CN112023897B - Preparation method of nanocellulose microspheres with selective adsorption and adsorption application to dye wastewater - Google Patents

Abstract

The invention relates to a preparation method of nano-cellulose microspheres with selective adsorbability and adsorption application of nano-cellulose microspheres to dye wastewater, and belongs to the field of preparation of bio-based materials. The preparation method comprises the following steps: adding the CNF suspension into HCl solution to form CNF microspheres; uniformly mixing the CNF microspheres and a silane coupling agent at 70-80 ℃, adding paraffin and Span-85 to react at 80-90 ℃ under the protection of inert gas, washing and freeze-drying to obtain a freeze-dried sample; and (3) refluxing, washing and drying the freeze-dried sample and the ionic liquid to obtain the nano-cellulose microspheres with selective adsorption. The adsorption selectivity of the modified CNF microspheres is adjusted by changing the pH of the dye solution, and the solid-to-liquid ratio of the CNF modified microspheres to the dye wastewater is 5-20 mg: 50 mL. f) And (4) recovering and recycling the CNF microspheres through centrifugal separation. The preparation method provided by the invention is simple, convenient to operate, strong in practicability, easy to recover and strong in environmental protection, and can solve the problem of water pollution in the current society.

Description

A kind of preparation method of nanocellulose microspheres with selective adsorption and adsorption application to dye wastewater

technical field

The invention belongs to the field of bio-based material preparation, in particular to a preparation method of a nano-cellulose microsphere adsorption material.

Background technique

The disclosure of information in this Background section is only for enhancement of understanding of the general background of the invention and should not necessarily be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person of ordinary skill in the art.

Cellulose nanofiber (CNF) is a renewable polymer material with high strength and high mechanical properties, which is abundant in sources. There are a large number of active hydroxyl groups on the surface of CNF, which is beneficial to the mutual penetration and modification with the polymer matrix. How to use the characteristics of CNF to prepare degradable modified bio-based materials, broaden their application properties and improve their market value is a problem that needs to be solved at present.

Dye wastewater has a wide variety, complex components, high pollutant content, certain color and high toxicity, so it is difficult to prepare materials that are universal and can effectively treat wastewater. Adsorption method has a wide range of uses in organic wastewater treatment, but cheap, efficient, renewable and degradable adsorption materials are the current research focus of dye wastewater.

SUMMARY OF THE INVENTION

To overcome the above deficiencies, the present invention provides a preparation method of CNF microspheres with selective adsorption. Using CNF as raw material to form microspheres in salt solution, and grafting ionic liquid on its surface, it has the ability of selective adsorption, which can be used for dye wastewater treatment and can be recycled, which can provide a new direction for the industrial application of CNF.

For realizing the above-mentioned technical purpose, the present invention adopts following technical scheme:

A first aspect of the present invention provides a method for preparing nanocellulose microspheres with selective adsorption, comprising:

The CNF suspension was added to the HCl solution to form CNF microspheres;

Mix CNF microspheres and silane coupling agent at 70℃～80℃ evenly, then add paraffin and Span-85 to react at 80℃～90℃ under the protection of inert gas, wash and freeze-dry to obtain freeze-dried samples;

The freeze-dried sample is refluxed with ionic liquid, washed and dried to obtain nanocellulose microspheres with selective adsorption.

After the CNF is modified by the method of the invention, the modified CNF microspheres can selectively adsorb anionic dyes and cationic dyes, and the nanocellulose can be degraded and regenerated, and is a green and pollution-free material.

The second aspect of the present invention provides nanocellulose microspheres with selective adsorption prepared by any of the above methods.

The modified CNF microsphere of the present invention has the ability of selectively adsorbing dyes, and can be recovered by centrifugal separation, and is a cleaning product.

The third aspect of the present invention provides the application of the above-mentioned nanocellulose microspheres with selective adsorption in the treatment of dye wastewater.

Since the modified nanocellulose microspheres of the present invention are used to treat dye wastewater, the use of chemicals is reduced, and the treatment efficiency is improved, so it is expected to be widely used in the treatment of dye wastewater.

The beneficial effects of the present invention are:

(1) The present invention uses CNF as a raw material, and has the advantages of environmental protection and regeneration.

(2) The modified CNF microspheres of the present invention have the ability to selectively adsorb dyes, and can be recovered by centrifugal separation, which is a cleaning product.

(3) The preparation method of the invention is simple, strong in adsorption capacity, strong in practicability, and has good economic and environmental benefits.

Detailed ways

It should be noted that the following detailed description is exemplary and intended to provide further explanation of the invention. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

It should be noted that the terminology used herein is for the purpose of describing specific embodiments only, and is not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly dictates otherwise, the singular is intended to include the plural as well, furthermore, it is to be understood that when the terms "comprising" and/or "including" are used in this specification, it indicates that There are features, steps, operations, devices, components and/or combinations thereof.

Terminology Explanation:

Span-85 refers to sorbitan trioleate (Span 85).

As mentioned in the background art, with the increasing attention to environmental problems, especially in the current situation where water resources are very scarce, the treatment of sewage is the only way to solve the water quality problem. Therefore, the present invention provides a preparation method of CNF microspheres that can be used for organic dye wastewater treatment.

One of the purposes of the invention is to provide a method for modifying CNF microspheres.

The second purpose of the invention is to use ionic liquid to modify the microspheres to achieve the purpose of selective adsorption.

The third purpose of the invention is to improve the reusability of the CNF adsorbent.

To achieve the above object, the present invention adopts the following technical solutions:

The method for preparing CNF microspheres with selective adsorption is to prepare and modify the microspheres with CNF as a raw material, so that they have the ability to selectively adsorb impurities in wastewater;

In some embodiments, the specific steps of the modification method are as follows: take 0.8-1.5wt% CNF suspension containing 10g, adjust the pH to neutrality, use a needle tube with a measuring range of 2.5mL and a needle diameter of 0.6mm to transfer the CNF The suspension was added dropwise to a slowly stirred 0.1 mol/L HCl solution. After the dropwise addition, 20wt% of silane coupling agent (relative to the mass of CNF) was added dropwise, stirred and reacted at 70°C for 2h and then transferred to a three-necked flask, paraffin and Span-85 were added according to the water-oil ratio of 1:2, The reaction was stirred at 80 °C for 2 h under the protection of N ₂ , washed with acetone and water for several times after the reaction, and lyophilized. In the toluene solution, the freeze-dried samples and the ionic liquid were refluxed for 24 h. After the reaction was completed, they were washed with acetone and water for several times and then vacuum-dried to obtain the desired CNF microspheres.

The specification of CNF is not particularly limited in this application. In some embodiments, the length of CNF is 500-2000 nm and the diameter is 10-50 nm, and the obtained CNF microspheres have better adsorption capacity and mechanical properties.

In some embodiments, the concentration of CNF used in the preparation of CNF microspheres is 0.8-1.5 wt%, so that the prepared microspheres have high density and easy adsorption;

The concentration of HCl is not specifically limited in this application. In some embodiments, the concentration of HCl used in the preparation of CNF microspheres is 0.1 mol/L to effectively improve the dispersibility of CNF;

In some embodiments, the amount of the silane coupling agent loaded on the surface of the CNF microspheres is 20 wt%, and the silane coupling agent grafted on the surface of the CNF microspheres can improve the surface hydrophobicity of the CNF microspheres, and couple ions through the silane coupling agent liquid;

In some embodiments, the silane coupling agent is selected as 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, 3-ethoxybromosilane, etc., to better combine with the ionic liquid;

In some embodiments, paraffin and Span-85 are simultaneously added to the three-necked flask to react with the CNF microspheres and the mass ratio of the oil phase to the water phase is 2:1 to prevent cross-linking of the pellets;

In some embodiments, the ionic liquid is selected to be 1-ethyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium chloride and 1-butyl-3-methylimidazolium bromide, ionic The liquid can further improve the adsorption performance of CNF microspheres and achieve selective adsorption;

In some embodiments, when CNF microspheres are modified with ionic liquid, the dosage ratio is 1:2-2:1. It was found that the amount of ionic liquid continued to increase, and the adsorption efficiency decreased, indicating that the amount of ionic liquid needed to be within an appropriate range and there was a peak value;

In some embodiments, the specific steps of selective adsorption are: mixing and stirring the modified CNF microspheres with dye wastewater for 1 hour, adjusting the adsorption selectivity of the modified CNF microspheres by changing the pH of the dye solution, and measuring by UV-Vis Changes in the content of adsorbed dyes in wastewater before and after adsorption. After the absorption is complete, the precipitate is collected and recovered by centrifugation, desorbed with 10% ammonia water, repeatedly washed with ethanol, dried and recycled for use.

In some embodiments, the solid-liquid ratio of CNF-modified microspheres to dye wastewater is 5-20 mg: 50 mL, so as to obtain better adsorption effect and removal rate.

In some embodiments, the dye wastewater is selected from organic cationic dyeing agent Bright Yellow 7GL, organic anionic dyeing agent Acid Orange 7 and organic cationic dyeing agent Bright Yellow 7GL/organic anionic dyeing agent Acid Orange 7 in a mass ratio of 1:1.

In some embodiments, the CNF microspheres are recovered by centrifugation and reused, so as to achieve the purpose of environmental protection and regeneration.

The present invention will be further described in detail below with reference to specific embodiments. It should be pointed out that the specific embodiments are intended to explain rather than limit the present invention.

Example 1

A preparation method of nanocellulose microspheres with selective adsorption, the specific steps are as follows:

1) Preparation of nanocellulose microspheres: a) Soak the eucalyptus pulp board in deionized water until it is completely de-ionized, beat to a beating degree of 48°SR, dehydrate and seal and balance for 12 hours and then measure the moisture for later use. b) Take an appropriate amount of slurry (compared to absolutely dry slurry) and place it in a three-necked flask, add an appropriate amount of 64wt% concentrated sulfuric acid in a ratio of 18:1 to acid slurry, and conduct acid hydrolysis in a 50°C water bath for 1 hour. After the reaction is completed, add The reaction was terminated with ionized water, washed by centrifugation until the pH of the supernatant was 3, and the precipitate was replaced by dialysis until the dialysate became neutral. c) Take out the precipitate, place it in an ultrasonic cell pulverizer for 30 minutes at a power of 1200W, and then homogenize it for 15 minutes through a high-pressure homogenizer at a pressure of 80 bar for the first valve and 350 bar for the second valve. d) Take the 1.0wt% CNF suspension containing 10g, adjust the pH to neutrality, and add the CNF suspension dropwise to the slowly stirred 0.1mol/L HCl solution with a needle tube with a measuring range of 2.5mL and a needle diameter of 0.6mm. . After the dropwise addition, 20wt% of 3-chloropropyltrimethoxysilane (relative to the mass of CNF) was added dropwise, stirred and reacted at 70°C for 2h, then transferred to a three-necked flask, and added in a volume ratio of 1:2 according to the water-oil ratio. The ratio of paraffin and Span-85 was 1:15, and the reaction was stirred at 80 °C for 2 h under the protection of N ₂ . After the reaction, washed with acetone and water for several times and lyophilized. e) In the toluene solution, the freeze-dried sample and 1-ethyl-3-methylimidazolium chloride were mixed in a mass ratio of 2:1, and then refluxed for 24 hours. After the reaction was completed, it was washed with acetone and water for several times and then vacuum-dried. The desired CNF microspheres were prepared.

2) Selective adsorption of dyes in water by nanocellulose microspheres: a) Prepare a mixed dye solution of bright yellow 7GL and acid orange 7 with a mass ratio of 1:1, control the dye concentration to 100mg/L, and measure the pHzp of the obtained CNF microspheres to 5.1 reaches the zero-point charge value. b) When the pH of the dye solution is adjusted to < pHzp is 4.5, the CNF microspheres and the dye solution are mixed and stirred at a ratio of 10 mg: 50 mL for 1 h; when the pH of the dye solution is adjusted > pHzp is 5.5, the CNF microspheres and the dye solution are mixed at a ratio of 10 mg: 50 mL Mixing and stirring for 1h was carried out in the proportion of 100%, centrifuged and filtered with a filter membrane, and then the content of the adsorbed dye in the dye solution before and after adsorption was determined by UV-Vis.

Example 2

A preparation method of nanocellulose microspheres with selective adsorption, the specific steps are as follows:

1) Preparation of nanocellulose microspheres: a) Soak the eucalyptus pulp board in deionized water until it is completely de-ionized, beat to a beating degree of 48°SR, dehydrate and seal and balance for 12 hours and then measure the moisture for later use. b) Take an appropriate amount of slurry (compared to absolutely dry slurry) and place it in a three-necked flask, add an appropriate amount of 64wt% concentrated sulfuric acid in a ratio of 18:1 to acid slurry, and conduct acid hydrolysis in a 50°C water bath for 1 hour. After the reaction is completed, add The reaction was terminated with ionized water, washed by centrifugation until the pH of the supernatant was 3, and the precipitate was replaced by dialysis until the dialysate became neutral. c) Take out the precipitate, place it in an ultrasonic cell pulverizer for 30 minutes at a power of 1200W, and then homogenize it for 15 minutes through a high-pressure homogenizer at a pressure of 80 bar for the first valve and 350 bar for the second valve. d) Take the 1.0wt% CNF suspension containing 10g, adjust the pH to neutrality, and add the CNF suspension dropwise to the slowly stirred 0.1mol/L HCl solution with a needle tube with a measuring range of 2.5mL and a needle diameter of 0.6mm. . After the dropwise addition, 20wt% of 3-chloropropyltrimethoxysilane (relative to the mass of CNF) was added dropwise, stirred and reacted at 70°C for 2h, then transferred to a three-necked flask, and added in a volume ratio of 1:2 according to the water-oil ratio. The ratio of paraffin and Span-85 was 1:15, and the reaction was stirred at 80 °C for 2 h under the protection of N ₂ . After the reaction, washed with acetone and water for several times and lyophilized. e) In the toluene solution, the freeze-dried sample and 1-ethyl-3-methylimidazolium chloride were mixed in a mass ratio of 1:1, and then refluxed for 24 hours. After the reaction, washed with acetone and water for several times and then vacuum-dried. The desired CNF microspheres were prepared.

2) Selective adsorption of dyes in water by nanocellulose microspheres: a) Prepare a mixed dye solution of bright yellow 7GL and acid orange 7 with a mass ratio of 1:1, control the dye concentration to 100mg/L, and measure the pHzp of the obtained CNF microspheres to 5.5 reaches the zero-point charge value. b) When the pH of the dye solution is adjusted to less than pH 5.0, the CNF microspheres and the dye solution are mixed and stirred at a ratio of 10 mg: 50 mL for 1 h; when the pH of the dye solution is adjusted to > pH 6.0, the CNF microspheres and the dye solution are mixed at a ratio of 10 mg: 50 mL. Mixed and stirred for 1 h at the same ratio, centrifuged and filtered with a filter membrane, and then determined the content change of the adsorbed dye in the dye solution before and after adsorption by UV-Vis.

Example 3

A preparation method of nanocellulose microspheres with selective adsorption, the specific steps are as follows:

1) Preparation of nanocellulose microspheres: a) Soak the eucalyptus pulp board in deionized water until it is completely de-ionized, beat until the beating degree is 48°SR, dehydrate and seal and balance for 12 hours, and then measure the moisture for later use. b) Take an appropriate amount of slurry (compared to absolutely dry slurry) and place it in a three-necked flask, add an appropriate amount of 64wt% concentrated sulfuric acid in a ratio of 18:1 to acid slurry, and conduct acid hydrolysis in a 50°C water bath for 1 hour. After the reaction is completed, add The reaction was terminated with ionized water, washed by centrifugation until the pH of the supernatant was 3, and the precipitate was replaced by dialysis until the dialysate became neutral. c) Take out the precipitate, place it in an ultrasonic cell pulverizer for 30 minutes at a power of 1200W, and then homogenize it for 15 minutes through a high-pressure homogenizer at a pressure of 80 bar for the first valve and 350 bar for the second valve. d) Take the 1.0wt% CNF suspension containing 10g, adjust the pH to neutrality, and add the CNF suspension dropwise to the slowly stirred 0.1mol/L HCl solution with a needle tube with a measuring range of 2.5mL and a needle diameter of 0.6mm. . After the dropwise addition, 20wt% of 3-chloropropyltrimethoxysilane (relative to the mass of CNF) was added dropwise, stirred and reacted at 70°C for 2h, then transferred to a three-necked flask, and added in a volume ratio of 1:2 according to the water-oil ratio. The ratio of paraffin and Span-85 was 1:15, and the reaction was stirred at 80 °C for 2 h under the protection of N ₂ . After the reaction, washed with acetone and water for several times and lyophilized. e) In the toluene solution, the freeze-dried sample and 1-ethyl-3-methylimidazolium chloride were mixed in a mass ratio of 1:2, and then refluxed for 24 hours. After the reaction was completed, it was washed with acetone and water for several times and then vacuum-dried. The desired CNF microspheres were prepared.

2) Selective adsorption of dyes in water by nanocellulose microspheres: a) Prepare 100 mg/L acid orange 7 to dissolve, and determine that the obtained CNF microspheres reach the zero point charge value when the pHzp is 5.9. b) When the pH of the dye solution is adjusted to < pHzp is 5.0, the CNF microspheres and the dye solution are mixed and stirred at a ratio of 10mg: 50mL for 1 hour; when the pH of the dye solution is adjusted to > pHzp is 6.5, the CNF microspheres and the dye solution are mixed in a ratio of 10mg: 50mL Mixed and stirred for 1 h at the same ratio, centrifuged and filtered with a filter membrane, and then determined the content change of the adsorbed dye in the dye solution before and after adsorption by UV-Vis.

Example 4

A preparation method of nanocellulose microspheres with selective adsorption, the specific steps are as follows:

1) Preparation of nanocellulose microspheres: a) Soak the eucalyptus pulp board in deionized water until it is completely de-ionized, beat to a beating degree of 48°SR, dehydrate and seal and balance for 12 hours and then measure the moisture for later use. b) Take an appropriate amount of slurry (compared to absolutely dry slurry) and place it in a three-necked flask, add an appropriate amount of 64wt% concentrated sulfuric acid in a ratio of 18:1 to acid slurry, and conduct acid hydrolysis in a 50°C water bath for 1 hour. After the reaction is completed, add The reaction was terminated with ionized water, washed by centrifugation until the pH of the supernatant was 3, and the precipitate was replaced by dialysis until the dialysate became neutral. c) Take out the precipitate, place it in an ultrasonic cell pulverizer for 30 minutes at a power of 1200W, and then homogenize it for 15 minutes through a high-pressure homogenizer at a pressure of 80 bar for the first valve and 350 bar for the second valve. d) Take the 0.8wt% CNF suspension containing 10g, adjust the pH to neutral, and add the CNF suspension dropwise to the slowly stirred 0.1mol/L HCl solution with a needle tube with a range of 2.5mL and a needle diameter of 0.6mm . After the dropwise addition, 20wt% of 3-chloropropyltriethoxysilane (relative to the mass of CNF) was added dropwise, stirred and reacted at 70°C for 2h, then transferred to a three-necked flask, and added according to the water-oil ratio of 1:2. Paraffin and Span-85 with a volume ratio of 1:15 were stirred and reacted at 80 °C for 2 h under the protection of N ₂ . e) In the toluene solution, the freeze-dried sample and 1-butyl-3-methylimidazolium chloride are mixed in a mass ratio of 1:1, and then refluxed for 24 hours. After the reaction is completed, wash with acetone and water for several times and then vacuum dry. The desired CNF microspheres were prepared.

2) Selective adsorption of dyes in water by nanocellulose microspheres: a) Prepare a bright yellow 7GL dye solution with a mass concentration of 100 mg/L, and determine that the obtained CNF microspheres reach a zero-point charge value when the pHzp is 5.3. b) When the pH of the dye solution is adjusted to < pHzp is 4.5, the CNF microspheres and the dye solution are mixed and stirred at a ratio of 10mg: 50mL for 1 hour; when the pH of the dye solution is adjusted to > pHzp is 6.0, the CNF microspheres and the dye solution are mixed at a ratio of 10mg: 50mL Mixed and stirred for 1 h at the same ratio, centrifuged and filtered with a filter membrane, and then determined the content change of the adsorbed dye in the dye solution before and after adsorption by UV-Vis.

Example 5

A preparation method of nanocellulose microspheres with selective adsorption, the specific steps are as follows:

1) Preparation of nanocellulose microspheres: a) Soak the eucalyptus pulp board in deionized water until it is completely de-ionized, beat to a beating degree of 48°SR, dehydrate and seal and balance for 12 hours and then measure the moisture for later use. b) Take an appropriate amount of slurry (compared to absolutely dry slurry) and place it in a three-necked flask, add an appropriate amount of 64wt% concentrated sulfuric acid in a ratio of 18:1 to acid slurry, and conduct acid hydrolysis in a 50°C water bath for 1 hour. After the reaction is completed, add The reaction was terminated with ionized water, washed by centrifugation until the pH of the supernatant was 3, and the precipitate was replaced by dialysis until the dialysate became neutral. c) Take out the precipitate, place it in an ultrasonic cell pulverizer for 30 minutes at a power of 1200W, and then homogenize it for 15 minutes through a high-pressure homogenizer at a pressure of 80 bar for the first valve and 350 bar for the second valve. d) Take the 1.0wt% CNF suspension containing 10g, adjust the pH to neutrality, and add the CNF suspension dropwise to the slowly stirred 0.1mol/L HCl solution with a needle tube with a measuring range of 2.5mL and a needle diameter of 0.6mm. . After the dropwise addition, 20wt% of 3-chloropropyltriethoxysilane (relative to the mass of CNF) was added dropwise, stirred and reacted at 70°C for 2h, then transferred to a three-necked flask, and added according to the water-oil ratio of 1:2. The paraffin wax and Span-85 with a volume ratio of 1:15 were stirred and reacted at 80 °C for 2 h under the protection of N ₂ . After the reaction, washed with acetone and water several times and lyophilized. e) In the toluene solution, the freeze-dried sample and 1-butyl-3-methylimidazolium chloride are mixed in a mass ratio of 1:1, and then refluxed for 24 hours. After the reaction is completed, wash with acetone and water for several times and then vacuum dry. The desired CNF microspheres were prepared.

2) Nanocellulose microspheres selectively adsorb dyes in water: a) Prepare a mixed dye solution of bright yellow 7GL and acid orange 7 with a mass ratio of 1:1, control the dye concentration to 100mg/L, and measure the pHzp of the obtained CNF microspheres to 5.3 reaches the zero-point charge value. b) When the pH of the dye solution is adjusted to < pHzp is 4.5, the CNF microspheres and the dye solution are mixed and stirred at the ratio of 20mg: 50mL for 1 hour; when the pH of the dye solution is adjusted to > pHzp is 6.0, the CNF microspheres and the dye solution are mixed at a ratio of 20mg: 50mL Mixed and stirred for 1 h at the same ratio, centrifuged and filtered with a filter membrane, and then determined the content change of the adsorbed dye in the dye solution before and after adsorption by UV-Vis.

Example 6

A preparation method of nanocellulose microspheres with selective adsorption, the specific steps are as follows:

1) Preparation of nanocellulose microspheres: a) Soak the eucalyptus pulp board in deionized water until it is completely de-ionized, beat until the beating degree is 48°SR, dehydrate and seal and balance for 12 hours, and then measure the moisture for later use. b) Take an appropriate amount of slurry (compared to absolutely dry slurry) and place it in a three-necked flask, add an appropriate amount of 64wt% concentrated sulfuric acid in a ratio of 18:1 to acid slurry, and conduct acid hydrolysis in a 50°C water bath for 1 hour. After the reaction is completed, add The reaction was terminated with ionized water, washed by centrifugation until the pH of the supernatant was 3, and the precipitate was replaced by dialysis until the dialysate became neutral. c) Take out the precipitate, place it in an ultrasonic cell pulverizer for 30 minutes at 1200W power, and then homogenize it for 15 minutes through a high-pressure homogenizer at a pressure of 80 bar for the primary valve and 350 bar for the secondary valve. d) Take the 1.2wt% CNF suspension containing 10g, adjust the pH to neutrality, and add the CNF suspension dropwise to the slowly stirred 0.1mol/L HCl solution with a needle tube with a range of 2.5mL and a needle diameter of 0.6mm. . After the dropwise addition, 20wt% of 3-ethoxybromosilane (relative to the mass of CNF) was added dropwise, stirred and reacted at 70°C for 2h and then transferred to a three-necked flask. 1:15 of paraffin and Span-85 were stirred and reacted at 80 °C for 2 h under the protection of N ₂ . After the reaction, washed with acetone and water for several times and lyophilized. e) In the toluene solution, the freeze-dried sample and 1-butyl-3-methylimidazolium bromide are mixed in a mass ratio of 1:1 and refluxed for 24 hours. After the reaction is completed, wash with acetone and water for several times and then vacuum dry. The desired CNF microspheres were prepared.

2) Selective adsorption of dyes in water by nanocellulose microspheres: a) Prepare a bright yellow 7GL dye solution with a concentration of 100 mg/L, and determine that the obtained CNF microspheres reach zero point charge value when the pHzp is 5.4. b) When the pH of the dye solution is adjusted to <pHzp of 4.8, the CNF microspheres and the dye solution are mixed and stirred at a ratio of 20mg: 50mL for 1 hour; when the pH of the dye solution is adjusted to > pHzp of 6.0, the CNF microspheres and the dye solution are mixed in a ratio of 20mg: 50mL Mixed and stirred for 1 h at the same ratio, centrifuged and filtered with a filter membrane, and then determined the content change of the adsorbed dye in the dye solution before and after adsorption by UV-Vis.

Example 7

A preparation method of nanocellulose microspheres with selective adsorption, the specific steps are as follows:

1) Preparation of nanocellulose microspheres: a) Soak the eucalyptus pulp board in deionized water until it is completely de-ionized, beat to a beating degree of 48°SR, dehydrate and seal and balance for 12 hours and then measure the moisture for later use. b) Take an appropriate amount of slurry (compared to absolutely dry slurry) and place it in a three-necked flask, add an appropriate amount of 64wt% concentrated sulfuric acid in a ratio of 18:1 to acid slurry, and conduct acid hydrolysis in a 50°C water bath for 1 hour. After the reaction is completed, add The reaction was terminated with ionized water, washed by centrifugation until the pH of the supernatant was 3, and the precipitate was replaced by dialysis until the dialysate became neutral. c) Take out the precipitate, place it in an ultrasonic cell pulverizer for 30 minutes at a power of 1200W, and then homogenize it for 15 minutes through a high-pressure homogenizer at a pressure of 80 bar for the first valve and 350 bar for the second valve. d) Take the 1.5wt% CNF suspension containing 10g, adjust the pH to neutrality, and add the CNF suspension dropwise to the slowly stirred 0.1mol/L HCl solution with a needle tube with a measuring range of 2.5mL and a needle diameter of 0.6mm. . After the dropwise addition, 20wt% of 3-chloropropyltrimethoxysilane (relative to the mass of CNF) was added dropwise, stirred and reacted at 70°C for 2h, then transferred to a three-necked flask, and added in a volume ratio of 1:2 according to the water-oil ratio. The ratio of paraffin and Span-85 was 1:15, and the reaction was stirred at 80 °C for 2 h under the protection of N ₂ . After the reaction, washed with acetone and water for several times and lyophilized. e) In the toluene solution, the freeze-dried sample and 1-butyl-3-methylimidazolium chloride were mixed in a mass ratio of 2:1, and then refluxed for 24 hours. After the reaction, washed with acetone and water for several times and then vacuum-dried. The desired CNF microspheres were prepared.

2) Selective adsorption of dyes in water by nanocellulose microspheres: a) Prepare a mixed dye solution of bright yellow 7GL and acid orange 7 with a mass ratio of 1:1, control the dye concentration to 100mg/L, and measure the pHzp of the obtained CNF microspheres to 4.9 reaches the zero-point charge value. b) When the pH of the dye solution is adjusted to less than pH 4.4, the CNF microspheres and the dye solution are mixed and stirred at a ratio of 5 mg: 50 mL for 1 hour; when the pH of the dye solution is adjusted to be > pHSp to 5.5, the CNF microspheres and the dye solution are mixed at a ratio of 5 mg: 50 mL. Mixed and stirred for 1 h at the same ratio, centrifuged and filtered with a filter membrane, and then determined the content change of the adsorbed dye in the dye solution before and after adsorption by UV-Vis.

Example 8

A preparation method of nanocellulose microspheres with selective adsorption, the specific steps are as follows:

1) Preparation of nanocellulose microspheres: a) Soak the eucalyptus pulp board in deionized water until it is completely de-ionized, beat to a beating degree of 48°SR, dehydrate and seal and balance for 12 hours and then measure the moisture for later use. b) Take an appropriate amount of slurry (compared to absolutely dry slurry) and place it in a three-necked flask, add an appropriate amount of 64wt% concentrated sulfuric acid in a ratio of 18:1 to acid slurry, and conduct acid hydrolysis in a 50°C water bath for 1 hour. After the reaction is completed, add The reaction was terminated with ionized water, washed by centrifugation until the pH of the supernatant was 3, and the precipitate was replaced by dialysis until the dialysate became neutral. c) Take out the precipitate, place it in an ultrasonic cell pulverizer for 30 minutes at a power of 1200W, and then homogenize it for 15 minutes through a high-pressure homogenizer at a pressure of 80 bar for the first valve and 350 bar for the second valve. d) Take the 1.5wt% CNF suspension containing 10g, adjust the pH to neutrality, and add the CNF suspension dropwise to the slowly stirred 0.1mol/L HCl solution with a needle tube with a measuring range of 2.5mL and a needle diameter of 0.6mm. . After the dropwise addition, 20wt% of 3-chloropropyltriethoxysilane (relative to the mass of CNF) was added dropwise, stirred and reacted at 70°C for 2h, then transferred to a three-necked flask, and added according to the water-oil ratio of 1:2. The paraffin wax and Span-85 with a volume ratio of 1:15 were stirred and reacted at 80 °C for 2 h under the protection of N ₂ . After the reaction, washed with acetone and water several times and lyophilized. e) In the toluene solution, the freeze-dried sample and 1-butyl-3-methylimidazolium chloride were mixed in a mass ratio of 2:1, and then refluxed for 24 hours. After the reaction, washed with acetone and water for several times and then vacuum-dried. The desired CNF microspheres were prepared.

2) Selective adsorption of dyes in water by nanocellulose microspheres: a) Prepare a bright yellow 7GL acid orange 7 dye solution with a concentration of 100 mg/L, and determine that the obtained CNF microspheres reach a zero-point charge value when the pHzp is 4.7. b) When the pH of the dye solution is adjusted to <pHzp of 4.2, the CNF microspheres and the dye solution are mixed and stirred at a ratio of 10mg: 50mL for 1 hour; when the pH of the dye solution is adjusted to > pHzp of 5.5, the CNF microspheres and the dye solution are mixed in a ratio of 10mg: 50mL Mixed and stirred for 1 h at the same ratio, centrifuged and filtered with a filter membrane, and then determined the content change of the adsorbed dye in the dye solution before and after adsorption by UV-Vis.

Example 9

A preparation method of nanocellulose microspheres with selective adsorption, the specific steps are as follows:

1) Preparation of nanocellulose microspheres: a) Soak the eucalyptus pulp board in deionized water until it is completely de-ionized, beat until the beating degree is 48°SR, dehydrate and seal and balance for 12 hours, and then measure the moisture for later use. b) Take an appropriate amount of slurry (compared to absolute dry slurry) and place it in a three-necked flask, add an appropriate amount of 64wt% concentrated sulfuric acid in a ratio of 18:1 to acid slurry, and conduct acid hydrolysis in a 50°C water bath for 1 hour. After the reaction is completed, add The reaction was terminated with ionized water, washed by centrifugation until the pH of the supernatant was 3, and the precipitate was replaced by dialysis until the dialysate became neutral. c) Take out the precipitate, place it in an ultrasonic cell pulverizer for 30 minutes at a power of 1200W, and then homogenize it for 15 minutes through a high-pressure homogenizer at a pressure of 80 bar for the first valve and 350 bar for the second valve. d) Take the 1.5wt% CNF suspension containing 10g, adjust the pH to neutrality, and add the CNF suspension dropwise to the slowly stirred 0.1mol/L HCl solution with a needle tube with a measuring range of 2.5mL and a needle diameter of 0.6mm. . After the dropwise addition, 20wt% of 3-ethoxybromosilane (relative to the mass of CNF) was added dropwise, stirred and reacted at 70°C for 2h and then transferred to a three-necked flask. 1:15 of paraffin and Span-85 were stirred and reacted at 80 °C for 2 h under the protection of N ₂ . After the reaction, washed with acetone and water for several times and lyophilized. e) In the toluene solution, the freeze-dried sample and 1-butyl-3-methylimidazolium bromide are mixed in a mass ratio of 2:1 and refluxed for 24 hours. After the reaction is completed, wash with acetone and water for several times and then vacuum dry. The desired CNF microspheres were prepared.

2) Selective adsorption of dyes in water by nanocellulose microspheres: a) Prepare a mixed dye solution of bright yellow 7GL and acid orange 7 with a mass ratio of 1:1, control the dye concentration to 100mg/L, and measure the pHzp of the obtained CNF microspheres to 4.8 reaches the zero-point charge value. b) When the pH of the dye solution is adjusted to < pHzp is 4.1, the CNF microspheres and the dye solution are mixed and stirred at a ratio of 20mg: 50mL for 1 h; when the pH of the dye solution is adjusted to > pHzp is 5.5, the CNF microspheres and the dye solution are mixed in a ratio of 10mg: 50mL Mixed and stirred for 1 h at the same ratio, centrifuged and filtered with a filter membrane, and then determined the content change of the adsorbed dye in the dye solution before and after adsorption by UV-Vis.

Comparative Example 1

1) Preparation of nanocellulose: a) The eucalyptus pulp board was soaked in deionized water until completely de-ionized, beaten to a beating degree of 48°SR, dehydrated and sealed for equilibration for 12 hours, and the moisture was measured for later use. b) Take an appropriate amount of slurry (compared to absolute dry slurry) and place it in a three-necked flask, add 64wt% concentrated sulfuric acid in a ratio of 18:1 to acid slurry, and conduct acid hydrolysis in a water bath at 50°C for 1 hour. After the reaction is completed, add deionized The reaction was terminated with water, washed by centrifugation until the pH of the supernatant was 3, and the precipitate was replaced by dialysis until the dialysate became neutral. c) Take out the precipitate, place it in an ultrasonic cell pulverizer for 30 minutes at a power of 1200W, and then homogenize it for 15 minutes through a high-pressure homogenizer at a pressure of 80 bar for the primary valve and 350 bar for the secondary valve, and configure a concentration of 1.0wt% CNF suspension.

2) Nanocellulose adsorption of dyes in water: a) Prepare a mixed dye solution of bright yellow 7GL and acid orange 7 with a mass ratio of 1:1, control the dye concentration to 100 mg/L, and measure the obtained CNF when the pHZp is 4.8. Zero point charge value. b) When the pH of the dye solution is adjusted to <pHzp of 4.0, the CNF and the dye solution are mixed and stirred for 1 hour; when the pH of the dye solution is adjusted to be > pHzp of 5.0, the CNF and the dye solution are mixed and stirred at a ratio of 10 mg: 50 mL for 1 hour, and after centrifugation The content of the adsorbed dye in the dye solution before and after adsorption was determined by UV-Vis after filtration with a filter membrane.

Comparative Example 2

1) Preparation of nanocellulose microspheres: a) Soak the eucalyptus pulp board in deionized water until it is completely de-ionized, beat until the beating degree is 48°SR, dehydrate and seal and balance for 12 hours, and then measure the moisture for later use. b) Take an appropriate amount of slurry (compared to absolute dry slurry) and place it in a three-necked flask, add 64wt% concentrated sulfuric acid in a ratio of 18:1 to acid slurry, and conduct acid hydrolysis in a water bath at 50°C for 1 hour. After the reaction is completed, add deionized The reaction was terminated with water, washed by centrifugation until the pH of the supernatant was 3, and the precipitate was replaced by dialysis until the dialysate became neutral. c) Take out the precipitate, place it in an ultrasonic cell pulverizer for 30 minutes at a power of 1200W, and then homogenize it for 15 minutes through a high-pressure homogenizer at a pressure of 80 bar for the first valve and 350 bar for the second valve. d) Take the 1.0wt% CNF suspension containing 10g, adjust the pH to neutrality, and add the CNF suspension dropwise to the slowly stirred 0.1mol/L HCl solution with a needle tube with a measuring range of 2.5mL and a needle diameter of 0.6mm. , freeze-dried to obtain the desired CNF microspheres.

2) Selective adsorption of dyes in water by nanocellulose microspheres: a) Prepare a mixed dye solution of bright yellow 7GL and acid orange 7 with a mass ratio of 1:1, control the dye concentration to 100mg/L, and measure the obtained CNF microspheres at pHHzp 4.6 The zero point charge value is reached. b) When the pH of the dye solution is adjusted < pHSp to 4.0, the CNF microspheres and the dye solution are mixed and stirred for 1 hour; when the pH of the dye solution is adjusted to be > pHSp to 5.0, the CNF microspheres and the dye solution are mixed and stirred at a ratio of 10 mg: 50 mL for 1 hour After centrifugation, the content of the adsorbed dye in the dye solution before and after adsorption was determined by UV-Vis after filtration with a filter membrane.

Performance Testing:

Taking the concentration of bright yellow 7GL and acid orange 7 in the solution as the performance test index, the residual bright yellow 7GL in the dye solution before and after CNF treatment in Comparative Example 1-2 and Example 1-9 was measured by UV-Vis spectrophotometer UV-Vis and Acid Orange 7 concentration. The test method is as follows: the dye solutions before and after treatment are respectively placed in a UV-Vis spectrophotometer to measure the absorbance, and the concentration is calculated according to the standard curve. The test results are shown in Table 2.

Table 1 UV-Vis absorbance of bright yellow 7GL and acid orange 7 standard samples

Bright yellow 7GL concentration/g/L 0.0005 0.001 0.0015 0.002 0.0025 Absorbance/T1% 0.02286 0.03159 0.04033 0.04915 0.05805 Acid orange 7 concentration/g/L 0.0005 0.001 0.0015 0.002 0.0025 Absorbance/T2% 0.03144 0.03866 0.04571 0.05298 0.06014

According to the calculation, it can be seen that the standard curve is Y1=17.588X1+0.014; Y2=14.344X2+0.0243

Among them, X1 is the concentration of bright yellow 7GL, g/L; Y1 is the absorbance of ultraviolet and visible light, T1%;

X2 is the concentration of acid orange 7, g/L; Y2 is the absorbance of ultraviolet and visible light, T2%.

Table 2 Adsorption performance of CNF microspheres prepared by Examples 1-9 and Comparative Examples 1 and 2 to dyes

As can be seen from Table 2, after CNF is modified by the method of the present invention, the modified CNF microspheres can selectively adsorb anionic dyes and cationic dyes, and nanocellulose can be degraded and regenerated, which is a A green and pollution-free material.

Finally, it should be noted that the above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, the Modifications may be made to the technical solutions described in the foregoing embodiments, or equivalent replacements may be made to some of them. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention. Although the specific embodiments of the present invention are described above, they are not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that on the basis of the technical solutions of the present invention, those skilled in the art do not need to pay creative work. Various modifications or deformations made are still within the protection scope of the present invention.

Claims (10)

1. a preparation method of nanocellulose microspheres with selective adsorption is characterized in that, comprising: The CNF suspension was added to the HCl solution to form CNF microspheres; Mix the CNF microspheres and the silane coupling agent uniformly at 70℃～80℃, then add paraffin and Span-85 to react at 80℃～90℃ under the protection of inert gas, wash and freeze-dry to obtain freeze-dried samples; The freeze-dried sample is refluxed with ionic liquid, washed and dried to obtain nanocellulose microspheres with selective adsorption. 2 . The method for preparing nanocellulose microspheres with selective adsorption according to claim 1 , wherein the CNF suspension is treated by sulfuric acid method combined with homogeneous treatment to prepare CNF. 3 . 3 . The method for preparing nanocellulose microspheres with selective adsorption according to claim 1 , wherein the concentration of the CNF suspension is 0.8-1.5 wt %. 4 . 4. the preparation method of the nanocellulose microspheres with selective adsorption as claimed in claim 1, is characterized in that, described silane coupling agent is 3-chloropropyl trimethoxysilane, 3-chloropropyl triethyl At least one of oxysilane and 3-ethoxybromosilane. 5 . The method for preparing nanocellulose microspheres with selective adsorption according to claim 1 , wherein the silane coupling agent is added in an amount of 20-25 wt % of CNF. 6 . 6. the preparation method of the nanocellulose microspheres with selective adsorption as claimed in claim 1, is characterized in that, described ionic liquid is 1-ethyl-3-methylimidazolium chloride, 1-butyl- At least one of 3-methylimidazolium chloride and 1-butyl-3-methylimidazolium bromide. 7 . The method for preparing nanocellulose microspheres with selective adsorption according to claim 1 , wherein the dosage ratio of the freeze-dried sample to the ionic liquid is 1-2:1-2. 8 . 8 . The method for preparing nanocellulose microspheres with selective adsorption according to claim 1 , wherein paraffin and Span-85 are added according to the mass ratio of oil phase and water phase being 2-4:1. 9 . 9. Nanocellulose microspheres with selective adsorption prepared by the method of any one of claims 1-8. 10 . The application of the selective adsorption nanocellulose microspheres of claim 9 in the treatment of dye wastewater. 11 .