Method for preparing MHP through cyclic utilization of manganese precipitation post-solution and application of MHP

Abstract

The invention provides a method for preparing MHP through cyclic utilization of manganese precipitation post-liquid and application, and the method comprises the following steps: mixing sodium hydroxide, magnesium oxide and the manganese precipitation post-liquid to obtain compound alkali slurry; mixing the iron and aluminum removed laterite-nickel ore liquid with the compound alkali slurry for precipitation reaction to obtain MHP slurry; performing thickening treatment and solid-liquid separation on the MHP slurry to obtain an MHP filter cake and filtrate; directly carrying out manganese precipitation treatment on the filtrate to obtain manganese slag and manganese-precipitated liquid; and reusing the manganese-deposited liquid in the preparation of the compound alkali slurry. According to the method disclosed by the invention, a sodium hydroxide and magnesium oxide compounding system is utilized, and a part of manganese-precipitated liquid is recycled in an alkali preparation process, so that an MHP precipitation process can be simplified to one step on the premise of ensuring the quality of the MHP, and the preparation cost of the MHP and the cost of wastewater treatment are greatly reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of hydrometallurgy and relates to a method for preparing MHP by recycling liquid after manganese precipitation and its application. Background Art

[0002] As we all know, for MHP (mixed nickel-cobalt hydroxide precipitate) prepared from laterite nickel ore, the key impurity monitoring element is Mg. Excessive Mg content will not only reduce the nickel content in MHP and increase its transportation cost, but also significantly increase the cost of extracting magnesium and separating nickel and cobalt in the subsequent extraction and refining stage P507 of MHP. Specifically, the main elements in the liquid after iron and aluminum removal from laterite nickel ore are Ni, Co, Mn and Mg, of which the Mg concentration is about 2 to 3 times the Ni concentration. In order to prepare high-quality MHP and reduce the content of impurity elements therein, the nickel-cobalt precipitation process is divided into two precipitation steps. Among them, the first precipitation step is the product grade, and the MHP prepared in the second precipitation step is used as the seed of the precipitation reaction in this step, and the rest is returned to the circulating leaching section of the previous section to use the residual acid in the high-pressure leaching solution to leach the nickel and cobalt in MHP. These nickel and cobalt finally re-enter the next round of nickel-cobalt precipitation process, which significantly increases the consumption of alkali in the nickel-cobalt precipitation process, thereby increasing the production cost of MHP. When nickel and cobalt are completely precipitated, the filtrate of this process mainly contains manganese and magnesium. The wastewater treatment end precipitates manganese, and then the manganese slag is filtered and landfilled. At this time, the main element in the filtrate after the manganese slag is Mg, which is generally neutralized with sulfuric acid due to its alkalinity and re-enters the ocean.

[0003] At present, sodium hydroxide or MgO is used in the industry to prepare MHP. In addition to being expensive, sodium hydroxide is also prone to local over-alkalinity due to its strong alkalinity, making the amount of alkali used in the MHP preparation process significantly greater than its theoretically calculated amount, which is not conducive to reducing the production cost of MHP. MgO is cheap, but it is difficult to dissolve, so the Mg content in MHP prepared using MgO is generally high.

[0004] People usually classify new energy batteries as processing and manufacturing industries, mainly because the raw material cost of the cathode materials used in the production of new energy batteries is high. Therefore, it is of great significance to optimize the MHP preparation process and significantly reduce the MHP production cost without affecting the quality of MHP itself, thereby reducing the cost of NCM / NCA new energy batteries. Summary of the invention

[0005] The object of the present invention is to provide a method for preparing MHP by recycling manganese precipitation liquid and its application, which can solve the technical problems of high preparation cost of MHP, complicated preparation precipitation process and ineffective resource utilization of manganese precipitation liquid.

[0006] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a method for preparing MHP by recycling a liquid after manganese precipitation, the method comprising the following steps:

[0008] (1) mixing sodium hydroxide, magnesium oxide and the manganese precipitation solution to obtain a composite alkali slurry;

[0009] (2) mixing the laterite nickel ore liquid after iron and aluminum removal with the composite alkali slurry described in step (1) to carry out precipitation reaction to obtain MHP slurry;

[0010] (3) performing a thickening treatment and solid-liquid separation on the MHP slurry of step (2) to obtain an MHP filter cake and a filtrate;

[0011] (4) subjecting the filtrate of step (3) to manganese precipitation to obtain manganese slag and manganese precipitation liquid;

[0012] (5) The manganese precipitation solution in step (4) is reused in the preparation of the composite alkali slurry in step (1).

[0013] The traditional method of preparing MHP by directly adding a strong alkaline precipitant can easily cause the precipitation system to form a local over-alkalinity, thus affecting the quality of MHP. Therefore, the existing technology usually divides the precipitation of MHP into two process stages, which not only makes the MHP preparation process cumbersome, but also increases the production cost of MHP. In addition, after the nickel and cobalt are completely precipitated, the manganese in the filtrate is precipitated by chemical methods. All enterprises generally further treat this part of the manganese precipitation liquid and discharge it into the ocean.

[0014] In view of this, the present invention provides a method for preparing MHP by recycling the liquid after manganese precipitation. The method utilizes a composite system of sodium hydroxide and magnesium oxide to recycle part of the liquid after manganese precipitation into the alkali preparation process, which not only simplifies the MHP precipitation process to one step while ensuring the quality of MHP, but also greatly reduces the cost of MHP preparation and the cost of wastewater treatment.

[0015] Preferably, the molar ratio of sodium hydroxide to magnesium oxide in step (1) is 1:(0.05-2), for example, it can be 1:0.05, 1:0.1, 1:0.5, 1:1, 1:1.5 or 1:2, but is not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable, preferably 1:(0.1-1.5).

[0016] The molar ratio of sodium hydroxide to magnesium oxide in the present invention will affect the quality of MHP. If the amount of magnesium oxide is too small compared to sodium hydroxide, it will cause local over-alkalinity, resulting in high manganese and magnesium contents and low nickel content in MHP; and if the amount of magnesium oxide is too large compared to sodium hydroxide, the magnesium content in the system will exceed the standard, resulting in a decrease in the nickel content in MHP, affecting the quality of MHP.

[0017] Preferably, the concentration of the composite alkali slurry in step (1) is 0.5-15wt%, for example, it can be 0.5wt%, 1wt%, 3wt%, 5wt%, 7wt%, 9wt%, 11wt%, 13wt% or 15wt%, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 2-8wt%.

[0018] Preferably, the concentration of the composite alkali slurry in step (1) is changed by changing the amount of the recycled solution after manganese precipitation.

[0019] The present invention controls the concentration of the compound alkali slurry by controlling the recycling amount of the liquid after manganese precipitation. The quality of MHP will be affected by the concentration of the compound alkali slurry. Within a specific concentration range, the concentration of the compound alkali slurry is appropriately reduced, which can very effectively reduce the content of Mn and Mg in MHP to increase the nickel content in MHP, that is, the quality of MHP is optimized by adjusting the recycling amount of the liquid after manganese precipitation. However, considering the utilization rate of the equipment and the production efficiency of MHP, the concentration of the compound alkali slurry is not easy to be too low.

[0020] Preferably, in the manganese precipitation solution of step (1), the concentration of magnesium ions is below 10 g / L, for example, it can be 10 g / L, 8 g / L, 6 g / L, 4 g / L or 2 g / L, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 2 to 10 g / L.

[0021] In the manganese precipitation solution of step (1) of the present invention, the concentration of magnesium ions is below a specific concentration, which is beneficial to increasing the nickel and cobalt content in MHP.

[0022] Preferably, the laterite nickel ore after iron and aluminum removal in step (2) includes 2 to 8 g / L of Ni (referring to Ni ions), for example, 2 g / L, 3 g / L, 4 g / L, 5 g / L, 6 g / L, 7 g / L or 8 g / L, and 0.15 to 0.8 g / L of Co (referring to cobalt ions), for example, 0.15 g / L, 0.25 g / L, 0.35 g / L, 0.45 g / L, 0.55 g / L, 0.65 g / L, 0.75 g / L, 0.80 g / L, 0.90 g / L, 100 g / L, 120 g / L, 140 g / L, 150 g / L, 160 g / L, 170 g / L, 180 g / L, 190 g / L, 200 g / L, 210 g / L, 220 g / L, 230 g / L, 240 g / L, 250 g / L, 260 g / L, 270 g / L, 280 g / L, 290 g / L, 300 g / L, 310 g / L, 320 g / L, 330 g / L, 340 g / L .65g / L, 0.75g / L or 0.8g / L, 1-6g / L Mn (referring to manganese ions), for example, can be 1g / L, 2g / L, 3g / L, 4g / L, 5g / L or 6g / L, 5-20g / L Mg (referring to magnesium ions), for example, can be 5g / L, 10g / L, 15g / L or 20g / L, but are not limited to the listed values, and other unlisted values ​​within the numerical range are equally applicable.

[0023] Preferably, the sum of twice the molar amount of the sodium element in the composite alkali slurry in step (2) and the molar amount of the magnesium element is A, and the sum of the molar amounts of the nickel and cobalt elements in the laterite nickel ore after iron and aluminum removal is B, A:B = (0.9-1): (1-1.1), that is, (Na×2+Mg): (Ni+Co) = (0.9-1.1): (1-1.1), for example, it can be 0.9:1, 0.95:1.05 or 1:1.1, but is not limited to the listed values, and other values ​​not listed within the numerical range are equally applicable.

[0024] Preferably, the precipitation reaction temperature in step (2) is 55-75°C, for example, 55°C, 60°C, 65°C, 70°C or 75°C, and the reaction time is 1-8h, for example, 1h, 2h, 3h, 4h, 5h, 6h, 7h or 8h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0025] Preferably, the solid-liquid separation in step (3) comprises filtration, and distilled water or industrial water is used to wash the MHP filter cake during filtration.

[0026] Preferably, the manganese precipitation treatment in step (4) comprises mixing the filtrate with an alkaline substance to adjust the pH, and then filtering to obtain manganese slag and manganese precipitation liquid.

[0027] Preferably, the alkaline substance comprises milk of lime.

[0028] Preferably, the pH is adjusted to 8-9, for example, 8, 8.5 or 9, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0029] Preferably, in the manganese precipitation solution of step (5), the concentration of magnesium ions is below 10 g / L, for example, it can be 10 g / L, 8 g / L, 6 g / L, 4 g / L or 2 g / L, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 2 to 10 g / L.

[0030] As a preferred technical solution of the method of the present invention, the method comprises the following steps:

[0031] (1) mixing sodium hydroxide, magnesium oxide and the manganese precipitation solution to obtain a composite alkali slurry;

[0032] The molar ratio of sodium hydroxide to magnesium oxide is 1:(0.1-1.5), and the concentration of the composite alkali slurry is 2-8wt%;

[0033] (2) mixing the laterite nickel ore liquid after iron and aluminum removal with the composite alkali slurry, and performing a precipitation reaction at a temperature of 55 to 75° C. for 1 to 8 hours to obtain an MHP slurry;

[0034] The laterite nickel ore after iron and aluminum removal liquid includes 2-8 g / L Ni, 0.15-0.8 g / L Co, 1-6 g / L Mn, and 5-20 g / L Mg; the sum of twice the molar amount of the sodium element in the compound alkali slurry and the molar amount of the magnesium element is A, and the sum of the molar amount of the nickel and cobalt elements in the laterite nickel ore after iron and aluminum removal liquid is B, A:B=(0.9-1.1):(1-1.1);

[0035] (3) thickening the MHP slurry to obtain a thick underflow;

[0036] (4) filtering the dense underflow and washing the MHP with distilled water or industrial water to obtain an MHP filter cake and a filtrate;

[0037] (5) mixing the filtrate with an alkaline substance to adjust the pH to 8-9, and then filtering to obtain manganese slag and manganese precipitation liquid;

[0038] The concentration of magnesium ions in the manganese precipitation solution is 2 to 10 g / L;

[0039] (6) The manganese precipitation solution of step (5) is reused in the preparation of the composite alkali slurry of step (1), and the concentration of the composite alkali slurry of step (1) is changed by changing the reuse amount of the manganese precipitation solution.

[0040] In a second aspect, the present invention provides an MHP, wherein the MHP is obtained by precipitation using the method described in the first aspect.

[0041] Preferably, in the MHP, the Ni content is 40-44wt%, for example, 40wt%, 40.5wt%, 41wt%, 41.5wt%, 42wt%, 43wt% or 44wt%, the Co content is 3.0-6.0wt%, for example, 3wt%, 4wt%, 5wt% or 6wt%, the Mn content is 3.5-8.0wt%, for example, 3.5wt%, 4.5wt%, 5.5wt%, 6.5wt%, 7.5wt% or 8wt%, and the Mg content is 0.2-3wt%, for example, 0.2wt%, 1.2wt%, 1.5wt%, 2.0wt% or 2.0wt% or 3.0wt%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0042] The MHP of the present invention can be used to prepare ternary precursor materials.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] The invention uses a sodium hydroxide and magnesium oxide compound system as a precipitant, thereby simplifying the MHP precipitation process to one step; at the same time, a part of the liquid after manganese precipitation is recycled to the MHP precipitation process section, thereby reducing the cost of wastewater treatment; and by controlling the circulation amount of the liquid after manganese precipitation, the magnesium content in MHP can be reduced, thereby reducing the cost of subsequent MHP extraction treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 This is a flow chart of the method for preparing MHP by recycling the liquid after manganese precipitation described in Example 1 of the present invention. DETAILED DESCRIPTION

[0046] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0047] The source of the laterite nickel ore solution after iron and aluminum removal used in the following examples and comparative examples is: the solution after iron and aluminum removal from laterite nickel ore after high-pressure acid leaching, the main components of which are as follows: nickel ion is 3.45 g / L, cobalt ion is 0.38 g / L, manganese ion is 2.59 g / L, and magnesium ion is 7.85 g / L.

[0048] Example 1

[0049] This embodiment provides a method for preparing MHP by recycling the liquid after manganese precipitation. The flow chart of the method is as follows: Figure 1 As shown, the method comprises the following steps:

[0050] (1) mixing sodium hydroxide and magnesium oxide in a molar ratio of 1:1 with a manganese precipitation solution (magnesium ion concentration of 7 g / L) to obtain a composite alkali slurry with a concentration of 7 wt%;

[0051] (2) mixing the compound alkali slurry with the laterite nickel ore after iron and aluminum removal, and reacting at a temperature of 65° C. for 5 hours to obtain an MHP slurry; wherein the ratio of the sum of the molar amounts of sodium and magnesium elements in the compound alkali slurry to the sum of the molar amounts of nickel and cobalt elements in the laterite nickel ore after iron and aluminum removal satisfies: (Na*2+Mg) / (Ni+Co)=1;

[0052] (3) thickening the MHP slurry to separate the supernatant and the MHP underflow;

[0053] (4) filtering the MHP underflow and washing the MHP with industrial water to obtain a filtrate and an MHP filter cake;

[0054] (5) adding lime milk to the filtrate obtained in step (4) to adjust the pH of the solution to 8.5 for manganese precipitation, and filtering to obtain manganese slag and manganese precipitation liquid;

[0055] (6) The solution after manganese precipitation is reused in the preparation process of the composite alkali slurry in step (1).

[0056] Example 2

[0057] This embodiment provides a method for preparing MHP by recycling a liquid after manganese precipitation. The method is the same as that of Embodiment 1 except that the molar ratio of sodium hydroxide to magnesium oxide in step (1) is 1:0.3.

[0058] Example 3

[0059] This embodiment provides a method for preparing MHP by recycling a liquid after manganese precipitation. The method is the same as that of Embodiment 1 except that the molar ratio of sodium hydroxide to magnesium oxide in step (1) is 1:1.5.

[0060] Example 4

[0061] This embodiment provides a method for preparing MHP by recycling the manganese precipitation solution. The method is the same as that of embodiment 1 except that the recycling amount of the manganese precipitation solution in step (5) is changed to make the concentration of the compound alkali slurry 4.5wt%.

[0062] Example 5

[0063] This embodiment provides a method for preparing MHP by recycling the manganese precipitation solution. The method is the same as that of embodiment 1 except that the recycling amount of the manganese precipitation solution in step (5) is changed to make the concentration of the compound alkali slurry 3wt%.

[0064] Comparative Example 1

[0065] This comparative example provides a method for preparing MHP, which is the same as Example 1 except that in step (1), the manganese precipitation solution is used and only sodium hydroxide is used as a precipitant to prepare the composite alkali slurry.

[0066] Comparative Example 2

[0067] This comparative example provides a method for preparing MHP, which is the same as Example 1 except that in step (1), the manganese precipitation solution is used and only magnesium oxide is used as a precipitant to prepare the composite alkali slurry.

[0068] Comparative Example 3

[0069] This embodiment provides a method for preparing MHP by recycling the manganese precipitation solution. The method is the same as that of embodiment 1 except that the recycling amount of the manganese precipitation solution in step (5) is changed to make the concentration of the compound alkali slurry 15wt%.

[0070] The components of the MHP obtained in the above examples and comparative examples were tested by ICP method, and the test results are shown in Table 1.

[0071] Table 1

[0072]

[0073]

[0074] From Table 1 we can see that:

[0075] (1) By comparing Example 1 with Comparative Example 1, it can be seen that when a strong alkaline precipitant is used, the precipitation rate of magnesium (manganese) is relatively high due to local over-alkalinity, which results in a high magnesium (manganese) content and a low nickel content in MHP, and correspondingly reduces the precipitation rate of nickel and cobalt.

[0076] (2) By comparing Example 1 with Comparative Example 2, it can be seen that when magnesium oxide is used alone as a precipitant, the precipitation reaction rate is controlled, so that the precipitation of Ni, Co, Mn and Mg is more inclined to the order of their equilibrium reaction, thereby reducing the manganese content in MHP. At the same time, the precipitation rates of nickel and cobalt are high. However, since MgO is not completely dissolved in the precipitation reaction, the Mg content in MHP exceeds the standard, thereby reducing the nickel content in MHP.

[0077] (3) By comparing Examples 1-3, it can be seen that increasing the magnesium oxide content in the composite alkali system will increase the magnesium content in MHP, which leads to a significant decrease in the nickel content in MHP and affects the quality of MHP. However, the magnesium oxide content in the composite alkali system should not be too low to avoid the problem of local over-alkali and increased precipitation rate of manganese and magnesium. Therefore, it is preferred that the sodium hydroxide and magnesium oxide in the composite alkali system are within a specific molar ratio range.

[0078] (4) By comparing Example 1 with Examples 4 and 5, it can be seen that the quality of MHP is very sensitive to the concentration of the compound alkali slurry. Appropriately reducing the concentration of sodium hydroxide and magnesium oxide slurry can effectively reduce the content of magnesium (manganese) in MHP, and the nickel-cobalt precipitation rate also increases. When the circulation volume of the liquid after manganese removal is increased and the concentration of the compound alkali slurry is reduced to 3wt%, the precipitation rates of nickel and cobalt both reach 98%, the Mg content in MHP can be reduced by about 0.5wt%, and the nickel content is as high as 42.76wt%. At this time, the MHP product quality is excellent. However, the concentration of the compound alkali slurry is not easy to be too low. If it is too low, on the one hand, it is not conducive to the improvement of the nickel-cobalt precipitation rate, and on the other hand, the utilization rate and production efficiency of the equipment will be reduced.

[0079] (5) Comparison of Examples 1-5 shows that, from the perspectives of nickel and cobalt precipitation rates and MHP quality, the present invention optimizes the quality of MHP products by optimizing the ratio of sodium hydroxide to magnesium oxide in the compounding system and the concentration of the alkali slurry in the compounding system. Under the premise of ensuring the quality of MHP, the MHP precipitation process can be shortened to one step, which not only greatly simplifies the process of the MHP preparation process section, but also reduces the alkali consumption used in the preparation of MHP. In addition, the alkali in the liquid after manganese precipitation is recycled to the preparation process section of the alkali slurry used in MHP, reducing the cost of wastewater treatment.

[0080] In summary, the present invention provides a method for preparing MHP by recycling manganese precipitation liquid and its application, which can solve the technical problems of high cost of preparing MHP, complicated preparation and precipitation process and ineffective resource utilization of manganese precipitation liquid.

[0081] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention are within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing MHP by recycling the liquid after manganese precipitation, characterized in that: The method comprises the following steps: (1) mixing sodium hydroxide, magnesium oxide and the manganese precipitation solution to obtain a composite alkali slurry; (2) mixing the laterite nickel ore liquid after iron and aluminum removal with the composite alkali slurry described in step (1) to carry out precipitation reaction to obtain MHP slurry; (3) performing a thickening treatment and solid-liquid separation on the MHP slurry of step (2) to obtain an MHP filter cake and a filtrate; (4) subjecting the filtrate of step (3) to manganese precipitation to obtain manganese slag and manganese precipitation liquid; (5) The manganese precipitation solution in step (4) is reused in the preparation of the composite alkali slurry in step (1).

2. The method according to claim 1, characterized in that: The molar ratio of sodium hydroxide to magnesium oxide in step (1) is 1:(0.05-2), preferably 1:(0.1-1.5).

3. The method according to claim 1 or 2, characterized in that: The concentration of the composite alkali slurry in step (1) is 0.5-15wt%, preferably 2-8wt%; Preferably, the concentration of the composite alkali slurry in step (1) is changed by changing the amount of the recycled solution after manganese precipitation.

4. The method according to any one of claims 1 to 3, characterized in that: In the manganese precipitation solution of step (1), the concentration of magnesium ions is below 10 g / L, preferably 2 to 10 g / L.

5. The method according to any one of claims 1 to 4, characterized in that: The laterite nickel ore liquid after iron and aluminum removal in step (2) comprises 2-8 g / L Ni, 0.15-0.8 g / L Co, 1-6 g / L Mn, and 5-20 g / L Mg; Preferably, the sum of twice the molar amount of the sodium element in the composite alkali slurry in step (2) and the molar amount of the magnesium element is A, and the sum of the molar amounts of the nickel and cobalt elements in the laterite nickel ore after iron and aluminum removal is B, A:B = (0.9-1.1): (1-1.1); Preferably, the precipitation reaction in step (2) is carried out at a temperature of 55 to 75° C. and for a time of 1 to 8 hours.

6. The method according to any one of claims 1 to 5, characterized in that: The solid-liquid separation in step (3) includes filtration, and distilled water or industrial water is used to wash the MHP filter cake during filtration.

7. The method according to any one of claims 1 to 6, characterized in that: The manganese precipitation treatment in step (4) comprises mixing the filtrate with an alkaline substance to adjust the pH, and then filtering to obtain manganese slag and manganese precipitation liquid; Preferably, the alkaline substance comprises milk of lime; Preferably, the pH is adjusted to 8-9; Preferably, in the manganese precipitation solution of step (5), the concentration of magnesium ions is below 10 g / L, preferably 2 to 10 g / L.

8. The method according to any one of claims 1 to 7, characterized in that: The method comprises the following steps: (1) mixing sodium hydroxide, magnesium oxide and the manganese precipitation solution to obtain a composite alkali slurry; The molar ratio of sodium hydroxide to magnesium oxide is 1:(0.1-1.5), and the concentration of the composite alkali slurry is 2-8wt%; (2) mixing the laterite nickel ore liquid after iron and aluminum removal with the composite alkali slurry, and performing a precipitation reaction at a temperature of 55 to 75° C. for 1 to 8 hours to obtain an MHP slurry; The laterite nickel ore after iron and aluminum removal liquid includes 2-8 g / L Ni, 0.15-0.8 g / L Co, 1-6 g / L Mn, and 5-20 g / L Mg; the sum of twice the molar amount of the sodium element in the compound alkali slurry and the molar amount of the magnesium element is A, and the sum of the molar amount of the nickel and cobalt elements in the laterite nickel ore after iron and aluminum removal liquid is B, A:B=(0.9-1.1):(1-1.1); (3) thickening the MHP slurry to obtain a thick underflow; (4) filtering the dense underflow and washing the MHP with distilled water or industrial water to obtain an MHP filter cake and a filtrate; (5) mixing the filtrate with an alkaline substance to adjust the pH to 8-9, and then filtering to obtain manganese slag and manganese precipitation liquid; The concentration of magnesium ions in the manganese precipitation solution is 2 to 10 g / L; (6) The manganese precipitation solution of step (5) is reused in the preparation of the composite alkali slurry of step (1), and the concentration of the composite alkali slurry of step (1) is changed by changing the reuse amount of the manganese precipitation solution.

9. An MHP, characterized in that The MHP is obtained by precipitation using the method according to any one of claims 1-8.

10. The MHP according to claim 9, characterized in that In the MHP, the Ni content is 40-44wt%, the Co content is 3.0-6.0wt%, the Mn content is 3.5-8.0wt%, and the Mg content is 0.2-3.0wt%.

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