Method for treating coffee waste, method for preparing composite material comprising same, and composite material comprising same

Abstract

Provided is a method for treating coffee waste. The method comprises a process of treating coffee grounds: mixing the coffee grounds with hydrogen peroxide under alkaline conditions to form a first mixture; and obtaining treated coffee grounds by means of a separation process. Further provided is a method for making a coffee waste polymer composite material, the material comprising the aforementioned treated coffee grounds.

Description

[0001] FIELD OF THE INVENTION The present invention relates to a process for treating coffee waste, and to using coffee waste treated according to the present invention as a material to form a composite material with a polymer. In particular, the present invention relates to a process for treating coffee husks and coffee grounds, and to using coffee husks and coffee grounds treated according to the present invention as a material to form a composite material with a polymer, such as polypropylene. BACKGROUND In recent years, with climate change and resource scarcity becoming increasingly serious, sustainable consumption and production have become issues of global concern. Converting low-value waste into more valuable products and achieving a circular economy are pressing challenges facing the world today. Coffee, the world's most consumed non-alcoholic beverage, generates a large amount of biowaste, such as coffee waste, during its processing. This coffee waste primarily exists in the form of coffee husks and coffee grounds. Currently, most coffee waste is not properly treated or effectively utilized. Blending coffee waste with polymer materials to prepare coffee waste-polymer composites is a feasible and environmentally friendly recycling method. However, due to performance issues of coffee waste-polymer composites, the amount of coffee waste added to the coffee waste-polymer composites currently used on the market is relatively low, limiting the efficiency of coffee waste resource recovery. In order to reduce the waste of coffee waste, improve the recycling efficiency of coffee waste, and further reduce costs, it is of great practical significance to appropriately increase the proportion of coffee waste added to the composite material while ensuring the necessary properties of the composite material. Since coffee grounds contain a large number of organic groups, coffee grounds are prone to bonding or agglomeration during processing. In addition, coffee grounds themselves are porous and easily cause stress concentration in their products, resulting in a decrease in the toughness of the composite material or easy failure of the product. Therefore, it is necessary to pretreat the coffee grounds to improve the mechanical properties of coffee waste polymer composite materials and the products prepared therefrom. In combination with the application needs of coffee waste polymer composite products, the present invention needs to pretreat the cellulose, hemicellulose, lignin, and oils contained in the coffee grounds, and bleach the coffee grounds at the same time, so as to prepare coffee waste polymer composite materials that meet the requirements of various colors, mechanical properties, washing resistance and high-temperature oil-discharging performance of the composite material. Or at least provide the public with an alternative solution. Summary of the invention The first aspect of the present invention relates to a method for treating coffee waste, the method comprising the steps of treating coffee grounds: (i) mixing coffee grounds with hydrogen peroxide under alkaline conditions to form a first mixture;(ii) Processed coffee grounds are obtained through a separation process. Preferably, in step (i), the alkaline conditions are at a pH of 8-10. More preferably, the alkaline conditions are maintained at a pH of 8-10 by adding an alkaline solution. In one embodiment, during the mixing in step (i), the weight ratio of the coffee grounds to hydrogen peroxide is between 1:0.125 and 1:3. Preferably, prior to step (i), the coffee grounds are mixed with an alkaline solution. In one embodiment, the alkaline solution is a mixture of an alkaline material and water, wherein the alkaline material can be selected from sodium hydroxide, potassium hydroxide, calcium hydroxide, or a combination thereof. In one embodiment, during the mixing in step (i), the concentration of the hydrogen peroxide is maintained at a weight ratio of 3% to 15%. In one embodiment, during the mixing in step (i), the weight ratio of the coffee grounds to hydrogen peroxide is between 1:0.125 and 1:5. In one embodiment, step (1) includes the following steps: (a) mixing the coffee grounds with water to form a stirring liquid, wherein the weight ratio of the coffee grounds to water is 1:X; (b) adding the hydrogen peroxide to the stirring liquid at least once and mixing to form a first mixture, wherein the weight ratio of the hydrogen peroxide to the stirring liquid in the first mixture is 1:Y; and (c) maintaining the alkaline conditions by adding an alkaline solution during the mixing in step (b). In one embodiment, in step (a), the weight ratio of the coffee grounds to water is 1:3 to 1:10; in step (b), the hydrogen peroxide is added to the stirred liquid in three portions and mixed to form the first mixture, wherein the weight ratio of the hydrogen peroxide to the stirred liquid is 1:4 to 1:22, and during mixing, the alkaline condition is maintained at a pH of 8-10 by adding the alkaline solution. In one embodiment, in step (a), the weight ratio of the coffee grounds to water is 1:3 to 1:10; in step (b), the hydrogen peroxide is added to the stirred liquid in three portions and mixed to form the first mixture, wherein the weight ratio of the hydrogen peroxide to the stirred liquid is 1:10, and during mixing, the alkaline condition is maintained at a pH of 8-9 by adding the alkaline solution. In one embodiment, in step (a), the weight ratio of the coffee grounds to water is 1:3 to 1:10;In step (b), the hydrogen peroxide is added to the stirred liquid in three portions and mixed to form the first mixture. In the first mixture, the weight ratio of the hydrogen peroxide to the stirred liquid is 1:5 to 1:10. During mixing, the alkaline conditions are maintained at a pH of 8-10 by adding the alkaline solution. In one embodiment, in step (a), the weight ratio of the coffee grounds to water is 1:3 to 1:10. In step (b), the hydrogen peroxide is added to the stirred liquid in three portions and mixed to form the first mixture. In the first mixture, the weight ratio of the hydrogen peroxide to the stirred liquid is 1:5. During mixing, the alkaline conditions are maintained at a pH of 8-9 by adding the alkaline solution. In one embodiment, before step (ii), a flocculant solution is mixed with the first mixture to form a second mixture. In one embodiment, before step (ii), a flocculant solution is mixed with the first mixture to form a second mixture. Preferably, the concentration of the flocculant in the flocculant solution is 0.05-3% by weight. More preferably, the concentration of the flocculant in the first mixture is 0.01-1% by weight. In one embodiment, the flocculant solution is selected from organic flocculants, particularly starch, protein, gelatin, sodium alginate, sodium methyl cellulose, polyacrylamide, sodium polyacrylate, polyvinylpyrrolidone, polyethyleneimine, or combinations thereof. In one embodiment, the flocculant solution is selected from inorganic flocculants, particularly aluminum salts, iron salts, calcium chloride, potassium aluminum sulfate, aluminum chloride, ferric sulfate, ferric chloride, polyaluminum chloride, polyaluminum sulfate, activated silica, or combinations thereof. In one embodiment, after forming the second mixture, the supernatant of the second mixture is removed; and water is added, at least once, to the second mixture from which the supernatant has been removed and mixed, wherein the weight ratio of the added water to the coffee grounds is 3:1 to 20:1. Preferably, after forming the second mixture, the supernatant of the second mixture is removed; water is added at least once to the second mixture from which the supernatant has been removed and mixed, wherein the weight ratio of the added water to the coffee grounds is 5:1 to 3:1. More preferably, after forming the second mixture, the supernatant of the second mixture is removed; water is added at least once to the second mixture from which the supernatant has been removed and mixed, wherein the weight ratio of the added water to the coffee grounds is 3:1 - 20:1. In one embodiment, before step (ordering), the following steps are further included: mixing a flocculant solution with the first mixture to form a second mixture; after forming the second mixture, removing the supernatant of the second mixture;Adding water at least once to the second mixture after removing the supernatant, and mixing, wherein the weight ratio of the water added to the coffee grounds is 5:1 to 3:1; and waiting for 4-24 hours. In one embodiment, before step (ii), the method further comprises the following steps: mixing a flocculant solution with the first mixture to form a second mixture; after forming the second mixture, removing the supernatant from the second mixture; adding water at least once to the second mixture after removing the supernatant, and mixing, wherein the weight ratio of the water added to the coffee grounds is 5:1 to 3:1; and waiting for 1 hour. In one embodiment, the method further comprises the step of treating coffee husks: (a) mixing coffee husks with water at a weight ratio of 1:3 to 1:20 under heating; and (b) obtaining treated coffee husks through a separation process. In one embodiment, the coffee husks and water are mixed under heating at a weight ratio of 1:5 to 1:10. Preferably, the coffee husks and water are mixed at 70-100°C for 2 hours. In one embodiment, the coffee husks are mixed with water at 80-90°C for 2 hours; the supernatant is removed; and the resulting coffee husks are mixed with water at 80-90°C for 2 hours, wherein the weight ratio of coffee husks to water is 1:3 to 1:5. A second aspect of the present invention relates to a coffee waste polymer composite material comprising coffee grounds treated by the method according to any one of claims 1-28 and / or coffee husks treated by the method according to any one of claims 29-32. In one embodiment, the polymer is polypropylene. In one embodiment, the composite material comprises polypropylene, a polyolefin elastomer, the coffee grounds, and the coffee husks. In one embodiment, the composite material further comprises a toughening agent and / or an antioxidant. In one embodiment, the polyolefin elastomer is maleic acid grafted polypropylene. In one embodiment, the composite material further comprises titanium dioxide. A third aspect of the present invention relates to a method for producing a coffee waste polymer composite material, comprising the following steps: (i) treating coffee grounds according to the method according to any one of claims 1 to 28; (ii) treating coffee husks according to the method according to any one of claims 29 to 32; (iii) mixing the coffee grounds with a polypropylene or polyolefin elastomer to form a mixed material;and (iv) adding the mixed material to a feeder to form the coffee waste-polymer composite. In one embodiment, a toughening agent and / or an antioxidant and / or titanium dioxide are further added to form the mixed material. In one embodiment, the polyolefin elastomer is maleic acid grafted onto polypropylene. BRIEF DESCRIPTION OF THE DRAWINGS Various exemplary embodiments of the present invention are described in detail based on the following drawings, in which: FIG1 Coffee husks are soaked at room temperature for 48 hours; FIG2 Color changes of the supernatant after boiling coffee husks for different times; FIG3A Untreated coffee grounds; FIG3B Coffee grounds treated with process 1; FIG3C Coffee grounds treated with process 2; FIG3D Coffee grounds treated with process 3; FIG3E Coffee grounds treated with process 4; FIG3F Coffee grounds treated with process 5; FIG3G Coffee grounds treated with process 5 (the left side of the figure is Example 3; the middle is Example 4; the right side is Example 5); FIG4A Boiling test results of coffee waste polymer composites made from untreated coffee grounds; FIG4B Boiling test results of coffee waste polymer composites made from coffee grounds treated with process 1; FIG4C Boiling test results of coffee waste polymer composites made from coffee grounds treated with process 2; FIG4D Boiling test results of coffee waste polymer composites made from coffee grounds treated with process 3; FIG4E Figure 4F shows the boiling test results of the coffee waste polymer composite material made from coffee grounds treated by process 4; Figure 4G shows the boiling test results of the coffee waste polymer composite material made from coffee grounds of Example 4; Figure 4H shows the boiling test results of the coffee waste polymer composite material made from coffee grounds of Example 5; Figure 5A shows the high-temperature oil release test results of the coffee waste polymer composite material made from untreated coffee grounds; Figure 5B shows the high-temperature oil release test results of the coffee waste polymer composite material made from coffee grounds treated by process 1; Figure 5C shows the high-temperature oil release test results of the coffee waste polymer composite material made from coffee grounds treated by process 2; Figure 5D shows the high-temperature oil release test results of the coffee waste polymer composite material made from coffee grounds treated by process 3; Figure 5E shows the high-temperature oil release test results of the coffee waste polymer composite material made from coffee grounds treated by process 4; Figure 5F shows the high-temperature oil release test results of the coffee waste polymer composite material made from coffee grounds treated by process 5; Figure 5G High-temperature oil release test results of coffee waste polymer composites made from coffee grounds in Examples 4 and 5;Figure 6 shows a slurry without flocculant added (left), a slurry with flocculant added and settled for 4 hours (center), and a slurry with flocculant added and settled for 24 hours (right) in Process 2. Figure 7A shows TGA test results of coffee grounds treated in Processes 4 and 5. Figure 7B shows TGA test results of coffee grounds treated in Examples 3-5. Figure 8 shows coffee grounds of different brands (before treatment with the process of the present invention). Figure 9 shows coffee grounds of different brands (after treatment with Process 4 of the present invention). Figure 10 shows coffee waste-polymer composite pellets prepared from coffee grounds treated in Process 4. Figure 11 shows coffee waste-polymer composite strips prepared from coffee grounds treated in Process 4. Figure 12 shows coffee waste-polymer composite pellets prepared from coffee grounds treated in Process 4 (with TiO2 added). Figure 13 shows coffee waste-polymer composite strips prepared from coffee grounds treated in Process 4 (with TiO2 added). DETAILED DESCRIPTION OF THE INVENTION The composite material of the present invention can be understood as comprising coffee waste treated in accordance with the present invention and a polymer. Unless otherwise specified, percentages herein are by weight. For the purpose of explaining the present invention, polypropylene will be used as an example of the polymer herein. However, it should be understood that this does not limit the embodiments of the present invention. Unless otherwise specified, the raw materials and chemicals used herein do not require special treatment before use. The main raw materials and reagents are as follows:

[0002] • Coffee grounds (SCG), brands A, B, C, and D;

[0003] • Polypropylene (PP);

[0004] • Toughening agents;

[0005] • Maleic acid grafted polypropylene (MAPP);

[0006] • Sodium hydroxide;

[0007] • 50% hydrogen peroxide (H2O2);

[0008] • Polyacrylamide;

[0009] • Antioxidant; • Antioxidant. The materials used in this article will be formulated in the following manner:

[0010] • Prepare 1% sodium hydroxide solution by dissolving 1 kg of sodium hydroxide in 99 kg of water and stirring until it is completely dissolved.

[0011] • Prepare 50% sodium hydroxide solution by dissolving 1 kg of sodium hydroxide in 1 kg of water and stirring until completely dissolved.

[0012] • Prepare the flocculant solution by dissolving less than 50 grams of flocculant in 1 kg of water and stirring until it is completely dissolved. The tests and characterizations disclosed in this article are described below:

[0013] • The melt index test uses a melt flow rate tester in accordance with ISO1133, with a test load of 2.16 kg and a temperature of 230°C.

[0014] • Density test is carried out in accordance with ISO1183.

[0015] • The tensile performance test is carried out in accordance with ISO527, and the tensile rate used in the experiment is 50mm / min.

[0016] • The bending performance test is carried out in accordance with ISO178, and the tensile rate used in the experiment is 2mm / min.

[0017] • The Izod notched impact performance is tested according to ISO180, and the pendulum energy used in the experiment is 2.75J.

[0018] • Boiling test: Place the specimen in a beaker and add enough water to completely immerse the specimen in water. After boiling for 6 hours, take out the sample, wipe off the moisture on the surface of the specimen, observe the sample surface with an optical microscope, and compare it with the specimen before boiling and after drying.

[0019] • High temperature oil release test: Place the sample in an oven at 80°C or 150°C and observe the surface condition of the sample after baking for a certain period of time.

[0020] • Color testing uses the CIE1976L*a*b* color system to measure lightness (L) and two chromaticity coordinates (a and b). L represents black and white, and the range is 0-

[0021] 100, 0 represents black, and 100 represents white; a represents red and green, with positive values ​​representing red and negative values ​​representing green; b represents yellow and blue, with positive values ​​representing yellow and negative values ​​representing blue. Effect of Coffee Grounds and Coffee Hull Treatment on Composite Material Properties: Coffee Hull Treatment: Coffee hulls are a crucial component of the composite material of the present invention, and their morphology and properties significantly influence the overall performance of the composite material. After soaking coffee hulls in water at room temperature (solid-to-liquid ratio by weight of 1:10, e.g., 1 kg of coffee hulls to 10 kg of water) for 36-48 hours, as shown in Figure 1, the supernatant is dark brown, with a significant amount of material leached from the coffee hulls. The experimental results indicate that untreated soluble, color-forming substances in the coffee hulls are readily leached by water. Considering that these substances may affect the wash resistance test results in the composite material, treatment of the coffee hulls is necessary. Example 1: Coffee hulls were boiled in water at a solid-to-liquid ratio by weight of 1:10, with the water changed every few hours. Figure 2 shows the color changes of the supernatant after different boiling times (from left to right, longer boiling times increase; the far right is the control group). Comparison reveals that after 4 hours of boiling, the supernatant color becomes significantly lighter (i.e., bottles 1 and 3 on the left in Figure 2), indicating a significant reduction in coffee husk precipitation. Considering large-scale production operability and cost, after optimization, a solid-to-liquid weight ratio of 1:5 and a 4-hour boiling time (with water changed every 2 hours) were selected for coffee husk treatment. In Example 1, the coffee husk treatment process is shown in Table 1. Treatment of coffee grounds The following different embodiments will explain the treatment process of coffee grounds according to the present invention. Example 2 without coffee grounds treatment process In order to improve the treatment effect of coffee grounds, the coffee grounds are initially crushed before being treated. The specific process of coffee grounds treatment is shown in the following table. As shown in Figure 3A, the color of the untreated coffee grounds is black. The untreated coffee grounds are used to prepare coffee waste polymer composites and then injection molded. The sample is then subjected to a water boiling test and a high-temperature oil discharge test. The test results are shown in Figures 4A and 5A. As can be seen from Figure 4A, the performance of the samples before and after the water boiling test is basically the same. After drying for 18 hours, the color of the samples becomes slightly lighter than that before water boiling. As can be seen from Figure 5A, after high-temperature treatment, the sample shows obvious oil leakage, and there is room for improvement. Treatment of coffee grounds The coffee grounds are treated by treatment process 1, as shown in the following table. Table 2 Coffee grounds treatment process 1 As can be seen from the table above, the total treatment time for Process 1 is approximately 92 hours, and the coffee grounds yield is approximately 48%. Those skilled in the art should understand that the processes in the table above are merely illustrative, and all parameters in the table should not be construed as limiting the present invention. For example, the stirring speed of 700 rpm during the sodium hydroxide treatment is merely illustrative and can be adjusted to meet actual operational requirements, as long as the stirring effect is maintained. The stirring time is generally between 1 and 24 hours. As shown in Figure 3B, the color of the coffee grounds becomes significantly lighter, exhibiting a pale yellowish color, after treatment in Process 1. Coffee waste polymer composites prepared from the coffee grounds treated according to Process 1 were then injection molded. The specimens were then subjected to a water boiling test and a high-temperature oil release test, with the test results shown in Figures 4B and 5B. Figure 4B shows that the samples performed essentially identically before and after the water boiling test, with the color of the samples slightly lighter after drying for 18 hours compared to before boiling. As shown in Figure 5B, the coffee waste polymer composites prepared in Process 1 exhibit no oil leakage after the high-temperature treatment. This is likely due to the removal of oily substances contained in the coffee grounds during the treatment in Process 1. In summary, after being treated by process 1, the color of coffee grounds and the oil-producing problem of the composite material are significantly improved. However, since the cellulose and other substances in the coffee grounds are prone to swelling under alkaline conditions, the coffee grounds are difficult to separate from the slurry during the treatment of the coffee grounds according to process 1. When 1 kg of coffee grounds is treated by process 1, the centrifugation step takes about 8 hours, and the separation of the coffee grounds is difficult, which is not suitable for large-scale production. In order to reduce the difficulty of production and improve production efficiency, the present invention optimizes the coffee grounds treatment process by adding a flocculant to the coffee grounds treatment process 2 on the basis of process 1. Coffee grounds treatment process 2 The coffee grounds are treated by process 2, as shown in the following table. Table 3 Coffee grounds treatment process 2 As can be seen from the table above, the total processing time for Process 2 was approximately 109 hours, and the coffee grounds yield was approximately 65%. The flocculant used in Process 2 is an organic flocculant, which primarily acts by "bridging" two or more dispersed phase particles, aggregating them to form a flocculent precipitate. A significant sedimentation effect was observed immediately after the flocculant was added to the slurry, with distinct stratification occurring after 4 hours and a clear supernatant after 24 hours, as shown in Figure 6. After the addition of the flocculant for sedimentation, the centrifugation step required only about half an hour to process 1 kg of coffee grounds, significantly reducing the difficulty of coffee grounds processing and reducing the total processing time to approximately 109 hours. Furthermore, the coffee grounds yield increased from 48% to 65%. A comparison of Figures 3B and 3C shows that the addition of a flocculant or not did not significantly affect the color of the treated coffee grounds. In Example 1, the flocculants used can be either inorganic or organic. Commonly used inorganic flocculants include aluminum salts, iron salts, calcium chloride, potassium aluminum sulfate (Aluminum Sulfate), aluminum chloride, ferric sulfate, ferric chloride, polyaluminum chloride, polyaluminum sulfate, activated silica, or combinations thereof. Commonly used organic flocculants include starch, protein, gelatin, sodium alginate, sodium methyl cellulose, polyacrylamide, sodium polyacrylate, polyvinylpyrrolidone, polyethyleneimine, or combinations thereof. Experimental results indicate that the total flocculant concentration in the coffee grounds slurry is recommended to be controlled between 0.01% and 1%. Coffee grounds treated according to Process 2 were then prepared into coffee waste-polymer composites and injection molded. The specimens were then subjected to water boiling tests and high-temperature oil release tests. The test results are shown in Figures 4C and 5C. Figure 4C shows that compared to Process 1, the coffee waste-polymer composites treated in Process 2 exhibited relatively little color change before and after the water boiling test. As shown in Figure 5C, after high-temperature treatment, the coffee waste-polymer composites prepared in Process 1 exhibited no oil leakage. In summary, Process 2 simplifies the coffee grounds treatment process to a certain extent, and the treatment effect is superior to that of Process 1. Considering that the processing time of process 2 is about 109 hours, the production cycle is long and the time cost is relatively high. In order to improve production efficiency and reduce production costs, the present invention intends to optimize the coffee grounds processing time and shorten the alkali treatment and H2O2 treatment standing time. At the same time, in order to ensure the deoiling and decolorization effect of coffee grounds, the present invention optimizes the coffee grounds processing process by adding a water washing step on the basis of process 2. Coffee grounds processing process 3 The coffee grounds are processed by processing process 3, as shown in the following table. Table 4 Coffee grounds processing process 3 Compared to Process 2, Process 3 reduced the total coffee grounds processing time from 109 hours to 82 hours, while the coffee grounds yield decreased from 65% to 47.6%. Compared to Process 3, Process 2 produced a darker color of the coffee grounds after treatment (see Figures 3C and 3D for comparison). This is primarily due to the shortened H₂O₂ treatment time and incomplete H₂O₂ reaction in Process 2. Experimental results indicate that during the water washing process, the solid-liquid ratio can be adjusted from 1:3 to 1:20, the stirring time can be adjusted between 10 minutes and 4 hours, and the resting time can be adjusted between 4 hours and 24 hours. Coffee waste-polymer composites prepared from coffee grounds treated according to Process 3 were then injection molded. The specimens were then subjected to water boiling tests and high-temperature oil release tests. The test results are shown in Figures 4D and 5D. Figure 4D shows that the color change before and after the water boiling test is relatively small in Process 3. As shown in Figure 5D, there was no significant change in the composite material sample after the high-temperature oil-out test. In summary, the processing time of process 3 is significantly shortened compared to process 2, but the decolorization effect has not changed significantly. Therefore, in order to improve the decolorization effect of coffee grounds, the present invention optimizes the addition method of H2O2 in the H2O2 treatment process on the basis of process 3 to increase the reaction activity of H2O2, while reducing the ineffective decomposition of H2O2 and improving the bleaching effect of H2O2. To this end, the present invention has formulated coffee grounds treatment process 4. Coffee grounds treatment process 4 The coffee grounds are treated by treatment process 4, as shown in the following table. Different from the previous process, considering that the solution is always alkaline during the optimized H2O2 treatment process, in order to optimize the coffee grounds treatment time, the coffee grounds alkali treatment process is removed in process 4, that is, the sodium hydroxide treatment in Table 2-4. Table 5 Coffee grounds treatment process 4

[0022] In coffee grounds processing process 4, during the H2O2 treatment process, H2O2 is added to the mixed solution in three separate batches. To ensure high reactivity, the pH of the solution is adjusted every 10 minutes (controlled between 8 and 10). Furthermore, to ensure effective deoiling and decolorization of the coffee grounds, further reduce the residual H2O2 content in the coffee grounds before drying, and eliminate potential risks during the drying process, a second water washing step is added to the coffee grounds processing process. Experimental results indicate that the recommended solid-to-liquid ratio for each water washing step is 1:3-1:20, the stirring time can be adjusted between 10 minutes and 4 hours depending on actual needs, and the resting time can be adjusted between 4 and 24 hours depending on actual needs. Furthermore, according to actual industrial production practices, the high oil content in untreated coffee grounds can easily lead to agglomeration during the pulverization process, making it difficult to pulverize. Therefore, the pulverization step before coffee grounds processing can be selectively eliminated to meet practical needs. Compared to Process 3, Process 4 slightly reduces the coffee grounds treatment time from 82 hours to 78 hours. The coffee grounds yield is essentially the same, around 50%. Compared to Process 4, Process 3 shows a significant improvement in coffee grounds color after treatment, as shown in Figures 3D and 3E. This is primarily due to the optimization of the H2O2 treatment process and the increased number of water washes. H2O2 generally has poor reactivity in acidic environments, but is more reactive in alkaline environments, resulting in better bleaching results. Process 3 does not adjust the solution pH. As the reaction proceeds, the solution pH decreases, and the H2O2 activity also decreases, resulting in poorer coffee grounds decolorization compared to Process 4. Increasing the number of water washes also helps further remove water-soluble colorants from the coffee grounds. Coffee grounds treated according to Process 4 were prepared into coffee waste-polymer composites and then injection molded. The specimens were then subjected to water boiling and high-temperature oil release tests. The test results are shown in Figures 4E and 5E. As shown in Figure 4E, the color change before and after the water boiling test in Process 4 was relatively small. As shown in Figure 5E, the composite material sample showed no significant change after the high-temperature oil removal test. In summary, Process 4 slightly shortens the processing time compared to Process 3, while significantly improving the decolorization of coffee grounds. To save production costs and achieve industrialized coffee grounds processing, the present invention proposes to further shorten the coffee grounds processing time by reducing the time required for H2O2 treatment, flocculation, and water washing. Furthermore, to ensure effective deoiling and decolorization during coffee grounds processing, the present application proposes to further optimize the process. Based on Process 4, the present application proposes to adjust the pH adjustment interval from 10 minutes to 5 minutes, thus developing Coffee Grounds Process 5.Coffee grounds treatment process 5 Coffee grounds are treated by treatment process 5 as shown in the following table. Table 6 Coffee grounds treatment process 5. In coffee grounds treatment process 5, during the H2O2 treatment process, 2% HCl was similarly added to the mixed solution in three separate additions. To ensure H2O2 reactivity, the pH of the solution was adjusted every 5 minutes (controlled between 8 and 10). Preferably, the interval between pH adjustments can be adjusted based on actual conditions. More preferably, industrial operations can utilize real-time instrumentation to maintain the pH within a stable range, such as pH 10, to provide the necessary alkaline environment. Compared to process 4, process 5 significantly reduces the coffee grounds treatment time from 78 hours to 22 hours, significantly improving production efficiency and further reducing production costs. Furthermore, the coffee grounds yield is essentially equivalent, both around 50%. The colors of coffee grounds treated in process 4 and process 5 are shown in Figures 3E and 3F. The color of the coffee grounds treated in process 5 is further lighter. Coffee waste-polymer composites prepared from the coffee grounds treated in process 5 were then injection molded. The specimens were then subjected to water boiling tests and high-temperature oil release tests. The test results are shown in Figures 4F and 5F. As shown in Figure 4F, the color change before and after the water boiling test in Process 5 was relatively small, and no significant change was observed in the composite material sample after the high-temperature oil extraction test, as shown in Figure 5F. To further confirm the differences between the coffee grounds treated by the two processes, thermogravimetric analysis (TGA) was performed on the two coffee grounds. As shown in Figure 7A, there was no significant difference in the TGA results between the two processes. To further save production costs, reduce wastewater generation during coffee grounds treatment, and improve the industrial production efficiency of coffee grounds treatment, the present invention further optimizes the coffee grounds treatment process based on Process 5. The solid-to-liquid ratio during the treatment process reduces raw material usage. Furthermore, to improve the industrial production efficiency of coffee grounds treatment, the coffee grounds treatment time was further shortened during the H2O2 treatment and water washing processes. Examples 3-5: Based on Coffee Grounds Treatment Process 5, Examples 3, 4, and 5 were prepared. The difference between Examples 3-5 lies in the H2O2 treatment. For ease of description, the following content only focuses on the H2O2 treatment, its total treatment time, and yield in Examples 3-5. In Example 3, a stirred tank was used to add 1 kg of a 30%-50% H2O2 solution and 7-9 kg of water to every 1 kg of coffee grounds in three separate additions. The mixture was stirred at 700 rpm for 5 hours (the pH of the mixed solution was adjusted to 8-10 with sodium hydroxide solution every 5 minutes). Total treatment time: 22 hours. In Example 4, a stirred tank was used to add 1 kg of a 30-50% H2O2 solution and 2-4 kg of water to every 1 kg of coffee grounds in three separate additions. The mixture was stirred at 700 rpm for 5 hours (the pH of the mixed solution was adjusted to 8-10 with sodium hydroxide solution every 5 minutes).Total treatment time: 19 hours. In Example 5, a stirred tank was used to add 0.3-0.5 kg of H₂O₂ solution and 2.5-4.5 kg of water to every 1 kg of coffee grounds in three separate additions. The mixture was stirred at 700 rpm for 5 hours (the pH of the mixed solution was adjusted to 8-10 with NaOH solution every 5 minutes). Total treatment time: 19 hours. Compared to Example 3, Examples 4 and 5 slightly reduced the coffee grounds treatment time from 22 hours to 19 hours. Furthermore, the solid-to-liquid ratio during the H₂O₂ treatment was reduced from 1:10 to 1:5. This also further reduced wastewater generation and production costs. Furthermore, the coffee grounds yield was essentially the same, at approximately 50%. The color of the coffee grounds after treatment in Examples 3-5 is shown in Figure 3G. Compared to Example 3, the color of the coffee grounds treated in Example 4 became lighter, while the color of the coffee grounds treated in Example 5 was slightly darker. This is likely related to the amount of H2O2 added and the concentration of HCl during the treatment. To further confirm the differences between the coffee grounds treated by the two processes, TGA analysis was performed on the coffee grounds from Examples 3-5 (see Figure 7B). The results showed that the thermal stability of Examples 4 and 5 decreased compared to Example 3, which is likely related to the amount and concentration of HCl used during the coffee grounds treatment. As the amount and concentration of HCl increased, the degree of oxidation of various components in the coffee grounds increased, and the thermal stability of the coffee grounds decreased accordingly. As shown in Figures 4G-4H, similar to Example 3, the color of the composite materials of Examples 4 and 5 did not change significantly before and after the water boiling test. As shown in Figure 5G, the composite materials did not show any significant changes after the high-temperature oil extraction test. Composite material performance testing: Coffee grounds and coffee husks, treated with various processes, were first dried in a 105°C oven for 2 hours. The dried coffee grounds and husks were then weighed and mixed with PP, MAPP, and antioxidants according to the experimental formula in Table 7. The mixture was then melt-mixed in a twin-screw extruder operating at a feed frequency of 20 Hz and a main engine speed of 20 Hz. The mixture was then water-cooled and pelletized to produce coffee waste-polymer composite particles. Table 7: Experimental formulation of coffee waste-polymer composite materials. The particles were added to a plastic molding machine and injection molded into standard specimens. The mechanical properties of the composite materials of coffee grounds treated with different processes are shown in Table 8. Table 8 Mechanical properties of coffee waste polymer composites As can be seen from the table above, the four materials exhibited comparable tensile strength, flexural modulus, and impact resistance. Compared to the other processes, Example 5 required a shorter treatment time of only 19 hours for coffee grounds. The treated coffee grounds exhibited higher thermal stability and lower processing costs. Although the coffee grounds obtained from Example 5 were darker in color than those from Examples 4 and 5, the visual difference in color between the resulting composites was not noticeable. Furthermore, the composites showed no abnormalities in the boiling and high-temperature oil extraction tests. Taking all factors into consideration, Example 5 represents a relatively superior coffee grounds treatment process. Table 8 shows that the physical properties of the coffee waste polymer composite #3C meet the mechanical performance requirements for composites in terms of tensile strength and flexural modulus, with slightly higher values. However, its impact resistance is relatively poor. Therefore, the addition of a toughening agent could be used to optimize the properties of the coffee waste polymer composite to meet the mechanical performance requirements. First, the coffee grounds and coffee shells treated in Example 5 were dried in an oven at 105°C for 2 hours. The dried coffee grounds and coffee shells were then weighed and mixed evenly with PP, POE, MAPP, antioxidants, etc. according to the experimental formula in Table 9. The mixture was then added to a twin-screw extruder with a feeding frequency of 20 Hz and a main engine speed of 20 Hz for melt mixing. Coffee ground PP composite particles were prepared through water cooling, pelletizing, and other processes. The particles were then added to an injection molding machine and injection molded into standard specimens. The mechanical properties of the prepared coffee ground PP composite are shown in Table 10. Table 9 Experimental formula of coffee waste polymer composite materials The particles were added to an injection molding machine and injection molded into standard specimens. The mechanical properties of the prepared coffee waste polymer composites are shown in Table 10. Table 10 Mechanical properties of coffee waste polymer composites As shown in the table above, the optimized coffee grounds-PP composites exhibited a slight decrease in tensile strength and flexural modulus, but both met the mechanical performance requirements of the composites. Furthermore, the impact strength was significantly improved, rising from 2.7 kJ / m² to 3.5 kJ / m². In summary, the optimized coffee grounds-PP composites all met the mechanical performance requirements of the composites. Preparation of Composites Using Coffee Grounds from Different Sources: Due to the varying composition or origin of coffee grounds from different batches, the color of the treated coffee grounds may vary somewhat between batches. To confirm the impact of different coffee ground colors on the composite color and ensure the stability of the production process, the present invention proposes to treat coffee grounds from three different sources—Brands B, C, and D—according to Process 4 and compare them with coffee grounds from Brand A. The untreated and treated coffee grounds from the four sources are shown in Figures 8 and 9. As shown in Figures 8 and 9, the colors of the four different sources of coffee grounds differ significantly after treatment. The treated coffee grounds from Brands A and B exhibit a relatively darker color, while the colors of Brands C and D are relatively lighter. This is related to the variety, components and grinding process of coffee beans. First, the processed coffee grounds and coffee shells from different sources are dried in an oven at 105°C for 2 hours, and then the dried coffee grounds, coffee shells, PP, MAPP, antioxidants, etc. are weighed according to the experimental formula in Table 11 and mixed evenly. The mixture is then added to a twin-screw extruder with a feeding frequency of 20Hz and a main engine speed of 20Hz for melt mixing, and is prepared into coffee waste polymer composite particles through processes such as water cooling and pelletizing. The particles are then added to an injection molding machine and injection molded into standard splines. The prepared coffee waste polymer composite pellets and splines are shown in Figures 10 and 11, respectively. Table 11 Experimental formula of coffee waste polymer composite materials As can be seen from Figure 10, the coffee waste polymer composite pellets from different sources have slight visual differences, which are consistent with the color depth of the processed coffee grounds. The colors of the composite materials No. 2# and No. 6# are relatively dark, and the colors of the composite materials No. 7# and No. 8# are relatively light, while the colors of the splines are basically similar visually. The coffee waste polymer composite splines from different sources were placed in a colorimeter for testing. The color data of the coffee waste polymer composites from different sources are shown in Table 12. Table 12 Color data of coffee waste polymer composites Note: L represents black and white, with 0 representing black and 100 representing white; a represents red and green, with positive values ​​representing red and negative values ​​representing green; b represents yellow and blue, with positive values ​​representing yellow and negative values ​​representing blue. The composite color data in the table above show that, consistent with visual observation, there is no significant color difference between the coffee waste-polymer composites from different sources. Preparation of Light-Colored Coffee Grounds Composites: Based on the present invention's need for preparing light-colored coffee waste-polymer composites, this paper proposes adding a certain amount of titanium dioxide (TiO2) to coffee waste-polymer composites from different sources to further determine the effect of different coffee grounds treatment on the color of the light-colored composites. First, coffee grounds and coffee husks from different sources, treated according to process 4 in Table 5, were dried in a 105°C oven for 2 hours. The dried coffee grounds, coffee husks, polypropylene, MAPP, and antioxidants were then mixed according to the formulation in Table 12, with a TiO2 weight ratio of approximately 1-3%. The mixed material was then added to a twin-screw extruder with a feeding frequency of 20 Hz and a main engine speed of 20 Hz for melt mixing, and was prepared into coffee grounds PP composite particles through water cooling, pelletizing and other processes. The particles were then added to an injection molding machine for injection molding into standard splines. The prepared coffee waste polymer composite pellets and splines are shown in Figures 12 and 13. As can be seen from Figure 12, there are slight differences in the size and size of the coffee waste polymer composite pellets and sample items from different sources. Also consistent with the color depth of the processed coffee grounds, the composite materials No. 9# and No. 10# are relatively dark in color, and the composite materials No. 11# and No. 12# are relatively light in color. The coffee waste polymer composite splines from different sources were placed in a colorimeter for testing, and the color data of the coffee waste polymer composites from different sources are shown in Table 13. Table 13 Color data of coffee waste polymer composites Note: L represents black and white, with 0 representing black and 100 representing white; a represents red and green, with positive values ​​representing red and negative values ​​representing green; b represents yellow and blue, with positive values ​​representing yellow and negative values ​​representing blue. The composite color data in the table above show that the addition of TiO2 to coffee waste-polymer composites from different sources significantly lightens the color, and the color differences between the composites also increase. It is recommended that color consistency of composites be adjusted using a color powder solution when using coffee grounds processed from different batches. Through the above examples, the present invention discloses optimized coffee hull and coffee ground processing processes, the conditions involved, and their physical properties. The alkaline treatment of the present invention not only converts cellulose I in plant fibers into cellulose II but also removes hemicellulose. Furthermore, H2O2 reacts with OH- in an alkaline environment to produce H2O and OOH-, with OOH- having a bleaching effect. As can be seen from the above examples, the alkaline treatment of the present invention can be used with different brands of coffee grounds. The present invention also discloses a process for preparing coffee waste-polymer composites, the conditions involved, and their physical properties. The present invention also discloses a color powder solution that can be used to adjust the color consistency of the composites. However, those skilled in the art will understand that the examples disclosed herein are intended only to illustrate the present invention and are not to be construed as limiting. For example, the compounds used herein, starting material concentrations, stirring speed and temperature during mixing, and centrifugation speed can be adjusted to actual operational conditions. In particular, the amount of compound added during the process varies depending on its starting material concentration. Therefore, the amounts and concentrations of the compounds in the examples disclosed herein are provided for illustrative purposes only. Those skilled in the art will understand that the relative weight ratios and solid-to-liquid ratios of the compounds disclosed herein are the key elements of the present invention. For example, the sodium hydroxide used in this specification can be replaced with a variety of alkaline compounds, such as potassium hydroxide and calcium hydroxide. Although the sodium hydroxide solution used in this specification is mixed at a 1% ratio with water, those skilled in the art will appreciate that the mixing ratio can range from 1% to 50%, or even higher, up to a saturated solution. In the examples herein, the raw material preparation and drying processes are performed in an oven at 105°C. However, depending on the actual situation, the oven temperature can be adjusted to a different setting, such as 80-120°C. Preferably, the moisture content of the dried coffee grounds is controlled to less than 2%. In the embodiment of this specification, the coffee hulls are boiled in water, and the process involves adding 5 kg of water to every 1 kg of coffee grounds, heating to 80-90°C, and stirring at 500 rpm for 2 hours. However, depending on the actual situation, the weight ratio of coffee grounds to water can be between 1:3 and 1:20, and the temperature can be between 70-100°C.Those skilled in the art should understand that the rotational speeds in the embodiments are merely examples and should not be construed as limiting the present invention; and the centrifugation process in the embodiments of this specification can be replaced by filter press depending on actual circumstances. Any numerical value within the numerical range disclosed in the present invention can be used as the end value of another numerical range, and any numerical value within the numerical range can be used to implement the present invention, and it should not be understood that the implementation of the present invention is limited to the numerical range disclosed herein. Although the present invention has been described in conjunction with specific embodiments of the present invention, based on the foregoing description, many replacements, modifications, and variations of these embodiments will be obvious to those of ordinary skill in the art. The embodiments of the present invention are intended to cover all such replacements, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiments of the present invention should be included in the scope of protection of the present invention.

Claims

Claims 1. A method for treating coffee waste, the method comprising the steps of treating coffee grounds: (i) mixing coffee grounds with hydrogen peroxide under alkaline conditions to form a first mixture; (ii) Processed coffee grounds are obtained through a separation process.

2. The method according to claim 1, characterized in that In step (1), the alkaline condition is a pH value of 8-10.

3. The method according to claim 1, characterized in that In the mixing of step (1), the weight ratio of the coffee grounds to hydrogen peroxide is 1:0.125 to 1:

3.

4. The method according to claim 1, characterized in that Before step (1), the coffee grounds are mixed with an alkaline solution.

5. The method according to claim 4, characterized in that The alkaline solution is a mixture of an alkaline material and water, wherein the alkaline material can be selected from sodium hydroxide, potassium hydroxide, calcium hydroxide or a combination thereof.

6. The method according to claim 1, characterized in that The alkaline condition is to maintain the pH value at 8-10 by adding alkaline solution.

7. The method according to claim 6, characterized in that The alkaline solution is a mixture of an alkaline material and water, wherein the alkaline material can be selected from sodium hydroxide, potassium hydroxide, calcium hydroxide or a combination thereof.

8. The method according to claim 6, wherein the alkaline solution is a mixture of an alkaline material and water, and the alkaline material can be selected from sodium hydroxide, potassium hydroxide, calcium hydroxide or a combination thereof.

9. The method according to claim 1, characterized in that: In step (1), the concentration of hydrogen peroxide during the mixing process is maintained at a weight ratio of 3% to 15%.

10. The method according to claim 6, characterized in that In step (1), the concentration of hydrogen peroxide during the mixing process is maintained at a weight ratio of 3% to 15%. H. The method according to claim 1, characterized in that In the mixing of step (1), the weight ratio of the coffee grounds to hydrogen peroxide is 1:0.125 to 1:

5. 23 12. The method according to claim 1, characterized in that Step (1) comprises the following steps: (a) mixing the coffee grounds with water to form a stirring liquid, wherein the weight ratio of the coffee grounds to water is 1: X ； (b) adding the hydrogen peroxide to the stirring liquid at least once and mixing them into the first mixture, wherein the weight ratio of the hydrogen peroxide to the stirring liquid in the first mixture is 1:Y; (c) during the mixing in step (b), maintaining the alkaline condition by adding an alkaline solution.

13. The method according to claim 12, characterized in that In step (a), the weight ratio of the coffee grounds to water is 1:3 to 1:10; in step (b), the hydrogen peroxide is added to the stirring liquid in three portions and mixed into the first mixture, in which the weight ratio of the hydrogen peroxide to the stirring liquid is 1:4 to 1:22, and during the mixing, the alkaline condition is maintained at a pH value of 8-10 by adding the alkaline solution.

14. The method according to claim 12, characterized in that In step (a), the weight ratio of the coffee grounds to water is 1:3 to 1:10; in step (b), the hydrogen peroxide is added to the stirring liquid three times and mixed into the first mixture, in which the weight ratio of the hydrogen peroxide to the stirring liquid is 1:10, and during the mixing, the alkaline condition is maintained at a pH value of 8-9 by adding the alkaline solution.

15. The method according to claim 12, characterized in that In step (a), the weight ratio of the coffee grounds to water is 1:3 to 1:10; in step (b), the hydrogen peroxide is added to the stirring liquid in three portions and mixed into the first mixture, in which the weight ratio of the hydrogen peroxide to the stirring liquid is 1:5 to 1:10, and during the mixing, the alkaline condition is maintained at a pH value of 8-10 by adding the alkaline solution.

16. The method according to claim 12, characterized in that In step (a), the weight ratio of the coffee grounds to water is 1:3 to 1:10; in step (b), the hydrogen peroxide is added to the stirring liquid in three portions and mixed into the first mixture, in which the weight ratio of the hydrogen peroxide to the stirring liquid is 1:5; during the mixing, the alkaline condition is maintained at a pH value of 8-9 by adding the alkaline solution.

17. The method according to claim 1, wherein: Before step (ii), a flocculant solution is mixed with the first mixture to form a second mixture.

18. The method according to any one of claims 1 to 16, wherein: Before step (ii), a flocculant solution is mixed with the first mixture to form a second mixture.

19. The method according to claim 17, wherein: The concentration of the flocculant in the flocculant solution is 0.05-3% by weight.

20. The method according to claim 18, wherein: The concentration of the flocculant in the flocculant solution is 0.05-3% by weight.

21. The method according to claim 19 or 20, wherein: The concentration of the flocculant in the first mixture is 0.01-1% by weight.

22. The method according to claim 21, wherein: The flocculant solution is selected from organic flocculants, in particular starch, protein, animal glue, sodium alginate, sodium methyl cellulose, polyacrylamide, sodium polyacrylate, polyethylene imine, or a combination thereof.

23. The method according to claim 21 or 22, wherein: The flocculant solution is selected from inorganic flocculants, in particular aluminum salts, iron salts, calcium chloride, potassium aluminum sulfate, aluminum chloride, iron sulfate, iron chloride, polyaluminum chloride, polyaluminum sulfate, activated silica, or a combination thereof.

24. The method according to claim 17, wherein: After forming the second mixture, the supernatant of the second mixture is removed; water is added, at least once, to the second mixture from which the supernatant has been removed and mixed, wherein the weight ratio of the added water to the coffee grounds is 3:1 - 20:

1.

25. The method according to claim 24, wherein: After forming the second mixture, the supernatant of the second mixture is removed; water is added, at least once, to the second mixture from which the supernatant has been removed and mixed, wherein the weight ratio of the added water to the coffee grounds is 5:1 to 3:

1.

26. The method according to claim 18, wherein: After forming the second mixture, the supernatant of the second mixture is removed; water is added, at least once, to the second mixture from which the supernatant has been removed and mixed, wherein the weight ratio of the added water to the coffee grounds is 3:1 - 20:

1.

27. The method according to claim 13, wherein: Before step (ii), the method further includes the following steps: mixing the flocculant solution with the first mixture to form a second mixture; after the second mixture is formed, removing the supernatant of the second mixture; adding, at least once, water to the second mixture from which the supernatant has been removed and mixing, wherein the weight ratio of the added water to the coffee grounds is 5:1 to 3:1; and waiting for 4-24 hours.

28. The method according to claim 14, 15 or 16, wherein: Before step (ii), the method further comprises the following steps: mixing the flocculant solution with the first mixture to form a second mixture; forming the second After the mixture is added, the supernatant of the second mixture is removed; and water is added, at least once, to the second mixture from which the supernatant is removed and mixed, wherein the weight ratio of the added water to the coffee grounds is 5: 1 to 3:1; wait for 1 hour.

29. The method according to claim 1 or 17 or 24, characterized in that The method further comprises the step of treating the coffee husks: (a) mixing coffee husks with water in a weight ratio of 1:3 to 1:20 under heating; (b) Treated coffee husks obtained through a separation process.

30. The method according to claim 29, characterized in that The coffee shells and water are mixed under heating at a weight ratio of 1:5 to 1:

10.

31. The method according to claim 30, characterized in that In step (a) of claim 29, the coffee husks are mixed with water at 70-100° CT for 2 hours.

32. The method according to claim 31, characterized in that The coffee shells are mixed with water at 80-90°C for 2 hours; the supernatant is removed; the obtained coffee shells are mixed with water at 80-90°C for 2 hours, wherein the weight ratio of the coffee shells to water is 1:3 to 1:

5.

33. A coffee waste polymer composite comprising coffee grounds treated according to the method of any one of claims 1 to 28 and / or comprising coffee husks treated according to the method of any one of claims 29 to 32.

34. The composite material according to claim 33, characterized in that The polymer is polypropylene.

35. The composite material according to claim 33, characterized in that The composite material includes: polypropylene, polyolefin elastomer, the coffee grounds, and the coffee shell.

36. The composite material according to claim 35, characterized in that The composite material further comprises a toughening agent and / or an antioxidant.

37. The composite material according to claim 35 or 36, characterized in that The polyolefin elastomer is maleic acid grafted polypropylene.

38. The composite material according to claim 35 or 36, characterized in that The composite material further comprises titanium dioxide. 26 39. A method of making a coffee waste polymer composite material comprising the following steps: (i) treating coffee grounds according to the method according to any one of claims 1 to 28; (ii) treating coffee husks according to the method of any one of claims 29 to 32; (iii) mixing the coffee grounds, the coffee grounds with polypropylene and polyolefin elastomer to form a mixed material; and (iv) adding the mixed material to a feeder to form the coffee waste polymer composite material.

40. The method according to claim 39, wherein in step (iii) of claim 39, a toughening agent and / or an antioxidant and / or titanium dioxide are further added to form the mixed material.

41. The method according to claim 39 or 40, characterized in that The polyolefin elastomer is maleic acid grafted polypropylene. 27

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