaction.

[0092] Example 6 Color changes during oxidation reaction: (Assuming iron orange S960 as the standard, see Table 6)

[0093] Table 6 Oxidation data of Example 6

[0094]

[0095] Example 7

[0096] This embodiment is a specific synthesis of an iron oxide orange pigment:

[0097] The difference between Example 7 and Example 1 is that the reaction temperature of the second oxidation was raised to 90° C. and air was introduced for oxidation. Samples were taken and analyzed at regular intervals during the reaction.

[0098] Example 7 Color changes during the oxidation reaction: (Assuming iron orange S960 as the standard, see Table 7)

[0099] Table 7 Oxidation data of Example 7

[0100]

[0101]

[0102] Oxidation data showed that the color reached the S960 color standard in 24 hours, but the higher temperature resulted in a faster oxidation rate and faster dehydration, resulting in a lower DB value and a higher DA value. The product was reddish.

[0103] Example 8

[0104] This embodiment is a specific synthesis of an iron oxide orange pigment:

[0105] The difference between Example 8 and Example 1 is that the reaction temperature of the second oxidation was lowered to 80° C. and air was introduced for oxidation. Samples were taken and analyzed at regular intervals during the reaction.

[0106] Example 8 Color changes during the oxidation reaction: (Assuming iron orange S960 as the standard, see Table 8)

[0107] Table 8 Oxidation data of Example 8

[0108]

[0109] Oxidation data show that the color meets the S960 requirement after 32-36 hours of oxidation, and the oxidation temperature of 80℃ causes the pigment red shade to be relatively low.

[0110] Comparative Example

[0111] Comparative Example 1 Synthesis of Iron Oxide Orange

[0112] Take 8750ml of water and add 1000ml of 30g / 100ml ferrous sulfate solution (heptahydrate) and 90.4g of sodium hydroxide solution at the same time under stirring (150r / min). The pH is about 12.3. 2.4m of air is introduced. 3 / h, the pH value continued to decrease during the reaction and finally stabilized at 10.38.

[0113] The pH of the seed crystal solution was adjusted to 3 with sulfuric acid, and ferrous sulfate solution was added so that the content of ferrous sulfate heptahydrate in the seed crystals was 3 g / 100 ml.

[0114] The prepared reaction mixture was placed in an oxidation kettle containing low carbon iron and oxidized by introducing air (6 L / min) at 85°C. Samples were taken for analysis at regular intervals during the reaction.

[0115] Comparative Example 1 Color change during oxidation reaction: (Assuming iron orange S960 as the standard, see Table 9)

[0116] Table 9 Comparative Example 1 Oxidation Data

[0117]

[0118]

[0119] The steps of Comparative Example 1 are basically different from those of Example 1 in that during the first oxidation process, no liquid caustic soda was added to maintain the reaction pH at 11-13. The oxidation color light showed that the pigment obtained by oxidation completely deviated from the target color system.

[0120] Comparative Example 2 Synthesis of Iron Oxide Orange

[0121] Take 8750ml of water and add 1000ml of 30g / 100ml ferrous sulfate solution (heptahydrate) and 87.16g of sodium hydroxide solution at the same time under stirring (150r / min). The pH is about 10.39. 2.4m of air is introduced. 3 / h, the pH value continued to decrease during the reaction, and liquid alkali was added dropwise to maintain the pH value between 10-11, and finally stabilized at 10.03 to obtain yellow-brown seed crystals.

[0122] The pH of the seed crystal solution was adjusted to 3 with sulfuric acid, and ferrous sulfate solution was added so that the content of ferrous sulfate heptahydrate in the seed crystals was 3 g / 100 ml.

[0123] The prepared seed crystals were placed in an oxidation kettle lined with iron sheets and oxidized by introducing air (6 L / min) at 85°C. Samples were taken and analyzed at regular intervals during the reaction.

[0124] Comparative Example 2 Color change during oxidation reaction: (Taking iron orange S960 as the standard, see Table 10)

[0125] Table 10 Comparative Example 2 Oxidation Data

[0126]

[0127] Comparative Example 2 differs from Example 1 in that the pH after neutralization of ferrous sulfate and liquid caustic soda was not maintained between 11 and 13, and liquid caustic soda was not added during the first oxidation process to maintain the pH between 11 and 13. The oxidation data show that the pigment color completely deviates from the target product.

[0128] Comparative Example 3 Synthesis of Iron Oxide Orange

[0129] Take 8750ml of water and add 1000ml of 30g / 100ml ferrous sulfate solution (heptahydrate) and 97.28g of sodium hydroxide solution at the same time under stirring (150r / min). The pH is about 13.34. 2.4m of air is introduced. 3 / h, as the pH value decreased, liquid alkali was added dropwise to maintain the pH value slightly above 13. After about 30 minutes of reaction, the pH value hardly decreased any more, and the reaction was finally controlled at 13.48, and the oxidation was completed to obtain yellow-brown seed crystals.

[0130] The pH of the seed crystal solution was adjusted to 3 with sulfuric acid, and ferrous sulfate solution was added so that the content of ferrous sulfate heptahydrate in the seed crystals was 3 g / 100 ml.

[0131] The prepared seed crystals were placed in an oxidation kettle lined with iron sheets and oxidized by introducing air (6 L / min) at 85°C. Samples were taken and analyzed at regular intervals during the reaction.

[0132] Comparative Example 3 Color change during oxidation reaction: (Taking iron orange S960 as the standard, see Table 11)

[0133] Table 11 Oxidation data of comparative example 3

[0134]

[0135] The basic difference between Comparative Example 3 and Example 1 is that the pH after neutralization with liquid alkali and ferrous sulfate is greater than 13, and the pH during the first oxidation process is greater than 13. The oxidation results show that the color is completely deviated from the target product.

[0136] Comparative Example 4 Synthesis of Iron Oxide Orange

[0137] The steps of Comparative Example 4 differ from those of Example 1 in that a high temperature of 95° C. is maintained throughout the oxidation process.

[0138] Comparative Example 4: Color change during oxidation reaction: (Assuming iron orange S960 as the standard, see Table 12)

[0139] Table 12 Oxidation data of comparative example 4

[0140]

[0141] The oxidized color has deviated from the iron orange series, with a significant decrease in DL, a significant increase in DA, and a significant decrease in DB, gradually developing towards iron red.

[0142] Comparative Example 5 Synthesis of Iron Oxide Orange

[0143] The difference between the steps of Comparative Example 5 and Example 1 is that the lower temperature of 78° C. is maintained throughout the second oxidation process.

[0144] Comparative Example 5 Color change during oxidation reaction: (Assuming iron orange S960 as the standard, see Table 13)

[0145] Table 13 Oxidation data of comparative example 5

[0146]

[0147] The oxidation results show that it is difficult to dehydrate the seed crystals at low temperatures, the reaction progresses slowly, the color completely deviates from the color system, and the pigment tinting strength is very low.

[0148] In summary, the preparation of iron orange seed crystals requires a relatively narrow reaction pH condition. The pH of the feed solution for the first oxidation to form the seed solution is 11-13. By regulating the pH value of the reaction system during the first oxidation process, the pH value of the reaction system is effectively prevented from shifting to the transitional color system and the generation of impurity crystals, which is a necessary condition for the preparation of seed crystals.

[0149] The reaction temperature in the second oxidation has a great influence on the pigment. If the temperature is too high, the color will be reddish and dark. If the temperature is too low, the reaction will be slow and the seed crystals will not be completely dehydrated, resulting in the material having no pigment properties.

[0150] The above examples are intended to illustrate the embodiments disclosed herein and are not to be construed as limiting the present invention. In addition, the various modifications listed herein and variations of the methods and compositions in the invention will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. Although the present invention has been specifically described in conjunction with various specific preferred embodiments of the present invention, it should be understood that the present invention should not be limited to these specific embodiments. In fact, various modifications apparent to those skilled in the art as described above to obtain the invention should be included within the scope of the present invention.

Claims

1. A method for preparing iron oxide orange, characterized in that: The steps include: 1) providing an alkaline aqueous solution of divalent iron salt as a feed solution; the pH of the feed solution is 11-13; 2) providing oxygen to perform a first oxidation on the feed liquid to form an oxidized material, and adjusting the pH of the reaction system to be not less than 11 during the first oxidation process; adjusting the pH of the reaction system to be 11-13 during the first oxidation process; and during the first oxidation process, the reaction temperature is less than or equal to 30° C.; 3) adjusting the pH of the oxide material to be acidic; 4) adding an aqueous solution of a divalent iron salt to form a reaction mass; 5) providing oxygen and iron to carry out a second oxidation on the reaction material until the target hue is reached, thereby obtaining an iron oxide orange pigment of the corresponding color system. The temperature of the second oxidation is 80-90° C.

2. The preparation method according to claim 1, characterized in that The first oxidation was stopped when the pH no longer changed.

3. The preparation method according to claim 1, characterized in that In step 2), the pH value and temperature of the system are regulated and sufficient oxygen is provided to form amorphous reddish-brown seed crystals.

4. The preparation method according to claim 1, characterized in that In step 3), the pH of the oxide material is adjusted to 2-4; and / or, in step 3), sulfuric acid is used to adjust the pH.

5. The preparation method according to claim 1, characterized in that In step 4), the concentration of divalent iron ions in the reaction material is 0.2 wt% to 1 wt%.

6. The preparation method according to claim 1, characterized in that The divalent iron salt is selected from one or more of ferrous sulfate or its hydrate, ferrous chloride or its hydrate, and ferrous nitrate or its hydrate.

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