Preparation and application of modified lignin-cellulose composite microspheres

Abstract

The present invention belongs to the field of high-value conversion of lignin, and specifically relates to the preparation and application of a modified lignin cellulose composite microsphere, comprising adding a phenylpropionyl chloride solution to a low-temperature aminated lignin solution, mixing uniformly, reacting under the protection of an inert gas, collecting the product, and dialyzing to obtain a modified lignin; dissolving the modified lignin in water to obtain an aqueous solution of the modified lignin, then adding sodium carboxymethyl cellulose, mixing uniformly, and then adding dropwise to a low-temperature aluminum chloride aqueous solution to obtain the product. The microspheres prepared by the present invention have uniform lignin dispersion and uniform particle size distribution; the prepared modified lignin cellulose composite microspheres have good adsorption effect on organic dyes in wastewater, and are easy to separate from the wastewater after adsorption; the process is simple, easy to operate, and convenient for industrial application.

Description

Technical Field

[0001] The present invention belongs to the field of high-value conversion of lignin, and specifically relates to the preparation and application of modified lignin-cellulose composite microspheres. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

[0003] Lignin, the most abundant renewable aromatic polymer in nature, has attracted widespread attention in areas such as drug delivery, composite materials, dye dispersion, and cosmetics due to its wide availability, environmental friendliness, and excellent biocompatibility. Furthermore, lignin possesses numerous surface active groups that effectively adsorb heavy metal ions and organic dyes from wastewater, making it a research hotspot in wastewater treatment. However, separating lignin from wastewater after adsorption is difficult, and currently requires filtration or centrifugation, which limits its application. Summary of the Invention

[0004] In order to solve the above problems, the present invention provides a preparation and application of modified lignin cellulose composite microspheres.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] The first aspect of the present invention provides a method for preparing modified lignocellulose composite microspheres, comprising:

[0007] The phenylpropionyl chloride solution is added to the low-temperature aminated lignin solution, mixed evenly, and reacted under the protection of inert gas. After the reaction is completed, dialyzed to obtain modified lignin;

[0008] The modified lignin is dissolved in water to obtain an aqueous solution of the modified lignin, and then sodium carboxymethyl cellulose is added, mixed evenly, and then added dropwise to a low-temperature aluminum chloride aqueous solution to obtain the modified lignin.

[0009] The present invention develops a lignin-based adsorption material that is highly efficient and easy to separate from wastewater, which is of great significance for wastewater treatment.

[0010] The second aspect of the present invention provides modified lignocellulose composite microspheres prepared by the above method.

[0011] The third aspect of the present invention provides the use of the modified lignin-cellulose composite microspheres in the preparation of adsorption materials.

[0012] Beneficial effects of the present invention

[0013] (1) In the present invention, lignin is evenly dispersed in cellulose and the particle size of the microspheres is evenly distributed;

[0014] (2) The modified lignin cellulose composite microspheres prepared by the present invention have a good adsorption effect on organic dyes in wastewater, and are easy to separate from the wastewater after adsorption;

[0015] (3) The process of the present invention is simple, easy to operate, and convenient for industrial application. DETAILED DESCRIPTION

[0016] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0017] A method for modifying lignin-cellulose composite microspheres comprises the following steps: first, modifying alkali lignin by amination to obtain aminated lignin. Phenylpropionic acid is dissolved in chloroform, and then thionyl chloride is added dropwise. The mixture is reacted for a period of time under nitrogen protection. After completion of the reaction, reduced pressure distillation is performed to remove thionyl chloride and chloroform to obtain phenylpropionyl chloride. A tetrahydrofuran solution of phenylpropionyl chloride is added dropwise to a low-temperature tetrahydrofuran solution of aminated lignin using a constant pressure funnel. The mixture is then stirred and reacted for a period of time under nitrogen protection, and dialyzed in deionized water to obtain modified lignin. The modified lignin is dissolved in deionized water to obtain an aqueous solution of the modified lignin, and then a certain amount of sodium carboxymethyl cellulose is added, stirred thoroughly, and then added dropwise to a low-temperature aqueous solution of aluminum chloride using a syringe to obtain modified lignin-cellulose composite microspheres.

[0018] In some embodiments, the alkali lignin includes alkali lignin extracted from coniferous wood, hardwood and grass raw materials through alkaline pulping black liquor, and also includes various types of commercially sold alkali lignin.

[0019] In some embodiments, the alkali lignin has a molecular weight of 3,000 to 7,000.

[0020] In some embodiments, the amination modification method is a Mannich reaction, and the amination reagent includes an amination modification reagent with a relative molecular mass greater than 200, such as tetraethylenepentamine and triethylenetetramine.

[0021] In some embodiments, the nitrogen content in the aminated modified lignin is 3-4%.

[0022] In some embodiments, the phenylpropionic acid is dissolved in chloroform at a molar concentration of 4 to 8 mol / L.

[0023] In some embodiments, the dropwise addition of thionyl chloride has a dropwise addition rate of 1 to 2 mL / min.

[0024] In some embodiments, the reaction is carried out under nitrogen protection for a period of time, the reaction temperature is 40-45° C., and the reaction time is 3-4 hours.

[0025] In some embodiments, the obtained phenylpropionyl chloride has a purity of 90-95%.

[0026] In some embodiments, the tetrahydrofuran solution of phenylpropionyl chloride is added dropwise to the tetrahydrofuran solution of low-temperature aminated lignin via a constant pressure funnel, and the concentration of phenylpropionyl chloride in tetrahydrofuran is 10-15%.

[0027] In some embodiments, the tetrahydrofuran solution of phenylpropionyl chloride is added dropwise to the tetrahydrofuran solution of low-temperature aminated lignin via a constant pressure funnel, and the concentration of aminated lignin in tetrahydrofuran is 5-10%.

[0028] In some embodiments, the tetrahydrofuran solution of phenylpropionyl chloride is added dropwise to the tetrahydrofuran solution of low-temperature aminated lignin via a constant pressure funnel, and the temperature of the tetrahydrofuran solution of aminated lignin is 1-4°C.

[0029] In some embodiments, the tetrahydrofuran solution of phenylpropionyl chloride is added dropwise to the tetrahydrofuran solution of low-temperature aminated lignin via a constant pressure funnel at a dropping speed of 0.5 to 1 mL / min.

[0030] In some embodiments, the mixture is stirred under nitrogen protection for a period of time at a temperature of 1 to 4° C., a time of 8 to 10 hours, and a rotation speed of 100 to 200 r / min.

[0031] In some embodiments, the dialysis treatment refers to dialysis treatment in deionized water at a temperature of 10-15° C., a dialysis bag with a cutoff of 2000-3000 Da, and a dialysis treatment duration of 36 hours.

[0032] In some embodiments, the modified lignin is dissolved in deionized water to obtain an aqueous solution of the modified lignin, and the concentration of the modified lignin is 1-5%.

[0033] In some embodiments, a certain amount of sodium carboxymethyl cellulose is added, and the glucose polymerization degree of the sodium carboxymethyl cellulose is 800-1200.

[0034] In some embodiments, a certain amount of sodium carboxymethyl cellulose is added, and the mass ratio of sodium carboxymethyl cellulose to modified lignin is 1:1-3.

[0035] In some embodiments, the modified lignin and sodium carboxymethyl cellulose are fully stirred for 12 to 24 hours at a rotation speed of 200 to 300 r / min.

[0036] In some embodiments, the solution is added dropwise to a low-temperature aluminum chloride aqueous solution with the aid of a syringe, and the inner diameter of the syringe needle is 0.8 to 1.0 mm.

[0037] In some embodiments, the method is added dropwise to a low-temperature aluminum chloride aqueous solution via a syringe at a dropping speed of 2 to 5 mL / min.

[0038] In some embodiments, the solution is added dropwise to a low-temperature aluminum chloride aqueous solution, the temperature of the aluminum chloride aqueous solution is 1-4° C., and the stirring speed is 300-350 r / min.

[0039] The present invention will be further described in detail below with reference to specific embodiments. It should be noted that the specific embodiments are intended to explain the present invention rather than to limit it.

[0040] In the following examples, the concentration of the aluminum chloride aqueous solution was 1.2 mol / L.

[0041] Example 1

[0042] Alkali lignin (molecular weight 4500) extracted from poplar alkali pulping black liquor is aminated with triethylenetetramine to obtain aminated lignin (nitrogen content 3.2%). Phenylpropionic acid is dissolved in chloroform, followed by dropwise addition of thionyl chloride. The mixture reacts under nitrogen for a period of time. After completion of the reaction, thionyl chloride and chloroform are removed by vacuum distillation to obtain phenylpropionyl chloride. A tetrahydrofuran solution of phenylpropionyl chloride is added dropwise to the low-temperature tetrahydrofuran solution of aminated lignin using a constant pressure funnel. The mixture is then stirred and reacted for a period of time under nitrogen, and dialyzed in deionized water to obtain modified lignin. The modified lignin is dissolved in deionized water to obtain an aqueous solution of the modified lignin. A certain amount of sodium carboxymethyl cellulose is then added, stirred thoroughly, and then added dropwise to a low-temperature aqueous solution of aluminum chloride using a syringe to obtain modified lignin-cellulose composite microspheres. The treatment conditions are as follows: the molar concentration of phenylpropionic acid in chloroform is 4 mol / L, the addition rate of thionyl chloride is 1 mL / min, the reaction is carried out under nitrogen protection for 3 h, the reaction temperature is 40° C., the purity of the prepared phenylpropionyl chloride is 90%, and the tetrahydrofuran solution of phenylpropionyl chloride (concentration 12%) is added dropwise to a 7% tetrahydrofuran solution of aminated lignin with the aid of a constant pressure funnel, the temperature of the tetrahydrofuran solution of aminated lignin is 4° C., the addition rate is 0.5 mL / min, and the reaction is stirred for a period of time under nitrogen protection at a temperature of 4° C., a time of 10 h, a rotation speed of 100 r / min, and the dialysis treatment is carried out with the aid of deionized water, the dialysis temperature is 10° C., the dialysis bag cutoff is 2000 Da, and the dialysis treatment is carried out for 36 h. Modified lignin was dissolved in deionized water at a concentration of 3%. A certain amount of sodium carboxymethyl cellulose (with a glucose polymerization degree of 1000) was added, with a mass ratio of sodium carboxymethyl cellulose to modified lignin of 1:1. The modified lignin and sodium carboxymethyl cellulose were thoroughly stirred for 12 hours at a speed of 200 r / min. The solution was then added dropwise to a low-temperature aluminum chloride aqueous solution (concentration of 1.2 mol / L) using a syringe with a 0.8 mm inner diameter needle. The addition rate was 2 mL / min. The temperature of the aluminum chloride aqueous solution was 1°C, and the rotation speed was 350 r / min.

[0043] The performance of the modified lignin-cellulose composite microspheres prepared in Example 1 in treating printing and dyeing industrial wastewater was tested. The specific test steps are as follows:

[0044] The modified lignin-cellulose composite microspheres prepared above were added to wastewater containing organic dyes, adjusted to pH 7, and shaken at room temperature for 2 hours. After treatment, the modified lignin-cellulose composite microspheres were removed directly from the wastewater system. The change in absorbance of the organic dye in the wastewater before and after adsorption was measured using a UV spectrophotometer, converted to concentration, and the adsorption capacity was calculated. The test results are shown in Table 1 below:

[0045] Table 1 Test results of modified lignin cellulose composite microspheres adsorbing organic dyes

[0046]

[0047]

[0048] From the data in Table 1, it can be seen that the modified lignin cellulose composite microspheres prepared by the above method have an adsorption capacity of 152.3 mg / g for methylene blue and an adsorption capacity of 212.3 mg / g for Congo red. After the adsorption treatment is completed, the modified lignin cellulose composite microspheres have good strength and are easily separated from the wastewater system.

[0049] Example 2

[0050] Alkali lignin (molecular weight 5200) extracted from pinewood alkaline pulping black liquor is aminated with tetraethylenepentamine to obtain aminated lignin (nitrogen content 3.6%). Phenylpropionic acid is dissolved in chloroform, followed by dropwise addition of thionyl chloride. The mixture reacts under nitrogen for a period of time. After completion of the reaction, thionyl chloride and chloroform are removed by vacuum distillation to obtain phenylpropionyl chloride. A tetrahydrofuran solution of phenylpropionyl chloride is added dropwise to the low-temperature tetrahydrofuran solution of aminated lignin using a constant pressure funnel. The mixture is then stirred and reacted for a period of time under nitrogen, and dialyzed in deionized water to obtain modified lignin. The modified lignin is dissolved in deionized water to obtain an aqueous solution of the modified lignin. A certain amount of sodium carboxymethyl cellulose is then added, stirred thoroughly, and then added dropwise to a low-temperature aqueous solution of aluminum chloride using a syringe to obtain modified lignin-cellulose composite microspheres. The treatment conditions are as follows: the molar concentration of phenylpropionic acid in chloroform is 6 mol / L, the dropping rate of thionyl chloride is 1.5 mL / min, the reaction is carried out under nitrogen protection for 4 h, the reaction temperature is 45° C., the purity of the prepared phenylpropionyl chloride is 92%, and the tetrahydrofuran solution of phenylpropionyl chloride (concentration 12%) is added dropwise to a 5% tetrahydrofuran solution of aminated lignin with the help of a constant pressure funnel, the temperature of the tetrahydrofuran solution of aminated lignin is 2° C., the dropping rate is 0.5 mL / min, and the reaction is stirred for a period of time under nitrogen protection at a temperature of 3° C., a time of 10 h, a rotation speed of 200 r / min, and the dialysis treatment is carried out with the help of deionized water, the dialysis temperature is 15° C., the dialysis bag cutoff is 3000 Da, and the dialysis treatment is carried out for 36 h. Modified lignin was dissolved in deionized water at a concentration of 3%. A certain amount of sodium carboxymethyl cellulose (with a glucose polymerization degree of 800) was added, with a mass ratio of sodium carboxymethyl cellulose to modified lignin of 1:2. The modified lignin and sodium carboxymethyl cellulose were stirred for 24 hours at a speed of 100 r / min. The solution was then added dropwise to a low-temperature aluminum chloride aqueous solution using a syringe with a needle inner diameter of 0.9 mm. The addition rate was 4 mL / min, the aluminum chloride aqueous solution was maintained at 4°C, and the rotation speed was 300 r / min.

[0051] The performance of the modified lignin-cellulose composite microspheres prepared in Example 2 in treating printing and dyeing industrial wastewater was tested. The specific test steps are as follows:

[0052] The modified lignin-cellulose composite microspheres prepared above were added to wastewater containing organic dyes, adjusted to pH 7, and treated with shaking at room temperature for 2 hours. After treatment, the modified lignin-cellulose composite microspheres were removed directly from the wastewater system. The change in absorbance of the organic dye in the wastewater before and after adsorption was measured using a UV spectrophotometer, and the concentration was converted to calculate the adsorption amount. The test results are shown in Table 2 below:

[0053] Table 2 Test results of modified lignin cellulose composite microspheres adsorbing organic dyes

[0054]

[0055] From the data in Table 2, it can be seen that the modified lignin cellulose composite microspheres prepared by the above method have an adsorption capacity of 145.6 mg / g for methylene blue and an adsorption capacity of 178.5 mg / g for Congo red. After the adsorption treatment is completed, the modified lignin cellulose composite microspheres have good strength and are easily separated from the wastewater system.

[0056] Example 3

[0057] Alkali lignin (molecular weight 3000) extracted from wheat straw alkali pulping black liquor is aminated with triethylenetetramine to obtain aminated lignin (nitrogen content 3.8%). Phenylpropionic acid is dissolved in chloroform, followed by dropwise addition of thionyl chloride. The mixture reacts under nitrogen for a period of time. After completion of the reaction, thionyl chloride and chloroform are removed by vacuum distillation to obtain phenylpropionyl chloride. A tetrahydrofuran solution of phenylpropionyl chloride is added dropwise to the low-temperature tetrahydrofuran solution of aminated lignin using a constant pressure funnel. The mixture is then stirred and reacted for a period of time under nitrogen, and dialyzed in deionized water to obtain modified lignin. The modified lignin is dissolved in deionized water to obtain an aqueous solution of the modified lignin. A certain amount of sodium carboxymethyl cellulose is then added, stirred thoroughly, and then added dropwise to a low-temperature aqueous solution of aluminum chloride using a syringe to obtain modified lignin-cellulose composite microspheres. The treatment conditions are as follows: the molar concentration of phenylpropionic acid in chloroform is 4 mol / L, the addition rate of thionyl chloride is 2 mL / min, the reaction is carried out under nitrogen protection for 4 h, the reaction temperature is 45° C., the purity of the prepared phenylpropionyl chloride is 95%, and the tetrahydrofuran solution of phenylpropionyl chloride (concentration 10%) is added dropwise to a 7% tetrahydrofuran solution of aminated lignin with the aid of a constant pressure funnel, the temperature of the tetrahydrofuran solution of aminated lignin is 4° C., the addition rate is 0.5 mL / min, and the reaction is stirred for a period of time under nitrogen protection at a temperature of 4° C., a time of 10 h, a rotation speed of 150 r / min, and the dialysis treatment is carried out with the aid of deionized water, the dialysis temperature is 10° C., the dialysis bag cutoff is 2000 Da, and the dialysis treatment is carried out for 36 h. Modified lignin was dissolved in deionized water at a concentration of 3%. A certain amount of sodium carboxymethyl cellulose (with a glucose polymerization degree of 1200) was added, with a mass ratio of sodium carboxymethyl cellulose to modified lignin of 1:2. The modified lignin and sodium carboxymethyl cellulose were stirred thoroughly for 12 hours at a speed of 200 r / min. The solution was then added dropwise to a low-temperature aluminum chloride aqueous solution using a syringe with an inner diameter of 0.8 mm. The addition rate was 2 mL / min, the aluminum chloride aqueous solution was maintained at a temperature of 1°C, and the rotation speed was 350 r / min.

[0058] The performance of the modified lignin-cellulose composite microspheres prepared in Example 3 in treating printing and dyeing industrial wastewater was tested. The specific test steps are as follows:

[0059] The modified lignin-cellulose composite microspheres prepared above were added to wastewater containing organic dyes, adjusted to pH 7, and shaken at room temperature for 2 hours. After treatment, the modified lignin-cellulose composite microspheres were removed directly from the wastewater system. The change in absorbance of the organic dye in the wastewater before and after adsorption was measured using a UV spectrophotometer, and the concentration was converted to calculate the adsorption amount. The test results are shown in Table 3 below:

[0060] Table 3 Test results of modified lignin cellulose composite microspheres adsorbing organic dyes

[0061]

[0062] From the data in Table 3, it can be seen that the modified lignin cellulose composite microspheres prepared by the above method have an adsorption capacity of 135.8 mg / g for methylene blue and an adsorption capacity of 178.1 mg / g for Congo red. After the adsorption treatment is completed, the modified lignin cellulose composite microspheres have good strength and are easily separated from the wastewater system.

[0063] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for preparing modified lignocellulose composite microspheres, characterized in that: include: The phenylpropionyl chloride solution is added to the low-temperature aminated lignin solution, mixed evenly, reacted under the protection of inert gas, and the product is collected and dialyzed to obtain modified lignin; The amination modification method is a Mannich reaction, the amination reagent is tetraethylenepentamine or triethylenetetramine, and the relative molecular mass of the amination modification reagent is greater than 200; The nitrogen content of the aminated lignin is 3-4%; The modified lignin is dissolved in water to obtain an aqueous solution of the modified lignin, and then sodium carboxymethyl cellulose is added, mixed evenly, and then added dropwise to a low-temperature aluminum chloride aqueous solution to obtain the modified lignin.

2. The method for preparing modified lignocellulose composite microspheres according to claim 1, wherein: The aminated lignin is obtained by amination modification of alkali lignin; Alternatively, the alkali lignin is extracted from black liquor of alkaline pulping of coniferous wood, hardwood and grass raw materials, or various types of commercially sold alkali lignin; Alternatively, the molecular weight of the alkali lignin is 3000-7000.

3. The method for preparing modified lignocellulose composite microspheres according to claim 1, wherein: The concentration of the phenylpropionyl chloride solution is 10-15%; Alternatively, the concentration of the aminated lignin solution is 5-10%.

4. The method for preparing modified lignocellulose composite microspheres according to claim 1, wherein: The temperature of the low-temperature amination lignin solution is 1-4°C; Alternatively, the rate of adding the phenylpropionyl chloride solution to the low-temperature aminated lignin solution is 0.5 to 1 mL / min.

5. The method for preparing modified lignocellulose composite microspheres according to claim 1, wherein: Phenylpropionyl chloride and aminated lignin solution were reacted at 1-4 °C for 8-10 h at a rotation speed of 100-200 r / min.

6. The method for preparing modified lignocellulose composite microspheres according to claim 1, wherein: Dialysis was performed in deionized water at a temperature of 10-15°C using a dialysis bag with a cutoff of 2000-3000 Da for 36-42 h.

7. The method for preparing modified lignocellulose composite microspheres according to claim 1, wherein: The concentration of the modified lignin aqueous solution is 1-5%; Alternatively, the mass ratio of sodium carboxymethyl cellulose to modified lignin is 1:1-3; Alternatively, the glucose polymerization degree of sodium carboxymethyl cellulose is 800-1200; Alternatively, the modified lignin and sodium carboxymethyl cellulose are fully stirred for 12 to 24 hours at a speed of 200 to 300 r / min.

8. The method for preparing modified lignocellulose composite microspheres according to claim 1, wherein: Add dropwise to the low-temperature aluminum chloride aqueous solution with the aid of a syringe with a needle having an inner diameter of 0.8-1.0 mm; Alternatively, the addition rate is 2 to 5 mL / min; Alternatively, the temperature of the aluminum chloride aqueous solution is 1-4° C., and the stirring speed is 300-350 r / min.

9. Modified lignocellulose composite microspheres prepared by the method according to any one of claims 1 to 8.

10. Use of the modified lignin cellulose composite microspheres according to claim 9 in the preparation of adsorption materials.

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