CN116393157B

CN116393157B - Catalyst capable of adjusting type and quantity of advanced oxidation active species, preparation method and application thereof

Info

Publication number: CN116393157B
Application number: CN202310546925.5A
Authority: CN
Inventors: 任逸; 李君�; 刘超
Original assignee: Sichuan University
Current assignee: Sichuan University
Priority date: 2023-05-15
Filing date: 2023-05-15
Publication date: 2024-09-13
Anticipated expiration: 2043-05-15
Also published as: CN116393157A

Abstract

The invention provides a preparation method of a catalyst capable of adjusting the types and the amounts of advanced oxidation active species, which comprises the following steps: (1) Uniformly mixing a carbon nitride precursor, an oxygen element donor, an iron source and a cerium source to obtain a precursor mixture; (2) Roasting the precursor mixture at 150-1000 ℃ for 1-72 h, and cleaning and drying the obtained roasted product to obtain a catalyst; the type and amount of active material generated by the catalyst activated oxidant can be adjusted by adjusting the proportion relation among the carbon nitride precursor, the oxygen element donor, the iron source and the cerium source and the roasting condition. The invention also provides application of the catalyst in degradation of water pollutants by activating an oxidant. The invention can flexibly and effectively regulate and control the types and the quantity of active species in the advanced oxidation catalytic process according to different water environmental media and pollution conditions, and expands a pollution system applicable to the catalyst, thereby better meeting the treatment requirements of organic pollutants in a multi-pollutant complex system.

Description

Catalyst capable of adjusting type and quantity of advanced oxidation active species, preparation method and application thereof

Technical Field

The invention belongs to the field of advanced oxidation for solid and liquid treatment, and relates to a catalyst capable of adjusting the types and the amounts of advanced oxidation active species, a preparation method and application thereof.

Background

With the demands of social development and ecological civilization construction, environmental pollution problems, in particular to water environmental pollution, gradually become a focus of attention. The water environment quality improvement mainly comprises means of point source pollution control, non-point source pollution control, water pollution treatment, silt and peripheral soil restoration and the like. The advanced oxidation treatment technology is used as an environment treatment repair technology with high efficiency, low cost and wide application range, can be applied to the improvement of the quality of water environment, and can effectively remove organic pollutants.

Advanced oxidation technologies typically use hydrogen peroxide, oxygen, ozone, peracetic acid, persulfates, high-valence metals, high-valence chlorine, etc. as oxidants, transition metals, carbon materials, etc. as catalysts, and activate the oxidants by the catalysts to produce active species with higher redox potentials to degrade organic contaminants in the water or in the solid phase. Advanced oxidation technology is divided into two types, i.e. homogeneous catalysis and heterogeneous catalysis, and the homogeneous catalysis faces the problems that a catalyst is not easy to recycle, secondary pollution is easy to generate, the pH application range is narrow, and the like. Thus, heterogeneous Fenton catalysis has received increasing attention in recent years, but current heterogeneous advanced oxidation technologies still face a number of challenges.

Currently, the mainstream heterogeneous Fenton catalysis mainly relies on active species such as sulfate radicals, hydroxyl radicals and the like to oxidatively degrade pollutants. These free radical active species have higher redox potentials, generally achieve non-selective oxidation, and have better treatment effects on single pollutants. However, because of their non-selectivity, they tend to lead to the indiscriminate oxidation of free radicals, and thus oxidation efficiency and oxidant utilization can be greatly adversely affected in systems where the contaminant components are complex. For example, there are often large amounts of non-toxic or low-toxic coexisting materials including chloride ions, humic acid, etc. in actual wastewater, which react with free radicals to cause a large quenching of the free radicals, resulting in a decrease in the oxidative degradation efficiency and the oxidant utilization efficiency of target pollutants. For another example, when treating wastewater containing a plurality of organic contaminants, the radicals may indifferently oxidize different contaminant precursors and degradation products thereof, and may not efficiently selectively oxidize target contaminants with a higher desired priority.

Accordingly, in recent years, researchers have developed novel active species generating systems such as high-valence metals and singlet oxygen. The active species have high oxidation selectivity, can perform high-efficiency conversion aiming at specific pollutants, and can shield interference of coexisting substances. However, degradation of organics with such active species alone still presents problems, for example: (1) The active species can only effectively convert specific pollutants, has extremely low mineralization efficiency, and cannot effectively remove the total organic carbon; (2) When the active species are used for converting certain pollutants, the toxicity of the pollutants can not be effectively reduced, and even the problem of toxicity improvement can be caused; (3) Because of the high selectivity of the active species, the active species cannot degrade different organic pollutants universally, and when wastewater with complex multi-pollutant composition is treated, the one-step high-efficiency purification is difficult to realize. Therefore, how to realize the efficient regulation and control of the types and the amounts of the active species according to different environmental media and pollution conditions is an effective means for solving the problems and effectively improving the treatment efficiency of the environmental pollution of the water body.

Disclosure of Invention

Aiming at the defect that the types and the amounts of active species in the advanced oxidation catalytic process are difficult to effectively regulate and control in the prior art, the invention provides a catalyst capable of regulating the types and the amounts of the advanced oxidation active species, and a preparation method and application thereof, so as to flexibly and effectively regulate and control the types and the amounts of the active species in the advanced oxidation catalytic process according to different water environment media and pollution conditions, expand a pollution system applicable to the catalyst, particularly meet the treatment requirements of organic pollutants in a multi-pollutant complex system, and improve the water environment pollution treatment efficiency.

In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:

A method for preparing a catalyst capable of adjusting the type and amount of a higher oxidizing active species, comprising the steps of:

(1) Uniformly mixing a carbon nitride precursor, an oxygen element donor, an iron source and a cerium source to obtain a precursor mixture; in the precursor mixture, the mass percent of the carbon nitride precursor is 40-80%, the mass percent of oxalic acid is 3-50%, the mass percent of the iron source is 0.5-40%, and the mass percent of the cerium source is 0.5-40%;

(2) Roasting the precursor mixture at 150-1000 ℃ for 1-72 h, cleaning the obtained roasted product to remove unreacted substances, and drying to obtain a catalyst;

The type and amount of active material generated by the catalyst activated oxidant can be regulated by regulating the ratio of the carbon nitride precursor, the oxygen donor, the iron source and the cerium source in the step (1), and the roasting temperature and time in the step (2).

In the technical scheme of the preparation method, the carbon nitride precursor is at least one of urea, melamine and dicyandiamide.

In the technical scheme of the preparation method, the oxygen element donor is oxalic acid.

In the technical scheme of the preparation method, the iron source is ferrous salt or/and ferric salt. Possible iron sources include at least one of ferric nitrate, ferric chloride, ferric sulfate, ferric perchlorate, ferrous nitrate, ferrous chloride, ferrous sulfate, and ferrous perchlorate.

In the technical scheme of the preparation method, the cerium source is trivalent cerium salt. Possible trivalent cerium salts include at least one of cerium nitrate, cerium chloride, and cerium sulfate.

In the technical scheme of the preparation method, in the precursor mixture, the mass percentage of the carbon nitride precursor is preferably 40% -80%, the mass percentage of oxalic acid is preferably 3% -45%, the mass percentage of the iron source is preferably 0.5% -35%, and the mass percentage of the cerium source is preferably 0.5% -35%.

In the technical scheme of the preparation method, the step (2) is performed in an atmosphere of air, oxygen, nitrogen, argon or a mixed gas atmosphere of the above gases.

In the technical scheme of the preparation method, in the step (1), a grinding method, a ball milling method or a solution mixing method can be adopted to uniformly mix the carbon nitride precursor, the oxygen element donor, the iron source and the cerium source to form a precursor mixture.

In the technical scheme of the preparation method, in the step (2), when the roasting product is cleaned, one or more of the cleaning modes of water cleaning, acid cleaning and alcohol cleaning can be adopted for cleaning.

The invention also provides a catalyst which is prepared by the method and can adjust the types and the amounts of the active substances generated by the catalyst activated oxidant by adjusting the contents of the components in the catalyst, wherein the catalyst consists of graphite carbon nitride, iron element, cerium element and oxygen element.

According to the catalyst capable of adjusting the types and the amounts of the high-grade oxidation active species, graphite carbon nitride is used as a base material to load iron oxide and cerium oxide, and the types and the amounts of the loaded iron oxide and cerium oxide can be adjusted according to different environmental media and pollution conditions by utilizing the special structural characteristics of the graphite carbon nitride.

The invention also provides application of the catalyst capable of adjusting the types and the amounts of the advanced oxidation active species in activating an oxidant to degrade water pollutants.

Further, when the catalyst and the oxidant are applied, the catalyst is added into the wastewater to be treated, and the oxidant is activated by the catalyst to generate free radicals or/and singlet oxygen to degrade organic pollutants in the wastewater, wherein the oxidant comprises at least one of hydrogen peroxide, oxygen, ozone, peroxyacetic acid, peroxymonosulfate, peroxydisulfate, ferrate, permanganate and perchlorate.

According to the different raw material proportions and process parameters in the preparation of the catalyst, the types (such as free radicals, high-valence iron, singlet oxygen and the like) and the amounts of active species generated by the catalyst in the activation of the oxidant are different, and in practical application, the catalyst is prepared in a targeted manner by selecting proper raw material proportions and process parameters according to the properties of the wastewater to be treated, such as the types and concentrations of pollutants and the types and concentrations of other substances in the wastewater, so that the active species generated by the catalyst in the activation of the oxidant can efficiently degrade target pollutants, and the wastewater treatment efficiency and effect are improved.

For example, in the preparation of the catalyst, the ability of the catalyst to activate the peroxymonosulfate to generate singlet oxygen active species may be promoted by increasing the addition ratio of oxalic acid, the ability of the catalyst to activate the peroxymonosulfate to generate free radical active species may be promoted by increasing the addition ratio of iron source, and the overall amount of active species generated by the catalyst to activate the peroxymonosulfate may be promoted by increasing the addition ratio of cerium source. Of course, the ability of the catalyst to activate the oxidant to produce active species can also be adjusted by adjusting the calcination process parameters for preparing the catalyst.

Further, the amounts of catalyst and oxidant added to the wastewater to be treated are determined based on the composition and concentration of contaminants in the wastewater to be treated. Generally, the catalyst and the oxidant are added into the wastewater to be treated in such amounts that the concentration of the catalyst in the wastewater to be treated is 200-1000 mg/mL, the concentration of the oxidant in the wastewater to be treated is 0.1-10 mmol/L, and the pH value of the wastewater to be treated is 2-7.

Compared with the prior art, the technical scheme of the invention has the following beneficial effects:

1. The invention provides a preparation method of a catalyst capable of adjusting the types and the amounts of advanced oxidation active species, which comprises the steps of uniformly mixing a carbon nitride precursor, an oxygen element donor, an iron source and a cerium source to prepare a precursor mixture and a roasting step. The variety and the quantity of active species generated by the catalyst activated oxidant can be adjusted by adjusting the raw material proportion and the roasting process parameters. In practical application, the raw material proportion and the roasting process parameters can be flexibly adjusted according to the characteristics of pollutants in an environmental medium, the targeted and efficient removal of different pollutants is realized, the method can be flexibly adapted to various pollution systems, and particularly can meet the treatment requirements of organic pollutants of a multi-pollutant complex system, and the treatment efficiency of water environmental pollution is effectively improved.

2. Experiments prove that the removal rate of the sulfamethoxazole is slightly reduced and is still higher than 85% when the sulfamethoxazole is degraded by activating the peroxymonosulfate by recycling the catalyst for 5 times. Experiments prove that the catalyst has good degradation capability on wastewater with pH value of 2-7 when the catalyst activates the peroxymonosulfate to degrade the wastewater. The catalyst has good recycling performance and wider pH value application range, is very beneficial to the application of the catalyst in engineering practice, and can reduce the wastewater treatment cost.

3. The catalyst disclosed by the invention has the advantages of simple preparation process, low-cost and easily available raw materials and low production cost, and is favorable for popularization and application in actual water environmental pollution treatment and restoration.

Drawings

FIG. 1 is an electron micrograph of the catalyst prepared in example 1.

FIG. 2 is a graph of the energy spectrum of the catalyst prepared in example 1.

FIG. 3 shows SMX removal rates of simulated wastewater at different pH values in application example 1.

FIG. 4 shows the SMX removal rate during the recycling of the catalyst in application example 1.

FIG. 5 shows the results of the quenching test in application example 1.

FIG. 6 shows the results of the quenching test in application example 2.

FIG. 7 shows the results of the quenching test in application example 3.

FIG. 8 shows the results of the quenching test in application example 4.

Detailed Description

The catalysts of the present invention, and methods for preparing and using the same, are further described below by way of examples, with respect to the types and amounts of the higher oxidation active species. It is to be noted that the following examples are given solely for the purpose of illustration and are not to be construed as limitations on the scope of the invention, since numerous insubstantial modifications and variations of the invention will become apparent to those skilled in the art in light of the above disclosure, and yet remain within the scope of the invention.

Example 1

The catalyst prepared in this example comprises the following steps:

(1) Primarily mixing urea, oxalic acid, ferric chloride hexahydrate and cerium nitrate hexahydrate, and then fully grinding and mixing until the components are uniformly mixed to obtain a precursor mixture; in the precursor mixture, the mass percentages of urea, oxalic acid, ferric chloride hexahydrate and cerium nitrate hexahydrate are as follows: 67.87%, 27.15%, 2.71% and 2.27%.

(2) The precursor mixture is placed in a muffle furnace, baked for 2h at 550 ℃ in air atmosphere, and the obtained baked product is washed by water to remove unreacted substances, so as to obtain the catalyst, wherein the electron microscope diagram is shown in figure 1, and the energy spectrum is shown in figure 2. As can be seen from fig. 2, the catalyst prepared in this example has iron and cerium elements in different valence states.

Application example 1

In this application example, the catalyst prepared in example 1 was used to activate Peroxymonosulfate (PMS) to degrade organic contaminants.

(1) Sulfamethoxazole (SMX) was dissolved in water to form a SMX solution having a concentration of 2mg/L, and the pH of the simulated wastewater was adjusted to 2,3, 4, 5, 6, 7, respectively, using the solution as the simulated wastewater.

The catalyst and PMS prepared in example 1 were added to the above simulated wastewater at pH levels of 400mg/L and 0.3mmol/L, respectively. After 30min of catalyst and PMS addition, samples were filtered through a 0.22. Mu.M filter, the concentration of SMX was tested, and the SMX removal rate was calculated, as shown in FIG. 3.

As can be seen from FIG. 3, when the pH value of the simulated wastewater is 3-7, the SMX removal rate is more than 90% after 30min of the catalyst prepared in example 1 and PMS are added.

(2) ① The catalyst and PMS prepared in example 1 were added to the above simulated wastewater with pH 7 in amounts of 400mg/L and 0.3mmol/L, respectively, and the catalyst was separated by filtration after 30min of treatment.

② The separated catalyst was added to fresh simulated wastewater having pH 7, PMS was then added in amounts of 400mg/L and 0.3mmol/L, and the catalyst was separated by filtration after 30 minutes of treatment.

③ The operation of step ② is repeated until the catalyst is recycled 5 times.

After 30min of each wastewater treatment, samples were filtered through a 0.22 μm filter, and the concentration of SMX was measured to calculate the SMX removal rate in each cycle, and the results are shown in fig. 4.

As can be seen from fig. 4, in the process of recycling the catalyst prepared in example 1 for 5 times, the SMX removal rate was only slightly reduced, and the SMX removal rate was still higher than 85% for 5 times of recycling, which indicates that the catalyst prepared in example 1 has excellent recycling applicability.

(3) Quenching experiments

Tert-butanol, methanol, dimethyl sulfoxide, chloroform, 2, 6-tetramethylpiperidine (in the figure, tetramethylpiperidine for short) are sequentially used as quenchers of hydroxyl radical, sulfate radical, high valence iron, superoxide radical and singlet oxygen.

Sulfamethoxazole (SMX) was dissolved in water to form a 2mg/L SMX solution, which was used as a simulated wastewater, and 5 experimental groups, 1 blank control group (no quencher added) were placed in parallel. The catalyst and PMS prepared in example 1 were added to the simulated wastewater of each experimental group in amounts of 400mg/L and 0.3mmol/L, respectively, and the corresponding quenchers were added to the simulated wastewater of each experimental group, respectively. After 30min of treatment, the concentration of SMX was sampled and tested, and the SMX removal rate was calculated, and the results are shown in FIG. 5.

As can be seen from fig. 5, the removal rate of SMX is the lowest in the experimental group to which dimethyl sulfoxide was added as a quencher, and since dimethyl sulfoxide is a quencher for high-valence iron, it is shown that the catalyst prepared in example 1 generates high-valence iron as a main active species when activating PMS, and also generates hydroxyl radicals and sulfate radicals, and the contribution of high-valence iron to SMX removal reaches more than 80% as seen from the data in fig. 5.

Example 2

The operation of preparing the catalyst in this comparative example is basically the same as that of example 1, except that the ratio of the components in the precursor mixture of step (1) is adjusted, and the mass percentages of urea, oxalic acid, ferric chloride hexahydrate, and cerium nitrate hexahydrate in the precursor mixture in this comparative example are as follows: 68.65%, 27.46%, 2.75% and 1.14%.

Application example 2

In this application example, the catalyst prepared in example 2 was used to activate PMS to degrade organic contaminants.

(1) SMX is dissolved in water to form SMX solution with the concentration of 2mg/L, the pH value is not adjusted, the initial pH value is between 6 and 7, and the SMX aqueous solution is used as simulated wastewater.

The catalyst and PMS prepared in example 2 were added to the simulated wastewater in amounts of 400mg/L and 0.3mmol/L, respectively. After 30min of catalyst and PMS addition, the sample was filtered with a 0.22. Mu.M filter membrane, and the SMX concentration was tested, and the SMX removal rate was calculated, resulting in a SMX removal rate of 52%.

(2) Quenching experiments

The simulated wastewater from step (1) was used, and 5 experimental groups and 1 blank control group (no quencher added) were placed in parallel. The catalyst and PMS prepared in example 2 were added to the simulated wastewater of each experimental group in amounts of 400mg/L and 0.3mmol/L, respectively, and the corresponding quenchers were added to the simulated wastewater of each experimental group, respectively. After 30min of treatment, the concentration of SMX was sampled and tested, and the SMX removal rate was calculated, and the results are shown in FIG. 6.

As can be seen from fig. 6, the removal rate of SMX was the lowest in the experimental group to which dimethyl sulfoxide was added as a quencher, and since dimethyl sulfoxide is a quencher for high-valence iron, it is illustrated that the catalyst prepared in example 2 generates high-valence iron as a main active species when PMS is activated, and also generates hydroxyl radicals and sulfate radicals. In combination with the SMX removal rate data in the quenching experiments of application example 1, it was found that increasing the addition amount of cerium salt during the preparation of the catalyst effectively increased the amount of active species generated by the catalyst activating PMS.

Example 3

The operation of preparing the catalyst in this example is basically the same as that in example 1, except that the ratio of the components in the precursor mixture in step (1) is adjusted, and the mass percentages of urea, oxalic acid, ferric chloride hexahydrate, and cerium nitrate hexahydrate in the precursor mixture in this comparative example are as follows: 52.45%, 43.71%, 2.10% and 1.74%.

Application example 3

The catalyst and PMS prepared in example 3 were added to the simulated wastewater in amounts of 400mg/L and 0.3mmol/L, respectively. After 30min of catalyst and PMS addition, samples were filtered with a 0.22. Mu.M filter membrane, and the SMX concentration was tested to calculate the SMX removal rate, which was found to be 62%.

(2) Quenching experiments

The simulated wastewater from step (1) was used, and 5 experimental groups and 1 blank control group (no quencher added) were placed in parallel. The catalyst and PMS prepared in example 3 were added to the simulated wastewater of each experimental group in amounts of 400mg/L and 0.3mmol/L, respectively, and the corresponding quenchers were added to the simulated wastewater of each experimental group, respectively. After 30min of treatment, the concentration of SMX was sampled and tested, and the SMX removal rate was calculated, and the results are shown in FIG. 7.

As can be seen from fig. 7, the removal rate of SMX was the lowest in the experimental group to which 2, 6-tetramethylpiperidine was added as a quencher, and since 2, 6-tetramethylpiperidine was a quencher for singlet oxygen, it was demonstrated that the catalyst prepared in example 3 produced singlet oxygen as a main active species when PMS was activated, and also produced hydroxyl radical, sulfate radical and high-valence iron. As seen in the data in fig. 7, the contribution of high-valence iron to SMX removal in this application example was about 30%. It is known from the SMX removal rate data of application examples 1-2 that increasing the amount of oxalic acid added during the preparation of the catalyst for activating PMS can effectively improve the ability of the catalyst to activate PMS to generate singlet oxygen active species.

Example 4

The operation of preparing the catalyst in this example is basically the same as that in example 1, except that the ratio of the components in the precursor mixture in step (1) is adjusted, and the mass percentages of urea, oxalic acid, ferric chloride hexahydrate, and cerium nitrate hexahydrate in the precursor mixture in this comparative example are as follows: 66.08%, 26.43%, 5.29% and 2.20%.

Application example 4

The catalyst and PMS prepared in example 4 were added to the simulated wastewater in amounts of 400mg/L and 0.3mmol/L, respectively. After 30min of catalyst and PMS addition, the sample was filtered with a 0.22. Mu.M filter membrane, and the SMX concentration was tested, and the SMX removal rate was calculated, resulting in a SMX removal rate of 64%.

(2) Quenching experiments

The simulated wastewater from step (1) was used, and 5 experimental groups and 1 blank control group (no quencher added) were placed in parallel. The catalyst and PMS prepared in example 4 were added to the simulated wastewater of each experimental group in amounts of 400mg/L and 0.3mmol/L, respectively, and the corresponding quenchers were added to the simulated wastewater of each experimental group, respectively. After 30min of treatment, the concentration of SMX was sampled and tested, and the SMX removal rate was calculated, and the results are shown in FIG. 8.

As can be seen from fig. 8, the SMX removal rate was relatively low in the experimental group to which methanol and dimethyl sulfoxide were added as quenchers, and the major active species generated when the catalyst prepared in example 4 was used to activate PMS were sulfate radicals and high-valence iron in combination with the SMX removal rate data of the other experimental groups. The contribution of the higher iron active species to the SMX removal rate in this application example was reduced and the contribution of the sulfate active species was significantly increased relative to application example 1. In combination with the SMX removal rate data of application example 1, it is known that increasing the amount of iron source added during the preparation of the catalyst can effectively increase the sulfate radical generating ability of the catalyst activated PMS.

From the experimental results of comprehensive application examples 1 to 4, it is known that, in the process of preparing the catalyst, for the active species generated by activating PMS with the catalyst provided by the present invention: the addition amount of cerium salt is increased, so that the generation amount of the active species can be increased; the addition amount of oxalic acid is increased, so that the generation of singlet oxygen active species can be promoted; the addition amount of the iron source is increased, so that the generation of free radical active species can be promoted. In practical application, the capacity of the catalyst for activating the oxidant to generate active species can be adjusted by properly adjusting the material proportion when preparing the catalyst according to the property of the wastewater to be treated, so that the high-efficiency degradation of different wastewater can be realized.

Example 5

The catalyst prepared in this example comprises the following steps:

(1) Dissolving melamine, oxalic acid, ferrous sulfate and cerium chloride in water, heating and drying to remove water and obtain a precursor mixture; in the precursor mixture, the mass percentages of melamine, oxalic acid, ferrous sulfate and cerium chloride are as follows: 70.42%, 28.18%, 0.70% and 0.70%.

(2) The precursor mixture was placed in a muffle furnace, calcined at 150 ℃ for 72 hours in an air atmosphere, and the obtained calcined product was washed with water to remove unreacted substances, to obtain a catalyst.

Application example 5

In this application example, the catalyst prepared in example 5 was used to activate peracetic acid (PAA) to degrade organics.

The carbamazepine is dissolved in water and then added with soil to form a water-soil mixture, wherein the concentration of the carbamazepine is 2mg/L and the soil content is 40 percent. The catalyst and PAA prepared in example 5 were added to the water-soil mixture in amounts of 200mg/L and 0.3mmol/L, respectively. After 30min of catalyst and PAA addition, sampling and filtration were performed, the concentration of carbamazepine was tested, and the removal rate of carbamazepine was calculated. As a result, it was found that the removal rate of carbamazepine was 88% after 30 minutes of addition of the catalyst and PAA.

Example 6

The catalyst prepared in this example comprises the following steps:

(1) Dissolving melamine, oxalic acid, ferric nitrate and cerium sulfate hexahydrate in water, and freeze-drying to obtain a precursor mixture; in the precursor mixture, the mass percentages of melamine, oxalic acid, ferric nitrate and cerium sulfate hexahydrate are as follows in sequence: 32.26%, 3.22%, 32.26% and 32.26%.

(2) The precursor mixture was placed in a muffle furnace, calcined at 1000 ℃ for 1 hour in a nitrogen atmosphere, and the obtained calcined product was washed with water and methanol to remove unreacted substances, to obtain a catalyst.

Application example 6

In this application example, the catalyst prepared in example 6 was used to activate PAA to degrade organics.

The carbamazepine is dissolved in water and then added with soil to form a water-soil mixture, wherein the concentration of the carbamazepine is 2mg/L and the soil content is 30 percent. The catalyst and PAA prepared in example 6 were added to the water-soil mixture in amounts of 500mg/L and 1mmol/L, respectively. After 30min of catalyst and PAA addition, samples were filtered through a 0.22 μm filter, the carbamazepine concentration was tested and the removal rate of carbamazepine was calculated. As a result, it was found that the removal rate of carbamazepine was 75% after 30 minutes of addition of the catalyst and PAA.

Example 7

The catalyst prepared in this example comprises the following steps:

(1) Dissolving melamine, oxalic acid, ferric perchlorate and cerium chloride in water, and freeze-drying to obtain a precursor mixture; in the precursor mixture, the mass percentages of melamine, oxalic acid, ferric perchlorate and cerium chloride are as follows in sequence: 40%, 50%, 5% and 5%.

(2) The precursor mixture was placed in a muffle furnace, calcined at 600 ℃ for 5 hours in an oxygen atmosphere, and the obtained calcined product was washed with ethanol to remove unreacted substances, to obtain a catalyst.

Application example 7

In this application example, the catalyst prepared in example 7 was used to activate hydrogen peroxide to degrade organics.

2Mg/L aqueous atrazine solution was used as simulated wastewater. The catalyst prepared in example 7 and hydrogen peroxide were added to the simulated wastewater in amounts of 1000mg/L and 10mmol/L, respectively. After 30min of catalyst and hydrogen peroxide addition, sampling and filtration were performed, the concentration of atrazine was tested, and the atrazine removal rate was calculated. As a result, it was found that the removal rate of atrazine was 70% after 30min of addition of the catalyst and PMS.

Example 8

The catalyst prepared in this example comprises the following steps:

(1) Dissolving dicyandiamide, oxalic acid, ferrous chloride and cerium sulfate in water, and freeze-drying to obtain a precursor mixture; in the precursor mixture, the mass percentages of dicyandiamide, oxalic acid, ferrous chloride and cerium sulfate are as follows: 76.93%, 7.69% and 7.69%.

(2) The precursor mixture was placed in a muffle furnace, baked at 400 ℃ for 2h in an argon atmosphere, and the obtained baked product was washed with water to remove unreacted substances, to obtain a catalyst.

Application example 8

In this application example, the catalyst prepared in example 7 was used to activate PMS to degrade organics.

The carbamazepine is dissolved in water and then added with soil to form a water-soil mixture, wherein the concentration of the carbamazepine is 2mg/L and the soil content is 40 percent. The catalyst and PMS prepared in example 8 were added to the water-soil mixture in amounts of 200mg/L and 0.3mmol/L, respectively. After 30min of catalyst and PMS addition, sampling and filtration were performed, the concentration of carbamazepine was tested, and the removal rate of carbamazepine was calculated. As a result, it was found that the removal rate of carbamazepine was 88% after 30 minutes of addition of the catalyst and PMS.

Claims

1. A method for preparing a catalyst capable of adjusting the type and amount of a higher oxidizing active species, comprising the steps of:

(1) Uniformly mixing a carbon nitride precursor, oxalic acid, an iron source and a cerium source to obtain a precursor mixture; in the precursor mixture, the mass percentage of the carbon nitride precursor is 40% -80%, the mass percentage of oxalic acid is 3% -50%, the mass percentage of the iron source is 0.5% -40%, and the mass percentage of the cerium source is 0.5% -40%;

The iron source is at least one of ferric nitrate, ferric chloride, ferric sulfate, ferric perchlorate, ferrous nitrate, ferrous chloride, ferrous sulfate and ferrous perchlorate; the cerium source is at least one of cerium nitrate, cerium chloride and cerium sulfate;

(2) Roasting the precursor mixture at 150-1000 ℃ for 1-72 h, cleaning the obtained roasting product to remove unreacted substances, and drying to obtain a catalyst;

The type and amount of active material generated by the catalyst activated oxidant can be adjusted by adjusting the ratio of the carbon nitride precursor, the oxygen donor, the iron source and the cerium source in step (1) and the calcination conditions in step (2).

2. The method of preparing a catalyst of adjustable class and amount of higher oxidation active species according to claim 1, wherein the carbon nitride precursor is at least one of urea, melamine, and dicyandiamide.

3. The method for preparing a catalyst of adjustable type and amount of higher oxidation active species according to claim 1 or 2, wherein the step (2) is carried out in an atmosphere of air, oxygen, nitrogen, argon or a mixed gas atmosphere of the above gases.

4. A catalyst of the type and amount of a regulatable higher oxidation active species prepared by the process of any one of claims 1 to 3.

5. The use of the adjustable higher oxidizing active species and amount of catalyst of claim 4 to activate an oxidizing agent to degrade water pollutants.

6. The use according to claim 5, wherein the catalyst of claim 4 is added to the wastewater to be treated and the catalyst is used to activate the oxidant to produce free radicals and/or singlet oxygen to degrade organic contaminants in the wastewater, the oxidant comprising at least one of hydrogen peroxide, oxygen, ozone, peracetic acid, peroxymonosulfate, peroxydisulfate, ferrate, permanganate, perchlorate.

7. The method according to claim 6, wherein the catalyst and the oxidant are added to the wastewater to be treated in such an amount that the concentration of the catalyst in the wastewater to be treated is 200-1000 mg/mL, the concentration of the oxidant in the wastewater to be treated is 0.1-10 mmol/L, and the pH value of the wastewater to be treated is 2-7.