CN113277594A - Treatment method and treatment system for wastewater polluted by composite pollutants - Google Patents

Abstract

The application discloses a treatment method and a treatment system for wastewater polluted by compound pollutants, wherein a self-bias double-photoelectrode system is adopted, the self-bias double-photoelectrode system comprises a main body reactor, an electrode fixing cover, a lead and a double-photoelectrode, the double-photoelectrode comprises a photocathode and a photocathode, and the compound pollutants comprise hexavalent chromium and phenol; the composite pollutant polluted wastewater to be treated is placed in a main reactor, a lead is connected with a photocathode and a photoanode and fixes the photocathode and the photoanode on an electrode fixing cover, and the photocathode and the photoanode are placed in parallel and can be used for treating the composite pollutant polluted wastewaterIrradiating reaction by using visible light; the photoelectric anode is BiVO₄/NH₂MIL125 photoanode; the photocathode is a NiO photocathode. The treatment method and the treatment system have good treatment effect on the organic matter-heavy metal composite pollutants.

Description

Treatment method and treatment system for wastewater polluted by composite pollutants

Technical Field

The application relates to the technical field of high-efficiency visible light photocatalytic materials, in particular to a treatment method and a treatment system for composite pollutant polluted wastewater.

Background

Heavy metal discharge and pollution are always main threats to water system, soil and ecological safety in China, heavy metals have high toxicity and cannot be decomposed in water, enrichment of heavy metal ions in aquatic organisms is easily caused, and serious harm can be caused to human bodies through a food chain. Taking chromium pollution as an example, about 2 ten thousand tons of chromium-containing wastewater is discharged every year in industries such as smelting, electroplating, tanning, printing and dyeing and the like in Zhejiang province, although the industries treat high-concentration wastewater by adding a reducing agent, and reduce Cr (VI) which is easy to migrate and strong in carcinogenicity into Cr (OH) which is 100 times less in toxicity and easy to form₃Precipitated Cr (III), but the removal limit is only 1.5mg/L, Cr (VI) and 0.5mg/L (electroplating pollutant discharge standard) of total chromium under the control of reduction efficiency and solubility product. In addition, because organic substances (COD) often coexist in the chromium-containing sewage, the formed composite pollution is extremely strong in toxicity, and due to the coordination and complexation of part of the organic substances and Cr (III), Cr (III) forms precipitates, and then is settled and enriched, so that the recovery difficulty is increased.

The main treatment methods at present are reduction precipitation, electrolysis, biological method, ion exchange method and the like, but the treatment technologies need step-by-step treatment, and the treatment technologies have large amount of chromium-containing sludge, low treatment efficiency and poor effect. To eliminate chromium contamination at low concentrations, it is necessary to provide for the simultaneous elimination of COD. Therefore, it is urgent to research and develop an economical, green, no/little secondary pollution generation method and an effective method for eliminating the combined pollution of chromium and organic matters at a low concentration level.

The photoelectrocatalysis technology is an advanced oxidation technology which is rapidly developed in recent years, and is limited by two factors of easy recombination of photogenerated electrons and holes and difficult recovery of a powder catalyst, so that the photoelectrocatalysis technology is difficult to be practically applied at present. The current main means introduces an external electric field (less than or equal to 3V) on the basis of the photocatalysis technology so as to promote the separation of electrons and holes in photocatalysis. The formed photoelectrocatalysis system (PEC) can effectively inhibit the recombination of electron-hole pairs and avoid the complex process of recovering the nano-catalyst.

Although the basic research of photocatalysis is mature, COD can be mineralized to the limit of 0ppm, but the photocatalysis is still difficult to be practically applied at present due to the restriction of two factors of easy recombination of photogenerated electrons and holes and difficult recovery of the powder catalyst. An important direction of the current domestic and foreign research is as follows: the nano photocatalyst is loaded on a conductive substrate to prepare a membrane electrode with a high specific surface, and photo-inert platinum sheet/titanium sheet/graphite and the like are taken as cathodes, under the action of an external voltage (less than or equal to 3V), photo-generated electrons are transferred to the cathodes through an external circuit to form a photo-electric catalytic system (PEC), so that the recombination of electron-hole pairs can be effectively inhibited, and the complex process of recovering the nano catalyst is avoided.

Although there has been some progress in PEC treatment of heavy metal-organic complex contamination, there is still a distance from practical application and there are major problems:

(1) the external bias increases the energy consumption and needs additional energy supply equipment;

(2) the cathode passively receives and transfers anode photoproduction electrons, the cathode electron selectivity is low, the utilization rate for reducing Cr (VI) is low, and dissolved O in water₂Easily reduced COD, H +, etc. compete with Cr (VI) for cathode electrons.

Disclosure of Invention

The application provides a treatment method of wastewater polluted by composite pollutants, which has a good degradation effect on organic matter-heavy metal composite pollutants.

A method for treating polluted wastewater of compound pollutants through photocatalysis adopts a self-bias double-photoelectrode system, wherein the self-bias double-photoelectrode system comprises a main body reactor, an electrode fixing cover, a lead and a double-photoelectrode, the double-photoelectrode comprises a photocathode and a photocathode, and the compound pollutants comprise hexavalent chromium and phenol;

placing the composite pollutant polluted wastewater to be treated in a main reactor, connecting a photoelectric cathode and a photoelectric anode by a lead, fixing the photoelectric cathode and the photoelectric anode on an electrode fixing cover, placing the photoelectric cathode and the photoelectric anode in parallel, and irradiating visible light for reaction;

the photoelectric anode is BiVO₄/NH₂MIL125 photoanode, prepared by the following method;

adding Bi (NO)₃)₃·5H₂O powder is completely dissolved in concentrated HNO₃Adding deionized water, stirring, adding NH₄VO₃Dissolving the powder and polyvinyl alcohol powder in the solution, performing ultrasonic treatment to obtain a solution A, coating the solution A on FTO, performing vacuum drying, and calcining in a muffle furnace to obtain BiVO₄A substrate; dissolving 2-amino terephthalic acid in a dimethylformamide solution to obtain a solution B; dropwise adding butyl titanate into a methanol solution to obtain a solution C; adding the solution B into the solution C, and mixing the solution B and the solution C uniformly to obtain BiVO₄Putting the substrate with the conductive surface facing downwards into a high-pressure kettle for hydrothermal treatment to obtain the BiVO₄/NH₂MIL125 photoanode;

the photocathode is a NiO photocathode and is prepared by the following steps:

dissolving nickel acetate in an ethanol solution of which the acid is adjusted by hydrochloric acid, refluxing to obtain a target solution, loading the target solution by using a soaking and pulling method on the foamed nickel, drying in vacuum, and calcining in a muffle furnace to obtain the NiO photocathode.

According to recent research findings in the field of Photocatalytic Fuel Cells (PFCs): an n-p type double-photoelectrode system is constructed, and based on the energy level difference of an n type anode (conduction band) and a p type cathode (valence band), an endogenous self-bias voltage can be generated to drive photoelectrons to be transferred from the anode to the cathode. Therefore, the photoresponse cathode replaces platinum sheet/titanium sheet/graphite and other photo-inert cathodes in a traditional PEC system, the dual-photon electrode system with matched energy level and quantum efficiency is designed to synergistically reduce composite pollution, and the problems of low cathode electron utilization rate and catalyst/electrode inactivation caused by heavy metal reduction product deposition are solved. Meanwhile, the double-photon electrode system can drive the transfer of photo-generated electrons by utilizing endogenous self-bias between the cathode and the anode without additional energy supply equipment.

The novel n-p type self-bias double-photoelectrode body system constructed by the application adopts BiVO₄/NH₂A photoanode of MIL125 and a photocathode of NiO/nickel foam,compared with the traditional electrode material, the MOF material of the anode has good porosity and specific surface area, and meanwhile, under the condition that a channel is formed by the anode and the cathode, self-bias is generated based on the capacity between the two materials, electron transfer is driven, and hexavalent chromium is reduced to harmless trivalent chromium at the cathode.

Several alternatives are provided below, but not as an additional limitation to the above general solution, but merely as a further addition or preference, each alternative being combinable individually for the above general solution or among several alternatives without technical or logical contradictions.

In order to provide uniform and sufficient illumination for the double-photoelectrode, a reaction device is designed to place the positive electrode plate and the negative electrode plate in parallel, and the surface of the load material faces the illumination source, so that the illumination utilization rate is greatly increased. Optionally, the load surfaces of the photoelectrode and the photoelectrode are both arranged towards the visible light source, and the distance between the two electrodes is 0.3-0.5 cm.

Optionally, the illumination intensity of visible light is 80W/m²～120W/m²The irradiation time of the visible light is 120-300 min.

Optionally, the concentration of hexavalent chromium in the wastewater to be treated is 20-160 micromoles/liter; the concentration of phenol is 1.5-7.5 mg/L. Further preferably, the concentration of the chromium-containing polluted wastewater is 40-120 mu mol/L; most preferably 80. mu. mol/L.

In a system with a liquid volume of 100mL, the length of the photocathode and the photocathode immersed in the liquid is 1.5-2.5 cm.

Optionally, the pH value of the wastewater needs to be adjusted to 3 when the wastewater is treated, and the original pH value is 5-6.

Optionally, when preparing solution A, Bi (NO)₃)₃·5H₂O powder, NH₄VO₃Powder, polyvinyl alcohol powder (purity 99%), 70% HNO₃And deionized water in a mass-to-volume ratio of 0.324g to 0.972 g: 0.078 g-0.234 g: 0.167g to 0.501 g: 1 ml-3 ml: 2ml to 6 ml; when preparing the solution B, the molar mass-volume ratio of the 2-amino terephthalic acid to the dimethylformamide is 1.5 mmol-4.5 mmol: 15ml to 45 ml; configuration ofIn the case of the solution C, the molar mass-to-volume ratio of the butyl titanate to the methanol is 0.5 mmol-1.5 mmol: 15ml to 45 ml; and mixing the solution B and the solution C in an equal volume ratio.

Further, when preparing the solution B, the molar mass-to-volume ratio of the 2-aminoterephthalic acid to the dimethylformamide is 1.5 mmol: 15 mlml; when preparing the solution C, the molar mass-to-volume ratio of the butyl titanate to the methanol is 0.5 mmol: 15 ml; and mixing the solution B and the solution C in an equal volume ratio.

Optionally, the sonication time for solution a is 1 hour.

Optionally, the solution A is coated on the FTO in a plurality of times, and the final coating thickness is 15-25 um.

Optionally, the hydrothermal temperature in the preparation of the photoelectric anode is 170-180 ℃; the hydrothermal time is 6-8 h.

Optionally, the vacuum drying conditions are: drying at 70 deg.C for 1 h.

Optionally, obtaining BiVO₄The calcination conditions of the substrate were: and calcining the vacuum-dried slices in a muffle furnace at 450 ℃ for 2h, wherein the temperature rise time is 150min, and the temperature reduction time is 90 min.

Optionally, in the preparation of the photocathode, when preparing the target solution: the mass-to-volume ratio of the nickel acetate to the ethanol solution is 5.304 g: 60 ml; the volume ratio of the concentrated hydrochloric acid to the ethanol solution is 0.5-1: 60, adding a solvent to the mixture; the reflux conditions were: refluxing for 0.5-1.5 h at 50-60 ℃.

Optionally, the loading thickness of the target solution on the foamed nickel is 15-25 um.

Optionally, the vacuum drying conditions for obtaining the photocathode are as follows: drying for 1h in a vacuum drying oven at 70 ℃; the calcination conditions were: and calcining the vacuum-dried slices in a muffle furnace at 300 ℃ for 2h, wherein the temperature is increased for 150min, and the temperature is decreased for 90 min.

Optionally, in the preparation of the photoelectric anode, the specification of the FTO electrode is 2 × 5cm, the thickness is 2.2mm, the resistance is 7 ohms, and the light transmittance is 80%; in the preparation of the photocathode, the foamed nickel is cut into a rectangular shape with the specification of 2 multiplied by 5cm and the thickness of 1.5 mm.

Most preferably, the preparation method of the photoelectric anode electrode is as follows:

(1) 0.324g of Bi (NO)₃)₃·5H₂O powder dissolved in 1ml 70% concentrated HNO₃Adding 2ml deionized water, stirring evenly, then adding 0.078g NH₄VO₃And 0.167g of polyvinyl alcohol (99%, PVA) was dissolved therein, and the target solution was obtained by sonication for 1 hour. Then coating the target solution on an FTO conductive surface, coating the FTO conductive surface with the thickness of 20 mu m for 3 times, performing vacuum drying at 70 ℃ for 1h, and calcining in a muffle furnace at 450 ℃ for 2h to obtain BiVO₄/NH₂MIL125 photoanode; the selected FTO conductive glass has the specification of 2 multiplied by 5cm, the thickness of 2.2mm, the resistance of 7 ohm and the light transmittance of 80 percent.

Most preferably, the preparation method of the photocathode is as follows:

dissolving 5.304g of nickel acetate in 60ml of ethanol obtained by adjusting the pH value of 0.5ml of concentrated hydrochloric acid, stirring for 10min at room temperature, refluxing for 1h at 60 ℃ by using a device to obtain a target solution, loading the target solution on the foamed nickel by using a soaking and pulling method, pulling for 5 times, soaking for 5s each time, and vacuum-drying for 1h at 70 ℃; and calcining the vacuum dried wafer in a muffle furnace at 300 ℃ for 2h, wherein the heating time is 150min, the cooling time is 90min, and the NiO/foamed nickel photocathode is obtained by calcining.

The application also provides a double-light electrode body system for bias photocatalytic treatment of composite pollutants in water, which comprises a main body reactor, an electrode fixing cover, a lead and a double-light electrode, wherein the double-light electrode comprises a photocathode and a photocathode;

the photoelectric anode is BiVO₄/NH₂MIL125 photoanode, prepared by the following method;

adding Bi (NO)₃)₃·5H₂O powder is completely dissolved in concentrated HNO₃Adding deionized water, stirring, adding NH₄VO₃Dissolving the powder and polyvinyl alcohol powder in the solution, performing ultrasonic treatment to obtain a solution A, coating the solution A on FTO, performing vacuum drying, and calcining in a muffle furnace to obtain BiVO₄A substrate; dissolving 2-amino terephthalic acid in a dimethylformamide solution to obtain a solution B; dropwise adding butyl titanate into a methanol solution to obtain a solution C; adding the solution B into the solution C, and mixing the solution B and the solution C uniformly to obtain BiVO₄Putting the substrate with the conductive surface facing downwards into a high-pressure kettle for hydrothermal treatment to obtain the BiVO₄/NH₂MIL125 photoanode;

the photocathode is a NiO photocathode and is prepared by the following steps:

dissolving nickel acetate in an ethanol solution of which the acid is adjusted by hydrochloric acid, refluxing to obtain a target solution, loading the target solution by using a soaking and pulling method on the foamed nickel, drying in vacuum, and calcining in a muffle furnace to obtain the NiO photocathode.

The method is used for degrading organic-heavy metal composite pollution in water, especially hexavalent chromium and phenol. The photoelectric cathode and anode matched with a conduction band and a valence band are prepared, under the condition of no external voltage, the organic-heavy metal composite pollutants in water are degraded through self-bias voltage generated by the double-photoelectrode under the illumination condition, the composite pollution in the real environment can be treated, and the universality and the practicability are better.

Drawings

FIGS. 1 to 3 are a top view, a left side view and a front view of a main reactor of the self-biased bipolar electrode system.

Fig. 4 to 6 are a top view, a left side view and a front view of the electrode fixing cover of the self-biased dual-photoelectrode system.

FIG. 7 is a graph of photocurrent curves of different photoelectrocatalytic electrode anodes in example 1 of the present application.

FIG. 8 is a time current curve of different photoelectrocatalytic electrode anodes in example 1 of the present application.

FIG. 9 is a graph of open circuit voltage of cathodes of different photoelectrocatalytic electrodes in example 2 of the present application.

FIG. 10 is a bar graph of hexavalent chromium reduction by photoelectrocatalytic cathode and anode of different material substrates in example 3 of the present application within 180 min.

FIG. 11 is a bar graph of the degradation of phenol by the photoelectrocatalytic cathode and anode of different material substrates in 180min according to example 3 of the present application.

FIG. 12 is a bar graph of hexavalent chromium reduction by bifocals within 180min under different pH conditions of example 4 of the present application.

FIG. 13 is a bar graph of the two-photon electrode degradation of phenol within 180min under different pH conditions of example 4 of the present application.

Detailed Description

The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

A preparation method of a self-bias double-photoelectrode system photocatalytic electrode comprises the following steps:

(1) 0.324g of Bi (NO)₃)₃·5H₂O powder dissolved in 1ml 70% concentrated HNO₃Adding 2ml deionized water, stirring evenly, then adding 0.078g NH₄VO₃And 0.167g of polyvinyl alcohol (99%, PVA) was dissolved therein, and subjected to sonication for 1 hour to obtain solution A. Then coating the solution A on an FTO conductive surface, coating 20 mu m each time, smearing for 3 times, after finishing vacuum drying for 1h at 70 ℃, putting the film into a muffle furnace, and calcining for 2h at 450 ℃ to obtain BiVO₄A substrate; the selected FTO conductive glass has the specification of 2 multiplied by 5cm, the thickness of 2.2mm, the resistance of 7 ohm and the light transmittance of 80 percent.

Dissolving 1.5mmol of 2-amino terephthalic acid in 15ml of dimethylformamide solution to obtain solution B; dropwise adding 0.5mmol of butyl titanate into 15ml of methanol solution to obtain solution C; adding the solution B into the solution C, and mixing the solution B and the solution C uniformly to obtain BiVO₄Putting the substrate with the conductive surface facing downwards into the mixed solution, and then carrying out hydrothermal treatment in a high-pressure kettle at the hydrothermal temperature of 180 ℃ for 8 hours to obtain the BiVO₄/NH₂MIL125 photoanode.

(2) Dissolving 5.304g of nickel acetate in 60ml of ethanol (absolute ethanol) which is adjusted in acid by 0.5ml of concentrated hydrochloric acid, stirring for 10min at room temperature, refluxing for 1h at 60 ℃ by using a device to obtain a target solution, loading the target solution by using a soaking and pulling method for nickel foam, pulling for five times, immersing for 5s each time, and vacuum drying for 1h at 70 ℃; and calcining the vacuum dried wafer in a muffle furnace at 300 ℃ for 2h, wherein the heating time is 150min, the cooling time is 90min, and the NiO/foamed nickel photocathode is obtained by calcining. The foamed nickel is cut into a rectangular shape with the specification of 2 multiplied by 5cm and the thickness of 1.5 mm.

The main reactor 1 is a round-corner cuboid (as shown in figures 1-3), and is made of quartz glass and can be used for a light path to pass through; the electrode fixing cover 2 is arranged on the main body reactor, two gaps 3 (shown in figures 4-6) are arranged in parallel on the electrode fixing cover, and the material is organic glass; the photoelectric cathode and the photoelectric anode respectively penetrate through the corresponding notches and are fixed, the lead is made of common copper and is connected with the photoelectric cathode and the photoelectric anode, and waste water is sent into the main body reactor when waste water is treated. The photocathode and the photocathode both face the light source in parallel, the plate surfaces of the two electrode plates are positioned in the same plane, and the distance between the photocathode and the photocathode is 0.3-0.5 cm.

The following dimension design is to ensure that the electrode is fully contacted with the solution and can fully receive the light source irradiation on the basis of the height of the electrode, the light source irradiation area and the volume of the reaction solution.

The main reactor is a round-corner cuboid open cup made of quartz glass, the radius of a round corner is 5mm, and the specific dimensions are that the length of the inner wall at the bottom is 5cm, the width is 4cm, and the height of the inner wall of the reactor is 5 cm; the thickness of the reactor glass is 2 mm.

The reactor electrode fixing cover is made of organic glass, two openings are arranged in parallel for inserting electrodes, the reactor electrode fixing cover is in a round-corner rectangular shape, the radius of the round corner is 5mm, and the specific size is that the outer length is 7.6cm and the outer width is 6.6 cm; the inner length is 5cm, the inner width is 4cm, 2mm of bulges are arranged, so that the cover can be just embedded into the main body reactor, the total thickness is 5mm, the 2mm of bulges comprise, and the thickness of the outer frame is 3 mm; the opening size is set to be 2.2cm long and 0.3cm wide, the distance between the two openings is 0.3cm, the distance between the two openings is 0.15cm from the center, and the opening center line is positioned at the center of the wide edge.

The application takes hexavalent chromium reduction and phenol degradation as models to investigate the photocatalytic activity of the prepared catalyst. Under the irradiation of visible light, after reacting for a certain time, measuring the content of hexavalent chromium in the solution by adopting a diphenyl carbonyl dihydrazide spectrophotometry, wherein the measurement is that the wavelength is 545 nm. Detecting the content of the phenol by a high performance liquid chromatograph, and determining the degradation efficiency of the phenol.

The experiment carried out degradation under the condition of adding visible light on simulated target pollutants of hexavalent chromium and phenol. Firstly, double-electrode BiVO₄/NH₂MIL125 and NiO/foamed nickel are connected by a lead and then are placed in a reactor in parallel, so that two electrodes are perpendicular to a light path; putting the double-light electrode into 100mL of mixed solution of hexavalent chromium with the concentration of 80 mu mol/L and phenol with the concentration of 5mg/L for dark adsorption for 30min, so that the reaction substrate reaches adsorption-desorption balance. And then turning on a light source to perform corresponding catalytic reaction, and sampling at regular time. The intensity of the visible light applied to the photocatalytic reactor was measured to be 100mW/m²During the 150min catalytic reaction, one sample was taken at 0, 30, 60, 90, 120, 150min each.

Example 1

In order to examine the photoresponse effect of the photoelectric anode, firstly, BiVO is prepared on FTO conductive glass separately₄、NH₂MIL125 and BiVO₄/HN₂The photo anode of MIL 125. It was determined that material incorporation had a significant effect on the enhancement of photoactivity of the photoanode.

Secondly, BiVO containing 4 different preparation proportions is selected₄/NH₂The MIL125 photoelectrocatalytic anode, through comparison of its photocurrent performance, identifies a photoelectrocatalytic anode with a stronger photoresponse. The preparation method comprises the following steps of respectively dissolving 0.75mmol, 1.5mmol, 2.25mmol and 3mmol of 2-amino terephthalic acid in 15ml of dimethylformamide solution to respectively obtain solution B1, solution B2, solution B3 and solution B4, and respectively adding 0.25mmol, 0.5mmol, 0.75mmol and 1mmol of butyl titanate in 15ml of methanol solution to respectively obtain solution C1, solution C2, solution C3 and solution C4. Mixing the two solutions (according to the combination: B1C1, B2C2, B3C3 and B4C4) at equal volume ratio, stirring, placing 15ml into a high-pressure reaction kettle, and placing clean BiVO with conductive surface facing downwards₄Carrying out hydrothermal reaction on an anode electrode substrate at 150 ℃ to obtain NH with different concentrations₂BiVO of MIL125₄Photocatalytic anodes, respectively named BiVO₄/0.5HN₂MIL125(B1C1)、BiVO₄/HN₂MIL125(B2C2)、BiVO₄/1.5HN₂MIL125(B3C3)、BiVO₄/2HN₂MIL125(B4C4)。

From FIGS. 7 and 8, it can be seen that the electrolyte solution was Na under visible light conditions with Pt as the counter electrode and Ag/AgCl as the reference electrode₂SO₄And Na₂SO₃The concentration of the compound is 0.1mol/L, and BiVO can be found₄/HN₂The visible light responsiveness of MIL-125(B2C2) is optimal, and the electrode is an optimally proportioned photoelectrocatalytic anode according to the positive and negative of its current and the magnitude.

Example 2

In order to examine the electrical response performance of the photocathode, 0.1mol/L KH is configured₂PO₄The solution was 100ml, the pH was adjusted to 7 with KOH, and the open circuit voltage was measured using a NiO/nickel foam photocathode as the working electrode and Pt as the counter electrode and Ag/AgCl as the reference electrode.

As can be seen from fig. 9, the NiO cathode has an extremely large open circuit voltage, and can generate a strong current with the photo-anode.

Example 3

After NiO is selected as a cathode material for the substrate, in order to improve the light response performance of the cathode, three different substrates are selected as carriers for the cathode to load NiO, and composite wastewater with the same concentration is degraded under the same pH and illumination conditions, wherein firstly, NiO is loaded on Ti sheets; secondly, NiO is loaded on the titanium dioxide nanotube; and thirdly, loading NiO for the foam nickel.

The specific degradation effect is shown in figures 10 and 11, and the figure shows that NiO is loaded on the foamed nickel to be used as a photocathode and BiVO₄/HN₂The MIL125 anode is combined into a double-light electrode which has the best degradation effect on Cr (VI) and phenol wastewater.

Example 4

In the selection of BiVO₄/HN₂ MAfter IL-125 is used as a photoelectric anode and NiO/nickel foam is used as a double-photoelectrode system formed by a photoelectric cathode, in order to investigate the influence of pH on a self-bias double-photoelectrode system in the degradation process, the influence of three groups of different pH with pH values of 2, 3 and 6 on the degradation effect of the composite wastewater is respectively selected in the experimental process. From fig. 12 and 13, it can be found that the more acidic the pH is, the stronger the degradation effect of the system on cr (vi) and phenol is.

It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, which falls within the scope of protection of the present application. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims (10)

1. A method for photocatalytic treatment of wastewater contaminated by composite pollutants, using a self-biased dual-photoelectrode system, the self-biased dual-photoelectrode system comprising a main body reactor, an electrode fixing cover, a wire and a dual-photoelectrode, the The double photoelectrode includes a photocathode and a photoanode, and the composite pollutants include hexavalent chromium and phenol; it is characterized in that, The composite pollutant polluted wastewater to be treated is placed in the main reactor, the wire is connected to the photocathode and the photoanode and the photocathode and the photoanode are fixed on the electrode fixing cover, the photocathode and the photoanode are placed in parallel, and the reaction is irradiated with visible light; The photoanode is BiVO ₄ /NH ₂ MIL125 photoanode, which is prepared by the following method; Dissolve Bi(NO ₃ ) ₃ ·5H ₂ O powder in concentrated HNO ₃ completely, add deionized water and stir well, then add NH ₄ VO ₃ powder and polyvinyl alcohol powder to dissolve in it, and obtain solution A after ultrasonication. A was smeared on FTO, vacuum-dried and calcined to obtain BiVO ₄ substrate; 2-aminoterephthalic acid was dissolved in dimethylformamide solution to obtain solution B; butyl titanate was added dropwise to methanol solution to obtain solution C; Add solution B to solution C, and after mixing evenly, put the conductive surface of the BiVO ₄ substrate into the mixed solution of solution B and solution C, and then hydrothermally heat it in an autoclave to obtain the BiVO ₄ /NH ₂ MIL125 photoelectric anode; Described photocathode is NiO photocathode, and is prepared by following method: The nickel acetate is dissolved in the ethanol solution adjusted with concentrated hydrochloric acid and refluxed to obtain the target solution, and then the nickel foam is loaded with the target solution by soaking and pulling method, and the NiO photocathode is obtained by vacuum drying and calcination. 2. The method according to claim 1, characterized in that, the load surfaces of the photocathode and the photoanode are all facing the visible light source, and the incident light of the visible light penetrates the photocathode and the photocathode vertically; The spacing between them is 0.3 to 0.5 cm. 3 . The method according to claim 1 , wherein the visible light intensity is 80W/m ² to 120W/m ² , and the visible light irradiation time is 120 to 300min. 4 . 4. The method according to claim 1, wherein the concentration of hexavalent chromium in the wastewater to be treated is 20-160 micromol/liter; the concentration of phenol is 1.5-7.5 mg/liter. 5. The method according to claim 1, characterized in that, when configuring solution A, Bi(NO ₃ ) ₃ .5H ₂ O powder, NH ₄ VO ₃ powder, polyvinyl alcohol powder, concentrated HNO ₃ and deionized water The mass to volume ratio is 0.324g～0.972g: 0.078g～0.234g: 0.167g～0.501g: 1ml～3ml: 2ml～6ml; when configuring solution B, the ratio of 2-aminoterephthalic acid and dimethylformamide The molar mass volume ratio is 1.5mmol～4.5mmol: 15ml～45ml; when configuring solution C, the molar mass volume ratio of butyl titanate and methanol is 0.5mmol～1.5mmol: 15ml～45ml; the solution B and solution C, etc. Volume ratio mixing. 6 . The method according to claim 1 , wherein when the solution A is applied on the FTO, it is applied in stages, and the final coating thickness is 15-25 um. 7 . 7 . The method according to claim 1 , wherein the hydrothermal temperature in the preparation of the photoanode is 170-180° C., and the hydrothermal time is 6-8 h. 8 . 8. The method according to claim 1, wherein, in the preparation of the photocathode, when preparing the target solution: the mass volume ratio of nickel acetate and ethanol solution is 5.0～5.5: 60ml; the volume ratio of concentrated hydrochloric acid and ethanol solution It is 0.5～1:60; the reflux condition is: 50～60 ℃ reflux 0.5～1.5h. 9 . The method according to claim 1 , wherein the coating thickness of the target solution on the nickel foam is 15-25 um. 10 . 10. A self-biased dual photoelectrode system for photocatalytic treatment of composite pollutants in water, comprising a main body reactor, an electrode fixing cover, a wire and a dual photoelectrode, wherein the dual photoelectrode comprises a photocathode and a photoanode; it is characterized in that , The photoanode is BiVO ₄ /NH ₂ MIL125 photoanode, which is prepared by the following method; Dissolve Bi(NO ₃ ) ₃ ·5H ₂ O powder in concentrated HNO ₃ completely, add deionized water and stir well, then add NH ₄ VO ₃ powder and polyvinyl alcohol powder to dissolve in it, and obtain solution A after ultrasonication. A was smeared on FTO, vacuum-dried and calcined to obtain BiVO ₄ substrate; 2-aminoterephthalic acid was dissolved in dimethylformamide solution to obtain solution B; butyl titanate was added dropwise to methanol solution to obtain solution C; Add solution B to solution C, and after mixing evenly, put the conductive surface of the BiVO ₄ substrate into the mixed solution of solution B and solution C, and then hydrothermally heat it in an autoclave to obtain the BiVO ₄ /NH ₂ MIL125 photoelectric anode; Described photocathode is NiO photocathode, and is prepared by following method: The nickel acetate is dissolved in the ethanol solution adjusted with hydrochloric acid and refluxed to obtain the target solution, and then the nickel foam is loaded with the target solution by the soaking and pulling method, and the NiO photocathode is obtained after vacuum drying and calcination.

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