Method for preparing iron oxide pigment from steel sulfuric acid pickling waste liquid and iron oxide pigment

Abstract

The method comprises the following steps that S1, the steel sulfuric acid pickling waste liquid is filtered through medium-speed filter paper, solid impurities are removed, and then a NaOH solution is used for adjusting the pH value; s2, placing the steel sulfuric acid pickling waste liquid with the adjusted pH value in a water bath kettle for heating and stirring treatment, and then naturally cooling; and S3, carrying out solid-liquid separation on the steel sulfuric acid pickling waste liquid treated in the step S2 to obtain a solid-phase precipitate and a supernatant, and washing, drying, grinding and screening the solid-phase precipitate to obtain the iron oxide pigment. According to the method, the sulfuric acid pickling waste liquid can be converted into the qualified ferric oxide pigment through a coprecipitation method, and the dual purposes of sulfuric acid pickling waste liquid treatment and resource recovery are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of iron oxide series pigments, and relates to a method for preparing iron oxide series pigments by waste water of sulfuric acid pickling of steel and iron oxide series pigments. Background Art

[0002] The sulfuric acid pickling waste liquid in the steel industry mainly comes from the pickling process in the steel production process. In steel production, pickling treatment is often carried out to remove the oxide layer and impurities on the surface of steel. In this process, the acid solution will form a pickling waste liquid containing a large amount of metal ions and other pollutants after contacting the steel. These waste liquids mainly contain iron ions, acid substances and a small amount of other metal ions. The iron in these pickling waste liquids is usually in the form of divalent iron ions (Fe 2+ ) exists in the form of , if it is discharged directly without treatment, it will cause pollution to the environment, so it needs to be treated to meet the emission standards or resource utilization, so as to reduce the harm to the environment. At present, the methods for treating pickling waste liquid mainly include membrane separation technology, acid-base neutralization, high-temperature roasting and biological method. Membrane separation technology is a treatment method with high environmental benefits. It can separate metal salts or utilize metal salts as resources to prepare high value-added products, but the frequent replacement of membranes will lead to high operating costs; the traditional acid-base neutralization method is simple and fast, but the treated sludge solid waste is difficult to handle and is prone to secondary pollution, which cannot achieve the purpose of resource treatment of waste liquid; separation technologies such as high-temperature roasting and biological method have many uncertain problems, such as high energy consumption of high-temperature roasting and inactivation of microorganisms in biological method. Therefore, the preparation of iron oxide pigments by chemical conversion of sulfuric acid pickling waste liquid in the steel industry provides an economically feasible idea for the resource treatment of steel pickling waste liquid.

[0003] Iron oxide pigments have a wide range of applications and are mainly used in coatings, plastics, rubber and other industries. They not only improve product color, but also have good weather resistance and stability. If iron oxide pigments can be prepared using sulfuric acid pickling wastewater from steel, the dual goals of sulfuric acid pickling wastewater treatment and resource recovery can be achieved.

[0004] Coprecipitation is a chemical conversion method that can be used to prepare ultrafine powders of composite oxides containing two or more metal elements. This method can also be used to prepare iron oxide. Usually, this method involves mixing divalent and trivalent metal salts in a certain molar ratio and then placing them in an alkaline solution. The precipitation rate and precipitation properties can be controlled by adjusting the pH value of the solution. After the reaction, the precipitate product is collected and washed and dried to obtain an iron oxide pigment. By adjusting the reaction conditions and the type and ratio of metal salts, the morphology, size and magnetic properties of the iron oxide pigment particles can be controlled to make it suitable for different application fields. However, the traditional coprecipitation method usually requires a higher temperature (>80°C) and a longer time (1 to 2h) during the preparation process, and additional substances need to be added to promote the reaction. Summary of the invention

[0005] In view of the above-mentioned defects existing in the prior art, the purpose of the present invention is to provide a method for preparing iron oxide pigments from steel sulfuric acid pickling waste liquid and iron oxide pigments. The sulfuric acid pickling waste liquid can be converted into qualified iron oxide pigments through co-precipitation, achieving the dual goals of sulfuric acid pickling waste liquid treatment and resource recovery.

[0006] To achieve the above object, the present invention adopts the following technical solution:

[0007] The first aspect of the present invention provides a method for preparing iron oxide pigments from steel sulfuric acid pickling wastewater, comprising the following steps:

[0008] S1, filtering the steel sulfuric acid pickling waste liquid through medium-speed filter paper to remove solid impurities;

[0009] S2, co-precipitation, adjusting the pH value of the steel sulfuric acid pickling waste liquid with a NaOH solution, then placing the steel sulfuric acid pickling waste liquid after the pH value is adjusted in a water bath for heating and stirring, and then naturally cooling;

[0010] S3, performing solid-liquid separation on the steel sulfuric acid pickling waste liquid treated in step S2 to obtain a solid phase precipitate and a supernatant, and the solid phase precipitate is washed, dried, ground, and sieved to obtain an iron oxide pigment.

[0011] Preferably, in step S1, the pH value of the steel sulfuric acid pickling waste liquid is 0.2-0.9, and the concentration of sulfate ions is 160-180 g / L.

[0012] Preferably, in step S2, the pH value of the steel sulfuric acid pickling waste liquid is adjusted to 8-10 with a NaOH solution.

[0013] Preferably, in step S2, the heating and stirring temperature is 50-80° C., and the heating and stirring time is 0.5-1.5 h.

[0014] Preferably, in step S3, the solid-liquid separation is performed using a centrifuge, the centrifugal speed is 3000-3500 r / min, and the centrifugal separation time is 10-15 min.

[0015] Preferably, in step S3, the washing process uses warm water at 50-60° C. for at least 3 times.

[0016] Preferably, in step S3, during the drying process, the drying temperature is 70-90° C., and the drying time is 24±5 h.

[0017] Preferably, in step S3, the removal rates of Mn, Fe, Zn and Ni metal ions in the supernatant are all above 99.9%.

[0018] The second aspect of the present invention provides an iron oxide pigment prepared by the method for preparing iron oxide pigments from steel sulfuric acid pickling waste water according to the first aspect of the present invention, wherein the iron oxide pigment has a Fe2O3 content ≥88%, a water-soluble matter content ≤0.55%, and a total calcium content ≤0.2%.

[0019] The present invention has the following beneficial effects:

[0020] 1. The present invention optimizes the coprecipitation method to achieve the preparation of iron oxide pigments at a lower temperature of 50 to 80°C and a shorter time of 0.5 to 1.5 hours. This improvement significantly improves production efficiency and reduces costs;

[0021] 2. The core advantage of the present invention is that it only needs to use sodium hydroxide to adjust the pH value without adding any other substances; this simplified process not only reduces the production cost, but also avoids the environmental pollution and operational complexity that may be caused by additional chemicals;

[0022] 3. The present invention uses a co-precipitation method to treat steel sulfuric acid pickling waste liquid, converting the iron in the steel sulfuric acid pickling waste liquid into iron oxide pigments, and at the same time, the removal rate of metal ions such as Mn, Fe, Zn, Ni in the waste liquid reaches more than 99.9%; the core of this process is to mix iron ions with alkaline solvents under appropriate conditions to promote their precipitation to form solid phase products; by adjusting the reaction conditions such as pH value, temperature, time, etc., the steel sulfuric acid pickling waste liquid finally reacts to generate iron oxide pigments; this method is economical, time-saving, does not require hydrothermal or other equipment, and is suitable for preparing iron oxide pigments from steel sulfuric acid pickling waste liquid;

[0023] 4. The present invention can achieve the dual goals of sulfuric acid pickling waste liquid treatment and resource recovery by preparing iron oxide pigment from steel sulfuric acid pickling waste liquid, thereby improving the sustainable development level of the steel industry and promoting green manufacturing and environmental protection;

[0024] 5. The present invention simplifies the process flow and is environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic flow chart of a method for preparing iron oxide pigments from steel sulfuric acid pickling waste liquid of the present invention;

[0026] Figure 2 The figures are the actual pictures of the iron oxide pigments prepared in the examples of the present invention, (a) is the iron oxide pigment prepared in Example 1; (b) is the iron oxide pigment prepared in Example 2; (c) is the iron oxide pigment prepared in Example 3;

[0027] Figure 3 1 and 2 are SEM images of the iron oxide pigments prepared in the embodiments of the present invention, (a) is a SEM image of the iron oxide pigment prepared in Example 1; (b) is a SEM image of the iron oxide pigment prepared in Example 2; (c) is a SEM image of the iron oxide pigment prepared in Example 3. DETAILED DESCRIPTION

[0028] In order to better understand the above technical solution of the present invention, the technical solution of the present invention is further described below in conjunction with embodiments.

[0029] Combination Figure 1 As shown, the present invention provides a method for preparing iron oxide pigments from steel sulfuric acid pickling waste liquid, comprising the following steps:

[0030] S1, filtering the steel sulfuric acid pickling waste liquid through medium-speed filter paper to remove solid impurities;

[0031] This step is mainly to remove impurities in the solution. The steel sulfuric acid pickling waste liquid is used as raw material and filtered using medium-speed filter paper to remove solid impurities in the steel sulfuric acid pickling waste liquid.

[0032] The steel sulfuric acid pickling waste liquid used in this step has the appearance of a dark green liquid, a pH value of 0.2-0.9, and a sulfate ion concentration of 160-180 g / L; these steel sulfuric acid pickling waste liquids mainly contain iron ions, acid substances and a small amount of other metal ions.

[0033] S2, co-precipitation, adjusting the pH value of the steel sulfuric acid pickling waste liquid with a NaOH solution, then placing the steel sulfuric acid pickling waste liquid after the pH value is adjusted in a water bath for heating and stirring, and then naturally cooling;

[0034] The coprecipitation method is a method for synthesizing ferrite nanoparticles. In this step, the filtered steel sulfuric acid pickling waste liquid is adjusted to a pH value of 8-10 (preferably a pH value of 9.0) using a NaOH solution (whose concentration can be 5 mol / L); then the steel sulfuric acid pickling waste liquid after the pH value is adjusted is placed in a water bath at 50-80°C (preferably a reaction temperature of 55°C) and heated and stirred for 0.5-1.5h (preferably a reaction time of 30min), and then cooled naturally after the reaction is completed.

[0035] S3, performing solid-liquid separation on the steel sulfuric acid pickling waste liquid treated in step S2 to obtain a solid phase precipitate and a supernatant, and the solid phase precipitate is washed, dried, ground, and sieved to obtain an iron oxide pigment.

[0036] In this step, a centrifuge is used to separate the cooled steel sulfuric acid pickling waste liquid into solid and liquid at a centrifugal speed of 3000-3500 r / min for 10-15 minutes until a solid precipitate and a supernatant are obtained; the solid precipitate is washed with warm water at 50-60°C for at least 3 times, and then dried at a temperature of 70-90°C for 24±5h, and then ground after drying, and the product iron oxide pigment is obtained after passing through a 45μm filter.

[0037] In this step, the supernatant was tested by ICP, and the removal rates of Mn, Fe, Zn, and Ni metal ions in the supernatant were all above 99.9%.

[0038] The present invention uses a coprecipitation method to treat steel sulfuric acid pickling waste liquid, converts the iron in the steel sulfuric acid pickling waste liquid into qualified iron oxide pigments, and at the same time, the removal rate of metal ions such as Mn, Fe, Zn, Ni in the waste liquid reaches more than 99.9%, which greatly improves the effluent water quality and significantly reduces its harm to the environment. The core of the above coprecipitation method is to mix iron ions with alkaline solvents under appropriate conditions to promote their precipitation to form solid phase products; by adjusting the reaction conditions such as pH value, temperature, time, etc., the steel sulfuric acid pickling waste liquid finally reacts to generate iron oxide pigments. The present invention can achieve the dual goals of sulfuric acid pickling waste liquid treatment and resource recovery, thereby improving the sustainable development level of the steel industry and promoting green manufacturing and environmental protection.

[0039] The iron oxide pigment prepared above has a Fe2O3 content of ≥88%, a water-soluble matter content of ≤0.55%, and a total calcium content of ≤0.2%, meeting the various index requirements of iron oxide brown A grade and iron oxide black B grade.

[0040] The method for preparing iron oxide pigments from steel sulfuric acid pickling wastewater and the iron oxide pigments of the present invention are further introduced below with reference to specific examples.

[0041] Example 1

[0042] The method for preparing iron oxide pigments by wastewater from steel sulfuric acid pickling is as follows:

[0043] First, 40 mL of the steel sulfuric acid pickling waste liquid was measured, and the steel sulfuric acid pickling waste liquid was filtered through a medium-speed filter paper to remove solid impurities; then 5 mol / L NaOH solution was added to adjust its pH value to 8. The steel sulfuric acid pickling waste liquid after adjusting the pH value was placed in a water bath and stirred at a specific water bath temperature of 50°C. When the required reaction time of 30 minutes was reached, it was naturally cooled; a centrifuge was used to separate the solid and liquid at 3500r / min for 15 minutes until a solid phase precipitate and a supernatant were obtained. The heavy metal residues in the supernatant were analyzed by ICP-AES, and the results are shown in Table 2; the solid phase precipitate was washed with warm water at 50°C for 3 times and then centrifuged, dried at 80°C for 24 hours, and the solid phase precipitate was ground into fine powder and passed through a 45μm sieve. The obtained product is an iron oxide pigment, and the product test results are shown in Table 1.

[0044] Example 2

[0045] The method for preparing iron oxide pigments by wastewater from steel sulfuric acid pickling is as follows:

[0046] First, 40 mL of the steel sulfuric acid pickling waste liquid was measured, and the steel sulfuric acid pickling waste liquid was filtered through a medium-speed filter paper to remove solid impurities; then 5 mol / L NaOH solution was added to adjust its pH value to 10. The steel sulfuric acid pickling waste liquid after adjusting the pH value was placed in a water bath and stirred at a specific water bath temperature of 60°C. When the required reaction time of 60 minutes was reached, it was naturally cooled; a centrifuge was used to separate the solid and liquid at 3000r / min for 10 minutes until a solid phase precipitate and a supernatant were obtained. The heavy metal residues in the supernatant were analyzed by ICP-AES, and the results are shown in Table 2; the solid phase precipitate was washed with warm water at 60°C for 3 times and then centrifuged, dried at 90°C for 19 hours, and the solid phase precipitate was ground into fine powder and passed through a 45μm sieve. The obtained product is an iron oxide pigment, and the product test results are shown in Table 1.

[0047] Example 3

[0048] The method for preparing iron oxide pigments by wastewater from steel sulfuric acid pickling is as follows:

[0049] First, 40 mL of the steel sulfuric acid pickling waste liquid was measured and filtered through medium-speed filter paper to remove solid impurities; then 5 mol / L NaOH solution was added to adjust its pH value to 10. The steel sulfuric acid pickling waste liquid after adjusting the pH value was placed in a water bath and stirred at a specific water bath temperature of 80°C. When the required reaction time of 90 min was reached, it was naturally cooled; a centrifuge was used to separate the solid and liquid at 3000r / min for 15 min until a solid phase precipitate and a supernatant were obtained. The heavy metal residues in the supernatant were analyzed by ICP-AES, and the results are shown in Table 2; the solid phase precipitate was washed with warm water at 60°C for 3 times and then centrifuged, dried at 70°C for 29h, and the solid phase precipitate was ground into fine powder and passed through a 45μm sieve. The obtained product is an iron oxide pigment, and the product test results are shown in Table 1.

[0050] Figure 2 The actual pictures of the iron oxide pigments prepared in Examples 1, 2 and 3 are respectively, and their appearance color is brown; Figure 3 The SEM images of the iron oxide pigments prepared in Examples 1, 2 and 3 respectively show granular crystals with a number of fine particles attached to the surface.

[0051] XRF was used to determine the content of Fe2O3 in iron oxide pigments, and the data was compared with the national standard of iron oxide pigments GB / T 1863-2008. Table 1 shows the index comparison of iron oxide pigments and standard iron oxide pigments. Table 2 shows the comparison of liquid metal concentration before and after the reaction of preparing iron oxide pigments from steel sulfuric acid pickling waste liquid.

[0052] Table 1 Comparison of indicators of iron oxide pigments and standard iron oxide pigments

[0053]

[0054] Table 2 Comparison of liquid metal concentration before and after the reaction of preparing iron oxide pigments from steel sulfuric acid pickling wastewater

[0055]

[0056] In summary, the present invention can convert steel sulfuric acid pickling waste liquid into qualified iron oxide pigments. The product meets the various index requirements of iron oxide brown (iron oxide black) grade B. At the same time, the waste liquid is processed into clear and impure effluent, achieving the dual goals of steel sulfuric acid pickling waste liquid treatment and resource recovery.

[0057] Those skilled in the art should recognize that the above embodiments are only used to illustrate the present invention, and are not intended to limit the present invention. As long as they are within the spirit of the present invention, any changes or modifications to the above embodiments will fall within the scope of the claims of the present invention.

Claims

1. A method for preparing iron oxide pigments from steel sulfuric acid pickling wastewater, characterized in that: The following steps are involved: S1, filtering the steel sulfuric acid pickling waste liquid through medium-speed filter paper to remove solid impurities; S2, co-precipitation, adjusting the pH value of the steel sulfuric acid pickling waste liquid with a NaOH solution, then placing the steel sulfuric acid pickling waste liquid after the pH value is adjusted in a water bath for heating and stirring, and then naturally cooling; S3, performing solid-liquid separation on the steel sulfuric acid pickling waste liquid treated in step S2 to obtain a solid phase precipitate and a supernatant, and the solid phase precipitate is washed, dried, ground, and sieved to obtain an iron oxide pigment.

2. The method for preparing iron oxide pigments from steel sulfuric acid pickling wastewater according to claim 1, characterized in that: In the step S1, the pH value of the steel sulfuric acid pickling waste liquid is 0.2-0.9, and the concentration of sulfate ions is 160-180 g / L.

3. The method for preparing iron oxide pigments from steel sulfuric acid pickling wastewater according to claim 1, characterized in that: In the step S2, the pH value of the steel sulfuric acid pickling waste liquid is adjusted to 8-10 with a NaOH solution.

4. The method for preparing iron oxide pigments from steel sulfuric acid pickling wastewater according to claim 1, characterized in that: In the step S2, the heating and stirring temperature is 50 to 80°C, and the heating and stirring time is 0.5 to 1.5 hours.

5. The method for preparing iron oxide pigments from steel sulfuric acid pickling wastewater according to claim 1, characterized in that: In step S3, the solid-liquid separation is performed using a centrifuge with a centrifugal speed of 3000-3500 r / min and a centrifugal separation time of 10-15 min.

6. The method for preparing iron oxide pigments from steel sulfuric acid pickling wastewater according to claim 1, characterized in that: In step S3, the washing process uses warm water at 50-60° C. for at least 3 times.

7. The method for preparing iron oxide pigments from steel sulfuric acid pickling wastewater according to claim 1, characterized in that: In the step S3, during the drying process, the drying temperature is 70-90° C. and the drying time is 24±5 h.

8. The method for preparing iron oxide pigments from steel sulfuric acid pickling wastewater according to claim 1, characterized in that: In step S3, the removal rates of Mn, Fe, Zn and Ni metal ions in the supernatant are all above 99.9%.

9. An iron oxide pigment prepared by the method for preparing iron oxide pigment by wastewater from sulfuric acid pickling of steel according to any one of claims 1 to 8, characterized in that: The Fe2O3 content of the iron oxide pigment is ≥88%, the water-soluble matter content is ≤0.55%, and the total calcium content is ≤0.2%.

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