CN103288186B - Electrolysis device for treating chlorinated organic wastewater under combined action of multiple electrodes - Google Patents

Abstract

The invention discloses an electrolysis device for removing persistent organic pollutants such as chlorinated organic matter in water with multi-electrodes working together, and belongs to the technical field of electrochemistry and environment. Its main structure includes a cathode chamber, an anode chamber, a gas chamber, an air inlet, a cathode, an anode, a card plate and a diaphragm, including two cathodes and a single anode, and the two cathodes are symmetrically located on both sides of the anode. The present invention adopts electrochemical cathodic reduction and cathodic and anode simultaneous oxidation coupling to degrade chlorinated organic pollutants, so that chlorinated organic pollutants are dechlorinated under the action of cathodic reduction, and the freed chlorine ions are oxidized to chlorine gas at the anode to leave the electrolytic system, and then Chlorine-containing organic compounds are treated under the coupled action of cathode and anode co-oxidation to degrade chlorine-containing organic pollutants. The invention does not need to add a catalyst in the dechlorination process, does not produce secondary pollution and waste of materials, saves resources, reduces energy consumption, and has high dechlorination efficiency, which can be popularized and used.

Description

An electrolysis device for treating chlorine-containing organic wastewater with multi-electrode cooperation

technical field

The invention relates to an electrolysis device for removing persistent organic pollutants such as chlorinated organic matter in water with the combined action of multiple electrodes, and belongs to the technical field of electrochemistry and environment.

Background technique

In recent years, with the development of the economy, more and more persistent organic pollutants such as chlorinated organic compounds have entered the environment, causing great damage to ecology and the environment. Since the amount of chlorinated organic matter in sewage components is relatively small, and it is difficult to remove, it is a difficult problem for scholars who study its treatment methods. In recent years, the research on the use of electrochemical technology to remove organic matter in wastewater has been increasing. Compared with other wastewater treatment methods, the electrochemical method has simple equipment, easy control, and low requirements for reaction conditions, but it mainly focuses on anodic oxidation and the treatment of chlorinated When dealing with organic pollutants, it is difficult for chlorine atoms to be completely removed from organic molecules, resulting in the existence of more chlorine-containing intermediate products after treatment, the removal rate of organic wastewater is relatively low, and the energy consumption is high. However, the reaction of generating hydrogen peroxide through the reduction of oxygen at the cathode will not directly generate active species such as hydroxyl radicals, which is a hot research topic now.

Qu Jiuhui's patent (publication number CN1350982A) is a reactor for wastewater treatment, which is characterized in that oxidation is carried out first and then reduction treatment is carried out, or reduction is carried out first and then oxidation treatment is carried out, or reduction treatment is carried out separately, although the reaction The device can achieve the purpose of improving the water purification effect of the electrochemical process and increasing the energy utilization rate, but because the cathode is made of nickel plate, no ventilation is required, so there is no gas chamber and air intake device, the treatment of wastewater is not thorough, and the negative and positive Manganese sand, anthracite and other fillers need to be added to the electrode chamber, which needs to be cleaned regularly, the operation is complicated, and the treatment efficiency is low.

Wang Wenhua's patent (publication number CN1285316A) is a wastewater treatment electrolysis device using a composite gas diffusion electrode. The anode is placed at the bottom of the reaction tank, and the composite gas diffusion electrode is placed above the anode as the cathode. It has the advantages of stable operation and low investment. It needs to add a catalyst supporting metal and its oxide active semiconductor material particles between the diffusion electrode and the anode, which brings certain difficulties to the operation of the process.

The electrolytic device described in Wang Jianlong's patent (publication number CN101434429A) carries out electrolytic treatment of wastewater with a two-electrode structure. Although its structure is simple, it has a better treatment effect on chlorine-containing organic wastewater and can reduce energy consumption. The electrode structure has a low treatment capacity and cannot be fully utilized, and the treatment efficiency for organic wastewater is low, and it cannot be expanded for application.

Generally speaking, the prior art cannot thoroughly treat chlorinated organic substances, will cause secondary pollution and waste of materials, needs to add catalysts or fillers, has low treatment efficiency, and cannot be popularized and used.

Contents of the invention

In order to overcome the above-mentioned deficiencies in the prior art, the present invention provides a kind of multi-electrode cooperating electrolysis device for removing persistent organic pollutants such as chlorinated organic matter in water, the main body of the present invention comprises cathode chamber (9,11), anode Chamber (10), gas chamber (1, 7), air inlet (8, 13), cathode (2, 6), anode (4), clamping plate (12) and diaphragm (3, 5), wherein, including Double cathode and single anode, the double cathode is a symmetrical structure separated on both sides of the anode.

The anode used in the present invention is an electrode with oxidation, especially a DSA electrode, preferably Ti/IrO ₂ /RuO ₂ electrode, which has a lower chlorine analysis overpotential, and the Cl produced in the process of degrading chlorinated organic matter ^is easily converted into Cl ₂ is separated out, which can avoid the generation of toxic chlorinated intermediates.

The cathode used in the present invention is a metal-loaded carbonaceous gas diffusion electrode, especially a palladium-loaded carbon nanotube, activated carbon, and graphene electrode, preferably a palladium-loaded graphene electrode. When passing through hydrogen, because the electrode has good hydrogen absorption and dechlorination performance, Reductive dechlorination reaction can fully occur when hydrogen is passed, and oxidation reaction can occur to generate H ₂ O ₂ when oxygen is passed, and further oxidize the intermediate product of the reaction, so that the chlorinated organic matter can be completely removed.

The diaphragm used in the present invention is a diaphragm with the function of separating two poles, especially a diaphragm made of organic synthetic materials, preferably polyester diaphragm, which is resistant to acid and alkali, allows ions to pass through, has stable chemical properties, is cheap in cost, and is easy to replace.

When the device of the present invention is ventilated, different gases can be passed into, preferably hydrogen gas is passed through some time ago, and then air is passed through; the concentration of sodium sulfate or other electrolytes added is 0.01～1.0mol/L, particularly 0.02～0.10mol/L, Preferably 0.05mol/L; the time for feeding different gases is 40-180min, especially 45-80min, preferably 60min; control the current density at 5-100mA/cm ² , especially 30-60mA/cm ² , preferably 50mA/cm ² ; the aeration rate is 1-80mL/s, especially 10-30mL/s preferably 25mL/s; the pH of the electrolyte in the cathodic chamber reaches 8-13, especially 9-11, preferably 10; the pH of the electrolyte in the anode chamber Reach 0.5-6.0, especially 1-3, preferably 2.

The invention adopts electrochemical cathode reduction and cathode and anode simultaneous oxidation coupling to degrade chlorinated organic pollutants. The reaction principle is as follows:

1 Mechanism of anode reaction

Pollutants can undergo direct electrochemical reactions on the anode with catalytic activity, and the strong oxidizing active substances (such as OH·, HO ₂ ·, etc.) produced by the anode can be used to transform the pollutants, thereby oxidizing and degrading organic matter. When the electrochemical reaction starts, the oxygen adsorbed on the surface of the anode becomes hydroxyl radicals adsorbed on the surface of the anode and oxygen atoms entering the oxide lattice, respectively. By controlling a certain anode voltage, the chlorine ions in the wastewater can be oxidized to chlorine gas and the wastewater can be degraded to a certain extent.

2 Cathodic reaction mechanism

Cathodic reactions include cathodic reduction and cathodic indirect oxidation reactions:

(1) Cathodic reduction reaction

Electrochemical reduction dechlorination method is to remove chlorine from chlorinated organic molecules under the condition of electrochemical reduction reaction. Compared with other methods, the reaction conditions of the electrochemical reduction dechlorination method are milder, and it has higher selectivity and practicability. When a certain cathode material is used and the appropriate reaction conditions are controlled, a hydrogen evolution reaction will occur on the cathode, and electrons are used as a strong reducing agent. By controlling the electrode potential to achieve the reduction of substances, chlorinated organic compounds can be completely or partially dechlorinated and transformed. It is a non-toxic or low-toxic hydrogenation product.

(2) Cathodic indirect oxidation reaction

Cathodic indirect oxidation refers to the Fenton-like reaction between hydrogen peroxide or ferrous ions produced by cathodic reduction and external reagents. Under the action of oxygen, a reduction reaction occurs on the surface of the cathode to generate H ₂ O ₂ , H ₂ O ₂ is converted into HO ₂ ^- under alkaline conditions, and further decomposed into OH ·, O ₂ ^- ·, due to its very active It can react with organic matter in water non-selectively and degrade it into CO ₂ and H ₂ O without secondary pollution.

Compared with prior art, the beneficial effect of the present invention is:

1. The metal-loaded carbonaceous gas diffusion cathode adopted in the present invention can not only reduce dechlorination, but also indirect oxidation to generate H ₂ O ₂ , can make full use of the effect of the cathode, improve the efficiency of electrolytic treatment and reduce the energy of reaction consumption.

2. In the present invention, the degradation of chlorinated organics in the cathode chamber is carried out under alkaline conditions, and the reaction process generates H ₂ O ₂ without additional iron salt catalyst, which simplifies the operation steps and reduces the process cost. cost, reducing secondary pollution.

3. The present invention adopts electrochemical cathodic reduction and simultaneous oxidation coupling of cathode and anode to degrade chlorinated organic pollutants. Firstly, the chlorinated organic matter is dechlorinated and detoxified through the reduction of the cathode, so that chloride ions are freed from the matrix, and then The mineralization of the precursor is treated jointly by anodic oxidation and oxidation of cathodic reduction products. This combination can give full play to the advantages of oxidation and reduction, can effectively remove chlorinated organic compounds, and can improve the removal efficiency.

4. The present invention adopts a three-electrode system. The structure of two cathodes and a single anode can make full use of the reduction of the cathode and the oxidation of the cathode and anode, significantly improve the removal efficiency of chlorinated organics, and increase the processing capacity of each operation, and also It can be further improved and applied to industrial wastewater treatment.

Description of drawings

The accompanying drawing is a structural schematic diagram of the electrolysis device of the present invention.

As shown in the figure, the reaction tank body of the electrolysis device is placed horizontally, the cathode chamber (9, 11), the anode chamber (10), the gas chamber (1, 7), the air inlet (8, 13), the cathode chamber (2, 6 ), the anode (4), the clamping plate (12) and the diaphragm (3, 5) are respectively in the positions shown in the figure, the cathode and the anode are fixed by the clamping plate, the air inlet holes are separated on both sides of the gas chamber, and the double cathodes are separated in a symmetrical structure on both sides of the anode.

Detailed ways

The technical solution of the present invention will be further described below in conjunction with the embodiments.

Example 1

In this example, the Ti/IrO ₂ /RuO ₂ electrode is used as the anode, the palladium-loaded multi-walled carbon nanotube electrode is used as the cathode, and the polyester diaphragm is used to treat 4-chlorophenol wastewater.

The initial conditions of the example are: the concentration of electrolyte sodium sulfate is 0.05mol/L; the initial pH is 7.0; the current density is 50mA/cm ² ; the aeration rate is 25mL/s; 100mL of 100mg/L 4-chlorophenol wastewater was treated.

After 120min electrochemical redox degradation, the conversion rate of 4-chlorophenol in the cathode and anode compartments finally reached 93.27% (anode), 94.17% (cathode 2) and 93.87% (cathode 6); the TOC degradation rate reached 86.5% ( anode), 81.8% (cathode 2) and 81.3% (cathode 6); the dechlorination rate of 4-chlorophenol was 90.5%.

Example 2

In this example, the Ti/IrO ₂ /RuO ₂ electrode is used as the anode, the palladium-loaded graphene gas diffusion electrode is used as the cathode, and the polyester diaphragm is used to treat 2,4-dichlorophenol wastewater.

The initial conditions of the example are: the concentration of electrolyte sodium sulfate is 0.05mol/L; the initial pH is 7.0; the current density is 50mA/cm ² ; the aeration rate is 25mL/s; 100mL of 100mg/L 2,4-dichlorophenol wastewater was treated.

After 120min electrochemical redox degradation, the conversion rate of 2,4-dichlorophenol in the anode and cathode compartments reached 94.25% (anode), 95.47% (cathode 2) and 95.18% (cathode 6) respectively at last; the TOC degradation rate reached respectively 87.2% (anode), 82.8% (cathode 2) and 82.3% (cathode 6); the dechlorination rate of 2,4-dichlorophenol was 92.8%.

Example 3

In this example, adopt two-electrode device and multi-electrode device of the present invention to treat 4-chlorophenol waste water respectively, all with Ti/IrO ₂ /RuO ₂ electrode is anode, with palladium-loaded graphene gas diffusion electrode as cathode, Features a polyester diaphragm.

The initial conditions of the example are: the concentration of electrolyte sodium sulfate is 0.05mol/L; the initial pH is 7.0; the current density is 50mA/cm ² ; the aeration rate is 25mL/s; 100mL of 100mg/L 4-chlorophenol wastewater was treated.

After 120 minutes of electrochemical redox degradation, the results of the conversion rate of 4-chlorophenol, TOC degradation rate and dechlorination rate of the two devices are shown in Table 1.

The removal effect of different devices in table 1

It can be seen that the device of the present invention has a better treatment effect on chlorinated organic compounds, and compared with the two-electrode device, the electrolysis device of the present invention has a greater dechlorination effect on chlorinated organic compounds.

The above is only a description of a part of the preferred embodiments that can be realized according to the present invention. As everyone knows, the scope of the present invention should not be interpreted as being limited to the above embodiments. All technical ideas should be included within the scope of the present invention.

Claims (5)

1. the coefficient electrolyzer for removing chlorinatedorganic in water of multi-electrode, be made up of two cathode compartments (9,11), anolyte compartment (10), two gas compartments (1,7), two air inlet ports (8,13), two negative electrodes (2,6), anode (4), clamp (12) and two barrier films (3,5), it is characterized in that it comprises three electrodes, be divided into two negative electrodes and single anode, two negative electrodes are symmetrical structure separation anode both sides; Cathode compartment and anolyte compartment separate by having the barrier film separating the two poles of the earth effect; There is Direct Electrochemistry reaction in described chlorinatedorganic and the strong oxidizing property active substance that utilizes anode to produce makes chlorinatedorganic generation oxidative degradation on anode; The chlorinatedorganic described in hydrogen peroxide degradation that described chlorinatedorganic reductive dechlorination occurs on negative electrode and utilizes cathodic reduction effect to produce.

2. the coefficient electrolyzer for removing chlorinatedorganic in water of a kind of multi-electrode according to claim 1, it is characterized in that its anode is for having oxygenizement electrode, negative electrode is the carbonaceous gas diffusion electrode carrying metal, with gas compartment and air inlet port on device.

3. the coefficient electrolyzer for removing chlorinatedorganic in water of a kind of multi-electrode according to claim 2, is characterized in that air inlet port will lead to 2 kinds of different gases as breather, for the previous period logical hydrogen, then blowing air or oxygen.

4. a kind of multi-electrode coefficient electrolyzer for remove in water chlorinatedorganic described arbitrarily according to claim 1-3, is characterized in that adopting electrochemical cathode reduction regulating YIN and YANG pole simultaneous oxidation coupling degradating chloro organic pollutant.

5. a kind of multi-electrode coefficient electrolyzer for remove in water chlorinatedorganic described arbitrarily according to claim 1-3, it is characterized in that the sodium sulfate that adds or other electrolytical concentration are 0.01 ~ 1.0mol/L, the time passing into gas with various is 40 ~ 180min, and control current density is 5 ~ 100mA/cm ², aeration rate is 1 ~ 80ml/s, and the pH of cathode compartment electrolyte inside reaches 8 ~ 13, and the pH of anolyte compartment's electrolyte inside reaches 0.5 ~ 6.0.