A method for enhancing the selective leaching of magnesium oxide from high-magnesium nickel sulfide minerals

Abstract

This invention discloses a method for enhancing the selective leaching of magnesium oxide from high-magnesium nickel sulfide minerals, belonging to the field of non-ferrous metal hydrometallurgical technology. The method employs a sulfuric acid solution leaching agent and a composite leaching aid (including component A and component B; where component A includes chloride salts, fluoride salts, etc.; component B includes phosphates, silicates, etc.) to leach high-magnesium nickel sulfide minerals under normal pressure. The resulting leaching residue is magnesium-removed nickel sulfide minerals, and the resulting leachate is a magnesium-rich solution. This method does not change the existing acid leaching process and equipment for magnesium removal from high-magnesium nickel sulfide minerals; it only utilizes the composite leaching aid to enhance the efficient and selective leaching of magnesium oxide from high-magnesium nickel sulfide raw materials, effectively reducing the difficulty and cost of subsequent recovery and impurity removal.

Description

Technical Field

[0001] This invention relates to a method for removing magnesium from high-magnesium nickel sulfide minerals, and more particularly to a method for enhancing the selective leaching of magnesium oxide from high-magnesium nickel sulfide minerals using a leaching aid, belonging to the field of non-ferrous metal hydrometallurgical technology. Background Technology

[0002] Nickel sulfide ore, being primarily composed of sulfides, has a high calorific value and low energy consumption when heated, making it mainly used in pyrometallurgical processes. A flash furnace is typically used for rough refining of nickel sulfide ore into nickel matte, followed by further refining. However, nickel sulfide ore deposits contain large amounts of magnesium silicate gangue minerals such as serpentine and talc. The high melting point of magnesium oxide in these minerals means that a large influx into the flash furnace would increase energy consumption. More seriously, it would increase slag viscosity, easily leading to nodule formation within the furnace, affecting production efficiency and operational safety. Nodules must be removed by blasting during flash furnace cold repairs, extending the overall maintenance period and potentially causing some damage to the furnace. Therefore, controlling the magnesium oxide content in the flash furnace feed is crucial.

[0003] In the mineral processing enrichment process, magnesium reduction treatment is typically performed on nickel sulfide ore. For example, in the grinding stage, short-column media are used to differentiate the particle size distribution of different minerals, thus achieving selective grinding. This ensures the liberation of valuable metal minerals while preventing over-grinding of magnesium silicate gangue minerals, which can lead to mud formation and encapsulation in the concentrate. In the flotation stage, the process is optimized to ensure the timely collection of valuable metal mineral particles, preventing the over-grinding of brittle magnesium silicate minerals and the resulting mud formation that encapsulates valuable mineral particles into the concentrate. Simultaneously, improvements are made to flotation equipment and methods, such as flash flotation, strong stirring and slurry conditioning, and acid flotation, to desorb gangue slime or improve heterogeneous agglomeration. Developing efficient flotation magnesium-reducing reagents is also an important direction for magnesium reduction in mineral processing. Sodium hexametaphosphate, CMC, and various combined reagents are used to inhibit the flotation of magnesium silicate gangue minerals, thereby reducing the magnesium oxide content in the resulting concentrate.

[0004] As nickel sulfide ore reserves continue to decline due to continuous mining, current mining of nickel sulfide ore resources is gradually shifting towards lean ore. However, lean ore has a lower nickel grade and a higher magnesium oxide content, making it increasingly difficult to reduce magnesium content during the beneficiation stage. In order to produce concentrate products with magnesium oxide content that meets the standards in the beneficiation enrichment process, the recovery rates of nickel and copper will decrease significantly. On the other hand, in order to ensure the recovery rates of nickel and copper, the magnesium oxide content in the concentrate products will exceed the standards. Therefore, the importance of reducing magnesium oxide content through acid leaching is becoming increasingly prominent. It can be used to process high magnesium nickel sulfide lean ore or high magnesium beneficiation products produced by flotation of raw ore.

[0005] During the acid leaching process, nickel, copper, and iron in high-magnesium nickel sulfide raw materials will enter the leachate in large quantities along with magnesium oxide, increasing the difficulty and cost of subsequent recovery and impurity removal. Therefore, it is necessary to strengthen the efficient and selective leaching of magnesium oxide in high-magnesium nickel sulfide raw materials. Since magnesium oxide is abundant in magnesium silicate gangue minerals, represented by serpentine, serpentine is a layered silicate mineral composed of a layer of silicon-oxygen tetrahedra (T-plates) and a layer of magnesium-oxygen-hydrogen octahedra (O-plates) in a 1:1 ratio. The curling or bending of the T-plates gives serpentine different allomorphs, such as foliated serpentine and chrysotile. However, all of them have unshared oxygen atoms attached to the magnesium atoms of the octahedral layers. The Si-O-Si bonds and O-Si-O bonds 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 through conventional leaching methods. Other strengthening methods can destroy the original stable structure of serpentine, making it easier to leach magnesium. For example, in the literature (“Enhancement of acid extraction of magnesium and silicon from serpentine by mechanochemical treatment”, Zhang Q, et al., Hydrometallurgy, 1997, 45(3): (323-331) The serpentine ore sample was ground using a planetary ball mill to disrupt its stable structure. After dry grinding for 240 minutes, the ore powder was leached with a low-concentration acid at room temperature, which dissolved and leached more than 90% of the magnesium and more than 70% of the silicon. The analysis of the leaching residue showed that after high-intensity grinding, the serpentine changed from a stable crystalline structure to an amorphous state, which facilitated the leaching of magnesium and silicon. Reference (“Experimental Study on Magnesium Extraction from Activated Acid-Leached Serpentine”, Zeng Ying, et al., Mining and Metallurgical Engineering, 2006, (02): (57-60) The authors disclosed that after grinding serpentine ore samples with a planetary ball mill for 1 hour, the resulting ore powder was calcined at 700℃ for 1 hour. Under the conditions of room temperature and a liquid-to-solid ratio of 15:1, 3 mol / L sulfuric acid solution was used for stirring and leaching. The leaching rate of magnesium oxide reached 93%. Furthermore, the differential thermal analysis of the initial ore sample indicated that serpentine loses adsorbed water at 100℃, loses interlayer water in the magnesium-oxygen octahedral structure at 650℃~800℃, and a new phase appears after 800℃. Therefore, serpentine loses a large amount of interlayer water at around 700℃, at which point the structure is most loose, and the magnesium atoms are most easily released. At the same time, the literature (“Extraction of magnesium and nickel from nickel-rich serpentine with sulfation roasting and water leaching”, Yang X, et al.) also supports this finding.The papers "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, disclose that the optimal heat treatment temperature for sulfation roasting-water leaching and calcination-ammonium sulfide leaching of serpentine samples is 650℃~700℃. Both methods disrupt the original stable structure of serpentine, resulting in magnesium leaching and recovery rates exceeding 90% and 80%, respectively.

[0006] Existing technologies have shown that mechanical grinding and high-temperature calcination can significantly enhance magnesium leaching by disrupting the stable structure of magnesium silicate minerals. However, mechanical grinding and high-temperature calcination consume a lot of energy, which increases costs significantly. At the same time, a large amount of nickel, copper, iron and other impurities in the raw materials will enter the leaching solution, which will significantly increase the difficulty and cost of subsequent recovery and impurity removal. Summary of the Invention

[0007] In the existing process of demagnesification of high-magnesium nickel sulfide minerals, a large amount of nickel, copper, and iron enters the leachate, increasing the difficulty of subsequent recovery and impurity removal. Furthermore, using mechanical grinding or high-temperature roasting to enhance the leaching of magnesium oxide in the minerals increases energy consumption and cost. The purpose of this invention is to provide a method for enhancing the selective leaching of magnesium oxide from high-magnesium nickel sulfide minerals. This method eliminates the need for high-energy ball milling or high-temperature roasting of the high-magnesium nickel sulfide minerals. It only requires the addition of a special leaching aid during the atmospheric pressure acid leaching process, without altering the existing process flow and equipment. This allows for highly selective leaching of magnesium oxide from the high-magnesium nickel sulfide minerals while preventing large amounts of nickel, copper, and iron from entering the leachate, effectively reducing the difficulty and cost of subsequent recovery and impurity removal.

[0008] To achieve the above-mentioned technical objectives, the present invention provides a method for enhancing the selective leaching of magnesium oxide in high-magnesium nickel sulfide minerals. The method involves using sulfuric acid solution as a leaching agent and a composite leaching aid to leach the high-magnesium nickel sulfide minerals at atmospheric pressure. The resulting leaching residue is magnesium-removed nickel sulfide minerals, and the resulting leaching solution is a magnesium-rich solution.

[0009] The composite impregnation aid comprises component A and component B;

[0010] Component A includes at least one of chloride salts, fluoride salts, nitrate salts, and organic carboxylic acids;

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

[0012] The key to this invention lies in the addition of a special composite leaching aid during the atmospheric pressure acid leaching process of high-magnesium nickel sulfide minerals. This composite leaching aid plays a crucial role in the efficient and selective leaching of magnesium oxide. Firstly, the composite leaching aid includes components that selectively disrupt the stable structure of magnesium silicate gangue in the mineral. This allows chemical reactions to break the chemical bonds in the original stable structure, forming a loose structure and opening the sulfuric acid leaching channels for the magnesium silicate gangue minerals. This improves the efficiency of magnesium leaching and reduces acid consumption. The selective disruption of the magnesium silicate gangue structure also enhances the selectivity of magnesium oxide leaching. Secondly, the composite leaching aid contains components that inhibit silica gel formation and promote silica gel dispersion. This reduces the impact of silica gel encapsulation on the minerals during acid leaching. Since silicate minerals will form silica gel (mSiO2·nH2O) during acid leaching, it easily encapsulates mineral particles, affecting further magnesium leaching. Adding the leaching aid inhibits silica gel formation or disperses existing silica gel, thereby reducing the encapsulation effect and making the acid leaching process more efficient. It is evident that the components in the composite leaching aid work synergistically to improve the leaching efficiency of magnesium oxide by disrupting the silicate gangue structure, inhibiting silica gel formation, and promoting silica gel dispersion.

[0013] As a preferred embodiment, 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, under acidic conditions, disrupt the stable structure of magnesium silicate gangue, thereby opening the sulfuric acid leaching channels of the magnesium silicate gangue minerals and improving the leaching efficiency of magnesium.

[0014] As a preferred embodiment, component B comprises 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 possesses surface-active properties that can inhibit the formation of silica gel or disperse existing silica gel, thereby reducing the impact of silica gel encapsulation and making the acid leaching process more efficient.

[0015] As a preferred embodiment, the composite leaching aid is composed of component A and component B in a mass ratio of 1:0.1~5.0. Compared to using component A or component B alone, the combined use of both components is more beneficial for the leaching of magnesium oxide from high-magnesium nickel sulfide minerals. Component A mainly serves to break down magnesium-containing silicate gangue, but the silica gel formed from these silicates easily encapsulates the minerals, increasing the difficulty of leaching. Component B's inhibitory effect on silica gel formation or its promotion of silica gel dispersion helps improve the leaching effect of magnesium oxide. As a more preferred embodiment, the composite leaching aid is composed of component A and component B in a mass ratio of 1:0.5~2.0.

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

[0017] As a preferred embodiment, 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 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 minerals. A lower liquid-to-solid ratio and a lower acid concentration are used when the magnesium oxide content is low; conversely, a higher liquid-to-solid ratio and a higher acid concentration are used when the magnesium oxide content is high. Excessively high acid concentrations can also increase the leaching rate of other metal ions.

[0018] The present invention provides a method for selective leaching of magnesium oxide from high-magnesium nickel sulfide feedstock, which includes 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 in size to prepare qualified samples. The magnesium oxide content is determined by chemical analysis. The magnesium oxide content of the leaching residue obtained subsequently is also determined by chemical analysis.

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

[0022] 4) Add composite leaching aid and high magnesium nickel sulfide raw material for atmospheric pressure acid leaching demagnesification: Add composite leaching aid according to a certain proportion based on the weight of high magnesium nickel sulfide raw material. After the composite leaching aid is added, add high magnesium nickel sulfide raw material for atmospheric pressure acid leaching demagnesification.

[0023] 5) After the reaction is completed, the leaching solution and leaching residue are obtained by filtration: After the atmospheric pressure acid leaching demagnesification reaction is completed, the slurry is filtered. The obtained leaching solution can be further recovered, and the obtained leaching residue is the raw material with the magnesium oxide content meeting the standard and can be used for pyrometallurgical smelting.

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

[0025] 1) This invention does not change the existing process and equipment for demagnesification of high-magnesium nickel sulfide, nor does it add any new operation steps. It only enhances the selective leaching and removal of magnesium oxide in high-magnesium nickel sulfide raw materials by 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) Adding leaching aids can enable the efficient and selective leaching of magnesium oxide in high-magnesium nickel sulfide raw materials. Under the premise that the magnesium oxide content in the obtained leaching residue meets the standard, the amount of sulfuric acid can be reduced. The concentration of nickel, copper and iron in the obtained leaching solution is low, which can significantly reduce costs in the subsequent leaching solution recovery and impurity removal process. Attached Figure Description

[0027] Figure 1 This is a process flow diagram of the present invention.

[0028] Figure 2 This is a schematic diagram of the structure of serpentine, the main magnesium silicate gangue mineral in high-magnesium nickel sulfide raw materials. As can be seen from the diagram, 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 silicate gangue minerals will form silica gel mSiO2·nH2O, which easily coats the surface of mineral particles and hinders further leaching. Detailed Implementation

[0030] The following comparative examples and embodiments are intended to further illustrate the content of 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 ore dressing plant has a magnesium oxide content of about 15%, an iron grade of about 30%, and a nickel and copper grade of about 3%.

[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-to-solid ratio of 4L:1kg, a reaction temperature of 80℃, and a reaction time of 3h. The effects of adding the leaching aid were evaluated based on the acid consumption and ion concentration in the leachate under the two conditions, provided that the magnesium oxide content in the resulting leaching residue met the standard (less than 7%). The specific results are shown in Table 1.

[0034] Table 1. Relevant data on the magnesium oxide content in the leaching residue obtained from the sulfuric acid leaching of magnesium oxide in high-magnesium nickel sulfide flotation concentrate without the addition of leaching aids and with the addition of a single leaching aid are as follows:

[0035]

[0036] As shown in Table 1, without adding any leaching aid, 150 g / L of 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 resulting leaching residue can meet the standard with a lower acid consumption (80~90 g / L). This indicates 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 reduction in acid consumption, the concentrations of nickel, copper, and iron in the resulting 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. In addition, the amount of leaching aid used is low, resulting in less additional cost.

[0037] Example 2

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

[0039] Table 2. Relevant data on the magnesium oxide content in the leaching residue obtained by adding composite leaching aid to assist sulfuric acid leaching of magnesium oxide in high-magnesium nickel sulfide flotation concentrate is as follows:

[0040]

[0041] As can be seen from Table 2, when the combination of sodium fluoride (0.5%) + sodium hexametaphosphate (0.5%) and sodium fluoride (0.5%) + water glass (0.5%) is used as leaching aids, the amount of sulfuric acid can be reduced to 50 g / L to achieve a magnesium oxide content of less than 7%, which has a significant effect on reducing the amount of acid used, demonstrating the selective leaching effect of the leaching aids on magnesium silicates.

[0042] Example 3

[0043] Based on Example 2, in order to compare the effects of temperature and reaction time on the effect of the leaching aid, with a fixed liquid-to-solid ratio of 4L:1kg, sodium fluoride (0.5%) + sodium hexametaphosphate (0.5%) was used as the leaching aid. The effects of adding this leaching aid under different temperatures and reaction times were examined with the same acid consumption and dosage as shown in Table 2, as detailed in Table 3.

[0044] Table 3 shows the effects of using sodium fluoride (0.5%) + sodium hexametaphosphate (0.5%) as an immersion aid under different temperatures and reaction times with the same acid consumption and dosage:

[0045]

[0046] Table 3 shows that after adding the leaching aid and simultaneously increasing the leaching temperature, the magnesium oxide content in the leaching residue decreased from 9.12% to 7.89%, while the magnesium ion concentration in the solution increased from 6.56 g / L to 8.03 g / L. The concentrations of other ions remained relatively unchanged. The experimental results indicate that the leaching aid, by coordinating 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 were leached at atmospheric pressure using sulfuric acid solution leaching agent and composite leaching aid. The resulting leaching residue was magnesium-removed nickel sulfide minerals, and the resulting leaching solution was a magnesium-rich solution. The composite impregnation aid comprises component A and component B; Component A includes at least one of chloride salts, fluoride salts, nitrate salts, and organic carboxylic acids; Component B includes at least one of sodium hexametaphosphate, sodium tripolyphosphate, water glass, potassium silicate, CMC, cationic starch, corn starch, chitosan, PEI, and PI.

2. The method for selectively leaching magnesium oxide from high-magnesium nickel sulfide minerals according to claim 1, characterized in that: Component A includes at least one of potassium chloride, sodium chloride, calcium fluoride, sodium fluoride, potassium nitrate, calcium nitrate, EDTA, and citric acid.

3. The method for selectively leaching magnesium oxide from high-magnesium nickel sulfide minerals according to claim 1, characterized in that: The composite impregnation aid is composed of component A and component B in a mass ratio of 1:0.1~5.

0.

4. A method for selectively leaching 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 aid is 0.1% to 10% of the high magnesium nickel sulfide mineral content.

5. The method for selectively leaching magnesium oxide from high-magnesium nickel sulfide minerals according to claim 4, characterized in that: The mass of the composite leaching aid is 1% to 3% of the high magnesium nickel sulfide mineral content.

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

7. The method for selectively leaching magnesium oxide from high-magnesium nickel sulfide minerals according to claim 1, characterized in that: The magnesium oxide content in the high-magnesium nickel sulfide mineral is 10% to 40% by mass.

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