CN110862483A - Preparation of fiber-based hydrogel and method for testing performance of fiber-based hydrogel - Google Patents

Abstract

The invention provides a method for preparing fiber-based hydrogel and testing the performance of the fiber-based hydrogel in the chemical field, which comprises the following steps of (1) preparing a material; (2) adding 2.5 g of cellulose powder into 50 mL of 85% concentrated phosphoric acid, and mechanically stirring at 0 ℃; (3) blowing with nitrogen for 30min, and completely discharging air; (4) adding 100 mg APS and 50 mg MBA to the cellulose solution, and stirring the mixture at 0 deg.C; (5) dropwise adding monomer AA by using a dropping funnel, stirring for 2 h, transferring the reaction mixture into a glass tube, and carrying out polymerization reaction for 24 h at the temperature of 0 ℃; (6) obtaining strip-shaped hydrogel, cutting the hydrogel into wafers with the thickness of 2-3 mm, and washing away residual raw materials and byproducts by using deionized water; (7) carrying out performance test on the dried hydrogel; (8) and carrying out a hydrogel heavy metal ion adsorption test.

Description

Preparation of fiber-based hydrogel and method for testing performance of fiber-based hydrogel

Technical Field

The invention belongs to the field of chemistry, and particularly relates to a method for preparing fiber-based hydrogel and testing the performance of the fiber-based hydrogel.

Background

Oxidized cellulose is a renewable, biodegradable, green resource with abundant reserves. Various derivatives of cellulose have been widely used in the fields of paper making, food, medical and health, cosmetics, petroleum industry, and the like. The hydrogel as a biomaterial with a cross-linked three-dimensional network structure only swells but does not dissolve in a solvent, can be applied to a plurality of fields such as drug release carriers, wound dressing, agriculture and forestry breeding and the like, and the preparation of the functional hydrogel by using a natural high polymer material has important environmental protection significance and economic significance.

lithium/N, N '-dimethylacetamide (LiCl/DMAC) is a green solvent which is recognized to be very effective, less in fiber degradation and environment-friendly at present, and the main defects of the lithium/N, N' -dimethylacetamide are that the reaction temperature is high (110 ℃) and the reaction time is long (4-5 hours).

Disclosure of Invention

Aiming at overcoming the defects in the prior art, the invention provides a method for preparing fiber-based hydrogel and testing the performance of the fiber-based hydrogel, which has the advantages of short reaction time and high efficiency.

The purpose of the invention is realized as follows: the preparation method of the fiber-based hydrogel and the performance test method thereof comprise the following steps:

(1) preparing experimental materials;

(2) 2.5 g of cellulose powder was added to 50 mL of 85% concentrated phosphoric acid and mechanically stirred at 0 ℃ until the mixture became a homogeneous, translucent gum;

(3) blowing with nitrogen for 30min, and completely discharging air;

(4) adding 100 mg of APS (as initiator) and 50 mg of MBA (as cross-linking agent) to the cellulose solution, and stirring the mixture sufficiently at 0 ℃ until uniform;

(5) slowly dripping different amounts of monomer AA (dripping off within about 30 min) by using a constant-pressure dropping funnel, continuously stirring for 2 h, transferring the reaction mixture into a glass tube (serving as a micro-reactor) with the diameter of 6 mm, and continuously carrying out polymerization reaction for 24 h at the temperature of 0 ℃;

(6) obtaining cylindrical strip-shaped hydrogel, cutting fresh hydrogel into wafers with the thickness of 2-3 mm, washing away residual raw materials and byproducts by using a large amount of deionized water, and drying in a drying oven at 50 ℃ to constant weight for later use;

(7) performing performance test on the dried hydrogel, and analyzing the results obtained by the test, including SEM analysis, FTIR analysis, conductivity titration determination of carboxyl content, determination of C-g-AA gel swelling behavior in different solvent media and adsorption determination of C-g-AA gel cationic dye;

(8) and carrying out a hydrogel heavy metal ion adsorption test.

As a further improvement of the present invention, the SEM analysis specifically includes:

(1) freeze-drying the C-g-AA hydrogel wafer which is swelled and balanced in advance at-45 ℃ for two days until all water is sublimated;

(2) rapidly freezing the gel wafer in liquid nitrogen, cracking the gel wafer into fragments, and spraying gold on the cracked surfaces;

(3) surface morphology images of fractured samples were recorded by a scanning electron microscope (Quanta 200, FEI Company) with a working voltage of 3 kV and a resolution of 10 nm, and five different positions were selected for each sample for scanning and pictures with repetitive features were selected for analysis.

As a further improvement of the present invention, said FTIR analysis is specifically:

(1) grinding the fully dried C-g-AA hydrogel into powder, and fully mixing the powder with spectrum-grade potassium bromide (KBr) powder in an agate mortar;

(2) pressing the powder mixture into a transparent sheet in a tablet press;

(3) an FTIR spectrogram of the gel is recorded and measured by a Bruker Vector 33 infrared spectrometer, and the measuring wavelength range is 4000-500 cm^-1；

(4) Pure cellulose was tabletted with KBr as a control for the experiment.

As a further improvement of the invention, the conductivity titration determination of the carboxyl content is specifically as follows:

(1) fully dispersing gel powder in 0.01 mol/L hydrochloric acid solution, and reacting with H in the solution⁺

Ion exchange of cation, fully exchange for 6H, and then use deionized water to remove residual H⁺Washing the ions until the solution is neutral;

(2) ensuring complete equilibrium between the aqueous phase and the gel phase by slow acid-base titration and obtaining quantitative data;

(3) the cellulose powder is processed in the same way to obtain a blank titration curve;

(4) each sample was titrated three times and the arithmetic mean was taken.

As a further improvement of the invention, the determination of the gel swelling behavior of C-g-AA in different solvent media is specifically as follows:

(1) placing the fully dried C-g-AA hydrogel wafer in different solutions including deionized water, pH buffer solution (pH: 2.0-11.0, ionic strength: I =0.2M), and salt solution (NaCl or CaCl)₂0.01-2.5 mol/L) of the raw material;

(2) taking out the gel in swelling at regular intervals, sucking off the water on the surface by using filter paper and weighing, then immersing the hydrogel into the original solution again for swelling, and taking out again after a preset time interval for operating as above and weighing.

As a further improvement of the invention, the adsorption determination of the C-g-AA gel cationic dye specifically comprises the following steps:

(1) placing the accurately weighed xerogel in deionized water for 24 hours until the gel is in swelling balance, then soaking the gel in swelling balance in MB solution, and placing the gel in a rotary shaking table (30 ℃, 85 rpm) to fully contact for 36 hours;

(2) MB absorbance at 664 nm was measured by an ultraviolet-visible spectrophotometer (Hitachi Z-5000, Japan) as adsorption quantitative data.

As a further development of the invention, the adsorption test comprises the following steps:

(701) various amounts of 0.01 mol/L HNO were added₃Or adjusting Ni by 0.01 mol/L NaOH dilute solution²⁺、Cd²⁺And Pb²⁺The pH value range of the solution (100 mL, 600 mg/L) is 2.0-6.0;

(702) putting 50 mg of xerogel samples into a series of prepared ionic solutions, and oscillating for 6 hours at constant temperature;

(703) adsorption isotherm experiments were performed in ionic solutions of pH 5.0, Ni²⁺、Cd²⁺、Pb²⁺The concentration of the solution is changed within the range of 200-2000 mg/L;

(704) 50 mg of xerogel sample are placed in a series of prepared ionic solutions and shaken for 6h at constant temperature.

As a further improvement of the invention, the method also comprises an adsorption kinetics test, and specifically comprises the following steps:

(a1) the pH of the solution was 5.0 and 500 mg of xerogel sample was added to 1L of Ni at a concentration of 1000 mg/L²⁺、Cd²⁺And Pb²⁺In solution;

(a2) sampling and analyzing the current residual ion concentration by using an injector at a preset time interval (5-500 min);

（a3）Ni²⁺、Cd²⁺and Pb²⁺The initial and final concentrations of the solution were measured by atomic absorption spectroscopy (AAS, ZEEnit700, Germany), and all tests were performed in parallel twice, taking the arithmetic mean.

Drawings

FIG. 1 is a diagram showing a mechanism of hydrogel synthesis.

FIG. 2 is an FTIR spectrum of raw cotton linters and C-g-AA hydrogel.

FIG. 3 is a graph showing the effect of solution pH on the amount of heavy metal ion adsorbed by a C-g-AA hydrogel.

FIG. 4 is a graph showing the effect of initial ion concentration on the amount of heavy metal ions adsorbed by a C-g-AA hydrogel.

Detailed Description

The preparation method of the fiber-based hydrogel and the performance test method thereof comprise the following steps:

(1) preparing experimental materials shown in table 1;

(2) 2.5 g of cellulose powder was added to 50 mL of 85% concentrated phosphoric acid and mechanically stirred at 0 ℃ until the mixture became a homogeneous, translucent gum;

(3) blowing with nitrogen for 30min, and completely discharging air;

(4) adding 100 mg of APS (as initiator) and 50 mg of MBA (as cross-linking agent) to the cellulose solution, and stirring the mixture sufficiently at 0 ℃ until uniform;

(5) slowly dripping different amounts of monomer AA (dripping off within about 30 min) by using a constant-pressure dropping funnel, continuously stirring for 2 h, transferring the reaction mixture into a glass tube (serving as a micro-reactor) with the diameter of 6 mm, and continuously carrying out polymerization reaction for 24 h at the temperature of 0 ℃;

(6) obtaining cylindrical strip-shaped hydrogel, cutting fresh hydrogel into wafers with the thickness of 2-3 mm, washing away residual raw materials and byproducts by using a large amount of deionized water, and drying in a drying oven at 50 ℃ to constant weight for later use;

(7) performing performance test on the dried hydrogel, and analyzing the results obtained by the test, including SEM analysis, FTIR analysis, conductivity titration determination of carboxyl content, determination of C-g-AA gel swelling behavior in different solvent media and adsorption determination of C-g-AA gel cationic dye;

(8) and carrying out a hydrogel heavy metal ion adsorption test.

The SEM analysis specifically comprises:

(1) freeze-drying the C-g-AA hydrogel wafer which is swelled and balanced in advance at-45 ℃ for two days until all water is sublimated;

(2) rapidly freezing the gel wafer in liquid nitrogen, cracking the gel wafer into fragments, and spraying gold on the cracked surfaces;

(3) surface morphology images of fractured samples were recorded by a scanning electron microscope (Quanta 200, FEI Company) with a working voltage of 3 kV and a resolution of 10 nm, and five different positions were selected for each sample for scanning and pictures with repetitive features were selected for analysis.

FTIR analysis specifically was:

(1) grinding the fully dried C-g-AA hydrogel into powder, and fully mixing the powder with spectrum-grade potassium bromide (KBr) powder in an agate mortar;

(2) pressing the powder mixture into a transparent sheet in a tablet press;

(3) an FTIR spectrogram of the gel is recorded and measured by a Bruker Vector 33 infrared spectrometer, and the measuring wavelength range is 4000-500 cm^-1；

(4) Pure cellulose was tabletted with KBr as a control for the experiment.

The conductivity titration determination of carboxyl content specifically comprises:

(1) fully dispersing gel powder in 0.01 mol/L hydrochloric acid solution, and reacting with H in the solution⁺

Ion exchange of cation, fully exchange for 6H, and then use deionized water to remove residual H⁺Washing the ions until the solution is neutral;

(2) ensuring complete equilibrium between the aqueous phase and the gel phase by slow acid-base titration and obtaining quantitative data;

(3) the cellulose powder is processed in the same way to obtain a blank titration curve;

(4) each sample was titrated three times and the arithmetic mean was taken.

The determination of the gel swelling behavior of C-g-AA in different solvent media specifically comprises the following steps:

(1) placing the fully dried C-g-AA hydrogel wafer in different solutions including deionized water, pH buffer solution (pH: 2.0-11.0, ionic strength: I =0.2M), and salt solution (NaCl or CaCl)₂0.01-2.5 mol/L) of the raw material;

(2) taking out the gel in swelling at regular intervals, sucking off the water on the surface by using filter paper and weighing, then immersing the hydrogel into the original solution again for swelling, and taking out again after a preset time interval for operating as above and weighing.

The specific measurement of the adsorption of the C-g-AA gel cationic dye is as follows:

(1) placing the accurately weighed xerogel in deionized water for 24 hours until the gel is in swelling balance, then soaking the gel in swelling balance in MB solution, and placing the gel in a rotary shaking table (30 ℃, 85 rpm) to fully contact for 36 hours;

(2) MB absorbance at 664 nm was measured by an ultraviolet-visible spectrophotometer (Hitachi Z-5000, Japan) as adsorption quantitative data.

TABLE 1 amounts of raw materials for preparing gels

。

The C-g-AA hydrogel samples, CA10, CA15 and CA20, are successfully prepared by experiments, the cellulose/AA molar ratios are respectively 1:2, 1:4 and 1:6, the appearance of the hydrogel is semitransparent, the surface of the hydrogel is smooth, soft and elastic, and SEM analysis is carried out on a gel fracture surface, the result shows that the hydrogel has a highly porous network structure, and the structure is favorable for diffusion of water molecules and subsequent adsorption of dye ions and metal ions; further experiments have shown that when the AA content of the hydrogel is too high, for example a cellulose/AA molar ratio of 1:8, the gel formed is so weak that it is difficult to shape.

In FIG. 2, two samples are shown at 3355 cm⁻¹And 3448 cm⁻¹Has obvious absorption peak, which is the characteristic peak of-OH groups participating in hydrogen bonding in the cellulose. Both also showed a characteristic peak at 2900 cm-1, which is the result of the asymmetric stretching of-CH 2-in the cellulose-CH 2OH group; the C-g-AA hydrogel is 1710-1569 cm⁻¹A broad peak in the range due to the stretching vibration of C = O in the-COOH group on the grafted acrylic branch; and 1411cm^-1The sharp characteristic peak is attributed to the symmetric stretching vibration of the-COO-group; 710-1569 cm^-1And 1411cm^-1The presence of carboxyl groups in the hydrogel structure after polymerization is evidenced by the absorption peaks at (a). In addition, the length of the cotton linter is 1060 cm^-1Compared with the absorption peak of C-g-AA hydrogel, the absorption peak of the C-g-AA hydrogel is 1069 cm^-1The intensity of the absorption peak, here the C-O stretching vibration peak in the-CH 2OH group, is significantly reduced, indicating that the graft polymerization reaction occurs mainly at the primary hydroxyl sites of the cellulose, where the reaction reduces the number of hydroxyl groups.

However, the presence of carboxyl groups may also be due to the incorporation of AA monomers or the presence of acrylic acid homopolymers, rather than being grafted onto the cellulose hydrogel. To demonstrate this, the hydrogel was soaked thoroughly in 0.01 mol/L NaOH solution for 48 h, then freeze dried and ground to a powder for FTIR observation. The results show that the hydrogels showed identical FTIR spectra regardless of whether they were washed with dilute alkali solution or not. This further demonstrates that the successful grafting of AA monomer onto the cellulose backbone, the reaction synthesizes a completely new polymer.

The adsorption test comprises the following steps:

(701) various amounts of 0.01 mol/L HNO were added₃Or adjusting Ni by 0.01 mol/L NaOH dilute solution²⁺、Cd²⁺And Pb²⁺The pH value range of the solution (100 mL, 600 mg/L) is 2.0-6.0;

(702) putting 50 mg of xerogel samples into a series of prepared ionic solutions, and oscillating for 6 hours at constant temperature;

(703) adsorption isotherm experiments were performed in ionic solutions of pH 5.0, Ni²⁺、Cd²⁺、Pb²⁺The concentration of the solution is changed within the range of 200-2000 mg/L;

(704) 50 mg of xerogel sample are placed in a series of prepared ionic solutions and shaken for 6h at constant temperature.

The method also comprises an adsorption kinetics test, and specifically comprises the following steps:

(a1) the pH of the solution was 5.0 and 500 mg of xerogel sample was added to 1L of Ni at a concentration of 1000 mg/L²⁺、Cd²⁺And Pb²⁺In solution;

(a2) sampling and analyzing the current residual ion concentration by using an injector at a preset time interval (5-500 min);

（a3）Ni²⁺、Cd²⁺and Pb²⁺The initial and final concentrations of the solution were measured by atomic absorption spectroscopy (AAS, ZEEnit700, Germany), and all tests were performed in parallel twice, taking the arithmetic mean.

Wherein the adsorption kinetics test is performed after the adsorption test.

Three kinds of Ni²⁺、Cd²⁺And Pb²⁺The concentration of the ions was 5 mmol/L or 10 mmol/L, respectively.

The present invention is not limited to the above embodiments, and based on the technical solutions disclosed in the present invention, those skilled in the art can make some substitutions and modifications to some technical features without creative efforts based on the disclosed technical solutions, and these substitutions and modifications are all within the protection scope of the present invention.

Claims (8)

1. The preparation method of the fiber-based hydrogel and the performance test method thereof are characterized by comprising the following steps:

(1) preparing experimental materials;

(2) 2.5 g of cellulose powder was added to 50 mL of 85% concentrated phosphoric acid and mechanically stirred at 0 ℃ until the mixture became a homogeneous, translucent gum;

(3) blowing with nitrogen for 30min, and completely discharging air;

(4) adding 100 mg of APS (as initiator) and 50 mg of MBA (as cross-linking agent) to the cellulose solution, and stirring the mixture sufficiently at 0 ℃ until uniform;

(5) slowly dripping different amounts of monomer AA (dripping off within about 30 min) by using a constant-pressure dropping funnel, continuously stirring for 2 h, transferring the reaction mixture into a glass tube (serving as a micro-reactor) with the diameter of 6 mm, and continuously carrying out polymerization reaction for 24 h at the temperature of 0 ℃;

(6) obtaining cylindrical strip-shaped hydrogel, cutting fresh hydrogel into wafers with the thickness of 2-3 mm, washing away residual raw materials and byproducts by using a large amount of deionized water, and drying in a drying oven at 50 ℃ to constant weight for later use;

(7) performing performance test on the dried hydrogel, and analyzing the results obtained by the test, including SEM analysis, FTIR analysis, conductivity titration determination of carboxyl content, determination of C-g-AA gel swelling behavior in different solvent media and adsorption determination of C-g-AA gel cationic dye;

(8) and carrying out a hydrogel heavy metal ion adsorption test.

2. The method for preparing hydrogel and testing the performance thereof according to claim 1, wherein the SEM analysis specifically comprises:

(1) freeze-drying the C-g-AA hydrogel wafer which is swelled and balanced in advance at-45 ℃ for two days until all water is sublimated;

(2) rapidly freezing the gel wafer in liquid nitrogen, cracking the gel wafer into fragments, and spraying gold on the cracked surfaces;

(3) surface morphology images of fractured samples were recorded by a scanning electron microscope (Quanta 200, FEI Company) with a working voltage of 3 kV and a resolution of 10 nm, and five different positions were selected for each sample for scanning and pictures with repetitive features were selected for analysis.

3. Method for hydrogel preparation and its performance testing according to claim 1 or 2, characterized in that said FTIR analysis is in particular:

(1) grinding the fully dried C-g-AA hydrogel into powder, and fully mixing the powder with spectrum-grade potassium bromide (KBr) powder in an agate mortar;

(2) pressing the powder mixture into a transparent sheet in a tablet press;

(3) an FTIR spectrogram of the gel is recorded and measured by a Bruker Vector 33 infrared spectrometer, and the measuring wavelength range is 4000-500 cm^-1；

(4) Pure cellulose was tabletted with KBr as a control for the experiment.

4. The method for preparing hydrogel and testing the performance of the hydrogel according to claim 2 or 3, wherein the conductivity titration determination of the carboxyl content is specifically as follows:

(1) fully dispersing gel powder in 0.01 mol/L hydrochloric acid solution, and reacting with H in the solution⁺

Ion exchange of cation, fully exchange for 6H, and then use deionized water to remove residual H⁺Washing the ions until the solution is neutral;

(2) ensuring complete equilibrium between the aqueous phase and the gel phase by slow acid-base titration and obtaining quantitative data;

(3) the cellulose powder is processed in the same way to obtain a blank titration curve;

(4) each sample was titrated three times and the arithmetic mean was taken.

5. The method for preparing hydrogel and testing the performance thereof according to claim 2 or 3, wherein the swelling behavior of C-g-AA gel in different solvent media is determined by:

(1) placing the fully dried C-g-AA hydrogel wafer in different solutions including deionized water, pH buffer solution (pH: 2.0-11.0, ionic strength: I =0.2M), and salt solution (NaCl or CaCl)₂0.01-2.5 mol/L) of the raw material;

(2) taking out the gel in swelling at regular intervals, sucking off the water on the surface by using filter paper and weighing, then immersing the hydrogel into the original solution again for swelling, and taking out again after a preset time interval for operating as above and weighing.

6. The method for preparing the hydrogel and testing the performance of the hydrogel according to any one of claims 1 to 5, wherein the C-g-AA gel cationic dye adsorption assay specifically comprises:

(1) placing the accurately weighed xerogel in deionized water for 24 hours until the gel is in swelling balance, then soaking the gel in swelling balance in MB solution, and placing the gel in a rotary shaking table (30 ℃, 85 rpm) to fully contact for 36 hours;

(2) MB absorbance at 664 nm was measured by an ultraviolet-visible spectrophotometer (Hitachi Z-5000, Japan) as adsorption quantitative data.

7. The method of claim 6, wherein the adsorption test comprises the steps of:

(701) various amounts of 0.01 mol/L HNO were added₃Or adjusting Ni by 0.01 mol/L NaOH dilute solution²⁺、Cd²⁺And Pb²⁺The pH value range of the solution (100 mL, 600 mg/L) is 2.0-6.0;

(702) putting 50 mg of xerogel samples into a series of prepared ionic solutions, and oscillating for 6 hours at constant temperature;

(703) adsorption isothermal compactionThe assay was carried out in an ionic solution at pH 5.0, Ni²⁺、Cd²⁺、Pb²⁺The concentration of the solution is changed within the range of 200-2000 mg/L;

(704) 50 mg of xerogel sample are placed in a series of prepared ionic solutions and shaken for 6h at constant temperature.

8. The method for preparing the fiber-based hydrogel and testing the performance of the fiber-based hydrogel according to claim 6 or 7, further comprising an adsorption kinetics test, which comprises the following steps:

(a1) the pH of the solution was 5.0 and 500 mg of xerogel sample was added to 1L of Ni at a concentration of 1000 mg/L²⁺，Cd²⁺And Pb²⁺In solution;

(a2) sampling and analyzing the current residual ion concentration by using an injector at a preset time interval (5-500 min);

（a3）Ni²⁺、Cd²⁺and Pb²⁺The initial and final concentrations of the solution were measured by atomic absorption spectroscopy (AAS, ZEEnit700, Germany), and all tests were performed in parallel twice, taking the arithmetic mean.

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