CN107814434B - Modified water-soluble chitosan flocculant and preparation method thereof - Google Patents
Modified water-soluble chitosan flocculant and preparation method thereof Download PDFInfo
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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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- C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
- C08B37/00—Preparation of polysaccharides not provided for in groups C08B1/00 - C08B35/00; Derivatives thereof
- C08B37/0006—Homoglycans, i.e. polysaccharides having a main chain consisting of one single sugar, e.g. colominic acid
- C08B37/0024—Homoglycans, i.e. polysaccharides having a main chain consisting of one single sugar, e.g. colominic acid beta-D-Glucans; (beta-1,3)-D-Glucans, e.g. paramylon, coriolan, sclerotan, pachyman, callose, scleroglucan, schizophyllan, laminaran, lentinan or curdlan; (beta-1,6)-D-Glucans, e.g. pustulan; (beta-1,4)-D-Glucans; (beta-1,3)(beta-1,4)-D-Glucans, e.g. lichenan; Derivatives thereof
- C08B37/0027—2-Acetamido-2-deoxy-beta-glucans; Derivatives thereof
- C08B37/003—Chitin, i.e. 2-acetamido-2-deoxy-(beta-1,4)-D-glucan or N-acetyl-beta-1,4-D-glucosamine; Chitosan, i.e. deacetylated product of chitin or (beta-1,4)-D-glucosamine; Derivatives thereof
Abstract
The invention discloses a modified water-soluble chitosan flocculant and a preparation method thereof, and the preparation method comprises the following carboxymethyl reaction steps: dispersing chitosan in a mixed solution of isopropanol and sodium hydroxide, stirring and alkalifying to obtain a reaction mixture; dissolving monochloroacetic acid in isopropanol, then dropwise adding the monochloroacetic acid into the reaction mixture, and reacting for 3-5 h; adding ethanol water solution to terminate the reaction; then washing and drying to obtain carboxymethyl chitosan; a crosslinking reaction step: dissolving carboxymethyl chitosan in hydrochloric acid, adjusting the pH value to 5, then dissolving 3, 4-dihydroxy phenylacetic acid in a certain amount of water, adding the mixture into a carboxymethyl chitosan solution, then dissolving a mixture of EDC and NHS in a mixed solution of water and ethanol, and adding the mixed solution into a reaction solution; and adding hydrogen peroxide into the reaction solution, stirring and maintaining the pH value of the reaction solution at 4.5-5.0, and reacting at room temperature for 9-11 hours to obtain the modified water-soluble chitosan flocculant. The flocculant of the invention has good water solubility and flocculation property.
Description
Technical Field
The invention relates to a flocculant, in particular to a modified water-soluble chitosan flocculant and a preparation method thereof.
Background
Inorganic flocculants and synthetic organic polymeric flocculants which are widely used at present inevitably have the possibility of secondary pollution, and natural high-molecular flocculants have become the trend of future development. Among a wide variety of natural polymers, chitosan has received much attention due to its own special structure and excellent properties. And the chitosan, which is a cationic polyelectrolyte due to the primary amine group, can be used as a flocculant, so that the chitosan can show good flocculation performance on heavy metal ions in a water body through complexation, neutralization with negatively charged suspended particles through electricity, and a series of different actions with microbial pollutants. However, the chitosan has strong hydrogen bonding effect in and among molecules, the molecular structure is in a compact crystalline state and is insoluble in water and most organic solvents, and the application of the chitosan is limited to a great extent.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention aims to provide a modified water-soluble chitosan flocculant which has good water solubility and flocculation property.
The invention also aims to provide a preparation method of the modified water-soluble chitosan flocculant.
One of the purposes of the invention is realized by adopting the following technical scheme:
the modified water-soluble chitosan flocculant is characterized in that chitosan is used as a main raw material, hydrogen peroxide is used as a cross-linking agent, and the carboxymethyl reaction and the cross-linking reaction are sequentially carried out to obtain the modified water-soluble chitosan flocculant.
The second purpose of the invention is realized by adopting the following technical scheme:
a preparation method of a modified water-soluble chitosan flocculant is characterized by comprising the following steps:
and (3) carboxymethyl reaction: dispersing chitosan in a mixed solution of isopropanol and sodium hydroxide, stirring and alkalifying to obtain a reaction mixture; dissolving monochloroacetic acid in isopropanol, then dropwise adding the monochloroacetic acid into the reaction mixture, and reacting for 3-5h after the dropwise adding is finished; after the reaction is finished, adding excessive ethanol water solution to stop the reaction, and adjusting the pH value of the system to 7; then washing and drying to obtain carboxymethyl chitosan;
a crosslinking reaction step: dissolving carboxymethyl chitosan in hydrochloric acid, and adjusting the p H value to 5 to obtain a carboxymethyl chitosan solution; then dissolving 3, 4-dihydroxy phenylacetic acid in a certain amount of water, and adding the solution into the carboxymethyl chitosan solution to obtain a reaction solution; then dissolving a mixture of EDC and NHS in a mixed solution of water and ethanol, and dropwise adding the mixture into the reaction solution; and adding hydrogen peroxide into the reaction solution, stirring and maintaining p H of the reaction solution at 4.5-5.0, and reacting at room temperature for 9-11 hours to obtain the modified water-soluble chitosan flocculant.
Further, in the carboxymethyl reaction step, the mass-to-volume ratio of the chitosan to the mixed solution of isopropanol and sodium hydroxide is 10-25 g: 100mL, and the mass-volume ratio of chitosan to monochloroacetic acid is 20 g: 40-80mL, the volume ratio of monochloroacetic acid to isopropanol is 40-80 mL: 50 mL.
Further, in the carboxymethyl reaction step, the volume ratio of isopropanol to sodium hydroxide in the mixed solution of isopropanol and sodium hydroxide is 2: 1.
Further, in the carboxymethyl reaction step, stirring and basification were performed in a water bath at 50 ℃ for 2 h.
Further, in the carboxymethyl reaction step, the reaction temperature was 50 ℃. The reaction temperature is 50 ℃ which is favorable for the maximum degree of substitution. The temperature is higher than 50 ℃, the hydrolysis of monochloro-acetic acid is accelerated, and the substitution reaction is not favorably carried out; on the contrary, the adhesion of the materials is reduced, and the substitution degree is reduced.
Further, in the step of crosslinking reaction, the mass-to-volume ratio of the carboxymethyl chitosan to the hydrochloric acid is 5-15 g: 60mL, the mass-volume ratio of the 3, 4-dihydroxy phenylacetic acid to the water is 5-30 g: 50mL, and the mass-volume ratio of the mixture of EDC and NHS to the mixed solution of water and ethanol is 15-40 g: 200mL, and the weight ratio of the hydrogen peroxide to the carboxymethyl chitosan is 5-20: 5.
Further, in the step of crosslinking reaction, the molar concentration of hydrochloric acid is 1 mol/L; the molar concentration of the sodium hydroxide is 5 mol/L.
Further, in the crosslinking reaction step, the molar mass ratio of EDC to NHS in the mixture of EDC and NHS is 1: 1.
further, in the step of crosslinking reaction, the volume ratio of water to ethanol in the mixed solution of water and ethanol is 1: 1.
compared with the prior art, the invention has the beneficial effects that:
the invention takes chitosan as raw material, chloroacetic acid and phenol group as modifying reagent, and adopts two-step method to prepare the modified water-soluble chitosan flocculant. The carboxymethyl chitosan has a remarkably widened soluble range and strong metal ion chelating capacity, and can form coordinate bonds with a plurality of metal ions, so that a complex is generated and precipitated, namely, the water solubility and metal ion complexing capacity of the chitosan are greatly improved due to the introduction of carboxyl; the structure of the quinone group is unstable, the quinone group is very active group and has strong reactivity, the quinone group can react with amino group to generate imine, generate Michael addition reaction or generate free-combined free radical to form biaryl and other chemical reactions, and can form irreversible covalent bonds with polar groups (-SO, Na, -OH, -NH) and the like on organic dye pollutants, thereby realizing the purposes of adsorption and condensation. Therefore, the product is a polymer with wider applicability, can be used as a flocculating agent and a heavy metal ion adsorbent, has high adsorption efficiency, can ensure that heavy metal ions are desorbed smoothly after adsorption, has higher flocculation speed and larger floc, is non-toxic and harmless, is easy to biodegrade, does not bring secondary pollution, and is an ideal water-soluble chitosan flocculating agent.
Detailed Description
The present invention is further described below with reference to specific embodiments, and it should be noted that, without conflict, any combination between the embodiments or technical features described below may form a new embodiment. The materials used in this example are all commercially available.
A modified water-soluble chitosan flocculant is prepared by using chitosan as a main raw material and hydrogen peroxide as a cross-linking agent through carboxymethyl reaction and cross-linking reaction in sequence.
The invention provides a novel modified water-soluble chitosan flocculant, which has the advantages that on one hand, due to the introduction of carboxymethyl groups, the quantity of negative charges carried by a molecular chain of the flocculant is greatly increased, so that the flocculant is favorable for removing pollutants with positive charges on the surface in a water body, and the flocculant has good water solubility, namely the application range of the flocculant is greatly widened due to the increase of the dissolution range of the flocculant. On the other hand, a metal chelation effect is generated between the catechol group and a metal substance to form a stable covalent bond, the catechol group can be easily oxidized to form the catechol under the action of enzyme or an inorganic catalyst, the quinone group has the capability of forming irreversible covalent bonds with sulfydryl groups, some polar groups (-SO, Na, -OH, -NH) and the like on organic dye pollutants, and the bonding bridging and net trapping sweeping effects on water pollutants are remarkably enhanced, SO that the adsorption and condensation performances are excellent. Therefore, based on the existence of amino in chitosan molecules, hydrogen peroxide is used as a cross-linking agent, and EDC/NHS (1-ethyl-3- (3-dimethylaminopropyl) -carbodiimide (EDC) and N-hydroxysuccinimide (NHS)) coupling reaction is carried out to graft catechol groups on the chitosan molecular structure, so that the modified water-soluble chitosan flocculant has good water solubility and flocculation property.
A preparation method of a modified water-soluble chitosan flocculant comprises the following steps:
and (3) carboxymethyl reaction: dispersing chitosan in a mixed solution of isopropanol and sodium hydroxide, stirring and alkalifying to obtain a reaction mixture; dissolving monochloroacetic acid in isopropanol, then dropwise adding the monochloroacetic acid into the reaction mixture, and reacting for 3-5h after the dropwise adding is finished; after the reaction is finished, adding excessive ethanol water solution to stop the reaction, and adjusting the pH value of the system to 7; then washing and drying to obtain carboxymethyl chitosan;
a crosslinking reaction step: dissolving carboxymethyl chitosan in hydrochloric acid, and adjusting the p H value to 5 to obtain a carboxymethyl chitosan solution; then dissolving 3, 4-dihydroxy phenylacetic acid in a certain amount of water, and adding the solution into the carboxymethyl chitosan solution to obtain a reaction solution; then dissolving a mixture of EDC and NHS (EDC/NHS for short) in a mixed solution of water and ethanol, and dropwise adding the mixture into the reaction solution; and adding hydrogen peroxide into the reaction solution, stirring and maintaining p H of the reaction solution at 4.5-5.0, and reacting at room temperature for 9-11 hours to obtain the modified water-soluble chitosan flocculant.
The synthetic route for preparing the modified water-soluble chitosan flocculant is as shown in formula 1:
wherein x is 200-.
In a preferred embodiment, in the carboxymethyl reaction step, the mass-to-volume ratio of the chitosan to the mixed solution of isopropanol and sodium hydroxide is 10 to 25 g: 100mL, and the mass-volume ratio of chitosan to monochloroacetic acid is 20 g: 40-80mL, the volume ratio of monochloroacetic acid to isopropanol is 40-80 mL: 50 mL.
In a preferred embodiment, in the carboxymethyl reaction step, the volume ratio of isopropanol to sodium hydroxide in the mixed solution of isopropanol and sodium hydroxide is 2: 1.
As a preferred embodiment, in the carboxymethyl reaction step, stirring and basification are performed in a water bath at 50 ℃ for 2 h.
In a preferred embodiment, the reaction temperature in the carboxymethyl reaction step is 50 ℃. The reaction temperature is 50 ℃ which is favorable for the maximum degree of substitution. The temperature is higher than 50 ℃, the hydrolysis of monochloro-acetic acid is accelerated, and the substitution reaction is not favorably carried out; on the contrary, the adhesion of the materials is reduced, and the substitution degree is reduced.
In a preferred embodiment, in the crosslinking reaction step, the mass-to-volume ratio of carboxymethyl chitosan to hydrochloric acid is 5 to 15 g: 60mL, the mass-volume ratio of the 3, 4-dihydroxy phenylacetic acid to the water is 5-30 g: 50mL, and the mass-volume ratio of the mixture of EDC and NHS to the mixed solution of water and ethanol is 15-40 g: 200mL, and the weight ratio of the hydrogen peroxide to the carboxymethyl chitosan is 5-20: 5.
In a preferred embodiment, the molar concentration of hydrochloric acid in the crosslinking reaction step is 1 mol/L; the molar concentration of the sodium hydroxide is 5 mol/L.
As a preferred embodiment, in the crosslinking reaction step, the molar mass ratio of EDC to NHS in the mixture of EDC and NHS is 1: 1.
in a preferred embodiment, in the crosslinking reaction step, the volume ratio of water to ethanol in the water-ethanol mixture is 1: 1.
example 1:
a preparation method of a water-soluble chitosan flocculant sequentially comprises the following steps:
and (3) carboxymethyl reaction: 25g of chitosan was dispersed in 100mL of a mixed solution of isopropyl alcohol and sodium hydroxide, stirred and alkalified for 2 hours in a water bath at 50 ℃ to obtain a reaction mixture. 60mL of monochloroacetic acid is dissolved in 50mL of isopropanol, slowly added into the reaction mixture dropwise through a constant pressure dropping funnel, and after the dropwise addition is finished, the reaction is carried out for 3-5h at the temperature of 50 ℃. After the reaction is finished, adding a large amount of ethanol aqueous solution to stop the reaction, and adjusting the pH of the system to 7 by using a prepared hydrochloric acid aqueous solution with the mass fraction of 10%. And then washing and drying to obtain the carboxymethyl chitosan.
A crosslinking reaction step: 10g of carboxymethyl chitosan is dissolved in 60mL of hydrochloric acid, then 40-100mL of water is added, and the pH value is adjusted to 5 by using NaOH solution, so as to obtain carboxymethyl chitosan solution. 10g of 3, 4-dihydroxyphenylacetic acid was dissolved in 50mL of water, and rapidly added to the carboxymethyl chitosan solution to obtain a reaction solution. 20g of EDC/NHS was dissolved in 200mL of a mixture of water and ethanol and added dropwise to the reaction solution. And adding 5g of hydrogen peroxide into the reaction solution, quickly stirring, maintaining p H of the reaction solution at 4.5-5.0, and reacting at room temperature for 10 hours to obtain the modified water-soluble chitosan flocculant.
Example 2:
a preparation method of a water-soluble chitosan flocculant sequentially comprises the following steps:
and (3) carboxymethyl reaction: 20g of chitosan was dispersed in 100mL of a mixed solution of isopropyl alcohol and sodium hydroxide, stirred and alkalinized for 2 hours in a water bath at 50 ℃ to obtain a reaction mixture. 80mL of monochloroacetic acid is dissolved in 50mL of isopropanol, slowly added into the reaction mixture dropwise through a constant pressure dropping funnel, and after the dropwise addition is finished, the reaction is carried out for 3-5h at the temperature of 50 ℃. After the reaction is finished, adding a large amount of ethanol aqueous solution to stop the reaction, and adjusting the pH of the system to 7 by using a prepared hydrochloric acid aqueous solution with the mass fraction of 10%. And then washing and drying to obtain the carboxymethyl chitosan.
A crosslinking reaction step: 15g of carboxymethyl chitosan is dissolved in 60mL of hydrochloric acid, then 40-100mL of water is added, and the pH value is adjusted to 5 by using NaOH solution, so as to obtain carboxymethyl chitosan solution. 20g of 3, 4-dihydroxyphenylacetic acid was dissolved in 50mL of water, and rapidly added to the carboxymethyl chitosan solution to obtain a reaction solution. 40g of EDC/NHS was dissolved in 200mL of a mixture of water and ethanol and added dropwise to the reaction solution. And adding 5g of hydrogen peroxide into the reaction solution, quickly stirring, maintaining p H of the reaction solution at 4.5-5.0, and reacting at room temperature for 10 hours to obtain the modified water-soluble chitosan flocculant.
Example 3:
a preparation method of a water-soluble chitosan flocculant sequentially comprises the following steps:
and (3) carboxymethyl reaction: 10g of chitosan was dispersed in 100mL of a mixed solution of isopropyl alcohol and sodium hydroxide, stirred and alkalinized for 2 hours in a water bath at 50 ℃ to obtain a reaction mixture. 40mL of monochloroacetic acid is dissolved in 50mL of isopropanol, slowly added into the reaction mixture dropwise through a constant pressure dropping funnel, and after the dropwise addition is finished, the reaction is carried out for 3-5h at the temperature of 50 ℃. After the reaction is finished, adding a large amount of ethanol aqueous solution to stop the reaction, and adjusting the pH of the system to 7 by using a prepared hydrochloric acid aqueous solution with the mass fraction of 10%. And then washing and drying to obtain the carboxymethyl chitosan.
A crosslinking reaction step: 5g of carboxymethyl chitosan is dissolved in 60mL of hydrochloric acid, then 40-100mL of water is added, and the pH value is adjusted to 5 by using NaOH solution, so as to obtain carboxymethyl chitosan solution. 30g of 3, 4-dihydroxyphenylacetic acid was dissolved in 50mL of water, and rapidly added to the carboxymethyl chitosan solution to obtain a reaction solution. 15g of EDC/NHS was dissolved in 200mL of a mixture of water and ethanol and added dropwise to the reaction solution. And adding 5g of hydrogen peroxide into the reaction solution, quickly stirring, maintaining p H of the reaction solution at 4.5-5.0, and reacting at room temperature for 10 hours to obtain the modified water-soluble chitosan flocculant.
Example 4:
a preparation method of a water-soluble chitosan flocculant sequentially comprises the following steps:
and (3) carboxymethyl reaction: 20g of chitosan was dispersed in 100mL of a mixed solution of isopropyl alcohol and sodium hydroxide, stirred and alkalinized for 2 hours in a water bath at 50 ℃ to obtain a reaction mixture. 80mL of monochloroacetic acid is dissolved in 50mL of isopropanol, slowly added into the reaction mixture dropwise through a constant pressure dropping funnel, and after the dropwise addition is finished, the reaction is carried out for 3-5h at the temperature of 50 ℃. After the reaction is finished, adding a large amount of ethanol aqueous solution to stop the reaction, and adjusting the pH of the system to 7 by using a prepared hydrochloric acid aqueous solution with the mass fraction of 10%. And then washing and drying to obtain the carboxymethyl chitosan.
A crosslinking reaction step: 10g of carboxymethyl chitosan is dissolved in 60mL of hydrochloric acid, then 40-100mL of water is added, and the pH value is adjusted to 5 by using NaOH solution, so as to obtain carboxymethyl chitosan solution. 25g of 3, 4-dihydroxyphenylacetic acid was dissolved in 50mL of water, and rapidly added to the carboxymethyl chitosan solution to obtain a reaction solution. 30g of EDC/NHS was dissolved in 200mL of a mixture of water and ethanol, and added dropwise to the reaction solution. And adding 5g of hydrogen peroxide into the reaction solution, quickly stirring, maintaining p H of the reaction solution at 4.5-5.0, and reacting at room temperature for 10 hours to obtain the modified water-soluble chitosan flocculant.
Effect verification:
under certain conditions, the prepared modified water-soluble chitosan flocculant is equivalently placed in a certain amount of hydrochloric acid or sodium hydroxide water which is added in advance, the magnetic stirring is adopted to fully disperse the substance to be detected, the solubility of the substance to be detected is observed by naked eyes, and the pH value of the fully dispersed system is measured, so that the dependency relationship of the solubility of the substance to be detected on the pH value is obtained.
Table 1 results of solubility tests of different flocculant samples at different pH conditions
| pH | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 |
| Chitosan | + | + | + | ± | - | - | - | - | - | - | - | - | - |
| Example 1 | + | + | + | + | ± | ± | ± | + | + | + | + | + | + |
| Example 2 | + | + | + | + | + | ± | ± | + | + | + | + | + | + |
| Example 3 | + | + | + | + | ± | - | ± | + | + | + | + | + | + |
| Example 4 | + | + | + | + | + | ± | + | + | + | + | + | + | + |
Note: +: is soluble; + -: partial dissolution; -: insoluble.
As can be seen from table 1, the chitosan used was only soluble in water at pH < 3; after the carboxymethyl groups are introduced, the solubility under the alkaline condition is greatly improved, mainly because the carboxyl exists in a carboxylate ion form under the alkaline condition, the hydration and dissolution processes of flocculant molecules are facilitated; compared with chitosan matrix, the four samples show superior dissolution performance under most conditions.
The flocculation performance of the printing and dyeing wastewater is measured by taking flocculant samples with different adding amounts under certain conditions (pH is 4), measuring the turbidity (NTU) of supernatant liquid after flocculation by using a turbidity meter, and calculating the residual turbidity Percentage (RT, percent) according to a formula.
TABLE 2 flocculation Properties of different flocculant samples on printing and dyeing wastewater
As can be seen from Table 2, for flocculation of the dye wastewater, after the chitosan is subjected to double modification by carboxymethyl and o-diphenol, the flocculation effect on the selected typical simulated dye wastewater is obvious, because the molecular structure of the modified chitosan has-COOH, and because the o-diphenol is easily oxidized into o-quinonediquinone, the quinonyl group is a very active group, and can react with amino to generate imine, Michael addition reaction or free radical capable of being freely combined to form biaryl and other chemical reactions, and can form irreversible covalent bonds with some polar groups (-SO, Na, -OH, -NH) and the like on organic dye pollutants, SO that the purposes of adsorption and flocculation are realized.
Under certain conditions, the same amount (0.1g/L) of different modified water-soluble chitosan flocculating agents are taken to be added into certain electroplating wastewater (pH is 5.3), the mixture is stirred and adsorbed at room temperature, then the residual concentrations of Cd, Pb and Cu are measured by an atomic absorption photometry, and the removal rate is calculated.
TABLE 3 removal rate of metal ions in electroplating wastewater
As can be seen from Table 3, the removal rate of the modified water-soluble chitosan flocculant on Cd, Pb and Cu is over 90%, and the treatment effect is good. The water solubility and the metal ion complexing ability of the chitosan are greatly improved due to the introduction of carboxyl, and a stable covalent bond is formed by the metal chelation between the catechol group and the metal substance, so that the modified water-soluble chitosan flocculant has feasibility of being applied to actual wastewater treatment.
The above embodiments are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited thereby, and any insubstantial changes and substitutions made by those skilled in the art based on the present invention are within the protection scope of the present invention.
Claims (10)
1. The modified water-soluble chitosan flocculant is characterized in that hydrogen peroxide is used as a cross-linking agent, and a catechol group is grafted on a chitosan molecular structure through a coupling reaction of 1-ethyl-3- (3-dimethylaminopropyl) -carbodiimide and N-hydroxysuccinimide to obtain the modified water-soluble chitosan flocculant.
2. The preparation method of the modified water-soluble chitosan flocculant of claim 1, which comprises:
and (3) carboxymethyl reaction: dispersing chitosan in a mixed solution of isopropanol and sodium hydroxide, stirring and alkalifying to obtain a reaction mixture; dissolving monochloroacetic acid in isopropanol, then dropwise adding the monochloroacetic acid into the reaction mixture, and reacting for 3-5h after the dropwise adding is finished; after the reaction is finished, adding excessive ethanol water solution to stop the reaction, and adjusting the pH value of the system to 7; then washing and drying to obtain carboxymethyl chitosan;
a crosslinking reaction step: dissolving carboxymethyl chitosan in hydrochloric acid, and adjusting the pH value to 5 to obtain a carboxymethyl chitosan solution; then dissolving 3, 4-dihydroxy phenylacetic acid in a certain amount of water, and adding the solution into the carboxymethyl chitosan solution to obtain a reaction solution; then dissolving the mixture of 1-ethyl-3- (3-dimethylaminopropyl) -carbodiimide and N-hydroxysuccinimide in a mixed solution of water and ethanol, and dropwise adding the mixture into the reaction solution; and adding hydrogen peroxide into the reaction solution, stirring and maintaining the pH value of the reaction solution at 4.5-5.0, and reacting at room temperature for 9-11 hours to obtain the modified water-soluble chitosan flocculant.
3. The method for preparing the modified water-soluble chitosan flocculant as claimed in claim 2, wherein in the carboxymethyl reaction step, the mass-to-volume ratio of the chitosan to the mixed solution of isopropanol and sodium hydroxide is 10-25 g: 100mL, and the mass-volume ratio of chitosan to monochloroacetic acid is 20 g: 40-80mL, the volume ratio of monochloroacetic acid to isopropanol is 40-80 mL: 50 mL.
4. The method for preparing the modified water-soluble chitosan flocculant as claimed in claim 3, wherein in the carboxymethyl reaction step, the volume ratio of isopropanol to sodium hydroxide in the mixed solution of isopropanol and sodium hydroxide is 2: 1.
5. The method for preparing the modified water-soluble chitosan flocculant of claim 3, wherein in the carboxymethyl reaction step, stirring and alkalization are performed in a water bath at 50 ℃ for 2 hours.
6. The method for preparing a modified water-soluble chitosan flocculant as claimed in claim 3, wherein the reaction temperature in the carboxymethyl reaction step is 50 ℃.
7. The method for preparing the modified water-soluble chitosan flocculant as claimed in claim 2, wherein in the step of crosslinking reaction, the mass-to-volume ratio of carboxymethyl chitosan to hydrochloric acid is 5-15 g: 60mL, the mass-volume ratio of the 3, 4-dihydroxy phenylacetic acid to the water is 5-30 g: the mass volume ratio of 50mL of the mixture of 1-ethyl-3- (3-dimethylaminopropyl) -carbodiimide and N-hydroxysuccinimide to the mixed solution of water and ethanol is 15-40 g: 200mL, and the weight ratio of the hydrogen peroxide to the carboxymethyl chitosan is 5-20: 5.
8. The method for preparing a modified water-soluble chitosan flocculant as claimed in claim 7, wherein in the step of crosslinking reaction, the molar concentration of hydrochloric acid is 1 mol/L; the molar concentration of the sodium hydroxide is 5 mol/L.
9. The method for preparing the modified water-soluble chitosan flocculant of claim 7, wherein in the crosslinking reaction step, the molar mass ratio of 1-ethyl-3- (3-dimethylaminopropyl) -carbodiimide to N-hydroxysuccinimide in the mixture of 1-ethyl-3- (3-dimethylaminopropyl) -carbodiimide and N-hydroxysuccinimide is 1: 1.
10. the method for preparing the modified water-soluble chitosan flocculant of claim 7, wherein in the step of the cross-linking reaction, the volume ratio of water to ethanol in the mixed solution of water and ethanol is 1: 1.
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| CN115121229A (en) * | 2022-07-01 | 2022-09-30 | 重庆工商大学 | Method for preparing heavy metal ion adsorbent by using flocs generated by flocculation |
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