CN117701273B - Photoluminescent material based on rare earth super-enriched plants and preparation method and application thereof - Google Patents

Abstract

The invention belongs to the technical field of luminescent materials, and particularly relates to a photoluminescent material obtained based on rare earth super-enriched plants, and a preparation method and application thereof. The invention adopts the combined technology of solvothermal treatment and steam gasification to realize the effect of preparing rare earth photoluminescent material, gasified oil and high-value synthetic gas products based on rare earth super-enriched plant harvest; the whole process is simple to operate, green and efficient, and the obtained product has higher optical performance, heat value and output value, has economic value and environmental benefit, and has wide application prospect in the field of comprehensive resource utilization of rare earth super-enriched plants.

Description

A photoluminescent material obtained from rare earth hyperaccumulator plants and its preparation method and application

Technical Field

The present invention belongs to the technical field of luminescent materials, and more specifically, relates to a photoluminescent material obtained from rare earth hyperaccumulator plants, and a preparation method and application thereof.

Background Art

Rare earth is an important strategic resource in my country, playing an important role in aerospace, high-tech, medical and health fields. Since rare earth ions have rich energy level structures and electronic transition characteristics, rare earth luminescent materials and optoelectronic devices are in great demand in lighting, display, laser and bio-imaging. Rare earth mining activities have been intensified with the surge in demand for rare earths, and while obtaining resources, they will also cause serious damage to the surrounding ecological environment.

In order to improve the damage to the soil caused by rare earth mining activities, the absorption and transport of rare earth elements by super-enriched plants can well repair the contaminated soil, which is an eco-friendly rare earth mining area pollution control technology. However, the rare earth plant harvest after repair needs to be resourced and harmlessly treated to avoid secondary pollution in order to further promote the industrialization and large-scale application of plant restoration technology, otherwise it will cause waste of resources or environmental pollution. At present, there are still great challenges in how to better utilize the harvest of plant restoration resources. Chinese patent application CN111020239A recovers rare earth oxides, pyrolysis oil and pyrolysis gas from super-enriched plants through a combined process of mechanical crushing, vacuum pyrolysis segmented condensation and rare earth leaching precipitation, but the rare earth oxides obtained by this process are of low purity and cannot be directly used. Therefore, it is urgent to provide a method for preparing high-utilization value materials by making full use of the rare earth elements in rare earth super-enriched plants.

Summary of the invention

The technical problem to be solved by the present invention is to overcome the defects and shortcomings of the existing products obtained by treating rare earth hyper-enriched plants, which are of low purity and require additional processing and cannot be directly utilized, and to provide a preparation method that can fully utilize the rare earth elements in rare earth hyper-enriched plants to obtain photoluminescent materials, gasified oil and synthesis gas with high utilization value.

The purpose of the present invention is to provide a photoluminescent material prepared by the preparation method.

Another object of the present invention is to provide application of the photoluminescent material.

The above-mentioned purpose of the present invention is achieved through the following technical solutions:

A method for preparing a photoluminescent material obtained from rare earth super-enriched plants, specifically comprising the following steps:

S1. Drying and crushing the harvested rare earth super-enriched plant material, adding sulfuric acid solution and ethanol, carrying out a solvent thermal reaction at 140-200° C. under a closed condition, cooling and separating to obtain a solid phase product;

S2. The solid phase product obtained in step S1 is subjected to water vapor gasification, the gasification temperature is 750-900° C., the water vapor flow rate is 5-150 μL/min, the carrier gas is nitrogen, the nitrogen flow rate is 50-200 mL/min, the gasification time is 5-30 min, the obtained gasified oil product is absorbed and collected by isopropanol, and the synthesis gas is collected by an air bag; after the reaction is completed, the photoluminescent material is cooled.

The present invention uses dilute sulfuric acid and ethanol for solvent thermal treatment, selectively enriches rare earth and calcium elements in the form of sulfate in the solid phase product, and then uses steam gasification for decarbonization, and regulates the carbon reduction of calcium sulfate to calcium sulfide, and thermally decomposes rare earth sulfate into rare earth oxide, thereby preparing a photoluminescent material doped with rare earth oxide and calcium sulfide. The entire super-enriched plant resource utilization and harmless treatment process uses the combined technology of solvent thermal treatment and steam gasification, and achieves the effect of preparing rare earth photoluminescent materials, gasified oil and high-value syngas products based on the harvest of rare earth super-enriched plants; the whole process is green and efficient, and the optical properties, calorific value and output value of the obtained products are relatively high, and it has broad application prospects in the field of comprehensive resource utilization of rare earth super-enriched plants.

Furthermore, in step S1, the concentration of the sulfuric acid solution is 0.1-0.5 mol/L. Preferably, the concentration of the sulfuric acid solution is 0.4 mol/L.

Furthermore, in step S1, the volume ratio of the sulfuric acid solution to ethanol is 1:(1-7); preferably, the volume ratio of the sulfuric acid solution to ethanol is 1:7.

Furthermore, in step S1, the ratio of the rare earth super-enriched plant harvest to the total volume of the sulfuric acid solution and ethanol is 1:(10-100) g/mL. Preferably, the ratio of the rare earth super-enriched plant harvest to the total volume of the sulfuric acid solution and ethanol is 1:20 g/mL.

Furthermore, in step S1, the solvent thermal reaction time is 1 to 3 hours. Preferably, the solvent thermal reaction time is 2 hours.

Preferably, in step S1, the solid phase product is collected by vacuum filtration.

Preferably, in step S1, the temperature of the solvothermal reaction is 160°C.

Furthermore, in step S2, the synthesis gas includes H ₂ , CO, and CH ₄ .

Preferably, in step S2, the vaporization temperature is 850°C, the water vapor flow rate is 100 μL/min, the carrier gas is nitrogen, the flow rate of nitrogen is 100 mL/min, and the vaporization time is 10 min.

The present invention adopts a water vapor gasification process, and while preparing a rare earth oxide doped calcium sulfide photoluminescent material, it can also obtain biomass high value-added synthesis gas and gasified oil. Further, the water vapor gasification with nitrogen as a carrier gas is used to treat the solid phase product obtained by the thermal reaction of dilute sulfuric acid and ethanol solvent, and the introduced sulfur element is fixed to the calcium sulfide to prevent it from being oxidized to sulfur dioxide or sulfur trioxide and discharged into the environment to pollute the air. At the same time, the crystal structure of the rare earth oxide doped calcium sulfide can be regulated by controlling the water vapor flow rate, and the luminous color and other properties of the photoluminescent material can be further regulated.

Furthermore, the rare earth hyperaccumulator plants are selected from one or more of American pokeweed, dicranopteris dichotoma, simple-leaved crescent fern, pubescent pecan, pecan, and black-haired fern.

In addition, the present invention claims protection for the photoluminescent material prepared by the preparation method.

Furthermore, the photoluminescent material is mainly rare earth-doped CaS, which emits fluorescence at 480-800nm under an excitation spectrum of 250-470nm.

In addition, the present invention also provides applications of the photoluminescent material in LED lighting, bioluminescence imaging, material structure characterization, and anti-counterfeiting.

The present invention has the following beneficial effects:

The present invention uses dilute sulfuric acid and ethanol to perform solvent thermal treatment on the harvested materials of rare earth super-enriched plants, selectively enriches rare earth and calcium elements in the form of sulfate in the solid phase product, and subsequently uses steam gasification for decarbonization, and regulates the carbon reduction of calcium sulfate to calcium sulfide, and thermally decomposes rare earth sulfate to rare earth oxide, thereby preparing a photoluminescent material doped with rare earth oxide and calcium sulfide. The entire super-enriched plant resource utilization and harmless treatment process uses the combined technology of solvent thermal treatment and steam gasification, and achieves the effect of preparing rare earth photoluminescent materials, gasified oil and high-value syngas products based on the harvested materials of rare earth super-enriched plants; the whole process is simple to operate, green and efficient, and the obtained product has high optical properties, calorific value and output value, and has both economic value and environmental benefits, and has broad application prospects in the field of comprehensive resource utilization of rare earth super-enriched plants.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a flow chart of the present invention for preparing photoluminescent materials, gasified oil and synthetic gas based on rare earth super-enriched plants.

FIG. 2 is an XRD diagram of the rare earth-doped calcium sulfide material obtained as the product in Examples 1, 2, and 3 of the present invention.

FIG3 is a color coordinate diagram of the optical properties of the rare earth-doped luminescent material obtained as a product in Example 1 of the present invention.

FIG. 4 is a color coordinate diagram of the optical properties of the rare earth-doped luminescent material obtained as a product in Example 2 of the present invention.

FIG. 5 is a color coordinate diagram of the optical properties of the rare earth-doped luminescent material obtained as a product in Example 3 of the present invention.

FIG. 6 is a color coordinate diagram of the optical properties of the rare earth-doped luminescent material obtained as a product in Example 4 of the present invention.

FIG. 7 is a color coordinate diagram of the optical properties of a blank sample without rare earth doping obtained in Comparative Example 1 of the present invention.

DETAILED DESCRIPTION

The present invention is further described below in conjunction with the accompanying drawings and specific examples, but the examples do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

Unless otherwise specified, the reagents and materials used in the following examples are commercially available.

The process of preparing the photoluminescent material in the embodiment of the present invention is shown in FIG1 , and the specific steps are shown in the following embodiments.

Example 1 A method for preparing a photoluminescent material based on rare earth hyperaccumulator plant Phytolacca americana Ce1

The rare earth hyperaccumulator plant Phytolacca americana Ce1 is obtained by hydroponically cultivating Phytolacca americana under CeCl ₃ stress, and the Ce content of the Ce1 sample powder is 978 mg/kg.

The material preparation specifically includes the following steps:

S1. The hydroponic American pokeweed Ce1 sample of the rare earth super-enriched plant harvest was air-dried and crushed into uniform powder using a crusher. 2 g of the powdered sample was placed in the lining of a hydrothermal reactor, and 5 mL of 0.4 mol/L sulfuric acid and 35 mL of ethanol were added. The sealed reactor was placed in an oven for solvothermal reaction at 160°C for 2 h, cooled to room temperature, collected and separated to obtain a solid phase product.

S2. 0.53 g of the solid phase product obtained in step S1 was analyzed for metal content by ICP-OES and ICP-MS, and it was found that 95.03% of Ce and 92.57% of Ca were still retained in the solid phase product;

S3, the solid phase product obtained in step S1 was subjected to a water vapor gasification experiment, the gasification temperature was 900°C, the time was 15 min, the water vapor flow rate was 100 μL/min, the carrier gas was nitrogen, the nitrogen flow rate was 100 mL/min, the gasified oil product was absorbed and collected by isopropanol, and the synthesis gas was collected by an air bag. After the reaction was completed, it was cooled to obtain a light yellow solid powder product;

S4. Perform XRD detection on the light yellow solid powder product obtained in step S3. The result is shown in FIG2. The diffraction peak of the sample matches the standard cards of CaS (PDF#08-0464) and CeO ₂ (PDF#04-0593), proving that the solid powder contains CaS and CeO _2. Perform fluorescence spectrum analysis on the light yellow solid powder product. The data show that the maximum emission spectrum is obtained at 513 nm under the 450 nm excitation spectrum, and the intensity reaches 367606.63 au. The optical property color coordinate diagram is shown in FIG3. The CIE color coordinates are (0.4136, 0.5265), indicating that the prepared rare earth doped CaS photoluminescent material has yellow-green fluorescence.

S5. Analyze the synthesis gas collected in step S3 by gas chromatography. The result shows that the yields of H ₂ , CO and CH ₄ are 18.51 mL/g, 97.87 mL/g and 2.44 mL/g respectively.

Example 2 A method for preparing rare earth photoluminescent materials based on rare earth hyperaccumulator plant Phytolacca americana Ce2

The rare earth hyperaccumulator plant Phytolacca americana Ce2 is obtained by hydroponically cultivating Phytolacca americana under CeCl ₃ stress, and the Ce content of the Ce2 sample powder is 2026 mg/kg.

The material preparation specifically includes the following steps:

S1. The hydroponic Ce2 sample of rare earth super-enriched plant harvested from American pokeweed was air-dried and crushed into uniform powder using a crusher. 2 g of the powdered sample was placed in the lining of a hydrothermal reactor, and 5 mL of 0.4 mol/L sulfuric acid and 35 mL of ethanol were added. The sealed reactor was placed in an oven at 160°C for solvothermal reaction for 2 h, cooled to room temperature, collected and separated to obtain a solid phase product.

S2. 0.67 g of the solid phase product obtained in step S1 was analyzed for metal content by ICP-OES and ICP-MS, and it was found that 97.03% of Ce and 94.48% of Ca were still retained in the solid phase product;

S3, the solid phase product obtained in step S1 was subjected to a water vapor gasification experiment, the gasification temperature was 850°C, the time was 10 min, the water vapor flow rate was 100 μL/min, the carrier gas was nitrogen, the nitrogen flow rate was 100 mL/min, the gasified oil product was absorbed and collected by isopropanol, and the synthesis gas was collected by an air bag. After the reaction was completed, it was cooled to obtain a light yellow solid powder product;

S4. Perform XRD detection on the light yellow solid powder product obtained in step S3. As shown in FIG2 , the diffraction peaks of the sample match the standard cards of CaS (PDF#08-0464) and CeO ₂ (PDF#04-0593), proving that the solid powder contains CaS and CeO ₂ . Fluorescence spectrum analysis is performed on the light yellow solid powder product. The data show that the maximum emission spectrum is obtained at 510 nm under the 450 nm excitation spectrum, and the intensity reaches 432270.78 au. The color coordinate diagram of optical properties is shown in FIG4 , and its CIE color coordinates are (0.4015, 0.5337), indicating that the prepared rare earth doped CaS photoluminescent material has yellow-green fluorescence.

S5. Analyze the synthesis gas collected in step S3 by gas chromatography. The results show that the yields of H ₂ , CO and CH ₄ are 30.35 mL/g, 129.34 mL/g and 2.05 mL/g, respectively.

Example 3 A method for preparing rare earth photoluminescent materials based on rare earth hyperaccumulator plant Phytolacca americana Ce2

The rare earth hyperaccumulator plant Phytolacca americana Ce2 is obtained by hydroponically cultivating Phytolacca americana under CeCl ₃ stress, and the Ce content of the Ce2 sample powder is 2026 mg/kg.

The material preparation specifically includes the following steps:

S1. The hydroponic Ce2 sample of rare earth super-enriched plant harvested from American pokeweed was air-dried and crushed into uniform powder using a crusher. 2 g of the powdered sample was placed in the lining of a hydrothermal reactor, and 5 mL of 0.4 mol/L sulfuric acid and 35 mL of ethanol were added. The sealed reactor was placed in an oven at 160°C for solvothermal reaction for 2 h, cooled to room temperature, collected and separated to obtain a solid phase product.

S2. 0.67 g of the solid phase product obtained in step S1 was analyzed for metal content by ICP-OES and ICP-MS, and it was found that 97.03% of Ce and 94.48% of Ca were still retained in the solid phase product;

S3, the solid phase product obtained in step S1 is subjected to a water vapor gasification experiment, the gasification temperature is 850°C, the time is 10 min, the water vapor flow rate is 10 μL/min, the carrier gas is nitrogen, the nitrogen flow rate is 100 mL/min, the gasified oil product is absorbed and collected by isopropanol, and the synthesis gas is collected by an air bag. After the reaction is completed, it is cooled to obtain a light yellow solid powder product;

S4. Perform XRD detection on the light yellow solid powder product obtained in step S3. As shown in FIG2 , the diffraction peaks of the sample match the standard cards of CaS (PDF#08-0464) and CeO ₂ (PDF#04-0593), proving that the solid powder contains CaS and CeO ₂ . Fluorescence spectrum analysis is performed on the light yellow solid powder product. The data show that the maximum emission spectrum is obtained at 515 nm under the 450 nm excitation spectrum, and the intensity reaches 368590.03 au. The optical property color coordinate diagram is shown in FIG5 , and its CIE color coordinates are (0.4446, 0.5094), indicating that the prepared rare earth doped CaS photoluminescent material has yellow-green fluorescence.

S5. Analyze the synthesis gas collected in step S3 by gas chromatography. The results show that the yields of H ₂ , CO and CH ₄ are 24.38 mL/g, 140.85 mL/g and 4.91 mL/g, respectively.

Example 4 A method for preparing rare earth photoluminescent materials based on rare earth hyperaccumulator plant Phytolacca americana La2

The rare earth hyperaccumulator plant Phytolacca americana La2 is obtained by hydroponically cultivating Phytolacca americana under LaCl ₃ stress, and the La content of the La2 sample powder is 2042 mg/kg.

The material preparation specifically includes the following steps:

S1. The La2 sample of the rare earth super-enriched plant harvested from hydroponic culture of American pokeweed was air-dried and crushed into uniform powder using a crusher. 2 g of the powdered sample was placed in the lining of a hydrothermal reactor, and 5 mL of 0.4 mol/L sulfuric acid and 35 mL of ethanol were added. The sealed reactor was placed in an oven for solvothermal reaction at 160°C for 2 h, cooled to room temperature, collected and separated to obtain a solid phase product.

S2. 0.56 g of the solid phase product obtained in step S1 was analyzed for metal content by ICP-OES and ICP-MS, and it was found that 90.59% of La and 92.44% of Ca were still retained in the solid phase product;

S3, the solid phase product obtained in step S1 was subjected to a water vapor gasification experiment, the gasification temperature was 850°C, the time was 20 min, the water vapor flow rate was 100 μL/min, the carrier gas was nitrogen, the nitrogen flow rate was 100 mL/min, the gasified oil product was absorbed and collected by isopropanol, and the synthesis gas was collected by an air bag. After the reaction was completed, it was cooled to obtain a white solid powder product;

S4. The white solid powder product obtained in step S3 is subjected to fluorescence spectrum analysis. The data show that the maximum emission spectrum is obtained at 591 nm under the 265 nm excitation spectrum, and the intensity reaches 3879978.5 a.u. The optical property color coordinate diagram is shown in FIG6 , and its CIE color coordinate is (0.5407, 0.4522), indicating that the prepared rare earth doped CaS photoluminescent material has orange-yellow fluorescence.

S5. Analyze the synthesis gas collected in step S3 by gas chromatography. The results show that the yields of H ₂ , CO and CH ₄ are 17.02 mL/g, 117.73 mL/g and 1.85 mL/g, respectively.

Comparative Example 1 A method for treating a hyperaccumulator plant Phytolacca americana CK

The hyperaccumulator plant Phytolacca americana CK is obtained by hydroponically cultivating Phytolacca americana without rare earth stress, and is a blank sample powder that does not contain rare earths; the processing method specifically comprises the following steps:

S1. The hydroponic American pokeweed CK sample of the rare earth super-enriched plant harvest was air-dried and crushed into uniform powder using a crusher. 2 g of the powdered sample was placed in the lining of a hydrothermal reactor, and 5 mL of 0.4 mol/L sulfuric acid and 35 mL of ethanol were added. The sealed reactor was placed in an oven for solvothermal reaction at 160°C for 2 h, cooled to room temperature, collected and separated to obtain a solid phase product.

S2. 0.51 g of the solid phase product obtained in step S1 was analyzed for metal content by ICP-OES, and it was found that 87.56% of Ca was still retained in the solid phase product;

S3, the solid phase product obtained in step S1 was subjected to a water vapor gasification experiment, the gasification temperature was 850°C, the time was 10 min, the water vapor flow rate was 100 μL/min, the carrier gas was nitrogen, the nitrogen flow rate was 100 mL/min, the gasified oil product was absorbed and collected by isopropanol, and the synthesis gas was collected by an air bag. After the reaction was completed, it was cooled to obtain a white solid powder product;

S4. Fluorescence spectrum analysis is performed on the white solid powder product obtained in step S3. As shown in FIG7 , its CIE color coordinates are (0.5407, 0.4522), and the sample has no obvious fluorescence under blue light irradiation, indicating that the non-rare earth-doped CaS sample does not have the fluorescence properties of the rare earth luminescent material in the embodiment.

The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims (9)

1. A method for preparing a photoluminescent material based on rare earth hyperaccumulator plants, characterized in that it specifically comprises the following steps: S1. Dry and crush the harvested rare earth super-enriched plant material, add sulfuric acid solution and ethanol, carry out complete solvent thermal reaction at 140-200°C under closed conditions, cool and separate to obtain a solid phase product; S2, vaporizing the solid phase product obtained in step S1 with water vapor, the vaporization temperature is 750-900°C, the water vapor flow rate is 5-150 μL/min, the carrier gas is nitrogen, the nitrogen flow rate is 50-200 mL/min, the vaporization time is 5-30 min, the obtained vaporized oil product is collected by isopropanol absorption, and the synthesis gas is collected by an air bag; after the reaction is completed, cooling to obtain a photoluminescent material; The rare earth hyperaccumulator plant is selected from one or more of American pokeweed, Dicranopteris dichotoma, Croton solani, Hickory chinensis, Hickory chinensis, and Pteris crescentrum; The photoluminescent material is mainly rare earth-doped CaS, which emits fluorescence at 480-800 nm under an excitation spectrum of 250-470 nm. 2. The preparation method according to claim 1, characterized in that, in step S1, the concentration of the sulfuric acid solution is 0.1~0.5 mol/L. 3. The preparation method according to claim 2, characterized in that, in step S1, the volume ratio of the sulfuric acid solution to ethanol is 1: (1-7). 4. The preparation method according to claim 3, characterized in that, in step S1, the ratio of the rare earth super-enriched plant harvest to the total volume of the sulfuric acid solution and ethanol is 1: (10~100) g/mL. 5. The preparation method according to claim 1, characterized in that in step S1, the time of the solvent thermal reaction is 1 to 3 hours. 6 . The preparation method according to claim 1 , characterized in that in step S2 , the synthesis gas comprises H ₂ , CO, and CH ₄ . 7. The photoluminescent material prepared by the preparation method according to any one of claims 1 to 6. 8. The photoluminescent material according to claim 7, characterized in that the photoluminescent material is mainly rare earth-doped CaS, and emits fluorescence at 480-800 nm under an excitation spectrum of 250-470 nm. 9. Application of the photoluminescent material according to claim 8 in LED lighting, bioluminescence imaging, material structure characterization, and anti-counterfeiting.