Method for recycling oxalic acid waste liquid

Abstract

The invention belongs to the field of oxalic acid waste liquid recycling, and particularly relates to a method for recycling oxalic acid waste liquid. According to the method for recycling the oxalic acid waste liquid, rare earth elements and oxalic acid can be classified and recycled, the recycling rate is high, and the recycling rate of oxalic acid is higher than 90%; according to the recycling method, little strong acid or strong alkali waste liquid is generated, the method is green and environmentally friendly, the process is simple, the cost is relatively low, meanwhile, the recycled oxalic acid, the sediment containing the rare earth elements and other products can be recycled, and the recycling efficiency and value are high.

Description

Technical Field

[0001] The present application relates to the field of oxalic acid waste liquid recovery, and specifically to a method for recovering and utilizing oxalic acid waste liquid. Background Art

[0002] Oxalic acid, also known as oxalic acid, is the simplest dibasic acid in nature. It is an important chemical raw material and is widely used in medicine, dyes, coatings, clothing bleaching, and the separation and purification of rare earth metals.

[0003] With the transformation of the domestic rare earth industry, rare earth oxides, as raw materials for new materials, have become increasingly widely used. At the same time, the production of high-purity rare earth oxides has gradually expanded. To meet the international market requirement for mixed rare earth oxides with a purity greater than 99.5%, oxalic acid is often used to precipitate rare earth chloride at the end of production. The precipitate is then converted into rare earth oxides. However, this precipitation process produces a large amount of highly acidic oxalic acid wastewater containing impurities. Furthermore, during the production of rare earth oxides, a small amount of low-concentration valuable metals still remains in the oxalic acid wastewater after precipitation. Due to variations in precipitation process conditions, incomplete precipitation and crystallization, the recovery rate of rare earth valuable metals and oxalic acid is low, and some valuable metals and oxalic acid still exist in the oxalic acid wastewater as solutions.

[0004] The treatment of oxalic acid wastewater typically involves neutralizing and precipitating the alkaline substances calcium oxide or calcium hydroxide before discharge. This precipitation results in a calcium oxalate precipitate, which then needs to be treated with sodium carbonate to remove excess calcium, producing even more insoluble calcium carbonate. This method results in high energy consumption, high costs, and environmental risks, while also producing difficult-to-handle calcium oxalate and calcium carbonate. Alternatively, the oxalic acid wastewater can be subjected to a series of acid recovery measures, including precipitation separation and impurity removal. However, this process is lengthy, requires complex equipment, and carries high production costs. Furthermore, direct precipitation separation of the oxalic acid wastewater can easily lead to impurities accumulating in the product, reducing the purity of the precipitated product. Existing oxalic acid wastewater treatment processes, such as high cost, complex treatment, and low purity of the recovered product, hinder their widespread application in industrial production. Furthermore, existing oxalic acid wastewater treatment methods not only have low oxalic acid recovery rates, but also fail to recycle residual rare earth elements, resulting in a low overall recycling value. Therefore, developing a method for the efficient and effective recovery of oxalic acid wastewater is crucial. Summary of the Invention

[0005] In response to the above-mentioned problems involving low recovery rates of oxalic acid and rare earth elements in oxalic acid waste liquid, this application will provide a method for recycling oxalic acid waste liquid.

[0006] To achieve the above objectives, the following technical solutions are specifically included:

[0007] A method for recycling oxalic acid waste liquid, comprising the following steps:

[0008] (1) filtering the oxalic acid waste liquid containing rare earth elements, removing oil by using activated carbon to obtain a liquid after oil removal;

[0009] (2) removing impurities from the liquid after oil removal by using adsorption resin chromatography to obtain a liquid after impurity removal and adsorption resin after impurity removal;

[0010] (3) eluting the adsorption resin after impurity removal by using a hydrochloric acid solution to obtain an eluted liquid; neutralizing the eluted liquid by using an alkaline solution, and filtering to obtain a rare earth element-containing precipitate and a neutralized liquid;

[0011] (4) performing primary membrane concentration treatment on the liquid after impurity removal to obtain a primary oxalic acid concentrated liquid and a primary permeate; performing secondary membrane concentration treatment on the primary permeate to obtain a secondary oxalic acid concentrated liquid and a secondary permeate.

[0012] In the method for recycling oxalic acid waste liquid, because there are precipitates and oil components such as organic extractants in the previous rare earth compound production process, the oxalic acid waste liquid needs to be filtered and oil-removed first to avoid the precipitates and oil components from blocking the membranes in the subsequent membrane concentration process, thereby improving the service life of the membranes; the liquid after oil removal is subjected to adsorption resin chromatography to adsorb the impurities and rare earth elements onto the resin, which not only separates the impurities, rare earth elements and oxalic acid, but also improves the purity of the subsequent product by removing the impurities; the adsorbed resin is desorbed by using hydrochloric acid to remove the rare earth elements on the resin, thereby separating the rare earth elements and impurities; the liquid after impurity removal is subjected to primary membrane concentration, and in the concentration process of this stage, most of the oxalic acid is enriched in the primary concentrated liquid, and a small amount of oxalic acid permeates the membrane and remains in the primary permeate; the primary permeate is subjected to secondary membrane concentration to concentrate the oxalic acid in the primary permeate, thereby obtaining a secondary oxalic acid concentrated liquid rich in oxalic acid and a secondary permeate; the secondary oxalic acid concentrated liquid can be used in the oil removal process again to improve the utilization rate of oxalic acid. The method can purify oxalic acid by first removing oil from the oxalic acid waste liquid and then adsorbing impurities and metal ions by using resin chromatography; the method can concentrate oxalic acid by two-stage membrane concentration; and the method can recover oxalic acid by neutralizing the eluted liquid with an alkaline solution. The method can also recover metal ions (including rare earth metals and other valuable metal ions) adsorbed by the resin by eluting the adsorbed resin with hydrochloric acid, thereby realizing the recovery of rare earth metals and part of the valuable metals. The method can classify and recycle oxalic acid, acid-base neutralization products, rare earth elements and the like, thereby improving the recovery rate of oxalic acid and rare earth elements and realizing efficient, high-value, high-purity and green and environmentally friendly comprehensive recycling of resources.

[0013] Preferably, in step (1), the rare earth elements in the oxalic acid waste liquid containing rare earth elements include at least one of lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, scandium and yttrium. The oxalic acid recycling method of the present application is suitable for oxalic acid waste liquid containing different rare earth elements, and is particularly suitable for recycling oxalic acid waste liquid generated after using oxalic acid precipitation process in the production of rare earth oxide containing oxides.

[0014] Preferably, in step (1), the iodine value of the activated carbon is ≥800 mg / g, and further preferably the iodine value of the activated carbon is 900 mg / g-1200 mg / g. The activated carbon has a porous structure, and the iodine value represents its adsorption capacity. The activated carbon has an iodine value of ≥800 mg / g, and the better the adsorption of oil, the better the effect of removing oil from the oxalic acid waste liquid. The oil components in the oxalic acid waste liquid can be effectively removed to avoid the influence of the oil components on the subsequent process.

[0015] Preferably, in step (1), the content of oil components in the oil-removed liquid is ≤2.5 mg / L. The content of oil components in the oil-removed liquid is small, which can avoid clogging the membrane in the subsequent membrane concentration process and release the rare earth elements in the oil phase into the water phase, thereby improving the recovery rate of the rare earth elements.

[0016] Preferably, in step (2), the flow rate of the liquid in the chromatography impurity removal is 100 mL / min-300 mL / min. In the chromatography impurity removal process, the oil-removed liquid is used as the mobile phase and the adsorption resin is used as the stationary phase. The resin is more likely to adsorb rare earth elements and impurities, thereby separating oxalic acid from rare earth elements and impurities. The flow rate of the mobile phase is 100 mL / min-300 mL / min, and the adsorption effect is better.

[0017] Preferably, in step (3), the mass percentage content of hydrochloric acid in the hydrochloric acid solution is 0.5%-10%. The use of the above concentration of hydrochloric acid solution can more easily elute the rare earth elements adsorbed on the resin, thereby increasing the recovery rate of the rare earth elements.

[0018] Preferably, in step (3), the basic solution includes at least one of sodium hydroxide solution and potassium hydroxide solution, the mass percentage content of basic substances in the basic solution is 20%-32%, and the pH value of the solution system during neutralization is 8-10. The use of the basic solution to neutralize and elute the eluted liquid can cause the rare earth elements in the eluted liquid to precipitate in the form of hydroxide and other precipitates in the basic system, and the pH value of 8-10 is more conducive to the precipitation of the rare earth elements.

[0019] Preferably, in step (3), when the basic solution is sodium hydroxide solution, the post-neutralization liquid is further subjected to evaporation treatment to recover sodium chloride crystals obtained by evaporation treatment. In this way, the method of the present application can further recover the products of the neutralizing agent, thereby reducing the loss of the reagent and increasing the use value of the recycling method of the present application.

[0020] Preferably, in step (4), the concentration of oxalic acid in the primary oxalic acid concentrated solution is ≥80 g / L, and further preferably, the concentration of oxalic acid in the primary oxalic acid concentrated solution is 80 g / L-85 g / L. Since the aforementioned process has removed impurities, the concentrated solution obtained after primary membrane concentration contains high-purity and high-concentration oxalic acid, which is conducive to subsequent reuse, such as being reused for the precipitation of chlorinated rare earths at the end of production.

[0021] Preferably, in step (4), the concentration of oxalic acid in the primary permeate is ≥3 g / L, and further preferably, the concentration of oxalic acid in the primary permeate is 5 g / L-8 g / L.

[0022] Preferably, in step (4), the concentration of oxalic acid in the primary oxalic acid concentrated solution is 70 g / L-80 g / L, and the concentration of oxalic acid in the secondary permeate is ≤0.3 g / L. In each stage of membrane concentration treatment, oxalic acid is enriched in one side solution, but the greater the concentration difference between the two sides, the greater the required driving force, resulting in a limited degree of enrichment of oxalic acid on one side. The present application adopts a two-stage concentration method, first enriches most of the oxalic acid through primary concentration treatment, and then further enriches the remaining oxalic acid through secondary concentration treatment, which is conducive to improving the recovery rate of oxalic acid.

[0023] Preferably, in step (4), the secondary oxalic acid concentrated solution is further treated by the following steps:

[0024] (4-1) removing oil with activated carbon to obtain an oil-removed solution;

[0025] (4-2) removing impurities from the oil-removed solution with adsorption resin to obtain an impurity-removed solution and impurity-removed adsorption resin;

[0026] (4-3) sequentially performing primary membrane concentration treatment and secondary membrane concentration treatment on the impurity-removed solution to obtain a tertiary oxalic acid concentrated solution, a quaternary concentrated solution, and a quaternary permeate.

[0027] Further removing oil, impurities, and concentrating the secondary concentrated solution further enriches the remaining oxalic acid, which is conducive to improving the recovery rate and purity of oxalic acid.

[0028] The recycling method of the present application can classify and recycle rare earth elements and oxalic acid, and has a high recovery rate, in which the recovery rate of oxalic acid is higher than 90%. The recycling method of the present application produces less strong acid or strong base waste liquid, is green and environmentally friendly, has a simple process, and relatively low cost. Meanwhile, the recycled oxalic acid and rare earth element-containing precipitates can be recycled, and the efficiency and value of the recycling are high. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 The flow chart of the oxalic acid waste liquid recycling method of the present application. DETAILED DESCRIPTION

[0030] In order to better illustrate the purpose, technical scheme and advantages of the present application, the present application will be further described below through specific examples. The test methods used in the examples and / or comparative examples are all conventional methods unless otherwise specified; and the materials, reagents and the like used are all commercially available unless otherwise specified.

[0031] The following examples use oxalic acid to precipitate the chlorinated rare earth at the end of production, and the oxalic acid wastewater produced thereby has a concentration of about 70-80 mg / L, and the rare earth elements together have a concentration of about 50-100 mg / L, wherein the types of rare earth elements can include lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, scandium, yttrium. The organic macroporous adsorption resin used in the following examples is a commercially available cation exchange resin, and the membrane in the membrane concentration system is a polyamide composite anti-pollution membrane.

[0032] Example 1

[0033] A method for recycling oxalic acid wastewater, the flow chart is as shown in Figure 1 , and specifically comprises the following steps:

[0034] (1) filtration and oil removal: obtaining the oxalic acid wastewater produced after the chlorinated rare earth at the end of production is precipitated using oxalic acid, performing precision filtration to obtain a clear solution, and then performing oil removal using macroporous activated carbon with an iodine value of 1000 mg / g to obtain an oil-removed liquid, wherein the oil content in the oil-removed liquid is 0.8 mg / L;

[0035] (2) resin impurity removal: injecting organic macroporous adsorption resin (cation exchange resin) into a chromatographic column, a total of 3 chromatographic columns, each column is filled with 50 mL of macroporous adsorption resin, after soaking with water, pumping the oil-removed liquid into the chromatographic column to start adsorption and impurity removal, adjusting the chromatographic column valve and controlling the flow rate of the solution at 100 mL / min, the treated oxalic acid wastewater starts to flow out from the bottom of the chromatographic column, when the impurities in the solution are <10 ppm and the oil content is <10 ppm, it is considered that the treatment is complete, obtaining an impurity-removed liquid and impurity-removed adsorption resin; then using a 1% hydrochloric acid solution to elute the impurity-removed adsorption resin to obtain an eluted liquid containing rare earth chlorides;

[0036] (3) eluted liquid treatment: adding a 20% sodium hydroxide solution to the eluted liquid containing rare earth chlorides to perform neutralization and precipitation, adjusting the pH of the system to 8, and then filtering to obtain rare earth hydroxide and sodium chloride wastewater; then evaporating the sodium chloride wastewater to remove the solvent to precipitate sodium chloride crystals and recover sodium chloride;

[0037] (4) Concentration: the impurity-removed liquid which meets the water inlet conditions (impurities <10 ppm, oil <10 ppm) is first introduced into a primary membrane concentration system for circulation treatment to obtain a primary oxalic acid concentrate and a primary permeate; when the concentration of oxalic acid in the primary permeate reaches 5 g / L, the primary permeate is introduced into a secondary membrane concentration system for treatment; the primary oxalic acid concentrate is discharged from the system, and the concentration of oxalic acid in the primary oxalic acid concentrate is 80 g / L; then the primary permeate is introduced into the secondary membrane concentration system for circulation treatment to obtain a secondary oxalic acid concentrate (72 g / L) and a secondary permeate; when the concentration of oxalic acid in the secondary permeate is less than or equal to 0.3 g / L, the secondary permeate is discharged from the system, and the concentration of oxalic acid in the secondary permeate is detected to calculate the oxalic acid recovery rate of the present embodiment, which is 96.6%;

[0038] (5) In addition, the secondary oxalic acid concentrate after the secondary membrane treatment can be further returned to the oil removal process and the resin impurity removal process, so that the secondary oxalic acid concentrate meets the condition of oil <10 ppm for membrane concentration water inlet, and the above step (4) concentration process (including two-stage concentration) is repeated to further obtain a tertiary oxalic acid concentrate, a quaternary oxalic acid concentrate and a quaternary permeate; the tertiary oxalic acid concentrate and the quaternary oxalic acid concentrate are recovered, and the quaternary permeate is discharged from the system when the concentration of oxalic acid reaches 0.1 g / L.

[0039] Any of the oxalic acid concentrates obtained in the above steps can be selected for the rare earth precipitation process, and the permeate of any of the above steps can be used for the wet leaching process of rare earths, which can improve the utilization rate of the reagent.

[0040] Example 2

[0041] A method for recycling oxalic acid waste liquid, a flow chart is shown as Figure 1 The method comprises the following steps:

[0042] (1) Filtration and oil removal: obtaining oxalic acid wastewater generated after chlorinated rare earths at the end of production are precipitated by oxalic acid, performing precision filtration to obtain a clear solution, and then performing oil removal by macroporous activated carbon with an iodine value of 1100 mg / g to obtain an oil-removed liquid, wherein the oil content in the oil-removed liquid is 0.5 mg / L;

[0043] (2) resin impurity removal: inject organic macroporous adsorption resin (cation exchange resin) into the chromatographic column, a total of 3 chromatographic columns, each column is filled with 180 mL macroporous adsorption resin, after soaking with water, pump the oil-removed liquid into the chromatographic column, start adsorption and impurity removal, adjust the chromatographic column valve, and control the flow rate of the solution at 300 mL / min, the treated oxalic acid wastewater starts to flow out from the bottom of the chromatographic column, when the impurities in the solution are <10 ppm and the oil content is <10 ppm, it is considered that the treatment is completed, and the impurity-removed liquid and the impurity-removed adsorption resin are obtained; then use 10% hydrochloric acid solution to elute the impurity-removed adsorption resin, and obtain the eluted liquid containing rare earth chlorides;

[0044] (3) eluted liquid treatment: add 32% sodium hydroxide solution to the eluted liquid containing rare earth chlorides, neutralize and precipitate, adjust the pH of the system to 10, and filter to obtain rare earth hydroxide and sodium chloride wastewater; then evaporate the sodium chloride wastewater to remove the solvent to precipitate sodium chloride crystals and recover sodium chloride;

[0045] (4) concentration: the impurity-removed liquid that meets the water inlet conditions (impurities <10 ppm, oil content <10 ppm) is first introduced into a primary membrane concentration system for cyclic treatment to obtain a primary oxalic acid concentrate and a primary permeate; when the oxalic acid concentration in the primary permeate reaches 6 g / L, the primary permeate is introduced into a secondary membrane concentration system, and the primary oxalic acid concentrate is discharged from the system, at this time, the oxalic acid concentration in the primary oxalic acid concentrate is 85 g / L; then the primary permeate is introduced into the secondary membrane concentration system for cyclic treatment to obtain a secondary oxalic acid concentrate (70 g / L) and a secondary permeate; when the oxalic acid concentration in the secondary permeate reaches 0.08 g / L, the secondary permeate is discharged from the system, and the concentration process ends; the oxalic acid concentrations in the oxalic acid concentrate and the permeate are detected, and the oxalic acid recovery rate of this embodiment is calculated to be 97.8%;

[0046] (5) In addition, the secondary oxalic acid concentrate after the secondary membrane treatment can be further returned to the oil removal process, so that the secondary oxalic acid concentrate meets the oil content <10 ppm condition for membrane concentration water inlet, and the above step (4) concentration process (including two-stage concentration) is repeated to further obtain a tertiary oxalic acid concentrate, a quaternary oxalic acid concentrate, and a quaternary permeate; the tertiary oxalic acid concentrate and the quaternary oxalic acid concentrate are recovered, and the quaternary permeate is discharged from the system when the oxalic acid concentration reaches 0.1 g / L.

[0047] The oxalic acid concentrate obtained in any of the above steps can be selected for the rare earth precipitation process, and the permeate of any of the above steps can be used in the wet leaching process for rare earths, which can improve the utilization rate of the recovered reagent.

[0048] Example 3

[0049] A method for recycling oxalic acid waste liquid, the flow chart is as followsFigure 1 As shown, specifically comprising the following steps:

[0050] (1) filtration, oil removal: obtain oxalic acid wastewater produced after the production end of chlorinated rare earth precipitate using oxalic acid, perform precision filtration to obtain a clear solution, then perform oil removal using macroporous activated carbon with an iodine value = 1000 mg / g to obtain an oil-removed liquid, the oil content in the oil-removed liquid being 1.9 mg / L;

[0051] (2) resin impurity removal: inject organic macroporous adsorption resin (cation exchange resin) into the chromatographic column, a total of 3 chromatographic columns, 100 mL of macroporous adsorption resin is loaded into each column, after soaking with water, pump the oil-removed liquid into the chromatographic column to start adsorption and impurity removal, adjust the chromatographic column valve and control the flow rate of the solution at 150 mL / min, the treated oxalic acid wastewater starts to flow out from the bottom of the chromatographic column, when the impurities in the solution are <10 ppm and the oil content is <10 ppm, it is considered that the treatment is complete, obtaining an impurity-removed liquid and impurity-removed adsorption resin; then elute the impurity-removed adsorption resin with a 6% mass fraction hydrochloric acid solution to obtain an eluted liquid containing rare earth chlorides;

[0052] (3) eluted liquid treatment: add a 25% mass fraction sodium hydroxide solution to the eluted liquid containing rare earth chlorides to perform neutralization and precipitation, the pH of the system is adjusted to 9, after filtration, rare earth hydroxide and sodium chloride wastewater are obtained; then evaporate the sodium chloride wastewater to remove the solvent to precipitate sodium chloride crystals and recover sodium chloride;

[0053] (4) concentration: the impurity-removed liquid after resin impurity removal and meeting the water inlet conditions (impurities <10 ppm, oil content <10 ppm) is pretreated, then enters a primary membrane concentration system, and is treated in a cycle to obtain a primary oxalic acid concentrate and a primary permeate; when the concentration of oxalic acid in the primary permeate reaches 7 g / L, it enters a secondary membrane concentration treatment system, and the primary oxalic acid concentrate is discharged from the system, at this time, the concentration of oxalic acid in the primary oxalic acid concentrate is 82 g / L; then the primary permeate enters the secondary membrane concentration system, and is treated in a cycle to obtain a secondary oxalic acid concentrate (71 g / L) and a secondary permeate, when the concentration of oxalic acid in the secondary permeate reaches 0.1 g / L, it is discharged from the system, ending the concentration, after detecting the concentration of oxalic acid in the oxalic acid concentrate and the permeate, the oxalic acid recovery rate of this embodiment is calculated to be 97.8%

[0054] (5) In addition, the secondary oxalic acid concentrate after the secondary membrane treatment can be further returned to the oil removal process, so that the secondary oxalic acid concentrate meets the condition that the oil content of the water for membrane concentration is less than 10 ppm, and the above step (4) concentration process (including two-stage concentration) is repeated to further obtain a tertiary oxalic acid concentrate, a quaternary oxalic acid concentrate and a quaternary permeate; the tertiary oxalic acid concentrate and the quaternary oxalic acid concentrate are recovered, and the quaternary permeate is discharged from the system when the concentration reaches 0.1 g / L.

[0055] In the above-mentioned method, the oxalic acid concentrate obtained in any of the steps can be selected for the rare earth precipitation process, and the permeate obtained in any of the steps can be used in the wet leaching process of rare earth, which can improve the utilization rate of the recovered reagent.

[0056] In the above-mentioned method, the oxalic acid recovery rate (%) = total amount of oxalic acid in all oxalic acid concentrates / total amount of oxalic acid in the oxalic acid wastewater x 100.

[0057] Table 1

[0058]

[0059] As can be seen from the above examples, the recycling method of the present application can classify and recycle rare earth elements and oxalic acid, and the recovery rate is high, wherein the recovery rate of oxalic acid is higher than 90%. The recycling method of the present application produces less strong acid or strong alkali waste liquid, is green and environmentally friendly, has a simple process, relatively low cost, and the recovered oxalic acid and rare earth element-containing precipitate and other products can be recycled. In addition, the present application increases the oil removal process, which can effectively remove oil components such as organic extractants, avoid the oil components from blocking the membrane of the subsequent membrane concentration process, and improve the service life of the membrane.

[0060] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application and not to limit the protection scope of the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present application.

Claims

1. A method for recycling oxalic acid waste liquid, characterized in that: The steps include: (1) filtering the oxalic acid waste liquid containing rare earth elements and removing oil with activated carbon to obtain a deoiled liquid; (2) performing chromatography on the deoiled liquid using an adsorption resin to remove impurities, thereby obtaining a deoiled liquid and a deoiled adsorption resin; (3) eluting the impurity-removed adsorption resin with a hydrochloric acid solution to obtain an eluted solution; neutralizing the eluted liquid with an alkaline solution, and filtering to obtain a rare earth element-containing precipitate and a neutralized liquid; (4) The impurity-removed liquid is subjected to a primary membrane concentration treatment to obtain a primary oxalic acid concentrated liquid and a primary permeate; and the primary permeate is subjected to a secondary membrane concentration treatment to obtain a secondary oxalic acid concentrated liquid and a secondary permeate.

2. The method for recycling oxalic acid waste liquid according to claim 1, wherein: In step (1), the rare earth elements in the oxalic acid waste liquid containing rare earth elements include at least one of lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, scandium, and yttrium.

3. The method for recycling oxalic acid waste liquid according to claim 1, wherein: In step (1), the iodine value of the activated carbon is ≥800 mg / g.

4. The method for recycling oxalic acid waste liquid according to claim 1, wherein: In step (1), the oil content in the deoiled liquid is ≤2.5 mg / L.

5. The method for recycling oxalic acid waste liquid according to claim 1, wherein: In step (2), during the chromatography impurity removal, the flow rate of the liquid is 100 mL / L-300 mL / L.

6. The method for recycling oxalic acid waste liquid according to claim 1, wherein: In step (3), the mass percentage of hydrochloric acid in the hydrochloric acid solution is 0.5%-10%.

7. The method for recycling oxalic acid waste liquid according to claim 1, wherein: In step (3), the alkaline solution includes at least one of a sodium hydroxide solution and a potassium hydroxide solution, the mass percentage of the alkaline substance in the alkaline solution is 20%-32%, and the pH value of the solution system during the neutralization is 8-10.

8. The method for recycling oxalic acid waste liquid according to claim 1, wherein: In step (4), the concentration of oxalic acid in the first-level oxalic acid concentrated solution is ≥80 g / L.

9. The method for recycling oxalic acid waste liquid according to claim 1, wherein: In step (4), the concentration of oxalic acid in the primary permeate is ≥3 g / L.

10. The method for recycling oxalic acid waste liquid according to claim 1, wherein: Include at least one of A or B below: A. In step (4), the concentration of oxalic acid in the secondary permeate is ≤ 0.1 g / L; B. In step (4), the secondary oxalic acid concentrate is further processed by the following steps: (4-1) removing oil using activated carbon to obtain a deoiled liquid; (4-2) performing chromatography on the deoiled liquid using an adsorption resin to remove impurities, thereby obtaining a deoiled liquid and a deoiled adsorption resin; (4-3) The impurity-removed liquid is sequentially subjected to a primary membrane concentration treatment and a secondary membrane concentration treatment to obtain a tertiary oxalic acid concentrated liquid, a quaternary concentrated liquid, and a quaternary permeate.

Images