Method for extracting and separating yttrium and neodymium in neodymium-doped yttrium aluminum garnet crystal waste by using non-aqueous phase solvent

Abstract

The invention discloses a method for extracting and separating yttrium and neodymium in neodymium-doped yttrium aluminum garnet by a non-aqueous phase solvent system. Cyanex 272 is used as an extracting agent, and a polar organic solvent such as polyethylene glycol (PEG 200) is mixed with water to obtain a high-polarity organic phase; 260 # solvent oil is used as a low-grade organic phase, and the two phases are mixed to jointly form a non-aqueous phase solvent extraction system. Under the condition of a 0.4 mol / L Cyanex 272-80 vol% PEG 200 non-aqueous phase solvent extraction system, the extraction efficiency of yttrium is as high as 97.99%, and the separation factor of yttrium and neodymium is as high as 3520. Besides, an experiment for actually extracting and separating yttrium and neodymium in the neodymium-doped yttrium aluminum garnet crystal waste is carried out under the optimal condition, the extraction efficiency of yttrium can reach 98.60%, the separation coefficient of yttrium and neodymium can reach 1010, and efficient separation of yttrium and neodymium is achieved. Therefore, the invention provides a new method and idea for efficiently separating and recycling yttrium and neodymium in the neodymium-doped yttrium aluminum garnet crystal waste.

Description

Technical Field

[0001] The invention belongs to the technical field of solvent extraction in the field of rare earth hydrometallurgy, and specifically relates to a method for extracting and separating rare earths in neodymium yttrium aluminum garnet crystal waste by using a non-aqueous solvent extraction system that uses a polar organic solvent to replace an aqueous phase in a traditional solvent extraction. Background Art

[0002] Rare earth elements are widely used in energy conservation, environmental protection, national defense, and electronic information due to their unique physical and chemical properties. Yttrium Aluminum Garnet series crystals (YAG), especially neodymium-doped yttrium aluminum garnet (Nd:YAG), have the characteristics of high hardness, high thermal conductivity, high optical quality, etc., and can maintain stable performance under high-power laser output, playing a vital role in solid laser applications. Therefore, Nd:YAG crystals have been widely used and rapidly developed in the fields of material processing, medicine, national defense security, and scientific research, and the output of Nd:YAG has been continuously expanded. Crystal materials inevitably produce a large amount of waste in the process of mechanical processing, such as waste, scraps, grinding powder, unqualified products, etc. This waste contains 55.8-56.3%wt of yttrium oxide and 0.7-1.3%wt of neodymium oxide and other valuable elements, and has extremely high recycling value. Therefore, the recovery and separation of rare earth elements yttrium and neodymium from Nd:YAG crystal waste is crucial to the sustainable development of rare earth resources. Efficient separation and purification of rare earths to obtain single high-purity rare earths is a key link in the industrial chain and an important prerequisite for high-performance applications. It is of great strategic significance to maintain my country's rare earth resource advantages, improve the dominance of the overall industrial chain, and achieve circular economy and environmental safety.

[0003] Green and efficient separation and purification of rare earths to obtain single high-purity rare earths is a key link in the industrial chain and an important prerequisite for high-performance applications. About 90% of the world's rare earth products are produced by extraction. Solvent extraction has made great progress after nearly 70 years of vigorous development, but some core technical problems have gradually been exposed from years of practical application, mainly concentrated in three aspects:

[0004] (1) The separation selectivity between medium and heavy rare earths is not high, and the separation coefficient is low; hundreds or thousands of extraction stages are required to obtain a single rare earth product;

[0005] (2) Trace impurities in the rare earth matrix cause serious emulsification, which seriously affects the quality of rare earths and has become a major problem in the industry;

[0006] (3) The extraction agent has extremely stringent requirements on pH and other conditions, causing serious pollution to the environment.

[0007] In the traditional solvent extraction system, the extractant in the organic phase is the key. Research work mainly focuses on the synthesis and application of new and efficient extractants. In addition, two or more extractants are added to the organic phase to form a synergistic extraction system; or phase modifiers are added, diluents are changed, etc. to improve the separation ability of the extraction system. However, these strategies have not yet achieved ideal results in the exploration of medium and heavy rare earth separation.

[0008] Based on the above reasons, this application is filed. Summary of the invention

[0009] Non-aqueous solvent extraction (NASX) is an extraction system that replaces most of the water in the aqueous phase with polar organic solvents (PMOSs) to form a dual organic phase. Due to the addition of polar organic solvents, the traditional aqueous phase becomes an organic-water mixed phase mainly composed of organic solvents, so it is defined as a "more polar organic phase" (MP). Correspondingly, the organic phase composed of the extractant and the diluent is called the "less polar organic phase" (LP). In the non-aqueous solvent extraction system, the addition of polar organic solvents mainly affects the extraction performance in two ways:

[0010] (1) Any measure that can eliminate the hydration of metal ions is beneficial to extraction;

[0011] (2) Change the mutual solubility, interfacial tension and mass transfer resistance of the two phases, promote interfacial phase separation, and thus reduce the loss of extractants and acids and bases. Therefore, changing the composition of the highly polar organic phase has an effect similar to changing the extractant. Using polar organic solvents to replace the aqueous phase can significantly improve the extraction efficiency. Therefore, non-aqueous solvent extraction weakens the effect of hydration on the rare earth extraction performance. It has significant advantages in improving extraction efficiency and improving the separation between rare earth elements, reducing the number of extraction stages, and reducing acid and alkali emissions in the process flow. It is a promising new technology for separating rare earths in a green and efficient manner.

[0012] The present invention aims to provide a non-aqueous solvent extraction system to improve the separation efficiency of yttrium and neodymium, and to apply the system to separate and recover yttrium and neodymium from Nd:YAG crystal waste. The extraction system uses a polar organic solvent to replace most of the water in the aqueous phase of a traditional solvent extraction system to form a high-polarity organic phase, and uses an acidic extractant, bis(2,4,4-trimethylpentyl)phosphonic acid (Cyanex 272), as a low-polarity organic phase to achieve low acid consumption.

[0013] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0014] A method for separating yttrium and neodymium from neodymium-doped yttrium aluminum garnet crystal waste by non-aqueous solvent extraction, comprising the following steps:

[0015] (1) diluting the acidic extractant with a diluent to obtain a low-polarity organic phase;

[0016] (2) dissolving a polar organic solvent in pure water according to a ratio, and mixing well to obtain a highly polar organic phase;

[0017] (3) adding a rare earth chloride solution obtained by crushing, alkali melting, water washing, acid dissolving and impurity removal of the Nd-doped yttrium aluminum garnet crystal waste to the high-polarity organic phase to obtain a high-polarity organic phase containing rare earth ions;

[0018] (4) mixing the high-polarity organic phase containing rare earth ions with the low-polarity organic phase according to a ratio, and then extracting the resulting mixed solution at 20 to 45° C. and under shaking conditions for 5 to 60 minutes; after the extraction is completed, centrifuging to obtain an yttrium-rich organic phase and a neodymium-rich raffinate;

[0019] (5) washing the yttrium-rich organic phase with an inorganic acid solution to remove a small amount of co-extracted neodymium, and then stripping the washed yttrium-rich organic phase with the inorganic acid solution to obtain a high-purity yttrium solution;

[0020] The neodymium in the raffinate is extracted using Cyanex 272, and then stripped using the inorganic acid solution to obtain a high-purity neodymium solution; that is, the separation of yttrium and neodymium is completed.

[0021] Furthermore, in the above technical solution, in a preferred embodiment of the present invention, the diluent in step (1) is No. 260 solvent oil.

[0022] Furthermore, in the above technical solution, in a preferred embodiment of the present invention, the acidic extractant is bis(2,4,4-trimethylpentyl)phosphonic acid (Cyanex 272).

[0023] Furthermore, in the above technical solution, the concentration of Cyanex 272 in the low-grade organic phase in step (1) does not exceed 1 mol / L, preferably 0.4 mol / L.

[0024] Furthermore, in the above technical solution, the polar organic solvent in step (2) includes at least one of polyethylene glycol 200 (PEG200), ethylene glycol (EG) or polyethylene glycol 300 (PEG 300); preferably PEG 200.

[0025] Furthermore, in the above technical solution, the volume fraction of the polar organic solvent in the highly polar organic phase in step (2) is less than 100 vol%, preferably 80 vol%.

[0026] Furthermore, in the above technical solution, in the high-polarity organic phase containing rare earth ions in step (3), the concentration of rare earth ions does not exceed 0.05 mol / L, and is preferably 0.025 mol / L.

[0027] Furthermore, in the above technical solution, the volume ratio of the high-polarity organic phase containing rare earth ions to the low-polarity organic phase in step (4) is 1:1.

[0028] Furthermore, in the above technical solution, the extraction time in step (4) is preferably 30 minutes; and the extraction temperature is preferably 25°C.

[0029] Furthermore, in the above technical solution, the oscillation speed in step (4) is 100-500 r / min, preferably 300 r / min.

[0030] Furthermore, in the above technical solution, the inorganic acid solution in step (5) is any one of a dilute hydrochloric acid solution, a dilute nitric acid solution or a dilute sulfuric acid solution.

[0031] Furthermore, in the above technical solution, the concentration of the inorganic acid solution in step (5) is 0.01 to 4 mol / L, preferably 0.01 mol / L.

[0032] Furthermore, in the above technical solution, the inorganic acid solution used in the stripping in step (5) is preferably a dilute hydrochloric acid solution.

[0033] Furthermore, in the above technical solution, the concentration of the dilute hydrochloric acid solution used in step (5) to wash the neodymium in the yttrium-rich organic phase is 0.01 mol / L.

[0034] Furthermore, in the above technical solution, the concentration of the dilute hydrochloric acid solution used for stripping the yttrium in the yttrium-rich organic phase in step (5) is 1 mol / L.

[0035] Compared with the prior art, the advantages of the present invention are:

[0036] The present invention adopts a polar organic solvent to replace part of the water in the aqueous phase of the traditional solvent extraction system to form a high-polarity organic phase, and a non-aqueous phase extraction system composed of a low-polarity organic phase composed of an extractant diluted by a diluent. Compared with the traditional solvent extraction system, the system increases the contact ion pairs formed between rare earth ions and chloride ions by adding a polar organic solvent with a lower dielectric constant to replace the water molecules in the traditional aqueous phase, reduces the hydration between water molecules and rare earth ions, improves the stability of the extraction complex, and thus improves the extraction and separation performance. Different rare earth ions have different solvation effects in different polar organic solvents, and selecting a suitable polar organic solvent is very important for achieving efficient extraction and separation of rare earth ions. In addition, the present invention selects the acidic extractant Cyanex 272, which has the advantages of high selectivity, excellent stability, low acidity required for the extraction process, and low stripping acid consumption, which can reduce the harm caused by the extraction process to the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0038] Figure 1 The figure shows the effect of different types of polar organic solvents on the extraction and separation of yttrium and neodymium in Example 1 of the present invention.

[0039] Figure 2 The figure shows the effect of the volume ratio of PEG 200 in the highly polar organic phase on the extraction and separation of yttrium and neodymium in Example 2 of the present invention.

[0040] Figure 3 The figure shows the effect of the non-aqueous solvent extraction system on the extraction and separation of yttrium and neodymium at different temperatures in Example 3 of the present invention.

[0041] Figure 4 The figure shows the effect of the non-aqueous solvent extraction system on the extraction and separation of yttrium and neodymium at different extraction times in Example 4 of the present invention.

[0042] Figure 5 The figure shows the effect of the non-aqueous solvent extraction system on the extraction and separation of yttrium and neodymium at different phase ratios in Example 5 of the present invention.

[0043] Figure 6 The figure shows the effect of the concentration of Cyanex 272 in the low polarity organic phase on the extraction and separation of yttrium and neodymium in Example 6 of the present invention.

[0044] Figure 7The figure shows the washing effect of different inorganic acid concentrations on neodymium in the yttrium-rich organic phase in Example 7 of the present invention.

[0045] Figure 8 The stripping effect of different inorganic acid concentrations on yttrium in the yttrium-rich organic phase in Example 8 of the present invention is shown.

[0046] Fig. 9 This is a method for extracting and separating yttrium and neodymium from waste generated by a certain enterprise in Chengdu processing neodymium-doped yttrium aluminum garnet crystals using a non-aqueous solvent in Example 9 of the present invention.

[0047] Fig.10 The present invention is a specific process flow chart. DETAILED DESCRIPTION

[0048] The present invention provides a method for extracting and separating yttrium and neodymium from Nd:YAG crystal waste using a non-aqueous solvent system. The present invention uses a polar organic solvent such as polyethylene glycol to mix with water to obtain a high polarity (MP) organic phase to replace the traditional aqueous phase, and uses an acidic extractant di(2,4,4-trimethylpentyl)phosphonic acid (Cyanex 272) diluted with No. 260 solvent oil as a low polarity (LP) organic phase. The two phases are mixed to form a non-aqueous solvent extraction system to extract and separate yttrium and neodymium. By using a non-aqueous solvent extraction system of 0.4 mol / L Cyanex 272-80 vol% PEG 200, the extraction efficiency of yttrium reaches 97.99%, and the separation factor of yttrium and neodymium is as high as 3520. In addition, under the optimal conditions, the actual extraction and separation of yttrium and neodymium in the Nd-doped YAG crystal waste material was carried out, and the extraction efficiency of yttrium can reach 98.60%, and the separation coefficient of yttrium and neodymium can reach 1010, realizing the efficient separation of yttrium and neodymium. Therefore, the present invention provides a new method and idea for the efficient separation and recovery of yttrium and neodymium in the Nd-doped YAG crystal waste material.

[0049] Compared with traditional solvent extraction, this system adds a polar organic solvent with a lower dielectric constant to replace the water molecules in the traditional aqueous phase, so that the contact ion pairs formed between the rare earth ions and the chloride ions are increased, the hydration between the water molecules and the rare earth ions is reduced, and the stability of the extraction complex is improved, thereby improving the extraction and separation performance. In addition, the present invention uses the acidic extractant Cyanex 272, which has the advantages of high selectivity, excellent stability, low acidity required for the extraction process, and low back extraction acid consumption, which can reduce the harm caused by the extraction process to the environment. Therefore, the present invention is a rare earth extraction process with high extraction and separation efficiency and green environmental protection.

[0050] The present invention is further described in detail below through implementation cases. To further understand the present invention, the preferred embodiments of the present invention are described below in conjunction with examples, but it should be understood that these descriptions are only to further illustrate the features and advantages of the present invention rather than the limitations of the patent requirements of the present invention.

[0051] The test methods shown in the following examples are conventional methods unless otherwise specified; the reagents and materials described are commercially available unless otherwise specified.

[0052] In the process of the present invention, after the extraction operation and the stripping operation, the rare earth concentrations in the raffinate and the stripping solution are measured by ICP-OES.

[0053] The calculation formulas for rare earth distribution ratio (D), extraction efficiency (%E), separation coefficient between rare earth ions (β) and stripping efficiency of each rare earth ion (%Strip) are as follows:

[0054]

[0055] Among them, C0 and C MP are the initial concentration and equilibrium concentration of rare earth ions in the highly polar organic phase; V MP and V LP are the volumes of the high polarity organic phase and the low polarity organic phase, respectively; D A and D B They represent the distribution ratio of rare earth ions A and B respectively; Cs is the concentration of rare earth ions in the stripping solution.

[0056] Example 1

[0057] Effects of different types of polar organic solvents on the extraction and separation of yttrium and neodymium, the method comprising the following steps:

[0058] The extractant Cyanex 272 diluted to 0.4 mol / L with No. 260 solvent oil is used as the low-polarity organic phase;

[0059] 2 ml of water was taken and mixed with 8 ml of PEG 200, EG and PEG 300 respectively to prepare a high polar organic phase containing 80 vol% of polar organic solvent, and 0.0897 g of neodymium chloride hexahydrate and 0.0758 g of yttrium chloride hexahydrate were weighed and dissolved in the high polar organic phase by heating and stirring to prepare a mixed rare earth solution containing 0.025 mol / L neodymium and 0.025 mol / L yttrium;

[0060] The above-mentioned high-polarity organic phase and low-polarity organic phase are mixed in a 1:1 ratio, and extracted in a constant temperature water bath oscillator. The extraction temperature is 25°C, the oscillator speed is 300r / min, and the oscillation time is 30min. After the extraction is completed, it is centrifuged at a speed of 2500r / min for 15min and then transferred into a 60ml separatory funnel for standing and stratification to obtain the yttrium-rich organic phase and the raffinate. The ion concentration in the raffinate is collected and determined using ICP-OES, and the extraction efficiency and separation coefficient of yttrium and neodymium are calculated. The yttrium-rich organic phase is then washed with HCl and stripped to obtain a high-purity yttrium chloride solution. The effects of different types of polar organic solvents on the extraction of yttrium and neodymium are as follows. Figure 1 As shown: According to calculations, compared with extraction from pure water, the addition of polar organic solvents can significantly improve the extraction efficiency of rare earths. The non-aqueous phase system composed of PEG 200 can increase the extraction efficiency of yttrium from 61% to 98%, and the separation coefficient of yttrium and neodymium is as high as 3760. Comprehensively comparing the extraction efficiency and separation coefficient, PEG 200 is the best polar organic solvent. Therefore, PEG200 is selected as the polar organic solvent for constructing the best non-aqueous phase solvent extraction system for separating yttrium and neodymium.

[0061] Example 2

[0062] Effect of the volume ratio of PEG 200 in a highly polar organic phase on the extraction and separation of yttrium and neodymium, the method comprising the steps of:

[0063] The extractant Cyanex 272 diluted to 0.4 mol / L with No. 260 solvent oil is a low polar phase;

[0064] Mix different proportions of water and different proportions of PEG 200 to prepare 10 ml of a high polarity organic phase containing 0 to 100 vol% PEG200, weigh 0.0897 g of neodymium chloride hexahydrate and 0.0758 g of yttrium chloride hexahydrate, heat and stir, dissolve in the high polarity organic phase to prepare a mixed rare earth solution containing 0.025 mol / L neodymium and 0.025 mol / L yttrium;

[0065] The high-polarity organic phase with different PEG 200 contents was mixed with the low-polarity organic phase in a ratio of 1:1, and extracted in a constant temperature water bath oscillator. The extraction temperature was 25°C, the oscillator speed was 300 r / min, and the oscillation time was 30 min. After the extraction was completed, it was centrifuged at 2500 r / min for 15 min and then transferred into a 60 ml separatory funnel for standing and stratification to obtain the yttrium-rich organic phase and the raffinate. The ion concentration in the raffinate was collected and determined using ICP-OES, and the extraction efficiency and separation coefficient of yttrium and neodymium were calculated. The yttrium-rich organic phase was then washed with HCl and stripped to obtain a high-purity yttrium chloride solution. The effect of the volume ratio of PEG 200 in the high-polarity organic phase on the extraction and separation of yttrium and neodymium is as follows. Figure 2 As shown: According to calculations, as the volume ratio of PEG 200 in the high-polarity organic phase increases, the extraction efficiency of yttrium and neodymium continues to increase. When the volume ratio is 80vol%, the extraction efficiency of yttrium reaches the maximum (97.86%), and the separation coefficient of yttrium and neodymium also reaches the maximum (3760). Then, as the proportion of PEG 200 continues to increase, the viscosity of the system increases, which causes the speed of the ship to slow down during the extraction process, and the extraction efficiency and separation ratio both decrease. Therefore, the optimal volume ratio of PEG 200 in the high-polarity organic phase is 80vol%.

[0066] Example 3

[0067] The effect of a non-aqueous solvent extraction system on the extraction and separation of yttrium and neodymium at different temperatures, the method comprising the following steps:

[0068] The extractant Cyanex 272 diluted to 0.4 mol / L with No. 260 solvent oil is used as the low-polarity organic phase;

[0069] 2 ml of water and 8 ml of PEG 200 were mixed evenly to prepare 10 ml of a highly polar organic phase containing 80 vol% PEG 200, and 0.0897 g of neodymium chloride hexahydrate and 0.0758 g of yttrium chloride hexahydrate were weighed and dissolved in the highly polar organic phase by heating and stirring to prepare a mixed rare earth solution containing 0.025 mol / L neodymium and 0.025 mol / L yttrium;

[0070] The above-mentioned high-polarity organic phase and low-polarity organic phase were mixed in a ratio of 1:1, and extracted in a constant temperature water bath oscillator. The extraction temperatures were 20°C, 25°C, 30°C, 35°C, 40°C, and 45°C, respectively. The oscillator speed was 300r / min, and the oscillation time was 30min. After the extraction was completed, the mixture was centrifuged at 2500r / min for 15min and then transferred into a 60ml separatory funnel for standing and stratification to obtain the yttrium-rich organic phase and the raffinate. The ion concentration in the raffinate was collected and determined using ICP-OES, and the extraction efficiency and separation coefficient of yttrium and neodymium were calculated. The yttrium-rich organic phase was then washed with HCl and stripped to obtain a high-purity yttrium chloride solution. The effect of the non-aqueous solvent extraction system on the extraction and separation of yttrium and neodymium at different temperatures is shown in Figure 2. Figure 3 As shown: After calculation, at different temperatures, the extraction efficiency of yttrium is 98.01%, 97.96%, 97.13%, 95.42% and 95.40% respectively. The temperature has little effect on the extraction and separation of yttrium and neodymium. We choose 25℃ for the extraction reaction.

[0071] Example 4

[0072] The effect of a non-aqueous solvent extraction system on the extraction and separation of yttrium and neodymium at different extraction times, the method comprising the following steps:

[0073] The extractant Cyanex 272 diluted to 0.4 mol / L with No. 260 solvent oil is used as the low-polarity organic phase;

[0074] 2 ml of water and 8 ml of PEG 200 were mixed evenly to prepare 10 ml of a highly polar organic phase containing 80 vol% PEG 200, and 0.0897 g of neodymium chloride hexahydrate and 0.0758 g of yttrium chloride hexahydrate were weighed and dissolved in the highly polar organic phase by heating and stirring to prepare a mixed rare earth solution containing 0.025 mol / L neodymium and 0.025 mol / L yttrium;

[0075] The above-mentioned high-polarity organic phase and low-polarity organic phase were mixed in a 1:1 ratio, and oscillated in a constant temperature water bath oscillator for different times (5min to 60min) for extraction. The extraction temperature was 25°C and the oscillator speed was 300r / min. After the extraction was completed, it was centrifuged at a speed of 2500r / min for 15min and then transferred into a 60ml separatory funnel for standing and stratification to obtain the yttrium-rich organic phase and the raffinate. The ion concentration in the raffinate was collected and determined using ICP-OES, and the extraction efficiency and separation coefficient of yttrium and neodymium were calculated. The yttrium-rich organic phase was then washed with HCl and stripped to obtain a high-purity yttrium chloride solution. The effect of the non-aqueous solvent extraction system on the extraction and separation of yttrium and neodymium at different extraction times is shown in the figure. Figure 4 As shown in the figure, the extraction efficiency of yttrium and neodymium increases with the increase of oscillation time. When the extraction time is 30 minutes, the extraction efficiency of yttrium reaches the maximum (98.31%), and the extraction efficiency remains basically unchanged when the extraction time is further increased. Therefore, in order to ensure sufficient extraction, we choose 30 minutes as the optimal extraction time.

[0076] Example 5

[0077] The effect of a non-aqueous solvent extraction system on the extraction and separation of yttrium and neodymium at different phases, the method comprising the following steps:

[0078] The extractant Cyanex 272 diluted to 0.4 mol / L with No. 260 solvent oil is used as the low-polarity organic phase;

[0079] 2 ml of water and 8 ml of PEG 200 were mixed evenly to prepare 10 ml of a highly polar organic phase containing 80 vol% PEG 200, and 0.0897 g of neodymium chloride hexahydrate and 0.0758 g of yttrium chloride hexahydrate were weighed and dissolved in the highly polar organic phase by heating and stirring to prepare a mixed rare earth solution containing 0.025 mol / L neodymium and 0.025 mol / L yttrium;

[0080] The above-mentioned high-polarity organic phase and low-polarity organic phase are mixed in different ratios (5:1 to 1:5), and extracted in a constant temperature water bath oscillator. The extraction temperature is 25°C, the oscillator speed is 300r / min, and the oscillation time is 30min. After the extraction is completed, it is centrifuged at a speed of 2500r / min for 15min and then transferred into a 60ml separatory funnel for standing and stratification to obtain the yttrium-rich organic phase and the raffinate. The ion concentration in the raffinate is collected and determined using ICP-OES, and the extraction efficiency and separation coefficient of yttrium and neodymium are calculated. The yttrium-rich organic phase is then washed with HCl and stripped to obtain a high-purity yttrium chloride solution. The effect of the non-aqueous solvent extraction system on the extraction and separation of yttrium and neodymium at different ratios is as follows. Figure 5 As shown: The extraction efficiency of yttrium is V LP :V MP The maximum value (97.87%) is reached when the ratio is 1:1, and the separation factor is also the maximum (4190), so V is selected. LP :V MP The optimal ratio of 1:1 is for the extraction and separation of yttrium and neodymium.

[0081] Example 6

[0082] Effect of the concentration of Cyanex 272 in a low-polarity organic phase on the extraction and separation of yttrium and neodymium, the method comprising the following steps:

[0083] The extractant Cyanex 272 diluted to 0-1 mol / L with No. 260 solvent oil is used as the low polarity organic phase;

[0084] 2 ml of water and 8 ml of PEG 200 were mixed evenly to prepare 10 ml of a highly polar organic phase containing 80 vol% PEG 200, and 0.0897 g of neodymium chloride hexahydrate and 0.0758 g of yttrium chloride hexahydrate were weighed and dissolved in the highly polar organic phase by heating and stirring to prepare a mixed rare earth solution containing 0.025 mol / L neodymium and 0.025 mol / L yttrium;

[0085] The above-mentioned high-polarity organic phase and low-polarity organic phase were mixed in a ratio of 1:1, and extracted in a constant temperature water bath oscillator. The extraction temperature was 25°C, the oscillator speed was 300r / min, and the oscillation time was 30min. After the extraction was completed, it was centrifuged at a speed of 2500r / min for 15min and then transferred into a 60ml separatory funnel for standing and stratification to obtain the yttrium-rich organic phase and the raffinate. The ion concentration in the raffinate was collected and determined using ICP-OES, and the extraction efficiency and separation coefficient of yttrium and neodymium were calculated. The yttrium-rich organic phase was then washed with HCl and stripped to obtain a high-purity yttrium chloride solution. The effect of the concentration of Cyanex 272 in the low-polarity organic phase on the extraction and separation of yttrium and neodymium is as follows: Figure 6As shown in the figure: the extraction efficiency of yttrium increases with the increase of Cyanex 272 concentration. When the concentration of Cyanex 272 is 0.4 mol / L, the extraction efficiency of yttrium reaches 97.99%, and the separation coefficient of yttrium and neodymium reaches the maximum (3520). When the concentration of Cyanex 272 continues to increase, the extraction efficiency of yttrium basically does not change, while the extraction efficiency of neodymium continues to increase, and the separation coefficient of yttrium and neodymium continues to decrease. Therefore, the Cyanex 272 concentration for the best separation of yttrium and neodymium is 0.4 mol / L.

[0086] Example 7

[0087] The washing effect of different inorganic acid concentrations on neodymium in a yttrium-rich organic phase, the method comprising the following steps:

[0088] The extractant Cyanex 272 diluted to 0.4 mol / L with No. 260 solvent oil is used as the low-polarity organic phase;

[0089] 2 ml of water and 8 ml of PEG 200 were mixed evenly to prepare 10 ml of a highly polar organic phase containing 80 vol% PEG 200, and 0.0897 g of neodymium chloride hexahydrate and 0.0758 g of yttrium chloride hexahydrate were weighed and dissolved in the highly polar organic phase by heating and stirring to prepare a mixed rare earth solution containing 0.025 mol / L neodymium and 0.025 mol / L yttrium;

[0090] The above-mentioned high-polarity organic phase and low-polarity organic phase are mixed in a ratio of 1:1, and extracted in a constant temperature water bath oscillator. The extraction temperature is 25°C, the oscillator speed is 300r / min, and the oscillation time is 30min. After the extraction is completed, it is centrifuged at a speed of 2500r / min for 15min in a centrifuge and then transferred into a 60ml separatory funnel for static stratification to obtain yttrium-rich organic phase and neodymium-rich raffinate. The ion concentration in the raffinate is collected and determined by ICP-OES, and the extraction efficiency and separation coefficient of yttrium and neodymium are calculated. The yttrium-rich organic phase is washed with 0.01-4mol / L HCl, HNO3, and H2SO4, respectively. The concentration of neodymium after washing is determined by ICP-OES, and the washing effect of neodymium is calculated. The washing effect of different inorganic acid concentrations on neodymium in the loaded organic phase is as follows. Figure 7 As shown: According to calculation, in this embodiment, about 1.37% of neodymium is extracted into the organic phase. HCl, HNO3 and H2SO4 can all effectively wash out neodymium from the LP phase, and the effect is not much different. We choose HCl, which is safer and more economical to minimize the impact on the environment. Using 0.01mol / L HCl can quantitatively wash out 96.31% of neodymium from the yttrium-rich organic phase, so the inorganic acid for washing neodymium is preferably 0.01mol / L HCl.

[0091] Example 8

[0092] The stripping effect of different inorganic acid concentrations on yttrium in a yttrium-rich organic phase, the method comprising the following steps:

[0093] The extractant Cyanex 272 diluted to 0.4 mol / L with No. 260 solvent oil is used as the low-polarity organic phase;

[0094] 2 ml of water and 8 ml of PEG 200 were mixed evenly to prepare 10 ml of a highly polar organic phase containing 80 vol% PEG 200, and 0.0897 g of neodymium chloride hexahydrate and 0.0758 g of yttrium chloride hexahydrate were weighed and dissolved in the highly polar organic phase by heating and stirring to prepare a mixed rare earth solution containing 0.025 mol / L neodymium and 0.025 mol / L yttrium;

[0095] The above-mentioned high-polarity organic phase and low-polarity organic phase are mixed in a ratio of 1:1, and extracted in a constant temperature water bath oscillator. The extraction temperature is 25°C, the oscillator speed is 300r / min, and the oscillation time is 30min. After the extraction is completed, it is centrifuged at a speed of 2500r / min for 15min in a centrifuge and then transferred into a 60ml separatory funnel for static stratification to obtain yttrium-rich organic phase and neodymium-rich raffinate. The ion concentration in the raffinate is collected and determined by ICP-OES, and the extraction efficiency and separation coefficient of yttrium and neodymium are calculated. The yttrium-rich organic phase is then washed with 0.01mol / L HCl to remove the co-extracted neodymium, and then stripped with 0.01-4mol / L HCl, HNO3, and H2SO4. The concentration of yttrium after stripping is determined by ICP-OES, and the stripping efficiency is calculated. The stripping effect of different inorganic acid concentrations on yttrium in the yttrium-rich organic phase is as follows. Figure 8 As shown: According to calculation, in this embodiment, about 97.99% of yttrium is extracted into the organic phase. HCl, HNO3 and H2SO4 can effectively strip yttrium from the LP phase, and the stripping efficiency is not much different. We choose HCl, which is safer and more economical to minimize the impact on the environment. At the same time, the stripping efficiency increases with the increase of HCl concentration, and remains basically unchanged after 1mol / L. Using 1mol / L HCl to strip yttrium, the stripping efficiency reaches 95.88%, and a high-purity yttrium chloride solution can be obtained. Therefore, the inorganic acid for stripping yttrium is preferably 1mol / L HCl.

[0096] Example 9

[0097] A method for extracting and separating yttrium and neodymium from waste generated by a certain enterprise in Chengdu processing neodymium-doped yttrium aluminum garnet crystals using a non-aqueous solvent in this embodiment comprises the following steps:

[0098] The extractant Cyanex 272 diluted to 0.4 mol / L with No. 260 solvent oil is used as the low-polarity organic phase;

[0099] According to the method of recovering rare earth from Nd-doped yttrium aluminum garnet crystals [J]. Journal of the Chinese Rare Earth Society, 2017, Vol. 35 (2): 225-230, a mixed rare earth solution containing 1.778 g / L yttrium and 0.027 g / L neodymium is obtained by a series of processes including crushing, alkali melting, water washing, acid dissolution, and impurity removal of Nd-doped yttrium aluminum garnet crystal waste, and 80 vol% PEG 200 is added as a high polar organic phase;

[0100] The above-mentioned high-polarity organic phase and low-polarity organic phase were mixed in a ratio of 1:1, and extracted in a constant temperature water bath oscillator. The extraction temperature was 25°C, the oscillator speed was 300r / min, and the oscillation time was 30min. After the extraction was completed, the mixture was centrifuged at 2500r / min for 15min and then transferred into a separatory funnel for standing and stratification to obtain yttrium-rich organic phase and neodymium-rich raffinate. The ion concentration in the raffinate was collected and determined using ICP-OES, and the extraction efficiency and separation coefficient of yttrium and neodymium were calculated. The yttrium-rich organic phase was then washed with 0.01mol / L HCl to remove the co-extracted neodymium, and then stripped with 1mol / L HCl to obtain a high-purity yttrium chloride solution. Three parallel experiments were carried out to obtain a method for extracting and separating yttrium and neodymium from neodymium-doped yttrium aluminum garnet crystal waste by non-aqueous solvent. The results are shown in the figure. Fig. 9 As shown: After calculation, in this embodiment, the extraction efficiency of yttrium reaches 98.46%, 98.58%, and 98.60%, respectively, and the separation coefficients of yttrium and neodymium reach 991, 1050, and 1010, respectively.

Claims

1. A method for separating yttrium and neodymium from neodymium-doped yttrium aluminum garnet crystal waste by non-aqueous solvent extraction, characterized in that: The following steps are involved: (1) diluting the acidic extractant with a diluent to obtain a low-polarity organic phase; (2) dissolving a polar organic solvent in pure water according to a ratio, and mixing well to obtain a highly polar organic phase; (3) adding a rare earth chloride solution obtained by crushing, alkali melting, water washing, acid dissolving and impurity removal of the Nd-doped yttrium aluminum garnet crystal waste to the high-polarity organic phase to obtain a high-polarity organic phase containing rare earth ions; (4) mixing the high-polarity organic phase containing rare earth ions with the low-polarity organic phase according to a ratio, and then extracting the resulting mixed solution at 20 to 45° C. and under shaking conditions for 5 to 60 minutes; after the extraction is completed, centrifuging to obtain an yttrium-rich organic phase and a neodymium-rich raffinate; (5) washing the yttrium-rich organic phase with an inorganic acid solution to remove a small amount of co-extracted neodymium, and then stripping the washed yttrium-rich organic phase with the inorganic acid solution to obtain a high-purity yttrium solution; The neodymium in the raffinate is extracted using Cyanex 272, and then stripped using the inorganic acid solution to obtain a high-purity neodymium solution; that is, the separation of yttrium and neodymium is completed.

2. The method according to claim 1, characterized in that: The acidic extractant is bis(2,4,4-trimethylpentyl)phosphonic acid.

3. The method according to claim 1, characterized in that: The concentration of Cyanex272 in the low-grade organic phase in step (1) does not exceed 1 mol / L.

4. The method according to claim 1, characterized in that: The polar organic solvent in step (2) includes at least one of polyethylene glycol 200, ethylene glycol or polyethylene glycol 300.

5. The method according to claim 1, characterized in that: The volume fraction of the polar organic solvent in the highly polar organic phase in step (2) is 80 vol%.

6. The method according to claim 1, characterized in that: The volume ratio of the high-polarity organic phase containing rare earth ions to the low-polarity organic phase in step (4) is 1:

1.

7. The method according to claim 1, characterized in that: The extraction time of step (4) is 30 minutes; the extraction temperature is 25°C.

8. The method according to claim 1, characterized in that: The inorganic acid solution in step (5) is any one of dilute hydrochloric acid solution, dilute nitric acid solution or dilute sulfuric acid solution.

9. The method according to claim 1, characterized in that: The concentration of the inorganic acid solution in step (5) is 0.01 to 4 mol / L.

10. The method according to claim 1, characterized in that: In step (5), the concentration of the dilute hydrochloric acid used to wash the neodymium in the yttrium-rich organic phase is 0.01 mol / L, and the concentration of the dilute hydrochloric acid solution used to strip the yttrium in the yttrium-rich organic phase is 1 mol / L.

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