Slow-release water-retaining composite material, its preparation method, vegetation bag containing the same, and application

Abstract

The present invention provides a slow-release water-retaining composite material, a preparation method thereof, a vegetation bag containing the same, and an application. The preparation method of the slow-release water-retaining composite material comprises the following steps: Step S1, mixing pure cotton grey cloth with a solvent, an alkaline aqueous solution, and urea, reacting for a period of time to obtain a pretreatment system; Step S2, adding chloroacetic acid to the pretreatment system for reaction, after the reaction is completed, washing and drying the pure cotton grey cloth to obtain pretreated pure cotton grey cloth; Step S3, putting the pretreated pure cotton grey cloth into water, keeping the temperature constant at 65-75 °C, adding a peroxide initiator and a neutralizing solution for grafting reaction, after cooling, washing and drying the grey cloth, boiling the dried grey cloth with water, and then drying to obtain a water-retaining layer; Step S4, coating a slow-release nutrient slurry and a coagulant on the water-retaining layer to obtain the slow-release water-retaining composite material. The slow-release water-retaining composite material has fast water absorption, a large water storage capacity, and a fast degradation rate, and does not hinder the growth of plants.

Description

Technical Field

[0001] The present invention relates to the field of mine soil improvement, and in particular, to a slow-release water-retaining composite material, a preparation method thereof, a vegetation bag containing the same, and an application thereof. Background Art

[0002] Most mines in China are exploited in an extensive manner, with the exploitation of large open-pit coal mines being dominant, and most open-pit coal mines are concentrated in arid or semi-arid ecologically fragile areas. The waste dump is a giant special landform formed during the exploitation of open-pit coal mines, which is artificially piled up by a large amount of overburden. The reconstruction of the disturbed surface ecosystem in the mining area and the reclamation of the newly constructed soil mass in the new waste dump have become the most urgent tasks in the current ecological environment construction of the mining area.

[0003] However, the soil of the waste dump in the mining area generally has poor water retention capacity, serious runoff, poor nutrients, and weak microbial activity, which is not conducive to plant growth. The organic combination of superabsorbent polymers, nutrient slow-release structures and planting bags can continuously provide stable water and fertilizer supply for plants within a certain period, maintain the relative balance of the water and fertilizer environment of the soil in the roots of the planted plants, and enable plants to have a stable growth environment in the initial stage of growth, which can greatly improve the survival rate of plants and provide technical support for the reconstruction of the surface ecosystem and the reclamation of the newly constructed soil mass in the new waste dump. Summary of the Invention

[0004] The main object of the present invention is to provide a slow-release water-retaining composite material, a preparation method thereof, a vegetation bag containing the same, and an application thereof, so as to solve the problems of poor water retention capacity, poor nutrients, and difficult plant growth in the soil of the waste dump in the prior art.

[0005] To achieve the above object, according to one aspect of the present invention, a preparation method of a slow-release water-retaining composite material is provided, and the preparation method includes the following steps: Step S1, mixing pure cotton grey cloth with a solvent, an alkaline aqueous solution, and urea, reacting for a period of time to obtain a pretreatment system; Step S2, adding chloroacetic acid to the pretreatment system for reaction, after the reaction is completed, washing and drying the pure cotton grey cloth to obtain a pretreated pure cotton grey cloth; Step S3, putting the pretreated pure cotton grey cloth into water, keeping the temperature constant at 65-75 °C, adding a peroxide initiator and a neutralizing solution for grafting reaction, after cooling, washing and drying the grey cloth, boiling the dried grey cloth with water, and then drying to obtain a water-retaining layer; Step S4, coating a slow-release nutrient slurry and a coagulant on the water-retaining layer to obtain a slow-release water-retaining composite material.

[0006] Further, in Step S1, the pure cotton grey cloth is a dried pure cotton grey cloth after removing surface impurities. Preferably, the thickness of the pure cotton grey cloth is 14-15 ounces; more preferably, the pure cotton grey cloth is placed in a polypropylene bag for reaction;

[0007] And / or, the solvent is absolute ethanol. Preferably, the liquor ratio is 1:2.5 - 3;

[0008] And / or, the alkaline aqueous solution is selected from one or more of sodium hydroxide aqueous solution and potassium hydroxide aqueous solution. Preferably, the concentration of the alkaline solution is 14 - 16%, and preferably, the dosage of the alkaline solution is 4 - 5% of the weight of the pure cotton grey fabric;

[0009] And / or, the dosage of urea is 0.1 - 0.3% of the weight of the pure cotton grey fabric;

[0010] Preferably, the reaction temperature in step S1 is 35 - 40°C, and more preferably, the reaction time is 20 - 30 min.

[0011] Further, step S2 includes: adding chloroacetic acid to the pretreatment system, raising the system temperature to 40 - 45°C, reacting for 20 - 30 min, raising the system temperature to 65 - 70°C, and reacting for another 40 - 50 min. Then, cooling the reaction system to room temperature, washing and drying the grey fabric to obtain the pretreated grey fabric and polypropylene bags. Preferably, the chloroacetic acid is an ethanol solution of chloroacetic acid with a concentration of 14 - 16%, and more preferably, the dosage of the ethanol solution of chloroacetic acid is 3 - 5% of the weight of the pure cotton grey fabric.

[0012] Further, step S3 includes: putting the pretreated grey fabric into water with a liquor ratio of 1:2.5 - 3, keeping the temperature constant at 65 - 75°C, adding an initiator and a neutralizing solution, stirring evenly. After cooling to room temperature, washing and drying the grey fabric. Then, boiling the dried grey fabric in water for 2 - 2.5 h. Preferably, change the water every 25 - 30 minutes. After boiling, dry the grey fabric to a constant weight to obtain the water retention layer. Preferably, the initiator includes any one or more of potassium persulfate and ammonium persulfate, and the dosage of the initiator is 3 - 5% of the weight of the grey fabric.

[0013] Further, the neutralizing solution is obtained through the following preparation method, which includes: cooling the container containing acrylic acid in an ice-water bath, adding 4 - 5% sodium bicarbonate aqueous solution until the neutralization degree reaches 70 - 80%, and then adding a crosslinking agent. The addition amount of the crosslinking agent is 0.1 - 0.3% of the mass of acrylic acid. Stir evenly to obtain the neutralizing solution. Preferably, the crosslinking agent includes N,N'-methylenebisacrylamide.

[0014] Further, by weight percentage, the raw materials of the slow-release nutrient slurry include: 10-20% corn starch, 20-30% wheat straw charcoal, 10-20% urea, 30-50% ethylene carbonate, 1-3% hydrochloric acid with a concentration of 36%-38%, and 1-3% phosphoric acid with a concentration of 85%; preferably, the slow-release nutrient slurry is prepared by the following method: mixing the raw materials, reacting at 100-150°C for 30-70 minutes, and cooling to below 100°C for standby; more preferably, the cooling is carried out by an ice-water bath;

[0015] And / or, the coagulant includes any one or more of cyclohexane diisocyanate, hexamethylene diisocyanate, and ethylene carbonate; preferably, by weight percentage, the coagulant includes: 30-50% cyclohexane diisocyanate, 40-60% hexamethylene diisocyanate, and 5-10% ethylene carbonate; more preferably, the coagulant is mixed evenly at 80-100°C for standby;

[0016] Preferably, the volume ratio of the slow-release nutrient slurry to the coagulant is 2.5-3:1.

[0017] Further, step S4 includes: first preheating the water-retaining layer to 65-75°C, and then coating the slow-release nutrient slurry and the coagulant on the water-retaining layer; preferably, the coating thickness of the slow-release nutrient slurry and the coagulant is 2-3 mm.

[0018] According to another aspect of the present application, a slow-release water-retaining composite material is provided, and the slow-release water-retaining composite material is prepared by any of the above preparation methods.

[0019] According to still another aspect of the present application, a slow-release water-retaining vegetation bag is provided, which is characterized in that the slow-release water-retaining vegetation bag is made of the above slow-release water-retaining composite material.

[0020] According to yet another aspect of the present application, an application of the slow-release water-retaining vegetation bag as described above in planting plants in the soil of a mining waste dump is provided.

[0021] Further, the slow-release water-retaining vegetation bag is placed and fixed in the soil, and sufficient watering is completed within 3 hours after planting the plants.

[0022] Applying the technical solution of the present invention, the slow-release water-retaining composite material obtained by the above preparation method has fast water absorption and large water storage capacity. Moreover, since the material has pores, plant roots can grow through it, avoiding the confinement of the plant roots by the made planting bags. In this application, the slow-release nutrient slurry and the coagulant are coated on the water-retaining layer, and the release rate of nutrients is slow. It is not only suitable for the stable growth of plants, but also can maintain the stable nutrient requirements of plant roots for a long time with less nutrient input, avoiding the nutrient loss during the application of traditional fertilizers, and being relatively economical and efficient. And this slow-release water-retaining composite material has a fast degradation rate and a continuous decrease in quality, avoiding secondary pollution to the soil environment and being safer and more reliable than traditional powdery water-absorbing resin water-retaining agents. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The specification drawings forming a part of this application are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0024] Figure 1 shows the curve of the water absorption multiple versus time according to Embodiment 1 of the present invention;

[0025] Figure 2 shows the curve of the water retention rate versus time according to Embodiment 1 of the present invention;

[0026] Figure 3 shows the survival rate of the restoration plants according to Application Example 1 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] It should be noted that, without conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the drawings and in combination with the embodiments.

[0028] As analyzed in the background art of this application, there are problems in the prior art that the soil water retention capacity of the waste dump in mining areas is poor, the nutrients are barren, and it is difficult for plants to grow. To solve this problem, this application provides a slow-release water-retaining composite material and its preparation method, a planting bag containing the same, and an application.

[0029] According to a typical embodiment of the present application, a method for preparing a slow-release water-retaining composite material is provided. The preparation method includes the following steps: Step S1, mixing pure cotton fabric with a solvent, an alkaline aqueous solution, and urea, reacting for a period of time to obtain a pretreatment system; Step S2, adding chloroacetic acid to the pretreatment system for reaction. After the reaction is completed, washing and drying the pure cotton fabric to obtain pretreated pure cotton fabric; Step S3, putting the pretreated pure cotton fabric into water, keeping the temperature constant at 65-75°C, adding a peroxide initiator and a neutralizing solution for grafting reaction. After cooling, washing and drying the fabric, boiling the dried fabric in water, and then drying to obtain a water-retaining layer; Step S4, coating the slow-release nutrient slurry and a coagulant on the water-retaining layer to obtain the slow-release water-retaining composite material.

[0030] The slow-release water-retaining composite material obtained by the above preparation method has fast water absorption and a large water storage capacity. Moreover, due to the pores in the material, plant roots can grow through it, avoiding the confinement of the plant roots by the formed planting bags. In the present application, the slow-release nutrient slurry and the coagulant are coated on the water-retaining layer, and the release rate of nutrients is slow, which is not only suitable for the stable growth of plants, but also can maintain the stable nutritional requirements of plant roots for a long time with less nutrient input, avoiding nutrient loss during the application of traditional fertilizers, and being relatively economical and efficient. And this slow-release water-retaining composite material has a fast degradation rate and a continuous decrease in quality, avoiding secondary pollution to the soil environment, and being safer and more reliable than traditional powdery water-absorbing resin water retainers.

[0031] Through the treatment of the above steps S1 and S2, a porous structure can be formed on the pure cotton grey fabric, and the prepared pretreated grey fabric has good water absorption and water storage capacity. Compared with other types of fabrics, such as geotextiles, the pure cotton grey fabric has appropriate strength, which is convenient for the growth of plant roots, avoids the confinement of the plant roots by the made planting bags, and is easy to degrade, thus avoiding pollution to the soil. The pure cotton grey fabric as the starting material can be selected from the prior art. In some embodiments of the present application, the pure cotton grey fabric is a dry pure cotton grey fabric after removing surface impurities. For example, impurities such as sizing agents on the surface of the pure cotton grey fabric are removed by washing with water to avoid the influence of impurities on subsequent treatment. The thickness of the above pure cotton grey fabric can be selected as needed. In some preferred embodiments of the present application, the pure cotton grey fabric is 500-800 g / ㎡, which not only has good water absorption and water storage performance, but also has appropriate toughness and is convenient to use. More preferably, the thickness of the pure cotton grey fabric is 14-15 ounces, and the comprehensive performance of the prepared water retention layer is better. In some embodiments, the pure cotton grey fabric is placed in a polypropylene bag for reaction. Since the solvent and other components in the solvent can pass through the polypropylene bag smoothly, laying the cotton cloth flat in the bag makes the cotton cloth more unfolded, which is beneficial to increasing the contact area between the cotton cloth and the reaction system, improving the reaction efficiency, and being placed in the bag is convenient for fishing the cotton cloth to avoid damaging the cotton cloth during the operation process; the cloth can be taken out of the bag after the subsequent grafting reaction is completed. Those skilled in the art should understand that the above bag for containing the pure cotton grey fabric is not limited to polypropylene material, and bags made of other materials with similar properties are also acceptable.

[0032] The type and dosage of the above solvent can be selected from the prior art. In some embodiments of the present application, the solvent is anhydrous ethanol, which not only has good solubility for each component of the reaction system, but also can pass through the polypropylene bag well to promote the formation of a porous structure on the cotton cloth. Among them, when anhydrous ethanol is used as the solvent, the effect is particularly prominent. Preferably, the liquor ratio is 1: 2.5-3, that is, the mass ratio of the pure cotton grey fabric to the solvent is 1: 2.5-3, which is beneficial to improving the reaction rate and effect.

[0033] The alkaline aqueous solution in step S1 can be selected from the prior art, such as one or more selected from sodium hydroxide aqueous solution and potassium hydroxide aqueous solution. Preferably, the concentration of the alkaline solution is 14-16%, and preferably, the dosage of the alkaline solution is 4-5% of the weight of the pure cotton grey fabric. Under the action of alkali, the pure cotton grey fabric can generate alkali cellulose, aiming to break hydrogen bonds and release more hydroxyl groups, which is beneficial to improving its water absorption performance. In some embodiments, the dosage of urea is 0.1-0.3% of the weight of the pure cotton grey fabric.

[0034] In some embodiments of the present application, the reaction temperature in step S1 is 35-40 °C, which has good conversion rate and relatively appropriate reaction rate. Preferably, the reaction time is 20-30 min.

[0035] In some embodiments of the present application, the above-mentioned step S2 includes: adding chloroacetic acid to the pretreatment system, raising the temperature of the system to 40-45°C, reacting for 20-30 minutes, raising the temperature of the system to 65-70°C, and then reacting for 40-50 minutes. Cool the reaction system to room temperature, wash and dry the greige cloth to obtain the pretreated greige cloth. Through the above treatment steps, the obtained pretreated greige cloth has more pore structures and the pore structures are more uniform, which is beneficial to further improving the water absorption capacity of the water retention layer. Preferably, the chloroacetic acid is an ethanol solution of chloroacetic acid with a concentration of 14-16%. More preferably, the dosage of the ethanol solution of chloroacetic acid is 3-5% of the weight of the pure cotton greige cloth.

[0036] The above-mentioned step S3 performs a grafting reaction on the pure cotton greige cloth to improve the water absorption capacity of the water retention layer. In some embodiments of the present application, step S3 includes: putting the pretreated greige cloth into water with a liquor ratio of 1:2.5-3, keeping the temperature constant at 65-75°C, adding an initiator and a neutralizing solution, stirring evenly, cooling to room temperature, washing and drying the greige cloth, boiling the dried greige cloth in water for 2-2.5 hours, and after boiling, drying the greige cloth to a constant weight to obtain the water retention layer. Through this step of treatment, the grafting effect of the water retention layer is better, and the water absorption capacity of the water retention layer can be further improved. Preferably, during the boiling process, the water is changed every 25-30 minutes, which can more fully remove the unreacted raw materials or impurities on the cloth. In some embodiments, the above-mentioned chloroacetic acid is an ethanol solution of chloroacetic acid with a concentration of 14-16%. More preferably, the dosage of the ethanol solution of chloroacetic acid is 3-5% of the weight of the pure cotton greige cloth.

[0037] In some embodiments of the present application, the above-mentioned neutralizing solution is prepared by the following steps: cooling the container containing acrylic acid in an ice-water bath, adding a 4-5% aqueous sodium bicarbonate solution until the neutralization degree reaches 70-80%, and then adding a crosslinking agent. The addition amount of the crosslinking agent is 0.1-0.3% of the mass of acrylic acid, and stirring evenly to obtain the neutralizing solution. The grafting effect of the neutralizing solution prepared by the above steps and the above-mentioned pretreated pure cotton greige cloth is better, and the water absorption effect and water storage capacity of the water retention layer can be further improved. The above-mentioned crosslinking agent can be selected from the prior art, such as N,N-methylenebisacrylamide.

[0038] The above-mentioned slow-release nutrient slurry can be selected from the prior art, and the present application does not make any limitations. In some embodiments of the present application, by weight percentage, the raw materials of the slow-release nutrient slurry include: 10-20% corn starch, 20-30% wheat straw charcoal, 10-20% urea, 30-50% ethylene carbonate, 1-3% hydrochloric acid with a concentration of 36%-38%, and 1-3% phosphoric acid with a concentration of 85%. The wheat straw charcoal has a small density, a large specific surface area, and contains a large number of oxygen-containing functional groups. When added to the soil, it can reduce the soil bulk density, increase the soil pH value, porosity, and field water holding capacity, thereby improving the adsorption capacity and biological availability of nutrients. At the same time, each kilogram of wheat straw charcoal contains 670 g of organic carbon, 82.2 mg of available phosphorus, and 1590 mg of available potassium, providing a stable phosphorus source and potassium source for plant growth; the urea contains rich amide nitrogen, and the amide nitrogen is absorbed by the crop roots after being converted into ammonium nitrogen, and its conversion is a relatively slow process. Therefore, on the basis of ensuring the effect of ammonium nitrogen, it will not cause the phenomenon of "ammonia toxicity", providing a stable nitrogen source for plants; under the action of ethylene carbonate, phosphoric acid, and hydrochloric acid, the corn starch increases its hydroxyl groups and reaction activity, and can accelerate the speed of film formation during the reaction with the coagulant. Preferably, the above-mentioned slow-release nutrient slurry is prepared by the following method: mixing the above raw materials, reacting at 100-150 °C for 30-70 minutes, cooling to below 100 °C for standby. The hydroxyl groups in the slow-release nutrient slurry prepared by this method are further increased, the reaction activity is further increased, and the speed of film formation during the reaction with the coagulant is further accelerated, thereby further improving the production efficiency and nutrient slow-release effect of the slow-release water-retaining composite material. The cooling method of the slow-release nutrient slurry can refer to the prior art. For example, an ice-water bath can be used.

[0039] The above-mentioned coagulant can be selected from the prior art, and the present application does not make any limitations. In some embodiments of the present application, the coagulant includes any one or more of cyclohexane dimethylene diisocyanate, hexamethylene diisocyanate, and ethylene carbonate. These coagulants have good curing effects and relatively fast speeds after being mixed with the slow-release nutrient slurry. Preferably, by weight percentage, the coagulant includes: 30-50% cyclohexane dimethylene diisocyanate, 40-60% hexamethylene diisocyanate, and 5-10% ethylene carbonate. The curing effect and speed of the coagulant with this composition are further improved. Especially, it can play a synergistic role with the above-mentioned preferred slow-release nutrient slurry, and the curing speed is particularly good, which is more conducive to the retention and slow release of nutrients and improves their utilization rate. In some preferred embodiments, the coagulant is mixed evenly at 80-100 °C for standby, which is convenient for spraying. In some preferred embodiments, the volume ratio of the above-mentioned slow-release nutrient slurry to the coagulant is 2.5-3:1, which is convenient for spraying and has a good curing effect.

[0040] In some embodiments, the above-mentioned step S4 includes: first preheating the water retention layer to 65-75 °C, and then applying the slow-release nutrient slurry and the coagulant to the water retention layer. Preheating the water retention layer before spraying can make the slow-release nutrient slurry and the coagulant combine with the water retention layer more evenly and firmly. In some embodiments, the slow-release nutrient slurry and the coagulant are first mixed evenly and then sprayed. In some embodiments, the coating thickness of the slow-release nutrient slurry and the coagulant is 2-3 mm, and the content of the nutrient components is more appropriate.

[0041] In another typical embodiment of the present application, a slow-release water retention composite material is provided, which is characterized in that the slow-release water retention composite material is prepared by any one of the above-mentioned preparation methods.

[0042] The slow-release water retention composite material of the present application has a fast water absorption rate and a large water storage capacity. Moreover, since the material has pores, the growth of plant roots can pass through it, avoiding the confinement of the plant roots by the made planting bags. In the present application, the slow-release nutrient slurry and the coagulant are applied to the water retention layer, and the release rate of the nutrients is slow. It is not only suitable for the stable growth of plants, but also can maintain the stable nutrient requirements of plant roots for a long time with less nutrient input, avoiding the nutrient loss during the application of traditional fertilizers, and being relatively economical and efficient. And this slow-release water retention composite material has a fast degradation rate and a continuous decrease in quality, avoiding secondary pollution to the soil environment, and being safer and more reliable than traditional powdery water-absorbing resin water retainers.

[0043] According to another typical embodiment of the present application, a slow-release water retention planting bag is provided, which is characterized in that the slow-release water retention planting bag is made of the above-mentioned slow-release water retention composite material.

[0044] For the above-mentioned slow-release water retention planting bag, due to its bag-like structure, it can maintain the stable nutrient requirements of plant roots for a long time with less nutrient input, avoiding the nutrient loss during the application of traditional fertilizers, and being relatively economical and efficient. And this planting bag has a fast degradation rate and a continuous decrease in quality, avoiding secondary pollution to the soil environment, and being safer and more reliable than traditional powdery water-absorbing resin water retainers.

[0045] The above-mentioned slow-release water retention planting bag is cut from the above-mentioned slow-release water retention composite material according to the usage requirements and sewn into a bag, and there are no restrictions on the shape and size. Exemplarily, it is cut into 10 cm × 5 cm for planting herbaceous seeds, 20 cm × 10 cm for planting woody seeds, and 40 cm × 20 cm for planting one- and two-year-old woody seedlings. The cut composite material is folded along the long side and sewn to obtain planting bags with specifications of 5 cm × 5 cm, 10 cm × 10 cm, and 20 cm × 20 cm.

[0046] According to another typical embodiment of the present application, an application of the above-mentioned slow-release water retention planting bag in planting plants in the soil of a mining waste dump is provided.

[0047] Since the slow-release water-retaining vegetation bag of the present application has a large water storage capacity and strong water-retaining performance, it can ensure the water requirements of common plants. The nutrient slow-release layer can maintain the content of soil nutrient elements around the roots. After use, it can significantly improve the nutrient components of the surrounding soil, maintain the water and nutrient conditions required for plant growth within the root range, and improve the survival rate of the planted plants. The high water-retaining slow-release fertilizer vegetation bag has a fast degradation rate and a continuous decrease in quality, and will not have an adverse impact on the environment, making it particularly suitable for the application of planting plants in the soil of the waste dump in the mining area, and contributing to the restoration of the soil in the waste dump of the mining area.

[0048] For the use of the above-mentioned slow-release water-retaining vegetation bag, reference can be made to the prior art. In some embodiments, the slow-release water-retaining vegetation bag is placed in the soil for fixation, and after planting the plants, sufficient watering is completed within 3 hours, and the survival rate of the plants is higher.

[0049] The following will further illustrate the beneficial effects that can be achieved by the present application in combination with examples and comparative examples.

[0050] Example 1

[0051] Preparation of water retention layer

[0052] 1) Select 14.5-ounce pure cotton grey cloth, wash it with water to remove impurities such as surface sizing agents, and then dry it. Put the treated grey cloth into a polypropylene bag, add anhydrous ethanol as a solvent, with a liquor ratio of 1:3, add a 15% sodium hydroxide aqueous solution and 0.2% urea according to 5% of the mass of the grey cloth, and react at 40 °C for 30 minutes. Then add ethanol of 15% chloroacetic acid according to 5% of the mass of the grey cloth, raise the temperature to 40 °C and react for 20 minutes. Then raise the temperature to 70 °C and react for 50 minutes. After cooling to room temperature, wash the grey cloth and the polypropylene bag together with distilled water and dry.

[0053] 2) Prepare a neutralization solution. Put acrylic acid 4-7 times the mass of the grey cloth in a beaker, cool it in an ice-water bath, and add a 5% sodium bicarbonate aqueous solution until the neutralization degree reaches 70%. Add N,N'-methylenebisacrylamide according to 0.2% of the mass of acrylic acid and stir evenly.

[0054] 3) Add distilled water to the grey cloth and the polypropylene bag, with a liquor ratio of 1∶3, keep the temperature constant at 70 °C, add potassium persulfate according to 5% of the mass of the grey cloth, add the prepared neutralization solution, and stir evenly. After cooling to room temperature, take out the grey cloth from the polypropylene bag, wash it with distilled water and dry; boil it in distilled water for 2 hours, change the water every half hour, and then dry it to a constant weight to obtain the water-retaining layer.

[0055] Accurately weigh 10 g of the water retention layer material, place it in a nylon bag and put it into a beaker filled with excessive pure water. Starting from the beginning of the experiment, measure the mass of the water retention layer material after water absorption at intervals of 1 min, 2 min, 4 min, 6 min, 8 min, 10 min, 30 min, 60 min, 120 min, 240 min, 360 min, 480 min, and 600 min respectively. Note that when measuring, lift the nylon bag from the beaker and place it on a standard sieve with 170 meshes, let it stand for 30 seconds until no liquid drips, and then weigh it. Calculate the water absorption multiple at different time points according to Equation 1 and draw a graph, as Figure 1 。

[0056]

[0057] In Equation 1, Q is the water absorption multiple, g / g; m 0 is the mass of the water absorption material, g; m 1 is the mass after water absorption, g.

[0058] Accurately weigh 100 g of the water retention layer material, put it into a beaker filled with excessive ultrapure water to absorb water for 24 h, and then divide it into two groups. One group is placed on a standard sieve with 170 meshes at 30 °C under normal pressure and left to stand, and its mass is weighed at regular intervals. The other group is placed on a standard sieve with 170 meshes at 30 °C and 2 kPa pressure and left to stand, and its mass is weighed at regular intervals. Calculate the water retention rate according to Equation 2 and draw a graph, as Figure 2 。

[0059]

[0060] In Equation 2, S is the water retention rate, %; m 0 is the mass of the water absorption material, g; m 1 is the mass of the water absorption material after 24 h of water absorption, g; m 2 is the mass of the water absorption material after standing for a certain period of time after 24 h of water absorption, g.

[0061] The water retention layer material can absorb nearly 160.2 g / g of distilled water within 1 min, reaching half of the saturated adsorption amount, and has a strong rapid water absorption ability. When the water absorption time of the water retention layer material reaches 360 min, the water absorption multiple has reached a basically stable and nearly saturated state, and the maximum water absorption multiple is 322.6 g / g, indicating a relatively high saturated water absorption capacity.

[0062] The water retention layer material has good water retention properties under both pressure and non-pressure conditions. At 30 °C, it can still retain nearly 80% and 60% of the water respectively after 24 h, which shows that the water retention layer material not only has a fast water absorption rate but also has good water retention properties under a certain pressure.

[0063] Field application test:

[0064] Application Example 1

[0065] Prepare the slow-release nutrient slurry: Its components are by weight percentage: 20% corn starch, 20% wheat straw charcoal, 15% urea, 40% ethylene carbonate, 3% hydrochloric acid with a concentration of 36%, 2% phosphoric acid with a concentration of 85%. Mix the above raw materials evenly, react at 120 °C for 60 minutes, and cool to about 100 °C with an ice-water bath for use.

[0066] Prepare the coagulant: Its components are by weight percentage: 40% cyclohexane dimethylene diisocyanate, 55% hexamethylene diisocyanate, 5% ethylene carbonate. Mix evenly at 100 °C for use.

[0067] Preheat the water-retaining layers prepared in Example 1 and Comparative Example 1 to 70 °C respectively. Then mix the above slow-release nutrient slurry and coagulant in a volume ratio of 3:1, and spray it onto the water-retaining layer to solidify it into a nutrient slow-release layer. The spraying thickness is 3 mm, and the obtained material is a nutrient slow-release water-retaining composite material. Cut and sew the above materials into corresponding vegetation bags. The specifications of the vegetation bags are 20 cm × 20 cm and 5 cm × 5 cm respectively. Among them, Caragana korshinskii and Hippohae rhamnoides use 20 cm × 20 cm vegetation bags with two-year-old woody seedlings, and Astragalus adsurgens and Medicago sativa use 5 cm × 5 cm vegetation bags with herbaceous plants.

[0068] Site selection: The inner waste dump in the mining area, and its soil is all reclaimed soil, which is relatively compacted due to the rolling of dump trucks. Among the soil particles at the site, the clay composition accounts for 12.25% - 18.34%, the sand composition accounts for 34.9% - 45.0%, and the silt and gravel composition accounts for 42.7% - 46.8%. The texture belongs to "loam" among the three major soil types.

[0069] To avoid the influence of terrain factors on the test results, select 9 plots with the same and relatively flat terrain conditions. The area of each plot is 10 m 2 , and the plot spacing is 5 m. The plots are divided into three groups, with three replicates in each group. One group is planted with vegetation bags containing high water-retaining slow-release fertilizer, and the other group is directly planted in the soil of the waste dump. Among them, Caragana korshinskii and Hippohae rhamnoides use two-year-old woody seedlings with a plant spacing of 50 cm × 50 cm, and Astragalus adsurgens and Medicago sativa use herbaceous plants with a seed sowing density of 30 seeds / m 2 , and rain shelters are added on the top for rain shelter treatment. Water the 6 plots thoroughly once. Start counting data after Astragalus adsurgens and Medicago sativa germinate completely on the 20th day. On the 20th, 30th, 40th, 50th, and 60th days respectively, measure the soil water content, available nitrogen, available phosphorus, available potassium and other indicators of the three groups of plots. The results are shown in Table 1; Count the number of surviving plants in Example 1 and the control group and calculate the survival rate. The results are as Figure 3 .

[0070] Table 1

[0071]

[0072] As can be seen from Table 1, the soil moisture of the composite vegetation bags in Example 1 and the control plot gradually decreases with time, and the water content of the composite vegetation bag plots in each period is higher than that of the control. The soil moisture content of the composite vegetation bags in Example 1 drops below 15% only after 50 days, while that of the control plot drops below 15% on the 30th day, which can ensure the water requirements of common plants. The available nitrogen, available phosphorus, and available potassium in the soil inside the composite material vegetation bags are increased several times compared to the soil in the control plot. The available nitrogen is increased by 6 times, the available phosphorus is increased by 11 times, and the available potassium is increased by 4 times. The contents of available nitrogen and available potassium gradually increase with time.

[0073] From Figure 3 it can be seen that the survival rate of the plants planted using the composite vegetation bags is higher than that of the control in all time periods. Among them, the survival rate of the control group drops rapidly after 30 days. The survival rate of the shrub Caragana korshinskii is lower than 15% at 60 days, and the survival rates of the two herbaceous plants Astragalus adsurgens and Medicago sativa are lower than 5%; the survival rates of the two shrubs Hippophae rhamnoides and Caragana korshinskii planted using the composite vegetation bags are higher than 60% at 60 days, and the survival rate is 6 times that of the control. The survival rates of the two herbaceous plants Astragalus adsurgens and Medicago sativa are higher than 40% at 60 days, and the survival rate is 8 times that of the control.

[0074] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects. The high water-retaining and slow-release fertilizer vegetation bag for the restoration of the waste dump in the mining area described in the present invention can quickly absorb water, and the water-retaining layer material can absorb nearly 160.2 g / g of water within 1 minute; it has a large water storage capacity, and the maximum water absorption multiple is 322.6 g / g; it has strong water-retaining performance and can ensure the water requirements of common plants within 50 days. And it can maintain the soil nutrient elements around the roots and meet the requirements of plants for nitrogen, phosphorus, and potassium for growth.

[0075] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of a sustained-release water-retaining composite material, characterized in that, it comprises the following steps: Step S1, mix pure cotton greige cloth with a solvent, an alkaline aqueous solution, and urea, react for a period of time to obtain a pretreatment system, the temperature of the reaction is 35-40 °C, and the reaction time is 20-30 min; Step S2, add chloroacetic acid to the pretreatment system, raise the temperature of the system to 40-45 °C, react for 20-30 min, raise the temperature of the system to 65-70 °C, and then react for 40-50 min. Cool the reaction system to room temperature, wash and dry the pure cotton greige cloth to obtain a pretreated pure cotton greige cloth; Step S3, put the pretreated pure cotton greige cloth into water, keep the temperature constant at 65-75 °C, add a peroxide initiator and a neutralizing solution for grafting reaction. After cooling, wash and dry the greige cloth, boil the dried greige cloth with water, and then dry it to obtain a water-retaining layer; Step S4, apply the sustained-release nutrient slurry and a coagulant to the water-retaining layer to obtain a sustained-release water-retaining composite material; The neutralizing solution is obtained by the following preparation method, and the preparation method includes: cool the container containing acrylic acid in an ice-water bath, add a 4-5% sodium bicarbonate aqueous solution until the neutralization degree is 70-80%, and then add a crosslinking agent. The addition amount of the crosslinking agent is 0.1-0.3% of the mass of acrylic acid, and stir evenly to obtain a neutralizing solution.

2. The preparation method according to claim 1, characterized in that, in the step S1, the pure cotton greige cloth is a dried pure cotton greige cloth after removing surface impurities.

3. The preparation method according to claim 2, characterized in that, the thickness of the pure cotton greige cloth is 14-15 ounces.

4. The preparation method according to claim 2, characterized in that, react the pure cotton greige cloth in a polypropylene bag; and / or, the solvent is anhydrous ethanol; and / or, the alkaline aqueous solution is selected from one or more of sodium hydroxide aqueous solution and potassium hydroxide aqueous solution; and / or, the dosage of urea is 0.1-0.3% of the weight of the pure cotton greige cloth.

5. The preparation method according to claim 4, characterized in that, the bath ratio of the solvent is 1:2.5-3.

6. The preparation method according to claim 4, characterized in that, the concentration of the alkaline aqueous solution is 14-16%.

7. The preparation method according to claim 6, characterized in that, the dosage of the alkaline aqueous solution is 4-5% of the weight of the pure cotton greige cloth.

8. The preparation method according to claim 1, characterized in that, the chloroacetic acid is an ethanol solution of chloroacetic acid with a concentration of 14-16%.

9. The preparation method according to claim 8, characterized in that, the dosage of the ethanol solution of chloroacetic acid is 3-5% of the weight of the pure cotton greige cloth.

10. The preparation method according to claim 1, characterized in that, Step S3 includes: putting the pretreated blank fabric into water with a bath ratio of 1:2.5 - 3, keeping the temperature constant at 65 - 75°C, adding an initiator and a neutralizing solution, stirring evenly, after cooling to room temperature, washing and drying the blank fabric, boiling the dried blank fabric in water for 2 - 2.5 h, and after the water boiling is completed, drying the blank fabric to a constant weight to obtain a water retention layer.

11. According to the preparation method described in claim 10, characterized in that, in step S3, during the process of boiling with water, change the water every 25 - 30 minutes.

12. According to the preparation method described in claim 10, characterized in that, the initiator includes any one or more of potassium persulfate and ammonium persulfate, and the dosage of the initiator is 3 - 5% of the weight of the blank fabric.

13. According to the preparation method described in claim 1, characterized in that, the crosslinking agent includes N,N - methylene bisacrylamide.

14. According to the preparation method described in claim 1, characterized in that, by weight percentage, the raw materials of the slow - release nutrient slurry include: 10 - 20% of corn starch, 20 - 30% of wheat straw charcoal, 10 - 20% of urea, 30 - 50% of ethylene carbonate, 1 - 3% of hydrochloric acid with a concentration of 36% - 38%, and 1 - 3% of phosphoric acid with a concentration of 85%; and / or, the coagulant includes any one or more of cyclohexane diisocyanate, hexamethylene diisocyanate, and ethylene carbonate.

15. According to the preparation method described in claim 14, characterized in that, the slow - release nutrient slurry is prepared by the following method: mixing the raw materials, reacting at 100 - 150°C for 30 - 70 minutes, and cooling to below 100°C for standby.

16. According to the preparation method described in claim 15, characterized in that, the cooling is carried out using an ice - water bath.

17. According to the preparation method described in claim 14, characterized in that, by weight percentage, the coagulant includes: 30 - 50% of cyclohexane diisocyanate, 40 - 60% of hexamethylene diisocyanate, and 5 - 10% of ethylene carbonate.

18. According to the preparation method described in claim 14, characterized in that, mix the coagulant evenly at 80 - 100°C for standby.

19. According to the preparation method described in claim 14, characterized in that, the volume ratio of the slow - release nutrient slurry to the coagulant is 2.5 - 3∶1.

20. According to the preparation method described in claim 14, characterized in that, step S4 includes: first preheating the water retention layer to 65 - 75°C, and then coating the slow - release nutrient slurry and the coagulant onto the water retention layer.

21. According to the preparation method described in claim 20, characterized in that, the coating thickness of the slow - release nutrient slurry and the coagulant is 2 - 3 mm.

22. A slow - release water - retaining composite material, characterized in that, the slow - release water - retaining composite material is prepared by the preparation method described in any one of claims 1 to 21.

23. A slow - release water - retaining vegetation bag, characterized in that, the slow - release water - retaining vegetation bag is made of the slow - release water - retaining composite material described in claim 22.

24. Application of the slow-release water-retaining vegetation bag as described in claim 23 in planting plants in the soil of the waste dump in the mining area.

25. According to the application described in claim 24, it is characterized in that the slow-release water-retaining vegetation bag is placed and fixed in the soil, and after planting the plants, sufficient watering is completed within 3 hours.

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