阅读说明：本技术 一种二元金属氧化物复合氮化碳催化剂及其制备方法与应用 (Binary metal oxide composite carbon nitride catalyst and preparation method and application thereof ) 是由 黄放 袁本琦 牛承岗 郑超文 魏勇红 刘利 于 2019-10-22 设计创作，主要内容包括：本发明公开了一种二元金属氧化物复合氮化碳催化剂及其制备方法与应用,所述二元金属氧化物中的金属为钴和锰。本发明方案构建的催化剂能够在室温下与过一硫酸盐构成反应体系,该催化剂可高效活化过一硫酸盐产生硫酸根自由基,羟基自由基和高价态的过渡金属配合物,从而有效降解废水中有机污染物,其处理效率高,处理能力强,实际应用强,实验条件易于操作,对水质的pH范围适用广,催化剂稳定性高,重复利用性好,经济性能优异,在有机废水治理领域具有很好的应用前景。(The invention discloses a binary metal oxide composite carbon nitride catalyst, and a preparation method and application thereof. The catalyst constructed by the scheme of the invention can form a reaction system with peroxymonosulfate at room temperature, can efficiently activate the peroxymonosulfate to generate sulfate radicals, hydroxyl radicals and high-valence transition metal complexes, thereby effectively degrading organic pollutants in wastewater, and has the advantages of high treatment efficiency, strong treatment capacity, strong practical application, easy operation of experimental conditions, wide application range of pH value of water quality, high stability of the catalyst, good reusability, excellent economic performance and good application prospect in the field of organic wastewater treatment.)

1. A binary metal oxide composite carbon nitride catalyst is characterized in that: the metal in the binary metal oxide is cobalt and manganese.

2. A method for preparing the binary metal oxide composite carbon nitride catalyst according to claim 1, wherein the method comprises the following steps: the method comprises the following steps:

s1, preparing a mixed reaction solution containing divalent manganese ions, divalent cobalt ions and dicyandiamide;

s2, stirring and heating the mixed reaction solution prepared in the step S1 until the water in the solution is evaporated to dryness to obtain crystals;

and S3, grinding and drying the crystal obtained in the step S2, and roasting to obtain the catalyst.

3. The method of claim 2, wherein: the molar ratio of manganese ions to cobalt ions is (1-2) to (1-4); preferably, the molar ratio of manganese ions to cobalt ions is 1: 3.

4. The method of claim 2, wherein: in the mixed reaction solution, the concentration of manganese ions is (0.05-0.1) mol/L, the concentration of cobalt ions is (0.1-0.4) mol/L, and the mass concentration of dicyandiamide is (0.1-0.15) g/ml.

5. The method of claim 2, wherein: the heating temperature in the step S2 is (70-90) DEG C; the reaction time in the step S2 is 2-3 h.

6. The method of claim 2, wherein: in the step S3, the roasting temperature is 560-590 ℃, and the roasting time is 3-6 h; preferably, the calcination temperature is 575 ℃ and the calcination time is 4 h.

7. The application of the catalyst in preparing the organic pollutant degradation catalyst is characterized in that: the catalyst is as defined in claim 1 or prepared by the preparation method defined in claim 2.

8. Use according to claim 7, characterized in that: the organic contaminant includes at least one of a hormone analog, a petrochemical organic contaminant, or an organic pharmaceutical contaminant.

9. A method for degrading organic pollutants in wastewater is characterized by comprising the following steps: the method comprises the following steps: the catalyst of claim 1 and a salt of peroxymonosulfate are added to a wastewater containing organic contaminants.

10. A method of degrading organic contaminants in wastewater according to claim 9 and further comprising: the peroxymonosulfate is potassium hydrogen persulfate composite salt.

Technical Field

The invention relates to the technical field of wastewater treatment, and particularly relates to a binary metal oxide composite carbon nitride catalyst and a preparation method and application thereof.

Background

With the rapid development of industry, the discharge amount of organic sewage is increased sharply. Among them, printing and dyeing wastewater and petrochemical wastewater have become the main sources of organic sewage due to their characteristics of large discharge amount, difficult degradation of pollutants, etc., and pose serious threats to the water environment and human health, so that the treatment of organic sewage is imperative. Among the various sewage treatment technologies, the advanced oxidation technology is a technology that utilizes free radicals (HO) generated by the reaction^·And SO₄ ^·-) The technology for degrading pollutants in water by carrying out reactions such as addition, substitution, electron transfer, chemical bond breakage and the like with organic pollutants is widely applied to removal of various organic pollutants difficult to degrade due to the advantages of high degradation efficiency, simplicity in operation, no secondary pollution and the like. In recent years, oxone complex salts generate hydroxyl radicals (HO)^·) And sulfate radical (SO)₄ ^·-) Has received wide attention, but only contains SO₄ ^·—And HO^·The system can only process organic compounds with stronger electronic activity quickly and depends on SO only₄ ^·—And HO^·Treatment of highly nitrated materials treatment of nitrobenzene and nitrobenzene homologues is less effective. During the research of advanced oxidation catalyst, transition metal complex (M) with high valence state^IV(O)/M^V(O)) has also been found to be present in catalytic systems and has received much attention due to their higher oxidation efficiency.

The activation and stabilization of the nitrogenous substrate by oxone complex salt is to produce M^IV(O)/M^V(O) and HO^·And SO₄ ^·-The key to advanced oxidation technology of active factors lies. Common activating modes of the potassium hydrogen persulfate composite salt comprise thermal activation, transition metal activation and ultraviolet light activation, wherein the transition metal activation becomes a research hotspot due to the advantages of good controllability, low energy consumption, high efficiency and the like. Cobalt and manganese are used as transition metal elements with rich natural content, can efficiently activate peroxymonosulfate to generate sulfate radicals and hydroxyl radicals, and simultaneously, various related researches show that the transition metals (such as Co, Mn and the like) of the first family can generate M^IV(O)/M^V(O). However, how to improve the structure of the transition metal oxide composite material to overcome the defects of the existing catalyst has become a key point and a difficulty of the current research, and the research also has important application value for industrial production and human health.

Disclosure of Invention

The present invention is directed to solving at least one of the problems of the prior art. Therefore, the invention provides a binary metal oxide composite carbon nitride catalyst which has a good degradation effect on organic pollutants such as nitrobenzene and the like.

The invention also provides a preparation method of the catalyst.

The invention also provides an application of the catalyst.

According to the binary metal oxide composite carbon nitride catalyst of the embodiment of the first aspect of the invention, the metals in the binary metal oxide are cobalt and manganese; preferably, the chemical composition of the catalyst is MnCo₂O₄/C₃N₄。

The catalyst provided by the embodiment of the invention has at least the following beneficial effects: the scheme of the invention takes the carbon nitride as a stable matrix rich in nitrogen, and can effectively form M for Co and manganese^IV(O)/M^V(O) provides advantageous conditions; the catalyst constructed by the scheme of the invention has strong degradation capability, high degradation efficiency, wide pH application range and good repeatability, and can make up for the problems of insufficient activation and the like of the traditional catalyst to a great extent.

A method of making an embodiment according to the second aspect of the invention comprises the steps of:

s1, preparing a mixed reaction solution containing manganese (II) ions, cobalt (II) ions, and Dicyandiamide (DCD);

s2, stirring and heating the mixed reaction solution prepared in the step S1 until the water in the solution is evaporated to dryness to obtain crystals;

and S3, grinding and drying the crystal obtained in the step S2, and roasting to obtain the catalyst.

The preparation method provided by the embodiment of the invention has at least the following beneficial effects: the method adopts a high-temperature oxygen-limiting method to prepare a catalyst with binary oxide compounded on carbon nitride, and uses dicyandiamide as a base material to synthesize the carbon nitride which can provide basic conditions for high-valence transition metal complexes, so that the morphology of the carbon nitride prepared by the method is more favorable for the catalysis; the method has the advantages of simple operation, simple preparation process, low energy consumption and good industrial application prospect.

According to some embodiments of the present invention, the molar ratio of manganese ions to cobalt ions in the mixed reaction solution is (1-2) to (1-4); preferably, the molar ratio of manganese ions to cobalt ions is 1: 3.

According to some embodiments of the present invention, in the mixed reaction solution, the concentration of manganese ions is (0.05-0.1) mol/L, the concentration of cobalt ions is (0.1-0.4) mol/L, and the mass concentration of dicyandiamide is (0.1-0.15) g/ml.

According to some embodiments of the present invention, the mixed reaction solution is prepared by dissolving a manganese salt, a cobalt salt and DCD in water to prepare a mixed reaction solution; preferably, the manganese salt is manganese acetate.

According to some embodiments of the invention, the cobalt salt is cobalt nitrate.

According to some embodiments of the invention, the heating temperature in the step S2 is (70-90) DEG C; preferably, the heating temperature is 80 ℃.

According to some embodiments of the invention, the reaction time in the step S2 is 2-3 h.

According to some embodiments of the present invention, the rotation speed of the stirring operation in the step S2 is 300-600 r/min.

According to some embodiments of the present invention, in the step S3, the drying temperature is (105-125) DEG C, and the drying time is (5-8) h; preferably, the drying temperature is 120 ℃.

According to some embodiments of the invention, the calcination temperature is (560-590) DEG C, and the calcination time is (3-6) h; preferably, the calcination temperature is 575 ℃ and the calcination time is 4 h.

According to the application of the third aspect embodiment of the invention, the application of the catalyst in the preparation of the organic pollutant degradation catalyst is that the catalyst is prepared by the catalyst or the preparation method.

According to some embodiments of the invention, the organic contaminant comprises at least one of a hormone analogue, a petrochemical-based organic contaminant, or an organic pharmaceutical-based contaminant.

According to some embodiments of the invention, the organic contaminants comprise at least one of nitrobenzene, phenol, 2,4-dichlorophen, bisphenol a, nitrobenzene homologues, and 2-ethylanthraquinone.

A method for degrading organic pollutants in wastewater comprises the following steps: the above catalyst and peroxymonosulfate are added to the wastewater containing organic contaminants.

According to some embodiments of the invention, the peroxymonosulfate is a oxone complex salt having the formula 2KHSO₅·KHSO₄·K₂SO₄。

According to some embodiments of the invention, the catalyst is added in an amount of (0.1-0.3) g/L, preferably the amount of catalyst is 0.2 g/L.

According to some embodiments of the invention, the amount of peroxymonosulfate added is (0.2-0.8) g/L, preferably the amount of peroxymonosulfate added is 0.4 g/L.

According to some embodiments of the invention, the concentration of the organic contaminant is no greater than 50 mg/L.

The application of the embodiment of the invention has at least the following beneficial effects: the catalyst constructed by the scheme of the invention can realize an advanced oxidation technology of organic pollution with peroxymonosulfate, has low requirement on water quality and environment when treating organic wastewater, has strong applicability, can quickly degrade and remove organic pollutants such as nitrobenzene and the like which are difficult to degrade in water, only needs a small amount of catalyst and oxidant, and has good economic performance; the catalyst provided by the scheme of the invention has better stability and energy efficiency, can be repeatedly utilized for many times, saves the cost, and is green and pollution-free; the degradation operation can be carried out at room temperature, the reaction condition is mild, the requirement on the pH value of the treated wastewater is low, the method is applicable to acid-base ranges, and the method has good industrial application prospect.

Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

Drawings

FIG. 1a is an XRD pattern of the catalyst obtained in example 1 of the present invention, and FIG. 1b is an EDS pattern of the catalyst obtained in example 1 of the present invention;

FIG. 2 is a TEM image of carbon nitride in example 1 of the present invention;

FIG. 3 is a graph showing the degradation profiles of different organic contaminants in example 2 of the present invention;

FIG. 4 is a graph showing the degradation curves of refractory nitrobenzene under different pH conditions in example 2 of the present invention.

FIG. 5 is a graph showing the degradation curve of COD in practical wastewater in example 3 of the present invention;

FIG. 6 is a graph showing the actual TOC degradation of wastewater in example 3 of the present invention;

FIG. 7 is a graph showing the experimental cycle degradation of nitrobenzene in example 3 of the present invention;

FIG. 8 is a diagram illustrating the mechanism of action of the catalysts of examples 2 to 3 of the present invention to activate peroxymonosulfate to degrade organic pollutants;

FIG. 9 is a graph showing the degradation profile of p-nitrobenzene in the presence of catalysts prepared in different molar ratios in example 4 of the present invention.

Detailed Description

In order to explain technical contents, achieved objects, and effects of the present invention in detail, the following description is made with reference to the accompanying drawings in combination with the embodiments.

Embodiment 1 of the present invention: a binary metal oxide composite carbon nitride catalyst is prepared from MnCo₂O₄/C₃N₄The preparation method comprises the following steps:

(1) 4.35g Co (NO) was weighed at room temperature₃)₂·6H₂O、1.23g Mn(CH₃COO)₂·4H₂O and 5g DCD were dispersed ultrasonically in 50mL deionized water and allowed to dissolve completely under magnetic stirring.

(2) And (2) heating the reaction solution obtained in the step (1) to 80 ℃ in magnetic stirring, and keeping for 2h until the deionized water in the solution system is completely evaporated and crystals are separated out.

(3) Grinding the obtained crystal substance into powder, drying the powder in an oven at 120 ℃ for 5h, transferring the powder into a muffle furnace, roasting the powder for 4h at 575 ℃ (the temperature of the muffle furnace is raised to 575 ℃ at the speed of 5 ℃/min), and thus obtaining MnCo₂O₄/C₃N₄A catalyst. The catalyst obtained in the above example was subjected to X-ray diffraction (XRD) analysis, and the result is shown in FIG. 1 a. FIG. 1a is the XRD pattern of the catalyst, which is compared to CoMn in the standard library₂O_XThe XRD patterns are most similar, but only the material and MnCo can be determined by the standard card₂O_4.5Cards (JCPD #32-0297) were similar and further validated by Energy Dispersive Spectroscopy (EDS) because of the larger baseline drift amplitude due to Co-containing oxides, as shown in fig. 1 b. The molecular ratio of O element to Mn element was calculated to be 4 to 1 by EDS, and the composition was further determined to be MnCo₂O₄/C₃N₄. Further, the obtained catalyst was analyzed by a transmission electron Microscope (transmission electron Microscope), and the results are shown in FIG. 2. As can be seen from FIG. 2, the carbon nitride is in the form of stacked sheets, and the layered morphology has a larger specific surface area, can improve the adhesion of pollutants on the material, and can increase the MnCo content₂O₄Reaction sites with contaminants, favoring contaminantsDegradation of (2).

The second embodiment of the invention is as follows: a method for treating organic wastewater, wherein the MnCo prepared in example 1 is used₂O₄/C₃N₄Catalyst activation of the peroxymonosulfate (Potassium peroxymonosulfate complex, PMS) was used to evaluate the catalytic activity of organic pollutants in wastewater.

10mg of the prepared catalyst is accurately weighed and placed in 50mL of different waste liquids (Bisphenol A (BPA), Phenol (Phenol), 2,4-Dichlorophenol (2,4-Dichlorophenol, 2, 4-DCP) and Nitrobenzene (Nitrobenzene, NB)) with the concentration of 50mg/L, and 20mg of peroxymonosulfate is added for degradation reaction under the condition of continuous stirring. Under different pH conditions (pH 3-10), the pH value of the wastewater containing nitrobenzene is adjusted by acid or alkali in advance to simulate different pH environments, and degradation is carried out according to the process, wherein all experiments are carried out at room temperature.

Taking solutions with different reaction times for concentration measurement, and drawing to obtain C_t/C₀The graphs of the-t relationship are shown in fig. 3 and 4, respectively. As can be seen from FIGS. 3 and 4, MnCo₂O₄/C₃N₄The catalyst combined with the peroxymonosulfate system shows high degradation performance on various organic pollutants. Wherein FIG. 3 is MnCo₂O₄/C₃N₄The catalyst activates the degradation curve of peroxymonosulfate to nitrobenzene which is difficult to degrade under different pH conditions. It can be seen from the figure that MnCo is present at pH 3-10₂O₄/C₃N₄The catalyst and the peroxymonosulfate system can effectively degrade nitrobenzene.

The third embodiment of the invention is as follows: a method for treating organic wastewater, namely preparing the obtained MnCo₂O₄/C₃N₄The catalyst activated peroxymonosulfate was used for degradation of organic pollutants in petrochemical wastewater to evaluate its practical applicability.

Accurately weighing 20mg of the prepared catalyst in 50mL of petrochemical wastewater, and adding 20mg of peroxymonosulfate for degradation reaction under the condition of continuous stirring. The initial COD value of the petrochemical wastewater is 262mgThe main components of the composition are nitrobenzene, nitrobenzene homologues, 2-ethyl anthraquinone, a small amount of hydrogen peroxide and the like. The COD value and the TOC value before and after degradation were measured by the potassium permanganate national standard method, and the results are shown in FIGS. 5 and 6. As can be seen from the figure, MnCo₂O₄/C₃N₄The catalyst combined with the peroxymonosulfate system shows high-efficiency degradation performance on petrochemical wastewater.

In order to verify the stability of the material in the scheme of the invention, the catalyst is taken out in a mode of an external magnetic field, washed and dried, and then put into the petrochemical wastewater again, and the operation is repeated three times, and the result is shown in fig. 7, and as can be seen from fig. 7, the catalyst still maintains higher catalytic activity after four cycles of experiments, which shows that MnCo has high catalytic activity after being subjected to MnCo experiments, and the stability of the material is improved₂O₄/C₃N₄The catalyst has high stability and can be repeatedly used.

The catalyst and persulfate in the embodiment of the invention are used for organic wastewater treatment, and the degradation of organic pollutants can be realized without illumination conditions, the action mechanism is shown in figure 8, and as can be seen from figure 8, the catalyst in the embodiment of the invention utilizes sulfate radicals, hydroxyl radicals and high-valence transition metal complexes generated in a system to degrade organic pollutants in wastewater.

The fourth embodiment of the invention is as follows: the catalytic activity of the catalysts prepared from Co and Mn with different molar ratios is verified by respectively taking Co: molar ratios of Mn of 3:1, 3:5, 1:3, 2:1, 1:2, 1:1 and 4:1 the catalyst was prepared according to the reaction conditions of example 1. The prepared catalysts with different metal ratios are used for treating nitrobenzene wastewater under the same condition, the result is shown in figure 9, and as can be seen from figure 8, when the molar ratio of Co to Mn is (1-4): 1-2), the prepared catalysts have better adsorption and degradation effects on nitrobenzene, wherein when the molar ratio of Co: when Mn is between (3/5-4) and 1, the degradation rate is about 80 percent or more than 80 percent, and when the molar ratio of Co to manganese is 3:1, the degradation rate of p-nitrobenzene can reach 96 percent.

All the experimental results show that the catalyst constructed by the invention has good application prospect in the degradation and removal of organic pollutants in wastewater by combining with a peroxymonosulfate system.

The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all equivalent changes made by using the contents of the present specification and the drawings, or applied directly or indirectly to the related technical fields, are included in the scope of the present invention.