Method for preparing near-infrared reflective pigment by using rare earth waste residue tailings and application thereof

Abstract

The application belongs to the field of pigment preparation, and particularly relates to a method for preparing near-infrared reflective pigments from rare earth waste residues and tailings and application thereof. The method for preparing near-infrared reflective pigments from rare earth waste residues and tailings comprises the following steps: using a high-temperature solid-phase sintering method or a mechanical grinding method to prepare raw materials containing rare earth waste residues and / or tailings into near-infrared reflective pigments. The preparation steps of the application are relatively simple, the cost is relatively low, and the waste raw materials polluting the environment are converted into products with application value.

Description

Technical Field

[0001] This invention belongs to the field of pigment preparation, and in particular relates to a method for preparing near-infrared reflective pigments using rare earth waste tailings and its application. Background Technology

[0002] Rare earth elements are a collective term for seventeen elements in the periodic table, including the lanthanides, scandium, and yttrium. Due to their unique physicochemical properties, they have been widely used in numerous fields such as electronics, petrochemicals, metallurgy, and energy, and are known as "industrial gold." Materials made from rare earth elements include catalytic materials, ceramic materials, and optoelectronic materials. The urban heat island effect refers to the phenomenon where the air temperature in a city is higher than the ambient temperature in the surrounding rural areas at any given time. The main causes of this phenomenon are large amounts of artificial waste heat, high-temperature heat storage bodies such as buildings and roads, and the reduction of green spaces. Among these, the surfaces of high-temperature heat storage bodies such as buildings and roads are mostly made of low-reflection materials. These low-reflection materials can absorb short-wave solar radiation, causing it to be reflected and captured again by buildings and streets. The obstruction of the sky by buildings causes heat to be intercepted by the surface of the obstacles and absorbed or radiated back into the city, which is a major factor contributing to the heat island effect.

[0003] Currently, the "heat island effect" is mainly mitigated through measures such as increasing vegetation and altering building and street surface materials. Ultraviolet radiation accounts for only 5% of solar radiation, visible light for 43%, and near-infrared radiation for 52%. Therefore, materials with high reflectivity in the near-infrared region can be used as a cooling agent for building exteriors. Research has found that using high near-infrared reflective coatings as coatings for building roofs and exterior walls can reduce heat radiation and mitigate the urban "heat island effect."

[0004] High near-infrared reflectance coatings are mostly white and light-colored. Although they can reflect sunlight well, the monotonous colors are difficult to meet people's aesthetic needs. Pigments are the main components that give coatings their color. The near-infrared reflectance of pigments directly affects the heat insulation performance of the coating. Most existing colored pigments contain heavy metals such as Pd, Cd, Co, and Cr, which not only have low near-infrared reflectance but also easily cause environmental pollution.

[0005] In recent years, rare earth elements have been used as substitutes for toxic heavy metals due to their good chemical stability, thermal stability, low toxicity and color diversity. They have been studied and used in many pigments. However, when using rare earth elements to prepare pigments, it is usually necessary to use rare earth elements with well-defined composition and content as raw materials, which leads to high costs. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method for preparing near-infrared reflective pigments using rare earth waste tailings and its application. This method uses rare earth tailings or waste as industrial waste as raw materials to prepare pigments with good near-infrared reflective properties, which is low in cost and can avoid environmental pollution caused by rare earth tailings.

[0007] In a first aspect, the present invention provides a method for preparing near-infrared reflective pigments using rare earth waste tailings, comprising the following steps:

[0008] Near-infrared reflective pigments are prepared using methods such as high-temperature solid-state sintering and mechanical grinding, using rare earth waste residue and / or tailings (hereinafter referred to as rare earth waste residue / tailings) as raw materials.

[0009] According to an embodiment of the present invention, the rare earth waste residue / tailings includes at least one of mixed rare earth tailings, ion-adsorption type rare earth tailings, mixed rare earth waste residue, and ion-adsorption type rare earth waste residue, preferably ion-adsorption type rare earth tailings, such as at least one of Longnan tailings (or waste residue), Longyan tailings (or waste residue), Xingguo tailings (or waste residue), fluorocarbon cerium tailings (or waste residue), and monazite tailings (or waste residue).

[0010] According to an embodiment of the present invention, the fluorocarbon cerium tailings are selected from fluorocarbon cerium tailings containing iron, silicon, and calcium.

[0011] According to an embodiment of the present invention, the raw material further includes a dopant, which is selected from at least one of the oxides or carbonates corresponding to elements such as iron, aluminum, and cobalt.

[0012] According to an embodiment of the present invention, the mass ratio of the rare earth waste residue / tailings to the dopant is (1:0.2) to (1:1), preferably, the mass ratio of the rare earth waste residue / tailings to the dopant is (1:0.4) to (1:0.8).

[0013] According to an embodiment of the present invention, the high-temperature solid-state sintering method includes the following steps: calcining rare earth tailings at a temperature of 500–1000°C for 200–400 min. For example, the calcination temperature is 900°C.

[0014] According to an embodiment of the present invention, before calcining the rare earth tailings, the following step is further included: grinding the rare earth tailings.

[0015] According to an embodiment of the present invention, grinding the rare earth tailings specifically includes the following steps: adding the rare earth tailings to a solvent for grinding, and then drying.

[0016] According to an embodiment of the present invention, the solvent is selected from volatile solvents such as ethanol or acetone, for example, acetone.

[0017] According to an embodiment of the present invention, the grinding includes grinding until the solvent evaporates, repeating the process several times. For example, rare earth tailings are added to acetone and ground until the acetone evaporates, then acetone is added again and ground until it evaporates, repeating the process 3 to 4 times.

[0018] According to an embodiment of the present invention, the drying includes drying at a temperature of 60-80°C for 100-120 minutes.

[0019] According to an embodiment of the present invention, before grinding the rare earth tailings, the following step is further included: drying the rare earth tailings.

[0020] According to an embodiment of the present invention, after calcining rare earth tailings by high-temperature solid-state sintering, the following steps are also included: cooling the reaction product to room temperature, grinding and drying it, for example, cooling the reaction product to room temperature and then wet grinding it 2 to 5 times, and then drying it.

[0021] According to an embodiment of the present invention, the drying includes placing the ground product at a temperature of 60-80°C and drying it for 100-120 minutes.

[0022] According to an embodiment of the present invention, the high-temperature solid-state sintering method for calcining rare earth tailings further includes the following steps: mixing, grinding, and calcining the rare earth tailings with iron, aluminum, cobalt, etc., to prepare pigments of different colors.

[0023] Secondly, the present invention also provides a near-infrared reflective pigment prepared by the above method, wherein the near-infrared reflectance of the pigment is greater than 90%, preferably greater than 93%, for example 97.71%, 96.34%, or 93.05%.

[0024] According to an embodiment of the present invention, after the pigment is soaked in an acidic or alkaline solution with a concentration of 2% for 24 hours, the color difference change ΔE* value is less than 2.3.

[0025] According to an embodiment of the present invention, after the pigment is soaked in a 5% acid or alkali solution for 24 hours, the color difference change ΔE* value is less than 2.1.

[0026] According to an embodiment of the present invention, the pigment has a basic as follows Figure 2 The XRD diffraction pattern shown.

[0027] According to an embodiment of the present invention, the pigment has a basic as follows Figure 3 The SEM image shown.

[0028] According to an embodiment of the present invention, the pigment has a basic as follows Figure 4 The particle size distribution diagram is shown.

[0029] According to an embodiment of the present invention, the pigment has a basic as follows Figure 5 The ultraviolet-visible reflectance spectrum is shown.

[0030] According to an embodiment of the present invention, the pigment has a basic as follows Figure 6 The UV-Vis absorption spectrum is shown.

[0031] Thirdly, the present invention also provides an application of the pigment prepared by the above method in near-infrared reflection, such as in vehicles, building walls, etc.

[0032] Fourthly, the present invention also provides a near-infrared reflective coating, the coating comprising the near-infrared reflective pigments as described above.

[0033] According to an embodiment of the present invention, the coating is yellow or red.

[0034] According to an embodiment of the present invention, the coating further includes a solvent selected from resins, oils and / or emulsions.

[0035] According to an embodiment of the present invention, the coating further includes auxiliary materials selected from at least one of dispersing agents, binders, film-forming agents, preservatives, leveling agents, and dispersants.

[0036] According to an embodiment of the present invention, the near-infrared reflective coating includes near-infrared reflective coatings and existing coatings, such as near-infrared reflective pigments, alkyd resins and / or protective varnishes.

[0037] Beneficial effects

[0038] (1) This invention uses rare earth tailings and / or rare earth waste residue as raw materials to prepare pigments with high near-infrared reflectivity through the traditional high-temperature solid-state sintering method. The preparation steps are relatively simple and the cost is low. Moreover, it transforms waste raw materials that pollute the environment into products with application value, turning waste into treasure.

[0039] (2) The near-infrared reflective pigment prepared by the present invention has a brightness value L* greater than 65, a reflectivity greater than 93%, and a ΔE* value less than 3, and has good acid and alkali resistance. Attached Figure Description

[0040] Figure 1 This is a flowchart of the method for preparing near-infrared reflective pigments using rare earth tailings in this invention;

[0041] Figure 2 (a) is the XRD diffraction pattern of the tailings pigment sample; Figure 2 (b) is the XRD diffraction pattern of the tailings sample;

[0042] Figure 3 SEM images of tailings samples and tailings pigment samples;

[0043] Figure 4 The particle size distribution diagrams are for the tailings pigment samples prepared in Examples 1-3.

[0044] Figure 5 The images show the UV-Vis reflectance spectra of tailings samples and tailings pigment samples.

[0045] Figure 6 The images show the UV-Vis absorption spectra of the tailings pigment samples prepared in Examples 1-3 after calcination.

[0046] Figure 7 The images show actual samples of tailings pigments prepared in Examples 1-3.

[0047] Figure 8 The CIE (chromaticity diagram) of the tailings pigment samples prepared in Examples 1-3 are shown. Detailed Implementation

[0048] The following detailed description, in conjunction with specific embodiments, further illustrates the pigment preparation method and application of the present invention. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0049] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0050] In the following examples, tailings from southern ionic rare earth mines are used as raw materials, namely Longnan tailings (NY), Longyan tailings (YY), and Xingguo tailings (XY). The tailings are converted into corresponding tailings pigments through appropriate methods: Longnan tailings pigment (NW), Longyan tailings pigment (YW), and Xingguo tailings pigment (XW).

[0051] Select a suitable inorganic material synthesis method, calcine it at 500-1200℃, select elements such as aluminum, cobalt or iron to dope it, and the doping concentration is (1:0.2) to (1:1), etc. Characterize and analyze the synthesized pigment, explore its reflectivity, color, particle size, acid and alkali resistance and other properties, prepare inorganic environmentally friendly pigments with high near-infrared reflectance and other excellent properties, and finally achieve the purpose of resource recycling and waste utilization.

[0052] Example 1

[0053] S101. Wash the tailings in 1000mL of deionized water and sieve them. After filtration, dry them to obtain Longnan tailings (NY).

[0054] S102. Add the Longnan tailings prepared in step S101 and 1-3 mL of acetone to a mortar and grind them wet. Grind the mixture in the presence of acetone until the acetone evaporates. Repeat the grinding process 3-4 times to obtain the ground mixture.

[0055] S103. Dry the ground mixture in an oven at 60°C for 120 min to obtain a dried sample.

[0056] S104. Place the dried sample into a corundum crucible and place it in a muffle furnace for solid-phase synthesis: first heat to 400℃ at a heating rate of 10℃ / min and hold for 120 minutes, then heat to 900℃ at a heating rate of 10℃ / min and hold for 180 minutes, then cool to room temperature to obtain the calcined product.

[0057] S4. Add 1-3 mL of acetone to the calcined product and wet-mill 3-4 times to obtain tailings pigment sample NW.

[0058] Example 2

[0059] In this embodiment, except for using Longyan ore instead of Longnan ore, all other steps are the same as in Example 1, and tailings pigment YW is obtained.

[0060] Example 3

[0061] In this embodiment, except for using Xingguo ore instead of Longnan ore, all other steps are the same as in Example 1, and tailings pigment sample XW is obtained.

[0062] Test Example 1 Phase Analysis

[0063] 1. XRD analysis of tailings samples and tailings pigment samples

[0064] See Figure 2 The image shows X-ray diffraction of rare earth tailings and pigments from tailings after high-temperature calcination. Figure 2 Figure (a) shows the tailings pigment samples (YW, NW, XW) after calcination, and (b) shows the tailings samples (YY, NY, XY) before calcination. Figure (b) shows that the main components of the tailings before calcination are SiO2, kaolin, and halloysite, while Figure (a) shows that the main component of the tailings pigment samples is SiO2, indicating that high-temperature calcination changed the main components of the tailings.

[0065] 2. SEM analysis of tailings samples and tailings pigment samples

[0066] To investigate the influence of sample surface morphology and particle size on the high near-infrared reflectance of pigments, scanning electron microscopy (SEM) was used to characterize tailings samples (YY, NY, XY) and tailings pigment samples (YW, NW, XW). See [link to SEM]. Figure 3As shown, the surface of the tailings sample before calcination exhibits a micro-needle-like structure, while the tailings pigment sample after calcination is relatively smooth, indicating that high temperature alters the surface morphology of the tailings.

[0067] 3. Particle size distribution analysis of tailings pigment samples

[0068] The particle size distribution of the three tailings pigment samples is as follows: Figure 4 As shown in Table 1, the pigment samples prepared by the method of the present invention have a relatively uniform particle size distribution. The average particle size of the tailings pigment sample YW prepared in Example 1 is 2341.50 nm, the average particle size of the tailings pigment sample NW prepared in Example 2 is 2389.77 nm, and the average particle size of the tailings pigment sample XW prepared in Example 3 is 1271.2 nm.

[0069] Table 1. Particle size distribution of three types of tailings pigments

[0070]

[0071]

[0072] 4. Analysis of the reflectance properties of tailings pigment samples

[0073] See Figure 5 The figure shows a comparison of the UV-Vis reflectance spectra of tailings samples (YY, NY, XY) and tailings pigment samples (YW, NW, XW). It can be seen from the figure that after high-temperature calcination, the reflectance of the three tailings pigment samples is significantly higher than that of the corresponding tailings samples, indicating that high-temperature calcination has a certain effect on pigment preparation.

[0074] See Figure 6 The image shows the UV-Vis absorption spectra of tailings samples (YY, NY, XY) and tailings pigment samples (YW, NW, XW). As can be seen from the image, the tailings pigment samples have strong absorption at around 300 nm.

[0075] 5. Colorimetric analysis of tailings pigment samples

[0076] See also Figure 7 The image shows actual photos of three tailings pigment samples (YW, NW, and XW). As can be seen from the image, tailings pigment sample XW has the darkest color, appearing as reddish-brown, tailings pigment sample NW is light orange, and tailings pigment sample YW is off-white.

[0077] Table 2 shows the color coordinates and reflectance of the three tailings pigment samples. The luminance L* of the three tailings pigment samples is greater than 65, and the reflectance is greater than 93%.

[0078] Table 2. Color coordinates and reflectance of three tailings pigment samples

[0079]

[0080] 6. Analysis of acid and alkali resistance of tailings pigment samples

[0081] Three tailings pigment samples (YW, NW, XW) were thoroughly immersed in 2% acid solution (H2SO4, HNO3, HCl), 5% acid solution (H2SO4, HNO3, HCl), 2% alkaline solution (NaOH, NH3·H2O), 5% alkaline solution (NaOH, NH3·H2O), and deionized water for 24 hours. After that, they were washed with deionized water and dried. The dried samples were measured with a colorimeter, and the L*a*b* values ​​of the three tailings pigment samples after immersion are shown in Tables 3 and 4.

[0082] △E* represents the color difference change of the tailings pigment sample before and after immersion. When △E*≤1, it indicates that the color has basically not changed; when △E*≤5, it indicates that the tailings pigment sample has good acid and alkali resistance.

[0083] As can be seen from the data in Table 3, the ΔE* values ​​of the three tailings pigment samples prepared in Examples 1-3 are all less than 3, which means that they all have good acid and alkali resistance.

[0084] Table 3 2% Acid and Alkali Resistance Test

[0085]

[0086] Table 4 5% Acid and Alkali Resistance Test

[0087]

[0088]

[0089] This paper takes rare earth tailings from Longnan, Longyan, and Xingguo as the research object and adopts the traditional high-temperature solid-state sintering method, calcining at 900℃. In summary, the near-infrared reflectance (R%) values ​​of the tailings pigment samples YW, NW, and XW prepared by this invention are all above 90%, specifically 97.71%, 96.34%, and 93.05%, respectively. Moreover, the tailings pigment samples have good chemical stability. At the same time, this invention confirms that industrial waste tailings from southern ionic rare earth mines can be used as raw materials to prepare pigments, which is of great significance for resource recycling and environmental protection.

[0090] The above methods are also applicable to the preparation of pigments using fluorocarbon cerium and monazite rare earth tailings containing iron, silicon, and calcium, as well as the doping and modification of rare earth tailings and waste by adding other metal ions.

[0091] The specific embodiments of the present invention have been described above by way of example. However, the scope of protection of the present invention is not limited to the above exemplary embodiments. Any modifications, equivalent substitutions, improvements, etc., made by those skilled in the art within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing near-infrared reflective pigments using rare earth tailings, characterized in that, Includes the following steps: Near-infrared reflective pigments were prepared from raw materials containing rare earth tailings using a high-temperature solid-state sintering method. The rare earth tailings are at least one of Longnan tailings, Longyan tailings, and Xingguo tailings. The high-temperature solid-state sintering method includes the following steps: calcining rare earth tailings at a temperature of 500~1000℃ for 200~400 min; Before calcining the rare earth tailings, the process further includes the following steps: adding the rare earth tailings to a solvent for grinding and drying, and repeating this process several times.

2. The method according to claim 1, characterized in that, The raw materials also include dopants, which are selected from salts or elements of iron, aluminum and cobalt, and the mass ratio of rare earth tailings to dopants is (1:0.2) to (1:1).

3. The method according to claim 1, characterized in that, After calcining rare earth tailings using the high-temperature solid-state sintering method, the following steps are also included: cooling the reaction product to room temperature, grinding it, and then drying it.

4. The method according to claim 3, characterized in that, After cooling the reaction product to room temperature, wet mill it 2-5 times, and then dry it.

5. The method according to claim 3, characterized in that, The drying process involves placing the ground product at a temperature of 60-80°C for 100-120 minutes.

6. A near-infrared reflective pigment prepared by the method according to any one of claims 1-5, characterized in that, The pigment has a near-infrared reflectance greater than 90%.

7. The near-infrared reflective pigment according to claim 6, characterized in that, The pigment has a near-infrared reflectance greater than 93%.

8. The near-infrared reflective pigment according to claim 6, characterized in that, After the pigment is soaked in a 2% acid or alkali solution for 24 hours, the color difference change ΔE* value is less than 2.

3.

9. The near-infrared reflective pigment according to claim 6, characterized in that, After the pigment is soaked in a 5% acid or alkali solution for 24 hours, the color difference change ΔE* value is less than 2.

1.

10. A pigment prepared by the method of any one of claims 1-5 for use in near-infrared reflection on vehicles and building walls.

11. A near-infrared reflective coating, characterized in that, The coating comprises a near-infrared reflective pigment prepared by the method of any one of claims 1-5.

12. The near-infrared reflective coating as described in claim 11, characterized in that, The paint is yellow or red.

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