Lignin phenol modified adsorbent as well as preparation method and application thereof

Abstract

The invention discloses a lignin phenol modified adsorbent and a preparation method and application thereof, the preparation method comprises the following steps: adding an organic solvent into a mixture of phenol and lignin, uniformly mixing, and then evaporating to remove the organic solvent; the preparation method comprises the following steps: adding lignin into a reaction kettle, then adding a sulfuric acid solution to carry out phenolation reaction, after the reaction is finished, adding acetone to carry out cross-linking reaction for 0.5-12 hours, and during the cross-linking reaction, the addition amount of the acetone is 10-1000% of the mass of the lignin; and after the reaction is finished, carrying out solid-liquid separation, washing and drying to obtain the phenolated lignin. The prepared adsorbent has a good adsorption effect on various metal ions, and is especially suitable for treatment of industrial dye sewage. The heavy metal ion adsorption material also has the characteristic of good stability, and can be conveniently recovered and recycled from water.

Description

Technical Field

[0001] The invention belongs to the technical field of lignin modification, and specifically relates to a lignin phenol modified adsorbent and a preparation method and application thereof. Background Art

[0002] The statements herein merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] Lignin is a biomass associated with cellulose and other substances. It is a highly branched amorphous polymer. It exists in large quantities as a non-food product and aromatic substance, with about 20 billion tons of biosynthesis each year. In addition, industrial lignin is produced in large quantities as a by-product of papermaking, with more than 50 million tons requiring incineration each year. The molecular weight of industrial lignin extracted from the by-products of the pulp and paper industry is between several hundred and several hundred thousand, with significant polydispersity, making it difficult to use directly. For example, as an adsorption material, due to the small number of active sites in lignin, the adsorption amount is small; in addition, due to its polydispersity, partial dissolution and other phenomena occur. Therefore, the value of industrial lignin as an adsorbent is not high.

[0004] Lignin contains aromatic ring structures and functional groups such as phenolic hydroxyl, alcoholic hydroxyl, and carboxyl, and can undergo a series of chemical reactions. For example, phenolic hydroxyl can undergo etherification reaction with epichlorohydrin to prepare epoxy resin; alcoholic hydroxyl can react with isocyanate to prepare polyurethane; phenolic hydroxyl, alcoholic hydroxyl, and carboxyl can undergo esterification reaction; the ortho position of the aromatic ring hydroxyl can undergo hydroxymethylation reaction with formaldehyde, etc., and the aromatic ring side chain of lignin can undergo phenolization reaction. Therefore, functional groups with adsorption properties can be introduced through chemical reactions to give lignin excellent properties.

[0005] The phenolation reaction of lignin refers to the reaction in which the carbon atoms of the side chains of lignin form carbon cations due to protonation under acid catalysis, attack phenolic molecules and condense, and connect with lignin in the form of CC bonds at the para or ortho position of the phenolic hydroxyl group. In the above-mentioned modification process, the phenolation of lignin can increase the content of phenolic hydroxyl groups in lignin, providing more abundant reaction sites for subsequent structural modification, but at the same time, it reduces the molecular weight of lignin and increases the water solubility of lignin, which is not conducive to its application as an adsorbent in wastewater treatment. If cross-linking is used with aldehydes, amines, etc., the acid catalyst needs to be removed and the experimental steps are increased. Summary of the invention

[0006] In view of the shortcomings of the prior art, the object of the present invention is to provide a lignin phenol modified adsorbent which can be directly cross-linked with acetone without separating the phenolic lignin, and a preparation method and application thereof.

[0007] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0008] In a first aspect, the present invention provides a method for preparing a lignin phenol modified adsorbent, comprising the following steps:

[0009] adding an organic solvent to the mixture of phenol and lignin, mixing them uniformly, and then evaporating and removing the organic solvent;

[0010] Then, sulfuric acid solution is added thereto for phenolization reaction. After the reaction is completed, acetone is added thereto for cross-linking reaction. The cross-linking reaction time is 0.5-12 hours. During the cross-linking reaction, the amount of acetone added is 10%-1000% of the lignin mass.

[0011] After the reaction is completed, the solid and liquid are separated, washed and dried to obtain phenolic lignin.

[0012] The requirements for the organic solvent are that it can dissolve phenol and lignin and has a low boiling point to facilitate evaporation and removal.

[0013] In some embodiments, the phenol is selected from at least one of phenol, catechol, resorcinol, hydroquinone, pyrogallol, phloroglucinol, tricholol and derivatives thereof.

[0014] In some embodiments, the lignin is alkali lignin or lignin sulfonate.

[0015] Preferably, the mass ratio of lignin to phenol is 1:0.08-12.5.

[0016] In some embodiments, the evaporative removal is carried out by heating to dryness, natural volatilization or rotary evaporation.

[0017] In some embodiments, the concentration of the sulfuric acid solution is 50-95 wt %.

[0018] Preferably, the concentration of the sulfuric acid solution is 68-75wt%.

[0019] Preferably, the amount of sulfuric acid added is 50%-500% of the mass of the lignin.

[0020] In some embodiments, the phenolization reaction time is 0.5-5 h.

[0021] In a second aspect, the present invention provides a ligninphenol modified adsorbent prepared by the preparation method.

[0022] In a third aspect, the present invention provides use of the ligninphenol modified adsorbent in heavy metal ion adsorption and / or dye adsorption.

[0023] Heavy metal ions include but are not limited to Cr(VI), Ni(II), Cu(II) and Pb(II), and dyes include but are not limited to Congo red, methyl blue and crystal violet.

[0024] In some embodiments, the heavy metal ion is Cr(VI) and the dye is Congo red.

[0025] The heavy metal ion and dye adsorption material can be used in the preparation of sewage treatment agents, or in combination with other active ingredients having sewage treatment effects to prepare sewage treatment agents.

[0026] The beneficial effects achieved by one or more embodiments of the present invention are as follows:

[0027] Phenol or polyphenols are used as phenolizing agents, and acetone is used as a cross-linking agent. Phenol or polyphenols contain phenolic hydroxyl groups, which are used to phenolize lignin, increase the content of phenolic hydroxyl groups in lignin, and increase its active sites. The use of phenol-based toxic phenolizing agents can be effectively reduced, and while providing the activity of the reaction product, the safety of the production environment can also be improved. After phenolization modification, an addition reaction is further carried out with acetone to prepare a lignin phenol modified material, which contains phenolic hydroxyl groups and has good water solubility, and is more conducive to the adsorption of heavy metal ions and dyes. It has a good adsorption effect on a variety of metal ions and is particularly suitable for the treatment of industrial dye wastewater. The heavy metal ion adsorption material also has the characteristics of good stability and can be easily recovered and recycled from water.

[0028] The modification method provided by the invention is simple and easy to implement, and the preparation process can be carried out at room temperature, so industrial scale-up production can be easily realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0030] Figure 1 2DHSQC spectra of the lignin phenol modified material and alkali lignin prepared in Example 1, wherein a is alkali lignin (X-axis range 0-5), b is alkali lignin (X-axis range 5-8), c is lignin phenol modified material (X-axis range 0-5), and d is lignin phenol modified material (X-axis range 5-8). DETAILED DESCRIPTION

[0031] It should be noted that the following detailed descriptions are illustrative 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.

[0032] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

[0033] Example 1

[0034] Weigh 5.0g of alkali lignin and 5.0g of pyrogallic acid into a single-necked flask, add 30ml of acetone and stir with a magnetic stirrer for 10min to mix evenly. Then, remove the acetone by rotary evaporation, then slowly drop 10ml of 72% H2SO4 into the flask, react at room temperature for 2h, add 2.5g of acetone, and continue to react for 8h. Wash and dry to obtain a lignin phenol modified material.

[0035] Figure 1 2D HSQC spectra of the lignin phenol modified material (PAL) and alkali lignin (AL) prepared in Example 1. Compared with AL, PAL has strong signals between H shift 0-2 and C shift around 30, indicating that acetone reacts with the ortho and para positions of the phenolic hydroxyl group and bonds to the benzene ring in the form of -C(CH3)2-.

[0036] The adsorption capacity of the adsorbent material prepared by the above method for Cr(VI) at room temperature (25°C, the same below) is 475 mg / g. The adsorption capacity for other metal ions such as Cu(II) is 45 mg / g. Compared with the unmodified lignin (Cr(VI) adsorption capacity 238 mg / g), the adsorption capacity is greatly improved.

[0037] Alkali lignin was dispersed in 10 ml of deionized water, and the insoluble matter was removed by centrifugation. The dissolved amount was measured to be greater than 1.1 g, and its solubility (the solubility in the examples is the solubility at 25°C) was equivalent to 110 mg / ml. The pH of 100 ml of deionized water was adjusted to 2-7 with hydrochloric acid and sodium carbonate, and the lignin phenol modified material was dispersed therein, and the insoluble matter was removed by centrifugation. The dissolved amount was measured to be less than 5.1 mg, and its solubility was equivalent to 0.05 mg / ml. That is, the solubility of the lignin phenol modified material in water is less than 0.1 mg / ml, and it is difficult to dissolve in water (pH 2-7).

[0038] Example 2

[0039] Weigh 6.0g of alkali lignin and 4.0g of catechol into a single-necked flask, add 40ml of acetone and stir with a magnetic force for 10min to mix evenly. Then remove the acetone by rotary evaporation, then slowly drop 6ml of 72% H2SO4 into the flask, react at room temperature for 1h, add 2.0g of acetone, and continue to react for 12h. Wash and dry to obtain a lignin phenol modified material.

[0040] The adsorption capacity of the adsorbent material prepared by the above method for Cr(VI) is 366 mg / g, and the adsorption capacity for other metal ions such as Ni(II) is about 37 mg / g.

[0041] The solubility of the lignin phenol modified material in water is 0.02 mg / ml, which is less than 0.1 mg / ml, and is difficult to dissolve in water (pH 2-7).

[0042] Example 3

[0043] Weigh 7.5g of alkali lignin and 2.5g of phenol into a single-necked flask and stir magnetically for 30 minutes to mix evenly. Then slowly drop 15ml of 80% H2SO4 into the flask, react at room temperature for 0.5h, add 10.0g of acetone, and continue to react for 4h. Wash and dry to obtain a lignin phenol modified material.

[0044] The adsorption capacity of the adsorbent material prepared by the above method for Cr(VI) is 305 mg / g, and the adsorption capacity for other metal ions such as Co(II) is 22 mg / g.

[0045] The solubility of the lignin phenol modified material in water is 0.01 mg / ml, which is less than 0.1 mg / ml and is difficult to dissolve in water (pH 2-7).

[0046] Example 4

[0047] Weigh 2.0g of alkali lignin, 0.5g of lignin sulfonate, and 2.5g of hydroquinone into a single-necked flask, add 40ml of acetone and stir with a magnetic force for 10min to mix evenly. Then, remove the acetone by rotary evaporation, and then slowly drop 10ml of 66% H2SO4 into the flask. After reacting for 4h at room temperature, add 2.0g of acetone and continue to react for 12h. Wash and dry to obtain a lignin phenol modified material.

[0048] The adsorption capacity of the adsorbent material prepared by the above method for Congo red is 285 mg / g, and the adsorption capacity for methyl blue and crystal violet is 52 and 132 mg / g respectively. Under the same conditions, the adsorption capacity of the unmodified lignin for the three is less than 27 mg / g, which is a significant improvement in adsorption capacity.

[0049] The solubility of the lignin phenol modified material in water is 0.07 mg / ml, which is less than 0.1 mg / ml, and is difficult to dissolve in water (pH 2-7).

[0050] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a lignin phenol modified adsorbent, characterized in that: The steps include: adding an organic solvent to the mixture of phenol and lignin, mixing them uniformly, and then evaporating and removing the organic solvent; Then, sulfuric acid solution is added thereto for phenolization reaction. After the reaction is completed, acetone is added thereto for cross-linking reaction. The cross-linking reaction time is 0.5-12 hours. During the cross-linking reaction, the amount of acetone added is 10%-1000% of the lignin mass. After the reaction is completed, the solid and liquid are separated, washed and dried to obtain phenolic lignin.

2. The method for preparing the ligninphenol modified adsorbent according to claim 1, characterized in that: The phenol is selected from at least one of phenol, catechol, resorcinol, hydroquinone, pyrogallol, phloroglucinol, tricholol and derivatives thereof.

3. The method for preparing the ligninphenol modified adsorbent according to claim 1, characterized in that: The lignin is alkali lignin or lignin sulfonate; Preferably, the mass ratio of lignin to phenol is 1:0.08-12.

5.

4. The method for preparing the ligninphenol modified adsorbent according to claim 1, characterized in that: The evaporative removal method is heating to dryness, natural volatilization or rotary evaporation.

5. The method for preparing the ligninphenol modified adsorbent according to claim 1, characterized in that: The concentration of the sulfuric acid solution is 50-95wt%.

6. The method for preparing the ligninphenol modified adsorbent according to claim 5, characterized in that: The concentration of the sulfuric acid solution is 68-75wt%; Preferably, the amount of sulfuric acid added is 50%-500% of the mass of the lignin.

7. The method for preparing the ligninphenol modified adsorbent according to claim 1, characterized in that: The phenolization reaction time is 0.5-5h.

8. A lignin phenol modified adsorbent, characterized in that: Prepared by the preparation method described in any one of claims 1 to 7.

9. Use of the ligninphenol modified adsorbent according to claim 8 in heavy metal ion adsorption and / or dye adsorption.

10. The use according to claim 9, characterized in that: The heavy metal ion is Cr(VI), and the dye is Congo red.

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