Method for separating iron, aluminum, rare earth and lithium in coal gangue hydrochloric acid leaching solution

Abstract

The invention discloses a method for separating iron, aluminum, rare earth and lithium in coal gangue hydrochloric acid leaching liquid, and belongs to the technical field of solid waste recycling. Carrying out oxidation treatment on the diluted coal gangue hydrochloric acid leaching; adding a complexing agent into the oxidized coal gangue hydrochloric acid leaching solution to obtain a first treatment solution; adjusting the pH value of the first treatment liquid system by using an alkaline precipitator, and reacting for a certain time to obtain a second treatment liquid; aging the second treatment liquid to obtain a supernatant and an iron-containing precipitate; separating liquid of the supernate sequentially passes through a microfiltration membrane and nanofiltration, and the ion content is measured. The method can be realized under the condition of room temperature, is simpler to operate, lower in energy consumption and lower in cost, solves the problems of complicated process, strict conditions, high cost and serious pollution in the prior art, fills the technical blank of a membrane separation technology in a coal gangue separation technology, and provides a new thought for separation of iron, aluminum, rare earth and lithium in an acidic complex system.

Description

Technical Field

[0001] This invention belongs to the field of solid waste resource utilization technology, specifically relating to a synergistic separation method of complexation precipitation-membrane separation of iron, aluminum, rare earth and lithium in hydrochloric acid leachate of coal gangue. Background Technology

[0002] Coal gangue is currently the industrial waste with the largest accumulation and annual production in my country, occupying the most dumping sites. It not only pollutes the atmosphere and ecological environment but also threatens human health, posing a risk of water and soil pollution, thus placing enormous pressure on the environment. Therefore, the comprehensive utilization of coal gangue is of great significance for its resource utilization and environmental protection. In terms of composition, coal gangue mainly consists of minerals such as kaolinite, illite, diaspore, and calcium carbonate, as well as a small amount of organic matter. It not only contains abundant elements such as Al, Si, and Fe but also enriches in various strategic metal elements such as Ga, REY, and Li, possessing good comprehensive utilization value. However, in the process of extracting strategic metal elements and other useful components from coal gangue and realizing high-value-added utilization, multiple metal ions coexist. How to effectively separate these elements has always been a research challenge in this field.

[0003] Currently, the main methods for the synergistic separation of iron, aluminum, rare earth elements, and lithium in coal gangue include precipitation, solvent extraction, ion exchange, adsorption, and membrane separation. The team led by Cheng Fangqin at Shanxi University has published invention patents (CN115418478B) on a method for the synergistic extraction of aluminum, iron, lithium, and gallium from an acidic system of high-alumina solid waste, and (CN107109523B) on a method for the selective separation of iron and aluminum. In this method, Cyphos IL101 and Aliquat 336 are used as both extractants and solvents to separate iron and aluminum in coal gangue leachate. While extraction methods offer advantages such as high selectivity and ease of industrial application, they also have significant limitations. The use of large amounts of extractants pollutes the environment and fails to meet the requirements of green production. Precipitation is a traditional separation method. For example, the team led by Zhai Yuchun at Northeastern University disclosed an invention patent (CN102424391B) for a method that comprehensively utilizes aluminum-containing materials, using the pyrite and goethite methods to prepare alumina and other products from aluminum-containing materials such as bauxite and coal gangue. However, given the similar ionic radii in coal gangue leachate, conventional precipitation methods suffer from poor selectivity, significant metal ion loss, and low product purity, making it difficult to simultaneously achieve efficient separation of multiple ions such as iron, aluminum, rare earth elements, and lithium. In addition, ion exchange and adsorption methods are also widely used in the synergistic separation of valuable elements in coal gangue. Shenhua Company disclosed an invention patent (CN115976324B) for a method to extract an aluminum-gallium-lithium system from coal gangue, using ion exchange resin to separate iron, aluminum, lithium, and gallium from coal gangue. While this method can achieve the separation of some elements, the process is relatively complex, and the separation effect on rare earth elements has not been fully optimized.

[0004] In addition, in recent years, membrane separation has received widespread attention due to its advantages such as high separation efficiency, low energy consumption, simple operation, and high equipment integration, and has already been applied in the field of lithium extraction from salt lakes. However, the separation technology for iron, aluminum, rare earth elements, and lithium in coal gangue is still a technological gap. Utilizing membrane separation technology to synergistically achieve the separation and concentration of iron, aluminum, rare earth elements, and lithium in coal gangue will be an important development direction in the future extraction and separation of iron, aluminum, rare earth elements, and lithium from coal gangue.

[0005] In summary, to address the problems of cumbersome processes, strict conditions, high costs, and severe pollution associated with existing methods, which fail to achieve the synergistic separation of iron, aluminum, rare earth elements, and lithium, and to fill the technological gap in membrane separation technology for coal gangue, a new, green, and efficient method for separating iron, aluminum, rare earth elements, and lithium from coal gangue leachate is urgently needed to realize the high-value-added comprehensive utilization of coal gangue. Summary of the Invention

[0006] The main objective of this invention is to provide a complexation-precipitation-membrane separation method for iron, aluminum, rare earth elements, and lithium in hydrochloric acid leachate of coal gangue. This method aims to solve the problems of cumbersome processes, strict conditions, high costs, and serious pollution associated with existing methods. At the same time, it fills the technological gap in membrane separation technology for coal gangue. Through a green and simple technical solution, it achieves efficient and synergistic separation of iron, aluminum, rare earth elements, and lithium ions, taking into account both environmental protection and industrial applicability. It also provides a new approach for the separation of iron, aluminum, rare earth elements, and lithium in acidic and complex systems.

[0007] Based on the first main aspect of the present invention, a method for separating iron, aluminum, rare earth elements and lithium from hydrochloric acid leachate of coal gangue is provided, comprising the following steps:

[0008] The solution to be treated is diluted. The solution contains iron ions, aluminum ions, rare earth elements and lithium ions, and the initial pH is not greater than 2.

[0009] The diluted solution to be treated was oxidized, and a complexing agent was added to the oxidized solution to obtain the first treatment solution.

[0010] The pH of the first treatment solution system was adjusted with an alkaline precipitant, and the reaction was carried out at room temperature for 0-120 min to obtain the second treatment solution.

[0011] The second treatment solution is aged at room temperature to obtain a supernatant and a precipitate, which is the third treatment solution.

[0012] After the aging process is completed, the third treatment liquid is subjected to solid-liquid separation to obtain the separated liquid of the supernatant and the separated precipitate.

[0013] The supernatant is passed sequentially through a microfiltration membrane and a nanofiltration membrane to obtain a permeate and a concentrate. The ion content in the permeate is then measured.

[0014] In the above experimental steps, for the solution to be treated with a pH not greater than 2, the ion concentration is controlled by dilution to avoid high concentration of ions interfering with subsequent reactions, and then oxidation treatment is used to convert low-valence iron ions into high-valence states that are easier to complex and precipitate.

[0015] By leveraging the directional binding ability of complexing agents to iron ions, the risk of co-precipitation between ions is reduced. Subsequently, an alkaline precipitant is used to adjust the pH to a suitable range for ion hydrolysis precipitation. Then, through room temperature aging, the small precipitate is dissolved and the large particles are densely grown using the principle of dissolution and recrystallization. Solid-liquid separation is completed by vacuum filtration, and finally, lithium is separated through a membrane separation process, thus constructing a mild and orderly separation process.

[0016] The entire process was operated at room temperature, simplifying the process steps and reducing energy consumption. The aging process effectively improved the particle density and purity of the iron-containing precipitate, reduced impurity adsorption, lowered the difficulty of subsequent filtration and washing operations, and also improved the quality of the separated products.

[0017] Through the synergistic effect of the complete steps, the complexation-precipitation-membrane separation of iron, aluminum, rare earth and lithium in hydrochloric acid leachate of coal gangue was achieved, taking into account both the convenience of the separation process and the stability of the separation effect.

[0018] As a further preferred embodiment, in the aforementioned method, the liquid to be treated is a coal gangue hydrochloric acid leachate;

[0019] The dilution process specifically includes: diluting with pure water at a dilution ratio of 0 to 2.

[0020] Pure water is used as the dilution medium to avoid introducing additional impurities that could interfere with subsequent oxidation, complexation, and aging reactions. At the same time, the dilution ratio is limited to 0-2 to avoid excessive dilution that could lead to too low an ion concentration and affect reaction efficiency. It also prevents co-precipitation caused by excessively high ion concentration in undiluted liquid, ensuring that the ion concentration of the liquid to be treated is within a reasonable range suitable for subsequent separation steps.

[0021] As a further preferred embodiment, in the aforementioned method, the concentration of iron ions in the liquid to be treated is 3~10 g / L, the concentration of aluminum ions is 10~30 g / L, and the concentration of lithium ions and rare earth elements is 0.05~0.3 g / L.

[0022] The scheme specifically defines the concentration of iron ions in the solution to be treated as 3~10 g / L, the concentration of aluminum ions as 10~30 g / L, and the concentration of lithium ions and rare earth elements as 0.05~0.3 g / L. This concentration range is an appropriate range determined based on the oxidation capacity of the subsequent oxidation treatment, the binding capacity of the complexing agent, and the precipitation capacity of the alkaline precipitant.

[0023] This range effectively avoids incomplete reactions due to excessively high ion concentrations, while also preventing inefficient reactions due to excessively low ion concentrations. This allows subsequent oxidation, complexation, and precipitation steps to function optimally at the appropriate ion concentration.

[0024] As a further preferred embodiment, in the aforementioned method, the oxidation treatment specifically includes: using hydrogen peroxide to perform the oxidation treatment, wherein the volume ratio of the hydrogen peroxide to the diluted liquid to be treated is 0~0.1.

[0025] Because hydrogen peroxide is used as the oxidant, its mild oxidizing properties are utilized to convert low-valence iron ions in the solution to be treated into high-valence iron ions.

[0026] Meanwhile, the product of the hydrogen peroxide reaction is water, which, due to its cleansing properties, does not introduce any additional impurities, thus improving the purity of the separated products. Controlling the volume ratio balances oxidation efficiency and reaction system purity, ensuring the smooth progress of subsequent separation steps.

[0027] As a further preferred embodiment, in the aforementioned method, the complexing agent is either disodium ethylenediaminetetraacetate or diethylenetriaminepentaacetic acid;

[0028] The ratio of the complexing agent to the iron content in the liquid to be treated is 0 to 3.

[0029] By selecting complexing agents such as disodium ethylenediaminetetraacetate and diethylenetriaminepentaacetic acid, and taking advantage of their high selectivity, while controlling the contrast value, the selectivity of ion separation is improved, the complexation effect is guaranteed, reagent waste is avoided, cost control of the separation process is taken into account, and excessive complexing agent adsorption of other ions is prevented from affecting the separation selectivity.

[0030] As a further preferred embodiment, in the aforementioned method, the alkaline precipitant includes one or more of ammonia, sodium hydroxide solution, and magnesium oxide.

[0031] Ammonia, sodium hydroxide solution, and magnesium oxide were selected as alkaline precipitants. Ammonia and sodium hydroxide solution can gently adjust the pH of the system by ionizing hydroxide ions, and the introduced ammonium and sodium ions are easy to handle in subsequent separation steps.

[0032] Magnesium oxide, on the other hand, slowly releases hydroxide ions through its reaction with acids, thus achieving a gradual regulation of pH.

[0033] The above-mentioned precipitants can promote the hydrolysis and precipitation of iron ions while reducing the impact on aluminum ions. Furthermore, the introduced components are easy to handle or leave no residue, reducing additional interference to the system and avoiding the introduction of impurities that are difficult to remove.

[0034] As a further preferred embodiment, in the aforementioned method, the sodium hydroxide concentration is 20% by mass, the ammonia concentration is a 1:1 volume aqueous solution, and the magnesium oxide is analytical grade magnesium oxide powder.

[0035] In this invention, the concentration of sodium hydroxide is 20% by mass, the concentration of ammonia is a 1:1 volume aqueous solution, and the magnesium oxide is analytical grade magnesium oxide powder. The fixed concentration of alkaline solution can stabilize the release rate of hydroxide ions, and the analytical grade magnesium oxide avoids the introduction of impurities.

[0036] By standardizing the parameters of the precipitant, the controllability of the pH adjustment process can be improved.

[0037] As a further preferred embodiment, in the aforementioned method, adjusting the pH value of the first treatment liquid system specifically includes:

[0038] During continuous stirring, the alkaline precipitant is mixed into the liquid to be treated, and the pH of the liquid to be treated is controlled to be 1.75~3.25 by the alkaline precipitant.

[0039] By adding an alkaline precipitant during continuous stirring, the abrupt pH change caused by excessively high hydroxide ion concentrations in local areas is avoided. Precise pH range control allows iron ions to precipitate fully while preserving the solubility of other ions to the greatest extent.

[0040] As a further preferred embodiment, in the aforementioned method, the aging process specifically includes:

[0041] The aging time is 0~72h, the aging conditions are room temperature, and the specific operation is: let it stand and settle naturally.

[0042] The specific method for solid-liquid separation is vacuum filtration.

[0043] By allowing the second treatment solution to stand for 0-72 hours at room temperature, the principle of dissolution-recrystallization is utilized to allow the small iron-containing precipitates to gradually dissolve due to their high solubility. The dissolved iron ions then recrystallize on the surface of the large precipitate particles, making the precipitate particles more compact and reducing the adsorption of other ions by the precipitate.

[0044] Solid-liquid separation is achieved by vacuum filtration, which accelerates the permeation rate of the filtrate by using negative pressure, shortens the overall process time, reduces the loss of iron-containing precipitates during the separation process, and ensures the efficiency of iron separation.

[0045] Based on a second key aspect of the present invention, an application of a method for separating iron, aluminum, rare earth elements and lithium in hydrochloric acid leachate of coal gangue is provided, wherein the application is to separate iron, aluminum, rare earth elements and lithium in an acidic complex system.

[0046] The initial pH of the acidic complex system It is an acidic liquid system containing one or more of the following ions: iron, aluminum, rare earth elements, and lithium, as well as at least one other target ion.

[0047] When applied, the complete steps of the separation method for iron, aluminum, rare earth elements and lithium in the hydrochloric acid leachate of coal gangue are followed, including dilution, oxidation, complexation, pH adjustment, room temperature reaction, aging, vacuum filtration and membrane separation.

[0048] By controlling the dilution ratio of pure water to 0-2, the volume ratio of hydrogen peroxide to the diluted solution to be treated to 0-0.1, the ratio of complexing agent to iron content in the solution to be treated to 0-3, and adjusting the pH of the system to 1.75-3.25, the separation of iron, aluminum, rare earth elements and lithium in an acidic complex system is achieved, while the target ions in the system are stably retained.

[0049] Compared with existing technologies, this invention has the advantages of simple process and low energy consumption. It does not require strict reaction conditions and can complete the separation process of iron, aluminum, rare earth and lithium at room temperature. The operation steps are clear and simple, which effectively overcomes the disadvantages of traditional precipitation process, strict control of reaction conditions and high energy consumption and acid consumption of existing technologies, and reduces the cost of industrial application.

[0050] Secondly, this invention achieves rapid and excellent separation of iron ions. By oxidizing ferrous ions to a higher valence state with an oxidant, and combining the targeted binding effect of a complexing agent with iron ions in the hydrochloric acid system, along with the chemical reaction of an alkaline precipitant, efficient and directional separation of iron ions is achieved. This effectively solves the problem of low selectivity caused by co-precipitation between ions with similar radii in traditional methods, thus improving the separation accuracy.

[0051] Furthermore, this invention optimizes precipitation performance through subsequent aging treatment. During the aging process, the precipitated particles dissolve and larger particles grow further, forming a dense precipitate product. This facilitates subsequent filtration and washing operations, reduces impurity adsorption, effectively improves precipitation purity, and overcomes the shortcomings of traditional conventional precipitation methods, such as loose precipitate particles, high separation difficulty, and low product purity.

[0052] Finally, this invention combines outstanding environmental benefits with industrial practical value. The entire separation process does not require the use of large amounts of polluting extractants, nor does it generate large amounts of hazardous waste iron and vanadium slag, thus avoiding secondary environmental pollution and conforming to the concept of green production. At the same time, the raw materials are readily available and the cost is controllable. Through membrane separation technology, it achieves the synergistic separation of iron, aluminum, rare earth, and lithium through complexation-precipitation-membrane separation, providing an efficient solution for the comprehensive utilization of coal gangue and a new approach for the efficient separation of multiple ions such as iron, aluminum, rare earth, and lithium in acidic complex systems. Attached Figure Description

[0053] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, obtaining other drawings based on these drawings without creative effort still falls within the scope of the present invention.

[0054] Figure 1A flowchart of a method for separating iron, aluminum, rare earth elements and lithium from hydrochloric acid leachate of coal gangue is shown in one embodiment of the present invention.

[0055] Figure 2 The diagram illustrates the iron and aluminum separation efficiency at different dilution ratios in a method for separating iron and aluminum in hydrochloric acid leachate of coal gangue according to an embodiment of the present invention.

[0056] Figure 3 The diagram illustrates the iron and aluminum separation efficiency corresponding to different hydrogen peroxide addition amounts in a method for separating iron, aluminum, rare earth elements, and lithium in a coal gangue hydrochloric acid leachate according to an embodiment of the present invention.

[0057] Figure 4 The diagram illustrates the iron and aluminum separation efficiency corresponding to different amounts of disodium ethylenediaminetetraacetate added in a method for separating iron, aluminum, rare earth elements, and lithium in a hydrochloric acid leachate of coal gangue according to an embodiment of the present invention.

[0058] Figure 5 The diagram illustrates the iron and aluminum separation efficiency of different alkaline precipitants in a method for separating iron, aluminum, rare earth elements, and lithium in a hydrochloric acid leachate of coal gangue according to an embodiment of the present invention.

[0059] Figure 6 The diagram illustrates the iron and aluminum separation efficiency at different pH values ​​corresponding to a method for separating iron, aluminum, rare earth elements, and lithium in a coal gangue hydrochloric acid leachate according to an embodiment of the present invention.

[0060] Figure 7 The diagram illustrates the iron and aluminum separation efficiency at different reaction times in a method for separating iron, aluminum, rare earth elements, and lithium from a coal gangue hydrochloric acid leachate according to an embodiment of the present invention.

[0061] Figure 8 The diagram illustrates the iron and aluminum separation efficiency at different aging times for a method for separating iron, aluminum, rare earth elements, and lithium in a coal gangue hydrochloric acid leachate according to an embodiment of the present invention. Detailed Implementation

[0062] The preferred embodiments of the present invention will be described in detail below to provide a clearer understanding of the purpose, features, and advantages of the invention. It should be understood that the following embodiments are not intended to limit the scope of the invention, but are merely illustrative of the essential spirit of the invention's technical solutions.

[0063] In the following description, certain specific details are set forth for the purpose of illustrating various disclosed embodiments in order to provide a thorough understanding of the various disclosed embodiments. However, those skilled in the art will recognize that the embodiments may be practiced without one or more of these specific details. In other instances, well-known techniques associated with the invention may not have been shown or described in detail to avoid unnecessarily obscuring the description of the embodiments.

[0064] Throughout this specification, references to "an embodiment" or "an embodiment" indicate that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment. Therefore, the appearance of "in an embodiment" or "an embodiment" in various places throughout the specification does not necessarily refer to the same embodiment. Furthermore, a particular feature, structure, or characteristic may be combined in any manner in one or more embodiments.

[0065] like Figure 1 As shown, in a feasible embodiment, a method for separating iron, aluminum, rare earth elements, and lithium from a coal gangue hydrochloric acid leachate specifically includes the following steps S110-S160:

[0066] S110, take a certain coal gangue hydrochloric acid leachate and dilute it, wherein the initial pH of the coal gangue hydrochloric acid leachate is not greater than 2;

[0067] S120, diluted coal gangue is leached with hydrochloric acid for oxidation treatment, and a complexing agent is added to the oxidation treatment solution to obtain the first treatment solution;

[0068] S130, adjust the pH value of the first treatment solution system with an alkaline precipitant, react at room temperature for 0~120 min to obtain the second treatment solution;

[0069] S140, the second treatment solution is aged at room temperature to obtain a supernatant and an iron-containing precipitate, which is the third treatment solution;

[0070] S150, after the aging process is completed, the third treatment liquid is subjected to solid-liquid separation to obtain the separated liquid of the supernatant and the separated precipitate.

[0071] S160, the supernatant is separated by membrane separation, passing through a microfiltration membrane and a nanofiltration membrane in sequence, and the ion content in the permeate is measured.

[0072] This invention utilizes methods such as adding oxidants, complexing agents, alkaline precipitants, and aging to efficiently separate iron, aluminum, rare earth elements, and lithium.

[0073] Specifically, the present invention adds an oxidant, a complexing agent, and an alkaline precipitant to the hydrochloric acid leachate of coal gangue to adjust it to a suitable pH range, and then ages the treated solution after adding the precipitant, and obtains the separated solution and precipitate after solid-liquid separation.

[0074] The following are specific embodiments of the present invention:

[0075] Example 1

[0076] (1) Take 500 mL of hydrochloric acid leachate from a certain coal gangue. The concentrations of iron ions and aluminum ions are 6 g / L and 26 g / L, respectively. The concentrations of lithium and rare earth are 0.2 g / L, and the pH is <1.

[0077] (2) At room temperature, add pure water to the hydrochloric acid leachate of coal gangue to dilute it by a ratio of 1:1.

[0078] (3) Add 100 mL of hydrogen peroxide and 3 g of disodium ethylenediaminetetraacetate to the diluent to obtain the first treatment solution.

[0079] (4) During continuous stirring, the pH of the first treatment solution system was adjusted to 2.30 with 20% sodium hydroxide solution, and the reaction was carried out at room temperature for 30 min to obtain the third treatment solution.

[0080] (5) The third treatment liquid is aged at room temperature for 24 hours by standing, so that the third treatment liquid is separated into supernatant and iron and aluminum precipitate.

[0081] (6) After the aging process is completed, the third treatment liquid is subjected to solid-liquid separation to obtain the separated liquid of the supernatant and the separated precipitate.

[0082] (7) The contents of iron, aluminum, lithium and rare earth in the separation liquid were determined, and the recovery rate of iron in the separation liquid was calculated to be 11.36%, the recovery rate of aluminum was 98.64%, the recovery rate of lithium was 98.31% and the recovery rate of rare earth was 99.33%.

[0083] (8) The supernatant is passed through a microfiltration membrane and a nanofiltration membrane in sequence. The membrane separator pressure is 3.00 MPa. The contents of iron, aluminum, lithium and rare earth in the permeate are measured respectively. The recovery rate of lithium in the permeate is calculated to be 76.87%, the recovery rate of rare earth is 0.83%, the recovery rate of aluminum is 0.59% and the recovery rate of iron is 0.86%.

[0084] Example 2

[0085] (1) Take 500 mL of hydrochloric acid leachate from a certain coal gangue (same as in Example 1).

[0086] (2) At room temperature, add pure water to the hydrochloric acid leachate of coal gangue to dilute it by a ratio of 1:1.

[0087] (3) Add 150 mL of hydrogen peroxide and 3.2 g of disodium ethylenediaminetetraacetate to the diluent to obtain the first treatment solution.

[0088] (4) During continuous stirring, the pH of the first treatment solution system was adjusted to 2.25 with 20% sodium hydroxide solution, and the reaction was carried out at room temperature for 30 min to obtain the third treatment solution.

[0089] (5) The third treatment liquid is aged at room temperature for 24 hours by standing, so that the third treatment liquid is separated into supernatant and iron and aluminum precipitate.

[0090] (6) After the aging process is completed, the third treatment liquid is subjected to solid-liquid separation to obtain the separated liquid of the supernatant and the separated precipitate.

[0091] (7) The contents of iron, aluminum, lithium and rare earth in the separation liquid were determined, and the recovery rate of iron in the separation liquid was calculated to be 13.86%, the recovery rate of aluminum was 99.12%, the recovery rate of lithium was 98.54%, and the recovery rate of rare earth was 99.67%.

[0092] (8) The supernatant is passed through a microfiltration membrane and a nanofiltration membrane in sequence. The membrane separator pressure is 3.00 MPa. The contents of iron, aluminum, lithium and rare earth in the permeate are measured respectively. The recovery rate of lithium in the permeate is calculated to be 75.98%, the recovery rate of rare earth is 0.69%, the recovery rate of aluminum is 0.61% and the recovery rate of iron is 0.89%.

[0093] Example 3

[0094] (1) Take 500 mL of hydrochloric acid leachate from a certain coal gangue (same as in Example 1).

[0095] (2) At room temperature, add pure water to the hydrochloric acid leachate of coal gangue to dilute it by a ratio of 1:1.

[0096] (3) Add 100 mL of hydrogen peroxide and 3 g of disodium ethylenediaminetetraacetate to the diluent to obtain the first treatment solution.

[0097] (4) During continuous stirring, the pH of the first treatment solution system was adjusted to 2.25 with 20% sodium hydroxide solution, and the reaction was carried out at room temperature for 15 minutes to obtain the third treatment solution.

[0098] (5) The third treatment liquid is aged at room temperature for 24 hours by standing, so that the third treatment liquid is separated into supernatant and iron and aluminum precipitate.

[0099] (6) After the aging process is completed, the third treatment liquid is subjected to solid-liquid separation to obtain the separated liquid of the supernatant and the separated precipitate.

[0100] (7) The contents of iron, aluminum, lithium and rare earth in the separation liquid were determined, and the recovery rate of iron in the separation liquid was calculated to be 14.74%, the recovery rate of aluminum was 97.33%, the recovery rate of lithium was 99.66%, and the recovery rate of rare earth was 98.75%.

[0101] (8) The supernatant is passed through a microfiltration membrane and a nanofiltration membrane in sequence. The membrane separator pressure is 3.00 MPa. The contents of iron, aluminum, lithium and rare earth in the permeate are measured respectively. The recovery rate of lithium in the permeate is calculated to be 78.84%, the recovery rate of rare earth is 0.75%, the recovery rate of aluminum is 0.53% and the recovery rate of iron is 0.63%.

[0102] Example 4

[0103] (1) Take 500 mL of hydrochloric acid leachate from a certain coal gangue (same as in Example 1).

[0104] (2) At room temperature, add pure water to the hydrochloric acid leachate of coal gangue to dilute it by a ratio of 1:1.

[0105] (3) Add 100 mL of hydrogen peroxide and 3 g of disodium ethylenediaminetetraacetate to the diluent to obtain the first treatment solution.

[0106] (4) During continuous stirring, the pH of the first treatment solution system was adjusted to 2.25 with 20% sodium hydroxide solution, and the reaction was carried out at room temperature for 15 minutes to obtain the third treatment solution.

[0107] (5) The third treatment liquid is aged at room temperature for 3 hours by standing, so that the third treatment liquid is separated into supernatant and iron and aluminum precipitate.

[0108] (6) After the aging process is completed, the third treatment liquid is subjected to solid-liquid separation to obtain the separated liquid of the supernatant and the separated precipitate.

[0109] (7) The contents of iron, aluminum, lithium and rare earth in the separation liquid were determined, and the recovery rate of iron in the separation liquid was calculated to be 27.16%, the recovery rate of aluminum was 92.28%, the recovery rate of lithium was 98.93% and the recovery rate of rare earth was 99.01%.

[0110] (8) The supernatant is passed through a microfiltration membrane and a nanofiltration membrane in sequence. The membrane separator pressure is 3.00 MPa. The contents of iron, aluminum, lithium and rare earth in the permeate are measured respectively. The recovery rate of lithium in the permeate is calculated to be 75.21%, the recovery rate of rare earth is 0.74%, the recovery rate of aluminum is 0.65% and the recovery rate of iron is 0.87%.

[0111] Example 5

[0112] (1) Take 500 mL of hydrochloric acid leachate from a certain coal gangue (same as in Example 1).

[0113] (2) At room temperature, add pure water to the hydrochloric acid leachate of coal gangue to dilute it by a ratio of 1:1.

[0114] (3) Add 100 mL of hydrogen peroxide and 3 g of diethylenetriaminepentaacetic acid to the diluent to obtain the first treatment solution.

[0115] (4) During continuous stirring, the pH of the first treatment solution system was adjusted to 2.55 with 20% sodium hydroxide solution, and the reaction was carried out at room temperature for 30 min to obtain the third treatment solution.

[0116] (5) The third treatment liquid is aged at room temperature for 12 hours by standing, so that the third treatment liquid is separated into supernatant and iron and aluminum precipitate.

[0117] (6) After the aging process is completed, the third treatment liquid is subjected to solid-liquid separation to obtain the separated liquid of the supernatant and the separated precipitate.

[0118] (7) The contents of iron, aluminum, lithium and rare earth in the separation liquid were determined, and the recovery rate of iron in the separation liquid was calculated to be 24.37%, the recovery rate of aluminum was 99.25%, the recovery rate of lithium was 99.71% and the recovery rate of rare earth was 98.54%.

[0119] (8) The supernatant is passed through a microfiltration membrane and a nanofiltration membrane in sequence. The membrane separator pressure is 3.00 MPa. The contents of iron, aluminum, lithium and rare earth in the permeate are measured respectively. The recovery rate of lithium in the permeate is calculated to be 74.78%, the recovery rate of rare earth is 0.77%, the recovery rate of aluminum is 0.46% and the recovery rate of iron is 0.58%.

[0120] Example 6

[0121] (1) Take 500 mL of hydrochloric acid leachate from a certain coal gangue. The concentrations of iron ions and aluminum ions are 6 g / L and 26 g / L, respectively. The concentrations of lithium and rare earth are 0.2 g / L, and the pH is <1.

[0122] (2) At room temperature, add pure water to the hydrochloric acid leachate of coal gangue to dilute it by a ratio of 1:1.

[0123] (3) Add 100 mL of hydrogen peroxide and 3 g of disodium ethylenediaminetetraacetate to the diluent to obtain the first treatment solution.

[0124] (4) During continuous stirring, the pH of the first treatment solution system was adjusted to 2.30 with 20% sodium hydroxide solution, and the reaction was carried out at room temperature for 30 min to obtain the third treatment solution.

[0125] (5) The third treatment liquid is aged at room temperature for 24 hours by standing, so that the third treatment liquid is separated into supernatant and iron and aluminum precipitate.

[0126] (6) After the aging process is completed, the third treatment liquid is subjected to solid-liquid separation to obtain the separated liquid of the supernatant and the separated precipitate.

[0127] (7) The contents of iron, aluminum, lithium and rare earth in the separation liquid were determined, and the recovery rate of iron in the separation liquid was calculated to be 12.35%, the recovery rate of aluminum was 99.66%, the recovery rate of lithium was 97.31% and the recovery rate of rare earth was 99.12%.

[0128] (8) The supernatant is passed through a microfiltration membrane and a nanofiltration membrane in sequence. The membrane separator pressure is 2.50 MPa. The contents of iron, aluminum, lithium and rare earth in the permeate are measured respectively. The recovery rate of lithium in the permeate is calculated to be 68.12%, the recovery rate of rare earth is 1.12%, the recovery rate of aluminum is 0.80% and the recovery rate of iron is 1.19%.

[0129] As one possible implementation, the following examples illustrate the results of different reaction conditions in a method for separating iron, aluminum, rare earth elements, and lithium from a coal gangue hydrochloric acid leachate, mainly focusing on the recovery efficiency of iron and aluminum ions:

[0130] Combination Figures 2 to 8 As shown, this invention explores seven key parameters through a series of experiments: dilution ratio, different amounts of hydrogen peroxide, different amounts of disodium ethylenediaminetetraacetate, different alkaline precipitants, different pH values ​​of the system, different reaction times, and different aging times, revealing the differences in ion recovery efficiency between the two types of ions.

[0131] At different dilution ratios, the aluminum recovery rate remained at a high level without significant fluctuations, indicating that the aluminum recovery rate was minimally affected by the dilution ratio.

[0132] The iron recovery efficiency fluctuates significantly with the dilution ratio. The efficiency is approximately 40% when the dilution ratio is undiluted, 4:1, and 2:1. When the dilution ratio is 1:1, it drops to 20%, and when the dilution ratio is 1:2, it rises to approximately 80%, indicating that the dilution ratio has an impact on iron separation.

[0133] Under different hydrogen peroxide addition conditions, the aluminum recovery efficiency remained at a high level close to 100%, without significant fluctuations as the amount of hydrogen peroxide added increased. This indicates that the aluminum recovery effect is stable and efficient, and is basically unaffected by different amounts of hydrogen peroxide added.

[0134] Iron recovery efficiency decreases with increasing amounts of hydrogen peroxide, and then stabilizes after reaching a certain level.

[0135] This indicates that different amounts of hydrogen peroxide added are key factors in regulating iron recovery efficiency.

[0136] Under different amounts of disodium ethylenediaminetetraacetate (EDTA), the aluminum recovery efficiency remained stable and efficient, and was basically unaffected by the different amounts of disodium ethylenediaminetetraacetate (EDTA). The iron recovery rate showed a fluctuating trend of first decreasing and then gradually increasing with the increase of different amounts of disodium ethylenediaminetetraacetate (EDTA).

[0137] This indicates that the amount of disodium ethylenediaminetetraacetate added is a key factor in controlling the iron recovery efficiency.

[0138] Under different alkaline precipitant conditions, this invention uses 20% sodium hydroxide, 1:1 ammonia, and magnesium oxide as comparisons. The aluminum recovery efficiency under different alkaline precipitant reactions ranges from approximately 80% to 100%, with minimal fluctuation.

[0139] The iron recovery efficiency varies significantly with different alkaline precipitants. Under the condition of 20% sodium hydroxide, the iron recovery efficiency is about 40%, under the condition of 1:1 ammonia water, the iron recovery efficiency is about 70%, and under the condition of magnesium oxide, the iron recovery efficiency is close to 90%.

[0140] This indicates that magnesium oxide is relatively ineffective as an alkaline precipitant for iron removal, while 20% sodium hydroxide is the most effective alkaline precipitant for iron removal.

[0141] Under different pH conditions, the aluminum recovery efficiency fluctuated slightly but remained at a high level close to 100%, without significant changes as the pH ranged from 1.5 to 3.5. The iron recovery efficiency showed a trend of first decreasing and then gradually increasing with pH changes.

[0142] This indicates that pH value is a key factor in regulating iron recovery efficiency.

[0143] Under different reaction time conditions, the aluminum recovery efficiency remained close to 100% within the reaction time range of 0 to 120 minutes, without significant fluctuations.

[0144] Similarly, the iron recovery efficiency, which started at about 20%, only fluctuated slightly with the increase of reaction time, and remained in a low range overall.

[0145] This indicates that changes in reaction time have no significant impact on the recovery efficiency of aluminum and iron.

[0146] Under different aging time conditions, the aluminum recovery efficiency remained at a high level close to 100% within the aging time range of 0 to 80 hours, without significant fluctuations.

[0147] Iron recovery efficiency decreases with increasing aging time. When the aging time is 0, the iron recovery efficiency is about 40%, and then it decreases rapidly and remains at a low level as the aging time continues.

[0148] This indicates that different aging times are key factors in regulating iron recovery efficiency.

[0149] In summary, these results clarify the stable recovery characteristics of aluminum and the parameter response law of iron. Precise control of iron recovery efficiency can be achieved by directional adjustment of key parameters, while ensuring stable and efficient aluminum recovery.

[0150] The technical terms, principles, or means related to the technical solutions of the present invention mentioned in the above embodiments, which are not described in detail above, are all well-known technologies or common practices that are known to those skilled in the art.

[0151] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for separating iron, aluminum, rare earth and lithium in coal gangue hydrochloric acid leaching solution, characterized in that, The method comprises the following steps: diluting a to-be-treated liquid containing iron ions, aluminum ions, rare earth and lithium ions, and having an initial pH of not more than 2; carrying out oxidation treatment on the diluted to-be-treated liquid, adding a complexing agent to the oxidation treatment liquid to obtain a first treatment liquid; adjusting the pH value of the first treatment liquid system by using an alkaline precipitant, and reacting at room temperature for 0-120 min to obtain a second treatment liquid; carrying out aging treatment on the second treatment liquid at room temperature to obtain supernatant and precipitate, i.e. a third treatment liquid; carrying out solid-liquid separation on the third treatment liquid after the aging treatment to obtain separated supernatant and separated precipitate; sequentially passing the separated supernatant through a microfiltration membrane and a nanofiltration membrane to obtain a permeate, and measuring the ion content in the permeate.

2. The method according to claim 1, wherein the method is characterized by, The to-be-treated liquid is a coal gangue hydrochloric acid leaching liquid. The dilution treatment specifically comprises dilution with pure water at a dilution ratio of 0-2.

3. The method according to claim 1, wherein the method is characterized by, In the to-be-treated liquid, the concentration of iron ions is 3-10 g / L, the concentration of aluminum ions is 10-30 g / L, and the concentration of lithium ions and rare earth is 0.05-0.3 g / L.

4. The method according to claim 1, wherein the method is characterized by, The oxidation treatment specifically comprises using hydrogen peroxide for the oxidation treatment, and the volume ratio of the hydrogen peroxide to the diluted to-be-treated liquid is 0-0.

1.

5. The method according to claim 1, wherein the method is characterized by, The complexing agent is any one of disodium ethylenediaminetetraacetate and diethylenetriamine pentaacetic acid. The ratio of the complexing agent to the iron content in the to-be-treated liquid is 0-3.

6. The method according to claim 1, wherein the method is characterized by, The alkaline precipitant comprises one or more of ammonia water, a sodium hydroxide solution and magnesium oxide.

7. The method according to claim 6, wherein the method is characterized by, The concentration of the sodium hydroxide is 20% by mass, the concentration of the ammonia water is a 1:1 aqueous solution by volume, and the magnesium oxide is an analytical pure magnesium oxide powder.

8. The method according to claim 1 or 5, wherein the method is characterized by, The adjustment of the pH value of the first treatment liquid system specifically comprises: mixing the alkaline precipitant into the to-be-treated liquid in a continuous stirring process, and controlling the pH of the to-be-treated liquid to be 1.75-3.25 by the alkaline precipitant.

9. The method according to claim 1, wherein the method is characterized by, The aging treatment specifically comprises: the aging time is 0-72 h, the aging condition is room temperature, and the specific operation is: standing and natural sedimentation. The specific method of the solid-liquid separation is vacuum filtration.

10. A method for separating iron, aluminum, rare earth and lithium from a coal gangue hydrochloric acid leaching solution according to any one of claims 1-9, characterized in that, The application is the separation of iron, aluminum, rare earth and lithium in an acidic complex system. The acidic complex system has an initial pH and contains iron, aluminum, rare earth, and lithium ions, any one or more of them, and at least one other target ion of the acidic liquid system.

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