A method for preparing hydrogel using waste cotton, the hydrogel and its application in the drying treatment of landfill leachate

Abstract

The present invention provides a method for preparing a hydrogel using waste cotton, the hydrogel and its application in the drying treatment of landfill leachate. The method comprises the following steps: waste cotton is subjected to bleaching treatment, alkalization reaction and etherification reaction to obtain sodium carboxymethylcellulose; graphene oxide, a sulfur source and a copper source are subjected to a hydrothermal reaction to obtain a copper sulfide-reduced graphene oxide nanocomposite; sodium carboxymethylcellulose, the copper sulfide-reduced graphene oxide nanocomposite and a chitosan compound are subjected to a crosslinking reaction to obtain a double-network hydrogel. The hydrogel of the present invention can rapidly absorb and retain a large amount of water, significantly improve the evaporation efficiency, can be used to absorb the leachate on the surface of the garbage, can rapidly form a hydrogel-vapor interface, and then perform light evaporation, thereby achieving the purpose of low-energy consumption and high-speed drying of landfill leachate.

Description

Technical Field

[0001] The present invention relates to the technical field of garbage drying, and particularly to a method for preparing hydrogel using waste cotton, the hydrogel and its application in the drying treatment of landfill leachate. Background Art

[0002] In order to treat domestic garbage, whether it is incineration or other heat treatment processes such as pyrolysis gasification, the raw garbage needs to be dried. In the drying process, the conventional treatment method is to use heating, which requires a large amount of energy. In this application, visible light is used to dry domestic garbage. While the photothermal material and the hydrogel are combined to evaporate water, photons can cleave water from the hydrogel-vapor interface, evaporating the water contained in the domestic garbage. With their synergistic effects, the drying of the garbage is completed. By combining the photothermal material and the hydrogel and combining the photon effect to evaporate the water in the domestic garbage, the garbage is dried, reducing the energy consumption of garbage drying.

[0003] When the raw garbage is stacked in the garbage storage tank, a certain amount of leachate will be generated, which is difficult to be completely separated. Therefore, it is necessary to dry the raw garbage based on the on-site environment of the garbage storage tank. An evaporator made by combining the theory that the water evaporation rate at the hydrogel-vapor interface is higher than the thermal evaporation under specific visible light irradiation and the photothermal material and the hydrogel can complete the drying of the garbage.

[0004] CN113149312A discloses a device and method for surface photothermal evaporation treatment of landfill leachate membrane separation concentrate, belonging to the technical field of landfill leachate membrane concentrate treatment. It includes a condenser, a reaction tank, an evaporation table, a hydrophilic porous material layer, a photothermal porous material layer, an inclined transparent condensation top cover, a transparent side wall, a crystal salt collection box, a condensed water collection tank and a condensed water outlet; the condenser is embedded in the inclined transparent condensation top cover; the inclined transparent condensation top cover and the transparent side wall cover the crystal salt collection box; the reaction tank is placed in the crystal salt collection box; the evaporation table is located at the edge of the reaction tank, and the evaporation table is successively attached with a hydrophilic porous material layer and a photothermal porous material layer from bottom to top, and the hydrophilic porous material layer extends to the side wall of the reaction tank. In this reactor, the air internal circulation is used to promote the air convection on the surface of the photothermal material and strengthen the surface evaporation rate of the photothermal material. In this method, a layer of hydrophilic porous material needs to be separately set to adsorb water, and then a layer of photothermal material needs to be set to catalyze the reaction to evaporate water, and it is also necessary to promote the evaporation rate of the garbage surface in the presence of a photocatalyst, which results in a relatively long time required to complete the drying of the garbage.

[0005] CN215855213U discloses a garbage leachate treatment device, including a reservoir, a photothermal evaporation sphere and a light-transmitting cover. The light-transmitting cover covers outside the reservoir, the photothermal evaporation sphere is laid inside the reservoir, a vapor flow fan is correspondingly arranged above the photothermal evaporation sphere, a fresh water tank is arranged around the reservoir, a condenser is further arranged inside the light-transmitting cover, and a water outlet pipe of the condenser is communicated with a water pump and is connected to the reservoir. This device uses the photothermal evaporation sphere to utilize light energy and convert it into heat energy to heat and evaporate the leachate, separating water, volatile small molecule substances, salts, heavy metals, suspended matter bacteria, etc. in the garbage leachate. However, it only discloses that the photothermal evaporation sphere is a spherical floating object structure wrapped by a flexible nano black gold material, and the black gold material is mostly a graphene material loaded with metals. Although it can utilize light energy and convert it into heat energy to heat and evaporate the leachate, it does not have the ability to adsorb liquids, which also results in a slow evaporation rate of the leachate and requires a relatively long time to complete the drying of the garbage.

[0006] In view of this, the present invention is specifically proposed. Summary of the Invention

[0007] The purpose of the present invention is to provide a method for preparing a hydrogel using waste cotton, the hydrogel and its application in the drying treatment of garbage leachate. The hydrogel prepared by the method of the present invention can effectively utilize photons to directly cleave water clusters at the hydrogel-vapor interface, and is compounded with a photothermal material to prepare a hydrogel. The evaporation rate is higher than that of common hydrogel materials. Using it can absorb the leachate on the surface of the garbage, quickly form a hydrogel-vapor interface, and then perform light evaporation to achieve rapid drying of the garbage leachate.

[0008] In order to achieve the above object of the present invention, the following technical solutions are specifically adopted:

[0009] In the first aspect, the present invention provides a method for preparing a hydrogel using waste cotton, and the method includes the following steps:

[0010] The waste cotton is subjected to bleaching treatment, alkalization reaction and etherification reaction to obtain sodium carboxymethyl cellulose;

[0011] Graphene oxide, a sulfur source and a copper source are subjected to a hydrothermal reaction to obtain a copper sulfide-reduced graphene oxide nanocomposite;

[0012] Sodium carboxymethyl cellulose, the copper sulfide-reduced graphene oxide nanocomposite and a chitosan compound are subjected to a cross-linking reaction to obtain a double-network hydrogel.

[0013] In the present invention, sodium carboxymethyl cellulose is first prepared from waste cotton, and at the same time, copper sulfide-reduced graphene oxide nano-photothermal material is prepared. Then, sodium carboxymethyl cellulose, copper sulfide-reduced graphene oxide nano-photothermal material and chitosan compounds are crosslinked to obtain chitosan compound-sodium carboxymethyl cellulose-CuS / rGO hydrogel. Finally, it is impregnated in a solution containing an iron source to obtain a double-network hydrogel. This hydrogel can absorb and retain a large amount of water, provide a humid environment for specific light-driven interfacial water evaporation, and improve the evaporation efficiency. Using it, the leachate on the surface of garbage can be absorbed, a hydrogel-vapor interface can be quickly formed, and then light evaporation is carried out to achieve rapid drying of the garbage leachate.

[0014] Among them, graphene oxide, sulfur source and copper source are subjected to a hydrothermal reaction to obtain a copper sulfide-reduced graphene oxide nano-composite material; in the present application, the network of macroporous graphene oxide modified by copper sulfide has better porosity and high specific surface area, and the defect structure of CuS particles can cause surface carrier migration, thus forming a plasmon resonance effect similar to that of noble metal nanoparticles to generate heat; in particular, the present application preferably uses acetylcysteine as the sulfur source, and the acetyl group contained therein can better improve the binding ability of CuS and graphene oxide. Moreover, the copper sulfide-reduced graphene oxide nano-composite material prepared by this method has better compatibility with sodium carboxymethyl cellulose and chitosan compounds. Therefore, in the present invention, the hydrogel can be doped with the photothermal material CuS-rGO to improve the absorbance of the hydrogel, increase the photothermal effect of the hydrogel, and achieve rapid drying of the garbage leachate.

[0015] Among them, after sodium carboxymethyl cellulose, copper sulfide-reduced graphene oxide nano-composite material and chitosan compounds are crosslinked, the obtained hydrogel has a large surface area and high porosity, which not only further improves the adsorption performance of the hydrogel, but also combines with the photo-molecular effect to efficiently evaporate the water at the hydrogel-air interface by using light, and the evaporation efficiency is much higher than that of thermal evaporation.

[0016] Among them, when impregnated in a solution containing an iron source, Fe 3+ acts as the central atom, and through sp 3 d 2 or d 2 sp 3 hybridization provides 6 empty orbitals, and the O in the carboxyl group can provide lone pair electrons, and a coordination bond is formed between the two, so as to realize the coordination of sodium carboxymethyl cellulose and Fe 3+ ; when preparing the hydrogel, metal ions coordinate with the carboxymethyl in sodium carboxymethyl cellulose to crosslink it to form a three-dimensional network structure, and wrap a large number of water molecules to form a hydrogel.

[0017] Preferably, the steps of the bleaching treatment include:

[0018] Soak the waste cotton in an aqueous solution of hydrogen peroxide, then wash, crush and dry it in sequence to obtain the bleached waste cotton.

[0019] Preferably, the temperature of the bleaching treatment is 70 - 80 °C, such as 70 °C, 72 °C, 74 °C, 76 °C, 78 °C, 80 °C, etc., and the time is 20 - 40 min, such as 20 min, 22 min, 24 min, 26 min, 28 min, 30 min, 32 min, 34 min, 36 min, 38 min, 40 min, etc.

[0020] Preferably, the hydrogen peroxide content in the aqueous solution of hydrogen peroxide is 5 - 25 wt%, such as 5 wt%, 6 wt%, 8 wt%, 10 wt%, 12 wt%, 14 wt%, 16 wt%, 18 wt%, 20 wt%, 22 wt%, 24 wt%, 25 wt%, etc.

[0021] Preferably, the liquor ratio of the bleaching treatment is 1:(5 - 25), such as 1:5, 1:6, 1:8, 1:10, 1:12, 1:14, 1:16, 1:18, 1:20, 1:22, 1:24, 1:25, etc. (This liquor ratio refers to the ratio of the mass of the waste cotton to the mass of the aqueous solution of hydrogen peroxide.)

[0022] Preferably, the steps of the alkalization reaction include:

[0023] Place the bleached waste cotton in a sodium hydroxide solution for heat treatment, and then dry it to obtain alkali cellulose.

[0024] Preferably, the temperature of the alkalization reaction is 30 - 40 °C, such as 30 °C, 32 °C, 34 °C, 36 °C, 38 °C, 40 °C, etc., and the time is 1 - 3 h, such as 1 h, 1.2 h, 1.4 h, 1.6 h, 1.8 h, 2 h, 2.2 h, 2.4 h, 2.6 h, 2.8 h, 3 h, etc.

[0025] Preferably, the sodium hydroxide content in the sodium hydroxide solution is 30 - 40 wt%, such as 30 wt%, 32 wt%, 34 wt%, 36 wt%, 38 wt%, 40 wt%, etc.

[0026] Preferably, the solvent in the sodium hydroxide solution is a mixed solution of water and ethanol.

[0027] Preferably, the volume ratio of water to ethanol is (5 - 15):1, such as 5:1, 6:1, 8:1, 10:1, 12:1, 14:1, 15:1, etc.

[0028] Preferably, the bath ratio of the alkalization reaction is 1:(10 - 20), for example, it can be 1:10, 1:12, 1:14, 1:16, 1:18, 1:20, etc. (This bath ratio refers to the ratio of the mass of the bleached waste cotton to the mass of the sodium hydroxide solution.)

[0029] Preferably, the steps of the etherification reaction include:

[0030] Mix the alkali cellulose, chloroacetic acid and ethanol, carry out the reaction, and then carry out drying to obtain sodium carboxymethyl cellulose.

[0031] Preferably, the mass ratio of the alkali cellulose, chloroacetic acid and ethanol is 1:(0.5 - 1.5):(5 - 15);

[0032] Among them, "0.5 - 1.5" can be, for example, 0.5, 0.6, 0.8, 1, 1.2, 1.5, etc.;

[0033] Among them, "5 - 15" can be, for example, 5, 6, 8, 10, 12, 14, 15, etc.

[0034] Preferably, the etherification reaction includes: first reacting at 45 - 55°C (for example, it can be 45°C, 46°C, 48°C, 50°C, 52°C, 54°C, 55°C, etc.) for 30 - 50 min (for example, it can be 30 min, 32 min, 34 min, 36 min, 38 min, 40 min, 42 min, 44 min, 46 min, 48 min, 50 min, etc.), and then raising the temperature to 70 - 80°C (for example, it can be 70°C, 72°C, 74°C, 76°C, 78°C, 80°C, etc.) and reacting for 1 - 2 h (for example, it can be 1 h, 1.2 h, 1.4 h, 1.6 h, 1.8 h, 2 h, etc.).

[0035] Preferably, the sodium carboxymethyl cellulose is prepared by the following steps:

[0036] S1. Bleaching treatment:

[0037] Place the waste cotton in an aqueous solution of hydrogen peroxide with a concentration of 5 - 25 wt%, soak it at 70 - 80°C for 20 - 40 min, and then wash, crush and dry it in sequence to obtain the bleached waste cotton.

[0038] S2. Alkalization reaction:

[0039] Place the bleached waste cotton in an ethanol aqueous solution of sodium hydroxide with a concentration of 30 - 40 wt%, heat and react at 30 - 40°C for 1 - 3 h, and then carry out drying to obtain alkali cellulose.

[0040] S3. Etherification reaction:

[0041] Mix alkali cellulose, chloroacetic acid, and ethanol with a mass ratio of 1:(0.5 - 1.5):(5 - 15), first react at 45 - 55 °C for 30 - 50 min, then raise the temperature to 70 - 80 °C and react for 1 - 2 h, and then perform drying to obtain sodium carboxymethyl cellulose.

[0042] Preferably, the copper sulfide-reduced graphene oxide nanocomposite is prepared by the following steps:

[0043] (a) Disperse graphene oxide in water, perform ultrasonic treatment to obtain a graphene oxide dispersion, and then add a sulfur source and stir to obtain a graphene oxide solution containing the sulfur source;

[0044] (b) Dissolve a copper source in water to obtain a copper source solution, and then add it to the graphene oxide solution containing the sulfur source to obtain a raw material solution;

[0045] (c) Place the raw material solution in a reaction kettle, perform hydrothermal reaction, and then wash and dry to obtain the copper sulfide-reduced graphene oxide nanocomposite.

[0046] Preferably, the mass ratio of the graphene oxide, sulfur source, and copper source is 1:(15 - 25):(1 - 10);

[0047] Among them, "15 - 25" can be, for example, 15, 16, 18, 20, 22, 24, 25, etc.;

[0048] Among them, "1 - 10" can be, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, etc.

[0049] Preferably, the sulfur source is acetylcysteine.

[0050] Preferably, the copper source includes any one or a combination of at least two of copper chloride, copper sulfate, copper nitrate, or copper acetate.

[0051] Preferably, in step (a), the power of the ultrasonic treatment is 100 - 200 W, which can be, for example, 100 W, 120 W, 140 W, 160 W, 180 W, 200 W, etc., and the time is 1 - 3 h, which can be, for example, 1 h, 1.5 h, 2 h, 2.5 h, 3 h, etc.

[0052] Preferably, in step (c), the temperature of the hydrothermal reaction is 100 - 200 °C, which can be, for example, 100 °C, 120 °C, 140 °C, 160 °C, 180 °C, 200 °C, etc., and the time is 5 - 15 h, which can be, for example, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h, 12 h, 13 h, 14 h, 15 h, etc.

[0053] Preferably, the graphene oxide is prepared by the following steps:

[0054] Mix graphite powder and concentrated sulfuric acid and stir; then add potassium permanganate and stir to react to obtain a first reaction solution; then add water to dilute the first reaction solution, and then add hydrogen peroxide to obtain a second reaction solution; then add dilute hydrochloric acid to the second reaction solution, let it stand overnight to obtain a crude product of graphene oxide; then wash and dry the crude product of graphene oxide in sequence to obtain the graphene oxide (GO).

[0055] Preferably, the graphene oxide is prepared by the following steps:

[0056] Mix graphite powder and concentrated sulfuric acid, and stir at a temperature below 5 °C (such as 5 °C, 4 °C, 3 °C, 2 °C, 1 °C, 0 °C, -1 °C, -2 °C, -3 °C, -4 °C, -5 °C, -6 °C, -8 °C, -10 °C, etc.) for 30 - 50 min (such as 30 min, 32 min, 34 min, 36 min, 38 min, 40 min, etc.);

[0057] After adding potassium permanganate, stir and react at 30 - 40 °C (such as 30 °C, 31 °C, 32 °C, 33 °C, 34 °C, 35 °C, 36 °C, 37 °C, 38 °C, 39 °C, 40 °C, etc.) for 2 - 4 h to obtain a first reaction solution;

[0058] Then add water to dilute the first reaction solution at a temperature below 5 °C (such as 5 °C, 4 °C, 3 °C, 2 °C, 1 °C, 0 °C, -1 °C, -2 °C, -3 °C, -4 °C, -5 °C, -6 °C, -8 °C, -10 °C, etc.), and then add hydrogen peroxide until no bubbles emerge to obtain a second reaction solution;

[0059] Then add dilute hydrochloric acid to the second reaction solution at a temperature below 35 °C (such as 35 °C, 30 °C, 25 °C, 20 °C, 15 °C, 10 °C, 5 °C, etc.), and let it stand at a temperature below 5 °C (such as 5 °C, 4 °C, 3 °C, 2 °C, 1 °C, 0 °C, -1 °C, -2 °C, -3 °C, -4 °C, -5 °C, -6 °C, -8 °C, -10 °C, etc.) for 6 - 18 h (such as 6 h, 8 h, 10 h, 12 h, 14 h, 16 h, 18 h, etc.) to obtain a crude product of graphene oxide;

[0060] Then centrifuge and wash the crude product of graphene oxide with water until the pH value of the washing waste liquid is neutral, and then freeze - dry the washed crude product of graphene oxide to obtain the graphene oxide (GO).

[0061] Preferably, the mass ratio of the graphite powder to the volume of concentrated sulfuric acid (98 wt%) is 1 g:(20 - 30) mL, for example, it can be 1 g:20 mL, 1 g:22 mL, 1 g:24 mL, 1 g:25 mL, 1 g:26 mL, 1 g:28 mL, 1 g:30 mL, etc.

[0062] Preferably, the mass ratio of the graphite powder to potassium permanganate is 1:(3 - 4), for example, it can be 1:3, 1:3.2, 1:3.4, 1:3.5, 1:3.6, 1:3.8, 1:4, etc.

[0063] Preferably, the mass ratio of the graphite powder to the volume of hydrogen peroxide (30 wt%) is 1 g:(8 - 12) mL, for example, it can be 1 g:8 mL, 1 g:8.5 mL, 1 g:9 mL, 1 g:9.5 mL, 1 g:10 mL, 1 g:10.5 mL, 1 g:11 mL, 1 g:11.5 mL, 1 g:12 mL, etc.

[0064] Preferably, the preparation method of the double - network hydrogel comprises the following steps:

[0065] (A) Mix the sodium carboxymethyl cellulose and the copper sulfide - reduced graphene oxide nanocomposite with water respectively to obtain an aqueous solution of sodium carboxymethyl cellulose and a dispersion of the copper sulfide - reduced graphene oxide nanocomposite; dissolve the chitosan - like compound in an acetic acid solution to obtain an acid solution of the chitosan - like compound;

[0066] (B) After mixing the aqueous solution of sodium carboxymethyl cellulose, the dispersion of the copper sulfide - reduced graphene oxide nanocomposite and the acid solution of the chitosan - like compound, carry out a cross - linking reaction under acidic conditions to obtain a cross - linked hydrogel.

[0067] Preferably, the mass ratio of the sodium carboxymethyl cellulose, the copper sulfide - reduced graphene oxide nanocomposite and the chitosan - like compound is (5 - 8):(2 - 4):(1 - 3);

[0068] Among them, "5 - 8" can be, for example, 5, 5.5, 6, 6.5, 7, 7.5, 8, etc.;

[0069] Among them, "2 - 4" can be, for example, 2, 2.5, 3, 3.5, 4, etc.;

[0070] Among them, "1 - 3" can be, for example, 1, 1.5, 2, 2.5, 3, etc.

[0071] Preferably, the chitosan - like compound includes carboxymethyl chitosan.

[0072] Preferably, in step (B), hydrochloric acid needs to be added before the cross - linking reaction.

[0073] Preferably, in step (B), the concentration of the hydrochloric acid is 1.0 - 1.5 mol·L -1 , for example, it can be 1.0 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, etc.

[0074] Preferably, in step (B), the addition amount of the hydrochloric acid accounts for 0.5 - 5% of the total mass of the mixed solution for the crosslinking reaction. For example, it can be 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc.

[0075] Preferably, in step (B), a crosslinking agent needs to be added before the crosslinking reaction.

[0076] Preferably, in step (B), the crosslinking agent is glutaraldehyde.

[0077] Preferably, in step (B), the addition amount of the glutaraldehyde is 0.5 - 5% of the mass of the sodium carboxymethylcellulose. For example, it can be 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc.

[0078] Preferably, in step (B), the temperature of the crosslinking reaction is 20 - 40 °C. For example, it can be 20 °C, 25 °C, 30 °C, 35 °C, 40 °C, etc., and the time is 6 - 18 h. For example, it can be 6 h, 8 h, 10 h, 12 h, 14 h, 16 h, 18 h, etc.

[0079] Preferably, the preparation method of the double-network hydrogel further includes the following steps, that is, after the above step (B), the following step (C) is also included;

[0080] Immerse the crosslinked hydrogel in the solution containing the iron source, and then wash and dry it to obtain the double-network hydrogel.

[0081] Preferably, in step (C), the concentration of the solution containing the iron source is 0.1 - 1 mol / L. For example, it can be 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, etc.

[0082] Preferably, in step (C), the iron source includes ferric chloride.

[0083] Preferably, in step (C), the temperature of the impregnation is below 5°C, for example, it can be 5°C, 4°C, 3°C, 2°C, 1°C, 0°C, etc., and the time is 1 - 3 h, for example, it can be 1 h, 1.5 h, 2 h, 2.5 h, 3 h, etc.

[0084] In a second aspect, the present invention provides a hydrogel, which is prepared by the method for preparing a hydrogel using waste cotton as described in the first aspect.

[0085] In a third aspect, the present invention provides an application of the hydrogel as described in the second aspect in the drying treatment of landfill leachate.

[0086] In the present invention, the hydrogel can be used in the drying treatment of landfill leachate. Not only is the photothermal material compounded with the hydrogel to improve the water evaporation rate, but also based on the theory in the photomolecular effect, liquid can be caused to evaporate from the surface of the garbage without the need for heat. When light irradiates the interface where air and water meet, water molecules can be decomposed and float into the air, that is, evaporation can be caused without any heat source.

[0087] In a fourth aspect, the present invention provides a method for drying landfill leachate, and the drying method includes the following steps:

[0088] Disperse the hydrogel as described in the second aspect in the landfill leachate and irradiate it with light to evaporate the solution in the landfill leachate and complete the drying of the garbage.

[0089] In the present invention, the double-network hydrogel prepared by the above method can be dispersed in the landfill leachate and irradiated with visible light in a certain wavelength range. When the light evaporates the moisture of the original garbage, the air temperature measured above the leachate surface is low and gradually tends to be stable, indicating that heat energy is not the driving force behind it, and it reaches a peak in green light with the best drying effect. The photomolecular effect shows that photons can cleave water clusters from the liquid surface and be released from the water-vapor interface. When light irradiates the interface between air and water, water molecules can be knocked off the water surface and enter the air, thus causing evaporation without any heat source. At the interface between water and air, light can directly cause water to evaporate without heating, and the evaporation efficiency is higher than that of thermal evaporation. Based on this, an evaporator made by compounding a photothermal material with a hydrogel further improves the evaporation efficiency.

[0090] When the leachate water molecules approach the surface of the double-network hydrogel, they will be attracted by the hydrogel, thus forming a biased charge distribution, that is, the water molecules on the surface will have a positive charge, while the hydrogel will have a negative charge. In this way, a strong electric field gradient is formed on the surface of the hydrogel, which will exert a force on the water molecules, called the quadrupole force. The quadrupole force refers to when a dipole molecule is in a non-uniform electric field, it will be subjected to a force that makes its dipole moment align with the direction of the electric field. The magnitude and direction of this force depend on the gradient of the electric field and the shape of the dipole molecule. When photons irradiate the surface of the hydrogel, they will be absorbed by the water molecules, thus exciting the vibration and rotation of the water molecules. These vibrations and rotations will change the dipole moment of the water molecules, thereby changing the quadrupole force they receive. If the energy of the photons is high enough, they can make the quadrupole force of the water molecules exceed the attraction of the hydrogel, so that the water molecules are separated from the surface of the hydrogel. Since the hydrogen bonds between water molecules are very strong, the separated ones are not single water molecules but water clusters, which can contain several to dozens of water molecules. These water clusters will fly away from the surface of the hydrogel and enter the air to form water vapor, thus achieving the reduction of the moisture content of the raw garbage.

[0091] Preferably, the wavelength of the light irradiation is 500 - 520 nm, for example, it can be 500 nm, 510 nm, 515 nm, 520 nm, etc.

[0092] In the present invention, light irradiation with a certain range of wavelengths is adopted. It is found that when the leachate liquid level is higher than the raw garbage, the evaporation rate is lower than the thermal limit, belonging to the normal thermal evaporation stage. When the liquid level is lower than the sample surface, the evaporation rate exceeds the thermal evaporation limit, and through experiments on light irradiation with different wavelengths, it is found that the evaporation rate in the range of 500 - 520 nm is the highest.

[0093] Preferably, the intensity of the light irradiation is 0.5 - 2 kW / m 2 For example, it can be 0.5 kW / m 2 、0.6 kW / m 2 、0.8 kW / m 2 、1 kW / m 2 、1.2 kW / m 2 、1.4 kW / m 2 、1.6 kW / m 2 、1.8 kW / m 2 、2 kW / m 2 etc.

[0094] In the fifth aspect, the present invention provides a drying device for garbage leachate, and the drying device for garbage leachate includes the hydrogel as described in the second aspect.

[0095] Preferably, the drying device for landfill leachate comprises a landfill leachate evaporation pond; wherein, a hydrogel layer formed by coating the side wall and / or the bottom of the landfill leachate evaporation pond with the hydrogel as described in the second aspect is provided.

[0096] Preferably, the drying device for landfill leachate further comprises an evaporation platform arranged at the edge of the landfill leachate evaporation pond; wherein, a hydrogel layer formed by coating the surface of the evaporation platform with the hydrogel as described in the second aspect is provided.

[0097] Compared with the prior art, the present invention has the following beneficial effects:

[0098] (1) The present invention makes full use of waste cotton in the original waste to prepare a hydrogel. The hydrogel has a large surface area and high porosity, and has good adsorption performance, thus fully realizing the utilization of waste cotton in the waste.

[0099] (2) The present invention uses sodium carboxymethyl cellulose, copper sulfide-reduced graphene oxide nanophotothermal material and chitosan compounds prepared from waste cotton for crosslinking to obtain a chitosan compound-sodium carboxymethyl cellulose-CuS / rGO hydrogel, and finally impregnates it in a solution containing an iron source to obtain a double-network hydrogel. This hydrogel can quickly absorb and retain a large amount of water, provide a humid environment for specific light-driven interfacial water evaporation, and significantly improve the evaporation efficiency. Using it can absorb the leachate on the surface of the waste, quickly form a hydrogel-vapor interface, and then perform light evaporation to realize the rapid drying of the landfill leachate.

[0100] (3) The present invention provides a method for treating landfill leachate. The hydrogel material is dispersed in the original landfill leachate to form a hydrogel-vapor interface layer. A visible light-emitting diode is arranged above the waste storage tank, and the hydrogel-vapor interface layer in the waste storage tank is irradiated to make the evaporation efficiency higher than the thermal evaporation efficiency. Detailed Embodiments

[0101] Unless otherwise defined herein, scientific and technical terms used in conjunction with the present invention shall have the meanings commonly understood by those of ordinary skill in the art. The meanings and scopes of the terms should be clear. However, in any case of potential ambiguity, the definitions provided herein shall prevail over any dictionary or extrinsic definition. In the present application, unless otherwise specified, the use of "or" means "and / or". In addition, the use of the term "comprising" and other forms is non-limiting.

[0102] It should be noted that specific details are set forth in the following description to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar generalizations without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0103] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0104] The present invention will be further described below through embodiments. Unless otherwise specified, the materials in the embodiments are prepared according to existing methods or directly purchased from the market.

[0105] Preparation Example 1

[0106] This preparation example provides a graphene oxide, which is prepared by the following steps:

[0107] Take 2 g of graphite powder and 50 mL of concentrated sulfuric acid (98%) and add them to a 500 mL three-necked flask. Stir in an ice bath for 40 min, and then add 7 g of potassium permanganate to the three-necked flask in batches. After adding, transfer the flask to an oil bath at 35 °C and stir for 3 h. At this time, the reaction system is a dark green viscous liquid; then transfer the three-necked flask to an ice bath, add 180 mL of deionized water to the three-necked flask under ice bath conditions, the reaction system is yellowish brown, and then add 20 mL of hydrogen peroxide (30%) dropwise until no bubbles emerge. At this time, the reaction system is bright yellow; then transfer the mixed solution in the three-necked flask to a 1000 mL beaker, add 100 mL of dilute hydrochloric acid (10 wt%), let it stand overnight to obtain a crude product of graphene oxide; then centrifuge and wash the crude product of graphene oxide with water until the pH value of the washing waste liquid is neutral to obtain a viscous black-brown product. Finally, freeze-dry the viscous black-brown product with a freeze dryer to obtain the product graphene oxide (GO).

[0108] Example 1

[0109] This example provides a method for preparing a hydrogel using waste cotton, and the method includes the following steps:

[0110] S1. Bleaching treatment:

[0111] Place the waste cotton in an aqueous solution of hydrogen peroxide at 15 wt%, with a liquor ratio of 1:15, soak at 75 °C for 30 min, rinse 3 times with distilled water to remove the impurities therein, break it and dry it to obtain the bleached waste cotton.

[0112] S2. Alkalization reaction:

[0113] Place the bleached waste cotton in an aqueous ethanol solution of sodium hydroxide at 35 wt% (V 水 :V 乙醇= 9:1), the bath ratio is 1:15, heated and reacted at 35 °C for 2 h, dried to obtain alkali cellulose.

[0114] S3. Etherification reaction:

[0115] Mix alkali cellulose, chloroacetic acid and ethanol with a mass ratio of 1:1.2:10, first react at 50 °C for 40 min, then raise the temperature to 75 °C and react for another 1.5 h to obtain sodium carboxymethyl cellulose, and dry to obtain sodium carboxymethyl cellulose powder.

[0116] S4. Preparation of hydrogel:

[0117] S4-1. Preparation of copper sulfide-reduced graphene oxide nanocomposite (CuS-rGO):

[0118] (a) Disperse 0.2 g of graphene oxide provided in Preparation Example 1 in 200 mL of deionized water, ultrasonicate at a power of 150 W for 2 h to obtain a 1 mg / mL graphene oxide dispersion, then add 4 g of N-acetylcysteine to the graphene oxide dispersion and stir until it is completely dissolved to obtain a graphene oxide solution containing N-acetylcysteine;

[0119] (b) Dissolve 1 g of copper chloride in 9 mL of deionized water, and slowly add the graphene oxide solution containing N-acetylcysteine to obtain a raw material solution;

[0120] (c) Place the above raw material solution in a reaction kettle, react at a constant temperature of 150 °C for 10 h, then wash the product 3 times with anhydrous ethanol and deionized water respectively, and the washed product will be freeze-dried to obtain CuS-rGO.

[0121] S4-2. Preparation of double-network hydrogel:

[0122] (A) Weigh 6 g of sodium carboxymethyl cellulose and mix it with 600 mL of deionized water to obtain an aqueous solution of sodium carboxymethyl cellulose; weigh 3 g of CuS-rGO and disperse it in 300 mL of deionized water to obtain a dispersion of CuS-rGO; weigh 1 g of carboxymethyl chitosan and mix it with 100 mL of 0.2 mol / L acetic acid aqueous solution to obtain an acid solution of carboxymethyl chitosan;

[0123] (B) After mixing the aqueous solution of sodium carboxymethyl cellulose, the dispersion of copper sulfide-reduced graphene oxide nanocomposite and the acid solution of carboxymethyl chitosan, add 2 wt% 1.2 mol / L hydrochloric acid aqueous solution and stir for 3 h, then add 0.12 g of glutaraldehyde and let it stand at room temperature for cross-linking for 12 h to obtain a cross-linked hydrogel;

[0124] (C) The crosslinked hydrogel was placed in an aqueous solution of 0.5 mol / L ferric chloride, impregnated at 0 °C for 2 h, and then the post-crosslinked hydrogel loaded was taken out. Subsequently, the gel was rinsed 3 times with deionized water to remove unreacted substances and excess salt solution. First, it was frozen in a -20 °C refrigerator for 12 h, and then freeze-dried in a freeze dryer for 48 h to completely remove the moisture in the hydrogel, obtaining the double-network hydrogel.

[0125] Example 2

[0126] This example provides a method for preparing a hydrogel using waste cotton, and the method includes the following steps:

[0127] S1. Bleaching treatment:

[0128] The waste cotton was placed in an aqueous solution of 10 wt% hydrogen peroxide with a liquor ratio of 1:20, soaked at 70 °C for 40 min, rinsed 3 times with distilled water to remove the impurities therein, broken and dried to obtain the bleached waste cotton.

[0129] S2. Alkalization reaction:

[0130] The bleached waste cotton was placed in an aqueous ethanol solution of 30 wt% sodium hydroxide (V 水 :V 乙醇 = 9:1) with a liquor ratio of 1:20, heated and reacted at 30 °C for 3 h, and dried to obtain alkali cellulose.

[0131] S3. Etherification reaction:

[0132] The alkali cellulose, chloroacetic acid and ethanol with a mass ratio of 1:1.5:15 were mixed, first reacted at 45 °C for 45 min, then the temperature was raised to 70 °C and reacted for another 2 h to obtain sodium carboxymethyl cellulose, and dried to obtain sodium carboxymethyl cellulose powder.

[0133] S4. Preparation of hydrogel:

[0134] S4-1. Preparation of copper sulfide-reduced graphene oxide nanocomposite (CuS-rGO):

[0135] (a) 0.2 g of graphene oxide provided in Preparation Example 1 was dispersed in 200 mL of deionized water, sonicated at a power of 150 W for 2 h to obtain a 1 mg / mL graphene oxide dispersion, and then 4 g of N-acetylcysteine was added to the graphene oxide dispersion and stirred until it was completely dissolved to obtain a graphene oxide solution containing N-acetylcysteine;

[0136] (b) 1 g of copper chloride was dissolved in 9 mL of deionized water, and slowly added to the graphene oxide solution containing N-acetylcysteine to obtain a raw material solution;

[0137] (c) Place the above raw material solution in a reaction kettle, react at a constant temperature of 120 °C for 12 h, then wash the product 3 times with anhydrous ethanol and deionized water respectively, and the washed product will be freeze-dried to obtain CuS-rGO.

[0138] S4-2. Preparation of double-network hydrogel:

[0139] (A) Weigh 5 g of sodium carboxymethylcellulose and mix it with 500 mL of deionized water to obtain an aqueous solution of sodium carboxymethylcellulose; weigh 2 g of CuS-rGO and disperse it in 200 mL of deionized water to obtain a dispersion of CuS-rGO; weigh 3 g of carboxymethyl chitosan and mix it with 300 mL of 0.2 mol / L acetic acid aqueous solution to obtain an acid solution of carboxymethyl chitosan.

[0140] (B) After mixing the aqueous solution of sodium carboxymethylcellulose, the dispersion of copper sulfide-reduced graphene oxide nanocomposite, and the acid solution of carboxymethyl chitosan, add 2 wt% 1.2 mol / L hydrochloric acid aqueous solution and stir for 3 h, then add 0.1 g of glutaraldehyde, and let it stand for crosslinking at room temperature for 12 h to obtain a crosslinked hydrogel.

[0141] (C) Place the crosslinked hydrogel in an aqueous solution of 0.5 mol / L ferric chloride, immerse it at 0 °C for 2 h, take out the loaded crosslinked hydrogel, and then rinse the gel 3 times with deionized water to remove unreacted substances and excess salt solution. First, freeze it in a -20 °C refrigerator for 12 h, and then freeze-dry it in a freeze dryer for 48 h to completely remove the water in the hydrogel and obtain the double-network hydrogel.

[0142] Example 3

[0143] This example provides a method for preparing a hydrogel using waste cotton, and the method includes the following steps:

[0144] S1. Bleaching treatment:

[0145] Place the waste cotton in an aqueous solution of 20 wt% hydrogen peroxide with a liquor ratio of 1:25, soak it at 80 °C for 20 min, rinse it 3 times with distilled water to remove the impurities therein, break it and dry it to obtain the bleached waste cotton.

[0146] S2. Alkalization reaction:

[0147] Place the bleached waste cotton in a 40 wt% aqueous solution of sodium hydroxide in ethanol (V 水 :V 乙醇 = 9:1) with a liquor ratio of 1:10, heat and react it at 40 °C for 1 h, and dry it to obtain alkali cellulose.

[0148] S3. Etherification reaction:

[0149] Mix alkali cellulose, chloroacetic acid, and ethanol with a mass ratio of 1:0.8:8. First, react at 55 °C for 30 min, then raise the temperature to 80 °C and react for another 1 h to obtain sodium carboxymethyl cellulose, and dry it to obtain sodium carboxymethyl cellulose powder.

[0150] S4. Preparation of hydrogel:

[0151] S4-1. Preparation of copper sulfide-reduced graphene oxide nanocomposite (CuS-rGO):

[0152] (a) Disperse 0.2 g of graphene oxide provided in Preparation Example 1 in 200 mL of deionized water, ultrasonicate at a power of 150 W for 2 h to obtain a 1 mg / mL graphene oxide dispersion, and then add 4 g of acetylcysteine to the graphene oxide dispersion and stir until it is completely dissolved to obtain a graphene oxide solution containing acetylcysteine;

[0153] (b) Dissolve 1 g of copper chloride in 9 mL of deionized water, and slowly add it to the graphene oxide solution containing acetylcysteine to obtain a raw material solution;

[0154] (c) Place the above raw material solution in a reaction kettle, react at a constant temperature of 180 °C for 8 h, then wash the product 3 times each with absolute ethanol and deionized water, and the washed product will be freeze-dried to obtain CuS-rGO.

[0155] S4-2. Preparation of double-network hydrogel:

[0156] (A) Weigh 7 g of sodium carboxymethyl cellulose and mix it with 700 mL of deionized water to obtain an aqueous solution of sodium carboxymethyl cellulose; weigh 2 g of CuS-rGO and disperse it in 200 mL of deionized water to obtain a dispersion of CuS-rGO; weigh 1 g of carboxymethyl chitosan and mix it with 100 mL of 0.2 mol / L acetic acid aqueous solution to obtain an acid solution of carboxymethyl chitosan;

[0157] (B) After mixing the aqueous solution of sodium carboxymethyl cellulose, the dispersion of copper sulfide-reduced graphene oxide nanocomposite, and the acid solution of carboxymethyl chitosan, add 2 wt% 1.2 mol / L hydrochloric acid aqueous solution and stir for 3 h, then add 0.14 g of glutaraldehyde and let it stand at room temperature for cross-linking for 12 h to obtain a cross-linked hydrogel;

[0158] (C) Place the cross-linked hydrogel in an aqueous solution of 0.5 mol / L ferric chloride, immerse it at 0 °C for 2 h, then take out the loaded cross-linked hydrogel, and then rinse the gel 3 times with deionized water to remove unreacted substances and excess salt solution. First, freeze it in a -20 °C refrigerator for 12 h, and then place it in a freeze dryer for freeze-drying for 48 h to completely remove the water in the hydrogel to obtain the double-network hydrogel.

[0159] Example 4

[0160] This example provides a method for preparing hydrogel using waste cotton. The difference from Example 1 is only that 4 g of L-cysteine is used to replace 4 g of acetylcysteine in step (a) of S4-1, and other steps are exactly the same as those in Example 1.

[0161] Example 5

[0162] This example provides a method for preparing hydrogel using waste cotton. The difference from Example 1 is only that the preparation method of S4-1, copper sulfide-reduced graphene oxide nanocomposite (CuS-rGO) is different, which is specifically as follows:

[0163] Weigh 20 mg of graphene oxide and place it in 30 mL of ethanol. Ultrasonic it for 2 h at a power of 150 W to obtain a graphene oxide dispersion liquid, and then add 15 mmol of urea, 0.1 mmol of copper chloride, and 0.1 mmol of thiourea respectively; then place the above raw material liquid in a reaction kettle and react at 160 °C for 12 h; then wash the product 3 times with absolute ethanol and deionized water respectively, and the washed product will be freeze-dried to obtain CuS-rGO.

[0164] Example 6

[0165] This example provides a method for preparing hydrogel using waste cotton. The difference from Example 1 is only that 1 g of hydroxypropyl chitosan is used to replace 1 g of carboxymethyl chitosan in step (A) of S4-2, and other steps are exactly the same as those in Example 1.

[0166] Example 7

[0167] This example provides a method for preparing hydrogel using waste cotton. The difference from Example 1 is only that 1 g of chitosan is used to replace 1 g of carboxymethyl chitosan in step (A) of S4-2, and other steps are exactly the same as those in Example 1.

[0168] Example 8

[0169] This example provides a method for preparing hydrogel using waste cotton. The difference from Example 1 is only that an aqueous solution of 0.5 mol / L copper chloride is used to replace the aqueous solution of 0.5 mol / L ferric chloride in step (C) of S4-2, and other steps are exactly the same as those in Example 1.

[0170] Example 9

[0171] This embodiment provides a method for preparing hydrogel using waste cotton. The difference from Example 1 is that instead of performing the operation of impregnating the aqueous solution of ferric chloride in step (C) of S4-2, the crosslinked hydrogel is directly placed in a -20°C refrigerator and frozen for 12 h, and then placed in a freeze dryer and freeze-dried for 48 h to completely remove the moisture in the hydrogel. Other steps are exactly the same as those in Example 1.

[0172] Comparative Example 1

[0173] This comparative example provides a method for preparing hydrogel using waste cotton. The method includes the following steps:

[0174] S1 to S3: Exactly the same as those in Example 1.

[0175] S4. Preparation of hydrogel:

[0176] (A) Weigh 6 g of sodium carboxymethylcellulose and mix it with 600 mL of deionized water to obtain an aqueous solution of sodium carboxymethylcellulose; weigh 1 g of carboxymethyl chitosan and mix it with 100 mL of 0.2 mol / L acetic acid aqueous solution to obtain an acid solution of carboxymethyl chitosan.

[0177] (B) After mixing the aqueous solution of sodium carboxymethylcellulose and the acid solution of carboxymethyl chitosan, add 2 wt% of 1.2 mol / L hydrochloric acid aqueous solution and stir for 3 h, then add 0.1 g of glutaraldehyde and let it stand at room temperature for crosslinking for 12 h to obtain a crosslinked hydrogel.

[0178] (C) Place the crosslinked hydrogel in an aqueous solution of 0.5 mol / L ferric chloride, impregnate it at 0°C for 2 h, then take out the loaded crosslinked hydrogel, and then rinse the gel 3 times with deionized water to remove unreacted substances and excess salt solution. First, place it in a -20°C refrigerator and freeze it for 12 h, and then place it in a freeze dryer and freeze-dry it for 48 h to completely remove the moisture in the hydrogel to obtain the double-network hydrogel.

[0179] Comparative Example 2

[0180] This comparative example provides a method for preparing hydrogel. The method includes the following steps:

[0181] S1. Weigh 3 g of CuS-rGO and disperse it in 300 mL of deionized water to obtain a dispersion of CuS-rGO; weigh 7 g of carboxymethyl chitosan and mix it with 100 mL of 0.2 mol / L acetic acid aqueous solution to obtain an acid solution of carboxymethyl chitosan.

[0182] S2. After mixing the dispersion of the copper sulfide-reduced graphene oxide nanocomposite and the acidic solution of carboxymethyl chitosan, add 2 wt% of 1.2 mol / L hydrochloric acid aqueous solution and stir for 3 h. Then add 0.05 g of glutaraldehyde and let it stand at room temperature for crosslinking for 12 h to obtain a crosslinked hydrogel;

[0183] (C) Place the crosslinked hydrogel in an aqueous solution of 0.5 mol / L ferric chloride, impregnate it at 0 °C for 2 h, then take out the post-loaded crosslinked hydrogel, and then rinse the gel 3 times with deionized water to remove unreacted substances and excess salt solution. First, freeze it in a -20 °C refrigerator for 12 h, and then freeze-dry it in a freeze dryer for 48 h to completely remove the water in the hydrogel and obtain the double-network hydrogel.

[0184] Comparative Example 3

[0185] This comparative example provides a method for preparing a hydrogel, and the method includes the following steps:

[0186] S1 - S3: Identical to Example 1.

[0187] S4. Preparation of hydrogel:

[0188] S4-1. Preparation of copper sulfide-reduced graphene oxide nanocomposite (CuS-rGO): Identical to Example 1.

[0189] S4-2. Preparation of double-network hydrogel:

[0190] (A) Weigh 7 g of sodium carboxymethyl cellulose and mix it with 600 mL of deionized water to obtain an aqueous solution of sodium carboxymethyl cellulose; weigh 3 g of CuS-rGO and disperse it in 300 mL of deionized water to obtain a dispersion of CuS-rGO;

[0191] (B) After mixing the aqueous solution of sodium carboxymethyl cellulose and the dispersion of copper sulfide-reduced graphene oxide nanocomposite, add 2 wt% of 1.2 mol / L hydrochloric acid aqueous solution and stir for 3 h. Then add 0.14 g of glutaraldehyde and let it stand at room temperature for crosslinking for 12 h to obtain a crosslinked hydrogel;

[0192] (C) Place the crosslinked hydrogel in an aqueous solution of 0.5 mol / L ferric chloride, impregnate it at 0 °C for 2 h, then take out the post-loaded crosslinked hydrogel, and then rinse the gel 3 times with deionized water to remove unreacted substances and excess salt solution. First, freeze it in a -20 °C refrigerator for 12 h, and then freeze-dry it in a freeze dryer for 48 h to completely remove the water in the hydrogel and obtain the double-network hydrogel.

[0193] Comparative Example 4

[0194] This comparative example provides a method for preparing a hydrogel, which is different from Example 1 in that 6 g of sodium carboxymethylcellulose in step (A) of S4-2 is replaced with 6 g of sodium alginate of equal mass, and the other steps are exactly the same as those in Example 1.

[0195] Comparative Example 5

[0196] This comparative example provides a method for preparing a hydrogel, which is different from Example 1 in that 3 g of CuS-rGO in step (A) of S4-2 is replaced with 3 g of TiO 2 -rGO, and the TiO 2 -rGO is prepared by the following steps:

[0197] (i) Disperse 0.2 g of graphene oxide provided in Preparation Example 1 in 200 mL of deionized water, and ultrasonicate it at a power of 150 W for 2 h to obtain a 1 mg / mL graphene oxide dispersion; then weigh 0.5 g of titanium dioxide powder and disperse it in 50 mL of absolute ethanol, and ultrasonicate it at a power of 150 W for 30 min to obtain a titanium dioxide dispersion;

[0198] (ii) Mix the graphene oxide dispersion and the titanium dioxide dispersion, and then slowly add ammonia water until the pH value of the solution in the blender reaches 10 to obtain a raw material solution;

[0199] (iii) Place the above raw material solution in a reaction kettle, keep it at a temperature of 200 °C for 12 h, cool it to room temperature after the reaction is completed, and then wash the product 3 times with absolute ethanol and deionized water respectively. The washed product will be freeze-dried to obtain the TiO 2 -rGO;

[0200] The other steps are exactly the same as those in Example 1.

[0201] Comparative Example 6

[0202] This comparative example provides a method for preparing a hydrogel, which is different from Example 1 in that 1 g of carboxymethyl chitosan in step (A) of S4-2 is replaced with 1 g of polyvinyl alcohol of equal mass, and the other steps are exactly the same as those in Example 1.

[0203] Test Example 1

[0204] Test samples: Hydrogels prepared in Examples 1-9 and hydrogels prepared in Comparative Examples 1-6.

[0205] Test method: Under the irradiation of a sunlight intensity, test the change of the surface temperature, the water absorption and swelling degree, and the sunlight-heated water evaporation rate of the above hydrogels; among them, the water absorption and swelling degree (%) = [(the mass of the gel after water absorption - the initial mass of the gel) / the initial mass of the gel] × 100%.

[0206] The specific test results are shown in Table 1 below:

[0207] Table 1

[0208]

[0209]

[0210] As shown by the data in Table 1, the surface temperature of the hydrogels prepared in Examples 1-9 increased by 20.1-39.7 °C under the irradiation of one sunlight intensity, showing good photothermal conversion efficiency; and the water absorption and swelling degree of the hydrogels of the present invention is 12.23-19.51%, and the photothermal evaporation rate is 2.423-3.531 kg·m -1 ·h -1 . This shows that the hydrogels of the present invention have excellent photothermal conversion efficiency and excellent water absorption performance.

[0211] Test Example 2

[0212] Test samples: Hydrogels prepared in Examples 1-9, hydrogels prepared in Comparative Examples 1-6.

[0213] Test method: The hydrogels were respectively dispersed in an evaporation pond containing landfill leachate and irradiated with light (wavelength 510 nm, intensity 0.5 kW / m 2 ), to evaporate the solution in the landfill leachate and complete the drying of the garbage.

[0214] The specific test results are shown in Table 2 below:

[0215] Table 2

[0216]

[0217]

[0218] As shown by Table 2, the energy required for the liquid water in the landfill leachate to be converted into gaseous water at the same temperature by the hydrogels prepared in Examples 1-9 is only 0.318×10 6 ~0.336×10 6 J, the evaporation rate is 17.2-23.6 L·m -1 ·h -1 , and the amount of landfill leachate treated per unit area per day is 137.6-188.8 L·m -2 ·d -1, the photothermal conversion efficiency is 92.1-97.7%. This shows that the hydrogel of the present invention can quickly absorb and retain a large amount of water, provide a humid environment for specific light-driven interfacial water evaporation, and significantly improve the evaporation efficiency. Using it can absorb the leachate on the surface of garbage, quickly form a hydrogel-vapor interface, and then perform light evaporation, achieving the purpose of low-energy consumption and high-speed drying of garbage leachate at the same time.

[0219] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing hydrogel using waste cotton, characterized in that: The method comprises the following steps: Waste cotton is bleached, alkalized and etherified to obtain sodium carboxymethyl cellulose; Dispersing graphene oxide in water, performing ultrasonic treatment to obtain a graphene oxide dispersion, adding a sulfur source, stirring to obtain a graphene oxide liquid containing a sulfur source; dissolving a copper source in water to obtain a copper source solution, adding the solution to the graphene oxide liquid containing a sulfur source to obtain a raw material solution; placing the raw material solution in a reactor, performing a hydrothermal reaction, washing and drying to obtain a copper sulfide-reduced graphene oxide nanocomposite material; wherein the sulfur source is acetylcysteine; The sodium carboxymethyl cellulose and the copper sulfide-reduced graphene oxide nanocomposite are mixed with water respectively to obtain an aqueous solution of sodium carboxymethyl cellulose and a dispersion of the copper sulfide-reduced graphene oxide nanocomposite; a chitosan compound is dissolved in an acetic acid solution to obtain an acid solution of the chitosan compound; the aqueous solution of the sodium carboxymethyl cellulose, the dispersion of the copper sulfide-reduced graphene oxide nanocomposite and the acid solution of the chitosan compound are mixed, and then a cross-linking reaction is carried out under acidic conditions to obtain a cross-linked hydrogel; wherein the chitosan compound is carboxymethyl chitosan; The cross-linked hydrogel is immersed in a solution containing an iron source, and then washed and dried to obtain a double network hydrogel; wherein the concentration of the solution containing the iron source is 0.1-1 mol / L; the immersion temperature is below 5°C, and the immersion time is 1-3 h.

2. The method for preparing hydrogel using waste cotton according to claim 1, characterized in that: The bleaching process comprises: The waste cotton is soaked in an aqueous solution of hydrogen peroxide, and then washed, crushed and dried in sequence to obtain bleached waste cotton.

3. The method for preparing hydrogel using waste cotton according to claim 2, characterized in that: The bleaching treatment is carried out at a temperature of 70-80°C and for a time of 20-40 min.

4. The method for preparing hydrogel using waste cotton according to claim 2, characterized in that: The content of hydrogen peroxide in the aqueous solution of hydrogen peroxide is 5-25 wt %.

5. The method for preparing hydrogel using waste cotton according to claim 2, characterized in that: The bath ratio of the bleaching treatment is 1:(5~25).

6. The method for preparing hydrogel using waste cotton according to claim 1, characterized in that: The steps of the alkalization reaction include: The bleached waste cotton is placed in a sodium hydroxide solution for heating treatment and then dried to obtain alkali cellulose.

7. The method for preparing hydrogel using waste cotton according to claim 6, characterized in that: The alkalization reaction is carried out at a temperature of 30-40°C and for a time of 1-3 h.

8. The method for preparing hydrogel using waste cotton according to claim 6, characterized in that: The content of sodium hydroxide in the sodium hydroxide solution is 30-40 wt %.

9. The method for preparing hydrogel using waste cotton according to claim 6, characterized in that: The solvent in the sodium hydroxide solution is a mixed solution of water and ethanol.

10. The method for preparing hydrogel using waste cotton according to claim 9, characterized in that: The volume ratio of water to ethanol is (5-15):

1.

11. The method for preparing hydrogel using waste cotton according to claim 6, characterized in that: The bath ratio of the alkalization reaction is 1:(10-20).

12. The method for preparing hydrogel using waste cotton according to claim 1, characterized in that: The steps of the etherification reaction include: Alkali cellulose, chloroacetic acid and ethanol are mixed, reacted and then dried to obtain sodium carboxymethyl cellulose.

13. The method for preparing hydrogel using waste cotton according to claim 12, characterized in that: The mass ratio of the alkali cellulose, chloroacetic acid and ethanol is 1:(0.5-1.5):(5-15).

14. The method for preparing hydrogel using waste cotton according to claim 13, characterized in that: The etherification reaction comprises: first reacting at 45-55° C. for 30-50 min, then heating to 70-80° C. for 1-2 h.

15. The method for preparing hydrogel using waste cotton according to claim 1, characterized in that: The mass ratio of the graphene oxide, the sulfur source and the copper source is 1:(15-25):(1-10).

16. The method for preparing hydrogel using waste cotton according to claim 1, characterized in that: The copper source includes any one of copper chloride, copper sulfate, copper nitrate or copper acetate, or a combination of at least two of them.

17. The method for preparing hydrogel using waste cotton according to claim 1, characterized in that: The power of the ultrasonic treatment is 100-200 W, and the time is 1-3 h.

18. The method for preparing hydrogel using waste cotton according to claim 1, characterized in that: The temperature of the hydrothermal reaction is 100-200° C. and the time is 5-15 h.

19. The method for preparing hydrogel using waste cotton according to claim 1, characterized in that: The mass ratio of the sodium carboxymethyl cellulose, the copper sulfide-reduced graphene oxide nanocomposite material and the chitosan compound is (5-8):(2-4):(1-3).

20. The method for preparing hydrogel using waste cotton according to claim 1, characterized in that: Hydrochloric acid needs to be added before the cross-linking reaction.

21. The method for preparing hydrogel using waste cotton according to claim 1, characterized in that: A cross-linking agent needs to be added before the cross-linking reaction.

22. The method for preparing hydrogel using waste cotton according to claim 21, characterized in that: The cross-linking agent is glutaraldehyde.

23. The method for preparing hydrogel using waste cotton according to claim 22, characterized in that: The added amount of the glutaraldehyde is 0.5-5% of the mass of the sodium carboxymethyl cellulose.

24. The method for preparing hydrogel using waste cotton according to claim 1, characterized in that: The cross-linking reaction is carried out at a temperature of 20 to 40° C. and for a time of 6 to 18 h.

25. The method for preparing hydrogel using waste cotton according to claim 1, characterized in that: The iron source includes ferric chloride.

26. A hydrogel, characterized in that The hydrogel is prepared by the method for preparing hydrogel using waste cotton as described in any one of claims 1 to 25.

27. Use of the hydrogel according to claim 26 in the drying treatment of landfill leachate.

28. A method for drying landfill leachate, characterized in that: The drying method comprises the following steps: The hydrogel as claimed in claim 26 is dispersed in landfill leachate and exposed to light to evaporate the solution in the landfill leachate, thereby completing the drying of the landfill; the light exposure is natural light or light at a specific wavelength.

29. The method for drying landfill leachate according to claim 28, characterized in that: The wavelength of the light is 500-520 nm.

30. The method for drying landfill leachate according to claim 28, characterized in that: The intensity of the light is 0.5~2 kW / m 2 .

31. A device for drying landfill leachate, characterized in that: The landfill leachate drying device comprises the hydrogel as claimed in claim 26.

32. The device for drying landfill leachate according to claim 31, characterized in that: The landfill leachate drying device comprises a landfill leachate evaporation pool; wherein the sidewall and / or bottom of the landfill leachate evaporation pool is coated with a hydrogel layer formed by the hydrogel according to claim 26.

33. The device for drying landfill leachate according to claim 31, characterized in that: The landfill leachate drying device further comprises an evaporation table arranged at the edge of the landfill leachate evaporation pool; wherein the surface of the evaporation table is coated with a hydrogel layer formed by the hydrogel as claimed in claim 26.

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