Treatment method of emulsion generated by extraction and separation of rare earth elements

Abstract

The invention discloses a treatment method of an emulsion generated by rare earth element extraction and separation, which comprises the following steps: adding an oxalic acid solution into the emulsion generated by rare earth element extraction and separation, stirring, decomposing the emulsion by oxalic acid, depolymerizing and layering; extracting supernatant liquid, filtering, and recovering an oxalic acid solution and an organic phase; and extracting a middle water phase, filtering together with the lower oxalate, recovering the oxalate and the oxalic acid solution, combining the oxalic acid solutions obtained twice, preparing the concentration, and returning to the emulsion decomposition and depolymerization process. According to the method, the emulsion is treated by oxalic acid, so that rare earth oxide and P507 organic phase in the emulsion are recovered, and the discharge amount of waste residues is reduced.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of rare earth hydrometallurgy, and particularly relates to a treatment method of emulsions generated in the extraction and separation of rare earth elements. BACKGROUND

[0002] The storage of rare earth resources in China accounts for about 23% of the global total, ranking first in the world. China is rich in rare earth resources, and the storage, production, export and consumption of rare earth resources all rank first in the world. In 2021, the global total rare earth production was 280,000 tons, of which China produced 168,000 tons, accounting for 60% of the global total. In short, China plays a crucial role in the world rare earth market.

[0003] In the process of wet smelting and separation of rare earth elements, P507 and other acidic phosphorus extractants occupy a dominant position and are widely used in rare earth extraction and separation enterprises and production process. In the process of extracting and separating rare earth elements using P507-kerosene system, various emulsions with different colors and forms are often generated in the rare earth saponification section, extraction section and washing section. The formation mechanism of emulsions is not the same, including over-saponification, suspended solids in the feed solution, and high content of iron, aluminum and silicon impurities in the feed solution. The formation and existence of emulsions seriously affect the clarification effect of the water phase and the organic phase in the extraction and separation process, reduce the clarification efficiency of the two phases, increase the entrainment of the two phases, and thus affect the efficiency of the extraction and separation stage. The emulsions are viscous and have poor flowability, which affects the flow and flow circulation, and even blocks the flow circulation phase. Since the emulsions are formed by the aggregation of water phase, organic phase and small particles, they are not easy to clarify and difficult to handle, which increases the organic phase consumption and reduces the yield of rare earth materials in the process.

[0004] Chinese Patent No. CN104131163A discloses a method for regenerating P507 extraction and separation of rare earth organic phase emulsions. The specific steps are as follows: in the reaction pot, P507 organic phase emulsion and 4mol / L-8mol / L sodium hydroxide solution with a temperature of 90-100℃ are added in sequence, stirred for 5-10 minutes, and then allowed to separate. The upper layer is a clear organic phase, the middle layer is a transparent water phase, and the lower layer is a precipitate containing rare earth hydroxide. The water phase and the precipitate are discharged from the bottom of the reaction pot, filtered, washed, dissolved with hydrochloric acid, and then the rare earth is recovered by oxalate precipitation method, with a yield of about 95%. This technology uses sodium hydroxide treatment and heating to 90-100℃, and the diluent in the upper organic phase volatilizes. Not only is the operating environment poor and the diluent lost, but also the organic phase is viscous, not easy to separate, and needs to be treated twice before being used. The lower layer of rare earth hydroxide is a colloidal solid, which is difficult to settle and separate, and has high impurities. The separated rare earth hydroxide also needs to be dissolved with hydrochloric acid and precipitated again. The overall treatment process is long, energy-consuming, requires a variety of raw materials, and is costly.

[0005] Chinese Publication No. CN2669953Y discloses a demulsification device for oil-water emulsion, an ultrasonic probe is installed at each end of the pipeline in the ultrasonic action zone, respectively generating a forward-flowing ultrasonic wave in the same direction as the oil-water flow direction and a reverse-flowing ultrasonic wave, and the ultrasonic probe is connected with the ultrasonic generator through an ultrasonic power line. The forward-flowing ultrasonic wave and the reverse-flowing ultrasonic wave are combined to act on the oil-water emulsion, the ultrasonic action time of the oil-water emulsion is prolonged, and finally the oil-water emulsion is fully demulsified. The oil-water mixture after demulsification is subjected to sedimentation separation or dehydration under the action of an electric field and then subjected to sedimentation separation. The ultrasonic demulsification only separates the oil-water mixture and solid materials, and the valuable part cannot be reused.

[0006] Chinese Publication No. CN109295302A discloses a method for treating emulsion in a rare earth extraction production process, comprising: using a pressing device to extrude a pressing plate in a vacuum filter, the pressing plate extruding a fiber cotton layer and a fiber ball layer until the pressure transmitter on the buffer tank displays that the pressure reaches a set pressure value; closing the vent valve on the buffer tank, starting the vacuum pump, and putting the emulsion into the vacuum filter for filtration; when the liquid level meter displays that the liquid level in the cavity of the vacuum filter reaches the upper control limit, closing the vacuum pump, opening the vent valve, and using the transfer pump to pump out the mixed liquid of the filtered organic phase and water phase. The method separates the emulsion first and then processes it, and the emulsion has a large viscosity and is difficult to separate from the organic phase.

[0007] In the production of rare earth extraction and separation, emulsion is often extracted at a fixed time and period, the emulsion is treated, and the organic phase and rare earth oxide therein are recovered, so as to reduce the organic consumption, increase the process yield, and ensure the smooth operation of the extraction and separation production. However, most of the emulsion is difficult to be treated by centrifugal separation, filtration method, mechanical method, and ordinary chemical treatment, and the emulsion is difficult to depolymerize, which puzzles the rare earth separation enterprises. SUMMARY

[0008] The purpose of the present application is to provide a method for treating emulsion generated in the extraction and separation of rare earth elements, which uses oxalic acid to treat the emulsion, realizes the recovery of rare earth oxides and P507 organic phase in the emulsion, and reduces the amount of waste slag discharged.

[0009] To achieve the above purpose, the technical solution used by the present application is as follows:

[0010] The method for treating emulsion generated in the extraction and separation of rare earth elements comprises:

[0011] Adding an oxalic acid solution to the emulsion generated in the extraction and separation of rare earth elements, stirring, and separating the emulsion after oxalic acid decomposition and depolymerization;

[0012] Extracting the upper liquid for filtration, recovering the oxalic acid solution and the organic phase;

[0013] The intermediate aqueous phase and the lower oxalate layer are extracted and filtered together to recover the oxalate and oxalic acid solutions. The oxalic acid solutions obtained from the two processes are combined, and after being prepared to a certain concentration, they are returned to the emulsion decomposition and depolymerization process.

[0014] Furthermore, after being decomposed and depolymerized by oxalic acid, the emulsion is divided into three layers: the upper layer is the precipitated blank organic phase and the emulsion that cannot be depolymerized, the middle layer is the aqueous phase, and the bottom layer is the oxalate of rare earth elements, etc.

[0015] Furthermore, the oxalic acid solution depolymerizes the emulsion, and the metal ions of the loaded organic phase of the emulsion are back-extracted into the oxalic acid solution, thus converting the loaded organic phase into a blank organic phase.

[0016] Furthermore, by utilizing the acidic back-extraction of oxalic acid to extract metal ions from the organic phase of the emulsion, the organic phase is converted into a blank organic phase, thereby reducing the viscosity and density of the emulsion and increasing its fluidity.

[0017] Furthermore, by utilizing the complexing properties of oxalate, metal ions in the clarified organic phase can enter the aqueous phase in the form of complexed ions.

[0018] Furthermore, by utilizing the precipitation properties of oxalic acid, rare earth ions in the emulsion are precipitated at the bottom of the aqueous phase in the form of oxalates.

[0019] Furthermore, oxalate and metal ions enter the aqueous phase as complex ions, while rare earth ions and oxalic acid form oxalate, which precipitates in the lower layer.

[0020] Furthermore, the upper liquid is extracted and filtered using a siphon method. The upper liquid is a mixture of undepolymerized oxalic acid solution and organic phase. The organic phase is separated from the mixture of oxalic acid solution and organic phase, and the oxalic acid solution is recovered.

[0021] The technical effects of this invention include:

[0022] 1. This invention uses oxalic acid to treat the emulsion generated during the extraction and separation process, and recovers valuable components such as rare earth oxides, P507 and kerosene mixtures therein; it can increase the yield of rare earth oxides, reduce the consumption of P507 and kerosene and other organic phases in the extraction and separation process, and reduce the cost of the extraction and separation process.

[0023] 2. This invention enables the recovery of rare earth oxides and P507 organic phase from emulsions, reducing waste discharge and emulsion treatment costs. It can reduce waste discharge from the extraction and separation process by over 80%, enabling the secondary utilization of emulsions and minimizing waste emissions.

[0024] 3. This invention transforms hazardous waste into general solid waste, reducing the cost of disposing of discharged waste. The transformation from hazardous solid waste to general solid waste not only reduces the volume by 82.15%, but also recovers valuable rare earth oxides and high-concentration P507 organic phase.

[0025] 4. Oxalic acid is a commonly used industrial product that is readily available and reasonably priced. This invention uses oxalic acid to treat, extract, and separate emulsions. The method is simple and easy to operate, and the equipment used is also simple and readily available. It can be widely applied in rare earth separation plants, non-ferrous metal hydrometallurgical plants, and scrap metal recycling plants.

[0026] A rare earth separation plant with a capacity of 60,000 tons of REO per year produces 4,500 tons of emulsion annually, including 743.4 m³ of P507 organic phase (P507 is 1.8-2 mol / L). 3 339.93 tons of rare earth oxides and 574.65 tons of solid slag were treated; 1633.5 m³ of wastewater from emulsion treatment was also treated. 3 The above data is calculated based on the minimum value of recyclable valuable components. The value of recycling organic materials is:

[0027] P507: (743.4 * 2 / 3) * 0.95 * 3 = 14,124,600 yuan;

[0028] Kerosene: (743.4 - 743.4 * 2 / 3) * 0.8 * 0.9 = 1,784,160 yuan;

[0029] The value of the recovered rare earth oxides is 339.93 * 8 = 27,194,400 yuan;

[0030] The total benefit from the recovery of valuable components in emulsions amounted to RMB 43,103,160. Attached Figure Description

[0031] Figure 1 This is a flowchart of the method for treating emulsions generated by rare earth element extraction and separation in this invention. Detailed Implementation

[0032] The following description fully illustrates specific embodiments of the present invention to enable those skilled in the art to practice and reproduce it. To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0033] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. In addition, the terms "first," "second," "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0034] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0035] like Figure 1 The diagram shown is a flowchart of the method for treating emulsions generated during the extraction and separation of rare earth elements in this invention.

[0036] Methods for treating emulsions generated during rare earth element extraction and separation include:

[0037] Step 1: Add oxalic acid solution to the emulsion produced by rare earth element extraction and separation, stir, and the emulsion will be divided into three layers after decomposition and depolymerization by oxalic acid. The upper layer is the precipitated blank organic phase and a small amount of organic phase (emulsion) that cannot be depolymerized, the middle layer is the aqueous phase, and the bottom layer is the oxalate of rare earth elements, etc.

[0038] The oxalic acid solution depolymerizes the emulsion, and the metal ions of the organic phase loaded in the emulsion are back-extracted into the oxalic acid solution, thus converting the organic phase into a blank organic phase.

[0039] In the rare earth extraction and separation process, the emulsion is treated and depolymerized by adding oxalic acid solution to the emulsion. Oxalic acid solution is used to depolymerize the emulsion; the acidity of oxalic acid allows for the back-extraction of metal ions loaded in the organic phase of the emulsion, converting them into a blank organic phase. This reduces the viscosity and density of the emulsion, increases its fluidity, and facilitates its clarification from the emulsion.

[0040] By utilizing the strong complexing properties of oxalate, metal ions of iron and aluminum impurities that are difficult to back-extract from the clarified organic phase are introduced into the aqueous phase in the form of complex ions, further increasing the fluidity of the organic phase and making it easier to clarify.

[0041] By utilizing the precipitation property of oxalic acid, rare earth ions in the emulsion are precipitated in the form of oxalate. Oxalate has a higher density, better separability, and the highest density in the separated system, so it settles at the bottom of the aqueous phase.

[0042] Step 2: Extract the upper liquid and filter it to recover the oxalic acid solution and organic phase;

[0043] The upper liquid is extracted and filtered using a siphon method. The upper liquid is a mixture of a small amount of undepolymerized organic residue, oxalic acid solution, and organic phase. The organic phase is separated and recovered from the mixture of oxalic acid solution and organic phase to obtain oxalic acid solution.

[0044] Step 3: The intermediate aqueous phase and the lower oxalate layer are filtered together to recover the oxalate and oxalic acid solutions; the oxalic acid solutions obtained from the two processes are combined, and after being prepared to a certain concentration, they are returned to the emulsion decomposition and depolymerization process.

[0045] Oxalate and metal ions enter the aqueous phase as complex ions, while rare earth ions and oxalic acid form oxalate, which precipitates in the lower layer.

[0046] Example 1

[0047] 83.84 g of emulsion and 400 mL of oxalic acid solution were mixed and stirred for 40 min. After stirring was stopped, the mixture separated into three layers after 10 min. The upper organic phase was filtered, and the filtrate was separated into aqueous phase 1 and 18 mL of organic phase using a separatory funnel. The filter cake contained 13.76 g of undecomposed organic residue. The middle and lower precipitates were filtered to obtain aqueous phase 2 and 25.67 g of rare earth oxalate. Aqueous phases 1 and 2 were combined to form a total of 380 mL. The amount of undecomposed organic residue remaining was 83.59% less than that of the emulsion before oxalic acid treatment.

[0048] Example 2

[0049] 72.66 g of emulsion and 400 mL of oxalic acid solution were mixed and stirred for 80 min. After stirring was stopped, the mixture separated into three layers after 10 min. The upper organic phase was filtered, and the filtrate was separated into aqueous phase 1 and 12 mL of organic phase using a separatory funnel. The filter cake contained 9.28 g of undecomposed organic residue. The middle and lower precipitates were filtered to obtain aqueous phase 2 and 25.38 g of rare earth oxalate. Aqueous phases 1 and 2 were combined to form 370 mL. The amount of undecomposed organic residue remaining was 87.23% less than that of the emulsion before oxalic acid treatment.

[0050] Example 3

[0051] 99.12 g of emulsion and 400 mL of oxalic acid solution were mixed and stirred for 50 min. After stirring was stopped, the mixture separated into three layers after 10 min. The upper organic phase was filtered, and the filtrate was separated into aqueous phase 1 and 22 mL of organic phase using a separatory funnel. The filter cake contained 17.69 g of undecomposed organic residue. The middle and lower precipitates were filtered to obtain aqueous phase 2 and 25.18 g of rare earth oxalate. Aqueous phases 1 and 2 were combined to form 360 mL. The amount of undecomposed organic residue remaining was 82.15% less than that of the emulsion before oxalic acid treatment.

[0052] The recovered organic phase is washed with water, adjusted in concentration, and then returned to the extraction and separation process for reuse; rare earth oxalates are calcined and acid-dissolved, and then returned to the raw material system in the form of mixed rare earth chlorides; the combined aqueous phase is adjusted in concentration and then returned to the emulsion decomposition and depolymerization process; the undecomposed organic residue is treated as hazardous waste.

[0053] The terminology used in this invention is descriptive and exemplary, not restrictive. Since this invention can be embodied in many forms without departing from the spirit or essence of the technical solution, it should be understood that the above embodiments are not limited to any of the foregoing details, but should be interpreted broadly within the spirit and scope defined by the appended claims. Therefore, all variations and modifications falling within the scope of the claims or their equivalents should be covered by the appended claims.

Claims

1. A method for treating emulsions produced in the extraction separation of rare earth elements, characterized in that, The application relates to a method for separating and purifying rare earth elements. The emulsate produced in the rare earth element extraction separation is added with oxalic acid solution, stirred, and then separated into three layers after oxalic acid decomposition and depolymerization; The upper liquid is extracted and filtered, and the oxalic acid solution and organic phase are recovered; The middle water phase is extracted and filtered together with the lower oxalate, and the oxalate and oxalic acid solution are recovered; the oxalic acid solutions obtained in two times are combined, and the combined oxalic acid solution is returned to the emulsate decomposition and depolymerization process after concentration preparation.

2. The method for treating emulsions produced in the extraction separation of rare earth elements according to claim 1, characterized in that, The emulsate is separated into three layers after oxalic acid decomposition and depolymerization; the upper layer is the separated blank organic phase and the emulsate which cannot be depolymerized; the middle layer is the water phase; and the bottom layer is the oxalate of rare earth elements.

3. The method for treating emulsions produced in the extraction separation of rare earth elements according to claim 1, characterized in that, The oxalic acid solution depolymerizes the emulsate, and the metal ions of the loaded organic phase of the emulsate are back-extracted into the oxalic acid solution, so that the loaded organic phase is converted into the blank organic phase.

4. The method for treating emulsions produced in the extraction separation of rare earth elements according to claim 1, characterized in that, The oxalic acid is used to back-extract the metal ions of the loaded organic phase in the emulsate, so that the organic phase is converted into the blank organic phase, the viscosity and density of the emulsate are reduced, and the flowability is increased.

5. The method for treating emulsions produced in the extraction separation of rare earth elements according to claim 1, characterized in that, The complexing performance of the oxalate is used to make the metal ions in the separated organic phase enter the water phase in the form of complex ions.

6. The method for treating emulsions produced in the extraction separation of rare earth elements according to claim 1, characterized in that, The precipitation performance of the oxalic acid is used to make the rare earth ions in the emulsate precipitate in the water phase in the form of oxalate.

7. The method of claim 1, wherein the emulsion produced by the rare earth extraction separation is treated by, The oxalate and the metal ions enter the water phase in the form of complex ions, the rare earth ions and the oxalic acid form the oxalate, and the oxalate is in the form of precipitation in the lower layer.

8. The method for treating emulsions produced in the extraction separation of rare earth elements according to claim 1, characterized in that, The upper liquid is extracted and filtered by using the siphon method; the upper liquid is the mixture of the non-depolymerized oxalic acid solution and the organic phase; the mixture of the oxalic acid solution and the organic phase is separated to recover the oxalic acid solution and the organic phase.

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