Charge-discharge energy-saving electro-catalysis sewage treatment method

Abstract

The invention discloses a charge-discharge energy-saving electro-catalysis sewage treatment method which comprises the following steps: step 1, cleaning a carbon electrode, inserting the carbon electrode into sewage as a cathode and an anode at the same time, and arranging a magnetic stirrer at the bottom of an electrochemical reaction tank; step 2, applying constant voltage or constant current to the working electrode to ensure that the voltage can degrade pollutants, the anode does not generate oxygen evolution reaction, and the cathode does not generate hydrogen evolution reaction; step 3, stopping applying voltage or current to the working electrode, monitoring open-circuit voltage, gradually reducing the open-circuit voltage, and continuously degrading pollutants by utilizing the electric energy stored by the electrode; and step 4, repeating the step 2 and the step 3 until the electrocatalytic degradation is completed. Under the condition that the removal effect is guaranteed, electric energy is saved, and about 30-90% of energy consumption is reduced; the constant-current charging catalysis step ensures that the current density is controllable, and safe production is ensured; the process is simple, does not need special equipment and materials, and is suitable for upgrading and reconstruction of existing sewage treatment systems.

Description

Technical Field

[0001] The invention belongs to a sewage treatment method, in particular to a charge-discharge energy-saving electrocatalytic sewage treatment method. Background Art

[0002] There are a large number of difficult-to-degrade pollutants in sewage, and their potential ecological and health toxicity has attracted great attention. It is difficult for existing biological treatment technologies to remove them efficiently. Electrocatalysis is a potential physicochemical treatment method with rapid reaction, wide application range, and high degree of degradation. There are more and more reports on its use for deep treatment. However, the electrocatalytic removal of pollutants in sewage has the problems of high energy consumption and low efficiency, which hinders its large-scale application. Studies have shown that the electron transfer rate in the electrocatalytic degradation process of most pollutants is slow, and the power consumed per unit time is limited, resulting in limited degradation kinetic rate. In addition, the electrocatalytic process needs to overcome concentration polarization and maintain some undesirable side reactions. Therefore, continuous power supply will inevitably consume excess electricity, and this process needs to be optimized.

[0003] By using electrodes with energy storage functions to develop new intermittent electrocatalytic technologies and further utilizing the electricity contributed by non-Faraday capacitance, it is expected to achieve efficient and energy-saving pollutant removal. Existing energy-saving technologies in electrocatalytic processes are mainly focused on developing three-dimensional electrodes to enhance diffusion and mass transfer, reducing electrode preparation costs, and optimizing reactor water and gas distribution conditions. Currently, there are no reports on related research on intermittent electrocatalytic technologies that utilize electrode plate energy storage. In addition, studies have shown that in the process of constructing the electrode plate, molecular imprinted polymers can not only selectively enrich low-concentration pollutants in wastewater, but the extremely large double-layer capacitance brought by the porous structure is also very suitable for intermittent electrocatalysis. Therefore, molecular imprinted polymer electrodes have great potential in energy-saving electrocatalysis.

[0004] The existing constant potential or constant current catalytic methods cannot match the slower electron transfer characteristics of a large number of environmental pollutants. A large amount of electrical energy is consumed in side reactions such as polarization, resulting in high degradation energy consumption and low electrical energy utilization. Summary of the invention

[0005] Purpose of the invention: In order to overcome the deficiencies in the prior art, the purpose of the present invention is to provide a low-cost, energy-saving and environmentally friendly charge-discharge energy-saving electrocatalytic sewage treatment method.

[0006] Technical solution: The charge-discharge energy-saving electrocatalytic wastewater treatment method described in the present invention comprises the following steps:

[0007] Step 1: clean the carbon electrode, use it as both cathode and anode, insert it into the sewage, and set up magnetic stirring at the bottom of the electrochemical reaction cell;

[0008] Step 2: applying a constant voltage or a constant current to the working electrode to ensure that the voltage can degrade the pollutants and that no oxygen evolution reaction occurs at the anode and no hydrogen evolution reaction occurs at the cathode;

[0009] Step 3, stop applying voltage or current to the working electrode, monitor the open circuit voltage, the open circuit voltage gradually decreases, and use the electrical energy stored in the electrode to continue to degrade the pollutants;

[0010] Step 4: repeat steps 2 and 3 until the electrocatalytic degradation is completed.

[0011] Furthermore, in step 1, the carbon electrode is any one of graphite, carbon paper, graphite-thiophene-based conductive molecular imprinted polymer, and carbon felt. The carbon electrode is cleaned by using H2SO4, NaOH, and acetonitrile in sequence.

[0012] Preferably, the carbon electrode is a graphite-thiophene based conductive molecularly imprinted polymer.

[0013] Furthermore, the pollutants in the sewage are azithromycin, bisphenol A or carbamazepine.

[0014] Furthermore, in step 1, the rotation speed of the magnetic stirring is 300-500 rpm.

[0015] Further, the ratio of the time of applying constant voltage or constant current in step 2 to the time of stopping applying voltage or current to the working electrode in step 3 is 1:2 to 19. Preferably, the ratio of the time of applying constant voltage or constant current in step 2 to the time of stopping applying voltage or current to the working electrode in step 3 is 1:19, which has the best energy saving effect.

[0016] Furthermore, in step 2, the constant voltage is ≥1.2V. The constant current is 0.01-0.1A / cm 2 .

[0017] Furthermore, in step three, the time for monitoring the open circuit voltage is 2 minutes to 19 minutes.

[0018] Furthermore, in step 4, the number of repetitions is 12 to 80 times.

[0019] Working principle: The "charge-discharge" energy-saving electrocatalytic technology includes a charging catalytic stage and a discharging catalytic stage, such as Figure 1 As shown, during the charging catalytic stage, a constant current or a constant voltage is applied to the working electrode to drive the electrocatalytic reaction, and during the discharging stage, the electricity stored in the high-capacitance plate during the charging catalytic process is used to achieve continuous degradation of pollutants.

[0020] Beneficial effects: Compared with the prior art, the present invention has the following significant features:

[0021] 1. Save electricity while ensuring the removal effect, reducing energy consumption by about 30-90%;

[0022] 2. The constant current charging catalytic step ensures that the current density is controllable and ensures safe production;

[0023] 3. The process is simple, does not require special equipment and materials, and is suitable for upgrading and renovating existing sewage treatment systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is the charge-discharge principle diagram of the present invention;

[0025] Figure 2 It is a voltage-time diagram of the energy-saving electrocatalytic process of the present invention in which the time ratio of the "charge-discharge" catalytic stage is 1:2;

[0026] Figure 3 It is the voltage and the amount of CO2 produced by mineralization of the electrode surface during the "charge-discharge" energy-saving electrocatalytic process of the present invention;

[0027] Figure 4 This is a diagram showing the effect of the energy-saving electrocatalytic process of the present invention on the removal of organic pollutants with a "charge-discharge" catalytic phase time ratio of 1:2;

[0028] Figure 5 It is a voltage-time diagram of the energy-saving electrocatalytic process of the present invention with a "charge-discharge" catalytic stage time ratio of 1:19;

[0029] Figure 6 The energy-saving electrocatalytic process of the present invention with a "charge-discharge" catalytic phase time ratio of 1:19 has an effect on the removal of organic pollutants;

[0030] Figure 7 This is a diagram of gas production caused by mineralization of azithromycin degradation on the electrode surface under different potentials. DETAILED DESCRIPTION

[0031] Example 1

[0032] A charge-discharge energy-saving electrocatalytic sewage treatment method comprises the following steps:

[0033] (1) A graphite electrode was calcined in a muffle furnace to remove residual organic matter on the surface, and then washed with pure water. The electrode was inserted into sewage containing 5 mg / L azithromycin and stirred at 500 rpm by a magnetic stirrer.

[0034] (2) Pulse charging catalytic stage: A constant voltage of 1.2 V was applied to the working electrode and maintained for 60 s.

[0035] (3) Discharge catalysis stage: Stop applying voltage to the working electrode and monitor its open circuit voltage within 120 s.

[0036] (4) Steps (2) and (3) were cycled 80 times for a total of 4 hours until the degradation was complete.

[0037] The voltage-time images of the working electrode in the first cycle and the 80th cycle in this embodiment are as follows: Figure 2 As shown, compared with the continuous power-on catalytic method, the power-on time of the "charge-discharge" catalytic method is only 33.3%, saving energy by about 30%.

[0038] Example 2

[0039] A charge-discharge energy-saving electrocatalytic sewage treatment method comprises the following steps:

[0040] (1) Use 0.1M H2SO4, 0.1M NaOH, and acetonitrile to wash the carbon paper in order to remove residual organic matter on the surface, and then wash it with pure water. Insert it into sewage containing 5mg / L bisphenol A and mix it with magnetic stirring.

[0041] (2) Pulse charging catalytic stage: A constant voltage of 1.2 V was applied to the working electrode and maintained for 180 s.

[0042] (3) Discharge catalysis stage: stop applying voltage to the working electrode and monitor its open circuit voltage within 500 s.

[0043] (4) An in-situ differential electrochemical mass spectrometer was used to monitor the gas generation on the working electrode surface in step (2) and step (3). Step (2) and step (3) were cycled 20 times for a total of 13,600 seconds, and the degradation was completed.

[0044] The voltage of the working electrode and the amount of CO2 produced by mineralization of the electrode surface in this embodiment are as follows: Figure 3 As shown, the results show that the voltage of the working electrode slowly decreases after power failure, accompanied by the continuous mineralization of pollutants to produce CO2.

[0045] Example 3

[0046] A charge-discharge energy-saving electrocatalytic sewage treatment method comprises the following steps:

[0047] (1) A graphite electrode was calcined in a muffle furnace to remove residual organic matter on the surface, and then a thiophene-based conductive molecular imprinting polymer was electropolymerized on the surface of the electrode and the template was removed. The electrode was inserted into sewage containing 5 mg / L azithromycin and stirred at a rate of 500 rpm by a magnetic stirrer.

[0048] (2) Pulse charging catalytic stage: A constant voltage of 1.2 V was applied to the working electrode and maintained for 60 s.

[0049] (3) Discharge catalysis stage: Stop applying voltage to the working electrode and monitor its open circuit voltage within 120 s.

[0050] (4) Steps (2) and (3) were cycled 80 times for a total of 4 hours until the degradation was complete.

[0051] Comparative Example 1

[0052] Another molecularly imprinted polymer-modified graphite electrode was used as a working electrode and catalyzed at a constant voltage of 1.2 V for 4 hours.

[0053] The removal effect of azithromycin is as follows Figure 4 As shown, the "charge-discharge" energy-saving electrocatalysis exhibited an azithromycin removal effect comparable to that of the constant potential catalysis of Comparative Example 1 with only 33.3% of the power-on time.

[0054] Example 4

[0055] A charge-discharge energy-saving electrocatalytic sewage treatment method comprises the following steps:

[0056] (1) The carbon felt was cleaned with 0.1 M H2SO4, 0.1 M NaOH, and acetonitrile in sequence to remove residual organic matter on the surface, and then washed with pure water, inserted into sewage containing 5 mg / L azithromycin, and stirred with a magnetic stirrer at a rate of 500 rpm.

[0057] (2) Pulse charging catalytic stage: A constant voltage of 1.2 V was applied to the working electrode and maintained for 1 minute.

[0058] (3) Discharge catalysis stage: Stop applying voltage to the working electrode and monitor its open circuit voltage within 19 minutes.

[0059] (4) Steps (2) and (3) were repeated 12 times for a total of 4 hours until the degradation was completed.

[0060] Comparative Example 2

[0061] Another carbon felt was used as the working electrode and catalyzed at a constant voltage of 1.2 V for 4 hours.

[0062] The voltage of the working electrode in the “charge-discharge” energy-saving electrocatalysis is as follows Figure 5 As shown in Figure 2, the removal effect of azithromycin is as follows Figure 6 As shown, the “charge-discharge” energy-saving electrocatalysis achieved 90% of the azithromycin removal effect compared with constant potential catalysis when the power-on time was only 5%, as shown in Table 1, and the power consumption was reduced by 89.1% compared with continuous power-on.

[0063] Table 1 Comparison of power consumption of “charge-discharge” catalysis and continuous power-on catalysis

[0064] Number of cycles "Charge-discharge" catalytic power consumption (C) Continuous catalytic power consumption (C) 1 0.4632 2 0.4289 3 0.3739 4 0.3434 5 0.3272 6 0.3128 7 0.3034 8 0.2947 9 0.2917 10 0.2856 11 0.2811 12 0.2759 total 3.9818 36.6

[0065] Example 5

[0066] A charge-discharge energy-saving electrocatalytic sewage treatment method comprises the following steps:

[0067] (1) A graphite electrode was calcined in a muffle furnace to remove residual organic matter on the surface, and then washed with pure water. The electrode was inserted into sewage containing 1 mg / L carbamazepine and stirred at 300 rpm using a magnetic stirrer.

[0068] (2) Pulse charging catalysis stage: 0.01A / cm is applied to the working electrode 2 The constant current was maintained for 120 s.

[0069] (3) Discharge catalysis stage: Stop applying current to the working electrode and monitor its open circuit voltage within 600 s.

[0070] (4) Steps (2) and (3) were repeated 20 times for a total of 4 hours until the degradation was completed.

[0071] Example 6

[0072] A charge-discharge energy-saving electrocatalytic sewage treatment method comprises the following steps:

[0073] (1) Use 0.1M H2SO4, 0.1M NaOH, and acetonitrile to wash the carbon paper in order to remove the residual organic matter on the surface, and then wash it with pure water. Insert the carbon paper containing 5mg / L azithromycin (C 38 H 72 N2O 12 ) in sewage and mix well with magnetic stirring.

[0074] (2) Pulse charge catalysis stage: constant voltages of 0.9 V, 1.0 V, 1.2 V, and 1.4 V were applied to the working electrode and maintained for 10 s.

[0075] (3) Discharge catalysis stage: Stop applying voltage to the working electrode and monitor its open circuit voltage within 110 s.

[0076] (4) Using an in-situ differential electrochemical mass spectrometer to monitor the gas generation on the working electrode surface in step (2) and step (3). Step (2) and step (3) were cycled 60 times for a total of 2 hours, and the degradation was completed.

[0077] The voltage of the working electrode in this embodiment and the amount of CO2 and NO2 produced by mineralization on the electrode surface are as follows: Figure 7 As shown, the results show that mineralization begins at 0.9V to produce CO2, indicating that azithromycin is partially degraded; mineralization begins at 1.2V to produce CO2, accompanied by significant NO2 production, indicating that the azithromycin molecules are completely mineralized, so the charging catalytic voltage is preferably ≥1.2V.

Claims

1. A charge-discharge energy-saving electrocatalytic wastewater treatment method, characterized in that: The following steps are involved: Step 1: clean the carbon electrode, use it as both cathode and anode, insert it into the sewage, and set up magnetic stirring at the bottom of the electrochemical reaction cell; Step 2: applying a constant voltage or a constant current to the working electrode to ensure that the voltage can degrade the pollutants and that no oxygen evolution reaction occurs at the anode and no hydrogen evolution reaction occurs at the cathode; Step 3, stop applying voltage or current to the working electrode, monitor the open circuit voltage, the open circuit voltage gradually decreases, and use the electrical energy stored in the electrode to continue to degrade the pollutants; Step 4: repeat steps 2 and 3 until the electrocatalytic degradation is completed.

2. A charge-discharge energy-saving electrocatalytic wastewater treatment method according to claim 1, characterized in that: In the step 1, the carbon electrode is any one of graphite, carbon paper, graphite-thiophene-based conductive molecular imprinted polymer, and carbon felt.

3. A charge-discharge energy-saving electrocatalytic wastewater treatment method according to claim 1, characterized in that: In the step 1, the carbon electrode is cleaned using H2SO4, NaOH and acetonitrile in sequence.

4. A charge-discharge energy-saving electrocatalytic wastewater treatment method according to claim 1, characterized in that: The pollutants in the sewage are azithromycin, bisphenol A or carbamazepine.

5. A charge-discharge energy-saving electrocatalytic wastewater treatment method according to claim 1, characterized in that: In the step 1, the rotation speed of the magnetic stirring is 300-500 rpm.

6. A charge-discharge energy-saving electrocatalytic wastewater treatment method according to claim 1, characterized in that: The ratio of the time of applying the constant voltage or constant current in step 2 to the time of stopping applying the voltage or current to the working electrode in step 3 is 1:2-19.

7. A charge-discharge energy-saving electrocatalytic wastewater treatment method according to claim 1, characterized in that: In the step 2, the constant voltage is ≥1.2V.

8. A charge-discharge energy-saving electrocatalytic wastewater treatment method according to claim 1, characterized in that: In step 2, the constant current is 0.01-0.1A / cm 2 .

9. A charge-discharge energy-saving electrocatalytic wastewater treatment method according to claim 1, characterized in that: In the step 3, the time for monitoring the open circuit voltage is 2 minutes to 19 minutes.

10. A charge-discharge energy-saving electrocatalytic wastewater treatment method according to claim 1, characterized in that: In the step 4, the number of repetitions is 12 to 80 times.

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