METHOD FOR TREATING MANGANESE-COPPER MIXED SOLUTION

Abstract

A method for treating a manganese-copper mixed solution is disclosed, including the following steps: adjusting a pH value of the manganese-copper mixed solution to 6.5 to 7 to obtain a solution defined as a first solution; adding an oxidant into the first solution to obtain a solution defined as a second solution, where the oxidant reacts with Mn.sup.2+ at a pH value of 6.5 to 7 to generate MnO.sub.2; and collecting a first precipitate. This method is time-saving in separating manganese ions, and can recover high-purity manganese ions. The recovered waste liquid is treated by a simple method and causes little pollution to the environment.

Claims

1. A method for treating a manganese-copper mixed solution, comprising the steps of: adjusting a pH value of the manganese-copper mixed solution to 6.5 to 7 to obtain a solution defined as a first solution; adding an oxidant into the first solution to obtain a solution defined as a second solution, wherein the oxidant reacts with Mn.sup.2+ at a pH value of 6.5 to 7 to generate MnO.sub.2; and collecting a first precipitate.

2. The method for treating a manganese-copper mixed solution according to claim 1, wherein the step of adding an oxidant into the first solution to obtain a solution defined as a second solution, wherein the oxidant reacts with Mn.sup.2+ at a pH value of 6.5 to 7 to generate MnO.sub.2, further comprises: adding the oxidant based on an amount of substance of Mn.sup.2+, wherein a ratio of an amount of substance of the oxidant to the amount of substance of Mn.sup.2+ is 3:1 to 30:1.

3. The method for treating a manganese-copper mixed solution according to claim 1, wherein the oxidant comprises at least one of H.sub.2O.sub.2, ammonium dithionate (NH.sub.4).sub.2S.sub.2O.sub.3, hypochlorous acid, hypochlorite salt, chloric acid, chlorate salt, or chlorine water.

4. The method for treating a manganese-copper mixed solution according to claim 1, wherein the oxidant is H.sub.2O.sub.2, and a ratio of an amount of substance of H.sub.2O.sub.2 to an amount of substance of Mn.sup.2+ is 11:1 to 17:1.

5. The method for treating a manganese-copper mixed solution according to claim 1, wherein in the step of adding an oxidant into the first solution to obtain a solution defined as a second solution, wherein the oxidant reacts with Mn.sup.2+ at a pH value of 6.5 to 7 to generate MnO.sub.2, the oxidant is added dropwise into the first solution.

6. The method for treating a manganese-copper mixed solution according to claim 1, wherein the manganese-copper mixed solution is a waste liquid obtained by dealloying a copper-manganese alloy in a process of preparing an electrode plate or current collector of a battery.

7. The method for treating a manganese-copper mixed solution according to claim 1, wherein after the step of collecting a first precipitate, the method further comprises: collecting a third solution, wherein the third solution is a solution left after completion of collecting the first precipitate; adding a precipitant into the third solution, wherein the precipitant reacts with Mn.sup.2+ and Cu.sup.2+ to generate a second precipitate; separating the second precipitate from a fourth solution, wherein the fourth solution is a solution left after removing the second precipitate; adding a pH regulator into the fourth solution; and adjusting a pH value of the fourth solution to 7 to 9.

8. The method for treating a manganese-copper mixed solution according to claim 7, wherein an amount of the precipitant added is ABC, wherein A is 5% to 15%, B is an amount of substance of Mn.sup.2+ in the third solution, and C is a molar mass of the precipitant.

9. The method for treating a manganese-copper mixed solution according to claim 7, wherein the precipitant is a carbonate salt or an alkaline substance.

10. The method for treating a manganese-copper mixed solution according to claim 9, wherein the precipitant comprises at least one of Na.sub.2CO.sub.3, K.sub.2CO.sub.3, NaHCO.sub.3, or NaOH.

11. The method for treating a manganese-copper mixed solution according to claim 7, wherein the pH regulator comprises at least one of acetic acid, citric acid, or carbonic acid.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0032] By reading the following detailed description of exemplary embodiments, a person of ordinary skill in the art becomes clearly aware of various other advantages and benefits. The drawings are merely intended to illustrate the exemplary embodiments, but not to limit this application. In all the drawings, the same reference numeral represents the same component. In the drawings:

[0033] FIG. 1 is a flowchart of a method for treating a manganese-copper mixed solution according to some embodiments of this application; and

[0034] FIG. 2 is a flowchart of a method for treating a manganese-copper mixed solution according to some embodiments of this application, where the method includes treatment of a third solution.

DETAILED DESCRIPTION

[0035] Some embodiments of the technical solutions of this application are described in detail below with reference to the drawings. The following embodiments are merely intended as examples to describe the technical solutions of this application more clearly, but not intended to limit the protection scope of this application.

[0036] Unless otherwise defined, all technical and scientific terms used herein bear the same meanings as what is normally understood by a person skilled in the technical field of this application. The terms used herein are merely intended to describe specific embodiments but not to limit this application. The terms include and contain and any variations thereof used in the specification, claims, and brief description of drawings of this application are intended as non-exclusive inclusion.

[0037] In the description of some embodiments of this application, the technical terms first and second are merely intended to distinguish between different items but not intended to indicate or imply relative importance or implicitly specify the number of the indicated technical features, specific order, or order of precedence. In the description of some embodiments of this application, unless otherwise expressly specified, a plurality of means two or more.

[0038] Reference to an embodiment herein means that a specific feature, structure or characteristic described with reference to this embodiment may be included in at least one embodiment of this application. Reference to this term in different places in the specification does not necessarily represent the same embodiment, nor does it represent an independent or alternative embodiment in a mutually exclusive relationship with other embodiments. A person skilled in the art explicitly and implicitly understands that the embodiments described herein may be combined with other embodiments.

[0039] A manganese-copper alloy is a precision resistance alloy that exhibits a good piezoresistive effect and a small temperature coefficient of resistance, and is increasingly applied to the process of preparing an electrode plate and a current collector of a battery.

[0040] The applicant has noticed that in a process of preparing an electrode plate or current collector of a battery, a waste liquid obtained by dealloying a manganese-copper alloy contains a large amount of manganese ions and a small amount of copper ions. Both types of ions fail to meet the discharge standard specified in the Integrated Wastewater Discharge Standard and are not suitable for being directly discharged. In addition, the manganese ion content in the waste liquid is more than 1000 times that of the copper ion content. The price of manganese is relatively high. In order to reduce save cost, it is necessary to separate and recover the manganese ions in the waste liquid obtained by dealloying the manganese-copper alloy. The existing method for separating manganese ions typically adopts extraction technology. However, the extraction technology used for separating manganese ions and copper ions takes a long time, incurs a low recovery rate, and results in a low purity of the obtained manganese ions. In addition, an organic solution needs to be used in the extraction process, thereby making the waste liquid treatment process complicated and hardly compliant with the discharge standard.

[0041] To solve the above technical problems, this application provide a method for treating a manganese-copper mixed solution. In this method, the pH value of the waste liquid is adjusted to 6.5 to 7, and an oxidant is added to react with Mn.sup.2+ at this pH value to generate a MnO.sub.2 precipitate, so that Mn.sup.2+ is separated after completion of precipitation. After the oxidant is added according to the method provided in this application, Mn.sup.2+ is quickly precipitated, and then Mn.sup.2+ is separated. The operation steps are simple and take just a short time. Because Cu.sup.2+ does not react with the oxidant in an environment with a pH value of 6.5 to 7, the separated Mn.sup.2+ is of high purity. Moreover, in this method, no organic solvent is added, and the subsequent waste liquid treatment is simple and brings little pollution to the environment.

[0042] The following describes this application in detail with reference to drawings and embodiments.

[0043] The method for treating a manganese-copper mixed solution according to an embodiment of this application is applicable to any manganese-copper mixed solution, and is not limited to use in separating and recovering manganese ions from the waste liquid obtained by dealloying a manganese-copper alloy in a battery preparation process.

[0044] Referring to FIG. 1, according to some embodiments of this application, this application provides a method for treating a manganese-copper mixed solution. The method includes the following steps: [0045] Step (S1): adjusting a pH value of the manganese-copper mixed solution to 6.5 to 7 to obtain a solution defined as a first solution; [0046] Step (S2): adding an oxidant into the first solution to obtain a solution defined as a second solution, where the oxidant reacts with Mn.sup.2+ at a pH value of 6.5 to 7 to generate MnO.sub.2; and [0047] Step (S3): collecting a first precipitate.

[0048] In this application, in step (S1), the amount of manganese-copper mixed solution may be selected according to experimental situation and experimental conditions. The method for recovering manganese from the manganese-copper mixed solution according to this application works regardless of the amount of the manganese-copper mixed solution. As an example, the amount of the manganese-copper mixed solution may be 1 mL, 5 mL, 10 mL, 200 mL, 30 L, 50 L, 100 L, 300 L, 1 t, 5 t, 30 t, or the like, or a range formed by any two thereof, for example, 1 mL to 10 mL, 200 mL to 30 L, 50 L to 300 L, 1 t to 30 t, or the like.

[0049] In step (S1), the content ratio of Mn.sup.2+ to Cu.sup.2+ in the manganese-copper mixture is not limited. As an example, in the manganese-copper mixture, the content of Mn.sup.2+ may be greater than the content of Cu.sup.2+, the content of Mn.sup.2+ may be equal to the content of Cu.sup.2+, or, the content of Mn.sup.2+ may be less than the content of Cu.sup.2+. In a practical process of preparing an electrode plate or current collector of a battery, the manganese ion content in the waste liquid obtained by dealloying the manganese-copper alloy by means of hydrochloric acid (HCL) is more than 1000 times that of the copper ion content.

[0050] As an example, the pH value of the manganese-copper mixture is adjusted to 6.5 to 7. The pH value of the manganese-copper mixture may be adjusted to: 6.5, 6.6, 6.7, 6.8, 6.9, 7, or 6.52, 6.55, 6.75, 6.77, 6.78, 6.79, or the like, or a range formed by any two thereof, for example, 6.5 to 6.7, 6.8 to 7, 6.52 to 6.75, 6.77 to 6.79, or the like. The pH value may be set to an appropriate value according to actual needs as long as the pH value of the manganese-copper mixture falls within the range of 6.5 to 7.

[0051] The slightly acidic conditions with a pH value of 6.5 to 7 can reduce consumption of the oxidant such as H.sub.2O.sub.2 caused by the decomposition of the oxidant such as H.sub.2O.sub.2 as catalyzed by the MnO.sub.2 precipitate generated in the subsequent step (S2).

[0052] In the method for treating a manganese-copper mixed solution according to this application, the pH value of the waste liquid is adjusted to 6.5 to 7, and an oxidant is added to react with Mn.sup.2+ at this pH value to generate a MnO.sub.2 precipitate, so that Mn.sup.2+ is separated after completion of precipitation. In this method, after the oxidant is added, Mn.sup.2+ is quickly precipitated, and then Mn.sup.2+ is separated by separating the precipitate. The operation steps are simple and take just a short time. Because Cu.sup.2+ does not react with the oxidant at all in an environment with a pH value of 6.5 to 7, the separated Mn.sup.2+ is of high purity. By adjusting the pH value of the waste liquid, the method of this application makes the redox reaction between the oxidant and Mn.sup.2+ relatively thorough, thereby making the recovery rate of manganese ions relatively high.

[0053] In some embodiments, in step (S1), the pH value of the manganese-copper mixed solution is adjusted to 6.5 to 7 by using an alkaline solution. As an example, the alkaline solution includes, but is not limited to, a NaOH solution, a KOH solution, or the like.

[0054] In step (S2), the oxidant reacts with Mn.sup.2+ to generate MnO.sub.2 at a pH range of 6.5 to 7, without reacting with Cu.sup.2+.

[0055] In some embodiments, step (S2) further includes: adding the oxidant based on an amount of substance of Mn.sup.2+, where a ratio of an amount of substance of the oxidant to the amount of substance of Mn.sup.2+ is 3:1 to 30:1.

[0056] As an example, the amount of the oxidant added is: the ratio of the amount of substance of the oxidant to the amount of substance of Mn.sup.2+ may be 3:1, 4:1, 7:1, 10:1, 14:1, 19:1, 25:1, 30:1, or 3.2:1, 5.3:1, 7.4:1, 10.5:1, 14.6:1, 19.7:1, 25.8:1, 29.9:1, or the like, or a range formed by any two thereof, for example, 3:1 to 7:1, 10:1 to 14:1, 19:1 to 30:1, 3.2:1 to 7.4:1, 10.5:1 to 19.7:1, 25.8:1 to 29.9:1, or the like. This ratio may be set to an appropriate value according to actual needs as long as the ratio of the amount of substance of the oxidant to the amount of substance of Mn.sup.2+ is 3:1 to 30:1.

[0057] If the amount of oxidant added is excessively small, the Mn.sup.2+ in the manganese-copper mixed waste liquid will be separated to a deficient extent, and the recovery rate will be low. If the amount of oxidant added is excessively large, a waste of cost will occur. By controlling the ratio of the amount of substance of the added oxidant to the amount of substance of Mn.sup.2+ to fall within the range of 3:1 to 30:1, the largest possible amount of Mn.sup.2+ ions in the manganese-copper mixed liquid is made to react with the oxidant to form a precipitate, thereby separating Mn.sup.2+ to the greatest extent without causing cost waste.

[0058] In some embodiments, the oxidant includes at least one of H.sub.2O.sub.2, ammonium dithionate (NH.sub.4).sub.2S.sub.2O.sub.3, hypochlorous acid, hypochlorite salt, chloric acid, chlorate salt, or chlorine water.

[0059] The H.sub.2O.sub.2, (NH.sub.4).sub.2S.sub.2O.sub.3, hypochlorous acid, hypochlorite salt, chloric acid,

[0060] chlorate salt, and chlorine water in this application are all inorganic compounds, thereby making the subsequent waste liquid treatment process simpler, more cost-efficient, more effective, and more environment-friendly.

[0061] Understandably, the oxidant of this application is not limited to H.sub.2O.sub.2, ammonium dithionite (NH.sub.4).sub.2S.sub.2O.sub.4, hypochlorous acid, hypochlorite salt, chloric acid, chlorate salt, chlorine water, or another inorganic oxidant, as long as the inorganic oxide reacts with Mn.sup.2+ to generate MnO.sub.2 at a pH value of 6.5 to 7 without reacting with Cu.sup.2+.

[0062] In some preferred embodiments, the oxidant is H.sub.2O.sub.2, and a ratio of an amount of substance of H.sub.2O.sub.2 to an amount of substance of Mn.sup.2+ is 11:1 to 17:1.

[0063] Under alkaline conditions, the generated MnO.sub.2 catalyzes the decomposition of H.sub.2O.sub.2 (generates O.sub.2), thereby increasing the amount of H.sub.2O.sub.2 consumed. Therefore, in step (S1), a slightly acidic condition, that is, a pH value of 6.5 to 7, is selected to suppress the decomposition of H.sub.2O.sub.2.

[0064] By controlling the amount of the added H.sub.2O.sub.2 to the extent that the ratio of the amount of substance of H.sub.2O.sub.2 to the amount of substance of Mn.sup.2+ is 11:1 to 17:1, the recovery efficiency of H.sub.2O.sub.2 for Mn.sup.2+ in the manganese-copper mixed solution is up to 92% or higher.

[0065] In some embodiments, in step (S2), the oxidant is added dropwise into the first solution.

[0066] After being added into the manganese-copper mixture, the H.sub.2O.sub.2 reacts with Mn.sup.2+ to generate MnO.sub.2 first. The generated MnO.sub.2 acts as a catalyst to catalyze the decomposition of H.sub.2O.sub.2. If the H.sub.2O.sub.2 is added dropwise at an excessively high speed, the H.sub.2O.sub.2 will decompose in large quantities, thereby impairing the oxidation effect. With the oxidant added dropwise into the first solution, the decomposition of H.sub.2O.sub.2 can be alleviated, and the oxidation effect can be improved.

[0067] In some embodiments, the manganese-copper mixed solution is a waste liquid obtained by dealloying a copper-manganese alloy in a process of preparing an electrode plate or current collector of a battery.

[0068] The manganese ion content in the waste liquid obtained by dealloying the manganese-copper alloy during the preparation of the electrode plate or current collector of the battery is more than 1000 times that of the copper ion content. The manganese ions in the waste liquid obtained by dealloying the manganese-copper alloy are separated and recovered by the method of this application, thereby reducing the production cost of the battery and alleviating the pollution of manganese ion emissions to the environment.

[0069] Referring to FIG. 2, in some embodiments, after step (S3), the method further includes: [0070] Step (S4): collecting a third solution, where the third solution is a solution left after completion of collecting the first precipitate; adding a precipitant into the third solution, where the precipitant reacts with Mn.sup.2+ and Cu.sup.2+ to generate a second precipitate; separating the second precipitate from a fourth solution, where the fourth solution is a solution left after removing the second precipitate; adding a pH regulator into the fourth solution; and adjusting a pH value of the fourth solution to 7 to 9.

[0071] This step can remove Cu.sup.2+ and residual Mn.sup.2+ in the third solution after most of the Mn.sup.2+ ions are separated after step (S4), and neutralize OH, so that the waste liquid meets the requirements of the Integrated Wastewater Discharge Standard with respect to the contents of manganese ions, copper ions, and OH.sup..

[0072] In some embodiments, an amount of the precipitant added is ABC, where A is 5% to 15%, B is an amount of substance of Mn.sup.2+ in the third solution, and C is a molar mass of the precipitant.

[0073] As an example, the value of A may be 5%, 6%, 7%, 9%, 11%, 12%, 13%, 14%, 15%, or 5.5%, 6.5%, 7.5%, 9.5%, 11.5%, 12.5%, 13.5%, 14.5%, or the like, or a range formed by any two thereof, for example, 5% to 9%, 11% to 13%, 14% to 15%, 5.5% to 7.5%, 9.5% to 11.5%, 12.5% to 14.5%, or the like. the value of A may be set to an appropriate value according to actual needs as long as the value of A falls within the range of 5% to 15%.

[0074] The amount of the precipitant to be added may be calculated by measuring the amount of manganese ions and copper ions in the third solution. In contrast to the waste liquid obtained by dealloying the manganese-copper alloy, the amount of manganese ions in the third solution is still much greater than the amount of copper ions. Therefore, the amount of the precipitant to be added is calculated by using the amount of substance of manganese ions, and the calculated value is sufficient to precipitate the copper ions and manganese ions in the third solution.

[0075] In some embodiments, the precipitant is a carbonate salt or an alkaline substance.

[0076] The carbonate or alkaline substance added can implement rapid precipitation of Cu.sup.2+ and residual Mn.sup.2+ in the third solution, and incur few side reactions.

[0077] In addition, adding a carbonate salt to precipitate Cu.sup.2+ and residual Mn.sup.2+ in the third solution can reduce the introduction of OH.sup. to some extent, facilitate subsequent adjustment of the pH value of the waste liquid to 7 to 9, save the consumption of weak acid, reduce cost, and shorten operation time.

[0078] In some embodiments, the precipitant includes at least one of Na.sub.2CO.sub.3, K.sub.2CO.sub.3, NaHCO.sub.3, or NaOH.

[0079] The added Na.sub.2CO.sub.3, K.sub.2CO.sub.3, NaHCO.sub.3, and NaOH can implement rapid precipitation of Cu.sup.2+ and residual Mn.sup.2+ in the third solution, and incur few side reactions. In addition, the Na.sub.2CO.sub.3, K.sub.2CO.sub.3, NaHCO.sub.3, and NaOH are inexpensive, thereby reducing cost.

[0080] In some embodiments, the pH regulator includes at least one of acetic acid, citric acid, or carbonic acid.

[0081] The acetic acid, citric acid, and carbonic acid are weak acids, and can adjust the pH value more accurately.

[0082] In some embodiments, in step (S3) and step (S4), the first precipitate and the second precipitate may be collected by, but not limited to, filtration, centrifugation, or the like.

[0083] The following provides specific embodiments and comparative embodiments to describe the preparation process and test data of this application.

Embodiment 1

[0084] Step (S1): Taking 30 mL of waste liquid obtained by dealloying a manganese-copper alloy, and measuring the contents of Mn.sup.2+ and Cu.sup.2+ in the waste liquid, where the mass percent of Cu.sup.2+ in the total mass of the waste liquid is 0.04%, and the mass percent of Mn.sup.2+ in the total mass of the waste liquid is 7.94%; adding 2 mol/L NaOH solution to adjust the pH value of the waste liquid obtained by dealloying the manganese-copper alloy to 6.5 to 7, so as to obtain a first solution.

[0085] Step (S2): Adding 15 mL of 30% H.sub.2O.sub.2 dropwise into the first solution obtained in step (S1), so as to obtain a second solution.

[0086] Step (S3): Leaving the second solution in step (S2) to stand for one hour, and then filtering out a first precipitate, where the solution obtained after filtering out the first precipitate is a third solution.

[0087] Step (S4): Waste liquid treatment 1: adding Na.sub.2CO.sub.3 into the third solution obtained in step (S3), where the amount of Na.sub.2CO.sub.3 added is: 10%'amount of substance of Mn.sup.2+ in the third solution106 g, and then filtering out a second precipitate to obtain a fourth solution; waste liquid treatment 2: adding acetic acid dropwise into the fourth solution, and measuring the pH value of the waste liquid by using pH test paper until the pH value falls within the range of 7 to 9.

Embodiments 2 to 5

[0088] Embodiments 2 to 5 are substantially identical to Embodiment 1 except that the volume of H.sub.2O.sub.2 added in step (S2) in Embodiments 2 to 5 is different from that in Embodiment 1. Other steps in Embodiments 2 to 5 are identical to those in Embodiment 1, as detailed in Table 1.

Embodiment 6

[0089] Embodiment 6 is substantially identical to Embodiment 1 except that 60 mL of 250 mg/L hypochlorous acid is added in step (S2) in Embodiment 6. Other steps in Embodiment 6 are identical to those in Embodiment 1, as detailed in Table 1.

Comparative Embodiment 1

[0090] Step (B1): Taking 30 mL of waste liquid obtained by dealloying a manganese-copper alloy, and measuring the contents of Mn.sup.2+ and Cu.sup.2+ in the waste liquid, where the mass percent of Cu.sup.2+ in the total mass of the waste liquid is 0.04%, and the mass percent of Mn.sup.2+ in the total mass of the waste liquid is 7.94%. [0091] Step (B2): Adding 2 mol/L NaOH dropwise until no more precipitate is produced, and filtering the precipitate. [0092] Step (B3): Waste liquid treatment 1: Adding Na.sub.2CO.sub.3 into the solution obtained after filtering out the precipitate in step (S1), and then filtering the product; waste liquid treatment 2: adding acetic acid dropwise into the filtered waste liquid, and measuring the pH value of the waste liquid by using pH test paper until the pH value falls within the range of 7 to 9.

TABLE-US-00001 TABLE 1 Experimental conditions and test data of embodiments and comparative embodiments Hydrogen Ratio of amount In the waste liquid after step (S3) in Embodiments 1 peroxide content of substance of to 5 and after step (B2) in Comparative Embodiment 1 Serial or hypochlorous H.sub.2O.sub.2/hypochlorous Mass concentration Mass concentration number acid volume (mL) acid:Mn.sup.2+ of Cu.sup.2+ (mg/L) of Mn.sup.2+ (mg/L) Embodiment 1 15 3:1 10.5 14,229.98 Embodiment 2 30 6:1 10.4 11,314.38 Embodiment 3 60 12:1 10.3 7,722.65 Embodiment 4 90 18:1 10.6 7,086.39 Embodiment 5 150 29:1 10.5 7,388.67 Embodiment 6 60 8:1 10.4 10,571.77 Comparative / / / / Embodiment 1 Manganese In the waste liquid after step (S4) in Embodiments 1 ion to 5 and after step (B3) in Comparative Embodiment 1 Recovery Serial recovery Mass concentration Mass concentration efficiency number rate of Cu.sup.2+ (mg/L) of Mn.sup.2+ (mg/L) (final) Embodiment 1 85% 1.03 7.47 99.99% Embodiment 2 88% 1.06 5.53 99.99% Embodiment 3 92% 0.93 5.64 99.99% Embodiment 4 93% 0.99 3.72 100.00% Embodiment 5 92% 0.98 4.71 100.00% Embodiment 6 89% 1.00 5.99 99.99% Comparative / 0.82 1.02 100.00% Embodiment 1

[0093] As can be seen from the results of Embodiments 1 to 5 in Table 1, the recovery rate of Mn.sup.2+ increases with the increase of the amount of H.sub.2O.sub.2 added. When the amount of H.sub.2O.sub.2 added reaches 60 mL, the recovery rate of Mn.sup.2+ remains basically unchanged even if the amount of H.sub.2O.sub.2 added continues to increase, thereby reaching a balance of this reaction. As can be concluded from the test results in Table 1, Embodiment 3 is a preferred embodiment. After step (S3), the recovery rate of manganese ions reaches 92%, that is, 92% of manganese ions are recovered and highly pure. After step (S4), the recovery rate of manganese ions and copper ions reaches 99.99%, that is, the residual manganese ions and copper ions are efficiently recovered.

[0094] In Comparative Embodiment 1 versus Embodiment 3, the Cu ions and Mn ions in the waste liquid after step (B3) in Comparative Embodiment 1 are almost completely precipitated, with a recovery rate of approximately 100%. However, the Mn precipitate is unable to be distinguished from the Cu precipitate, and the effect of separating Mn and Cu is not achieved.

[0095] The results of Embodiment 6 show that when the oxidant is hypochlorous acid, the recovery rate of the manganese ions in the waste liquid obtained by dealloying a manganese-copper alloy reaches 89%, indicating that the recovery rate of manganese ions is also relatively high when the oxidant is hypochlorous acid.

[0096] As can be seen from the comparison between the embodiment and the comparative embodiment, in the method for treating a manganese-copper mixed solution according to this application, the pH value of the waste liquid is adjusted to the corresponding value, and an oxidant that reacts with Mn.sup.2+ but does not react with Cu.sup.2+ at this pH value is added so that a precipitate is produced and Mn.sup.2+ is separated. After the oxidant is added according to the method provided in this application, Mn.sup.2+ is quickly precipitated, and then Mn.sup.2+ is separated. The operation steps are simple and take just a short time. Because Cu.sup.2+ does not react with the oxidant at all, the separated Mn.sup.2+ is of high purity. The recovery rate of manganese is up to 92% or even higher, thereby achieving a relatively high recovery rate.

[0097] Moreover, in the method of this application, no organic solvent is added, and the waste liquid treatment is simple and brings little pollution to the environment. Furthermore, after the waste liquid in this application is treated, the Cu.sup.2+, Mn.sup.2+, and OH.sup. in the waste liquid substantially meet the requirements of the Integrated Wastewater Discharge Standard.

[0098] Finally, it is hereby noted that the foregoing embodiments are merely intended to describe the technical solutions of this application but not to limit this application. Although this application has been described in detail with reference to the foregoing embodiments, a person of ordinary skill in the art understands that modifications may still be made to the technical solutions described in the foregoing embodiments, or equivalent replacements may still be made to some or all technical features in the technical solutions. Such modifications and equivalent replacements fall within the scope of the claims and specification hereof without making the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of this application. Particularly, to the extent that no structural conflict exists, various technical features mentioned in different embodiments may be combined in any manner. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.