阅读说明：本技术 一种复合光催化剂以及基于该光催化剂的间歇式处理废水的方法 (Composite photocatalyst and batch wastewater treatment method based on same ) 是由 刘少敏 张建树 王笑笑 于 2019-08-27 设计创作，主要内容包括：本发明公开了一种CuC<Sub>2</Sub>O<Sub>4</Sub>/g-C<Sub>3</Sub>N<Sub>4</Sub>复合光催化剂以及基于该光催化剂的间歇式处理废水的方法。本发明CuC<Sub>2</Sub>O<Sub>4</Sub>/g-C<Sub>3</Sub>N<Sub>4</Sub>复合光催化剂具有将Fe<Sup>3+</Sup>还原成Fe<Sup>2+</Sup>的能力,可以在过硫酸盐/Fe(II)废水处理体系中建立Fe<Sup>3+</Sup>/Fe<Sup>2+</Sup>循环,该处理废水的方法包括(1)进水加药阶段；(2)光照降解阶段；(3)静置沉淀阶段；(4)排水阶段。在整个降解过程中,CuC<Sub>2</Sub>O<Sub>4</Sub>/g-C<Sub>3</Sub>N<Sub>4</Sub>复合光催化剂产生的空穴与光生电子分别以羟基自由基和硫酸自由基的形态参加到污染物的降解过程中,不仅提高了电子和空穴的分离效率,而且光能的利用率得到极大地提升。(The invention discloses a CuC 2 O 4 /g‑C 3 N 4 A composite photocatalyst and a method for intermittently treating wastewater based on the photocatalyst. CuC of the invention 2 O 4 /g‑C 3 N 4 The composite photocatalyst comprises Fe 3+ Reduction to Fe 2+ Ability to establish Fe in persulfate/Fe (II) wastewater treatment systems 3+ /Fe 2+ Circulating, wherein the method for treating the wastewater comprises (1) a water inlet dosing stage; (2) a light degradation stage; (3) standing and precipitating; (4) and (5) a water drainage stage. During the whole degradation process, CuC 2 O 4 /g‑C 3 N 4 Composite lightThe holes and photo-generated electrons generated by the catalyst are respectively added to the degradation process of pollutants in the forms of hydroxyl radicals and sulfuric acid radicals, so that the separation efficiency of the electrons and the holes is improved, and the utilization rate of light energy is greatly improved.)

1. CuC₂O₄/g-C₃N₄The composite photocatalyst is characterized by being prepared by the following method:

(1)g-C₃N₄preparation and modification of

The method comprises the steps of taking melamine as a precursor, carrying out calcination treatment on the melamine, wherein the specific process of the calcination treatment comprises the steps of heating to 500-600 ℃ at a heating rate of 10 ℃/min, keeping for 1-3 h, then naturally cooling to room temperature, then grinding a product obtained by the calcination treatment, soaking for 3-6 h by using 4-6 mol/L nitric acid for modification, then washing to neutrality by using deionized water, and drying for 2-4 h at 105 ℃ to obtain g-C₃N₄；

(2)CuC₂O₄Preparation of

And (3) according to a molar ratio of 1-3: 1, weighing oxalic acid and CuSO₄Then dissolving oxalic acid in ethanol to obtain oxalic acid solution, and adding CuSO₄Dissolving in ultrapure water to obtain CuSO₄Solution, then adding CuSO₄Adding the solution into an oxalic acid solution, stirring at a constant temperature of 30-70 ℃ for 1-4 h, standing at room temperature for aging for 4-24 h, centrifuging, washing the solid obtained by centrifuging with ethanol and ultrapure water in sequence, drying at 40-60 ℃, and grinding to obtain CuC₂O₄Powder;

(3)CuC₂O₄/g-C₃N₄preparation of

G to C₃N₄And CuC₂O₄Mixing the powders, addingPure water, stirring for 80-100 min at 45-55 ℃, centrifuging, washing the solid obtained by centrifuging with ethanol and ultrapure water in sequence, drying at 40-60 ℃, and grinding to obtain CuC₂O₄/g-C₃N₄A composite photocatalyst is provided.

2. The CuC of claim 1₂O₄/g-C₃N₄The composite photocatalyst is characterized in that in the step (3), g-C₃N₄And CuC₂O₄The mass ratio of the powder is 12: 1 to 12.

3. CuC according to claim 1 or 2₂O₄/g-C₃N₄The method for intermittently treating the wastewater by using the composite photocatalyst is characterized by comprising the following steps of:

(1) water feeding and chemical adding stage

Mixing CuC₂O₄/g-C₃N₄The composite photocatalyst and Fe (II) and/or Fe (III) are put into a wastewater treatment container, and then wastewater is input into the wastewater treatment container to ensure that CuC₂O₄/g-C₃N₄The composite photocatalyst and Fe (II) and/or Fe (III) are dispersed in the wastewater, and Na is added at the same time₂S₂O₈Until the pH value of the waste water is reduced to below 3;

(2) degradation stage by illumination

Applying illumination to the wastewater, and simultaneously stirring the wastewater or carrying out aeration treatment to carry out illumination degradation;

(3) standing and precipitating stage

Maintaining the illumination of the wastewater, stopping stirring the wastewater or aerating, and adding Ca (OH)₂Until the pH value of the wastewater is increased to more than 4, and then standing for treatment;

(4) drainage stage

And (4) turning off the light source, and discharging the supernatant in the wastewater treatment container.

4. The C-based alloy of claim 3uC₂O₄/g-C₃N₄The method for intermittently treating the wastewater by using the composite photocatalyst is characterized in that in the step (2), the illumination applied to the wastewater is visible light illumination or ultraviolet illumination.

5. The CuC-based according to claim 3 or 4₂O₄/g-C₃N₄The method for intermittently treating the wastewater by using the composite photocatalyst is characterized in that after the step (4) is finished, a degradation period is finished, and then the next degradation period is started without adding Fe (II) and/or Fe (III) into a wastewater treatment container.

Technical Field

The invention relates to the field of wastewater treatment, in particular to a composite photocatalyst and a method for intermittently treating wastewater based on the photocatalyst.

Background

Nowadays, water treatment technology is gradually mature, but for some refractory pollutants to be treated, such as dyes, pesticides and the like, deep research is still needed, and the search for green and efficient treatment methods is an important direction of current scientific research.

The mass production and use of synthetic dyes improve the quality of life of people, but the synthetic dyes flowing into the natural environment have a lot of negative effects on aquatic organisms and human beings, such as rhodamine B (RhB), an artificial synthetic dye with bright peach red color, which has been widely used in textile, leather, food and other industries, but with the research of researchers, the rhodamine B has carcinogenic and mutagenic effects on all organisms, and simultaneously the dye can block the penetration of light in a water body, thereby affecting the photosynthesis of aquatic plants and further interfering natural purification, so that the rhodamine B in dye wastewater needs to be completely removed to avoid the damage of the dye wastewater to the ecological environment.

Since 1894, the Fenton method has been developed for many years, and the method for generating highly oxidative active species by metal ion activation has deeply influenced the development of the catalytic field. Compared with methods such as light, ultrasonic and thermal activation, the metal ion activation does not need a large amount of energy consumption, and the metal ions can release high-oxidizing free radicals in a chemical reaction mode. Hydroxyl radical is currently the most widely studied and used, and in recent years, a sulfuric acid radical having a high redox potential similar to hydroxyl radical has been attracting attention of researchers because sulfuric acid radical (30-40 μ s) is compared with hydroxyl radical (10 μ s)^-3Mus) has longer half-life, which means that the sulfuric acid radical and the pollutant have higher contact efficiency, and the oxidation-reduction potential of the sulfuric acid radical (2.8V) is slightly higher than that of the hydroxyl radical (2.7V). These two advantages are deeply attracting the interest of researchers.

At present, Fe has been used²⁺Techniques for activating persulfates, however Fe²⁺Activation of persulfate is an irreversible process, followed by activation (formula Fe)²⁺+S₂O₈ ^2-→Fe³⁺+SO₄·^-+SO₄ ^2－) Is carried out of (Fe)²⁺Conversion to Fe³⁺Final Fe²⁺When the consumption is over, the reaction is terminated and the formation of sulfate radicals is interrupted. Therefore, the search for a method for continuously activating a persulfate would increase the possibility of the persulfate entering into practical wastewater treatment.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a method for promoting the establishment of Fe in a persulfate/Fe (II) wastewater treatment system³⁺/Fe²⁺A recycled photocatalyst and a method for batch treatment of wastewater based on the photocatalyst.

In order to solve the technical problems, the invention adopts the following technical scheme: CuC₂O₄/g-C₃N₄The composite photocatalyst is prepared by the following method:

(1)g-C₃N₄preparation and modification of

The method comprises the steps of taking melamine as a precursor, carrying out calcination treatment on the melamine, wherein the specific process of the calcination treatment comprises the steps of heating to 500-600 ℃ at a heating rate of 10 ℃/min, keeping for 1-3 h, then naturally cooling to room temperature, then grinding a product obtained by the calcination treatment, soaking for 3-6 h by using 4-6 mol/L nitric acid for modification, then washing to neutrality by using deionized water, and drying for 2-4 h at 105 ℃ to obtain g-C₃N₄；

(2)CuC₂O₄Preparation of

And (3) according to a molar ratio of 1-3: 1, weighing oxalic acid and CuSO₄Then dissolving oxalic acid in ethanol to obtain oxalic acid solution, and adding CuSO₄Dissolving in ultrapure water to obtain CuSO₄Solution, then adding CuSO₄Adding the solution into an oxalic acid solution, stirring at a constant temperature of 30-70 ℃ for 1-4 h, standing at room temperature for aging for 4-24 h, centrifuging, washing the solid obtained by centrifuging with ethanol and ultrapure water in sequence, drying at 40-60 ℃, and grinding to obtain CuC₂O₄Powder;

(3)CuC₂O₄/g-C₃N₄preparation of

G to C₃N₄And CuC₂O₄Mixing the powder, adding ultrapure water, stirring for 80-100 min at 45-55 ℃, centrifuging, washing the solid obtained by centrifuging with ethanol and ultrapure water in sequence, drying at 40-60 ℃, and grinding to obtain CuC₂O₄/g-C₃N₄A composite photocatalyst is provided.

Further, in the step (3), g to C₃N₄And CuC₂O₄The mass ratio of the powder is 12: 1 to 12. In the process of implementing the invention, the inventor finds that the obtained photocatalyst reduces Fe in the proportion³⁺The effect of (2) is better, and the efficiency is higher.

Based on CuC₂O₄/g-C₃N₄The method for intermittently treating the wastewater by using the composite photocatalyst comprises the following steps:

(1) water feeding and chemical adding stage

Mixing CuC₂O₄/g-C₃N₄The composite photocatalyst and Fe (II) and/or Fe (III) are put into a wastewater treatment container, and then wastewater is input into the wastewater treatment container to ensure that CuC₂O₄/g-C₃N₄The composite photocatalyst and Fe (II) and/or Fe (III) are dispersed in the wastewater, and Na is added at the same time₂S₂O₈Until the pH value of the waste water is reduced to below 3;

in this stage, Fe (II) and/or Fe (III) are gradually dissolved to release Fe with the decrease of pH²⁺And/or Fe³⁺If sludge is accumulated at the bottom of the wastewater treatment container after the water body is stable, the sludge can be removed; fe (III) may be selected from, but not limited to, Fe₂(SO₄)₃Or Fe (OH)₃Fe (II) can be selected from but not limited to FeSO₄Or Fe (OH)₂。

(2) Degradation stage by illumination

Applying illumination to the wastewater, and simultaneously stirring the wastewater or carrying out aeration treatment to carry out illumination degradation;

at this stage, CuC₂O₄/g-C₃N₄The composite photocatalyst absorbs photons to generate photo-generated electrons, and then the photo-generated electrons convert Fe³⁺Reduction to Fe²⁺，Fe²⁺And S₂O₈ ^2-Reaction (Fe)²⁺+S₂O₈ ^2-→Fe³⁺+SO₄·^-+SO₄ ^2－) Free radical sulfuric acid is generated, thereby establishing Fe³⁺/Fe²⁺Recycling, simultaneously, CuC₂O₄/g-C₃N₄The hole of the composite photocatalyst reacts with water to generate a hydroxyl radical, the hydroxyl radical and a sulfuric acid radical jointly oxidize pollutants in the wastewater, and the oxidizing capability is greatly improved; stirring or aerating to increase CuC₂O₄/g-C₃N₄Composite photocatalyst, light absorption efficiency and active Species (SO)₄·^2-、·OH、Fe³⁺Etc.) efficiency of contact with contaminants;

the stage is a main degradation stage, the generated active species are utilized to strongly oxidize pollutants, and the duration is sufficient for ensuring the degradation rate due to Fe³⁺/Fe²⁺The establishment of a cycle, and therefore here either the addition of Fe (II), or Fe (III), or a mixture of both;

(3) standing and precipitating stage

Maintaining the illumination of the wastewater, stopping stirring the wastewater or aerating, and adding Ca (OH)₂Until the pH value of the wastewater is increased to more than 4, and then standing for treatment;

at this stage, Fe³⁺Will be Fe (OH)₃Form precipitate, on the other hand Ca²⁺With SO produced after the reaction₄ ^2-Formation of CaSO₄Precipitating, wherein the two precipitates generate flocculation and agglomeration effects to carry catalysts, pollutants and the like to be precipitated to the bottom, and the continuous illumination can promote the rest S₂O₈ ^2-Decomposing and continuing to degrade;

(4) drainage stage

And (4) turning off the light source, and discharging the supernatant in the wastewater treatment container.

At this stage, the treated water body is discharged, and a decanter is generally used for discharging water, so that the disturbance of the water body can be effectively avoided.

Further, in the step (2), the light applied to the wastewater is visible light or ultraviolet light. CuC of the invention₂O₄/g-C₃N₄The composite photocatalyst can generate photoproduction electrons to reduce Fe under the visible light illumination and the ultraviolet illumination³⁺The visible light can be selected from but not limited to solar light or xenon light, and the ultraviolet light can be selected from but not limited to mercury lamp light.

Further, after the step (4) is finished, a degradation period is finished, then Fe (II) and/or Fe (III) do not need to be added into the wastewater treatment container, and the next degradation period is started.

The invention has the beneficial effects that:

CuC of the invention₂O₄/g-C₃N₄The application of the composite photocatalyst breaks out the limitation of ultraviolet light, and the composite photocatalyst can absorb photons to generate photoproduction electrons under the ultraviolet light and the visible light, so that Fe can be converted into Fe through the photoproduction electrons³⁺Reduction to Fe²⁺Can promote the establishment of Fe when used in a persulfate/Fe (II) wastewater treatment system³⁺/Fe²⁺And (4) circulating to realize the recycling of the raw materials.

The method for intermittently treating the wastewater utilizes the CuC₂O₄/g-C₃N₄The photo-generated electrons generated by the composite photocatalyst convert Fe³⁺Reduction to Fe²⁺To build Fe³⁺/Fe²⁺Circulation, the activation reaction of the persulfate can be continuously carried out to generate sulfuric acid free radicals, the activation efficiency and the utilization efficiency of the persulfate are improved, and the CuC₂O₄/g-C₃N₄The holes of the composite photocatalyst can react with water to generate hydroxyl radicals, and the hydroxyl radicals and the sulfuric acid radicals jointly oxidize pollutants, so that the oxidizing capability is greatly improved.

Persulfates can decompose in response to ultraviolet light to produce free radicals of sulfuric acid,but does not respond to visible light and cannot treat pollutants under the visible light alone, and the intermittent wastewater treatment method can respond under the visible light to generate photo-generated electrons and establish Fe³⁺/Fe²⁺And the purpose of continuously activating persulfate is realized, the photoresponse waveband of persulfate is indirectly widened, and the application of persulfate is expanded.

During the whole degradation process, CuC₂O₄/g-C₃N₄The hole and the photo-generated electron generated by the composite photocatalyst are respectively added to the degradation process of pollutants in the forms of hydroxyl radical and sulfuric acid radical, so that the separation efficiency of the electron and the hole is improved, the utilization rate of light energy is greatly improved, the composite photocatalyst is not limited to one of the hole and the photo-generated electron, and a reference is provided for efficiently degrading the pollutants which are difficult to degrade by the aid of a photocatalytic combination Fenton-like reaction in the future.

Drawings

FIG. 1 is CuC₂O₄/g-C₃N₄Composite photocatalyst for reducing Fe³⁺Capability test result chart of (1).

FIG. 2 is a CuC-based optical disk of the present invention₂O₄/g-C₃N₄A process flow chart of a method for intermittently treating wastewater by using the composite photocatalyst.

FIG. 3 is a CuC-based optical disk of the present invention₂O₄/g-C₃N₄The method for intermittently treating wastewater by using the composite photocatalyst and a result chart of an effect test of treating rhodamine B aqueous solution by using a control group.

Detailed Description

The invention is further described below with reference to the following examples:

the various starting materials used in the following examples are all commercially available products known in the art unless otherwise specified.