CN107162161B - Separated venturi tube type hybrid electrocatalytic ozonization method and device - Google Patents

Abstract

The invention discloses a method and a device for the separation type Venturi tube type mixed electrocatalytic ozonation, belonging to the technical field of water treatment and environmental protection. The present invention combines the high-efficiency ozone dissolution and the novel pollutant removal process of the carbon material three-dimensional penetrating electrode. The present invention is economical and efficient, and can be used for refractory new pollutants (drug and personal care product pollutants PPCPs such as antibiotics, Endocrine Disrupting Chemicals, EDCs), drinking water disinfection by-products Drinking-water Disinfection By-Products ( DBPs), representative compounds of perfluoroorganic compounds, perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA), brominated flame retardants polybrominated diphenyl ethers (PBDEs), etc.) have high removal ability and complete removal. . The mineralization removal rate of the target pollutants in the treated effluent is higher than 90%, and the water quality safety can be guaranteed.

Description

A kind of separate venturi tube type hybrid electrocatalytic ozonation method and device

technical field

The invention belongs to the technical field of water treatment and environmental protection, in particular to a method and a device for a separation type Venturi tube type hybrid electrocatalytic ozonation.

Background technique

Advanced oxidation processes (AOPs) was proposed by Glaze in 1987, and it is defined as a method of destroying the structure of macromolecular organic matter by generating a large number of hydroxyl radicals ( OH) to achieve the purpose of removing organic matter. class method. Currently commonly used methods are: Fenton method, O ₃ and its combined oxidation method (such as O ₃ /catalyst method, O ₃ /UV method, O ₃ /UV/catalyst method, O ₃ /H ₂ O ₂ method, O ₃ / UV/ _H2O2 method, etc. ₎ , photochemical oxidation method (such as UV method, UV/catalyst method, UV/ _H2O2 method, UV/ _H2O2 / _catalyst method, etc. ₎ , electrochemical oxidation method and other advanced Oxidation method.

The mechanism of O ₃ oxidation of organic compounds is complex, and the reaction types are mainly divided into direct oxidation and indirect oxidation. Direct oxidation is where dissolved _O3 molecules react directly with organic matter in an aqueous environment. O ₃ is a strong oxidant with strong oxidizing ability, and its oxidation potential is E ₀ =2.07V. However, _O3 molecules have strong selectivity and are generally easier to react with substituted aromatic compounds, and not easy to react with other organic compounds. When the target organic compounds are degraded in the water environment, many intermediate products are often generated, which cannot be completely mineralized into inorganic compounds. Indirect oxidation is that ozone generates hydroxyl radicals (·OH) through decomposition or reaction. ·OH is more oxidative than O ₃ molecules, and has an oxidation potential E ₀ =2.86V. At the same time, it has no selectivity and can react with almost all organic substances.

Weiss' experiments demonstrated that the oxidation mechanism of _O3 changes with pH. Under acidic conditions, the _O3 molecule dissolved in water is relatively stable, and when the pH rises, O3 is more easily decomposed into OH.

In addition, the mechanism of ozonolysis can also be summarized by the free radical chain reaction proposed by Staehelin, Hoigne and Bader, namely the SBH model.

The biggest feature of the reaction of O ₃ with organics is that it can quickly react with compounds containing unsaturated bonds to form reaction products such as aldehydes, ketones, and carboxylic acids. Ozone can not only effectively degrade toxic substances, but also decompose itself into oxygen during the oxidation process, without causing secondary pollution. At the same time, due to the strong selectivity _of O molecule, it is generally easier to react with substituted aromatic compounds, and it is not easy to react with other organic compounds. When the target organic compounds are degraded in the water environment, many intermediate products are often generated, which cannot be completely mineralized into inorganic compounds. However, the ecological safety of these intermediate products has not been fully tested, which undoubtedly brings hidden dangers to the entire ecological safety. Therefore, if it can control the generation of intermediate products and improve the mineralization rate when it degrades the target organic matter, it will have a good promotion effect on the application of ozone advanced oxidation technology in the removal of environmental endocrine disruptors.

In order to improve the mineralization degree of organic pollutants and further improve the degradation efficiency, _O3 was combined with other methods to enable _O3 to generate more OH. Ozone combined oxidation methods include: O ₃ /catalyst method, O ₃ /UV method, O ₃ /UV/catalyst method, O ₃ /H2O2 method, O ₃ /UV/H ₂ O ₂ method, etc. Catalytic ozonation is the rapid oxidation and decomposition of most organic compounds (including some highly stable and refractory organic compounds) by the rapid oxidation and decomposition of OH produced by ozone under the action of a catalyst. In this study, carbon nanotubes were used as catalysts to carry out catalytic ozonation research.

Catalytic ozonation uses the characteristics and adsorption capacity of catalysts combined with the strong oxidizing properties of ozone to remove organic pollutants, which is also a hot research issue. According to the phase state of the catalyst, the catalyst can be divided into homogeneous catalyst and heterogeneous catalyst. Most of the heterogeneous catalysts are solid-phase catalysts. The catalysts in the catalytic ozone method are divided into transition metal catalysts (such as Mn, Fe, Cu, etc.), transition metal oxide catalysts (such as TiO2, _MnO2 , etc.) and activated carbon. Nahum A et al. compared the three methods of O ₃ /AC, O ₃ /H ₂ O ₂ and O ₃ for the removal of diethyl phthalate (DEP), and considered that the most effective method for the removal of diethyl phthalate It is the _O3 /activated carbon method. Activated carbon can catalyze the decomposition of O ₃ to generate OH, which increases the removal of diethyl phthalate.

Carbon materials have a wide range of sources, different morphologies, and a wide range of uses, especially carbon nanomaterials, which have the characteristics of high specific surface area, fast electron conduction speed, and easy modification. Its mechanical, chemical and electronic properties can be further optimized. Nitrogen-doped carbon nanotubes have broad application prospects in the fields of nanoelectronic devices, energy storage materials and catalysts. Doping carbon materials with nitrogen can make the structure of the material disordered and change its mechanical properties. Graphene doping with nitrogen atoms can induce high local charge/spin density on its surface to improve its chemical activity. Nitrogen doping can improve the carrier density and electron mobility, which makes the oxygen reduction reaction of doped carbon nanomaterials easier. The introduction of nitrogen can change the local charge density of the material to generate more active sites, and nitrogen doping produces pyridine, pyrrole and graphitic nitrogen functional groups in the carbon lattice. Pyridine-type nitrogen functional groups increase redox reaction (ORR) activity, and pyrrolic-type functional groups account for only a small percentage of total nitrogen functional groups. The pyridine-type nitrogen function has lone pair electrons in addition to the electrons donated to the conjugated π system, and thus can provide an electron-rich nitrogen site. There are a variety of ways that materials behave as metals. Overall, nitrogen doping leads to high chemical activity, high electron density in local areas, and the defects caused by doping can further enhance the activity of the material and promote the electrocatalysis of redox reactions. Theoretical calculation results show that nitrogen doping reduces the activation energy and dissociation energy of oxygen on carbon-based materials, that is, nitrogen-doped carbon-based materials are beneficial to the activation and dissociation of oxygen. Therefore, using nitrogen-doped carbon nanomaterials as catalysts for catalytic ozonation should theoretically achieve a more efficient catalytic effect.

The combination of ozone and electrolysis is one of the advanced oxidation technologies. Takusagawa et al. first reported the advanced oxidation of ozone electrolysis in 1976. (2005) Kishimoto et al. proposed its advanced oxidation mechanism as follows, wherein (1) is a cathode reaction:

·O ₃ ^- +H ₂ O→ ·OH+O ₂ +OH ^- (2)

Few ozone electrolysis reactors are known to be developed, and the earliest ozone electrolysis reactors were sequencing batch single-compartment reactors in which electrodes were inserted directly into the ozone bubble column. The second-generation reactor is a flow-type two-chamber reactor, which is divided into an anode compartment and a cathode compartment by a glass filter or an ion-exchange membrane, and ozone is directly injected into the cathode compartment. However, the ozone depletion efficiency in these reactors is relatively low due to the short gas-liquid contact time.

In the present invention, considering that the generation of hydroxyl radicals in the ozone decomposition reaction is the fundamental driving force for the advanced ozone oxidation reaction, carbon materials are used as the cathode, and an electric field is applied to the catalyst for cathodic protection during the carbon catalytic ozonation process, so as to prolong the life of the catalyst and reduce the process At the same time, by controlling the electron supply of the cathode reaction, the single-electron reduction reaction of ozone is realized to generate hydroxyl radicals. The reaction formula is as follows:

HO ₃ ·→HO · +O ₂ (5)

Water pollution is an indisputable fact, but the existing technology cannot effectively treat a variety of specific pollutants in water, and the present invention is devoted to research and solve this key technical problem. Combining emerging carbon nanomaterials and traditional ozone advanced oxidation technology to form a green and efficient electrocatalytic ozonation technology system featuring non-selective oxidation, which can efficiently degrade target pollutants. The specific ideas are as follows:

Various types of carbon materials are used as catalysts for electrocatalytic ozonation reaction. By controlling the electron supply of the cathode reaction, the single-electron reduction reaction of ozone is promoted to generate a large number of hydroxyl radicals, forming a strong oxidizing atmosphere, non-selective oxidation of target pollutants and Intermediate products do not produce secondary pollutants, and achieve the ultimate goal of completely eliminating pollution and ensuring ecological security. Cathodic protection of the catalyst by an external electric field during the catalytic ozonation can also achieve the purpose of prolonging the life of the catalyst and reducing the cost of the process.

SUMMARY OF THE INVENTION

The object of the present invention is to analyze the above-mentioned techniques and the existing problems, and provide a fast and efficient, wide application range, and convenient separation type Venturi tube type hybrid electrocatalytic ozonation method and device. Utilizing this method can conveniently realize a new type of ozonation in water. Rapid and efficient removal of pollutants; a device for a separation-type venturi-type hybrid electrocatalytic ozonation method is provided, which has a simple structure and low investment cost.

Technical scheme of the present invention:

A separate venturi tube type hybrid electrocatalytic ozonation method, the steps are as follows:

1) the first step, turn on the sewage pump, and use the sewage pump to pump the sewage Venturi tube containing the target pollutants into the tubular reactor;

2) In the second step, turn on the ozone generator, adjust the flow, and adjust the pressure to an appropriate level. The throat of the venturi tube generates negative pressure to inhale the ozone, mixes in the diffusion zone, and enters the carbon material three-dimensional electrode chamber after passing through the tubular mixing reaction unit. ;

3) In the third step, turn on the DC power supply, apply 0-32v voltage to the separated carbon material three-dimensional electrode chamber, and the sewage starts to be electrofiltered;

4) In the fourth step, the sewage flows through the separated carbon material three-dimensional electrode chamber, and after electrofiltration, an electrocatalytic ozonation reaction occurs, and the target pollutants are oxidized and removed, and then returned to the water storage tank;

5) In the fifth step, an appropriate circulation ratio is set according to the residual concentration of the target pollutant in the reaction effluent, and the above reaction process is carried out cyclically. Or the above process is carried out in N-stage series, and N is 1-10, and the target pollutant is finally completely removed.

The present invention also provides a device for the separate venturi tube type hybrid electrocatalytic ozonation method, including a sewage storage tank, a water pump, a venturi tube, an ozone generator, a helical tube reactor, a three-dimensional carbon material Electrode chamber and water storage tank, sewage storage tank is connected with the inlet of the water pump through pipes and is equipped with a flowmeter, the outlet of the water pump is connected with the inlet of the venturi tube, the outlet of the venturi tube is connected with the inlet of the spiral tube reactor, the ozone generator It is connected with the throat of the venturi tube through a pipeline and is provided with a gas-liquid separator. The outlet of the spiral tube reactor is connected with the inlet of the carbon material three-dimensional electrode reaction chamber through a pipeline and is provided with a valve, and the outlet of the carbon material three-dimensional electrode chamber passes through The pipeline is connected with the water storage tank, and the carbon material three-dimensional electrode chamber is provided with a tail gas outlet which is treated and discharged.

The working mechanism of the device:

The sewage containing the target pollutants first enters the Venturi tube at a high speed through the pump, and generates negative pressure at the throat of the Venturi tube to inhale the ozone, mixes with the sewage containing the target pollutants in the diffusion zone, and then enters the tubular mixing reaction unit. The separated carbon material three-dimensional electrode chamber with 0-32v voltage undergoes electrocatalytic ozonation reaction, and the target pollutants are oxidized and removed into the water storage tank, and the above reaction process is cyclically carried out. The number of cycles is determined according to the residual concentration of the target pollutant in the reaction effluent, or the above-mentioned Venturi tube, tubular reactor, and carbon material three-dimensional electrode chamber are connected in series in N stages (N is 1-10), and the target pollutant is finally completely removed. .

The beneficial effects of the present invention are:

The invention combines ozone and electrolysis, uses carbon material as a catalyst for electrocatalytic ozonation reaction, and promotes the single-electron reduction reaction of ozone by controlling the electron supply of the cathode reaction, thereby generating a large number of hydroxyl radicals, forming a strong oxidizing atmosphere, and having no choice. The target pollutants and intermediate products are oxidized, and secondary pollutants are not generated, so as to achieve the ultimate goal of completely eliminating pollution and ensuring ecological safety; in the process of catalytic ozonation, the cathodic protection of the catalyst by an external electric field can also extend the life of the catalyst. The purpose of reducing process cost.

attached drawings

FIG. 1 is a schematic diagram of the reaction apparatus of the present invention.

1. Sewage storage tank, 2. Flow meter, 3. Sewage pump, 4. Venturi tube, 5. Ozone generator, 6. Spiral tube reactor, 7. Carbon material three-dimensional electrode chamber, 8. Water storage tank, 9 .Gas-liquid separator, 10.Valve.

Detailed ways

A device for the separate venturi type hybrid electrocatalytic ozonation method, comprising a sewage storage tank 1, a water pump 2, a venturi tube 3, an ozone generator 4, a helical tube reactor 5, a three-dimensional carbon material The electrode chamber 6 and the water storage tank 7, the sewage storage tank 1 is connected with the inlet of the water pump 2 through a pipeline and is provided with a flow meter 8, the outlet of the water pump 2 is connected with the inlet of the venturi tube 3, and the outlet of the venturi tube 3 reacts with the spiral tube. The inlet of the device 5 is connected, the ozone generator 4 is connected with the throat of the Venturi tube 3 through a pipeline and is provided with a gas-liquid separator 9, and the outlet of the helical tube reactor 5 is connected with the inlet of the carbon material three-dimensional electrode chamber 6 through a pipeline. A valve 10 is also provided, the outlet of the carbon material three-dimensional electrode chamber 6 is connected to the water storage tank 7 through a pipeline, and the carbon material three-dimensional electrode chamber 6 is provided with a tail gas outlet that is processed and discharged.

The specific implementation method of the present invention is to start the water pump, pump the sewage containing the target pollutants through the venturi tube into the tubular reactor at high speed, the water flow will generate negative pressure at the throat of the venturi tube, turn on the ozone generator, and output The ozone is connected to the throat opening of the venturi tube, and the ozone is brought into the fluid by the negative pressure, mixed in the diffusion zone, and enters the separated carbon material three-dimensional electrode chamber with appropriate voltage after passing through the tubular mixing reaction unit. Filtration, in the process of electrofiltration, electrocatalytic ozonation reaction occurs, and the target pollutants are oxidized and removed, and then returned to the water storage tank to cycle through the above reaction process. The number of cycles is determined according to the residual concentration of the target pollutants in the reaction effluent, or the above processes are connected in series in N stages, and the target pollutants are finally completely removed.

Below in conjunction with embodiment, the present invention is described in detail:

Example 1.

Prepare 500ml of sewage containing 10mg/l of bisphenol A (BPA), use a self-made nitrogen-doped carbon nanotube membrane electrode as the cathode, the counter electrode is a titanium sheet, the DC voltage is 3V, the initial reaction pH is 10.2, the initial current is 15mA, and the ozone generation concentration is 8 %, flow 0.5L/min. The reaction apparatus of Figure 1 was used. Determination of the removal rate of effluent TOC:

time (min) TOC(mg/l) removal rate 0 7.692 0 5.00 6.526 15.16% 15.00 4.186 45.58% 30.00 3.585 53.39% 60.00 2.618 65.96% 120.00 1.389 81.94% 180.00 1.186 84.58%

Example 2.

Prepare 500ml of sewage containing 10mg/l of bisphenol A (BPA), use a self-made nitrogen-doped carbon nanotube membrane electrode as the anode, the counter electrode is a titanium sheet, the DC voltage is 3V, the initial reaction pH is 10.2, the initial current is 15mA, and the ozone generation concentration is 8 %, flow 0.5L/min. The reaction apparatus of Figure 1 was used. Determination of the removal rate of effluent TOC:

time (min) TOC(mg/l) removal rate 0 7.776 0 5.00 4.609 40.73% 15.00 3.28 57.82% 30.00 2.815 63.80% 60.00 1.899 75.58% 120.00 1.175 84.89% 180.00 1.054 86.45%

Example 3.

Prepare 500ml of sewage containing 10mg/l of bisphenol A (BPA), make a self-made multi-wall carbon nanotube membrane electrode as the cathode, the counter electrode is a titanium sheet, the DC voltage is 3V, the initial reaction pH is 10.2, the initial current is 15mA, and the ozone generation concentration is 8 %, flow 0.5L/min. The reaction apparatus of Figure 1 was used. Determination of the removal rate of effluent TOC:

time (min) TOC(mg/l) removal rate 0 7.654 0 15.00 2.443 68.08% 30.00 1.001 86.92% 60.00 0.723 90.55% 120.00 0.692 90.96% 180.00 0.67 91.25%

Example 4.

500ml of sewage containing 10mg/l of bisphenol A (BPA) was prepared, a self-made multi-wall carbon nanotube membrane electrode was used as the anode, the counter electrode was a titanium sheet, the DC voltage was 3V, the initial reaction pH was 10.2, the initial current was 15mA, and the ozone generation concentration was 8 %, flow 0.5L/min. The reaction apparatus of Figure 1 was used. Determination of the removal rate of effluent TOC:

time (min) TOC(mg/l) removal rate 0 7.654 0 15.00 3.462 54.77% 30.00 2.632 65.61% 60.00 1.646 78.49% 120.00 1.415 81.51% 180.00 1.511 80.26%

Example 5.

Oil extraction wastewater, containing various pollutants, diluted to about 10mg/l TOC, self-made multi-wall carbon nanotube membrane electrode as anode, counter electrode as titanium sheet, DC voltage 3V, initial reaction pH 10.2, initial current 15mA, ozone generation concentration 8%, flow 0.5L/min. The reaction apparatus of Figure 1 was used. Determination of the removal rate of effluent TOC:

time (min) TOC(mg/l) removal rate 0 10.37 0.00% 30 6.3 39.25% 60 4.38 57.76% 90 3.21 69.05% 150 1.933 81.36% 200 1.021 90.15%

Example 6.

Oil extraction wastewater, containing various pollutants, diluted to about TOC10mg/l, self-made multi-wall carbon nanotube membrane electrode as cathode, counter electrode as titanium sheet, DC voltage 3V, initial reaction pH 10.2, initial current 15mA, ozone generation concentration 8%, flow 0.5L/min. The reaction apparatus of Figure 1 was used. Determination of the removal rate of effluent TOC:

time (min) TOC(mg/l) removal rate 0 10.37 0.00% 15 6.588 36.47% 30 4.661 55.05% 60 3.374 67.46% 90 2.354 77.30% 180 1.384 86.65%

Claims (5)

1. a separate venturi tube type mixed electrocatalytic ozonation method, is characterized in that, step is as follows: 1) the first step, turn on the sewage pump, and use the sewage pump to pump the sewage Venturi tube containing the target pollutants into the tubular reactor; 2) In the second step, turn on the ozone generator, adjust the flow, and adjust the pressure to an appropriate level. The throat of the venturi tube generates negative pressure to inhale the ozone, mixes in the diffusion zone, and enters the carbon material three-dimensional electrode chamber after passing through the tubular mixing reaction unit. ; 3) In the third step, turn on the DC power supply, apply 3-32v voltage to the separated carbon material three-dimensional electrode chamber, and the sewage starts to be electrofiltered; 4) In the fourth step, the sewage flows through the separated carbon material three-dimensional electrode chamber, and after electrofiltration, an electrocatalytic ozonation reaction occurs, and the target pollutants are oxidized and removed, and then returned to the water storage tank; 5) In the fifth step, the circulation ratio is set according to the residual concentration of the target pollutant in the reaction effluent, and the above reaction process is carried out cyclically; 2 . The method according to claim 1 , wherein the sewage is a liquid mixture in which target pollutants are dissolved. 3 . 3. The method according to claim 1, wherein the ozone concentration is 8% to 20%. 4. a device using the described separate venturi tube type hybrid electrocatalytic ozonation method of claim 1, characterized in that it comprises a sewage storage tank, a water pump, a venturi tube, an ozone generator, a helical tube reactor, a carbon Materials Three-dimensional electrode chamber and water storage tank, sewage storage tank is connected with the inlet of the water pump through pipes and is equipped with a flowmeter, the outlet of the water pump is connected with the inlet of the venturi tube, the outlet of the venturi tube is connected with the inlet of the spiral tube reactor, ozone The generator is connected with the throat of the venturi tube through a pipeline and is provided with a gas-liquid separator. The outlet of the spiral tube reactor is connected with the inlet of the carbon material three-dimensional electrode reaction chamber through a pipeline and is provided with a valve. The outlet is connected to the water storage tank through a pipeline, and the carbon material three-dimensional electrode chamber is provided with a tail gas outlet that is treated and discharged. 5. the device of separation type Venturi tube type hybrid electrocatalytic ozonation method according to claim 4, is characterized in that described Venturi tube can produce low pressure near the fluid that utilizes high-speed flow, thereby produces the phenomenon of adsorption, A venturi tube is made, and an opening is set at the negative pressure position of the throat of the venturi tube to introduce ozone.

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