A bifunctional chestnut shell spherical biochar loaded with carbon quantum dots and its preparation method and application

Abstract

The present invention discloses a carbon quantum dot-loaded bifunctional chestnut shell spherical biochar, as well as its preparation method and application. The method belongs to the field of indoor air purification technology. The method comprises the following steps: washing discarded chestnut shells with deionized water, drying, and grinding into powder; then adding a 70% ethanol solution, soaking, filtering out the solution, and lyophilizing into powder after rotary evaporation; taking the chestnut shell extract powder alone or in a mixture with amino acids in deionized water, ultrasonicating, and then heating for reaction; separating the reaction product to obtain a solid, rinsing it with deionized water, and drying it to prepare the carbon quantum dot-loaded bifunctional chestnut shell spherical biochar. The carbon quantum dot-loaded bifunctional chestnut shell spherical biochar described in the present invention is a biochar formaldehyde removal material that can effectively remove formaldehyde. It has broad application prospects.

Description

Technical Field

[0001] The present invention belongs to the technical field of indoor air purification, and in particular relates to a bifunctional chestnut shell spherical biochar loaded with carbon quantum dots, and a preparation method and application thereof. Background Art

[0002] With the acceleration of urbanization, the quality of indoor living environments is receiving increasing attention. Formaldehyde is a crucial synthetic material in the modern chemical industry. Its high water solubility and strong reducing properties make it widely used in the preparation of materials such as phenolic resins. However, most indoor furniture and decorative materials use adhesives containing formaldehyde, which releases free formaldehyde over time, posing a significant threat to human health. Therefore, the efficient and environmentally friendly removal of indoor formaldehyde has become a hot topic.

[0003] Currently, common household formaldehyde removal methods include activated carbon adsorption, chlorine dioxide chemical oxidation, and photocatalysis. Considering that the chlorine dioxide produced by chemical oxidation may be harmful to the human body, and photocatalysis is not effective in removing formaldehyde indoors due to the limitation of light intensity, the adsorption method has the advantages of high cost performance, being green and non-toxic, and having little impact on the environment. However, common activated carbon mainly uses physical adsorption, and has the disadvantage of being easily desorbed and causing secondary pollution. Therefore, it is particularly important to prepare an adsorption material with low cost, large adsorption capacity, and not easy to desorb. At the same time, accurate detection of formaldehyde is of great significance for identifying environmental pollution, but traditional formaldehyde detection methods such as colorimetric method and chromatography are time-consuming and labor-intensive, and it is difficult to quickly and accurately detect formaldehyde concentration. Therefore, materials that can quickly remove formaldehyde and detect formaldehyde concentration in real time are urgently needed.

[0004] Carbon quantum dots (CQDs), a new member of the carbon nanomaterial family, are discrete, quasi-spherical carbon nanoparticles with a particle size less than 10 nm. Since their discovery in 2004, they have become a rising star in zero-dimensional carbon nanomaterials due to their high solubility, low toxicity, excellent biocompatibility, and controllable fluorescence. This invention in situ grows CQDs on the surface of biochar, enabling rapid fluorescence detection of formaldehyde and creating a highly efficient adsorption material for formaldehyde. Summary of the Invention

[0005] To overcome the shortcomings of the above-mentioned existing technologies and realize the green development concept of "using waste to treat waste" and resource recycling, the present invention uses waste biomass materials to prepare carbon quantum dots. The carbon quantum dot-loaded biochar generated during the preparation of nitrogen-doped carbon quantum dots is used to efficiently adsorb and fix formaldehyde in the air. At the same time, because the loaded carbon quantum dots also have the function of fluorescent formaldehyde detection, this dual-functional material has the advantages of low cost, good formaldehyde removal effect, and environmental protection.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] The present invention provides a carbon quantum dot-loaded bifunctional chestnut shell spherical biochar. The carbon quantum dot-loaded bifunctional chestnut shell spherical biochar is a spherical structure prepared from natural materials and has the dual functions of rapidly detecting formaldehyde concentration and removing formaldehyde.

[0008] The present invention also provides a method for preparing bifunctional chestnut shell spherical biochar loaded with carbon quantum dots, the method comprising the following steps:

[0009] (1) The discarded chestnut shells were washed with deionized water, dried and ground into powder, and then added with 70% ethanol solution. After soaking, the solution was filtered out, and then lyophilized to obtain chestnut shell extract powder after rotary evaporation.

[0010] (2) The chestnut shell extract powder alone or in a mixture with amino acids is placed in deionized water, subjected to ultrasound, and then heated to react to obtain a reaction product; the solid obtained by separating the reaction product is rinsed with deionized water and then dried to prepare a bifunctional chestnut shell spherical biochar loaded with carbon quantum dots.

[0011] In the step (1), there is no special limitation on the type of the discarded chestnut shells.

[0012] In the step (1), the soaking time is 12-36 hours; preferably, 24 hours.

[0013] In the step (2), the amino acid is one or more of L-lysine, L-phenylalanine, etc.; preferably, it is a mixture of L-lysine and L-phenylalanine.

[0014] Wherein, the mass ratio of L-lysine to L-phenylalanine is 1:1.

[0015] In the step (2), the mass ratio of the chestnut shell extract powder to deionized water is (1-4):50; preferably, 2:50.

[0016] In the step (2), the ultrasound is preferably placed in a polytetrafluoroethylene liner for ultrasound.

[0017] In the step (2), the ultrasonication time is 5-10 minutes; preferably, 5 minutes.

[0018] In the step (2), the heating reaction time is 6-10 hours; preferably, 8 hours.

[0019] In the step (2), the temperature of the heating reaction is 160-200°C; preferably, 180°C.

[0020] The present invention also provides bifunctional chestnut shell spherical biochar loaded with carbon quantum dots prepared by the above method.

[0021] The bifunctional chestnut shell spherical biochar loaded with carbon quantum dots has a highly efficient ability to capture and fix formaldehyde. By adding amino acids as nitrogen-doped biochar, a large number of amino groups and other functional groups are loaded on the surface of the material, which can react with formaldehyde in the environment to produce a Schiff base reaction, thereby significantly improving the formaldehyde removal effect of biochar.

[0022] The carbon quantum dot-loaded bifunctional chestnut shell spherical biochar water dispersion solution has a fluorescence reaction due to the carbon quantum dots on its surface. When the surface groups of the carbon quantum dots react with formaldehyde to quench the fluorescence, fluorescence detection of formaldehyde in an aqueous solution is achieved.

[0023] Therefore, the chestnut shell biochar synthesized through a one-pot method, which contains carbon quantum dots with dual adsorption and detection functions, effectively adsorbs formaldehyde while also largely solving the problem of "secondary pollution" caused by the rapid desorption of formaldehyde after adsorption by the carbon material through chemical adsorption. Furthermore, the loading of carbon quantum dots enables fluorescent detection of formaldehyde, expanding the application range of this material.

[0024] The present invention also provides the use of the carbon quantum dot-loaded biochar in removing formaldehyde and detecting formaldehyde in aqueous solution.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The present invention discloses a method for preparing biochar loaded with carbon quantum dots. First, a discarded chestnut shell extract is prepared. The extract is then prepared into carbon quantum dots by a hydrothermal method. The carbon quantum dot solution and solid biochar are separated. After drying, a biochar adsorption material that efficiently adsorbs formaldehyde is formed. The material has a certain fluorescence that can detect formaldehyde. The material has excellent capture ability for formaldehyde and is not easy to desorb. At the same time, the material uses biomass as raw material from the beginning of the preparation of carbon quantum dots. Its source is widely distributed and renewable. In addition, the material is derived from biochar produced in the process of preparing carbon quantum dots, which conforms to the green development concept of resource recycling. It is simple to prepare and low in cost, and has great application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following is a brief introduction to the drawings required for use in the description of the embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0028] Figure 1 FTIR spectra of Example 2 and Comparative Example 3 of the present invention;

[0029] Figure 2The SEM images of Comparative Example 3 and Example 2 of the present invention are shown;

[0030] Figure 3 This is the fluorescence spectrum of Example 2 of the present invention;

[0031] Figure 4 The formaldehyde adsorption test results of Example 2, Comparative Example 1, Comparative Example 2 and Comparative Example 3 of the present invention are shown;

[0032] Figure 5 This is the formaldehyde adsorption cycle test of Example 2 of the present invention;

[0033] Figure 6 This is the formaldehyde adsorption cycle test of Comparative Example 3 of the present invention;

[0034] Figure 7 This is the static desorption test of Example 2 of the present invention and Comparative Example 3;

[0035] Figure 8 The fluorescence intensity changes of the aqueous solution of Example 2 of the present invention in formaldehyde solutions of different concentrations are shown. DETAILED DESCRIPTION

[0036] The present invention will be further described in detail with reference to the following specific examples and accompanying drawings. The processes, conditions, experimental methods, etc. for implementing the present invention, except for those specifically mentioned below, are common knowledge and common common sense in the art and are not particularly limited by the present invention.

[0037] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention, its application, or use. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are intended to fall within the scope of protection of the present invention.

[0038] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0039] The present invention discloses a carbon quantum dot-loaded bifunctional chestnut shell spherical biochar, as well as its preparation method and application. The method belongs to the field of indoor air purification technology. The method comprises the following steps: washing discarded chestnut shells with deionized water, drying, and grinding into powder; then adding a 70% ethanol solution, soaking, filtering out the solution, and lyophilizing into powder after rotary evaporation; taking the chestnut shell extract powder alone or in a mixture with amino acids in deionized water, ultrasonicating, and then heating for reaction; separating the reaction product to obtain a solid, rinsing it with deionized water, and drying it to prepare the carbon quantum dot-loaded bifunctional chestnut shell spherical biochar. The carbon quantum dot-loaded bifunctional chestnut shell spherical biochar described in the present invention is a biochar formaldehyde removal material that can effectively remove formaldehyde. It has broad application prospects.

[0040] The specific embodiments of the present invention are further described below. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other. The experimental methods in the following examples, unless otherwise specified, are all conventional methods, and the test materials used in the following examples, unless otherwise specified, can be purchased through conventional commercial channels.

[0041] Example 1:

[0042] The invention provides a method for preparing a waste chestnut shell extract, which is used for removing formaldehyde because the waste chestnut shell extract is rich in tannic acid.

[0043] Take 100g of discarded chestnut shells, wash them with deionized water and then dry them. Grind them into powder in a grinder and add 70% ethanol solution at a material-liquid ratio of 1:10. Soak them at room temperature for 24 hours, filter out the solution, evaporate and concentrate them using a rotary evaporator, and then freeze-dry them into powder.

[0044] Example 2:

[0045] The present invention provides a method for preparing carbon quantum dot-loaded biochar.

[0046] 2g of the freeze-dried powder of the discarded chestnut shell extract prepared in Example 1 of the present invention was added with 1g of L-lysine and 1g of L-phenylalanine, and dissolved in 50ml of deionized water. After sonication for 10 minutes, the mixture was transferred to a polytetrafluoroethylene-lined reactor and treated at 180°C for 8 hours. After cooling, the solution in the reactor was poured into a vacuum filtration tank to separate the black solid. The solid was then rinsed with deionized water and dried in an oven at 60°C for 24 hours to obtain carbon quantum dot-loaded biochar.

[0047] Comparative Example 1

[0048] This comparative example was carried out using similar steps to Example 2 of the present invention, except that 2 g of L-lysine was added separately into the formula.

[0049] Comparative Example 2

[0050] This comparative example was carried out using similar steps to Example 2 of the present invention, except that 2 g of L-phenylalanine was added to the formula.

[0051] Comparative Example 3

[0052] This comparative example was carried out using steps similar to those of Example 2 of the present invention, except that L-lysine and L-phenylalanine were not added to the formula.

[0053] Application Example 1

[0054] The following experiments demonstrate the formaldehyde removal effect of the carbon quantum dot-loaded biochar (hereinafter referred to as biochar) prepared by the present invention.

[0055] (1) Formaldehyde adsorption test:

[0056] According to QB / T2761-2006 standard, the biochar prepared in Example 2, Comparative Example 1, Comparative Example 2 and Comparative Example 3 of the present invention was placed in a 0.2m 3 The tests were conducted in a glass glove box. Each group had the same formaldehyde concentration, with an initial release of 60 µL of a 1.8% formaldehyde solution. Detection was performed using phenol reagent spectrophotometry. The test results are shown in Tables 1-1, 1-2, 1-3, and 1-4. Example 2 of the present invention, which showed the best adsorption effect, was selected and subsequently tested against Comparative Example 3, which did not contain amino acid doping.

[0057]

[0058]

[0059] (2) Formaldehyde adsorption cycle test:

[0060] According to QB / T2761-2006 standard, the biochar prepared in Example 2 and Comparative Example 3 of the present invention was placed in a 0.2m 3 The tests were conducted in a glass glove box. Each group had the same formaldehyde concentration. The initial formaldehyde release was 60µL of a 1.8% formaldehyde solution, which was released three times in a cycle. The detection method was phenol reagent spectrophotometry. The test results are shown in Tables 2-1 and 2-2.

[0061]

[0062]

[0063] (3) Static desorption test after adsorption:

[0064] The biochar prepared in Example 2 and Comparative Example 3 after saturation of formaldehyde adsorption was placed in a 0.2 m 3 The test was carried out in a glass glove box to detect the formaldehyde content within 48 hours. The detection method was a formaldehyde sensor. The test results are shown in Tables 3-1 and 3-2.

[0065]

[0066] Tables 1-1, 1-2, 1-3, and 1-4 show that the biochar prepared in Example 2 of the present invention has a high formaldehyde adsorption capacity at certain formaldehyde concentrations. Compared with Comparative Examples 1, 2, and 3, the addition of L-lysine to L-phenylalanine in a 1:1 ratio significantly increased the formaldehyde adsorption capacity of the biochar, reaching 1.455 mg / g within 48 hours. This is higher than the adsorption capacity of biochar doped with L-lysine or L-phenylalanine alone. Furthermore, the formaldehyde adsorption cycle test results in Tables 2-1 and 2-2 demonstrate that the biochar prepared in Example 2 of the present invention maintains a good formaldehyde removal effect over three adsorption cycles. Furthermore, the post-adsorption static desorption test results in Tables 3-1 and 3-2 show that the biochar prepared in Example 2 of the present invention desorbed very little formaldehyde within 48 hours, a decrease of 18.23% compared to the comparative examples. This demonstrates the feasibility of effective formaldehyde removal in practical applications.

[0067] Application Example 2

[0068] The following experiments demonstrate the fluorescence detection effect of formaldehyde by the carbon quantum dot-loaded biochar (hereinafter referred to as biochar) prepared by the present invention.

[0069] Take 3 mg of the biochar prepared in Example 2 of the present invention and disperse it in 30 ml of deionized water to form a fluorescence detection solution. Then take a 36% formaldehyde solution and prepare it into a 1~5 mg / L formaldehyde solution. Take 5 ml of formaldehyde solution of different concentrations and add 50 μL of the fluorescence detection solution. After standing at room temperature for 30 minutes, put it into a fluorescence spectrophotometer to record the fluorescence intensity corresponding to the formaldehyde standard solution of different concentrations. The ratio of the fluorescence intensity corresponding to the formaldehyde standard solution of different concentrations to the fluorescence intensity corresponding to the standard solution with a concentration of 0 is used as the vertical coordinate, and the concentration of different formaldehyde standard solutions is used as the horizontal coordinate. Draw a standard curve and solve the fitting equation. See the specific results for details. Figure 8 ,from Figure 8 It can be seen that when the formaldehyde concentration of the solution decreases, the fluorescence intensity of the biochar material is significantly enhanced. The fluorescence intensity ratio F0 / F is linearly related to the formaldehyde concentration. The linear regression equation is: F0 / F=0.105X 甲醛+ 0.9987 (R 2 = 0.9957). Therefore, the biochar material has the ability to be used in actual situations to detect formaldehyde.

[0070] Figure 1 It shows that the waste biochar (Example) has amine functional groups after nitrogen doping with amino acids.

[0071] Figure 2 Both are smooth spherical carbon particles; Figure 2 a is the image of the powder of Comparative Example 3 after magnification 1000 times; Figure 2 b is the image of the powder of Comparative Example 3 after magnification 10000 times; Figure 2 c is the image of the powder in comparative example 3 after magnification 30,000 times; Figure 2 d is the image of the powder of Example 2 after magnification 1000 times; Figure 2 e is the image of the powder of Example 2 after magnification 3000 times; Figure 2 f is an image of the powder from Example 2 at 50,000x magnification. Comparing the SEM images of Example 3 with those of Example 2 reveals that the waste biochar particles without amino acid addition are well-dispersed spherical particles, while the biochar particles doped with L-lysine and L-phenylalanine exhibit some agglomeration, with 2-3 particles stacked like grapes.

[0072] Figure 4 It shows that Example 2 has a better adsorption effect.

[0073] Figure 5 It shows that there is still good adsorption capacity after three formaldehyde release-adsorption cycles.

[0074] Figure 6 It shows that its adsorption capacity under three formaldehyde release-adsorption cycles is significantly lower than that of Example 2.

[0075] Figure 7 It can be seen that after adsorption saturation, the amount of formaldehyde desorbed by Example 2 is quite small, and is also significantly lower than that of Comparative Example 3.

[0076] The embodiments of the present invention are described in detail above, but the present invention is not limited to the described embodiments. It is apparent to those skilled in the art that various changes, modifications, substitutions, and variations of these embodiments may be made without departing from the principles and spirit of the present invention, and the changes still fall within the scope of protection of the present invention.

[0077] Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0078] As used in the present invention, the term "comprising" is an open expression, that is, including the contents specified in the present invention, but not excluding other aspects.

[0079] As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0080] Although the embodiments of the present disclosure have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and alterations may be made to the embodiments without departing from the principles and spirit of the present disclosure, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing bifunctional chestnut shell spherical biochar loaded with carbon quantum dots, characterized in that: The method comprises the following steps: (1) The discarded chestnut shells were washed with deionized water, dried and ground into powder, and then added with 70% ethanol solution. After soaking, the solution was filtered out, and then lyophilized to obtain chestnut shell extract powder after rotary evaporation; (2) taking a mixture of the chestnut shell extract powder and amino acids in deionized water, performing ultrasonication, and then heating the reaction to obtain a reaction product; the solid obtained by separating the reaction product was rinsed with deionized water and then dried to prepare a bifunctional chestnut shell spherical biochar loaded with carbon quantum dots; the amino acids were a mixture of L-lysine and L-phenylalanine in a mass ratio of 1:1; The dual-functional chestnut shell spherical biochar loaded with carbon quantum dots is a spherical structure prepared from natural materials and has the dual functions of rapidly detecting formaldehyde concentration and removing formaldehyde.

2. The preparation method according to claim 1, wherein In the step (1), the soaking time is 12-36 hours.

3. The preparation method according to claim 1, wherein In the step (2), the mass ratio of the chestnut shell extract powder to deionized water is (1-4):

50.

4. The preparation method according to claim 1, wherein In the step (2), the ultrasonication time is 5-10 minutes.

5. The preparation method according to claim 1, wherein In the step (2), the heating reaction time is 6-10 h; and / or the heating reaction temperature is 160-200 °C.

6. A bifunctional chestnut shell spherical biochar loaded with carbon quantum dots, characterized in that: The bifunctional chestnut shell spherical biochar loaded with carbon quantum dots is prepared by the method according to any one of claims 1 to 5.

7. Application of a bifunctional chestnut shell spherical biochar loaded with carbon quantum dots in formaldehyde removal and formaldehyde detection in aqueous solution, characterized in that: The bifunctional chestnut shell spherical biochar loaded with carbon quantum dots is the bifunctional chestnut shell spherical biochar as claimed in claim 6.

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