Difunctional chestnut shell spherical charcoal loaded with carbon quantum dots as well as preparation method and application thereof

Abstract

The invention discloses difunctional chestnut shell spherical biochar loaded with carbon quantum dots and a preparation method and application thereof, and belongs to the technical field of indoor air purification.The method comprises the following steps that waste chestnut shells are washed with deionized water and then dried and ground into powder, then a 70% ethanol solution is added, the solution is filtered out after soaking, and a carbon quantum dot solution is obtained; performing freeze-drying to obtain powder after rotary evaporation; putting the chestnut shell extract powder alone or a mixture of the chestnut shell extract powder and amino acid into deionized water, carrying out ultrasonic treatment, and then carrying out heating reaction; and separating the reaction product to obtain a solid, washing the solid with deionized water, and drying to prepare the carbon quantum dot loaded bifunctional chestnut shell spherical charcoal. The difunctional chestnut shell spherical biochar loaded with the carbon quantum dots is a biochar formaldehyde removal material and can effectively remove formaldehyde. Wide application prospects are realized.

Description

Technical Field

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

[0002] At present, with the acceleration of the urbanization process, the quality of the indoor living environment has attracted more and more attention. Formaldehyde is a very important synthetic material in modern chemical industry. It has good water solubility and strong reducibility, and is widely used in the preparation of materials such as phenolic resins. Most indoor furniture and decoration materials release free formaldehyde for a long time due to the use of adhesives containing formaldehyde, which poses a major threat to human health. Therefore, how to remove indoor formaldehyde greenly and efficiently has become the focus of people's attention.

[0003] Currently, common household formaldehyde removal methods include activated carbon adsorption, chlorine dioxide chemical oxidation, and photocatalysis. Considering that chlorine dioxide produced by chemical oxidation may be harmful to the human body, and photocatalysis has poor formaldehyde removal effect indoors due to the limitation of light intensity, the adsorption method has the advantages of high cost performance, green non-toxicity, and little environmental impact. However, common activated carbon mainly relies on physical adsorption and has the disadvantage of easy desorption and secondary pollution. Therefore, it is particularly important to prepare an adsorption material with low cost, large adsorption capacity, and difficult desorption. At the same time, the accurate detection of formaldehyde is of great significance for identifying environmental pollution. However, traditional formaldehyde detection methods such as colorimetry and chromatography are time-consuming and laborious, and it is difficult to quickly and accurately detect the formaldehyde concentration. Therefore, materials for quickly removing formaldehyde and real-time detecting the formaldehyde concentration are urgently needed.

[0004] Carbon quantum dots are new members of the family of carbon nanomaterials, which are discrete quasi-spherical carbon nanoparticles with a particle size less than 10 nm. Since they were discovered in 2004, due to their high solubility, low toxicity, good biocompatibility, and controllable fluorescence, they have become a new star in zero-dimensional carbon nanomaterials. In the present invention, carbon quantum dots are in-situ grown on the surface of biochar to realize rapid fluorescence detection of formaldehyde and a high-efficiency adsorption material for formaldehyde. Summary of the Invention

[0005] In order to overcome the deficiencies of the above-mentioned prior art and realize the green development concept of "treating waste with waste" and resource recycling, the present invention uses waste biomass materials to prepare carbon quantum dots, and uses the biochar loaded with carbon quantum dots generated during the preparation of nitrogen-doped carbon quantum dots to efficiently adsorb and fix formaldehyde in the air. At the same time, because the loaded carbon quantum dots have the function of fluorescence detection of formaldehyde, this bifunctional material has the characteristics 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 as follows: The present invention provides a bifunctional chestnut shell spherical biochar loaded with carbon quantum dots. The bifunctional 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 the formaldehyde concentration and removing formaldehyde.

[0007] The present invention also provides a preparation method of a bifunctional chestnut shell spherical biochar loaded with carbon quantum dots, and the method comprises the following steps: (1) Cleaning the waste chestnut shells with deionized water, drying and grinding them into powder, then adding a 70% ethanol solution, soaking and filtering out the solution, and freeze-drying after rotary evaporation to obtain chestnut shell extract powder.

[0008] (2) Taking the chestnut shell extract powder alone or in a mixture with an amino acid in deionized water, performing ultrasonic treatment, and then heating and reacting to obtain a reaction product; separating the solid obtained from the reaction product, rinsing it with deionized water and drying it to prepare a bifunctional chestnut shell spherical biochar loaded with carbon quantum dots.

[0009] In the step (1), there is no special limitation on the type of the waste chestnut shells.

[0010] In the step (1), the soaking time is 12 - 36 h; preferably, it is 24 h.

[0011] 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.

[0012] Among them, the mass ratio of L-lysine to L-phenylalanine is 1:1.

[0013] In the step (2), the mass ratio of the chestnut shell extract powder to deionized water is (1 - 4):50; preferably, it is 2:50.

[0014] In the step (2), the ultrasonic treatment is preferably carried out in a polytetrafluoroethylene inner liner.

[0015] In the step (2), the ultrasonic treatment time is 5 - 10 min; preferably, it is 5 min.

[0016] In the step (2), the heating reaction time is 6 - 10 h; preferably, it is 8 h.

[0017] In the step (2), the heating reaction temperature is 160 - 200 °C; preferably, it is 180 °C.

[0018] The present invention also provides a bifunctional chestnut shell spherical biochar loaded with carbon quantum dots prepared by the above method.

[0019] The bifunctional chestnut shell spherical biochar loaded with carbon quantum dots has high-efficiency capture and fixation ability for 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 this material, which can react with formaldehyde in the environment through Schiff base reaction, significantly improving the formaldehyde removal effect of biochar.

[0020] The aqueous dispersion solution of the bifunctional chestnut shell spherical biochar loaded with carbon quantum dots has a fluorescence reaction due to the carbon quantum dots on its surface. When the surface groups of carbon quantum dots react with formaldehyde, the fluorescence is quenched, realizing the fluorescence detection of formaldehyde in aqueous solution.

[0021] Therefore, the chestnut shell biochar with adsorption-detection dual functions and loaded with carbon quantum dots synthesized by the "one-pot method" can efficiently adsorb formaldehyde and, to a great extent, solve the problem of "secondary pollution" caused by the rapid desorption of formaldehyde from carbon materials through chemical adsorption. At the same time, the fluorescence detection of formaldehyde is realized by loading carbon quantum dots, expanding the application range of this material.

[0022] The present invention also provides the application of the biochar loaded with carbon quantum dots in removing formaldehyde and detecting formaldehyde in aqueous solution.

[0023] Compared with the prior art, the beneficial effects of the present invention are: The present invention discloses a preparation method of biochar loaded with carbon quantum dots. First, an extract of waste chestnut shells is prepared, and then the extract is prepared into carbon quantum dots by hydrothermal method. The carbon quantum dot solution and solid biochar are separated, and after drying, a biochar adsorption material with high-efficiency formaldehyde adsorption is formed. This material has certain fluorescence and can realize the detection of formaldehyde. This material has excellent capture ability for formaldehyde and is not easy to desorb. At the same time, this material uses biomass as the raw material from the preparation of carbon quantum dots. Its source is widely distributed and renewable. In addition, this material is derived from the biochar produced during the preparation of carbon quantum dots, which conforms to the green development concept of resource recycling. The preparation is simple and the cost is low, and it has great application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0025] Figure 1 It is the FTIR spectrogram of Example 2 and Comparative Example 3 of the present invention; Figure 2 It is the SEM diagram of Comparative Example 3 and Example 2 of the present invention; Figure 3 It is the fluorescence spectrogram of Embodiment 2 of the present invention; Figure 4 It is the formaldehyde adsorption test results of Embodiment 2, Comparative Example 1, Comparative Example 2 and Comparative Example 3 of the present invention; Figure 5 It is the formaldehyde adsorption cycle test of Embodiment 2 of the present invention; Figure 6 It is the formaldehyde adsorption cycle test of Comparative Example 3 of the present invention; Figure 7 It is the static desorption test of Embodiment 2 and Comparative Example 3 of the present invention; Figure 8 It is the change of fluorescence intensity of the aqueous solution of Embodiment 2 of the present invention in formaldehyde solutions with different concentrations. Detailed implementation manners

[0026] Combined with the following specific embodiments and drawings, the present invention will be further described in detail. The processes, conditions, experimental methods, etc. for implementing the present invention, except for the specifically mentioned content below, are all common knowledge and well-known common sense in the art, and the present invention has no particularly restricted content.

[0027] The following description of at least one exemplary embodiment is actually only illustrative and in no way limits the present invention and its application or use. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0028] In all the examples shown and discussed here, any specific value should be construed as merely exemplary and not as a limitation. Therefore, other examples of the exemplary embodiments may have different values.

[0029] The present invention discloses a bifunctional chestnut shell spherical biochar loaded with carbon quantum dots, its preparation method and application, belonging to the technical field of indoor air purification. The method includes the following steps: washing the waste chestnut shells with deionized water, drying and grinding them into powder, then adding a 70% ethanol solution, soaking and filtering out the solution, rotary evaporating and freeze-drying into powder; taking the chestnut shell extract powder alone or in a mixture with amino acids in deionized water, performing ultrasonic treatment, and then heating and reacting; separating the solid obtained from the reaction product, rinsing it with deionized water and drying it to prepare a bifunctional chestnut shell spherical biochar loaded with carbon quantum dots. The bifunctional chestnut shell spherical biochar loaded with carbon quantum dots of the present invention is a biochar formaldehyde removal material and can effectively remove formaldehyde. It has broad application prospects.

[0030] The following further describes the specific embodiments of the present invention. It should be noted here that the description of these embodiments is for helping to understand the present invention, but does not constitute a limitation to 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 are all conventional methods unless otherwise specified, and the test materials used in the following examples are all available through conventional commercial channels unless otherwise specified.

[0031] Example 1: The present invention provides a method for preparing an extract of waste chestnut shells, which is used for formaldehyde removal because it is rich in tannic acid.

[0032] Take 100 g of waste chestnut shells, wash them with deionized water and then dry them. After grinding them into powder in a grinder, add a 70% ethanol solution according to a solid-liquid ratio of 1:10. Soak for 24 h at room temperature and then filter out the solution. After evaporation and concentration by a rotary evaporator, it is freeze-dried into powder.

[0033] Example 2:

[0034] The present invention provides a method for preparing carbon quantum dot-loaded biochar.

[0035] Take 2 g of the freeze-dried powder of the waste chestnut shell extract prepared in Example 1 of the present invention, add 1 g of L-lysine and 1 g of L-phenylalanine, and dissolve them in 50 ml of deionized water. After ultrasonic treatment for 10 min, transfer it into a reaction kettle with a polytetrafluoroethylene inner liner and treat it at 180 °C for 8 h. After cooling, pour the solution in the reaction kettle into a vacuum filtration tank to separate the black solid, wash it with deionized water, and then put it into an oven to dry at 60 °C for 24 h to obtain carbon quantum dot-loaded biochar.

[0036] Comparative Example 1 This comparative example is carried out using steps similar to those in Example 2 of the present invention, except that in the formula, it is changed to doping 2 g of L-lysine alone.

[0037] Comparative Example 2 This comparative example is carried out using steps similar to those in Example 2 of the present invention, except that in the formula, it is changed to doping 2 g of L-phenylalanine alone.

[0038] Comparative Example 3 This comparative example is carried out using steps similar to those in Example 2 of the present invention, except that in the formula, L-lysine and L-phenylalanine are not added.

[0039] Application Example 1 The following experimentally demonstrates the formaldehyde removal effect of the carbon quantum dot-loaded biochar (hereinafter referred to as biochar) prepared by the present invention.

[0040] (1)Formaldehyde adsorption capacity test: Referring to the standard QB / T2761-2006, the biochars prepared in Example 2, Comparative Example 1, Comparative Example 2, and Comparative Example 3 of the present invention were placed in a glass glove box with a volume of 0.2 m 3 for testing. The formaldehyde concentration in each group was the same, and the initial release amount of formaldehyde was 60 µL of 1.8% formaldehyde solution. The detection method was the phenol reagent spectrophotometry method. The test results are shown in Table 1-1, Table 1-2, Table 1-3, and Table 1-4. The one with the best adsorption effect was selected as Example 2 of the present invention and was used for subsequent tests together with Comparative Example 3 without doped amino acids.

[0041]

[0042]

[0043] (2)Formaldehyde adsorption cycle test: Referring to the standard QB / T2761-2006, the biochars prepared in Example 2 and Comparative Example 3 of the present invention were placed in a glass glove box with a volume of 0.2 m 3 for testing. The formaldehyde concentration in each group was the same, and the initial release amount of formaldehyde was 60 µL of 1.8% formaldehyde solution and was released cyclically three times. The detection method was the phenol reagent spectrophotometry method. The test results are shown in Table 2-1 and Table 2-2.

[0044]

[0045]

[0046] (3)Static desorption test after adsorption: The biochars prepared in Example 2 and Comparative Example 3 of the present invention after being saturated with adsorbed formaldehyde were placed in a glass glove box with a volume of 0.2 m 3 for testing. The formaldehyde content within 48 h was detected. The detection method was a formaldehyde sensor. The test results are shown in Table 3-1 and 3-2.

[0047]

[0048] According to Table 1-1, Table 1-2, Table 1-3 and Table 1-4, it can be seen that the biochar prepared in Example 2 of the present invention has a large formaldehyde adsorption capacity under a certain concentration of formaldehyde. Compared with Comparative Example 1, Comparative Example 2 and Comparative Example 3, when the doping ratio of L-lysine and L-phenylalanine is 1:1, the addition of biochar significantly increases the adsorption amount of formaldehyde, and the adsorption amount of formaldehyde within 48 h can reach 1.455 mg / g, which is higher than that of biochar doped with L-lysine or L-phenylalanine alone. At the same time, the formaldehyde adsorption cycle test results in Table 2-1 and Table 2-2 show that the biochar prepared in Example 2 of the present invention still has good formaldehyde removal effect during three adsorption cycles. In addition, the static desorption test results after adsorption in Table 3-1 and Table 3-2 show that the amount of formaldehyde desorbed by the biochar prepared in Example 2 of the present invention within 48 h is very small, and it decreases by 18.23% compared with the comparative example. This provides feasibility for its effective removal of formaldehyde in practical applications.

[0049] Application Example 2 The following demonstrates the fluorescence detection effect of formaldehyde by the biochar loaded with carbon quantum dots prepared by the present invention (hereinafter referred to as biochar) through experiments.

[0050] 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 a formaldehyde solution with a concentration of 1-5 mg / L. Take 5 ml of formaldehyde solutions with different concentrations and add 50 μL of the fluorescence detection solution. After standing at room temperature for 30 min, put it into a fluorescence spectrophotometer to record the fluorescence intensity corresponding to formaldehyde standard solutions with different concentrations. Take the ratio of the fluorescence intensity corresponding to formaldehyde standard solutions with different concentrations to the fluorescence intensity corresponding to the standard solution with a concentration of 0 as the ordinate, and the concentration of different formaldehyde standard solutions as the abscissa to draw a standard curve and solve the fitting equation. The specific results are shown in Figure 8 , from Figure 8 it can be seen that when the formaldehyde concentration in the solution decreases, the fluorescence intensity of the biochar material increases significantly, and the ratio of fluorescence intensity F0 / F has a linear relationship with the formaldehyde concentration. The linear regression equation is: F0 / F = 0.105X 甲醛 + 0.9987 (R 2 = 0.9957). Therefore, this biochar material has the ability to detect formaldehyde in actual situations.

[0051] Figure 1 It shows that there are amine functional groups in its waste biochar (Example) after nitrogen doping by adding amino acids.

[0052] Figure 2 It shows that both are smooth spherical carbon particles; among them, Figure 2 a is an image of the powder of Comparative Example 3 magnified 1000 times;Figure 2 b is an image of the powder of Comparative Example 3 magnified 10,000 times; Figure 2 c is an image of the powder of Comparative Example 3 magnified 30,000 times; Figure 2 d is an image of the powder of Example 2 magnified 1,000 times; Figure 2 e is an image of the powder of Example 2 magnified 3,000 times; Figure 2 f is an image of the powder of Example 2 magnified 50,000 times. Through the SEM images of Comparative Example 3 and Example 2, it is found that the waste biochar particles without added amino acids are well-dispersed spherical particles, while after doping with L-lysine and L-phenylalanine, the biochar particles show a certain degree of agglomeration phenomenon, and the whole shows a stacked shape like 2 - 3 grape-like particles.

[0053] Figure 4 It shows that Example 2 has a better adsorption effect.

[0054] Figure 5 It shows that there is still good adsorption capacity after three formaldehyde release-adsorption cycles.

[0055] Figure 6 It shows that its adsorption capacity is significantly lower than that of Example 2 under three formaldehyde release-adsorption cycles.

[0056] Figure 7 It can be seen that the amount of desorbed formaldehyde in Example 2 after adsorption saturation is quite small, and is also significantly lower than that of Comparative Example 3.

[0057] The above has described the embodiments of the present invention in detail, but the present invention is not limited to the described embodiments. For those skilled in the art, without departing from the principle and spirit of the present invention, various changes, modifications, substitutions, and variations made to these embodiments still fall within the protection scope of the present invention.

[0058] Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the description of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention.

[0059] As used in the present invention, the term "comprising" is an open expression, that is, it includes the content specified by the present invention, but does not exclude other aspects.

[0060] As used in the present invention, the term "and / or" includes any one and all combinations of one or more of the related listed items.

[0061] Although embodiments of the present description have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present description, and the scope of the present description is defined by the appended claims and their equivalents.

Claims

1. 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 a spherical structure prepared from natural materials, and has the dual functions of rapidly detecting the formaldehyde concentration and removing formaldehyde.

2. A preparation method of a bifunctional chestnut shell spherical biochar loaded with carbon quantum dots, characterized in that, The method includes the following steps: (1) Wash the waste chestnut shells with deionized water, dry them and grind them into powder, then add 70% ethanol solution, soak and filter out the solution, rotary evaporate and freeze dry to obtain chestnut shell extract powder; (2) Take the chestnut shell extract powder alone or in a mixture with an amino acid in deionized water, perform ultrasonic treatment, and then heat and react to obtain a reaction product; wash the solid obtained by separating the reaction product with deionized water and dry it to prepare the bifunctional chestnut shell spherical biochar loaded with carbon quantum dots.

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

4. The preparation method according to claim 2, wherein, In the step (2), the amino acid is one or two of L-lysine and L-phenylalanine.

5. The preparation method according to claim 4, characterized in that, The mass ratio of the L-lysine to the L-phenylalanine is 1:

1.

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

50.

7. The preparation method according to claim 2, wherein In the step (2), the ultrasonic treatment time is 5 - 10 min.

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

9. 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 2 to 8.

10. Application of bifunctional chestnut shell spherical biochar loaded with carbon quantum dots in formaldehyde removal and detection of formaldehyde in aqueous solution, characterized in that, The bifunctional chestnut shell spherical biochar loaded with carbon quantum dots is the bifunctional chestnut shell spherical biochar according to claim 1 or 9.

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