A method for leaching valuable elements from nickel concentrate and purifying nickel solutions

Abstract

This invention discloses a method for leaching valuable elements from nickel concentrate and purifying the nickel solution. A secondary leaching solution and sodium chloride are added to the nickel concentrate. After complexation leaching (primary leaching), solid-liquid separation is performed to obtain a primary leaching solution and a primary leaching residue. The primary leaching residue is then leached with hydrochloric acid (secondary leaching) to obtain a secondary leaching solution and a secondary leaching residue. The secondary leaching residue is used to recover copper. The secondary leaching solution undergoes a complexation reaction with the nickel concentrate. An anionic extractant or anion exchange resin is added to the primary leaching solution for extraction to obtain a nickel chloride solution. This invention cleverly utilizes the complexation effect of chloride ions in conventional acid leaching operations, causing impurity elements to complex with chloride ions to form anions in the solution, while nickel exists in the solution as a cation. Therefore, the impurity elements can be efficiently separated by anionic extractants or anion exchange resins, significantly improving the efficiency of nickel separation and extraction from impurity elements.

Description

Technical Field

[0001] This invention belongs to the field of hydrometallurgical technology, specifically relating to a method for leaching valuable elements from nickel concentrate and purifying nickel solution. Background Technology

[0002] Nickel is a strategic metal, with proven global land-based nickel ore resources containing a total of 130 million tons of nickel. It is widely used in aerospace, batteries, electron microscopy, and healthcare. Currently, the nickel market is primarily driven by stainless steel production, which accounts for more than two-thirds of total nickel consumption. However, with the emergence of new battery technologies for electric vehicles, the market landscape is changing.

[0003] In the global distribution of nickel ore resources, lateritic nickel ore accounts for approximately 55%, sulfide nickel ore for approximately 28%, and nickel ore in seafloor iron nodules for approximately 17%. Due to factors such as mining technology and marine pollution, seafloor iron nodules have not yet been practically developed. According to data released by the U.S. Geological Survey in 2015, the world's proven basic nickel reserves are approximately 81 million tons, with total resources of 148 million tons. Lateritic nickel ore accounts for approximately 60% of the basic reserves, and sulfide nickel ore accounts for approximately 40%.

[0004] Currently, the common industrial process for processing nickel sulfide ore is pyrometallurgical refining: nickel concentrate is smelted in a flash furnace, then smelted in a converter, processed into anode plates, and finally electrolytically refined. During electrolytic refining, nickel plates are produced by electrowinning / electrolysis in a sulfuric acid or sulfur / hydrochloric acid mixed acid system. The product generally contains high levels of impurities such as sulfur, making it difficult to obtain nickel suitable for high-temperature alloys. Currently, wet leaching methods for nickel mainly include sulfation roasting-leaching and oxygen pressure leaching, both of which have good leaching effects. However, nickel and impurities such as iron, copper, lead, zinc, and cobalt exist in cationic form in the solution, making deep separation difficult. Furthermore, 40% of the cobalt remains in the pyrometallurgical slag, which is difficult to recover. Cobalt is a very important strategic resource. Therefore, adopting a green and efficient wet metallurgical technology to process nickel sulfide ore and leach nickel and cobalt while separating nickel from other impurities is of profound significance for resource utilization, environmental protection, and economic benefits.

[0005] Wang Yongqian and others from Jinchuan Group proposed a method for extracting nickel and cobalt from low-grade laterite nickel ore using a wet process, which utilizes Fe in the atmospheric pressure leaching solution. 3+ The protons released from the hydrolysis into precipitate are then leached from the low-silicon magnesium high-iron ore, followed by Fe under pressure and heating conditions. 3+ Hydrolysis results in a precipitate that is filtered out, reducing sulfuric acid consumption. Furthermore, the iron content in the pressure leaching residue after solid-liquid separation is relatively high, reaching 58-65%.

[0006] Wu Biaoben et al. from the Beijing General Research Institute of Nonferrous Metals proposed a selective bioleaching process for high-iron, low-grade nickel sulfide ores. Employing a stirred bioleaching process, this method controls the redox potential during leaching by regulating the growth of sulfiding bacteria, pH value, temperature, and aeration rate. This effectively inhibits the dissolution of iron-bearing sulfide minerals such as pyrite, achieving selective leaching of nickel-bearing sulfide minerals. The resulting cathode nickel metal has a purity exceeding 99.95%.

[0007] Tang Hejun et al. from the Chinese Academy of Geological Sciences proposed a graded leaching method for nickel-cobalt sulfide ores. This method separates high-nickel-content sulfide ores, such as pyrrhotite, from low-nickel-content pyrrhotite through flotation, yielding high-nickel-content nickel concentrate and low-nickel-content nickel concentrate. The high-nickel-content concentrate is then crushed to obtain a slurry. This slurry is mixed with a dispersant and sulfuric acid and subjected to oxygen pressure leaching under low temperature and low oxygen partial pressure conditions. This reduces the oxidation of pyrite and chalcopyrite, achieving nickel and cobalt leaching rates greater than 96%, iron leaching rate less than 12%, and copper leaching rate less than 30%.

[0008] Gong Jibao and others from Jinchuan Group proposed a method for leaching high-magnesium, low-nickel sulfide nickel ore under atmospheric pressure. The method involves uniformly mixing the raw material with water, adding hydrochloric acid for reaction, and then separating the liquid and solid to obtain a magnesium-washing solution and a magnesium-washed material with a magnesium content reduced by more than 90%. The magnesium-washed material is then uniformly mixed with water, and sulfuric acid and nitric acid are added for reaction. After the reaction, liquid-solid separation is performed to obtain a leaching solution and leaching residue. This method achieves a nickel leaching rate of ≥98%. Simultaneously, regarding cobalt recovery, Jinchuan Group's flash furnace pyrometallurgical cobalt direct recovery rate is approximately 53%, and the top-blown furnace cobalt direct recovery rate is approximately 50%.

[0009] Nickel sulfide concentrate is one of the main ores used for extracting and producing metallic nickel. However, in addition to nickel, nickel sulfide concentrate may also contain other metallic elements, such as iron, copper, and cobalt. Due to the high cobalt loss rate during pyrometallurgical processes, the elements entering the anolyte are not ideal. Therefore, conventional acid leaching operations may lead to the formation of some byproducts, and metal ions such as iron, cobalt, copper, and zinc may also be leached out, making subsequent separation and extraction difficult. Summary of the Invention

[0010] To address the problems existing in the prior art, the present invention aims to provide a method for leaching valuable elements from nickel concentrate and purifying nickel solution. The purpose is to achieve efficient leaching of valuable metals such as nickel, cobalt, and copper from nickel sulfide ore and separation of nickel from cobalt, copper, and iron, providing a theoretical and technical route for preparing high-quality nickel chloride from nickel sulfide ore.

[0011] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows:

[0012] This invention provides a method for leaching valuable elements from nickel concentrate and purifying nickel solution, comprising the following steps:

[0013] Step 1

[0014] A sodium chloride solution is added to nickel concentrate, and a single leaching reaction is performed. Solid-liquid separation is then conducted to obtain a primary leaching solution and a primary leaching residue. The sodium chloride solution is obtained by adding sodium chloride to an acid solution, and the concentration of sodium chloride in the solution is 1–6 mol / L. The liquid-to-solid volume ratio of the sodium chloride solution to the nickel concentrate is 2–20 ml:1 g.

[0015] Step Two

[0016] The residue from the primary leaching process is added to a hydrochloric acid solution for a secondary leaching reaction. Solid-liquid separation yields a secondary leachate and a secondary leaching residue. The secondary leachate is returned to step one as an acid solution. The hydrochloric acid solution contains HCl at a concentration of 1–8 mol / L.

[0017] Step 3

[0018] An anionic extractant or ion exchange resin is added to the primary leachate. After the extraction reaction, a loaded organic phase and a nickel chloride solution are obtained.

[0019] In this invention, a countercurrent leaching method is used. Step one involves complexation leaching of the nickel concentrate by adding a sodium chloride-containing solution. The sodium chloride-containing solution consists of an acid solution (secondary leaching solution) and sodium chloride. The secondary leaching solution provides H₂O. + Sodium chloride provides Cl- ions to form complexes with metal elements. The inventors discovered that chloride ions have a complexing effect on metal elements, capable of complexing leached impurities such as iron, cobalt, and a small amount of copper into anions that exist in the solution. Nickel is also leached into the solution, but exists in the form of cations, while most of the copper remains in the leaching residue. Then, the leaching residue from step one, where most of the nickel and cobalt have been separated, is further leached with hydrochloric acid solution to obtain a secondary leaching solution containing iron, cobalt, and nickel, and a secondary leaching residue containing copper. The secondary leaching residue enters the copper system to recover copper, while the secondary leaching solution can continue to provide H+. + Therefore, after adding sodium chloride, the nickel concentrate is leached (complexed) once in step one, so that impurity elements such as iron, cobalt, and a small amount of copper are complexed to form anions in the solution, while nickel exists in the solution as a cation. In the subsequent extraction and separation process, anionic extractants or anion exchange resins are used to transfer the impurity elements from the aqueous phase to the organic phase or resin, while the nickel cations remain in the aqueous phase, thereby achieving the separation of nickel from the impurity elements and obtaining an extractant or resin loaded with impurity elements and a nickel chloride solution, thus realizing the extraction of nickel.

[0020] In this invention, to ensure that impurities such as iron, cobalt, copper, lead, and zinc exist in the form of anionic complexes, it is crucial to control the concentrations of hydrochloric acid, chloride ions, and the liquid-to-solid volume ratio of the hydrochloric acid and sodium chloride mixed solution to the nickel concentrate within the range specified in this invention. This is because the concentration of hydrochloric acid not only provides acidity during the two leaching processes but also provides chloride ions (Cl-) to form complex anions. - This directly affects the leaching of various elements, especially in step one, where the addition of sodium chloride leads to excessive Cl... - This process allows impurities such as iron, cobalt, copper, lead, and zinc to leach out as anionic complexes, while nickel exists in the solution as a cation (Ni). 2+ Nickel will exist in a cationic state with hydrogen ions, rather than forming anionic complexes.

[0021] A low liquid-to-solid volume ratio between the mixed solution of hydrochloric acid and sodium chloride and nickel concentrate may result in insufficient contact between the solid and hydrochloric acid, thereby reducing the dissolution rate of metal ions and the complexation of impurity elements with hydrochloric acid. A high liquid-to-solid ratio may lead to excessive dilution, affecting the concentration of metal ions in the solution and weakening the complexation effect.

[0022] In a preferred embodiment, in step one, the acid solution is selected from hydrochloric acid solution during the first reaction, wherein the concentration of HCl in the hydrochloric acid solution is 1-8 mol / L, preferably 4-6 mol / L, and the acid solution is selected from secondary leachate during subsequent reactions.

[0023] In the continuous industrial production of leached nickel concentrate, an equal volume of nickel concentrate is used. When continuous production is interrupted, the volume can be changed, effectively starting a new continuous production cycle. Hydrochloric acid solution is used as the acid solution in the first reaction. In other words, in industrial production, the reaction can be interrupted and the reaction rate adjusted according to the needs of scaling up production.

[0024] In a preferred embodiment, in step one, the concentration of sodium chloride in the sodium chloride-containing solution is 2–4 mol / L, and the liquid-to-solid volume ratio of the hydrochloric acid solution to the nickel concentrate is 10–20 ml: 1 g. The inventors have discovered that controlling the concentration of sodium chloride to the liquid-to-solid volume ratio of the nickel concentrate within this preferred range results in the strongest complexation effect between the impurity elements and the hydrochloric acid, leading to the optimal separation effect.

[0025] In a preferred embodiment, in step one, the temperature of the first leaching reaction is 15–95°C, and the time of the first leaching reaction is 0.5–4 hours.

[0026] In a further preferred embodiment, in step one, the temperature of the leaching reaction is 80–95°C, and the leaching time is 2–4 hours. The inventors have found that controlling the leaching temperature within this preferred range yields the best leaching effect. This is because, during hydrochloric acid leaching, higher temperatures can alter the equilibrium of the complexation reaction, facilitating the formation of anionic complexes between more impurity elements and chloride ions. However, excessively high temperatures may trigger unnecessary side reactions or lead to over-dissolution.

[0027] In actual operation, after the leaching reaction is completed, solid and liquid are separated to obtain leaching residue and leaching solution. The leaching solution contains complex anions formed by impurity elements such as iron and cobalt with chloride ions, as well as nickel cations.

[0028] In a preferred embodiment, in step two, the concentration of HCl in the hydrochloric acid solution is 4–6 mol / L.

[0029] In the preferred embodiment, in step two, the liquid-to-solid volume ratio of the hydrochloric acid solution to the primary leaching residue is 2–20 ml: 1 g.

[0030] In the preferred embodiment, in step two, the temperature of the secondary leaching reaction is 15–95°C, and the time of the secondary leaching reaction is 0.5–4 hours.

[0031] In a further preferred embodiment, in step two, the temperature of the secondary leaching reaction is 80–95°C, and the time of the secondary leaching reaction is 2–4 hours.

[0032] In a preferred embodiment, in step three, the anionic extractant is selected from N-series extractants, preferably N235 or N1923, and more preferably N235. The inventors have found that the extraction effect is optimal when using N235 extractant.

[0033] In a preferred embodiment, in step three, the ion exchange resin is an anion exchange resin.

[0034] In a preferred embodiment, in step three, the volume ratio of the leachate to the anionic extractant or ion exchange resin is 1:0.5 to 5.

[0035] In the preferred embodiment, in step three, the temperature of the extraction reaction is 5–40°C, and the extraction reaction time is 5–20 min.

[0036] In the preferred embodiment, in step three, the extraction reaction is of 1 to 3 stages, preferably 3 stages.

[0037] The inventors discovered that controlling the temperature and time of the extraction reaction within the aforementioned range yields the best extraction results. Excessively high temperatures may lead to excessively rapid reaction rates, potentially causing uncontrollable side reactions or unstable products, thus affecting the selectivity and efficiency of the extraction process. High temperatures may also cause the extractant to evaporate or decompose, resulting in extractant loss, increased operating costs, and resource waste. Conversely, excessively low temperatures may result in slow reaction rates, prolonged extraction times, and reduced efficiency. Low temperatures may also lead to incomplete extraction of the target substance, affecting the extraction and removal rates. Furthermore, some reactions or extractants may be unstable at low temperatures, leading to unpredictability in the extraction process. Excessively long reaction times may result in over-dissolution of the target substance or other unnecessary reactions, reducing extraction efficiency. Conversely, excessively short reaction times may also lead to incomplete extraction of the target substance, affecting the extraction and removal rates. A short reaction time may also prevent the achievement of the required reaction degree, resulting in unstable or substandard product quality.

[0038] Principles and advantages

[0039] The present invention targets nickel concentrates with complex chemical compositions and where separating nickel from impurity elements is difficult. Typically, sulfuric acid is used for leaching this type of nickel concentrate. However, sulfuric acid leaching results in high leaching rates for impurities such as iron and cobalt. Even at leaching temperatures as high as 105–120°C, while nickel leaching reaches 95%, copper and cobalt leaching rates can also reach 90%, making separation and extraction difficult. The present invention employs a two-stage countercurrent leaching process. The first step involves adding a sodium chloride-containing solution to the nickel concentrate for complexation leaching. This sodium chloride-containing solution consists of a secondary leaching solution and sodium chloride, with the secondary leaching solution providing H₂O. + Sodium chloride provides Cl- ions to form complexes with metal elements. The inventors discovered that chloride ions have a complexing effect on metal elements, capable of complexing leached impurities such as iron and cobalt into anions that exist in the solution. Nickel is also leached into the solution, but exists in the form of cations, while copper is mainly retained in the leaching residue. Then, the leaching residue from step one, where most of the nickel and cobalt have been separated, is further leached with hydrochloric acid solution to obtain a secondary leaching solution containing iron, cobalt, and nickel, and a secondary leaching residue containing copper. The secondary leaching residue enters the copper system to recover copper, while the secondary leaching solution can continue to provide H+. + Therefore, after adding sodium chloride, the nickel concentrate is leached (complexed) in step one, so that impurity elements such as iron and cobalt are complexed to form anions in the solution, while nickel exists in the solution as cations. In the subsequent extraction and separation process, an anionic extractant is used to transfer the impurity elements from the aqueous phase to the organic phase, thereby achieving the separation of nickel from the impurity elements and obtaining a nickel chloride solution, thus realizing the extraction of nickel.

[0040] The method provided by this invention achieves a nickel leaching rate >90%, an iron leaching rate >85%, a cobalt leaching rate >90%, and a copper recovery rate >99% during the leaching reaction. Finally, after three stages of extraction, the removal rates of impurities are: zinc >92%, cobalt >95%, iron >95%, copper >95%, and lead >80%.

[0041] This invention employs a novel process that overcomes the shortcomings of traditional processes in separating nickel from impurity metals such as iron, copper, and cobalt. It has advantages such as simple process, low cost, and good separation effect, and is highly applicable. Attached Figure Description

[0042] Figure 1 The process flow diagram of this invention. Detailed Implementation

[0043] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below in conjunction with the specification and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0044] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0045] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0046] The main elemental composition of the nickel concentrate in the various embodiments and comparative examples of the present invention is as follows: Ni: 56.61%, Fe: 2.72%, Co: 1.01%, Cu: 4.11%.

[0047] Example 1

[0048] First reaction:

[0049] 20g of nickel concentrate was leached with 200ml of an acid solution containing sodium chloride at 80℃ for 2 hours by heating and stirring. The sodium chloride solution was obtained by adding sodium chloride to a 4mol / L hydrochloric acid solution, with a sodium chloride concentration of 4mol / L. Solid-liquid separation was performed to obtain a primary leaching solution and a primary leaching residue. 20g of the primary leaching residue was added to 200ml of the 4mol / L hydrochloric acid solution, and leaching was performed with heating and stirring at 80℃ for 2 hours. Solid-liquid separation was then performed to obtain a secondary leaching solution and a secondary leaching residue. Analysis showed that the leaching rate of nickel in the primary leaching solution was 94.29%, the leaching rate of iron was 86.88%, the leaching rate of cobalt was 93.85%, and the leaching rate of copper was 0.71%. Then, N235 extractant was added to the primary leaching solution at a volume ratio of leaching solution to extractant of 2:1, and extraction was performed at 40℃ for 15 minutes. Analysis showed that after three stages of extraction, the removal rates of impurities were as follows: zinc > 92%, cobalt > 95%, iron > 95%, copper > 95%, and lead > 80%. Ultimately, the leaching rate of nickel was 97.19%, the recovery rate of cobalt was 96.12%, and the recovery rate of copper was 99.26%.

[0050] Example 2

[0051] 200 ml of a sodium chloride solution was added to 20 g of nickel concentrate, and the mixture was heated and stirred at 80 °C for 2 h for leaching. The sodium chloride solution was obtained by adding sodium chloride to a secondary leaching solution (from Example 1), wherein the concentration of sodium chloride was 4 mol / L. Solid-liquid separation was performed to obtain a primary leaching solution and a primary leaching residue. 20 g of the primary leaching residue was added to 200 ml of a 4 mol / L hydrochloric acid solution, and the mixture was heated and stirred at 80 °C for 2 h for leaching. Solid-liquid separation was performed to obtain a secondary leaching solution and a secondary leaching residue. Analysis showed that the leaching rate of nickel in the primary leaching solution was 92.41%, the leaching rate of iron was 84.81%, the leaching rate of cobalt was 91.65%, and the leaching rate of copper was 0.40%. Then, N235 extractant was added to the primary leaching solution at a volume ratio of leaching solution to extractant of 2:1, and extraction was performed at a reaction temperature of 40 °C for 15 min. Analysis showed that after primary extraction, the removal rates were 84.21% for iron, 96.77% for zinc, 92.20% for cobalt, 58.31% for lead, and 67.00% for copper. After tertiary extraction, the removal rates of impurities were greater than 92% for zinc, greater than 95% for cobalt, greater than 95% for iron, greater than 95% for copper, and greater than 80% for lead. Ultimately, the leaching rate of nickel was 96.59%, the recovery rate of cobalt was 95.89%, and the recovery rate of copper was 95.04%.

[0052] Example 3

[0053] 200 ml of a sodium chloride solution was added to 20 g of nickel concentrate, and the mixture was heated and stirred at 80 °C for 2 h for leaching. The sodium chloride solution was obtained by adding sodium chloride to a secondary leaching solution (from Example 2), wherein the concentration of sodium chloride was 4 mol / L. Solid-liquid separation was performed to obtain a primary leaching solution and a primary leaching residue. 20 g of the primary leaching residue was added to 200 ml of a 4 mol / L hydrochloric acid solution, and the mixture was heated and stirred at 80 °C for 2 h for leaching. Solid-liquid separation was performed to obtain a secondary leaching solution and a secondary leaching residue. Analysis showed that the leaching rate of nickel in the primary leaching solution was 92.41%, the leaching rate of iron was 84.81%, the leaching rate of cobalt was 91.65%, and the leaching rate of copper was 0.40%. Then, N235 extractant was added to the primary leaching solution at a volume ratio of leaching solution to extractant of 2:1, and extraction was performed at a reaction temperature of 25 °C for 15 min. Analysis showed that the primary extraction yielded a 74.26% removal rate for iron, a 95.34% removal rate for zinc, an 89.32% removal rate for cobalt, a 63.20% removal rate for lead, and a 68.32% removal rate for copper. Ultimately, the leaching rate for nickel was 95.24%, the recovery rate for cobalt was 95.19%, and the recovery rate for copper was 97.34%.

[0054] Example 4

[0055] 200 ml of a sodium chloride solution was added to 20 g of nickel concentrate, and the mixture was heated and stirred at 80 °C for 2 h for leaching. The sodium chloride solution was obtained by adding sodium chloride to a secondary leaching solution (from Example 3), wherein the concentration of sodium chloride was 4 mol / L. Solid-liquid separation was performed to obtain a primary leaching solution and a primary leaching residue. 20 g of the primary leaching residue was added to 200 ml of a 4 mol / L hydrochloric acid solution, and the mixture was heated and stirred at 80 °C for 2 h for leaching. Solid-liquid separation was performed to obtain a secondary leaching solution and a secondary leaching residue. Analysis showed that the leaching rate of nickel in the primary leaching solution was 92.41%, the leaching rate of iron was 84.81%, the leaching rate of cobalt was 91.65%, and the leaching rate of copper was 0.40%. Then, N235 extractant was added to the primary leaching solution at a volume ratio of leaching solution to extractant of 2:1, and extraction was performed at a reaction temperature of 25 °C for 20 min. Analysis showed that the primary extraction yielded a 65.61% removal rate for iron, a 93.70% removal rate for zinc, an 85.02% removal rate for cobalt, a 58.43% removal rate for lead, and a 65.98% removal rate for copper. Ultimately, the leaching rate for nickel was 96.58%, the recovery rate for cobalt was 95.87%, and the recovery rate for copper was 99.00%.

[0056] Example 5

[0057] 200 ml of a sodium chloride solution was added to 20 g of nickel concentrate, and the mixture was heated and stirred at 80 °C for 2 h for leaching. The sodium chloride solution was obtained by adding sodium chloride to a secondary leaching solution (from Example 4), wherein the concentration of sodium chloride was 2 mol / L. Solid-liquid separation was performed to obtain a primary leaching solution and a primary leaching residue. 20 g of the primary leaching residue was added to 200 ml of a 6 mol / L hydrochloric acid solution, and the mixture was heated and stirred at 80 °C for 2 h for leaching. Solid-liquid separation was performed to obtain a secondary leaching solution and a secondary leaching residue. Analysis showed that the leaching rate of nickel in the primary leaching solution was 95.44%, the leaching rate of iron was 93.20%, the leaching rate of cobalt was 93.13%, and the leaching rate of copper was 0.20%.

[0058] Example 6

[0059] 20g of nickel concentrate was leached in 200ml of a sodium chloride solution at 95°C with stirring for 2 hours. The sodium chloride solution was obtained by adding sodium chloride to a secondary leaching solution (from Example 5), with a sodium chloride concentration of 4 mol / L. Solid-liquid separation was performed to obtain a primary leaching solution and a primary leaching residue. 20g of the primary leaching residue was added to 200ml of a 4 mol / L hydrochloric acid solution, and leached in 95°C with stirring for 2 hours. Solid-liquid separation was then performed to obtain a secondary leaching solution and a secondary leaching residue. Analysis showed that the leaching rate of nickel in the primary leaching solution was 92.38%, the leaching rate of iron was 87.20%, the leaching rate of cobalt was 90.19%, and the leaching rate of copper was 0.36%.

[0060] Example 7

[0061] 200 ml of a sodium chloride solution was added to 20 g of nickel concentrate, and the mixture was heated and stirred at 80 °C for 0.5 h for leaching. The sodium chloride solution was obtained by adding sodium chloride to a secondary leaching solution (from Example 6), wherein the concentration of sodium chloride was 4 mol / L. Solid-liquid separation was performed to obtain a primary leaching solution and a primary leaching residue. 20 g of the primary leaching residue was added to 200 ml of a 4 mol / L hydrochloric acid solution, and the mixture was heated and stirred at 80 °C for 0.5 h for leaching. Solid-liquid separation was performed to obtain a secondary leaching solution and a secondary leaching residue. Analysis showed that the leaching rate of nickel in the primary leaching solution was 89.73%, the leaching rate of iron was 97.46%, the leaching rate of cobalt was 88.85%, and the leaching rate of copper was 0.70%.

[0062] Example 8

[0063] 20g of nickel concentrate was leached with 200ml of a sodium chloride solution at 80°C with stirring for 1 hour. The sodium chloride solution was obtained by adding sodium chloride to a secondary leaching solution (from Example 7), with a sodium chloride concentration of 4mol / L. Solid-liquid separation was performed to obtain a primary leaching solution and a primary leaching residue. 20g of the primary leaching residue was added to 200ml of a 4mol / L hydrochloric acid solution, and leached with stirring at 80°C for 1 hour. Solid-liquid separation was performed to obtain a secondary leaching solution and a secondary leaching residue. Analysis showed that the leaching rate of nickel in the primary leaching solution was 91.90%, the leaching rate of iron was 99.63%, the leaching rate of cobalt was 89.29%, and the leaching rate of copper was 0.36%.

[0064] Example 9

[0065] 20g of nickel concentrate was leached with 200ml of a sodium chloride solution at 80°C with stirring for 3 hours. The sodium chloride solution was obtained by adding sodium chloride to a secondary leaching solution (from Example 8), with a sodium chloride concentration of 4mol / L. Solid-liquid separation was performed to obtain a primary leaching solution and a primary leaching residue. 20g of the primary leaching residue was added to 200ml of a 4mol / L hydrochloric acid solution, and leached with stirring at 80°C for 3 hours. Solid-liquid separation was performed to obtain a secondary leaching solution and a secondary leaching residue. Analysis showed that the leaching rate of nickel in the primary leaching solution was 95.05%, the leaching rate of iron was 88.44%, the leaching rate of cobalt was 93.34%, and the leaching rate of copper was 0.36%.

[0066] Example 10

[0067] 20g of nickel concentrate was leached with 200ml of a sodium chloride solution at 80°C with stirring for 4 hours. The sodium chloride solution was obtained by adding sodium chloride to a secondary leaching solution (from Example 9), with a sodium chloride concentration of 4mol / L. Solid-liquid separation was performed to obtain a primary leaching solution and a primary leaching residue. 20g of the primary leaching residue was added to 200ml of a 4mol / L hydrochloric acid solution, and leached with stirring at 80°C for 4 hours. Solid-liquid separation was performed to obtain a secondary leaching solution and a secondary leaching residue. Analysis showed that the leaching rate of nickel in the primary leaching solution was 95.81%, the leaching rate of iron was 87.03%, the leaching rate of cobalt was 96.72%, and the leaching rate of copper was 0.24%.

[0068] Example 11

[0069] 400 ml of a sodium chloride solution was added to 20 g of nickel concentrate, and the mixture was heated and stirred at 80 °C for 2 h for leaching. The sodium chloride solution was obtained by adding sodium chloride to a secondary leaching solution (from Example 10), wherein the concentration of sodium chloride was 4 mol / L. Solid-liquid separation was performed to obtain a primary leaching solution and a primary leaching residue. 20 g of the primary leaching residue was added to 400 ml of a 4 mol / L hydrochloric acid solution, and the mixture was heated and stirred at 80 °C for 2 h for leaching. Solid-liquid separation was performed to obtain a secondary leaching solution and a secondary leaching residue. Analysis showed that the leaching rate of nickel in the primary leaching solution was 95.06%, the leaching rate of iron was 82.76%, the leaching rate of cobalt was 92.06%, and the leaching rate of copper was 0.40%.

[0070] Example 12

[0071] 20g of nickel concentrate was leached with 200ml of a sodium chloride solution at 80°C with stirring for 2 hours. The sodium chloride solution was obtained by adding sodium chloride to a secondary leaching solution (from Example 11), with a sodium chloride concentration of 6mol / L. Solid-liquid separation was performed to obtain a primary leaching solution and a primary leaching residue. 20g of the primary leaching residue was added to 200ml of a 4mol / L hydrochloric acid solution, and leached with stirring at 80°C for 2 hours. Solid-liquid separation was performed to obtain a secondary leaching solution and a secondary leaching residue. Analysis showed that the leaching rate of nickel in the primary leaching solution was 96.41%, the leaching rate of iron was 88.81%, the leaching rate of cobalt was 92.65%, and the leaching rate of copper was 0.82%.

[0072] Example 13

[0073] N235 extractant was added to the primary leachate at a volume ratio of 1:1 (leaching solution to extractant), and extraction was carried out at 25°C for 15 minutes. Analysis showed that the removal rates were 68.67% for iron, 90.51% for zinc, 58.31% for lead, 63.22% for copper, and 82.32% for cobalt.

[0074] Comparative Example 1

[0075] 20g of nickel concentrate was added to 200ml of 2.5mol / L sulfuric acid solution, and the mixture was heated and stirred at 80℃ for 2h for leaching. Solid-liquid separation yielded filter residue and a filtrate containing nickel, iron, and cobalt. Analysis showed that the leaching rates of nickel, iron, cobalt, and copper in the filtrate were 42.89%, 83.45%, 43.60%, and 0.01%, respectively.

[0076] Comparative Example 2

[0077] Compared to Example 1, the only difference was that the sodium chloride solution concentration was 0.5 mol / L. Under these conditions, the leaching solution obtained showed that the leaching rate of nickel was 66.54%, the leaching rate of iron was 73.60%, the leaching rate of cobalt was 63.13%, and the leaching rate of copper was 0.36%.

[0078] Comparative Example 3

[0079] The other conditions were the same as in Example 1, except that the liquid-to-solid ratio was 1:2. That is, 20g of primary leaching residue was added to 10ml of 4mol / L hydrochloric acid solution, and 10ml of sodium chloride solution was added to 20g of nickel concentrate. Under these conditions, the leaching solution obtained showed that the leaching rate of nickel was 23.21%, the leaching rate of iron was 66.26%, the leaching rate of cobalt was 53.10%, and the leaching rate of copper was 0.09%.

[0080] Comparative Example 4

[0081] The other conditions were the same as in Example 1, except that the liquid-to-solid ratio was 1:1. That is, 20g of primary leaching residue was added to 20ml of 4mol / L hydrochloric acid solution, and 20ml of sodium chloride solution was added to 20g of nickel concentrate. Under these conditions, the leaching solution obtained showed that the leaching rate of nickel was 32.84%, the leaching rate of iron was 91.68%, the leaching rate of cobalt was 63.23%, and the leaching rate of copper was 0.08%.

[0082] Comparative Example 5

[0083] Other conditions were the same as in Example 1, except that the hydrochloric acid concentration was different, which was 0.5 mol / L. Under these conditions, the leaching solution obtained showed that the leaching rate of nickel was 12.29%, the leaching rate of iron was 60.12%, the leaching rate of cobalt was 53.90%, and the leaching rate of copper was 0.15%.

[0084] Comparative Example 6

[0085] The other conditions were the same as in Example 1, except that the hydrochloric acid concentration was different, which was 1 mol / L. Under these conditions, the leaching solution obtained showed that the leaching rate of nickel was 25.95%, the leaching rate of iron was 79.93%, the leaching rate of cobalt was 56.06%, and the leaching rate of copper was 0.19%.

Claims

1. A method for leaching valuable elements from nickel concentrate and purifying nickel solution, characterized in that: Includes the following steps: Step 1 A sodium chloride solution is added to nickel concentrate, and a single leaching reaction is performed. Solid-liquid separation is then conducted to obtain a primary leaching solution and a primary leaching residue. The sodium chloride solution is obtained by adding sodium chloride to an acid solution, and the concentration of sodium chloride in the solution is 1–6 mol / L. The liquid-to-solid volume ratio of the sodium chloride solution to the nickel concentrate is 2–20 ml: 1 g. In step one, during the first reaction, the acid solution is selected from hydrochloric acid solution, wherein the concentration of HCl in the hydrochloric acid solution is 1-8 mol / L. During subsequent reactions, the acid solution is selected from the secondary leachate. Step Two The residue from the primary leaching process is added to a hydrochloric acid solution for a secondary leaching reaction. Solid-liquid separation yields a secondary leachate and a secondary leaching residue. The secondary leachate is returned to step one as an acid solution. The hydrochloric acid solution contains HCl at a concentration of 1–8 mol / L. Step 3 An anionic extractant or ion exchange resin is added to the primary leachate. After the extraction reaction, a loaded organic phase and a nickel chloride solution are obtained.

2. The method for leaching valuable elements from nickel concentrate and purifying nickel solution according to claim 1, characterized in that: In step one, the concentration of sodium chloride in the sodium chloride solution is 2-4 mol / L, and the liquid-solid volume-to-mass ratio of the hydrochloric acid solution to the nickel concentrate is 10-20 ml: 1 g.

3. The method for leaching valuable elements from nickel concentrate and purifying nickel solution according to claim 1, characterized in that: In step one, the temperature of the leaching reaction is 15–95°C, and the time of the leaching reaction is 0.5–4 hours.

4. The method for leaching valuable elements from nickel concentrate and purifying nickel solution according to claim 1, characterized in that: In step two, the concentration of HCl in the hydrochloric acid solution is 4–6 mol / L.

5. The method for leaching valuable elements from nickel concentrate and purifying nickel solution according to claim 1, characterized in that: In step two, the liquid-to-solid volume ratio of the hydrochloric acid solution to the primary leaching residue is 2-20 ml: 1 g.

6. The method for leaching valuable elements from nickel concentrate and purifying nickel solution according to claim 1, characterized in that: In step two, the temperature of the secondary leaching reaction is 15–95°C, and the time of the secondary leaching reaction is 0.5–4 hours.

7. The method for leaching valuable elements from nickel concentrate and purifying nickel solution according to claim 1, characterized in that: In step three, the anionic extractant is an N-series extractant, and the ion exchange resin is an anion exchange resin.

8. The method for leaching valuable elements from nickel concentrate and purifying nickel solution according to claim 1, characterized in that: In step three, the volume ratio of the leachate to the anionic extractant or ion exchange resin is 1:0.5 to 5.

9. A method for leaching valuable elements from nickel concentrate and purifying nickel solution according to claim 1, characterized in that: In step three, the temperature of the extraction reaction is 5–40°C, and the extraction time is 5–20 min; in step three, the extraction reaction is of 1–3 stages.

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