Lignin / gelatin / alginate composite hydrogel material and preparation method thereof

Abstract

The invention discloses a lignin / gelatin / alginate composite hydrogel material and a preparation method thereof, and belongs to the field of biomass materials and environmental materials. The preparation method comprises the following steps: respectively preparing a gelatin solution A, a modified lignin solution B and a soluble alginate and carbodiimide solution C, mixing the gelatin solution A, the modified lignin solution B and the soluble alginate and carbodiimide solution C with a slow-release ionic cross-linking agent, pouring the mixture into a mold, and reacting for 2-48 hours to obtain the hydrogel. According to the hydrogel, a stable three-dimensional network structure is constructed through crosslinking of covalent bonds among three components of modified lignin, gelatin and alginate. Meanwhile, full biomass modification is adopted, and natural high polymer materials and renewable resources are used; the prepared hydrogel has good crosslinking controllability, is basically recoverable under 70% compressive strain, has excellent performance through 1000 times of compression resilience tests under 30% compressive strain, has excellent fatigue resistance and mechanical stability, also has the advantages of low toxicity, low cost and simple and convenient preparation process, and has wide application potential in the fields of medical treatment, electronics and the like.

Description

Technical Field

[0001] The invention relates to the field of biomass materials and composite functional materials, and in particular to a lignin / gelatin / alginate composite hydrogel material and a preparation method thereof. Background Art

[0002] Hydrogels are a type of material that forms a three-dimensional network structure through intermolecular non-covalent and covalent cross-linking. However, due to its liquid properties and relatively weak interactions between polymer chains, especially biomass-based hydrogels, they usually exhibit low mechanical strength. They are soft and lack rigidity, and are easily deformed under external pressure or tension. They have weak compression and shear resistance, and are prone to breakage or irreversible deformation when subjected to excessive loads. In addition, the preparation cost of hydrogels is generally high and their stability is poor. These problems seriously limit their wide application in many fields. Despite the above defects, hydrogels have unique advantages such as softness, plasticity, biodegradability and environmental responsiveness, which make them still have potential application value in biomedicine, environmental remediation and other fields. In recent years, the development of biomass-based hydrogel materials with excellent mechanical properties, harmless degradation byproducts, and simple and low-cost preparation processes has become a research focus and hot direction in related fields.

[0003] Sodium alginate (SA) is a natural anionic polysaccharide connected by β-1,4-glycosidic bonds. It has excellent biocompatibility, low cost and non-toxicity. 2+ The sodium alginate hydrogels are cross-linked with divalent metal ions to form membrane structures and gels with excellent performance. However, alginate hydrogels that rely solely on ionic cross-linking have certain limitations in terms of cross-linking speed, molding effect, and mechanical stability. In order to improve the controllability of the cross-linking process and improve its mechanical properties, and obtain composite hydrogels with more perfect structures, chemical modification of sodium alginate becomes a necessary means.

[0004] Gelatin (GL) is obtained by hydrolysis of collagen. Its molecular chain contains abundant active hydrophilic groups and can be modified by grafting to form a gel. Although gelatin-based hydrogels have been widely used in many application scenarios, their mechanical properties are relatively weak and the cross-linking process is poorly controllable. By constructing an interpenetrating network structure through physical and chemical modification, the advantages of gelatin and other polymers can be effectively integrated to significantly improve their mechanical properties. However, previous studies have shown that gelatin / alginate composite hydrogels still have a lot of room for improvement in resilience and fatigue resistance, and it is difficult to meet some application scenarios with high requirements for material performance.

[0005] Lignin is the second most abundant natural polymer compound in nature after cellulose. It has significant advantages such as non-toxicity, renewability, and biodegradability, and is regarded as a green chemical raw material with great potential. After introducing functional groups (amino groups, carboxyl groups, or sulfonic acid groups, etc.) into the lignin molecular structure through chemical modification, its crosslinking performance is significantly improved, the compatibility with other polymer materials is enhanced, and the mechanical strength and stability of the composite material can be effectively improved. In addition, the modified lignin still maintains excellent biocompatibility and biodegradability, showing broad application prospects in the fields of biomedicine and environmental protection. It can undergo covalent crosslinking reactions with other polymers or crosslinking agents to form a stable three-dimensional network structure, further enhancing the mechanical and anti-aging properties of the composite material, and is very suitable for the preparation of high-performance composite materials.

[0006] In summary, aiming at the problems existing in the existing hydrogel materials, the present invention is committed to developing a lignin / gelatin / alginate bio-based hydrogel with stable mechanical properties, excellent anti-fatigue properties and service performance, and at the same time having the characteristics of low price, simple production process, and environmental friendliness, as well as its preparation method. Summary of the Invention

[0007] In view of this, the purpose of the present invention is to propose a preparation method of a lignin / gelatin / alginate composite hydrogel material that is simple and convenient in preparation process, environmentally friendly, low in cost, and stable in mechanical properties.

[0008] In order to achieve the above technical objectives, the technical solutions adopted by the present invention are as follows:

[0009] A preparation method of a lignin / gelatin / alginate composite hydrogel material, which includes: mixing a solution A in which gelatin is dissolved, a solution B in which modified lignin is dispersed, a solution C in which soluble alginate and carbodiimide are dissolved, and a slow-release ionic crosslinking agent, and then reacting the mixed solution under preset temperature and humidity conditions for 2 to 48 hours to obtain the hydrogel material. Specifically, it includes the following steps:

[0010] S1. Dissolve gelatin in deionized water, and completely dissolve the gelatin under preset temperature and stirring conditions to prepare solution A;

[0011] S2. Mix modified lignin with sodium hydroxide solution to dissolve the modified lignin in the sodium hydroxide solution to prepare solution B;

[0012] S3. Dissolve soluble alginate and carbodiimide in deionized water, and under stirring conditions, dissolve and mix them evenly to prepare solution C;

[0013] S4. Mix solution C, solution A, solution B, and the slow-release ionic crosslinking agent evenly according to a preset ratio, and then react for 2 to 48 hours under preset temperature and humidity conditions to fully crosslink the system and obtain the hydrogel material.

[0014] As a preferred implementation option, preferably, in step S1 of this solution, gelatin is dissolved in deionized water at a solid-liquid ratio of 0.1 to 0.3 g / ml, and the gelatin is completely dissolved at a preset temperature of 60°C and a stirring condition of 120 r / min to obtain solution A.

[0015] As a preferred implementation option, preferably, in step S2 of this solution, the modified lignin is any one or more of aminated lignin, sulfonate lignin, oxidized modified lignin, and graft copolymerization modified lignin.

[0016] As a preferred implementation option, preferably, in step S02 of this solution, the modified lignin is mixed with a sodium hydroxide solution with a concentration of 0.05 to 0.15 mol / L at a solid-liquid ratio of 0.005 to 0.05 g / ml, and the modified lignin is evenly dispersed therein by ultrasonic or stirring treatment at room temperature to obtain solution B.

[0017] As a preferred implementation option, preferably, in step S3 of this solution, the soluble alginate is any one or more of sodium alginate, potassium alginate, or oxidized alginic acid.

[0018] As a preferred implementation option, preferably, in step S3 of this solution, the soluble alginate is dissolved in deionized water at a solid-liquid ratio of 0.02 to 0.04 g / ml, and the carbodiimide is dissolved in deionized water at a solid-liquid ratio of 0.005 to 0.01 g / ml.

[0019] As a preferred implementation option, preferably, in step S4 of this solution, the slow-release ionic crosslinking agent is 2+ Ca 2+ Zn 2+ Ba 2+ Cu 2+ Sr 3+ any one or more of metal ion slow-release salts such as Fe, etc.

[0020] As a preferred implementation option, preferably, in S4, after mixing solution C, solution A, solution B, and the slow-release ionic crosslinking agent evenly according to a preset ratio, it can be poured into a forming mold and allowed to react for 2 to 48 hours under preset temperature and humidity conditions to fully crosslink the system and obtain a hydrogel material with a specific shape.

[0021] As a preferred implementation option, preferably, in the present solution S04, the sustained-release ionic crosslinking agent is calcium carbonate, which, when in use, is also mixed with glucono delta-lactone at a mass ratio of 1:5.

[0022] As a preferred implementation option, preferably, in steps S1-S4 of the present solution, the mass ratio of gelatin: modified lignin: alginate: carbodiimide: sustained-release ionic crosslinking agent is 1-3: 0.05-0.5: 2-4: 0.05-1: 0.1-0.3.

[0023] Based on the above, the present solution also proposes a lignin / gelatin / alginate composite hydrogel material, which is prepared by the above-mentioned preparation method.

[0024] Adopting the above technical solution, compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. Innovative covalent crosslinking strategy: In this solution, by introducing modified lignin and making it chemically react with the gelatin / alginate matrix to form covalent bond crosslinking, a stable three-dimensional network structure is constructed. This innovative covalent crosslinking strategy effectively enhances the mechanical properties, antioxidant properties and weather resistance of the material, significantly improving the comprehensive performance of the hydrogel, and has important innovative significance in the field of hydrogel performance optimization.

[0026] 2. Green and sustainable preparation method: This solution adopts a full-biomass modification method, and the gelatin, sodium alginate and lignin used are all natural polymer materials, belonging to renewable resources. This preparation method not only conforms to the concept of environmental protection and sustainable development, but also has low cost and simple production process, highly coinciding with the current development trend of green chemistry.

[0027] 3. Excellent mechanical and anti-fatigue properties: The introduction of modified lignin in this solution significantly enhances the mechanical properties and antioxidant properties of the composite material. The experimental results show that the material can basically return to its original state under a 70% compression strain, and still exhibits excellent anti-fatigue properties after 1000 compression-rebound tests under a 30% compression strain. This fully demonstrates that the hydrogel has excellent elasticity and fatigue resistance under large compression strain conditions, and can meet a variety of high-demand application scenarios.

[0028] In summary, the hydrogel material prepared by this solution has significant advantages such as simple preparation process, low cost and excellent performance, providing new ideas and methods for the preparation of green hydrogel materials, and having important theoretical and practical significance in promoting the application of biomass materials in new technologies and new materials fields. Description of the Drawings

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required for the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings.

[0030] Figure 1 It is a digital photo of the hydrogel materials prepared in Examples 1, 2, 3, and 4, visually showing the appearance morphology of the hydrogels prepared with different formulations, providing a basis for the preliminary evaluation of the forming effect of the hydrogels.

[0031] Figure 2 It is an SEM image of the blank gelatin / alginate hydrogel material prepared in Example 3, clearly presenting the microscopic structural characteristics of the blank hydrogel, providing a reference for the comparison of the microscopic structure of the hydrogel after adding lignin.

[0032] Figure 3 It is an SEM image of the lignin / gelatin / alginate hydrogel material provided in Example 4 of the present invention, showing the microscopic structure of the hydrogel after adding aminated lignin, which helps to deeply understand the influence mechanism of aminated lignin on the microscopic structure of the hydrogel.

[0033] Figure 4 It is a 70% strain compression and rebound data graph of the hydrogel materials provided in Examples 1, 2, 3, and 4 of the present invention, visually reflecting the rebound performance of different hydrogels under 70% compression strain in the form of a graph, providing quantitative data for the evaluation of the elasticity of the hydrogels.

[0034] Figure 5 It is a tensile data graph of the gelatin / alginate hydrogel materials with and without lignin added provided in Examples 3 and 4 of the present invention, comparing and showing the change in the tensile performance of the hydrogel before and after adding aminated lignin, providing important data support for studying the influence of modified lignin on the mechanical properties of the hydrogel.

[0035] Figure 6 It is an anti-fatigue data graph of the lignin / gelatin / alginate hydrogel material provided in Example 4 of the present invention, visually presenting the anti-fatigue performance of the hydrogel after multiple compression and rebound tests under 30% compression strain, fully demonstrating its excellent fatigue resistance characteristics.

[0036] Figure 7 It is a swelling data graph of the gelatin / alginate hydrogel materials with and without lignin added provided in Examples 3 and 4 of the present invention, comparing and analyzing the change in the swelling performance of the hydrogel before and after adding aminated lignin, which helps to deeply understand the water absorption characteristics of the hydrogel and its influencing factors.

[0037] Figure 8 This is the antioxidant property data graph of the hydrogel materials provided in Embodiments 1, 2, 3, and 4 of the present invention. It shows the antioxidant properties of different hydrogels in the form of a chart, providing an important reference for evaluating the stability of hydrogels under different environmental conditions. Detailed implementation manners

[0038] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be specifically noted that the following embodiments are only used to illustrate the present invention, but do not limit the scope of the present invention. Similarly, the following embodiments are only partial embodiments of the present invention rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0039] Embodiment 1

[0040] Preparation of blank alginate hydrogel

[0041] As one of the control examples, this embodiment is the preparation of a blank alginate hydrogel, and its steps are as follows:

[0042] Accurately weigh 3 g of sodium alginate, place it in 100 mL of deionized water, and stir at a stirring speed of 150 r / min at room temperature for 20 min to ensure that the sodium alginate is fully dissolved.

[0043] Add 0.5 g of carbodiimide (EDC) as a catalyst, 0.2 g of calcium carbonate, and 1 g of glucono-delta-lactone to the above solution in sequence, and continue to stir for 15 min to make the components mix evenly.

[0044] Pour the evenly mixed solution into a mold with a specific shape, and react for 24 hours in an environment with a temperature of 25 °C and a relative humidity of 50% to obtain a blank alginate hydrogel.

[0045] Embodiment 2

[0046] Preparation of lignin / alginate hydrogel

[0047] As the second control example, this embodiment is the preparation of a lignin / alginate hydrogel, and its steps are as follows:

[0048] Accurately weigh 0.2 g of aminated lignin, add it to 10 mL of a sodium hydroxide solution with a concentration of 0.1 mol / L, and stir at room temperature for 30 min until the aminated lignin is completely dissolved.

[0049] Accurately weigh 3 g of sodium alginate, put it into 90 mL of deionized water, stir evenly at a stirring speed of 200 r / min, then add 0.5 g of carbodiimide (EDC) as a catalyst and the above-prepared aminated lignin solution, and continue to stir for 40 min.

[0050] Then, 0.2 g of calcium carbonate and 1 g of glucono-delta-lactone were added, and stirred for 20 min to make them evenly mixed; then the mixed solution was poured into a mold and reacted for 24 hours in an environment with a temperature of 25 °C and a relative humidity of 50% to obtain the lignin / alginate hydrogel.

[0051] Example 3

[0052] Preparation of gelatin / alginate hydrogel

[0053] This example is used as the third control example, which is the preparation of gelatin / alginate hydrogel, and its steps are as follows:

[0054] Accurately weigh 2 g of gelatin, place it in 10 ml of deionized water, and stir and dissolve it in a constant temperature water bath at 60 °C at a stirring speed of 100 r / min.

[0055] Weigh 3 g of sodium alginate, place it in 90 mL of deionized water, stir for 20 min at a stirring speed of 150 r / min, and then add 0.5 g of carbodiimide (EDC) as a catalyst and the above-prepared gelatin solution, and stir for 40 min.

[0056] Then add 0.2 g of calcium carbonate and 1 g of glucono-delta-lactone, and stir for 20 min to make them evenly mixed. Pour the mixed solution into a mold and react for 24 hours in an environment with a temperature of 25 °C and a relative humidity of 50% to obtain the gelatin / alginate hydrogel.

[0057] Example 4: Preparation of lignin / gelatin / alginate composite hydrogel material

[0058] This example is for the preparation of lignin / gelatin / alginate composite hydrogel material, and its steps are as follows:

[0059] Accurately weigh 2 g of gelatin, place it in 10 mL of deionized water, and stir and dissolve it in a constant temperature water bath at 60 °C at a stirring speed of 120 r / min to prepare solution A.

[0060] Accurately weigh 0.2 g of aminated lignin, add it to 10 mL of sodium hydroxide solution with a concentration of 0.1 mol / L, and stir for 30 min at room temperature to dissolve it to prepare solution B.

[0061] Weigh 3 g of sodium alginate, place it in 80 mL of deionized water, and stir for 20 min at a stirring speed of 180 r / min; then add 0.5 g of carbodiimide (EDC) as a catalyst, mix to prepare solution C, and then add the above-prepared gelatin solution (solution A) and aminated lignin solution (solution B), and stir for 40 min.

[0062] Finally, add 0.2 g of calcium carbonate as a slow-release ionic crosslinking agent, add it together with 1 g of glucono delta-lactone, and then stir for 20 min to make them evenly mixed. Then pour the mixed solution into a mold and react for 24 hours in an environment with a temperature of 25 °C and a relative humidity of 50% to fully crosslink the system, obtaining a lignin / gelatin / alginate hydrogel material.

[0063] In Example 4 of this scheme, the mass ratios of the components were determined by a three-factor and three-level orthogonal experiment. By exploring the relationship among the mechanical properties of the lignin / gelatin / alginate composite hydrogel material, the ratio of alginate to gelatin (A), the dosage of aminated lignin (B), and the dosage of calcium carbonate (C), the optimal process was explored.

[0064] In this scheme, since calcium carbonate (CaCO₃) itself does not directly crosslink alginate, it needs to gradually release Ca²⁺ under acidic conditions (such as the acidic environment generated by the hydrolysis of glucono delta-lactone), 2+ and then undergo ionic crosslinking with alginate. Therefore, in the experiment, calcium carbonate (0.1 g, 0.2 g, 0.3 g) was used as a slow-release ionic crosslinking agent, which was mixed with a fixed amount of glucono delta-lactone (1 g) and then used. Among them, the mass ratios of calcium carbonate to glucono delta-lactone were 10%, 20%, and 30% respectively (see Table 1).

[0065] Among them, the factor level design of the orthogonal experiment is shown in Table 1, and the experimental results are listed in Table 2.

[0066] Table 1 Single-factor design table of aminated lignin / gelatin / alginate composite hydrogel

[0067]

[0068] Table 2 Orthogonal experiment analysis and results

[0069]

[0070]

[0071] It can be seen from the table that the lignin / gelatin / alginate composite hydrogel material prepared with a ratio of alginate to gelatin of 3:2, 0.2 g of aminated lignin, and 0.2 g of calcium carbonate has the best compression and resilience performance. Among them, the digital photos of the hydrogel materials prepared in Examples 1-4 are as Figure 1 shown, which visually shows the appearance morphology of the hydrogels prepared with different formulas and provides a basis for the preliminary evaluation of the forming effect of the hydrogels.

[0072] Figure 2It is the SEM image of the blank gelatin / alginate hydrogel material prepared in Example 3, which clearly presents the microscopic structural characteristics of the blank hydrogel and provides a reference for comparing with the microscopic structure of the hydrogel after adding lignin.

[0073] Figure 3 It is the SEM image of the lignin / gelatin / alginate hydrogel material provided in Example 4 of the present invention, which shows the microscopic structure of the hydrogel after adding aminated lignin and helps to deeply understand the influence mechanism of aminated lignin on the microscopic structure of the hydrogel.

[0074] The hydrogel materials prepared in Examples 1-4 were tested for mechanical properties and fatigue resistance according to the following standards: the environmental temperature during sample preparation and testing was strictly controlled at (20±2)°C, and the relative humidity was controlled at 55%±2%; for the samples used to test the compressive strength, the specimen shape was processed into a cylinder with flat upper and lower surfaces, and the compression test rate was set at 2 mm / min. The test results are as Figure 1 、 Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 shown.

[0075] Among them, Figure 4 It is the 70% strain compression and rebound data graph of the hydrogel materials provided in Examples 1, 2, 3, and 4 of the present invention, which intuitively reflects the rebound performance of different hydrogels under 70% compression strain through a chart form and provides quantitative data for evaluating the elasticity of the hydrogel.

[0076] Figure 5 It is the tensile data graph of the gelatin / alginate hydrogel materials with and without lignin added provided in Examples 3 and 4 of the present invention, which comparatively shows the change in the tensile performance of the hydrogel before and after adding aminated lignin and provides important data support for studying the influence of modified lignin on the mechanical properties of the hydrogel.

[0077] Figure 6 It is the fatigue resistance data graph of the lignin / gelatin / alginate hydrogel material provided in Example 4 of the present invention, which intuitively presents the fatigue resistance of the hydrogel after multiple compression and rebound tests under 30% compression strain and fully proves its excellent fatigue resistance characteristics.

[0078] Figure 7 It is the swelling data graph of the gelatin / alginate hydrogel materials with and without lignin added provided in Examples 3 and 4 of the present invention, which comparatively analyzes the change in the swelling performance of the hydrogel before and after adding aminated lignin and helps to deeply understand the water absorption characteristics of the hydrogel and its influencing factors.

[0079] It can be significantly seen from the test result graph that after adding aminated lignin, the lignin / gelatin / algae acid hydrogel prepared by the above method has been significantly improved in terms of compression and resilience performance, anti-fatigue performance, and water resistance. In addition, this material also has outstanding advantages such as excellent service performance, good environmental friendliness, low cost, and simple production process. These excellent properties make it show broad application potential in many fields such as medical treatment and electronics.

[0080] Figure 8 It is a graph of the antioxidant data of the hydrogel materials provided in Examples 1, 2, 3, and 4 of this solution, which shows the antioxidant performance of different hydrogels in the form of a graph and provides an important reference for evaluating the stability of hydrogels under different environmental conditions.

[0081] In summary, the research results of this study provide important theoretical basis and practical guidance for the preparation and high-value application of bio-based hydrogel materials, and have important scientific significance and practical application value for promoting the wide application of biomass materials in new technologies and new materials fields.

[0082] The above are only partial embodiments of the present invention, and thus do not limit the protection scope of the present invention. Any equivalent device or equivalent process transformation made by using the content of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, shall be equally included in the patent protection scope of the present invention.

Claims

1. A preparation method of a lignin / gelatin / al alginate composite hydrogel material, characterized in that, It includes: Mix the A solution in which gelatin is dissolved, the B solution in which modified lignin is dispersed, the C solution in which soluble alginate and carbodiimide are dissolved, and a sustained-release ionic crosslinking agent, and then keep the mixed solution under preset temperature and humidity conditions for reaction for 2 to 48 h to obtain a hydrogel material.

2. The preparation method of a lignin / gelatin / al alginate composite hydrogel material according to claim 1, characterized in that, It includes the following steps: S1. Dissolve gelatin in deionized water, and completely dissolve the gelatin under preset temperature and stirring conditions to obtain the A solution. S2. Mix modified lignin with sodium hydroxide solution to dissolve the modified lignin in the sodium hydroxide solution to obtain the B solution. S3. Dissolve soluble alginate and carbodiimide in deionized water, and under stirring conditions, dissolve and mix them evenly to obtain the C solution. S4. Mix the C solution, the A solution, the B solution, and the sustained-release ionic crosslinking agent evenly according to a preset ratio, and then under preset temperature and humidity conditions, react for 2 to 48 hours to fully crosslink the system to obtain a hydrogel material.

3. The preparation method of a lignin / gelatin / algal composite hydrogel material according to claim 2, wherein In S1, dissolve gelatin in deionized water at a solid-liquid ratio of 0.1 to 0.3 g / ml, and completely dissolve the gelatin under a preset temperature of 60 °C and a stirring condition of 120 r / min to obtain the A solution.

4. The preparation method of a lignin / gelatin / algal composite hydrogel material according to claim 2, characterized in that In S2, the modified lignin is any one or more of aminated lignin, sulfonate lignin, oxidized modified lignin, and graft copolymerization modified lignin.

5. The preparation method of a lignin / gelatin / alginate composite hydrogel material according to claim 4, characterized in that, In S02, mix modified lignin with a sodium hydroxide solution with a concentration of 0.05 to 0.15 mol / L at a solid-liquid ratio of 0.005 to 0.05 g / ml, and uniformly disperse the modified lignin therein at room temperature to obtain the B solution.

6. The preparation method of a lignin / gelatin / algal composite hydrogel material according to claim 2, characterized in that, In S3, the soluble alginate is any one or more of sodium alginate, potassium alginate, or oxidized alginic acid.

7. The preparation method of a lignin / gelatin / al alginate composite hydrogel material according to claim 6, characterized in that, In S3, dissolve the soluble alginate in deionized water at a solid-liquid ratio of 0.02 to 0.04 g / ml, and dissolve carbodiimide in deionized water at a solid-liquid ratio of 0.005 to 0.01 g / ml.

8. The preparation method of a lignin / gelatin / algal composite hydrogel material according to claim 2, characterized in that, In S4, the sustained-release ionic crosslinking agent is Ca 2+ 、Zn 2+ , Ba 2+ , Cu 2+ , Sr 2+ , Fe 3+ Any one or more of the metal ion slow-release salts; Among them, mix the C solution, the A solution, the B solution, and the sustained-release ionic crosslinking agent evenly according to a preset ratio, and then under a preset temperature of 25 °C and a relative humidity condition of 50%, react for 2 to 48 hours to fully crosslink the system to obtain a hydrogel material.

9. The preparation method of a lignin / gelatin / al ginate composite hydrogel material according to any one of claims 1 to 8, characterized in that, In S04, the sustained-release ionic crosslinking agent is calcium carbonate, and when in use, it is also mixed with glucono delta-lactone at a mass ratio of 1:

5. In steps S1 - S4, the mass ratio of gelatin:modified lignin:alginate:carbodiimide:sustained-release ionic crosslinking agent is 1 - 3:0.05 - 0.5:2 - 4:0.05 - 1:0.1 - 0.

3.

10. A lignin / gelatin / alginate composite hydrogel material, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 9.

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