Guar gum hydrogel powder as well as preparation method and application thereof

Abstract

The invention provides guar gum hydrogel powder as well as a preparation method and application thereof, and belongs to the technical field of biological materials. The preparation method of the guar gum hydrogel powder comprises the following steps: mixing guar gum powder and deionized water, dissolving, standing, adding a sodium tetraborate decahydrate solution, stirring, and standing to obtain hydrogel; unreacted borax on the surface of the hydrogel is washed clean, and then the hydrogel is crushed and dried to obtain guar gum hydrogel powder. After water is added into the prepared hydrogel powder, the original shape and appearance of the hydrogel can be restored, the hydrogel powder can keep the regeneration capacity of the hydrogel for a long time even if the hydrogel powder is ground into powder, and water and soil loss can be prevented while water retention is achieved. The process of regenerating the guar gum hydrogel powder from dry particles is simple and can be repeated for multiple cycles, and convenience is provided for storage and forming of the water-retaining hydrogel material.

Description

Technical Field

[0001] The present invention relates to the technical field of biomaterials, and particularly relates to a guar gum hydrogel powder, a preparation method thereof, and an application thereof. Background Art

[0002] Soil is the most fundamental factor for crop growth. However, due to the complex effects of natural and human factors, approximately 33% of the soil globally suffers from drought and desertification. Xinjiang is located in arid and semi-arid regions, with loose soil structure and poor water retention capacity, exacerbating the shortage of regional fresh water resources. Therefore, improving the water absorption and retention rate of soil has become the key to improving local soil desertification. Hydrogels are super hydrophilic materials with a three-dimensional cross-linked network structure, having excellent water absorption capacity, low cost, and the ability to optimize soil structure. However, currently common high water-absorbing materials (for example, sodium polyacrylate, polyacrylamide, hydroxyethyl polymethacrylate, etc.) are usually prepared from acrylic acid, acrylonitrile, or acrylamide monomers derived from petroleum products. Although they have wide applications, they generally have defects such as poor biocompatibility, difficulty in degradation, complex synthesis, and high cost.

[0003] However, currently natural hydrogels have problems such as poor water absorption capacity, few cycle times, and high preparation difficulty and cost. Therefore, it is crucial to find a natural polymer to replace petroleum products and have a hydrogel with the ability of multiple absorption / desorption cycles. Summary of the Invention

[0004] The purpose of the present invention is to provide a guar gum hydrogel powder, a preparation method thereof, and an application thereof. The hydrogel powder prepared by the present invention can restore the original shape and appearance of the hydrogel after adding water. These hydrogel powders can maintain the hydrogel regeneration ability even for a long time after being ground into powder, and can prevent soil erosion while retaining water. The process of regenerating the guar gum hydrogel powder from its dry particles is simple and can be repeated for multiple cycles, providing convenience for the storage and shaping of the water-retaining hydrogel material.

[0005] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0006] In the first aspect, the present invention provides a preparation method of a guar gum hydrogel powder, including the following steps:

[0007] Mix and dissolve guar gum powder with deionized water, let it stand, then add a sodium tetraborate decahydrate solution, stir and let it stand to obtain a hydrogel;

[0008] Wash the unreacted borax on the surface of the hydrogel, then crush and dry the hydrogel to obtain the guar gum hydrogel powder.

[0009] Guar gum is a natural polysaccharide, and its molecular structure contains a large number of hydroxyl groups (-OH). Borax (the main component is sodium tetraborate, Na2B4O7·10H2O) will undergo hydrolysis in aqueous solution to produce boric acid (H3BO3) and borate ions. On the one hand, boric acid can react with the hydroxyl groups on the guar gum molecule to form borate ester bonds; on the other hand, the borate ions produced by the hydrolysis of borax can combine with the hydroxyl groups in the guar gum molecule through electrostatic interaction and hydrogen bond interaction, further promoting the formation of a crosslinked network. These interactions enable the formation of a stable three-dimensional network structure among the guar gum molecules. Specifically, the boron atom in the boric acid molecule has an empty orbital, while the oxygen atom in the hydroxyl group on the guar gum molecule has a lone pair of electrons. The lone pair of electrons of the oxygen atom can enter the empty orbital of the boron atom to form a coordination bond, thereby connecting the guar gum molecules and achieving crosslinking.

[0010] Preferably, the mass ratio of the guar gum powder to sodium tetraborate decahydrate is 4:(1 - 4).

[0011] Preferably, the mass-volume ratio of the guar gum powder to deionized water is (0.2 - 0.6) g:(10 - 30) mL.

[0012] Preferably, the standing times are respectively 0.5 - 3 h.

[0013] Preferably, the stirring time is 5 - 30 min.

[0014] Preferably, the drying temperature is 50 - 60 °C.

[0015] In the second aspect, the present invention provides a guar gum hydrogel powder, and the guar gum hydrogel powder is prepared by the above-mentioned preparation method.

[0016] In the third aspect, the present invention provides the application of the above-mentioned guar gum hydrogel powder in soil water retention.

[0017] Preferably, the soil includes mine soil, sandy soil, and alkaline soil.

[0018] Preferably, the dosage of the guar gum hydrogel powder when used for soil water retention is hydrogel:soil = 1:100.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The hydrogel prepared by the present invention uses natural polymers as raw materials, which has important environmental protection and economic significance. And it adopts a one-step method, with a simple preparation process, no generation of toxic and harmful substances, strong reproducibility, and the potential for large-scale production.

[0021] The guar gum hydrogel powder prepared by the invention not only has water-retaining performance, but also can prevent water and soil loss in sandy soil.

[0022] The hydrogel powder prepared by the invention is portable, convenient to recycle, renewable, and has good stability. The powder can be converted into block-shaped homogeneous guar gum hydrogel by simply adding water, and the molding process is simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a process flow chart of the guar gum hydrogel powder prepared in Example 1 of the present invention.

[0024] Figure 2 This is a scanning electron microscope image (SEM) of the guar gum hydrogel prepared in Example 1 of the present invention.

[0025] Figure 3 This is a diagram showing the swelling performance of the guar gum hydrogel powder obtained in Example 1 of the present invention.

[0026] Figure 4 (a) Water absorption trend of guar gum hydrogel powder; (b) Water loss trend of guar gum hydrogel.

[0027] Figure 5 This is a trend chart of guar gum hydrogel powder before and after swelling after absorbing water (pH=3, 5, 7, 9, 11).

[0028] Figure 6 This is a graph showing the cyclic water absorption test of the guar gum hydrogel powder prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0029] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0030] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0031] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Although this invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of this invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to those documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0032] Without departing from the scope or spirit of this invention, various modifications and variations can be made to the specific embodiments of the description of this invention, which are obvious to those skilled in the art. Other embodiments obtained from the description of this invention are obvious to those skilled in the art. The description and examples of this application are merely exemplary.

[0033] Regarding the use of "comprising", "including", "having", "containing", etc. in this article, they are all open-ended terms, meaning including but not limited to.

[0034] As used in this invention, "room temperature" and "normal temperature" are both calculated as 25 ± 2 °C unless otherwise specified.

[0035] All raw materials used in the following examples of this invention are obtained commercially.

[0036] Example 1

[0037] This example provides a method for preparing guar gum hydrogel powder:

[0038] First, put 0.4 g of guar gum powder into a dry 50 mL beaker, then add 20 mL of deionized water to the beaker to dissolve the guar gum and keep it at room temperature for 1 h to make the guar gum dissolve evenly. Then add 0.2 g of dissolved sodium tetraborate decahydrate, and then stir the mixture with a glass rod for 10 min and let it stand for a period of time to obtain a hydrogel. After that, wash the surface of the hydrogel with distilled water to remove the unreacted borax. Finally, crush the hydrogel and dry it in an oven at 60 °C to obtain hydrogel powder (GG-0.2 hydrogel powder).

[0039] The scanning electron micrograph of the guar gum hydrogel prepared in this example is as Figure 2 shown. The prepared guar gum hydrogel has an internal cross-linked network structure, showing an interconnected porous network structure with relatively large pores between them. The porous structure helps the diffusion of aqueous fluids in the polymer network, thus resulting in a higher swelling capacity in the hydrogel.

[0040] The swelling performance graph of the guar gum hydrogel obtained in this example is as Figure 3As shown, the prepared guar gum hydrogel is in a powdery structure before water absorption, significantly swells after water absorption, and within a certain range, the hydrogel powder can exhibit self-healing behavior after water absorption. When immersed in water, it will connect together while absorbing and retaining water, and when placed in soil, it can play a role in preventing soil erosion. It is easy to recycle and can be reused without causing environmental pollution.

[0041] Example 2:

[0042] This example has the same preparation method as Example 1, except that the amount of sodium tetraborate decahydrate is 0.1 g; the obtained hydrogel powder is denoted as GG-0.1 hydrogel powder.

[0043] Example 3:

[0044] This example has the same preparation method as Example 1, except that the amount of sodium tetraborate decahydrate is 0.3 g; the obtained hydrogel powder is denoted as GG-0.3 hydrogel powder.

[0045] Example 4

[0046] This example provides a preparation method for guar gum hydrogel powder:

[0047] First, put 0.6 g of guar gum powder into a dry 50 mL beaker, then add 30 mL of deionized water to the beaker to dissolve the guar gum and keep it at room temperature for 3 h to make the guar gum dissolve evenly. Then add 0.6 g of dissolved sodium tetraborate decahydrate, and then stir the mixture with a glass rod for 30 min and let it stand for a while to obtain a hydrogel. After that, wash the surface of the hydrogel with distilled water to remove the unreacted borax. Finally, crush the hydrogel and dry it in an oven at 60 °C to obtain the hydrogel powder.

[0048] Example 5

[0049] This example provides a preparation method for guar gum hydrogel powder:

[0050] First, put 0.2 g of guar gum powder into a dry 50 mL beaker, then add 10 mL of deionized water to the beaker to dissolve the guar gum and keep it at room temperature for 2 h to make the guar gum dissolve evenly. Then add 0.1 g of dissolved sodium tetraborate decahydrate, and then stir the mixture with a glass rod for 5 min and let it stand for a while to obtain a hydrogel. After that, wash the surface of the hydrogel with distilled water to remove the unreacted borax. Finally, crush the hydrogel and dry it in an oven at 50 °C to obtain the hydrogel powder.

[0051] Comparative Example 1

[0052] This example has the same preparation method as Example 1, except that sodium tetraborate decahydrate is not added.

[0053] This comparative example cannot form a wide cross-linked network structure nor a hydrogel.

[0054] Experimental Example

[0055] The guar gum hydrogel powders in Examples 1 - 3 were tested for water absorption and retention performance.

[0056] 1. Take 0.1 g of the guar gum hydrogel powder samples obtained in each example and add them to 10 mL of distilled water respectively, soak for 24 h, and detect the swelling trend over time; then take them out and detect the water loss trend over time, see Figure 4 .

[0057] 2. Take 0.1 g of the guar gum hydrogel powder samples obtained in each example and add them to 10 mL of solutions with pH = 3, 5, 7, 9, 11 respectively, soak for 24 h. Weigh the hydrogel at different times respectively to evaluate the water absorption capacity of the guar gum hydrogel, see Figure 5 .

[0058] Calculation method of water absorption amount:

[0059]

[0060] Ws is the weight of the swollen hydrogel, and Wd is the initial weight of the freeze-dried hydrogel.

[0061] The guar gum hydrogel powder sample obtained in Example 1 was repeatedly subjected to water absorption and dehydration for cyclic water absorption tests. The hydrogel powder was fully dried to a constant weight under appropriate conditions to remove any possible moisture, and then it was ground evenly and stored for later use. A certain mass of the hydrogel powder, m0, was accurately weighed using an electronic balance and placed in a conical flask of known mass. Excess deionized water was added to the conical flask to ensure that the hydrogel powder was completely immersed, and then the conical flask was placed in a constant temperature water bath and left to stand for 24 h at the set temperature (25 °C) to allow the hydrogel powder to fully absorb water and reach swelling equilibrium. The water-absorbed hydrogel was taken out with tweezers, and the excess water on the surface was gently blotted dry with filter paper and quickly weighed on an electronic balance to obtain its wet weight (denoted as m1). The first water absorption rate Q1 was calculated according to the formula Q1 = (m1 - m0) / m0 × 100%. The water-absorbed hydrogel sample was placed in a constant temperature drying oven and dried to a constant weight at 60 °C, and the mass after drying was recorded (denoted as m2). It could be weighed every once in a while during drying until the mass change was less than 0.005 g. The dried hydrogel sample was again placed in a conical flask containing excess deionized water, and the second water absorption was carried out under the same temperature and time conditions as the first water absorption step. The wet weight was weighed, and the second water absorption rate Q2 was calculated. According to the above drying and water absorption steps, multiple cyclic tests were repeated, and the water absorption rate after each cycle was recorded. Five cycles were carried out. During the test, each sample was tested 3 times, and the average value was taken as the test result to reduce errors. The results are shown in Figure 6 .

[0062] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing guar gum hydrogel powder, characterized in that: The following steps are involved: The guar gum powder is mixed with deionized water, dissolved and allowed to stand, and then a sodium tetraborate decahydrate solution is added, stirred and allowed to stand to obtain a hydrogel; The unreacted borax on the surface of the hydrogel is washed away, and then the hydrogel is crushed and dried to obtain guar gum hydrogel powder.

2. The preparation method according to claim 1, characterized in that: The mass ratio of the guar gum powder to sodium tetraborate decahydrate is 4:(1-4).

3. The preparation method according to claim 1, characterized in that: The mass volume ratio of the guar gum powder to deionized water is (0.2-0.6) g: (10-30) mL.

4. The preparation method according to claim 1, characterized in that: The standing time is 0.5-3h respectively.

5. The preparation method according to claim 1, characterized in that: The stirring time is 5-30 min.

6. The preparation method according to claim 1, characterized in that: The drying temperature is 50-60°C.

7. A guar gum hydrogel powder, characterized in that: The guar gum hydrogel powder is prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the guar gum hydrogel powder according to claim 7 in soil water conservation.

9. The use according to claim 8, characterized in that: The soil includes mine soil, sandy soil and alkaline soil.

10. The use according to claim 8, characterized in that: The dosage of the guar gum hydrogel powder when used for soil water retention is hydrogel: soil = 1g: 100g.

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