Method for enriching scandium from MHP intermediate product obtained by hydrometallurgy of laterite-nickel ore

Abstract

The invention relates to a method for enriching scandium from an MHP intermediate product obtained by hydrometallurgy of laterite-nickel ore, which comprises the following steps: first acid leaching: carrying out first acid leaching treatment on a cobalt nickel hydroxide raw material to obtain a first acid leaching solution; first neutralization: adding a first neutralizer into the first acidic leaching solution to adjust the pH value to 3.8-6.3 for precipitation, and carrying out first solid-liquid separation to obtain a neutralized precipitate and a neutralized solution; second acid leaching: carrying out second acid leaching treatment on the neutralized precipitate to obtain a second acid leaching solution; and second neutralization: adding a second neutralizer into the second acidic leachate to adjust the pH value to 4.1-6.5, carrying out scandium enrichment precipitation, and carrying out second solid-liquid separation on the slurry after scandium enrichment precipitation to obtain a scandium-containing concentrate. According to the method, through the fractional precipitation process, the nickel-cobalt matrix is separated firstly and then precipitated in the scandium-rich system, the waste scandium-containing precipitate is converted into the scandium-containing concentrate for refining, and the problem that the cost is high when a huge low-concentration system is treated is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hydrometallurgy, and particularly relates to a method for enriching scandium from MHP intermediate products of hydrometallurgy of laterite nickel ore. BACKGROUND

[0002] With the increasing demand for strategic metal scandium (Sc) in the fields of aerospace, aviation, missiles, ships and nuclear industry, it has become a technical problem in the industry to economically and efficiently recover scandium from the intermediate product of hydrometallurgy of laterite nickel ore, i.e. nickel cobalt hydroxide (MHP). In the traditional MHP refining process of "acid leaching-neutralization-extraction", there are inherent defects in the flow and recovery of scandium: 1) ineffective storage and loss of scandium-containing iron and aluminum slag: after the first neutralization to remove iron and aluminum, most of the scandium in the raw material is precipitated together with the iron and aluminum slag, which essentially forms a scandium concentrate. However, due to the presence of a large amount of nickel and cobalt, the concentrate is usually subjected to secondary acid leaching, and the core objective of the process is to recover the nickel and cobalt entrained therein, rather than the recovery of scandium. In this process, although scandium can be redissolved by acid leaching, it lacks an independent and effective recovery path and is only circulated in the system, eventually being lost with the waste slag discharged regularly, resulting in the loss of scandium resources. 2) Scandium interference in the system: the scandium remaining in the liquid phase enters the nickel and cobalt extraction system, which is difficult to separate from the extraction system designed for nickel and cobalt, and also enters the extraction agent, which is difficult to remove. Not only is scandium itself not recovered, but it also pollutes the extraction organic phase, leading to poisoning of the extraction agent, reduction of separation efficiency, and significant increase in operating costs and impact on system stability.

[0003] In recent years, although some newly built MHP refining plants have begun to add scandium extraction processes, the mainstream technical route still faces challenges in terms of economy and efficiency: currently, direct extraction of leaching solution is mainly used, i.e. the leaching solution with very low scandium concentration is directly extracted after MHP acid leaching. Although this method can recover some scandium, the high equipment investment and operating cost caused by the large amount of treatment result in poor economic benefits. SUMMARY

[0004] Therefore, the technical problem to be solved by the present application is to overcome the defect of high investment and operating cost caused by the use of direct extraction of leaching solution to treat a large low-concentration system in the existing MHP refining process, and to provide a method for enriching scandium from MHP intermediate products of hydrometallurgy of laterite nickel ore. The method constructs a fractional precipitation process to preferentially separate nickel and cobalt main metals, and performs secondary precipitation in a scandium-rich system, significantly improving the grade of scandium in the concentrate, and providing key technical support for efficient and economic recovery of scandium.

[0005] To achieve the above-mentioned purposes, the present application provides the following technical solutions: The present application provides a method for enriching scandium from MHP intermediate products of hydrometallurgy of laterite nickel ore, comprising the following steps: First acid leaching: The nickel-cobalt hydroxide raw material is subjected to a first acid leaching treatment to obtain a first acid leaching solution; First neutralization: A first neutralizing agent is added to the first acidic leachate to adjust the pH value to 3.8-6.3 for precipitation. After a first solid-liquid separation, a neutralized precipitate and a neutralized liquid are obtained. For example, the first neutralizing agent can be added to the first acidic leachate to adjust the pH value to 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3, and any sub-range of any two values ​​between these values. Second acid leaching: The neutralized precipitate is subjected to a second acidic leaching treatment to obtain a second acidic leachate; Second neutralization: A second neutralizing agent is added to the second acidic leachate to adjust the pH to 4.1-6.5 for scandium enrichment and precipitation. The slurry after scandium enrichment and precipitation is then subjected to a second solid-liquid separation to obtain scandium-containing concentrate. For example, the second neutralizing agent can be added to the second acidic leachate to adjust the pH to 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, or any sub-range of any two values ​​between these values.

[0006] The core of this invention lies in utilizing staged precipitation and the concentration effect: the precipitation of metal ions is a gradual process occurring within a specific pH range, rather than being instantaneous. The first neutralization step, within the pH range of 3.8 to 6.3, primarily aims to neutralize Fe... 3+ Al 3+ Cu 2+ Plasma gradually precipitates within this pH range, while most of the nickel and cobalt remain in the liquid phase due to the higher precipitation pH. During this process, Sc... 3+ Precipitation occurs gradually with increasing pH, resulting in partial precipitation enrichment. Subsequently, a second acid leaching process dissolves the scandium-rich precipitate, yielding a second acidic leachate with significantly reduced nickel and cobalt concentrations and a relatively increased scandium concentration. During the second neutralization in this scandium-rich system, Sc... 3+ Due to its increased concentration, the precipitation process is more complete within the pH range of 4.1 to 6.5, resulting in a concentrate with a significantly increased scandium grade.

[0007] Furthermore, in the second neutralization step, a pre-neutralizing agent may be selectively added before scandium enrichment precipitation to adjust the pH of the second acidic leachate to 3.5-4.0 for pre-neutralization and impurity removal. This utilizes the difference in pH range for precipitation of various metal ions to preferentially promote the precipitation of residual Fe within this pH range. 3+ Al 3+ Cu 2+ Wait until the impurities have fully settled, and Sc 3+ The precipitation rate is relatively low, thus purifying the scandium enrichment system. After this pretreatment, directional precipitation of scandium can significantly improve the scandium grade in the final concentrate. For example, optionally, a pre-neutralizing agent can be added to adjust the pH of the second acidic leachate to 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, or any sub-range of two values ​​between these values. It should be understood that this pre-neutralization and impurity removal treatment is an optional step, not an essential technical feature for achieving the objectives of this invention.

[0008] Furthermore, the pre-neutralization and impurity removal process is as follows: using carbonates and / or hydroxides as pre-neutralizing agents, the pH value of the second acidic leachate is directly adjusted to 3.5~4.0 for pre-neutralization and impurity removal; Alternatively, nickel-cobalt hydroxide slurry (i.e., MHP slurry) can be used as a pre-neutralizing agent to adjust the pH of the second acidic leachate to 1-2, taking advantage of its characteristic that it does not easily induce nickel-cobalt precipitation at low pH values ​​(Ni 2+ / Co 2+ (It does not hydrolyze at pH < 3), initially neutralizes part of the free acid to save subsequent alkali consumption, and then uses carbonates and / or hydroxides as pre-neutralizing agents to adjust the pH value to 3.5~4.0 for pre-neutralization and impurity removal treatment.

[0009] The enrichment mechanism of this invention is based on the solubility product principle of metal ion hydrolysis precipitation and a stepwise precipitation strategy: First neutralization step: Control pH ≈ 3.8~6.3, utilizing the differences in pH range for precipitation of various ions. Fe 3+ / Al 3+ / Cu 2+ Plasma gradually precipitates completely within this pH range; Ni 2+ / Co 2+ Because its precipitate has a high pH, ​​it is essentially retained in the liquid phase; Sc 3+ Precipitation occurs in the middle to later part of this pH range, achieving partial co-precipitation and preliminary enrichment.

[0010] Pre-neutralization step (optional): Control pH ≈ 3.5~4.0, located at Sc 3+ Before the initial stage of a large precipitation in the pH range. Under these conditions, residual Fe 3+ / Al 3+Impurities can be further precipitated, while Sc 3+ The sedimentation rate is relatively low, thus achieving deep purification of impurities.

[0011] Second neutralization step: Control pH ≈ 4.1~6.5, cover Sc 3+ The main pH range for precipitation is approximately 4.1–5.0. This is due to the presence of Sc in the second acid leaching solution. 3+ With a significantly increased concentration, the precipitation process in this pH range is more thorough and complete; at the same time, a small amount of Ni is allowed. 2+ / Co 2+ Co-precipitation begins when pH > 6.0, eventually forming a concentrate with significantly improved Sc grade (Sc concentration can reach 1.2~3.4wt%), providing optimized raw materials for subsequent economical and efficient extraction of high-purity scandium products.

[0012] Further, the first neutralizing agent is at least one of nickel-cobalt hydroxide slurry (i.e., MHP slurry), carbonate, and hydroxide, preferably nickel-cobalt hydroxide slurry; And / or, the second neutralizing agent is at least one of carbonate and hydroxide.

[0013] Furthermore, the carbonate includes at least one of sodium carbonate and nickel carbonate; And / or, the hydroxide includes at least one of sodium hydroxide and nickel hydroxide.

[0014] Furthermore, the nickel-cobalt hydroxide slurry is a slurry material prepared from nickel-cobalt hydroxide raw materials and water, or a nickel-cobalt mixed hydroxide product from a high-pressure acid leaching process.

[0015] Furthermore, the first acid leaching treatment and the second acid leaching treatment use the same acid. Using different acids would introduce anionic impurities, which is not allowed according to the process specifications.

[0016] Furthermore, the leaching temperatures of the first acid leaching treatment and the second acid leaching treatment are each independently selected from 60 to 99°C; for example, the leaching temperature of the first acid leaching treatment can be selected as 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 99°C, and any sub-range of any two values ​​between these values; the leaching temperature of the second acid leaching treatment can be 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 99°C, and any sub-range of any two values ​​between these values. And / or, the leaching time of the first acid leaching treatment and the second acid leaching treatment are each independently selected from 2 to 5 hours; for example, the leaching time of the first acid leaching treatment can be selected as 2 hours, 3 hours, 4 hours, 5 hours, and any sub-range of any two values ​​between these values; the leaching time of the second acid leaching treatment can be 2 hours, 3 hours, 4 hours, 5 hours, and any sub-range of any two values ​​between these values. And / or, the acid used in the first acid leaching treatment is an inorganic acid.

[0017] Furthermore, the inorganic acid includes at least one of sulfuric acid, hydrochloric acid, and nitric acid, preferably sulfuric acid.

[0018] Furthermore, the solid-liquid ratio of the slurry during the first acid leaching treatment and the second acid leaching treatment (in this invention, the solid-liquid ratio is the ratio of solid mass (g) to liquid volume (ml)) is independently selected from 0.01 to 1; for example, the solid-liquid ratio of the slurry during the first acid leaching treatment can be selected as 0.01, 0.1, 0.2, 0.4, 0.6, 1, and any sub-range of any two values ​​between these values; the solid-liquid ratio of the slurry during the second acid leaching treatment can be 0.01, 0.05, 0.1, 0.2, 0.4, 0.6, 1, and any sub-range of any two values ​​between these values; And / or, the concentrations of acid in the first and second acidic leachates are each independently selected from 10 to 100 g / L. For example, the concentration of acid in the slurry during the first acidic leaching treatment can be 10 g / L, 20 g / L, 30 g / L, 40 g / L, 50 g / L, 60 g / L, 70 g / L, 80 g / L, 90 g / L, 100 g / L, or any sub-range of any two values ​​between these values; the concentration of acid in the slurry during the second acidic leaching treatment can be 10 g / L, 20 g / L, 30 g / L, 40 g / L, 50 g / L, 60 g / L, 70 g / L, 80 g / L, 90 g / L, 100 g / L, or any sub-range of any two values ​​between these values.

[0019] Furthermore, the first solid-liquid separation and the second solid-liquid separation are each independently selected from at least one of filtration and centrifugation.

[0020] In this invention, the scandium-containing concentrate is in the form of scandium-containing nickel hydroxide (the second neutralizing agent is a hydroxide to obtain nickel hydroxide) or nickel carbonate (the second neutralizing agent is a carbonate to obtain nickel carbonate), which can be directly used as a scandium extraction raw material or sold as a product.

[0021] The technical solution of this invention has the following advantages: 1. A method for enriching scandium from MHP intermediates produced by hydrometallurgical processing of laterite nickel ore, comprising the following steps: First acid leaching: subjecting nickel-cobalt hydroxide raw material to a first acid leaching treatment to obtain a first acid leaching solution; First neutralization: adding a first neutralizing agent to the first acid leaching solution to adjust the pH value to 3.8-6.3 for precipitation, and obtaining a neutralized precipitate and a neutralized liquid after a first solid-liquid separation; Second acid leaching: subjecting the neutralized precipitate to a second acid leaching treatment to obtain a second acid leaching solution; Second neutralization: adding a second neutralizing agent to the second acid leaching solution to adjust the pH value to 4.1-6.5 for scandium enrichment precipitation, and performing a second solid-liquid separation on the slurry after scandium enrichment precipitation to obtain a scandium-containing enriched product.

[0022] To overcome the high investment and operating costs associated with the existing MHP refining process, which uses direct extraction of the leaching solution to treat a large, low-concentration system, this invention constructs a staged enrichment process. Utilizing the pH range characteristics of metal ion precipitation, the nickel and cobalt main metals are separated in the first step, resulting in a system with a relatively high scandium concentration after the second acid leaching. In the second acid leaching stage, the pH value is precisely controlled within the range of 4.1-6.5 to cover Scandium. 3+ The main pH range of precipitation, using Sc 3+ The high concentration of scandium at this concentration allows for a more complete precipitation process, resulting in high-grade scandium concentrate. This technique achieves highly efficient scandium enrichment, significantly increasing the enrichment level. Simultaneously, the enrichment process concentrates trace amounts of scandium previously dispersed in a large volume of solution into a scandium-enriched precipitate, drastically reducing the material flow rate in subsequent processing systems and effectively lowering equipment investment and energy consumption. The resulting scandium-containing concentrate can be directly recycled in the extraction process or sold externally as an independent product, creating additional economic value.

[0023] 2. In the method for enriching scandium from MHP intermediates obtained by hydrometallurgical processing of laterite nickel ore according to the present invention, a significant technical breakthrough is achieved by performing a pre-neutralization and impurity removal treatment (adjusting the pH of the second acidic leachate to 3.5-4.0) before adding the precipitant: this step utilizes the reaction of impurity ions with Scandium. 3+ The difference in the pH range of precipitation allows for the preferential precipitation and removal of easily hydrolyzable impurities such as iron, aluminum, and copper within this specific pH range, effectively purifying the scandium enrichment system and significantly improving the selectivity of subsequent scandium precipitation processes. This optimization further enhances the scandium grade in the final enrichment (up to 3.4 wt%), while significantly reducing impurity content, achieving high-value utilization of the resource. This pre-neutralization step fundamentally solves the problem of high subsequent processing costs caused by high impurity content and insufficient scandium grade in the secondary leachate in the background technology. By synergistically improving the impurity open-loop and scandium grade, it significantly reduces the load and difficulty of subsequent separation processes, and significantly improves the economics of scandium recovery.

[0024] 3. In the pre-neutralization and impurity removal step of the method for enriching scandium from MHP intermediates produced by hydrometallurgical processing of laterite nickel ore according to the present invention, nickel-cobalt hydroxide slurry is preferentially used as a pre-neutralizing agent to adjust the pH of the second acidic leachate to 1-2. Under this low pH environment, the hydrogen ion concentration is high, which ensures that nickel and cobalt ions are completely stable in the liquid phase. The core purpose of this step is to neutralize a large amount of free acid using inexpensive nickel-cobalt hydroxide slurry, thereby significantly reducing the amount of subsequent expensive neutralizing agents and achieving cost reduction and efficiency improvement. Subsequently, carbonates and / or hydroxides are used to precisely adjust the pH to 3.5-4.0 for selective precipitation of iron and aluminum impurities. It should be understood that in the subsequent scandium enrichment and precipitation step (pH 4.1-6.5), some nickel and cobalt ions will inevitably co-precipitate and enter the scandium-containing concentrate. The advancement of this process lies in achieving two major objectives through the aforementioned pre-neutralization and impurity removal, as well as precise pH control: firstly, it significantly reduces the total amount of iron and aluminum impurities entering the scandium enrichment stage, lowering the difficulty of subsequent separation; secondly, it concentrates the unavoidable loss of nickel and cobalt into the high-value scandium concentrate, rather than allowing it to disperse in the low-value iron and aluminum waste. The resulting scandium-containing concentrate, due to its significantly increased scandium grade (see example, up to 3.4 wt%), is sufficient to cover the value of the entrained nickel and cobalt, making the entire recycling process economically feasible and efficient. Detailed Implementation

[0025] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0026] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0027] Unless otherwise specified, all pH values ​​in the following examples and comparative examples are real-time values ​​(hot pH) measured using a high-temperature calibrated pH meter at the operating temperature (e.g., 60~90℃). The elemental composition of the nickel-cobalt hydroxide raw materials used is shown in Table 1 below.

[0028] Table 1 Composition of nickel-cobalt hydroxide raw materials

[0029] Example 1 This embodiment provides a method for enriching scandium from MHP intermediates obtained by hydrometallurgical processing of laterite nickel ore. The specific steps are as follows: 1) First acid leaching: With a solid-liquid ratio (the ratio of solid mass (g) to liquid volume (ml)) of 0.6, nickel-cobalt hydroxide raw material (its composition is shown in Table 1) was mixed with a sulfuric acid aqueous solution with a mass fraction of 50wt%, and acid leaching treatment was carried out at 90℃ for 3 hours to obtain the first acid leachate. The concentration of free acid in the leachate was 50g / L. 2) First neutralization: Add the first neutralizing agent (MHP slurry, a nickel-cobalt mixed hydroxide product from the high-pressure acid leaching process, the same below) to the first acidic leachate to adjust the pH value to 4 for precipitation. After filtration, the neutralized precipitate and the neutralized liquid (filtrate) are obtained. The scandium content in the neutralized precipitate is 0.8 wt%. The neutralized liquid is sent to the extraction process of the main metal nickel-cobalt recovery system for nickel-cobalt extraction and recovery. 3) Second acid leaching: The neutralized precipitate and a sulfuric acid aqueous solution with a mass fraction of 48wt% were mixed according to a solid-liquid ratio of 0.6, and then acid leaching treatment was carried out at 90℃ for 3 hours to obtain the second acid leachate. The concentration of free acid in the leachate was 36g / L. 4) Second Neutralization: A second neutralizing agent (32wt% sodium hydroxide aqueous solution) was added to the second acidic leachate to adjust the pH to 5.5 for scandium enrichment and precipitation. The slurry after scandium enrichment and precipitation was filtered to obtain a scandium-containing concentrate. Testing showed that the scandium concentration in this concentrate was 1.8wt%, representing a 2.25-fold further enrichment compared to the first neutralization precipitation (0.8wt% scandium content); and a 36-fold enrichment compared to the raw material (0.05wt% scandium content). This significantly improved the relative grade of scandium and laid an important foundation for subsequent deep extraction and refining of scandium.

[0030] Example 2 This embodiment provides a method for enriching scandium from MHP intermediates obtained by hydrometallurgical processing of laterite nickel ore. The specific steps are as follows: 1) First acid leaching: With a solid-liquid ratio of 0.1, nickel-cobalt hydroxide raw material (its composition is shown in Table 1) was mixed with a sulfuric acid aqueous solution with a mass fraction of 15wt%, and acid leaching treatment was carried out at 95℃ for 2 hours to obtain the first acid leaching solution. The concentration of free acid in the solution was 65g / L. 2) First neutralization: Add the first neutralizing agent (MHP slurry) to the first acidic leachate to adjust the pH value to 3.8 for precipitation. After filtration, the neutralized precipitate and the neutralized liquid (filtrate) are obtained. The scandium content in the neutralized precipitate is 0.5 wt%. The neutralized liquid is sent to the extraction process of the main metal nickel-cobalt recovery system for nickel-cobalt extraction and recovery. 3) Second acid leaching: The neutralized precipitate and a 50wt% sulfuric acid aqueous solution were mixed at a solid-liquid ratio of 0.6, and then acid leaching was carried out at 60℃ for 5 hours to obtain the second acid leachate. The concentration of free acid in the leachate was 60g / L. 4) Second Neutralization: A second neutralizing agent (32wt% sodium hydroxide aqueous solution) was added to the second acidic leachate to adjust the pH to 6.5 for scandium enrichment and precipitation. The slurry after scandium enrichment and precipitation was filtered to obtain a scandium-containing concentrate. Testing showed that the scandium concentration in this concentrate was 2.1wt%, representing a 4.2-fold further enrichment compared to the first neutralization precipitation (0.5wt% scandium content); and a 42-fold enrichment compared to the raw material (0.05wt% scandium content). This significantly improved the relative grade of scandium and laid an important foundation for subsequent deep extraction and refining of scandium.

[0031] Example 3 This embodiment provides a method for enriching scandium from MHP intermediates obtained by hydrometallurgical processing of laterite nickel ore. The specific steps are as follows: 1) First acid leaching: With a solid-liquid ratio of 0.8, nickel-cobalt hydroxide raw material (its composition is shown in Table 1) was mixed with a sulfuric acid aqueous solution with a mass fraction of 60wt%, and acid leaching treatment was carried out at 60℃ for 5h to obtain the first acid leachate. The concentration of free acid in the leachate was 100g / L. 2) First neutralization: Add the first neutralizing agent (MHP slurry) to the first acidic leachate to adjust the pH value to 6.3 for precipitation. After filtration, the neutralized precipitate and the neutralized liquid (filtrate) are obtained. The scandium content in the neutralized precipitate is 1.0 wt%. The neutralized liquid is sent to the extraction process of the main metal nickel-cobalt recovery system for nickel-cobalt extraction and recovery. 3) Second acid leaching: The neutralized precipitate and a sulfuric acid aqueous solution with a mass fraction of 54wt% were mixed according to a solid-liquid ratio of 0.6, and then acid leaching was carried out at 96℃ for 2 hours to obtain the second acid leachate. The concentration of free acid in the leachate was 10g / L. 4) Second Neutralization: A second neutralizing agent (32wt% sodium hydroxide aqueous solution) was added to the second acidic leachate to adjust the pH to 4.1 for scandium enrichment and precipitation. The slurry after scandium enrichment and precipitation was filtered to obtain a scandium-containing concentrate. Testing showed that the scandium concentration in this concentrate was 1.2wt%, representing a 1.2-fold further enrichment compared to the first neutralization precipitation (scandium content 1.0wt%); and a 24-fold enrichment compared to the raw material (scandium content 0.05wt%). This significantly improved the relative grade of scandium and laid an important foundation for subsequent deep extraction and refining of scandium.

[0032] Example 4 This embodiment provides a method for enriching scandium from MHP intermediates obtained by hydrometallurgical processing of laterite nickel ore. The specific steps are as follows: 1) First acid leaching: With a solid-liquid ratio of 0.6, nickel-cobalt hydroxide raw material (its composition is shown in Table 1) was mixed with a sulfuric acid aqueous solution with a mass fraction of 50wt%, and acid leaching treatment was carried out at 90℃ for 3 hours to obtain the first acid leachate. The concentration of free acid in the leachate was 50g / L. 2) First neutralization: Add the first neutralizing agent (MHP slurry) to the first acidic leachate to adjust the pH value to 4 for precipitation. After filtration, the neutralized precipitate and the neutralized liquid (filtrate) are obtained. The scandium content in the neutralized precipitate is 0.8 wt%. The neutralized liquid is sent to the extraction process of the main metal nickel-cobalt recovery system for nickel-cobalt extraction and recovery. 3) Second acid leaching: The neutralized precipitate and a sulfuric acid aqueous solution with a mass fraction of 48wt% were mixed according to a solid-liquid ratio of 0.6, and then acid leaching treatment was carried out at 90℃ for 3 hours to obtain the second acid leachate. The concentration of free acid in the leachate was 36g / L. 4) Second Neutralization: A 32wt% sodium hydroxide aqueous solution was used as a pre-neutralizing agent to adjust the pH of the second acidic leachate to 4.0 for pre-neutralization and impurity removal. After filtration, another 32wt% sodium hydroxide aqueous solution was added to the filtrate to adjust the pH to 5.5 for scandium enrichment and precipitation. The slurry after scandium enrichment and precipitation was then filtered to obtain a scandium-containing concentrate. Testing showed that the scandium concentration in this concentrate was 3.4wt%, representing a 4.25-fold further enrichment compared to the first neutralization precipitation (0.8wt% scandium content); and a 68-fold enrichment compared to the raw material (0.05wt% scandium content). This significantly improved the relative grade of scandium and laid an important foundation for subsequent deep extraction and refining of scandium.

[0033] Example 5 This embodiment provides a method for enriching scandium from MHP intermediates obtained by hydrometallurgical processing of laterite nickel ore. The specific steps are as follows: 1) First acid leaching: With a solid-liquid ratio of 0.6, nickel-cobalt hydroxide raw material (its composition is shown in Table 1) was mixed with a sulfuric acid aqueous solution with a mass fraction of 50wt%, and acid leaching treatment was carried out at 90℃ for 3 hours to obtain the first acid leachate. The concentration of free acid in the leachate was 50g / L. 2) First neutralization: Add the first neutralizing agent (MHP slurry) to the first acidic leachate to adjust the pH value to 4 for precipitation. After filtration, the neutralized precipitate and the neutralized liquid (filtrate) are obtained. The scandium content in the neutralized precipitate is 0.8 wt%. The neutralized liquid is sent to the extraction process of the main metal nickel-cobalt recovery system for nickel-cobalt extraction and recovery. 3) Second acid leaching: The neutralized precipitate and a sulfuric acid aqueous solution with a mass fraction of 48wt% were mixed according to a solid-liquid ratio of 0.6, and then acid leaching treatment was carried out at 90℃ for 3 hours to obtain the second acid leachate. The concentration of free acid in the leachate was 36g / L. 4) Second Neutralization: First, the pH of the second acidic leachate was adjusted to 2.0 using MHP slurry. Then, a 32wt% sodium hydroxide aqueous solution was used to further adjust the pH to 4.0 for pre-neutralization and impurity removal. After filtration, another 32wt% sodium hydroxide aqueous solution was added to the filtrate to adjust the pH to 5.5 for scandium enrichment and precipitation. The slurry after scandium enrichment and precipitation was then filtered to obtain a scandium-containing concentrate. Testing showed that the scandium concentration in this concentrate was 3.2wt%, representing a 4.0-fold further enrichment compared to the first neutralization precipitation (0.8wt% scandium content); and a 64-fold enrichment compared to the raw material (0.05wt% scandium content). This significantly improved the relative grade of scandium and laid an important foundation for subsequent deep extraction and refining of scandium.

[0034] Comparative Example 1 This comparative example provides a method for enriching scandium from nickel cobalt hydroxide. The difference between this method and Example 1 is that, in the first neutralization step, the pH of the first acidic leachate is adjusted to 3.0, while other conditions remain the same as in Example 1. Because the pH of the first neutralization step in this comparative example is controlled outside the preferred range (3.8~6.3) and below Sc... 3+ The pH range where significant precipitation begins results in only partial precipitation of elements such as iron, aluminum, and scandium. This leads to the dispersion of scandium, causing two serious consequences: First, most of the scandium remains in the liquid phase: this portion of scandium enters the nickel-cobalt extraction system with the neutralized liquid. Scandium ions are difficult to separate effectively in the nickel-cobalt extraction system and will continuously accumulate in the closed-loop circulation of the system, eventually causing extractant poisoning and severely damaging the separation performance of nickel-cobalt extraction. Second, a very small portion of scandium enters the solid phase due to adsorption and co-precipitation: this portion of scandium mainly combines with a small amount of co-precipitated iron and aluminum hydroxide precipitates through surface adsorption or mechanical entrainment and enters the subsequent second-stage processing. Due to the small initial amount of precipitate and its complex composition, the so-called "enriched product" obtained at the end actually has an extremely low scandium grade (only 0.01%) and still contains a certain amount of iron and aluminum impurities, resulting in low economic recovery value and essentially wasting scandium resources.

[0035] Comparative Example 2 This comparative example provides a method for enriching scandium from nickel cobalt hydroxide. The difference from Example 1 is that in the second neutralization step, the pH of the second acidic leachate is adjusted to 3.8 for scandium enrichment and precipitation; other conditions are the same as in Example 1. Because the second neutralization pH in this comparative example is lower, Scandium... 3+ It is difficult to precipitate effectively, while impurity ions such as iron, aluminum, and copper can still precipitate to a considerable extent. This results in the final concentrate mainly consisting of impurity precipitates, with scandium's relative proportion significantly reduced due to its low precipitation rate, failing to achieve efficient scandium enrichment.

[0036] Comparative Example 3 This comparative example provides a method for enriching scandium from nickel-cobalt hydroxide. The difference from Example 1 is that in the second neutralization step, the pH of the second acidic leachate is adjusted to 7.0 for scandium enrichment and precipitation; other conditions are the same as in Example 1. In this comparative example, because the hot pH at the neutralization endpoint was too high (hot pH = 7.0), exceeding the preferred pH control range of this invention, the precipitation rates of nickel hydroxide (Ni(OH)2) and cobalt hydroxide (Co(OH)2) increased with increasing pH. Under the condition of hot pH = 7.0, the hydrolysis and precipitation of nickel and cobalt ions were already very significant. Ultimately, the nickel and cobalt content in the resulting precipitate increased sharply (see Table 2; the Ni content in Comparative Example 3 was as high as 24.0%), severely diluting the scandium grade and resulting in a significant decrease in its enrichment degree (scandium grade only 0.4%). This result indicates that the product obtained under these high pH conditions is a mixture with high nickel and cobalt content and low scandium grade, unsuitable as a qualified raw material for subsequent scandium refining.

[0037] Table 2. Component content (wt%) in scandium-enriched concentrates

[0038] Based on the above test results, the scandium content in the scandium-containing concentrates obtained in Examples 1 to 5 of this invention is consistently between 1.2 and 3.4 wt%. This result verifies the core mechanism of this invention: preferential separation of nickel and cobalt main metals through the first neutralization step significantly increases the scandium content in the second acid leaching solution. 3+ The relative concentration of Sc; in the second neutralization step, 3+ Due to its increased concentration, precipitation is more complete within a specific pH range, achieving a further enrichment of 1.2-4.25 times compared to the first neutralization precipitation. Simultaneously, this process effectively controls the entrainment of valuable metals such as nickel (3.1-16.1 wt%) and cobalt (0.4-2.3 wt%), as well as the co-precipitation ratio of impurities such as iron (0.5-3.4 wt%), aluminum (2.8-20.2 wt%), and copper (0.8-12.2 wt%), demonstrating excellent separation selectivity.

[0039] In contrast, Comparative Example 1 failed to reach the Sc target due to excessively low pH control during a single neutralization (pH=3.0). 3+ The effective precipitation pH range resulted in scandium failing to accumulate effectively in the solid phase (scandium content was only 0.01 wt%) and remaining in the liquid phase, thus causing poisoning of the extraction system; Comparative Example 2 had a lower secondary neutralization pH (pH=3.8), Sc 3+ The precipitation pH range was not fully covered, resulting in insufficient precipitation rate, and impurities were not completely removed (high levels of residual iron, aluminum, and copper). Comparative Example 3 had an excessively high secondary neutralization pH (pH=7.0), exceeding the Sc... 3+ The optimal precipitation range for scandium is within the significant precipitation range of nickel and cobalt, leading to excessive precipitation of the target metal, thus failing to achieve efficient enrichment of scandium.

[0040] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for enriching scandium from MHP intermediates obtained by hydrometallurgical processing of laterite nickel ore, characterized in that, Includes the following steps: First acid leaching: The nickel-cobalt hydroxide raw material is subjected to a first acid leaching treatment to obtain a first acid leaching solution; First neutralization: Add the first neutralizing agent to the first acidic leachate to adjust the pH value to 3.8~6.3 to induce precipitation. After the first solid-liquid separation, the neutralized precipitate and the neutralized liquid are obtained. Second acid leaching: The neutralized precipitate is subjected to a second acidic leaching treatment to obtain a second acidic leachate; Second neutralization: Add a second neutralizing agent to the second acidic leachate to adjust the pH value to 4.1~6.5 to enrich and precipitate scandium. Perform a second solid-liquid separation on the slurry after scandium enrichment and precipitation to obtain scandium-containing concentrate.

2. The method according to claim 1, characterized in that, In the second neutralization step, before the scandium enrichment and precipitation, a pre-neutralizing agent is added to adjust the pH of the second acidic leachate to 3.5-4.0 for pre-neutralization and impurity removal.

3. The method according to claim 2, characterized in that, The pre-neutralization and impurity removal process is as follows: using carbonates and / or hydroxides as pre-neutralizing agents, the pH value of the second acidic leachate is directly adjusted to 3.5~4.0 for pre-neutralization and impurity removal. Alternatively, nickel-cobalt hydroxide slurry can be used as a pre-neutralizing agent to adjust the pH of the second acidic leachate to 1-2, and then carbonates and / or hydroxides can be used as pre-neutralizing agents to adjust the pH to 3.5-4.0 for pre-neutralization and impurity removal.

4. The method according to claim 1, characterized in that, The first neutralizing agent is at least one of nickel-cobalt hydroxide slurry, carbonate, and hydroxide, preferably nickel-cobalt hydroxide slurry; And / or, the second neutralizing agent is at least one of carbonate and hydroxide.

5. The method according to claim 4, characterized in that, The carbonate includes at least one of sodium carbonate and nickel carbonate; And / or, the hydroxide includes at least one of sodium hydroxide and nickel hydroxide.

6. The method according to claim 3 or 4, characterized in that, The nickel-cobalt hydroxide slurry is a slurry material prepared by mixing nickel-cobalt hydroxide raw materials with water, or a nickel-cobalt mixed hydroxide product from a high-pressure acid leaching process.

7. The method according to any one of claims 1 to 6, characterized in that, The first acid leaching treatment and the second acid leaching treatment use the same acid; And / or, the leaching temperatures of the first acid leaching treatment and the second acid leaching treatment are each independently selected from 60 to 99°C; And / or, the leaching time of the first acid leaching treatment and the second acid leaching treatment are each independently selected from 2 to 5 hours; And / or, the acid used in the first acid leaching treatment is an inorganic acid.

8. The method according to claim 7, characterized in that, The inorganic acid includes at least one of sulfuric acid, hydrochloric acid, and nitric acid, preferably sulfuric acid.

9. The method according to any one of claims 1 to 6, characterized in that, The solid-liquid ratio of the slurry during the first acid leaching treatment and the second acid leaching treatment is independently selected from 0.01 to 1; And / or, the concentration of acid in the first acidic leachate and the second acidic leachate are each independently selected from 10 to 100 g / L.

10. The method according to any one of claims 1 to 6, characterized in that, The first solid-liquid separation and the second solid-liquid separation are each independently selected from at least one of filtration and centrifugation.

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