Method for stepwise directional separation of copper, nickel and iron from nickel leaching tailings

Abstract

This invention belongs to the field of hydrometallurgical technology, and specifically relates to a method for the tiered directional separation of copper, nickel, and iron from nickel leaching tailings. This method targets high-copper and high-nickel nickel leaching tailings. First, the tailings are activated at room temperature with an acidic nickel-containing solution within the nickel smelting system. Then, pressure leaching is performed to achieve highly selective nickel leaching, yielding high-grade copper slag and a leachate containing nickel and iron. Finally, the leachate is subjected to pressure iron removal to obtain iron concentrate and a pure nickel sulfate solution. This invention overcomes the shortcomings of existing technologies in handling high-nickel materials through a unique three-stage process of "activation treatment – ​​selective nickel leaching – pressure iron removal," achieving efficient separation and full resource recovery of copper, nickel, and iron. Furthermore, the process is closely coupled with the main smelting system, resulting in low cost and environmental friendliness.

Description

Technical Field

[0001] This invention relates to the field of hydrometallurgical technology, and in particular to a method for the directional separation of copper, nickel and iron from nickel leaching tailings. Background Technology

[0002] Nickel leaching tailings generated during nickel smelting are a high-value secondary resource, typically composed of 40-60% Cu, 8-25% Ni, and 1-5% Fe. While valuable, this slag is complex, with tightly packed copper and nickel deposits. Traditional acid leaching processes struggle to achieve efficient and selective nickel extraction, often resulting in low nickel leaching rates, severe copper-nickel entrainment in the leachate, and high subsequent separation costs. Existing technologies have explored some methods for treating nickel-containing copper materials. For example, patent application CN118389830A discloses a hydrometallurgical process for treating nickel-containing copper concentrate, primarily targeting primary sulfide copper concentrate, with the aim of reducing the nickel content. The core idea of ​​this patent is to use a "single-stage pressure leaching" process to leach copper concentrate with a nickel content of 2.0%-4.0% by adding 10-30% sulfuric acid and 20-50% copper sulfate by the concentrate mass, depending on the nickel content in the raw materials. However, for copper concentrate with a nickel content of 4.0%-6.5%, a two-stage leaching process of "atmospheric pressure + pressure" is used. Under atmospheric pressure and pressure conditions, 15-30% sulfuric acid and 20-50% copper sulfate by the concentrate mass and 10-20% sulfuric acid and 10-25% copper sulfate by the concentrate mass are added, respectively. The reaction mainly relies on the action of the additional sulfuric acid and copper sulfate, which can reduce the nickel content in the copper concentrate to below 0.5%. Patent application publication number CN115558797A discloses a method for treating high-grade nickel matte oxygen pressure leaching residue. It uses sulfuric acid and sulfur dioxide for pressurized and enhanced leaching, so that all valuable metals such as copper, nickel, and iron are transferred into the leaching solution. Only iron in the leaching solution is recovered (to produce ferrous sulfate heptahydrate product), while copper and nickel still coexist in the form of mixed sulfate solution, failing to achieve effective separation and separate recovery of the two.

[0003] However, for nickel leaching tailings with a nickel content as high as 8-25%, the complex phase composition makes it difficult to directly apply the existing processes described above, resulting in poor nickel leaching and separation selectivity. Therefore, there is an urgent need to develop a new process that can efficiently break down complex phases and achieve selective separation of copper, nickel, and iron without the need for additional gas introduction or the addition of reagents such as sulfuric acid or copper sulfate. Summary of the Invention

[0004] (a) Technical problems to be solved

[0005] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a method for the stepwise directional separation of copper, nickel and iron in nickel immersion tailings, which solves the technical problems of difficult copper-nickel separation and large reagent consumption when the existing process is used to process high-nickel, lattice-stable nickel immersion tailings.

[0006] (II) Technical Solution

[0007] To achieve the above objectives, the main technical solutions adopted by the present invention include:

[0008] This invention provides a method for the directional separation of copper, nickel, and iron in nickel leaching tailings, comprising the following steps:

[0009] S1. Activation at room temperature: The nickel leaching tailings are mixed with acidic nickel-containing dilute acid solution produced by the nickel smelting system and 4% to 25% of the copper slag after roasting. The mixture is then activated at room temperature and pressure to obtain a mixed slurry.

[0010] S2, First-stage pressure leaching: The activated slurry obtained in step S1 is transferred into a closed pressure vessel and subjected to pressure leaching reaction at a temperature of 190~210℃; after the reaction is completed, liquid-solid separation is performed to obtain copper-rich copper slag and leaching solution containing iron and nickel.

[0011] S3. Two-stage hot-pressing iron removal: An alkaline neutralizing agent is added to the leachate obtained in step S2 to adjust the pH value of the solution. Then, the solution is transferred to a closed pressure vessel and heated to carry out a hydrolysis precipitation reaction. After the reaction is completed, liquid-solid separation is performed to obtain iron slag and nickel sulfate purified solution. The iron slag is purified to obtain iron concentrate as a by-product.

[0012] In the method described above, preferably, in step S1, the main components of the nickel immersion tailings are: Cu 40-60%, Ni 8-25%, and Fe 1-5%;

[0013] The acidic nickel-containing dilute acid solution contains sulfuric acid or hydrochloric acid with a concentration of 20-100 g / L, Ni 2+ It is 60~80g / L.

[0014] Furthermore, the acidic nickel-containing dilute acid solution is the anolyte produced during the nickel electrolytic refining process or a similar acidic raffinate from the nickel hydrometallurgical process.

[0015] Furthermore, the acidic nickel-containing dilute acid solution and the nickel leaching tailings are mixed at a liquid-to-solid ratio of 6-13 mL: 1 g.

[0016] In the method described above, preferably, in step S1, when processing the nickel immersion tailings for the first time, the copper slag is the copper slag obtained by roasting the nickel immersion tailings at 300~900℃ for 30~120min; the copper slag used in subsequent processing is the copper slag obtained in step S2 of this method, which is then roasted at 300~900℃ for 30~120min, and the copper slag can be recycled.

[0017] In the method described above, preferably, in step S2, the leaching reaction time is 0.5 to 1 hour.

[0018] In the method described above, preferably, in step S2, the copper slag obtained contains Cu content ≥70%, Ni content ≤0.3%, and Fe content ≤0.3%; the leachate obtained contains Cu concentration <0.1 g / L, Ni concentration 50~98 g / L, and Fe concentration 2~5 g / L.

[0019] In the method described above, preferably, in step S3, the neutralizing agent is an alkaline substance, including but not limited to one or more of sodium carbonate, calcium carbonate, calcium oxide, calcium hydroxide, nickel carbonate, basic nickel carbonate, and nickel hydroxide.

[0020] In the method described above, preferably, in step S3, the pH value of the adjusted solution is 2.0 to 4.0.

[0021] In the method described above, preferably, in step S3, the heating temperature is 120~160℃, and the hydrolysis precipitation reaction time is 2~6h.

[0022] As described above, preferably, in step S3, the iron slag purification process involves washing the iron slag 2-3 times with 5%-10% dilute sulfuric acid at a liquid-to-solid ratio of 3-5 mL:1 g, or by countercurrent washing, and then roasting it at 300-500°C for 0.5-2 h to obtain the by-product iron concentrate.

[0023] (III) Beneficial Effects

[0024] The beneficial effects of this invention are:

[0025] This invention provides a method for the tiered directional separation of copper, nickel, and iron from nickel leaching tailings. By inducing lattice distortion of the insoluble phase through material circulation within the system, combined with a stepwise pressure leaching and tiered separation strategy, copper is enriched in the slag phase, iron is converted into iron concentrate, and nickel is purified and recovered. This achieves the selective separation and high-value utilization of multiple valuable metals in complex secondary resources.

[0026] This invention provides a method for the tiered directional separation of copper, nickel, and iron from nickel leaching tailings. The tailings are secondary residues generated after a smelting process at a certain temperature (e.g., 120-150°C). These materials have undergone intense physicochemical reactions in the early stages, resulting in a "triple difficulty in processing" characteristic; their stable crystal lattice makes nickel leaching difficult. This invention, without introducing oxygen or adding exogenous reagents such as sulfuric acid or copper sulfate, achieves a stable nickel leaching rate of over 97% through the synergistic effect of "copper-containing material activation + selective pressure leaching," with nickel residue in the slag ≤0.3%. This method overcomes the limitations of existing technologies on the nickel content of materials, providing a universal solution for enterprises and significantly improving the versatility and industrial value of the process.

[0027] The method of this invention also achieves the stepwise separation of copper, nickel, and iron. This invention solves the problem of difficult separation of copper-nickel mixed solutions in existing technologies through a stepwise separation strategy of activation pretreatment and two-stage pressurization.

[0028] ① Copper separation: During a pressurization process, based on the difference in thermodynamic stability, copper is enriched in the slag phase in solid form, realizing the initial separation of copper from nickel and iron, and producing high-copper slag that can be directly sold as copper concentrate.

[0029] ② Nickel recovery: After the two-stage pressurization is completed, the iron content in the nickel sulfate solution is <0.1g / L, and a high-purity nickel sulfate solution is obtained, which can be further used to produce nickel salts or electrolytic nickel.

[0030] ③ Iron Resource Utilization: The two-stage hot pressing process, through high-temperature hydrolysis, transforms iron into a dense iron concentrate precipitate with high iron content and few impurities. This concentrate can be sold directly as a byproduct, achieving resource utilization of iron. Compared to the existing patent application CN115558797A, which only recovers iron (ferrous sulfate heptahydrate), leaving copper and nickel as a mixed solution, this invention achieves the separate recovery of all three metals, significantly improving resource utilization.

[0031] This invention provides a method for the tiered directional separation of copper, nickel, and iron from nickel leaching tailings. It eliminates the need to purchase reagents such as copper sulfate and sulfuric acid, significantly reducing production costs. The method utilizes copper-containing materials within the system as an activator, allowing for recycling. Compared to the method described in patent application CN118389830A, which requires the addition of 10-30 wt% sulfuric acid and 10-50 wt% copper sulfate, this invention offers the following advantages:

[0032] ① Save reagent costs: Replacing purchased copper sulfate and sulfuric acid with copper-containing materials reduces production costs by approximately RMB 35 million to 85 million per 10,000 tons of material processed.

[0033] ② No accumulation of impurities: The activator originates from within the system and does not introduce external anions, thus avoiding the impact of impurity accumulation on product quality and reducing the cost of purification and impurity removal processes.

[0034] ③ Zero loss of copper: After the activation process is completed, the copper in the activator is eventually recovered in the form of high copper slag, achieving "two uses for one product". Attached Figure Description

[0035] Figure 1 This is a schematic flowchart of a method for the tiered directional separation of copper, nickel, and iron from nickel leaching tailings according to the present invention. Detailed Implementation

[0036] Nickel leaching tailings with a Ni content greater than 8% and a Cu content of 40-60% are secondary residues generated after a smelting process at a certain temperature and pressure. These materials have undergone intense physicochemical reactions in the early stages, resulting in three difficult-to-process characteristics: ① The residual minerals underwent recrystallization in the earlier processes, resulting in well-developed crystals with few defects; ② Valuable metals such as nickel are contained in thermodynamically stable sulfide lattices (such as Ni3S2, NiS, etc.), exhibiting strong chemical inertness; ③ Although they are tailings, the nickel content is still as high as 8-25%, possessing high recycling value, but extremely difficult to leach due to the stability of the lattice. Based on these material characteristics, conventional acid leaching or oxidative leaching is insufficient to effectively disrupt the lattice. A lattice distortion-induced approach must be adopted to disrupt its stability from within, rather than relying solely on external acid and heating. According to conventional understanding in this field, such materials require strong oxidizing acid leaching or high-temperature, high-pressure oxygen leaching to achieve effective nickel extraction. For example, the existing patent application CN118389830A essentially promotes chemical reaction equilibrium by increasing the concentration of reagents. This is costly and introduces foreign impurities. It involves adding 10-30 wt% sulfuric acid and 10-50 wt% copper sulfate. The role of these reagents is to provide hydrogen ions and copper ions to assist the leaching process.

[0037] The object of this invention is nickel leaching tailings produced during the smelting process. These are secondary sulfide ores with a nickel content of 8-25%, characterized by high crystallinity and stable crystal lattice. To address this characteristic, this invention utilizes internal material recycling to disrupt the crystal stability of insoluble phases such as nickel sulfide in the tailings through common ion effects or lattice distortion induction, making them easier to dissociate under high-temperature, acidic conditions. Its significant advantage lies in eliminating the need to purchase additional reagents such as copper sulfate, achieving internal material recycling, and significantly reducing production costs.

[0038] Extensive experimental research has revealed that this invention employs a pressure leaching process. First, nickel and a small amount of iron are selectively leached into the solution, while copper is enriched in the leaching residue, achieving preliminary copper separation (copper content in the leaching solution is less than 0.1 g / L). Subsequently, an alkaline neutralizing agent is added to the iron- and nickel-containing leaching solution, followed by pressure treatment to obtain a solid iron concentrate byproduct, along with a purified nickel sulfate solution (Fe < 0.1 g / L). Through this stepwise separation strategy, this invention achieves efficient separation and resource recovery of copper, nickel, and iron.

[0039] This invention discovers a "self-activation" mechanism achieved by utilizing internal material recycling within the system, such as the acidic nickel-containing solution produced by the nickel smelting system itself. This mechanism works by suppressing certain side reactions through the common ion effect, directionally promoting the target reaction pathway, and disrupting the stability of insoluble phases such as nickel sulfide in the nickel leaching tailings. This significantly reduces the dissociation energy of nickel sulfides under subsequent high-temperature acidic conditions, resulting in a significant increase in the leaching rate. The advantage lies in not relying on additional reagent purchases, achieving internal material recycling, and reducing production costs by approximately 35-85 million yuan per 10,000 tons of material processed. The preferred concentration of sulfuric acid or hydrochloric acid in the acidic nickel-containing solution is 20-100 g / L. 2+ The content is 60~80g / L.

[0040] Extensive experimental research has revealed that using acidic nickel-containing solutions within this acid concentration range, H + Sufficient thermodynamic driving force to break the nickel sulfide lattice, allowing S in the sulfide to... 2- Protonation generates H2S or further oxidation, thus significantly reducing the dissociation energy; simultaneously, this acidity is similar to that of 60-80 g / L Ni. 2+ This achieves a good synergistic effect, ensuring the leaching rate while avoiding ineffective acid consumption and severe corrosion. When the acid concentration is below 20 g / L, H... + The concentration is insufficient to effectively corrode the nickel sulfide surface; the reaction is limited to localized pitting corrosion and cannot achieve overall lattice destruction, resulting in a significant decrease in leaching rate. When the acid concentration exceeds 100 g / L, the corrosion rate on the equipment increases sharply, and excessively high H... + Concentration will interfere with Ni 2+ The common ion effect reduces reaction selectivity, causing an abnormally high leaching rate of impurities such as Fe and Cu, increasing the burden on subsequent solution purification, and resulting in poor economic efficiency.

[0041] When you 2+ At a concentration of 60-80 g / L, it not only provides a sufficiently strong common ion effect, effectively inhibiting the hydrolysis of iron and copper ions to form hydroxides or basic salt precipitates, preventing the formation of a passivation film on the surface of the tailings; but also, at this concentration, the solution viscosity is moderate, and the ion diffusion rate is fast, which is conducive to maintaining the kinetic equilibrium of the "self-activation" reaction; when Ni 2+ When the concentration is below 60 g / L, the common ion effect is insufficient, and impurity iron ions are easily hydrolyzed to form Fe(OH)3 colloids or pyrite precipitates. These substances will densely coat the surface of the nickel leaching tailings, significantly hindering mass transfer, resulting in impaired dissociation of nickel sulfide, a sharp decrease in the leaching rate, and an increase in the nickel content in the leaching residue; when Ni 2+When the concentration is higher than 80 g / L, the solution viscosity increases significantly, the ion diffusion coefficient decreases, and the reaction kinetics slow down. At the same time, the excessive salt effect may inhibit the formation of key intermediates in the target reaction pathway, turning "self-activation" into "self-inhibition". In addition, high-concentration nickel salts are prone to crystallization such as NiSO4·6H2O or NiCl2·nH2O when the temperature fluctuates, causing pipeline blockage and system instability.

[0042] This invention provides a method for the cascaded directional separation of copper, nickel, and iron from nickel leaching tailings. The method employs a first-stage pressurization to separate copper from nickel and iron, where nickel and iron enter the solution, while copper is enriched in the slag. A second-stage pressurization is then applied to the solution, utilizing a high-temperature hydrolysis mechanism to separate nickel from iron. Iron precipitates as dense iron concentrate (Fe₂O₃), while nickel remains in the solution. This achieves efficient cascaded recovery of the three main metallic elements—copper, nickel, and iron—avoiding the problem of difficult separation of mixed copper-nickel solutions. Compared to the resource utilization process of high-pressure nickel matte leaching slag disclosed in CN11555879A, which only achieves the resource recovery of iron, while copper and nickel remain in a mixed form and fail to be effectively separated and recovered individually, this invention achieves efficient separation of all components, demonstrating significant effectiveness.

[0043] Extensive experiments have revealed that the alkaline neutralizing agent used in this invention slowly provides OH- to solutions containing iron and nickel. - The pH of the system was precisely adjusted to 2-4, thereby inducing Fe... 3+ A uniform hydrolysis and precipitation reaction at high temperature avoids localized over-alkaliness that could lead to the formation of amorphous Fe(OH)3 colloids or basic ferric sulfate precipitates. It reacts with SO4 in the solution. 2- Ni 2+ A synergistic regulatory relationship can be generated between the components: Under the conditions of introducing a neutralizing agent and a certain temperature, Fe... 3+ It preferentially undergoes hydrolysis and transforms into well-crystallized Fe2O3 (hematite), while Ni... 2+ Because the hydrolysis pH is significantly higher than that of Fe 3+ Within a pH range of 2-4, it remains in an ionic state and is not precipitated, thus achieving efficient separation of nickel and iron; if the pH is too high, some Ni... 2+ It is prone to hydrolysis to form Ni(OH)2, resulting in nickel loss; below pH 2, Fe 3+ Incomplete precipitation results in poor iron-nickel separation; therefore, a pH value of 2-4 is preferred.

[0044] The preferred temperature for the hydrolysis precipitation reaction in this invention is 120-160℃, at which temperature the reaction can be significantly accelerated for Fe. 3+The hydrolysis kinetics are controlled and the crystal transformation of the precipitate products is regulated, causing the amorphous Fe(OH)3 colloid or FeOOH (goethite) that is easily formed at room temperature to be directionally transformed into Fe2O3 with complete crystal structure, thereby improving the filtration performance of the precipitate and the quality of iron concentrate. At the same time, Ni 2+ Because the critical pH for hydrolysis and precipitation increases further at high temperatures, it remains more stably in the solution, thus achieving a rapid and dense precipitation of iron and enhanced separation of nickel in the liquid at temperatures of 120-160℃. If the temperature is below 120℃, the hydrolysis reaction rate is insufficient, and the precipitate products are mostly goethite or hydrated iron oxide, making filtration difficult and resulting in low-grade iron concentrate. If the temperature is too high, such as above 160℃, although the precipitation rate is faster, the pressure resistance requirements of the equipment increase significantly, and it may trigger Ni precipitation. 2+ The co-precipitation or crystallization of sulfate in solution significantly increases energy consumption and cost. Therefore, the optimal temperature for the hydrolysis precipitation reaction is 120~160℃.

[0045] The present invention provides a method for the tiered directional separation of copper, nickel, and iron from nickel leaching tailings. First, an alkaline neutralizing agent is added to adjust the pH value and the reaction is continued. The iron and nickel-containing solution is sealed and heated to 120-160°C. Under the condition of maintaining this temperature, iron can be precipitated from the solution in the form of hematite, which is easy to wash and filter. After solid-liquid separation, a clear nickel sulfate solution and iron concentrate by-products that can be directly used as raw materials for ironmaking or cement additives are obtained, thereby achieving the goal of low-cost, low residual iron, and high selectivity nickel-iron separation.

[0046] This invention provides a method for the directional separation of copper, nickel, and iron in nickel leaching tailings, the process flow diagram of which is shown below. Figure 1 As shown, it includes the following steps:

[0047] S1. Room temperature activation: The nickel leaching tailings (main components: Cu: 40~60%, Ni: 8~25%, Fe: 1~5%) are reacted with an acidic nickel-containing dilute acid solution (main components: sulfuric acid or hydrochloric acid, concentration: 20~100 g / L, Ni...) produced by the nickel smelting system. 2+ The mixture consists of 60-80 g / L nickel leaching tailings and 4%-25% roasted copper slag. The first batch of nickel leaching tailings is roasted to obtain copper slag. Subsequent batches of nickel leaching tailings can be recycled. The copper slag obtained in S2 of this method is roasted. An acidic nickel-containing dilute acid solution is mixed with the nickel leaching tailings at a liquid-to-solid ratio (L / S) of 6-13 mL:1 g. The mixture is activated at room temperature and pressure for 20-60 minutes to obtain a mixed slurry.

[0048] S2, First-stage pressure leaching: The activated slurry obtained in step S1 is transferred into a closed pressure vessel without adding any gas. The pressure leaching reaction is carried out for 0.5 to 1 hour at a temperature of 190 to 210°C using the self-generated pressure from heating. After the reaction, liquid-solid separation is performed to obtain copper-rich copper slag and a leachate containing iron and nickel.

[0049] S3. Two-stage hot-pressing iron removal: Add an alkaline neutralizing agent to the leachate obtained in step S2 to adjust the pH value of the solution to 2.0~4.0, then transfer it to a closed pressure vessel and heat it to 120~160℃ for hydrolysis precipitation reaction for 2~6 hours; after the reaction, perform liquid-solid separation to obtain iron slag and nickel sulfate purified solution (Fe<0.1g / L); the iron slag is purified to obtain iron concentrate as a by-product.

[0050] Furthermore, in step S1, the calcined copper slag is used as an activator. In the first experiment, the copper slag added to the first batch of nickel leaching tailings is the copper slag after the nickel leaching tailings have been calcined in a calcining furnace at 300-900°C for 30-120 minutes. In subsequent experiments, other batches of nickel leaching tailings can use the copper slag obtained in step S2 of the method of the present invention, which has been calcined at 300-900°C for 30-120 minutes. The role of this copper slag is to induce lattice distortion and dissociation of the insoluble phase in the nickel leaching tailings, creating favorable conditions for subsequent selective nickel leaching.

[0051] Furthermore, in step S1, the acidic nickel-containing solution produced by the smelting system is preferably the anolyte produced during the nickel electrolytic refining process or a similar acidic raffinate from the nickel hydrometallurgical process, which realizes the resource recycling within the system and significantly reduces the consumption of new acid.

[0052] Further, in step S1, the acidic nickel-containing dilute acid solution and the nickel leaching tailings are mixed at a liquid-to-solid ratio of 6-13 mL:1 g.

[0053] Furthermore, in step S1, the activation treatment at room temperature and pressure lasts for 20 to 60 minutes. The purpose of this activation treatment is to destroy the lattice structure of insoluble phases such as nickel sulfide in the nickel leaching tailings and reduce their lattice stability, thereby reducing their dissociation energy under high temperature and acidic conditions and significantly improving the leaching rate.

[0054] Furthermore, in step S2, the copper slag obtained contains Cu content ≥70%, Ni content ≤0.3%, and Fe content ≤0.3%; the leachate obtained contains Cu concentration <0.1 g / L, Ni concentration of 50~98 g / L, and Fe concentration of 2~5 g / L.

[0055] Furthermore, in step S3, the neutralizing agent is an alkaline substance, including but not limited to one or more of sodium carbonate, calcium carbonate, calcium oxide, calcium hydroxide, nickel carbonate, basic nickel carbonate, and nickel hydroxide.

[0056] Further, in step S3, the iron slag purification process involves washing the iron slag 2-3 times with 5%-10% dilute sulfuric acid, and then roasting it at 300-500℃ for 0.5-2 hours to obtain the by-product iron concentrate.

[0057] To better explain the present invention, exemplary embodiments of the invention will be described in more detail below. However, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a clearer and more thorough understanding of the invention and to fully convey the scope of the invention to those skilled in the art. In the embodiments of the present invention, the determination of the Cu, Ni, and Fe elemental contents is performed using titration, and the nickel leaching rate is calculated using the formula: Leaching rate = (1 - Mass of nickel in the copper slag after leaching / Mass of nickel in the nickel leaching tailings) × 100%.

[0058] Example 1

[0059] This embodiment provides a method for the directional separation of copper, nickel, and iron in nickel immersion tailings, which includes the following steps:

[0060] S1. Take 500g of nickel leaching tailings, whose main components are: Cu 49.68%, Ni 8.25%, Fe 1.56%. Mix this nickel leaching tailings with a solution containing 40.12g / L sulfuric acid and Ni. 2+ The acidic raffinate from the nickel electrolysis system with a concentration of 68.19 g / L was mixed with a liquid-solid ratio of 8 mL: 1 g, and then 75 g of nickel leaching tailings that had been roasted at 500 °C for 60 min were added. The mixture was then activated at room temperature for 30 min.

[0061] S2. Transfer the activated slurry from step S1 into a closed pressure vessel, heat to 190℃, and react for 1 hour; filter to separate 440g of copper slag and leachate. (The contents of Cu, Ni, and Fe in the copper slag and leachate were measured by titration). The measured values ​​for the copper slag were: Cu 71.8%, Ni 0.22%, Fe 0.21%; the leachate contained: Cu 0.053 g / L, Ni 75.51 g / L, Fe 3.02 g / L, and the nickel leaching rate was 97.65%.

[0062] S3. The pH of the leachate was adjusted to 3.5 by adding nickel carbonate. The leachate was then transferred to a sealed pressure vessel and reacted at 150°C for 4 hours to complete the pressurized iron precipitation. After the reaction, the mixture was filtered to obtain nickel sulfate purified solution and iron slag. The iron slag was washed three times countercurrently with 10% dilute sulfuric acid, with a washing solution-to-solid ratio of L / S = 4 mL: 1 g. The washed residue was then calcined at 500°C for 2 hours to obtain hematite concentrate product conforming to GB / T 36704-2018 standard. The filtrate was combined with the aforementioned nickel sulfate purified solution to obtain total NiSO4 purified solution, in which the iron ion concentration was controlled to Fe < 0.1 g / L.

[0063] Example 2

[0064] This embodiment provides a method for the directional separation of copper, nickel, and iron in nickel immersion tailings, which includes the following steps:

[0065] S1. Take 500g of nickel leaching tailings (main components: Cu 52.3%, Ni 8.69%, Fe 2.10%) and mix it with the anolyte produced from the Ni electrolysis workshop (sulfuric acid concentration: 61.26 g / L, Ni...). 2+ The mixture (62.54 g / L) was mixed at a liquid-solid ratio of 6 mL:1 g, and then 20 g of copper slag produced in step S2 of Example 1 and roasted at 300℃ for 90 min was added. The mixture was then activated at room temperature for 50 min.

[0066] S2. The activated slurry was transferred to a closed pressure vessel, heated to 210℃, and reacted for 1 hour. After filtration, 439.7g of copper slag and leachate were obtained. The copper slag was found to contain 73.28% Cu, 0.25% Ni, and 0.18% Fe. The leachate contained 0.023g / L Cu, 67.51g / L Ni, and 3.52g / L Fe, with a nickel leaching rate of 97.47%.

[0067] S3. Adjust the pH of the leachate from step S2 to 2.8 using nickel hydroxide, then transfer it to a sealed pressure vessel and react at 160℃ for 2 hours to complete the pressurized iron precipitation reaction. After the reaction, filter to obtain nickel sulfate purified solution and iron slag. Wash the iron slag three times with 6% dilute sulfuric acid at a washing liquid-to-solid ratio of L / S = 4 mL: 1 g. After washing, calcine the filter residue at 400℃ for 2 hours for purification to obtain hematite concentrate product conforming to GB / T 36704-2018. Combine the filtrate with the aforementioned nickel sulfate purified solution to obtain total NiSO4 purified solution (Fe < 0.1 g / L).

[0068] Example 3

[0069] This embodiment provides a method for the directional separation of copper, nickel, and iron in nickel immersion tailings, which includes the following steps:

[0070] S1. Take 500g of nickel leaching tailings (main components: Cu 43.38%, Ni 20.45%, Fe 2.45%) and mix them with the anolyte produced from the Ni electrolysis workshop (sulfuric acid concentration: 80.23 g / L, Ni...). 2+ Mix 65.66 g / L) at a liquid-to-solid ratio of 10:1 (mL:g), add 100g of copper slag produced in step S2 of Example 2 and roasted at 600℃ for 120min, and activate at room temperature for 40min.

[0071] S2. The activated slurry from step S1 is transferred to a closed pressure vessel and heated to 200℃ for 1 h. Filtering separates 401.7 g of copper slag and leachate. The copper slag contains 72.52% Cu, 0.28% Ni, and 0.11% Fe; the leachate contains 0.01 g / L Cu, 96.01 g / L Ni, and 2.70 g / L Fe, with a nickel leaching rate of 98.90%.

[0072] S3. Add basic nickel carbonate to the leachate to adjust the pH to 3.2, transfer to a sealed pressure vessel, and react at 150℃ for 4 hours. After the reaction, filter to obtain nickel sulfate purified solution and iron slag. The iron slag is washed three times with 8% dilute sulfuric acid at a washing liquid-to-solid ratio of L / S = 4 mL: 1 g. The washed filter residue is calcined at 300℃ for 2 hours to obtain hematite concentrate conforming to GB / T 36704-2018. The filtrate is combined with the aforementioned nickel sulfate purified solution to obtain total NiSO4 purified solution (Fe < 0.1 g / L).

[0073] Example 4

[0074] This embodiment provides a method for the directional separation of copper, nickel, and iron in nickel immersion tailings, which includes the following steps:

[0075] S1. Take 500g of nickel leaching tailings (main components: Cu 42.67%, Ni 23.21%, Fe 2.33%) and mix it with the anolyte produced from the Ni electrolysis workshop (sulfuric acid concentration: 78.49 g / L, Ni...). 2+ Mix 70.62 g / L) at a liquid-to-solid ratio of 12:1 (mL:g), add 100g of copper slag produced in step S2 of Example 3 and roasted at 500℃ for 60 min, and perform activation pretreatment at room temperature for 60 min.

[0076] S2. The activated slurry from step S1 is transferred to a closed pressure vessel and heated to 210℃ for 1 h. Filtering separates 402.3 g of copper slag and leachate. The copper slag was found to have the following properties: Cu 75.57%, Ni 0.30%, Fe 0.23%; the leachate contained 0.047 g / L Cu, 93.74 g / L Ni, 2.52 g / L Fe, and a nickel leaching rate of 98.96%.

[0077] S3. Add calcium carbonate to the leachate obtained in S2 above to adjust the pH value to 3.2, and transfer it to a closed pressure vessel for reaction at 140℃ for 6 hours. After the reaction, filter to obtain nickel sulfate purified solution and iron slag. The iron slag is washed three times with 5% dilute sulfuric acid at a washing liquid-to-solid ratio of L / S = 4mL:1g. The washed filter residue is calcined at 500℃ for 1 hour to obtain hematite concentrate conforming to GB / T 36704-2018. The filtrate is combined with the aforementioned nickel sulfate purified solution to obtain total NiSO4 purified solution (Fe < 0.1 g / L).

[0078] The composition of the iron concentrate products obtained in Examples 1-4 is shown in Table 1, and the physicochemical indicators (mass fraction %) of hematite concentrate according to GB / T 36704-2018 are shown in Table 2.

[0079] Table 1: Composition of iron concentrate products from Examples 1-4 (unit: %)

[0080]

[0081] Table 2: GB / T 36704-2018 Physicochemical Properties of Hematite Concentrate (Mass Fraction %)

[0082]

[0083] Comparative Example 1

[0084] Take 500g of the same nickel leaching tailings as in Example 1 (Cu 49.68%, Ni 8.25%, Fe 1.56%), and mix it with the acidic raffinate from the nickel electrolysis system (sulfuric acid concentration: 40.12 g / L, Ni...). 2+ Mix 68.19 g / L) at a liquid-to-solid ratio of 8:1 (mL:g), add 15% of the mass of nickel leaching tailings produced in Example 1 and treated by roasting at 700°C for 60 min, without activation treatment, directly transfer to a closed pressure vessel, and react under pressure at 190°C for 1 hour.

[0085] After the reaction, 442g of copper slag and leachate were obtained by filtration. The copper slag was found to contain 70.23% Cu, 0.98% Ni, and 0.36% Fe. The final slag contained significantly more nickel than the result of Example 1, and the Ni leaching rate was only 89.5%, indicating that directly using pressure leaching without activation treatment is generally ineffective.

[0086] Comparative Example 2

[0087] Take 500g of the same nickel leaching tailings as in Example 2 (main components: Cu 52.3%, Ni 8.69%, Fe 2.10%), and mix it with the anolyte produced from the Ni electrolysis workshop (sulfuric acid: 61.26 g / L, Ni...). 2+The copper slag (62.54 g / L) was mixed at a liquid-to-solid ratio of 6:1 (mL:g), and 10% of the mass of the nickel leaching tailings was added. This mixture consisted of copper slag produced in Example 1 and calcined at 500°C for 120 min. The mixture was then activated at room temperature for 50 min without pressurization and directly filtered. Filtration yielded 472 g of copper slag and leachate. The copper slag was found to contain 49.86% Cu, 8.93% Ni, and 1.96% Fe, with a nickel leaching rate of less than 5%. This indicates that activation alone cannot achieve effective nickel leaching from the nickel leaching tailings.

[0088] Comparative Example 3

[0089] 500g of the same nickel leaching tailings as in Example 3 (main components: Cu 43.38%, Ni 20.45%, Fe 2.45%) was used for leaching under normal pressure: a liquid-to-solid ratio of 10:1 (mL:g) was used, with the addition of 150g concentrated sulfuric acid (density 1.84 g / mL), 250g copper sulfate, and 4918 mL of water to bring the liquid-to-solid ratio to 10:1. The slurrying time was 4 hours, and the slurrying temperature was 90℃. For pressure leaching, a liquid-to-solid ratio of 10:1 (mL:g) was used, with the addition of 200g concentrated sulfuric acid (density 1.84 g / mL), 125g copper sulfate, and 4891 mL of water to bring the liquid-to-solid ratio to 10:1. The temperature was raised to 180℃ and the reaction was carried out for 6 hours. Filtering yielded 461g of copper slag and leachate. The copper slag was found to have a Cu content of 52.52%, Ni content of 8.97%, and Fe content of 0.70%. This indicates that existing patented technologies are insufficient for effectively separating nickel from high-nickel materials.

[0090] Comparative Example 4

[0091] Take 500g of the same nickel leaching tailings as in Example 2 (main components: Cu 52.3%, Ni 8.69%, Fe 2.10%), and mix it with the anolyte produced from the Ni electrolysis workshop (sulfuric acid: 61.26 g / L, Ni...). 2+ The copper slurry (62.54 g / L) was mixed at a liquid-to-solid ratio of 6:1 (mL:g), activated at room temperature for 50 minutes, and then transferred to a closed pressure vessel. The temperature was raised to 210℃, and the reaction was carried out for 1 hour. Filtration yielded 369g of copper slag and leachate. The copper slag was found to have the following composition: Cu grade 62.7%, Ni 1.72%, Fe 0.35%, and nickel leaching rate 85.40%. This indicates that without the addition of roasted copper slag, the nickel leaching tailings have a lower nickel leaching rate.

[0092] Comparative Example 5

[0093] Take 500g of the same nickel leaching tailings as in Example 2 (main components: Cu 52.3%, Ni 8.69%, Fe 2.10%), and add anolyte produced from the Ni electrolysis workshop diluted 5 times (sulfuric acid: 12.25 g / L, Ni...). 2+12.52 g / L) was mixed at a liquid-to-solid ratio of 6:1 (mL:g), and then 20 g of copper slag produced in step S2 of Example 1 and roasted at 300℃ for 90 min was added. The mixture was activated at room temperature for 50 min, and the activated slurry was transferred to a closed pressure vessel, heated to 210℃, and reacted for 1 hour. After filtration, 368.7 g of copper slag and leachate were obtained. The copper slag was found to have the following properties: Cu grade 59.69%, Ni 3.85%, Fe 0.69%, and nickel leaching rate 67.33%. This indicates that the low-acid, low-nickel solution affects the effective leaching of nickel from the nickel leaching tailings.

[0094] In the description of this specification, the terms "one embodiment," "some embodiments," "embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0095] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make modifications, alterations, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for stepwise directional separation of copper, nickel, iron from nickel leaching tailings, characterized in that, It includes the following steps: S1. Activation at room temperature: The nickel leaching tailings are mixed with acidic nickel-containing dilute acid solution produced by the nickel smelting system and 4% to 25% of the copper slag after roasting. The mixture is then activated at room temperature and pressure to obtain a mixed slurry. S2, First-stage pressure leaching: The activated slurry obtained in step S1 is transferred into a closed pressure vessel and subjected to pressure leaching reaction at a temperature of 190~210℃; after the reaction is completed, liquid-solid separation is performed to obtain copper-rich copper slag and leaching solution containing iron and nickel. S3. Two-stage hot-pressing iron removal: An alkaline neutralizing agent is added to the leachate obtained in step S2 to adjust the pH value of the solution. Then, the solution is transferred to a closed pressure vessel and heated to carry out a hydrolysis precipitation reaction. After the reaction is completed, liquid-solid separation is performed to obtain iron slag and nickel sulfate purified solution. The iron slag is purified to obtain iron concentrate as a by-product.

2. The method of claim 1, wherein, In step S1, the main components of the nickel-plated tailings are: Cu 40-60%, Ni 8-25%, and Fe 1-5%. The acidic nickel-containing dilute acid solution is an acidic solution containing sulfuric acid or hydrochloric acid with a concentration of 20-100 g / L, Ni 2+ 60-80 g / L.

3. The method of claim 2, wherein, The acidic nickel-containing dilute acid solution is the anolyte produced during the nickel electrolytic refining process or a similar acidic raffinate from the nickel hydrometallurgical process.

4. The method of claim 1, wherein, In step S1, the acidic nickel-containing dilute acid solution and the nickel leaching tailings are mixed at a liquid-to-solid ratio of 6-13 mL: 1 g.

5. The method of claim 1, wherein, In step S1, during the initial processing of nickel immersion tailings, the copper slag is the copper slag obtained after calcining the nickel immersion tailings at 300~900℃ for 30~120min; the copper slag used in subsequent processing is the copper slag obtained in step S2 of this method after calcining at 300~900℃ for 30~120min, and the copper slag is recycled.

6. The method of claim 1, wherein, In step S2, the copper slag obtained contains Cu content ≥70%, Ni content ≤0.3%, and Fe content ≤0.3%; the leachate obtained contains Cu concentration <0.1g / L, Ni concentration of 50~98g / L, and Fe concentration of 2~5g / L.

7. The method of claim 1, wherein, In step S3, the neutralizing agent is an alkaline substance, including but not limited to one or more of sodium carbonate, calcium carbonate, calcium oxide, calcium hydroxide, nickel carbonate, basic nickel carbonate, and nickel hydroxide.

8. The method of claim 1, wherein, In step S3, the pH value of the adjusted solution is 2.0~4.

0.

9. The method of claim 1, wherein, In step S3, the temperature for heating is 120~160℃, and the precipitation reaction time is 2~6h.

10. The method as described in claim 1, characterized in that, In step S3, the iron slag purification process involves washing the iron slag 2-3 times with 5%-10% dilute sulfuric acid at a liquid-to-solid ratio of 3-5 mL:1 g, or by countercurrent washing, and then roasting it at 300-500℃ for 0.5-2 h to obtain the by-product iron concentrate.

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