A Cu-based mixed-ligand photo-Fenton catalyst, its preparation method and application

Abstract

The present invention relates to a Cu-based mixed ligand photo-Fenton catalyst, a preparation method thereof and an application thereof. The adopted technical solution is as follows: First, an organic ligand 4,4'-bis(3-pyridinecarboxamido)diphenylmethane is synthesized by a one-step method using 4,4'-diaminodiphenylmethane and nicotinic acid as raw materials; Secondly, the above organic ligand is used as the main ligand, and isophthalic acid is used as the auxiliary ligand to coordinate with copper chloride dihydrate to construct a novel Cu-based mixed ligand photo-Fenton catalyst. The innovation of the present invention lies in directly degrading organic pollutants by the Fenton catalysis method under visible light irradiation. Compared with the traditional degradation method, the method of the present invention has high degradation efficiency, low material cost, remarkable treatment effect, and the added hydrogen peroxide will not cause environmental pollution, and is suitable for large-scale treatment of tetracycline antibiotics in wastewater.

Description

Technical Field

[0001] The present invention belongs to the field of photo-Fenton catalysis, and particularly relates to a Cu-based mixed-ligand photo-Fenton catalyst, a preparation method thereof, and an application thereof in degrading organic pollutants. Background Art

[0002] Tetracycline antibiotics are a class of typical organic pollutants, which are widely used in the fields of animal husbandry, aquaculture, etc. At present, due to the large-scale use of such antibiotics, the pollution of the ecological environment is becoming increasingly serious. Therefore, great attention has been paid to the preparation and determination methods of materials for efficiently removing tetracycline antibiotics. The photo-Fenton catalysis technology has attracted great interest from scientific researchers due to its advantages such as simple process, green and pollution-free, and high treatment efficiency. Coordination polymers, also known as inorganic-organic hybrid materials, have been widely used in the fields of gas storage, electrochemical detection, fluorescence detection, separation, drug transportation, etc. due to their characteristics such as long-range order, controllable structure, and many active sites. Coordination polymers with semiconductor properties have been one of the research focuses in the field of photo-Fenton catalysis in recent years. In particular, copper-containing coordination polymers are suitable for photo-Fenton catalytic degradation of organic pollutants due to their stable structure, containing metal active sites and various organic functional groups, and have the advantages of not introducing secondary pollution and high catalytic efficiency. Summary of the Invention

[0003] One of the purposes of the present invention is to select 4,4'-diaminodiphenylmethane and nicotinic acid as raw materials, and obtain a multidentate ligand 4,4'-bis(3-pyridinecarboxamido)diphenylmethane containing a bipyridine bisamide group through an organic synthesis method. Pyridine nitrogen, amide groups, etc. in this ligand are easy to coordinate with metal salts.

[0004] Another purpose of the present invention is to introduce isophthalic acid as a co-ligand to form a mixed-ligand system with 4,4'-bis(3-pyridinecarboxamido)diphenylmethane, which is more likely to form a stable structure after coordinating with metal salts, and thus be used as an excellent photo-Fenton catalyst.

[0005] The technical solution adopted by the present invention is as follows: A Cu-based mixed ligand photo-Fenton catalyst. The Cu-based mixed ligand photo-Fenton catalyst has a crystal form belonging to the triclinic system and a space group of P-1. In an asymmetric unit, it contains an isophthalic acid anion, a 4,4'-bis(3-pyridinecarboxamido)diphenylmethane ligand molecule, a divalent copper ion, and a coordinated water molecule. Each divalent copper ion has a five-coordination mode and coordinates with the nitrogen atoms N1 and N2#2 in two different 4,4'-bis(3-pyridinecarboxamido)diphenylmethane ligands, the two oxygen atoms O1 and O4#1 in two isophthalic acid anions, and a coordinated water molecule O1W; among them, the bond length of Cu1–N1 is The bond length of Cu1–N2#2 is The bond length of Cu–O is in the range.

[0006] A preparation method of a Cu-based mixed ligand photo-Fenton catalyst includes the following steps:

[0007] 1) Using 4,4'-diaminodiphenylmethane and nicotinic acid as raw materials, the organic ligand 4,4'-bis(3-pyridinecarboxamido)diphenylmethane is synthesized by a one-step method;

[0008] 2) Using the organic ligand 4,4'-bis(3-pyridinecarboxamido)diphenylmethane as the main ligand and isophthalic acid as the auxiliary ligand, coordinating with copper dichloride dihydrate to construct a Cu-based mixed ligand photo-Fenton catalyst.

[0009] Further, in the above preparation method of a Cu-based mixed ligand photo-Fenton catalyst, step 1) is specifically: slowly transfer the pyridine solution containing nicotinic acid to the pyridine solution containing 4,4'-diaminodiphenylmethane, stir at room temperature for 30 min, then dropwise add triphenyl phosphite until it turns reddish-brown, heat under reflux for 10 h, concentrate the reaction product, leave it at room temperature for 24 h, filter by suction, wash with water, recrystallize with a mixed solution of DMF and water, and dry to obtain the organic ligand 4,4'-bis(3-pyridinecarboxamido)diphenylmethane.

[0010] Further, by molar ratio, 4,4'-diaminodiphenylmethane:nicotinic acid = 1:2.

[0011] Further, for the mixed solution of DMF and water, by volume ratio, DMF:water = 1:1.

[0012] Further, in the above preparation method of a Cu-based mixed ligand photo-Fenton catalyst, step 2) is specifically: in a reaction kettle, successively add CuCl 2 ·2H 2An aqueous solution, an organic ligand 4,4'-bis(3-pyridylcarboxamido)diphenylmethane, and isophthalic acid were used. After adjusting the pH of the system to 6.5 - 7.5, the reaction kettle was placed in an oven at 120 °C for a constant-temperature reaction for 4 days. After natural cooling, a mixture of blue block crystals and black precipitate was obtained. The mixture was subjected to ultrasonic treatment, washed with water, filtered, and dried. The blue block crystals were taken as the Cu-based mixed-ligand photocatalytic Fenton catalyst.

[0013] Further, in terms of molar ratio, 4,4'-bis(3-pyridylcarboxamido)diphenylmethane:isophthalic acid:CuCl 2 ·2H 2 O = 1:1.5 - 3:2 - 4.

[0014] The present invention provides the application of the Cu-based mixed-ligand photocatalytic Fenton catalyst in the photocatalytic degradation of organic pollutants.

[0015] Further, the method is as follows: In a solution containing organic pollutants, hydrogen peroxide and the Cu-based mixed-ligand photocatalytic Fenton catalyst are added, and the organic pollutants are photocatalytically degraded under visible light irradiation.

[0016] Further, the organic pollutant is a tetracycline antibiotic. Preferably, the tetracycline antibiotic is chlortetracycline, oxytetracycline, and tetracycline.

[0017] The beneficial effects of the present invention are as follows: The present invention provides a method for the heterogeneous Fenton degradation of tetracycline organic pollutants with visible light response, which has good spectral adaptability. The photocatalytic Fenton catalyst of the present invention has the characteristics of low dosage, high catalytic efficiency, and small environmental impact. Compared with traditional degradation methods, this method has high degradation efficiency, low material cost, remarkable treatment effect, and the added hydrogen peroxide will not cause environmental pollution, and is suitable for large-scale treatment of tetracycline antibiotics in wastewater. Therefore, it can be applied in the degradation of organic pollutants. Description of the Drawings

[0018] Figure 1 It is a diagram of the coordination environment of divalent copper ions in the Cu-based mixed-ligand photocatalytic Fenton catalyst prepared in Example 1.

[0019] Figure 2 It is a one-dimensional chain diagram of the Cu-based mixed-ligand photocatalytic Fenton catalyst prepared in Example 1.

[0020] Figure 3 It is a comparison between the powder X-ray diffraction pattern of the Cu-based mixed-ligand photocatalytic Fenton catalyst prepared in Example 1 and the simulated single-crystal data diagram;

[0021] Among them, (a) is the simulated single-crystal data diagram; (b) is the powder X-ray diffraction pattern.

[0022] Figure 4It is the graph of the photocatalytic degradation efficiency of the Cu-based mixed-ligand Fenton catalyst prepared in Example 1 for three antibiotics;

[0023] Among them, (a) CTC; (b) OTC; (c) TC. Detailed implementation manners

[0024] Example 1 A Cu-based mixed-ligand Fenton catalyst

[0025] (1) The preparation method is as follows:

[0026] 1. Synthesis of the organic ligand 4,4'-bis(3-pyridinecarboxamido)diphenylmethane

[0027]

[0028] Dissolve 4,4'-diaminodiphenylmethane (9.9 g, 0.05 mol) in 20 mL of pyridine solution, and dissolve nicotinic acid (12.3 g, 0.10 mol) in 35 mL of pyridine solution. Then slowly transfer the nicotinic acid pyridine solution to the 4,4'-diaminodiphenylmethane pyridine solution. After stirring at room temperature for 30 min, dropwise add triphenyl phosphite (15.5 g, 0.05 mol) within 15 min until it turns reddish-brown, heat under reflux for 10 h, and then concentrate the reaction product to 10 mL. After standing at room temperature for 24 h, a light brown solid precipitates. Filter by suction, wash with water, and recrystallize with a DMF-water mixed solution (V DMF :V 水 = 1:1). Place the product in a vacuum drying oven to dry, and obtain a pale yellow powdery solid, which is the organic ligand 4,4'-bis(3-pyridinecarboxamido)diphenylmethane.

[0029] 2. Synthesis of the Cu-based mixed-ligand Fenton catalyst

[0030] Accurately weigh CuCl 2 ·2H 2 O (0.034 g, 0.2 mmol) and add it to a 25 mL hydrothermal reactor, and then add 8 mL of water to completely dissolve it. Add 4,4'-bis(3-pyridinecarboxamido)diphenylmethane (0.041 g, 0.1 mmol) and isophthalic acid (0.025 g, 0.15 mmol) to the above 25 mL hydrothermal reactor in sequence. Add 4 mL of 0.1 mol / L sodium hydroxide solution to adjust the pH to 7.5. Place the hydrothermal reactor in an oven at 120 °C for 4 days, and let it cool naturally to obtain a mixture of blue block crystals and black precipitate. Ultrasonic the mixture, wash with water, filter and dry it. Take the blue block crystals, which are the Cu-based mixed-ligand Fenton catalyst, and the yield is about 40%.

[0031] (2) Characterization

[0032] Determination and Structural Analysis of the Structure of Cu-based Mixed Ligand Photo-Fenton Catalyst

[0033] On a Bruker D8-ray diffractometer, graphite monochromatization radiation was used as the diffraction light source to collect the diffraction data of single crystals. The prepared blue bulk crystals (i.e., Cu-based mixed ligand photo-Fenton catalyst) were taken, and the crystal data obtained from the diffraction data are shown in Table 1. And its structure was further analyzed, as Figure 1 shown. Its crystal form belongs to the triclinic system, and the space group is P-1. In an asymmetric unit, it contains an isophthalic acid anion, a 4,4'-bis(3-pyridinecarboxamido)diphenylmethane ligand molecule, a divalent copper ion, and a stoichiometric water molecule. Each divalent copper ion has a pentacoordination mode and coordinates with the nitrogen atoms (N1 and N2#2) in two different 4,4'-bis(3-pyridinecarboxamido)diphenylmethane ligands, two oxygen atoms (O1 and O4#1) in two isophthalic acid anions, and a coordinated water molecule (O1W). Among them, the bond length of Cu1–N1 is The bond length of Cu1–N2#2 is The bond length of Cu–O is in the range of (The main bond length and bond angle parameters are shown in Table 2). Two 4,4'-bis(3-pyridinecarboxamido)diphenylmethane ligands connect two adjacent divalent copper ions through pyridine nitrogen atoms to form a binuclear ring structure, and the deprotonated isophthalic acid anion connects adjacent binuclear subunits to form a 1D double-chain structure ( Figure 2 ).

[0034] The powder X-ray diffraction analysis of the crystal was carried out using a Bruker D8 Advance X-ray powder diffractometer. Graphite monochromatized CuKα radiation was used, with a wavelength solid detector, a step size of 0.01°, a step time of 0.3 sec, and a scanning range of 5° ≤ 2θ ≤ 50°. The powder X-ray diffraction pattern of the prepared Cu-based mixed ligand photo-Fenton catalyst matches the simulated pattern of the single crystal data ( Figure 3 ).

[0035] Table 1 Crystallographic Parameters of the Target Product

[0036]

[0037] Table 2 Bond Lengths and Bond Angles (°) Parameters of the Target Product

[0038]

[0039] Example 2 A preparation method of a Cu-based mixed ligand photo-Fenton catalyst (I) is as follows:

[0040] 1. Synthesis of organic ligand 4,4'-bis(3-pyridinecarboxamido)diphenylmethane

[0041] Same as Example 1

[0042] 2. Synthesis of Cu-based mixed ligand photo-Fenton catalyst

[0043] Accurately weigh CuCl 2 ·2H 2 O (0.034 g, 0.2 mmol) and add it to a 25 mL hydrothermal reactor. Then add 8 mL of water to completely dissolve it. Sequentially add 4,4'-bis(3-pyridinecarboxamido)diphenylmethane (0.041 g, 0.1 mmol) and isophthalic acid (0.042 g, 0.25 mmol) to the above 25 mL hydrothermal reactor. Add 4 mL of 0.1 mol / L sodium hydroxide solution to adjust the pH to 7.0. Place the hydrothermal reactor in an oven and keep it at 120 °C for 4 days. Let it cool naturally to obtain a mixture of blue block crystals and black precipitate. Ultrasonicate, wash with water, filter, and dry the mixture. Take the blue block crystals, which are the Cu-based mixed ligand photo-Fenton catalyst, and the yield is about 42%.

[0044] Example 3 A preparation method of a Cu-based mixed ligand photo-Fenton catalyst (I) is as follows:

[0045] 1. Synthesis of organic ligand 4,4'-bis(3-pyridinecarboxamido)diphenylmethane

[0046] Same as Example 1

[0047] 2. Synthesis of Cu-based mixed ligand photo-Fenton catalyst

[0048] Accurately weigh CuCl 2 ·2H 2 O (0.034 g, 0.2 mmol) and add it to a 25 mL hydrothermal reactor. Then add 7 mL of water to completely dissolve it. Sequentially add 4,4'-bis(3-pyridinecarboxamido)diphenylmethane (0.041 g, 0.1 mmol) and isophthalic acid (0.050 g, 0.30 mmol) to the above 25 mL hydrothermal reactor. Add 5 mL of 0.1 mol / L sodium hydroxide solution to adjust the pH to 6.5. Place the hydrothermal reactor in an oven and keep it at 120 °C for 4 days. Let it cool naturally to obtain a mixture of blue block crystals and black precipitate. Ultrasonicate, wash with water, filter, and dry the mixture. Take the blue block crystals, which are the Cu-based mixed ligand photo-Fenton catalyst, and the yield is about 35%.

[0049] Example 4 A preparation method of a Cu-based mixed ligand photo-Fenton catalyst (I) is as follows:

[0050] 1. Synthesis of the organic ligand 4,4'-bis(3-pyridinecarboxamido)diphenylmethane

[0051] Same as Example 1

[0052] 2. Synthesis of the Cu-based mixed-ligand photo-Fenton catalyst

[0053] Accurately weigh CuCl 2 ·2H 2 O (0.068 g, 0.4 mmol) and add it to a 25 mL hydrothermal reactor. Then add 7 mL of water to completely dissolve it. Sequentially add 4,4'-bis(3-pyridinecarboxamido)diphenylmethane (0.041 g, 0.1 mmol) and isophthalic acid (0.050 g, 0.30 mmol) to the above 25 mL hydrothermal reactor. Add 5 mL of 0.1 mol / L sodium hydroxide solution to adjust the pH to 6.8. Place the hydrothermal reactor in an oven at 120 °C for 4 days, and let it cool naturally to obtain a mixture of blue block crystals and black precipitate. Ultrasonicate, wash with water, filter, and dry the mixture. Take the blue block crystals, which are the Cu-based mixed-ligand photo-Fenton catalyst, and the yield is about 30%.

[0054] Example 5 Application of the Cu-based mixed-ligand photo-Fenton catalyst in the degradation of organic pollutants

[0055] Using the target pollutants chlortetracycline (CTC), oxytetracycline (OTC), and tetracycline (TC) as the treatment objects, a 300 W xenon lamp equipped with a 420 nm filter is used to provide a visible light source, and the photo-Fenton catalytic activity of the sample prepared in Example 1 under visible light irradiation is evaluated.

[0056] Method: Weigh three groups of 20 mg of the Cu-based mixed-ligand photo-Fenton catalyst and add them to 40 mL of aqueous solutions containing three organic pollutants (CTC concentration is 50 mg / L, OTC concentration is 50 mg / L, and TC concentration is 20 mg / L) respectively. Magnetically stir the suspension for 30 min. Then, add 1500 ppm H 2 O 2 for photo-Fenton catalytic degradation. Take 3 mL of the supernatant of the reaction solution every 20 min and test it with a UV-visible spectrophotometer. The results are as Figure 4 .

[0057] As Figure 4 shown in (a) below, after 20 min of photo-Fenton catalysis, the CTC removal rate reached 69.5%, and the removal rate reached 87% at 120 min. As Figure 4 shown in (b) below, after 20 min of photo-Fenton catalysis, the OTC removal rate reached 63.1%, and the removal rate reached 79.7% at 120 min. As Figure 4As shown in (c), after 20 min of photo-Fenton catalysis, the TC removal rate reached 59.8%, and at 120 min, the removal rate reached 73.8%.

[0058] The Cu-based dual mixed-ligand photo-Fenton catalyst of the present invention can effectively catalyze the degradation of CTC, OTC, and TC, and has good spectral adaptability. The photo-Fenton catalyst of the present invention has the characteristics of low dosage, high catalytic efficiency, and small environmental impact, so it can be applied to the degradation of organic pollutants.

Claims

1. A Cu-based mixed-ligand photo-Fenton catalyst, characterized in that, The Cu-based mixed ligand photocatalytic Fenton catalyst has a crystal form belonging to the triclinic system and a space group of P -1. In an asymmetric unit, it contains an isophthalic acid anion, a 4,4'-bis(3-pyridylcarboxamido)diphenylmethane ligand molecule, a divalent copper ion, and a coordinated water molecule. Each divalent copper ion has a pentacoordination mode and coordinates with the nitrogen atoms N1 and N2#2 in two different 4,4'-bis(3-pyridylcarboxamido)diphenylmethane ligands, the two oxygen atoms O1 and O4#1 in two isophthalic acid anions, and a coordinated water molecule O1W. Among them, the bond length of Cu1–N1 is 2.017(1) Å, the bond length of Cu1–N2#2 is 2.027(1) Å, and the bond length of Cu–O is in the range of 1.992(1)–2.155(1) Å; the molecular formula is C 33 H 26 CuN 4 O 7 , a (Å) is 8.4061(3), b(Å) is 10.5586(4), c (Å) is 16.9623(6), α(deg) is 72.3700(10), β(deg) is 84.8230(10), and γ(deg) is 85.5710(10).

2. A preparation method of the Cu-based mixed-ligand photo-Fenton catalyst according to claim 1, characterized in that, comprises the following steps: 1) Using 4,4'-diaminodiphenylmethane and nicotinic acid as raw materials, the organic ligand 4,4'-bis(3-pyridinecarboxamido)diphenylmethane is synthesized by a one-step method; 2) Using the organic ligand 4,4'-bis(3-pyridinecarboxamido)diphenylmethane as the main ligand and isophthalic acid as the auxiliary ligand, coordinating with copper chloride dihydrate to construct a Cu-based mixed-ligand photo-Fenton catalyst.

3. According to the preparation method of the Cu-based mixed-ligand photo-Fenton catalyst described in claim 2, characterized in that, Step 1) is specifically: slowly transfer the pyridine solution containing nicotinic acid to the pyridine solution containing 4,4'-diaminodiphenylmethane, stir at room temperature for 30 min, then dropwise add triphenyl phosphite until it turns reddish-brown, heat under reflux for 10 h, concentrate the reaction product, leave it at room temperature for 24 h, filter by suction, wash with water, recrystallize with a mixed solution of DMF and water, and dry to obtain the organic ligand 4,4'-bis(3-pyridinecarboxamido)diphenylmethane.

4. According to the preparation method of the Cu-based mixed-ligand photo-Fenton catalyst described in claim 3, characterized in that, By molar ratio, 4,4'-diaminodiphenylmethane:nicotinic acid = 1:

2.

5. According to the preparation method of the Cu-based mixed-ligand photo-Fenton catalyst described in claim 3, characterized in that, For the mixed solution of DMF and water, by volume ratio, DMF:water = 1:

1.

6. According to the preparation method of the Cu-based mixed-ligand photo-Fenton catalyst described in claim 2, characterized in that, Step 2) Specifically: In a reaction kettle, CuCl is added successively 2 ·2H 2 O aqueous solution, organic ligand 4,4'-bis(3-pyridylcarboxamido)diphenylmethane and isophthalic acid. After adjusting the pH of the system to 6.5 - 7.5, the reaction kettle is placed in an oven at 120 o °C for constant-temperature reaction for 4 days, and then cooled naturally to obtain a mixture of blue block crystals and black precipitate. The mixture is subjected to ultrasonic treatment, washed with water, filtered and dried, and the blue block crystals are taken as the Cu-based mixed-ligand photocatalytic Fenton catalyst.

7. According to the preparation method of the Cu-based mixed-ligand photo-Fenton catalyst described in claim 6, characterized in that, In terms of molar ratio, 4,4'-bis(3-pyridinecarboxamido)diphenylmethane:isophthalic acid:CuCl 2 ·2H 2 O = 1:1.5 - 3:2 - 4。 8. Application of the Cu-based mixed-ligand photo-Fenton catalyst described in claim 1 in photocatalytic degradation of chlortetracycline, oxytetracycline and tetracycline.

9. According to the application described in claim 8, characterized in that, The method is as follows: in a solution containing chlortetracycline, oxytetracycline and tetracycline, add hydrogen peroxide and the Cu-based mixed-ligand photo-Fenton catalyst, and photocatalytically degrade organic pollutants under visible light irradiation.

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