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

Abstract

The invention provides application of zinc oxide coated mesoporous silica particles in wastewater containing refractory organic pollutants, and belongs to the field of advanced sewage treatment. The zinc oxide coated mesoporous silica particle is a spherical particle with a core-shell structure, the mesoporous silica particle is used as a core, and zinc oxide is used as a shell. The preparation method comprises the following steps: dissolving dodecylamine or hexadecyl trimethyl ammonium bromide in an organic solvent, adding a silicon source solution, carrying out water bath reaction, carrying out solid-liquid separation to obtain a solid phase, carrying out primary roasting on the solid phase to obtain mesoporous silica, and dispersing the mesoporous silica in water to obtain an aqueous solution containing the mesoporous silica; and dropwise adding the zinc source solution into the aqueous solution containing the mesoporous silica under an ultrasonic condition to obtain a mixed solution, adjusting the mixed solution to be alkaline, and roasting the obtained solid substance for the second time to obtain the zinc oxide coated mesoporous silica particles. The preparation method and the application method are simple, the raw materials are cheap and easy to obtain, the sewage treatment cost is low, the catalytic efficiency is high, and large-scale sewage treatment is facilitated.

Description

Technical Field

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

[0002] Sewage discharge introduces many refractory organic pollutants into natural water bodies, such as pharmaceuticals and personal care products (PPCPs), endocrine disruptors (EDCs), etc., 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 difficult removal by traditional methods. Among them, some phenolic pollutants, such as bisphenol A, nonylphenol, halogenated phenols, etc., are classified as new pollutants because of their chemical structural 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 - ·) 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 wastewater background components, which in turn affects their degradation of organic pollutants.

[0004] Potassium permanganate (KMnO4), also known as potassium permanganate, is an economical, easy-to-store and relatively stable strong oxidant widely used in water treatment processes. Potassium permanganate has a high redox potential, produces fewer disinfection by-products, is easy to store and has a low price. It is one of the commonly used oxidants in water treatment processes. However, potassium permanganate oxidation technology also has defects such as high dosage, low oxidation rate, and easy residual color. Especially for emerging pollutants, some pollutants are difficult to remove stably and efficiently using potassium permanganate oxidation technology alone due to their stable chemical properties.

[0005] Mesoporous silica (MSNs) is a new type of material with unique structures and properties such as high specific surface area, adjustable pore size, good hydrothermal stability, and a stable skeleton that is easy to functionalize. It has significant advantages in adsorbing pollutants in wastewater. For silica materials, their physical and chemical properties can be adjusted. For example, the size, shape and porosity can be easily controlled, and surface modification can be introduced to change the chemical properties of silica materials. However, the development of a single silica base is limited due to factors such as its relatively simple structure and performance and low biodegradability.

[0006] Zinc oxide has become a catalyst that people pay close attention to due to its good reducibility and high catalytic efficiency. It has been widely used in the catalytic degradation of organic matter in dye wastewater, while avoiding secondary pollution. However, zinc oxide has poor stability and is easily inactive 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] In order to solve the above technical problems, the present invention provides an application of zinc oxide-coated mesoporous silica particles (MSNs@ZnO) in wastewater containing refractory organic pollutants. The preparation method and application method of the present invention are relatively simple, the raw materials are cheap and easy to obtain, the cost of treating wastewater is low, the catalytic efficiency is high, and it is conducive to large-scale wastewater treatment.

[0009] The object of the present invention is to provide an application of zinc oxide-coated mesoporous silica particles in wastewater containing refractory organic pollutants, wherein the zinc oxide-coated mesoporous silica particles 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.

[0010] 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; 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.

[0011] In some embodiments of the present invention, the concentration of the excessive organic pollutants is 0.1-100 mg / L; The organic pollutants include phenolic organic pollutants; 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.

[0012] The peroxymonosulfate is selected from one or more of potassium peroxymonosulfate, sodium peroxymonosulfate and ammonium peroxymonosulfate.

[0013] In some embodiments of the present invention, the method for preparing zinc oxide-coated mesoporous silica particles comprises the following steps: S1, dissolving dodecylamine (DDA) in an organic solvent, adding a silicon source solution, reacting in a water bath, separating the solid and the liquid to obtain a solid phase, calcining the obtained solid phase for the first time to obtain mesoporous silica, dispersing it in water, and obtaining a suspension containing mesoporous silica; 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.

[0014] In some embodiments of the present invention, in step S1, the organic solvent is selected from ethanol and / or tetrahydrofuran; The molar ratio of dodecylamine to the organic solvent is 1:(34-40).

[0015] In some embodiments of the present invention, in step S1, the silicon source is selected from tetraethyl orthosilicate (TEOS); 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.

[0016] 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; The solvent of the zinc source solution is ethanol and / or tetrahydrofuran.

[0017] In the zinc source solution, n(Zn):n(C2H5OH):n(H2O)=1:3.5:10; 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).

[0018] In some embodiments of the present invention, 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.

[0019] The above technical solution of the present invention has the following advantages compared with the prior art: Aiming at the practical problem of deep treatment of phenolic organic pollutants in sewage, the present invention prepares zinc oxide-coated mesoporous silica particles MSNs@ZnO, and potassium permanganate oxidizes phenolic organic pollutants to produce hexavalent manganese, and hexavalent manganese forms a stable hexavalent manganese complex on the surface of MSNs@ZnO. The MSNs@ZnO prepared by the present invention has mesoporous silica as its core, has rich pore structure and high specific surface area, and can load more zinc oxide. The reaction principle of MSNs@ZnO is to form an alkaline environment on the surface of the material, and provide adsorption sites to adsorb hexavalent manganese generated during the potassium permanganate reaction, thereby stabilizing the presence of hexavalent manganese, and permonosulfate reacts with the hexavalent manganese complex on the surface of the material to oxidize it into heptavalent manganese, thereby realizing the circulation of manganese in different valence states on the surface of the material, and permonosulfate (PMS) can be decomposed into hydroxyl radicals and sulfate radicals. In the reaction system, heptavalent manganese and sulfate radicals and hydroxyl radicals jointly undergo oxidation to achieve 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 the electrons of phenolic organic pollutants in the water environment, and accelerate the degradation of phenolic organic pollutants.

[0020] In the prior art, the catalytic oxidation of potassium permanganate usually relies on the reduction of potassium permanganate, while the catalysis of the zinc oxide-coated mesoporous silica particles in the present invention does not rely on the reduction of potassium permanganate, but allows manganese in different valence states to circulate on the surface of the material to jointly degrade organic pollutants in water, greatly improving the utilization rate of potassium permanganate and providing an effective method for deep treatment of wastewater containing phenolic organic pollutants for new pollutants in sewage.

[0021] 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.

[0022] , , Although silicon dioxide is an inert catalyst for catalytic reactions and generally has no catalytic effect, the present invention utilizes the high specific surface area, high porosity and strong adsorption properties of mesoporous silicon dioxide to load zinc oxide thereon to obtain a heterogeneous millimeter-scale catalyst. Accompanied by the alkaline environment regulated by ammonia water, the meso-particles formed have a high degree of order, providing rich possibilities for catalytic reactions.

[0023] 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.

[0024] The method of coating silicon dioxide with zinc oxide in the present invention is applicable to silicon from different sources, such as wood and straw biomass, general industrial solid waste and natural minerals, and has the advantages of low cost, renewability and high silicon content, and meets the preparation requirements of mesoporous silicon materials. The surface of the prepared MSNs@ZnO is alkaline, not only has unique catalytic activity, but also allows manganese in different valence states to circulate on the surface of the material, and the reaction simultaneously generates sulfate radicals and hydroxyl radicals, which further play an oxidizing role, realize the efficient treatment of phenolic pollutants in sewage, and improve the utilization rate of electrons in wastewater.

[0025] The potassium permanganate of the present invention is added in a small amount, and will not cause the problem of water color and manganese dioxide blockage. Moreover, under the condition of a small amount of potassium permanganate, the phenol-containing pollutants can be quickly removed. DETAILED DESCRIPTION

[0026] The present invention is further described below in conjunction with specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0027] Embodiment 1: This embodiment provides a method for preparing zinc oxide-coated mesoporous silica, comprising the following steps: (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, 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.

[0028] (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 then dripped into the aqueous solution containing mesoporous silica under ultrasonic conditions. Ammonia water was added to adjust the pH to 10, and the reaction was stirred for 10 hours. After centrifugation and washing, the solution was calcined at 500°C for 4 hours to obtain zinc oxide-coated mesoporous silica particles, which were sieved with a sieve with a mesh size of 10 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 the electrons of new pollutants in sewage, and thus accelerate the decomposition of difficult-to-degrade organic pollutants. The reaction simultaneously generates sulfate radicals and hydroxyl radicals, which further exert an oxidative effect. Zinc oxide-coated mesoporous silica particles catalyze potassium permanganate for deep sewage treatment, achieving efficient removal of difficult-to-degrade organic pollutants in sewage, and at the same time helping to improve the utilization rate of electrons in sewage.

[0029] Example 2 This embodiment provides a method for preparing zinc oxide-coated mesoporous silica, comprising the following steps: (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, 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.

[0030] (2) Preparation of zinc oxide-coated mesoporous silica particles: At room temperature, weigh 100 mg of the mesoporous silica obtained in step (1) and disperse it in 40 ml of ultrapure water to obtain a suspension containing mesoporous silica. Dissolve 62.62 g of Zn(NO3)2·6H2O in 40 ml of 32% ethanol solution, and drip it into the aqueous solution containing mesoporous silica under ultrasonic conditions. Add ammonia water to adjust the pH to 10, stir the reaction for 12 h, centrifuge, wash, and calcine at 540°C for 5 h to obtain zinc oxide-coated mesoporous silica particles, which are sieved with a 10-mesh sieve to obtain spherical particles with a particle size of 2 mm.

[0031] Application Example 1: The MSNs@ZnO particles, potassium permanganate and potassium permonosulfate prepared in Example 1 were put into simulated sewage at a mass ratio of 1:(0.007-0.03):0.5. The sewage contained 11.4 mg / L of bisphenol A, and the concentration of MSNs@ZnO, potassium permanganate and potassium permonosulfate was 1 g / L, 7.9 mg / L and 0.5 g / L, respectively. The same concentrations of potassium permanganate and potassium permonosulfate were used as a control group and put into the same volume of simulated sewage. The experiments were carried out at pH values ​​of 7 and 8, respectively.

[0032] 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.

[0033] Table 1 Bisphenol A removal rate (%)

[0034] From Table 1, we can see that under the condition of pH 7, adding MSNs@ZnO will promote The degradation of bisphenol A was promoted, but the degradation effect was not as significant as that at pH 8.

[0035] Application Comparative Example 1: Different from Application Example 1, only potassium permanganate and bisphenol A of the same concentration were added to the simulated sewage. The pH of the reaction mixture was controlled at 8. The change of the removal rate of bisphenol A over time is shown in Table 2.

[0036] Application Comparative Example 2: Different from Application Example 1, only potassium permanganate, MSNs@ZnO and bisphenol A of the same concentration were added to the simulated sewage. The pH of the reaction mixture was controlled at 8. The change of the removal rate of bisphenol A over time is shown in Table 2.

[0037] Application Comparative Example 3: Different from Application Example 1, only potassium permanganate, potassium persulfate and bisphenol A of the same concentration were added to the simulated sewage. The pH of the mixed solution was controlled at 8. The change of the removal rate of bisphenol A over time is shown in Table 2.

[0038] Table 2 Bisphenol A removal rate (%)

[0039] 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.

[0040] Application Comparative Example 4: The MSNs@ZnO prepared in Example 1 (two groups of comparison, zinc oxide alone and mesoporous silica alone) and potassium permanganate and potassium permonosulfate were added to the simulated sewage at a mass ratio of 1: (0.007-0.03): 0.5. The sewage contained 11.4 mg / L of bisphenol A, and the concentration of MSNs@ZnO / zinc oxide / mesoporous silica was 1 g / L, the concentration of potassium permanganate was 7.9 mg / L, and the concentration of potassium permonosulfate was 0.5 g / L. The control group was treated with potassium permanganate, potassium permonosulfate, and bisphenol A at the same concentration. The experimental pH value was 8. The change of the removal rate of bisphenol A over time is shown in Table 3.

[0041] Table 3 Bisphenol A removal rate (%)

[0042] 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 by the present invention.

[0043] Obviously, the above embodiments are merely examples for clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the protection scope of the invention.

Claims

1. Application of zinc oxide-coated mesoporous silica particles in wastewater containing refractory organic pollutants, characterized in that: The zinc oxide-coated mesoporous silica particles 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 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.

2. The use according to claim 1, characterized in that: The mass ratio of the zinc oxide-coated mesoporous silica particles, potassium permanganate and peroxymonosulfate is 1:(0.007-0.03):0.

5.

3. The use according to claim 1, characterized in that: The concentration of the organic pollutant is 0.1-100 mg / L; 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.

4. 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.

5. The use according to claim 1, characterized in that: The method for preparing 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 the 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, 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.

6. The use according to claim 5, characterized in that: In step S1, the organic solvent is selected from ethanol and / or tetrahydrofuran; The molar ratio of dodecylamine or hexadecyltrimethylammonium bromide to the organic solvent is 1:(34-40).

7. The use according to claim 5, characterized in that: In step S1, the silicon source is selected from tetraethyl 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.

8. The use according to claim 5, characterized in that: 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; The solvent of the zinc source solution is ethanol and / or tetrahydrofuran.

9. The use according to claim 5, characterized in that: In step S2, the mass ratio of zinc to silicon in the mixed solution is (1:1)-(1:10).

10. The use according to claim 5, 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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