CN110746636A - Temperature-sensitive sodium alginate/cellulose ether composite hydrogel and preparation method and application thereof - Google Patents

Temperature-sensitive sodium alginate/cellulose ether composite hydrogel and preparation method and application thereof Download PDF

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CN110746636A
CN110746636A CN201910999083.2A CN201910999083A CN110746636A CN 110746636 A CN110746636 A CN 110746636A CN 201910999083 A CN201910999083 A CN 201910999083A CN 110746636 A CN110746636 A CN 110746636A
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cellulose ether
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田野
刘鹰
代明允
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Dalian Ocean University
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Abstract

The invention belongs to the technical field of gel preparation, and particularly relates to a temperature-sensitive sodium alginate/cellulose ether composite hydrogel and a preparation method and application thereof. Reacting cellulose with an etherifying agent to obtain temperature-sensitive alkyl cellulose ether; adding sodium alginate into temperature-sensitive alkyl cellulose ether to obtain a mixed solution; and crosslinking the mixed solution with a crosslinking agent to obtain the temperature-sensitive composite hydrogel. The Volume Phase Transition Temperature (VPTT) can be adjusted within the range of 15.5-75.8 ℃ by changing the mass ratio of the alkyl cellulose ether to the sodium alginate. The sodium alginate/cellulose ether composite hydrogel prepared by the invention has excellent temperature sensitivity, has the characteristics of low price, good biocompatibility, low toxicity, degradability and the like, and simultaneously shows good adsorption capacity to heavy metal ions.

Description

Temperature-sensitive sodium alginate/cellulose ether composite hydrogel and preparation method and application thereof
Technical Field
The invention belongs to the technical field of gel preparation, and particularly relates to a temperature-sensitive sodium alginate/cellulose ether composite hydrogel and a preparation method and application thereof.
Background
The stimuli-responsive hydrogel is a polymer with a self network structure and physicochemical characteristics which are mutated under the stimulation of tiny changes of external environment (temperature, pH, light and the like). Temperature-sensitive hydrogels are the most interesting class of hydrogels in many stimuli-responsive types because the temperature change is relatively easy to implement and control, and can be efficiently applied to the aspects of heavy metal ion adsorption, drug controlled release, soft tissue repair, and the like. At present, temperature-responsive hydrogels are mainly classified into two types: the first type is a synthetic temperature-sensitive hydrogel, poly-N-isopropylacrylamide (PNIPAAm) hydrogel is the most representative and widely researched synthetic temperature-sensitive hydrogel, and the phase transition temperature (VPTT) of the hydrogel is close to the human body temperature (32 ℃), so that the hydrogel is considered to be the most suitable hydrogel material applied to the field of biotechnology. However, PNIPAAm has poor biocompatibility, is not easy to degrade, and is expensive and toxic. In order to improve the biodegradability and biocompatibility of hydrogel materials, researchers introduce polysaccharide into hydrogel structures to prepare another type of temperature-sensitive hydrogel which is widely researched. The temperature-sensitive polymer is grafted to a polysaccharide macromolecular skeleton to synthesize a series of novel polysaccharide-based temperature-sensitive hydrogels, and the introduction of the polysaccharide relatively improves the biodegradability and biocompatibility of the hydrogels. However, since the host structure is still a synthetic polymer, the biocompatibility and degradability of the gel itself cannot be fundamentally improved.
Disclosure of Invention
The invention aims to provide a temperature-sensitive sodium alginate/cellulose ether composite hydrogel as well as a preparation method and application thereof.
In order to achieve the purpose, the invention adopts the technical scheme that:
a preparation method of temperature-sensitive sodium alginate/cellulose ether composite hydrogel comprises the steps of reacting cellulose with an etherifying agent to obtain temperature-sensitive alkyl cellulose ether; adding sodium alginate into temperature-sensitive alkyl cellulose ether to obtain a mixed solution; and crosslinking the mixed solution with a crosslinking agent to obtain the temperature-sensitive composite hydrogel.
Further, the following steps are carried out:
(1) preparing temperature-sensitive alkyl cellulose ether: alkalizing cellulose pulp by alkali at 60-70 ℃ for 1-1.5 hours, adding an etherifying agent into reaction liquid after alkalization, stirring and reacting at 70-90 ℃ for 6-9 hours, cooling to room temperature after reaction, adjusting the system to be neutral, and dialyzing by a dialysis bag after adjustment until the electric conductivity of the reaction liquid is less than 10 mus/cm to obtain temperature-sensitive alkyl cellulose ether;
(2) mixing the solution: dissolving the obtained temperature-sensitive alkyl cellulose ether in water, adding sodium alginate, and reacting for 0.5-2h in ice bath to obtain a mixed solution;
(3) preparing temperature-sensitive hydrogel through crosslinking: and (2) carrying out ultrasonic treatment on the obtained mixed solution in an ice-water bath in alkali for 15-30 minutes, adding a composite cross-linking agent containing calcium ions after ultrasonic treatment, continuing to carry out ultrasonic treatment in the ice-water bath for 30-50 minutes after adding, carrying out ultrasonic dispersion, and carrying out cross-linking reaction at 20-60 ℃ for 0.5-2 hours to obtain the temperature-sensitive composite hydrogel.
The step 1) adding sodium hydroxide with the cellulose mass of 2-25% into cellulose pulp with the mass concentration of 10-60%, uniformly stirring, and alkalizing for 1-1.5 hours at the temperature of 60-70 ℃; and then, according to the mass ratio of the etherifying agent to the cellulose of 0.2-2.5: 1, dripping an etherifying agent, and stirring and reacting at 70-90 ℃ for 6-9 hours; then diluting the reaction solution by water, cooling to room temperature, adjusting the pH of the reaction solution to 7 by acid, dialyzing the adjusted reaction solution in a dialysis bag with the molecular weight of 7000 14000 until the conductivity of the reaction solution is less than 10 mu s/cm, and concentrating and drying after dialysis to obtain powder or blocky solid alkyl cellulose ether; wherein, the etherifying agent is alkyl glycidyl ether.
The alkyl glycidyl ether is propyl glycidyl ether, isobutyl glycidyl ether or amyl glycidyl ether.
The step 2) is to crush the obtained temperature-sensitive alkyl cellulose ether, and the crushed alkyl cellulose ether is dissolved in deionized water at 50 ℃ to obtain a solution, wherein the concentration of the alkyl cellulose ether solution in the solution is 6-11 wt%; adding sodium alginate into the solution, and reacting for 0.5-2 hr in ice bath to obtain mixed solution; wherein the mass ratio of sodium alginate to temperature-sensitive alkyl cellulose ether is 1-3: 1. the deionized water at 50 ℃ is slowly stirred until the deionized water is dissolved (foaming is avoided as much as possible) through the water dissolving process.
Adding NaOH into the mixed solution of sodium alginate and cellulose ether under the stirring condition in the step 3), and then carrying out ultrasonic treatment on the mixture in an ice-water bath for 15-30 minutes; adding a composite cross-linking agent containing calcium ions into the mixed solution after ultrasonic treatment, performing ultrasonic treatment in an ice-water bath for 30-50 minutes, performing cross-linking reaction at 20-60 ℃ for 0.5-2h h after ultrasonic dispersion, alternately washing the hydrogel by using cold and hot deionized water after the cross-linking reaction until the color of the hydrogel is changed from light yellow to milky white and the conductivity of leacheate is less than 10 mu s/cm, and then drying to obtain the temperature-sensitive composite hydrogel; wherein the mass ratio of NaOH to the sodium alginate/cellulose ether mixture is 0.08-0.8: 3, the volume ratio of the composite cross-linking agent to the sodium alginate/cellulose ether mixture solution is 0.11-1.20: 26.
further, the method for purifying the sodium alginate/cellulose ether composite hydrogel comprises the following steps: heating the prepared composite hydrogel product to above VPTT to enable the volume of the composite hydrogel product to shrink, pouring out residual liquid, and injecting low-temperature deionized water to enable the gel to swell, wherein the process mainly comprises the step of removing reactants such as unreacted cross-linking agent, sodium hydroxide and the like. The purification process is repeated for a plurality of times until the hydrogel is changed from light yellow to milk white and the conductivity of the leacheate is less than 10 mu s/cm, so that the temperature-sensitive sodium alginate/cellulose ether composite hydrogel is obtained.
The composite cross-linking agent containing calcium ions is a mixture of inorganic salt containing calcium ions and polyethylene glycol diglycidyl ether, epichlorohydrin, vinyl sulfone or glutaraldehyde; wherein the volume ratio of the calcium ion-containing inorganic salt to the other 4 crosslinking agents is 9: 2-12.
The inorganic salt containing calcium ions, such as calcium chloride, calcium sulfate, and the like.
The purified sodium alginate/cellulose ether composite hydrogel is frozen at the temperature of-5 ℃, and then the frozen gel is frozen at the temperature of-80 ℃ and the pressure of 20pa for 6 hours.
The temperature-sensitive sodium alginate/cellulose ether composite hydrogel is prepared by the method, and the volume phase transition temperature of the temperature-sensitive sodium alginate/cellulose ether composite hydrogel can be adjusted within the range of 15.5-75.8 ℃.
The application of the temperature-sensitive sodium alginate/cellulose ether composite hydrogel in heavy metal adsorption is provided.
The composite gel can be further applied after being recycled and regenerated after heavy metal ions are adsorbed.
The invention has the beneficial effects that:
1. the sodium alginate/cellulose ether composite hydrogel is composed of pure polysaccharide, has excellent, adjustable and controllable temperature-sensitive performance, and has the advantages of low price, good biocompatibility, low toxicity, degradability and the like compared with petroleum-based temperature-sensitive hydrogel;
2. the composite hydrogel has double functions: the cellulose ether component endows the composite hydrogel with excellent temperature sensitivity; sodium alginate can be used as an important component for adsorbing heavy metal ions in the hydrogel;
3. the sodium alginate/cellulose ether composite hydrogel disclosed by the invention has a porous network structure, is beneficial to rapid diffusion of heavy metal ions in the hydrogel and sufficient contact with adsorption sites (carboxyl), and further greatly improves the adsorption capacity of the composite hydrogel on the heavy metal ions;
4. the sodium alginate/cellulose ether composite hydrogel shows higher adsorption selectivity to copper (II) ions and lead (II) ions;
5. the temperature sensitivity of the sodium alginate/cellulose ether composite hydrogel can be utilized to realize quick and convenient recycling. Compared with the traditional gel for adsorbing heavy metal ions, the recovery mode is more convenient, faster, economic and environment-friendly.
Drawings
FIG. 1 is a schematic diagram of preparing a temperature-sensitive composite hydrogel according to an embodiment of the present invention.
FIG. 2 is a graph showing the temperature-dependent change in swelling ratio of temperature-sensitive composite hydrogel according to the present invention
FIG. 3 is a macroscopic morphology and Scanning Electron Microscope (SEM) image of the temperature-sensitive composite hydrogel prepared by the embodiment of the invention at different temperatures.
Fig. 4 is a diagram showing the effect of adsorption of heavy metal ions (mixed solution of copper (II), lead (II), cadmium (II), zinc (II), and manganese (II)) by the temperature-sensitive composite hydrogel prepared in the embodiment of the present invention.
FIG. 5 is a diagram of the recovery process of preparing temperature-sensitive composite hydrogel according to the embodiment of the present invention.
Detailed Description
The following examples are presented to further illustrate embodiments of the present invention, and it should be understood that the embodiments described herein are for purposes of illustration and explanation only and are not intended to limit the invention.
The temperature sensitivity of the sodium alginate/cellulose ether composite hydrogel is measured, namely the Volume Phase Transition Temperature (VPTT) is measured by the following method: the hydrogel was allowed to swell the gel sample in deionized water at a temperature range (0-60 ℃) for at least 12 hours in a water bath. The hydrogel was then transferred to a dry glass container and weighed to determine the swelling weight at each temperature, with the surface water wiped off with filter paper before each measurement. The swelling ratio was calculated as follows:
SR＝(Wt-Wd)/Wd
wherein Wt (g) is the weight of the gel at a given temperature, and Wd (g) is the weight of the xerogel. The swelling ratio is a curve along with the change of temperature, and the curve takes the temperature corresponding to the condition that the slope of the tangent line is large as the volume phase transition temperature.
Example 1
As shown in fig. 1, the preparation method of the temperature-sensitive sodium alginate/cellulose ether composite hydrogel comprises the following steps:
(1) preparation of 2-hydroxy-3-pentoxypropyl cellulose:
5g of cellulose are placed in a 100ml three-necked flask, 12.5 ml of water are added and dispersed, and the mixture is heated to 70 ℃ with stirring. 0.58g of 40% sodium hydroxide is added dropwise into a three-necked flask and alkalized for 1h at 70 ℃. Then, 5g of pentyloxy glycidyl ether was added dropwise to the alkalinized reaction solution, followed by reaction at 70 ℃ for 9 hours. After the reaction is finished, diluting with 100ml of water, cooling to room temperature, neutralizing with hydrochloric acid until the pH value is 7, then putting into a dialysis bag with the molecular weight of 7000-14000 and putting into deionized water for dialysis, removing most of water by using a rotary evaporator when the deionized water conductivity is less than 10 mu s/cm after the dialysis is finished, and drying by using a freeze dryer to obtain the blocky solid 2-hydroxy-3-pentoxypropyl cellulose.
(2) Crushing the obtained 2-hydroxy-3-pentoxypropyl cellulose by a crusher, placing the crushed 2-hydroxy-3-pentoxypropyl cellulose in a beaker, adding 2g of crushed 2-hydroxy-3-pentoxypropyl cellulose into 26mL of deionized water with the temperature of 50 ℃, and slowly stirring until the cellulose is dissolved (avoiding foaming as much as possible). Then, 1g of sodium alginate powder was dissolved in the above solution under ice bath condition for use.
(3) Preparation of composite gel: 2g of 40 wt% NaOH was slowly dropped into the mixed solution prepared in (2), and then the mixed solution was subjected to ultrasonic treatment in an ice-water bath for 30 minutes. A composite crosslinking agent (a mixture of two crosslinking agents, in which the calcium chloride concentration is 1 wt%) in which 300. mu.L of polyethylene glycol diglycidyl ether and 900. mu.L of a calcium chloride solution were mixed was slowly dropped into the mixed solution and subjected to ultrasonic treatment in an ice-water bath for 30 minutes. Finally, the beaker is kept still in a water bath kettle at 50 ℃ for crosslinking reaction for 2 hours.
(4) And heating the obtained composite gel to 60 ℃ to ensure that the composite gel is dehydrated and contracted until the volume of the gel is not changed, removing residual liquid, injecting deionized water at 20 ℃ to ensure that the gel is swelled until the volume is not changed, purifying the composite gel, and repeatedly treating the gel according to the purification process until the color of the gel is changed from light yellow to milky white and the conductivity of leacheate is less than 10 mu s/cm, thus obtaining the temperature-sensitive sodium alginate/cellulose ether composite gel. The purification process mainly comprises the step of removing unreacted reactants such as the cross-linking agent, sodium hydroxide, sodium alginate and the like.
(5) And (2) freezing the sodium alginate/cellulose ether composite gel in a refrigerator at the temperature of-5 ℃ for 3 hours, and freeze-drying the frozen gel in an ultralow-temperature freeze dryer (wherein the set parameters of the ultralow-temperature freeze dryer are that the temperature is-80 ℃, the pressure is 20pa, and the freeze-drying time is 6 hours) to obtain white dry composite gel, which is marked as SC-1 and has the mass of 1.21 g.
Application example
The SC-1 complex gel obtained above was measured for its Volume Phase Transition Temperature (VPTT):
the composite gel sample obtained above was swollen in deionized water at 5 ℃ for at least 12 hours in a water bath. Then, the hydrogel was transferred to a dry glass container and weighed to determine the swelling weight at 5 ℃, 10 ℃, 15 ℃, 20 ℃, 25 ℃, 30 ℃, 35 ℃, 40 ℃, 45 ℃, and the surface water was wiped off with filter paper before each measurement. The swelling ratio was calculated as follows:
SR＝(Wt-Wd)/Wd
wherein, Wt(g) Is the weight of the hydrogel at different temperatures, Wd(g) Is the weight of the xerogel. As shown in FIG. 2, the swelling ratio is plotted as a function of temperature, and the temperature corresponding to the case where the slope of the tangent line is large is the volume phase transition temperature, i.e., 22.9 ℃.
Observing the SEM effects of the obtained temperature-sensitive composite hydrogel SC-1 at different temperatures (see figure 3):
the preparation method of the composite hydrogel SC-1 sample for SEM experiment is as follows: (1) the gel is soaked in deionized water at 20 ℃ for full swelling, then the gel is taken out for freezing and is put into a vacuum freeze dryer for drying for 6 hours, and the section is taken out to prepare a sample a to be tested (see figure 3A). (2) The gel is soaked in deionized water at 50 ℃ for shrinkage, then the gel is taken out and is frozen and shaped by liquid nitrogen rapidly, the gel is placed into a vacuum freeze dryer for drying for 6 hours, and the section is taken out to prepare a sample B to be tested (see figure 3B).
When the temperature is 20 ℃ in SEM pictures (see figure 3) of the obtained temperature-sensitive composite hydrogel SC-1 at different temperatures, the composite hydrogel SC-1 shows a porous network structure; when the temperature is 50 ℃, the porous network structure of the composite hydrogel SC-1 is shrunk, and the surface of the gel is smooth.
The prepared temperature-sensitive hydrogel SC-1 was subjected to heavy metal ion adsorption assay (see FIG. 4):
placing the obtained composite gel SC-1 sample in a 100mL conical flask, adding 50mL of mixed solution of copper (II), lead (II), cadmium (II), zinc (II) and manganese (II) ions with initial concentrations of 100mg/L into the conical flask, oscillating for 3 hours at a constant temperature of 20 ℃, and detecting the concentrations of various heavy metal ions by using an atomic absorption spectrometer in a staged manner until the concentrations of various metal ions are not changed any more; and (3) measuring the concentration of heavy metal ions in the solution before and after adsorption by using an atomic absorption spectrometer. The adsorption capacity formula is as follows:
Figure BDA0002240708870000051
wherein q iseThe total adsorption capacity (mg/g) of the composite gel to the heavy metal ions is obtained; v is the volume (L) of the added heavy metal solution; coThe initial concentration (mg/L) of heavy metal ions; ceThe concentration (mg/L) of the heavy metal ion solution after the adsorption experiment is adopted; m is the mass (g) of the xerogel.
The total adsorption capacity of the sodium alginate/cellulose ether composite gel SC-1 prepared by the calculation on the heavy metal ions in the mixed solution is 273.8 mg/g. The competitive adsorption result of heavy metal ions is shown in fig. 4, and as can be seen from fig. 4, the competitive adsorption experiment result shows that, in the heavy metal ion mixed solution, the competitive adsorption order of the composite gel to various heavy metal ions is as follows: cu (II) Pb (II) Cd (II) Zn (II) Mn (II).
And (3) recycling the composite gel SC-1 after adsorption treatment:
taking out the SC-1 hydrogel adsorbed with heavy metal ions from the solution and placing the SC-1 hydrogel into the solution
And (3) putting the beaker into a water bath at 30 ℃ for heating for 20 minutes in a 10mL empty beaker, reducing the volume of the SC-1 gel due to dehydration shrinkage, taking out the shrunk SC-1 gel, putting the shrunk SC-1 gel into a 2mL hydrochloric acid solution at 0.5mol/L, and eluting heavy metal ions in the gel by ultrasonic oscillation for 10 minutes. The SC-1 gel was taken out, and was then placed in 2mL of 0.5mol/L sodium hydroxide solution for regeneration for 5 minutes. Taking out the SC-1 gel again, freeze-drying for 6 hours by using a vacuum freeze dryer, weighing, and recovering and regenerating the SC-1 gel, wherein the mass of the SC-1 gel is 0.255 g; calculating the recovery efficiency: the initial gel mass (dry)/the recovered gel mass (dry) x 100%, the recovery efficiency was 85.0%.
Example 2
This example is substantially the same as example 1, except that in (3), the crosslinking agent is 200 μ L of epichlorohydrin and 900 μ L of calcium chloride solution, and the specific reaction conditions are shown in table 1;
testing the composite gel obtained in the embodiment according to the application example, wherein the adsorption capacity of the sodium alginate/cellulose ether composite gel SC-2 to the heavy metal ions is 251.2 mg/g; the mass of the recovered and regenerated SC-2 gel was 0.267g, and the recovery efficiency was 89.0%.
TABLE 1
Figure BDA0002240708870000061
Example 3
This example is essentially the same as example 1 except that in (3), the amount of NaOH used is 0.3g (40%), the crosslinking agent is 50. mu.L of vinylsulfone and 60. mu.L of calcium chloride solution, the reaction temperature is 20 ℃ and the reaction time is 0.5h, and the specific reaction conditions are shown in Table 2;
testing the composite gel obtained in the embodiment according to the application example, wherein the adsorption capacity of the sodium alginate/cellulose ether composite gel SC-3 to the heavy metal ions is 138.9 mg/g; the mass of the recovered and regenerated SC-3 gel was 0.289g, and the recovery efficiency was 96.3%.
TABLE 2
Figure BDA0002240708870000062
Example 4
This example is substantially the same as example 1, except that in (3), the crosslinking agent is 80. mu.L of glutaraldehyde and 60. mu.L of calcium chloride solution, the reaction time is 1h, and the specific reaction conditions are shown in Table 3;
testing the composite gel obtained in the embodiment according to the application example, wherein the adsorption capacity of the sodium alginate/cellulose ether composite gel SC-4 to the heavy metal ions is 208.8 mg/g; the mass of the recovered and regenerated SC-4 gel was 0.271g, and the recovery efficiency was 90.3%.
TABLE 3
Figure BDA0002240708870000071
Example 5
This example is essentially the same as the experimental procedure of example 1, except that in (1), the preparation conditions of 2-hydroxy-3-propoxypropyl cellulose are shown in Table 4; (2) in the formula (I), the mass ratio of (A) to (B) is 3:1 preparing 8.5 percent of mixed solution of 2-hydroxy-3-propoxypropyl cellulose and sodium alginate; (3) in the method, the components of the mixed solution are 2-hydroxy-3-propoxypropyl cellulose and sodium alginate, and the specific reaction conditions are shown in Table 5;
testing the composite gel obtained in the embodiment according to the application example, wherein the adsorption capacity of the sodium alginate/cellulose ether composite gel SC-5 to the heavy metal ions is 145.6 mg/g; the mass of the recovered and regenerated SC-5 gel was 0.252g, and the recovery efficiency was 84.0%.
TABLE 4
TABLE 5
Figure BDA0002240708870000073
Example 6
This example is essentially the same as the experimental procedure of example 1, except that in (1), the preparation conditions of 2-hydroxy-3-propoxypropyl cellulose are shown in Table 4; (2) in the formula (I), the mass ratio of (A) to (B) is 3:1 preparing 8.5 percent of mixed solution of 2-hydroxy-3-propoxypropyl cellulose and sodium alginate; (3) in the method, the components of the mixed solution are 2-hydroxy-3-propoxypropyl cellulose and sodium alginate, the cross-linking agent is 200 mu L of epichlorohydrin and 900 mu L of calcium chloride solution, and the specific reaction conditions are shown in Table 6;
testing the composite gel obtained in the embodiment according to the application example, wherein the adsorption capacity of the sodium alginate/cellulose ether composite gel SC-6 to the heavy metal ions is 145.6 mg/g; the mass of the recovered and regenerated SC-6 gel was 0.268g, and the recovery efficiency was 89.3%.
TABLE 6
Figure BDA0002240708870000081
Example 7
This example is essentially the same as the experimental procedure of example 1, except that in (1), the preparation conditions of 2-hydroxy-3-propoxypropyl cellulose are shown in Table 4; (2) in the formula (I), the mass ratio of (A) to (B) is 3:1 preparing 8.5 percent of mixed solution of 2-hydroxy-3-propoxypropyl cellulose and sodium alginate; (3) in the method, the using amount of NaOH is 0.3g (40%), the components of the mixed solution are 2-hydroxy-3-propoxypropyl cellulose and sodium alginate, 50 mu L of vinyl sulfone as a cross-linking agent and 60 mu L of calcium chloride solution, the reaction temperature is 20 ℃, the reaction time is 0.5h, and the specific reaction conditions are shown in Table 7;
testing the composite gel obtained in the embodiment according to the application example, wherein the adsorption capacity of the sodium alginate/cellulose ether composite gel SC-7 to heavy metal ions is 129.9 mg/g; the mass of the recovered and regenerated SC-7 gel was 0.285g, and the recovery efficiency was 95.0%.
TABLE 7
Figure BDA0002240708870000082
Example 8
This example is essentially the same as the experimental procedure of example 1, except that in (1), the preparation conditions of 2-hydroxy-3-propoxypropyl cellulose are shown in Table 4; (2) in the formula (I), the mass ratio of (A) to (B) is 3:1 preparing 8.5 percent of mixed solution of 2-hydroxy-3-propoxypropyl cellulose and sodium alginate; (3) in the method, the components of the mixed solution are 2-hydroxy-3-propoxypropyl cellulose and sodium alginate, the cross-linking agent is 80 mu L of glutaraldehyde and 60 mu L of calcium chloride solution, the reaction temperature is 35 ℃, and the specific reaction conditions are shown in Table 8;
testing the composite gel obtained in the embodiment according to the application example, wherein the adsorption capacity of the sodium alginate/cellulose ether composite gel SC-8 to the heavy metal ions is 178.6 mg/g; the mass of the recovered and regenerated SC-8 gel was 0.269g, and the recovery efficiency was 89.7%.
TABLE 8
Figure BDA0002240708870000083
Example 9
This example is substantially the same as the experimental method of example 1, except that in (1), the preparation conditions of 2-hydroxy-3-isobutoxypropyl cellulose are shown in Table 9; (2) in the formula (I), the mass ratio of (1): 1 preparing a mixed solution of 7.0 percent of 2-hydroxy-3-isobutoxypropyl cellulose and sodium alginate; (3) in the method, the components of the mixed solution are 2-hydroxy-3-isobutoxypropyl cellulose and sodium alginate, and the specific reaction conditions are shown in Table 10;
testing the composite gel obtained in the embodiment according to the application example, wherein the adsorption capacity of the sodium alginate/cellulose ether composite gel SC-9 to the heavy metal ions is 187.6 mg/g; the mass of the recovered and regenerated SC-9 gel was 0.291g, and the recovery efficiency was 97.0%.
TABLE 9
Figure BDA0002240708870000091
Watch 10
Figure BDA0002240708870000092
Example 10
This example is substantially the same as the experimental method of example 1, except that in (1), the preparation conditions of 2-hydroxy-3-isobutoxypropyl cellulose are shown in Table 9; (2) in the formula (I), the mass ratio of (1): 1 preparing a mixed solution of 7.0 percent of 2-hydroxy-3-isobutoxypropyl cellulose and sodium alginate; (3) in the method, the components of the mixed solution are 2-hydroxy-3-isobutoxypropyl cellulose and sodium alginate, the cross-linking agent is 200 mu L of epichlorohydrin/900 mu L of calcium chloride solution, and the specific reaction conditions are shown in Table 11;
testing the composite gel obtained in the embodiment according to the application example, wherein the adsorption capacity of the sodium alginate/cellulose ether composite gel SC-10 to heavy metal ions is 157.9 mg/g; the mass of the recovered and regenerated SC-10 gel was 0.268g, and the recovery efficiency was 89.3%.
TABLE 11
Figure BDA0002240708870000093
Example 11
This example is substantially the same as the experimental method of example 1, except that in (1), the preparation conditions of 2-hydroxy-3-isobutoxypropyl cellulose are shown in Table 9; (2) in the formula (I), the mass ratio of (1): 1 preparing a mixed solution of 7.0 percent of 2-hydroxy-3-isobutoxypropyl cellulose and sodium alginate; (3) in the method, the components of the mixed solution are 2-hydroxy-3-isobutoxypropyl cellulose and sodium alginate, the dosage of NaOH is 0.2g, the cross-linking agent is 50 mu L of vinyl sulfone/60 mu L of calcium chloride, the reaction temperature is 10 ℃, the reaction time is 0.2h, and the specific reaction conditions are shown in Table 12;
testing the composite gel obtained in the embodiment according to the application example, wherein the adsorption capacity of the sodium alginate/cellulose ether composite gel SC-11 to the heavy metal ions is 97.9 mg/g; the mass of the recovered and regenerated SC-11 gel was 0.219g, and the recovery efficiency was 73.0%.
TABLE 12
Figure BDA0002240708870000101
Example 12
This example is substantially the same as the experimental method of example 1, except that in (1), the preparation conditions of 2-hydroxy-3-isobutoxypropyl cellulose are shown in Table 9; (2) in the formula (I), the mass ratio of (1): 1 preparing a mixed solution of 7.0 percent of 2-hydroxy-3-isobutoxypropyl cellulose and sodium alginate; (3) wherein the components of the mixed solution are 2-hydroxy-3-isobutoxypropyl cellulose and sodium alginate, the cross-linking agent is 80 mu L of glutaraldehyde/60 mu L of calcium chloride solution, the reaction temperature is 35 ℃, the reaction time is 1.5h, and the specific reaction conditions are shown in Table 13;
testing the composite gel obtained in the embodiment according to the application example, wherein the adsorption capacity of the sodium alginate/cellulose ether composite gel SC-12 to heavy metal ions is 87.1 mg/g; the mass of the recovered and regenerated SC-12 gel was 0.248g, and the recovery efficiency was 82.7%.
Watch 13
Figure BDA0002240708870000102

Claims (10)

1. A preparation method of temperature-sensitive sodium alginate/cellulose ether composite hydrogel is characterized by comprising the following steps: reacting cellulose with an etherifying agent to obtain temperature-sensitive alkyl cellulose ether; adding sodium alginate into temperature-sensitive alkyl cellulose ether to obtain a mixed solution; and crosslinking the mixed solution with a crosslinking agent to obtain the temperature-sensitive composite hydrogel.
2. The method for preparing the temperature-sensitive sodium alginate/cellulose ether composite hydrogel according to claim 1, which is characterized in that:
(1) preparing temperature-sensitive alkyl cellulose ether: alkalizing cellulose pulp by alkali at 60-70 ℃ for 1-1.5 hours, adding an etherifying agent into reaction liquid after alkalization, stirring and reacting at 70-90 ℃ for 6-9 hours, cooling to room temperature after reaction, adjusting the system to be neutral, and dialyzing by a dialysis bag after adjustment until the electric conductivity of the reaction liquid is less than 10 mus/cm to obtain temperature-sensitive alkyl cellulose ether;
(2) mixing the solution: dissolving the obtained temperature-sensitive alkyl cellulose ether in water, adding sodium alginate, and reacting for 0.5-2h in ice bath to obtain a mixed solution;
(3) preparing temperature-sensitive hydrogel through crosslinking: and (2) carrying out ultrasonic treatment on the obtained mixed solution in an ice-water bath in alkali for 15-30 minutes, adding a composite cross-linking agent containing calcium ions after ultrasonic treatment, continuing to carry out ultrasonic treatment in the ice-water bath for 30-50 minutes after adding, carrying out ultrasonic dispersion, and carrying out cross-linking reaction at 20-60 ℃ for 0.5-2 hours to obtain the temperature-sensitive composite hydrogel.
3. The method for preparing the temperature-sensitive sodium alginate/cellulose ether composite hydrogel according to claim 2, which is characterized in that: the step 1) adding sodium hydroxide with the cellulose mass of 2-25% into cellulose pulp with the mass concentration of 10-60%, uniformly stirring, and alkalizing for 1-1.5 hours at the temperature of 60-70 ℃; and then, according to the mass ratio of the etherifying agent to the cellulose of 0.2-2.5: 1, dripping an etherifying agent, and stirring and reacting at 70-90 ℃ for 6-9 hours; then diluting the reaction solution by water, cooling to room temperature, adjusting the pH of the reaction solution to 7 by acid, dialyzing the adjusted reaction solution in a dialysis bag with the molecular weight of 7000 14000 until the conductivity of the reaction solution is less than 10 mu s/cm, and concentrating and drying after dialysis to obtain powder or blocky solid alkyl cellulose ether; wherein, the etherifying agent is alkyl glycidyl ether.
4. The method for preparing the temperature-sensitive sodium alginate/cellulose ether composite hydrogel according to any one of claims 1 to 3, wherein: the alkyl glycidyl ether is propyl glycidyl ether, isobutyl glycidyl ether or amyl glycidyl ether.
5. The method for preparing the temperature-sensitive sodium alginate/cellulose ether composite hydrogel according to claim 2, which is characterized in that: the step 2) is to crush the obtained temperature-sensitive alkyl cellulose ether, and the crushed alkyl cellulose ether is dissolved in deionized water at 50 ℃ to obtain a solution, wherein the concentration of the alkyl cellulose ether solution in the solution is 6-11 wt%; adding sodium alginate into the solution, and reacting for 0.5-2 hr in ice bath to obtain mixed solution; wherein the mass ratio of the sodium alginate to the temperature-sensitive alkyl cellulose ether is 1-3: 1.
6. The method for preparing the temperature-sensitive sodium alginate/cellulose ether composite hydrogel according to claim 2, which is characterized in that: adding NaOH into the mixed solution of sodium alginate and cellulose ether under the stirring condition in the step 3), and then carrying out ultrasonic treatment on the mixture in an ice-water bath for 15-30 minutes; adding a composite cross-linking agent containing calcium ions into the mixed solution after ultrasonic treatment, performing ultrasonic treatment in an ice-water bath for 30-50 minutes, performing cross-linking reaction at 20-60 ℃ for 0.5-2h h after ultrasonic dispersion, alternately washing the hydrogel by using cold and hot deionized water after the cross-linking reaction until the color of the hydrogel is changed from light yellow to milky white and the conductivity of leacheate is less than 10 mu s/cm, and then drying to obtain the temperature-sensitive composite hydrogel; wherein the mass ratio of NaOH to the sodium alginate/cellulose ether mixture is 0.08-0.8: 3, the volume ratio of the composite cross-linking agent to the sodium alginate/cellulose ether mixture solution is 0.11-1.20: 26.
7. the method for preparing the temperature-sensitive sodium alginate/cellulose ether composite hydrogel according to claim 2 or 6, which is characterized in that: the composite cross-linking agent containing calcium ions is a mixture of inorganic salt containing calcium ions and polyethylene glycol diglycidyl ether, epichlorohydrin, vinyl sulfone or glutaraldehyde; wherein the volume ratio of the inorganic salt containing calcium ions to the other 4 crosslinking agents is 9: 2-12.
8. The temperature-sensitive sodium alginate/cellulose ether composite hydrogel prepared by the method of claim 1, which is characterized in that: the temperature-sensitive sodium alginate/cellulose ether composite hydrogel obtained by the method of claim 1, wherein the volume phase transition temperature can be adjusted within the range of 15.5-75.8 ℃.
9. The use of the temperature-sensitive sodium alginate/cellulose ether composite hydrogel according to claim 1, wherein: the temperature-sensitive sodium alginate/cellulose ether composite hydrogel is applied to adsorption of heavy metals.
10. The use of the temperature-sensitive sodium alginate/cellulose ether composite hydrogel according to claim 9, wherein: the composite gel can be further applied after being recycled and regenerated after heavy metal ions are adsorbed.
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