Method for preparing MHP by cyclic utilization of manganese precipitation post-solution

Abstract

The invention discloses a method for preparing MHP by cyclic utilization of manganese precipitation post-solution, which comprises the following steps: mixing sodium hydroxide, magnesium oxide and manganese precipitation post-solution to obtain compound alkali slurry; mixing the laterite-nickel ore liquid subjected to iron and aluminum removal with the compound alkali slurry, and carrying out precipitation reaction to obtain MHP slurry; carrying out thickening treatment on the MHP slurry to obtain a dense underflow; filtering the dense underflow 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 invention, a sodium hydroxide and magnesium oxide compounded system is utilized, so that the MHP precipitation process can be simplified to one step. And meanwhile, part of the manganese-deposited liquid is recycled to the alkali preparation process, so that the wastewater treatment cost is reduced, and the magnesium content in the MHP can be reduced by controlling the circulation amount of the manganese-deposited liquid, and the cost of preparing crystals through subsequent fine extraction of the MHP is reduced.

Description

Technical Field

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

[0002] It's well known that magnesium (Mg) is a key impurity element to monitor for MHP produced from laterite nickel ore. Excessive Mg content not only reduces the nickel content in MHP and increases transportation costs, but also significantly increases the cost of magnesium extraction and nickel-cobalt separation in the subsequent MHP extraction and refining stage (P507). Specifically, the primary elements in the liquid after iron and aluminum removal from laterite nickel ore are nickel, cobalt, manganese, and magnesium, with the Mg concentration approximately two to three times that of nickel. To produce high-quality MHP and reduce its impurity content, the nickel-cobalt precipitation process is divided into two precipitation steps. The first precipitation step produces product-grade MHP. The MHP produced in the second precipitation step is used as seed for this precipitation reaction, and the remaining MHP is returned to the preceding circulating leaching stage, where the residual acid in the high-pressure leachate extracts the nickel and cobalt from the MHP. This nickel and cobalt then re-enters the next nickel-cobalt precipitation step, significantly reducing alkali consumption in the nickel-cobalt precipitation process and increasing production costs. Once the nickel and cobalt precipitation is complete, the filtrate from this step primarily contains manganese and magnesium. At the wastewater treatment end, manganese is precipitated and the manganese slag is filtered and landfilled. At this time, the main element in the filtrate after filtering the manganese slag is Mg. Due to its alkalinity, it is generally neutralized with sulfuric acid and then re-enters the ocean.

[0003] Currently, the industry uses sodium hydroxide or MgO to produce MHP. Besides being expensive, sodium hydroxide's strong alkalinity can easily lead to localized over-alkalinity, resulting in significantly greater alkali usage during the MHP production process than theoretically calculated. This hinders cost reduction. MgO is inexpensive, but difficult to dissolve, so MHP produced using MgO typically contains a high magnesium content.

[0004] New energy batteries are often categorized as part of the manufacturing industry, primarily due to the high cost of cathode materials used in their production. Therefore, optimizing the MHP preparation process to significantly reduce MHP production costs, and thus the cost of NCM / NCA new energy batteries, without compromising MHP quality, is crucial for advancing humanity into a green, renewable energy era. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a method for recycling the manganese precipitation liquid to prepare MHP, which solves the technical problems of high cost and high magnesium content in the preparation of MHP, complicated preparation and precipitation process, and inability to effectively recycle the manganese precipitation liquid.

[0006] To achieve the above object, the technical solution provided by the present invention is: The present invention provides a method for preparing MHP by recycling a liquid after manganese precipitation, comprising 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 compound alkali slurry to carry out precipitation reaction to obtain MHP slurry; (3) thickening the MHP slurry to obtain a dense underflow; (4) Filter the dense underflow and wash the MHP with distilled water or industrial water to obtain MHP filter cake and filtrate; (5) Directly subjecting the filtrate to manganese precipitation treatment to obtain manganese slag and manganese precipitation liquid; (6) The liquid after manganese precipitation is reused in the preparation of compound alkali slurry.

[0007] The present invention utilizes the precipitation equilibrium principle of nickel, cobalt, manganese and magnesium and uses a composite system of sodium hydroxide and magnesium oxide as a precipitant, thereby simplifying the MHP precipitation process to one step. At the same time, a portion of the liquid after manganese precipitation is creatively recycled to the MHP precipitation process, thereby reducing the cost of wastewater treatment. Moreover, by controlling the circulation volume of the liquid after manganese precipitation, the magnesium content in MHP can be reduced, thereby lowering the cost of subsequent MHP extraction treatment.

[0008] Preferably, in step (1), the molar ratio of sodium hydroxide to magnesium oxide is (1:0.1) to (1:4).

[0009] Preferably, in step (1), the concentration of the compounded alkali slurry is 1 to 15 wt%.

[0010] Preferably, in step (2), the laterite nickel ore liquid after iron and aluminum removal contains 2-8 g / L Ni, 0.15-0.8 g / L Co, 1-6 g / L Mn, and 5-20 g / L Mg.

[0011] Preferably, in step (2), the ratio of the sum of the molar amounts of sodium and magnesium elements in the composite 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)=(0.9~1):(1~1.1).

[0012] Preferably, in step (2), the temperature of the precipitation reaction is 55 to 70 o C, reaction time is 1~8 h.

[0013] Preferably, in step (5), the concentration of magnesium ions in the solution after manganese precipitation is 2 to 10 g / L.

[0014] The beneficial effects of the present invention are: The present invention utilizes a composite system of sodium hydroxide and magnesium oxide as a precipitant, thereby simplifying the MHP precipitation process to one step; at the same time, a portion of the liquid after manganese precipitation is recycled to the MHP precipitation process, thereby reducing the cost of wastewater treatment; and by controlling the circulation volume 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

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings of the embodiments.

[0016] Figure 1 The present invention is a flow chart of a method for preparing MHP by recycling the liquid after manganese precipitation. DETAILED DESCRIPTION

[0017] The following will be combined with 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 some embodiments of the present invention, not all 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.

[0018] The traditional method of directly adding a strong alkaline precipitant easily causes the precipitation system to become locally over-alkaline. As a result, when nickel, cobalt, and manganese precipitate, a small portion of magnesium ions also hydrolyze and nucleate together in a short period of time. Therefore, to produce high-quality MHP, the existing technology generally divides nickel and cobalt precipitation into two process stages, and the subsequent manganese precipitation liquid is difficult to effectively utilize. In view of this, the present invention provides a method for recycling the manganese precipitation liquid to prepare MHP, which comprises the following steps: mixing sodium hydroxide and magnesium oxide with the manganese precipitation liquid to obtain a compound alkali slurry; mixing the iron and aluminum-removed liquid from laterite nickel ore with the compound alkali slurry and subjecting it to a precipitation reaction to obtain MHP slurry; concentrating the MHP slurry to obtain a concentrated underflow; filtering the concentrated underflow and washing the MHP with distilled water or industrial water to obtain an MHP filter cake and filtrate; directly subjecting the filtrate to manganese precipitation to obtain manganese slag and manganese precipitation liquid; and recycling the manganese precipitation liquid to the preparation of the compound alkali slurry. The present invention utilizes a composite system of sodium hydroxide and magnesium oxide, which can simplify the MHP precipitation process to one step, and at the same time, recycles part of the liquid after manganese precipitation into the alkali preparation process, thereby reducing the cost of wastewater treatment. In addition, 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.

[0019] To make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be described in further detail below.

[0020] The source of the laterite nickel ore de-ironized and aluminumized solution used in the examples and comparative examples is: the solution after de-ironized and aluminumized laterite nickel ore is subjected to high-pressure acid leaching, and its main components 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.

[0021] Example 1 A method for preparing MHP by recycling a liquid after manganese precipitation, comprising the following steps: (1) Sodium hydroxide and magnesium oxide were mixed with the manganese precipitation solution (magnesium ion concentration 7 g / L) in a molar ratio of 1:1 to obtain a composite alkali slurry with a concentration of 10 wt%. (2) The compound alkali slurry was mixed with the laterite nickel ore after iron and aluminum removal, and the mixture was reacted at 60 °C for 5 h to obtain 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 satisfied the following equation: (Na×2+Mg) / (Ni+Co)=1.

[0022] (3) The MHP slurry is concentrated and separated to obtain the supernatant and the MHP underflow.

[0023] (4) Filter the MHP underflow and wash the MHP with industrial water to obtain filtrate and MHP filter cake.

[0024] (5) Add lime milk to the filtrate obtained in step (4) to adjust the pH of the solution to 8.5 for manganese precipitation, and obtain manganese slag and manganese precipitation liquid after filtration.

[0025] (6) The liquid after manganese precipitation is reused in the preparation process of the composite alkali slurry in step (1).

[0026] Example 2 The only difference from Example 1 is that the concentration of the composite alkali slurry is adjusted to 15 wt % using the post-manganese precipitation solution. The other steps and conditions are the same as those in Example 1.

[0027] Example 3 The only difference from Example 1 is that the concentration of the composite alkali slurry is adjusted to 5 wt % using the post-manganese precipitation solution. The other steps and conditions are the same as those in Example 1.

[0028] Comparative Example 1 The only difference from Example 1 is that the molar ratio of sodium hydroxide to magnesium oxide is adjusted to 1:9, and the other steps and conditions are the same as those in Example 1.

[0029] Comparative Example 2 The only difference from Example 1 is that the composite alkali slurry is prepared by using the manganese precipitation solution and only sodium hydroxide as the precipitant. The other steps and conditions are the same as those in Example 1.

[0030] Comparative Example 3 The only difference from Example 1 is that the composite alkali slurry is prepared by using the manganese precipitation solution and only using magnesium oxide as a precipitant. Other steps and conditions are the same as those in Example 1.

[0031] Performance Testing The components of the MHP obtained in the embodiment and the comparative example were tested, and the results are shown in Table 1.

[0032] Table 1 Ni, Co precipitation rates and MHP compositions

[0033] As can be seen from Table 1, compared with Comparative Example 2, Example 1 uses a strong alkaline precipitant. Due to local over-alkalinity, the precipitation rates of manganese and magnesium are higher, which results in high manganese and magnesium contents and low nickel content in MHP, and correspondingly reduces the precipitation rates of nickel and cobalt.

[0034] Comparing Example 1 with Comparative Examples 1-3, it can be seen that using magnesium oxide alone as a precipitant controls the precipitation reaction rate, resulting in the precipitation of Ni, Co, Mn, and Mg in an order closer to their equilibrium reaction, thereby reducing the manganese content in the MHP. Simultaneously, the precipitation rates of nickel and cobalt are high. However, due to incomplete dissolution of MgO during the precipitation reaction, the magnesium content in the MHP exceeds the standard, thereby reducing the nickel content in the MHP.

[0035] Comparing Examples 2 and 3 with Example 1, it can be seen that the quality of MHP is very sensitive to the concentration of sodium hydroxide and magnesium oxide slurries. Appropriately reducing the concentration of sodium hydroxide and magnesium oxide slurries can very effectively reduce the Mn and Mg contents in MHP, while also increasing the nickel and cobalt precipitation rate. When the circulation rate of the manganese-removed liquid is increased to reduce the alkali slurry concentration to 5%, the nickel and cobalt precipitation rates both reach 97%, and the Mg content in MHP can be reduced to <1.5%. The nickel content is very high, and the MHP product quality is excellent at this point. Therefore, considering both nickel and cobalt precipitation rates and MHP quality, optimizing the process conditions for preparing MHP using a sodium hydroxide and magnesium oxide slurry composite system can achieve single-stage MHP precipitation. In addition, it is not difficult to find that the actual precipitation rate of nickel and cobalt for precipitation of this composite system during the MHP preparation process is very close to the theoretically calculated value. In other words, the utilization efficiency of the composite alkali during the precipitation reaction is very high, which can significantly reduce the cost of the nickel and cobalt precipitation process of the MHP product.

[0036] Comparing Comparative Example 1 with Example 1 reveals that increasing the ratio of magnesium oxide in the composite system to 0.9 significantly increases the magnesium content in the MHP, leading to a significant decrease in nickel content and severely impacting MHP quality. Therefore, controlling the ratio of sodium hydroxide to magnesium oxide in the composite system is crucial for improving MHP quality.

[0037] It should be noted that the above embodiments all belong to the same inventive concept, and the description of each embodiment has its own focus. For any details not described in individual embodiments, reference may be made to the description in other embodiments.

[0038] The above-described embodiments merely illustrate the implementation methods of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make various modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A method for preparing MHP by recycling the liquid after manganese precipitation, characterized in that: The following steps are involved: (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 compound alkali slurry to carry out precipitation reaction to obtain MHP slurry; (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) subjecting the filtrate to manganese precipitation treatment to obtain manganese slag and manganese precipitation liquid; (6) The manganese precipitation solution is reused in the preparation of the composite alkali slurry in step (1).

2. The method for preparing MHP by recycling the liquid after manganese precipitation according to claim 1, characterized in that: In step (1), the molar ratio of the sodium hydroxide to the magnesium oxide is (1:0.1) to (1:4).

3. The method for preparing MHP by recycling the liquid after manganese precipitation according to claim 1, characterized in that: In step (1), the concentration of the compounded alkali slurry is 1 to 15 wt%.

4. The method for preparing MHP by recycling the liquid after manganese precipitation according to claim 1, characterized in that: In step (2), the laterite nickel ore liquid after iron and aluminum removal contains 2-8 g / L Ni, 0.15-0.8 g / L Co, 1-6 g / L Mn, and 5-20 g / LMg.

5. The method for preparing MHP by recycling the liquid after manganese precipitation according to claim 1, characterized in that: In step (2), the ratio of the sum of the molar amounts of sodium and magnesium elements in the composite 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)=(0.9~1):(1~1.1).

6. The method for preparing MHP by recycling the liquid after manganese precipitation according to claim 1, characterized in that: In step (2), the temperature of the precipitation reaction is 55-70 o C.

7. The method for preparing MHP by recycling the liquid after manganese precipitation according to claim 1, characterized in that: In step (2), the reaction time of the precipitation reaction is 1 to 8 hours.

8. The method for preparing MHP by recycling the liquid after manganese precipitation according to claim 1, characterized in that: In step (5), the concentration of magnesium ions in the manganese precipitation solution is 2 to 10 g / L.

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