A method for preparing a material having photoelectric coupling catalytic performance

Abstract

The present invention provides a material with photoelectric coupling catalytic performance and a preparation method thereof. The raw materials used in the process of the present invention are cheap and easy to obtain. The material base uses carbonized alginate aerogel with a porous structure and rich functional groups on the surface, which is conducive to the adsorption and degradation of pollutants. Good electrical conductivity is conducive to the transfer of photogenerated carriers and the conduction of electrons in electrochemistry. At the same time, the excess zinc nitrate and iron nitrate on the surface decompose at high temperature to produce P-type semiconductor zinc oxide and iron oxide, respectively, to form a P-N heterojunction with TiO2, greatly improving the number and oxidizability of photogenerated holes on the titanium dioxide surface. Secondly, the presence of an electric field in the reactor causes anions such as Cl to be enriched at the anode and oxidized to active substances such as Cl· by the photogenerated holes on the anode surface, which are used to oxidize organic pollutants. By changing the voltage to control the electrochemical oxidation potential, the byproducts of salt ion radical oxidation are reduced and the effective circulation of Cl· / Cl· is promoted.

Description

Technical Field

[0001] The present invention belongs to the field of wastewater treatment, and in particular relates to a method for preparing a material with photoelectric coupling catalytic performance, and application of the material in treating high-salt organic wastewater. Background Art

[0002] High-salt wastewater comes from a wide range of sources. With the rapid development of industries such as chemical, pharmaceutical, and printing and dyeing, the amount of high-salt wastewater to be treated has also increased year by year. The composition of high-salt wastewater is complex and its treatment is relatively difficult. Traditional wastewater treatment methods mainly include biological methods, physicochemical methods, and a combination of the two, but traditional methods have obvious shortcomings in the treatment of high-salt wastewater. The disadvantage of biological treatment is that high concentrations of salt substances have an inhibitory effect on microorganisms, and the treatment effect is not ideal; the disadvantage of physicochemical treatment is that the investment is large, the operating costs are high, and it is difficult to achieve the expected purification effect. Therefore, finding and improving treatment technologies and processes for high-salt wastewater remains a focus of research at home and abroad.

[0003] In recent years, advanced oxidation technologies (ADTs) have become an effective method for treating organic wastewater. These technologies primarily include electrocatalytic oxidation, photocatalytic oxidation, and photoelectrocatalytic oxidation. Photocatalytic oxidation offers advantages such as minimal secondary pollution, ease of operation, and excellent degradation performance. TiO2 is a typical N-type semiconductor. Under illumination, electrons in the valence band gain energy and transition to the conduction band, generating free electrons in the conduction band, exhibiting the electrochemical properties of a semiconductor. Therefore, it has been widely used in the degradation of organic pollutants. However, in the photoelectrocatalytic degradation of organic matter, TiO2 nanotubes exhibit only weak electrocatalytic activity. The applied voltage only serves to promote the separation of photogenerated electrons and holes, resulting in TiO2 nanotubes acting solely as a photocatalyst and exhibiting poor electrocatalytic performance. Electrocatalytic oxidation is another advanced oxidation technology with great potential. Electrode material is a key factor in determining treatment efficiency. The earliest and most commonly used graphite electrodes are inexpensive, but they lack mechanical strength, catalytic activity for the oxidation of organic matter, and low oxygen evolution potential and current efficiency. Diamond electrodes have wide electrochemical windows, low background current, high chemical stability and low adsorption properties, but their high preparation cost limits their application in water treatment.

[0004] Patent Publication No. CN200810103518.2 discloses a BDD-TiO2 electrode with PN junction characteristics, consisting of N-type TiO2 / P-type boron-doped diamond (BDD). This electrode further enhances the electrocatalytic activity of the BDD electrode and the photoelectrocatalytic activity of TiO2, increasing the quantum yield and the electrode's service life. However, this method still suffers from drawbacks such as high preparation cost and complex preparation steps. Therefore, it is necessary to develop a photoelectrocatalyst with simple methods, controllable costs, and excellent performance, which can effectively mediate photoelectrocatalytic synergy to achieve efficient oxidative degradation of high-salinity wastewater. Summary of the Invention

[0005] In response to the above technical problems, the present invention provides a material with photoelectric coupling catalytic performance and a preparation method thereof. The catalytic material can be used as an anode in a photoelectric coupling reactor to selectively catalyze and oxidize the organic pollutants in high-salt wastewater.

[0006] The present invention provides a material with photoelectric coupling catalytic properties and a preparation method thereof. Alginate hydrogel is generated by a replacement reaction between ferric nitrate and zinc nitrate and sodium alginate. The alginate aerogel is modified and prepared using a freeze-drying method. After calcination, a carbon skeleton with an aerogel structure is formed, exhibiting good conductivity and a rich porous structure. Calcination under a nitrogen atmosphere causes the ferric nitrate and zinc nitrate attached to the aerogel to form P-type semiconductor zinc oxide and iron oxide, which form a PN heterojunction with titanium dioxide (TiO2), significantly increasing the number of photogenerated holes on the TiO2 surface and its oxidizability. Furthermore, hydrothermal modification of the TiO2 to form nanotubes increases the specific surface area of ​​the TiO2 and its loading on the aerogel, facilitating the exposure of the photogenerated holes, their contact with pollutants and salt ions, and their catalytic reaction.

[0007] The technical solution of the present invention is summarized as follows:

[0008] S1, preparing a 2 wt% to 5 wt% alginate aqueous solution;

[0009] S2, mixing a zinc salt solution having a molar concentration of 0.03 to 0.06 mol / L and an iron salt solution having a molar concentration of 0.03 to 0.06 mol / L in a volume ratio of 1:5 to 5:1 to form a precursor solution;

[0010] S3, slowly dripping the prepared alginate aqueous solution into the precursor solution and continuously stirring to make it evenly dispersed;

[0011] S4, pouring the mixed solution after stirring evenly into a mold and standing it at 10-40° C. for 24-48 hours to form a cross-linked alginate hydrogel;

[0012] S5, rinsing the surface of the alginate hydrogel with deionized water and freeze-drying it at -40 to 80°C to obtain alginate aerogel;

[0013] S6, calcining the alginate aerogel at 300-500° C. for 6-10 hours in a nitrogen, argon or neon atmosphere to obtain a carbonized alginate aerogel having a porous three-dimensional structure;

[0014] S7, modifying TiO2 by a hydrothermal method, so that the modified TiO2 is in situ deposited and loaded onto the surface of the carbonized alginate aerogel;

[0015] S8, washing the material obtained in the previous step twice with a corresponding dilute acid solution with a molar volume of 0.1-0.5 mol / L, then washing it three times with deionized water, and then drying it at 80-100° C. for 12-24 hours to obtain the material with photoelectric coupling catalytic performance.

[0016] Among them, the zinc salt solution and the iron salt solution described in step S2 have the same anion type, including zinc nitrate solution and ferric nitrate solution, zinc chloride solution and ferric chloride solution, zinc sulfate solution and ferric sulfate solution, and zinc acetate solution and ferric acetate solution; the dilute acid solution described in step S7 includes dilute nitric acid, dilute hydrochloric acid, dilute sulfuric acid or dilute acetic acid, corresponding to the anion type of the zinc salt solution and the iron salt solution described in S2.

[0017] The specific steps of modifying TiO2 by hydrothermal method are: adding TiO2 to a sodium hydroxide solution with a molar concentration of 10-20 mol / L and mixing evenly, pouring the mixed solution and the carbonized aerogel into a hydrothermal reactor, and reacting at 150-200°C for 24-48 hours.

[0018] Preferably, the molar concentration of the ferric nitrate and zinc nitrate solutions used to prepare the precursor solution is 0.03-0.06 mol / L, and the volume ratio of the ferric nitrate and zinc nitrate solutions is 1:2-2:1.

[0019] Preferably, the alginate includes sodium alginate, potassium alginate, calcium alginate or magnesium alginate. Further preferably, the alginate can be sodium alginate.

[0020] Preferably, the zinc salt and the iron salt include zinc nitrate and ferric nitrate, zinc chloride and ferric chloride, zinc sulfate and ferric sulfate or zinc acetate and ferric acetate, and the dilute acid solution described in S8 includes dilute nitric acid, dilute hydrochloric acid, dilute sulfuric acid or dilute acetic acid, corresponding to the anion type of the metal salt used. And when the metal salt is sulfate, the alginate cannot use calcium alginate. Further preferably, the zinc salt and the iron salt can be selected from zinc nitrate and ferric nitrate, and the dilute acid solution can be selected from dilute nitric acid.

[0021] Preferably, the TiO2 added during the hydrothermal modification of TiO2 is titanium dioxide P25, and the amount added is 3-10 g / L.

[0022] The beneficial effects of the present invention are as follows:

[0023] The present invention provides a material with photoelectric coupling catalytic properties and a preparation method thereof. The raw materials used in the process are inexpensive and readily available. Alginate can be extracted from seaweed, which is widely found in nature. Iron salts, zinc salts, and titanium dioxide P25 are all mature chemical products, which facilitates large-scale production. The material substrate uses carbonized alginate aerogel, which has a porous structure and abundant surface functional groups, which facilitates the adsorption and degradation of pollutants. The excellent electrical conductivity facilitates the transfer of photogenerated carriers and the conduction of electrons in electrochemical processes. Simultaneously, excess zinc nitrate and iron nitrate on the surface decompose at high temperatures to produce P-type semiconductors zinc oxide and iron oxide, respectively, which form a p-n heterojunction with TiO2, significantly increasing the number and oxidizability of photogenerated holes on the titanium dioxide surface. Furthermore, the presence of an electric field in the reactor causes anions such as Cl- to accumulate at the anode. These anions are oxidized by the photogenerated holes on the anode surface into active substances such as Cl·, which are used to oxidize organic pollutants. By varying the voltage to control the electrochemical oxidation potential, the byproducts of salt ion free radical oxidation are reduced and the efficient Cl- / Cl· cycle is promoted. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a graph showing the COD changes of pollutants catalytically degraded by the photoelectric coupling materials prepared in Examples 1 to 4 of the present invention in combination with comparative experiments.

[0025] Figure 2 This is a graph showing salinity changes in the catalytic degradation of pollutants by the photoelectric coupling materials prepared in Examples 1 to 4 of the present invention in combination with comparative experiments. DETAILED DESCRIPTION

[0026] The present invention is described below by specific embodiments. Unless otherwise specified, the technical means used in the present invention are methods well known to those skilled in the art. In addition, the embodiments should be understood to be illustrative rather than limiting the scope of the present invention, and the spirit and scope of the present invention are limited only by the claims. For those skilled in the art, without departing from the spirit and scope of the present invention, these embodiments are subjected to several equivalent transformations and substitutions, and these equivalent transformations and substitutions should also be considered to belong to the scope of protection of the present invention.

[0027] Example 1:

[0028] In this embodiment, the specific preparation method of the photoelectric coupling catalytic material is as follows:

[0029] (1) Dissolve 3 mmol of ferric nitrate and 3 mmol of zinc nitrate in 100 mL of deionized water and stir for 30 min; weigh 2 g of sodium alginate and disperse it in 100 mL of deionized water. Use a disposable syringe to slowly drop it into the ferric nitrate and zinc nitrate precursor solution, pour it into a mold and let it stand at room temperature for 24 h to form a cross-linked alginate hydrogel.

[0030] (2) The hydrogel was removed from the mold and the surface was rinsed with deionized water, and then freeze-dried at -40 °C for 12 h to obtain alginate aerogel.

[0031] (3) The aerogel was calcined at 300°C in a N2 environment for 6 h to obtain alginate aerogel with a porous three-dimensional structure after carbonization.

[0032] (4) 0.3 g of titanium dioxide P25 was added to 100 mL of sodium hydroxide solution with a concentration of 10 mol / L and mixed evenly. The mixed solution and the carbonized aerogel were poured into a hydrothermal reactor, and the hydrothermal reactor was placed in a constant temperature oil bath and reacted at 150 ° C for 24 h. The reaction was rinsed twice with 0.1 mol / L dilute nitric acid, and then rinsed three times with deionized water and dried at 80 ° C for 12 h to obtain a photoelectric coupling catalytic material.

[0033] The catalytic material is placed as follows: the photoelectric coupling catalytic material is placed in a photoelectric coupling reactor as the anode material, with the titanium dioxide surface facing the ultraviolet light. 1 L of high-salt organic wastewater with a salinity of 40 ppt and a COD content of 5000 mg / L is added to the reactor. The power of the photoelectric coupling reactor is turned on, and the reaction is carried out for 60 minutes. The water sample is taken out to detect the remaining COD content and salinity changes.

[0034] Example 2:

[0035] In this embodiment, the specific preparation method of the photoelectric coupling catalytic material is as follows:

[0036] (1) Dissolve 4 mmol of ferric nitrate and 4 mmol of zinc nitrate in 100 mL of deionized water and stir for 30 min; weigh 3 g of sodium alginate and disperse it in 100 mL of deionized water. Use a disposable syringe to slowly drop it into the ferric nitrate and zinc nitrate precursor solution, pour it into a mold and let it stand at room temperature for 24 h to form a cross-linked alginate hydrogel.

[0037] (2) The hydrogel was removed from the mold and the surface was rinsed with deionized water, and then freeze-dried at -40 °C for 12 h to obtain alginate aerogel.

[0038] (3) The aerogel was calcined at 400°C in a N2 environment for 6 h to obtain alginate aerogel with a porous three-dimensional structure after carbonization.

[0039] (4) 0.4 g of titanium dioxide P25 was added to 100 mL of sodium hydroxide solution with a concentration of 10 mol / L and mixed evenly. The mixed solution and the carbonized aerogel were poured into a hydrothermal reactor, and the hydrothermal reactor was placed in a constant temperature oil bath and reacted at 150 ° C for 24 h. The reaction was rinsed twice with 0.1 mol / L dilute nitric acid, rinsed three times with deionized water, and dried at 80 ° C for 12 h to obtain a photoelectric coupling catalytic material.

[0040] The catalytic material is placed as follows: the photoelectric coupling catalytic material is placed in a photoelectric coupling reactor as the anode material, with the titanium dioxide surface facing the ultraviolet light. 1 L of high-salt organic wastewater with a salinity of 40 ppt and a COD content of 5000 mg / L is added to the reactor. The power of the photoelectric coupling reactor is turned on, and the reaction is carried out for 60 minutes. The water sample is taken out to detect the remaining COD content and salinity changes.

[0041] Example 3:

[0042] In this embodiment, the specific preparation method of the photoelectric coupling catalytic material is as follows:

[0043] (1) Dissolve 4 mmol of ferric nitrate and 4 mmol of zinc nitrate in 100 mL of deionized water and stir for 30 min; weigh 5 g of sodium alginate and disperse it in 100 mL of deionized water. Use a disposable syringe to slowly drop it into the ferric nitrate and zinc nitrate precursor solution, pour it into a mold and let it stand at room temperature for 24 h to form a cross-linked alginate hydrogel.

[0044] (2) The hydrogel was removed from the mold and the surface was rinsed with deionized water, and then freeze-dried at -40 °C for 12 h to obtain alginate aerogel.

[0045] (3) The aerogel was calcined at 500°C in a N2 environment for 8 h to obtain alginate aerogel with a porous three-dimensional structure after carbonization.

[0046] (4) 0.5 g of titanium dioxide P25 was added to 100 mL of sodium hydroxide solution with a concentration of 10 mol / L and mixed evenly. The mixed solution and the carbonized aerogel were poured into a hydrothermal reactor, and the hydrothermal reactor was placed in a constant temperature oil bath and reacted at 150 ° C for 24 h. The reaction was rinsed twice with 0.1 mol / L dilute nitric acid, rinsed three times with deionized water, and dried at 80 ° C for 12 h to obtain a photoelectric coupling catalytic material.

[0047] The catalytic material is placed as follows: the photoelectric coupling catalytic material is placed in a photoelectric coupling reactor as the anode material, with the titanium dioxide surface facing the ultraviolet light. 1 L of high-salt organic wastewater with a salinity of 40 ppt and a COD content of 5000 mg / L is added to the reactor. The power of the photoelectric coupling reactor is turned on, and the reaction is carried out for 60 minutes. The water sample is taken out to detect the remaining COD content and salinity changes.

[0048] Example 4:

[0049] In this embodiment, the specific preparation method of the photoelectric coupling catalytic material is as follows:

[0050] (1) Dissolve 5 mmol of ferric nitrate and 5 mmol of zinc nitrate in 100 mL of deionized water and stir for 30 min; weigh 7.5 g of sodium alginate and disperse it in 150 mL of deionized water. Use a disposable syringe to slowly drop it into the ferric nitrate and zinc nitrate precursor solution, pour it into a mold, and let it stand at room temperature for 24 h to form a cross-linked alginate hydrogel.

[0051] (2) The hydrogel was removed from the mold and the surface was rinsed with deionized water, and then freeze-dried at -40 °C for 12 h to obtain alginate aerogel.

[0052] (3) The aerogel was calcined at 500°C for 10 h in a N2 environment to obtain alginate aerogel with a porous three-dimensional structure after carbonization.

[0053] (4) 0.5 g of titanium dioxide P25 was added to 100 mL of sodium hydroxide solution with a concentration of 10 mol / L and mixed evenly. The mixed solution and the carbonized aerogel were poured into a hydrothermal reactor, and the hydrothermal reactor was placed in a constant temperature oil bath and reacted at 150 ° C for 24 h. The reaction was rinsed twice with 0.1 mol / L dilute nitric acid, rinsed three times with deionized water, and dried at 80 ° C for 12 h to obtain a photoelectric coupling catalytic material.

[0054] The catalytic material is placed as follows: the photoelectric coupling catalytic material is placed in a photoelectric coupling reactor as the anode material, with the titanium dioxide surface facing the ultraviolet light. 1 L of high-salt organic wastewater with a salinity of 40 ppt and a COD content of 5000 mg / L is added to the reactor. The power of the photoelectric coupling reactor is turned on, and the reaction is carried out for 60 minutes. The water sample is taken out to detect the remaining COD content and salinity changes.

[0055] Comparative experiment 1:

[0056] When there is no photoelectric coupling catalytic material, add 1L of high-salt organic wastewater with a salinity of 40ppt and a COD content of 5000mg / L into the photoelectric coupling reactor, turn on the power of the photoelectric coupling reactor, react for 60 minutes, and take out the water sample to detect its residual COD content and salinity changes.

[0057] Comparative experiment 2:

[0058] Using the photoelectric coupled catalytic material prepared in Example 3, 1 L of high-salt organic wastewater with a salinity of 40 ppt and a COD content of 5000 mg / L was added to the photoelectric coupled reactor. The photoelectric coupled reactor was turned on without ultraviolet light and reacted for 60 minutes. The water sample was taken out to detect the remaining COD content and salinity change.

[0059] Comparative experiment 3:

[0060] Using the photoelectric coupled catalytic material prepared in Example 3, 1 L of high-salt organic wastewater with a salinity of 40 ppt and a COD content of 5000 mg / L was added to a photoelectric coupled reactor. The reaction was carried out under ultraviolet light alone for 60 minutes, and the water sample was taken out to detect the residual COD content and salinity change.

Claims

1. A method for preparing a material having photoelectric coupled catalytic performance, characterized in that: The preparation steps are as follows: S1, preparation of alginate aqueous solution; S2, preparing a zinc salt solution and an iron salt solution, and mixing the two to form a precursor solution; S3, uniformly mixing the prepared alginate aqueous solution and the precursor solution, and allowing to stand to obtain a cross-linked alginate hydrogel; S4, washing the surface of the alginate hydrogel and freeze-drying it to obtain alginate aerogel; S5, calcining the alginate aerogel at a high temperature in a nitrogen, argon or neon atmosphere to obtain a carbonized alginate aerogel; S6, adding TiO2 to the sodium hydroxide solution and mixing evenly, then pouring the mixture and the carbonized aerogel into a hydrothermal reactor for reaction; S7, washing the material obtained in the previous step with a dilute acid solution, washing with water, and drying to obtain the material having photoelectric coupling catalytic performance.

2. The preparation method according to claim 1, wherein: The weight percentage of the alginate aqueous solution is 2wt% to 5wt%.

3. The preparation method according to claim 1, wherein: The alginate includes sodium alginate, potassium alginate, calcium alginate or magnesium alginate; wherein, when the zinc salt and the iron salt described in S2 are sulfates, calcium alginate cannot be used as the alginate.

4. The preparation method according to claim 1, wherein: The zinc salt solution and the iron salt solution described in step S2 include zinc nitrate solution and ferric nitrate solution, zinc chloride solution and ferric chloride solution, zinc sulfate solution and ferric sulfate solution, and zinc acetate solution and ferric acetate solution. The dilute acid solution described in step S7 includes dilute nitric acid, dilute hydrochloric acid, dilute sulfuric acid or dilute acetic acid, corresponding to the anion species of the zinc salt solution and the iron salt solution described in step S2.

5. The preparation method according to claim 1, wherein: The precursor solution is prepared by mixing a zinc salt solution with a molar concentration of 0.03 to 0.06 mol / L and an iron salt solution with a molar concentration of 0.03 to 0.06 mol / L in a volume ratio of 1:5 to 5:

1.

6. The preparation method according to claim 1, wherein: Step S6 is to add TiO2 to a sodium hydroxide solution with a molar concentration of 10-20 mol / L and mix them evenly, then pour the mixed solution and the carbonized aerogel into a hydrothermal reactor and react at 150-200°C for 24-48 hours.

7. The preparation method according to claim 1, wherein: The TiO2 used is titanium dioxide P25, and the amount of the added amount is 3-10 g / L.

8. A material obtained by the preparation method according to any one of claims 1 to 7.

9. Use of a material according to claim 8, characterized in that: It is used to treat organic pollutants in wastewater.

10. The use according to claim 9, characterized in that: The material is placed in a photoelectric coupled catalytic reactor as an anode electrode to treat high-salt organic dye wastewater; this material as an anode electrode can remove organic pollutants in water through photocatalytic oxidation, and can also degrade organic pollutants in water through electrochemical oxidation.

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