Combined treatment method for acid wastewater

Abstract

The invention relates to the technical field of sewage treatment, and discloses a combined treatment method of acid wastewater. The combined treatment method of the acid wastewater comprises the following steps: introducing the acid wastewater generated in an industrial process into an electrochemical device, loading a nonmetallic mineral material on an anode of the electrochemical device, and neutralizing the acid wastewater and extracting heavy metals through electrochemical treatment; the solution subjected to electrochemical treatment enters a sedimentation tank, carbon dioxide in the air is captured and fixed, and then the treated solution meeting the environmental quality standard for surface water is directly discharged. The acid wastewater treatment method is simple, efficient and easy to operate, meanwhile, heavy metal recovery is achieved, non-metallic minerals which are easy to obtain and environmentally friendly are introduced into the anode of the electrochemical device, hydrogen ions released in the electrolysis process are consumed, inhibition of the hydrogen ions on heavy metal deposition is reduced, and the extraction rate of the heavy metal in the wastewater is increased. And the solution subjected to electrochemical treatment is used for capturing and fixing the carbon dioxide, so that the treatment liquid is directly discharged.

Description

Technical Field

[0001] The invention relates to the technical field of sewage treatment, and in particular to a combined treatment method for acidic wastewater. Background Art

[0002] Acidic wastewater mainly comes from human activities such as chemical industry, electroplating, metal smelting and mining. According to statistics, billions to tens of billions of cubic meters of acidic wastewater are produced on average every year in the world. Its high acidity and strong corrosiveness can easily damage pipelines and infrastructure, and contain high concentrations of highly toxic heavy metals such as copper, cadmium, zinc, etc. If these wastewaters are discharged at will or improperly treated, they will seriously damage the self-purification capacity of the environment, have a negative impact on biological growth, and cause a large amount of valuable metal resources (such as copper, cadmium, zinc) to be wasted. At present, common treatment methods include neutralization precipitation, ion exchange, membrane separation and biological treatment. However, these methods are costly, have low treatment efficiency, are prone to secondary pollution, and cannot effectively recover metal resources in wastewater, which is inconsistent with the modern concept of sustainable development. For example, the widely used neutralization method usually requires the addition of expensive chemical reagents and produces a large amount of heavy metal-containing sludge, resulting in secondary pollution and waste of metal resources. In recent years, electrochemical method has attracted much attention as an emerging technology for treating acidic wastewater. It achieves neutralization and heavy metal removal in wastewater 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 acidic wastewater, which has become one of the bottlenecks in the development of technology. For example, the prior art (CN117865291A) treats acidic wastewater through an electrochemical membrane reactor and achieves neutralization and heavy metal removal, but the treatment process is complicated and requires additional costs for membrane configuration and replacement. The prior art (CN116282400A) treats acidic wastewater through a double-pulse low-voltage electrocoagulation method, achieving 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 of the invention

[0004] In view of the above-mentioned deficiencies in the prior art, the purpose of the present invention is to provide a combined treatment method for acidic wastewater, aiming to solve the problems of existing acidic wastewater treatment methods having high cost, low treatment efficiency, easy to cause secondary pollution, and inability to effectively recover metal resources in wastewater.

[0005] The technical solution of the present invention is as follows:

[0006] The present invention provides a combined treatment method for acidic wastewater, comprising the steps of:

[0007] The acidic wastewater generated in the industrial process is passed into an electrochemical device, the anode of the electrochemical device is loaded with non-metallic mineral materials, and the acidic wastewater is neutralized and heavy metals are extracted through electrochemical treatment;

[0008] The solution after electrochemical treatment enters the sedimentation tank, captures and fixes carbon dioxide in the air, and obtains a treated solution that meets the "Surface Water Environmental Quality Standards" and is directly discharged.

[0009] Optionally, the acidic 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, magnesia ore, 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 conditions of the electrochemical treatment are: rated voltage of 2-15V, rated current of 10-100mA, and time of 1-15h.

[0013] Optionally, in the extraction of the 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 combined treatment method for acidic wastewater, wherein the step of allowing the electrochemically treated solution to enter a sedimentation tank to capture and fix carbon dioxide in the air, is specifically: the electrochemically treated solution is alkaline, and after entering a sedimentation tank exposed to air, the carbon dioxide in the air dissolves in the alkaline solution, reacts with calcium or magnesium ions to form calcium carbonate or magnesium carbonate precipitates, and the carbon dioxide is captured and fixed, so that the final treated solution meets the "Surface Water Environmental Quality Standards" and is then directly discharged.

[0015] Optionally, the pH value of the solution after the electrochemical treatment is 7.0-10.5, and the concentration of calcium ions or magnesium ions is ≥2 mM.

[0016] Optionally, in the solution after the electrochemical treatment, the Cu ion concentration is ≤0.01 mg / L, the Cd ion concentration is ≤0.01 mg / L, and the Zn ion concentration is ≤0.01 mg / L.

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

[0018] Beneficial effects:

[0019] The present invention provides a combined treatment method for acidic wastewater that is simple, efficient, easy to operate, can achieve heavy metal recovery, and can capture and fix carbon dioxide. The present invention introduces cheap, easily available, and environmentally friendly non-metallic mineral materials into an electrochemical device, fixes them near the anode through a barrier, and can efficiently and continuously consume the hydrogen ions generated by the wastewater and the anode during the electrochemical treatment process, reducing the inhibition of hydrogen ions on heavy metal deposition, thereby enhancing the recovery effect of heavy metals in the wastewater. The pH of the solution after electrochemical treatment is alkaline, and combined with the high concentration of calcium and magnesium ions released by non-metallic minerals, it can directly capture carbon dioxide in the air, generate precipitation for fixation, and discharge a treatment solution that meets the "Surface Water Environmental Quality Standards". Compared with existing acidic wastewater treatment technologies, the present invention is simple and convenient to operate, and can achieve neutralization of acidic wastewater and in-situ recovery of heavy metals under the conditions of a single reaction device, and can achieve carbon fixation, with significant environmental benefit potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of the process of treating acidic wastewater provided by the present invention.

[0021] Figure 2 This is a schematic diagram of the electrochemical device used in the acidic wastewater treatment method of the present invention.

[0022] Figure 3 This is a diagram showing the results of heavy metal extraction from acidic wastewater after electrochemical treatment in Example 1 of the present invention.

[0023] Figure 4 This is a graph showing the cadmium extraction rate results of acidic wastewater with different initial cadmium ion concentrations after electrochemical treatment in Example 2 of the present invention.

[0024] Figure 5 This is a graph showing the cadmium extraction rate results after electrochemical treatment of acidic wastewater with different initial pH values ​​in Example 3 of the present invention.

[0025] Figure 6 This is a graph showing the changes in concentration of various heavy metal ions, changes in pH value, and the extraction of various heavy metals in the acidic wastewater discharged from the mine in Example 4 of the present invention after electrochemical treatment.

[0026] Figure 7 This is a result diagram of the change in pH value of the final treated liquid, heavy metal extraction and carbon dioxide capture and fixation after the acidic wastewater is subjected to combined treatment in Example 5 of the present invention.

[0027] Figure 8 This is a result diagram of heavy metal extraction rate and carbon dioxide capture and fixation after combined treatment of acidic wastewater in Example 6 of the present invention. DETAILED DESCRIPTION

[0028] The present invention provides a combined treatment method for acidic wastewater. To make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0029] Unless otherwise defined, all technical terms and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0030] The embodiment of the present invention provides a combined treatment method for acidic wastewater, comprising the steps of:

[0031] S1. Passing acidic wastewater generated in an industrial process into an electrochemical device, wherein the anode of the electrochemical device is loaded with non-metallic mineral materials, and the acidic wastewater is neutralized and heavy metals are extracted through electrochemical treatment;

[0032] S2. The electrochemically treated solution enters the sedimentation tank to capture and fix the carbon dioxide in the air, and then obtains a treated solution that meets the "Surface Water Environmental Quality Standards" and is directly discharged.

[0033] In step S1, in some embodiments, the acidic 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, magnesia ore, wollastonite, olivine and phosphogypsum. The non-metallic mineral material may 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 conditions of the electrochemical treatment are: rated voltage of 2-15V, rated current of 10-100mA, and time of 1-15h.

[0037] Water electrolysis technology uses direct current to decompose water into hydrogen and oxygen, and releases hydrogen ions and hydroxide ions at the anode and cathode. The hydroxide released at the cathode can consume the acidity (hydrogen ions) in the wastewater and increase the pH value of the acidic wastewater. 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 hydroxide generated at the cathode and compete with heavy metals for electrons, resulting in reduced wastewater neutralization efficiency and heavy metal extraction efficiency. Therefore, traditional electrochemical technology usually requires high energy consumption and complex structure and operation methods. The electrochemical treatment method for acidic wastewater provided by the present invention introduces the natural mineral limestone which is cheap, easy to obtain, environmentally friendly and has been widely used for acidic wastewater treatment. By fixing the limestone as a barrier near the anode to form an integrated electrochemical device, on the one hand, the wastewater and hydrogen ions released by the anode during the electrolysis process are efficiently and continuously consumed, so that the hydroxide generated by the cathode accumulates in the solution, and the pH value of the wastewater solution is increased, thereby reducing the inhibition of heavy metal deposition by hydrogen ions in the electrochemical process and enhancing the recovery effect of heavy metals in the wastewater. The greater the applied current and voltage, the higher the treatment efficiency. In the case 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 lowered 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 allowing the electrochemically treated solution to enter a sedimentation tank to capture and fix carbon dioxide in the air is specifically as follows: the electrochemically treated solution is alkaline, and after entering a sedimentation tank exposed to air, the 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, and the carbon dioxide is captured and fixed, so that the final treated solution meets the "Surface Water Environmental Quality Standards" and is then directly discharged.

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

[0041] In some embodiments, in the solution after the electrochemical treatment, the Cu ion concentration is ≤0.01 mg / L, the Cd ion concentration is ≤0.01 mg / L, and the Zn ion concentration is ≤0.01 mg / L. According to the Class V standard limit of the "Surface Water Environmental Quality Standard" (GB 3838-2002), copper is 1 mg / L, zinc is 2.0 mg / L, and cadmium is 0.01 mg / L. The standard for judging the water discharge is that the electrochemical treatment of the wastewater is completed when the heavy metal ions are reduced to the corresponding environmental quality standard concentration. It can be seen that after the present invention performs combined treatment on the acidic wastewater, the treated solution obtained meets the standard for direct discharge.

[0042] In some embodiments, the pH value of the treatment solution after capturing and fixing carbon dioxide is 6.0-9.0.

[0043] The following describes it in detail through specific embodiments.

[0044] Example 1

[0045] like Figure 1 The acid wastewater treatment process flow chart shown in FIG. 1 includes electrochemical treatment and carbon dioxide capture and fixation. The electrochemical treatment uses an integrated electrochemical reaction device, such as Figure 2 As shown, the integrated electrochemical reaction device consists of four parts: a rod-shaped titanium anode plated with ruthenium and 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, and the limestone particles are directly filled in the barrier around the anode, 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 electrochemical treatment of acidic wastewater are:

[0047] The acidic wastewater is introduced into the integrated electrochemical reaction device through a pump, and a direct current is applied to the electrochemical reaction device, with a rated voltage of 3V and a rated current of 20mA, and the electrochemical treatment is carried out for 5h. The initial pH value of the acidic wastewater is 1.5, and the metal ion concentrations contained in the acidic wastewater are: Cu is 10mg / L, Cd is 2mg / L, Zn is 300mg / L, and Ca is 73mg / L.

[0048] During the treatment process, samples were taken to test various indicators of the solution. The test results are shown in Table 1 below:

[0049] Table 1

[0050]

[0051] Heavy metals are deposited at the cathode in the electrochemical device. The deposition mass of each heavy metal is shown in Table 2:

[0052] Table 2

[0053]

[0054] It can be seen from Table 1 that the pH of the solution after the electrochemical treatment of this embodiment rises to 7.8, and the concentration of heavy metals is greatly reduced, making Cu≤0.01mg / L, Cd≤0.01mg / L, and Zn≤0.01mg / L, achieving zero pollution discharge and at the same time achieving the deposition of heavy metals at the cathode. The corresponding extraction rate is calculated according to the deposition mass of each heavy metal at the cathode of the electrochemical device, as shown in Figure 3 As shown, the results show that the electrochemical treatment of 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 calculation method of the extraction rate is as follows: heavy metal extraction rate (%) = mass of cathode deposited heavy metals / (volume of treated wastewater*initial heavy metal ion concentration in wastewater).

[0056] Example 2

[0057] Electrochemical Treatment of Acidic Wastewater with Different Initial Cadmium Ion Concentrations

[0058] Firstly, three solutions with a pH of 3.0 and cadmium ion concentrations of 2, 20, and 200 mg / L were selected as simulated acidic wastewaters. 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, to test the changes in pH value of the solution after electrochemical treatment and the extraction of cadmium.

[0059] Depend on Figure 4 As shown in the results, this embodiment increases the pH of acidic wastewater containing three different cadmium concentrations from 3.0 to 8.4, 9.7, and 9.3 respectively through electrochemical treatment, and at the same time, achieves cadmium extraction rates of 95.2%, 96.8%, and 98.0% respectively.

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

[0061] Example 3

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

[0063] Solutions with initial pH values ​​of 2.0, 3.0, and 4.0 and a cadmium ion concentration of 20 mg / L were selected as simulated acidic wastewater. Under the condition of providing an external constant current power supply (rated voltage 3V, rated current 20mA), the solutions were treated for 15, 4, and 2.5 hours, respectively, and the changes in pH values ​​of the solutions after electrochemical treatment and the extraction of cadmium were tested.

[0064] Depend on Figure 5 As shown in the results, this embodiment increases the pH of three different wastewaters from 2.0 to 7.8, from 3.0 to 9.7, and from 4.0 to 10.1 through electrochemical treatment, and at the same time, achieves cadmium extraction rates of 98.0%, 96.8%, and 95.3%, respectively.

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

[0066] Example 4

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

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

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

[0070] Example 5

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

[0072] Experimental Group:

[0073] (1) Electrochemical treatment

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

[0075] (2) Capture and fixation of carbon dioxide

[0076] The specific steps are: the alkaline solution that has undergone electrochemical treatment is pumped into the sedimentation tank, where it comes into direct contact with the air. The high concentration of hydroxide accelerates the dissolution of carbon dioxide in the air and reacts with calcium ions in the solution to form calcium carbonate precipitates. After carbon dioxide capture and fixation reaction, the hydroxide concentration in the solution decreases and the pH value of the solution drops to 7.8, meeting the "Surface Water Environmental Quality Standards" for direct discharge.

[0077] Comparison group:

[0078] The control group used an ordinary electrochemical device (calcium carbonate mineral particles were not set at the anode), and introduced a solution containing a pH of 3.0 and copper, cadmium, and zinc ion concentrations of 20 mg / L respectively as simulated acidic wastewater into the ordinary electrochemical reaction device for comparison. The electrochemical treatment was only carried out for 4 hours, and then the pH value changes and heavy metal extraction before and after the acidic wastewater treatment were tested.

[0079] The changes in pH value of the wastewater solution and the extraction of heavy metals after the two groups of treatments were compared. Figure 7 As shown in a and b in . It can be seen from the results that the electrochemical treatment method adopted in the embodiment of the present 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%. Among them, the calculation method of the extraction rate is: heavy metal extraction rate (%) = cathode deposited heavy metal mass / (volume of treated wastewater*initial heavy metal ion concentration in the wastewater). Figure 7 As shown in c, the captured and fixed carbon dioxide reaches 11.2 mg / L. The specific test data are shown in Tables 3 and 4.

[0080] Table 3

[0081]

[0082] Table 4

[0083] Cu(mg) Cd(mg) Zn(mg) Heavy metal mass at the cathode after the control group treated 1 liter of wastewater 19.8 0.2 0.1 Heavy metal mass at the cathode after the experimental group treated 1 liter of wastewater 19.9 19.8 18.8

[0084] Example 6

[0085] (1) Electrochemical treatment

[0086] The specific steps are: pumping acidic wastewater (pH value of 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 an integrated electrochemical reaction device, wherein the anode of the electrochemical reaction device is loaded with limestone particles (particle size: 0.1-10 cm), and the electrochemical reaction device is connected to a DC power supply with a rated voltage of 3V and a rated current of 20mA, and electrochemical treatment is carried out for 4 hours.

[0087] (2) Capture and fixation of carbon dioxide

[0088] The specific steps are: the alkaline solution that has undergone electrochemical treatment is pumped into the sedimentation tank, where it comes into direct contact with the air. The high concentration of hydroxide accelerates the dissolution of carbon dioxide in the air and reacts with calcium ions in the solution to form calcium carbonate precipitates. After carbon dioxide capture and fixation reaction, the hydroxide concentration in the solution decreases and the pH value of the solution drops to 8.0, meeting the "Surface Water Environmental Quality Standards" for direct discharge.

[0089] Sampling tests were carried out during the processing, and the test results are shown in Table 5 below:

[0090] Table 5

[0091] Solution pH Cu(mg / L) Cd(mg / L) Zn(mg / L) Ca(mg / L) Inorganic carbon (mg / L) Acidic wastewater 3.0 200 200 15 0 0.2 Electrochemically treated solution 9.4 0.01 0.01 0.01 92 49.2 Water is discharged after capturing and fixing carbon dioxide 8.0 0.01 0.01 0.01 80 55.2

[0092] Heavy metals are deposited at the cathode in the electrochemical device. The deposition mass of each heavy metal is shown in Table 6:

[0093] Table 6

[0094] Heavy metal deposition Cu(mg) Cd(mg) Zn(mg) Heavy metal mass at the cathode of 1 liter of wastewater treated by electrochemical treatment 9.9 1.9 272.7

[0095] As can be seen from Table 5, after electrochemical treatment, the pH of the solution increased to 9.4, and the heavy metal ion concentration decreased to 0.01 mg / L for Cu, 0.01 mg / L for Cd, and 0.01 mg / L for Zn, which met the "Surface Water Environmental Quality Standards", and the calcium ion concentration was above 92 mg / L.

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

[0097] Calculated based on the change in inorganic carbon content, such as Figure 8 As shown in b, the solution captured and fixed 9.6 mg / L of carbon dioxide after electrochemical treatment, indicating that the acidic wastewater after the combined treatment of the present invention not only removed and recovered harmful heavy metal elements, but also had good potential for carbon dioxide fixation.

[0098] It should be understood that the application of the present invention is not limited to the above examples. For ordinary technicians in this field, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A combined treatment method for acidic wastewater, characterized in that: Includes steps: The acidic wastewater generated in the industrial process is passed into an electrochemical device, the anode of the electrochemical device is loaded with non-metallic mineral materials, and the acidic wastewater is neutralized and heavy metals are extracted through electrochemical treatment; The solution after electrochemical treatment enters the sedimentation tank, captures and fixes carbon dioxide in the air, and obtains a treated solution that meets the "Surface Water Environmental Quality Standards" and is directly discharged.

2. The combined treatment method for acidic wastewater according to claim 1, characterized in that: The acidic 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.

3. The combined treatment method for acidic wastewater according to claim 1, characterized in that: The non-metallic mineral material is selected from one or more of limestone, dolomite, magnesia ore, wollastonite, olivine and phosphogypsum.

4. 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.

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

6. The electrochemical treatment method for acidic wastewater according to claim 1, characterized in that: In the extraction of the 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%.

7. The combined treatment method for acidic wastewater according to claim 1, characterized in that: The step of allowing the electrochemically treated solution to enter a sedimentation tank to capture and fix carbon dioxide in the air is specifically as follows: the electrochemically treated solution is alkaline, and after entering a sedimentation tank exposed to air, 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, capturing and fixing carbon dioxide, and directly discharging the final treated solution after it meets the "Surface Water Environmental Quality Standards".

8. The combined treatment method for acidic wastewater according to claim 7, characterized in that: The pH value of the solution after the electrochemical treatment is 7.0-10.5, and the concentration of calcium ions or magnesium ions is ≥2mM.

9. The combined treatment method for acidic wastewater according to claim 7, characterized in that: In the solution after the electrochemical treatment, the Cu ion concentration is ≤0.01 mg / L, the Cd ion concentration is ≤0.01 mg / L, and the Zn ion concentration is ≤0.01 mg / L.

10. The combined treatment method for acidic wastewater according to claim 7, characterized in that: The pH value of the treatment solution after the carbon dioxide is captured and fixed is 6.0-9.0.

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