Paired electro-catalysis treatment method and device for purifying high-salt nitrogen-containing organic sewage and producing hydrogen peroxide at same time

Abstract

The invention provides a paired electro-catalysis treatment method and device for purifying high-salt nitrogen-containing organic sewage and producing hydrogen peroxide at the same time, and the paired electro-catalysis treatment method and device are applied to simulated coal chemical industry wastewater to realize efficient removal of organic / inorganic composite pollutants and generation of valuable products, and system energy consumption is reduced at the same time. Metal oxide (IrO2 / TiO2 / Ti, MMO) is used as an anode electrode to remove organic / inorganic combined pollution, the removal rates of phenol and ammonia nitrogen respectively reach 95.25% and 70.79%, an air active diffusion cathode (NADE) is adopted to convert oxygen in air into hydrogen peroxide value products without aeration, and the accumulated concentration after the reaction is finished can reach 761.2 mg / L. According to the invention, not only can the composite pollutants be efficiently treated, but also the energy consumption can be saved, and compared with a single electro-catalysis system for treating the pollutants, the paired electro-catalysis system can save about 47.77% of electric energy consumption. A green, efficient and promising treatment scheme is provided for high-salt nitrogen-containing organic matter sewage such as coal chemical industry wastewater, and the problems that a single electro-catalysis system is low in utilization rate and high in energy consumption are solved.

Description

Technical Field

[0001] The invention relates to the technical field of sewage treatment, in particular to a treatment method and device for purifying high-salt nitrogen-containing organic sewage and simultaneously producing hydrogen peroxide. Background Art

[0002] High-salinity nitrogen-containing organic wastewater is a typical type of difficult-to-treat wastewater. Its sources are wide, mainly including: industrial wastewater such as coal chemical industry, pharmaceutical chemical industry, petrochemical industry, food processing, agricultural wastewater such as livestock and poultry breeding, aquaculture and agricultural irrigation drainage, and domestic sewage under certain circumstances. The common characteristics of this type of wastewater are high salt content, complex water quality, and poor biodegradability. Taking coal chemical wastewater as an example, the ammonia nitrogen concentration of the wastewater can reach 70-3000 mg / L, and the COD content is as high as 1000-8000 mg / L. Therefore, if this type of wastewater is not properly treated, it will not only pollute the water environment, but also pose a serious threat to human health and the ecological environment. At present, there are mainly physical methods, biological methods and chemical methods to remove high-salinity nitrogen-containing organic composite wastewater. Combining multiple processes can effectively play their respective advantages and avoid disadvantages for different pollutants. For example, high-temperature steam stripping is used to remove ammonia nitrogen, and then combined with activated sludge or advanced oxidation methods to remove organic matter in water to reduce the COD of the effluent. However, the combined process includes multiple treatment methods, which are cumbersome and complex to operate, and cannot efficiently purify high-salinity nitrogen-containing wastewater. In summary, the current treatment of high-salinity nitrogen-containing organic wastewater has the problems of complex removal process, low efficiency of simultaneous degradation of organic and inorganic pollutants, and high energy consumption. Therefore, it is very necessary to construct a green, efficient, easy-to-operate and efficient sewage purification method and device.

[0003] Electrochemical Advanced Oxidation Processes (EAOPs) are a process that uses electrochemical reactions to produce strong oxidants (such as • OH), thereby oxidizing and degrading organic pollutants. EAOPs consume only electricity and do not require external reagents. They also have the advantages of small footprint, easy automation, high safety, and high selectivity. Electrochemical oxidation technology has advantages in treating high-salinity nitrogen-containing organic composite wastewater. On the one hand, high-salinity wastewater has high conductivity and no electrolyte needs to be added. On the other hand, high-salinity wastewater usually contains Cl - and SO 4 2- Under the action of anodic oxidation, highly oxidizing active chlorine species (RCS, HOCl, • ClO, etc.) and • SO 4 2-Free radicals such as chlorinated organic matter can be simultaneously promoted to remove organic matter. Therefore, EAOPs is a green treatment process with a simple process and easy operation. However, it currently focuses on the treatment of single pollutants by anodic oxidation or cathodic reduction systems, and does not fully utilize the functions of the anode and cathode to achieve efficient removal of combined pollution such as common organic matter and inorganic matter such as ammonia nitrogen, resulting in high treatment costs or no additional benefits. It is still necessary to develop efficient paired electrocatalytic treatment devices and methods that utilize the combined functions of the anode and cathode. Summary of the invention

[0004] The present invention aims at the problems of difficulty in simultaneously treating organic and inorganic composite pollution, complicated treatment process and high energy consumption in high-salt nitrogen-containing organic sewage. A diaphragm-type paired electrocatalytic system is constructed, and a scheme of coupling cathode and anode to treat composite pollution and produce hydrogen peroxide value-added products is proposed. The anode is directly and indirectly oxidized to form active chlorine oxidant to remove composite pollution such as phenol and ammonia nitrogen, while the cathode produces H by electro-reducing oxygen. 2 O 2 , achieving the purpose of purifying high-salt nitrogen-containing organic wastewater and producing hydrogen peroxide at the same time, with both environmental and economic benefits.

[0005] The technical principle of this paired electrocatalytic method is as follows:

[0006] In the anode chamber of the paired electrocatalytic system, active chlorine species are produced by anodic oxidation to oxidize ammonia nitrogen into nitrogen gas, achieving the purpose of harmless treatment. The specific reaction equations are shown in equations (1.1-1.4); at the same time, organic matter in water (such as phenol) can also be oxidized by active species, and finally completely mineralized into carbon dioxide and water, etc., as shown in equation (1.5). In the cathode chamber, oxygen is reduced by two electrons through the natural air diffusion electrode (NADE) to generate H 2 O 2 , and its reaction is shown in equation (1.6). By coupling the oxidation reaction at the anode and the reduction reaction at the cathode, the catalytic effects of the cathode and cathode are fully utilized, which can not only remove pollutants but also produce high value-added H 2 O 2 , thereby improving the overall energy efficiency.

[0007] NH 3 + HOCl → NH 2 Cl + H 2 O (1.1) NH 2 Cl + HOCl → NHCl 2 + H 2 O (1.2) NHCl 2 + HOCl → NCl3 + H 2 O (1.3) NH 3 + 3HOCl → N 2 + 3H 2 O + 3H + + 3Cl - (1.4) R → CO 2 + H 2 O + e - (1.5) O 2 + 2H 2 O + 2e - → H 2 O 2 + 2OH - (1.6)

[0008] The present invention is achieved through the following technical solutions:

[0009] A paired electrocatalytic treatment method and device for purifying high-salt nitrogen-containing organic sewage and producing hydrogen peroxide at the same time, characterized in that the device comprises: (1) an air active diffusion cathode that does not require aeration, (2) a metal oxide anode, (3) a proton exchange membrane, (4) a double-chamber reaction tank, and (5) a direct current power supply; the device is divided into two chambers by the proton exchange membrane (3), the air active diffusion cathode (1) is fixed on one side of the cathode reaction tank, one side contacts the air, and the other side contacts the sodium sulfate solution; the metal oxide anode (2) is placed in the anode reaction tank in the sewage to be treated, and when purifying the sewage, the power supply is turned on to adjust the current to treat the sewage.

[0010] The paired electrocatalytic treatment method and device are characterized in that the sewage to be treated is organic wastewater containing chlorine and ammonia nitrogen, including wastewater from coal chemical industry, pharmaceutical chemical industry, petrochemical industry, food processing industry, agricultural wastewater from livestock and poultry breeding, aquaculture and agricultural irrigation, and domestic sewage under specific circumstances.

[0011] Paired electrocatalytic treatment method and apparatus characterized by a metal oxide anode comprising IrO 2 , PbO 2 SnO 2 and a dimensionally stable anode.

[0012] The present invention has the following outstanding features:

[0013] (1) The wastewater treatment device couples the degradation of composite pollution by anodic oxidation and the production of H by cathode reduction of oxygen. 2 O 2The electrochemical advantages greatly improve the energy utilization efficiency. Compared with a single electrocatalytic system for treating pollutants, the paired electrocatalytic system can save about 50% of the electricity consumption to treat the same amount of pollutants.

[0014] (2) The sewage treatment device can use active chlorine species at the anode to oxidize and remove organic matter (phenol) and inorganic matter (ammonia nitrogen). Under appropriate current conditions, the removal rates can reach 93% and 66% respectively. At the same time, the removal rates of chemical oxygen demand (COD) and total nitrogen (TN) can reach 71% and 62% respectively.

[0015] (3) The sewage treatment device uses NADE at the cathode that does not require aeration, which avoids the waste of aeration energy compared to ordinary gas diffusion electrodes.

[0016] (4) The sewage treatment device has a good treatment effect on sewage under different pH conditions (3-10), and the removal rates of phenol, ammonia nitrogen, COD and TN are 94-96%, 59-70%, 36-75% and 58-65%, respectively. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic diagram of a reaction device of the present invention;

[0018] Figure 2 This is a comparison chart of the removal rates of phenol and ammonia nitrogen treated by the reaction device of the present invention and a single anode electrocatalytic system;

[0019] Figure 3 A comparison diagram of the reaction energy consumption of the reaction device of the present invention and the single anode electrocatalytic system in treating equal amounts of phenol and ammonia nitrogen;

[0020] Figure 4 The reaction device of the present invention reduces oxygen to synthesize H at the cathode 2 O 2 Concentration and costing.

[0021] Figure 5 The figure shows the effect of different currents on the performance of removing phenol and ammonia nitrogen in the reaction device of the present invention.

[0022] Figure 6 The different currents in the reaction device of the present invention are used to synthesize H 2 O 2 impact on performance.

[0023] Figure 7 It is the removal rate of phenol and ammonia nitrogen by the reaction device of the present invention at different pH values.

[0024] Figure 8 The reaction device of the present invention synthesizes H at different pH 2 O 2concentration. DETAILED DESCRIPTION

[0025] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0026] The present invention provides a method and device for simultaneously purifying high-salt nitrogen-containing organic sewage and efficiently producing hydrogen peroxide by paired electrocatalysis, referring to Figure 1 The reaction device consists of: (1) an effective area of ​​12.5 cm 2 The cathode is an air active diffusion cathode (NADE) without aeration. (2) The effective area is 9.0 cm 2 The paired electrocatalytic reaction device is divided into two chambers by a proton exchange membrane. The air active diffusion cathode (1) and the commercial metal oxide anode (2) are placed in the cathode chamber (actual solution volume is 50 mL) and the anode chamber (actual solution volume is 40 mL), respectively, and are connected to the negative and positive electrodes of the DC power supply, respectively. Embodiment 1

[0027] Compared with a single pollution treatment device, this paired electrocatalytic device can effectively ensure the efficient removal of organic phenol, and can also remove ammonia nitrogen at the anode at the same time, and only needs to be at the same voltage, which reduces energy consumption. Figure 2 In the single pollution system, the removal rates of phenol and ammonia nitrogen were 98.53% and 98.27% at 90 min, respectively. In the composite pollution system containing two pollutants, the removal rates of phenol and ammonia nitrogen reached 98.38% and 73.15%, respectively. The results show that when both phenol and ammonia nitrogen are present, the removal rate of phenol remains basically unchanged, while an additional 73.15% of ammonia nitrogen removal can be guaranteed. In addition, compared with the single pollution system (only ammonia nitrogen removal), the presence of phenol in the composite system inhibits the removal of ammonia nitrogen, which is due to the competitive relationship between the removal of phenol and ammonia nitrogen.

[0028] refer to Figure 3 By comparing the energy consumption required to remove the same mass of pollutants, the energy consumption of the two reaction systems was indirectly compared. To remove the same mass of pollutants (1.981g phenol + 0.878g ammonia nitrogen), the energy consumption of the single pollution system was 0.275 kWh, and the energy consumption of the combined pollution system was 0.144 kWh. In other words, the combined pollution system can save about 47.77% of energy consumption.

[0029] refer to Figure 4In the paired electrocatalytic system, at a current of 30 mA (current density of 2.4 mA / cm 2 ) and reacted for 90 min. 2 O 2 The cumulative concentration can reach 337 mg / L, and the corresponding hydrogen peroxide yield is 16.85 mg. In addition, a preliminary economic calculation of the entire paired electrocatalytic system was carried out, and the corresponding electricity cost for treating unit volume of simulated coal chemical wastewater was 0.342 $ / m 3 . refer to Figure 5 The hydrogen peroxide produced at the cathode is calculated based on the market price of 0.479 $ / kg. When the anode chamber treats 1 m 3 While simulating coal chemical wastewater, the cathode chamber can produce 0.42 kg / m 3 of hydrogen peroxide, the corresponding income is 0.201 $ / m 3 , so the net cost is 0.140 $ / m 3 Therefore, the cathode-cathode coupled electrocatalytic system has the advantages of high energy efficiency and cost saving. Embodiment 2

[0030] In this paired electrocatalytic device, different currents have different effects on sewage purification. The effects of current on the removal of phenol and ammonia nitrogen in the anode chamber and the generation of H in the cathode chamber were also measured. 2 O 2 Performance impact. Reference Figure 5 When the applied current increased from 10 mA to 70 mA, the removal rates of phenol were 93.38%, 98.58%, 97.73%, and 98.29% after 90 min, respectively, and the corresponding phenol degradation rate constants were 0.031 min -1 , 0.063 min -1 , 0.065 min -1 , 0.082 min -1 , gradually increases with the current. 4 + The concentration changes of NH-N were monitored. When the current was increased from 10 mA to 30 mA, 4 + The removal rate of -N increased from 26.59% to 66.06%. 4 + The -N removal rate did not increase, and even decreased slightly. Figure 6 When the applied current was 10, 30, 50, and 70 mA, the H in the cathode chamber was 2 O 2The cumulative concentrations of are 128.50 mg / L, 592.96 mg / L, 857.31 mg / L, and 1121.67 mg / L, respectively. Obviously, the larger the current, the more favorable it is for H 2 O 2 Generation of. Embodiment 3

[0031] In this paired electrocatalytic device, the effect of different pH in the anode chamber on the purification effect was determined. The removal of phenol and ammonia nitrogen and the effect of the cathode on H production were also determined. 2 O 2 Performance impact. Reference Figure 7 When the pH value of the anode chamber was 3.0, 5.0, 7.0, and 10.0, the removal rates of phenol were 96.15%, 95.25%, 94.05%, and 95.12% after 90 minutes, all higher than 94%. The removal rates of ammonia nitrogen were 64.79%, 70.79%, 64.03%, and 59.99%, respectively. Figure 8 At the same time, the pH of the anode chamber was investigated at 3.0, 5.0, 7.0, and 10.0. The H 2 O 2 The cumulative concentrations were 481.88, 761.21, 784.74 and 671.36 mg / L respectively.

[0032] In summary, the paired electrocatalytic treatment method and device for purifying high-salt nitrogen-containing organic sewage and efficiently producing hydrogen peroxide proposed in the present invention can be combined with the water quality of actual sewage, activate active chlorine species at the anode to remove organic and inorganic pollutants, such as phenol and ammonia nitrogen, and synthesize hydrogen peroxide using NADE electrodes at the cathode. More advantageously, the paired electrocatalytic device can utilize both the anode and cathode, greatly reducing energy consumption. This is an effective purification measure for high-salt nitrogen-containing organic sewage, and provides a potential new solution for efficient and low-consumption resource treatment of composite wastewater.

Claims

1. A paired electrocatalytic treatment method and device for purifying high-salt nitrogen-containing organic wastewater and producing hydrogen peroxide, characterized in that The device comprises: (1) an air active diffusion cathode that does not require aeration, (2) a metal oxide anode, (3) a proton exchange membrane, (4) a double-chamber reaction tank, and (5) a direct current power supply; the device is divided into two chambers by the proton exchange membrane (3); the air active diffusion cathode (1) is fixed on one side of the cathode reaction tank, one side contacts the air, and the other side contacts the sodium sulfate solution; the metal oxide anode (2) is placed in the anode reaction tank in the sewage to be treated, and when purifying the sewage, the power supply is turned on to adjust the current to treat the sewage.

2. The paired electrocatalytic treatment method and device according to claim 1, characterized in that The sewage to be treated is organic wastewater containing chlorine and ammonia nitrogen, including wastewater from coal chemical industry, pharmaceutical chemical industry, petrochemical industry, food processing industry, agricultural wastewater from livestock and poultry breeding, aquaculture and agricultural irrigation, and domestic sewage under specific circumstances.

3. The paired electrocatalytic treatment method and device according to claim 1, characterized in that Metal oxide anodes, including IrO2, PbO2, SnO2 and shape-stable anodes.

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