A manganese dioxide hydrogel, a preparation method thereof, and an application thereof

Abstract

The present invention relates to a manganese dioxide hydrogel, a preparation method thereof, and an application. The application of the manganese dioxide hydrogel in removing organic pollutants in water includes the following steps: preparing a phenol solution with a concentration of 25 mg / L to simulate the pollutants in chemical industrial wastewater, adding the manganese dioxide hydrogel to the phenol solution, and performing photothermal catalytic degradation of phenol through xenon lamp irradiation. The manganese dioxide hydrogel prepared by the present invention can effectively remove organic pollutants in water, has a wide application range and high stability, and can also efficiently solve the pollution problem of carcinogenic volatile pollutant phenol in water.

Description

Technical Field

[0001] The present invention relates to the technical field of water treatment, and particularly relates to a manganese dioxide hydrogel, a preparation method thereof, and an application thereof. Background Art

[0002] With the growth of the population and the development of the economy, the demand for fresh water resources by humans is increasing continuously, and the discharge of industrial wastewater is gradually increasing. Organic dyes and volatile pollutants in industrial wastewater not only have carcinogenicity but also can damage the ecological environment. Therefore, using solar steam for continuous seawater desalination and wastewater purification is considered to be one of the effective methods to solve this problem. At present, in the field of interfacial photothermal conversion distillation, VOCs are prevented from entering the condensed fresh water through the evaporation process by means of photocatalysis and membrane interception. Physical selective interception has been proven to be an effective strategy to prevent the co-evaporation of VOCs and water vapor, but VOCs will accumulate and be stored in the source water. In-situ degradation of VOCs by means of photocatalysis has become a more promising treatment strategy. Introducing photocatalysis into the photothermal evaporation system can synergistically solve the problems existing in a single system, such as reactive oxygen species components can oxidize the deposited organic matter, prevent the formation of microbial membranes, and the problem that nano-powder photocatalysts are difficult to recycle and reuse. To achieve a higher photothermal conversion rate and realize the water evaporation technology, first of all, a good light-absorbing material is needed, which can eliminate transmission and reflection as much as possible in a wide wavelength range to achieve high-efficiency light absorption and energy conversion. At the same time, the matrix material needs to construct a suitable pore structure to continuously supply water to the evaporation surface to achieve the removal of organic pollutants by photothermal conversion. Summary of the Invention

[0003] An object of the present invention is to provide an application of a manganese dioxide hydrogel in removing organic pollutants in water. The manganese dioxide hydrogel can effectively remove volatile organic pollutants, and by combining photothermal evaporation and photothermal catalytic degradation of volatile organic pollutants difficult to remove in water, it provides a new way for the removal of organic pollutants and VOCs by photothermal conversion.

[0004] Another object of the present invention is to provide a preparation method of a manganese dioxide hydrogel. The preparation method is synthesized by a foaming cross-linking polymerization method, and the preparation process is simple and can realize industrial mass production.

[0005] A third object of the present invention is to provide a manganese dioxide hydrogel, which has the advantages of easy preparation, thermal stability, excellent photothermal conversion ability, etc.

[0006] The present invention solves its technical problems by adopting the following technical solutions.

[0007] The present invention proposes an application of a manganese dioxide hydrogel in removing organic pollutants in water.

[0008] It includes the following steps:

[0009] Configure a phenol solution with a concentration of 25 mg / L to simulate the pollutants in chemical industrial wastewater, add manganese dioxide hydrogel to the phenol solution, and carry out photothermal catalytic degradation of phenol through xenon lamp illumination.

[0010] The present invention also proposes a preparation method of manganese dioxide hydrogel, and this method includes the following steps:

[0011] Add manganese dioxide nanomaterials, acrylamide, and N,N-methylenebisacrylamide into distilled water to form a homogeneous mixed solution;

[0012] Add a foaming agent to the mixed solution under rapid mechanical stirring, and continuously stir to make the mixed solution foam;

[0013] After the mixed solution is fully foamed, add a catalyst to cause a cross-linking polymerization reaction to form a fluid hydrogel, and finally add a shaping agent to make the fluid hydrogel quickly turn into a solid hydrogel, obtaining the product, porous manganese dioxide hydrogel.

[0014] The present invention also proposes a manganese dioxide hydrogel prepared by the above preparation method.

[0015] Compared with the prior art, the beneficial effects of the present invention are:

[0016] (1) The manganese dioxide hydrogel prepared by the present invention has good mechanical stability, can effectively remove organic pollutants in water, has a wide application range and high stability. It can not only effectively remove common dye pollutants in wastewater, but also efficiently solve the problem of phenol pollution, a carcinogenic volatile pollutant in water, and is suitable for water bodies in different environments.

[0017] (2) The manganese dioxide hydrogel of the present invention has a sponge-like porous structure, thus achieving excellent light absorption and high evaporation efficiency of the evaporator.

[0018] (3) The manganese dioxide hydrogel prepared by the present invention can effectively remove volatile organic pollutants, is synthesized by a foaming cross-linking polymerization method, has a simple preparation process, and can achieve industrial mass production. Description of the Drawings

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as a limitation of the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0020] Figure 1XRD pattern of β-MnO2-PH during preparation in Example 1 of the present invention;

[0021] Figure 2 FT-IR pattern of β-MnO2-PH during preparation in Example 1 of the present invention;

[0022] Figure 3 Stress-strain curve of β-MnO2-PH during preparation in Example 1 of the present invention;

[0023] Figure 4 Comparison chart of evaporation rates of four groups of manganese dioxide hydrogels (β-MnO2-PH) with different thicknesses of 0.5 - 2 cm under 1 sunlight radiation intensity in Example 2 of the present invention;

[0024] Figure 5 Comparison chart of evaporation rates of 1.5 cm thick manganese dioxide hydrogels (β-MnO2-PH) under four different solar radiation intensity conditions of 0.5 - 2.0 kw in Example 2 of the present invention;

[0025] Figure 6 Comparison chart of photothermal adsorption / catalytic degradation rates of β-MnO2-PH under different temperature conditions in Example 3 of the present invention. Detailed implementation manners

[0026] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Those not specified in the embodiments are carried out according to conventional conditions or conditions recommended by the manufacturer. Those reagents or instruments not specified by the manufacturer can all be obtained as conventional products through commercial purchase.

[0027] The following specifically describes a manganese dioxide hydrogel, a preparation method and an application thereof according to an embodiment of the present invention.

[0028] The embodiment of the present invention provides an application of a manganese dioxide hydrogel in removing organic pollutants in water.

[0029] Furthermore, in a preferred embodiment of the present invention, the application includes the following steps:

[0030] Prepare a phenol solution with a concentration of 25 mg / L to simulate the pollutants in chemical industrial wastewater, add manganese dioxide hydrogel to the phenol solution, and carry out photothermal catalytic degradation of phenol through xenon lamp illumination.

[0031] The present invention also provides a preparation method of a manganese dioxide hydrogel, and the method includes the following steps:

[0032] Add manganese dioxide nanomaterials, acrylamide, and N,N-methylenebisacrylamide to distilled water to form a homogeneous mixture.

[0033] Add a foaming agent to the mixture under rapid mechanical stirring, and continuously stir to foam the mixture.

[0034] After the mixture is fully foamed, add a catalyst to cause a cross-linking polymerization reaction to form a hydrogel. Finally, add a shaping agent to quickly turn the hydrogel into a solid hydrogel, obtaining the product, porous manganese dioxide hydrogel.

[0035] Furthermore, in a preferred embodiment of the present invention, the preparation method of the manganese dioxide nanomaterials is as follows:

[0036] Add analytical pure manganese sulfate monohydrate and sodium persulfate to deionized water at room temperature to form a homogeneous solution, then transfer it to a reaction kettle and keep it at 120 °C for 12 hours. After the reaction is completed, obtain a black solid product, which is filtered, washed, and dried to obtain manganese dioxide nanomaterials.

[0037] Furthermore, in a preferred embodiment of the present invention, the volume ratio of the analytical pure manganese sulfate monohydrate to the sodium persulfate is 1:1.

[0038] Furthermore, in a preferred embodiment of the present invention, the foaming agent is sodium dodecyl sulfate.

[0039] Furthermore, in a preferred embodiment of the present invention, the catalyst is N,N,N′,N′-tetramethylethylenediamine.

[0040] Furthermore, in a preferred embodiment of the present invention, the shaping agent is an aqueous sulfate solution.

[0041] The present invention also provides the manganese dioxide hydrogel prepared by the above preparation method.

[0042] The features and properties of the present invention will be further described in detail below in conjunction with examples.

[0043] Example 1: Preparation and Characterization of Manganese Dioxide Hydrogel (β-MnO2-PH)

[0044] (1) First, add 0.8 mol of analytical pure manganese sulfate monohydrate and an equal amount of sodium persulfate to 60 mL of deionized water at room temperature to form a homogeneous solution, then transfer it to a stainless steel lined with Teflon and keep it at 120 °C for 12 hours. After the reaction is completed, filter the obtained black solid product, wash it with deionized water to remove possible residual ions in the product, and finally dry it in an oven at 60 °C for 24 h to obtain MnO2 nanoparticles.

[0045] (2) First, 7.0 g of β-MnO2 obtained in step (1), 7.2 g of acrylamide, and 0.6 g of N,N-methylenebisacrylamide were added to 20 mL of deionized water to form a homogeneous solution. Then, 0.3 g of sodium dodecyl sulfate was added to the mixture under rapid mechanical stirring, and the mixture was continuously stirred to foam. After the mixture was fully foamed, 0.7 mL of N,N,N′,N′-tetramethylethylenediamine was added as a catalyst to the mixture to cause a cross-linking polymerization reaction to form a hydrogel. Finally, 5 mL of ammonium persulfate was added as a forming agent to rapidly transform the hydrogel into a solid hydrogel.

[0046] (3) Figure 1 XRD pattern of the manganese dioxide hydrogel (β-MnO2-PH) material prepared for Example 1. The results show that the manganese dioxide hydrogel (β-MnO2-PH) contains characteristic peaks of β-type manganese dioxide at 28.7°, 37.3°, 41.0°, 42.8°, 56.7°, 59.4°, 64.8°, 67.2°, and 72.4°, indicating the successful synthesis of the β-MnO2 material.

[0047] (4) Figure 2 FT-IR spectra of the manganese dioxide powder and the hydrogel (β-MnO2-PH) material prepared for Example 1. From the FT-IR spectra of the manganese dioxide powder and the hydrogel (β-MnO2-PH), it can be found that the characteristic peak at 3425.1 cm -1 appearing in the middle is the stretching vibration of N-H. The characteristic peak at 1678.3 cm -1 appearing in the middle between 1900 - 1650 cm -1 is the stretching vibration of C=O. The characteristic peaks at 2362.4 cm -1 and 2328.7 cm -1 correspond to -OH. These characteristic peaks come from polyacrylamide and N,N-methylenebisacrylamide. The water-soluble groups in these polymer chains, such as hydroxyl (-OH), amino (-NH2), and carboxyl (-COOH), can form bonds with water molecules through non-covalent interactions such as hydrogen bonds and electrostatic interactions. The presence of these hydrophilic functional groups is beneficial to the hydrophilicity of the hydrogel. Compared with the blank hydrogel, the spectrum of β-MnO2-PH has a stretching vibration peak of Mn-O at 521.6 cm -1 , representing the successful loading of β-MnO2 nanoparticles on the hydrogel. -1

[0048] (5) Figure 3Stress-strain curve of the manganese dioxide hydrogel (β-MnO2-PH) material prepared for Case 1 under 50% strain. It can be seen from the experimental results that under the condition of 50% strain, the stress of this hydrogel is 5.35 Mpa. After 100 cyclic tests, the hydrogel can still maintain 90% of its original compressive strength, and no surface cracking is observed. Therefore, β-MnO2-PH has good mechanical stability and broad development prospects in the practical application of photothermal water purification.

[0049] Example 2: Influence of different experimental conditions on the evaporation rate of manganese dioxide hydrogel (β-MnO2-PH)

[0050] (1) Figure 4 This is a comparison chart of the evaporation rates of four groups of manganese dioxide hydrogels (β-MnO2-PH) with different thicknesses from 0.5 to 2 cm under a solar radiation intensity in Experiment Case 2. By simulating sunlight irradiation with a xenon lamp, an electronic balance was used to record the mass change within 360 min under the condition of one solar radiation, and the evaporation rate of β-MnO2-PH was measured and calculated. The experimental results show that when the thickness of the hydrogel increases from 0 cm to 1.5 cm, the evaporation efficiency increases accordingly. The evaporation efficiency of the manganese dioxide hydrogel with a thickness of 1.5 cm is the highest, which is 3.4824 kg·m -2 ·h -1 , while when the thickness increases from 1.5 cm to 2.0 cm, the evaporation efficiency begins to decline. The decrease in evaporation efficiency may be due to the too long transmission distance of water from the water surface to the surface of β-MnO2-PH, resulting in a decrease in transmission efficiency and insufficient water supply on the gel surface.

[0051] (2) Figure 5 This is a comparison chart of the evaporation rates of 1.5-cm-thick manganese dioxide hydrogels (β-MnO2-PH) under four different solar radiation intensity conditions from 0.5 to 2.0 kw in Experiment Case 2. The enhancement of solar radiation can generate more steam. By adjusting the xenon lamp to simulate different solar radiation intensity conditions, a comparison chart of the evaporation rates of β-MnO2-PH was obtained. It can be seen from the slope of the curve that the evaporation efficiency at 2 solar radiation intensities (5.5142 kg·m -2 ·h -1 ) is undoubtedly the highest. With the strengthening of solar radiation, the evaporation efficiency gradually increases. The increase in evaporation efficiency is mainly due to the increase in the surface temperature of the solar evaporator.

[0052] Example 3: Degradation of organic pollutants by β-MnO2-PH

[0053] (1) The pollutant concentration of the simulated chemical wastewater containing phenol was measured by collecting and analyzing the samples to verify the photothermal catalytic effect of the catalyst. Based on β-MnO2 nanoparticles, a water-cooling device was used to control the temperature series of the reaction solution (25 - 50 °C), and xenon lamp (3000w) illumination was used for the photothermal catalytic degradation of phenol. In the experiment, the concentration of the phenol solution was 25 mg / L, the volume of the solution was 50 mL, and the dosage of the photothermal catalyst β-MnO2 was 25 mg. After 30 min of dark adsorption, 1.5 mL of the suspension was quantitatively sampled every 30 min and filtered through a 0.45 μm water-based membrane. The above samples were analyzed quantitatively by an ultraviolet spectrophotometer, and the degradation rate curve of the phenol solution was plotted.

[0054] (2) Experimental results: As Figure 6 shown, during the photothermal catalytic degradation of phenol, only 1% of the phenol concentration volatilized under dark conditions. Under photothermal conditions, the degradation rate was 63.7% at 25 °C and reached 69.7% at 50 °C. By comparing the phenol degradation rates under different temperature conditions, it can be shown that heating the solution can improve the photothermal catalytic activity of β-MnO2 nanoparticles. β-MnO2 nanoparticles are a catalyst with good photothermal catalytic degradation performance.

[0055] The embodiments described above are some, but not all, of the embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

Claims

1. Application of manganese dioxide hydrogel in removing organic pollutants in water, characterized in that: Including the following steps: Configure a phenol solution with a concentration of 25 mg / L to simulate the pollutants in chemical industrial wastewater, add manganese dioxide hydrogel to the phenol solution, and carry out photothermal catalytic degradation of phenol through xenon lamp illumination.

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