CN114835916A - Threonine modified lignin flocculant and preparation method thereof - Google Patents
Threonine modified lignin flocculant and preparation method thereof Download PDFInfo
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- CN114835916A CN114835916A CN202210667602.7A CN202210667602A CN114835916A CN 114835916 A CN114835916 A CN 114835916A CN 202210667602 A CN202210667602 A CN 202210667602A CN 114835916 A CN114835916 A CN 114835916A
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- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08H—DERIVATIVES OF NATURAL MACROMOLECULAR COMPOUNDS
- C08H6/00—Macromolecular compounds derived from lignin, e.g. tannins, humic acids
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
- C02F1/5263—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using natural chemical compounds
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
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- C02F1/00—Treatment of water, waste water, or sewage
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- C02F1/54—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using organic material
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- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
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- Y02W10/37—Wastewater or sewage treatment systems using renewable energies using solar energy
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Abstract
The invention relates to a threonine modified lignin flocculant. The preparation method comprises two steps, firstly extracting refined lignin from papermaking black liquor, then dissolving the refined lignin in sodium hydroxide solution with certain concentration, fully stirring, adding formaldehyde solution and threonine solution, reacting at a constant temperature for a certain time, after the reaction is finished, acidifying with dilute sulfuric acid with certain concentration, centrifugally separating, washing the precipitate with distilled water for several times until the washed distilled water is neutral, and drying under a proper condition to obtain the threonine modified lignin flocculant. The flocculant can be used for treating pigment such as methylene blue, ethyl violet, fuchsin and the like and Cu 2+ 、Cr 3+ 、Co 2+ 、Hg 2+ 、Pb 2+ The metal ions have good flocculation effect, and the removal rate of the pigment can be improved when the dosage is 0.5g/LThe removal rate of the metal ions is over 60 percent, and the method has good application prospect in the aspect of industrial wastewater treatment.
Description
Technical Field
The invention relates to a threonine modified lignin flocculant and a preparation method thereof, belonging to the technical field of sewage treatment.
Background
Lignin, abbreviated as lignin, is a complex natural polymer compound that is present in most terrestrial plants along with cellulose and hemicellulose. The content of lignin in biomass is very high, and can reach 10% -35%, and the quantity produced by photosynthesis is very large, and can reach 500 hundred million tons every year. However, lignin has a complex molecular structure and is one of the most difficult natural polymers to recognize and utilize at present. The papermaking wastewater in China accounts for 30% of the national industrial wastewater, and the main pollutant in the papermaking wastewater is lignin. The lignin is extracted from the papermaking black liquor, and is further modified to prepare a functional material, so that the method not only can utilize wastes and reduce environmental pollution, but also can greatly improve the utilization rate of biological resources and improve the added value of the lignin, and therefore, the method has social value and economic value in many aspects.
Lignin contains three basic building blocks: guaiacyl phenylpropane (G), syringyl phenylpropane (S) and p-hydroxyphenylpropane (H). They generate three-dimensional network structures through various connection modes and irregular coupling. Generally, lignin obtained from pulping and papermaking waste liquor contains several to dozens of phenylpropane structural units, and the lignin is generally stable in chemical property and low in activity and is difficult to directly utilize without treatment. The usual way of treatment is to modify the lignin to some extent in order to increase its reactivity.
The flocculation technology is one of the important methods for treating wastewater, and lignin as a natural polymeric flocculant has the unique properties of high efficiency and no toxicity. However, the lignin has low average molecular weight and few active adsorption sites, which directly influences the flocculation performance. Usually, crosslinking reaction, condensation reaction, graft copolymerization and other methods are adopted to change the spatial configuration of lignin, increase the molecular weight of lignin, and introduce functional groups with flocculation performance to improve the flocculation performance of lignin.
Disclosure of Invention
The present invention provides a method for activating lignin with threonine to obtain a novel flocculant.
Yet another object of the present invention is to: provides a product prepared by the preparation method.
The lignin benzene ring structure contains electron-donating groups such as alkyl, alkoxy, hydroxyl and the like, so that ortho-position hydrogen of phenolic hydroxyl is more active, and Mannich reaction can be carried out under certain conditions to introduce aminomethyl and carboxyl. The modified lignin is easier to have a chelating reaction with metal ions, and the adsorption performance of the lignin to various pigments can also be improved. The Mannich (Mannich) reaction occurring from lignin, formaldehyde and threonine can be represented by the following formula.
The invention aims to provide a preparation method of a threonine modified lignin-based flocculant, which comprises the following specific preparation steps.
(1) Weighing a certain amount of crude lignin or lignin black liquor (with strong basicity) and placing the crude lignin or the lignin black liquor in a beaker, adding water, heating to a certain temperature, continuously stirring until the crude lignin or the lignin black liquor is completely dissolved, then adding dilute sulfuric acid in batches to adjust the liquid in the beaker to be acidic, cooling to room temperature, then centrifugally separating out precipitate, washing the precipitate with distilled water, then centrifuging, repeating the step until the distilled water obtained after washing the precipitate is neutral, and drying the washed precipitate to obtain black solid refined lignin.
(2) Weighing a certain amount of refined lignin, dissolving the refined lignin in a sodium hydroxide solution with a certain concentration, adding a certain amount of formaldehyde solution with a certain concentration after fully stirring, then dropwise adding a threonine solution with a certain concentration while stirring, reacting at a constant temperature for a certain time after dropwise adding, acidifying with dilute sulfuric acid with a certain concentration after the reaction is finished, performing centrifugal separation, washing the precipitate with distilled water for several times until the washed distilled water is neutral, and then taking out the solid and drying under appropriate conditions to obtain the threonine modified lignin-based flocculant.
The refining temperature in the step (1) is between room temperature and 100 ℃, and the concentration of dilute sulfuric acid is between 5 and 70 percent.
In the step (2), the concentration of the sodium hydroxide solution is 5% -70%, the concentration of the formaldehyde solution is 5% -60%, the concentration of the threonine solution is 5% -60%, and the concentration of the dilute sulfuric acid is 5% -70%.
The mass ratio of the refined lignin, the formaldehyde and the threonine in the step (2) is preferably 1 (0.1-2) to 0.5-2, the reaction temperature of the refined lignin, the formaldehyde and the threonine is preferably 20-90 ℃, the reaction time is preferably 0.5-4h, and the drying condition is preferably low-temperature freeze drying or vacuum normal-temperature drying or less than 50 o And C, slowly drying.
The invention also provides a threonine modified lignin-based flocculant prepared according to the method.
The invention has the beneficial effects that:
1) according to the invention, amino, hydroxyl and carboxyl are introduced into a lignin benzene ring by utilizing Mannich reaction, so that on one hand, active adsorption sites (such as formation of hydrogen bonds, increase of intermolecular force caused by polarity increase and the like) for various pigments are increased, on the other hand, the coordination capacity with metal ions is increased, and both the active adsorption sites and the intermolecular force are favorable for adsorption.
2) The threonine modified lignin-based flocculant prepared by the invention can be used for treating pigments such as methylene blue, ethyl violet, fuchsin and the like and Cu 2 + 、Cr 3+ 、Co 2+ 、Hg 2+ 、Pb 2+ The metal ions have good flocculation effect, when the dosage is 0.5g/L, the removal rate of the pigment can reach more than 85%, and the removal rate of the metal ions is more than 60%, so that the method has good application prospect in the aspect of industrial wastewater treatment.
3) The lignin used by the invention is derived from the papermaking black liquor, the production cost is low, and the product can be completely biodegraded without causing environmental pollution, so the popularization and the application of the threonine modified lignin-based flocculant have double meanings of reducing the pollution of the papermaking black liquor and effectively utilizing resources.
Detailed Description
In order to better understand the present invention, the following embodiments further illustrate the technical solution of the present invention.
Example 1
Weighing 50 g of lignin black liquor, putting the lignin black liquor into a beaker, adding 60 ml of water, adjusting the temperature to 50 ℃, and continuously stirring until the lignin black liquor is completely dissolved. And then slowly adding 12% dilute sulfuric acid to adjust the pH =2 of the liquid in the beaker, heating at constant temperature for 10 minutes, cooling to room temperature, performing centrifugal separation, pouring out the upper layer liquid, cleaning the precipitate with distilled water, centrifuging again, repeating the step until the pH = 6-7 of the washed distilled water, taking out the washed precipitate, putting the precipitate into a 40 ℃ oven for drying, finally weighing the refined lignin with the mass of 3.04 g, representing the structure of the refined lignin by infrared spectroscopy (figure 1), and observing the appearance of the refined lignin by a Scanning Electron Microscope (SEM) (figure 2).
Weighing 2.0 g of refined lignin, dissolving in 20 ml of 10% sodium hydroxide solution, fully stirring, adding 1.5 ml of 40% formaldehyde solution, dropwise adding 20 ml of 10% threonine solution while stirring, and placing in a 70 ℃ water bath kettle for reacting for 4 hours at constant temperature. After the reaction is finished, acidifying with 20% sulfuric acid, pouring into a centrifuge tube, placing in a centrifuge for separation, washing the precipitate for several times with dilute sulfuric acid, then washing with distilled water to be neutral, taking out the solid, and freeze-drying to obtain 2.12 g of threonine modified lignin. The IR spectrum thereof is shown at 1734 cm -1 Has a medium-intensity peak which is a C = O telescopic vibration area in carboxyl, and is at 3400- -1 Has a broad peak at 3630 cm, which is a carboxyl peak -1 There was a weak, slightly sharp peak, which was an N-H stretching vibration (FIG. 3), and SEM images showed a significant change in surface morphology (FIG. 4).
Example 2
The methylene blue solution at 20 mg/L was diluted to 1mg/L, 2mg/L, 4mg/L, 6mg/L and 8mg/L, respectively, and the absorbance at 667 nm was measured with an ultraviolet-visible spectrophotometer to plot a standard curve (FIG. 5).
100mL of 20 mg/L methylene blue solution is placed in a beaker, 50mg of threonine modified lignin prepared in example 1 is added into the solution, the solution is stirred for 5 min at room temperature and is kept stand for 24h, then an ultraviolet-visible spectrophotometer is used for measuring the absorbance of a supernatant, and the concentration of the methylene blue solution is calculated, so that the result shows that the methylene blue removal rate is 94%, and a very obvious removal effect can be seen by naked eyes (figure 6). When the amount of threonine modified lignin is increased to 1000mg/L, the removal rate can reach 99%, and the results are shown in the following table:
| concentration of threonine-modified Lignin (mg/L) | 100 | 200 | 500 | 1000 |
| Methylene blue removal (%) | 71 | 85 | 94 | 99 |
Example 3.
50 mug/ml Hg are taken 2+ 100ml of the solution was placed in a beaker, 100mg of threonine-modified lignin prepared in example 1 was added to the solution, stirred at room temperature for 5 min, allowed to stand for 24h, and then Hg in the supernatant after adsorption was measured by atomic absorption 2+ And (4) concentration. The quantitative method adopts a standard addition method, the measurement wavelength is 254nm, and the flame is air-acetylene flame. The results show that Hg in the supernatant after adsorption 2+ The concentration was only 16. mu.g/ml, and the removal rate was 68%. When the amount of threonine modified lignin is increased to 2g/L, the removal rate can reach 77%, and the results are shown in the following table:
| concentration of threonine-modified Lignin (mg/L) | 500 | 1000 | 2000 |
| Hg 2+ Removal Rate (%) | 61 | 68 | 77 |
Example 4.
Taking 100ml of 0.010 mol/L copper sulfate solution, placing the copper sulfate solution in a beaker, adding 100mg of threonine modified lignin prepared in the example 1 into the solution, stirring the solution for 5 min at room temperature, standing the solution for 24h, and measuring Cu in the solution before and after adsorption by a spectrophotometer at 590nm by adopting a standard curve method 2+ The results show that Cu is contained in the supernatant after adsorption 2+ The concentration is only 0.001 mol/L, the removal rate is 90%, and a very obvious removal effect can be seen by naked eyes (no picture is provided because the picture is adjusted to be in a gray scale mode and a remarkable contrast effect is not easy to observe). When the amount of threonine modified lignin is increased to 2g/L, the removal rate can reach 94%, and the results are shown in the following table:
| concentration of threonine-modified Lignin (mg/L) | 500 | 1000 | 2000 |
| Cu 2+ Removal Rate (%) | 73 | 90 | 94 |
Example 5.
The adsorption effect of the threonine modified lignin-based flocculant prepared by the invention on fuchsin, ethyl violet, isatin, indigo, activated yellow 3 and activated orange 16 can be tested according to the same method as that of example 2, when the dosage of threonine modified lignin is 0.5g/L, the removal rate of the threonine modified lignin on the fuchsin and the ethyl violet can reach 86% and 85%, but the threonine modified lignin is not adsorbed on the isatin and the indigo basically, and the threonine modified lignin has weaker adsorption effect on the activated yellow 3 and the activated orange 16; the adsorption effect of the threonine modified lignin-based flocculant prepared by the invention on other metal ions can be tested according to the same method as in example 3, and Cr is adsorbed when the dosage of threonine modified lignin is 0.5g/L 3+ 、Co 2+ 、Pb 2+ The removal rate of (1) can reach 65%, 61% and 69%, but for Fe 3+ 、Ni 2+ And Cd 2+ The adsorption effect of (2) is weak.
Drawings
FIG. 1 shows the IR spectrum of refined lignin.
Figure 2 is an SEM image of refined lignin.
FIG. 3 is an IR spectrum of threonine-modified lignin.
Figure 4 is an SEM image of threonine modified lignin.
FIG. 5 is a standard curve of spectrophotometric determination of methylene blue absorbance.
FIG. 6 is a graph comparing the effect of threonine-modified lignin before and after adsorption of methylene blue (after adsorption on the left, before adsorption on the right, converted to a grayscale photograph as required).
Claims (4)
1. A preparation method of a threonine modified lignin flocculant comprises the following steps:
(1) weighing a certain amount of crude lignin or lignin black liquor (with strong basicity) and placing the crude lignin or the lignin black liquor in a beaker, adding water, heating to a certain temperature, continuously stirring until the crude lignin or the lignin black liquor is completely dissolved, then adding dilute sulfuric acid in batches to adjust the liquid in the beaker to be acidic, cooling to room temperature, then centrifugally separating out precipitate, washing the precipitate with distilled water, then centrifuging, repeating the step until the distilled water obtained after washing the precipitate is neutral, and drying the washed precipitate to obtain black solid refined lignin;
(2) weighing a certain amount of refined lignin, dissolving the refined lignin in a sodium hydroxide solution with a certain concentration, fully stirring, adding a certain amount of formaldehyde solution with a certain concentration, then dropwise adding a threonine solution with a certain concentration while stirring, reacting at a constant temperature for a certain time after dropwise adding, acidifying with dilute sulfuric acid with a certain concentration after the reaction is finished, performing centrifugal separation, washing the precipitate with distilled water for several times until the washed distilled water is neutral, taking out the solid, and drying under a proper condition to obtain the threonine modified lignin-based flocculant.
2. The method of claim 1, wherein the threonine-modified lignin flocculant is prepared by: the refining temperature in the step (1) is between room temperature and 100 ℃, and the concentration of dilute sulfuric acid is between 5 and 70 percent; in the step (2), the concentration of the sodium hydroxide solution is 5% -70%, the concentration of the formaldehyde solution is 5% -60%, the concentration of the threonine solution is 5% -60%, and the concentration of the dilute sulfuric acid is 5% -70%; the mass ratio of the refined lignin, the formaldehyde and the threonine in the step (2) is preferably 1 (0.1-2) to 0.5-2, the reaction temperature of the refined lignin, the formaldehyde and the threonine is preferably 20-90 ℃, the reaction time is preferably 0.5-4h, and the drying condition is preferably low-temperature freeze drying or vacuum normal-temperature drying or less than 50 o And C, slowly drying.
3. A threonine modified lignin flocculant is characterized in that: prepared according to the method of claim 1.
4. The use of a threonine-modified lignin flocculant according to claim 3 in the field of sewage treatment, wherein: the sewage is mainly dye or heavy metal containing sewage discharged in the industrial production processes of printing and dyeing, mining and metallurgy, mechanical manufacturing, chemical engineering, electronics and instruments.
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4455257A (en) * | 1982-10-12 | 1984-06-19 | Reed Lignin, Inc. | Cationic reaction product of kraft lignin with aldehyde and polyamine |
| CN101157459A (en) * | 2007-09-17 | 2008-04-09 | 长沙理工大学 | Method for reclaiming lignin and alkali from boiling black liquor |
| CN101254970A (en) * | 2007-02-28 | 2008-09-03 | 中国科学院大连化学物理研究所 | Decolorizing coagulant as well as preparation method and uses thereof |
| CN108607519A (en) * | 2018-05-31 | 2018-10-02 | 河南工程学院 | A kind of sludge passivator and its application |
| CN112915971A (en) * | 2021-01-20 | 2021-06-08 | 南京工业大学 | Lignin grafted polyamino acid type heavy metal adsorbent and preparation method and application thereof |
-
2022
- 2022-06-14 CN CN202210667602.7A patent/CN114835916A/en active Pending
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4455257A (en) * | 1982-10-12 | 1984-06-19 | Reed Lignin, Inc. | Cationic reaction product of kraft lignin with aldehyde and polyamine |
| CN101254970A (en) * | 2007-02-28 | 2008-09-03 | 中国科学院大连化学物理研究所 | Decolorizing coagulant as well as preparation method and uses thereof |
| CN101157459A (en) * | 2007-09-17 | 2008-04-09 | 长沙理工大学 | Method for reclaiming lignin and alkali from boiling black liquor |
| CN108607519A (en) * | 2018-05-31 | 2018-10-02 | 河南工程学院 | A kind of sludge passivator and its application |
| CN112915971A (en) * | 2021-01-20 | 2021-06-08 | 南京工业大学 | Lignin grafted polyamino acid type heavy metal adsorbent and preparation method and application thereof |
Non-Patent Citations (2)
| Title |
|---|
| RUN FANG等: "Synthesis of lignin-base cationic flocculant and its application in removing anionic azo-dyes from simulated wastewater", 《BIORESOURCE TECHNOLOGY》 * |
| 郭建欣: "木质素类絮凝剂的合成及应用研究", 《造纸化学品》 * |
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