A method for recovering rare earths from low concentration rare earth waste solutions

Abstract

A method for recovering rare earth from low-concentration rare earth waste solution, comprising the following steps: a) contacting the low-concentration rare earth waste solution with amino phosphonic acid resin to carry out resin adsorption reaction, and obtaining rich rare earth resin and adsorbed solution respectively; b) contacting the rich rare earth resin obtained in step a) with low-titanium solution to carry out first-stage desorption reaction, and obtaining rich rare earth solution and first-stage desorption resin respectively; c) contacting the first-stage desorption resin obtained in step b) with high-titanium solution to carry out second-stage desorption reaction, and obtaining second-stage desorption solution and rich titanium resin respectively; d) contacting the rich titanium resin obtained in step c) with mixed hydrogen peroxide and hydrochloric acid solution to carry out resin regeneration reaction, and obtaining regenerated amino phosphonic acid resin and titanium complex solution respectively; and e) carrying out aging decomposition on the titanium complex solution obtained in step d) to release oxygen, and obtaining regenerated high-titanium solution. The present application makes amino phosphonic acid resin circulate for recovery of low-concentration rare earth based on strengthened desorption process.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of waste resource utilization, and more particularly to a method for recovering rare earth from low-concentration rare earth waste liquid. BACKGROUND

[0002] In the process of rare earth resource development and utilization, a large amount of low-concentration rare earth wastewater will be produced; for example, tail water of in-situ leaching of rare earth mines, and acid wastewater composed of extraction wastewater, oxalic acid precipitation mother liquor and washing water of rare earth separation plants. Low-concentration rare earth waste liquid with a concentration of less than 0.1 g / L is difficult to be economically recovered by existing processes due to its low concentration and complex matrix composition, resulting in loss of rare earth resources.

[0003] In order to recover low-concentration rare earth by extraction method, a larger A / O ratio (A represents the aqueous phase, and O represents the organic phase) needs to be set, which poses certain challenges in engineering. In addition, when treating in-situ leaching tail water, the potential environmental risk of residual organic matter in the raffinate also needs to be addressed.

[0004] The use of precipitation method requires the development of a highly selective precipitant to reduce the co-precipitation of matrix elements and rare earth. At present, there are few types of precipitants for selectively extracting low-concentration rare earth from high-magnesium, high-calcium, high-iron, high-aluminum and high-acid solutions, and most of them are organic substances, which are expensive. The stability and reliability of long-term cyclic use need to be further confirmed.

[0005] In terms of ion exchange resins, although cation exchange resins have higher selectivity for high-valence cations, the ion exchange mechanism relies on the electrical attraction of ions with different charges. Other coexisting cations in low-concentration rare earth solution, including hydrogen ions, will significantly affect the ion exchange process. The higher the concentration of impurity ions, the lower the adsorption rate of rare earth by ion exchange resins. On the other hand, for low-concentration rare earth waste liquid containing sulfate ions, since a part of rare earth can react with sulfate ions to form complex anions, it is difficult to completely adsorb rare earth elements if cation exchange resins are used, and if anion exchange resins are used, it is necessary to ensure that all rare earth elements are converted into complex anions, and also to ensure that other anions in the solution do not affect the adsorption of rare earth complex anions. The above two reasons make it difficult for ion exchange resins to recover low-concentration rare earth from solutions with complex matrix composition.

[0006] In the aspect of chelating resin, the amino phosphonic acid resin has strong binding force to rare earth ions, can cope with the competitive adsorption of other low valence state cations in solution, and even shows good adsorption effect in strong acidic solution, so it can deal with various low concentration rare earth waste liquid produced in the industry at present. However, due to the strong binding force between rare earth and amino phosphonic acid resin, the rare earth ions enriched on the amino phosphonic acid resin are difficult to be desorbed by high concentration acid solution, resulting in the difficulty of recycling the resin. SUMMARY

[0007] Therefore, the purpose of the present application is to provide a method for recovering rare earth from low concentration rare earth waste liquid, which makes the amino phosphonic acid resin recycle for the recovery of low concentration rare earth based on the strengthened desorption process.

[0008] The present application provides a method for recovering rare earth from low concentration rare earth waste liquid, comprising the following steps:

[0009] a) contacting the low concentration rare earth waste liquid with the amino phosphonic acid resin to carry out resin adsorption reaction, and obtaining the rare earth-rich resin and the adsorbed solution respectively;

[0010] b) contacting the rare earth-rich resin obtained in step a) with low titanium solution to carry out one-stage desorption reaction, and obtaining the rare earth-rich solution and one-stage desorption resin respectively;

[0011] c) contacting the one-stage desorption resin obtained in step b) with high titanium solution to carry out two-stage desorption reaction, and obtaining the two-stage desorption solution and titanium-rich resin respectively;

[0012] d) contacting the titanium-rich resin obtained in step c) with a mixed solution of hydrogen peroxide and hydrochloric acid to carry out resin regeneration reaction, and obtaining the regenerated amino phosphonic acid resin and titanium complex solution respectively;

[0013] e) aging and decomposing the titanium complex solution obtained in step d) to release oxygen, and obtaining the regenerated high titanium solution.

[0014] Preferably, the concentration of rare earth ions in the low concentration rare earth waste liquid in step a) is ≤1g / L.

[0015] The amount of the amino phosphonic acid resin is 20 times to 60 times of the total mass of rare earth in the low concentration rare earth waste liquid.

[0016] Preferably, the way of contacting the low concentration rare earth waste liquid with the amino phosphonic acid resin in step a) is mixing and stirring the low concentration rare earth waste liquid with the amino phosphonic acid resin, or loading the amino phosphonic acid resin into an adsorption column to make the low concentration rare earth waste liquid flow through.

[0017] Preferably, the temperature of the resin adsorption reaction in step a) is 20℃ to 35℃, and the time is 2h to 8h.

[0018] Preferably, the concentration of titanium ions in the low-titanium solution in step b) is 2-10 g / L.

[0019] The temperature of the first desorption reaction is 20-35°C, and the time is 1-3 h.

[0020] Preferably, the concentration of titanium ions in the high-titanium solution in step c) is greater than 10 g / L and less than or equal to 40 g / L.

[0021] The temperature of the second desorption reaction is 20-35°C, and the time is 1-3 h.

[0022] Preferably, the concentration of hydrogen peroxide in the hydrogen peroxide-hydrochloric acid mixed solution in step d) is 10-50 g / L, and the concentration of hydrochloric acid is 20-150 g / L.

[0023] Preferably, the temperature of the resin regeneration reaction in step d) is 20-35°C, and the time is 2-6 h.

[0024] Preferably, the temperature of the aging decomposition in step e) is 20-80°C, and the time is calculated according to the following formula:

[0025] Aging decomposition time = 36000 g·h·L -1 · ℃ / hydrochloric acid concentration / aging decomposition temperature, wherein the unit of hydrochloric acid concentration is g / L, the unit of aging decomposition time is h, and the unit of aging decomposition temperature is ℃.

[0026] Preferably, the regenerated high-titanium solution obtained in step e) is recycled as the high-titanium solution in step c).

[0027] The regenerated amino phosphonic acid resin obtained in step d) is recycled as the amino phosphonic acid resin in step a).

[0028] The second desorption solution obtained in step c) is recycled as the low-titanium solution in step b).

[0029] The application provides a method for recovering rare earth from low-concentration rare earth waste liquid, comprising the following steps: a) contacting the low-concentration rare earth waste liquid with an amino phosphonic acid resin to perform a resin adsorption reaction, and obtaining a rare earth-rich resin and an adsorbed liquid; b) contacting the rare earth-rich resin obtained in step a) with a low-titanium solution to perform a first-stage desorption reaction, and obtaining a rare earth-rich solution and a first-stage desorption resin; c) contacting the first-stage desorption resin obtained in step b) with a high-titanium solution to perform a second-stage desorption reaction, and obtaining a second-stage desorption liquid and a titanium-rich resin; d) contacting the titanium-rich resin obtained in step c) with a hydrogen peroxide hydrochloric acid mixed solution to perform a resin regeneration reaction, and obtaining a regenerated amino phosphonic acid resin and a titanium complex solution; and e) performing aging decomposition on the titanium complex solution obtained in step d) to release oxygen, and obtaining a regenerated high-titanium solution. Compared with the prior art, the application adopts specific process steps to realize overall good interaction, and based on the strengthened desorption process, the amino phosphonic acid resin is recycled for recovery of low-concentration rare earth, and no pollution is caused to the environment. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 A process flow chart of the method for recovering rare earth from low-concentration rare earth waste liquid is provided for the embodiments of the application. DETAILED DESCRIPTION

[0031] The technical solutions of the application will be described clearly and completely below with reference to the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the application.

[0032] The application provides a method for recovering rare earth from low-concentration rare earth waste liquid, comprising the following steps:

[0033] a) contacting the low-concentration rare earth waste liquid with an amino phosphonic acid resin to perform a resin adsorption reaction, and obtaining a rare earth-rich resin and an adsorbed liquid;

[0034] b) contacting the rare earth-rich resin obtained in step a) with a low-titanium solution to perform a first-stage desorption reaction, and obtaining a rare earth-rich solution and a first-stage desorption resin;

[0035] c) contacting the first-stage desorption resin obtained in step b) with a high-titanium solution to perform a second-stage desorption reaction, and obtaining a second-stage desorption liquid and a titanium-rich resin;

[0036] d) contacting the titanium-rich resin obtained in step c) with a hydrogen peroxide hydrochloric acid mixed solution to perform a resin regeneration reaction, and obtaining a regenerated amino phosphonic acid resin and a titanium complex solution;

[0037] e) aging and decomposing the titanium complex solution obtained in step d) to release oxygen and obtain a regenerated high-titanium solution.

[0038] The application discloses a method for recovering rare earth elements from low-concentration rare earth waste liquid, which comprises the following steps: contacting the low-concentration rare earth waste liquid with amino phosphonic acid resin and / or regenerated amino phosphonic acid resin obtained in step d) to perform a resin adsorption reaction, so that rare earth ions in the waste liquid are adsorbed onto the resin to obtain a rare earth-rich resin and an adsorbed liquid; then contacting the rare earth-rich resin with a newly prepared low-titanium solution and / or a second-stage desorption liquid obtained in step c) to perform a first-stage desorption reaction, so that the rare earth ions on the rare earth-rich resin are separated from the resin to obtain a rare earth-rich solution and a first-stage desorption resin; further contacting the first-stage desorption resin with a newly prepared high-titanium solution and / or a regenerated high-titanium solution obtained in step e) to perform a second-stage desorption reaction, so that the remaining rare earth ions on the first-stage desorption resin are separated from the resin to obtain a second-stage desorption liquid and a titanium-rich resin; then contacting the titanium-rich resin with a hydrogen peroxide hydrochloric acid mixed solution to perform a resin regeneration reaction, so that titanium ions on the resin form a complex with hydrogen peroxide and are eluted into an aqueous solution to obtain regenerated amino phosphonic acid resin and a titanium complex solution; finally, aging and decomposing the titanium complex solution at a certain temperature to release oxygen, so that most of the hydrogen peroxide and the titanium-hydrogen peroxide complex are decomposed, and a regenerated high-titanium solution is obtained.

[0039] In the application, the low-concentration rare earth waste liquid is first contacted with the amino phosphonic acid resin to perform a resin adsorption reaction, and a rare earth-rich resin and an adsorbed liquid are obtained.

[0040] In the application, the concentration of the rare earth ions in the low-concentration rare earth waste liquid is preferably ≤1 g / L; and the amount of the amino phosphonic acid resin is preferably 20 to 60 times the total mass of the rare earth in the low-concentration rare earth waste liquid.

[0041] The application has no special limitation on the source of the amino phosphonic acid resin, and a commercially available product known to those skilled in the art can be used. At present, the amino phosphonic acid resin adsorption of rare earth is widely used, and the innovation of the application lies in solving the problem of difficult desorption of rare earth. For example, the prior art generally uses a 6 mol / L hydrochloric acid solution for desorption, but in fact, the desorption rate of rare earth is only about 20% when using a 6 mol / L hydrochloric acid solution for desorption. However, the application uses titanium ions with stronger adsorption capacity on the amino phosphonic acid resin to desorb rare earth, so that the desorption rate can reach more than 90% without relying on the concentration of hydrochloric acid in the desorption liquid. Then, the titanium ions are desorbed by using a hydrogen peroxide hydrochloric acid mixed solution, and a small amount of hydrochloric acid is present to promote the decomposition of hydrogen peroxide. In addition, the presence of hydrochloric acid also promotes the decomposition of the titanium-hydrogen peroxide complex, which is one of the innovations of the application. Thus, the above steps a) to e) are coupled to form a complete technical solution.

[0042] In the present application, the contacting mode of the low-concentration rare earth waste solution with the amino phosphonic acid resin is preferably mixing and stirring the low-concentration rare earth waste solution with the amino phosphonic acid resin, or loading the amino phosphonic acid resin into an adsorption column and making the low-concentration rare earth waste solution flow through the column; the contacting mode in the subsequent steps is the same as that in the previous steps, and will not be described herein.

[0043] In the present application, the temperature of the resin adsorption reaction is preferably 20-35°C, more preferably 25-31°C, and the time is preferably 2-8h, more preferably 4-8h.

[0044] After obtaining the rare earth-rich resin, the present application contacts the obtained rare earth-rich resin with a low-titanium solution to perform a first desorption reaction, and obtains a rare earth-rich solution and a first desorption resin, respectively.

[0045] In the present application, the contacting mode is the same as that in the previous step, and will not be described herein.

[0046] In the present application, the concentration of titanium ions in the low-titanium solution is preferably 2-10g / L, more preferably 2.4-7g / L; either a newly prepared solution or a recycled solution can be used. In the preferred embodiment of the present application, the low-titanium solution also contains hydrogen ions, and the concentration thereof is preferably 0.5-0.8mol / L.

[0047] In the present application, the temperature of the first desorption reaction is preferably 20-35°C, more preferably 23-28°C, and the time is preferably 1-3h.

[0048] After obtaining the first desorption resin, the present application contacts the obtained first desorption resin with a high-titanium solution to perform a second desorption reaction, and obtains a second desorption solution and a titanium-rich resin, respectively.

[0049] In the present application, the contacting mode is the same as that in the previous step, and will not be described herein.

[0050] In the present application, the concentration of titanium ions in the high-titanium solution is preferably greater than 10g / L and less than or equal to 40g / L; either a newly prepared solution or a recycled solution can be used.

[0051] In the present application, the temperature of the second desorption reaction is preferably 20-35°C, more preferably 20-28°C, and the time is preferably 1-3h.

[0052] After obtaining the titanium-rich resin, the present application contacts the obtained titanium-rich resin with a mixed solution of hydrogen peroxide and hydrochloric acid to perform a resin regeneration reaction, and obtains regenerated amino phosphonic acid resin and a titanium complex solution, respectively.

[0053] In the present application, the concentration of hydrogen peroxide in the hydrogen peroxide hydrochloric acid mixed solution is preferably 10-50 g / L, and the concentration of hydrochloric acid is preferably 20-150 g / L.

[0054] In the present application, the temperature of the resin regeneration reaction is preferably 20-35℃, more preferably 22-26℃, and the time is preferably 2-6 h.

[0055] After obtaining the titanium complex solution, the obtained titanium complex solution is subjected to aging decomposition to release oxygen, and a regenerated high-titanium solution is obtained.

[0056] In the present application, the temperature of the aging decomposition is preferably 20-80℃, more preferably 60-80℃, and the time of the aging decomposition is related to the concentration of hydrochloric acid and the reaction temperature, and is preferably calculated according to the following formula:

[0057] Aging decomposition time = 36000 g·h·L -1 ·℃ / hydrochloric acid concentration / aging decomposition temperature, wherein the unit of the concentration of hydrochloric acid is g / L, the unit of the aging decomposition time is h, and the unit of the aging decomposition temperature is ℃.

[0058] In the preferred embodiment of the present application, the concentration of hydrochloric acid is 29 g / L, the aging decomposition temperature is 25.8℃, and the aging decomposition time is 48 h.

[0059] In the present application, the obtained regenerated high-titanium solution is preferably recycled as the high-titanium solution in step c), the regenerated amino phosphonic acid resin obtained in step d) is preferably recycled as the amino phosphonic acid resin in step a), and the two-stage desorption solution obtained in step c) is preferably recycled as the low-titanium solution in step b).

[0060] The technical principle adopted in the present application is as follows:

[0061] The adsorption capacity of the amino phosphonic acid resin for rare earth ions is significantly stronger than that of Fe 3+ , Al 3+ , Mg 2+ , Ca 2+ , Na + , K + , NH 4+ , etc., so that the resin can be used to selectively adsorb rare earth ions from low-concentration rare earth waste liquid with complex components; the rare earth-loaded amino phosphonic acid resin is contacted with a titanium ion solution, and Ti 4+The stronger adsorption capacity of the amino phosphonic acid resin makes the rare earth ions desorbed and enriched in the solution, and the titanium-enriched amino phosphonic acid resin is obtained; the titanium-enriched resin is contacted with an acidic solution of hydrogen peroxide, and the coordination of titanium and hydrogen peroxide is utilized to make the titanium on the resin desorbed into the solution, and the amino phosphonic acid resin is regenerated, so that it can be returned to the adsorption process for recycling. In the presence of hydrochloric acid, the peroxide has poor stability and slowly decomposes; the aging of hydrogen peroxide and the complex of titanium and hydrogen peroxide is utilized to decompose, and a titanium ion solution without hydrogen peroxide complex can be obtained; the high-titanium solution regenerated can be returned to the desorption process for use.

[0062] The present application can achieve the following beneficial effects:

[0063] The present application uses amino phosphonic acid resin to treat low-concentration rare earth waste liquid, and selectively adsorbs rare earth ions therein, and the adsorption rate of rare earth can reach 99.2%; in view of the difficulty of desorption of the rare earth-enriched amino phosphonic acid resin, the stronger adsorption capacity of titanium ions is utilized to desorb the rare earth ions, and through two-stage desorption reaction, the desorption rate of rare earth can reach 99.7%; on this basis, the present application provides a process in which the resin and titanium ions can be recycled and regenerated, that is, the coordination of titanium and hydrogen peroxide is utilized to make titanium ions into a complex and be eluted, so that the resin can be regenerated; then, in the presence of hydrochloric acid, the hydrogen peroxide complex of titanium is aged and decomposed to obtain a reusable high-titanium solution. The coupling of the overall process realizes the recycling of the amino phosphonic acid resin and titanium ions. The main reagent consumed by the present application is hydrogen peroxide, and its decomposition product is oxygen, which does not pollute the environment.

[0064] The present application provides a method for recovering rare earth from low-concentration rare earth waste liquid, comprising the following steps: a) contacting the low-concentration rare earth waste liquid with amino phosphonic acid resin to carry out resin adsorption reaction, and obtaining rare earth-enriched resin and adsorbed liquid, respectively; b) contacting the rare earth-enriched resin obtained in step a) with low-titanium solution to carry out one-stage desorption reaction, and obtaining rare earth-enriched solution and one-stage desorption resin, respectively; c) contacting the one-stage desorption resin obtained in step b) with high-titanium solution to carry out two-stage desorption reaction, and obtaining two-stage desorption liquid and titanium-enriched resin, respectively; d) contacting the titanium-enriched resin obtained in step c) with a mixed solution of hydrogen peroxide and hydrochloric acid to carry out resin regeneration reaction, and obtaining regenerated amino phosphonic acid resin and titanium complex solution, respectively; e) aging and decomposing the titanium complex solution obtained in step d) to release oxygen, and obtaining regenerated high-titanium solution. Compared with the prior art, the present application adopts specific process steps for low-concentration rare earth waste liquid, realizes overall good interaction, and based on the strengthened desorption process, the amino phosphonic acid resin is recycled for the recovery of low-concentration rare earth, which does not pollute the environment.

[0065] In order to further illustrate the present application, the following examples are used for detailed description.

[0066] Example 1

[0067] Take the rare earth concentration of 0.16 g / L extraction waste liquid 3L, with 30 g amino phosphonic acid resin (produced by Ningbo Zhengguang Resin Co., Ltd., brand D860) mixed, 60 rpm under the speed of slow stirring, room temperature 25 ℃ conditions for adsorption reaction, reaction time is 5 hours, the adsorption rate of rare earth is 91.7%.

[0068] Then the above rich rare earth resin and adsorption after liquid separation, and the resin is divided into 3 parts, respectively, 0.1L different desorption agent, and in 60 rpm under the speed of slow stirring, room temperature 26 ℃ conditions for desorption reaction, reaction time is 2 hours, the desorption rate of rare earth is shown in table 1.

[0069] Table 1

[0070] Serial number 1# 2# 3# Desorbent type 3 mol / L hydrochloric acid 6 mol / L hydrochloric acid Titanium solution (hydrochloric acid concentration 0.6 mol / L, titanium ion concentration 7 g / L) Rare earth desorption rate (%) 9.5 22.1 92.7

[0071] Example 2

[0072] Take the rare earth concentration of 0.19 g / L oxalic acid precipitation waste liquid 5L, with 40 g amino phosphonic acid resin (produced by Ningbo Zhengguang Resin Co., Ltd., brand D860) mixed, 60 rpm under the speed of slow stirring, room temperature 27 ℃ conditions for adsorption reaction. According to time interval sampling, the results of adsorption rate with time change are shown in table 2.

[0073] Table 2

[0074] Sampling time (hours) 0.5 1 2 3 4 5 6 8 Adsorption rate (%) 58.9 75.7 83.5 85.3 87.6 89.0 90.7 92.1

[0075] Then the above rich rare earth resin and adsorption after liquid separation, and the resin is divided into 4 parts, respectively, 0.1L different titanium ion concentration of low titanium solution, the hydrogen ion concentration of low titanium solution is 0.6 mol / L, and in 60 rpm under the speed of slow stirring, room temperature 28 ℃ conditions for a desorption reaction, reaction time is 3 hours, the desorption rate of rare earth is shown in table 3.

[0076] Table 3

[0077] Serial number 4# 5# 6# 7# Titanium concentration (g / L) 1 2 5 10 Rare earth desorption rate (%) 78.7 91.6 97.2 98.5

[0078] The above 4 one stage desorption resin is combined, and 0.25L of 40g / L high titanium solution is contacted, and the two stage desorption reaction is carried out at room temperature 25 ℃, 60 rpm under the speed of slow stirring, reaction time is 3 hours, the rare earth analysis rate can reach 99.7%, and the rich titanium resin is obtained.

[0079] The titanium-rich resin is then contacted with 0.1 L of a mixed solution of hydrogen peroxide and hydrochloric acid, the concentration of hydrogen peroxide is 11 g / L, the concentration of hydrochloric acid is 29 g / L, and the reaction is carried out under slow stirring at a rotation speed of 60 rpm for 6 hours; the desorption rate of titanium ions on the titanium-rich resin is 96.1%, and the obtained titanium complex solution is left to stand and age at room temperature of 21-30°C for 48 hours, and the decomposition rate of the titanium hydrogen peroxide complex can reach 96.6%.

[0080] Example 3

[0081] The reaction of treating low-concentration rare earth waste solution by using the amino phosphonic acid resin can be carried out by mixing the solution with the resin and stirring, or the resin can be loaded into a cylindrical adsorption column, and the liquid flows through the adsorption column to react.

[0082] 100 g of the amino phosphonic acid resin is loaded into the adsorption column, 5 L of 0.97 g / L rare earth waste solution is taken, and the solution is slowly flowed through the adsorption column at a linear speed of 10 cm / min to contact the solution with the resin and carry out the adsorption reaction, the reaction is carried out at room temperature of 31°C for 5 hours. The concentration of rare earth in the flowed-out adsorbed solution is determined, and compared with the initial concentration of rare earth in the waste solution, and the adsorption rate of the resin to the rare earth is calculated to be 99.2%.

[0083] 0.5 L of the two-stage desorption solution with a titanium concentration of 2.4 g / L is taken, and slowly flowed through the above-mentioned adsorption column to carry out the first-stage desorption reaction of the rare earth-rich resin, the reaction is carried out at room temperature of 28°C for 1 hour. According to the change of the concentration of rare earth in the solution, the first-stage desorption rate of rare earth is calculated to be 83.9%.

[0084] 0.5 L of the high-titanium solution with a titanium concentration of 23.7 g / L is taken, and slowly flowed through the above-mentioned adsorption column to carry out the second-stage desorption reaction of the first-stage desorption resin, the reaction is carried out at room temperature of 23°C for 2 hours. According to the change of the concentration of rare earth in the solution, the second-stage desorption rate of rare earth is calculated to be 98.2%.

[0085] 0.5 L of a mixed solution of hydrogen peroxide 50 g / L and hydrochloric acid 150 g / L is taken, and slowly flowed through the above-mentioned adsorption column to carry out the regeneration reaction of the titanium-rich resin, the reaction is carried out at room temperature of 26°C for 2 hours. The desorption rate of titanium ions on the titanium-rich resin is 97.4%, and the regenerated amino phosphonic acid resin and the titanium complex solution are obtained. The obtained titanium complex solution is equally divided into 4 parts, and left to stand and age at different temperatures for 4 hours, and the obtained results are shown in Table 4.

[0086] Table 4

[0087] Serial number 8# 9# 10# 11# Aging decomposition temperature (°C) 20 40 60 80 Titanium peroxide decomposition rate (%) 31.7 42.6 98.5 99.1

[0088] Example 4

[0089] The 200g of aminophosphonic acid resin is loaded into an adsorption column, 12L of 0.28g / L rare earth waste solution is taken and slowly flows through the adsorption column at a linear speed of 10cm / min, so that the solution contacts the resin and an adsorption reaction occurs, and the reaction is carried out at room temperature of 27℃ for 6 hours. The rare earth concentration in the effluent after adsorption is determined, and compared with the initial rare earth concentration in the waste solution, and the adsorption rate of the resin for the rare earth is calculated to be 97.1%.

[0090] 1L of low-titanium solution with a titanium concentration of 6.3g / L is taken and slowly flows through the above adsorption column to carry out a first-stage desorption reaction on the rare earth-rich resin, and the reaction is carried out at room temperature of 23℃ for 2 hours. According to the change of the rare earth concentration in the solution, the rare earth desorption rate of the first-stage desorption reaction is calculated to be 87.2%.

[0091] 1L of regenerated high-titanium solution with a titanium concentration of 10.6g / L is taken and slowly flows through the above adsorption column to carry out a second-stage desorption reaction on the first-stage desorption resin, and the reaction is carried out at room temperature of 20℃ for 1 hour. According to the change of the rare earth concentration in the solution, the rare earth desorption rate of the second-stage desorption reaction is calculated to be 97.3%.

[0092] 1L of mixed solution of hydrogen peroxide 32g / L and sulfuric acid 15g / L is taken and slowly flows through the above adsorption column to carry out a regeneration reaction on the titanium-rich resin, and the reaction is carried out at room temperature of 22℃ for 3.5 hours. The desorption rate of titanium ions on the titanium-rich resin is 96.1%, and the regenerated aminophosphonic acid resin and titanium complex solution are obtained. The obtained titanium complex solution is equally divided into 4 parts, and hydrochloric acid is added to make it age at different hydrochloric acid concentrations, and the obtained results are shown in Table 5.

[0093] Table 5

[0094] Serial number 12# 13# 14# 15# Hydrochloric acid concentration (g / L) 0 30 60 90 Titanium peroxide decomposition rate (%) 16.5 57.7 84.0 98.6

[0095] From the experimental results, after adding hydrochloric acid to the titanium complex solution, bubbles are obviously generated. For the 9# sample, 5g of sodium chloride is also added to it, and bubbles can also be seen, indicating that chloride ions in the acidic solution can promote the decomposition of hydrogen peroxide in the titanium complex solution.

[0096] The above description of disclosed embodiments enables those skilled in the art to carry out or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for recovering rare earth elements from low-concentration rare earth waste liquid, comprising the following steps: a) Low-concentration rare earth waste liquid is contacted with aminophosphonic acid resin to carry out resin adsorption reaction, and rare earth-rich resin and adsorbed liquid are obtained respectively. b) The rare earth-rich resin obtained in step a) is contacted with a low titanium solution to carry out a desorption reaction, and a rare earth-rich solution and a desorption resin are obtained respectively. c) The first-stage desorption resin obtained in step b) is contacted with a high-titanium solution to carry out a second-stage desorption reaction, and the second-stage desorption solution and titanium-rich resin are obtained respectively. d) The titanium-rich resin obtained in step c) is contacted with a mixed solution of hydrogen peroxide and hydrochloric acid to carry out a resin regeneration reaction, and regenerated aminophosphonic acid resin and titanium complex solution are obtained respectively. e) The titanium complex solution obtained in step d) is aged and decomposed to release oxygen, resulting in a regenerated high-titanium solution.

2. The method for recovering rare earth from low-concentration rare earth waste liquid according to claim 1, characterized in that, The concentration of rare earth ions in the low-concentration rare earth waste liquid mentioned in step a) is ≤1g / L; The amount of aminophosphonic acid resin used is 20 to 60 times the total mass of rare earth elements in the low-concentration rare earth waste liquid.

3. The method for recovering rare earth from low-concentration rare earth waste liquid according to claim 1, characterized in that, The method of contacting the low-concentration rare earth waste liquid with aminophosphonic acid resin in step a) is either by mixing and stirring the low-concentration rare earth waste liquid with aminophosphonic acid resin, or by loading aminophosphonic acid resin into an adsorption column and allowing the low-concentration rare earth waste liquid to flow through it.

4. The method for recovering rare earth from low-concentration rare earth waste liquid according to claim 1, characterized in that, The temperature of the resin adsorption reaction in step a) is 20℃~35℃, and the time is 2h~8h.

5. The method for recovering rare earth from low-concentration rare earth waste liquid according to claim 1, characterized in that, The titanium ion concentration in the low-titanium solution described in step b) is 2 g / L to 10 g / L; The desorption reaction is carried out at a temperature of 20℃ to 35℃ for 1 hour to 3 hours.

6. The method for recovering rare earth elements from low-concentration rare earth waste liquid according to claim 1, characterized in that, The titanium ion concentration in the high-titanium solution described in step c) is greater than 10 g / L and less than or equal to 40 g / L; The temperature of the two-stage desorption reaction is 20℃~35℃, and the time is 1h~3h.

7. The method for recovering rare earth from low-concentration rare earth waste liquid according to claim 1, characterized in that, In step d), the hydrogen peroxide concentration in the hydrogen peroxide-hydrochloric acid mixed solution is 10 g / L to 50 g / L, and the hydrochloric acid concentration is 20 g / L to 150 g / L.

8. The method for recovering rare earth from low-concentration rare earth waste liquid according to claim 1, characterized in that, The temperature of the resin regeneration reaction in step d) is 20℃~35℃, and the time is 2h~6h.

9. The method for recovering rare earth elements from low-concentration rare earth waste liquid according to claim 1, characterized in that, The aging and decomposition temperature described in step e) is 20℃~80℃, and the aging and decomposition time is calculated according to the following formula: Aging and decomposition time = 36000 g·h·L -1 •℃ / hydrochloric acid concentration / aging decomposition temperature, where the unit of hydrochloric acid concentration is g / L, the unit of aging decomposition time is h, and the unit of aging decomposition temperature is℃.

10. The method for recovering rare earth from low-concentration rare earth waste liquid according to claim 1, characterized in that, The regenerated high-titanium solution obtained in step e) is recycled as the high-titanium solution in step c). The regenerated aminophosphonic acid resin obtained in step d) is recycled as the aminophosphonic acid resin in step a). The second-stage desorption solution obtained in step c) is recycled as the low-titanium solution in step b).

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