CN114380344A - A kind of preparation method of alumina modified soda lime glass microbead filter material - Google Patents

Abstract

The invention discloses a preparation method of an alumina modified soda-lime glass bead filter material, which comprises the following steps: screening the obtained soda-lime glass microsphere raw material by a screen with a specific mesh number, sequentially and repeatedly cleaning the raw material by using deionized water, ethanol and acetone, and then carrying out acid washing by using a human-eating acid solution to remove organic impurities on the surface; adding an aluminum chloride solution and a sodium hydroxide solution, baking the mixture in an oven for 24 hours, and putting the baked mixture into a muffle furnace for high-temperature calcination to obtain the modified soda-lime-glass bead filter material attached with the alumina, wherein the modified soda-lime-glass bead filter material has better removal effect on negative electric pollutants such as micro-plastics and escherichia coli in water. The alumina modified soda-lime glass bead filter material obtained by the invention is more convenient in approach and cheaper in price, is more beneficial to removing micro-plastics in water, and can improve the treatment efficiency of the filter and the quality of the effluent.

Description

A kind of preparation method of alumina modified soda lime glass microbead filter material

technical field

The invention belongs to the field of environmental protection material preparation and drinking water treatment, and in particular relates to a preparation method of an alumina modified soda lime glass microbead filter material.

Background technique

In the industrial process of drinking water purification and wastewater treatment, the quality of the filtration process often determines the treatment efficiency and effluent quality of a water plant. Filtration generally refers to the process of retaining water impurities with a granular filter material layer such as quartz sand, thereby making the water clarified. Filtration can not only remove suspended solids in water to reduce turbidity, but also reduce BOD, COD, heavy metal ions and grease. In recent years, the water quality shortage has become more and more serious, and the water quality standards have been improved. The traditional quartz sand filter gradually exposed some inherent defects in the use process, such as negative surface charge, less surface voids, small specific surface area, and porosity. Small wait. Secondly, the country has gradually increased the requirements for energy conservation and emission reduction, the development of green circular sustainable economy and environmental governance, and the mining and processing of quartz sand filter materials are highly polluting industries, resulting in the price of quartz sand has been rising in recent years. Therefore, the traditional production and processing technology of quartz sand can no longer meet the requirements of energy saving and emission reduction at this stage.

On the other hand, as a new type of pollutant, microplastics are widely distributed in the natural environment. Since American researchers found microplastics in bottled water, the latest research released at the Society of the European Joint Gastroenterology Week on October 22, 2018 confirmed for the first time that as many as 9 different types of microplastics have been found in the human body. In 2019, the World Health Organization published a report titled "Microplastics in Drinking Water". The traditional water treatment process can process more than 70% of the large-sized microplastics, and the filtration process plays an irreplaceable role. However, whether it is quartz sand filter media, or other types of filter media such as anthracite, ceramics, etc., the zeta potential is negative, and the zeta potential of microplastics is also negative. Very small microplastics are difficult to retain. In addition to microplastics, the zeta potential of most other common pollutants such as bacteria, antibiotics, and oils is also negative. According to the DLVO theory, when the zeta potential of the filter material is increased, it is more conducive to adsorb pollutants in the water during the filtration process, thereby improving the quality of the effluent.

SUMMARY OF THE INVENTION

The purpose of the present invention is to overcome the deficiencies in the prior art, aiming at the defects of negative charge on the surface of the traditional quartz sand filter material, few surface voids, small specific surface area and small porosity in the existing filtration technology, and the current situation that the use cost increases year by year. , proposes a preparation method of alumina-modified soda-lime glass microbead filter material. Using this method to obtain alumina-modified soda-lime glass microbead filter material is more convenient, cheaper, and more conducive to removing microplastics in water. It can improve the treatment efficiency of the filter tank and improve the effluent quality.

The object of the present invention is achieved through the following technical solutions.

The preparation method of the alumina-modified soda-lime glass microbead filter material of the invention comprises the following steps: after the soda-lime glass microbead raw material is subjected to surface pretreatment and cleaning, the alumina is attached to the surface to realize the charging function of the soda-lime glass microbead filter material. The modified soda-lime glass microbead filter material of specific mesh is made.

Specifically include the following steps:

(1) Surface pretreatment of soda lime glass beads

A certain amount of soda-lime glass microbead raw materials are screened through a screen with a specific mesh number, and the above-mentioned raw materials are repeatedly washed with excellent grade pure anhydrous ethanol for 5-6 times; Ultrasonic for 10min each in a beaker with deionized water, ethanol, and acetone; put the raw glass beads cleaned by ultrasonic into the "cannibal acid" solution, and then pickled in a water bath at 95°C for 2 hours; The acid solution remaining on the glass beads was repeatedly rinsed with deionized water, and then placed in anhydrous ethanol for future use;

(2) Modification of soda lime glass beads

Weigh the pretreated soda-lime glass beads in step (1), put them into an oven to dry for later use; configure a sufficient amount of aluminum chloride solution and sodium hydroxide solution, add them into the soda-lime glass beads, stir evenly, and put them in again. Bake in an oven for 24 hours; in order to ensure that the filter material is heated evenly, stir every one hour in the early stage of heating, and take out the filter material after 24 hours of heating; repeat the above operation once; finally, add aluminum chloride solution and sodium hydroxide solution to the filter material , stir evenly; after that, put it in the muffle furnace, and take it out after baking for a certain period of time; after the filter material is cooled, rinse it with tap water to remove the coating that is not firmly adhered to the surface; rinse it with distilled water three times, and dry it. Standby to obtain alumina-modified soda-lime glass microbead filter material.

In step (1), the particle size of the soda-lime glass microbeads is 20-40 mesh, the volume fraction of the absolute ethanol is 99.8%, the volume fraction of the acetone is 99.5%, and the "cannibal acid" The solution is composed of concentrated sulfuric acid and hydrogen peroxide, and the volume ratio of concentrated sulfuric acid and hydrogen peroxide is 7:3.

In step (2), the concentration of aluminum chloride solution is 3mol/L, the concentration of sodium hydroxide solution is 10mol/L, and the consumption ratio of aluminum chloride solution and sodium hydroxide solution is 20:1; Put the glass microbeads into a 50°C drying oven for later use, add aluminum chloride solution and sodium hydroxide solution, add aluminum chloride solution and sodium hydroxide solution and stir the soda-lime glass microbeads into a 100°C-120°C oven Bake for 24 hours, and set the muffle furnace temperature to 240°C-550°C.

Compared with the prior art, the beneficial effects brought by the technical solution of the present invention are:

The invention realizes the attachment of the surface positive electro-adsorption point and the precise control of the particle size of the filter material. Compared with the traditional quartz sand filter material, the price of the filter material is lower, the surface pores and ravines are less, and due to the positive adsorption points on its surface, according to the DLVO theory, this filter material can maintain the original filtration performance while maintaining the original filter performance. Effectively remove microplastics and other negatively charged pollutants in water, which has both economic value and environmental protection significance.

Description of drawings

Fig. 1 is the SEM picture after modification of soda-lime glass microbead alumina in step 2 of Example 1 of the present invention;

Fig. 2 is the energy spectrum picture after modification of soda lime glass microbead alumina in step 2 of Example 1 of the present invention;

Fig. 3 is the test result of zeta potential after modification of alumina of soda lime glass microbeads in step 2 of Example 1 of the present invention.

Detailed ways

The present invention will be further described below with reference to the accompanying drawings and embodiments. This example is provided for better understanding and is by no means intended to limit the present invention.

The preparation method of the alumina-modified soda-lime glass microbead filter material of the present invention is based on a large number of experiments. The charged functionalization of the bead filter material has successfully made the modified soda-lime glass microbead filter material with a specific mesh number of alumina adsorption sites attached to the surface. Specifically include the following steps:

Step 1, Soda-lime glass microbead surface pretreatment

A certain amount of soda-lime glass microbead raw materials are screened through a screen with a specific mesh number, and the above-mentioned raw materials are repeatedly washed 5-6 times with excellent grade pure (GR) absolute ethanol; the cleaned soda-lime glass microbead raw materials are sequentially Put it into a beaker containing deionized water, ethanol, and acetone and sonicate for 10 minutes each; put the ultrasonically cleaned glass microbead raw material into the "cannibal acid" solution, and then pickle it in a water bath for 2 hours at 95 °C; pickle it in a water bath After completion, the residual acid solution on the glass microbeads was repeatedly rinsed with deionized water, and then placed in absolute ethanol for future use. The main purpose of this step is to wash away the organic impurities on the surface of the soda lime glass microbeads.

Among them, the cheap soda-lime glass microbeads purchased from the manufacturer were used as raw materials, the particle size ranged from 20 mesh to 40 mesh, and the stacking volume was 200ml. Homogeneous glass microbeads or heterogeneous glass microbeads were used according to the experimental requirements , and use absolute ethanol to preserve the raw material of soda-lime glass microbeads after pickling, so as to isolate the possible influence of impurities in the air on the surface potential of glass beads as much as possible. The volume fraction of the absolute ethanol is 99.8%, the volume fraction of the acetone is 99.5%, and the "cannibal acid" solution is composed of concentrated sulfuric acid and hydrogen peroxide, and the volume ratio of concentrated sulfuric acid and hydrogen peroxide is 7:3.

Step 2, Soda-lime glass microbead modification treatment

Weigh the pretreated soda-lime glass beads in step 1, put them into a 50°C oven to dry for later use; configure a sufficient amount of aluminum chloride (AlCl ₃ ) solution and sodium hydroxide (NaOH) solution, add soda-lime glass beads Stir evenly, put it into the oven at 100°C-120°C again for 24 hours; in order to ensure that the filter material is heated evenly, stir it every one hour in the early stage of heating, and take out the filter material after 24 hours of heating; repeat the above operation once; Add aluminum chloride (AlCl ₃ ) solution and sodium hydroxide (NaOH) solution to the filter material, stir evenly; after that, put it in a muffle furnace at 240°C-550°C and bake for a certain period of time (6-12h), then take out; to be filtered After the material is cooled, it is slowly rinsed with tap water to remove the coating that is not firmly adhered to the surface; rinsed three times with distilled water, and dried for use to obtain alumina-modified soda-lime glass microbead filter material.

Wherein, the concentration of aluminum chloride solution is 3mol/L, the concentration of sodium hydroxide solution is 10mol/L, and the consumption ratio of aluminum chloride solution and sodium hydroxide solution is 20:1, and its purpose is to act as sodium hydroxide (NaOH) ) solution, the following chemical reaction occurs between aluminum chloride (AlCl ₃ ) and sodium hydroxide (NaOH): AlCl ₃ +3NaOH=3NaCl+Al(OH) ₃ ↓. Then, the reaction of 2Al(OH) ₃ =Al ₂ O ₃ +3H ₂ O occurs in a high temperature environment, so as to realize the adhesion of alumina on the surface of soda-lime glass microbeads. When the sodium hydroxide (NaOH) solution is excessive, the aluminum hydroxide precipitation cannot be formed normally, but the reaction of AlCl ₃ +4NaOH=3NaCl+NaAlO ₂ +2H2O occurs, which is not conducive to the formation and adhesion of alumina in the subsequent high temperature environment. The zeta potential of alumina in neutral water environment is positive, while the zeta potential of soda-lime glass beads in neutral water environment is negative. The surface of the glass microbeads builds a positive adsorption potential, thereby improving the adsorption effect of negatively charged pollutants.

After the alumina-modified soda-lime glass microbead filter material is prepared by the method of the present invention, it is characterized by SEM and energy spectrum analysis, so as to verify whether the alumina is attached to the surface of the soda-lime glass microbeads. The zeta potential of the soda lime glass microbead filter material was measured, and the change of the surface potential properties of the filter material was observed.

(1) The surface composition of modified soda-lime glass microbeads was determined by SEM and energy spectrum analysis.

Take the modified soda-lime glass microbead filter material in step 2, spray gold to prepare samples, put it into the tank, vacuumize, adjust the voltage, contrast and brightness, use a scanning electron microscope to find a suitable area to take pictures, and X-ray for ordinary Energy spectrum scanning, using X-ray energy spectrum analysis and detection method to analyze and obtain the concentration of various elements that make up the sample material. Among them, the vacuum should reach 5*10 ^-3 Pa, and the voltage should reach 20kv during point scanning.

Scanning Electron Micrograph (SEM) uses secondary electron signal imaging to observe the surface morphology of the sample, that is, to scan the sample with a very narrow electron beam, and produce various effects through the interaction between the electron beam and the sample. Secondary electrons can produce an enlarged topography of the sample surface. This image is established in chronological order as the sample is scanned, ie a magnified image is obtained by point-by-point imaging. The most commonly used method of electron microscopy is X-ray Energy Dispersive Spectrum (EDS). The method has a component analysis function. First, the elements contained in the sample are identified by automatic qualitative analysis, and then the concentration of various elements that make up the sample material is obtained by using the X-ray intensity by semi-quantitative analysis.

(2) Zeta potential of filter media before and after modification was measured by ZetaCAD solid surface Zeta potential analyzer.

Take an appropriate amount of the soda-lime glass microbead filter material sample pretreated in step 1, put it into the zetaCAD sample packing column, pass sodium chloride electrolyte, add mixed phosphate solution, control the pH to 7, and read the change at this time. Zeta potential of soda-lime glass microbead filter media before sex.

In the same way, take an appropriate amount of modified soda-lime glass microbead filter material samples treated in step 2, put them into the zetaCAD sample packed column, pass sodium chloride electrolyte, add mixed phosphate solution, and control the pH to be 7. When reading the zeta potential of the modified soda-lime glass microbead filter material.

Wherein, the specifications of the sample packed column are 1.45cm in diameter and 1.8cm in length, the concentration of the sodium chloride electrolyte is 0.019mol/L, the conductivity is 2.67mS/cm, and the concentration of the mixed phosphate solution is 0.025mol/L, resulting in its conductivity rising to 3.4mS/cm. The soda-lime glass microbeads before and after modification do not have conductivity, and it is necessary to enhance the conductivity of the sample by spraying gold to improve the SEM photographing effect.

ZetaCAD Solid Surface Zeta Potential Analyzer is a Zeta Potential Analyzer that directly measures flowing potential/flowing current, helping researchers improve and adjust surface features in the fields of chemistry and materials science. Suitable for deposition of large particles, fibers, and flat surfaces, or curved glue or hollow fiber samples through electrolyte research under a pressure gradient, including polymers, textiles, ceramics, glass, etc. Both solid and powder materials are suitable.

Example 1:

Step 1: Use a 30-32 mesh screen to screen out soda-lime glass microbeads with a stacking volume of 200ml, and use the excellent grade pure (GR) 99.8% absolute ethanol to repeatedly wash the above raw materials 5-6 times; The raw materials of calcium glass microbeads are placed in a beaker containing deionized water, ethanol and acetone in turn for 10 minutes each; 7:3), and then pickled in a water bath for 2 hours at 95°C; after the pickling in a water bath, the residual acid solution on the glass beads was repeatedly rinsed with deionized water, and then placed in anhydrous ethanol for later use.

Step 2: Weigh 30 g of pretreated soda-lime glass microbeads, put them in an oven (50° C.) to dry for later use; configure aluminum chloride (AlCl ₃ ) solution 3mol/L, sodium hydroxide (NaOH) solution 10mol/L L, add soda-lime glass microbeads and stir evenly, then put it into the oven (100°C) again to bake for 24 hours; in order to ensure that the filter material is heated evenly, stir once every hour in the early stage of heating, and take out the filter material after heating for 24 hours; repeat The above operation was performed once; finally, an appropriate amount of aluminum chloride (AlCl ₃ ) solution and sodium hydroxide (NaOH) solution were added to the filter material, and the dosage ratio was 20:1, and stirred evenly; Take it out after 6 hours of preparation; after the filter material is cooled, slowly rinse with tap water to remove the coating that is not firmly adhered to the surface; rinse with distilled water three times, and dry for use to obtain alumina-modified soda-lime glass beads filter material.

Step 3: Take an appropriate amount of the sample processed in Step 2, spray gold to prepare the sample, put it into the tank, vacuumize to 5*10 ^-3 Pa, adjust the voltage to 20kv, contrast and brightness, and use a scanning electron microscope to find a suitable area to take pictures , as shown in Figure 1, X-rays are scanned by ordinary energy spectrum, and the concentration of various elements that make up the sample material is obtained by using the X-ray energy spectrum analysis and detection method, as shown in Figure 2.

Step 4: Take an appropriate amount of the sample processed in step 2, directly fill it into a column with a diameter of 1.45cm and a length of about 1.8cm, and pass into the sodium chloride electrolyte, and the electrolyte solution is a mass fraction of 0.13%NaCl (0.019mol/L), Its initial conductivity is 2.67mS/cm. Due to the need to control the pH value between 7, adding mixed phosphate (0.025mol/L) causes its conductivity to rise to 3.4mS/cm, and then read the zeta potential of the modified soda-lime glass microbead filter material, such as shown in Figure 3.

Example 2:

Step 1: Use a 20-22 mesh screen to screen out soda-lime glass microbeads with a stacking volume of 200ml, and use the excellent grade pure (GR) 99.8% absolute ethanol to repeatedly wash the above raw materials for 5-6 times; The raw materials of calcium glass microbeads are placed in a beaker containing deionized water, ethanol and acetone in turn for 10 minutes each; 7:3), and then pickled in a water bath for 2 hours at 95°C; after the pickling in a water bath, the residual acid solution on the glass beads was repeatedly rinsed with deionized water, and then placed in anhydrous ethanol for later use.

Step 2: Weigh 30 g of pretreated soda-lime glass microbeads, put them in an oven (50° C.) to dry for later use; configure aluminum chloride (AlCl ₃ ) solution 3mol/L, sodium hydroxide (NaOH) solution 10mol/L L, add soda-lime glass microbeads and stir evenly, and then put it into the oven (110°C) to bake for 24 hours; in order to ensure that the filter material is heated evenly, stir once every hour in the early stage of heating, and take out the filter material after heating for 24 hours; repeat The above operations were performed once; finally, an appropriate amount of aluminum chloride (AlCl ₃ ) solution and sodium hydroxide (NaOH) solution were added to the filter material, and the dosage ratio was 20:1, and stirred evenly; Take out after 8 hours of preparation; after the filter material is cooled, slowly rinse with tap water to remove the coating that is not firmly adhered to the surface; rinse with distilled water three times, and dry for use to obtain alumina-modified soda-lime glass microbeads filter material.

Step 3: Take an appropriate amount of the sample processed in Step 2, spray gold to prepare the sample, put it into the tank, vacuumize to 5*10 ^-3 Pa, adjust the voltage to 20kv, contrast and brightness, and use a scanning electron microscope to find a suitable area to take pictures , X-ray scans the ordinary energy spectrum, and uses the X-ray energy spectrum analysis and detection method to analyze and obtain the concentration of various elements that make up the sample material.

Step 4: Take an appropriate amount of the sample processed in step 2, directly fill it into a column with a diameter of 1.45cm and a length of about 1.8cm, and pass into the sodium chloride electrolyte, and the electrolyte solution is a mass fraction of 0.13%NaCl (0.019mol/L), Its initial conductivity is 2.67mS/cm. Due to the need to control the pH value between 7, adding mixed phosphate (0.025mol/L) causes its conductivity to rise to 3.4mS/cm, and then read the zeta potential of the modified soda-lime glass microbead filter material.

Example 3:

Step 1: Use a 20-22 mesh screen to screen out soda-lime glass microbeads with a stacking volume of 200ml, and use the excellent grade pure (GR) 99.8% absolute ethanol to repeatedly wash the above raw materials for 5-6 times; The raw materials of calcium glass microbeads are placed in a beaker containing deionized water, ethanol and acetone in turn for 10 minutes each; 7:3), and then pickled in a water bath for 2 hours at 95°C; after the pickling in a water bath, the residual acid solution on the glass beads was repeatedly rinsed with deionized water, and then placed in anhydrous ethanol for later use.

Step 2: Weigh 30 g of pretreated soda-lime glass microbeads, put them in an oven (50° C.) to dry for later use; configure aluminum chloride (AlCl ₃ ) solution 3mol/L, sodium hydroxide (NaOH) solution 10mol/L L, add soda-lime glass microbeads and stir evenly, then put it into the oven (120°C) to bake for 24 hours; in order to ensure that the filter material is heated evenly, stir once every hour in the early stage of heating, and take out the filter material after 24 hours of heating; repeat The above operation was performed once; finally, an appropriate amount of aluminum chloride (AlCl ₃ ) solution and sodium hydroxide (NaOH) solution were added to the filter material, and the dosage ratio was 20:1, and stirred evenly; Take it out after 12 hours of preparation; after the filter material is cooled, slowly rinse with tap water to remove the coating that is not firmly adhered to the surface; rinse with distilled water three times, and dry for use to obtain alumina-modified soda-lime glass microbeads filter material.

Step 3: Take an appropriate amount of the sample processed in Step 2, spray gold to prepare the sample, put it into the tank, vacuumize to 5*10 ^-3 Pa, adjust the voltage to 20kv, contrast and brightness, and use a scanning electron microscope to find a suitable area to take pictures , X-ray scans the ordinary energy spectrum, and uses the X-ray energy spectrum analysis and detection method to analyze and obtain the concentration of various elements that make up the sample material.

Step 4: Take an appropriate amount of the sample processed in step 2, directly fill it into a column with a diameter of 1.45cm and a length of about 1.8cm, and pass into the sodium chloride electrolyte, and the electrolyte solution is a mass fraction of 0.13%NaCl (0.019mol/L), Its initial conductivity is 2.67mS/cm. Due to the need to control the pH value between 7, the addition of mixed phosphate (0.025mol/L) caused its conductivity to rise to 3.4mS/cm. At this time, the zeta potential of the soda-lime glass microbead filter material before modification was read.

Although the functions and working process of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the above-mentioned specific functions and working processes. Under the inspiration of the present invention, those of ordinary skill in the art can also make many forms without departing from the scope of the present invention and the protection scope of the claims, which all belong to the protection of the present invention.

Claims (4)

1. a preparation method of alumina-modified soda-lime glass microbead filter material, is characterized in that, with soda-lime glass microbead raw material, after surface pretreatment cleaning, alumina is attached to the surface, realizes soda-lime glass microbeads. The charged functionalization of the bead filter material can make the modified soda-lime glass microbead filter material with a specific mesh number. 2. the preparation method of alumina modified soda-lime glass microbead filter material according to claim 1, is characterized in that, specifically comprises the following steps: (1) Surface pretreatment of soda lime glass beads A certain amount of soda-lime glass microbead raw materials are screened through a screen with a specific mesh number, and the above-mentioned raw materials are repeatedly washed with excellent grade pure anhydrous ethanol for 5-6 times; Ultrasonic for 10min each in a beaker with deionized water, ethanol, and acetone; put the raw glass beads cleaned by ultrasonic into the "cannibal acid" solution, and then pickled in a water bath at 95°C for 2 hours; The acid solution remaining on the glass beads was repeatedly rinsed with deionized water, and then placed in anhydrous ethanol for future use; (2) Modification of soda lime glass beads Weigh the pretreated soda-lime glass beads in step (1), put them into an oven to dry for later use; configure a sufficient amount of aluminum chloride solution and sodium hydroxide solution, add them into the soda-lime glass beads, stir evenly, and put them in again. Bake in an oven for 24 hours; in order to ensure that the filter material is heated evenly, stir every one hour in the early stage of heating, and take out the filter material after 24 hours of heating; repeat the above operation once; finally, add aluminum chloride solution and sodium hydroxide solution to the filter material , stir evenly; after that, put it in the muffle furnace, and take it out after baking for a certain period of time; after the filter material is cooled, rinse it with tap water to remove the coating that is not firmly adhered to the surface; rinse it with distilled water three times, and dry it. Standby to obtain alumina-modified soda-lime glass microbead filter material. 3. The preparation method of alumina-modified soda-lime glass microbead filter material according to claim 2, wherein the particle size of the soda-lime glass microbeads described in step (1) is 20-40 mesh, so The volume fraction of the anhydrous ethanol is 99.8%, the volume fraction of the acetone is 99.5%, the "cannibal acid" solution is composed of concentrated sulfuric acid and hydrogen peroxide, and the volume ratio of concentrated sulfuric acid and hydrogen peroxide is 7:3. 4. the preparation method of alumina modified soda lime glass microbead filter material according to claim 2, is characterized in that, in step (2), the concentration of aluminum chloride solution is 3mol/L, and the concentration of sodium hydroxide solution It is 10mol/L, and the dosage ratio of aluminum chloride solution and sodium hydroxide solution is 20:1; the pretreated soda-lime glass beads are placed in a 50 ℃ oven to dry for use, and aluminum chloride solution and sodium hydroxide solution are used. , the soda-lime glass microbeads after adding aluminum chloride solution and sodium hydroxide solution and stirring evenly are placed in an oven at 100°C-120°C for 24 hours, and the temperature of the muffle furnace is set at 240°C-550°C.

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