Method and system for detoxifying lithium ore smelting slag based on nanofiltration treatment

Abstract

The invention provides a detoxification method and system based on nanofiltration treatment of lithium ore smelting slag, and the method comprises the following steps: step S1: carrying out acid leaching treatment on the lithium ore smelting slag by using an inorganic acid liquid, so that acid-soluble components in the lithium ore smelting slag are dissolved in the inorganic acid liquid to obtain an acid leaching liquid and detoxified smelting slag; s2, the acid leaching solution is subjected to oxidation treatment, metal ions with intermediate valence in the acid leaching solution are oxidized into metal ions with high valence, and an oxidized acid leaching solution is obtained; s3, carrying out nanofiltration treatment on the oxidized pickle liquor to intercept high-valence metal ions in the oxidized pickle liquor so as to obtain concentrated liquor and permeate liquor; s4, using the permeate liquid as the inorganic acid liquid in the step S1 for acid leaching treatment. According to the method, toxic components in the lithium ore smelting slag can be fully separated, and resource utilization is easier.

Description

Technical Field

[0001] The present application belongs to the technical field of harmless treatment of smelting waste, and specifically relates to a detoxification method and system for lithium ore smelting slag based on nanofiltration treatment. Background Art

[0002] More than 85% of domestic lithium salt products come from lithium ore extraction. However, lithium ore extraction will produce a large amount of lithium slag. Generally, 8 to 10 tons of lithium slag will be produced for every ton of lithium salt produced. The main components of lithium slag are a mixture of oxides and minerals such as silicon oxide, aluminum oxide, and calcium oxide. It also contains a small amount of sulfur, alkali, and toxic and harmful components such as fluorine, thallium, and beryllium. It cannot be used on a large scale in the future, resulting in the accumulation of a large amount of lithium smelting slag, which also brings serious environmental impacts. In order to achieve large-scale consumption of lithium smelting slag, it is necessary to dissociate and replace the toxic components in the lithium smelting slag from the smelting slag, so that the smelting slag is easier to use on a large scale in the future. Summary of the invention

[0003] In view of this, the present application provides a detoxification method and system for lithium ore smelting slag based on nanofiltration treatment, which aims to remove and separate the heavy metal toxic components in the lithium ore smelting slag, so that the lithium ore smelting slag and toxic components are easier to be utilized as resources.

[0004] In a first aspect, the present application provides a detoxification method for lithium ore smelting slag based on nanofiltration treatment, comprising the following steps: Step S1: using an inorganic acid solution to acid-leach the lithium ore smelting slag, so that the acid-soluble components in the lithium ore smelting slag are dissolved in the inorganic acid solution to obtain an acid leaching solution and detoxified smelting slag; Step S2: subjecting the acid leaching solution to oxidation treatment to oxidize the intermediate-valent metal ions in the acid leaching solution into high-valent metal ions to obtain an oxidized acid leaching solution; Step S3: performing nanofiltration treatment on the oxidizing acid leaching solution to intercept high-valent metal ions in the oxidizing acid leaching solution to obtain a concentrated solution and a permeate; Step S4: using the permeate as the inorganic acid solution in step S1 for acid leaching treatment.

[0005] Based on the present application, by using inorganic acid to carry out acid leaching treatment on lithium ore smelting slag, the toxic heavy metal elements in the lithium ore smelting slag can be dissolved and fixed in the acid leaching solution, and then oxidation treatment can be carried out to oxidize the heavy metal elements in the intermediate valence state into high-valence metal elements, so that they are easier to be intercepted, separated and concentrated in the nanofiltration treatment. The permeate also contains unreacted inorganic acid, and because the content of toxic heavy metal ions in the permeate is low, it can continue to be used for acid leaching treatment, further reducing the content of toxic heavy metal elements in the detoxified smelting slag, which is beneficial to its subsequent resource utilization; in addition, the concentration of toxic metal elements in the concentrated solution is relatively high, and the content of other inorganic ions is low, which is beneficial to the separation and resource utilization of toxic metal elements in the concentrated solution.

[0006] In some embodiments, the inorganic acid solution includes at least one of hydrochloric acid, aqueous sulfuric acid, or aqueous nitric acid.

[0007] In some embodiments, the concentration of the inorganic acid solution is 1-5 mol / L.

[0008] In some embodiments, the lithium ore in the lithium ore smelting slag includes at least one of spodumene, lepidolite, pyroxene or petalite.

[0009] In some embodiments, the lithium ore smelting slag is a particle size of 30 to 100 meshes.

[0010] In some embodiments, the conditions for the acid leaching treatment include: the mass ratio of the lithium ore smelting slag and the inorganic acid solution is 1:1~20; the acid leaching temperature is 15~100°C; and the acid leaching method is one of intermittent leaching and continuous percolation.

[0011] In some embodiments, the leaching time of the intermittent leaching is 0.5~3h.

[0012] In some embodiments, the leaching time of the continuous diafiltration is 0.5 to 2 hours.

[0013] In some embodiments, in step S2, the oxidation treatment includes: oxidizing the acid leaching solution using an oxidant, and the oxidant includes at least one of air, oxygen, ozone, hypochlorous acid or hydrogen peroxide.

[0014] In some embodiments, in step S3, before the nanofiltration treatment, the oxidizing acid leaching solution is subjected to microfiltration treatment to remove insoluble solids in the oxidizing acid leaching solution, and then the nanofiltration treatment is performed.

[0015] In some embodiments, in step S3, the conditions of the nanofiltration treatment include: allowing the oxidizing acid leaching solution to pass through the nanofiltration membrane at a pressure of 0.5-3 MPa at 15-40° C., and the water production rate of the nanofiltration treatment is 70%-95%.

[0016] In some embodiments, the step S4 includes: adding an inorganic acid to the permeate to make the concentration of the inorganic acid in the permeate to be 1-5 mol / L, and then using the inorganic acid solution in step S1 for acid leaching.

[0017] In the second aspect, a detoxification system for treating lithium ore smelting slag based on nanofiltration comprises: Acid leaching unit, used for acid leaching of lithium ore smelting slag; An oxidation unit connected to the acid leaching unit, used to oxidize metal ions in the acid leaching solution from the acid leaching unit into high-valent metal ions; The nanofiltration unit connected to the acid leaching unit is used to intercept and separate high-valent metal ions in the oxidized acid leaching liquid from the acid leaching unit; the nanofiltration unit is connected to the acid leaching unit and is used to transfer the permeate from the nanofiltration unit to the acid leaching unit.

[0018] Based on the present application, the detoxification system can be used for the detoxification of the lithium ore smelting slag of the first aspect, and therefore has the beneficial effect of the first aspect, namely, the toxic heavy metal elements in the lithium ore smelting slag can be removed and separated, making the detoxified lithium ore smelting slag and the toxic heavy metal elements easier to utilize as resources.

[0019] In some embodiments, a microfiltration unit is included between the oxidation unit and the nanofiltration unit to remove insoluble solids in the oxidizing acid leaching liquid from the acid leaching unit.

[0020] In some embodiments, an acid supplement unit is included between the nanofiltration unit and the acid leaching unit to increase the concentration of inorganic acid in the permeate from the nanofiltration unit.

[0021] In some embodiments, the microfiltration unit includes at least one of a centrifuge, a microfiltration device, or a plate and frame filter.

[0022] In some embodiments, the nanofiltration unit includes at least one of a spiral membrane separator, a tubular membrane separator, or a hollow fiber membrane separator.

[0023] In some embodiments, the nanofiltration unit comprises a nanofiltration membrane having a molecular weight cutoff of 200-400.

[0024] In some embodiments, the nanofiltration membrane is an inorganic nanofiltration membrane and / or an organic nanofiltration membrane.

[0025] In some embodiments, the material of the nanofiltration membrane includes at least one of cellulose, cellulose acetate, sulfonated polysulfone, polyamide, polyimide, polyethersulfone, sulfonated polyethersulfone, polypiperazine or polyvinyl alcohol.

[0026] Compared with the prior art, the beneficial effects of the present application are at least: 1. This method uses the nanofiltration process to remove harmful high-valent metal ion components from the leachate in a timely manner during the leaching process, thereby reducing the concentration of harmful ions in the leachate in the leaching equipment and improving the leaching efficiency and the elution rate of harmful metals.

[0027] 2. The nanofiltration process uses pressure to drive inorganic acid to penetrate through the separation membrane. There is no phase change process, so the cost of concentrating harmful ions is much lower than the heating concentration process.

[0028] 3. This method uses nanofiltration to separate and concentrate high-valent ions, so that the permeate after leaching can be purified and reused, thereby reducing the amount of inorganic acid solution that needs to be treated. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a process flow chart of a detoxification method for lithium ore smelting slag based on nanofiltration treatment in one embodiment of the present application. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the present application more clear, the present application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described here are only used to explain the present application and are not used to limit the present application.

[0031] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the implementation or examples are included in at least one implementation or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same implementation or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more implementations or examples in a suitable manner.

[0032] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0033] At present, the commonly used method for enhanced dissociation and detoxification of smelting slag is usually to use a liquid elution medium solution to contact the solid smelting slag, use the elution medium to achieve the dissociation of harmful components, and use the concentration gradient between the solid phase and the liquid phase to diffuse and transfer harmful components from the solid phase to the liquid phase. The commonly used medium solution is an inorganic acid solution. On the one hand, in order to enhance the elution effect, after the elution is completed, the eluent will still contain a certain amount of inorganic acid, and at the same time contain a large amount of eluted inorganic ions, which makes it difficult to further separate and utilize the toxic components; on the other hand, during the elution process, the concentration of harmful ions in the eluent accumulates to a certain extent, and the concentration gradient of harmful ions between the medium solution and the slag phase becomes smaller, which inhibits the further transfer of ions from the solid phase to the liquid phase, thereby greatly reducing the elution efficiency in the later stage of elution.

[0034] Aiming at the problems of large consumption of inorganic acid, difficulty in subsequent disposal, low elution efficiency caused by concentration difference suppression in the direct acid medium leaching and elution process of lithium ore smelting slag, the present application provides a detoxification method for lithium ore smelting slag based on nanofiltration treatment, combining the membrane separation process with the leaching and elution process. In the leaching and elution process, after a certain period of time after the basic elution process starts, the eluent is continuously transported from the elution equipment to the membrane equipment. The membrane separation process uses a nanofiltration separation membrane with interception performance for the main eluted harmful ions. Under pressure, inorganic acid and low-valent ions such as lithium ions pass through the nanofiltration membrane, and high-valent harmful ions such as beryllium and thallium and other eluted calcium, magnesium, aluminum, and iron ions are intercepted and concentrated. The concentrated solution enters the subsequent section for deep treatment of harmful ions, and the permeate with harmful components removed is immediately returned to the leaching and elution equipment to continue acid leaching of lithium ore smelting slag, thereby overcoming the problems existing in the relevant technology at the same time. The specific implementation method of the present application is described in detail below.

[0035] In a first aspect, the present application provides a detoxification method for lithium ore smelting slag based on nanofiltration treatment, comprising the following steps: Step S1: using an inorganic acid solution to acid-leach the lithium ore smelting slag, so that the acid-soluble components in the lithium ore smelting slag are dissolved in the inorganic acid solution to obtain an acid leaching solution and detoxified smelting slag; Step S2: subjecting the acid leaching solution to oxidation treatment to oxidize the intermediate-valent metal ions in the acid leaching solution into high-valent metal ions, thereby obtaining an oxidized acid leaching solution; Step S3: performing nanofiltration treatment on the oxidizing acid leaching solution to intercept high-valent metal ions in the oxidizing acid leaching solution to obtain a concentrated solution and a permeate; Step S4: using the permeate as the inorganic acid solution in step S1 for acid leaching treatment.

[0036] Based on the present application, by using inorganic acid to carry out acid leaching treatment on lithium ore smelting slag, the toxic heavy metal elements in the lithium ore smelting slag can be dissolved and fixed in the acid leaching solution, and then oxidation treatment can be carried out to oxidize the heavy metal elements in the intermediate valence state into high-valence metal elements, so that they are easier to be intercepted, separated and concentrated in the nanofiltration treatment. The permeate also contains unreacted inorganic acid, and because the content of toxic heavy metal ions in the permeate is low, it can continue to be used for acid leaching treatment, further reducing the content of toxic heavy metal elements in the detoxified smelting slag, which is beneficial to its subsequent resource utilization; in addition, the concentration of toxic metal elements in the concentrated solution is relatively high, and the content of other inorganic ions is low, which is beneficial to the separation and resource utilization of toxic metal elements in the concentrated solution.

[0037] Specifically, in step S1, the lithium ore smelting slag is subjected to acid leaching treatment using an inorganic acid solution. Since generally toxic metal elements exist in the lithium ore smelting slag as metal oxides, most of them can react with the inorganic acid solution to be dissolved and fixed in the acid leaching solution, thereby being separated from the lithium ore smelting slag; In step S2, the acid leaching solution is subjected to oxidation treatment. Since oxidation reaction generally does not occur during the acid leaching process, some toxic metal elements exist in the form of intermediate valence. As an example, monovalent thallium ions in the acid leaching solution can be oxidized to trivalent thallium ions after oxidation treatment. High-valent metal ions are more easily rejected by nanofiltration membranes due to their higher positive charge and smaller hydration radius, and are more easily retained and enriched by nanofiltration membranes, thereby being more easily separated from other ions during the nanofiltration treatment process, which is beneficial to the resource utilization of toxic metal elements. In step S3, the oxidizing acid leaching liquid is subjected to nanofiltration treatment, that is, the high-valent toxic metal elements can be separated from inorganic anions (such as inorganic acid radicals), hydrogen ions and low-valent metal ions (such as lithium ions), and the high-valent toxic metal elements can be fixed in the concentrated solution. In addition, since there is still unreacted inorganic acid in the permeate and the content of high-valent toxic metal elements is low, it still has a good leaching effect on the toxic metal elements in the lithium ore smelting slag. Therefore, it can be used in the acid leaching treatment of step S1, further reducing the content of toxic metal elements in the detoxified smelting slag and saving the amount of inorganic acid solution.

[0038] In some embodiments, the inorganic acid solution includes at least one of hydrochloric acid, sulfuric acid aqueous solution or nitric acid aqueous solution. Based on the above embodiments, the use of the above-mentioned inorganic acid solutions can effectively fix the toxic metal elements in the lithium ore smelting slag into the acid leaching solution, and it is also easier to pass through the nanofiltration membrane, further improving the detoxification and separation effect. Preferably, the inorganic acid solution is hydrochloric acid. Hydrochloric acid is easier to pass through the nanofiltration membrane, and the detoxification and separation effect is better.

[0039] In some embodiments, the concentration of the inorganic acid solution is 1 to 5 mol / L. Based on the above embodiments, the above concentration can improve the efficiency of the acid leaching treatment and the detoxification and separation effect, which is beneficial to the resource utilization of lithium ore smelting slag and toxic metal elements.

[0040] At least one of quartz or petalite. Based on the above embodiments, the detoxification method has a good detoxification effect on the smelting slag of the above several lithium ores.

[0041] In some embodiments, the lithium ore smelting slag is a particle size of 30 to 100 meshes. Based on the above embodiments, the lithium ore smelting slag has a larger specific surface area, and the removal efficiency of toxic metal elements in the lithium ore smelting slag is higher and the removal effect is better.

[0042] In some embodiments, the conditions for acid leaching include: the mass ratio of lithium ore smelting slag to inorganic acid solution is 1:1-20; the acid leaching temperature is 15-100°C; the acid leaching method is one of intermittent leaching and continuous percolation. Based on the above embodiment, under the above conditions, it is conducive to the full leaching of toxic metal elements in lithium ore smelting slag, thereby being more conducive to the resource utilization of lithium ore smelting slag and toxic metal elements.

[0043] In some embodiments, the leaching time of intermittent leaching is 0.5 to 3 hours. In some of the above embodiments, the equipment required for intermittent leaching is simpler, which is conducive to reducing costs.

[0044] In some embodiments, the leaching time of continuous diafiltration is 0.5 to 2 hours. In some of the above embodiments, continuous diafiltration can reduce the leaching time, which is beneficial to improving the detoxification efficiency.

[0045] It should be noted that the leaching time of the acid leaching treatment in this application does not refer to the time of a single acid leaching, that is, it includes the time for acid leaching using inorganic acid solution, and also includes the time between subsequent acid leaching using permeate for acid leaching treatment, that is, the sum of the time for acid leaching treatment of the same batch of lithium ore smelting slag.

[0046] In some embodiments, in step S2, the oxidation treatment includes: oxidizing the pickling solution with an oxidant, the oxidant including at least one of air, oxygen, ozone, hypochlorous acid or hydrogen peroxide. In some of the above embodiments, the use of the above oxidants for oxidation can reduce the introduction of new impurity ions into the pickling solution. Preferably, the oxidant is air, which can further reduce costs and does not introduce impurities.

[0047] In some embodiments, the oxidant is air, and the ratio of the acid leaching solution to the air is 1L:5-20L.

[0048] In some embodiments, in step S3, before the nanofiltration treatment, the oxidizing acid leaching solution is subjected to microfiltration treatment to remove insoluble solids in the oxidizing acid leaching solution, and then the nanofiltration treatment is performed. In some of the above embodiments, a small amount of insoluble solids may exist in the oxidizing acid leaching solution. By performing the microfiltration treatment and then the nanofiltration treatment, the adverse effects of the insoluble solids on the nanofiltration treatment are reduced, thereby improving the efficiency of the nanofiltration treatment and reducing the damage to the nanofiltration treatment device.

[0049] In some embodiments, in step S3, the conditions of the nanofiltration treatment include: passing the oxidized acid leaching solution through the nanofiltration membrane at a pressure of 0.5-3 MPa at 15-40°C, and the water production rate of the nanofiltration treatment is 70%-95%. Based on the above embodiment, under this condition, the toxic heavy metal ions can be separated from the inorganic acid radical ions, hydrogen ions and low-valent metal ions to obtain a concentrated solution enriched with toxic heavy metal ions and a permeate containing almost no toxic heavy metal ions, which are used for resource utilization of toxic heavy metal ions and for acid leaching treatment, respectively.

[0050] In some embodiments, the molecular weight cut-off of the nanofiltration membrane is 200-400.

[0051] In some embodiments, the nanofiltration membrane is an inorganic nanofiltration membrane and / or an organic nanofiltration membrane.

[0052] In some embodiments, the material of the nanofiltration membrane includes at least one of cellulose, cellulose acetate, sulfonated polysulfone, polyamide, polyimide, polyethersulfone, sulfonated polyethersulfone, polypiperazine or polyvinyl alcohol.

[0053] In some embodiments, step S4 includes: adding inorganic acid to the permeate to make the concentration of the inorganic acid in the permeate to be 1-5 mol / L, and then using the inorganic acid solution in step S1 for acid leaching. Based on the above embodiment, since the acid concentration in the permeate is reduced, it can be used for acid leaching after acid replenishment, which can further improve the efficiency and effect of subsequent acid leaching.

[0054] In the second aspect, a detoxification system for treating lithium ore smelting slag based on nanofiltration comprises: Acid leaching unit, used for acid leaching of lithium ore smelting slag; An oxidation unit connected to the acid leaching unit is used to oxidize metal ions in the acid leaching solution from the acid leaching unit into high-valent metal ions; The nanofiltration unit is connected to the acid leaching unit and is used to intercept and separate high-valent metal ions in the oxidized acid leaching liquid from the acid leaching unit; the nanofiltration unit is connected to the acid leaching unit and is used to transfer the permeate from the nanofiltration unit to the acid leaching unit.

[0055] Based on the present application, the detoxification system can be used for the detoxification of the lithium ore smelting slag of the first aspect, and therefore has the beneficial effect of the first aspect, namely, the toxic heavy metal elements in the lithium ore smelting slag can be removed and separated, making the detoxified lithium ore smelting slag and the toxic heavy metal elements easier to utilize as resources.

[0056] Specifically, lithium ore smelting slag and inorganic acid solution can be acid-leached in an acid leaching unit. After a period of treatment, the acid leaching liquid enters an oxidation unit to undergo oxidation treatment. After the oxidation treatment, the oxidized acid leaching liquid enters a nanofiltration unit to intercept high-valent metal ions, wherein the concentrated solution obtained by interception is also used for resource utilization of high-valent metal ions. The permeate enters an acid leaching unit to further acid-leach the lithium ore smelting slag.

[0057] In some embodiments, a microfiltration unit is included between the oxidation unit and the nanofiltration unit to remove insoluble solids in the oxidized acid leaching solution from the acid leaching unit.

[0058] In some embodiments, an acid supplement unit is included between the nanofiltration unit and the acid leaching unit to increase the concentration of inorganic acid in the permeate from the nanofiltration unit.

[0059] In some embodiments, the microfiltration unit includes at least one of a centrifuge, a microfiltration device, or a plate and frame filter. Based on the above embodiments, the above devices can effectively remove insoluble solids in the oxidizing acid leaching solution. Preferably, the microfiltration device is a ceramic microfiltration device.

[0060] In some embodiments, the nanofiltration unit comprises at least one of a spiral membrane separator, a tubular membrane separator or a hollow fiber membrane separator, preferably a spiral membrane separator.

[0061] In some embodiments, the nanofiltration unit comprises a nanofiltration membrane having a molecular weight cutoff of 200-400.

[0062] In some embodiments, the nanofiltration membrane is an inorganic nanofiltration membrane and / or an organic nanofiltration membrane, preferably an organic nanofiltration membrane.

[0063] In some embodiments, the material of the nanofiltration membrane includes at least one of cellulose, cellulose acetate, sulfonated polysulfone, polyamide, polyimide, polyethersulfone, sulfonated polyethersulfone, polypiperazine or polyvinyl alcohol.

[0064] The scheme of the present application is described below in conjunction with the following specific examples. Unless otherwise specified, the raw materials used in the following examples are all from common commercial products, and the devices or equipment used are all purchased from conventional market sales channels.

[0065] Example 1 The volume of the leaching equipment is 3L. 2L of 3mol / L hydrochloric acid solution and 200g of lithium ore smelting slag raw material are added. After soaking at 25℃ for 30 minutes, the leached eluent is taken out at the bottom of the leaching equipment, 20L of air is introduced into the eluent, and then the suspended particles are filtered out through the ceramic microfiltration device, and the membrane assembly is pressurized to 2.0MPa. The membrane assembly uses a nanofiltration membrane made of polyamide material and a molecular weight cutoff of 200. Under pressure, water, hydrochloric acid and monovalent ions pass through the separation membrane, and beryllium, thallium (trivalent), calcium, magnesium, aluminum and iron in the leaching are all intercepted. The operating parameters of the membrane separation process are adjusted to make the water production rate of the nanofiltration concentration process reach 90%, that is, 90% of the hydrochloric acid in the leachate entering the membrane system is purified through the membrane, and the concentrated liquid enters the subsequent process. The permeate is directly returned to the leaching tank. After the membrane separation process is carried out for 1 hour (the total acid leaching time is 1.5h), the leaching operation is stopped and the remaining leachate is continued to be concentrated. After concentration, about 1.5L of leaching acid solution and 0.5L of concentrated solution were obtained.

[0066] The beryllium content in the concentrated liquid was measured to be 32.0 mg / L, while the beryllium content in the final permeate was less than 0.1 mg / L. The hydrochloric acid concentration was 1.5 mol / L. After appropriate acid replenishment, it can be used for acid leaching of the next batch of lithium ore smelting slag, thus realizing resource recycling.

[0067] Example 2 The volume of the leaching equipment is 3L. 2L of 3mol / L hydrochloric acid solution and 200g of lithium ore smelting slag raw material are added. After soaking at 25℃ for 30 minutes, the leached eluent is taken out at the bottom of the leaching equipment, and 40L of air is introduced into the eluent. Then, the suspended particles are filtered out through the ceramic microfiltration device, and the membrane assembly is pressurized to 2.0MPa. The membrane assembly uses a nanofiltration membrane with a polyimide material and a molecular weight cutoff of 300. Under pressure, water, hydrochloric acid and monovalent ions pass through the separation membrane, and beryllium, thallium (trivalent), calcium, magnesium, aluminum and iron in the leaching are all intercepted. The operating parameters of the membrane separation process are adjusted to make the water production rate of the nanofiltration concentration process reach 80%, that is, 80% of the hydrochloric acid in the leachate entering the membrane system is purified through the membrane, and the concentrated liquid enters the subsequent process. The permeate is directly returned to the leaching tank. After the membrane separation process is carried out for 1 hour (the total acid leaching time is 1.5h), the leaching operation is stopped and the remaining leachate is continued to be concentrated. After concentration, about 1.2L of leaching acid solution and 0.8L of concentrated solution were obtained.

[0068] The beryllium content in the concentrated liquid was measured to be 19.8 mg / L, while the beryllium content in the final permeate was less than 0.1 mg / L. The hydrochloric acid concentration was 1.5 mol / L. After appropriate acid replenishment, it can be used for acid leaching of the next batch of lithium ore smelting slag, thus realizing resource recycling.

[0069] Embodiment 3: Process flow chart Figure 1As shown, the volume of the leaching equipment is 3L, 2L of 3mol / L hydrochloric acid solution and 200g of lithium ore smelting slag raw material are added, and after soaking at 25℃ for 30 minutes, the leached eluent is taken out at the bottom of the leaching equipment, 45L of air is introduced into the eluent, and then the suspended particles are filtered out through the ceramic microfiltration device, and the membrane assembly is pressurized to 2.0MPa. The membrane assembly uses a nanofiltration membrane with a polyimide material and a molecular weight cutoff of 300. Under pressure, water, hydrochloric acid and monovalent ions pass through the separation membrane, and beryllium, thallium (trivalent), calcium, magnesium, aluminum and iron in the leaching are all intercepted. The operating parameters of the membrane separation process are adjusted so that the concentration ratio of the nanofiltration concentration process reaches 1:9, that is, 90% of the hydrochloric acid in the leachate entering the membrane system is purified through the membrane, and the concentrated liquid enters the subsequent process. The permeate is supplemented with 8mol / L hydrochloric acid in proportion to the amount of the concentrated liquid and then returned to the leaching tank. After the membrane separation process was carried out for 1 hour, the leaching operation was stopped and the remaining leachate was concentrated. After the concentration was completed, about 2.0L of leaching acid solution and 0.5L of concentrated solution were obtained.

[0070] The beryllium content in the concentrated solution was measured to be 32.4 mg / L. At the same time, the beryllium content in the final permeate was less than 0.1 mg / L, and the hydrochloric acid concentration was 1.5 mol / L. After appropriate acid supplementation, it can be used for acid leaching of the next batch of lithium ore smelting slag, realizing resource recycling.

[0071] Comparative Example 1 The volume of the leaching equipment is 3L. 2L of 3mol / L hydrochloric acid solution and 200g of lithium ore smelting slag raw material are added. After soaking at 25°C for 1.5h, the leached eluent is taken out from the bottom of the leaching equipment.

[0072] The beryllium content in the leaching solution was measured to be 7.1 mg / L, and the volume of the leaching solution was close to 2 L, so it was not easy to separate and utilize the beryllium element. In addition, due to the high beryllium content and the small difference in beryllium between the slag phase and the liquid phase, the effect of fixing the beryllium element was poor even after acid supplementation treatment. Therefore, it was not easy to repeat the acid leaching treatment, resulting in a waste of resources.

[0073] According to Examples 1 to 3 and Comparative Example 1, the method provided in the present application can effectively increase the leaching amount of toxic metal elements, fully detoxify the lithium ore smelting slag, and at the same time concentrate the leaching solution, so that the lithium ore smelting slag and the toxic metal elements therein are easier to utilize as resources, and realize the reuse of inorganic acid solution, which can effectively save costs.

[0074] According to Examples 1 to 3, the nanofiltration process-enhanced lithium ore smelting slag elution process adds hydrochloric acid during separation to keep the solid-liquid ratio of the leaching process unchanged. Under the same time, the elution rate of toxic components can be increased, so that the detoxification effect of lithium ore smelting slag is better.

[0075] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the principles of the present application should be included in the protection scope of the present application.

Claims

1. A detoxification method for lithium ore smelting slag based on nanofiltration treatment, characterized in that: The following steps are involved: Step S1: using an inorganic acid solution to acid-leach the lithium ore smelting slag, so that the acid-soluble components in the lithium ore smelting slag are dissolved in the inorganic acid solution to obtain an acid leaching solution and detoxified smelting slag; Step S2: subjecting the acid leaching solution to oxidation treatment to oxidize the intermediate-valent metal ions in the acid leaching solution into high-valent metal ions to obtain an oxidized acid leaching solution; Step S3: performing nanofiltration treatment on the oxidizing acid leaching solution to intercept high-valent metal ions in the oxidizing acid leaching solution to obtain a concentrated solution and a permeate; Step S4: using the permeate as the inorganic acid solution in step S1 for acid leaching treatment.

2. The detoxification method according to claim 1, characterized in that: In step S1, at least one of the following conditions is met: 1) The inorganic acid solution includes at least one of hydrochloric acid, sulfuric acid aqueous solution or nitric acid aqueous solution; 2) The concentration of the inorganic acid solution is 1-5 mol / L; 3) The lithium ore in the lithium ore smelting slag includes at least one of spodumene, lepidolite, pyroxenite or petalite; 4) The lithium ore smelting slag is a particle size of 30-100 mesh.

3. The detoxification method according to claim 1, characterized in that: The acid leaching treatment conditions include: the mass ratio of the lithium ore smelting slag to the inorganic acid solution is 1:1-20; the acid leaching temperature is 15-100°C; the acid leaching method is one of intermittent leaching and continuous percolation; The acid leaching treatment satisfies one of the following conditions: 1) The leaching time of the intermittent leaching is 0.5 to 3 hours; 2) The continuous percolation leaching time is 0.5 to 2 hours.

4. The detoxification method according to claim 1, characterized in that: In the step S2, the oxidation treatment includes: oxidizing the pickling solution using an oxidant, and the oxidant includes at least one of air, oxygen, ozone, hypochlorous acid or hydrogen peroxide.

5. The detoxification method according to claim 1, characterized in that: In the step S3, before the nanofiltration treatment, the oxidizing acid leaching solution is subjected to microfiltration treatment to remove insoluble solids in the oxidizing acid leaching solution, and then the nanofiltration treatment is performed.

6. The detoxification method according to claim 1, wherein: In step S3, the conditions of the nanofiltration treatment include: allowing the oxidizing acid leaching solution to pass through the nanofiltration membrane at a pressure of 0.5-3 MPa at a temperature of 15-40° C., and a water production rate of 70%-95% for the nanofiltration treatment.

7. The detoxification method according to claim 1, characterized in that: The step S4 comprises: Inorganic acid is added to the permeate to make the concentration of the inorganic acid in the permeate to be 1-5 mol / L, and then used as the inorganic acid solution in step S1 for acid leaching treatment.

8. A detoxification system for lithium ore smelting slag based on nanofiltration treatment, characterized in that: include: Acid leaching unit, used for acid leaching of lithium ore smelting slag; An oxidation unit connected to the acid leaching unit, used to oxidize metal ions in the acid leaching solution from the acid leaching unit into high-valent metal ions; The nanofiltration unit connected to the acid leaching unit is used to intercept and separate high-valent metal ions in the oxidized acid leaching liquid from the acid leaching unit; the nanofiltration unit is connected to the acid leaching unit and is used to transfer the permeate from the nanofiltration unit to the acid leaching unit.

9. The detoxification system according to claim 8, characterized in that: A microfiltration unit is included between the oxidation unit and the nanofiltration unit for removing insoluble solids in the oxidation acid leaching liquid from the acid leaching unit.

10. The detoxification system according to claim 8, characterized in that: An acid supplement unit is included between the nanofiltration unit and the acid leaching unit, which is used to increase the concentration of inorganic acid in the permeate from the nanofiltration unit.

11. The detoxification system according to claim 9, characterized in that: The detoxification system satisfies at least one of the following conditions: 1) The microfiltration unit includes at least one of a centrifuge, a microfiltration device or a plate and frame filter; 2) The nanofiltration unit includes at least one of a spiral membrane separator, a tubular membrane separator or a hollow fiber membrane separator; 3) The nanofiltration unit comprises a nanofiltration membrane, and the molecular weight cutoff of the nanofiltration membrane is 200-400; 4) The nanofiltration unit includes a nanofiltration membrane, and the nanofiltration membrane is an inorganic nanofiltration membrane and / or an organic nanofiltration membrane; 5) The nanofiltration unit comprises a nanofiltration membrane, and the material of the nanofiltration membrane comprises at least one of cellulose, cellulose acetate, sulfonated polysulfone, polyamide, polyimide, polyether sulfone, sulfonated polyether sulfone, polypiperazine or polyvinyl alcohol.

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