Preparation method of flaky spherical manganese dioxide, obtained manganese dioxide and application thereof

Abstract

The present invention provides a preparation method of a flaky spherical manganese dioxide, the obtained manganese dioxide and its application. In the preparation method of the present application, the following steps are included: a manganese precursor and an alkali ion template are mixed with water respectively and the pH value is adjusted to 2-5 to obtain a manganese precursor aqueous solution and an alkali ion template aqueous solution, the alkali ion template aqueous solution is dripped into the manganese precursor aqueous solution and mixed, and calcined to obtain a manganese dioxide with a flaky spherical morphology; wherein the mixing temperature of the manganese precursor aqueous solution and the alkali ion template aqueous solution is 10-30 ° C, and the mixing time is 2-4 h; the calcination temperature is 300-500 ° C, the calcination time is 5-7 h, and the calcination preset heating rate is 10-20 ° C / min. The flaky spherical manganese dioxide obtained by the preparation method of the present application has a controllable flaky spherical morphology, has a large specific surface area, can effectively adsorb cobalt ions and nickel ions in the solution, and meets the development goals of green energy saving and environmental protection.

Description

Technical Field

[0001] The present invention relates to the technical field of metal oxide preparation, and in particular to a preparation method of flaky spherical manganese dioxide, the obtained manganese dioxide and applications. Background Art

[0002] Manganese dioxide is an important environmental material, widely used in heavy metal ion removal, organic pollutant degradation, and environmental catalysis. Manganese dioxide has a variety of morphologies, each with unique physical and chemical properties, making it suitable for diverse applications. Among them, flaky spherical manganese dioxide is a novel manganese dioxide material, its unique morphology and structure providing significant advantages for the adsorption and recovery of cobalt and nickel. As an important functional material, manganese dioxide has been widely used in the environmental field, and flaky spherical manganese dioxide represents an innovative improvement to the traditional manganese dioxide structure.

[0003] Co and Ni are important metals in the energy and alloy fields. Currently, wastewater and waste liquid pollution caused by Co and Ni ions has become a major issue in the environmental and resource fields. Manganese dioxide, as a material with adsorption properties, has the potential to recycle and remove Co and Ni under environmentally friendly conditions. Manganese dioxide with different morphologies has different specific surface areas, pore structures, and crystal structures, which affect its adsorption capacity and selectivity. Manganese dioxide with a spherical structure provides a larger specific surface area, increasing the opportunity for contact with target ions, thereby significantly improving adsorption capacity.

[0004] While progress has been made in the preparation and application of manganese dioxide, some limitations remain. Certain preparation methods may require expensive reagents or complex processing conditions, limiting their feasibility for large-scale production. Furthermore, the resulting manganese dioxide cannot be well shaped, and may be prone to aggregation, deactivation, or unstable performance, requiring further improvement and optimization.

[0005] In summary, there is an urgent need for a preparation method of flaky and spherical manganese dioxide, the obtained manganese dioxide and its application to solve the problems existing in the related technologies. Summary of the Invention

[0006] The main purpose of the present invention is to provide a method for preparing manganese dioxide, the obtained manganese dioxide and its application, so as to solve the technical problems in the related art such as high preparation cost, complex process and easy aggregation, deactivation or unstable performance of the obtained manganese dioxide.

[0007] To achieve the above object, the present invention provides a method for preparing flaky spherical manganese dioxide, comprising the following steps:

[0008] A manganese precursor and an alkali ion template are mixed with water respectively and the pH value is adjusted to 2-5 to obtain a manganese precursor aqueous solution and an alkali ion template aqueous solution. The alkali ion template aqueous solution is added dropwise into the manganese precursor aqueous solution for mixing, and calcined to obtain manganese dioxide with a flaky spherical morphology. The mixing temperature of the manganese precursor aqueous solution and the alkali ion template aqueous solution is 10-30°C, and the mixing time is 2-4h. The calcination temperature is 300-500°C, the calcination time is 5-7h, and the preset calcination heating rate is 10-20°C / min.

[0009] Preferably, the manganese precursor includes manganese sulfate or manganese chloride.

[0010] Preferably, the alkali ion template comprises sodium bicarbonate or potassium bicarbonate.

[0011] Preferably, the addition ratio of the manganese precursor, alkali ion template and water is (5-15) mmol: (40-80) mmol: (50-70) ml.

[0012] Preferably, after the calcination step, the calcined product is further washed and dried, wherein the washing step comprises washing with deionized water and anhydrous ethanol in sequence, repeatedly for 2-4 times, with each washing lasting 25-35 seconds.

[0013] Preferably, the drying method is low vacuum drying; the drying temperature is 60-80° C., and the drying vacuum is 1000-5000 Pa.

[0014] The beneficial effects of the present invention are:

[0015] The present invention provides a method for preparing manganese dioxide with low preparation cost and simple process. Manganese dioxide can be obtained by mixing a manganese precursor, an alkali ion template and water and then calcining the mixture. During the preparation process, manganese dioxide with a flaky spherical morphology can be obtained by simply controlling the appropriate mixing temperature, mixing time, calcination temperature and calcination time. In addition, since the pH value is adjusted to 2-5 during the preparation process, the phenomenon of manganese hydroxide precipitation caused by the hydrolysis of manganese ions during the mixing process is effectively reduced, thereby reducing the occurrence of manganese impurities in other valence states during the subsequent calcination process.

[0016] The present invention also provides manganese dioxide prepared by the above preparation method.

[0017] The beneficial effects of the present invention are:

[0018] The manganese dioxide prepared by the invention has a flaky spherical morphology and structure, has a large specific surface area, is not easy to aggregate and has stable performance.

[0019] The present invention also provides a manganese dioxide prepared by the above preparation method or the use of the above manganese dioxide in recovering heavy metal ions in waste liquid.

[0020] Preferably, the heavy metal ions include at least one of cobalt ions and nickel ions.

[0021] Preferably, the recovery step comprises: adjusting the pH value of the waste liquid to 3-6; adding manganese dioxide having a flaky spherical morphology; the addition concentration of the manganese dioxide is ≤0.5 g / L; separating the manganese dioxide from the waste liquid, and calculating the recovered cobalt ion amount and the recovered nickel ion amount.

[0022] The beneficial effects of the present invention are:

[0023] The manganese dioxide produced by the present invention has a large specific surface area, is not prone to aggregation, and has stable performance. It can effectively adsorb cobalt and nickel ions in the solution, achieving resource recycling and reducing heavy metal ion pollution to the environment, in line with the development goals of green energy conservation and environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0025] Figure 1 2 is a flow chart of a method for preparing manganese dioxide according to one embodiment of the present application, wherein MnSO4·2H2O represents manganese sulfate dihydrate, NaHCO3 represents sodium bicarbonate, and ε-MnO2 represents manganese dioxide having a flaky spherical morphology;

[0026] Figure 2 is an XRD pattern (X-ray diffraction pattern) of manganese dioxide according to one embodiment of the present application, wherein Intensity (au) represents intensity, 2Theta (degree) represents double the diffraction angle, and JCPDS files represent the PDF "JCPDS Files" issued by the Joint Conference on Powder Diffraction Standards.

[0027] Figure 3 1 is a SEM image (scanning electron microscope image) and a TEM image (transmission electron microscope image) of manganese dioxide according to one embodiment of the present application, wherein (a) is a SEM image and (b) is a TEM image;

[0028] Figure 4: This is an XPS diagram (X-ray photoelectron spectroscopy) of manganese dioxide according to an embodiment of the present application, wherein (a) is a Mn 3s diagram of manganese dioxide; (b) is an O1s diagram of manganese dioxide, ε represents the ε-MnO2 test, AOS represents the average oxidation state of manganese, Intensity (au) represents intensity, Binding energy represents binding energy, eV represents electron volt, and O represents the average oxidation state of manganese. vacancy Indicates the oxygen defect peak, O lattice represents the lattice oxygen peak;

[0029] Figure 5 This is a BET diagram (nitrogen adsorption and desorption diagram) of manganese dioxide according to one embodiment of the present application. Relative Pressure (P / P0) represents the relative partial pressure, and Quantity Adsorbed (cm 3 / g STP) represents the amount of nitrogen adsorption and desorption, Average pore size represents the average pore size, S BET represents the specific surface area;

[0030] Figure 6 This is a graph of the recovery efficiency of cobalt and nickel ions of manganese dioxide according to one embodiment of the present application, wherein Recoveryperformance represents the recovery efficiency of cobalt and nickel ions, Initialconcentration represents the initial concentration, Dosage represents the dosage of manganese dioxide, pH represents the acidity or alkalinity, μg represents micrograms, g represents grams, t represents time, Co represents cobalt, and Ni represents nickel;

[0031] Figure 7 This is a SEM-EDS image (scanning electron microscope-energy dispersive spectrometer spectrum) of commercially available manganese dioxide for comparison in this application.

[0032] The realization of the objectives, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0033] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0034] It should be noted that all directional indications (such as up, down, etc.) in the embodiments of the present invention are only used to explain the relative position relationship and movement status of various components in a certain specific posture. If the specific posture changes, the directional indication will also change accordingly.

[0035] In addition, the terms "first," "second," and so on, used in this disclosure are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, features specified as "first" or "second" may explicitly or implicitly include at least one of these features.

[0036] Moreover, the technical solutions between the various embodiments of the present invention may be combined with each other, but this must be based on the fact that ordinary technicians in this field can implement them. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0037] The present invention provides a method for preparing flaky spherical manganese dioxide, comprising the following steps:

[0038] A manganese precursor and an alkali ion template are mixed with water respectively and the pH value is adjusted to 2-5 to obtain a manganese precursor aqueous solution and an alkali ion template aqueous solution. The alkali ion template aqueous solution is added dropwise into the manganese precursor aqueous solution for mixing, and calcined to obtain manganese dioxide with a flaky spherical morphology. The mixing temperature of the manganese precursor aqueous solution and the alkali ion template aqueous solution is 10-30°C, and the mixing time is 2-4h. The calcination temperature is 300-500°C, the calcination time is 5-7h, and the preset calcination heating rate is 10-20°C / min.

[0039] The present invention provides a method for preparing manganese dioxide with low preparation cost and simple process. Manganese dioxide can be obtained by mixing a manganese precursor, an alkali ion template and water and then calcining the mixture. During the preparation process, manganese dioxide with a flaky and spherical morphology can be obtained by simply controlling the appropriate mixing temperature, mixing time, calcination temperature and calcination time. In addition, since the pH value is adjusted to 2-5 during the preparation process, the phenomenon of manganese hydroxide precipitation caused by hydrolysis of manganese ions during the mixing process is effectively reduced, and the occurrence of manganese impurities of other valence states during the subsequent calcination process is reduced.

[0040] By controlling the preset heating rate during the calcination process and the gas generation rate in the reaction system, the size of the obtained manganese dioxide can be increased on the one hand to avoid fragmentation due to excessive impact of the airflow; on the other hand, the risk of explosion due to a huge increase in gas pressure can be avoided, thereby improving the safety of the preparation.

[0041] The alkali ion template is allowed to react with the manganese precursor by dropwise addition to form a precipitate for collection, effectively controlling the reaction rate so that it reacts and precipitates gradually, rather than directly mixing and reacting quickly to avoid the formation of blocky precipitates.

[0042] In some embodiments, the manganese precursor includes manganese sulfate or manganese chloride. A manganese salt with good water solubility is selected as the raw material for preparing manganese dioxide so that it can be fully mixed with the complexing agent and alkali ion template in the subsequent preparation process to produce a manganese dioxide product with uniform texture and stable performance.

[0043] In some embodiments, the alkali ion template comprises sodium bicarbonate or potassium bicarbonate. The alkali ion templates used in the present invention are all inorganic acid salts, which will be separated from the product in the form of carbon dioxide, oxygen, and water during the subsequent calcination process, reducing the content of impurities in the final product and improving the performance stability of the obtained manganese dioxide. At the same time, due to the non-directional nature of the gas, the escape of carbon dioxide, oxygen, and water during the calcination process will cause the surface of the obtained manganese dioxide to produce a mesoporous structure with uniform pores, which can effectively increase the specific surface area of the manganese dioxide prepared by the preparation method of the present application and improve its adsorption capacity.

[0044] In addition, the lithium ions and sodium ions in the alkali ion template can be doped into manganese dioxide. Through the supporting effect of lithium ions and sodium ions, a good interlayer gap can be formed, making manganese dioxide not easy to aggregate and deactivate, and having stable performance and a large specific surface area.

[0045] In some embodiments, the addition ratio of the manganese precursor, alkali ion template, and water is (5-15) mmol: (40-80) mmol: (50-70) ml.

[0046] By controlling the appropriate ratio between the manganese precursor and the alkali ion template, the conversion rate of the manganese element can be improved. In addition, the amount of gas generated when the alkali ion template decomposes can be indirectly controlled. While increasing the number of mesoporous structures on the surface of manganese dioxide, the stability of the manganese dioxide structure is ensured to avoid fragility.

[0047] In some embodiments, after the calcination step, the calcined product is further washed and dried, wherein the washing step comprises washing with deionized water and anhydrous ethanol in sequence, repeated three times, with each washing lasting 25 to 35 seconds.

[0048] During the preparation process, impurities and unreacted organic and inorganic salts may remain. These impurities and residues may negatively impact the material's performance and application. Repeated washing with deionized water and anhydrous ethanol effectively removes these impurities and residues, improving product purity.

[0049] In some embodiments, the drying method is low vacuum drying; the drying temperature is 60-80° C., and the drying vacuum is 1000-5000 Pa.

[0050] It is worth noting that the last washing step is to rinse with anhydrous ethanol. After the washing step, anhydrous ethanol remains in the interlayer gaps of the manganese dioxide obtained in the present invention. By low vacuum drying, the anhydrous ethanol escapes from the surface of the manganese dioxide in the form of gas, while clearing the mesoporous structure on the surface of the manganese dioxide, thereby improving the adsorption capacity of the manganese dioxide.

[0051] The present invention also provides manganese dioxide prepared by the above preparation method.

[0052] The manganese dioxide prepared by the invention has a flaky spherical morphology and structure, has a large specific surface area, is not easy to aggregate and has stable performance.

[0053] The present invention also provides a manganese dioxide prepared by the above preparation method or the use of the above manganese dioxide in recovering heavy metal ions in waste liquid.

[0054] In some embodiments, the heavy metal ions include at least one of cobalt ions and nickel ions.

[0055] In some embodiments, the recovery step includes: adjusting the pH value of the waste liquid to 3-6; adding manganese dioxide with a flaky spherical morphology; the addition concentration of the manganese dioxide is ≤0.5g / L; separating the manganese dioxide from the waste liquid, and calculating the recovered cobalt ion amount and the recovered nickel ion amount.

[0056] The manganese dioxide produced by the present invention has a large specific surface area, is not prone to aggregation, and has stable performance. It can effectively adsorb cobalt and nickel ions in the solution, achieving resource recycling and reducing heavy metal ion pollution to the environment, in line with the development goals of green energy conservation and environmental protection.

[0057] Example 1

[0058] See also Figure 1 A method for preparing flaky spherical manganese dioxide comprises the following steps:

[0059] A manganese precursor (manganese sulfate) and an alkali ion template (sodium bicarbonate) were mixed with water respectively, and nitric acid was added to adjust the pH value to 3 to obtain a manganese precursor aqueous solution and an alkali ion template aqueous solution. The alkali ion template aqueous solution was added dropwise into the manganese precursor aqueous solution and mixed (the stirring method was magnetic stirring). The mixing temperature was 20°C and the mixing time was 3 hours. The calcination was carried out at a calcination temperature of 400°C and a calcination time of 6 hours. The preset heating rate for the calcination was 15°C / min.

[0060] After cooling, centrifugal separation is performed to obtain manganese dioxide with a flaky spherical structure;

[0061] The product was rinsed with deionized water and anhydrous ethanol three times in sequence, with each rinse lasting 30 seconds, to obtain manganese dioxide (ε-MnO2) with a flaky spherical morphology.

[0062] In this embodiment, the addition ratio of the manganese precursor, alkali ion template and water is 1:6g:60ml.

[0063] In this embodiment, the drying method is low vacuum drying; the drying temperature is 60° C., and the drying vacuum is 5000 Pa.

[0064] The reaction process is as follows:

[0065] Manganese sulfate reacts with sodium bicarbonate:

[0066] MnSO4+2NaHCO3→MnCO3+Na2SO4+H2O+CO2;

[0067] Manganese carbonate is calcined to form ε-MnO2:

[0068] 2MnCO3+O2→2ε-MnO2+2CO2;

[0069] When manganese sulfate and sodium bicarbonate are calcined under high temperature to generate ε-MnO2, the overall reaction process is as follows:

[0070] 4NaHCO3+2MnSO4+O2→2ε-MnO2+2Na2SO4+4CO2+2H2O.

[0071] The morphology and structure determination of the flaky spherical manganese dioxide prepared in the present application comprises the following steps:

[0072] 1. Characterization of the crystal structure of manganese dioxide

[0073] See also Figure 2 It can be seen that the crystals of manganese dioxide synthesized in this application are very close to the corresponding peak positions and intensities in the standard PDF card, and the

[100] crystal plane of ε-MnO2 is its dominant crystal plane, and its interlayer spacing is It has a lamellar stacked extruded spherical morphology.

[0074] 2. Characterization of manganese dioxide morphology

[0075] See also Figure 3 The manganese dioxide synthesized in this application has a spherical morphology with a particle size distribution of 0.5-2 μm. Electron microscopy also revealed that the manganese dioxide spheres are evenly distributed with no obvious agglomeration, which is beneficial for the subsequent recovery of cobalt and nickel ions.

[0076] 3. Determination of valence state and bonding structure of manganese dioxide

[0077] according to Figure 4 The average oxidation state (AOS) of Mn was calculated using Mn 3s, and it was found that ε-MnO2 was 3.58. In addition, the oxygen defect content of ε-MnO2 was found to be as high as 25.66% through O1s. Lower redox states and more oxygen defects are beneficial for providing more active sites for the recovery of cobalt and nickel ions, thereby improving recovery performance. The AOS of the ε-MnO2 prepared in this example is much less than 4, and there are many oxygen defects, indicating its great potential for the recovery of cobalt and nickel ions.

[0078] 4. Determination of specific surface area and pore structure of manganese dioxide

[0079] See also Figure 5 It can be seen that the specific surface area of manganese dioxide synthesized in this application is 114.95m 2 / g, with an average pore size of 7.89nm, and the pore size distribution mostly ranging from 2-20nm, which is a typical mesoporous structure. The manganese dioxide synthesized and prepared by this patented method has a high specific surface area. The larger specific surface area is conducive to providing more active sites for the adsorption and recovery of cobalt and nickel ions. In addition, the typical mesoporous structure of manganese dioxide can also promote the diffusion and fixation of cobalt and nickel ions, thereby enhancing their recovery performance.

[0080] Example 2

[0081] Study on the recovery performance of cobalt and nickel ions by flaky and spherical manganese dioxide

[0082] A sample solution (cobalt ion concentration of 10 mg / L and nickel ion concentration of 10 mg / L in the sample solution) was prepared by mixing 5 mg of the manganese dioxide prepared in Example 1 with 10 mL of the sample solution. The adsorption temperature was fixed at 30°C, the pH was adjusted to 3 with HNO3 and NaOH solutions, and the mixture was shaken in an oscillation box at 150 rpm for 4 h. The remaining cobalt ion concentration and nickel ion concentration in the sample solution were measured, and the cobalt ion recovery and nickel ion recovery were calculated.

[0083] The pH test instrument was a pH meter (pHS-3G, Shanghai Leici); the cobalt and nickel ion concentrations were analyzed and determined by an ICP-OES measuring instrument. The values of three different adsorption bands were taken, and the minimum RSDs were selected as the data reference.

[0084] Example 3: The difference from Example 2 is that the pH value is adjusted to 4 using HNO3 and NaOH solutions.

[0085] Example 4: The difference from Example 2 is that the pH value is adjusted to 5 using HNO3 and NaOH solutions.

[0086] Example 5: The difference from Example 2 is that the pH value is adjusted to 6 using HNO3 and NaOH solutions.

[0087] Comparative Example 1: The difference from Example 1 is that the manganese precursor (manganese sulfate) and the alkali ion template (potassium bicarbonate) are mixed with water separately, and nitric acid is added to adjust the pH to 3 to obtain a manganese precursor aqueous solution and an alkali ion template aqueous solution. After the alkali ion template aqueous solution is directly mixed with the manganese precursor aqueous solution, a large amount of flaky and flocculent substances are formed, rather than the desired individual particles. It is believed that this is because the two solutions are not mixed uniformly during the direct mixing process; and the direct mixing method has a too fast reaction rate, making it difficult to accurately control the occurrence and termination of the reaction; therefore, the local concentration exceeds saturation, the product precipitates rapidly, and individual manganese carbonate particles cannot be formed.

[0088] Comparative Example 2: Commercially available manganese dioxide.

[0089] Commercial manganese dioxide was purchased for comparison. Figure 7 As shown, commercially available manganese dioxide has no obvious crystal morphology and is a powder with a relatively coarse particle size (~5 μm) and a manganese content of 67.93%. The particles have no obvious impurities other than manganese and oxygen.

[0090] The recovery results of cobalt and nickel ions by manganese dioxide prepared in Examples 2-5 are shown in Table 1 and Figure 6 .

[0091] Table 1 Recovery results of cobalt and nickel ions by manganese dioxide obtained in Examples 2-5

[0092]

[0093]

[0094] From Table 1 and Figure 6 The data show that the stamen layer type manganese dioxide prepared by the present invention has very good recovery performance for cobalt and nickel ions. When pH = 3-6, the stamen layer type manganese dioxide prepared by the present invention has a cobalt ion recovery rate of 2060-3554 μg / g and a nickel ion recovery rate of 476-1990 μg / g.

[0095] The above technical solutions of the present invention are only preferred embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made by using the contents of the present invention's description and drawings under the technical concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A method for preparing flaky spherical manganese dioxide, characterized in that: The following steps are involved: A manganese precursor and an alkali ion template are mixed with water respectively and the pH value is adjusted to 2-5 to obtain a manganese precursor aqueous solution and an alkali ion template aqueous solution. The alkali ion template aqueous solution is added dropwise into the manganese precursor aqueous solution, mixed, and calcined to obtain manganese dioxide with a flaky spherical morphology. The mixing temperature of the manganese precursor aqueous solution and the alkali ion template aqueous solution is 10-30° C., the mixing time is 2-4 hours, the calcination temperature is 300-500° C., the calcination time is 5-7 hours, and the preset calcination heating rate is 10-20° C. / min. The manganese precursor includes manganese sulfate or manganese chloride; The alkali ion template includes sodium bicarbonate or potassium bicarbonate.

2. The preparation method according to claim 1, characterized in that The addition ratio of the manganese precursor, alkali ion template and water is (5-15) mmol: (40-80) mmol: (50-70) ml.

3. The preparation method according to claim 1, characterized in that After the calcination step, the calcined product is washed and dried. The washing step comprises washing with deionized water and anhydrous ethanol in sequence, repeatedly for 2-4 times, and each washing lasts for 25-35 seconds.

4. The preparation method according to claim 3, characterized in that The drying method is low vacuum drying; the drying temperature is 60-80° C., and the drying vacuum is 1000-5000 Pa.

5. Manganese dioxide obtained by the preparation method according to any one of claims 1 to 4.

6. Use of the manganese dioxide prepared by the preparation method according to any one of claims 1 to 4 or the manganese dioxide according to claim 5 in recovering heavy metal ions in waste liquid.

7. The use according to claim 6, characterized in that The heavy metal ions include at least one of cobalt ions and nickel ions.

8. The use according to claim 6, characterized in that The recovery step comprises: adjusting the pH value of the waste liquid to 3-6; adding manganese dioxide with a flaky spherical structure; the addition amount of the manganese dioxide is ≤0.5g / L; separating the manganese dioxide from the waste liquid, and calculating the recovered amount of cobalt ions and nickel ions.

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