CN112023971A

CN112023971A - Application of cyano-modified carbon nitride in phenol photo-mineralization field

Info

Publication number: CN112023971A
Application number: CN202010866969.2A
Authority: CN
Inventors: 郑占丰; 柳美仙; 谷献模; 谭浩; 王瑞义
Original assignee: Shanxi Institute of Coal Chemistry of CAS
Current assignee: Shanxi Institute of Coal Chemistry of CAS
Priority date: 2020-08-26
Filing date: 2020-08-26
Publication date: 2020-12-04
Anticipated expiration: 2040-08-26
Also published as: CN112023971B

Abstract

The invention relates to the technical field of phenol mineralization, in particular to a preparation method of cyano-modified carbon nitride and application of the cyano-modified carbon nitride in the field of phenol mineralization, and aims to solve the technical problem that phenol is easy to polymerize in the process of carrying out phenol mineralization by adopting a nonmetal semiconductor photocatalyst. The following technical scheme is adopted: the application of the cyano-modified carbon nitride in the field of phenol photo-mineralization is to use the cyano-modified carbon nitride as a photocatalyst in the phenol photo-mineralization process, wherein the cyano-modified carbon nitride is prepared by selecting trithiocyanuric acid as a carbon nitride precursor and putting the carbon nitride precursor into a muffle furnace for roasting.

Description

Application of cyano-modified carbon nitride in phenol photo-mineralization field

Technical Field

The invention relates to the technical field of phenol mineralization, in particular to application of cyano-modified carbon nitride in the field of phenol mineralization.

Background

Phenol is the phenolic substance with the simplest chemical structure, and with the rapid development of industry, phenol is used as an important chemical raw material, so that the application is wide, and the demand is increased day by day. Phenol can be used as a raw material for preparing phenolic resin, bisphenol A, halogenated phenol, salicylic acid, ethoxyaniline and the like, and phenol is contained in wastewater in various industrial fields. Phenol is toxic and can affect the normal behaviors of microorganisms, so that the growth and development of animals and plants are abnormal, adverse reactions such as allergy, red swelling, respiratory system abnormality and the like can be generated to a human body after the phenol is contacted for a long time, and the removal of the phenol before the industrial wastewater is discharged is very necessary. The existing phenol is generally mineralized by a semiconductor material photocatalysis technology, and the principle is that under the action of incident light, active oxygen species are generated on the surface of a semiconductor material photocatalyst in a catalytic mode, so that degradation and mineralization of organic pollutants are achieved.

The semiconductor material photocatalyst mainly comprises a metal oxide semiconductor photocatalyst and a nonmetal semiconductor photocatalyst. Most of metal oxide semiconductor photocatalysts with stable photocatalytic conditions only have activity under ultraviolet light, and the ultraviolet light only accounts for 5% of the sunlight, so that the process has low utilization rate of the sunlight, a large amount of organic pollutants such as phenol and the like have strong absorption under the ultraviolet light, direct photolysis can be carried out, polymerization can be carried out among the excited phenol, the polymerization products are difficult to degrade and can be attached to the surface of the catalyst to prevent the catalyst from further acting, and the phenol mineralization efficiency is greatly reduced; the non-metal semiconductor photocatalyst is mainly a carbon nitride photocatalyst, is non-toxic, rich in raw materials, stable in chemical properties and capable of utilizing visible light, and can solve the technical problem that the sunlight utilization rate of the metal oxide semiconductor photocatalyst is low, but the polymerization phenomenon of phenol in the photodegradation process is still difficult to solve, and the light mineralization efficiency is low.

Disclosure of Invention

The invention aims to solve the technical problem of low photo-mineralization efficiency when carbon nitride is used as a photocatalyst in the phenol photo-mineralization process.

The technical scheme adopted by the invention for solving the technical problems is as follows:

the application of cyano-modified carbon nitride in the field of phenol photo-mineralization is characterized in that the cyano-modified carbon nitride is used as a photocatalyst in the phenol photo-mineralization process, and the cyano-modified carbon nitride is prepared by selecting trithiocyanuric acid as a carbon nitride precursor and putting the carbon nitride precursor into a muffle furnace for roasting. Wherein the roasting temperature is heated from 20 ℃ to 450 ℃ at the heating rate of 2-10 ℃/min and kept for 2-8 h.

The mode of adsorption of phenol on cyano-modified carbon nitride was explored as follows:

placing cyano-modified carbon nitride (CN-10.0) and common carbon nitride (CN-0) in a phenol solution (100 mg/L), stirring for half an hour, filtering, taking out, vacuum drying at 60 ℃ to remove physically adsorbed phenol and water molecules, and measuring an infrared absorption spectrum of the phenol and the water molecules by taking a pure catalyst as a background to obtain an infrared absorption peak which can reflect the interaction of the phenol and the catalyst. In order to eliminate the effect of chemisorbed water, the catalyst was likewise stirred in a pure aqueous solution for half an hour and then removed, dried under vacuum at 60 ℃ and the infrared absorption spectrum was measured against the pure catalyst.

The measured infrared absorption spectrum is shown in fig. 1 and 2, and analysis shows that hydrogen on the phenolic hydroxyl group of phenol is adsorbed on N connected with cyano group, and the benzene ring of phenol is anchored on the triazine ring structure of carbon nitride through pi-pi interaction, namely shown in fig. 3.

The invention has the beneficial effects that:

1) when the cyano-modified carbon nitride is applied to phenol photodegradation, the cyano group on the surface of the carbon nitride catalyst can promote the adsorption of nitrogen atoms connected with the cyano group on hydrogen atoms on phenolic hydroxyl groups, and is favorable for the adsorption of phenol on the surface of the catalyst, so that the phenol photodegradation efficiency is improved;

2) when the cyano-modified carbon nitride is applied to phenol photodegradation and photo-mineralization, the cyano groups on the surface of the carbon nitride catalyst can inhibit the decomposition of hydrogen peroxide generated in situ to hydroxyl radicals, so that the polymerization phenomenon of phenol after being excited by the hydroxyl radicals is reduced, and the efficiency of phenol photo-mineralization is improved;

3) compared with other methods for introducing cyano groups, the cyano-group modified carbon nitride prepared by the method for roasting the trithiocyanuric acid can keep a triazine ring structure of the carbon nitride, so that when the method is applied to phenol photo-mineralization, pi-pi interaction between the triazine ring and a phenol benzene ring is kept, the adsorption and anchoring effects of the surface of the catalyst on phenol are improved, and the photo-degradation and photo-mineralization of the phenol are further facilitated.

Drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative efforts.

FIG. 1 is a first infrared spectrum of the action of a catalyst on phenol;

FIG. 2 is a second infrared spectrum of the action of the catalyst on phenol;

FIG. 3 is a schematic view of the adsorption of cyano-modified carbon nitride with phenol in accordance with the present invention;

FIG. 4 is a graph of the infrared spectra of a first set of experiments;

FIG. 5 is a graph showing a comparison of the change in the structure of carbon nitride before and after introduction of a cyano group according to the preparation method of the present invention;

FIG. 6 is a graph of the infrared spectra of a second set of experiments;

FIG. 7 is a graph comparing the change in the carbon nitride structure before and after introduction of a cyano group in comparative example 5;

FIG. 8 is an infrared spectrum of a third set of experiments;

FIG. 9 is a graph comparing the change in carbon nitride structure before and after introduction of a cyano group in comparative example 6;

FIG. 10 is an ultraviolet-visible absorption spectrum analysis of example 3 and comparative example 1;

FIG. 11 is C of example 3 and comparative examples 1 to 4₀C and CO₂Yield chart of (1).

Detailed Description

In order to make the objects, technical solutions and advantages of the present application more apparent, the present application is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.

Example 1

Selecting trithiocyanuric acid as a carbon nitride precursor, placing the carbon nitride precursor into a muffle furnace for roasting, heating the roasting temperature from 20 ℃ to 450 ℃ at the heating rate of 2 ℃/min, and keeping the temperature for 8 hours to obtain the cyano-modified carbon nitride.

10 mg of the above cyano-modified carbon nitride and 2 ml of a phenol solution (100 mg/l) were placed in a reaction glass vial having a volume of 10 ml, the vial was filled with oxygen gas at one atmospheric pressure, and a white LED lamp (300 mW. cm) was placed at 30 ℃^-2) Blocking reaction under action for 60 minutes.

Example 2

Selecting cyanuric acid as a carbon nitride precursor, placing the precursor into a muffle furnace for roasting, heating the roasting temperature from 20 ℃ to 600 ℃ at the heating rate of 10 ℃/min, and keeping the temperature for 2h to prepare the cyano-modified carbon nitride.

Example 3

Cyanuric acid is selected as a carbon nitride precursor, and is put into a muffle furnace for roasting, the roasting temperature is heated to 540 ℃ from 20 ℃ at the heating rate of 5 ℃/min, and is kept for 4.5 hours, and the cyano-modified carbon nitride is prepared, and is recorded as CN-10.0.

Comparative example 1

Selecting melamine as a carbon nitride precursor, wherein the mass of the melamine is the same as that of the trithiocyanuric acid in the embodiment 3, placing the melamine into a muffle furnace for roasting, heating the roasting temperature from 20 ℃ to 540 ℃ at the heating rate of 5 ℃/min, and keeping the roasting temperature for 4.5 hours to obtain the cyano-modified carbon nitride, which is recorded as CN-0.

Comparative example 2

Selecting a mixture of trithiocyanuric acid and melamine as a precursor, wherein the total mass of the mixture is the same as that of the trithiocyanuric acid in example 3, the mass ratio of the melamine to the trithiocyanuric acid is 3:1, placing the mixture into a muffle furnace for roasting, heating the mixture from 20 ℃ to 540 ℃ at the heating rate of 5 ℃/min, and keeping the temperature for 4.5 hours to obtain cyano-modified carbon nitride, which is recorded as CN-2.5.

Comparative example 3

Selecting a mixture of trithiocyanuric acid and melamine as a precursor, wherein the total mass of the mixture is the same as that of the trithiocyanuric acid in example 3, the mass ratio of the melamine to the trithiocyanuric acid is 1:1, placing the mixture into a muffle furnace for roasting, heating the mixture from 20 ℃ to 540 ℃ at the heating rate of 5 ℃/min, and keeping the temperature for 4.5 hours to obtain cyano-modified carbon nitride, which is recorded as CN-5.0.

Comparative example 4

Selecting a mixture of trithiocyanuric acid and melamine as a precursor, wherein the total mass of the mixture is the same as that of the trithiocyanuric acid in example 3, the mass ratio of the melamine to the trithiocyanuric acid is 1:3, placing the mixture into a muffle furnace for roasting, heating the mixture from 20 ℃ to 540 ℃ at the heating rate of 5 ℃/min, and keeping the temperature for 4.5 hours to obtain cyano-modified carbon nitride, which is recorded as CN-7.5.

Comparative example 5

Urea is selected as a carbon nitride precursor, and potassium hydroxide is introduced to introduce a cyano group.

Comparative example 6

Carbon nitride materials are subjected to a secondary heat treatment at different temperatures to introduce cyano groups by defect production.

The following three experiments prove that the preparation method of the specific cyano-modified carbon nitride does not damage triazine ring:

first, example 3 and comparative examples 1 to 4 were used as a group, and these five experiments were conducted by introducing cyano groups in different amounts by the specific method of the present invention, and the obtained carbon nitrides were separately subjected to infrared analysis, as shown in FIG. 4, in which the more the content of thiocyanic acid increases, the more the peak value at the cyano position increases, the more the cyano group is introduced, and the more the triazine ring infrared oscillation peak position is at 1800cm in 900-^-1Meanwhile, if the infrared vibration peak in the area is weakened, the number of the triazine ring structures is reduced, namely part of the triazine ring structures are damaged, and the thickness of the infrared vibration peak in the area is 900-1800cm in FIG. 4^-1The peak value is not reduced when the area between the two rings is higher, which indicates that the introduction of the cyano group does not cause the damage of the triazine ring structure, and the comparison of the structures before and after the introduction of the cyano group by adopting the specific method of the invention can be seen in fig. 5, the triazine ring structure is formed in the middle three rings, and the triazine ring structure is not damaged before and after the introduction of the cyano group can be seen in fig. 5.

Second, comparative example 5 was subjected to a series of experiments including seven experiments in which cyano groups were introduced by the method of comparative example 5 except that the amount of the introduced cyano groups was varied, and the obtained carbon nitrides were respectively subjected to infrared analysis as shown in FIG. 6It is shown that the peak value at the position of the cyano group is larger downwards, the more cyano groups are introduced downwards, and the infrared vibration peak position of the triazine ring is 1800cm at 900-^-1Meanwhile, if the infrared vibration peak in the area is weakened, the number of the triazine ring structures is reduced, namely part of the triazine ring structures are damaged, and the thickness of the infrared vibration peak in the area is 900-1800cm in FIG. 6^-1The lower the peak value of the area in between, the damage of the triazine ring structure caused by the introduction of the cyano group is illustrated, and the comparison of the structures before and after the introduction of the cyano group by the method can be seen in fig. 7, wherein the three rings in the middle are the triazine ring structure, and the triazine ring structure is damaged after the introduction of the cyano group can be seen in fig. 7.

In the third group, comparative example 6 was subjected to a series of experiments including seven experiments in which cyano groups were introduced by the method of comparative example 6 except that the amount of the introduced cyano groups was varied, and the obtained carbon nitrides were subjected to infrared analysis, respectively, as shown in FIG. 8, in which the larger the peak at the position of the cyano group, the more the cyano group was introduced, and the infrared vibration peak position of the triazine ring was at 900-1800cm^-1Meanwhile, if the infrared vibration peak in the area is weakened, the number of the triazine ring structures is reduced, namely, part of the triazine ring structures are damaged, and the thickness of the infrared vibration peak in the area is 900-1800cm in FIG. 8^-1The higher the area in between, the lower the peak value, which shows that the introduction of cyano group causes the destruction of triazine ring structure, the comparison of the structure before and after the introduction of cyano group by the method can be seen in fig. 9, the three rings in the middle are triazine ring structure, and it can be seen from fig. 9 that the triazine ring structure is destroyed after the introduction of cyano group.

Compared with other methods for introducing cyano groups, the specific method disclosed by the invention can keep a complete triazine ring structure of carbon nitride, so that when the method is applied to phenol mineralization, pi-pi interaction between the triazine ring and a phenol benzene ring can be kept, the adsorption effect of the surface of the catalyst on phenol is improved, and the method is favorable for phenol mineralization.

The inhibition of phenol polymerization by cyano groups is demonstrated below by example 3 and comparative example 1:

the catalyst is filtered after the reaction of the example 3 and the comparative example 1, the reaction filtrate is analyzed by high-resolution liquid chromatography, the analysis result is shown in FIG. 10, the absorption peak of the 300-800 nm wave band can be attributed to the absorption peak of the conjugated aromatic structure of the polymerization product generated in the phenol photodegradation process, and if the absorption peak intensity is higher in the range of 300-800 nm, the polymerization phenomenon generated in the phenol photodegradation process is more serious. In FIG. 10, the absorption peak intensity in the range of 300-800 nm of CN-10.0 is smaller than that in the range of 300-800 nm of CN-0, which shows that the phenol polymerization phenomenon in example 3 is significantly lower than that in comparative example 1, and the only difference between example 3 and comparative example 1 is that cyano group is introduced into example 3, so it can be concluded that the cyano group modified carbon nitride prepared by the method of the present invention has an inhibitory effect on the polymerization phenomenon in the phenol photo-mineralization process.

The benefit of the cyano group for phenol photodegradation and mineralization by light is demonstrated below by example 3 and comparative examples 1-4:

the products of example 3 and comparative examples 1 to 4 were examined, as shown in FIG. 11, C₀The lower the concentration of phenol after photodegradation, the higher the phenol photodegradation efficiency; CO 2₂The higher the yield, the higher the phenol mineralization. It can be seen from the figure that the phenol photodegradation efficiency and the mineralization efficiency are higher as the number of cyano groups is increased. The reason is analyzed in principle and has two points: firstly, the more the cyano groups are, the more the nitrogen atoms connected with the cyano groups can promote the adsorption of hydrogen atoms on phenolic hydroxyl groups, and the adsorption of phenol on the surface of the catalyst is more facilitated, so that the phenol photodegradation efficiency is improved; secondly, the more the cyano groups are, the polymerization of phenol can be inhibited, thereby improving the light mineralization efficiency of phenol.

The above description is only exemplary of the present application and should not be taken as limiting the present application, as any modification, equivalent replacement, or improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. The application of cyano-modified carbon nitride in the field of phenol photo-mineralization is characterized in that the cyano-modified carbon nitride is used as a photocatalyst in the phenol photo-mineralization process, and the cyano-modified carbon nitride is prepared by selecting trithiocyanuric acid as a carbon nitride precursor and putting the carbon nitride precursor into a muffle furnace for roasting.

2. Use according to claim 1, characterized in that: the roasting temperature is heated from 20 ℃ to 450 ℃ at the heating rate of 2-10 ℃/min and is kept for 2-8 h.