Method for simultaneously removing microplastics and micro-pollutants in water by electro-oxidation flocculation and application

Abstract

The application belongs to the technical field of sewage treatment, and particularly relates to a method and application for removing microplastics and micro-pollutants in water by electro-oxidation flocculation, which is based on electro-catalytic oxidation technology, sets up a bipolar electrode, constructs an electro-oxidation flocculation system based on the bipolar electrode, places the bipolar electrode in the electro-oxidation system for a period of time, removes the bipolar electrode, and removes the microplastics and micro-pollutants in water by using active substances generated by electro-oxidation and flocculants. An anode of the electro-oxidation flocculation system is set as a BDD electrode, a cathode is set as a titanium mesh, and a bipolar electrode is set as an iron electrode. The micro-pollutants include plasticizers and pharmaceutical pollutants. The method can be used for secondary effluent treatment in sewage plants. Compared with the prior art, the electro-oxidation process of the application can effectively degrade organic pollutants, and microplastics can be efficiently captured and removed by electro-flocculation, which simplifies the water purification step and improves the treatment efficiency.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to a method and application for the simultaneous removal of microplastics and micropollutants from water via electro-oxidation flocculation. Background Technology

[0002] Microplastics (MPs) are widely found in the atmosphere, soil, oceans, freshwater, and even sediments in Arctic freshwater lakes. The accumulation of MPs in organisms poses immeasurable harm to the ecological environment and human health. This is mainly due to the small size of MPs (particle fragments are typically less than 5 mm), making them easily ingested by organisms and causing mechanical damage. Their high specific surface area allows them to act as carriers for various trace organic pollutants, and they also contribute to the leaching of additives from complex compositions. Furthermore, microplastics can form complex pollution with micropollutants (MCs, such as antibiotics, pharmaceutical compounds, and plasticizers), which can have a greater impact on organisms.

[0003] Wastewater treatment plants, as both a source and a sink for microplastics, play a crucial role in the flow of microplastics. While most microplastics are removed through wastewater treatment processes, a significant amount still enters the aquatic environment. To degrade or remove microplastics from the aquatic environment, physical, chemical, and biological treatment technologies are commonly employed.

[0004] Membrane technology is a highly efficient physical treatment method that has been successfully used to remove microplastics from polluted aquatic environments. However, the efficiency of membrane technology is affected by a variety of factors, including membrane durability, influent flux, and the size and concentration of microplastics; microbial degradation methods require a long time and face challenges in scaling up and treating the secondary microplastics generated; photocatalytic degradation using nanomaterials is also a promising method, but changes in the structure of microplastics during photocatalysis may increase their toxicity.

[0005] Advanced oxidation processes (AOPs) are widely used to remove recalcitrant micropollutants from water. AOP systems generate non-selective free radicals, such as hydroxyl radicals (·OH) and singlet oxygen radicals (·OH). 1 Ozone (O2) and other organic pollutants can degrade most organic pollutants into smaller molecules. This method includes ozone treatment, photocatalytic treatment, Fenton oxidation, ultraviolet oxidation, and electrocatalytic oxidation. However, ozone oxidation suffers from high energy consumption and interference from byproducts and free radical scavengers; Fenton oxidation has shown high efficiency in some experiments, but it also has limitations such as secondary pollution from iron sludge and long reaction times; micro-pollutants can also absorb light or radiation and decompose, however, most of these methods have drawbacks, such as complex operating procedures, high maintenance costs, and a tendency to cause secondary pollution.

[0006] Current water purification technologies do not simultaneously consider the combined pollution of microplastics and micropollutants. Therefore, there is an urgent need to develop an advanced treatment technology to achieve this goal. Given the potential hazards, low concentrations, and difficulty in treating microplastics and micropollutants present in secondary effluent from wastewater treatment plants, a water purification technology is urgently needed. Summary of the Invention

[0007] The purpose of this invention is to provide a method and application for the simultaneous removal of microplastics and micropollutants from water by electro-oxidation flocculation, in order to solve at least one of the above-mentioned problems. This addresses the issue of low concentrations of microplastics and micropollutants in the secondary effluent of wastewater treatment plants, which is difficult to treat, and achieves the simultaneous removal of microplastics and micropollutants from wastewater, thereby improving treatment efficiency.

[0008] The objective of this invention is achieved through the following technical solution:

[0009] One of the technical solutions of this invention is to provide a method for simultaneously removing microplastics and micropollutants from water through electro-oxidation flocculation. The method is based on electrocatalytic oxidation technology, and a bipolar electrode is set to construct an electro-oxidation flocculation system based on the bipolar electrode. By placing the bipolar electrode in the electro-oxidation system for a period of time and then removing it, the active substances and flocculants generated by the electro-oxidation synergistic electro-flocculation reaction are used to remove microplastics and micropollutants from the water. The anode of the electro-oxidation flocculation system is set as a BDD electrode, the cathode is set as a titanium mesh, and the bipolar electrode is set as an iron electrode. The micropollutants include plasticizers and pharmaceutical pollutants.

[0010] Furthermore, the bipolar electrode is preferably an iron plate.

[0011] Furthermore, the effective immersion area of ​​the electrode is 7.5-8.5 cm². 2 .

[0012] Furthermore, the microplastics include polystyrene microplastics (PS), the plasticizers include bisphenol A (BPA) and diethyl phthalate (DEP), and the drug contaminants include sulfadiazine (SDZ), carbamazepine (CBZ), and florfenicol (FF).

[0013] The iron plate carries a positive induced charge on the side near the cathode, which can act as the anode to undergo an oxidation reaction, oxidizing the iron to Fe. 2+ / Fe 3+ Fe 2+ It will be oxidized to Fe by active or inactive oxidizing substances in the solution. 3+ The anodic electro-oxidation system produces ·OH and 1Active substances such as O2 can remove micropollutants. ·OH groups polymerize with metal ions to form hydroxyl-bridged structures. Under the influence of the remaining isolated electron pairs and the unsaturated coordination ability of the hydroxyl groups, mononuclear low-polymer iron complex flocculants are ultimately formed. After being bridged by hydroxyl groups, mononuclear metal complexes polymerize into hydroxyl-rich polynuclear polymeric network structures, ultimately forming amorphous high-polymer flocculants. Mononuclear low-polymer flocculants mainly remove microplastic particles through adsorption, while high-polymer flocculants, due to their numerous surface groups and large specific surface area, can remove microplastic particles through capture and scavenging. Flocculants are beneficial for microplastic removal.

[0014] This invention utilizes two main methods: firstly, the active substances generated by the anodic electro-oxidation system degrade micropollutants; secondly, the electrocoagulant generated by the bipolar electrode allows microplastics in wastewater to naturally deposit at the bottom of the electro-oxidation tank through electrostatic adsorption, capture, and scavenging of flocs during the electrocoagulation process. This flocculation and sedimentation effectively removes microplastics from the wastewater. Compared to existing related technologies, this method also has the advantages of shorter processing time and higher efficiency.

[0015] Furthermore, the distance L1 between the anode and the bipolar electrode is equal to the distance L2 between the bipolar electrode and the cathode.

[0016] Furthermore, L1 and L2 are 2-4 cm in size. With the cathode, anode, and bipolar electrodes arranged in this way, this electro-oxidative flocculation system can precipitate a large amount of iron flocs in a short time at a low current density, thereby removing microplastics through the electrostatic adsorption, capture, and scavenging action of the flocs.

[0017] Furthermore, the current density applied in the electro-oxidative flocculation system is 4-8 mA / cm². 2 The current density can be adjusted according to the specific wastewater being treated to achieve the best removal effect for microplastics and micropollutants.

[0018] Furthermore, the power supply of the present invention is configured to provide a current density of 4-8 mA / cm². 2 The direct current supplied by this power supply is sufficient to provide the electro-oxidation synergistic electrocoagulation system of this application with a sufficient current density to ensure the removal effect of microplastics and micropollutants in wastewater.

[0019] Furthermore, the electro-oxidation reaction time is 120-240 min. An electro-oxidation reaction time exceeding 120 min can effectively remove microplastics and micropollutants from the secondary wastewater treatment effluent.

[0020] Furthermore, the bipolar electrode is placed in the electro-oxidation system for 10-20 minutes and then removed. When the iron plate is placed for 20 minutes, the electrocoagulation effect on microplastics is the best. Increasing the iron plate placement time will improve the removal efficiency of micro-pollutants, but will not have much impact on microplastics. Moreover, the excessive reducing iron generated by placing the iron plate for a long time will reduce the oxidizing power of the system and consume the ·OH in the system.

[0021] Furthermore, after the electro-oxidation synergistic electrocoagulation treatment is completed, the mixture is allowed to stand and settle for 10-20 hours to allow the microplastics and electrocoagulant to settle.

[0022] Furthermore, magnetic stirring is applied during the electro-oxidation synergistic electrocoagulation treatment process, with the stirring speed being 500-600 r / min.

[0023] The second technical solution of the present invention is to provide an application of the method for simultaneous removal of microplastics and micropollutants from water by electro-oxidation flocculation as described above in the secondary effluent treatment of sewage treatment plants.

[0024] The electro-oxidative flocculation method of the present invention provides advanced treatment for secondary effluent from wastewater treatment plants. In the electro-oxidative flocculation system of the present invention, the electro-oxidation process can effectively degrade organic pollutants, while microplastics can be efficiently captured and removed through electro-flocculation. This treatment method combines tertiary wastewater treatment with primary drinking water treatment, simplifies water purification steps, improves treatment efficiency, and realizes the possibility of direct resource recovery of wastewater effluent.

[0025] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] 1. This invention adds a bipolar electrode iron plate to the electro-oxidation technology. The iron plate has a positive induced charge on the side near the cathode, which can act as the anode to undergo an oxidation reaction, oxidizing iron to Fe. 3+ The anodic electro-oxidation system produces ·OH and 1 Active substances such as O2 and ·OH polymerize with metal ions to form hydroxyl-bridged structures. Under the influence of the remaining isolated electron pairs and the unsaturated coordination ability of hydroxyl groups, mononuclear low-polymer iron complex flocculants are finally formed. After being bridged by hydroxyl groups, mononuclear metal complexes polymerize into hydroxyl-rich polynuclear polymeric network structures, ultimately forming amorphous high-polymer flocculants. Mononuclear low-polymer flocculants mainly remove microplastic particles through adsorption, while high-polymer flocculants, due to their numerous surface groups and large specific surface area, can remove microplastic particles through capture and sweeping. Flocculants are beneficial for the removal of microplastics. Bipolar electrode iron plates undergo electrocoagulation reactions in wastewater, and the microplastic removal rate is 95% after 20 minutes.

[0028] 2. The present invention utilizes the active substance ·OH generated by anodic electro-oxidation and 1 O2 and other substances degrade micro-pollutants in wastewater. At the same time, the present invention incorporates a bipolar electrode, which enables the electro-oxidation technology and the electrocoagulation technology to react synergistically. Experimental results show that the addition of a bipolar electrode is also beneficial to the removal of micro-pollutants in wastewater. When the bipolar electrode iron plate is placed for 10 minutes, the removal rate of micro-pollutants within 2 hours is 50-100%, and when the bipolar electrode iron plate is placed for 10 minutes, the removal rate of micro-pollutants within 2 hours is 80-100%.

[0029] 3. The method of this invention can perform advanced treatment of secondary effluent from wastewater treatment plants. The electro-oxidation process can effectively degrade organic pollutants, while the flocculant generated by electrocoagulation can remove microplastics through electrostatic adsorption, capture, and scavenging. This advanced treatment method combines the advantages of tertiary wastewater treatment and primary drinking water treatment. Compared with traditional tertiary wastewater treatment and primary drinking water treatment, this invention has higher treatment efficiency and lower energy consumption. The method of simply combining tertiary wastewater treatment and primary drinking water treatment can improve the treatment effect to a certain extent, but it cannot separate microplastics and micropollutants from the water. This invention simplifies the water purification steps, improves treatment efficiency, and is conducive to realizing the direct resource utilization of wastewater effluent and maximizing resource utilization.

[0030] 4. The device of the present invention is simple, low in cost, easy to operate and implement, and reduces sludge production, thus having broad application prospects. Attached Figure Description

[0031] Figure 1 This is a schematic diagram illustrating the principle of a method for simultaneously removing microplastics and micropollutants from water using electro-oxidation flocculation, according to the present invention.

[0032] Figure 2 The following figures illustrate the concentration changes of microplastics and micropollutants in wastewater treated by the electro-oxidative flocculation method provided in the examples. Figure (A) shows the concentration changes of micropollutants in wastewater within 120 minutes after the iron plate was placed for 10 minutes in Example 1; Figure (B) shows the concentration changes of microplastics in wastewater within 20 minutes after the iron plate was placed for 10 minutes in Example 1; Figure (C) shows the concentration changes of micropollutants in wastewater within 120 minutes after the iron plate was placed for 20 minutes in Example 2; Figure (D) shows the concentration changes of microplastics in wastewater within 20 minutes after the iron plate was placed for 20 minutes in Example 2. FF represents florfenicol; SDZ represents sulfadiazine; CBZ represents carbamazepine; BPA represents bisphenol A; DEP represents diethyl phthalate; and PS represents polystyrene microplastics.

[0033] Figure 3The image shows the water quality after the iron plate was placed for 10 minutes and the water was left to stand for 16 hours following the electro-oxidation flocculation method for simultaneously removing microplastics and micropollutants from water, as provided in Example 1. Detailed Implementation

[0034] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0035] Unless otherwise specified, all experimental reagents and raw materials used in this invention are commercially available.

[0036] Unless otherwise specified, the experimental methods described below follow conventional methods and conditions, or are selected according to the product instructions. Unless otherwise specified, all experimental instruments used in this invention are standard laboratory instruments.

[0037] Example 1

[0038] like Figures 1-2 As shown in the figure, this embodiment provides a method for simultaneously removing microplastics and micropollutants from water through electro-oxidation and flocculation. The method is based on electrocatalytic oxidation technology, employs a bipolar electrode, and constructs an electro-oxidation and flocculation system based on the bipolar electrode. The active substances generated by the electro-oxidation synergistic with the electro-flocculation reaction, along with the flocculant, remove microplastics and micropollutants from the water. The specific method is as follows:

[0039] This embodiment selects polystyrene microplastics (PS) and their leaching plasticizers bisphenol A (BPA) and diethyl phthalate (DEP), as well as the drugs sulfadiazine (SDZ), carbamazepine (CBZ), and florfenicol (FF) as research objects. A secondary effluent treatment technology for wastewater based on bipolar electrodes and electro-oxidation flocculation is constructed. The anode is BDD, the cathode is a titanium mesh, and the bipolar electrode is an iron plate. The effective immersion area of ​​the three electrodes is 7.5 cm². 2 The current density is 4 mA / cm². 2 After placing the bipolar electrode iron plate for 10 minutes, it was removed. The electro-oxidation time was 120 minutes. After the electro-oxidation was completed, the solution was allowed to stand for 16 hours to allow the microplastics and electrocoagulant to settle.

[0040] Example 2

[0041] like Figures 1-3As shown in the figure, this embodiment provides a method for simultaneously removing microplastics and micropollutants from water through electro-oxidation and flocculation. The method is based on electrocatalytic oxidation technology, employs a bipolar electrode, and constructs an electro-oxidation and flocculation system based on the bipolar electrode. The active substances generated by the electro-oxidation synergistic with the electro-flocculation reaction, along with the flocculant, remove microplastics and micropollutants from the water. The specific method is as follows:

[0042] This embodiment selects polystyrene microplastics (PS) and their leaching plasticizers bisphenol A (BPA) and diethyl phthalate (DEP), as well as the drugs sulfadiazine (SDZ), carbamazepine (CBZ), and florfenicol (FF) as research objects. A secondary effluent treatment technology for wastewater based on bipolar electrodes and electro-oxidation flocculation is constructed. The anode is a BDD, the cathode is a titanium mesh, and the bipolar electrode is an iron plate. The effective immersion area of ​​the three electrodes is 7.5 cm². 2 The current density is 4 mA / cm². 2 After the bipolar electrode iron plate was placed for 20 minutes, it was removed. The electro-oxidation time was 120 minutes. After the electro-oxidation was completed, the solution was allowed to stand for 16 hours to allow the microplastics and electrocoagulant to settle.

[0043] like Figure 1 As shown, water molecules in the solution are oxidized to ·OH on the surface of the BDD electrode, and the electro-oxidation system simultaneously generates… 1 O2, these active substances can remove micro pollutants. ·OH combines with metal ions, and under the action of the remaining isolated electron pairs and the unsaturated coordination ability of hydroxyl groups, it finally forms mononuclear low-polymer iron complex flocculants and amorphous high-polymer flocculants, which are beneficial to the removal of microplastics.

[0044] The removal results of microplastics and micropollutants in Examples 1 and 2 are as follows: Figure 2 As shown:

[0045] Figure 2 (A) shows the concentration changes of micropollutants in wastewater in Example 1 over 120 minutes. Figure 2 (B) shows the concentration change of microplastics in wastewater in Example 1 within 20 minutes. As can be seen from the figure, after the iron plate was placed as a bipolar electrode for 10 minutes in Example 1, the removal rate of micropollutants within 2 hours was as follows: DEP and FF were removed by 50%, SDZ was removed by 100%, and BPA and CBZ were removed by 90% and 80%, respectively. After 16 hours of settling, the removal rate of microplastics was approximately 91%.

[0046] Figure 2 (C) shows the concentration changes of micropollutants in the wastewater of Example 2 over 120 minutes. Figure 2(D) shows the concentration change of microplastics in wastewater in Example 2 within 20 minutes. As can be seen from the figure, after the iron plate was placed as a bipolar electrode for 20 minutes in Example 2, the removal rate of micropollutants within 2 hours was as follows: DEP, FF and SDZ were removed by 100%, while BPA and CBZ were removed by 80% and 90%, respectively. After standing for 16 hours, the removal rate of microplastics was 95%. In summary, electro-oxidative flocculation treatment can efficiently remove micropollutants and microplastics in the system. Increasing the placement time of the iron plate generally improves the removal efficiency of micropollutants.

[0047] Figure 3 In Example 2, after electro-oxidative flocculation treatment, the water became colorless and transparent after 16 hours of sedimentation, indicating that the microplastics in the water had all settled to the bottom through the electro-flocculation reaction.

[0048] In summary, the method described in this invention can simultaneously remove microplastics and micropollutants from water, with removal rates of both microplastics and micropollutants ranging from 80% to 90%. Furthermore, the method is simple and has high treatment efficiency.

[0049] The above description is only a preferred embodiment of this application. The treatment parameters such as the material of the anode and cathode and bipolar electrodes, the spacing between the electrodes, the selected power supply, the current density, the reaction time and the settling time should be considered according to the actual situation of the wastewater. This embodiment does not make specific limitations.

[0050] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for simultaneously removing microplastics and micropollutants from water via electro-oxidation flocculation, characterized in that, The method is based on electrocatalytic oxidation technology, and sets up a bipolar electrode to construct an electro-oxidation flocculation system based on the bipolar electrode. By placing the bipolar electrode in the electro-oxidation system for a period of time and then taking it out, the active substances and flocculants generated by the electro-oxidation synergistic electro-flocculation reaction are used to remove microplastics and micropollutants in the water. The anode of the electro-oxidation flocculation system is set as a BDD electrode, the cathode is set as a titanium mesh, and the bipolar electrode is an iron plate. The micropollutants include plasticizers and drug pollutants. The microplastics include polystyrene microplastics, the plasticizers include bisphenol A and diethyl phthalate, and the drug contaminants include sulfadiazine, carbamazepine, and florfenicol; The applied current density in the electro-oxidation flocculation system is 4-8 mA / cm². 2 ; The bipolar electrode is removed after being placed in the electro-oxidation system for 10-20 minutes. Increasing the placement time of the iron plate will improve the removal efficiency of micro-pollutants, but will have little effect on microplastics. Furthermore, the excessive reducing iron generated by placing the iron plate for a long time will reduce the oxidizing power of the system and consume the ·OH in the system. The active substances generated by the anodic electro-oxidation system degrade micro-pollutants, while the electrocoagulant generated by the bipolar electrode allows microplastics in the wastewater to naturally deposit at the bottom of the electro-oxidation tank through the electrostatic adsorption, capture, and scavenging of flocs during the electrocoagulation process. This effectively removes microplastics from the wastewater through flocculation and sedimentation.

2. The method for simultaneously removing microplastics and micropollutants from water via electro-oxidation flocculation according to claim 1, characterized in that, The distance L1 between the anode and the bipolar electrode is equal to the distance L2 between the bipolar electrode and the cathode.

3. The method for simultaneously removing microplastics and micropollutants from water via electro-oxidation flocculation according to claim 2, characterized in that, The dimensions of L1 and L2 are 2-4 cm.

4. The method for simultaneously removing microplastics and micropollutants from water via electro-oxidation flocculation according to claim 1, characterized in that, The reaction time for the electro-oxidation is 120-240 min.

5. The method for simultaneously removing microplastics and micropollutants from water via electro-oxidation flocculation according to claim 1, characterized in that, After the electro-oxidation and electrocoagulation treatment is completed, the mixture is allowed to stand for sedimentation for 10-20 hours.

6. The method for simultaneously removing microplastics and micropollutants from water by electro-oxidation flocculation according to claim 1, characterized in that, The electro-oxidation synergistic electrocoagulation process is subjected to magnetic stirring at a speed of 500-600 r / min.

7. The application of the method for simultaneous removal of microplastics and micropollutants from water by electro-oxidation flocculation as described in claim 1 in the secondary effluent treatment of wastewater treatment plants.

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