CN113461978B - A method for preparing high-yield lignin nanoparticles assisted by ball milling pretreatment - Google Patents

Abstract

The invention belongs to a preparation method for preparing high-yield lignin nanoparticles by ball milling pretreatment assistance, which comprises the following components: the concentration of the ethanol solution is 0 to 100 percent, the concentration of the lignin suspension is 0.5 to 10 weight percent, and the preparation method comprises the following steps: 1) Weighing 1.5-30 g of lignin, dispersing in 0-100% ethanol solution to prepare 0.5-10 wt% lignin/ethanol suspension, and ball-milling at 500-3000rpm for 0-48h; 2) Centrifuging the ball-milled lignin at 1000-10000 rpm for 5-60min; 3) Dissolving the separated solid in gamma-valerolactone, dripping 1-10 times volume of deionized water into the solution at the speed of 0.1-10 mL/min, and stirring for 1-10h under the magnetic stirring condition of 100-1000rpm to form a lignin nanoparticle colloidal solution; 4) Simultaneously, dropwise adding distilled water into the supernatant under the same conditions to form a lignin nanoparticle colloidal solution; 5) Centrifuging the prepared colloidal solution at 4000-15000rpm for 5-60min, washing with deionized water, and freeze drying to obtain lignin nanoparticles with high yield and uniform size.

Description

A method for preparing high-yield lignin nanoparticles assisted by ball milling pretreatment

technical field

The invention belongs to the field of nanomaterials, and mainly relates to a method for preparing high-yield lignin nanoparticles assisted by ball milling pretreatment, which can be applied to the treatment of organic pollutants, drug carriers, ultraviolet shielding, catalytic carriers, antioxidant materials, etc. field.

technical background

Lignin is the most abundant natural aromatic polymer in nature, which widely exists in the woody parts of trees and other vascular plants. Lignin is a polyphenolic biomolecule that has many unique properties such as corrosion resistance, anti-bioerosion, UV shielding, high hardness and anti-oxidation. Therefore, lignin has the potential to produce high-value products as a raw material with large reserves. However, most lignin can only be dissolved in water system under alkaline environment, which greatly limits its wide application. The preparation of lignin water-dispersed nano-system provides a new way for the wide application of lignin. Nanostructured lignin, especially lignin nanoparticles with a size distribution in the range of 1-100nm, has the advantages of large specific surface area, which endows it with unique properties. Lignin nanoparticles are widely used in the fields of replacing toxic nanoparticles, drug loading systems, hydrophobic materials, UV barriers, antibacterial, antioxidative, and electrode materials. At present, there are various methods for the preparation of lignin nanoparticles, mainly including solvent exchange method, acid precipitation method, reverse micelle formation method, _CO2 precipitation method and so on. Among them, the solvent exchange method is the most commonly used method for preparing lignin nanoparticles in recent years. Chinese patent CN110452396B authorizes a preparation method of lignin micro/nanospheres, adding lignin to an organic solvent and emulsifying it with water to form emulsion, and then volatilize the organic solvent in the mixed emulsion to obtain the lignin micro/nanosphere-water mixture, and finally carry out solid-liquid separation, washing and freeze-drying to obtain the product. The organic solvents are ethyl acetate, dichloromethane and three One or more of methyl chloride, and the added water contains a certain amount of surfactant. However, the organic solvent used has certain toxicity, and the use of surfactant increases the complexity of the preparation process, and the prepared lignin balls are large and uneven in size. Chinese patent CN109012609A discloses a green preparation method of lignin nanospheres, using ethylene glycol to dissolve lignin, adding acid and water of different concentrations to it at a constant rate at room temperature, and finally performing solid-liquid separation through one-step centrifugation. Lignin Nanospheres. The preparation method of the lignin-based nano-microspheres is easy to operate, and effectively avoids the chemical structure change of lignin and the use of toxic reagents, but the use of acid will cause corrosion to the equipment, which increases the equipment requirements, and the prepared lignin The particles are irregular in shape and are not microspheres in the true sense. Mechanical treatment is a very promising method for preparing lignin nanoparticles, which has the advantages of high yield, convenient operation, and environmental protection. Iulian AndreiGilca et al. (Gilca IA, Popa VI, Crestini C. Obtaining lignin nanoparticles bysonication [J]. Ultrasonics Sonochemistry, 2015, 23: 369-375.) proposed a physical method for ultrasonically modifying lignin to prepare lignin nanoparticles. In the method, the lignin is dispersed in water, and the suspension is treated with ultrasonic horn vibration to obtain a uniform and stable nano-dispersion. But the morphology of the prepared lignin nanoparticles is irregular. Dry-wet ball milling is widely used in the process of nanomaterials such as CNC, nano-electrocatalyst and nano-carbon material preparation. US Patent US9102801B1 discloses a method for synthesizing lignin nanoparticles. Lignosulfonate is dried at 105° C. to remove residual moisture, and then transferred to a ball mill for ball milling to prepare lignin nanoparticles. The average size of the lignin nanoparticles prepared by the method is less than 40nm, but the shape of the nanoparticles is irregular. Therefore, it is very necessary to prepare size-stable and uniform lignin nanoparticles with regular shape using mechanical activation assisted organic solvents.

Contents of the invention

The purpose of the present invention is to develop a method for preparing lignin nanoparticles with high yield by assisting ball milling pretreatment. The mechanical method—ball milling method is used for pretreatment, which improves the yield of lignin nanoparticles and obtains uniform and stable size. , regular-shaped nanostructures.

The present invention is realized through the following technical solution steps:

Step 1: Weigh 1.5g-30g of lignin, disperse it in an ethanol solution with a concentration of 0-100% to make a lignin/ethanol suspension of 0.5wt%-10wt%, and ball mill it under the condition of 500-3000rpm 0- 48h;

Step 2: Centrifuge the ball-milled lignin at 1000rpm-10000rpm for 5-60min;

Step 3: Dissolve the solid separated in step 2 in γ-valerolactone, and add 1-10 times the volume of deionized water to the solution at a rate of 0.1mL/min-10mL/min Stir for 1-10 hours under magnetic stirring conditions to form a colloidal solution of lignin nanoparticles;

Step 4: Add 1-10 times the volume of deionized water to the supernatant of step 2 at the same time at a speed of 0.1mL/min-10mL/min and stir for 1-10h under the condition of 100-1000rpm magnetic stirring to form lignin Colloidal solution of nanoparticles;

Step 5: Centrifuge the colloid solution prepared in steps 3 and 4 at 4000-15000rpm for 5-60min, wash with deionized water, remove the upper liquid, and freeze-dry to obtain lignin nanoparticles with a yield of >80% and uniform size particles.

The mechanical pretreatment method is ball milling pretreatment.

The concentration of the ethanol solution is 0-100%.

The concentration of the lignin-ethanol suspension is 0.5wt%-10wt%.

The rotating speed of the ball milling pretreatment is 500rpm-3000rpm.

The time for the ball milling treatment is 0-48h.

The yield of obtained lignin nanoparticles is >80%.

The present invention uses ball milling as a mechanical pretreatment method, which destroys the structure of lignin, reduces the size and molecular weight of lignin, and promotes the dissolution of lignin by organic solvents to obtain higher yields of lignin nanoparticles. At the same time, the shape of the formed lignin nanoparticles is modified by dissolving the lignin with an organic solvent, thereby improving the size uniformity of the lignin nanoparticles. Therefore, the present invention provides a high-yield preparation method of lignin nanoparticles pretreated by ball milling, which makes the industrial production and application of lignin nanoparticles of great significance.

Description of drawings

Fig. 1 is a transmission electron micrograph of lignin nanoparticles obtained from the supernatant after ball milling for 3 hours; Fig. 2 is a transmission electron micrograph of lignin nanoparticles obtained from insolubles redissolved after ball milling for 3 hours.

detailed description

The present invention will be more fully and more easily understood with reference to the following examples, which are given to illustrate the present invention more clearly, but not to limit the present invention in any way.

The ball mill used in each implementation case is a CSN0.3 laboratory nano-sand mill. The invention is not limited.

Example 1

3g of lignin was weighed and added to a certain mass of 100% ethanol solution so that the concentration of lignin was 1wt%, ball milled at 2000rpm for 3h and then centrifuged at 10000rpm for 20min for solid-liquid separation. The isolated solid was dissolved in 10 mL of γ-valerolactone. Add 4.5 times the volume of deionized water to the lignin/γ-valerolactone solution and the separated supernatant at a rate of 2.5 mL/min, and stir for 1 h under magnetic stirring at 600 rpm to form lignin nanoparticle colloids. solution. The prepared colloidal solution of lignin nanoparticles was centrifuged at 10,000 rpm for 20 min, washed with deionized water, the upper liquid was removed, and lignin nanoparticles were obtained after freeze-drying.

Example 2

6g of lignin was weighed and added to a certain mass of 100% ethanol solution so that the concentration of lignin was 2wt%, ball milled at 2000rpm for 3h, and then centrifuged at 10000rpm for 20min for solid-liquid separation. The isolated solid was dissolved in 10 mL of γ-valerolactone. Add 4.5 times the volume of deionized water to the lignin/γ-valerolactone solution and the separated supernatant at a rate of 2.5 mL/min, and stir for 1 h under magnetic stirring at 600 rpm to form lignin nanoparticles colloidal solution. The prepared colloidal solution of lignin nanoparticles was centrifuged at 10,000 rpm for 20 min, washed with deionized water, the upper liquid was removed, and lignin nanoparticles were obtained after freeze-drying.

Example 3

3g of lignin was weighed and added to a certain mass of 70% ethanol solution to make the lignin concentration 1wt%, ball milled at 2000rpm for 3h, and then centrifuged at 10000rpm for 20min for solid-liquid separation. The isolated solid was dissolved in 10 mL of γ-valerolactone. Add 4.5 times the volume of deionized water to the lignin/γ-valerolactone solution and the separated supernatant at a rate of 2.5 mL/min, and stir for 1 h under magnetic stirring at 600 rpm to form lignin nanoparticles colloidal solution. The prepared colloidal solution of lignin nanoparticles was centrifuged at 10,000 rpm for 20 min, washed with deionized water, the upper liquid was removed, and lignin nanoparticles were obtained after freeze-drying.

Example 4

3g of lignin was weighed and added to a certain mass of 100% ethanol solution so that the concentration of lignin was 1 wt%, ball milled at 1000rpm for 3h, and then centrifuged at 10000rpm for 20min for solid-liquid separation. The isolated solid was dissolved in 10 mL of γ-valerolactone. Add 4.5 times the volume of deionized water to the lignin/γ-valerolactone solution and the separated supernatant at a rate of 2.5 mL/min, and stir for 1 h under magnetic stirring at 600 rpm to form lignin nanoparticles colloidal solution. The prepared colloidal solution of lignin nanoparticles was centrifuged at 10,000 rpm for 20 minutes, washed with deionized water, the upper liquid was removed, and lignin nanoparticles were obtained after freeze-drying.

Example 5

3g of lignin was weighed and added to a certain mass of 100% ethanol solution so that the concentration of lignin was 1wt%, ball milled at 2000rpm for 12h, and then centrifuged at 10000rpm for 20min for solid-liquid separation. The isolated solid was dissolved in 10 mL of γ-valerolactone. Add 4.5 times the volume of deionized water to the lignin-γ-valerolactone solution and the separated supernatant at a rate of 2.5 mL/min, and stir for 1 h under magnetic stirring at 600 rpm to form lignin nanoparticles colloidal solution. The prepared colloidal solution of lignin nanoparticles was centrifuged at 10,000 rpm for 20 min, washed with deionized water, the upper liquid was removed, and lignin nanoparticles were obtained after freeze-drying.

Example 5

3g of lignin was weighed and added to a certain mass of 100% ethanol solution so that the lignin concentration was 1wt%, ball milled at 2000rpm for 3h, and then centrifuged at 5000rpm for 40min for solid-liquid separation. The isolated solid was dissolved in 10 mL of γ-valerolactone. Add 8 times the volume of deionized water to the lignin/γ-valerolactone solution and the separated supernatant at a rate of 4 mL/min, and stir for 5 h under magnetic stirring at 800 rpm to form lignin nanoparticle colloids. solution. The prepared colloidal solution of lignin nanoparticles was centrifuged at 10,000 rpm for 20 min, washed with deionized water, the upper liquid was removed, and lignin nanoparticles were obtained after freeze-drying.

Example 6

Weigh 3g of lignin and add a certain mass of deionized water to make the lignin concentration 1wt%, ball mill at 2000rpm for 3h, dilute to a certain number of times, and freeze-dry to obtain lignin nanoparticles.

The above-mentioned embodiment is a preferred embodiment of the present invention, but the embodiment of the present invention is not limited by the above-mentioned embodiment, and any other changes, modifications, substitutions, combinations, Simplifications should be equivalent replacement methods, and all are included in the protection scope of the present invention.

Claims (2)

1. A preparation method for preparing high-yield lignin nanoparticles with the assistance of ball milling pretreatment is characterized by comprising the following steps:

step 1: weighing 1.5g-30g of lignin, dispersing in 70-100% ethanol solution to prepare 0.5wt% -10wt% lignin/ethanol suspension, and ball-milling at 500-3000rpm for 0-48h;

step 2: centrifugally separating the ball-milled lignin at 1000-10000 rpm for 5-60min;

and step 3: dissolving the separated solid in gamma-valerolactone to obtain a lignin-gamma-valerolactone solution, respectively dripping deionized water with the volume of 1-10 times of that of the lignin-gamma-valerolactone solution and the supernatant obtained by separation in the step 2 at the speed of 0.1-10 mL/min, and stirring for 1-10 hours under the magnetic stirring condition of 100-1000rpm to form a lignin nanoparticle colloidal solution;

and 4, step 4: centrifuging the prepared lignin nanoparticle colloidal solution at 4000-15000rpm for 5-60min, washing with deionized water, removing the upper layer liquid, and freeze drying to obtain lignin nanoparticles with high yield and uniform size.

2. The method of claim 1, wherein: the yield of the lignin nano-particles is more than 80 percent.

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