Step-by-step removal method for heavy metals nickel, cobalt and manganese in ammonia-containing wastewater

Abstract

The invention provides a step-by-step removal method for heavy metal nickel, cobalt and manganese in ammonia-containing wastewater. The step-by-step removal method comprises the following steps: firstly, removing the heavy metal nickel and cobalt through a first precipitation reaction, then adding an oxidant, removing the heavy metal manganese through a second precipitation reaction, and finally, obtaining a gypsum product through a third precipitation reaction. According to the step-by-step removal method, the ammonia-containing wastewater containing nickel, cobalt and manganese metal ions is subjected to step-by-step treatment, heavy metal nickel and cobalt are removed firstly, then manganese is removed through an oxidation method, the heavy metal manganese ions can be efficiently removed, the quality of gypsum is improved, a new thought is provided for treatment of the ammonia-containing wastewater, and the situation that due to a conventional process, the cost is low can be avoided. The total discharged heavy metal concentration of the wastewater exceeds the standard; and the gypsum quality is poor.

Description

Technical Field

[0001] The invention relates to the field of heavy metal wastewater treatment, and in particular to a step-by-step removal method for heavy metals nickel, cobalt and manganese in ammonia-containing wastewater. Background Art

[0002] In the recycling process of regenerating cobalt and nickel resources, the leaching liquid of cobalt and nickel waste undergoes a series of extraction reactions to obtain a finished nickel and cobalt sulfate liquid. The finished liquid evaporates and crystallizes to obtain battery-grade nickel sulfate or cobalt sulfate crystals as battery raw materials. The raffinate generated during the extraction and purification process is used as wastewater and needs to be further recovered and purified and discharged after meeting the emission standards. The traditional extraction process uses liquid alkali and extractants to carry out saponification reactions. The large amount of liquid alkali used increases production costs. At the same time, the high salt content of the raffinate will increase the downstream water treatment load.

[0003] In order to reduce production costs and reduce wastewater emissions, the prior art discloses a process of replacing sodium with ammonia, using ammonia water instead of liquid alkali for saponification, and then transferring ammonia to soap-transforming wastewater through a soap-transforming process, and recycling the heavy metals, sulfate and ammonia in the soap-transforming wastewater to achieve the purpose of reducing production costs and reducing emissions. CN108928985A discloses a recycling process for wastewater containing cobalt and nickel heavy metal ions, including heavy metal recovery, solid-liquid separation, primary filtration, SO4 removal, etc. 2- , primary cyclone separation, gypsum drying, re-precipitation, stripping, tertiary precipitation, re-filtration, and neutralization process. The present invention uses ammonia water instead of NaOH to reduce the production cost of the enterprise and the salt content of the discharged water; reuse heavy metals cobalt and nickel; recycle ammonia; generate income from gypsum sales; and achieve standard discharge of wastewater. Add precision filtration and other processes, use multiple precipitations, multiple filtrations and other processes, deeply recover heavy metals such as cobalt, nickel, and manganese, so that the salt content of the discharged wastewater is lower and the concentration of heavy metal ions is lower, so as to achieve the recycling of heavy metal ions and the harmless discharge of wastewater. After being treated by this process, the wastewater NH4 + 、Co 2+ 、Ni 2+ 、SO4 2- The concentrations were reduced from 27.32 g / L, 55.49 mg / L, 60-65 mg / L, and 103.62 g / L to 15 mg / L, 1 mg / L, 1 mg / L, and almost completely recovered.

[0004] At present, the main components of the soap-transforming wastewater obtained by nickel-cobalt hydrometallurgy are ammonium sulfate and a small amount of heavy metal nickel and cobalt ions (Ni 100-1000 mg / L, Co 5-50 mg / L). The conventional process is to return the heavy metals to the leaching system after adding sulfide precipitation, and then add lime to generate calcium sulfate, and the remaining ammonia water enters the stripping tower for deammoniation. However, after research, the inventor found that when the nickel sulfate solution used for soap-transforming contains trace manganese ions (Mn20-200 mg / L), trace manganese ions enter the soap-transforming wastewater after soap-transforming. Due to the presence of ammonia nitrogen in the soap-transforming wastewater, the low-valent manganese ions cannot be completely precipitated during the process of adding sulfide to remove weight. On the one hand, the total heavy metal concentration of the wastewater exceeds the standard. On the other hand, the residual impurity ions will cause poor quality of gypsum, affecting the use of downstream customers.

[0005] Therefore, it is necessary to develop a step-by-step removal method for the heavy metals nickel, cobalt and manganese in ammonia-containing wastewater, especially one that can effectively remove manganese ions. Summary of the invention

[0006] In view of the problems existing in the prior art, the present invention provides a step-by-step method for removing heavy metals nickel, cobalt and manganese from ammonia-containing wastewater, comprising: first removing heavy metals nickel and cobalt through a first precipitation reaction, then adding an oxidant, removing heavy metal manganese through a second precipitation reaction, and finally obtaining a gypsum product through a third precipitation reaction. The step-by-step removal method of the present invention treats ammonia-containing wastewater containing nickel, cobalt and manganese metal ions in steps, first removing heavy metals nickel and cobalt, and then removing manganese by oxidation, which can achieve efficient removal of heavy metal manganese ions, improve the quality of gypsum, provide a new idea for the treatment of ammonia-containing wastewater, and avoid the problems of excessive total heavy metal concentration in wastewater and poor gypsum quality caused by conventional processes.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] The object of the present invention is to provide a step-by-step method for removing heavy metals nickel, cobalt and manganese from ammonia-containing wastewater, the step-by-step removal method comprising the following contents:

[0009] (1) adding a precipitant to the ammonia-containing wastewater, controlling the pH to 6 to 8, and performing a first precipitation reaction. After the reaction is completed, adding a flocculant, and performing solid-liquid separation to obtain a first de-weighted liquid and a first de-weighted residue;

[0010] (2) adding an oxidant to the first deweighting liquid of step (1), adjusting the pH to 8 to 10, and performing a second precipitation reaction. After the reaction is completed, performing solid-liquid separation to obtain a second deweighting liquid and a second deweighting residue;

[0011] (3) adding lime milk to the second deweighting liquid in step (2), adjusting the pH to carry out a third precipitation reaction, and after the reaction is completed, performing solid-liquid separation to obtain a gypsum product and a mother liquor.

[0012] The step-by-step removal method of the present invention treats ammonia-containing wastewater containing nickel, cobalt and manganese metal ions in steps. Since ammonia nitrogen exists in the wastewater, low-valent manganese ions cannot be completely removed by traditional precipitants. Therefore, nickel and cobalt are removed first, and then manganese is removed by oxidation. This can achieve step-by-step and efficient removal of heavy metal nickel, cobalt and manganese ions, improve the quality of gypsum, and provide a new idea for the treatment of ammonia-containing wastewater.

[0013] In the present invention, a precipitant is added to the ammonia-containing wastewater to control the pH to 6 to 8, such as 6, 6.5, 7, 7.5 or 8. It should be noted that, generally, the pH of the ammonia-containing wastewater is 6 to 8 and no adjustment is required.

[0014] In the present invention, an oxidant is added to the first deweighting liquid in step (1) to adjust the pH to 8 to 10, such as 8, 8.5, 9, 9.5 or 10.

[0015] As a preferred technical solution of the present invention, the ammonia-containing wastewater in step (1) includes any one of the nickel-cobalt P204 extraction line, the nickel-cobalt P507 extraction line or the nickel-cobalt C272 extraction line soap solution, or a mixture of at least two of them.

[0016] As a preferred technical solution of the present invention, the precipitant in step (1) includes any one of sodium sulfide, ammonium sulfide, sodium hydrosulfide, ammonium hydrosulfide or hydrogen sulfide gas, or a combination of at least two thereof.

[0017] Preferably, the amount of the precipitant added in step (1) is 300 to 1000 g / m 3 , for example 300g / m 3 , 400g / m 3 , 500g / m 3 , 600g / m 3 , 700g / m 3 , 800g / m 3 , 900g / m 3 or 1000g / m 3 wait.

[0018] Preferably, the amount of flocculant added in step (1) is 1 to 5 kg / m 3 , for example 1kg / m 3 , 2kg / m 3 , 3kg / m 3 , 4kg / m 3 or 5kg / m 3 wait.

[0019] It should be noted that the amount of precipitant and flocculant added in step (1) of the present invention is relative to the unit volume of ammonia-containing wastewater, and the specific added mass is determined based on the theoretical amount of nickel and cobalt concentration in the ammonia-containing wastewater.

[0020] As a preferred technical solution of the present invention, the reaction time of the first precipitation reaction in step (1) is 2 to 6 h, for example, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h, 5.5 h or 6 h, and the reaction temperature is 30 to 60 ° C, for example, 30 ° C, 35 ° C, 40 ° C, 45 ° C, 50 ° C, 55 ° C or 60 ° C, etc.

[0021] As a preferred technical solution of the present invention, the pH adjustment in step (2) is carried out using ammonia water or liquid alkali.

[0022] As a preferred technical solution of the present invention, the oxidant in step (2) includes any one of air, oxygen, ozone or hydrogen peroxide.

[0023] As a preferred technical solution of the present invention, the amount of the oxidant added in step (2) is 5 to 10 times the theoretical amount of manganese oxide ions, for example, 5 times, 6 times, 7 times, 8 times, 9 times or 10 times.

[0024] As a preferred technical solution of the present invention, the reaction time of the second precipitation reaction in step (2) is 2 to 6 h, for example, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h, 5.5 h or 6 h, and the reaction temperature is 30 to 60 ° C, for example, 30 ° C, 35 ° C, 40 ° C, 45 ° C, 50 ° C, 55 ° C or 60 ° C, etc.

[0025] As a preferred technical solution of the present invention, the pH of the third precipitation reaction in step (3) is 11.5-12.5, for example, 11.5, 11.8, 12, 12.1, 12.3 or 12.5, and the reaction time is 2-6h, for example, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h or 6h.

[0026] As a preferred technical solution of the present invention, the step-by-step removal method includes the following contents:

[0027] (1) adding a precipitant to the ammonia-containing wastewater, controlling the pH to 6 to 8, performing a first precipitation reaction, the reaction time to 2 to 6 hours, the reaction temperature to 30 to 60° C., adding a flocculant after the reaction is completed, and performing solid-liquid separation to obtain a first de-heavy liquid and a first de-heavy residue;

[0028] The ammonia-containing wastewater includes any one of the nickel-cobalt P204 extraction line, the nickel-cobalt P507 extraction line or the nickel-cobalt C272 extraction line soap solution or a mixture of at least two of them; the precipitant includes any one of sodium sulfide, ammonium sulfide, sodium hydrosulfide, ammonium hydrosulfide or hydrogen sulfide gas or a combination of at least two of them; the addition amount of the precipitant is 300-1000 g / m 3 The amount of flocculant added is 1 to 5 kg / m 3;

[0029] (2) adding an oxidant to the first deweighting liquid of step (1), controlling the amount of the oxidant added to be 5 to 10 times the theoretical amount of manganese oxide ions, adjusting the pH to 8 to 10 using ammonia water or liquid alkali, and performing a second precipitation reaction, the reaction time is 2 to 6 hours, the reaction temperature is 30 to 60° C., and after the reaction is completed, performing solid-liquid separation to obtain a second deweighting liquid and a second deweighting residue;

[0030] Wherein, the oxidant includes any one of air, oxygen, ozone or hydrogen peroxide;

[0031] (3) adding lime milk to the second deweighting liquid of step (2), adjusting the pH to carry out a third precipitation reaction, wherein the pH is 11.5 to 12.5, and the reaction time is 2 to 6 hours. After the reaction is completed, solid-liquid separation is carried out to obtain a gypsum product and a mother liquor.

[0032] It should be noted that the first heavy residue removed in step (1) and the second heavy residue removed in step (2) are returned to the leaching process as raw materials for recovering nickel, cobalt and manganese.

[0033] It should be noted that in step (3), the solid obtained by the solid-liquid separation is filtered and acid washed to obtain a gypsum product.

[0034] It should be noted that in step (3), the mother liquor enters the ammonia water recovery system.

[0035] Compared with the prior art solutions, the present invention has at least the following beneficial effects:

[0036] The step-by-step removal method of the present invention treats ammonia-containing wastewater containing nickel, cobalt and manganese metal ions in steps, first removing heavy metal nickel and cobalt, and then removing manganese by oxidation, which can achieve efficient removal of heavy metal manganese ions and improve the quality of gypsum, providing a new idea for the treatment of ammonia-containing wastewater, and avoiding the problems of excessive heavy metal concentration in total discharged wastewater and poor gypsum quality caused by conventional processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a schematic flow chart of the step-by-step removal method of heavy metals nickel, cobalt and manganese in ammonia-containing wastewater described in Example 1 of the present invention. DETAILED DESCRIPTION

[0038] The technical solution of the present invention is further described below with reference to the accompanying drawings and through specific implementation methods.

[0039] To better illustrate the present invention and facilitate understanding of the technical solution of the present invention, typical but non-limiting embodiments of the present invention are as follows:

[0040] Example 1

[0041] This embodiment provides a step-by-step method for removing heavy metals nickel, cobalt and manganese from ammonia-containing wastewater, wherein the ammonia-containing wastewater is an extraction line-converted soap solution, and the step-by-step removal method includes the following contents:

[0042] (1) Sodium sulfide was added as a precipitant to ammonia-containing wastewater with a pH of 6 to 8. The amount of precipitant added was 600 g / m 3 The first precipitation reaction was carried out for 4 hours at a temperature of 45°C. After the reaction was completed, anionic polyacrylamide with a molecular weight of 12 million was added as a flocculant. The amount of flocculant added was 3 kg / m 3 , through solid-liquid separation, a first de-weighted liquid and a first de-weighted residue are obtained;

[0043] (2) adding hydrogen peroxide as an oxidant to the first deweighting liquid of step (1), controlling the amount of the oxidant added to be 8 times the theoretical amount of manganese oxide ions, adjusting the pH to 9.26 with liquid alkali, and performing a second precipitation reaction, the reaction time is 4 hours, the reaction temperature is 45° C., and after the reaction is completed, performing solid-liquid separation to obtain a second deweighting liquid and a second deweighting residue;

[0044] (3) adding lime milk to the second deweighting liquid of step (2), adjusting the pH to carry out a third precipitation reaction, the pH being 12.02, the reaction time being 4 hours, and after the reaction is completed, performing solid-liquid separation to obtain a gypsum product and a mother liquor.

[0045] Example 2

[0046] This embodiment provides a step-by-step method for removing heavy metals nickel, cobalt and manganese from ammonia-containing wastewater, wherein the ammonia-containing wastewater is an extraction line-converted soap solution, and the step-by-step removal method includes the following contents:

[0047] (1) Sodium hydrosulfide was added as a precipitant to ammonia-containing wastewater with a pH of 6 to 8. The amount of precipitant added was 300 g / m 3 The first precipitation reaction was carried out for 2 hours at a temperature of 30°C. After the reaction was completed, anionic polyacrylamide with a molecular weight of 12 million was added as a flocculant. The amount of flocculant added was 1 kg / m 3 , through solid-liquid separation, a first de-weighted liquid and a first de-weighted residue are obtained;

[0048] (2) adding oxygen as an oxidant to the first deweighting liquid of step (1), controlling the amount of the oxidant added to be 5 times the theoretical amount of manganese oxide ions, adjusting the pH to 8.47 with liquid alkali, and performing a second precipitation reaction, the reaction time is 2 hours, the reaction temperature is 30° C., and after the reaction is completed, performing solid-liquid separation to obtain a second deweighting liquid and a second deweighting residue;

[0049] (3) adding lime milk to the second deweighting liquid in step (2), adjusting the pH to carry out a third precipitation reaction, the pH being 11.83, the reaction time being 2 h, and after the reaction is completed, performing solid-liquid separation to obtain a gypsum product and a mother liquor.

[0050] Example 3

[0051] This embodiment provides a step-by-step method for removing heavy metals nickel, cobalt and manganese from ammonia-containing wastewater, wherein the ammonia-containing wastewater is an extraction line-converted soap solution, and the step-by-step removal method includes the following contents:

[0052] (1) Add ammonium hydrogen sulfide as a precipitant to ammonia-containing wastewater with a pH of 6 to 8. The amount of precipitant added is 1000 g / m 3 The first precipitation reaction was carried out for 6 hours at a temperature of 60°C. After the reaction was completed, anionic polyacrylamide with a molecular weight of 12 million was added as a flocculant. The amount of flocculant added was 5 kg / m 3 , through solid-liquid separation, a first de-weighted liquid and a first de-weighted residue are obtained;

[0053] (2) adding hydrogen peroxide as an oxidant to the first deweighting liquid of step (1), controlling the amount of the oxidant added to be 10 times the theoretical amount of manganese oxide ions, adjusting the pH to 9.86 with liquid alkali, and performing a second precipitation reaction, the reaction time is 6 hours, the reaction temperature is 60° C., and after the reaction is completed, performing solid-liquid separation to obtain a second deweighting liquid and a second deweighting residue;

[0054] (3) adding lime milk to the second deweighting liquid in step (2), adjusting the pH to carry out a third precipitation reaction, the pH being 12.18, the reaction time being 6 hours, and after the reaction is completed, performing solid-liquid separation to obtain a gypsum product and a mother liquor.

[0055] Comparative Example 1

[0056] This comparative example provides a method for treating heavy metals nickel, cobalt and manganese in ammonia-containing wastewater. Compared with Example 1, the only difference is that step (2) is completely omitted, that is, lime milk is directly added to the first deweighting liquid in step (1).

[0057] Comparative Example 2

[0058] This comparative example provides a step-by-step method for removing heavy metals nickel, cobalt and manganese from ammonia-containing wastewater. Compared with Example 1, the only difference is that in step (2), pH is less than 8, specifically pH = 7.26.

[0059] Comparative Example 3

[0060] This comparative example provides a step-by-step method for removing heavy metals nickel, cobalt and manganese from ammonia-containing wastewater. Compared with Example 1, the only difference is that in step (2), pH>10, specifically pH=10.84.

[0061] According to the methods described in the above embodiments and comparative examples, the content of the liquid phase in each stage was tested respectively, and the performance of the gypsum product was tested respectively. The specific test results are shown in Table 1.

[0062] Table 1

[0063]

[0064] Note: “ / ” means not performed.

[0065] It can be seen from Table 1 that:

[0066] (1) In Examples 1 to 3, the initial Ni concentration of the ammonia-containing wastewater is 100 to 1000 mg / L, the Co concentration is 5 to 50 mg / L, and the Mn concentration is 10 to 200 mg / L. After the first precipitation reaction, the Ni concentration in the first deweighting liquid is reduced to less than 5 mg / L, the Co concentration is reduced to 0.1 mg / L, and the Mn concentration is reduced to less than 50 mg / L. After the second precipitation reaction, the Ni and Co concentrations in the second deweighting liquid are reduced to less than 2 mg / L, and the Mn concentration is reduced to less than 20 mg / L. The whiteness of the obtained gypsum product is 55 to 65, and the appearance is white, which belongs to qualified gypsum, and the mother liquor discharged after the gypsum is precipitated meets the requirements that the concentrations of Ni and Co are less than 1 mg / L;

[0067] (2) In Comparative Example 1, step (2) was completely omitted, i.e., no oxidant was added to carry out the second precipitation reaction, and lime milk was directly added to the first deweighting liquid in step (1). Since the concentration of Mn in the first deweighting liquid could not be reduced to below 20 mg / L, the whiteness of the obtained gypsum product was less than 30, and the appearance was dark brown;

[0068] (3) In Comparative Examples 2 and 3, the pH of the second precipitation reaction in step (2) exceeds 8 to 10. Under conditions where the pH is too low or too high, the concentration of Mn in the second deweighting liquid obtained after the second precipitation reaction cannot be reduced to below 20 mg / L, and the whiteness of the obtained gypsum product is less than 30, and the appearance is brown.

[0069] The present invention illustrates the detailed structural features of the present invention through the above embodiments, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the components selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0070] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0071] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0072] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A step-by-step method for removing heavy metals nickel, cobalt and manganese from ammonia-containing wastewater, characterized in that: The step-by-step removal method comprises the following: (1) adding a precipitant to the ammonia-containing wastewater, controlling the pH to 6 to 8, and performing a first precipitation reaction. After the reaction is completed, adding a flocculant, and performing solid-liquid separation to obtain a first de-weighted liquid and a first de-weighted residue; (2) adding an oxidant to the first deweighting liquid of step (1), adjusting the pH to 8 to 10, and performing a second precipitation reaction. After the reaction is completed, performing solid-liquid separation to obtain a second deweighting liquid and a second deweighting residue; (3) adding lime milk to the second deweighting liquid in step (2), adjusting the pH to carry out a third precipitation reaction, and after the reaction is completed, performing solid-liquid separation to obtain a gypsum product and a mother liquor.

2. The step-by-step removal method according to claim 1, characterized in that: The ammonia-containing wastewater in step (1) includes any one of the nickel-cobalt P204 extraction line, the nickel-cobalt P507 extraction line or the nickel-cobalt C272 extraction line soap solution, or a mixture of at least two of them.

3. The step-by-step removal method according to claim 1, characterized in that: The precipitant in step (1) comprises any one of sodium sulfide, ammonium sulfide, sodium hydrosulfide, ammonium hydrosulfide or hydrogen sulfide gas, or a combination of at least two thereof; Preferably, the amount of the precipitant added in step (1) is 300 to 1000 g / m 3 ; Preferably, the amount of flocculant added in step (1) is 1 to 5 kg / m 3 .

4. The step-by-step removal method according to claim 1, characterized in that: The reaction time of the first precipitation reaction in step (1) is 2 to 6 hours, and the reaction temperature is 30 to 60°C.

5. The step-by-step removal method according to claim 1, characterized in that: The pH adjustment in step (2) is carried out using ammonia water or liquid alkali.

6. The step-by-step removal method according to claim 1, characterized in that: The oxidant in step (2) includes any one of air, oxygen, ozone or hydrogen peroxide.

7. The step-by-step removal method according to claim 1, characterized in that: The amount of the oxidant added in step (2) is 5 to 10 times the theoretical amount of manganese oxide ions.

8. The step-by-step removal method according to claim 1, characterized in that: The reaction time of the second precipitation reaction in step (2) is 2 to 6 hours, and the reaction temperature is 30 to 60°C.

9. The step-by-step removal method according to claim 1, characterized in that: The pH of the third precipitation reaction in step (3) is 11.5 to 12.5, and the reaction time is 2 to 6 hours.

10. The step-by-step removal method according to claim 1, characterized in that: The step-by-step removal method comprises the following: (1) adding a precipitant to the ammonia-containing wastewater, controlling the pH to 6 to 8, performing a first precipitation reaction, the reaction time to 2 to 6 hours, the reaction temperature to 30 to 60° C., adding a flocculant after the reaction is completed, and performing solid-liquid separation to obtain a first de-heavy liquid and a first de-heavy residue; The ammonia-containing wastewater includes any one of the nickel-cobalt P204 extraction line, the nickel-cobalt P507 extraction line or the nickel-cobalt C272 extraction line soap solution or a mixture of at least two of them; the precipitant includes any one of sodium sulfide, ammonium sulfide, sodium hydrosulfide, ammonium hydrosulfide or hydrogen sulfide gas or a combination of at least two of them; the addition amount of the precipitant is 300-1000 g / m 3 The amount of flocculant added is 1 to 5 kg / m 3 ; (2) adding an oxidant to the first deweighting liquid of step (1), controlling the amount of the oxidant added to be 5 to 10 times the theoretical amount of manganese oxide ions, adjusting the pH to 8 to 10 using ammonia water or liquid alkali, and performing a second precipitation reaction, the reaction time is 2 to 6 hours, the reaction temperature is 30 to 60° C., and after the reaction is completed, performing solid-liquid separation to obtain a second deweighting liquid and a second deweighting residue; Wherein, the oxidant includes any one of air, oxygen, ozone or hydrogen peroxide; (3) adding lime milk to the second deweighting liquid of step (2), adjusting the pH to carry out a third precipitation reaction, wherein the pH is 11.5 to 12.5, and the reaction time is 2 to 6 hours. After the reaction is completed, solid-liquid separation is carried out to obtain a gypsum product and a mother liquor.

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