Charging-discharging energy-saving electrocatalytic wastewater treatment method

Abstract

The application discloses a kind of energy-saving electrocatalytic sewage treatment methods of charge-discharge, comprising the following steps: step one, carbon electrode is washed, simultaneously as cathode and anode, insert into sewage, set up magnetic stirring at the bottom of electrochemical reaction cell;Step two, constant voltage or constant current is applied to working electrode, ensure that voltage can degrade pollutants and anode does not occur oxygen evolution reaction, cathode does not occur hydrogen evolution reaction;Step three, stop applying voltage or current to working electrode, monitor open-circuit voltage, open-circuit voltage gradually decreases, continue to degrade pollutants using the stored electrical energy of electrode;Step four, repeat step two and step three, until electrocatalytic degradation is completed.The application saves electrical energy under the condition of ensuring removal effect, reduces energy consumption by about 30-90%;Constant-current charging catalytic step ensures that current density is controllable, ensures safe production;Simple process, no special equipment and materials are needed, suitable for upgrading and modification of existing sewage treatment system.

Description

Technical Field

[0001] This invention pertains to wastewater treatment methods, specifically a charge-discharge energy-saving electrocatalytic wastewater treatment method. Background Technology

[0002] Wastewater contains a large number of recalcitrant pollutants, whose potential eco- and health toxicity has attracted great attention, and existing biological treatment technologies are insufficient for their efficient removal. Electrocatalysis is a promising physicochemical treatment method, characterized by rapid reactions, wide applicability, and high degradation rates, and its application in advanced treatment is increasingly reported. However, the high energy consumption and low efficiency of electrocatalytic removal of pollutants from wastewater hinder its large-scale application. Existing studies have shown that the electron transfer rate during the electrocatalytic degradation of most pollutants is slow, and the power consumed per unit time is limited, thus restricting the degradation kinetic rate. Furthermore, the electrocatalytic process needs to overcome concentration polarization and maintain some undesirable side reactions, so continuous energization will inevitably consume excess power, and this process needs optimization.

[0003] Developing novel intermittent electrocatalytic technologies using electrodes with energy storage capabilities, and further utilizing the charge contributed by non-Ladaic capacitance, holds promise for achieving efficient and energy-saving pollutant removal. Existing energy-saving technologies in electrocatalysis mainly focus on developing three-dimensional electrodes to enhance diffusion mass transfer, reducing electrode fabrication costs, and optimizing reactor water and gas distribution conditions. Currently, there are no research reports on intermittent electrocatalytic technologies utilizing electrode plates for energy storage. Furthermore, research indicates that during the construction of electrode plates, molecularly imprinted polymers can not only selectively enrich low-concentration pollutants in wastewater, but the large double-layer capacitance resulting from their porous structure is also highly suitable for intermittent electrocatalysis. Therefore, molecularly imprinted polymer electrodes have great potential in energy-saving electrocatalysis.

[0004] Existing constant potential or constant current catalysis methods cannot match the slow 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 shortcomings of the existing technology, the purpose of this invention is to provide a low-cost, energy-saving and environmentally friendly charge-discharge energy-saving electrocatalytic wastewater treatment method.

[0006] Technical solution: The present invention provides a charge-discharge energy-saving electrocatalytic wastewater treatment method, comprising the following steps:

[0007] Step 1: Clean the carbon electrode and use it as both the cathode and anode. Insert it into the sewage and set up a magnetic stirrer at the bottom of the electrochemical reaction cell.

[0008] Step 2: Apply a constant voltage or constant current to the working electrode to ensure that the voltage can degrade 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. As the open circuit voltage gradually decreases, the electrical energy stored in the electrode continues to degrade pollutants.

[0010] Step four: Repeat steps two and three until the electrocatalytic degradation is complete.

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

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

[0013] Furthermore, the pollutants in the wastewater were azithromycin, bisphenol A, or carbamazepine.

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

[0015] Furthermore, the ratio of the time for applying constant voltage or current in step two to the time for stopping the application of voltage or current to the working electrode in step three is 1:2 to 19. Preferably, the ratio of the time for applying constant voltage or current in step two to the time for stopping the application of voltage or current to the working electrode in step three is 1:19, which achieves the best energy-saving effect.

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

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

[0018] Furthermore, in step four, 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, in the charging catalysis stage, the working electrode is driven by a constant current or constant voltage to perform an electrocatalytic reaction, while in the discharge stage, the high capacitance plate utilizes the electricity stored during the charging catalysis process to achieve the continuous degradation of pollutants.

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

[0021] 1. Saves energy while ensuring effective removal, reducing energy consumption by approximately 30-90%;

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

[0023] 3. The process is simple, requiring no special equipment or materials, and is suitable for upgrading and retrofitting existing sewage treatment systems. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the charging and discharging principle of the present invention;

[0025] Figure 2 This 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 This refers to the voltage and the amount of CO2 generated by mineralization on the electrode surface during the "charge-discharge" energy-saving electrocatalysis process of this invention.

[0027] Figure 4 This is a diagram illustrating the removal effect of the energy-saving electrocatalytic process of the present invention, in which the "charge-discharge" catalytic stage time ratio is 1:2, on organic pollutants.

[0028] Figure 5 This 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 1:19.

[0029] Figure 6 This invention demonstrates the effectiveness of an energy-saving electrocatalytic process with a "charge-discharge" catalytic stage time ratio of 1:19 in removing organic pollutants.

[0030] Figure 7 This is a graph showing the gas production from the degradation of azithromycin on the electrode surface under different applied potentials. Detailed Implementation

[0031] Example 1

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

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

[0034] (2) Pulse charging catalytic stage: Apply a constant voltage of 1.2V to the working electrode and maintain it for 60s.

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

[0036] (4) Repeat steps (2) and (3) 80 times, for a total of 4 hours, until degradation is complete.

[0037] In this embodiment, the voltage-time graphs of the working electrode in the 1st and 80th cycles are as follows: Figure 2 As shown, compared with the continuous electrocatalytic method, the "charge-discharge" catalytic method has an electrolytic time of only 33.3% and saves about 30% of energy.

[0038] Example 2

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

[0040] (1) Clean the carbon paper sequentially with 0.1M H2SO4, 0.1M NaOH, and acetonitrile to remove residual organic matter on the surface, and then rinse with pure water. Insert it into wastewater containing 5 mg / L bisphenol A and mix it magnetically.

[0041] (2) Pulse charging catalytic stage: Apply a constant voltage of 1.2V to the working electrode and maintain it for 180s.

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

[0043] (4) The gas generation on the working electrode surface in steps (2) and (3) was monitored using an in-situ differential electrochemical mass spectrometer. Steps (2) and (3) were repeated 20 times, for a total of 13600 s, until the degradation was completed.

[0044] In this embodiment, the voltage of the working electrode and the amount of CO2 generated by mineralization on the electrode surface are as follows: Figure 3 As shown, the results indicate that the voltage of the working electrode decreases slowly after power failure, accompanied by the continuous mineralization of pollutants into CO2.

[0045] Example 3

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

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

[0048] (2) Pulse charging catalytic stage: Apply a constant voltage of 1.2V to the working electrode and maintain it for 60s.

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

[0050] (4) Repeat steps (2) and (3) 80 times, for a total of 4 hours, until degradation is complete.

[0051] Comparative Example 1

[0052] Another graphite electrode modified with a molecule of imprinted polymer was used as the working electrode, and catalysis was performed at a constant voltage of 1.2V for 4 hours.

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

[0054] Example 4

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

[0056] (1) Use 0.1M H2SO4, 0.1M NaOH and acetonitrile to clean the carbon felt in sequence to remove residual organic matter on the surface, and rinse with pure water. Insert it into sewage containing 5mg / L azithromycin and stir with a magnetic stirrer at a speed of 500rpm.

[0057] (2) Pulse charging catalytic stage: Apply a constant voltage of 1.2V to the working electrode and maintain it 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) Repeat steps (2) and (3) 12 times, for a total of 4 hours, until degradation is complete.

[0060] Comparative Example 2

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

[0062] The voltage of the working electrode in the "charge-discharge" energy-saving electrocatalysis is as follows: Figure 5 As shown, the removal effect of azithromycin is as follows: Figure 6 As shown in Table 1, the "charge-discharge" energy-saving electrocatalysis achieves 90% of the azithromycin removal effect as constant potential catalysis with only 5% power supply time. The power consumption is reduced by 89.1% compared with continuous power supply.

[0063] Table 1 Comparison of electricity consumption between "charge-discharge" catalysis and continuous catalysis

[0064] 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 wastewater treatment method includes the following steps:

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

[0068] (2) Pulse charging catalytic stage: Apply 0.01 A / cm to the working electrode. 2 A constant current is applied and maintained for 120 seconds.

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

[0070] (4) Repeat steps (2) and (3) 20 times, for a total of 4 hours, until degradation is complete.

[0071] Example 6

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

[0073] (1) Clean the carbon paper sequentially with 0.1M H2SO4, 0.1M NaOH, and acetonitrile to remove residual organic matter on the surface, and then rinse with pure water. Insert a solution containing 5 mg / L azithromycin (C 38 H 72 N2O 12 The wastewater was mixed using magnetic stirring.

[0074] (2) Pulse charging catalytic stage: Apply constant voltages of 0.9V, 1.0V, 1.2V and 1.4V to the working electrode and maintain them for 10s.

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

[0076] (4) Use in-situ differential electrochemical mass spectrometry to monitor the gas generation on the working electrode surface in steps (2) and (3). Repeat steps (2) and (3) 60 times for a total of 2 hours to complete the degradation.

[0077] In this embodiment, the voltage of the working electrode and the amount of CO2 and NO2 generated by mineralization on the electrode surface are as follows: Figure 7 As shown, the results indicate that mineralization begins to produce CO2 at 0.9V, indicating that azithromycin is partially degraded; mineralization begins to produce CO2 at 1.2V, accompanied by significant NO2 production, indicating that the azithromycin molecule is completely mineralized. Therefore, the preferred charging catalytic voltage is ≥1.2V.

Claims

1. A charge-discharge energy-saving electrocatalytic wastewater treatment method, characterized in that, Includes the following steps: Step 1: Clean the carbon electrode and use it as both the cathode and anode. Insert it into the sewage and set up a magnetic stirrer at the bottom of the electrochemical reaction cell. Step 2: Apply a constant voltage or constant current to the working electrode to ensure that the voltage can degrade 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. As the open circuit voltage gradually decreases, the electrical energy stored in the electrode continues to degrade pollutants. Step four: Repeat steps two and three until the electrocatalytic degradation is complete; The ratio of the time for applying constant voltage or current in step two to the time for stopping applying voltage or current to the working electrode in step three is 1:2~19.

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

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

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

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

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

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

8. The charge-discharge energy-saving electrocatalytic wastewater treatment method according to claim 1, characterized in that: In step three, the monitoring time for open-circuit voltage is 2 min to 19 min.

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

Images