Method for the extraction of microplastics in a solid beverage infusion

Abstract

The application discloses a kind of solid beverage granules in the extraction method of microplastic, comprising: S1, to the solid beverage granules containing microplastic, add alkaline solution, shake up, then water bath heating, during water bath heating, intermittently add hydrogen peroxide solution, the addition frequency of hydrogen peroxide solution is 0.5mL / 10min;S2, after water bath heating is completed, reduce water bath temperature reaction, after reaction is completed, hot suction filtration and using surfactant flush, suction filtration obtains microplastic, extraction is completed.The application can be directed to animal and vegetable fat, protein and cellulose in the composition of solid beverage granules are digested, solve the problem that many steps in prior art, time-consuming, solid beverage granules digestion efficiency is low and prone to cause microplastic loss, improve microplastic extraction accuracy, to realize quantitative detection and research to microplastic in solid beverage granules.

Description

Technical Field

[0001] This invention relates to the field of microplastic extraction technology from solid beverage powders, specifically to a method for extracting microplastics from solid beverage powders. Background Technology

[0002] Microplastics (plastics with a diameter of less than 5 mm) have complex and diverse shapes, are widely present in the environment, and pose certain environmental risks due to their small size, large specific surface area, and chemical stability. Existing research has found large quantities of microplastics in air, soil, and water. Reports indicate that large amounts of microplastics have been detected in animal and human bodies and in their excrement. Further studies have found large amounts of microplastics in tea bags, drinking water, and food packaged in plastic. As a major source of beverages for modern people, instant coffee and milk powder rely heavily on plastics in their production and packaging, making them highly likely to contain microplastics. However, no pretreatment methods for extracting microplastics from these instant beverages have yet been developed. Pretreatment of environmental media (such as soil, sediment, and water) typically involves oxidative digestion to remove organic interference before flotation collection of microplastics. However, instant coffee and milk powder contain large amounts of fats, soybean meal, starch, and crude fiber, which are difficult to remove through gentle digestion methods. Many interfering substances have similar density and surface hydrophilicity / hydrophobicity to microplastics, making them difficult to separate by flotation. Therefore, interference from such substances must be eliminated in the digestion step.

[0003] Some organic components in solid beverage powders, such as tannins, acids, and other antioxidants, may react with chemical digestive agents, leading to a decrease in the effectiveness of the digestive agents. During the digestion process, some organic components may form encapsulations or aggregates with microplastics, and may also form viscous substances that are difficult to completely digest. Strong acids and strong alkalis used for complete digestion, while removing impurities and interference, can also cause serious damage to microplastics.

[0004] Because solid beverage powders contain a large amount of animal and plant fats, proteins, and cellulose, it is impossible to completely remove interfering components using only existing methods. This results in residual solid matter after digestion, multiple steps, long processing time, low removal efficiency, and easy loss of microplastics, leading to inaccurate microplastic extraction. Consequently, it is impossible to accurately detect the microplastic content in solid beverage powders, making it difficult to quantitatively detect and study microplastics in solid beverage powders. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a method for extracting microplastics from solid beverage powders.

[0006] A method for extracting microplastics from a solid beverage powder includes the following steps:

[0007] S1. Add an alkaline solution with a mass concentration of 2-8% to the solid beverage powder containing microplastics at a ratio of 1g: 5-10mL, shake well, and then heat in a water bath at 65-75℃ for 3-6 hours. During the water bath heating, add hydrogen peroxide solution with a mass concentration of 10-30% intermittently at a frequency of 0.5mL / 10min.

[0008] S2. After the water bath heating is completed, reduce the water bath temperature to 40-60℃ and react for 6-12 hours. After the reaction is completed, filter while hot and wash with surfactant. Obtain microplastics by filtration, and the extraction is complete.

[0009] Note: The above method avoids the problem in existing technologies where mixing hydrogen peroxide and alkaline solution results in a violent reaction that prevents each substance from exerting its effect. At the same time, using hydrogen peroxide to react with alkaline solution can remove substances such as fats and proteins while retaining microplastics relatively completely, facilitating subsequent extraction and analysis.

[0010] Furthermore, the solid beverage powder includes two-in-one coffee, three-in-one coffee, milk powder, and soy powder.

[0011] Note: The above-mentioned solid beverage powders usually contain a variety of ingredients, such as coffee powder, milk powder, sugar, non-dairy creamer, flavoring, stabilizers and preservatives. These ingredients may affect the extraction and detection of microplastics during digestion. In addition, some of these ingredients may be heat-sensitive, causing them to react with microplastics during digestion. Therefore, certain experimental conditions should be set to avoid the reaction between the ingredients in the solid beverage powders and microplastics.

[0012] Furthermore, the microplastics include one or more MPs such as PE, PS, PVC, or PET.

[0013] Note: The plastics mentioned above are microplastics commonly used in the production and packaging of solid beverage powders.

[0014] Furthermore, the alkaline solution is a KOH solution, and the surfactant is Tween 20 with a mass concentration of 5-15%.

[0015] Note: The above solution selection is more suitable for the processing of solid beverage powders.

[0016] Furthermore, in the reaction process described in S2, 200-300W ultrasonic waves are used for assistance.

[0017] Note: The ultrasonic-assisted reaction described above can accelerate the process of using KOH and hydrogen peroxide to treat fats, proteins, and other substances in solid beverage powders. Furthermore, by setting the parameters described above, the damaging effects of KOH and hydrogen peroxide on microplastics can be avoided, thereby improving the extraction accuracy of microplastics while increasing the digestion speed.

[0018] The beneficial effects of this invention are:

[0019] This invention addresses the challenges of existing technologies in digesting animal and plant fats, proteins, and cellulose in solid beverage powders. It overcomes the problems of numerous steps, long processing times, low digestion efficiency, and easy loss of microplastics in solid beverage powders, improving the accuracy of microplastic extraction and enabling quantitative detection and research of microplastics in solid beverage powders. Through comparative analysis of microplastic (MP) digestion and separation methods in solid beverage powders, and by purposefully selecting and optimizing factors such as the type of digestion reagent, the frequency of H2O2 addition, and digestion steps, the method based on the influence of organic matter digestion on MPs can more efficiently separate MPs. Experimental results demonstrate that, compared to existing technologies, the method of this invention is more effective in separating MPs from solid coffee beverages. Furthermore, the frequency of H2O2 addition affects the separation effect. This invention further reveals a preferred separation method for high-fat solid coffee beverages, providing relevant reference and theoretical support for the control and research of MP contamination in foods rich in animal and plant fats and proteins. Attached Figure Description

[0020] Figure 1 This is a technical flow chart of the method for extracting microplastics from solid beverage powder according to an embodiment of the present invention;

[0021] Figure 2 The images show the beaker states of the three-in-one coffee from this invention after digestion with Fenton's and KOH+H2O2, respectively.

[0022] Figure 3 These are filter membrane photographs in the embodiments of the present invention, where a represents the digestion and removal rate of BDC-1 after digestion by Fenton's and KOH+H2O2, and the filter membrane photograph after digestion and filtration into the PTFE filter membrane; Figure 3 b shows the digestion and removal rate of different coffees by KOH+H2O2 and a photo of the filter membrane after digestion and filtration into the PTFE filter membrane;

[0023] Figure 4 These are photographs taken in an embodiment of the present invention, where a is a PE standard sample with a diameter of 75-90 μm; Figure 4 b is a photo taken before the PE standard was added (for manual counting); Figure 4 c is a photograph taken on the black mesh filter membrane after the PE standard was recycled (for manual counting);

[0024] Figure 5 These are photos of the filter membrane in an embodiment of the present invention, wherein a represents the PE recovery rate of BDC-1 after two digestion treatments and a photo of the filter membrane after digestion and filtration into the black mesh filter membrane; Figure 5 b shows the PE recovery rate after KOH+H2O2 digestion treatment of different coffees and a photo of the filter membrane after digestion and filtration into the black mesh filter membrane;

[0025] Figure 6 These are micrographs of the original samples of 12 MPs (ABS, HDPE, LDPE, PA66, PBS, PET, PHA, PLA, POM, PP, PS, PVC) of the present invention, and after being digested with KOH+H2O2 at 70°C for 5 hours and then incubated at 50°C for 10 hours.

[0026] Figure 7 This is a diagram illustrating the experimental process of adding 1-2 ml of 30% hydrogen peroxide solution to 15 ml of 5% alkaline solution at room temperature, resulting in the generation of a large number of bubbles.

[0027] Figure 8 This is a graph showing the number of microplastics ≥20μm in embodiments CK, BC-1, BDC-1, BDC-2, and BDC-3 of the present invention (CK: control group, BC-1: black coffee, BDC-1: 3-in-1 coffee No. 1, BDC-2: 3-in-1 coffee No. 2, BDC-3: 2-in-1 coffee, BDC-4: 3-in-1 coffee No. 3).

[0028] Figure 9 These are microplastics of different sizes and their quantities detected in BDC-1.

[0029] Figure 10 This is a graph showing the percentage of various microplastics in different coffee samples. Detailed Implementation

[0030] To further illustrate the methods and effects of this invention, the technical solution of this invention will be clearly and completely described below in conjunction with experiments.

[0031] The present invention will be explained below with reference to embodiments. Those skilled in the art will understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the claims and their equivalents. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the art. The materials, reagents, and instruments mentioned are all conventional products that can be obtained commercially.

[0032] Solid beverage powders generally contain fats, proteins, and cellulose. These components may affect the extraction and detection of microplastics during the digestion process. At the same time, some components may react with microplastics during digestion, and some components may not be completely removed or may even adhere to and encapsulate microplastics, making the digestion of solid beverage powders more difficult. There is a lack of relevant research in the existing technology.

[0033] Furthermore, as can be seen from the problems mentioned in the background art, the existing digestion methods cannot effectively digest the animal and plant fats, proteins and cellulose in solid beverage powders. Moreover, if strong digestion methods (such as strong acids) are used, they may react with microplastics and fail to achieve the effect of extracting microplastics.

[0034] Specifically, treatment with H2O2, Fenton's, and KOH can partially digest solid beverage powders. This is because H2O2 and Fenton's release strong oxidizing substances such as singlet oxygen and hydroxyl radicals, which have good digestion effects on complex organic matter in environmental media, such as fulvic acid, humic acid, proteins, and polysaccharides, and are therefore widely used for the extraction of microplastics from various environmental media. KOH, with its strong alkalinity and corrosiveness, has good digestion effects on animal fats and proteins, and is widely used for the digestion of various biological samples and the extraction and detection of microplastics.

[0035] However, when using KOH or H2O2 alone, or Fenton's method, to digest fats, proteins, and cellulose in solid beverage powders, these components cannot be completely digested. Furthermore, both methods exhibit low efficiency in digesting microplastics and slow reaction rates. If KOH and H2O2 are used simultaneously, it becomes impossible to conduct experiments (because the mixture produces a large number of bubbles that carry microplastics and overflow, making further experiments impossible). Figure 7 As shown, when 1-2 ml of 30% hydrogen peroxide solution is poured into 15 ml of 5% alkaline solution at room temperature, bubbles are immediately generated, making it impossible to continue the operation. If the concentrations of both are reduced, the digestion process cannot be achieved. Therefore, in existing technologies, KOH and H2O2 compounds are usually not used simultaneously to extract microplastics.

[0036] The present invention has found that when KOH combines with H₂O₂, a strong oxidizing environment is formed. Under this environment, H₂O₂ can decompose into water and oxygen under the catalysis of KOH, releasing a large number of free radicals such as (·OH). These free radicals have extremely high oxidizing power and can oxidize organic matter. However, it is necessary to avoid the generation and overflow of the aforementioned bubbles, and also to avoid the degradation of microplastics caused by prolonged use of KOH and H₂O₂ alone. Therefore, the present invention provides the following solutions:

[0037] Example 1: A method for extracting microplastics from solid beverage powder, comprising the following steps:

[0038] S1. Add 15 ml of a 5% alkaline solution to 2 g of a solid beverage powder containing microplastics, shake well, and then heat in a water bath at 70°C for 5 hours. During the water bath heating, intermittently add a 30% hydrogen peroxide solution at a frequency of 0.5 mL / 10 min. The solid beverage powder includes 2-in-1 coffee, 3-in-1 coffee, milk powder, and soy powder. For example, in this embodiment, black coffee BC-1 is selected.

[0039] S2. After the water bath heating is completed, the water bath temperature is reduced to 50℃ and the reaction is carried out for 10 hours. During the reaction, 250W ultrasonic wave is used for assistance. After the reaction is completed, the mixture is filtered while hot and washed with surfactant. Microplastics are obtained by filtration, and the extraction is completed.

[0040] The alkaline solution is a KOH solution, and the surfactant is Tween 20 with a mass concentration of 10%; the microplastics include one or more MPs such as PE, PS, PVC, or PET.

[0041] Results: Following the above procedures, BC-1 was extracted as described above. Testing revealed the presence of microplastics in the solid beverage powder. The microplastic content was as follows: Figure 8 As shown.

[0042] Relevant Principles: In Embodiment 1 of this invention, the above-described implementation method avoids the generation of bubbles during the reaction of potassium hydroxide and hydrogen peroxide. By setting the temperature and time parameters and the addition method, the reaction efficiency can be improved, while avoiding the generation and overflow of bubbles during the mixing of KOH and H2O2. Specifically, in the strongly alkaline and strongly oxidizing environment formed by the combination of potassium hydroxide and hydrogen peroxide, the organic substances such as fat, protein, and cellulose in the solid beverage powder of this invention undergo the following reaction mechanism:

[0043] ① Saponification of fats: Under strongly alkaline conditions, fats and oils undergo a saponification reaction, where fatty acid glycerides react with the alkali to produce fatty acid salts (soap) and glycerol. This process can be represented as: RCOOCH2CH(OH)CH2OR' + 3KOH → 3RCOOK + CH2OHCHOHCH2OH; where R and R' represent fatty acid chains. ② Under alkaline and strongly oxidizing conditions, the peptide bonds of proteins can be hydrolyzed, leading to protein degradation into smaller peptide chains or even amino acids. Strong oxidation can significantly accelerate this process, generating hydroxyl radicals. These radicals can attack peptide bonds: R-NH-CO-R' + H2O → R-NH2 + R'-COOH; where R and R' represent amino acid residues. Although KOH alone can promote protein hydrolysis, the addition of H2O2 may accelerate this process because it generates hydroxyl radicals that can attack peptide bonds, thereby accelerating protein degradation and increasing the efficiency of the hydrolysis. ③ The hydrogen bonds and van der Waals forces between cellulose molecular chains make its structure stable and difficult to be destroyed by simple chemical reactions. By utilizing the combination of KOH and H₂O₂, KOH provides OH⁻. - The ions can react with the hydroxyl groups (-OH) in cellulose molecules, breaking the β-1,4-glycosidic bonds in the cellulose molecular chain. Simultaneously, under alkaline conditions, H₂O₂ can decompose to generate hydroxyl radicals (·OH), which have extremely high oxidizing power and can further attack the cellulose molecular chain, accelerating its breakage. The combination of KOH and H₂O₂ in this invention can avoid potential side reactions during cellulose degradation and simultaneously disrupt the stability of vitamins, thereby accelerating the oxidation process. Therefore, the specific reaction mechanism achieved by the combination of KOH and H₂O₂ mainly accelerates protein hydrolysis and cellulose oxidation, which cannot be achieved by using KOH or H₂O₂ alone.

[0044] In summary, the method of the present invention firstly overcomes the problem of bubble generation during the digestion of solid beverage powder caused by the mixing of KOH and H2O2, a problem that has not been considered or addressed in the prior art; secondly, it accelerates the digestion reaction and improves the digestion efficiency, a beneficial effect that cannot be achieved using the prior art (see Comparative Examples 1-7 for a detailed comparison of the effects).

[0045] Example 2: This example is largely the same as Example 1, except that the KOH concentration is different. In S1, a 2% KOH solution is added to the solid beverage powder containing microplastics at a ratio of 1g:7.5mL.

[0046] Example 3: This example is largely the same as Example 1, except that the KOH concentration is different. In S1, an 8% KOH solution is added to the solid beverage powder containing microplastics at a ratio of 1g:7.5mL.

[0047] Example 4: This example is largely the same as Example 1, except that the temperature parameters are different. In S1, the water bath is heated at 75°C for 5 hours.

[0048] Example 5: This example is largely the same as Example 1, except that the temperature parameters are different. In S1, the water bath is heated at 65°C for 5 hours.

[0049] Example 6: This example is largely the same as Example 1, except that the incubation time is different, and the reaction time in S2 is 6 hours.

[0050] Example 7: This example is largely the same as Example 1, except that the incubation time is different, and the reaction in S2 is 12h.

[0051] Example 8: This example is largely the same as Example 1, except that the concentration of hydrogen peroxide solution is different. A 10% hydrogen peroxide solution is intermittently added in S1.

[0052] Example 9: This example is largely the same as Example 1, except that the concentration of hydrogen peroxide solution is different. A 20% hydrogen peroxide solution is intermittently added in S1.

[0053] Example 10: This example is largely the same as Example 1, except that the ultrasonic parameters are different. In S2, a 200W ultrasonic wave is used for assistance.

[0054] Example 11: This example is largely the same as Example 1, except that the ultrasonic parameters are different. In S2, a 300W ultrasonic wave is used for assistance.

[0055] Example 12: This example is largely the same as Example 1, except that the raw material ratio is different. In S1, an alkaline solution is added to the solid beverage powder containing microplastics at a ratio of 1g:5mL.

[0056] Example 13: This example is largely the same as Example 1, except that the raw material ratio is different. In S1, an alkaline solution is added to the solid beverage powder containing microplastics at a ratio of 1g:10mL.

[0057] Example 14: This example is largely the same as Example 1, except that the water bath temperature is reduced to 40°C in S2.

[0058] Example 15: This example is largely the same as Example 1, except that the water bath temperature is reduced to 60°C in S2.

[0059] Example 16: This example is largely the same as Example 1, except that water bath heating is performed for 6 hours in S1.

[0060] Example 17: This example is largely the same as Example 1, except that water bath heating is performed for 3 hours in S1.

[0061] Experimental Example 1: This experimental example is a blank group. Packed 3-in-1 Coffee No. 1 solid beverage powder was added, and the experiment was set up directly according to the method of Example 1. That is, 15 mL of 5% KOH solution was added, and the beaker was shaken and agitated to mix the coffee and solution evenly. Then, 30% H2O2 was added at a frequency of 0.5 mL / 10 min, and the mixture was placed in a 70℃ water bath for 5 h for digestion. After that, the addition was stopped, the temperature was lowered to 50℃ and incubated for 10 h. During the process, 250W ultrasonic waves were used to assist digestion. After digestion, the microplastic content of the 3-in-1 Coffee No. 1 itself was obtained by machine calculation.

[0062] To demonstrate the advantages of the present invention, the following experimental examples and comparative examples were provided. Examples 2-4 and the comparative examples all involved adding fluorescently stained microplastic samples to demonstrate whether the method has a dissolving and detrimental effect on microplastics, and its dissolving effect on solid beverage powders, thus highlighting the effectiveness of the present invention.

[0063] Experimental Example 2: Figure 1 As shown, 3-in-1 Coffee No. 1 was used as the experimental sample, with three replicate control groups for each experiment. 2g of 3-in-1 Coffee No. 1 powder was added to a beaker, along with PE (75-90μm) standard and 15mL of 5% KOH solution. The beaker was shaken and agitated to mix the coffee and solution thoroughly. Then, 30% H2O2 was added at a frequency of 0.5mL / 10min, and the mixture was placed in a 70℃ water bath for 5 hours to digest. Afterward, the addition was stopped, and the temperature was lowered to 50℃ for incubation for 10 hours. A 250W ultrasonic wave was used to assist digestion during the process. The condition of the beaker after digestion is shown in the image. Figure 2 (The beaker on the right), see the digestion and removal rate results. Figure 3 a. See the micrographs of the PE standard, and the photos taken before and after addition and recycling. Figure 4 The PE recovery rate after digestion is shown in the figure. Figure 5 a. The morphological images of the 12 MPs (ABS, HDPE, LDPE, PA66, PBS, PET, PHA, PLA, POM, PP, PS, PVC) before and after digestion using the same digestion protocol are shown below. Figure 6 Vacuum filtration: The digestion solution was filtered using a circulating water vacuum pump. A black acetate mesh filter membrane (5 μm, 47 mm) was used. The beakers and glassware used for vacuum filtration were rinsed with Tween 20 solution diluted with ultrapure water to prevent MPs from sticking to the walls and being lost due to experimental procedures. See the image of the black mesh filter membrane after filtration. Figure 4c. Photography and Counting: After filtration, the black mesh filter membrane is photographed using a low-power microscope or a close-up camera. Based on the photographs, manual counting is performed using ImageJ to calculate the PE recovery rate (PE recovery rate = microplastics obtained from photographing and counting after digestion / microplastics obtained from photographing and counting before digestion).

[0064] Experiment Example 3: Three types of multi-in-one coffee (3-in-1 Coffee No. 2, 3-in-1 Coffee No. 3, and 2-in-1 Coffee) were used as experimental samples, with three replicate control groups for each experiment. 2g of multi-in-one coffee powder, PE (75-90μm) standard, and 15mL of 5% KOH solution were added to a beaker. The beaker was shaken and agitated to mix the coffee and solution thoroughly. 30% H2O2 was added at a frequency of 0.5mL / 10min, and the mixture was placed in a 70℃ water bath for 5 hours for digestion. Afterward, the addition was stopped, the temperature was lowered to 50℃, and the mixture was incubated for 10 hours. 250W ultrasonic waves were used to assist digestion during the process. The condition of the beaker after digestion is shown in the image. Figure 2 (The beaker on the right), see the digestion and removal rate results. Figure 3 b. See the micrographs of the PE standard, and the photos taken before and after addition and recycling. Figure 4 The PE recovery rate after digestion is shown in the figure. Figure 5 b. The morphological images of the 12 MPs (ABS, HDPE, LDPE, PA66, PBS, PET, PHA, PLA, POM, PP, PS, PVC) before and after digestion using the same digestion protocol are shown below. Figure 6 Vacuum filtration: The digestion solution was filtered using a circulating water vacuum pump. A black acetate mesh filter membrane (5 μm, 47 mm) was used. The beakers and glassware used for vacuum filtration were rinsed with Tween 20 solution diluted with ultrapure water to prevent MPs from sticking to the walls and being lost due to experimental procedures. See the image of the black mesh filter membrane after filtration. Figure 4 c. Photography and Counting: After the black mesh filter membrane is filtered, it is photographed using a low-power microscope or a close-focus camera. Based on the photographs, the PE recovery rate is calculated by manually counting using ImageJ.

[0065] Example 4: No experimental sample was added. Three replicate control groups were set up for each experiment. PE (75-90μm) standard was added, followed by 15mL of 5% KOH solution. The beaker was shaken and agitated to mix the coffee with the solution thoroughly. 30% H2O2 was added at a frequency of 0.5mL / 10min, and the mixture was placed in a 70℃ water bath for 5h for digestion. Addition was then stopped, and the temperature was lowered to 50℃ for incubation for 10h. Ultrasonic digestion was assisted using 250W during the process. The PE recovery rate was calculated after digestion.

[0066] Based on the experimental setup described above, since coffee itself contains microplastics (microplastics are generated in current raw materials, food processing, and packaging processes), the microplastic content in the coffee used in this embodiment and experiment was first calculated using the method of Experiment 1 (CK). Figure 10 The percentage of different types of microplastics in the coffee sample described above was used to calculate the microplastic recovery rate in subsequent Experiments 2, 3, and 4, as well as all examples including Example 1 (BC-1), after removing the microplastic content of the coffee itself. The results are as follows: Figure 8 , Figure 9 As shown.

[0067] After conducting experiments in Examples 1, 2, and 3, the recovery rates are shown in Table 1 below:

[0068] Table 1 Microplastic Recovery Rate

[0069]

[0070] As shown in Table 1 above, in Experiment 4, the microplastic recovery rate reached 99%, proving that the reagents and operating methods used in the present invention can achieve good treatment results. Furthermore, in Experiment 2 and Example 3, after adding different solid beverage powders for treatment, the microplastic recovery rate reached over 89% after the solid beverage powders were digested, proving that the impact and loss of microplastics after digestion treatment of solid beverage powders in the present invention is small, indicating that the method of the present invention can be used to extract microplastics from solid beverage powders.

[0071] Comparative Example 1: First, bagged BDC-1 3-in-1 coffee was used as the experimental sample, with three replicate control groups for each experiment. 2g of BDC-1 coffee powder, PE (75-90μm) standard, and 15mL of 0.05M Fe were added to a beaker. 2+ A solution of (7.5g FeSO4^7H2O + 500mL H2O) was prepared by shaking and agitating the beaker to thoroughly mix the coffee with the solution. 30% H2O2 was added at a rate of 1mL / 10min, and the mixture was placed in a 70℃ water bath for 6 hours to digest. Ultrasonic digestion was used to assist the process with 250W ultrasound. The condition of the beaker after digestion is shown in the image. Figure 2 (The beaker on the left), the digestion and removal rate effect is shown in the image. Figure 3 a. Microscopic photographs of PE standard products, and photographs taken before and after addition and recycling, for reference. Figure 4 The PE recovery rate after digestion is shown in the figure. Figure 5a. Vacuum filtration: The digestion solution was filtered using a circulating water vacuum pump. A black acetate mesh filter membrane (5μm, 47mm) was used. The beakers and glassware used for vacuum filtration were rinsed with Tween 20 solution diluted with ultrapure water to prevent MPs from sticking to the walls and being lost due to experimental procedures. See the image of the black mesh filter membrane after filtration. Figure 4 c. Photography and Counting: After the black mesh filter membrane is filtered, it is photographed using a low-power microscope or a close-focus camera. Based on the photographs, the PE recovery rate is calculated by manually counting using ImageJ.

[0072] Comparative Example 2: BDC-1 3-in-1 coffee in packets was used as the experimental sample, with three replicate control groups in each experiment. 2g of BDC-1 coffee powder, PE (75-90μm) standard, and 30mL of 30% H2O2 were added to a beaker. The beaker was shaken and agitated to mix the coffee and solution thoroughly. The mixture was then placed in a 70℃ water bath for 5 hours for digestion, assisted by 250W ultrasound. Filtration: The digested solution was filtered using a circulating water filtration pump with a PTFE-PP (10μm, 47mm) membrane. Due to incomplete digestion, some organic components in the coffee flocculated and agglomerated, forming flocculent matter and causing significant caking, which in turn blocked the membrane and prevented filtration. Therefore, Comparative Example 2 could not effectively digest the 3-in-1 coffee.

[0073] The recovery rates obtained after conducting experiments on Comparative Example 1 and Comparative Example 2 are shown in Table 2 below:

[0074] Table 2 Microplastic Recovery Rate

[0075] parameter Microplastic recycling rate Comparative Example 1 70％ Comparative Example 2 31％

[0076] As shown in Table 2 above, when the prior art method of Comparative Example 1 is used to extract microplastics, the recovery rate of microplastics is low, at 70% or less. This indicates that changing the steps or using other methods in the experiment will affect the microplastics, making it impossible to extract them accurately. In contrast, the recovery rates of microplastics in Experimental Example 2 and Experimental Example 3 are both high. Therefore, the method in the embodiments of the present invention is preferred.

[0077] Furthermore, the experimental results showed that the solution of Comparative Example 2 was relatively turbid after digestion, and fat clumps could be clearly seen after cooling. This is because H2O2 does not have the function of removing fat. Therefore, the microplastics in Comparative Example 2 may be largely contained in substances such as fat, making them difficult to extract.

[0078] Comparative Example 4: The extraction of microplastics from 3-in-1 coffee using enzymatic digestion technology was found to take one week to several months to partially digest the 3-in-1 coffee. Therefore, Comparative Example 4 cannot be compared with the extraction efficiency in the embodiments of the present invention.

[0079] Comparative Example 5: Figure 2 As shown, Comparative Example 1, using Fenton's technology to extract microplastics from 3-in-1 coffee, found that numerous bubbles were generated that caused MPs to adhere to the beaker wall, resulting in an MP recovery rate at least 20% lower than that of Comparative Example 2. Therefore, the processing in Comparative Example 5 affects the recovery of microplastics from solid beverage powders, making this method unsuitable for the extraction of microplastics from solid beverage powders.

[0080] Comparative Example 6: 15 ml of 1% KOH alkaline solution was slowly mixed with 15 ml of 10% hydrogen peroxide solution. Before all the solution was added, a large number of bubbles were generated, which prevented the reaction from proceeding.

[0081] Comparative Example 7: The difference from Experimental Example 1 is that the mass concentration of KOH in the alkaline solution is 1% and the hydrogen peroxide solution is 10%. After experimentation, it was found that the recovery rate of microplastics in Comparative Example 6 was less than 80%. Therefore, the parameters in Experimental Example 1, which is also the parameters in Example 1 of the present invention, are more preferred.

Claims

1. A method for extracting microplastics from solid beverage powder, characterized in that, Includes the following steps: S1. Add an alkaline solution with a mass concentration of 2-8% to the solid beverage powder containing microplastics at a ratio of 1g: 5-10mL, shake well, and then heat in a water bath at 65-75℃ for 3-6 hours. During the water bath heating, add hydrogen peroxide solution with a mass concentration of 10-30% intermittently at a frequency of 0.5mL / 10min. S2. After the water bath heating is completed, reduce the water bath temperature to 40~60℃ and react for 6~12 hours. After the reaction is completed, filter while hot and wash with surfactant. Obtain microplastics by filtration, and the extraction is complete. The alkaline solution is a KOH solution; the surfactant is Tween 20.

2. The method for extracting microplastics from solid beverage powder as described in claim 1, characterized in that, The solid beverage powders include 2-in-1 coffee, 3-in-1 coffee, yeast melanin coffee, milk powder, and soy powder.

3. The method for extracting microplastics from solid beverage powder as described in claim 1, characterized in that, The microplastics are one or more of PE, PS, PVC, and PET.

4. The method for extracting microplastics from a solid beverage powder as described in claim 1, characterized in that, The surfactant is Tween20 with a mass concentration of 5-15%.

5. The method for extracting microplastics from a solid beverage powder as described in claim 1, characterized in that, In the reaction process described in S2, 200~300W ultrasonic waves are used for assistance.

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