CN113281395B - Pollutant degradation and monitoring system and construction method and application thereof - Google Patents

Abstract

The invention belongs to the technical field of water pollution treatment, and discloses a pollutant degradation and monitoring system, and a construction method and application thereof. The pollutant degradation and monitoring system comprises a working electrode, a counter electrode, a reference electrode, an electrochemical workstation and a light source; the working electrode, the counter electrode and the reference electrode are all connected with an electrochemical workstation; the working electrode has both photocatalytic degradation and electrocatalytic detection properties. The pollutant degradation and monitoring system provided by the invention can realize degradation and real-time monitoring of pollutants at the same time, is simple to operate, does not need pretreatment, and greatly improves the treatment efficiency of the pollutants. The system has low manufacturing cost, is convenient to carry, does not need a specific working environment, can be used on site and is simple and convenient to operate; the complex pretreatment of the target pollutants is not needed, and the efficiency is higher. The system realizes the simultaneous removal of pollutants in the water body and the online monitoring of trace amount.

Description

A pollutant degradation and monitoring system and its construction method and application

technical field

The invention belongs to the technical field of water pollution control, and in particular relates to a pollutant degradation and monitoring system and a construction method and application thereof.

Background technique

With the rapid increase in the discharge of wastewater containing pollutants, some pollutants that have certain bioaccumulation and ecotoxicity and are difficult to self-degrade, have adverse effects on human health and the growth and reproduction of animals and plants. For example, the heavy metal hexavalent chromium (Cr(VI)) can be easily absorbed by the human body and cause cancer. Cr(VI) compounds exceeding 10ppm can cause the death of aquatic organisms. Cr(VI) compounds have been classified as a human by the International Agency for Research on Cancer. Serious carcinogen. Common phenolic pollutants, prolonged exposure can cause skin and neurological diseases, and excessive intake can cause poisoning. Therefore, the monitoring and treatment of pollutants needs to be highly valued. At present, the degradation and monitoring of pollutants are mostly handled separately. Generally, the operation is complicated, requires pretreatment or special equipment, has many processes, takes a long time, and is expensive. Commonly used treatment methods have many shortcomings, such as biodegradation method has a long treatment period and limited treatment capacity; adsorption method consumes large energy for regeneration; chemical method reagents are expensive and easy to cause secondary pollution. The monitoring method also has some disadvantages, such as chromatography requiring pretreatment, requiring specialized personnel and expensive instruments, easy contamination of sensor analysis, poor repeatability, and inability to perform on-site work.

Therefore, there is an urgent need to provide a rapid and efficient method of pollutant treatment that is simple to operate, does not require pretreatment.

SUMMARY OF THE INVENTION

The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention proposes a pollutant degradation and monitoring system, which can realize the degradation and real-time monitoring of pollutants at the same time, is simple in operation, does not require pretreatment, and can efficiently treat pollutants.

A first aspect of the present invention provides a pollutant degradation and monitoring system.

Specifically, a pollutant degradation and monitoring system includes a working electrode, a counter electrode, a reference electrode, an electrochemical workstation and a light source; the working electrode, the counter electrode and the reference electrode are all connected to the electrochemical workstation; the The working electrode has both photocatalytic degradation and electrocatalytic detection performance.

Conventionally, the degradation and monitoring of pollutants are carried out separately and separately, and need to be sampled separately. The system provided by the present invention integrates the two to carry out simultaneously, which greatly simplifies the degradation and monitoring process, and greatly improves the efficiency.

Preferably, the working electrode comprises at least one of noble metal-containing titanium dioxide nanomaterials, noble metal-containing zinc oxide materials, titanium dioxide single crystals or phosphorus-doped carbon nitride nanomaterials. For example, silver-doped titanium dioxide nanoparticles prepared by TNRavishankar et al. (TNRavishankar: Electrochemical detection and photochemical detoxification of hexavalent chromium(Cr(VI)) byAg doped TiO ₂ nanoparticles, Anal.Methods, 2015,7,3493), prepared by Yu Hanqing et al. Surface-customized titanium dioxide single crystal (Yu Hanqing Photochemical Anti-Fouling Approach for Electrochemical Pollutant Degradation on Facet-Tailored TiO ₂ Single Crystals Environ. Sci. Technol. 2017, 51, 11326-11335), Ag/In ₂ S ₃ prepared by Wei et al. /ZnO (Wei Construction of Z-scheme Ag/In ₂ S ₃ /ZnO nanorods composite photocatalysts for degradation of 4-nitrophenol Junwei Wei et al 2021 Nanotechnology 32 105706) etc.

Further preferably, the noble metal in the noble metal-containing titanium dioxide nanomaterial is at least one of gold, silver or platinum.

Preferably, the counter electrode is a platinum counter electrode or a carbon counter electrode.

Preferably, the reference electrode is selected from one of Ag/AgCl electrode, Hg/HgO electrode, saturated calomel electrode or Hg/HgSO ₄ electrode.

Preferably, the light source is a xenon light source or sunlight.

The second aspect of the present invention provides a method for constructing a pollutant degradation and monitoring system.

Specifically, the construction method includes the following steps:

(1) Prepare a material with both photocatalytic degradation and electrocatalytic detection performance into a working electrode;

(2) Connect the counter electrode, the reference electrode and the working electrode obtained in step (1) to the electrochemical workstation respectively, place them in the liquid to be treated, prepare a light source, and obtain the degradation and monitoring of the pollutants. system.

Preferably, the material with both photocatalytic degradation and electrocatalytic detection performance described in step (1) is a noble metal-containing titanium dioxide nanomaterial, and the preparation method of the noble metal-containing titanium dioxide nanomaterial includes the following steps:

(a) using a titanium source as a raw material, in-situ growth of TiO ₂ on a conductive substrate (such as carbon cloth, CC) to obtain a conductive substrate with TiO ₂ grown;

(b) soaking the conductive substrate with TiO ₂ grown in step (a) in a solution of a carbon source precursor, reacting to obtain a precipitate, and annealing the precipitate to obtain carbon-coated TiO ₂ ;

(c) depositing noble metal nanoparticles on the carbon-coated TiO ₂ obtained in step (b) by an electrochemical deposition method or a photoreduction method to prepare the noble metal-containing titanium dioxide nanomaterials.

In this method, a noble metal-containing titanium dioxide nanomaterial was designed and synthesized by means of heat treatment and electrodeposition. The material not only has good photocatalytic performance and electrocatalytic detection performance, but also further promotes the separation of photo-generated holes and electrons in the presence of an external voltage, and promotes photocatalytic reaction and electrode surface cleaning under the synergistic effect of photocatalytic reaction and electrode surface cleaning. The performance is further improved.

Preferably, in step (a), the titanium source is organic titanium or inorganic titanium salts, such as tetrabutyl titanate, tetraisopropyl titanate and titanium tetrachloride.

Preferably, in step (a), the conductive substrate is selected from at least one of conductive carbon cloth, carbon paper, titanium sheet (mesh), stainless steel mesh, foamed copper or foamed nickel.

Preferably, in step (b), the carbon source precursor is selected from at least one of dopamine, glucose, aniline or pyrrole.

Preferably, in step (b), the annealing temperature is 600-1000°C, and the annealing time is 1-6h; further preferably, in step (b), the annealing temperature is 700-1000°C At 900°C, the annealing time is 2-5h.

Preferably, in step (b), the annealing process is performed in a reducing gas atmosphere such as hydrogen, CO, CH ₄ , C ₂ H ₄ and the like.

Preferably, in step (1), the liquid to be treated contains heavy metal ions (such as hexavalent chromium (Cr(VI)), manganese, lead), phenols (such as bisphenol, phenol, chlorophenol, nitro phenol), antibiotics (such as tetracycline), etc.

Preferably, the liquid to be treated also contains an electrolyte, such as hydrochloric acid, phosphate buffer solution, and the like.

A third aspect of the present invention provides the application of a pollutant degradation and monitoring system.

The pollutant degradation and monitoring system is applied to waste water and sewage treatment. Such as wastewater or sewage containing heavy metal ions (such as hexavalent chromium (Cr(VI)), manganese, lead), phenols (such as bisphenol, phenol, chlorophenol, nitrophenol), antibiotics (such as tetracycline).

With respect to the prior art, the beneficial effects of the present invention are as follows:

(1) The present invention uses a material with both photocatalytic degradation and electrocatalytic detection performance as a working electrode, and constructs a pollutant degradation and monitoring system together with a counter electrode and a reference electrode, which can realize the degradation and real-time monitoring of pollutants at the same time, The operation is simple, no pretreatment is required, and the treatment efficiency of pollutants is greatly improved.

(2) The pollutant degradation and monitoring system provided by the present invention has low cost, is easy to carry, does not require a specific working environment, can be used on-site, and is simple and convenient to operate; it does not require cumbersome pretreatment of target pollutants, and the efficiency is relatively high. high. The system realizes simultaneous removal and trace online monitoring of pollutants in water.

Description of drawings

Fig. 1 is the scanning electron microscope image of the gold-containing titanium dioxide nanomaterial obtained in Example 1;

Fig. 2 is the time-current curve of dropwise addition of different concentrations of Cr(VI) under no illumination in Application Example 1;

Figure 3 is a graph showing the relationship between different concentrations of Cr(VI) and the response current under no illumination in Application Example 1;

Fig. 4 is the time-current curve of dropwise addition of different concentrations of Cr(VI) under illumination in Application Example 1;

Figure 5 is a graph showing the relationship between different concentrations of Cr(VI) and the response current under illumination in Application Example 1;

Fig. 6 is the time current ampere curve in application example 1;

Figure 7 is a graph showing the relationship between degradation rate, photocurrent and time in Application Example 1;

Figure 8 is a graph showing the relationship between photodegradation, photodegradation rate and time in Application Example 1;

Fig. 9 is the differential pulse voltammetry response curve of different pH electrolytes to 2,6 dichlorophenol in Application Example 2;

Fig. 10 is the DPV response curve of different concentrations of 2,6 dichlorophenol in Application Example 2;

Figure 11 is the DPV response curve of different concentrations of 2,4 dichlorophenol in Application Example 2;

FIG. 12 is the DPV response curve of different electrodes in Application Example 2 to 2,6-dichlorophenol.

Detailed ways

In order to make those skilled in the art understand the technical solutions of the present invention more clearly, the following examples are now given for illustration. It should be noted that the following examples do not limit the protection scope of the present invention.

The raw materials, reagents or devices used in the following examples can be obtained from conventional commercial channels unless otherwise specified, or can be obtained by existing known methods.

Example 1

A preparation method of a gold-containing titanium dioxide nanomaterial, comprising the following steps:

First, the conductive carbon cloth (CC) was pretreated, and the conductive carbon was placed in an ethanol solution containing 0.05mol of tetrabutyl titanate, sonicated for 20 minutes, and then placed in a muffle furnace and annealed at 400 °C for 30 minutes. Treated conductive carbon cloth;

Then mix 15ml of acetone, 15ml of HCl and 1.5ml of tetrabutyl titanate, add the pretreated conductive carbon cloth, transfer it to the reaction kettle and place it in an oven, react at 200 ° C for 90 minutes, filter to obtain a precipitate, The obtained precipitate was washed with distilled water and ethanol, and then put into a Tris-HCl buffer solution (pH 8.5) containing dopamine (30 μg/mL), stirred for 3 hours, filtered to obtain a precipitate, and the precipitate was dried and placed In the crucible, it was placed in a tube furnace, and treated at 800° C. for 3 hours in a hydrogen atmosphere. After the reaction, in a buffer solution containing 0.1 mM tetrachloroauric acid (pH 7.4), cyclic voltammetry was performed in the range of -1.25V to -0.7V (relative to Ag/AgCl) for three times to deposit on the surface of the material, Gold-containing titanium dioxide nanomaterials are obtained. The obtained gold-containing titania nanomaterials were analyzed by scanning electron microscopy. As shown in Figure 1, it can be observed that the composite material is composed of nanowires, grows neatly and evenly, and has gold particles attached to the surface.

Example 2

A pollutant degradation and monitoring system includes a working electrode, a platinum electrode and a silver-silver chloride electrode, the working electrode, the platinum electrode and the silver-silver chloride electrode are respectively connected to an electrochemical workstation, and the light source is a xenon lamp.

The construction of a pollutant degradation and monitoring system includes the following steps:

(1) Prepare a working electrode, cut the gold-containing titanium dioxide nanomaterial obtained in Example 1 into 1 cm × 1.25 cm, and use conductive glue, insulating glue and copper wire to prepare an electrode with an exposed area of 1 square centimeter, to obtain working electrode;

(2) Connect the working electrode, the platinum electrode and the silver-silver chloride electrode to the electrochemical workstation respectively.

Example 3

A pollutant degradation and monitoring system includes a working electrode, a platinum electrode and a silver-silver chloride electrode. The working electrode, the platinum electrode and the silver-silver chloride electrode are respectively connected to an electrochemical workstation, and the light source is a xenon lamp. The working electrode comprises silver-doped TiO2 nanoparticles prepared by T.N.Ravishankar et al. (For the specific preparation process, see T.N.Ravishankar: Electrochemical detection and photochemical detoxification of hexavalent chromium(Cr(VI)) byAg-doped TiO2 nanoparticles, Anal.Methods, 2015,7 , 3493).

The construction of a pollutant degradation and monitoring system includes the following steps:

(1) Prepare the working electrode, cut the silver-doped titanium dioxide nanoparticle material prepared by T.N.Ravishankar et al. into 1 cm × 1.25 cm, and use conductive glue, insulating glue and copper wire to prepare an exposed area of 1 cm2. electrode, the working electrode;

(2) Connect the working electrode, the platinum electrode and the silver-silver chloride electrode to the electrochemical workstation respectively.

Application example 1

The pollutant degradation and monitoring system constructed in Example 2 was used to treat the sewage containing Cr(VI), each electrode was placed in the HCl electrolyte solution containing Cr(VI), the xenon lamp was turned on or off, and the electrochemical workstation was started. And test the ability to treat sewage containing Cr(Ⅵ).

Application example 2

Example 2 was used to construct a pollutant degradation and monitoring system to treat phenolic pollutants. Each electrode was placed in a phosphate buffer solution containing phenolic contaminants, the xenon lamp was turned on, and the electrochemical workstation was started. And test the ability to deal with phenolic pollutants.

Product effect test

(1) Treatment of sewage containing Cr(VI).

In the test of treating sewage containing Cr(VI), different concentrations of Cr(VI) were added dropwise to the electrolyte of Application Example 1 under the condition of with and without light respectively, and the detection condition was tested. Figure 2 is the time current curve of dropwise addition of different concentrations of Cr(VI) in the absence of light. In Figure 2, the abscissa is time and the ordinate is Current density. 2, 4, and 10 μM Cr(VI) were added dropwise for 50 s for several times, and the current density changed with the dropwise Cr(VI) concentration. Figure 3 is a graph showing the relationship between different concentrations of Cr(VI) and the response current in the absence of light. In Figure 3, the abscissa is the concentration (Concentration), and the ordinate is the current density (Current density). The change of Cr(VI) concentration showed a certain linear relationship. Figure 4 shows the time-current curves of dropwise addition of different concentrations of Cr(VI) under illumination. In Figure 4, the abscissa is time and the ordinate is Photocurrent. The graph of the result of continuous multiple dropwise addition of Cr(VI) in 0.1M HCl. Figure 5 is a graph showing the relationship between different concentrations of Cr(VI) and the response current under illumination. In Figure 5, the abscissa is the concentration (Concentration), and the ordinate is the photocurrent intensity (Photocurrent). The change of Cr(VI) concentration showed a certain linear relationship. It can be seen from Figure 2-5 that the response current of the electrode and the concentration of Cr(VI) show a good linear relationship with and without illumination, and the electrochemical monitoring performance is excellent.

The degradation and monitoring performance of the system was further tested. Figure 6 is the photocurrent time curve, where the abscissa is time and the ordinate is photocurrent. In Figure 6, 100s, 200s, and 300s are the instants of turning on the lights, and 150s, 250s, and 350s are the instants of turning off the lights. It can be seen from Figure 6 that the overall photocurrent response is very fast. When 120μMCr(Ⅵ) was added dropwise at 400s, the photocurrent dropped instantaneously. At 500s, the photocurrent was illuminated (xenon lamp 300W), and the photocurrent gradually recovered as the illumination time increased. After 24 minutes of continuous illumination, it can be seen that Cr(VI) is completely degraded, and the results are consistent with the test results of UV-Vis spectrophotometer. And the relationship between the current and the concentration during the degradation process is still linear, indicating that the pollutant degradation and monitoring system provided in Example 2 achieves simultaneous degradation and monitoring of Cr(VI).

Fig. 7 and Fig. 8 are transformed from Fig. 6. Fig. ₇ is a graph showing the relationship between degradation rate, photocurrent and time. The right ordinate is the photocurrent intensity (Photocurrent), and the curves represent the degradation rate and the photocurrent intensity (Photocurrent), respectively. It can be seen from Figure 7 that with the increase of illumination time, the current gradually increases, that is, Cr(VI) is gradually reduced, and 120 μM Cr(VI) is completely reduced within 24 minutes. When illuminated, samples were taken every 4 minutes for UV-Vis spectrum test, and the electrode data were consistent with the UV-Vis spectrum test results. Fig. 8 is a graph showing the relationship between photodegradation, photoelectric degradation rate and time. In Fig. 8, the abscissa is time and the ordinate is degradation rate (C/C ₀ ). The curves represent applied light and electricity (PEC) and only Light is applied and no electricity is applied (PC). It can be seen from Fig. 8 that the system can reduce 97.9% of Cr(VI) at 1440s, and the reduction effect is weaker than that of the applied voltage. It can be seen that the photoelectric synergy can improve the reduction efficiency, and the electrode generates photogenerated electrons under illumination conditions, and the applied voltage also accelerates the transfer of electrons.

(2) Treatment of phenolic pollutants.

Using Example 2 to build a pollutant degradation and monitoring system to treat phenolic pollutants (application example 2), the performance of the pollutant degradation and monitoring system was studied in electrolytes with different pH and different concentrations of phenolic pollutants. Figure 9 is the DPV response curve (differential pulse voltammetry curve) of electrolytes with different pH to 2,6 dichlorophenol. In Figure 9, the abscissa is the voltage (Potential/V), the ordinate is the current, and 50 μA is the unit length is 50 microamps. It can be seen from Figure 9 that pH affects the sensitivity of the electrode.

Figure 10 is the DPV response curve of different concentrations of 2,6 dichlorophenol, the abscissa is the voltage (Potential/V), the ordinate is the current (Current), and each curve represents different concentrations of 2,6 dichlorophenol. It can be seen from Figure 10 that the peak current is also different with different concentrations, and the current will also change when the concentration of the substance is changed, so that quantitative detection can be performed to a certain extent.

FIG. 11 is the DPV response curve of different concentrations of 2,4 dichlorophenol, the abscissa is the voltage (Potential/V), the ordinate is the current (Current), and each curve represents different concentrations of 2,4 dichlorophenol respectively. It can be seen from Figure 11 that the peak current is also different with different concentrations, and the current will also change when the concentration of the substance is changed, so that quantitative detection can be performed to a certain extent.

Figure 12 is the DPV response curve of different electrodes to 2,6 dichlorophenol, the abscissa is the voltage (Potential/V), the ordinate is the current (Current), and the three curves represent the working electrodes ( A new electrode), a contaminated electrode (contaminated electrode) of the working electrode prepared in Example 2 after repeated use, and a regenerated electrode (regenerated electrode) obtained by subjecting the contaminated electrode to light treatment. It can be seen from Figure 12 that the new electrode has obvious peaks, the polluted electrode peaks become less obvious, and the regenerated electrode has obvious peaks, indicating that the electrode has good regeneration performance.

It can be seen from Figure 9-12 that the pollutant degradation and monitoring system also has good degradation and monitoring performance for phenolic pollutants.

Claims (8)

1. A pollutant degradation and monitoring system is characterized by comprising a working electrode, a counter electrode, a reference electrode, an electrochemical workstation and a light source; the working electrode, the counter electrode and the reference electrode are all connected with the electrochemical workstation; the working electrode has photocatalytic degradation and electrocatalytic detection performances at the same time;

the working electrode comprises a titanium dioxide nano material containing noble metal, and the preparation method of the titanium dioxide nano material containing noble metal comprises the following steps:

(a) Growing TiO on a conductive substrate in situ by using a titanium source as a raw material ₂ To obtain a film grown with TiO ₂ The conductive substrate of (1);

(b) Growing TiO on the obtained product in the step (a) ₂ Soaking the conductive substrate in a solution of a carbon source precursor, reacting to obtain a precipitate, and annealing the precipitate to obtain carbon-coated TiO ₂ ；

(c) By electrochemical deposition or reductionThe carbon-coated TiO produced in step (b) of the process ₂ And depositing noble metal nano particles to prepare the titanium dioxide nano material containing noble metal.

2. A pollutant degradation, monitoring system according to claim 1, in which the counter electrode is a platinum or carbon counter electrode; the reference electrode is selected from Ag/AgCl electrode, hg/HgO electrode, saturated calomel electrode or Hg/HgSO electrode ₄ One of the electrodes.

3. A pollutant degradation, monitoring system according to claim 1, wherein in step (a) the source of titanium is an organic or inorganic titanium salt; the conductive substrate is selected from at least one of conductive carbon cloth, carbon paper, titanium sheet, stainless steel net, copper foam or nickel foam.

4. A pollutant degradation, monitoring system according to claim 1, wherein in step (b) the carbon source precursor is selected from at least one of dopamine, glucose, aniline or pyrrole.

5. A contaminant degradation, monitoring system according to claim 1, wherein in step (b), the annealing temperature is 600-1000 ℃ and the annealing time is 1-6h.

6. The method of constructing a pollutant degradation, monitoring system according to any one of claims 1 to 5, comprising the steps of:

(1) Preparing a material with photocatalytic degradation and electrocatalytic detection performance into a working electrode;

(2) And (2) respectively connecting the counter electrode, the reference electrode and the working electrode prepared in the step (1) with an electrochemical workstation, placing the electrochemical workstation in a solution to be treated, and preparing a light source to obtain the pollutant degradation and monitoring system.

7. The constructing method according to claim 6, wherein in the step (2), the liquid to be treated further contains an electrolytic solution.

8. Use of a contaminant degradation, monitoring system according to any one of claims 1 to 5 for the treatment of wastewater.

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