Method for improving photocatalytic degradation efficiency of organic pollutants

Abstract

The invention provides a method for improving photocatalytic degradation efficiency of organic pollutants, and belongs to the technical field of photocatalysis. Comprising the following steps: (1) dissolving simulated organic pollutants into water to prepare a solution with a certain concentration; (2) adding metal ions into the solution obtained in the step (1), and stirring for reaction; (3) adding a photocatalyst into the solution obtained in the step (2), and stirring for dark reaction; (4) reacting the solution obtained in the step (3) under light irradiation; and (5) in the reaction process, sequentially sucking the solutions in the step (4) according to a certain time interval, and measuring the concentration of the organic matters by using an absorbance spectrophotometry. Organic matter molecules and metal ions can form a coordination effect, and if the coordination effect has an activation effect on the organic matter molecules, the photocatalytic degradation efficiency of the organic matter can be improved through the method.

Description

Technical Field

[0001] The invention relates to the technical field of photocatalysis, and in particular to a method for improving the photocatalytic degradation efficiency of organic pollutants. Background Art

[0002] Photocatalytic technology is one of the effective strategies to solve the problem of organic wastewater discharge and pollution. An effective photocatalytic process depends on two aspects: on the one hand, it depends on the structure of the photocatalyst. For the oxidation and degradation reaction of organic wastewater, highly active photocatalysts must have good visible light response characteristics, efficient photogenerated charge separation efficiency and low photogenerated charge recombination efficiency, and high valence band position to ensure that they have good oxidation ability. Therefore, the current focus of photocatalytic research is mainly on the design and synthesis of highly active catalysts. On the other hand, it depends on the oxidizability of organic molecules. Generally speaking, organic molecules with π electron systems are more easily oxidized and degraded, and the π electron delocalization effect is enhanced, and the oxidizability of organic molecules is correspondingly enhanced, and vice versa. Therefore, from the perspective of oxidized and degraded organic molecules, if the π electron delocalization effect can be enhanced, its photocatalytic degradation efficiency will be greatly improved. However, without changing the catalyst, there are relatively few studies on simply enhancing the π electron delocalization effect of organic molecules to improve the photodegradation efficiency of organic matter. According to the viewpoint of coordination chemistry, after organic molecules form complexes with metal ions, the π electrons of organic molecules are redistributed under the induction of metal ions, and the polarity of the molecules changes. When the π electron delocalization effect is enhanced, the molecules are activated, the interaction between organic molecules and catalysts is enhanced, and the photocatalytic degradation efficiency of organic molecules is increased. When the π electron delocalization effect is weakened, the molecules are passivated, the interaction between organic molecules and catalysts is weakened, and the photocatalytic degradation efficiency of organic molecules is reduced. Therefore, activating organic molecules through coordination, reducing the activation energy of the reaction, and improving the reactivity of organic molecules will also become an important direction of photocatalytic research. Summary of the invention

[0003] In order to solve the problem of low efficiency of photocatalytic degradation of organic pollutants, the present invention provides a simple and efficient method for photocatalytic degradation of organic pollutants.

[0004] The present invention provides a method for improving the photocatalytic degradation efficiency of organic pollutants. Compared with traditional photocatalytic degradation methods of organic pollutants, the method provided by the present invention has a significant effect on improving the degradation efficiency of organic matter, and has low cost and simple operation.

[0005] The technical solution of the present invention is achieved in this way: The present invention provides a method for improving the photocatalytic degradation efficiency of organic pollutants, comprising the following steps: Dissolve the simulated organic pollutants in water to prepare a solution of a certain concentration; Add metal ions to the solution obtained in step (1), and stir to react for 30 minutes; Add a certain amount of photocatalyst to the solution obtained in step (2), and stir to react in the dark for 30 minutes; reacting the solution obtained in step (3) under light irradiation; During the reaction, 5 mL of the solution in step (4) was taken at regular time intervals and the concentration of organic matter was determined by absorption photometry.

[0006] In the above experiments, unless otherwise specified, the experiments were carried out at room temperature.

[0007] In the above step (1), the simulated organic pollutants are methyl orange, methylene blue, tetracycline and imidacloprid, and may also be other organic pollutants.

[0008] In the above step (1), the water used is deionized water, distilled water or high-purity water.

[0009] In the above step (1), the solution concentration is 5-100 mg / L.

[0010] In the above step (2), the metal ion used is Fe 3+ , Fe 2+ ,Co 2+ , Ni 2+ , Cu 2+ , Zn 2+ ， Other metal ions may also be present.

[0011] In the above step (2), the concentration of metal ions added to the solution is adjusted according to the concentration of organic pollutants, and the molar concentration of organic pollutants: the molar concentration of metal ions is 6:1-1:1.

[0012] In the above step (2), the stirring reaction time is 10-30 minutes, the purpose of which is to allow the organic molecules to fully coordinate with the metal ions.

[0013] In the above step (3), the mass of the photocatalyst is 10-100 mg.

[0014] In the above step (3), the stirring dark reaction time is 10-60 minutes, the purpose of which is to allow the catalyst to reach adsorption-desorption equilibrium in the organic solution.

[0015] In the above step (3), the catalyst is graphite carbon nitride, TiO2, CdS, BiVO4, or other photocatalysts.

[0016] In the above step (4), the light source used is a Xe lamp, and may also be other visible light sources or ultraviolet-visible light sources.

[0017] In the above step (4), the light irradiation reaction time can be 5-60 minutes according to the enhancement effect of different metal ions on the catalytic effect.

[0018] In the above step (4), the reaction is carried out under constant temperature conditions.

[0019] In the above step (5), the time interval for absorbing the solution can be 5-10 minutes.

[0020] In the above step (5), the catalyst is separated from the 5 mL solution by centrifugation.

[0021] In the above step (5), the method for determining the concentration of organic matter may be other methods such as liquid chromatography in addition to the absorption spectrophotometry.

[0022] The present invention discloses a method for improving the photocatalytic degradation efficiency of organic pollutants. Metal ions are added to an aqueous solution of organic pollutants, and the degradation efficiency of organic pollutants is improved by utilizing the coordination effect between organic molecules and metal ions under light conditions.

[0023] The present invention has the following beneficial effects: The present invention adds metal ions to the organic pollutant solution, utilizes the coordination chemistry between the metal ions and the organic molecules, excites and activates the organic molecules, improves the reactivity of the organic matter, and thus improves its photocatalytic degradation efficiency. The method is simple and feasible, low-cost, and effective, and has certain reference significance for the deep treatment of organic wastewater.

[0024] The method proposed in the present invention has good universality. Experiments show that organic molecules can form coordination effects with metal ions. If this coordination effect has an activation effect on organic molecules, this method can be used to improve the photocatalytic degradation efficiency of organic matter. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] In the following examples, the degradation effect of the method on organic pollutants is characterized by the photocatalytic degradation efficiency of methyl orange, methylene blue, tetracycline, and imidacloprid. Methyl orange, methylene blue, tetracycline, and imidacloprid are dissolved in deionized water, distilled water, or ultrapure water to prepare an organic pollutant solution, and the solution concentration is 10 mg L -1A certain amount of metal ions (the molar concentration of organic pollutants: the molar concentration of metal ions is 3:1) was added to the above solution. After stirring for 30 minutes, 30 mg of the catalyst was evenly dispersed in the above solution. The reaction was carried out in the dark for 30 minutes to reach adsorption-desorption equilibrium. Under light, 5 mL of the reaction solution was taken every 5 or 10 minutes. After centrifugation to separate the catalyst, the absorbance of the solution was determined by UV-visible spectrophotometry, and the concentration of the solution was calculated according to the standard curve.

[0027] Example 1 1.1 Dissolve 10 mg of methyl orange in 1 L of deionized water to obtain a concentration of 10 mg L -1 of methyl orange solution.

[0028] 1.2 Pipette 100 mL of methyl orange solution into a thermostatic reactor.

[0029] 1.3 Weigh 30 mg of graphite carbon nitride and evenly disperse it into the solution in step 1.2. React in the dark for 30 minutes.

[0030] 1.4 Under constant temperature conditions, use a Xe lamp as the light source (with a 420 nm filter) and react for 60 minutes.

[0031] 1.5 After starting the reaction, pipette 5 mL of the solution from step 1.4 every 10 minutes.

[0032] 1.6 Separate the catalyst from the solution in step 1.5 using centrifugation.

[0033] 1.7 Use UV-Visible spectrophotometry to measure the absorbance of the solution of the catalyst separated in step 1.6 and calculate the concentration of the solution.

[0034] 1.8 The solution concentration obtained in step 1.7 was divided by the initial concentration of methyl orange to obtain the degradation rate of methyl orange solution at different reaction times. The degradation rate of methyl orange after 60 minutes was 55.5%.

[0035] Example 2 The experimental scheme was the same as that of Example 1, except that the catalyst was changed to CdS. The degradation rate of methyl orange was 39.3% in 60 minutes.

[0036] Example 3 The experimental scheme was the same as that of Example 1, except that the catalyst was changed to TiO2, and the degradation rate of methyl orange was 0% in 60 minutes.

[0037] Example 4 1.1 Dissolve 20 mg of methyl orange in 1 L of deionized water to obtain a concentration of 20 mg L -1 of methyl orange solution.

[0038] 1.2 Dissolve 30 mg FeCl3 in 1 L deionized water to obtain FeCl3 solution.

[0039] 1.3 Pipette 50 mL of methyl orange solution and 50 mL of FeCl3 solution respectively, mix well, and stir for 30 minutes.

[0040] 1.4 Weigh 30 mg of graphite carbon nitride and evenly disperse it into the solution in step 1.3. React in the dark for 30 minutes.

[0041] 1.5 Under constant temperature conditions, use a Xe lamp as the light source (with a 420 nm filter) and react for 60 minutes.

[0042] 1.6 After starting the reaction, pipette 5 mL of the solution from step 1.5 every 10 minutes.

[0043] 1.7 Separate the catalyst from the solution in step 1.6 using centrifugation.

[0044] 1.8 Use UV-Visible spectrophotometry to measure the absorbance of the solution of the catalyst separated in step 1.7 and calculate the concentration of the solution.

[0045] 1.9 The solution concentration obtained in step 1.8 was divided by the initial concentration of methyl orange to obtain the degradation rate of methyl orange solution at different reaction times. The degradation rate of methyl orange was 97.2% in 30 minutes.

[0046] Example 5 The experimental scheme was the same as that of Example 4, except that the catalyst was changed to CdS. The degradation rate of methyl orange was 85.4% in 60 minutes.

[0047] Example 6 The experimental scheme was the same as that of Example 4, except that the catalyst was changed to TiO2. The degradation rate of methyl orange was 80.1% in 60 minutes.

[0048] Example 7 The experimental scheme was the same as in Example 1, except that the organic matter was changed to methylene blue. The degradation rate of methylene blue was 51.3% in 60 minutes.

[0049] Example 8 The experimental scheme was the same as that of Example 4, except that the organic matter was changed to methylene blue, and the degradation rate of methylene blue was 99.6% in 60 minutes.

[0050] Example 9 The experimental scheme is the same as that of Example 4, except that the metal ion is changed to Co 2+ The degradation rate of methyl orange was 75.8% in 60 minutes.

[0051] Example 10 The experimental scheme is the same as in Example 1, except that the catalyst graphite phase carbon nitride is replaced by Fe 3+ The degradation rate of methyl orange for supported graphite phase carbon nitride was 66.5% in 60 minutes.

[0052] Embodiment 11 The experimental scheme was the same as that of Example 1, except that the catalyst graphite phase carbon nitride was changed to TiO2, and the Xe lamp light source (with a 420 nm filter) was changed to a Xe lamp light source. The degradation rate of methyl orange was 99.5% in 20 minutes.

[0053] Example 12 The experimental scheme was the same as that of Example 4, except that the catalyst graphite phase carbon nitride was replaced by TiO2, and the Xe lamp light source (with a 420 nm filter) was replaced by a Xe lamp light source. The degradation rate of methyl orange was 99.9% in 5 minutes.

[0054] The present invention improves the degradation efficiency of organic pollutants under light conditions by adding metal ions to the organic pollutant solution and utilizing the coordination chemistry between organic molecules and metal ions. The method of the invention is simple, low-cost, effective, and has good universality. It has good reference value for the deep treatment of organic wastewater. Experimental verification shows that: In the experiments on catalytic degradation of organic matter by different photocatalysts, the catalytic effect was significantly changed when the same metal ions were added to the organic wastewater.

[0055] (2) In the experiment of catalytic degradation of organic matter by the same photocatalyst, the catalytic effect was significantly changed by adding different metal ions to the organic wastewater.

[0056] (3) In the experiment of catalytic degradation of organic matter by the same photocatalyst, the catalytic effect was significantly changed when the same metal ions were added to different organic wastewaters.

[0057] (4) In the photocatalytic degradation of organic matter experiment, the catalytic effect of adding metal ions to organic wastewater is significantly better than the catalytic effect of combining metal ions with photocatalysts.

[0058] (5) In the photocatalytic degradation experiment of organic pollutants, different metal ions have different effects on the degradation rate of organic matter.

[0059] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for improving the efficiency of photocatalytic degradation of organic pollutants, characterized in that: The following steps are involved: Dissolve the simulated organic pollutants in water to prepare a solution of a certain concentration; Adding metal ions to the solution obtained in step (1) and stirring to react; Adding the photocatalyst to the solution obtained in step (2) and stirring the solution to react; reacting the solution obtained in step (3) under light irradiation; During the reaction, the solution of step (4) is taken in turn at regular time intervals, and the concentration of the organic matter is determined by the spectrophotometric method.

2. The method according to claim 1, characterized in that In step (1), the simulated organic pollutant is at least one of methyl orange, methylene blue, tetracycline and imidacloprid.

3. The method according to claim 1, characterized in that In step (1), the water used is deionized water, distilled water or high-purity water; the concentration of the solution is 5-100 mg / L.

4. The method according to claim 1, characterized in that: In step (2), the metal ion used is Fe 3+ , Fe 2+ ,Co 2 + , Ni 2+ , Cu 2+ , Zn 2+ At least one of the organic pollutants: the metal ions have a substance concentration ratio of 6:1-1:1, and the stirring reaction time is 10-30 minutes.

5. The method according to claim 1, characterized in that In step (3), the mass of the photocatalyst is 10-100 mg, the time of the stirring dark reaction is 10-60 minutes, and the catalyst is at least one of graphite phase carbon nitride, TiO2, CdS, and BiVO4.

6. The method according to claim 1, characterized in that In step (4), the light source used is a Xe lamp, or other visible light sources or ultraviolet-visible light sources. The reaction time under the light irradiation is 5-60 minutes.

7. The method according to claim 1, characterized in that In step (5), the time interval for absorbing the solution is 5-10 minutes.

8. The method according to claim 1, characterized in that The experiments were carried out at room temperature.