Method for strengthening selective leaching of magnesium oxide in high-magnesium nickel sulfide mineral

Abstract

The invention discloses a method for strengthening selective leaching of magnesium oxide in high-magnesium nickel sulfide minerals, and belongs to the technical field of non-ferrous metal hydrometallurgy. According to the method, a sulfuric acid solution leaching agent and a composite leaching assistant agent (including a component A and a component B, the component A includes chlorine salt, villiaumite and the like, and the component B includes phosphate, silicate and the like) are adopted for conducting normal-pressure leaching on the high-magnesium nickel sulfide minerals, obtained leaching residues are magnesium-removed nickel sulfide minerals, and obtained leaching liquid is a magnesium-rich solution; according to the method, an existing technological process and equipment for removing magnesium from the high-magnesium nickel sulfide mineral through acid leaching are not changed, efficient selective leaching of magnesium oxide in the high-magnesium nickel sulfide raw material can be enhanced only through the composite leaching aid, and the difficulty and cost of follow-up recycling and impurity removal are effectively reduced.

Description

Technical Field

[0001] The invention relates to a method for removing magnesium from high-magnesium nickel sulfide minerals, and in particular to a method for enhancing the selective leaching of magnesium oxide from high-magnesium nickel sulfide minerals by utilizing a leaching aid, and belongs to the technical field of non-ferrous metal hydrometallurgy. Background Art

[0002] Nickel sulfide ore is mainly used for pyrometallurgy because it is mainly composed of sulfides, has high calorific value and low energy consumption when used for heating. Usually, a flash furnace is used to roughly refine the nickel sulfide ore into nickel matte, which is then further refined. Since there are a large number of magnesium silicate gangue minerals such as serpentine and talc in the nickel sulfide ore deposits, and the magnesium oxide therein has a high melting point, a large amount of it entering the flash furnace will increase energy consumption. More seriously, it will cause the slag viscosity to increase, and it is easy to form nodules in the furnace, affecting production efficiency and operational safety. The nodules in the furnace need to be removed by blasting during the cold repair of the flash furnace, which will extend the overall maintenance period and may cause a certain degree of damage to the furnace body. Therefore, it is very necessary to control the magnesium oxide content in the flash furnace feed raw materials.

[0003] Usually, the nickel sulfide ore is treated to reduce magnesium in the mineral processing and enrichment process. For example, short columnar media is used in the grinding stage to make the particle size distribution of different minerals different, thereby achieving selective grinding. Under the premise of ensuring the dissociation of valuable metal mineral monomers, the over-grinding of magnesium silicate gangue minerals can be avoided, resulting in mud covering and being carried into the concentrate product in large quantities. In the flotation stage, the process flow is optimized to enable the valuable metal mineral particles to be collected as early as possible, and to avoid a large amount of brittle magnesium silicate minerals from being over-grinded and mud-coated, thereby entraining valuable mineral particles into the concentrate product. At the same time, the flotation equipment and methods are improved, and flash flotation, strong stirring slurry mixing, acid flotation and other equipment and methods are used to desorb the gangue ore mud or improve the heterogeneous coagulation phenomenon. The development of efficient flotation magnesium reduction agents is also an important direction for mineral processing magnesium reduction. Sodium hexametaphosphate, CMC and various combination agents are used to inhibit the flotation of magnesium silicate gangue minerals, so as to reduce the magnesium oxide content in the resulting concentrate product.

[0004] Due to the continuous mining of nickel sulfide rich ores, its reserves are gradually decreasing. Currently, the mining of nickel sulfide ore resources is gradually shifting to lean ores. However, the nickel grade in lean ores is lower and the magnesium oxide content is higher, which makes it increasingly difficult to reduce magnesium in the mineral processing stage. In order to produce concentrate products with magnesium oxide content that meets the standards in the mineral processing and enrichment process, the nickel and copper recovery rates will be significantly reduced. In order to ensure the nickel and copper recovery rates, the magnesium oxide content in the concentrate products will greatly exceed the standards. Therefore, the importance of reducing the magnesium oxide content by acid leaching is becoming increasingly prominent. It can be used to treat the mined high-magnesium nickel sulfide lean ores or the high-magnesium mineral processing products produced by the flotation process of the original ore.

[0005] During the acid leaching process, nickel, copper and iron in the high-magnesium nickel sulfide raw material will enter the leachate in large quantities along with the leaching of magnesium oxide, which increases the difficulty and cost of subsequent recovery and impurity removal. Therefore, the efficient and selective leaching of magnesium oxide in the high-magnesium nickel sulfide raw material should be strengthened. Since magnesium oxide exists in large quantities in magnesium silicate gangue minerals represented by serpentine, serpentine is a layered silicate mineral composed of a layer of silicon-oxygen tetrahedron (T sheet) and a layer of magnesium-oxygen-hydrogen octahedron (O sheet) in a 1:1 ratio, and the curling or bending of the T sheet makes serpentine have different isomorphs, such as leaf serpentine and chrysotile, but all of them have unshared oxygen atoms attached to the magnesium atoms of the octahedral sheet, and the Si-O-Si bond and the O-Si-O bond are connected in pairs to form a dense six-membered ring. Therefore, the original serpentine mineral has a stable structure, and it is difficult to release the magnesium element in it through conventional leaching methods. Other enhancement methods can destroy the original stable structure in serpentine, making it easier to leach magnesium, such as: "Enhancement of acid extraction of magnesium and silicon from serpentine by mechanochemical treatment", Zhang Q, et al., Hydrometallurgy, 1997, 45(3): 323-331) A planetary ball mill was used to grind serpentine ore samples to destroy their stable structure. After dry grinding for 240 minutes, the ore powder was leached with a low concentration of acid at room temperature, which allowed more than 90% of the magnesium and more than 70% of the silicon to be dissolved and leached. The test of the leached residue showed that after high-intensity grinding, the serpentine was transformed from a stable crystalline structure to an amorphous state, which facilitated the leaching of magnesium and silicon. Reference ("Experimental Study on Extraction of Magnesium from Serpentine by Activated Acid Leaching", Zeng Ying et al., Mining and Metallurgical Engineering, 2006, (02): 57-60) disclose that a serpentine sample was ground using a planetary ball mill for 1 hour, the resulting ore powder was calcined at 700°C for 1 hour, and then stirred and leached using a 3 mol / L sulfuric acid solution at room temperature and a liquid-to-solid ratio of 15:1. The leaching rate of magnesium oxide reached 93%. Analysis of the differential thermal curve of the initial sample indicated that serpentine lost adsorbed water at 100°C and lost interlayer water in the magnesium hydroxide octahedral structure at 650°C-800°C. A new phase appeared after 800°C. Therefore, at around 700°C, serpentine lost a large amount of interlayer water, at which point the structure was most loose, and the magnesium atoms therein were most easily released. Meanwhile, the literature (“Extraction of magnesium and nickel from nickel-rich serpentine with sulfation roasting and water leaching”, Yang X, et al.)Metals, 2022, 12(2): 318) and (“Dissolution kinetics of magnesium from calcined serpentine in NH4Cl solution”, Gao W, Industrial & Engineering Chemistry Research, 2014, 53(19): 7947-7955) disclosed that the optimal heat treatment temperature for serpentine ore samples during sulfuric acid roasting-water leaching and calcination-ammonium sulfide leaching was 650℃~700℃, both of which destroyed the original stable structure of serpentine, and the final magnesium leaching rate and recovery rate could exceed 90% and 80% respectively.

[0006] In the existing technology, the stable structure of magnesium silicate minerals is destroyed by mechanical grinding, high-temperature calcination, etc. to enhance the leaching effect of magnesium, which is significant. However, the energy consumption of mechanical grinding and high-temperature calcination is high, which greatly increases the cost. At the same time, nickel, copper, iron, etc. in the raw materials will enter the leachate in large quantities, resulting in a significant increase in the difficulty and cost of subsequent recovery and impurity removal. Summary of the Invention

[0007] In view of the defects that in the prior art, during the demagnesiuming process of high-magnesium nickel sulfide minerals, a large amount of nickel, copper and iron will enter the leachate, making subsequent recovery and impurity removal more difficult, and the use of mechanical grinding or high-temperature roasting to enhance the leaching of magnesium oxide in the mineral will increase energy consumption and cost. The present invention aims to provide a method for enhancing the selective leaching of magnesium oxide in high-magnesium nickel sulfide minerals. The method does not require high-energy ball milling or high-temperature roasting of the high-magnesium nickel sulfide minerals. It only requires adding a special leaching aid during the normal pressure acid leaching demagnesiuming process without changing the existing process flow and equipment. The magnesium oxide in the high-magnesium nickel sulfide mineral can be highly selectively leached, while preventing the nickel, copper and iron in the raw materials from entering the leachate in large quantities, effectively reducing the difficulty and cost of subsequent recovery and impurity removal.

[0008] In order to achieve the above technical objectives, the present invention provides a method for enhancing the selective leaching of magnesium oxide in high-magnesium nickel sulfide minerals, wherein the method comprises the following steps: using a sulfuric acid solution leaching agent and a composite leaching aid to leach the high-magnesium nickel sulfide mineral at normal pressure; the obtained leaching residue is the magnesium-free nickel sulfide mineral, and the obtained leachate is a magnesium-rich solution;

[0009] The composite soaking agent includes component A and component B;

[0010] The component A includes at least one of chloride salt, fluoride salt, nitrate, and organic carboxylic acid;

[0011] The B component includes at least one of phosphate, silicate, modified natural fiber, modified starch, natural fiber, starch, and amine polymer.

[0012] The key to the present invention is the addition of a special composite leaching aid during the normal pressure acid leaching and magnesium removal process of high-magnesium nickel sulfide minerals. The composite leaching aid plays an important role in the efficient and highly selective leaching of magnesium oxide. On the one hand, the composite leaching aid includes a component that can selectively destroy the stable structure of magnesium-containing silicate gangue in the mineral, thereby breaking the chemical bonds in the original stable structure through a chemical reaction to form a loose structure, thereby opening the sulfuric acid leaching channel of the magnesium-containing silicate gangue mineral, thereby improving the leaching and removal efficiency of magnesium therein and reducing acid consumption. Based on the selective destruction of the magnesium-containing silicate gangue structure, the selectivity of magnesium oxide leaching is also improved. On the other hand, the composite leaching aid also includes components that inhibit the formation of silica gel and promote the dispersion of silica gel, which can reduce the coating effect of silica gel on the mineral during the acid leaching process. Since silicate minerals will form silica gel mSiO2·nH2O during the acid leaching process, which is easily coated on mineral particles and affects further leaching and magnesium removal, the addition of the leaching aid can inhibit the formation of silica gel or disperse the already formed silica gel, thereby reducing the coating effect of silica gel and making the acid leaching process more efficient. It can be seen that the components in the composite leaching agent work synergistically to improve the leaching efficiency of magnesium oxide by destroying the silicate gangue structure, inhibiting the formation of silica gel and promoting the dispersion of silica gel.

[0013] As a preferred embodiment, the component A includes at least one of potassium chloride, sodium chloride, calcium fluoride, sodium fluoride, potassium nitrate, calcium nitrate, EDTA, and citric acid. The preferred component A can provide chloride ions, fluoride ions, nitrate ions, etc., which have a destructive effect on the stable structure of magnesium-containing silicate gangue under acidic conditions, thereby opening up sulfuric acid leaching channels in the magnesium-containing silicate gangue minerals and improving the leaching and removal efficiency of magnesium therein.

[0014] As a preferred embodiment, the component B includes at least one of sodium hexametaphosphate, sodium tripolyphosphate, water glass, potassium silicate, CMC, cationic starch, corn starch, chitosan, PEI, and PI. The preferred component B has a surface active effect that can inhibit the formation of silica gel or disperse existing silica gel, thereby reducing the impact of silica gel wrapping and making the acid leaching process more efficient.

[0015] As a preferred embodiment, the composite leaching agent comprises component A and component B in a mass ratio of 1:0.1 to 5.0. Compared to using either component A or component B alone, the combined use of these two components is more conducive to the leaching of magnesium oxide from high-magnesium nickel sulfide minerals. Component A primarily destroys magnesium-containing silicate gangue, but the silica gel converted from these silicates easily wraps around the mineral, making leaching more difficult. Component B, on the other hand, inhibits silica gel formation or promotes silica gel dispersion, thereby improving the leaching efficiency of magnesium oxide. As a more preferred embodiment, the composite leaching agent comprises component A and component B in a mass ratio of 1:0.5 to 2.0.

[0016] As a preferred embodiment, the weight of the composite leaching aid is 0.1% to 10% of the mass of the high-magnesium nickel sulfide mineral. When the weight ratio of the composite leaching aid is too low, the improvement in the leaching effect of magnesium oxide from the high-magnesium nickel sulfide mineral is not significant. When the weight ratio of the composite leaching aid reaches a certain level, the increase in the leaching effect of magnesium oxide from the high-magnesium nickel sulfide mineral is not significant. Therefore, the weight of the composite leaching aid is more preferably 1% to 3% of the mass of the high-magnesium nickel sulfide mineral.

[0017] As a preferred solution, the atmospheric pressure leaching conditions are: a liquid-to-solid ratio of 2-8 L:1 kg, a sulfuric acid solution concentration of 50 g / L-200 g / L, a temperature of 10°C-80°C, and a leaching time of 1-8 hours. The liquid-to-solid ratio and sulfuric acid concentration are determined based on the magnesium oxide content in the high-magnesium nickel sulfide ore. When the magnesium oxide content is low, a lower liquid-to-solid ratio and a lower acid concentration are used; when the magnesium oxide content is high, a higher liquid-to-solid ratio and a higher acid concentration are used. Excessively high acid concentrations can also increase the leaching rate of other metal ions.

[0018] The method for enhancing the selective leaching of magnesium oxide from a high-magnesium nickel sulfide raw material provided by the present invention comprises the following steps:

[0019] 1) Determination of magnesium oxide content in high-magnesium nickel sulfide raw materials: The high-magnesium nickel sulfide raw materials are crushed, dried, and reduced to prepare qualified samples. The magnesium oxide content therein is determined by chemical analysis, and the magnesium oxide content is also determined by chemical analysis on the subsequent leaching residue.

[0020] 2) Determine the required liquid-to-solid ratio and sulfuric acid concentration: Determine the liquid-to-solid ratio and acid concentration used for acid leaching and magnesium removal based on the specific content of magnesium oxide in the raw material. To ensure the leaching effect and the magnesium concentration in the resulting leachate, a lower liquid-to-solid ratio and a lower acid concentration are used when the magnesium oxide content is low; and a higher liquid-to-solid ratio and a higher acid concentration are used when the magnesium oxide content is high.

[0021] 3) Prepare sulfuric acid solution according to the weight of high-magnesium nickel sulfide raw material: Prepare a certain amount of sulfuric acid solution according to the determined liquid-to-solid ratio and acid concentration and according to the weight of high-magnesium nickel sulfide raw material.

[0022] 4) Adding composite leaching aid and high-magnesium nickel sulfide raw material for atmospheric pressure acid leaching and magnesium removal: adding composite leaching aid in a certain proportion according to the weight of high-magnesium nickel sulfide raw material, and after the addition of composite leaching aid is completed, adding high-magnesium nickel sulfide raw material for atmospheric pressure acid leaching and magnesium removal.

[0023] 5) After the reaction is completed, the leaching liquid and leaching residue are obtained by filtration: After the atmospheric pressure acid leaching magnesium removal reaction is completed, the slurry is filtered, and the obtained leaching liquid can be further recovered, and the obtained leaching residue is the raw material with magnesium oxide content that meets the standard and can be used for pyrometallurgy.

[0024] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0025] 1) The present invention does not change the existing process and equipment for removing magnesium from high-magnesium nickel sulfide, and does not add any new operating steps. The selective leaching and removal of magnesium oxide from high-magnesium nickel sulfide raw materials can be enhanced by simply adding a composite leaching aid during the atmospheric pressure acid leaching process. At the same time, the composite leaching aid used has no effect on the atmospheric pressure acid leaching process.

[0026] 2) After adding the leaching aid, the magnesium oxide in the high-magnesium nickel sulfide raw material can be leached efficiently and selectively. The amount of sulfuric acid can be reduced while ensuring that the magnesium oxide content in the obtained leaching residue meets the standard. The concentrations of nickel, copper and iron in the obtained leachate are low, which can significantly reduce the cost in the subsequent leachate recovery and impurity removal process. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a process flow chart of the present invention.

[0028] Figure 2 This is a schematic diagram of the structure of serpentine, the main magnesium-containing silicate gangue mineral in high-magnesium nickel sulfide raw materials. It can be seen from the figure that the Si-O-Si bonds in serpentine are interconnected to form a dense six-membered ring structure that hinders the leaching of magnesium.

[0029] Figure 3 During the acid leaching process of high-magnesium nickel sulfide raw materials, magnesium-containing silicate gangue minerals will form silica gel mSiO2·nH2O, which is easily wrapped on the surface of mineral particles and hinders further leaching. DETAILED DESCRIPTION

[0030] The following comparative examples and embodiments are provided to further illustrate the present invention, but are not intended to limit the scope of protection of the claims of the present invention.

[0031] The high-magnesium nickel sulfide flotation concentrate produced by a certain mineral processing plant contains about 15% magnesium oxide, about 30% iron grade, and about 3% nickel and copper grades.

[0032] Example 1

[0033] Using high-magnesium nickel sulfide flotation concentrate as raw material, conventional atmospheric pressure acid leaching was carried out with a fixed liquid-solid ratio of 4L:1kg, a reaction temperature of 80℃ and a reaction time of 3h. No leaching aid was added or a single leaching aid was added as a comparison. Under the premise that the magnesium oxide content in the obtained leaching residue met the standard (less than 7%), the effect of adding a leaching aid was evaluated based on the acid consumption and the ion concentration in the leachate under the two conditions, as shown in Table 1.

[0034] Table 1. Relevant data when the magnesium oxide content in the leached residue is less than 7% when no leaching aid is added or when a single leaching aid is added to assist the leaching of magnesium oxide from high-magnesium nickel sulfide flotation concentrate.

[0035]

[0036] It can be seen from Table 1 that when no leaching aid is added, 150 g / L sulfuric acid is required to reduce the magnesium oxide content to below 7%. After adding different types of leaching aids, the magnesium oxide content in the obtained leaching residue can meet the standard at a lower acid consumption (80-90 g / L), indicating that the addition of leaching aids can enhance the selective leaching of magnesium oxide in high-magnesium nickel sulfide raw materials. At the same time, due to the reduced acid consumption, the nickel concentration, copper concentration and iron concentration in the obtained leachate are all reduced, which can effectively reduce the difficulty and cost of subsequent recovery and impurity removal without changing the existing process and equipment. At the same time, the amount of leaching aid used is low, and the additional cost is relatively small.

[0037] Example 2

[0038] Based on Example 1, leaching experiments were carried out on high-magnesium nickel sulfide flotation concentrate raw materials using different leaching aid combinations. The conditions were all a liquid-to-solid ratio of 4L:1kg, a reaction temperature of 80°C, and a reaction time of 3h. Under the premise that the magnesium oxide content in the obtained leached residue met the standard (less than 7%), the effects of adding different leaching aid combinations were evaluated based on acid consumption and ion concentration in the leachate, as shown in Table 2.

[0039] Table 2. The relevant data when the magnesium oxide content in the leached residue obtained by adding composite leaching aids to assist sulfuric acid leaching of magnesium oxide in high-magnesium nickel sulfide flotation concentrate is less than 7% are as follows:

[0040]

[0041] It can be seen from Table 2 that when the leaching aids of the combination of sodium fluoride (0.5%) + sodium hexametaphosphate (0.5%) and the combination of sodium fluoride (0.5%) + water glass (0.5%) are used, the amount of sulfuric acid can be reduced to 50 g / L to achieve the leaching of magnesium oxide content to below 7%, which has the effect of significantly reducing the amount of acid, reflecting the selective leaching effect of the leaching aid on magnesium-containing silicate.

[0042] Example 3

[0043] In order to compare the effects of temperature and reaction time on the effect of the soaking agent based on Example 2, the liquid-solid ratio was fixed at 4L:1kg, and sodium fluoride (0.5%) + sodium hexametaphosphate (0.5%) was used as the soaking agent as an example. The effect after addition was investigated under different temperature and reaction time conditions with the same acid consumption and dosage of the soaking agent in Table 2, as shown in Table 3.

[0044] Table 3 shows the effects of sodium fluoride (0.5%) + sodium hexametaphosphate (0.5%) as leaching aids under different temperature and reaction time conditions with the same acid consumption and dosage:

[0045]

[0046] As can be seen from Table 3, after adding a leaching aid and simultaneously increasing the leaching temperature, the magnesium oxide content in the leached residue decreased from 9.12% to 7.89%, the magnesium ion concentration in the solution increased from 6.56 g / L to 8.03 g / L, and the concentrations of other ions remained unchanged. These results indicate that the addition of a leaching aid and the increase in leaching temperature can further enhance the selective leaching of magnesium oxide.

Claims

1. A method for enhancing the selective leaching of magnesium oxide from high-magnesium nickel sulfide minerals, characterized in that: High-magnesium nickel sulfide minerals are leached at normal pressure using a sulfuric acid solution leaching agent and a composite leaching aid, the resulting leaching residue is magnesium-free nickel sulfide minerals, and the resulting leachate is a magnesium-rich solution; The composite immersion agent includes component A and component B; The component A includes at least one of chloride salt, fluoride salt, nitrate, and organic carboxylic acid; The B component includes at least one of phosphate, silicate, modified natural fiber, modified starch, natural fiber, starch, and amine polymer.

2. The method for enhancing the selective leaching of magnesium oxide from high-magnesium nickel sulfide minerals according to claim 1, wherein: The component A comprises at least one of potassium chloride, sodium chloride, calcium fluoride, sodium fluoride, potassium nitrate, calcium nitrate, EDTA, and citric acid; The B component includes at least one of sodium hexametaphosphate, sodium tripolyphosphate, water glass, potassium silicate, CMC, cationic starch, corn starch, chitosan, PEI, and PI.

3. The method for enhancing the selective leaching of magnesium oxide from high-magnesium nickel sulfide minerals according to claim 1, wherein: The composite soaking agent consists of component A and component B in a mass ratio of 1:0.1-5.

0.

4. The method for enhancing the selective leaching of magnesium oxide from high-magnesium nickel sulfide minerals according to any one of claims 1 to 3, characterized in that: The mass of the composite leaching agent is 0.1% to 10% of the mass of the high-magnesium nickel sulfide mineral.

5. The method for enhancing the selective leaching of magnesium oxide from high-magnesium nickel sulfide minerals according to claim 4, wherein: The mass of the composite leaching agent is 1% to 3% of the mass of the high-magnesium nickel sulfide mineral.

6. A method for enhancing the selective leaching of magnesium oxide from high-magnesium nickel sulfide minerals according to any one of claims 1, 2, 3 or 5, characterized in that: The conditions for the atmospheric pressure leaching are: a liquid-solid ratio of 2-8 L:1 kg, a sulfuric acid solution concentration of 50 g / L-200 g / L, a temperature of 10° C.-80° C., and a time of 1 h-8 h.

7. The method for enhancing the selective leaching of magnesium oxide from high-magnesium nickel sulfide minerals according to claim 1, wherein: The mass content of magnesium oxide in the high-magnesium nickel sulfide mineral is 10% to 40%.

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