Method for promoting degradation of cellulose acetate by using nano quantum dot material

Abstract

The invention discloses a method for promoting degradation of cellulose acetate by a nano quantum dot material. Aiming at the problems that high-substitution-degree CA is poor in biodegradability and a traditional photosensitizer is low in light utilization efficiency, bismuth-based nano quantum dots with the size of 17-20 nm are adopted as the photosensitizer, the photo-thermal / photoelectric effect of the bismuth-based nano quantum dots is excited through ultraviolet light, free radicals are generated to attack CA molecular chains, and breakage of the molecular chains is accelerated. Experiments show that a CA sample added with 2.5 wt%-10 wt% of bismuth-based nano quantum dots is irradiated under 365 nm ultraviolet light for 15 days, the mass loss rate can reach 9.3%, and the degradation efficiency is remarkably improved. The method is suitable for a seawater environment with the salinity of 3.3%-3.7% and the pH value of 7.8-8.4, and an efficient degradation technology is provided for solving CA pollution.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of cellulose acetate degradation, and particularly relates to a method for promoting cellulose acetate degradation by using nano quantum dot materials. BACKGROUND

[0002] Cellulose, as the largest natural polymer in nature, has become one of the hot research directions for replacing petroleum-based polymers due to its advantages of complete degradability, good biocompatibility and low price. Cellulose acetate (CA) is an important derivative of cellulose, which has excellent mechanical and chemical properties. Cellulose acetate with different degrees of substitution (DS) has a wide range of applications in the fields of cigarettes, textiles, wastewater treatment and biomedicine. However, this also determines that a large amount of cellulose acetate waste will be generated every year, part of which will be directly discharged into the natural environment, causing serious “white pollution” and “marine pollution”. Although cellulose acetate has a certain potential for biodegradation, the biodegradability will decrease or even be completely inhibited with the increase of the degree of substitution. Therefore, developing a method for promoting the efficient degradation of cellulose acetate under natural conditions not only has important academic research value and application value, but also has far-reaching significance for environmental protection, energy saving and emission reduction.

[0003] Patent CN102892317B discloses a degradable scheme for cellulose acetate-based cigarette filters. By mixing strong acid precursor substances that can be hydrolyzed, such as phosphorus pentoxide, the release of strong acid is promoted by the moisture in the environment, thereby promoting the hydrolysis process of cellulose acetate. Similarly, the addition of alkaline substances is also used as a method to promote the degradation of cellulose acetate. For example, CN107001701A studies alkaline additives such as MgO, Mg(OH)2, MgCO3, CaO, Ca(OH)2, etc. It is found that the weight loss of the product reaches 29% in two months in the presence of 5wt% MgO. However, these methods inevitably encounter uncontrollable degradation problems in storage environments, and the effective pH of the system is also affected due to the dilution effect of the water environment, thus failing to achieve the expected degradation effect.

[0004] Cellulose acetate modification is also a research direction for realizing the degradation of cellulose acetate. For example, CN115160654A uses cellulose acetate mixed with biodegradable polyester to improve the biodegradation rate. Patents CN110170250A and CN1067415C add polylactic acid and low-substituted cellulose acetate, respectively, to increase the overall degradation rate of cellulose acetate. However, although these methods can promote the degradation process of cellulose acetate to some extent by increasing the exposed area, they also lose part of the material properties.

[0005] Photocatalytic degradation is an important field of research in the degradation of cellulose acetate. Studies have shown that the maximum absorption wavelength of cellulose acetate is around 260 nm, while the wavelength of sunlight reaching the ground through the atmosphere is around 300 nm. The mismatch of effective wavelengths makes it almost impossible for cellulose acetate to be effectively degraded under natural conditions. However, the addition of photocatalysts or photosensitizers can greatly promote the photocatalytic degradation of cellulose acetate. The most commonly used photosensitizer is based on titanium dioxide. Patent CA1073581 discloses the use of titanium dioxide particles to promote the photocatalytic degradation of polyolefins. Subsequently, titanium dioxide has also been introduced into the study of cellulose acetate degradation. WO-A-93 / 24685, EP716117A1, US-A-5,491,024, etc. all introduce the application of titanium dioxide and its structural modification derivatives in the degradation of cellulose acetate. Patent CN106046428A uses carbon-modified titanium dioxide to study the photocatalytic degradation of cellulose acetate. In 36 weeks, the degradation rate reaches 24.2%. CN103619200A discloses a photocatalytic degradation method by adding Kronos 1071 titanium dioxide to cellulose. After 9 months of light exposure, the weight loss reaches 50-60%. CN103607913A studies the photocatalytic degradation effect of titanium dioxide with different sizes and different states, and finds that the mixed phase of anatase and rutile has the best degradation effect, with a weight loss of 65%. CN110613163A mixes cellulose acetate with purple grass extract, perilla extract, alkali and TiO2, and after 240 hours of light exposure, the weight loss is about 4.5%. Although these works demonstrate the advantages of photosensitizers in the photocatalytic degradation of cellulose acetate, these methods are basically applied in simple scenarios such as roofs or concrete, and due to the complexity of natural water systems, especially seawater systems, there are few related applications in seawater.

[0006] Minna Hakkarainen et al. reported a method of using carbon dots as photosensitizers to promote the degradation of cellulose acetate in seawater. Compared with the 5% reduction in weight average molecular weight Mw of the sample without adding photosensitizers, the sample with carbon dot photosensitizers reduced Mw by 77%, and the number average molecular weight Mn also reduced by 45%. Although the degradation of cellulose acetate in seawater has been significantly improved under the action of carbon dot photosensitizers, the synthesis of carbon dot photosensitizers is very cumbersome and involves harsh reaction conditions such as strong acid and high temperature, thus limiting its application potential.

[0007] Therefore, for the increasingly serious pollution of cellulose acetate waste in the marine system and the difficulty of its degradation in the marine system, it is necessary to introduce environmentally friendly photosensitive materials to increase the effective light absorption range and promote the degradation process of cellulose acetate in seawater systems and improve the degradation efficiency. SUMMARY

[0008] The application aims to provide an environmentally friendly photosensitive material assisted cellulose acetate degradation method, to promote efficient degradation of cellulose acetate in marine environment by expanding the effective light absorption range, to solve the problems of cellulose acetate marine waste pollution and low degradation efficiency in the prior art, and to take into account the controllability of material performance and degradation process.

[0009] To achieve the above technical purposes, the application provides a method for promoting degradation of cellulose acetate by using nanometer quantum dot material, which uses nanometer quantum dot material with excellent photoelectric / photothermal performance as a photosensitive reagent to promote the degradation process of cellulose acetate under light conditions, so as to realize the breaking and efficient degradation of the molecular chain of cellulose acetate.

[0010] Further, the nanometer quantum dot material is a bismuth-based nanometer quantum dot material.

[0011] Further, the chemical formula of the bismuth-based nanometer quantum dot material is Bi.

[0012] Further, the size of the bismuth-based nanometer quantum dot is 17-20 nm.

[0013] Further, the method comprises the following steps:

[0014] Step (1) dissolving cellulose acetate in acetone solvent to obtain a uniform dispersion liquid;

[0015] Step (2) adding nanometer quantum dot material as a photosensitive agent to the dispersion liquid, and continuously stirring until the sample is uniformly dispersed;

[0016] Step (3) adding the prepared dispersion liquid into a mold, drying into a film, and preparing a sample to be tested;

[0017] Step (4) placing the sample to be tested in an application environment, irradiating under ultraviolet light for a period of time, and promoting the breaking and degradation of the molecular chain of cellulose acetate through photocatalytic reaction.

[0018] Further, the nanometer quantum dot material in step (2) is a bismuth-based nanometer quantum dot material, and the addition amount of the bismuth-based nanometer quantum dot material is 0.5wt%-10wt% of the mass of cellulose acetate.

[0019] Further, the degree of substitution (DS) of the cellulose acetate in step (1) is ≦2.45.

[0020] Further, the application environment in step (4) is soil, lake water or seawater.

[0021] Further, the application environment in step (4) is seawater.

[0022] Further, the salinity of the seawater is 3.3%-3.7%, and the pH value is 7.8-8.4.

[0023] Further, the wavelength of the ultraviolet light in step (4) is 350-460 nm, and the light intensity is 100 mW / cm 2 , and the time is 15-60 days.

[0024] Further, the bismuth-based nanomaterial in step (2) is prepared by a solvothermal method, and the specific steps are as follows: bismuth nitrate and a surfactant are dissolved in glycerol and ethylene glycol, a reducing agent is added under room temperature stirring conditions, and after the reaction is completed, 17-20 nm bismuth-based nanometer quantum dots are obtained by multiple centrifugal separation / washing and vacuum drying.

[0025] Further, the surfactant is polyvinylpyrrolidone, the reducing agent is sodium borohydride, and the reaction time is 1 minute.

[0026] A method for promoting the degradation of cellulose acetate according to the nanometer quantum dot material is applied to promote the degradation of cellulose acetate in soil, lake water or seawater.

[0027] The main technical principle of the application is:

[0028] The bismuth-based nanomaterial can promote the absorption of photons and the migration of photoelectrons under light conditions, form free radicals, and then act on and break the cellulose acetate chain. Seawater has abundant electrolytes, which can greatly improve the photoelectric effect of the bismuth-based nanomaterial. Path one: free radicals act on the glycosidic bond of the cellulose acetate main chain, promote the glycosidic bond to break, and thus degrade the cellulose acetate; Path two: free radicals act on the ester group of cellulose acetate, realize the hydrolysis of the ester group, reduce the degree of substitution of cellulose acetate, improve the degradability of cellulose acetate in the natural environment, and then decompose into carbon dioxide and water under natural conditions, and further degrade through the mineralization of marine organisms. According to the time / temperature equivalence, the excellent photo-thermal performance of the bismuth-based nanomaterial can microscopically increase the reaction site temperature, thereby promoting the action efficiency between the nanomaterial and the cellulose acetate, accelerating the occurrence of chemical reactions, and thus improving the degradation rate.

[0029] The application uses bismuth-based nanometer quantum dot material as a photosensitizer to promote the degradation process of cellulose acetate in seawater environment and improve the catalytic degradation efficiency, and the beneficial effects are reflected in the following aspects:

[0030] 1. The degradation efficiency is significantly improved

[0031] The experimental data show that the mass loss rate of the CA sample added with 5.0wt%-10.0wt% bismuth-based nano quantum dots can reach 9.3% (initial mass 20.5 mg, remaining 18.6 mg) under irradiation of 365 nm ultraviolet light for 15 days. After irradiation for 30 days, the number average molecular weight (Mn) decreases from 26100 to 17100 (decrease of 34%), the weight average molecular weight (Mw) decreases from 201000 to 147000 (decrease of 27%), and the dispersity (Mw / Mn) increases from 7.66 to 9.01, indicating that the molecular chain is broken more severely, and the degradation efficiency is much higher than that of the non-added group.

[0032] 2. High light utilization efficiency

[0033] The bismuth-based nano quantum dot material has excellent photo-thermal / photo-electric performance, can efficiently absorb ultraviolet light and convert it into free radicals, and solves the problem of low efficiency of traditional photosensitizers (such as TiO2) which only utilize short-wave ultraviolet light.

[0034] 3. Strong environmental adaptability

[0035] The experiment verifies that the method is effective in seawater environments of different salinity and pH. In contrast, traditional photosensitizers are easily disabled by ion interference in complex seawater environments. The present application improves dispersibility and enhances environmental adaptability through surface modification of quantum dots (such as polyvinylpyrrolidone).

[0036] 4. Wide application scenarios

[0037] The present application is suitable for degradation of CA with high degree of substitution (DS = 2.45), and thus also has degradation effect on CA with low degree of substitution, and can be popularized to CA waste treatment in the fields of cigarette filters, textile materials, biomedical products, etc., effectively alleviating the "white pollution" of the ocean. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 : Transmission electron microscopy (TEM) image of bismuth-based nano quantum dots. DETAILED DESCRIPTION

[0039] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application will be described in detail below with reference to the drawings. It can be understood that the specific embodiments described herein are only used to explain the present application, but not to limit the present application. In addition, it should be noted that only parts related to the present application are shown in the drawings for convenience of description, but not all features. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0040] Reference to an "embodiment" herein means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily mutually exclusive of one another. As will be apparent to those of ordinary skill in the art, embodiments described herein can be combined with other embodiments.

[0041] The application will be described in detail below with reference to the embodiments and drawings.

[0042] The bismuth-based nano quantum dots described in the embodiments of the application are synthesized by the following method:

[0043] Bismuth nitrate and surfactant polyvinylpyrrolidone are dissolved in glycerol and ethylene glycol, and stirred at room temperature to form a uniform phase. A reducing agent, sodium borohydride, is added under rapid stirring, and the reaction is carried out for 1 minute, accompanied by the generation of a large amount of black material, and the stirring is stopped. The reaction system is transferred to a centrifuge tube, and centrifuged at a speed of 17000 rpm to remove the supernatant. Ethanol is added to the residual system, and ultrasonic cleaning is carried out, followed by centrifugation. Distilled water is then added, and ultrasonic cleaning is carried out again, followed by centrifugation. The above separation / washing operation is repeated 3 times, and the bismuth-based nano quantum dots are obtained after vacuum drying for 24 hours.

[0044] The prepared bismuth-based nano quantum dots are observed under a transmission electron microscope (TEM), as shown in FIG. 1, and it can be seen that in the TEM image of 50 nm scale, the bismuth-based nano quantum dots of 17-20 nm are spherical, and some regions are loosely aggregated in particle units, and there is no obvious chemical bonding between the aggregated units. Figure 1

[0045] Example 1

[0046] 1 g of cellulose acetate with a degree of substitution of 2.45 is fully dissolved in acetone, and stirring is continued until the sample is uniformly dispersed. The prepared dispersion is added to a mold, and dried to obtain a sample to be tested. The sample to be tested is added to seawater, and then subjected to an aging experiment under ultraviolet light for 15 days.

[0047] Example 2

[0048] 1 g of cellulose acetate with a degree of substitution of 2.45 is fully dissolved in acetone, and then 2.5 wt% of bismuth-based nano quantum dots with a size of 17-20 nm are added as an additive, and stirring is continued until the sample is uniformly dispersed. The prepared dispersion is added to a mold, and dried to obtain a sample to be tested. The sample to be tested is added to seawater, and then subjected to an aging experiment under ultraviolet light (350 nm, 100 mW / cm 2 ) for 15 days.

[0049] Example 3​

[0050] Take 1 g of cellulose acetate with a degree of substitution of 2.45, fully dissolved with acetone, then add 5.0wt% of bismuth-based nanometer quantum dots with a size of 17-20 nm as an additive, continue to stir until the sample is uniformly dispersed. Add the prepared dispersion to the mold, dry, and thus prepare the test sample. Add the test sample to seawater, then perform a 15-day aging experiment under ultraviolet light (350 nm, 100 mW / cm 2 ) irradiation.

[0051] Example 4

[0052] Take 1 g of cellulose acetate with a degree of substitution of 2.45, fully dissolved with acetone, then add 5.0wt% of bismuth-based nanometer quantum dots with a size of 17-20 nm as an additive, continue to stir until the sample is uniformly dispersed. Add the prepared dispersion to the mold, dry, and thus prepare the test sample. Add the test sample to seawater, then perform a 15-day aging experiment under ultraviolet light (350 nm, 100 mW / cm 2 ) irradiation.

[0053] Table 1 Mass change of CA sample after 15 days of ultraviolet light irradiation under different bismuth-based nanometer quantum dot additive amounts (seawater environment)

[0054]

[0055] As can be seen from Table 1, the CA sample without bismuth-based nanometer quantum dot addition (Example 1) has no change in mass; after adding bismuth-based nanometer quantum dots, the mass loss increases significantly with the increase of the additive amount (9.3% loss at 10.0wt% additive amount), which preliminarily verifies the promoting effect of bismuth-based materials on CA degradation.

[0056] Table 2 Molecular weight change of CA sample after 15 days of ultraviolet light irradiation under different bismuth-based nanometer quantum dot additive amounts (seawater environment)

[0057]

[0058] As can be seen from Table 2, the molecular weight of the non-addition group (Example 1) is close to that of the control sample (without degradation), indicating weak natural degradation; after adding bismuth-based nanometer quantum dots, the number average molecular weight (Mn) and the weight average molecular weight (Mw) decrease significantly, and the dispersity (Mw / Mn) increases, indicating that the CA molecular chain breaks more severely, and the degradation efficiency increases with the increase of the additive amount.

[0059] Example 5

[0060] Take 1 g of cellulose acetate with a degree of substitution of 2.45, fully dissolved with acetone, then add 2.5wt% of bismuth-based nanometer quantum dots with a size of 17-20 nm as an additive, continue to stir until the sample is uniformly dispersed. Add the prepared dispersion to the mold, dry, and thus prepare the test sample. Add the test sample to seawater, then perform a 30-day aging experiment under ultraviolet light (350 nm, 100 mW / cm 2 ) irradiation.

[0061] Example 6

[0062] Take 1 g of cellulose acetate with a degree of substitution of 2.45, fully dissolved with acetone, then add 2.5wt% of bismuth-based nanometer quantum dots with a size of 17-20 nm as an additive, continue to stir until the sample is uniformly dispersed. Add the prepared dispersion to the mold, dry, and thus prepare the test sample. Add the test sample to seawater, then perform a 30-day aging experiment under ultraviolet light (350 nm, 100 mW / cm 2 ) irradiation.

[0063] Example 7

[0064] Take 1 g of cellulose acetate with a degree of substitution of 2.45, fully dissolved with acetone, then add 2.5wt% of bismuth-based nanometer quantum dots with a size of 17-20 nm as an additive, continue to stir until the sample is uniformly dispersed. Add the prepared dispersion to the mold, dry, and thus prepare the test sample. Add the test sample to seawater, then perform a 30-day aging experiment under ultraviolet light (350 nm, 100 mW / cm 2 ) irradiation.

[0065] Table 3 Change in molecular weight of CA sample after 30 days of ultraviolet light irradiation under different bismuth-based nanometer quantum dot additive amounts (seawater environment)

[0066]

[0067]

[0068] As can be seen from Table 3, after the irradiation is extended to 30 days, the Mn and Mw of each additive amount group further decrease (such as the 10.0wt% group Mn decreases to 17100), indicating that the molecular chain of the high additive amount group is more completely broken under long-term irradiation.

[0069] Example 8

[0070] Take 1 g of cellulose acetate with a degree of substitution of 2.45, fully dissolved with acetone, then add 0.5 wt% of bismuth-based nanometer quantum dots with a size of 17-20 nm as an additive, continue to stir until the sample is uniformly dispersed. Add the prepared dispersion to the mold, dry, and thus prepare the sample to be tested. Add the sample to be tested to seawater, then perform an aging experiment under ultraviolet light (350 nm, 100 mW / cm 2 ) irradiation for 45 days.

[0071] Example 9

[0072] Take 1 g of cellulose acetate with a degree of substitution of 2.45, fully dissolved with acetone, then add 1.0 wt% of bismuth-based nanometer quantum dots with a size of 17-20 nm as an additive, continue to stir until the sample is uniformly dispersed. Add the prepared dispersion to the mold, dry, and thus prepare the sample to be tested. Add the sample to be tested to seawater, then perform an aging experiment under ultraviolet light (350 nm, 100 mW / cm 2 ) irradiation for 45 days.

[0073] Example 10

[0074] Take 1 g of cellulose acetate with a degree of substitution of 2.45, fully dissolved with acetone, then add 2.5 wt% of bismuth-based nanometer quantum dots with a size of 17-20 nm as an additive, continue to stir until the sample is uniformly dispersed. Add the prepared dispersion to the mold, dry, and thus prepare the sample to be tested. Add the sample to be tested to seawater, then perform an aging experiment under ultraviolet light (350 nm, 100 mW / cm 2 ) irradiation for 45 days.

[0075] Example 11

[0076] Take 1 g of cellulose acetate with a degree of substitution of 2.45, fully dissolved with acetone, then add 5.0 wt% of bismuth-based nanometer quantum dots with a size of 17-20 nm as an additive, continue to stir until the sample is uniformly dispersed. Add the prepared dispersion to the mold, dry, and thus prepare the sample to be tested. Add the sample to be tested to seawater, then perform an aging experiment under ultraviolet light (350 nm, 100 mW / cm 2 ) irradiation for 45 days.

[0077] Example 12

[0078] Take 1 g of cellulose acetate with a degree of substitution of 2.45, fully dissolved with acetone, then add 10.0wt% bismuth-based nanometer quantum dots with a size of 17-20 nm as an additive, continue to stir until the sample is uniformly dispersed. Add the prepared dispersion to the mold, dry, and thus prepare the test sample. Add the test sample to seawater, then perform a 45-day aging experiment under ultraviolet light (350 nm, 100 mW / cm 2 ) irradiation.

[0079] Table 4 Change in molecular weight of CA samples after 45 days of ultraviolet light irradiation under different bismuth-based nanometer quantum dot additive amounts (seawater environment)

[0080]

[0081] As can be seen from Table 4, under 45 days of light irradiation, the Mn of the low additive amount (0.5wt%-2.5wt%) group decreased to 15500-16610, and the molecular weight of the high additive amount (5.0wt%-10.0wt%) group continued to decrease, with the highest Mw / Mn of 10.8, indicating that the molecular chain breakage was more significant.

[0082] Example 13

[0083] Take 1 g of cellulose acetate with a degree of substitution of 2.45, fully dissolved with acetone, then add 10.0wt% bismuth-based nanometer quantum dots with a size of 17-20 nm as an additive, continue to stir until the sample is uniformly dispersed. Add the prepared dispersion to the mold, dry, and thus prepare the test sample. Add the test sample to seawater, then perform a 45-day aging experiment under ultraviolet light (350 nm, 100 mW / cm 2 ) irradiation.

[0084] Example 14

[0085] Take 1 g of cellulose acetate with a degree of substitution of 2.45, fully dissolved with acetone, then add 10.0wt% bismuth-based nanometer quantum dots with a size of 17-20 nm as an additive, continue to stir until the sample is uniformly dispersed. Add the prepared dispersion to the mold, dry, and thus prepare the test sample. Add the test sample to seawater, then perform a 45-day aging experiment under ultraviolet light (350 nm, 100 mW / cm 2 ) irradiation.

[0086] Example 15

[0087] Take 1 g of cellulose acetate with a degree of substitution of 2.45, fully dissolved with acetone, then add 2.5wt% of bismuth-based nanometer quantum dots with a size of 17-20 nm as an additive, continue to stir until the sample is uniformly dispersed. Add the prepared dispersion to the mold, dry, and thus prepare the test sample. Add the test sample to lake water, then perform a 45-day aging experiment under ultraviolet light (350 nm, 100 mW / cm 2 ) irradiation.

[0088] Example 16

[0089] Take 1 g of cellulose acetate with a degree of substitution of 2.45, fully dissolved with acetone, then add 5.0wt% of bismuth-based nanometer quantum dots with a size of 17-20 nm as an additive, continue to stir until the sample is uniformly dispersed. Add the prepared dispersion to the mold, dry, and thus prepare the test sample. Add the test sample to lake water, then perform a 45-day aging experiment under ultraviolet light (350 nm, 100 mW / cm 2 ) irradiation.

[0090] Example 17

[0091] Take 1 g of cellulose acetate with a degree of substitution of 2.45, fully dissolved with acetone, then add 10.0wt% of bismuth-based nanometer quantum dots with a size of 17-20 nm as an additive, continue to stir until the sample is uniformly dispersed. Add the prepared dispersion to the mold, dry, and thus prepare the test sample. Add the test sample to lake water, then perform a 45-day aging experiment under ultraviolet light (350 nm, 100 mW / cm 2 ) irradiation.

[0092] Table 5 Change in molecular weight of CA sample after 45 days of ultraviolet light irradiation under different bismuth-based nanometer quantum dot additive amounts (lake water environment)

[0093]

[0094] As can be seen from Table 5, in the lake water environment, the Mn and Mw of the low additive amount (0.5wt%-5.0wt%) group are close to those in the sea water environment, but the Mn of the 10.0wt% additive amount group unexpectedly rises to 25900 (close to the control sample), which may be due to the influence of the ion composition (such as calcium and magnesium ions) in the lake water on the dispersibility of bismuth-based nanometer quantum dots, resulting in a decrease in photocatalytic efficiency.

[0095] Example 18

[0096] Take 1 g of acetate cellulose with a degree of substitution of 2.45, fully dissolved with acetone, then add 0.5wt% of bismuth-based nanometer quantum dots as an additive, continue to stir until the sample is uniformly dispersed. Add the prepared dispersion to the mold, dry, and thus prepare the sample to be tested. Add the sample to be tested to the soil, then perform a 45-day aging experiment under ultraviolet light (350 nm, 100 mW / cm 2 ) irradiation.

[0097] Example 19

[0098] Take 1 g of acetate cellulose with a degree of substitution of 2.45, fully dissolved with acetone, then add 1.0wt% of bismuth-based nanometer quantum dots with a size of 17-20 nm as an additive, continue to stir until the sample is uniformly dispersed. Add the prepared dispersion to the mold, dry, and thus prepare the sample to be tested. Add the sample to be tested to the soil, then perform a 45-day aging experiment under ultraviolet light (350 nm, 100 mW / cm 2 ) irradiation.

[0099] Example 20

[0100] Take 1 g of acetate cellulose with a degree of substitution of 2.45, fully dissolved with acetone, then add 2.5wt% of bismuth-based nanometer quantum dots with a size of 17-20 nm as an additive, continue to stir until the sample is uniformly dispersed. Add the prepared dispersion to the mold, dry, and thus prepare the sample to be tested. Add the sample to be tested to the soil, then perform a 45-day aging experiment under ultraviolet light (350 nm, 100 mW / cm 2 ) irradiation.

[0101] Example 21

[0102] Take 1 g of acetate cellulose with a degree of substitution of 2.45, fully dissolved with acetone, then add 5.0wt% of bismuth-based nanometer quantum dots with a size of 17-20 nm as an additive, continue to stir until the sample is uniformly dispersed. Add the prepared dispersion to the mold, dry, and thus prepare the sample to be tested. Add the sample to be tested to the soil, then perform a 45-day aging experiment under ultraviolet light (350 nm, 100 mW / cm 2 ) irradiation.

[0103] Example 22

[0104] Take 1 g of cellulose acetate with a degree of substitution of 2.45, fully dissolved with acetone, then add 10.0wt% bismuth-based nanometer quantum dots with a size of 17-20 nm as an additive, continue to stir until the sample is uniformly dispersed. Add the prepared dispersion to the mold, dry, and thus prepare the test sample. Add the test sample to the soil, then perform a 45-day aging experiment under ultraviolet light (350 nm, 100 mW / cm 2 ) irradiation.

[0105] Table 6 Change in molecular weight of CA sample after 45 days of ultraviolet light irradiation under different amounts of bismuth-based nanometer quantum dot addition (soil environment)

[0106]

[0107]

[0108] As can be seen from Table 6, in the soil environment, the Mn and Mw of each addition amount group are less different from the control sample (such as the 5.0wt% group Mn = 25500, close to the control sample 26100), indicating that the blocking effect of light by the soil, the poor air medium between the soil and the sample, or microorganisms, organic matter, etc. in the soil may inhibit the photocatalytic reaction, so that the degradation promotion effect of bismuth-based materials on CA is weaker than that in seawater and lake water.

[0109] Example 23

[0110] Take 1 g of cellulose acetate with a degree of substitution of 2.45, fully dissolved with acetone, then add 5.0wt% bismuth-based nanometer quantum dots with a size of 17-20 nm as an additive, continue to stir until the sample is uniformly dispersed. Add the prepared dispersion to the mold, dry, and thus prepare the test sample. Add the test sample to the seawater, then perform a 30-day aging experiment under blue light (415 nm, 100 mW / cm 2 ) irradiation.

[0111] Example 24

[0112] Take 1 g of cellulose acetate with a degree of substitution of 2.45, fully dissolved with acetone, then add 5.0wt% bismuth-based nanometer quantum dots with a size of 17-20 nm as an additive, continue to stir until the sample is uniformly dispersed. Add the prepared dispersion to the mold, dry, and thus prepare the test sample. Add the test sample to the seawater, then perform a 30-day aging experiment under blue light (460 nm, 110 mW / cm 2 ) irradiation.

[0113] Example 25

[0114] Take 1 g of cellulose acetate with a degree of substitution of 2.45, fully dissolved with acetone, then add 5.0wt% of bismuth-based nanometer quantum dots with a size of 17-20 nm as an additive, continue to stir until the sample is uniformly dispersed. Add the prepared dispersion to the mold, dry, and thus prepare the sample to be tested. Add the sample to be tested to seawater, then perform a 30-day aging experiment under green light (550 nm, 110 mW / cm 2 ) irradiation.

[0115] Table 7 Change in molecular weight of CA samples after 30 days of light irradiation under different light sources

[0116]

[0117]

[0118] As can be seen from Table 7, under the condition of 5.0% bismuth nanometer material addition, when the wavelength of the light source is between 350 nm and 460 nm, the additive has a good promoting effect on the degradation process of cellulose acetate, but when the wavelength is greater than 460 nm (such as 550 nm), the promoting effect of the additive is completely inhibited, indicating that the light source in the range of 350 nm to 460 nm can well match the electronic energy level of bismuth-based nanometer quantum dots, thereby significantly promoting the degradation of cellulose acetate.

[0119] Example 26

[0120] Take 0.375 g of cellulose acetate with a degree of substitution of 2.45 and 0.125 g of bismuth-based nanometer quantum dot additives with a size of 17-20 nm, add to seawater (10 mL), then perform a 30-day aging experiment under ultraviolet light (350 nm, 100 mW / cm 2 ) irradiation. Test the content of acetate in the liquid phase.

[0121] Example 27

[0122] Take 0.375 g of cellulose acetate with a degree of substitution of 2.45 and 0.062 g of bismuth-based nanometer quantum dot additives with a size of 17-20 nm, add to seawater (10 mL), then perform a 30-day aging experiment under ultraviolet light (350 nm, 100 mW / cm 2 ) irradiation. Test the content of acetate in the liquid phase.

[0123] Example 28

[0124] Take 0.375 g of cellulose acetate with a degree of substitution of 2.45 and 0.031 g of bismuth-based nanometer quantum dot additives with a size of 17-20 nm, add to seawater (10 mL), then perform a 30-day aging experiment under ultraviolet light (350 nm, 100 mW / cm 2The aging experiment of 30 days of light. Test the acetate content in the liquid phase.

[0125] Example 29

[0126] Take 0.375 g of cellulose acetate with a degree of substitution of 2.45 and 0.016 g of bismuth-based nanometer quantum dot additives with a size of 17-20 nm, add to seawater (10 mL), and then perform ultraviolet light (350 nm, 100 mW / cm 2 The aging experiment of 30 days of light. Test the acetate content in the liquid phase.

[0127] Table 8 Liquid phase acetate content of samples after 30 days of ultraviolet light under different mass ratios of bismuth-based nanometer quantum dots to CA (seawater environment)

[0128] Bismuth-based nano quantum dot addition amount Acetate content (mg / L) Comparative sample No addition 4.0 Example 26 25％ 34.0 Example 27 14％ 34.0 Example 28 7％ 29.7 Example 29 4％ 17.1

[0129] As can be seen from Table 8, when the mass ratio of bismuth-based nanometer quantum dots to CA is ≥14% (Examples 26-27), the acetate content is stable at 34.0 mg / L (about 8.5 times that of the comparative sample); when the mass ratio is reduced to below 7%, the acetate content decreases significantly (17.1 mg / L), indicating that the promotion of high proportion of additives to the ester bond rupture of CA is more significant, and also indicating that bismuth-based nanometer quantum dots can promote the ester bond rupture of cellulose acetate to release acetate.

[0130] Example 30

[0131] Take 1 g of cellulose acetate with a degree of substitution of 2.45, fully dissolve it with acetone, then add bismuth-based nanometer quantum dot additives of hypobromous acid with a mass fraction of 2.5 wt%, and continuously stir until the sample is uniformly dispersed. Add the prepared dispersion to the mold, dry, and thus prepare the sample to be tested. Add the sample to be tested to seawater, then perform the ultraviolet light (350 nm, 100 mW / cm 2 ) light aging experiment for 30 days.

[0132] Example 31

[0133] Take 1 g of cellulose acetate with a degree of substitution of 2.45, fully dissolve it with acetone, then add bismuth-based nanometer quantum dot additives of hypobromous acid with a mass fraction of 5.0 wt%, and continuously stir until the sample is uniformly dispersed. Add the prepared dispersion to the mold, dry, and thus prepare the sample to be tested. Add the sample to be tested to seawater, then perform the ultraviolet light (350 nm, 100 mW / cm 2 ) light aging experiment for 30 days.

[0134] Example 32

[0135] Take 1 g of degree of substitution of 2.45 cellulose acetate, fully dissolved with acetone, then add 10.0wt% of bismuthyl hypobromite-based nanometer quantum dots as an additive, continue to stir until the sample is uniformly dispersed. Add the prepared dispersion to the mold, dry, thereby preparing the sample to be tested. Add the sample to be tested to seawater, then perform ultraviolet lamp (350 nm, 100 mW / cm 2 ) light aging experiment, 30 days.

[0136] Table 9 Change in molecular weight of CA sample after 30 days of ultraviolet light irradiation under the addition of bismuthyl hypobromite-based nanometer quantum dots (seawater environment)

[0137]

[0138] As can be seen from Table 9, the Mn and Mw of the bismuthyl hypobromite-based nanometer quantum dot addition group are higher than the bismuth-based nanometer quantum dot group (such as 5.0wt% group Mn = 22100 vs bismuth-based nanometer quantum dot group 17500), indicating that its photocatalytic efficiency is much lower than that of pure bismuth-based nanometer quantum dots.

[0139] Example 33

[0140] Take 1 g of degree of substitution of 2.45 cellulose acetate, fully dissolved with acetone, then add 2.5wt% of nanometer bismuth oxide as an additive, continue to stir until the sample is uniformly dispersed. Add the prepared dispersion to the mold, dry, thereby preparing the sample to be tested. Add the sample to be tested to seawater, then perform ultraviolet lamp (350 nm, 100 mW / cm 2 ) light aging experiment, 30 days.

[0141] Example 34

[0142] Take 1 g of degree of substitution of 2.45 cellulose acetate, fully dissolved with acetone, then add 2.5wt% of nanometer bismuth sulfide as an additive, continue to stir until the sample is uniformly dispersed. Add the prepared dispersion to the mold, dry, thereby preparing the sample to be tested. Add the sample to be tested to seawater, then perform ultraviolet lamp (350 nm, 100 mW / cm 2 ) light aging experiment, 30 days.

[0143] Example 35

[0144] Take 1 g of degree of substitution of 2.45 cellulose acetate, fully dissolved with acetone, then add 2.5wt% of nanometer bismuth selenide as an additive, continue to stir until the sample is uniformly dispersed. Add the prepared dispersion to the mold, dry, thereby preparing the sample to be tested. Add the sample to be tested to seawater, then perform ultraviolet lamp (350 nm, 100 mW / cm 2 ) light aging experiment, 30 days.

[0145] Example 36

[0146] Take 1 g of cellulose acetate with a degree of substitution of 2.45, fully dissolved with acetone, then add 2.5 wt% of 100 nm elemental bismuth as an additive, continue stirring until the sample is uniformly dispersed. Add the prepared dispersion to the mold, dry, and thus prepare the sample to be tested. Add the sample to be tested to seawater, then conduct a UV lamp (350 nm, 100 mW / cm 2 ) light aging experiment for 30 days.

[0147] Example 37

[0148] Take 1 g of cellulose acetate with a degree of substitution of 2.45, fully dissolved with acetone, then add 2.5 wt% of 500 nm elemental bismuth as an additive, continue stirring until the sample is uniformly dispersed. Add the prepared dispersion to the mold, dry, and thus prepare the sample to be tested. Add the sample to be tested to seawater, then conduct a UV lamp (350 nm, 100 mW / cm 2 ) light aging experiment for 30 days.

[0149] Table 10 Change in molecular weight of CA sample after 30 days of UV light under different bismuth-based material addition (seawater environment)

[0150]

[0151]

[0152] From Table 10, the Mn and Mw of cellulose acetate in the non-quantum dot bismuth-based material group (such as bismuth oxide, bismuth sulfide) did not change significantly compared to the control group. The degradation process of bismuth oxide and bismuth sulfide groups on cellulose acetate has a certain degree of promotion, but is lower than the bismuth-based nanometer quantum dot group under the same conditions. Increasing the size of bismuth nanomaterials greatly weakens its catalytic effect, so that the results are similar to the control group, indicating that nanometer size, especially quantum dot level, is the key to the high efficiency of bismuth-based nanomaterials.

[0153] Example 38

[0154] Take 1 g of cellulose acetate with a degree of substitution of 2.45, fully dissolved with acetone, then add 5.0 wt% of bismuth-based nanometer quantum dots with a size of 17-20 nm as an additive, continue stirring until the sample is uniformly dispersed. Add the prepared dispersion to the mold, dry, and thus prepare the sample to be tested. Add the sample to be tested to prepared seawater (salinity 3.3%, pH 7.0), then conduct a UV lamp (350 nm, 100 mW / cm 2 ) light aging experiment for 30 days.

[0155] Example 39

[0156] 1 g of cellulose acetate with a degree of substitution of 2.45 was dissolved thoroughly in acetone. Then, 5.0 wt% of bismuth-based quantum dots with a size of 17-20 nm were added as an additive, and the mixture was stirred continuously until the sample was uniformly dispersed. The prepared dispersion was added to a mold and dried to obtain the sample to be tested. The sample was then added to prepared seawater (salinity 3.3%, pH 7.8) and subjected to ultraviolet light (350 nm, 100 mW / cm²). 2 Aging experiment with 30 days of light exposure.

[0157] Example 40

[0158] 1 g of cellulose acetate with a degree of substitution of 2.45 was dissolved thoroughly in acetone. Then, 5.0 wt% of bismuth-based quantum dots with a size of 17-20 nm were added as an additive, and the mixture was stirred continuously until the sample was uniformly dispersed. The prepared dispersion was added to a mold and dried to obtain the sample to be tested. The sample was then added to prepared seawater (salinity 3.3%, pH 8.4) and subjected to ultraviolet light (350 nm, 100 mW / cm²). 2 Aging experiment with 30 days of light exposure.

[0159] Example 41

[0160] 1 g of cellulose acetate with a degree of substitution of 2.45 was dissolved thoroughly in acetone. Then, 5.0 wt% of bismuth-based quantum dots with a size of 17-20 nm were added as an additive, and the mixture was stirred continuously until the sample was uniformly dispersed. The prepared dispersion was added to a mold and dried to obtain the sample to be tested. The sample was then added to prepared seawater (salinity 3.7%, pH 8.4) and subjected to ultraviolet light (350 nm, 100 mW / cm²). 2 Aging experiment with 30 days of light exposure.

[0161] Table 11. Molecular weight changes of CA samples after 30 days of UV irradiation with bismuth-based nanomaterials (different seawater preparations).

[0162] Name Mn Mw Polydispersity Comparative sample 26100 201000 7.66 Example 5 19800 175000 8.83 Example 38 25300 199000 7.86 Example 39 20800 177000 8.50 Example 40 20100 180000 8.95 Example 41 20300 178000 8.77

[0163] As shown in Table 11, in seawater prepared under different conditions, neutral conditions (pH 7.0) did not promote the degradation of cellulose acetate by bismuth-based quantum dots, while under weakly alkaline conditions (pH 7.8-8.4), the molecular weight of cellulose acetate decreased significantly, approaching the effect in natural seawater.

[0164] Example 42

[0165] Bismuth metal powder was added to N-methyl pyrrolidone, and the system was placed in a 400W ultrasonic instrument at 5°C for ultrasonic treatment for 24 hours. The reaction system was transferred to a centrifuge tube and centrifuged at a speed of 6000 rpm, and the supernatant was transferred to a new centrifuge tube and centrifuged at a speed of 18000 rpm. The supernatant was removed, and after vacuum drying for 24 hours, bismuth nanomaterials were obtained. 0.1 g of cellulose acetate with a degree of substitution of 2.45 was fully dissolved in acetone, and then 5.0wt% of the bismuth nanomaterials were added as an additive, and the sample was continuously stirred until it was uniformly dispersed. The prepared dispersion was added to a mold and dried to obtain a sample to be tested. The sample to be tested was added to seawater, and then an aging experiment was carried out under ultraviolet light (350nm, 100mW / cm 2 ) irradiation for 30 days.

[0166] Example 43

[0167] Bismuth neodecanoate was added to 1-octadecene, and the system was placed in a vacuum at 120°C for 2 hours. Then the temperature was adjusted to 80°C, 1-dodecanethiol was added under vigorous stirring, and the system was incubated for 5 minutes. The temperature was adjusted to 70°C, 2mL of trioctylphosphine heated to 45°C in advance was quickly added to the reaction system, and the system was incubated for 2 minutes. The reaction system was transferred to a centrifuge tube and centrifuged at a speed of 18000 rpm, and the supernatant was removed and replaced with a solution of acetone / tetrahydrofuran at a volume ratio of 10:1. After ultrasonic washing and centrifugation, the washing / centrifugation operation was repeated three times. The obtained solid was vacuum dried for 24 hours to obtain bismuth nanomaterials. 0.1 g of cellulose acetate with a degree of substitution of 2.45 was fully dissolved in acetone, and then 5.0wt% of the bismuth nanomaterials were added as an additive, and the sample was continuously stirred until it was uniformly dispersed. The prepared dispersion was added to a mold and dried to obtain a sample to be tested. The sample to be tested was added to seawater, and then an aging experiment was carried out under ultraviolet light (350nm, 100mW / cm 2 ) irradiation for 30 days.

[0168] Table 12 Change in molecular weight of CA samples after 30 days of ultraviolet light irradiation of bismuth-based nanomaterials obtained by different synthesis methods

[0169] Name Mn Mw Polydispersity Comparative sample 26100 201000 7.66 Example 5 19800 175000 8.83 Example 42 26300 209000 7.94 Example 43 21800 186000 8.53

[0170] As shown in Table 12, compared with the bismuth nanomaterial obtained by the polyvinylpyrrolidone system, the bismuth nanomaterial obtained by direct ultrasonic does not show a promoting effect on the degradation of cellulose acetate, which may be due to the fact that the bismuth material is prone to unintended chemical reactions, such as oxidation, in complex seawater, thereby deactivating the material and failing to play a role. The bismuth nanomaterial prepared in 1-octadecene shows a good promoting effect on the degradation of cellulose acetate in seawater, and the effect is close to that of the bismuth nanomaterial prepared by the polyvinylpyrrolidone system.

[0171] The application utilizes the photocatalytic effect of bismuth-based nanometer quantum dot material to significantly improve the degradation efficiency of CA in seawater, and the technical parameters (addition amount, illumination time) and environmental adaptability are clear. Because the smaller the degree of substitution of cellulose acetate is, the easier it is to be degraded, therefore, the CA with a degree of substitution less than or equal to 2.45 in the embodiments of the application is effective. The degradation product in the application is safe and meets the environmental protection requirements, and has important practical application value.

[0172] The above related descriptions and the description of the embodiments are for the convenience of the ordinary skilled in the art to understand and apply the application. Those skilled in the art can obviously easily make various modifications to these contents, and apply the general principles described herein to other embodiments without creative labor. The application is not limited to the above related descriptions and the description of the embodiments. The improvements and modifications made by those skilled in the art according to the disclosure of the application without departing from the scope of the application should be within the protection scope of the application.

Claims

1. A method for promoting degradation of cellulose acetate by nanometer quantum dot material, characterized in that, The application discloses a method for promoting degradation of cellulose acetate by using nano quantum dot material with excellent photoelectricity and photothermal performance as a photosensitive reagent to promote the degradation process of cellulose acetate under light conditions, so as to realize the chain rupture and efficient degradation of cellulose acetate molecular chains.

2. The method of claim 1, wherein the cellulose acetate is degraded by the nanometer quantum dot material. The nano quantum dot material is a bismuth-based nano quantum dot material.

3. The method of claim 2, wherein the cellulose acetate is degraded by the nanometer quantum dot material. The chemical formula of the bismuth-based nano quantum dot material is Bi.

4. The method of claim 3, wherein the cellulose acetate is degraded by the nanometer quantum dot material. The size of the bismuth-based nano quantum dot material is 17-20 nm.

5. The method of claim 1, wherein the cellulose acetate is degraded by the nanometer quantum dot material. The method comprises the following steps: Step (1) dissolving cellulose acetate in acetone solvent to obtain a uniform dispersion liquid; Step (2) adding the nano quantum dot material as a photosensitive reagent into the dispersion liquid, and continuously stirring until the sample is uniformly dispersed; Step (3) adding the prepared dispersion liquid into a mold, drying into a film, and preparing a sample to be tested; Step (4) placing the sample to be tested in an application environment, irradiating under ultraviolet light for a period of time, and promoting the chain rupture and degradation of cellulose acetate molecular chains through a photocatalytic reaction.

6. The method of claim 5, wherein the cellulose acetate is degraded by the nanometer quantum dot material. The nano quantum dot material in step (2) is a bismuth-based nano quantum dot material, and the addition amount of the bismuth-based nano quantum dot material is 0.5wt%-10wt% of the mass of cellulose acetate.

7. The method of claim 5, wherein the cellulose acetate is degraded by the nanometer quantum dot material. The degree of substitution DS of the cellulose acetate in step (1) is ≦2.

45.

8. The method of claim 5, wherein the cellulose acetate is degraded by the nanometer quantum dot material. The application environment in step (4) is soil, lake water or sea water.

9. The method of claim 8, wherein the cellulose acetate is degraded by the nanometer quantum dot material. The application environment in step (4) is sea water.

10. The method of claim 9, wherein the cellulose acetate is degraded by the nanometer quantum dot material. The salinity of the sea water is 3.3%-3.7%, and the pH value is 7.8-8.

4.

11. The method of claim 5, wherein the cellulose acetate is degraded by the nanometer quantum dot material. The wavelength of the ultraviolet light is 350-460 nm, and the light intensity is 100 mW / cm 2 , and the time is 15-60 days.

12. Application of the method for promoting degradation of cellulose acetate by using the nano quantum dot material in any one of claims 1 to 7 in promoting degradation of cellulose acetate in soil, lake water or sea water.

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