A modified aluminum-based heterogeneous catalyst and its preparation method and application

Abstract

The present invention belongs to the technical field of photovoltaic wastewater treatment, and specifically discloses a modified aluminum-based heterogeneous catalyst and a preparation method and application thereof. The present invention first grafts and modifies aluminum hydroxide to obtain amino-grafted aluminum hydroxide; then, the amino-grafted aluminum hydroxide, transition metal salt, rare earth metal salt, binder and water are mixed and granulated to obtain raw material balls; and then, the raw material balls are roasted to obtain a modified aluminum-based heterogeneous catalyst. The modified aluminum-based heterogeneous catalyst prepared by the present invention can increase the positive charge density due to the presence of amino groups on the catalyst surface, form affinity with ozone, and is conducive to the catalytic reaction of ozone; there is a synergistic catalytic effect between transition metals and rare earth metals, which can greatly increase the decomposition efficiency of ozone; in addition, the catalyst surface active component content of the present invention is high, and compared with the effect of photovoltaic wastewater oxidation by ozone alone, the COD removal rate is greatly improved, and the water quality of the effluent meets the discharge standard.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic wastewater treatment, and in particular to a modified aluminum-based heterogeneous catalyst and a preparation method and application thereof. Background Art

[0002] Photovoltaic wastewater comes from the process of producing semiconductors and other components. The wastewater contains a variety of organic matter, metal ions, fluoride ions, ammonia nitrogen and other pollutants. The pollutants are complex and toxic. Untreated sewage discharged into natural water bodies exceeds the self-purification capacity of the water body and causes damage to the environment. With the improvement of wastewater discharge quality standards, the optimization of tail water deep treatment process has become a difficult problem. If the treatment problem of photovoltaic wastewater is solved, the photovoltaic industry will be cleaner, greener and more environmentally friendly than traditional industries, and its development will have more advantages. Therefore, the treatment of photovoltaic wastewater is particularly important. Photovoltaic wastewater has the characteristics of a large fluctuation range of pollutant concentrations, high toxicity and high output.

[0003] In the deep treatment stage, the wastewater after biological treatment contains a certain amount of metal ions and difficult-to-degrade organic pollutants, so a deep treatment process is needed to further treat the water quality. Ozone itself has a relatively strong oxidizing property, but ozone has a special selectivity in reacting with pollutants, resulting in a relatively low degree of mineralization, and the effluent after treatment does not meet the standards. Therefore, it is necessary to add a heterogeneous catalyst to the ozone oxidation system to improve this problem. Heterogeneous catalysts can promote the decomposition of ozone into hydroxyl radicals with stronger oxidizing ability, improve the utilization efficiency of ozone and thus increase the removal efficiency of pollutants, and ultimately make the effluent meet the standards. Therefore, it is very necessary to disclose an ozone heterogeneous catalyst suitable for deep treatment of photovoltaic wastewater. Summary of the invention

[0004] In view of this, the present invention provides a modified aluminum-based heterogeneous catalyst and a preparation method and application thereof, so as to solve the problem that the traditional photovoltaic wastewater treatment process is prone to effluent not meeting the standards.

[0005] In order to achieve the above object, the present invention adopts the following technical solution:

[0006] A method for preparing a modified aluminum-based heterogeneous catalyst comprises the following steps:

[0007] 1) Grafting and modifying aluminum oxyhydroxide to obtain amino-grafted aluminum oxyhydroxide;

[0008] 2) Mixing and granulating the amino-grafted hydroxyaluminum oxide, transition metal salt, rare earth metal salt, binder and water to obtain raw material balls;

[0009] 3) The raw material balls are calcined to obtain a modified aluminum-based heterogeneous catalyst.

[0010] Preferably, the grafting modification operation in step 1) is as follows:

[0011] Aluminum oxyhydroxide, a silane coupling agent containing amino groups and ethanol are mixed and grafted to obtain amino-grafted aluminum oxyhydroxide.

[0012] Preferably, the mass ratio of the aluminum oxyhydroxide, the amino-containing silane coupling agent and ethanol is 10:0.1-0.5:100-200.

[0013] Preferably, the graft modification temperature is 15-60° C., and the graft modification time is 5-12 hours.

[0014] Preferably, the amino-containing silane coupling agent includes one or more of γ-aminopropyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane and N-aminoethyl-γ-aminopropyltrimethoxysilane.

[0015] Preferably, the mass ratio of the amino-grafted aluminum hydroxide oxide, the transition metal salt, the rare earth metal salt, the binder and water is 80-90:10-15:1-5:5-15:15-20.

[0016] Preferably, the transition metal salt includes one or more of iron salt, copper salt, cobalt salt and manganese salt;

[0017] The rare earth metal salt includes one or more of cerium salt, lanthanum salt and gallium salt;

[0018] The binder includes one or more of clay, natural rubber, silica sol and synthetic resin.

[0019] Preferably, the calcination temperature in step 3) is 500-650° C., and the calcination time is 2-4 hours.

[0020] Another object of the present invention is to provide a modified aluminum-based heterogeneous catalyst prepared by the preparation method.

[0021] Another object of the present invention is to provide an application of a modified aluminum-based heterogeneous catalyst in the deep treatment of photovoltaic wastewater.

[0022] It can be seen from the above technical solutions that, compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The present invention obtains a modified aluminum-based heterogeneous catalyst by amino grafting modification of aluminum oxyhydroxide. In the process of catalyzing ozone, the amino group can be protonated to increase the positive charge density on the surface of the substrate. At the same time, based on the high electron density of the oxygen atom in the ozone molecule, it forms an affinity with the catalyst, thereby improving the adsorption of ozone on the surface of the modified aluminum-based heterogeneous catalyst, facilitating the attachment of ozone, and thus increasing the degree of catalytic reaction of ozone.

[0024] 2. The present invention utilizes the synergistic catalytic effect between transition metals and rare earth metals to greatly increase the decomposition efficiency of ozone and increase the removal capacity of the catalytic ozone oxidation system. Compared with the traditional impregnation-calcination catalyst preparation method, the content of the surface active components of the modified aluminum-based heterogeneous catalyst prepared by the present invention is increased by more than 10 times, and the catalyst has the advantages of high mechanical strength and large specific surface area. Compared with the effect of ozone oxidation of photovoltaic wastewater alone, the COD removal rate is greatly improved, and the water quality of the effluent meets the discharge standard.

[0025] 3. The catalyst preparation method of the present invention is simple, the production cost is low, and it can be produced and used in industry on a large scale. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0027] Figure 1 This is a physical picture of the modified aluminum-based heterogeneous catalyst prepared in Example 1;

[0028] Figure 2 This is a SEM image of the modified aluminum-based heterogeneous catalyst prepared in Example 1;

[0029] Figure 3 The experimental results of catalytic ozone oxidation using the modified aluminum-based heterogeneous catalyst obtained in Example 1;

[0030] Figure 4 The experimental results of catalytic ozone oxidation using the modified aluminum-based heterogeneous catalyst obtained in Example 2 are shown. DETAILED DESCRIPTION

[0031] The present invention provides a method for preparing a modified aluminum-based heterogeneous catalyst, comprising the following steps:

[0032] 1) Grafting and modifying aluminum oxyhydroxide to obtain amino-grafted aluminum oxyhydroxide;

[0033] 2) Mixing and granulating the amino-grafted hydroxyaluminum oxide, transition metal salt, rare earth metal salt, binder and water to obtain raw material balls;

[0034] 3) The raw material balls are calcined to obtain a modified aluminum-based heterogeneous catalyst.

[0035] In the present invention, the operation of grafting modification in step 1) is as follows:

[0036] Aluminum oxyhydroxide, a silane coupling agent containing amino groups and ethanol are mixed and grafted to obtain amino-grafted aluminum oxyhydroxide.

[0037] In the present invention, the mass ratio of the aluminum oxide, the amino-containing silane coupling agent and ethanol is 10:0.1-0.5:100-200, preferably 10:0.2-0.4:120-180, further preferably 10:0.25-0.35:140-160, and further preferably 10:0.3:150.

[0038] In the present invention, the temperature of the grafting modification is 15-60°C, specifically 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C; the time of the grafting modification is 5-12h, specifically 6h, 7h, 8h, 9h, 10h, 11h.

[0039] In the present invention, the amino group-containing silane coupling agent includes one or more of γ-aminopropyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane and N-aminoethyl-γ-aminopropyltrimethoxysilane.

[0040] In the present invention, the mass ratio of the amino-grafted hydroxy aluminum oxide, transition metal salt, rare earth metal salt, binder and water is 80-90:10-15:1-5:5-15:15-20, preferably 82-88:12-14:2-4:8-12:16-18, and more preferably 85:13:3:10:17.

[0041] In the present invention, the transition metal salt includes one or more of iron salts, copper salts, cobalt salts and manganese salts, and specifically may be ferric chloride, ferrous chloride, ferric sulfate, copper sulfate, copper nitrate, manganese nitrate, and cobalt chloride.

[0042] In the present invention, the rare earth metal salt includes one or more of cerium salt, lanthanum salt and gallium salt, and specifically may be cerium nitrate, lanthanum nitrate and gallium nitrate.

[0043] In the present invention, the binder includes one or more of clay, natural rubber, silica sol and synthetic resin.

[0044] In the present invention, the diameter of the raw ball is preferably 3-5 mm, specifically 3.2 mm, 3.4 mm, 3.5 mm, 3.6 mm, 3.8 mm, 4 mm, 4.2 mm, 4.5 mm, and 4.8 mm.

[0045] In the present invention, the calcination temperature in step 3) is 500-650°C, specifically 520°C, 550°C, 580°C, 600°C, 620°C; the calcination time is 2-4h, specifically 2.2h, 2.5h, 2.8h, 3h, 3.2h, 3.5h, 3.8h.

[0046] The present invention also provides a modified aluminum-based heterogeneous catalyst prepared by the preparation method.

[0047] The present invention also provides an application of a modified aluminum-based heterogeneous catalyst in the deep treatment of photovoltaic wastewater.

[0048] In the present invention, the treatment process of the wastewater treatment plant can be a sequential process of high-efficiency precipitation for silicon and hardness removal, multi-mode AO biological pool, high-efficiency precipitation pool for fluorine removal, filtration, catalytic ozone oxidation pool, moving bed membrane bioreactor, magnetic coagulation precipitation, ultrafiltration, and reverse osmosis; the modified aluminum-based heterogeneous catalyst described in the present invention is used in the catalytic ozone oxidation pool.

[0049] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0050] Example 1

[0051] The aluminum hydroxide was cleaned with deionized water to remove impurities and oil stains on the surface, and then dispersed in ethanol after drying. After being fully dispersed, γ-aminopropyltriethoxysilane was added dropwise, and grafting modification was performed at 40°C for 8 hours to obtain amino-grafted aluminum hydroxide. The mass ratio of aluminum hydroxide, ethanol and silane coupling agent was 10:0.4:150.

[0052] Then, 85 parts of amino-grafted hydroxyalumina, 10 parts of manganese nitrate, 2 parts of cerium nitrate, 10 parts of clay and 15 parts of water were mixed and granulated. The rare earth metal salt and water were pre-mixed and mixed with other components in the form of spray to obtain 3-5 mm raw balls; the raw balls were then calcined at 600°C for 3 h to obtain a modified aluminum-based heterogeneous catalyst.

[0053] The physical image and SEM image of the modified aluminum-based heterogeneous catalyst obtained in this example are shown in FIG. Figure 1 and Figure 2 The specific surface area or pore volume is shown in Table 1 (the pure alumina in Table 1 is commercially available).

[0054] Table 1 Surface area or pore volume related information

[0055]

[0056] from Figure 1 and Figure 2 As can be seen from Table 1, the specific surface area of ​​the modified aluminum-based heterogeneous catalyst prepared by the present invention is greater than that of pure aluminum oxide, proving that the modified aluminum-based heterogeneous catalyst has a relatively good ability to adsorb and catalyze ozone. From the SEM image, it can be seen that the active components of the catalyst are distributed on the catalyst surface in a layered structure.

[0057] The photovoltaic wastewater after biochemical treatment in a sewage treatment plant in a photovoltaic industrial park in Inner Mongolia was used for heterogeneous catalytic ozone oxidation experiments. The water quality of the photovoltaic wastewater is shown in Table 2:

[0058] Table 2 Water quality indicators

[0059]

[0060] The experimental steps are as follows: (1) Soak the catalyst in water before the experiment to remove dust on the catalyst surface; (2) Turn on the ozone generator, adjust to the set ozone concentration and air intake, and stabilize for a period of time; (3) Add the above-mentioned modified aluminum-based heterogeneous catalyst and test water sample into the reactor, start the timer, and take samples at a certain experimental interval (at the same time, set up a control group without adding modified aluminum-based heterogeneous catalyst), and record them as heterogeneous and ozone respectively; (4) After the experiment, measure the COD value of the effluent.

[0061] The ozone concentration in the heterogeneous catalytic ozone oxidation process section is 60mg / L, the air intake is 0.5L / min, and the treated water sample is 15L. The catalyst dosage is 50g / L. The COD of the influent of the heterogeneous catalytic ozone oxidation is: 83mg / L. The experimental results are as follows Figure 3 As shown, after 30 minutes of reaction, the effluent COD was 33 mg / L and the COD removal rate (COD / COD0) was 60.24%, which was much higher than the COD removal rate of ozone oxidation alone (24.52%). In addition, after adding the modified aluminum-based heterogeneous catalyst, the △O3 / △COD was 1.2, which was lower than that of ozone oxidation alone (2.85), indicating that the utilization rate of ozone was improved after the addition of the catalyst.

[0062] Example 2

[0063] The amino-grafted hydroxy aluminum oxide obtained in Example 1 is used for later use.

[0064] 80 parts of amino-grafted hydroxyalumina, 15 parts of manganese nitrate, 1 part of cerium nitrate, 10 parts of clay and 15 parts of water were mixed and granulated. The rare earth metal salt and water were pre-mixed and mixed with other components in the form of spray to obtain 3-5 mm raw balls; then the raw balls were calcined at 650°C for 3 h to obtain a modified aluminum-based heterogeneous catalyst.

[0065] The heterogeneous catalytic ozone oxidation experiment was carried out using the wastewater from a sewage treatment plant of a photovoltaic chip factory in Wuxi. The quality of the raw water is shown in Table 3:

[0066] Table 3 Water quality indicators

[0067]

[0068] The experimental process was similar to that in Example 1, and the experimental group and the control group were respectively recorded as heterogeneous phase and ozone.

[0069] The ozone concentration in the heterogeneous catalytic ozone oxidation process section is 45 mg / L, the air intake is 0.2 L / min, and the water sample is 3 L. The catalyst dosage is 40 g / L. The COD of the influent of the heterogeneous catalytic ozone oxidation is: 41 mg / L. The experimental results are as follows Figure 4 As shown in the figure, after 15 minutes of reaction, the effluent COD was 20 mg / L and the COD removal efficiency was 51.21%, which was higher than the COD removal efficiency of ozone oxidation alone (25%).

[0070] Example 3

[0071] The aluminum hydroxide was cleaned with deionized water to remove impurities and oil stains on the surface, and then dispersed in ethanol after drying. After being fully dispersed, N-aminoethyl-γ-aminopropyltrimethoxysilane was added dropwise, and grafting modification was performed at 20°C for 12 hours to obtain amino-grafted aluminum hydroxide. The mass ratio of aluminum hydroxide, ethanol and silane coupling agent was 10:0.3:100.

[0072] Then, 90 parts of amino-grafted hydroxyalumina, 6 parts of ferric chloride, 6 parts of copper nitrate, 4 parts of cerium nitrate, 15 parts of clay and 20 parts of water were mixed and granulated. The rare earth metal salt and water were pre-mixed and mixed with other components in the form of spray to obtain raw balls. The raw balls were then calcined at 500°C for 2 h to obtain a modified aluminum-based heterogeneous catalyst.

[0073] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0074] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a modified aluminum-based heterogeneous catalyst for deep ozone treatment of photovoltaic wastewater, characterized in that: The steps include: 1) Grafting and modifying aluminum oxyhydroxide to obtain amino-grafted aluminum oxyhydroxide; 2) Mixing and granulating the amino-grafted hydroxyaluminum oxide, transition metal salt, rare earth metal salt, binder and water to obtain raw material balls; 3) calcining the raw material balls to obtain a modified aluminum-based heterogeneous catalyst; The mass ratio of the amino-grafted hydroxy aluminum oxide, transition metal salt, rare earth metal salt, binder and water is 80-90:10-15:1-5:5-15:15-20; The operation of graft modification in step 1) is as follows: Aluminum oxyhydroxide, a silane coupling agent containing amino groups and ethanol are mixed and grafted to obtain amino-grafted aluminum oxyhydroxide.

2. The method for preparing a modified aluminum-based heterogeneous catalyst for deep ozone treatment of photovoltaic wastewater according to claim 1, characterized in that: The mass ratio of the aluminum oxide hydroxide, the amino-containing silane coupling agent and ethanol is 10:0.1-0.5:100-200.

3. The method for preparing a modified aluminum-based heterogeneous catalyst for deep ozone treatment of photovoltaic wastewater according to claim 2, characterized in that: The temperature of the graft modification is 15-60° C., and the time of the graft modification is 5-12 hours.

4. A method for preparing a modified aluminum-based heterogeneous catalyst for deep ozone treatment of photovoltaic wastewater according to any one of claims 1 to 3, characterized in that: The amino-containing silane coupling agent includes one or more of γ-aminopropyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane and N-aminoethyl-γ-aminopropyltrimethoxysilane.

5. The method for preparing a modified aluminum-based heterogeneous catalyst for deep ozone treatment of photovoltaic wastewater according to claim 1, characterized in that: The transition metal salt includes one or more of iron salt, copper salt, cobalt salt and manganese salt; The rare earth metal salt includes cerium salt and / or lanthanum salt; The binder includes one or more of clay, natural rubber, silica sol and synthetic resin.

6. The method for preparing a modified aluminum-based heterogeneous catalyst for deep ozone treatment of photovoltaic wastewater according to claim 5, characterized in that: The calcination temperature in step 3) is 500-650° C. and the calcination time is 2-4 hours.

7. The modified aluminum-based heterogeneous catalyst prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the modified aluminum-based heterogeneous catalyst according to claim 7 in deep ozone treatment of photovoltaic wastewater.

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