Method for treating bromine-containing organic wastewater based on electro-activated persulfate

Abstract

The invention discloses a method for degrading benzene series in wastewater and inhibiting generation of bromate by electrically activating persulfate. The method is suitable for treatment of bromine-containing water. According to the method, a persulfate electrochemical activation technology is adopted, the current density and the persulfate concentration are controlled, sulfate free radicals (SO4 <.->) and hydroxyl free radicals (HO <.->) generated by an electro-activated persulfate system can effectively degrade benzene series, and meanwhile, effective inhibition on generation of bromate is realized by utilizing a cathode reduction effect; meanwhile, organic pollutants in the water body are efficiently removed. The technology does not need additional reducing agents, is green and environment-friendly, and is suitable for drinking water and industrial wastewater treatment.

Description

Technical Field

[0001] The invention relates to the technical field of water treatment, in particular to a method for inhibiting the generation of bromate by electrochemically activating persulfate in coordination with a cathode action. Background Art

[0002] With the advancement of industrialization, water pollution is becoming increasingly serious. The safety of drinking water has received more and more attention. Advanced oxidation technology (AOPs), as an effective method for degrading organic pollutants, has been widely used in drinking water treatment.

[0003] Persulfate advanced oxidation technology is a new type of advanced oxidation technology that generates sulfate free radicals (SO 4 · - ) and hydroxyl radicals (HO·) and other strong oxidizing substances. Traditional persulfate advanced technology (ultraviolet light activation, transition metal ion activation, high-valent oxygen-containing metal acid salts, thermal activation) equipment operation is complex and energy-intensive; the consumption and dissolution of metal ions during transition metal activation will produce a large amount of metal precipitates, which limits the large-scale application of persulfate advanced oxidation technology.

[0004] In addition, the traditional persulfate advanced oxidation technology will produce an oxidation byproduct, bromate, while removing pollutants during the treatment of bromine-containing water. Bromate is classified as a Class 2B carcinogen by the International Agency for Research on Cancer due to its high toxicity and high carcinogenicity. The World Health Organization, the U.S. Environmental Protection Agency and other agencies have successively set a limit of 10μg / L for the bromate content in drinking water.

[0005] Therefore, how to simultaneously achieve efficient removal of organic pollutants and control bromate generation remains a huge challenge facing water treatment technology. It is necessary to develop a method that can effectively, economically and feasiblely inhibit bromate generation while maintaining the oxidation capacity of the advanced oxidation system. Summary of the invention

[0006] In order to overcome the shortcomings of the existing persulfate advanced oxidation technology, the present invention provides an electrochemically activated persulfate technology, specifically a method for treating bromine-containing organic wastewater based on electroactivated persulfate, which controls the generation of bromate through the coordinated cathode reduction action of an electrochemical reactor and can efficiently remove organic pollutants in water.

[0007] To achieve the above purpose, the technical solution is as follows:

[0008] A method for treating bromine-containing organic wastewater based on electro-activated persulfate comprises an electrochemical reaction system, wherein the electrochemical reaction system comprises a cathode plate, an anode plate, a proton exchange membrane and a power source; the cathode plate is connected to the negative electrode of the power source, and the anode plate is connected to the positive electrode of the power source.

[0009] As a preferred embodiment, the anode plate is made of ruthenium, iridium and titanium. Ruthenium, iridium and titanium as anode plates have the advantages of high electrochemical efficiency, low redox potential and high stability, and have energy-saving effects.

[0010] As a preferred embodiment, the cathode plate is made of copper mesh.

[0011] As a preferred embodiment, the reaction area of ​​the anode and the cathode is 4 cm×4 cm.

[0012] As a preferred embodiment, the working voltage of the power supply is lower than 24V, and the current density is 0-20mA / cm 2 , using extremely low current density and low voltage, safe and reliable, with a wide range of applications.

[0013] As a preferred embodiment, the reaction solution is added into the electrolytic cell from the upper opening of the electrochemical reaction system.

[0014] As a preferred embodiment, the reaction solution uses Na 2 SO 4 As the basic electrolyte to ensure the conductivity of the solution.

[0015] As a preferred embodiment, the bottom of the electrochemical reactor is equipped with a magnetic stirring device to ensure uniform temperature and concentration distribution inside the reaction system.

[0016] As a preferred embodiment, the persulfate is peroxydisulfate, such as K 2 S 2 O 8 , the persulfate concentration is controlled at 0.2-5.0mmol / L.

[0017] As a preferred embodiment, when the current density is 5 mA / cm 2 When the concentration of persulfate solution is 1.0 mM, the degradation rate of organic matter in the electrochemical reaction system is 0.0231 min -1 .

[0018] As a preferred embodiment, there is SO in the electrochemical reaction system 4 · - and HO· two free radicals, and SO 4 · - The concentration is much higher than HO·.

[0019] Beneficial effects:

[0020] The method of electrochemically activating persulfate and coordinating cathode reduction of bromate in the present invention provides an efficient and environmentally friendly water treatment technology, which is particularly suitable for the treatment of bromine-containing water bodies. On the basis of effectively regulating free radicals, the electro-activated persulfate system can effectively inhibit bromate, and the generation rate is only 8%. Specifically, compared with the traditional AOPs technology, the present invention has the following advantages:

[0021] (1) Efficient removal of organic pollutants: Through electrochemical activation of persulfate to generate strong oxidizing free radicals, it can effectively degrade the organic pollutant phenol in water with a removal rate of up to 73.9%.

[0022] (2) Significantly inhibit the formation of bromate: The cathode effectively inhibits the formation of bromate through direct and indirect reduction reactions, and the generation rate is controlled within 8%, which is better than other advanced fireworks processes based on persulfate.

[0023] (3) Green and environmentally friendly: No additional chemical reagents are required, which reduces the use of chemical reagents and the risk of secondary pollution, and meets the requirements of green and environmental protection.

[0024] (4) Wide applicability: This method can be applied to drinking water treatment, industrial wastewater treatment and other bromine-containing water treatment, and is particularly suitable for situations where strict control of bromate by-products is required. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the structure of the device for electrochemically activating persulfate of the present invention.

[0026] Figure 2 Schematic diagram of the degradation ratio of phenol in electrochemically activated persulfate, thermally activated persulfate and UV-activated persulfate systems

[0027] Figure 3 EPR spectrum during electrochemical activation of persulfate.

[0028] Figure 4 Schematic diagram of bromate formation in electrochemically activated persulfate, thermally activated persulfate, and UV-activated persulfate systems.

[0029] Figure 5 Schematic diagram of bromate formation when treating bromine-containing water in different electrode compartments in an electrochemically activated persulfate system. DETAILED DESCRIPTION

[0030] The following is a detailed description of an embodiment of the present invention in conjunction with the accompanying drawings: This embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation method and a specific operation process are given, but the protection scope of the present invention is not limited to the following embodiments.

[0031] like Figure 1The figure shows the structure of the device for the electro-activated persulfate system of the present invention. The device uses a copper electrode as the cathode and a ruthenium-iridium-titanium electrode as the anode. 2 SO 4 It is used as a basic electrolyte to ensure that the solution has good conductivity. Organic wastewater containing bromide ions is added to the reactor through the sampling port on the top of the device, and a certain concentration of persulfate solution is added at the same time. The DC power supply used is powered at a constant current density. To ensure uniform mixing of the solution, a magnetic stirring device is installed at the bottom of the electrolytic cell.

[0032] The following further examples are given to illustrate the present invention in detail. It should also be understood that the following examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention belong to the scope of protection of the present invention. The specific process parameters and the like in the following examples are also only examples within a suitable range, that is, those skilled in the art can make a selection within a suitable range through the description herein, and are not limited to the specific values ​​​​exemplified below.

[0033] Embodiment 1:

[0034] In order to evaluate the oxidation performance of the electro-activated persulfate system of the present invention, a typical organic compound phenol was used as a target pollutant to investigate and compare the degradation effects of phenol when the same concentration of persulfate was activated by different persulfate advanced oxidation systems.

[0035] The electro-activated persulfate system uses a copper electrode as the cathode and a ruthenium-iridium-titanium electrode as the anode. The electrode immersion area is 4 cm × 4 cm. 1.0 mM persulfate solution is added to the reaction solution as an oxidant. Na 2 SO 4 Used as the basic electrolyte to ensure that the solution has good conductivity. The DC power supply used is 5mA / cm 2 The device is powered by a constant current density of 10000 Ω. An electrochemical workstation is used to ensure the electrode potential under the current density condition. The target pollutant phenol solution is added into the reactor through the sampling port on the top of the device, and the total volume of the reaction solution is 100 mL. A magnetic stirring device is equipped at the bottom to ensure that the reaction solution is fully mixed. Samples are taken regularly to determine the residual concentration of phenol in the water body, and the degradation curves of phenol at different reaction times are drawn to evaluate its degradation effect.

[0036] Comparative Example 1:

[0037] Thermally activated persulfate system: A closed 250 mL reactor was used for the experiment. Before the experiment, a 1.0 mM peroxydisulfate solution was pre-prepared and placed in a 90 ° C water bath, and the temperature was maintained for 30 minutes to ensure that the reaction solution reached the desired experimental temperature. Subsequently, peroxydisulfate, phenol, and phosphate buffer solution were quickly added to the reactor, and the timing was started to start the reaction. During the entire experiment, the pH value of the solution was maintained at around 7.0 ± 0.05 by adding 2 mM phosphate buffer solution. Samples were taken at regular intervals to determine the residual concentration of phenol in the water, and the phenol degradation curve under different reaction times was drawn.

[0038] Comparative Example 2:

[0039] UV-activated persulfate system: The stable operation of the equipment was ensured by preheating the low-pressure mercury lamp for more than 10 minutes. After the UV lamp was preheated, the prepared reaction solution, including 1.0mM persulfate and phenol, was quickly poured into the reactor to start the experiment. During the experiment, the pH value of the solution was controlled at about 7.0±0.05 by using 2mM phosphate buffer solution. Samples were taken regularly to determine the residual concentration of phenol in the water body, and the phenol degradation curve under different reaction times was drawn.

[0040] The results are as follows Figure 2 As shown, phenol is degraded as the reaction time progresses under the three systems. In the thermally activated persulfate system, the removal rate of phenol is 50.1% after 1 hour of reaction. The degradation effect of phenol in ultraviolet activated persulfate is close to that of thermally activated persulfate, and the removal rate of phenol is 45.2% after 1 hour of reaction. However, under the action of the electro-activated persulfate system, the phenol removal rate reaches 73.9%, which is better than other systems. It shows that the oxidation performance of the electro-activated system of the present invention is significantly higher than that of the thermally activated persulfate and ultraviolet activated persulfate systems.

[0041] Embodiment 2:

[0042] The steps of implementation case 2 are basically the same as those of implementation case 1, except that phenol solution is not added to the reaction solution. Electron paramagnetic resonance (EPR) technology is used to investigate the main free radical species of the elect / PDS system. The results are as follows: Figure 3 As shown, there is SO in the system 4 ·- and HO· free radicals, and no free radicals were observed in the EPR spectrum. 2 · - The corresponding signal peaks exclude O 2 · - existence.

[0043] Table 1 Comparison of free radical steady-state concentrations in electroactivated persulfate systems and other persulfate systems

[0044] Reaction system <![CDATA[[HO·] ss mol / L]]> <![CDATA[[SO 4 ·-] ss mol / L]]> Electro-activated persulfate <![CDATA[1.28×10 -13 ]]> <![CDATA[5.11×10 -12 ]]> Heat activated persulfate <![CDATA[2.15×10 -12 ]]> <![CDATA[9.67×10 -12 ]]> UV-activated persulfate <![CDATA[4.98×10 -12 ]]> <![CDATA[1.14×10 -11 ]]>

[0045] The organic probe method was used to calculate the HO· and SO 4 The results are shown in Table 1. The concentration of HO· in the electro-activation system is only SO 4 ·- one fortieth of the concentration. 4 · - The dominant position in the system. The steady-state concentration of free radicals in the electro-activated persulfate system was compared with that in other persulfate-activated systems. The SO 4 · - The concentration is about twice that of elect / PDS. However, the difference in HO· concentration is more obvious, with the thermally activated persulfate system and the UV persulfate system being 17 and 39 times that of the electroactivated persulfate system, respectively. HO· has a decisive influence on the formation of bromate, so the electroactivated system of the present invention has the potential to control the formation of bromate to a certain extent.

[0046] Embodiment 3:

[0047] The steps of Example 2 are the same as those of Example 1, except that phenol is not added to the reaction solution. Each system is reacted with 20 μM bromide ions. Samples are taken at regular intervals to determine the concentration of bromate in the solution. Figure 4 As shown in the figure, the UV-activated persulfate system achieves complete conversion of bromide ions to bromate within 10 minutes, and the thermally activated persulfate system achieves a bromate conversion rate of 0.2 within 60 minutes. Compared with the UV-activated persulfate system and the thermally activated persulfate system, the bromate conversion rate of the electrically activated persulfate system is close to 0 within 60 minutes. It can be seen that the elect / PDS system can effectively inhibit the formation of bromate.

[0048] Embodiment 4:

[0049] This implementation case aims to explore the formation of bromate under different electrode forms. The experiment uses a bromine-containing water sample, sets the initial bromide ion concentration to 20μM, the peroxydisulfate concentration to 1.0mM, and the current density to 5mA / cm 2The experiment was conducted under constant conditions. First, the experiment was conducted in a two-chamber device without a proton exchange membrane, allowing the solutions in the anode chamber and the cathode chamber to mix freely, and the effect of PDS activation and the formation of bromate in the overall electrochemical system were investigated. Secondly, by adding a proton exchange membrane to the device, a separate cathode chamber and a separate anode chamber were constructed, and the activation effect of PDS and the influence on the formation of bromate in bromine-containing water samples under the action of a separate cathode and a separate anode were studied respectively. The use of a proton exchange membrane ensures that the solutions in the anode chamber and the cathode chamber are not mixed, so that the influence of each electrode on PDS can be studied separately. In addition, a control experiment was conducted, that is, the electrochemical system was used to treat the bromine-containing water sample alone without the addition of PDS, and the bromate formation in the absence of PDS was analyzed. Samples were taken at regular intervals during the experiment to determine the amount of bromate generated in the water samples under each condition.

[0050] like Figure 5 As shown in the figure, when the anode was working alone, the formation of bromate was detected in the anode chamber within 120 minutes. At the end of the reaction, the molar ratio of bromate to the initial bromide ion [BrO 3 - ] / [Br - ] 0 Reach 0.4. Differently, the conversion rate of bromate is significantly lower when only the cathode acts, and the formation rate is less than 10% after 120 minutes. It is worth noting that the formation rate of bromate under the combined action of the anode and cathode, that is, under the dual-chamber conditions, is similar to that under the action of the cathode alone, which is about 8%. This shows that although the anode can promote the formation of bromate, the synergistic effect of the cathode may lead to the inhibition or reduction of the formation of bromate, resulting in a lower total amount of bromate generated in the electro-activated persulfate system.

[0051] Embodiment 5:

[0052] To study the effect of initial PDS concentration on bromate formation, this experiment used PDS solutions of different concentrations, and used a device without a proton exchange membrane to allow the solutions in the anode and cathode chambers to mix freely. The initial bromide concentration was fixed at 20 μM, and the PDS concentrations were set at 0.2 mM, 1.0 mM, and 5.0 mM, respectively. The current density was maintained at 5 mA / cm 2 By adjusting the initial persulfate concentration, the effect of electroactivation on the formation of bromate under different persulfate concentrations was investigated. During the reaction, samples were taken at regular intervals to measure the formation rate and concentration change of bromate under different persulfate concentrations.

[0053] Table 2 The formation of bromate in the electro-activated persulfate system under the addition of different concentrations of persulfate

[0054] Persulfate concentration (mM) <![CDATA[Bromate conversion rate ([BrO 3 - / [Br - )]]> 0.2 0.05 1.0 0.06 2.0 0.13 5.0 0.16

[0055] The results are shown in Table 2. As the PDS concentration increases, BrO 3 - When the PDS concentration was 1.0 and 2.0 mM, the bromate formation trend was very similar. After 120 minutes of reaction, the conversion rate [BrO 3 -] / [Br-] were 0.06 and 0.05, both less than 10%. When the PDS concentration was 1.0 mM, the bromate generation rate accelerated and gradually increased with the reaction time. 3 - ] / [Br - ] reached 0.13. Overall, although the PDS concentration was increased to 5.0 mM, the formation rate of bromate was only 0.16, less than 20%. As the PDS concentration increased, although the free radical activation concentration increased and the reduction of bromate at the cathode was competed with the reduction of PDS, it was still significantly lower than the formation rate of bromate in other homogeneous activated persulfate systems, proving the effective control effect of the electro-activated persulfate system on the formation of bromate.

[0056] Embodiment 6:

[0057] The experiment was conducted in a two-chamber electrochemical device without a proton exchange membrane, with a copper electrode as the cathode and a ruthenium-iridium-titanium electrode as the anode. The electrode immersion area was 4 cm × 4 cm. 20 μM bromide ions and 1.0 mM persulfate were added to the solution. 2 SO 4 As electrolyte to ensure conductivity. Different current density conditions (5 mA / cm 2 , 10mA / cm 2 , 15mA / cm 2 and 20mA / cm 2 ), and the electrode potential was maintained stable by an electrochemical workstation. The entire reaction process was carried out under stirring conditions, and samples were taken at regular intervals. The formation of bromate in the solution was determined using an ion chromatograph. By comparing the bromate formation rate under different current densities, the effect of current density on the formation of bromate in the electroactivated persulfate system was analyzed.

[0058] The results are shown in Figure 3. The current density is 5 mA / cm 2 Increase to 20mA / cm 2 When the current density increases, the bromate generation rates are 0.062, 0.243, 0.258 and 0.351 respectively. The increase in current density enhances the oxidation of the anode, the bromide ions are further oxidized, and the reduction of the cathode is inhibited, which further promotes the generation of bromate.

[0059] Table 3. Formation of bromate in electroactivated persulfate system under different current density conditions

[0060]

[0061]

[0062] in conclusion:

[0063] The present invention proposes an innovative electrochemical water treatment technology that can efficiently activate persulfate and achieve effective control of bromate generation in coordination with cathode reduction. By optimizing electrode design and reaction conditions, the system successfully inhibits the generation of bromate while oxidizing and removing organic pollutants, demonstrating high practical application value. This technology provides a more environmentally friendly and economical solution and can be widely used in the fields of drinking water and industrial wastewater treatment.

[0064] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for treating bromine-containing organic wastewater based on electro-activated persulfate, characterized in that: The invention comprises an electrochemical reaction system, which comprises a cathode plate, an anode plate, a proton exchange membrane and a power source; the cathode plate is connected to the negative electrode of the power source, and the anode plate is connected to the positive electrode of the power source.

2. A method for treating bromine-containing organic wastewater based on electro-activated persulfate according to claim 1, characterized in that: The anode plate is made of ruthenium, iridium and titanium. Ruthenium, iridium and titanium as anode plates have the advantages of high electrochemical efficiency, low redox potential and high stability, and have energy-saving effects. The cathode plate is made of copper mesh.

3. The method for treating bromine-containing organic wastewater based on electro-activated persulfate according to claim 1, characterized in that: The reaction area of ​​the anode and cathode is 4 cm×4 cm.

4. The method for treating bromine-containing organic wastewater based on electro-activated persulfate according to claim 1, characterized in that: The working voltage of the power supply is lower than 24V, and the current density is 0-20mA / cm 2 , using extremely low current density and low voltage, safe and reliable, with a wide range of applications.

5. The method for treating bromine-containing organic wastewater based on electro-activated persulfate according to claim 1, characterized in that: The reaction solution is added into the electrolytic cell from the upper opening of the electrochemical reaction system.

6. The method for treating bromine-containing organic wastewater based on electro-activated persulfate according to claim 1, characterized in that: The reaction solution uses Na2SO4 as the basic electrolyte to ensure the conductivity of the solution.

7. The method for treating bromine-containing organic wastewater based on electro-activated persulfate according to claim 1, characterized in that: The bottom of the electrochemical reactor is equipped with a magnetic stirring device to ensure uniform temperature and concentration distribution inside the reaction system.

8. The method for treating bromine-containing organic wastewater based on electro-activated persulfate according to claim 1, characterized in that: The persulfate used is peroxydisulfate, such as K2S2O8, and the persulfate concentration is controlled at 0.2-5.0mmol / L.

9. The method for treating bromine-containing organic wastewater based on electro-activated persulfate according to claim 1, characterized in that: When the current density is 5 mA / cm 2 When the concentration of persulfate solution is 1.0 mM, the degradation rate of organic matter in the electrochemical reaction system is 0.0231 min -1 .

10. The method for treating bromine-containing organic wastewater based on electro-activated persulfate according to claim 1, characterized in that: There is SO4 in the electrochemical reaction system. - and HO· two free radicals, and SO4· - The concentration is much higher than HO·.

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