A method for the pretreatment of electrophoresis wastewater

Abstract

The application discloses an electrophoretic wastewater pretreatment method, which comprises the following steps: performing electrochemical treatment on electrophoretic wastewater in an electrochemical reactor to obtain treated electrophoretic wastewater. The material of an anode plate in the electrochemical reactor comprises at least one of ruthenium iridium titanium, platinum gold titanium, iridium tantalum titanium, diamond, 316L stainless steel and a titanium plate; and the material of a cathode plate in the electrochemical reactor comprises at least one of 316L stainless steel, foamed nickel, a titanium mesh and a titanium plate. The electrophoretic wastewater pretreatment method reduces the sludge production amount, has no secondary pollution, and has high and stable wastewater treatment effect, thereby effectively reducing the treatment cost of the electrophoretic wastewater.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, and specifically relates to a pretreatment method for electrophoretic wastewater. Background Technology

[0002] Electrophoretic coating is a special coating formation method that has been developed in the last 30 years. It is the most practical construction process for water-based coatings. It has the characteristics of water solubility, non-toxicity, easy automation control, uniform coating, high film hardness, corrosion resistance and impact resistance. It has been rapidly and widely used in automobiles, building materials, hardware, home appliances, instruments, agricultural machinery and other fields.

[0003] The automotive industry is currently developing rapidly, and electrophoretic coating plays a crucial role in this process. During electrophoretic coating, the car body needs to be rinsed with a large amount of water to remove adhering paint and sediment; the resulting water is called electrophoretic wastewater. The large volume of electrophoretic wastewater generated not only increases production costs but also causes environmental pollution. Automotive industry electrophoretic wastewater contains large amounts of resin, pigments, fillers, and organic solvents. These substances exist in the wastewater in the form of colloidal particles or suspended solids, exhibiting characteristics such as high levels of COD, SS, and color; a wide variety of pollutants; complex wastewater composition; large discharge volume; significant water quality fluctuations; irregular discharge patterns; poor biodegradability; and difficulty in degradation and treatment.

[0004] Therefore, there is an urgent need to develop a low-cost, efficient, and stable pretreatment method for electrophoretic wastewater. Summary of the Invention

[0005] This invention is based on the inventor's discovery and understanding of the following facts and problems: Current pretreatment methods for electrophoresis wastewater involve mixing electrophoresis wastewater, paint spraying wastewater, etc., in a specific ratio, and then directly subjecting the mixed wastewater to coagulation and sedimentation. While this process is characterized by low energy consumption, moderate operating costs, and low investment, it requires the addition of large amounts of chemicals, generates a large amount of sludge during treatment, and sludge is a solid waste, resulting in high treatment costs. Furthermore, the effluent quality is unstable, making it difficult to meet discharge standards, and the treatment effect is unsatisfactory.

[0006] This invention aims to at least partially solve one of the technical problems in related technologies. To this end, embodiments of this invention propose a pretreatment method for electrophoresis wastewater, which reduces sludge production, eliminates secondary pollution, and provides highly efficient and stable wastewater treatment, effectively lowering the overall treatment cost of electrophoresis wastewater.

[0007] The pretreatment method for electrophoretic wastewater in this embodiment of the invention involves electrochemically treating the electrophoretic wastewater in an electrochemical reactor to obtain treated electrophoretic wastewater.

[0008] The advantages and technical effects of the electrophoresis wastewater pretreatment method of this invention are as follows:

[0009] 1. The pretreatment method of this invention pretreats electrophoretic wastewater in an electrochemical reactor. Positively charged organic matter in the electrophoretic wastewater undergoes a reduction reaction on the cathode, thereby electrophoretically depositing on the cathode, thus achieving pretreatment of the electrophoretic wastewater and reducing the COD in the wastewater.

[0010] 2. The pretreatment method of this invention does not require the introduction of flocculants and does not generate sludge. It uses electrophoretic deposition coupled with electrochemical oxidation to pretreat automotive electrophoretic wastewater. The treatment method is simple, has low implementation costs, and has good treatment effect. It avoids the need for large amounts of chemical agents to be added for coagulation and sedimentation in existing pretreatment technologies, greatly reduces the amount of sludge generated, effectively reduces the treatment cost of automotive electrophoretic wastewater, and achieves the purpose of pollution reduction and carbon reduction in the treatment of electrophoretic wastewater.

[0011] In some embodiments, the pH value of the adjusted electrophoretic wastewater is 1.5-9.

[0012] In some embodiments, the anode plate in the electrochemical reactor is made of at least one of ruthenium-iridium-titanium, platinum-titanium, iridium-tantalum-titanium, diamond, 316L stainless steel, and titanium plate.

[0013] In some embodiments, the cathode plate in the electrochemical reactor is made of at least one of 316L stainless steel, nickel foam, titanium mesh, and titanium plate.

[0014] In some embodiments, the anode plate in the electrochemical reactor is made of diamond, and the cathode plate is made of 316L stainless steel.

[0015] In some embodiments, the distance between the cathode and the anode in the electrochemical reactor is 3-10 mm.

[0016] In some embodiments, the voltage of the electrochemical treatment is 15-80V.

[0017] In some embodiments, the voltage of the electrochemical treatment is a constant DC voltage.

[0018] In some embodiments, the electrochemical reactor is magnetically stirred using a magnetic stir bar at a speed of 600-1000 rpm.

[0019] In some embodiments, the temperature of the electrochemical treatment is 10-30°C, and the time of the electrochemical treatment is 30-165 min. Attached Figure Description

[0020] Figure 1This is a schematic diagram illustrating the principle of the electrophoretic wastewater pretreatment method according to an embodiment of the present invention. Detailed Implementation

[0021] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0022] The pretreatment method for electrophoretic wastewater in this embodiment of the invention involves electrochemically treating the electrophoretic wastewater in an electrochemical reactor to obtain treated electrophoretic wastewater.

[0023] like Figure 1 As shown in the embodiment of the present invention, the pretreatment method for electrophoretic wastewater pretreatment is performed in an electrochemical reactor. Positively charged organic matter in the electrophoretic wastewater undergoes a reduction reaction on the cathode, thereby electrophoretically depositing on the cathode, thus achieving pretreatment of the electrophoretic wastewater and reducing the COD in the wastewater.

[0024] The pretreatment method of this invention does not require the introduction of flocculants and does not generate sludge. It uses electrophoretic deposition coupled with electrochemical oxidation to pretreat automotive electrophoretic wastewater. The treatment method is simple, has low implementation costs, and has good treatment effect. It avoids the large amount of chemical reagents added by existing pretreatment technologies for coagulation and sedimentation, significantly reduces sludge production, effectively reduces the overall treatment cost of automotive electrophoretic wastewater, and achieves the goal of pollution reduction and carbon reduction in the treatment of electrophoretic wastewater.

[0025] In some embodiments, the pH value of the adjusted electrophoretic wastewater is 1.5-9, preferably 1.5-2, and most preferably 1.95. In this embodiment of the invention, controlling the pH value of the electrophoretic wastewater can change the charged properties of the organic matter in the wastewater, thereby adjusting the effectiveness of the electrochemical treatment of the wastewater. If the pH is low, the organic matter in the wastewater will carry a positive charge, making it easier for the organic matter to be electrophoretically deposited on the cathode. If the pH is high, on the one hand, the electrophoretic wastewater will undergo an acid-base neutralization reaction, causing some organic matter to precipitate, thus causing the wastewater to separate into layers: the upper layer is the supernatant, and the bottom layer is sludge, which can remove some organic matter; on the other hand, some organic matter in the wastewater will change from a positive charge to a negative charge under alkaline conditions, so under the action of direct current, the organic matter in the supernatant will undergo electrophoretic deposition on both the anode and cathode. Negatively charged organic matter will deposit on the anode, and positively charged organic matter will deposit on the cathode. Some organic matter will undergo an electrochemical oxidation reaction at the anode. Although the method of the present invention can effectively remove organic matter from electrophoretic wastewater in both acidic and alkaline environments, the energy consumption is higher in alkaline environments. Therefore, in the embodiments of the present invention, electrochemical treatment is preferably carried out in an acidic environment.

[0026] In some embodiments, the anode plate in the electrochemical reactor is made of at least one of ruthenium-iridium-titanium, platinum-titanium, iridium-tantalum-titanium, diamond, 316L stainless steel, and titanium plate. Preferably, the anode plate in the electrochemical reactor is made of at least one of ruthenium-iridium-titanium, platinum-titanium, iridium-tantalum-titanium, and diamond, and more preferably diamond. In the embodiments of the present invention, preferred materials such as ruthenium-iridium-titanium, platinum-titanium, iridium-tantalum-titanium, and diamond are used as the anode plate. Figure 1 As shown, some organic matter can also undergo electrochemical oxidation at the anode to decompose the organic matter, further improving the removal rate of organic matter, and maintaining low energy consumption while improving the removal rate of organic matter.

[0027] In some embodiments, preferably, the cathode plate in the electrochemical reactor is made of at least one of 316L stainless steel, nickel foam, titanium mesh, and titanium plate, and more preferably 316L stainless steel. Using preferred materials as the cathode plate in these embodiments facilitates the electrophoretic deposition of positively charged substances in the electrophoretic wastewater onto the cathode, achieving pollutant removal. The cathode after electrophoretic deposition can be cleaned by methods such as electrode reversal and slag scraping. The method in these embodiments uses preferred materials as the cathode plate, which improves the organic matter deposition effect while maintaining low energy consumption, and the cathode material is easy to clean and reuse.

[0028] In some embodiments, the distance between the cathode and anode in the electrochemical reactor is 3-10 mm, preferably 3-5 mm. In this embodiment of the invention, the preferred distance between the cathode and anode can improve the efficiency of electrophoretic deposition and electrochemical oxidation treatment of electrophoretic wastewater while reducing energy consumption. If the electrode spacing is small, the current efficiency is generally higher, which can shorten the diffusion distance of oxidants such as hydroxyl radicals (·OH) generated by the electrodes, allowing them to react more quickly with organic pollutants in the electrophoretic wastewater, accelerating the mass transfer rate, facilitating the reaction, shortening the reaction time, and increasing the removal rate. Simultaneously, the electron migration rate also increases due to the reduced electrode spacing, which helps reduce power consumption while achieving the same treatment effect. However, the electrode spacing cannot be too small, as the electrode surface is prone to passivation, leading to increased energy consumption, reduced electrolysis efficiency, and potential short circuits. When the electrode spacing increases, the current efficiency decreases and the treatment time increases because the increased electrode spacing increases the cell voltage, thereby increasing power consumption. Furthermore, increasing the electrode spacing also increases the diffusion distance of generated oxidants such as hydroxyl radicals (·OH), leading to a decrease in the oxidation rate. If the electrode spacing is too large, the resistance between the electrodes increases, the voltage rises, and energy consumption also increases. In this embodiment of the invention, the spacing between the cathode and anode is controlled within a suitable range, which effectively reduces energy consumption while improving the organic matter removal rate.

[0029] In some embodiments, the voltage of the electrochemical treatment is 15-80V, preferably 20-40V. In these embodiments, the preferred voltage for electrochemical treatment is beneficial for the electrophoretic deposition of positively charged materials on the cathode. If the voltage is too high, it may exceed the electrode's limiting current density, affecting electrode lifespan. Although a high voltage significantly shortens the reaction time, it not only fails to effectively improve the electrochemical treatment effect but also increases unnecessary energy consumption. If the voltage is too low, it cannot provide sufficient driving force for electrophoretic deposition and electrochemical oxidation, resulting in poor electrochemical treatment performance.

[0030] In some embodiments, the voltage of the electrochemical treatment is a constant DC voltage.

[0031] In some embodiments, a magnetic stir bar is used for magnetic stirring in the electrochemical reactor; preferably, the stirring speed is 600-1000 rpm.

[0032] In some embodiments, the electrochemical treatment temperature is 10-30°C, and the electrochemical treatment time is 30-165 min. The method of this embodiment can be carried out at room temperature and is easy to apply. The electrochemical treatment time in this embodiment is also the residence time of the electrophoretic wastewater in the electrochemical reactor, which is determined based on the removal of organic matter in the electrophoretic wastewater. When the organic matter removal rate no longer increases significantly, the electrochemical treatment ends.

[0033] The present invention will now be described in detail with reference to the embodiments.

[0034] Example 1

[0035] Pretreatment was performed on electrophoresis wastewater from an automotive workshop. The wastewater had a pH of 5.25 and a COD of [missing value]. cr It is 9600 mg / L.

[0036] 600 mL of electrophoretic wastewater was adjusted to pH 4.00 with dilute hydrochloric acid and then introduced into an electrochemical reactor. Anode and cathode plates were inserted into the reactor's electrode slots, using 316L stainless steel as the cathode and BDD (diamond-coated silica) as the anode, with an electrode spacing of 3 mm. Magnetic stirring was used at 600 rpm, and the DC regulated power supply was adjusted to constant voltage mode at 20 V. During electrochemical treatment, positively charged organic matter in the wastewater underwent reduction at the cathode and was electrophoretically deposited there. Some organic matter underwent electrochemical oxidation at the anode, achieving organic matter removal. The residence time of the wastewater in the electrochemical reactor was 120 min, and the reaction temperature was room temperature.

[0037] The COD of the electrophoretic wastewater treated in this embodiment Cr The removal rate was 78.8%, and the energy consumption was 46.6 kWh / g.

[0038] Example 2

[0039] The wastewater and pretreatment method used in Example 1 are the same, except that the pH value of the electrophoretic wastewater is not adjusted. The electrophoretic wastewater with a pH value of 5.25 is directly fed into the electrochemical reactor for electrochemical treatment, and the residence time of the electrophoretic wastewater in the electrochemical reactor is 150 min.

[0040] The COD of the electrophoretic wastewater treated in this embodiment Cr The removal rate was 73.9%, and the energy consumption was 42.8 kWh / g.

[0041] Example 3

[0042] The wastewater and pretreatment method used in Example 1 are the same, except that the pH value of the electrophoretic wastewater is adjusted to 1.95 and the residence time of the electrophoretic wastewater in the electrochemical reactor is 50 min.

[0043] The COD of the electrophoretic wastewater treated in this embodiment Cr The removal rate was 85.4%, and the energy consumption was 32.6 kWh / g.

[0044] Example 4

[0045] The wastewater and pretreatment method used in Example 1 are the same, except that the pH value of the electrophoretic wastewater is adjusted to 8.04 and the residence time of the electrophoretic wastewater in the electrochemical reactor is 120 min.

[0046] The COD of the electrophoretic wastewater treated in this embodiment Cr The removal rate was 86.0%, and the energy consumption was 73.4 kWh / g.

[0047] Example 5

[0048] The wastewater and pretreatment methods used in Example 1 are the same, except that the voltage value for electrochemical treatment is 40V and the residence time of the electrophoretic wastewater in the electrochemical reactor is 40min.

[0049] The COD of the electrophoretic wastewater treated in this embodiment Cr The removal rate was 68.6%, and the energy consumption was 38.5 kWh / g.

[0050] Example 6

[0051] The wastewater and pretreatment methods used in Example 1 are the same, except that the voltage value for electrochemical treatment is 60V and the residence time of the electrophoretic wastewater in the electrochemical reactor is 30min.

[0052] The COD of the electrophoretic wastewater treated in this embodiment CrThe removal rate was 62.4%, and the energy consumption was 35.9 kWh / g.

[0053] Example 7

[0054] The wastewater and pretreatment methods used in Example 1 are the same, except that ruthenium-iridium-titanium is used as the anode.

[0055] The COD of the electrophoretic wastewater treated in this embodiment Cr The removal rate was 63.8%, and the energy consumption was 50.2 kWh / g.

[0056] Example 8

[0057] The wastewater and pretreatment methods used in Example 1 are the same, except that a titanium mesh is used as the cathode.

[0058] The COD of the electrophoretic wastewater treated in this embodiment Cr The removal rate was 71.2%, and the energy consumption was 55.5 kWh / g.

[0059] Example 9

[0060] The wastewater and pretreatment methods used in Example 1 are the same, except that 316L stainless steel is used as the anode.

[0061] The COD of the electrophoretic wastewater treated in this embodiment Cr The removal rate was 60.1%, and the energy consumption was 47.2 kWh / g.

[0062] Example 10

[0063] The wastewater and pretreatment method used in Example 1 are the same, except that the distance between the cathode and anode is 5 mm and the residence time of the electrophoretic wastewater in the electrochemical reactor is 135 min.

[0064] The COD of the electrophoretic wastewater treated in this embodiment Cr The removal rate was 81.1%, and the energy consumption was 66.4 kWh / g.

[0065] Example 11

[0066] The wastewater and pretreatment methods used in Example 1 are the same, except that the distance between the cathode and anode is 7.5 mm, and the residence time of the electrophoretic wastewater in the electrochemical reactor is 165 min.

[0067] The COD of the electrophoretic wastewater treated in this embodiment Cr The removal rate was 82.5%, and the energy consumption was 83.0 kWh / g.

[0068] Example 12

[0069] The wastewater and pretreatment methods used in Example 1 are the same, except that the distance between the cathode and anode is 10 mm and the residence time of the electrophoretic wastewater in the electrochemical reactor is 165 min.

[0070] The COD of the electrophoretic wastewater treated in this embodiment Cr The removal rate was 82.0%, and the energy consumption was 76.5 kWh / g.

[0071] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0072] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A pretreatment method for electrophoretic wastewater, characterized in that, Electrophoretic wastewater is electrochemically treated in an electrochemical reactor by electrophoretic deposition coupled with electrochemical oxidation to obtain treated electrophoretic wastewater. The pH value of the electrophoretic wastewater is adjusted to 1.5-2 before the electrochemical treatment so that the organic matter in the electrophoretic wastewater carries a positive charge and undergoes electrophoretic deposition on the cathode.

2. The pretreatment method for electrophoretic wastewater according to claim 1, characterized in that, The anode plate in the electrochemical reactor is made of at least one of the following materials: ruthenium-iridium-titanium, platinum-titanium, iridium-tantalum-titanium, diamond, 316L stainless steel, and titanium plate.

3. The pretreatment method for electrophoretic wastewater according to claim 1, characterized in that, The cathode plate in the electrochemical reactor is made of at least one of the following materials: 316L stainless steel, nickel foam, titanium mesh, and titanium plate.

4. The pretreatment method for electrophoretic wastewater according to claim 1, characterized in that, The anode plate in the electrochemical reactor is made of diamond, and the cathode plate is made of 316L stainless steel.

5. The pretreatment method for electrophoretic wastewater according to claim 1, characterized in that, In the electrochemical reactor, the distance between the cathode and the anode is 3-10 mm.

6. The pretreatment method for electrophoretic wastewater according to claim 1, characterized in that, The voltage for the electrochemical treatment is 15-80 V.

7. The pretreatment method for electrophoretic wastewater according to claim 6, characterized in that, The voltage for the electrochemical treatment is 20-40 V.

8. The pretreatment method for electrophoretic wastewater according to claim 1, characterized in that, The voltage for the electrochemical treatment is a constant DC voltage.

9. The pretreatment method for electrophoretic wastewater according to claim 1, characterized in that, The electrochemical reactor is magnetically stirred using a magnetic stir bar at a speed of 600-1000 rpm.

10. The pretreatment method for electrophoretic wastewater according to claim 1, characterized in that, The electrochemical treatment is performed at a temperature of 10-30 °C for a duration of 30-165 min.

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