Cobalt disulfide / graphite phase carbon nitride nano-composite catalyst as well as preparation method and application thereof

Abstract

The invention discloses a cobalt disulfide / graphite phase carbon nitride nano-composite catalyst as well as a preparation method and application thereof. The preparation method of the cobalt disulfide / graphite phase carbon nitride nano composite catalyst comprises the following steps: dispersing g-C3N4 in deionized water, and stirring to obtain a g-C3N4 solution; dispersing a Co source in deionized water and stirring to obtain a Co source solution, and dispersing an S source in deionized water and stirring to obtain an S source solution; a Co source solution and an S source solution are sequentially added into a g-C3N4 solution to be stirred to obtain a mixed solution, the mixed solution is stirred, cooled, washed and dried at the temperature of 175-183 DEG C to obtain the cobalt disulfide / graphite phase carbon nitride nano-composite catalyst, 100% tetracycline can be removed by the cobalt disulfide / graphite phase carbon nitride nano-composite catalyst within 10 min, the cobalt dissolution concentration is 0.782 mg / L, and the cobalt dissolution concentration is 0.782 mg / L; and the cobalt standard limit value in China Environmental Quality Standards for Surface Water is met.

Description

Technical Field

[0001] The invention belongs to the technical field of water treatment technology and environmental functional materials, and specifically relates to a cobalt disulfide / graphite phase carbon nitride nanocomposite catalyst and a preparation method and application thereof. Background Art

[0002] Antibiotic pollution, especially tetracycline antibiotic pollution, has become a global environmental problem. Traditional biological treatment methods have limited removal efficiency for tetracycline antibiotics, while advanced oxidation techniques (AOPs) have become a research hotspot due to their high efficiency and thoroughness. Among them, the Fenton-like system based on peroxymonosulfate (PMS) has attracted much attention due to its mild reaction conditions, strong oxidation ability and wide range of applications.

[0003] The Fenton-like system uses a solid catalyst to activate PMS to produce strong oxidizing free radicals (such as OH and SO 4 ·- ), thereby efficiently degrading organic pollutants. However, the development of efficient and stable catalysts remains a challenge in this field.

[0004] Graphitic carbon nitride (gC 3 N 4 ) is a non-metallic semiconductor material with advantages such as high chemical stability, thermal stability, suitable energy band structure and low-cost preparation. However, pure gC 3 N 4 The disadvantages of high recombination rate of photogenerated electron-hole pairs and low visible light utilization rate limit its application in heterogeneous Fenton-like systems. Combining it with an effective co-catalyst is a foreseeable way to overcome these disadvantages. Cobalt-based materials (such as Co 3 O 4 , CoO and CoS 2 etc.) as co-catalysts have attracted much attention due to their excellent PMS activation performance.

[0005] Existing cobalt-based materials are mainly made of cobalt oxides (such as Co 3 O 4 Cobalt oxide (CO) and CoO (CoO2) loaded graphite phase carbon nitride as catalyst, but the electronic structure of cobalt in cobalt oxide is not conducive to the effective activation of persulfate, so that the free radical yield is low, and cobalt particles are easy to agglomerate, produce clusters, reduce specific surface area and catalytic efficiency. At the same time, the catalyst dissolves cobalt seriously during the degradation process, especially in an acidic environment, cobalt ions dissolve in large quantities, leading to catalyst deactivation and environmental pollution. Acidic conditions are often required in the preparation of catalysts, which will produce a large amount of wastewater containing acid, metal ions and organic matter. If the wastewater is discharged directly without treatment, it will cause serious pollution to the water body, cause water acidification, affect the survival of aquatic organisms, and may also acidify the soil and destroy the ecological balance. Summary of the invention

[0006] In view of the deficiencies of the prior art, the object of the present invention is to provide a cobalt disulfide / graphite phase carbon nitride nanocomposite catalyst.

[0007] Another object of the present invention is to provide a method for preparing a cobalt disulfide / graphite phase carbon nitride nanocomposite catalyst.

[0008] Another object of the present invention is to provide an application of a cobalt disulfide / graphite phase carbon nitride nanocomposite catalyst in removing tetracycline.

[0009] The purpose of the present invention is achieved through the following technical solutions.

[0010] A method for preparing a cobalt disulfide / graphite phase carbon nitride nanocomposite catalyst comprises the following steps:

[0011] G C 3 N 4 Disperse in deionized water and stir evenly to obtain gC 3 N 4 solution; dispersing the Co source in deionized water and stirring evenly to obtain a Co source solution, dispersing the S source in deionized water and stirring evenly to obtain an S source solution; under stirring, the Co source solution and the S source solution are sequentially added to the gC 3 N 4 The mixture was stirred for 11.5 to 12.5 hours to obtain a mixed solution, and the mixed solution was stirred at 175 to 183° C. for 15.5 to 16.5 hours (hydrothermal reaction), cooled naturally to room temperature, washed, and vacuum dried to obtain a cobalt disulfide / graphite phase carbon nitride nanocomposite catalyst, wherein, by weight, the mixed solution contained gC 3 N 4 , the ratio of the Co source in the mixed solution to the S source in the mixed solution is 5:(0.07~0.13):(0.5~0.89).

[0012] In the above steps, by mass, gC 3 N 4 , the ratio of the Co source in the mixed solution to the S source in the mixed solution is preferably 5:(0.11-0.13):(0.84-0.89).

[0013] In the above steps, gC is obtained 3 N 4 The method comprises: heat treating urea at 547-553°C for 3.8-4.5 hours, cooling to room temperature, washing, drying, grinding, and obtaining gC 3 N 4 .

[0014] In the above steps, the cleaning operation includes: ultrasonication and rinsing with deionized water in sequence.

[0015] In the above steps, the frequency of the ultrasound is 50 to 200 kHz, and the time of the ultrasound is 55 to 70 minutes.

[0016] In the above steps, the heating rate of the heat treatment is 4.8-5.2°C / min. -1 .

[0017] In the above steps, the Co source is CoCl 2 6H 2 O, the S source is thiourea.

[0018] In the above steps, gC 3 N 4 Disperse evenly in deionized water, stir at room temperature of 20-25°C for 1.7-2.1h until uniform, and obtain gC 3 N 4 Solution, where gC 3 N 4 gC in solution 3 N 4 The concentration is 31-35g / L.

[0019] In the above steps, the concentration of Co element in the Co source solution is 11.7-12.3 mol / L, and the concentration of S element in the S source solution is 80-89 mol / L.

[0020] In the above steps, the vacuum drying temperature is 55-65° C., and the vacuum drying time is 6-48 hours.

[0021] In the above steps, the sample was filtered and washed at least 3 times with deionized water and ethanol respectively.

[0022] The cobalt disulfide / graphite phase carbon nitride nanocomposite catalyst obtained by the preparation method.

[0023] Application of a cobalt disulfide / graphite phase carbon nitride nanocomposite catalyst in removing tetracycline.

[0024] In the above technical solution, the cobalt disulfide / graphite phase carbon nitride nanocomposite catalyst degrades tetracycline in a Fenton-like manner.

[0025] In the above technical scheme, the cobalt disulfide / graphite phase carbon nitride nanocomposite catalyst activates PMS to generate free radicals ·OH and free radicals SO 4 ·- and non-free radicals 1 O 2 .

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) The cobalt disulfide / graphite phase carbon nitride nanocomposite catalyst of the present invention can achieve 100% removal of tetracycline within 10 minutes, with faster degradation and simultaneous generation of free radicals (·OH and SO 4 ·- ) and non-free radicals 1 O 2 , providing new ideas and methods for the removal of tetracycline in water.

[0028] (2) The cobalt dissolution concentration of the cobalt disulfide / graphite phase carbon nitride nanocomposite catalyst of the present invention is 0.782 mg / L, which is lower than the standard limit of cobalt in the specific project of centralized drinking water surface water sources in China's "Surface Water Environmental Quality Standard" (GB 3838-2002) (the standard limit is 1.0 mg / L).

[0029] (3) The raw materials (urea, thiourea and CoCl) used in the preparation method of the present invention 2 6H 2 O) The cost is extremely low, the preparation is simple, the raw materials are easily available, it is economical and environmentally friendly, and it is conducive to large-scale promotion.

[0030] (4) The present invention does not require acid leaching in the preparation method, making the synthesis more sustainable and environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The NC catalyst prepared in Comparative Example 1 and the CoS prepared in Comparative Example 2 2 XRD patterns of the catalyst and the cobalt disulfide / graphite phase carbon nitride nanocomposite catalyst prepared in Example 1;

[0032] Figure 2 The cobalt disulfide / graphite phase carbon nitride nanocomposite catalyst prepared in Example 1, the NC catalyst prepared in Comparative Example 1, and the CoS prepared in Comparative Example 2 2 Degradation effect of catalysts;

[0033] Figure 3 The degradation effect of the cobalt disulfide / graphite phase carbon nitride nanocomposite catalyst prepared in Examples 1 to 5;

[0034] Figure 4 The cobalt disulfide / graphite phase nitrided carbon nanocomposite catalyst prepared in Example 1 and the CoS prepared in Comparative Example 2 2 OH and SO in the catalyst solution and PMS solution 4 ·- Electron paramagnetic resonance spectrum of

[0035] Figure 5The cobalt disulfide / graphite phase nitrided carbon nanocomposite catalyst prepared in Example 1 and the CoS prepared in Comparative Example 2 2 The catalyst test solution and PMS solution 1 O 2 Electron paramagnetic resonance spectrum. DETAILED DESCRIPTION

[0036] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0037] Examples 1 to 5

[0038] A method for preparing a cobalt disulfide / graphite phase carbon nitride nanocomposite catalyst comprises the following steps:

[0039] G C 3 N 4 Disperse evenly in deionized water and stir at room temperature of 20-25℃ for 2h until uniform to obtain gC 3 N 4 solution; Co source (Co source is CoCl 2 6H 2 O) is dispersed in deionized water and stirred evenly to obtain a Co source solution, and a S source (the S source is thiourea) is dispersed in deionized water and stirred evenly to obtain an S source solution; under stirring, the Co source solution and the S source solution are slowly added to the gC 3 N 4 The mixed solution was placed in a 200 mL stainless steel high pressure reactor and stirred for 12 hours to obtain a mixed solution, which was then naturally cooled to room temperature, filtered and washed with deionized water and ethanol three times each to remove surface impurities, and vacuum dried at 60°C for 6 hours to obtain a cobalt disulfide / graphite phase carbon nitride nanocomposite catalyst. 3 N 4 , the ratio of Co source in the mixed solution to S source in the mixed solution is W; gC 3 N 4 gC in solution 3 N 4 The concentration of gC is 33.3 g / L, the concentration of Co in the Co source solution is 12 mol / L, and the concentration of S in the S source solution is 84 mol / L. 3 N 4 The method includes: grinding urea for 20 minutes, placing it in a ceramic crucible, and heating it at 5℃ / min -1The temperature was raised to 550°C at a heating rate and heat treated at 550°C for 4 hours, cooled to room temperature, ultrasonicated with deionized water at a frequency of 100 kHz for 60 minutes, rinsed with deionized water three times, vacuum dried at 60°C for 48 hours, and ground to obtain gC 3 N 4 .

[0040] The W and serial numbers of the cobalt disulfide / graphite phase carbon nitride nanocomposite catalysts prepared in Examples 1 to 5 are shown in Table 1.

[0041] Table 1

[0042] Example W serial number Example 1 5：0.12：0.84 <![CDATA[5wt%CoS 2 / NC]]> Example 2 5：0.02：0.17 <![CDATA[1wt%CoS 2 / NC]]> Example 3 5：0.07：0.5 <![CDATA[3wt%CoS 2 / NC]]> Example 4 5：0.19：1.34 <![CDATA[8wt%CoS 2 / NC]]> Example 5 5：0.24：1.68 <![CDATA[10wt%CoS 2 / NC]]>

[0043] Comparative Example 1

[0044] A NC catalyst, which is the gC in Example 1 3 N 4 .

[0045] Comparative Example 2

[0046] A CoS 2 The preparation method of the catalyst is basically the same as that of Example 1, except that the mixed solution is as follows: the Co source solution and the S source solution are slowly added to deionized water in sequence and stirred for 12 hours under stirring to obtain a mixed solution, wherein the volume of the deionized water is the same as that of gC in Example 1. 3 N 4 The solutions are the same, the volume of the Co source solution is the same as in Example 1, and the volume of the S source solution is the same as in Example 1.

[0047] Figure 1 The NC catalyst prepared in Comparative Example 1 and the CoS prepared in Comparative Example 2 2 The X-ray diffraction (XRD) patterns of the catalyst and the cobalt disulfide / graphite phase carbon nitride nanocomposite catalyst prepared in Example 1 are shown in FIG. Figure 1 It can be seen that the XRD spectrum of the cobalt disulfide / graphite phase carbon nitride nanocomposite catalyst prepared in Example 1 has a diffraction peak at 27.38° corresponding to gC 3 N 4 The (002) plane of the CoS 2 The (200), (210), (211), (210) and (311) crystal planes of (standard card: PDF#89-1492) indicate the successful preparation of the cobalt disulfide / graphite phase carbon nitride nanocomposite catalyst prepared in Example 1.

[0048] Example 6

[0049] The cobalt disulfide / graphite phase carbon nitride nanocomposite catalysts prepared in Examples 1 to 5, the NC catalyst prepared in Comparative Example 1, and the CoS prepared in Comparative Example 2 were tested. 2 The Fenton-like degradation effect of the catalyst on tetracycline (TC) is as follows:

[0050] (1) The catalyst was added to a 100 mL beaker containing 50 mL of TC solution to obtain a suspension, and the suspension was magnetically stirred for 30 min under natural light conditions to achieve adsorption-desorption equilibrium, wherein the concentration of the catalyst in the suspension was 0.2 g / L, and the catalysts were the cobalt disulfide / graphite phase carbon nitride nanocomposite catalysts prepared in Examples 1 to 5, the NC catalyst prepared in Comparative Example 1, and the CoS prepared in Comparative Example 2. 2 One of the catalysts, the concentration of TC in the TC solution (C 0 ) is 15ppm.

[0051] (2) PMS was added to the above suspension to make the final concentration of PMS in the suspension 0.3 g / L to obtain a test solution, and the test solution was magnetically stirred for 20 min. The test solution was taken once at the Tth minute of stirring, T = 1 min, 2 min, 3 min, 5 min, 10 min, 15 min and 20 min, and 2 mL of the test solution was taken each time and filtered with a 0.22 μm filter membrane, and the concentration of TC (C) in the test solution was determined by high performance liquid chromatography, and the removal rate of the pollutant by the catalyst at T = 10 min and the degradation rate constant within 10 min were calculated. The removal rate and the degradation rate constant are shown in Table 2. The removal rate formula is as follows:

[0052]

[0053] The cobalt disulfide / graphite phase carbon nitride nanocomposite catalyst prepared in Example 1, the NC catalyst prepared in Comparative Example 1, and the CoS prepared in Comparative Example 2 2 The degradation effect of the catalyst is as follows Figure 2 As shown, the degradation effects of the cobalt disulfide / graphite phase carbon nitride nanocomposite catalysts prepared in Examples 1 to 5 are as follows Figure 3 As shown by Figure 2 , Figure 3 As shown in Table 2, the cobalt disulfide / graphite phase carbon nitride nanocomposite catalyst prepared in Example 1 has the best TC degradation efficiency, with a removal rate of 100%, which is much higher than the cobalt disulfide / graphite phase carbon nitride nanocomposite catalysts prepared in Example 2 and Example 4, the NC catalyst prepared in Comparative Example 1, and the CoS prepared in Comparative Example 2. 2The catalyst was prepared by using the cobalt disulfide / graphite phase carbon nitride nanocomposite catalyst of Example 3 and Example 5, and the removal of TC by about 90% was achieved within 20 minutes. The cobalt disulfide / graphite phase carbon nitride nanocomposite catalyst prepared in Example 1 achieved the removal of 100% of TC within 10 minutes, and the degradation rate constant was 0.09319 min -1 .

[0054] Table 2

[0055] Example / Comparative Example Removal rate <![CDATA[Degradation rate constant (unit: min -1 )]]> Example 2 49％ 0.04711 Example 3 84％ 0.08383 Example 1 100％ 0.09319 Example 4 49％ 0.04782 Example 5 76％ 0.07645 Comparative Example 1 3.5％ 0.06224 Comparative Example 2 62.3％ 0.00366

[0056] Example 6

[0057] To gain a deeper understanding of the mechanism of the degradation process, electron paramagnetic resonance (EPR) was used to detect the active species generated after the catalyst activated PMS. EPR spectroscopy measurements were performed using a Bruker A300 spectrometer at room temperature.

[0058] Detection OH and SO 4 ·- : Add 30 μL of capture agent to 3 mL of water and shake for 5 min to obtain a capture agent solution; take 1 mL of PMS aqueous solution and 1.25 mg of catalyst and add them to 2 mL of water to obtain a test solution, use a capillary to draw 100 μL of the test solution or PMS aqueous solution and add it to the above capture agent solution, shake for 3 min, and perform EPR spectrum measurement in a spectrometer, wherein the capture agent is 5,5-dimethylpyrroline N-oxide (DMPO), the catalyst is the cobalt disulfide / graphite phase carbon nitride nanocomposite catalyst prepared in Example 1 and the CoS prepared in Comparative Example 2 2 One of the catalysts, the concentration of the catalyst in the test solution is 1.25g / L, the concentration of PMS in the PMS aqueous solution is 1.875g / L, the measurement results are as follows Figure 4 shown.

[0059] Detection 1 O 2 : Detection of OH and SO 4 ·- The difference is the capture agent, which is 2,2,6,6-tetramethylpiperidinyl oxide (TEMP). The measurement results are as follows Figure 5 shown.

[0060] Depend on Figure 4 and Figure 5 It can be seen that since the strength of the peak represents the response intensity of different active species, under the same response intensity, the main active species in the test solution of the cobalt disulfide / graphite phase carbon nitride nanocomposite catalyst prepared in Example 1 are OH, SO 4 ·- as well as1 O 2 , while the catalyst is CoS prepared in Comparative Example 2 2 The main active species of the catalyst solution (·OH, SO 4 ·- as well as 1 O 2 ) intensity can be ignored. Therefore, the cobalt disulfide / graphite phase carbon nitride nanocomposite catalyst prepared in Example 1 has a stronger ability to activate PMS to degrade TC, which confirms the above-mentioned degradation effect.

[0061] The test catalyst is the cobalt disulfide / graphite phase carbon nitride nanocomposite catalyst prepared in Example 1. The cobalt dissolution concentration of the test solution (T=20min) in Example 5 is 0.782 mg / L, which is lower than the standard limit of cobalt in the specific project of centralized drinking water surface water sources in China's "Surface Water Environmental Quality Standard" (GB 3838-2002) (the standard limit is 1.0 mg / L), and is suitable for surface water in different functional areas such as Class II and Class III.

[0062] The present invention is described above by way of example. It should be noted that, without departing from the core of the present invention, any simple deformation, modification or other equivalent replacement that can be made by those skilled in the art without inventive effort falls within the protection scope of the present invention.

Claims

1. A method for preparing a cobalt disulfide / graphite phase carbon nitride nanocomposite catalyst, characterized in that: The following steps are involved: Disperse g-C3N4 in deionized water and stir evenly to obtain a g-C3N4 solution; disperse a Co source in deionized water and stir evenly to obtain a Co source solution; disperse a S source in deionized water and stir evenly to obtain an S source solution; under stirring, sequentially add the Co source solution and the S source solution to the g-C3N4 solution, stir for 11.5 to 12.5 hours to obtain a mixed solution, stir the mixed solution at 175 to 183° C. for 15.5 to 16.5 hours, naturally cool to room temperature, wash, and vacuum dry to obtain a cobalt disulfide / graphite phase carbon nitride nanocomposite catalyst, wherein, by mass, the ratio of g-C3N4 in the mixed solution, the Co source in the mixed solution, and the S source in the mixed solution is 5:(0.07 to 0.13):(0.5 to 0.89).

2. The preparation method according to claim 1, characterized in that: The method for obtaining g-C3N4 includes: heat treating urea at 547-553°C for 3.8-4.5 hours, cooling to room temperature, washing, drying, and grinding to obtain g-C3N4.

3. The preparation method according to claim 2, characterized in that: The cleaning operation includes: ultrasonication and rinsing with deionized water in sequence; The frequency of the ultrasound is 50 to 200 kHz, and the time of the ultrasound is 55 to 70 minutes; The heating rate of the heat treatment is 4.8-5.2°C / min -1 .

4. The preparation method according to claim 1, characterized in that: Disperse g-C3N4 uniformly in deionized water, stir at room temperature of 20-25°C for 1.7-2.1 hours until uniform, to obtain a g-C3N4 solution, wherein the concentration of g-C3N4 in the g-C3N4 solution is 31-35 g / L.

5. The preparation method according to claim 1, characterized in that: The concentration of the Co element in the Co source solution is 11.7-12.3 mol / L, and the concentration of the S element in the S source solution is 80-89 mol / L.

6. The preparation method according to claim 1, characterized in that: The vacuum drying temperature is 55 to 65° C., and the vacuum drying time is 6 to 48 hours; Filter and wash with deionized water and ethanol at least 3 times each.

7. The cobalt disulfide / graphite phase carbon nitride nanocomposite catalyst obtained by the preparation method according to claim 1.

8. Use of the cobalt disulfide / graphite phase carbon nitride nanocomposite catalyst according to claim 7 in removing tetracycline.

9. The use according to claim 8, characterized in that: Fenton-like degradation of tetracycline by cobalt disulfide / graphitic carbon nitride nanocomposite catalyst.

10. The use according to claim 8, characterized in that: Cobalt disulfide / graphite carbon nitride nanocomposite catalyst activates PMS to produce free radicals ·OH and free radical SO4 ·- and non-free radicals 1 O2.

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