Preparation of renewable hydrogel material for degrading organic dye

Abstract

The invention relates to preparation of a renewable hydrogel material capable of degrading organic dye, which is characterized in that acrylamide is used as a monomer, a dispersing agent is not added, and copper-barium titanate composite hydrogel with a double-layer structure is prepared by utilizing sedimentation of copper-barium titanate in a hydrogel precursor solution. The copper-barium titanate enriched in the lower layer serves as an efficient piezoelectric catalysis center, the piezoelectric property of the copper-barium titanate is remarkably enhanced through copper doping, and under the action of external mechanical stress, the copper-barium titanate can generate a stronger piezoelectric effect, so that persulfate is efficiently activated, and strong oxidizing free radicals are continuously generated to degrade organic dye. The preparation method disclosed by the invention is simple and convenient and low in cost, and the obtained hydrogel material is relatively high in catalytic efficiency and relatively good in cycling stability and shows a wide application prospect in the field of organic wastewater degradation treatment.

Description

TECHNICAL FIELD

[0001] The application relates to preparation of a renewable hydrogel material for degrading organic dyes, and belongs to the technical field of high polymer materials. BACKGROUND

[0002] As a kind of flexible material rich in a large amount of water, the hydrogel is internally composed of a stable three-dimensional network pore framework through polymer chain crosslinking, has excellent physical and chemical properties, and is thus regarded as a new type of efficient adsorption material. The material has controllable mechanical behavior, excellent surface adhesion capacity, good electrical conductivity and excellent biocompatibility, and thus shows great development potential in many frontier technology fields. In particular, in wastewater treatment, the hydrogel can effectively adsorb organic pigments, but can only realize the transfer of the hydrogel pollutants and is difficult to solve the subsequent treatment problem. By compounding the hydrogel with a catalyst, the adsorption and degradation processes of the pollutants can be simultaneously completed, the dye removal efficiency is improved, the catalyst can be collected and reused, and thus the recycling of the material is realized.

[0003] Acrylamide is a white crystal generated by hydrolysis of acrylonitrile and has excellent water solubility. A three-dimensional network structure can be constructed by free radical polymerization of acrylamide as a monomer, a crosslinking agent and an initiator, so as to fix water to form a hydrogel. By adjusting the concentration of the crosslinking agent and the reaction temperature, the mechanical properties of the material can be controlled from elastic softness to rigidity hardness. In addition to being used for wastewater treatment and soil moisture retention, the hydrogel is also widely used in biomedical fields such as drug carriers and wound dressings, flexible electronic sensors and agricultural water conservation.

[0004] Advanced oxidation processes (AOPs) are recognized as an effective solution for treating recalcitrant organic pollutants. The technical essence is to activate the oxidant precursor through energy or catalysis to generate highly active radical species, including hydroxyl radicals and sulfate radicals. Among common oxidants, persulfate and peroxymonosulfate have become widely used oxidation media in the field of water treatment due to their economy and excellent treatment efficiency. In order to improve the yield of sulfate radicals, various activation methods of persulfate have been developed, including thermal activation, ultraviolet radiation, metal ion catalysis and emerging piezocatalysis. Among them, piezocatalysis technology induces polarization electric field of piezoelectric materials through mechanical vibration, without adding chemical reagents or consuming a large amount of energy, and provides an environmentally friendly solution for the treatment of refractory organic wastewater. It is particularly worth noting that the combined application of piezocatalysis and persulfate advanced oxidation system shows a significant synergistic enhancement effect, and has considerable development potential in the field of environmental pollution treatment.

[0005] Barium titanate (BaTiO3) as an environmentally friendly lead-free piezoelectric material in the perovskite family has attracted continuous attention in the field of functional materials due to its excellent biocompatibility. Barium titanate exhibits spontaneous polarization properties in tetragonal phase, and generates significant piezoelectric response when subjected to external mechanical stimuli, forming internal polarization electric field. This electric field can effectively drive the generation and migration of charge carriers, which in turn interact with oxygen molecules or water medium in the solution to produce reactive oxygen species (including hydroxyl radicals and superoxide radicals), creating the necessary conditions for the decomposition of organic pollutants. Although barium titanate has shown application prospects in the field of piezoelectric catalysis, its catalytic efficiency is still limited by factors such as fast charge recombination rate and limited surface active sites. Therefore, the development of barium titanate composite catalysts with enhanced piezoelectric properties is of crucial significance for promoting the practicalization process of this material in wastewater treatment. SUMMARY

[0006] The present application mainly provides a preparation method of a renewable hydrogel for degrading organic dyes. First, barium titanate is prepared by a hydrothermal method, then copper-barium titanate is synthesized by a liquid phase adsorption method, and finally based on a free radical polymerization reaction, acrylamide is used as a monomer without adding a dispersing agent, and the settlement phenomenon of copper-barium titanate in the hydrogel precursor solution is utilized to prepare a copper-barium titanate composite hydrogel with a double-layer structure, thereby obtaining a renewable hydrogel material with piezoelectric catalytic properties, degradable organic dyes, and easy recovery. The technical scheme of the present application is as follows:

[0007] Step one, using titanium dioxide as a titanium source and barium hydroxide octahydrate as a barium source, barium titanate is synthesized by a hydrothermal method:

[0008] 0.8g of titanium dioxide is dispersed in 30mL of anhydrous ethanol to obtain liquid A; 4.73g of barium hydroxide octahydrate is dissolved in 10mL of deionized water to obtain liquid B; liquid A is slowly added to liquid B to form a mixed suspension C; liquid C is transferred to a high-pressure reaction kettle and hydrothermal reaction is carried out at 200℃ for 48h; after the reaction is completed, the obtained precipitate is centrifuged, washed, dried, and calcined to obtain barium titanate nanoparticles.

[0009] Step two, copper-barium titanate is prepared by a liquid phase adsorption method:

[0010] The barium titanate prepared in step one is dispersed in 50mL of deionized water to obtain a barium titanate suspension; then, copper chloride dihydrate is dissolved in 5mL of deionized water to prepare a copper chloride solution; the copper chloride solution is then added to the barium titanate suspension, and stirred at room temperature overnight; the obtained precipitate is centrifuged, washed, and dried to obtain copper-barium titanate nanoparticles.

[0011] Step three, copper-barium titanate composite hydrogel is prepared based on a free radical polymerization reaction:

[0012] Dissolve acrylamide monomer in 10 mL of deionized water, magnetically stir until completely transparent; add 2 g of copper-barium titanate, uniformly dispersed by ultrasonic; then, under stirring, add crosslinking agent N,N'-methylene bisacrylamide, initiator ammonium persulfate, accelerator N,N,N',N'-tetramethyl ethylenediamine, mix quickly and pour into a mold to obtain copper-barium titanate composite hydrogel.

[0013] Preferably, the centrifugation in step one is at a speed of 6000 r / min for 10 min, and the washing is alternating washing with deionized water and anhydrous ethanol for 3 times.

[0014] Preferably, the drying in step one is vacuum drying at 80℃ for 12 h, and the calcination is heating to 1100℃ at a rate of 10℃ / min in a muffle furnace, and calcining at 1100℃ for 2 h.

[0015] Preferably, the mass ratio of barium titanate to copper chloride dihydrate in step two is 100:1.

[0016] Preferably, the centrifugation in step two is at a speed of 6000 r / min for 10 min, and the washing is alternating washing with deionized water and anhydrous ethanol for 3 times.

[0017] Preferably, the drying in step two is air drying at 60℃ for 12 h.

[0018] Preferably, the mass of acrylamide in step three is 3 g, and the mass ratio of acrylamide, N,N'-methylene bisacrylamide, ammonium persulfate, N,N,N',N'-tetramethyl ethylenediamine is 1000:1:9:6.

[0019] Preferably, the ultrasonic time in step three is 10 min, and the mold is a glass culture dish with a diameter of 90 mm.

[0020] Compared with the prior art, the present application has the following benefits:

[0021] 1. Raw materials are easy to obtain and the process is simple: using cheap titanium dioxide and barium hydroxide octahydrate as precursors, copper-barium titanate nanoparticles with enhanced piezocatalytic performance are successfully prepared by hydrothermal method combined with simple liquid phase adsorption method, which effectively improves the degradation efficiency of organic pollutants.

[0022] 2. Double-layer structure design: without adding any dispersant, copper-barium titanate composite hydrogel with double-layer structure is successfully synthesized, which uses the copper-barium titanate enriched in the lower layer as a stress concentration area to produce greater deformation under external mechanical action, thereby significantly enhancing the piezoelectric polarization electric field strength.

[0023] 3、Copper-barium titanate composite hydrogel can activate persulfate (PDS) under ultrasound through piezocatalysis to generate free radicals and degrade organic dyes efficiently. In the dark and ice water bath, the degradation rate of copper-barium titanate composite hydrogel to 20 mg / L rhodamine B can reach 98.85% within 30 min. The degradation process is efficient, rapid, green and environmentally friendly, and does not rely on external light sources, but only uses the widely existing mechanical energy in the environment.

[0024] 4、Multifunctional synergy: The hydrogel itself has good mechanical properties and porous structure, which can effectively adsorb organic dyes containing benzene rings. At the same time, the functional filler copper-barium titanate can continuously activate persulfate (PDS) through piezocatalysis to realize stable and efficient oxidative degradation of pollutants.

[0025] 5、Strong renewability and great application potential: The material is easy to recycle and has excellent recycling performance. The degradation rate remains above 90% after 5 cycles, showing outstanding practical application advantages and sustainable development potential. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 The figures are the physical pictures of the prepared copper-barium titanate composite hydrogel. (a) is the front view, (b) is the back view, and (c) is the side view.

[0027] Figure 2 The figures are the X-ray diffraction patterns of the prepared barium titanate, copper-barium titanate, hydrogel, barium titanate composite hydrogel, and copper-barium titanate composite hydrogel.

[0028] Figure 3 The figure is the ultraviolet absorption spectrum curve of 20 mg / L rhodamine B under ultrasound and persulfate (PDS).

[0029] Figure 4 The figure is the ultraviolet absorption spectrum curve of 20 mg / L rhodamine B under ultrasound and barium titanate + persulfate (PDS).

[0030] Figure 5 The figure is the ultraviolet absorption spectrum curve of 20 mg / L rhodamine B under ultrasound and copper-barium titanate + persulfate (PDS).

[0031] Figure 6 The figure is the ultraviolet absorption spectrum curve of 20 mg / L rhodamine B under ultrasound and copper-barium titanate composite hydrogel + persulfate (PDS).

[0032] Figure 7 The figure is the removal rate change graph of 20 mg / L rhodamine B degraded by copper-barium titanate composite hydrogel + persulfate (PDS) for five times. DETAILED DESCRIPTION

[0033] The specific embodiments of the present invention will be described below with reference to examples, so as to better understand the present invention.

[0034] Example 1

[0035] Step 1: Using titanium dioxide as the titanium source and barium hydroxide octahydrate as the barium source, barium titanate is synthesized by hydrothermal method:

[0036] Weigh 0.8 g of titanium dioxide and disperse it in 30 mL of anhydrous ethanol to obtain solution A; then weigh 4.73 g of barium hydroxide octahydrate and dissolve it in 10 mL of deionized water to obtain solution B; slowly add solution A dropwise to solution B to form a mixed suspension C; transfer solution C to a high-pressure reactor and hydrothermally react at 200 °C for 48 h; after the reaction, collect the precipitate by centrifugation, wash it three times each with deionized water and anhydrous ethanol by alternating centrifugation, and then vacuum dry it at 80 °C for 24 h to obtain a dry powder; finally, place the dry powder in a muffle furnace, heat it to 1100 °C at a rate of 10 °C / min, and calcine it at this temperature for 2 h to obtain barium titanate nanoparticles.

[0037] Step 2: Copper-barium titanate was prepared using a liquid-phase adsorption method.

[0038] First, 1g of barium titanate obtained in step one was weighed and dispersed in 50mL of deionized water to obtain a barium titanate suspension. Then, 0.01g of copper chloride dihydrate was dissolved in 5mL of deionized water to prepare a copper chloride solution. The copper chloride solution was added dropwise to the barium titanate suspension and stirred overnight at room temperature. The precipitate was collected by centrifugation and washed three times alternately with deionized water and anhydrous ethanol. The resulting solid was dried in air at 60℃ for 12h to obtain copper-barium titanate.

[0039] Step 3: Preparation of copper-barium titanate composite hydrogel based on free radical polymerization:

[0040] 3g of acrylamide monomer was dissolved in 10mL of deionized water and magnetically stirred until completely transparent. 2g of copper-barium titanate was added and ultrasonically dispersed for 10min to form a uniform suspension. Then, while stirring, 0.003g of N,N'-methylenebisacrylamide, 0.27g of ammonium persulfate, and 23uL of N,N,N',N'-tetramethylethylenediamine were added sequentially. After rapid mixing, the mixture was poured into a mold to obtain copper-barium titanate composite hydrogel.

[0041] The actual image of the copper-barium titanate composite hydrogel prepared in Example 1 is shown below. Figure 1 As shown, its front side is a porous upper layer with sparse copper-barium titanate nanoparticles, its back side is a dense lower layer composed of copper-barium titanate nanoparticles, and its side side shows the bilayer structure of the hydrogel.

[0042] The X-ray diffraction (XRD) patterns of the barium titanate, copper-barium titanate hydrogel, barium titanate composite hydrogel, and copper-barium titanate composite hydrogel prepared in Example 1 are shown below. Figure 2 As shown, barium titanate mainly exists in two crystal forms: tetragonal and cubic. Only the non-centrosymmetric tetragonal phase possesses spontaneous polarization characteristics. The spectra show that the prepared barium titanate exhibits a distinct double peak near 45°, a feature perfectly consistent with the standard card (PDF#05-0626) for tetragonal barium titanate. Furthermore, the positions and intensities of each diffraction peak correspond one-to-one, confirming the successful synthesis of a tetragonal barium titanate structure. After copper doping, the XRD pattern of copper-barium titanate showed no significant change compared to barium titanate, and no impurity phase peaks such as copper oxides appeared, indicating that copper doping did not alter the crystal structure of barium titanate. In addition, except for the blank hydrogel, all other composite hydrogels clearly showed the characteristic diffraction peaks of barium titanate, proving that barium titanate and copper-barium titanate were successfully composited within the hydrogel network.

[0043] A method for using copper-barium titanate composite hydrogels for piezoelectric catalytic degradation of organic dyes:

[0044] S1. Establishing a degradation system: A copper-barium titanate composite hydrogel with dimensions of 45mm×10mm×2mm was placed into a container containing 20mg / L organic dye wastewater. Then, 5mL of a 10mM persulfate solution was added to initiate the reaction. The persulfate was ammonium persulfate solution. The organic dye was Rhodamine B.

[0045] S2. Allow the degradation system to stand in the dark for 50 minutes to reach adsorption-desorption equilibrium;

[0046] S3. Piezoelectric catalytic degradation experiment: Under dark and ice-water bath conditions, the degradation system was placed in an ultrasonic cell disruptor for treatment. From the start of the reaction, samples were taken every 5 minutes, with 3 mL of liquid sample taken each time. An equal volume of 20 mg / L organic dye solution was immediately added to the system to maintain a constant volume. The absorbance of the samples was immediately measured using a UV-Vis spectrophotometer to calculate the real-time concentration and degradation rate of the dye. The actual power of the ultrasonic cell disruptor was 500 W, with a working time of 3 s and an interval of 1 s.

[0047] The removal efficiency of copper-barium titanate composite hydrogel and persulfate (PDS) for 20 mg / L rhodamine B is as follows: Figure 6 As shown.

[0048] For comparison, persulfate (PDS), 0.5g barium titanate with persulfate (PDS), and 0.5g copper-barium titanate with persulfate (PDS) were respectively added to wastewater containing Rhodamine B at a concentration of 20mg / L. Piezoelectric catalytic degradation experiments were conducted under the same conditions, and the results were compared with those from hydrogel degradation experiments.Figure 3 , Figure 4 , Figure 5 As shown.

[0049] Degradation experiments showed that the degradation of Rhodamine B was negligible when PDS was used alone; the degradation effect was significantly improved when PDS was combined with barium titanate; the degradation efficiency was further enhanced when copper was introduced to form a copper-barium titanate composite material; it is worth noting that when the above copper-barium titanate material was combined with hydrogel, its catalytic activity in the piezoelectrically activated PDS system was completely maintained without any attenuation.

[0050] Following the piezoelectric catalytic degradation experiment, the hydrogel material was recovered, cleaned, dried, and then directly incorporated into a new round of reaction to evaluate its regenerative properties. For example... Figure 7 As shown, the catalytic activity of the material did not show significant decay after five consecutive uses, and the degradation rate of organic dyes remained above 90%, demonstrating excellent cycle stability and reusability.

Claims

1. Preparation of a renewable hydrogel material that degrades organic dyes, characterized in that: The hydrogel is composed of a hydrogel network formed by the polymerization of acrylamide monomers and copper-barium titanate nanoparticles.

2. The preparation method of a renewable hydrogel material for degrading organic dyes according to claim 1, characterized in that: The copper-barium titanate nanoparticles were not treated with a dispersant.

3. The preparation of a renewable hydrogel material for degrading organic dyes according to claim 1, characterized in that: The hydrogel has a bilayer structure consisting of a dense lower layer enriched with copper-barium titanate nanoparticles and a porous upper layer with sparse nanoparticles.

4. The preparation of a renewable hydrogel material for degrading organic dyes according to claim 1, characterized in that: Includes the following steps: Step 1: Using titanium dioxide as the titanium source and barium hydroxide octahydrate as the barium source, barium titanate is synthesized by hydrothermal method: 0.8g of titanium dioxide is dispersed in 30mL of anhydrous ethanol to obtain solution A; then 4.73g of barium hydroxide octahydrate is dissolved in 10mL of deionized water to obtain solution B; solution A is slowly added dropwise to solution B to obtain suspension C; suspension C is transferred to a high-pressure reactor and hydrothermally reacted at 200℃ for 48h. After the reaction, the resulting precipitate is centrifuged, washed, dried, and calcined to obtain barium titanate nanoparticles; the centrifugation is performed at 6000r / min for 10min; the washing is performed by alternating washing with deionized water and anhydrous ethanol 3 times; the drying is performed by vacuum drying at 80℃ for 12h; the calcination is performed by heating to 1100℃ in a muffle furnace at a rate of 10℃ / min and calcining at 1100℃ for 2h. Step 2: Prepare copper-barium titanate nanoparticles using liquid phase adsorption: Disperse the barium titanate synthesized in Step 1 in 50 mL of deionized water to obtain a barium titanate suspension. Subsequently, copper chloride dihydrate was dissolved in 5 mL of deionized water to prepare a copper chloride solution; then, the copper chloride solution was added dropwise to a barium titanate suspension, and stirred overnight at room temperature. The resulting precipitate was centrifuged, washed, and dried to obtain copper-barium titanate nanoparticles; the mass ratio of barium titanate to copper chloride dihydrate was 100:1; the centrifugation was performed at 6000 r / min for 10 min; the washing was performed by alternating washing with deionized water and anhydrous ethanol three times; and the drying was performed by air drying at 60℃ for 12 h. Step 3: Preparation of copper-barium titanate composite hydrogel based on free radical polymerization: Dissolve acrylamide monomer in 10 mL of deionized water and stir magnetically until completely transparent; add 2 g of copper-barium titanate and disperse evenly by ultrasonication; then, while stirring, add 0.003 g of N,N'-methylenebisacrylamide, 0.27 g of ammonium persulfate, and 23 μL of N,N,N',N'-tetramethylethylenediamine in sequence, mix quickly and pour into a mold to form a copper-barium titanate composite hydrogel.

5. The preparation of a renewable hydrogel material for degrading organic dyes according to claim 1, characterized in that: For the degradation of organic dyes, the following steps are included: S1. Establishing a degradation system: A copper-barium titanate composite hydrogel with dimensions of 45mm×10mm×2mm was placed into a container containing 20mg / L organic dye wastewater, and 5mL of a 10mM persulfate solution was added to maintain the dye concentration. The persulfate was ammonium persulfate solution; the organic dye was Rhodamine B. S2. Allow the degradation system to stand in the dark for 50 minutes to reach adsorption-desorption equilibrium; S3. Piezoelectric catalytic degradation experiment: Under dark and ice-water bath conditions, the degradation system was placed in an ultrasonic cell disruptor for treatment. From the start of the reaction, samples were taken every 5 minutes, with 3 mL of liquid sample taken each time. An equal volume of 20 mg / L organic dye solution was immediately added to the system to maintain a constant volume. The absorbance of the samples was immediately measured using a UV-Vis spectrophotometer to calculate the real-time concentration and degradation rate of the dye. The actual power of the ultrasonic cell disruptor was 500 W, with a working time of 3 s and an interval of 1 s.

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