A combined treatment method of acid wastewater

Abstract

The application belongs to the technical field of sewage treatment, and discloses a combined treatment method of acid wastewater. The combined treatment method of acid wastewater comprises the following steps: introducing acid wastewater generated in an industrial process into an electrochemical device, loading non-metallic mineral materials on an anode of the electrochemical device, neutralizing the acid wastewater and extracting heavy metals through electrochemical treatment; introducing the solution after the electrochemical treatment into a sedimentation tank, capturing and fixing carbon dioxide in the air, and directly discharging the treated solution meeting the Environmental Quality Standards for Surface Water. The acid wastewater treatment method is simple, efficient, easy to operate, and can realize the recovery of heavy metals at the same time. The non-metallic mineral which is easy to obtain and environment-friendly is introduced into the anode of the electrochemical device, hydrogen ions released in the electrolysis process are consumed, the inhibition of hydrogen ions on the deposition of heavy metals is reduced, and the extraction rate of heavy metals in the wastewater is improved. The solution after the electrochemical treatment is used for capturing and fixing carbon dioxide, and the treated solution can be directly discharged.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sewage treatment, in particular to a combined treatment method of acid wastewater. BACKGROUND

[0002] Acid wastewater mainly comes from human activities such as chemical industry, electroplating, metal smelting and mining. The high acidity and strong corrosiveness of acid wastewater can easily damage pipelines and infrastructure, and contain high concentrations of highly toxic heavy metals such as copper, cadmium and zinc. If these wastewaters are discharged or improperly treated, they will seriously damage the self-purification ability of the environment, have a negative impact on biological growth, and cause a large amount of valuable metal resources (such as copper, cadmium and zinc) to be wasted. The common treatment methods at present include neutralization precipitation method, ion exchange method, membrane separation method and biological treatment method, etc. However, these methods have high cost, low treatment efficiency, are easy to cause secondary pollution, and cannot effectively recover metal resources in wastewater. For example, the widely used neutralization method usually needs to add expensive chemical reagents, and generates a large amount of sludge containing heavy metals, resulting in secondary pollution and waste of metal resources. In recent years, electrochemical method as a new technology for treating acid wastewater has attracted much attention, which realizes wastewater neutralization and heavy metal removal through electrolysis, and has high selectivity and environmental friendliness. However, the traditional electrochemical method has problems such as complex design, low efficiency and high energy consumption when treating acid wastewater, which has become one of the bottlenecks of technological development. For example, the prior art (CN117865291A) treats acid wastewater by an electrochemical membrane reactor and realizes neutralization and heavy metal removal, but the treatment process is complex and needs to spend extra for the configuration and replacement of the membrane. The prior art (CN116282400A) treats acid wastewater by a double pulse low voltage electroflocculation method, realizes acid neutralization and co-precipitation removal of heavy metal chromium, but this process increases the difficulty of subsequent heavy metal recovery.

[0003] Therefore, the prior art still needs to be improved and developed. SUMMARY

[0004] In view of the above problems of the prior art, the purpose of the present application is to provide a combined treatment method of acid wastewater, which aims to solve the problems of high cost, low treatment efficiency, easy to cause secondary pollution and unable to effectively recover metal resources in wastewater of the existing acid wastewater treatment method.

[0005] The technical scheme of the present application is as follows:

[0006] The present application provides a combined treatment method of acid wastewater, comprising the steps of:

[0007] The acid wastewater generated in the industrial process is introduced into an electrochemical device, and the anode of the electrochemical device is loaded with non-metallic mineral materials, which realizes neutralization and heavy metal extraction of the acid wastewater through electrochemical treatment;

[0008] The electrochemically treated solution is introduced into a precipitation tank, carbon dioxide in the air is captured and fixed, and a treated solution meeting the Surface Water Environmental Quality Standard is obtained, which is directly discharged.

[0009] Optionally, the acid wastewater has a pH value of 1-5, a copper ion concentration of 10-200 mg / L, a cadmium ion concentration of 2-200 mg / L, and a zinc ion concentration of 15-300 mg / L.

[0010] Optionally, the non-metallic mineral material is selected from one or more of limestone, dolomite, huntite, wollastonite, olivine, and phosphogypsum.

[0011] Optionally, the non-metallic mineral material is limestone particles with a particle size of 0.1-10 cm.

[0012] Optionally, the electrochemical treatment has a rated voltage of 2-15 V, a rated current of 10-100 mA, and a time of 1-15 h.

[0013] Optionally, in the extraction of heavy metals, the extraction rate of copper is 99.3%-99.5%, the extraction rate of cadmium is 95.2%-99.1%, and the extraction rate of zinc is 90.9%-95.1%.

[0014] The combination treatment method of the acid wastewater, wherein the step of introducing the electrochemically treated solution into a precipitation tank to capture and fix carbon dioxide in the air is specifically: the electrochemically treated solution is alkaline, and after being introduced into an air-exposed precipitation tank, carbon dioxide in the air is dissolved in the alkaline solution, reacts with calcium or magnesium ions to form calcium carbonate or magnesium carbonate precipitates, captures and fixes the carbon dioxide, and the final treated solution meets the Surface Water Environmental Quality Standard, and is directly discharged.

[0015] Optionally, the pH value of the electrochemically treated solution is 7.0-10.5, and the concentration of calcium ions or magnesium ions is greater than or equal to 2 mM.

[0016] Optionally, in the electrochemically treated solution, the concentration of Cu ions is less than or equal to 0.01 mg / L, the concentration of Cd ions is less than or equal to 0.01 mg / L, and the concentration of Zn ions is less than or equal to 0.01 mg / L.

[0017] Optionally, the pH value of the treated solution after capturing and fixing the carbon dioxide is 6.0-9.0.

[0018] Beneficial effects:

[0019] The application provides a combined treatment method for acid wastewater, which is simple, efficient, easy to operate, and can realize heavy metal recovery and carbon dioxide capture and fixation. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 The flowchart of the acid wastewater treatment method provided by the application is shown.

[0021] Figure 2 The schematic diagram of the electrochemical device used in the acid wastewater treatment method is shown.

[0022] Figure 3 The result graph of the heavy metal extraction of the acid wastewater after electrochemical treatment in Example 1 of the application is shown.

[0023] Figure 4 The result graph of the cadmium extraction rate of the acid wastewater with different initial cadmium ion concentrations after electrochemical treatment in Example 2 of the application is shown.

[0024] Figure 5 The result graph of the cadmium extraction rate of the acid wastewater with different initial pH values after electrochemical treatment in Example 3 of the application is shown.

[0025] Figure 6 The result graph of the concentration change of each heavy metal ion, the pH value change, and the heavy metal extraction of the acid wastewater discharged by a mine after electrochemical treatment in Example 4 of the application is shown.

[0026] Figure 7 The result graph of the pH value change, the heavy metal extraction, and the carbon dioxide capture and fixation of the final treatment liquid of the acid wastewater after combined treatment in Example 5 of the application is shown.

[0027] Figure 8 The result graph of the heavy metal extraction rate and the carbon dioxide capture and fixation of the acid wastewater after combined treatment in Example 6 of the application is shown. DETAILED DESCRIPTION

[0028] The application provides a combined treatment method of acid wastewater. In order to make the purpose, technical scheme and effect of the application more clear and explicit, the application is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the application and are not intended to limit the application.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0030] The application provides a combined treatment method of acid wastewater, comprising the steps of:

[0031] S1, passing the acid wastewater generated in the industrial process into an electrochemical device, wherein the anode of the electrochemical device is loaded with non-metallic mineral materials, and the acid wastewater is neutralized and heavy metal extraction through electrochemical treatment;

[0032] S2, passing the solution after electrochemical treatment into a sedimentation tank, capturing and fixing carbon dioxide in the air to obtain a treated solution meeting the Environmental Quality Standards for Surface Water, and directly discharging.

[0033] In some embodiments, the acid wastewater has a pH value of 1-5, a copper ion concentration of 10-200 mg / L, a cadmium ion concentration of 2-200 mg / L, and a zinc ion concentration of 15-300 mg / L.

[0034] In some embodiments, the non-metallic mineral material is selected from one or more of limestone, dolomite, huntite, wollastonite, olivine and phosphogypsum. The non-metallic mineral material can be derived from natural minerals or solid waste.

[0035] In some embodiments, the non-metallic mineral material is limestone particles with a particle size of 0.1-10 cm.

[0036] In some embodiments, the electrochemical treatment is performed under the following conditions: rated voltage of 2-15 V, rated current of 10-100 mA, and time of 1-15 h.

[0037] Water electrolysis technology uses direct current to decompose water into hydrogen and oxygen, and releases hydrogen ions and hydroxyl ions at the anode and cathode. The hydroxyl ions released at the cathode can consume the acidity (hydrogen ions) in the wastewater, increase the pH value of the acidic wastewater, and at the same time, the negatively charged cathode can attract heavy metal cations and deposit them on the electrode surface through electron transfer and local high pH. However, during the electrolysis process, the hydrogen ions released at the anode will consume the hydroxyl ions generated at the cathode, and compete with the heavy metals for electrons, resulting in a decrease in wastewater neutralization efficiency and heavy metal extraction efficiency. Therefore, traditional electrochemical technology usually requires high energy consumption and complex structure and operation mode. The electrochemical treatment method for acidic wastewater provided by the present application introduces limestone, which is cheap, easy to obtain, environmentally friendly and has been widely used for acidic wastewater treatment, and by fixing limestone as a barrier near the anode to form an integrated electrochemical device, on the one hand, the hydrogen ions released at the anode during the electrolysis process are efficiently and continuously consumed, so that the hydroxyl ions generated at the cathode accumulate in the solution, the pH value of the wastewater solution is increased, thereby reducing the inhibition of hydrogen ions on heavy metal deposition during the electrochemical process, and the recovery effect of heavy metals in the wastewater is enhanced. The greater the applied current and voltage, the higher the treatment efficiency. In the face of wastewater with high pollutant concentration, the treatment rate can be accelerated by increasing the current and voltage, and for wastewater with low concentration, the voltage and current can be reduced to reduce energy consumption.

[0038] In some embodiments, in the extraction of heavy metals, the extraction rate of copper is 99.3%-99.5%, the extraction rate of cadmium is 95.2%-99.1%, and the extraction rate of zinc is 90.9%-95.1%.

[0039] In step S2, in some embodiments, the step of capturing and fixing carbon dioxide in the air after the electrochemically treated solution enters the precipitation tank is specifically: the electrochemically treated solution is alkaline, after entering the air-exposed precipitation tank, the carbon dioxide in the air is dissolved in the alkaline solution, reacts with calcium or magnesium ions to form calcium carbonate or magnesium carbonate precipitate, and the carbon dioxide is captured and fixed. After the final treated solution meets the "Surface Water Environmental Quality Standard", it is directly discharged.

[0040] In some embodiments, the pH value of the electrochemically treated solution is 7.0-10.5, and the concentration of calcium ions or magnesium ions is ≥2mM.

[0041] In some embodiments, the concentration of Cu ions in the electrochemically treated solution is ≤0.01 mg / L, the concentration of Cd ions is ≤0.01 mg / L, and the concentration of Zn ions is ≤0.01 mg / L. According to the V-class standard limit value of the Environmental Quality Standards for Surface Water (GB 3838-2002), the standard for copper is 1 mg / L, the standard for zinc is 2.0 mg / L, and the standard for cadmium is 0.01 mg / L. It can be determined that the water standard is that the wastewater is electrochemically treated until the concentration of heavy metal ions is reduced to the corresponding environmental quality standard concentration. It can be seen that the treated solution obtained after the combined treatment of the acidic wastewater according to the present application meets the direct discharge standard.

[0042] In some embodiments, the pH value of the treated solution after the carbon dioxide is captured and fixed is 6.0-9.0.

[0043] The following will be described in detail through specific examples.

[0044] Example 1

[0045] As shown in the acid wastewater treatment flowchart, Figure 1 the treatment method of the acid wastewater includes electrochemical treatment and carbon dioxide capture and fixation. The electrochemical treatment uses an integrated electrochemical reaction device, as shown in Figure 2 The integrated electrochemical reaction device is composed of four parts: a rod-shaped titanium anode plated with ruthenium iridium, industrial-grade granular limestone particles (particle size: 0.1-10 cm), a porous barrier for filling limestone, and a stainless steel cathode. The anode is installed in the middle of the barrier, the limestone particles are directly filled around the anode in the barrier, and the cathode is installed outside the barrier. The limestone particles are loaded on the anode of the electrochemical reaction device.

[0046] The specific steps of the electrochemical treatment of the acid wastewater are as follows:

[0047] The acid wastewater is introduced into the integrated electrochemical reaction device by a pump, a direct current is applied to the electrochemical reaction device, the rated voltage is 3 V, the rated current is 20 mA, and the electrochemical treatment is performed for 5 h. The initial pH value of the acid wastewater is 1.5, and the concentrations of the metal ions contained therein are as follows: Cu is 10 mg / L, Cd is 2 mg / L, Zn is 300 mg / L, and Ca is 73 mg / L.

[0048] During the treatment process, the solution is sampled and tested for various indicators, and the test result data is shown in Table 1 below:

[0049] Table 1

[0050]

[0051] The cathode in the electrochemical device deposits heavy metals, and the deposition mass of each heavy metal is shown in Table 2:

[0052] Table 2

[0053]

[0054] Table 1 shows that the solution treated electrochemically in this embodiment had a pH of 7.8, while significantly reducing the concentration of heavy metals to Cu ≤ 0.01 mg / L, Cd ≤ 0.01 mg / L, and Zn ≤ 0.01 mg / L, achieving zero pollution emissions. Simultaneously, heavy metal deposition at the cathode was also achieved. The extraction rate was calculated based on the deposition mass of each heavy metal at the cathode of the electrochemical device, such as... Figure 3 As shown, the results indicate that the electrochemical treatment in this embodiment achieved a copper extraction rate of 99.5%, a cadmium extraction rate of 95.8%, and a zinc extraction rate of 90.9%.

[0055] The extraction rate is calculated as follows: Heavy metal extraction rate (%) = mass of heavy metals deposited at the cathode / (volume of treated wastewater * initial concentration of heavy metal ions in the wastewater).

[0056] Example 2

[0057] Electrochemical treatment of acidic wastewater with different initial cadmium ion concentrations

[0058] First, three simulated acidic wastewater solutions with a pH of 3.0 and cadmium ion concentrations of 2, 20, and 200 mg / L were selected. Then, under the condition of providing an external constant current power supply (rated voltage 3V, rated current 20mA), electrochemical treatment was carried out for 2.5, 4, and 8 hours, respectively, and the pH value change and cadmium extraction of the solutions after electrochemical treatment were tested.

[0059] Depend on Figure 4 The results show that, through electrochemical treatment, the pH of acidic wastewater containing three different cadmium concentrations was increased from 3.0 to 8.4, 9.7, and 9.3, respectively, and cadmium extraction rates of 95.2%, 96.8%, and 98.0% were achieved, respectively.

[0060] The extraction rate is calculated as follows: Heavy metal extraction rate (%) = mass of heavy metals deposited at the cathode / (volume of treated wastewater * initial concentration of heavy metal ions in the wastewater).

[0061] Example 3

[0062] Electrochemical treatment of acidic wastewater with different initial pH values

[0063] The initial pH is 2.0, 3.0, 4.0 respectively, and the cadmium ion concentration is 20 mg / L solution as simulated acid wastewater, under the condition of providing external constant current power (rated voltage 3V, rated current 20mA), respectively processing 15, 4, 2.5 hours, testing the corresponding pH value change of the solution after electrochemical treatment and the cadmium extraction.

[0064] The results shown in Figure 5 show that, by electrochemical treatment, the pH of the wastewater containing three different wastewaters is increased from 2.0 to 7.8, from 3.0 to 9.7, and from 4.0 to 10.1, respectively, while the corresponding cadmium extraction rates of 98.0%, 96.8% and 95.3% are achieved, respectively.

[0065] The calculation method of extraction rate: heavy metal extraction rate (%) = cathode deposition heavy metal mass / (treated wastewater volume * initial heavy metal ion concentration in wastewater).

[0066] Example 4

[0067] The difference between this embodiment and example 5 is that the mine drainage from a mine in Shaoguan City, Guangdong Province is selected as the treatment object, and after electrochemical treatment for 10 hours under the condition of providing external constant current power (rated voltage 3V, rated current 20mA), the concentration change of heavy metal ions in the wastewater solution after electrochemical treatment, the pH value change, and the extraction of each heavy metal are tested, and the test results are shown in Figure 6 .

[0068] The results in Figure 6 show that the electrochemical treatment of this embodiment can effectively remove heavy metal ions such as copper, cadmium and zinc in wastewater. At the same time, the pH of the wastewater can be increased from 2.5 to 7.8 (as shown in Figure 6 b), and according to the mass of heavy metals deposited on the cathode in the electrochemical device, the copper extraction rate of 99.5%, the cadmium extraction rate of 95.8% and the zinc extraction rate of 90.9% are achieved (as shown in Figure 6 c).

[0069] The calculation method of extraction rate: heavy metal extraction rate (%) = cathode deposition heavy metal mass / (treated wastewater volume * initial heavy metal ion concentration in wastewater).

[0070] Example 5

[0071] Combined treatment of acid wastewater containing multiple heavy metal ions

[0072] Experimental group:

[0073] (1) Electrochemical treatment

[0074] An integrated electrochemical reaction device was selected to simulate acidic wastewater containing a solution with pH 3.0 and copper, cadmium, and zinc ion concentrations of 20 mg / L. Electrochemical treatment was carried out for 4 hours under the condition of providing an external constant current power supply (rated voltage 3V, rated current 20mA).

[0075] (2) Capture and fix carbon dioxide

[0076] The specific steps are as follows: The alkaline solution, which has undergone electrochemical treatment, is pumped into the sedimentation tank and comes into direct contact with the air. The high concentration of hydroxide ions accelerates the dissolution of carbon dioxide in the air and reacts with calcium ions in the solution to form calcium carbonate precipitate. After the carbon dioxide capture and fixation reaction, the hydroxide concentration in the solution decreases and the pH of the solution drops to 7.8, meeting the "Surface Water Environmental Quality Standard", and is then directly discharged.

[0077] Control group:

[0078] The control group used a conventional electrochemical device (without calcium carbonate mineral particles at the anode). A solution containing 20 mg / L copper, cadmium, and zinc ions at pH 3.0 was introduced into the conventional electrochemical reactor as a control. Electrochemical treatment was performed for 4 hours, and then the pH change and heavy metal extraction were tested before and after the acidic wastewater treatment.

[0079] The changes in pH value and heavy metal extraction of the two treated wastewater solutions are as follows: Figure 7 As shown in a and b in the figure. The results show that the electrochemical treatment method used in this embodiment of the invention can effectively increase the pH of the wastewater to 9.3, while achieving a copper extraction rate of 99.5%, a cadmium extraction rate of 99.0%, and a zinc extraction rate of 94.2%. The extraction rate is calculated as follows: Heavy metal extraction rate (%) = mass of heavy metals deposited at the cathode / (volume of treated wastewater * initial concentration of heavy metal ions in the wastewater). Figure 7 As shown in c, the captured and fixed carbon dioxide concentration reached 11.2 mg / L. Specific test data are shown in Tables 3 and 4.

[0080] Table 3

[0081]

[0082] Table 4

[0083]

[0084] Example 6

[0085] (1) Electrochemical treatment

[0086] The specific steps are: pumping the acid wastewater (pH value is 3.0, heavy metal ion concentration (Cu is 200 mg / L, Cd is 200 mg / L, Zn is 15 mg / L), inorganic carbon content is 0.2 mg / L) into the integrated electrochemical reaction device, wherein the anode of the electrochemical reaction device is loaded with limestone particles (particle size: 0.1-10 cm), the electrochemical reaction device is connected with a direct current power supply, the rated voltage is 3V, the rated current is 20mA, and the electrochemical treatment is carried out for 4h.

[0087] (2) Capture and fix carbon dioxide

[0088] The specific steps are: the alkaline solution treated by electrochemical treatment is pumped into the precipitation tank under the action of the pump, directly contacts with air, the high concentration of hydroxyl ions accelerates the dissolution of carbon dioxide in the air, and reacts with calcium ions in the solution to form calcium carbonate precipitate; after the carbon dioxide capture and fixation reaction, the concentration of hydroxyl ions in the solution decreases, the pH of the solution decreases to 8.0, reaches the "Surface Water Environmental Quality Standard", and is directly discharged.

[0089] Sampling tests are carried out during the treatment process, and the test results are shown in Table 5 as follows:

[0090] Table 5

[0091]

[0092] The cathode deposits heavy metals in the electrochemical device, and the deposition mass of each heavy metal is shown in Table 6:

[0093] Table 6

[0094]

[0095] As can be seen from Table 5, after electrochemical treatment, the pH of the solution increases to 9.4, the heavy metal ion concentration decreases to Cu 0.01 mg / L, Cd 0.01 mg / L, and Zn 0.01 mg / L, which meets the "Surface Water Environmental Quality Standard", and the calcium ion concentration is above 92 mg / L.

[0096] After combined treatment, the pH of the wastewater solution that can be discharged is finally maintained at 8.0, and the heavy metal ion concentration is also greatly reduced, so that Cu≤0.01 mg / L, Cd≤0.01 mg / L, and Zn≤0.01 mg / L, realizing zero pollution discharge of acid wastewater, and at the same time, achieving copper extraction rate of up to 99.3%, cadmium extraction rate of 99.1%, and zinc extraction rate of 95.1%, as shown in a of Figure 8 The calculation method of extraction rate: heavy metal extraction rate (%) = cathode deposition heavy metal mass / (treatment wastewater volume*initial heavy metal ion concentration in wastewater).

[0097] According to the change of inorganic carbon content, it is calculated that the solution captures 9.6 mg / L of the fixed carbon dioxide after the electrochemical treatment, as shown by b in the figure. Figure 8 It is shown that the acidic wastewater after the combined treatment of the application not only removes and recovers the harmful heavy metal elements, but also has good potential for carbon dioxide fixation.

[0098] It should be understood that the application of the application is not limited to the above examples, and those skilled in the art can improve or change according to the above description, and all these improvements and changes shall belong to the protection scope of the appended claims of the application.

Claims

1. A combined treatment method for acidic wastewater, characterized in that, Includes the following steps: Acidic wastewater generated during industrial processes is fed into an electrochemical device for electrochemical treatment to neutralize the acidic wastewater and extract heavy metals. Heavy metals are deposited at the cathode in the electrochemical device. The electrochemical device is an integrated electrochemical reaction device, which consists of a ruthenium-iridium plated rod-shaped titanium anode, non-metallic mineral material particles, a porous barrier for filling the non-metallic mineral material particles, and a stainless steel cathode. The anode is installed in the middle of the barrier, the non-metallic mineral material particles are directly filled in the barrier around the anode, and the cathode is installed on the outside of the barrier. The solution after electrochemical treatment is alkaline. After entering the air-exposed sedimentation tank, carbon dioxide in the air dissolves in the alkaline solution and reacts with calcium or magnesium ions to form calcium carbonate or magnesium carbonate precipitates, thereby capturing and fixing carbon dioxide. The final treated solution meets the "Surface Water Environmental Quality Standard" and is then directly discharged. The non-metallic mineral material is selected from one or more of limestone, dolomite, magnesia, wollastonite, and olivine.

2. The combined treatment method for acidic wastewater according to claim 1, characterized in that, The acidic wastewater has a pH of 1-5, a copper ion concentration of 10-200 mg / L, a cadmium ion concentration of 2-200 mg / L, and a zinc ion concentration of 15-300 mg / L.

3. The combined treatment method for acidic wastewater according to claim 1, characterized in that, The non-metallic mineral material is limestone particles with a particle size of 0.1-10 cm.

4. The combined treatment method for acidic wastewater according to claim 1, characterized in that, The conditions for the electrochemical treatment are: rated voltage of 2-15V, rated current of 10-100mA, and time of 1-15h.

5. The combined treatment method for acidic wastewater according to claim 1, characterized in that, In the heavy metal extraction, the extraction rate of copper was 99.3%-99.5%, the extraction rate of cadmium was 95.2%-99.1%, and the extraction rate of zinc was 90.9%-95.1%.

6. The combined treatment method for acidic wastewater according to claim 1, characterized in that, The solution after electrochemical treatment has a pH value of 7.0~10.5 and a calcium or magnesium ion concentration ≥2mM.

7. The combined treatment method for acidic wastewater according to claim 1, characterized in that, The electrochemically treated solution has a Cu ion concentration ≤ 0.01 mg / L, a Cd ion concentration ≤ 0.01 mg / L, and a Zn ion concentration ≤ 0.01 mg / L.

8. The combined treatment method for acidic wastewater according to claim 1, characterized in that, The pH of the treatment solution after carbon dioxide capture and fixation is 6.0-9.0.

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