Method for synergistically removing heavy metal complex in high-salinity wastewater by E-UV and recovering heavy metals step by step

Abstract

The application discloses a method for removing heavy metal complexes in high-salinity wastewater and recovering heavy metals step by step in cooperation with E-UV, and belongs to the technical field of wastewater treatment. The method adopts a series connection type two-stage reactor: the first stage is a pure electrochemical unit (DSA anode + carbon felt cathode), which is used for breaking the complex of easily degradable heavy metal complexes and depositing and recovering the first target metal; the second stage is an electrochemical-ultraviolet cooperative unit (DSA anode, carbon felt cathode and ultraviolet lamp are arranged in the same chamber), which is used for breaking the complex of difficult-to-degrade complexes by ultraviolet activation and strengthening free radicals and recovering the second target metal. High-salinity wastewater containing heavy metal complexes flows through the two-stage reactor in sequence, and selective heavy metal complex breaking and step-by-step recovery are realized by adjusting and controlling the on-off time of the ultraviolet lamp. The application breaks through the bottleneck of high-salinity system treatment, and when a double complex system is simultaneously treated, the metal recovery rate is greater than or equal to 95%, the TOC removal rate is greater than 90%, and no chemical reagent needs to be added, so that the application has high efficiency and environmental protection.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to a method for the synergistic removal of heavy metal complexes from high-salinity wastewater by E-UV and the stepwise recovery of heavy metals. Background Technology

[0002] High-salinity industrial wastewater typically contains large amounts of heavy metal ions and high concentrations of inorganic ions such as chloride and sulfate ions. These heavy metal ions combine with organic complexing agents (such as complexing agents, brighteners, and stabilizers) in the wastewater to form stable heavy metal complexes. Traditional water treatment methods (such as chemical precipitation, adsorption, and membrane separation) have limited effectiveness in removing these heavy metal complexes, especially in high-salinity wastewater where treatment efficiency is even lower. These heavy metal complexes are not only difficult to remove, but the heavy metals they contain (such as copper, nickel, and chromium) have high recovery value. Therefore, how to recover heavy metals while removing these pollutants has become a crucial issue.

[0003] Currently, advanced electrochemical oxidation technology possesses the dual functions of anodic oxidation to break up complexes and cathodic reduction to recover metals, offering certain advantages in treating heavy metal complexes and recovering heavy metals. Through electrochemical reactions, heavy metal complexes can be oxidized at the anode, releasing heavy metal ions, which can then be recovered at the cathode through reduction reactions or electroadsorption. However, existing electrochemical methods suffer from low efficiency and poor recovery rates when removing heavy metal complexes, especially in complex, high-salinity wastewater, where the removal effect is even more limited. Furthermore, taking industrial wastewater from copper electroplating as an example, the electroplating process may utilize metal salts such as Ni, Cr, and Co (e.g., Cu-Ni alloy wastewater and Cu-Co alloy wastewater), and these heavy metal ions can also complex with organic complexing agents to form stable heavy metal complexes. To address these issues, synergistic degradation methods combining electrochemistry and ultraviolet (UV) light technology have become a research hotspot in recent years. UV irradiation can activate oxidants, generating highly oxidizing free radicals, thereby enhancing the destructive ability against heavy metal complexes. Simultaneously, electrochemical technology can further recover the heavy metal ions released after complex breaking. However, traditional ultraviolet photocatalysis and electrochemical technologies still face problems of low oxidation efficiency and recovery rate, and can only process one heavy metal complex and recover one heavy metal at a time.

[0004] Chinese invention patent CN105819560A, entitled "A Method for Photocatalytic Oxidation of Heavy Metal Complexes Enhanced by Persulfate and Recovery of Heavy Metals," describes a technology that introduces persulfate and utilizes ultraviolet light and a cathode to jointly activate and generate highly oxidizing sulfate and hydroxyl radicals, thereby significantly improving the oxidation and destruction efficiency of heavy metal complexes and increasing the recovery efficiency of metal ions at the cathode. However, this method suffers from low recovery rates when recovering heavy metals, fails to completely solve the electrochemical treatment problem in high-salinity wastewater, and can only process one type of heavy metal complex at a time.

[0005] Therefore, this invention proposes a method for gradually removing heavy metal complexes and recovering heavy metals step by step in high-salt wastewater using electrochemical-ultraviolet synergy. Summary of the Invention

[0006] The purpose of this invention is to provide a method for the synergistic removal of heavy metal complexes from high-salinity wastewater using E-UV technology and the stepwise recovery of heavy metals. By optimizing the synergistic effect of electrochemistry and ultraviolet light, the method solves the problems of low removal efficiency and low recovery rate of heavy metal complexes in high-salinity wastewater. By controlling the presence or absence of ultraviolet light irradiation, the generation of Cl· can be effectively controlled, thereby achieving selective complex breaking for various heavy metal complexes with different characteristics. In the absence of ultraviolet light, heavy metal complexes that are easier to break are removed, while those that are more difficult to break are removed when ultraviolet light is present. Through photoelectric synergy, not only can heavy metal complexes be removed efficiently and selectively, but heavy metals can also be recovered stepwise with a high recovery rate.

[0007] To achieve the above objectives, the present invention provides a method for the synergistic removal of heavy metal complexes from high-salt wastewater by E-UV and the stepwise recovery of heavy metals, which is implemented by a series two-stage reactor. The series two-stage reactor includes a first-stage reactor with a built-in first anode plate and a first cathode plate, and a second-stage reactor with a built-in second anode plate, a second cathode plate and an ultraviolet lamp.

[0008] Specifically, the following steps are included:

[0009] (1) Wastewater containing heavy metal complexes is mixed with electrolyte and then introduced into the first-stage reactor for electrochemical complex breaking treatment, and the first target heavy metal is deposited on the first cathode plate.

[0010] (2) The water from step (1) is introduced into the second-stage reactor, and the ultraviolet lamp is turned on to perform photoelectric synergistic complex breaking treatment, and the second target heavy metal is deposited on the second cathode plate.

[0011] (3) After the reaction is complete, the first cathode plate and the second cathode plate are removed, and the heavy metals on the two cathode plates are recovered by acid washing.

[0012] Preferably, the first-stage reactor and the second-stage reactor are connected in series via a peristaltic pump. The outlet end of the peristaltic pump is connected to the side of the first-stage reactor near the first anode plate, and the inlet end of the peristaltic pump is connected to the side of the second-stage reactor near the second cathode plate.

[0013] Preferably, the series-connected two-stage reactor is powered by a DC regulated power supply, and both the first-stage and second-stage reactors are equipped with built-in magnetic stirrers.

[0014] Preferably, both the first anode plate and the second anode plate are DSA anode plates; both the first cathode plate and the second cathode plate are carbon felt cathode plates.

[0015] Preferably, in step (1), the heavy metal complex is one of Cu-EDTA and Ni-EDTA, Cu-EDTA and Fe-EDTA, or Cu-EDTA and Co-EDTA.

[0016] Preferably, in step (1), the electrolyte is 50 mmol / L Na2SO4 and 640 mmol / L LCl4. - A mixed solution.

[0017] Preferably, in step (1), the electrochemical complex-breaking treatment time is 120 min.

[0018] Preferably, in step (2), the ultraviolet lamp is a 254nm ultraviolet lamp, and the photoelectric synergistic network breaking treatment time is 180min.

[0019] Therefore, the present invention employs the above-mentioned method for the synergistic removal of heavy metal complexes from high-salinity wastewater by E-UV and the stepwise recovery of heavy metals, which has the following beneficial effects:

[0020] (1) High efficiency and selectivity: This invention has significant advantages in removing heavy metal complexes in high-salt systems. By using photoelectric synergy, especially by controlling the irradiation time of ultraviolet light, the complex-breaking effect on heavy metal complexes is enhanced, so as to simultaneously remove two heavy metal complexes in wastewater. Furthermore, by utilizing electroadsorption, electrodeposition, and electroreduction, heavy metals are sorted and recovered by replacing the carbon felt cathode, eliminating the need for subsequent steps to classify the two heavy metals, saving operation steps and recovery costs. It also achieves a high removal and recovery rate. Moreover, the electrochemical and ultraviolet light treatment methods can be flexibly adjusted according to the different characteristics of wastewater. Compared with the limitations of existing technologies that can only treat one type of heavy metal complex, the method provided by this invention has stronger adaptability and a wider range of applicable scenarios.

[0021] (2) Environmental friendliness: Compared with traditional chemical methods, the method of the present invention is more environmentally friendly. It can remove pollutants and recover heavy metals without using other chemical agents. Heavy metals are recovered through physical and chemical processes such as electro-adsorption and electrodeposition, which reduces costs and the risk of secondary pollution.

[0022] (3) Ease of operation: The reactor used in this invention has a simple structure and the electrodes and ultraviolet lamps can be replaced independently. Compared with the complex multi-equipment combination in the prior art, the reactor of this invention has strong convenience.

[0023] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the structure of the series two-stage reactor used in the methods of Embodiments 1-3 of the present invention;

[0025] Figure 2 This is a graph showing the heavy metal removal rate of the method in Embodiment 1 of the present invention on mixed wastewater containing Cu-EDTA and Ni-EDTA.

[0026] Figure 3 This is a graph showing the heavy metal removal rate of the method in Embodiment 2 of the present invention on mixed wastewater containing Cu-EDTA and Fe-EDTA.

[0027] Figure 4 This is a graph showing the heavy metal removal rate of the method in Example 3 of the present invention on mixed wastewater containing Cu-EDTA and Co-EDTA.

[0028] Figure Labels

[0029] 1. First-stage reactor; 11. First anode plate; 12. First cathode plate;

[0030] 2. Second-stage reactor; 21. Second anode plate; 22. Second cathode plate;

[0031] 3. Magnetic stirrer; 4. DC regulated power supply; 5. Peristaltic pump; 6. UV lamp. Detailed Implementation

[0032] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0033] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0034] Example 1

[0035] This embodiment provides a method for electrochemical-ultraviolet synergistic degradation to remove mixed wastewater containing both Cu-EDTA and Ni-EDTA and to recover heavy metals, employing methods such as... Figure 1 The illustrated two-stage reactor is powered by a DC regulated power supply 4. The two-stage reactor includes a first-stage reactor 1 with a built-in first anode plate 11 (DSA anode plate), a first cathode plate 12 (carbon felt cathode plate), and a magnetic stirrer 3; and a second-stage reactor 2 with a built-in second anode plate 21 (DSA anode plate), a second cathode plate 22 (carbon felt cathode plate), a UV lamp 6 (254nm), and a magnetic stirrer 3. The second anode plate 21, second cathode plate 22, and UV lamp 6 are housed in the same chamber and fixed independently of the second-stage reactor by the same external support. The first-stage reactor 1 and the second-stage reactor 2 are connected in series via a peristaltic pump 5. The outlet of the peristaltic pump 5 is connected to the side of the first-stage reactor 1 closest to the first anode plate 11, and the inlet of the peristaltic pump 5 is connected to the side of the second-stage reactor 2 closest to the second cathode plate 22.

[0036] After wastewater is added to the reactor, a DC regulated power supply connected to a metal conductive wire is turned on to power the electrode plates, and a magnetic stirrer is simultaneously turned on to stir the mixture. The reaction begins, and heavy metal complexes are degraded within the reactor. The specific steps include:

[0037] Step S1: Add 400 mL of simulated wastewater containing 0.1 mmol / L copper disodium ethylenediaminetetraacetate (Cu-EDTA) and 0.1 mmol / L nickel disodium ethylenediaminetetraacetate (Ni-EDTA), along with 50 mmol / L anhydrous sodium sulfate and 640 mmol / L HCl to a beaker. - The mixed solution was placed on a magnetic stirrer and mixed evenly at a speed of 800 r / min to obtain solution A.

[0038] Step S2: Insert the carbon felt and the size-stabilized DSA anode as cathode and anode plates into the series-connected two-stage reactor, respectively. Add solution A into the series-connected two-stage reactor, turn on the peristaltic pump and the DC regulated power supply connected to the cathode and anode plates to supply power to the electrode plates, and the reaction begins.

[0039] Step S3: After the reaction proceeds for 120 minutes, turn on the UV lamp in the secondary reactor and continue the reaction for another 180 minutes. During the entire process, the heavy metal complex is broken in both stages of the reactor. After the complex is broken, the free heavy metals are electroadsorbed, electrodeposited, or electroreduced onto the cathode carbon felt cathode plates of each stage.

[0040] Step S4: After the reaction is complete, the heavy metals on the cathode plate are recovered by acid washing.

[0041] The results are as follows Figure 2 As shown, the removal rate of Cu reached 97% after 120 min, and the removal rate of Ni reached 88% after 300 min, with a total TOC removal rate exceeding 90%. Furthermore, before and after illumination, the proportions of Cu and Ni on the cathode carbon felt were 98.6% and 97.0%, respectively.

[0042] Example 2

[0043] This embodiment provides a method for electrochemical-ultraviolet synergistic degradation to remove mixed wastewater containing both Cu-EDTA and Fe-EDTA and to recover heavy metals. It is implemented using the same series two-stage reactor as in Example 1, and the reactor structure will not be described again here.

[0044] Specifically, the following steps are included:

[0045] Step S1: Add 400 mL of simulated wastewater containing Cu-EDTA and Fe-EDTA (both with a molar concentration of 0.1 mmol / L), anhydrous sodium sulfate (with a molar concentration of 50 mmol / L), and Cl (with a molar concentration of 640 mmol / L) to a beaker. - The mixed solution was placed on a magnetic stirrer and mixed evenly at a speed of 800 r / min to obtain solution B.

[0046] Step S2: Insert the carbon felt and the size-stabilized DSA anode as cathode and anode plates into the series-connected two-stage reactor, respectively. Add solution B to the series-connected two-stage reactor, turn on the peristaltic pump and the DC regulated power supply connected to the cathode and anode plates to supply power to the electrode plates, and the reaction begins.

[0047] Step S3: After the reaction proceeds for 120 minutes, turn on the UV lamp in the secondary reactor and continue the reaction for another 180 minutes. During the entire process, the heavy metal complex is broken in both stages of the reactor. After the complex is broken, the free heavy metals are electroadsorbed, electrodeposited, or electroreduced onto the cathode carbon felt cathode plates of each stage.

[0048] Step S4: After the reaction is complete, the heavy metals on the cathode plate are recovered by acid washing.

[0049] The results are as follows Figure 3 As shown, the removal rate of Cu reached 98% after 120 min, and the removal rate of Fe reached 100% after 300 min, with a total TOC removal rate of over 92%. Furthermore, before and after illumination, the proportions of Cu and Fe on the cathode carbon felt were 94% and 98.3%, respectively.

[0050] Example 3

[0051] This embodiment provides a method for electrochemical-ultraviolet synergistic degradation to remove mixed wastewater containing both Cu-EDTA and Co-EDTA and to recover heavy metals. It is implemented using the same series two-stage reactor as in Example 1, and the reactor structure will not be described again here.

[0052] Specifically, the following steps are included:

[0053] Step S1: Add 400 mL of simulated wastewater containing Cu-EDTA and Co-EDTA (both with a molar concentration of 0.1 mmol / L), anhydrous sodium sulfate (with a molar concentration of 50 mmol / L), and Cl (with a molar concentration of 640 mmol / L) to a beaker. - The mixed solution was placed on a magnetic stirrer and mixed evenly at a speed of 800 r / min to obtain solution C.

[0054] Step S2: Insert the carbon felt and the size-stabilized DSA anode as cathode and anode plates into the series-connected two-stage reactor, respectively. Add solution C to the series-connected two-stage reactor, turn on the peristaltic pump and the DC regulated power supply connected to the cathode and anode plates to supply power to the electrode plates, and the reaction begins.

[0055] Step S3: After the reaction proceeds for 120 minutes, turn on the UV lamp in the secondary reactor and continue the reaction for another 180 minutes. During the entire process, the heavy metal complex is broken in both stages of the reactor. After the complex is broken, the free heavy metals are electroadsorbed, electrodeposited, or electroreduced onto the cathode carbon felt cathode plates of each stage.

[0056] Step S4: After the reaction is complete, the heavy metals on the cathode plate are recovered by acid washing.

[0057] The results are as follows Figure 4As shown, the removal rate of Cu reached 98.4% after 120 min, and the removal rate of Co reached 100% after 300 min, with a total TOC removal rate of over 90%. Furthermore, before and after illumination, the proportions of Cu and Co on the cathode carbon felt were 96% and 98%, respectively.

[0058] The above results indicate that by reasonably controlling the reaction time of UV, it is possible to effectively achieve the stepwise recovery of different metals. This invention provides a feasible strategy for the treatment of wastewater containing multiple heavy metals and the recovery of metals.

[0059] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for the synergistic removal of heavy metal complexes from high-salinity wastewater by E-UV and the stepwise recovery of heavy metals, characterized in that: The process is achieved using a series two-stage reactor, which includes a first-stage reactor with a built-in first anode plate and a first cathode plate, and a second-stage reactor with a built-in second anode plate, a second cathode plate, and an ultraviolet lamp. Specifically, the following steps are included: (1) Wastewater containing heavy metal complexes is mixed with electrolyte and then introduced into the first-stage reactor for electrochemical complex breaking treatment, and the first target heavy metal is deposited on the first cathode plate. (2) The water from step (1) is introduced into the second-stage reactor, and the ultraviolet lamp is turned on to carry out photoelectric synergistic complex breaking treatment, and the second target heavy metal is deposited on the second cathode plate. (3) After the reaction is complete, the first cathode plate and the second cathode plate are removed, and the heavy metals on the two cathode plates are recovered by acid washing.

2. The method for synergistic removal of heavy metal complexes from high-salinity wastewater and stepwise recovery of heavy metals according to claim 1, characterized in that: The first-stage reactor and the second-stage reactor are connected in series via a peristaltic pump. The inlet of the peristaltic pump is connected to the side of the first-stage reactor near the first anode plate, and the outlet of the peristaltic pump is connected to the side of the second-stage reactor near the second cathode plate.

3. The method for synergistic removal of heavy metal complexes from high-salinity wastewater and stepwise recovery of heavy metals according to claim 1, characterized in that: The series-connected two-stage reactor is powered by a DC regulated power supply, and both the first-stage and second-stage reactors are equipped with built-in magnetic stirrers.

4. The method for synergistic removal of heavy metal complexes from high-salinity wastewater and stepwise recovery of heavy metals according to claim 1, characterized in that: Both the first anode plate and the second anode plate are DSA anode plates; both the first cathode plate and the second cathode plate are carbon felt cathode plates.

5. The method for synergistic removal of heavy metal complexes from high-salinity wastewater and stepwise recovery of heavy metals according to claim 1, characterized in that: In step (1), the heavy metal complex is one of Cu-EDTA and Ni-EDTA, Cu-EDTA and Fe-EDTA, or Cu-EDTA and Co-EDTA.

6. The method for synergistic removal of heavy metal complexes from high-salinity wastewater and stepwise recovery of heavy metals according to claim 1, characterized in that: In step (1), the electrolytes are 50 mmol / L Na2SO4 and 640 mmol / L Cl. - A mixed solution.

7. The method for synergistic removal of heavy metal complexes from high-salinity wastewater and stepwise recovery of heavy metals according to claim 1, characterized in that: In step (1), the electrochemical complex-breaking treatment time is 120 min.

8. The method for synergistic removal of heavy metal complexes from high-salinity wastewater and stepwise recovery of heavy metals according to claim 1, characterized in that: In step (2), the UV lamp is a 254nm UV lamp, and the photoelectric synergistic complex breaking treatment time is 180min.

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