Closed-loop dressing and smelting process for coal-series associated rare earth mineral resources based on DESs solvent

Abstract

The invention belongs to the field of rare earth extraction processes, and particularly relates to a closed-loop dressing and smelting process for coal-series associated rare earth mineral resources based on a DESs solvent. Comprising the following steps: taking a sample, carrying out ball milling, adding a leaching agent into the sample after ball milling, leaching the ion adsorption type rare earth elements in the sample, and stirring to obtain a turbid solution; adding a precipitant into the leachate, and then carrying out solid-liquid separation to obtain supernate and precipitates; taking supernate and analyzing the extraction efficiency of the rare earth elements through inductively coupled plasma mass spectrometry (ICP-MS); and adding deionized water into the obtained supernate to recover the leaching agent for next use. The invention aims to obtain a series of deep eutectic solvent (DESs) systems capable of efficiently leaching coal series associated rare earth mineral resources, so that the efficient separation and leaching of ion adsorption type rare earth elements in coal ores are realized; and by utilizing the reversibility of DESs, the recycling of the DESs solvent and the closed-loop dressing and smelting process of coal-series associated rare earth mineral resources are realized.

Description

Technical Field

[0001] This application belongs to the field of rare earth extraction processes, and more specifically, relates to a closed-loop beneficiation and smelting process for coal-associated rare earth mineral resources based on DESs solvents. Background Art

[0002] Rare earth elements include lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, scandium, yttrium, etc. The occurrence and composition of rare earth elements in coal measures are complex. The association of coal and rare earths constitutes a "coal-type rare earth deposit", which is the most promising source of rare earth resources. In addition, coal measures also contain an important new energy strategic resource - lithium. Therefore, studying the beneficiation and smelting technologies for coal-associated lithium and rare earth mineral resources is of great significance for realizing "selective exploitation of rich ores", and is also crucial for understanding their environmental and geological significance.

[0003] Lithium and rare earth mineral resources associated with coal measures mostly exist in finer minerals in the form of isomorphism, ion adsorption, etc. At present, the beneficiation and smelting methods for lithium and rare earth metals are mainly pyrometallurgical beneficiation, hydrometallurgical beneficiation, etc. These two methods have the following problems in aspects such as metal leaching and separation, and solvent recycling:

[0004] (1) The leaching process consumes a large amount of inorganic acids, and at the same time generates a large amount of acidic wastewater and waste gas, causing serious pollution to the environment.

[0005] (2) The problem of waste liquid treatment in the rare earth separation process. During the precipitation separation of lithium or rare earth metal ions, in addition to acidic wastewater, some waste liquids such as organic solvents, carbonates, and hydroxides that can pollute water sources and soil will also be generated. These waste liquids need to be specially treated and disposed of.

[0006] (3) The problem that the leaching solvent cannot be reused. For the separation of lithium or rare earth elements, alkaline or carbonate / sulfate complex salts are usually added as precipitants, and the precipitants will destroy the structure and properties of the leaching solvent, resulting in the leaching agent being unable to be reused. Summary of the Invention

[0007] Aiming at the defects of the prior art, the purpose of this application is to obtain a series of eutectic solvents (DESs) systems that can efficiently leach coal-associated rare earth mineral resources, and utilize the selectivity of DESs for lithium and rare earth elements to achieve the efficient separation and leaching of ion-adsorbed rare earth elements in coal ores; utilize the reversibility of DESs to realize the recycling of DESs solvents and the closed-loop beneficiation and smelting process for coal-associated rare earth mineral resources.

[0008] To achieve the above purpose, this application provides a closed-loop beneficiation and smelting process for coal-associated rare earth mineral resources based on DESs solvents, including the following steps:

[0009] S1. Take the samples collected from the coal mining area, conduct ball milling, then add a leaching agent to the milled samples, leach the ion-adsorbed rare earth elements and stir to obtain a turbid liquid;

[0010] S2. Take the turbid liquid obtained in step S1, add a precipitating agent to the leachate therein, and then perform solid-liquid separation to obtain a supernatant and a precipitate;

[0011] S3. Analyze the extraction efficiency of rare earth elements in the supernatant obtained in step S2 by inductively coupled plasma mass spectrometry (ICP-MS);

[0012] S4. Add the supernatant obtained in step S2 to deionized water in a certain ratio to recover the leaching agent for reuse.

[0013] Further, the rotation speed of the ball milling is 250 - 350 rpm.

[0014] Further, for the stirring, the conditions are magnetic stirring at 80 - 100 °C and 200 - 400 r / min for 3 - 5 h.

[0015] Further, the leaching agent is DESs, which is prepared from a hydrogen bond donor (HBD) and a hydrogen bond acceptor (HBA). The hydrogen bond acceptor (HBA) is choline chloride (ChCl), and the hydrogen bond donor (HBD) is at least one of p-toluenesulfonic acid, oxalic acid, malonic acid, lactic acid, ethylene glycol, and urea.

[0016] Further, the precipitating agent is at least one of an 8 - 12 wt% oxalic acid solution and an 8 - 12 wt% sodium carbonate solution.

[0017] Further, the certain ratio in step S4 is 1:1 - 1:5.

[0018] In summary, the present application has the following beneficial effects:

[0019] The leaching agent used in this application is a deep eutectic solvent (DESs). As an emerging green solvent, it has shown great potential in the extraction of lithium and rare earth elements. Deep eutectic solvents (DESs) are liquid eutectic mixtures with low melting points formed by the hydrogen bond interaction of two or more compounds, usually composed of a hydrogen bond acceptor (HBA) and a hydrogen bond donor (HBD) mixed in a certain proportion. DESs have the characteristics of adjustable structure, one-step solvent-free preparation, low toxicity, high biodegradability, etc., and have a good dissolving effect on metal oxides. The tunability of the composition and properties of DESs provides the required coordination environment for lithium and rare earth metal ions, is selective for lithium and rare earth elements, and simplifies the stepwise precipitation / separation process of traditional hydrometallurgy and pyrometallurgy. In addition, the DESs leaching technology avoids the damage and pollution of the solvent properties by the leaching agent and the separating agent in the traditional method, and realizes the reuse of DESs and the closed-loop recovery process. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0021] Figure 1 It is the leaching effect diagram of ion-adsorbed rare earth elements in M6758 by DESs prepared with choline chloride: oxalic acid (ChCl: OA);

[0022] Figure 2 It is the leaching effect diagram of ion-adsorbed rare earth elements in M6759 by DESs prepared with choline chloride: oxalic acid (ChCl: OA);

[0023] Figure 3 It is the leaching effect diagram of ion-adsorbed rare earth elements in the M6759 sample within the range of 3 - 5 h by different DESs at the same temperature and stirring speed;

[0024] Figure 4 It is the rare earth element extraction efficiency diagram after the leaching solutions of two DESs, choline chloride: malonic acid (ChCl: C3H4O4) and choline chloride: p-toluenesulfonic acid (ChCl: PTSA), are treated with oxalic acid precipitation;

[0025] Figure 5 It is the change diagram after adding deionized water to the supernatant of the ion-adsorbed rare earth elements in the M6758 and M6759 samples after extraction with choline chloride: p-toluenesulfonic acid (ChCl: PTSA). DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0027] The raw materials involved in the specific implementation mode of this application are of analytical purity. In addition, the samples are collected from coal mining areas in Guizhou Province. The distribution of rare earth elements in its minerals is shown in Table 1, labeled M6758 and M6759, and the unit of each component is μg / g.

[0028] Table 1: Distribution of rare earth elements in the original ore

[0029] Lanthanum La Cerium Ce Praseodymium Pr Neodymium Nd Samarium Sm Europium Eu Gadolinium Gd Terbium Tb M6758 1436.7 2389.0 384.2 1763.4 334.0 42.8 345.1 47.7 M6759 1767.8 3735.0 556.7 2292.5 395.0 35.3 336.8 42.7

[0030] Continued:

[0031] Dysprosium Dy Holmium Ho Erbium Er Thulium Tm Ytterbium Yb Lutetium Lu Scandium Sc Yttrium Y M6758 246.28 47.07 133.1 17.0 107.2 15.2 43.0 1280.0 M6759 192.19 34.38 92.12 10.2 53.7 7.35 38.7 926.0

[0032] Example 1

[0033] The leaching agent used in this example is DESs. Its hydrogen bond acceptor (HBA) is choline chloride, and the hydrogen bond donor (HBD) is oxalic acid, which is prepared according to a mass ratio of 1:1.

[0034] The closed-loop beneficiation and smelting process of coal-related associated rare earth mineral resources based on DESs solvent specifically includes the following steps:

[0035] S1. Take 5 g of the sample collected from the coal mining area and perform ball milling for 45 min (the large, medium, and small steel balls are graded according to 4:3:3, and the rotation speed is 300 rpm). Then add 30 mL of DESs to the ball-milled sample to leach the ion-adsorbed rare earth elements, and perform magnetic stirring at 90 °C and 300 r / min for 4 h to obtain a turbid liquid.

[0036] S2. Take the turbid liquid obtained in step S1, add 10 wt% oxalic acid solution to the leachate for precipitation titration to the end point (let it stand for 1 h, take the supernatant and drop one drop of 10 wt% oxalic acid solution, and no turbidity means reaching the end point). Then perform solid-liquid separation with filter paper to obtain the supernatant and the precipitate.

[0037] S3. Analyze the extraction efficiency of rare earth elements in the supernatant obtained in step S2 by inductively coupled plasma mass spectrometry (ICP-MS).

[0038] S4. Add deionized water to the supernatant obtained in step S2 according to a volume ratio of 1:1 to recover DESs for use next time.

[0039] Example 2

[0040] The leaching agent used in this example is DESs. Its hydrogen bond acceptor (HBA) is choline chloride, and its hydrogen bond donor (HBD) is p-toluenesulfonic acid, which is prepared according to a mass ratio of 1:1.

[0041] The closed-loop beneficiation and metallurgy process of coal-associated rare earth mineral resources based on DESs solvent specifically includes the following steps:

[0042] S1. Take 5 g of the sample collected from the coal mine area and carry out ball milling for 45 min (the large, medium, and small steel balls are graded at 4:3:3, and the rotation speed is 300 rpm). Then add 30 mL of DESs to the ball-milled sample to leach the ion-adsorbed rare earth elements. Stir magnetically at 90 °C and 300 r / min for 4 h to obtain a turbid liquid.

[0043] S2. Take the turbid liquid obtained in step S1, add 10 wt% oxalic acid solution to the leaching solution for precipitation titration to the end point (let it stand for 1 h, take the supernatant and add a drop of 10 wt% oxalic acid solution. If there is no turbidity, it reaches the end point). Then carry out solid-liquid separation with filter paper to obtain the supernatant and the precipitate.

[0044] S3. Analyze the rare earth element extraction efficiency of the supernatant obtained in step S2 by inductively coupled plasma mass spectrometry (ICP-MS).

[0045] S4. Add deionized water to the supernatant obtained in step S2 according to a volume ratio of 1:1 to recover DESs for the next use.

[0046] Example 3

[0047] The leaching agent used in this example is DESs. Its hydrogen bond acceptor (HBA) is choline chloride, and its hydrogen bond donor (HBD) is malonic acid, which is prepared according to a mass ratio of 1:1.

[0048] The closed-loop beneficiation and metallurgy process of coal-associated rare earth mineral resources based on DESs solvent specifically includes the following steps:

[0049] S1. Take 5 g of the sample collected from the coal mine area and carry out ball milling for 45 min (the large, medium, and small steel balls are graded at 4:3:3, and the rotation speed is 300 rpm). Then add 30 mL of DESs to the ball-milled sample to leach the ion-adsorbed rare earth elements. Stir magnetically at 90 °C and 300 r / min for 4 h to obtain a turbid liquid.

[0050] S2. Take the turbid liquid obtained in step S1, add 10 wt% oxalic acid solution to the leaching solution for precipitation titration to the end point (let it stand for 1 h, take the supernatant and add a drop of 10 wt% oxalic acid solution. If there is no turbidity, it reaches the end point). Then carry out solid-liquid separation with filter paper to obtain the supernatant and the precipitate.

[0051] S3. Analyze the extraction efficiency of rare earth elements from the supernatant obtained in step S2 by inductively coupled plasma mass spectrometry (ICP-MS).

[0052] S4. Add deionized water to the supernatant obtained in step S2 at a volume ratio of 1:1 to recover the DESs for the next use.

[0053] Example 4

[0054] The leaching agent used in this example is DESs, whose hydrogen bond acceptor (HBA) is choline chloride and hydrogen bond donor (HBD) is lactic acid, prepared at a mass ratio of 1:1.

[0055] The closed-loop beneficiation and smelting process for coal-related associated rare earth mineral resources based on DESs solvent specifically includes the following steps:

[0056] S1. Take 5 g of the sample collected from the coal mining area, grind it for 45 min (the large, medium, and small steel balls are graded at 4:3:3, and the rotation speed is 300 rpm), then add 30 mL of DESs to the ground sample to leach the ion-adsorbed rare earth elements, and stir magnetically at 90 °C and 300 r / min for 4 h to obtain a turbid liquid.

[0057] S2. For the turbid liquid obtained in step S1, take the leaching solution therein, add 10 wt% oxalic acid solution for precipitation titration to the end point (let it stand for 1 h, take the supernatant and drop one drop of 10 wt% oxalic acid solution, and if there is no turbidity, it reaches the end point), then perform solid-liquid separation with filter paper to obtain the supernatant and the precipitate.

[0058] S3. Analyze the extraction efficiency of rare earth elements from the supernatant obtained in step S2 by inductively coupled plasma mass spectrometry (ICP-MS).

[0059] S4. Add deionized water to the supernatant obtained in step S2 at a volume ratio of 1:1 to recover the DESs for the next use.

[0060] Example 5

[0061] The leaching agent used in this example is DESs, whose hydrogen bond acceptor (HBA) is choline chloride and hydrogen bond donor (HBD) is urea, prepared at a mass ratio of 1:1.

[0062] The closed-loop beneficiation and smelting process for coal-related associated rare earth mineral resources based on DESs solvent specifically includes the following steps:

[0063] S1. Take 5 g of the sample collected from the coal mining area and ball mill it for 45 min (the large, medium, and small steel balls are graded at 4:3:3, and the rotation speed is 300 rpm). Then, add 30 mL of DESs to the ball-milled sample to leach the ion-adsorbed rare earth elements. Magnetically stir for 4 h at 90 °C and 300 r / min to obtain a turbid liquid;

[0064] S2. Take the turbid liquid obtained in step S1, add 10 wt% oxalic acid solution to the leachate for precipitation titration until the end point (let it stand for 1 h, take the supernatant, add one drop of 10 wt% oxalic acid solution, and no turbidity indicates the end point). Then, perform solid-liquid separation with filter paper to obtain the supernatant and the precipitate;

[0065] S3. Analyze the extraction efficiency of rare earth elements in the supernatant obtained in step S2 by inductively coupled plasma mass spectrometry (ICP-MS);

[0066] S4. Add deionized water to the supernatant obtained in step S2 at a volume ratio of 1:1 to recover DESs for the next use.

[0067] Example 6

[0068] The leaching agent used in this example is DESs. Its hydrogen bond acceptor (HBA) is choline chloride, and its hydrogen bond donor (HBD) is ethylene glycol, which is prepared according to a mass ratio of 1:1.

[0069] The closed-loop beneficiation and smelting process of coal-associated rare earth mineral resources based on DESs solvent specifically includes the following steps:

[0070] S1. Take 5 g of the sample collected from the coal mining area and ball mill it for 45 min (the large, medium, and small steel balls are graded at 4:3:3, and the rotation speed is 300 rpm). Then, add 30 mL of DESs to the ball-milled sample to leach the ion-adsorbed rare earth elements. Magnetically stir for 4 h at 90 °C and 300 r / min to obtain a turbid liquid;

[0071] S2. Take the turbid liquid obtained in step S1, add 10 wt% oxalic acid solution to the leachate for precipitation titration until the end point (let it stand for 1 h, take the supernatant, add one drop of 10 wt% oxalic acid solution, and no turbidity indicates the end point). Then, perform solid-liquid separation with filter paper to obtain the supernatant and the precipitate;

[0072] S3. Analyze the extraction efficiency of rare earth elements in the supernatant obtained in step S2 by inductively coupled plasma mass spectrometry (ICP-MS);

[0073] S4. Add deionized water to the supernatant obtained in step S2 at a volume ratio of 1:1 to recover DESs for the next use.

[0074] Performance Test

[0075] The leaching effects of the systems in Examples 1 - 6 were tested, and the results are as follows:

[0076] Figure 1 and Figure 2 are the leaching effects of the DESs prepared with choline chloride: oxalic acid ((ChCl:OA)) on the ion-adsorbed rare earth elements in M6758 and M6759, respectively. The results show that under magnetic stirring at 90 °C and 300 r / min for 4 h, the solution turns green, indicating that the rare earth elements are completely leached.

[0077] Figure 3 are the leaching effect diagrams of the ion-adsorbed rare earth elements in the M6759 sample by different DESs within the range of 3 - 5 h at the same temperature and stirring speed. As can be seen from the figure, all DESs have good leaching effects on rare earth elements, but due to the differences in the active functional groups of the hydrogen bond donors, the colors of the leaching solutions are different.

[0078] Oxalic acid was used to precipitate the leaching solutions of two DESs, choline chloride: malonic acid (ChCl:C3H4O4) and choline chloride: p-toluenesulfonic acid (ChCl:PTSA), and the extraction efficiency of rare earth elements was analyzed by inductively coupled plasma mass spectrometry (ICP-MS), as Figure 4 shown. As can be seen from the figure, the oxides after precipitation with oxalic acid are still rare earth mixtures, but have high selectivity for scandium (Sc) and yttrium (Y). Especially for the DESs prepared according to the mass ratio of ChCl:PTSA of 1:1, the extraction efficiencies for Sc and Y reach 99.56% and 99.94% respectively. Attachment: Extraction efficiency = content of rare earth elements after extraction / content of rare earth elements before extraction × 100%.

[0079] Figure 5 is the change after adding deionized water to the leaching solution of the ion-adsorbed rare earth elements in the M6758 and M6759 samples after extraction with choline chloride: p-toluenesulfonic acid (ChCl:PTSA). As can be seen from the figure, after adding deionized water, the leaching solution becomes a transparent liquid, indicating that the DESs have strong reversibility, and through the replenishment of hydrogen bonds in deionized water, recycling is achieved.

[0080] This application studied a series of eutectic solvent (DESs) systems that can efficiently leach rare earth minerals associated with coal measures, and achieved efficient extraction of rare earth elements. By using the selectivity of two DESs, choline chloride: malonic acid (ChCl:C3H4O4) and choline chloride: p-toluenesulfonic acid (ChCl:PTSA), extraction efficiencies of ≥95% were obtained for Sc and Y elements. In addition, through the replenishment of hydrogen bonds in deionized water, the recycling of the DESs solvent was achieved.

[0081] The above content is only an example and explanation of the present invention. Those skilled in the art to which the present technology pertains can make various modifications or supplements to the described specific embodiments or use similar methods for substitution. As long as they do not deviate from the invention or exceed the scope defined by the claims of the present invention, they shall fall within the protection scope of the present invention.

Claims

1. A closed-loop beneficiation and smelting process for rare earth associated mineral resources in coal measures based on DESs solvents, characterized in that, It includes the following steps: S1. Take a sample for ball milling, then add a leaching agent to the ball-milled sample and stir to obtain a turbid liquid; S2. Take the leachate from the turbid liquid obtained in step S1, add a precipitating agent, and then perform solid-liquid separation to obtain a supernatant and a precipitate; S3. Analyze the extraction efficiency of rare earth elements in the supernatant obtained in step S2 by inductively coupled plasma mass spectrometry; S4. Add the supernatant obtained in step S2 to deionized water in a certain ratio to recover the leaching agent for the next use.

2. The closed-loop beneficiation and metallurgy process for coal-related associated rare earth mineral resources based on DESs solvents according to claim 1, characterized in that, The rotation speed of the ball milling is 250 - 350 rpm.

3. The closed-loop beneficiation and smelting process of coal-related associated rare earth mineral resources based on DESs solvent according to claim 1, characterized in that, For the stirring, the conditions are magnetic stirring at 80 - 100 °C and 200 - 400 r / min for 3 - 5 h.

4. The closed-loop beneficiation and smelting process of coal-related associated rare earth mineral resources based on DESs solvent according to claim 1, characterized in that, The leaching agent is DESs, which is prepared from a hydrogen bond donor and a hydrogen bond acceptor.

5. The closed-loop beneficiation and smelting process of coal-associated rare earth mineral resources based on DESs solvent according to claim 4, characterized in that, The hydrogen bond acceptor is choline chloride, and the hydrogen bond donor is at least one of p-toluenesulfonic acid, oxalic acid, malonic acid, lactic acid, ethylene glycol, and urea.

6. The closed-loop beneficiation and smelting process of coal-associated rare earth mineral resources based on DESs solvent according to claim 1, characterized in that, The precipitating agent is at least one of an 8 - 12 wt% oxalic acid solution and an 8 - 12 wt% sodium carbonate solution.

7. The closed-loop beneficiation and metallurgy process of coal-related associated rare earth mineral resources based on DESs solvents according to claim 1, characterized in that, The certain ratio in step S4 is 1:1 - 1:5.

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