Application of zinc oxide-coated mesoporous silica particles in wastewater containing refractory organic pollutants

Abstract

The present invention provides an application of zinc oxide-coated mesoporous silica particles in wastewater containing refractory organic pollutants, belonging to the field of deep sewage treatment. The zinc oxide-coated mesoporous silica particles are spherical particles with a core-shell structure, with mesoporous silica particles as the core and zinc oxide as the shell. Preparation method: dissolve dodecylamine or hexadecyltrimethylammonium bromide in an organic solvent, add a silicon source solution, react in a water bath, separate the solid and liquid to obtain a solid phase, and perform a first roasting of the solid phase to obtain mesoporous silica, which is dispersed in water to obtain an aqueous solution containing mesoporous silica; the zinc source solution is dripped into the aqueous solution containing mesoporous silica under ultrasonic conditions to obtain a mixed solution, the mixed solution is adjusted to alkaline, and the obtained solid matter is roasted for a second time to obtain zinc oxide-coated mesoporous silica particles. The preparation method and application method of the present invention are simple, the raw materials are cheap and easy to obtain, the cost of treating sewage is low, the catalytic efficiency is high, and it is conducive to large-scale sewage treatment.

Description

Technical Field

[0001] The present invention relates to the technical field of advanced sewage treatment, and in particular to the application of zinc oxide-coated mesoporous silica particles in wastewater containing refractory organic pollutants. Background Art

[0002] Wastewater discharge introduces many refractory organic pollutants into natural water bodies, such as pharmaceuticals and personal care products (PPCPs) and endocrine disruptors (EDCs), which have adverse effects on the natural environment and human health. Refractory organic pollutants generally have the following characteristics: long residence time, accumulation in organisms, and difficulty in removal by traditional methods. Some phenolic pollutants, such as bisphenol A, nonylphenol, and halogenated phenols, are classified as new pollutants due to their chemical stability, low bioavailability, and non-traditional toxicity due to the presence of benzene rings and substituents in their structures. Therefore, there is an urgent need to develop effective, stable, low-cost, and green deep treatment processes.

[0003] At present, advanced oxidation processes (AOPs) are considered to be an effective water treatment technology for eliminating refractory organic pollutants due to their economic benefits, environmental benefits and convenient operating conditions. - ), sulfate radical (SO4 - Oxidatively active species such as free radicals ( ) can play an important role in the degradation of organic pollutants. However, these free radicals have high energy consumption, low activation efficiency, and are easily captured by background components in wastewater, which in turn affects their ability to degrade organic pollutants.

[0004] Potassium permanganate (KMnO4), also known as potassium permanganate, is a strong oxidant widely used in water treatment processes as an economical, easy-to-store, and relatively stable agent. Potassium permanganate has a high redox potential, produces few disinfection byproducts, is easy to store, and is inexpensive, making it a commonly used oxidant in water treatment processes. However, potassium permanganate oxidation technology also has drawbacks such as high dosage, low oxidation rate, and the tendency to produce residual color. This is particularly true for emerging pollutants, some of which have stable chemical properties, making it difficult to achieve stable and efficient removal using potassium permanganate oxidation alone.

[0005] Mesoporous silica (MSNs) are an emerging class of materials with unique structures and properties, including high specific surface area, adjustable pore size, good hydrothermal stability, and a stable framework that can be easily functionalized. They offer significant advantages in adsorbing pollutants from wastewater. Silica materials can be manipulated to adjust their physical and chemical properties. For example, size, shape, and porosity can be easily controlled, while surface modifications can be introduced to alter the chemical properties of silica materials. However, the development of single silica-based materials is limited by factors such as their relatively simple structure and properties and low biodegradability.

[0006] Zinc oxide has attracted significant attention as a catalyst due to its excellent reducing properties and high catalytic efficiency. It has been widely used in the catalytic degradation of organic matter in dye wastewater, while also preventing secondary pollution. However, zinc oxide has poor stability and easily loses its activity in water.

[0007] Therefore, the present invention proposes a method for deep treatment of phenol-containing wastewater by catalyzing potassium permanganate with zinc oxide-coated mesoporous silica particles. Summary of the Invention

[0008] To address the above technical issues, the present invention provides the use of zinc oxide-coated mesoporous silica particles (MSNs@ZnO) in wastewater containing difficult-to-degrade organic pollutants. The present invention features simple preparation and application methods, utilizes readily available and inexpensive raw materials, reduces wastewater treatment costs, and offers high catalytic efficiency, making it suitable for large-scale wastewater treatment.

[0009] The object of the present invention is to provide a zinc oxide-coated mesoporous silica particle for use in wastewater containing refractory organic pollutants. The zinc oxide-coated mesoporous silica particle is a spherical particle with a core-shell structure, with the mesoporous silica particle as the core and the zinc oxide as the shell.

[0010] The particle size of the spherical particles is 1.4-2 mm.

[0011] In some embodiments of the present invention, the mass ratio of the zinc oxide-coated mesoporous silica particles, potassium permanganate, and peroxymonosulfate is 1:(0.007-0.03):0.5;

[0012] The application is to use the zinc oxide-coated mesoporous silica particles to catalyze potassium permanganate and peroxymonosulfate to deeply treat wastewater containing difficult-to-degrade organic pollutants.

[0013] In some embodiments of the present invention, the concentration of the excessive organic pollutants is 0.1-100 mg / L;

[0014] The organic pollutants include phenolic organic pollutants;

[0015] The phenolic organic pollutants include one or more of phenol, methylphenol, nitrophenol, aminophenol, halogenated phenol, p-tert-butylphenol, nonylphenol, octylphenol, bisphenol A, bisphenol S, bisphenol F, bisphenol AF, hydroquinone and naphthol.

[0016] The peroxymonosulfate is selected from one or more of potassium peroxymonosulfate, sodium peroxymonosulfate, and ammonium peroxymonosulfate.

[0017] In some embodiments of the present invention, the method for preparing zinc oxide-coated mesoporous silica particles comprises the following steps:

[0018] S1. dissolving dodecylamine (DDA) in an organic solvent and adding a silicon source solution, reacting in a water bath, separating the solid and liquid to obtain a solid phase, calcining the obtained solid phase for the first time to obtain mesoporous silica, and dispersing it in water to obtain a suspension containing mesoporous silica;

[0019] S2. Provide a zinc source solution, drop it into an aqueous solution containing mesoporous silica under ultrasonic conditions to obtain a mixed solution, adjust the mixed solution to neutral or alkaline, stir the reaction, and calcine the obtained solid material for a second time to obtain zinc oxide-coated mesoporous silica particles MSNs@ZnO.

[0020] In some embodiments of the present invention, in step S1, the organic solvent is selected from ethanol and / or tetrahydrofuran;

[0021] The molar ratio of dodecylamine to the organic solvent is 1:(34-40).

[0022] In some embodiments of the present invention, in step S1, the silicon source is selected from tetraethyl orthosilicate (TEOS);

[0023] The molar ratio of the silicon source to the organic solvent is 1:(3.4-5);

[0024] The conditions of the water bath reaction are: reaction temperature is 70-85°C, and reaction time is 20-24h;

[0025] The conditions for the first calcination are as follows: the calcination temperature is 350-500° C., and the calcination time is 3-5 hours.

[0026] In some embodiments of the present invention, in step S2, the zinc source in the zinc source solution is selected from one or more of Zn(NO3)2·6H2O, ZnSO4·7H2O and ZnCl2;

[0027] The solvent of the zinc source solution is ethanol and / or tetrahydrofuran.

[0028] In the zinc source solution, n(Zn):n(C2H5OH):n(H2O)=1:3.5:10;

[0029] In some embodiments of the present invention, in step S2, the mass ratio of zinc to silicon in the mixed solution is (1:1)-(1:10).

[0030] In some embodiments of the present invention, in step S2, the alkaline pH value is greater than 7;

[0031] The reaction stirring time is 10-12h;

[0032] The conditions for the second calcination are as follows: the calcination temperature is 500-540° C., and the calcination time is 4-6 hours.

[0033] The above technical solution of the present invention has the following advantages over the prior art:

[0034] To address the practical problem of deep treatment of phenolic organic pollutants in wastewater, this invention prepares zinc oxide-coated mesoporous silica particles (MSNs@ZnO). Potassium permanganate oxidizes phenolic organic pollutants to produce hexavalent manganese, which then forms a stable hexavalent manganese complex on the surface of the MSNs@ZnO. The MSNs@ZnO prepared in this invention uses mesoporous silica as its core, which has a rich pore structure and high specific surface area, allowing it to load a large amount of zinc oxide. The reaction principle of the MSNs@ZnO is to create an alkaline environment on the surface of the material, providing adsorption sites for the hexavalent manganese produced during the potassium permanganate reaction, thereby stabilizing the hexavalent manganese. Permonosulfate reacts with the hexavalent manganese complex on the surface of the material, oxidizing it to heptavalent manganese, thereby enabling the circulation of manganese in different valence states on the surface. Permonosulfate (PMS) decomposes into hydroxyl radicals and sulfate radicals. In the reaction system, the heptavalent manganese, sulfate radicals, and hydroxyl radicals jointly oxidize each other, achieving efficient treatment of phenolic organic pollutants. Zinc oxide-coated mesoporous silica particles can enable hexavalent manganese and heptavalent manganese to circulate on the surface of the material, efficiently capture electrons of phenolic organic pollutants in the water environment, and accelerate the degradation of phenolic organic pollutants.

[0035] In the prior art, the catalytic oxidation of potassium permanganate usually relies on the reduction of potassium permanganate. However, the catalysis of zinc oxide-coated mesoporous silica particles in the present invention does not rely on the reduction of potassium permanganate. Instead, it enables manganese of different valence states to circulate on the surface of the material and jointly degrade organic pollutants in water, greatly improving the utilization rate of potassium permanganate and providing an effective method for the deep treatment of wastewater containing phenolic organic pollutants, a new pollutant in sewage.

[0036] The present invention selects mesoporous silica as a carrier and generates silica based on the hydrolysis and condensation of tetraethyl orthosilicate (TEOS), a silicon source.

[0037] ,

[0038] ,

[0039] Although silica is an inert catalyst and generally lacks catalytic activity, the present invention utilizes the high specific surface area, high porosity, and strong adsorption properties of mesoporous silica to load zinc oxide onto it, creating a heterogeneous, millimeter-scale catalyst. The alkaline environment regulated by ammonia creates a highly ordered mesoporous particle structure, providing a wide range of catalytic reaction possibilities.

[0040] The wastewater containing phenolic organic pollutants of the present invention is a common type of wastewater in the environment, and phenol is the most important phenolic organic pollutant. The reason why the present invention is applicable to phenolic organic pollutants is that permanganate is more effective for phenolic compounds, and secondly, permanganate oxidation of phenolic compounds can undergo a single-electron reaction to generate hexavalent manganese, thereby forming a hexavalent manganese stable complex on the catalyst surface, which can further react with PMS to regenerate heptavalent manganese and free radicals. Therefore, the present invention provides a novel and efficient method for accelerating the purification of wastewater containing phenolic organic pollutants.

[0041] The zinc oxide-coated silica method of the present invention is applicable to silicon from various sources, such as wood and straw biomass, general industrial solid waste, and natural minerals. It offers the advantages of low cost, renewable availability, and high silicon content, meeting the requirements for preparing mesoporous silicon materials. The resulting MSNs@ZnO has an alkaline surface, which not only exhibits unique catalytic activity but also allows manganese of varying valence states to circulate on the material surface. The reaction simultaneously generates sulfate and hydroxyl radicals, further enhancing oxidation, enabling efficient treatment of phenolic pollutants in wastewater and improving electron utilization in the wastewater.

[0042] The method of the present invention has a small amount of potassium permanganate added, does not cause water color and manganese dioxide clogging problems, and can achieve rapid removal of phenolic pollutants under the condition of a small amount of potassium permanganate added. DETAILED DESCRIPTION

[0043] The present invention will be further described below with reference to specific examples so that those skilled in the art can better understand the present invention and implement it, but the examples are not intended to limit the present invention.

[0044] Example 1:

[0045] This embodiment provides a method for preparing zinc oxide-coated mesoporous silica, comprising the following steps:

[0046] (1) Preparation of mesoporous silica: Dissolve 0.36 g of dodecylamine (DDA) in 50 ml of anhydrous ethanol and stir at room temperature for 45 min. Dissolve 35.68 g of tetraethyl orthosilicate (TEOS) in the above solution and react in a water bath at 80°C for 20 h. Centrifuge, wash, and calcine at 350°C for 4 h to obtain mesoporous silica.

[0047] (2) Preparation of zinc oxide-coated mesoporous silica particles: At room temperature, 50 mg of the mesoporous silica obtained in step (1) was weighed and dispersed in 20 ml of ultrapure water to obtain a suspension containing mesoporous silica. 31.31 g of Zn(NO3)2·6H2O was dissolved in 20 ml of 32% ethanol solution and added dropwise to the aqueous solution containing mesoporous silica under ultrasonic conditions. Ammonia was added to adjust the pH to 10. The reaction was stirred for 10 hours, centrifuged, washed, and calcined at 500°C for 4 hours to obtain zinc oxide-coated mesoporous silica particles. The particles were sieved with a 10-mesh sieve to obtain spherical particles with a particle size of 2 mm. The spherical particles had good dispersibility, which may be due to the steric hindrance effect of the polymer compounds dodecylamine and ethyl orthosilicate. The zinc oxide-coated mesoporous silica particles of the present invention can enable heptavalent manganese and hexavalent manganese to circulate on the surface of the material, capture electrons of new pollutants in sewage, and thus accelerate the decomposition of difficult-to-degrade organic pollutants. The reaction simultaneously generates sulfate and hydroxyl radicals, further contributing to the oxidative effect. Zinc oxide-coated mesoporous silica particles catalyze potassium permanganate for deep wastewater treatment, effectively removing difficult-to-degrade organic pollutants from wastewater while also improving the utilization rate of electrons in wastewater.

[0048] Example 2

[0049] This embodiment provides a method for preparing zinc oxide-coated mesoporous silica, comprising the following steps:

[0050] (1) Preparation of mesoporous silica: Dissolve 0.36 g of dodecylamine (DDA) in 50 ml of anhydrous ethanol and stir at room temperature for 45 min. Dissolve 35.68 g of tetraethyl orthosilicate (TEOS) in the above solution and react in a water bath at 80°C for 20 h. Centrifuge, wash, and calcine at 500°C for 5 h to obtain mesoporous silica.

[0051] (2) Preparation of zinc oxide-coated mesoporous silica particles: 100 mg of the mesoporous silica obtained in step (1) was weighed and dispersed in 40 ml of ultrapure water at room temperature to obtain a suspension containing mesoporous silica. 62.62 g of Zn(NO3)2·6H2O was dissolved in 40 ml of 32% ethanol solution and added dropwise to the aqueous solution containing mesoporous silica under ultrasonic conditions. Ammonia water was added to adjust the pH to 10. The reaction was stirred for 12 h, centrifuged, washed, and calcined at 540°C for 5 h to obtain zinc oxide-coated mesoporous silica particles. The particles were sieved through a 10-mesh sieve to obtain spherical particles with a particle size of 2 mm.

[0052] Application Example 1:

[0053] The MSNs@ZnO particles prepared in Example 1, potassium permanganate, and potassium permonosulfate were added to simulated sewage at a mass ratio of 1:(0.007-0.03):0.5. The sewage contained 11.4 mg / L of bisphenol A. The concentrations of MSNs@ZnO, potassium permanganate, and potassium permonosulfate were 1 g / L, 7.9 mg / L, and 0.5 g / L, respectively. A control group containing the same concentrations of potassium permanganate and potassium permonosulfate was added to the same volume of simulated sewage. The experiments were conducted at pH values ​​of 7 and 8, respectively.

[0054] High performance liquid chromatography (HPLC) was used to determine the concentration of organic matter in the simulated wastewater and to detect the change of bisphenol A concentration in the wastewater over time. The removal rates of bisphenol A in the two groups of experiments are shown in Table 1.

[0055] Table 1 Bisphenol A removal rate (%)

[0056]

[0057] From Table 1, we can see that under the condition of pH 7, the addition of MSNs@ZnO will promote

[0058] The degradation of bisphenol A was promoted, but the degradation effect was not as significant as that at pH 8.

[0059] Application Comparative Example 1:

[0060] Unlike Application Example 1, only potassium permanganate and bisphenol A at the same concentration were added to the simulated wastewater. The pH of the reaction mixture was controlled at 8. The changes in the removal rate of bisphenol A over time are shown in Table 2.

[0061] Application Comparative Example 2:

[0062] Unlike Application Example 1, only potassium permanganate, MSNs@ZnO, and bisphenol A were added to the simulated wastewater at the same concentrations. The pH of the reaction mixture was controlled at 8. The changes in bisphenol A removal rate over time are shown in Table 2.

[0063] Application Comparative Example 3:

[0064] Unlike Application Example 1, only potassium permanganate, potassium permonosulfate, and bisphenol A were added to the simulated wastewater at the same concentrations. The pH of the mixed solution was controlled at 8. The changes in the removal rate of bisphenol A over time are shown in Table 2.

[0065] Table 2 Bisphenol A removal rate (%)

[0066]

[0067] From the data in Table 2, it can be seen that the zinc oxide-coated mesoporous silica material prepared by the present invention has an insignificant catalytic effect when only potassium permanganate is used as an oxidant; when potassium permanganate and potassium permonosulfate are present as oxidants, the catalytic oxidation effect is greatly improved.

[0068] Application Comparative Example 4:

[0069] The MSNs@ZnO prepared in Example 1 (two comparison groups, zinc oxide alone and mesoporous silica alone) were added to simulated wastewater at a mass ratio of 1:(0.007-0.03):0.5. The wastewater contained 11.4 mg / L of bisphenol A. The concentrations of MSNs@ZnO / zinc oxide / mesoporous silica were 1 g / L, potassium permanganate was 7.9 mg / L, and potassium permonosulfate was 0.5 g / L. A control group was treated with the same concentrations of potassium permanganate, potassium permonosulfate, and bisphenol A. The experimental pH was 8. The changes in bisphenol A removal efficiency over time are shown in Table 3.

[0070] Table 3 Bisphenol A removal rate (%)

[0071]

[0072] From the data in Table 3, it can be seen that the addition of mesoporous silica alone is inert to the degradation reaction and basically does not catalyze the oxidation process of potassium permanganate. Although the addition of zinc oxide has a certain catalytic oxidation effect on potassium permanganate, it is not as significant as the MSNs@ZnO prepared in the present invention.

[0073] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A method for treating wastewater containing refractory organic pollutants by catalyzing potassium permanganate and peroxymonosulfate with mesoporous silica particles coated with zinc oxide. The mesoporous silica particles coated with zinc oxide are spherical particles with a core-shell structure, with the mesoporous silica particles as the core and the zinc oxide as the shell. The particle size of the spherical particles is 1.4-2 mm; The organic pollutants include phenolic organic pollutants; The surface of zinc oxide-coated mesoporous silica particles is alkaline; The phenolic organic pollutants include one or more of phenol, methylphenol, nitrophenol, aminophenol, halogenated phenol, p-tert-butylphenol, nonylphenol, octylphenol, bisphenol A, bisphenol S, bisphenol F, bisphenol AF, hydroquinone and naphthol; The preparation method of the zinc oxide-coated mesoporous silica particles comprises the following steps: S1. dissolving dodecylamine or hexadecyltrimethylammonium bromide in an organic solvent, adding a silicon source solution, reacting in a water bath, separating the solid and liquid to obtain a solid phase, calcining the obtained solid phase for the first time to obtain mesoporous silica, and dispersing it in water to obtain a suspension containing mesoporous silica; S2. Provide a zinc source solution, add it dropwise to an aqueous solution containing mesoporous silica under ultrasonic conditions to obtain a mixed solution, adjust the mixed solution to alkaline, react and stir, and calcine the obtained solid material for a second time to obtain zinc oxide-coated mesoporous silica particles MSNs@ZnO; The mass ratio of the zinc oxide-coated mesoporous silica particles, potassium permanganate and peroxymonosulfate is 1:(0.007-0.03):0.

5.

2. The use according to claim 1, characterized in that The concentration of the organic pollutants is 0.1-100 mg / L.

3. The use according to claim 1, characterized in that The peroxymonosulfate is selected from one or more of potassium peroxymonosulfate, sodium peroxymonosulfate, and ammonium peroxymonosulfate.

4. The use according to claim 1, characterized in that In step S1, the organic solvent is selected from ethanol or tetrahydrofuran; The molar ratio of dodecylamine or hexadecyltrimethylammonium bromide to the organic solvent is 1:(34-40).

5. The use according to claim 1, characterized in that In step S1, the silicon source is selected from ethyl orthosilicate; The molar ratio of the silicon source to the organic solvent is 1:(3.4-5); The conditions of the water bath reaction are: reaction temperature is 70-85°C, and reaction time is 20-24h; The conditions for the first calcination are as follows: the calcination temperature is 350-500° C., and the calcination time is 3-5 hours.

6. The use according to claim 1, characterized in that In step S2, the zinc source in the zinc source solution is selected from Zn(NO3)2·6H2O, ZnSO4·7H2O or ZnCl2; The solvent of the zinc source solution is ethanol or tetrahydrofuran.

7. The use according to claim 1, characterized in that In step S2, the mass ratio of zinc to silicon in the mixed solution is (1:1)-(1:10).

8. The use according to claim 1, characterized in that In step S2, the alkaline pH value is greater than 7; The reaction stirring time is 10-12h; The conditions for the second calcination are as follows: the calcination temperature is 500-540° C., and the calcination time is 4-6 hours.

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