A method for separating yttrium and neodymium in neodymium-doped yttrium aluminum garnet crystal waste by non-aqueous phase solvent extraction

Abstract

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

Description

Technical Field

[0001] This invention belongs to the field of solvent extraction technology in rare earth hydrometallurgy, specifically relating to a method for extracting and separating rare earth elements from Nd:yttrium aluminum garnet crystal waste using a polar organic solvent instead of a non-aqueous solvent extraction system with an aqueous phase in traditional solvent extraction. Background Technology

[0002] Rare earth elements, due to their unique physical and chemical properties, are widely used in energy conservation, environmental protection, national defense, and electronic information fields. Yttrium aluminum garnet (YAG) crystals, especially neodymium-doped yttrium aluminum garnet (Nd:YAG), possess high hardness, high thermal conductivity, and high optical quality, maintaining stable performance under high-power laser output and playing a crucial role in solid-state laser applications. Therefore, Nd:YAG crystals have seen widespread application and rapid development in materials processing, medicine, national defense, and scientific research, with Nd:YAG production continuously expanding. During the machining of crystal materials, a large amount of waste is inevitably generated, such as scrap, offcuts, grinding powder, and defective products. This waste contains 55.8–56.3% wt of yttrium oxide and 0.7–1.3% wt of neodymium oxide, possessing extremely high recycling value. Therefore, the recovery and separation of rare earth elements yttrium and neodymium from Nd:YAG crystal waste is crucial for the sustainable development of rare earth resources. Efficient separation and purification of rare earth elements to obtain single high-purity rare earths is a key link in the industrial chain and an important prerequisite for achieving high-performance applications. It is of significant strategic importance for maintaining my country's rare earth resource advantage, enhancing the overall control of the industrial chain, and achieving a circular economy and environmental security.

[0003] The green and efficient separation and purification of rare earth elements to obtain single high-purity rare earth elements is a key link in the industrial chain and an important prerequisite for achieving high-performance applications. Globally, approximately 90% of rare earth products are produced by extraction methods. Solvent extraction has made significant progress over the past 70 years, but years of practical application have gradually revealed some core technical challenges, mainly concentrated in three aspects:

[0004] (1) The separation selectivity between medium and heavy rare earth elements 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 severe emulsification, which seriously affects the quality of rare earth and has become a major problem in the industry.

[0006] (3) The extractant has extremely strict requirements for pH and other conditions, which causes serious environmental pollution.

[0007] In traditional solvent extraction systems, the extractant in the organic phase is crucial. Research has primarily focused on the synthesis and application of novel, highly efficient extractants. Furthermore, methods such as adding two or more extractants to the organic phase to form a synergistic extraction system, or adding phase modifiers and altering diluents, have been employed to improve the separation capability of the extraction system. However, these strategies have not yet yielded ideal results for the separation of medium and heavy rare earth elements.

[0008] Based on the above reasons, this application is hereby submitted. Summary of the Invention

[0009] Non-aqueous solvent extraction (NASX) is an extraction system that uses polar molecular organic solvents (PMOSs) to replace most of the water in the aqueous phase, forming a two-phase organic system. Due to the addition of polar organic solvents, the traditional aqueous phase becomes an organic-water mixture mainly composed of organic solvents, and is therefore defined as a "more polar organic phase" (MP). Correspondingly, the organic phase composed of the extractant and diluent is called a "less polar organic phase" (LP). In non-aqueous solvent extraction systems, the addition of polar organic solvents mainly affects extraction performance in two ways:

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

[0011] (2) By altering the mutual solubility, interfacial tension, and mass transfer resistance of the two phases, interfacial phase separation is promoted, thereby reducing the loss of extractant and acids / bases. Therefore, changing the composition of the highly polar organic phase has an effect similar to changing the extractant; replacing the aqueous phase with a polar organic solvent can significantly improve extraction efficiency. Thus, non-aqueous solvent extraction weakens the impact of hydration on rare earth extraction performance. It offers significant advantages in improving extraction efficiency, enhancing the separation of rare earth elements, reducing the number of extraction stages, and minimizing acid / base emissions during the process, making it a promising new green and efficient technology for rare earth separation.

[0012] The purpose of this invention is to provide a non-aqueous solvent extraction system to improve the separation efficiency of yttrium and neodymium, and to apply it to the separation and recovery of yttrium and neodymium from Nd:YAG crystal waste. This extraction system uses a polar organic solvent to replace most of the water in the aqueous phase of traditional solvent extraction systems, forming a highly polar organic phase, and uses the acidic extractant bis(2,4,4-trimethylpentyl)phosphonic acid (Cyanex 272) as a low-polarity organic phase to achieve low acid consumption.

[0013] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

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

[0015] (1) The acidic extractant is diluted with a diluent to obtain a low-polarity organic phase;

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

[0017] (3) The rare earth chloride solution obtained by sequentially crushing, alkali melting, water washing, acid dissolution and impurity removal of neodymium-doped yttrium aluminum garnet crystal waste is added to the highly polar organic phase to obtain a highly polar organic phase containing rare earth ions;

[0018] (4) Mix the high polarity organic phase containing rare earth ions with the low polarity organic phase according to the ratio, and then extract the resulting mixture at 20-45℃ under shaking conditions for 5-60 min; after extraction, centrifuge to obtain yttrium-rich organic phase and neodymium-rich raffinate.

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

[0020] The neodymium in the raffinate was extracted using a Cyanex 272, and then back-extracted using the inorganic acid solution to obtain a high-purity neodymium solution; thus completing the separation of yttrium and neodymium.

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

[0022] Furthermore, 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-level organic phase described in step (1) does not exceed 1 mol / L, and is 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 highly polar organic phase containing rare earth ions described in step (3), the concentration of rare earth ions does not exceed 0.05 mol / L, 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 min; the extraction temperature is preferably 25℃.

[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 dilute hydrochloric acid solution, dilute nitric acid solution, or 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 step (5) for back-extraction 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 back-extracting yttrium from 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 as follows:

[0036] This invention employs a polar organic solvent to replace a portion of the water in the aqueous phase of a traditional solvent extraction system, forming a highly polar organic phase. This, together with a low-polarity organic phase composed of an extractant diluted with a diluent, constitutes a non-aqueous extraction system. Compared to traditional solvent extraction systems, this system, by adding a polar organic solvent with a lower dielectric constant to replace water molecules in the traditional aqueous phase, increases the number of contact ion pairs formed between rare earth ions and chloride ions, reduces the hydration between water molecules and rare earth ions, improves the stability of the extracted complex, and thus enhances extraction and separation performance. Different rare earth ions exhibit varying solvation effects in different polar organic solvents; therefore, selecting a suitable polar organic solvent is crucial for achieving efficient extraction and separation of rare earth ions. Furthermore, this invention uses the acidic extractant Cyanex 272, which possesses advantages such as high selectivity, excellent stability, low acidity required for the extraction process, and low acid consumption during back-extraction, thereby reducing the environmental harm caused by the extraction process. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 This illustrates 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 This illustrates 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 this invention.

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

[0041] Figure 4 This illustrates 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 This illustrates the effect of the non-aqueous solvent extraction system on the extraction and separation of yttrium and neodymium under different phase ratios in Example 5 of the present invention.

[0043] Figure 6 This describes 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 7This illustrates the effect of different inorganic acid concentrations on the washing of neodymium in a yttrium-rich organic phase in Example 7 of the present invention.

[0045] Figure 8 This illustrates the effect of different inorganic acid concentrations on the back-extraction of yttrium in the yttrium-rich organic phase in Example 8 of the present invention.

[0046] Figure 9 This is a method for separating yttrium and neodymium from waste generated by a company in Chengdu during the processing of neodymium-doped yttrium aluminum garnet crystals using a non-aqueous solvent extraction according to Example 9 of the present invention.

[0047] Figure 10 This is a process flow diagram for a specific implementation of the present invention. Detailed Implementation

[0048] This invention provides a method for the extraction and separation of yttrium and neodymium from Nd:YAG crystal waste using a non-aqueous solvent system. The invention employs a highly polar (MP) organic phase obtained by mixing a polar organic solvent such as polyethylene glycol with water, replacing the traditional aqueous phase. An acidic extractant, bis(2,4,4-trimethylpentyl)phosphonic acid (Cyanex 272), diluted with solvent oil No. 260, is used as the low-polarity (LP) organic phase. The two phases are mixed to form a non-aqueous solvent extraction system for the extraction and separation of yttrium and neodymium. Using a 0.4 mol / L Cyanex 272-80 vol% PEG 200 non-aqueous solvent extraction system, the extraction efficiency of yttrium reaches 97.99%, and the separation factor of yttrium and neodymium is as high as 3520. Furthermore, experiments were conducted under optimal conditions to extract and separate yttrium and neodymium from neodymium-doped yttrium aluminum garnet crystal waste. The extraction efficiency of yttrium reached 98.60%, and the separation coefficient between yttrium and neodymium reached 10¹⁰, achieving highly efficient separation of yttrium and neodymium. Therefore, this invention provides a new method and approach for the efficient separation and recovery of yttrium and neodymium from neodymium-doped yttrium aluminum garnet crystal waste.

[0049] Compared to traditional solvent extraction, this system replaces water molecules in the traditional aqueous phase with a polar organic solvent with a low dielectric constant. This increases the number of contact ion pairs formed between rare earth ions and chloride ions, reduces the hydration effect between water molecules and rare earth ions, and improves the stability of the extracted complex, thereby enhancing extraction and separation performance. Furthermore, this invention uses the acidic extractant Cyanex 272, which has advantages such as high selectivity, excellent stability, low acidity required for the extraction process, and low acid consumption during back-extraction, thus reducing the environmental harm caused by the extraction process. Therefore, this invention is a rare earth extraction process with high extraction and separation efficiency and is environmentally friendly.

[0050] The present invention will be further described in detail below through implementation examples. To further understand the present invention, preferred embodiments of the present invention will be described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention and not for limiting the scope of the present invention's patent claims.

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

[0052] In the process of this invention, after the extraction and back-extraction operations, the rare earth concentrations in the raffinate and back-extraction solution are determined by ICP-OES.

[0053] The formulas for calculating the rare earth partition ratio (D), extraction efficiency (%E), separation coefficient (β) between rare earth ions, and back-extraction efficiency (%Strip) of each rare earth ion are as follows:

[0054]

[0055] Among them, C0 and C MP These represent the initial and equilibrium concentrations of rare earth ions in the highly polar organic phase, respectively; V MP and V LP These represent the volumes of the highly polar organic phase and the low polar organic phase, respectively; D A and D B These represent the distribution ratios of rare earth ions A and B, respectively; Cs is the concentration of rare earth ions in the back-extraction solution.

[0056] Example 1

[0057] The effect 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 solvent oil No. 260, is a low-polarity organic phase;

[0059] Take 2 ml of water and mix it evenly with 8 ml of PEG 200, EG and PEG 300 respectively to prepare a highly polar organic phase containing 80 vol% polar organic solvent. Weigh 0.0897 g of neodymium chloride hexahydrate and 0.0758 g of yttrium chloride hexahydrate respectively, heat and stir to dissolve in the highly polar organic phase to prepare a mixed rare earth solution containing 0.025 mol / L neodymium and 0.025 mol / L yttrium.

[0060] The highly polar organic phase and the low-polar organic phase were mixed in a 1:1 ratio and extracted in a constant-temperature water bath shaker at 25°C for 30 min at a shaking speed of 300 rpm. After extraction, the mixture was centrifuged at 2500 rpm for 15 min and then transferred to a 60 ml separatory funnel for separation to obtain a yttrium-rich organic phase and a raffinate. The ion concentration in the raffinate was collected and determined using ICP-OES to calculate the extraction efficiency and separation coefficient of yttrium and neodymium. The yttrium-rich organic phase was then washed with HCl and back-extracted 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, calculations indicate that the addition of polar organic solvents significantly improves the extraction efficiency of rare earth elements compared to extraction from pure water. Specifically, the non-aqueous phase system composed of PEG 200 increased the extraction efficiency of yttrium from 61% to 98%, with a separation coefficient of 3760 for yttrium and neodymium. Considering both extraction efficiency and separation coefficient, PEG 200 is the optimal polar organic solvent. Therefore, PEG 200 is selected as the polar organic solvent for constructing the optimal non-aqueous solvent extraction system for separating yttrium and neodymium.

[0061] Example 2

[0062] The 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 following steps:

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

[0064] Different proportions of water and different proportions of PEG 200 were mixed to prepare 10 ml of highly polar organic phases containing 0-100 vol% PEG200 respectively. 0.0897 g of neodymium chloride hexahydrate and 0.0758 g of yttrium chloride hexahydrate were weighed and dissolved in the highly polar organic phases by heating and stirring to prepare mixed rare earth solutions containing 0.025 mol / L neodymium and 0.025 mol / L yttrium.

[0065] The high-polarity organic phases with different PEG 200 contents were mixed with low-polarity organic phases at a 1:1 ratio and extracted in a constant-temperature water bath shaker at 25°C, 300 rpm, and 30 min. After extraction, the mixture was centrifuged at 2500 rpm for 15 min and then transferred to a 60 ml separatory funnel for separation to obtain a yttrium-rich organic phase and raffinate. The ion concentrations in the raffinate were collected and determined using ICP-OES to calculate the extraction efficiency and separation coefficients of yttrium and neodymium. The yttrium-rich organic phase was then washed with HCl and back-extracted 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, calculations revealed that the extraction efficiency of yttrium and neodymium continuously increased with the increase of the volume ratio of PEG 200 in the highly polar organic phase. The extraction efficiency of yttrium reached its maximum (97.86%) at a volume ratio of 80 vol%, at which point the separation coefficient between yttrium and neodymium also reached its maximum (3760). Subsequently, as the proportion of PEG 200 continued to increase, the viscosity of the system increased, leading to a slower extraction speed and a decrease in both extraction efficiency and separation ratio. Therefore, the optimal volume ratio of PEG 200 in the highly polar organic phase is 80 vol%.

[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 was investigated, and the method included the following steps:

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

[0069] Take 2 ml of water and 8 ml of PEG 200 and mix them evenly to prepare 10 ml of highly polar organic phase containing 80 vol% PEG 200. Weigh 0.0897 g of neodymium chloride hexahydrate and 0.0758 g of yttrium chloride hexahydrate, heat and stir to dissolve them in the highly polar organic phase to prepare a mixed rare earth solution containing 0.025 mol / L neodymium and 0.025 mol / L yttrium.

[0070] The highly polar organic phase and the low polar organic phase were mixed in a 1:1 ratio and extracted in a constant-temperature water bath shaker at temperatures of 20℃, 25℃, 30℃, 35℃, 40℃, and 45℃. The shaker speed was 300 rpm, and the shaking time was 30 min. After extraction, the mixture was centrifuged at 2500 rpm for 15 min and then transferred to a 60 ml separatory funnel for separation to obtain a yttrium-rich organic phase and a 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 back-extracted 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 as follows. Figure 3 As shown, calculations showed that the extraction efficiencies of yttrium at different temperatures were 98.01%, 97.96%, 97.13%, 95.42%, and 95.40%, respectively. Temperature had little effect on the extraction and separation of yttrium and neodymium, so we chose 25℃ for the extraction reaction.

[0071] Example 4

[0072] The effect of non-aqueous solvent extraction systems on the extraction and separation of yttrium and neodymium at different extraction times was investigated. The method includes the following steps:

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

[0074] Take 2 ml of water and 8 ml of PEG 200 and mix them evenly to prepare 10 ml of highly polar organic phase containing 80 vol% PEG 200. Weigh 0.0897 g of neodymium chloride hexahydrate and 0.0758 g of yttrium chloride hexahydrate, heat and stir to dissolve them in the highly polar organic phase to prepare a mixed rare earth solution containing 0.025 mol / L neodymium and 0.025 mol / L yttrium.

[0075] The highly polar organic phase and the low polar organic phase were mixed in a 1:1 ratio and extracted in a constant temperature water bath shaker for different times (5 min to 60 min) at an extraction temperature of 25℃ and a shaker speed of 300 r / min. After extraction, the mixture was centrifuged at 2500 r / min for 15 min and then transferred to a 60 ml separatory funnel for separation to obtain a yttrium-rich organic phase and a 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 back-extracted 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 as follows. Figure 4 As shown, the extraction efficiency of yttrium and neodymium increases with increasing oscillation time. The extraction efficiency of yttrium reaches its maximum (98.31%) at an extraction time of 30 min, and further increases in extraction time do not significantly alter the extraction efficiency. Therefore, to ensure sufficient extraction, we selected 30 min as the optimal extraction time.

[0076] Example 5

[0077] The effect of non-aqueous solvent extraction systems on the extraction and separation of yttrium and neodymium under different phase ratios, the method comprising the following steps:

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

[0079] Take 2 ml of water and 8 ml of PEG 200 and mix them evenly to prepare 10 ml of highly polar organic phase containing 80 vol% PEG 200. Weigh 0.0897 g of neodymium chloride hexahydrate and 0.0758 g of yttrium chloride hexahydrate, heat and stir to dissolve them in the highly polar organic phase to prepare a mixed rare earth solution containing 0.025 mol / L neodymium and 0.025 mol / L yttrium.

[0080] The above-mentioned highly polar organic phase and low polar organic phase were mixed at different ratios (5:1 to 1:5) and extracted in a constant temperature water bath shaker at 25℃, 300 r / min, and for 30 min. After extraction, the mixture was centrifuged at 2500 r / min for 15 min and then transferred to a 60 ml separatory funnel for separation to obtain a yttrium-rich organic phase and 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 back-extracted to obtain a high-purity yttrium chloride solution. The effect of different ratios of the non-aqueous solvent extraction system on the extraction and separation of yttrium and neodymium is as follows. Figure 5 As shown: the extraction efficiency of yttrium in V LP :V MP The separation efficiency reaches its maximum (97.87%) at a ratio of 1:1, at which point the separation coefficient also reaches its maximum (4190). Therefore, V is chosen. LP :V MP A 1:1 ratio is the optimal ratio for the extraction and separation of yttrium and neodymium.

[0081] Example 6

[0082] The effect of Cyanex 272 concentration 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 with solvent oil No. 260 to 0-1 mol / L, is a low-polarity organic phase;

[0084] Take 2 ml of water and 8 ml of PEG 200 and mix them evenly to prepare 10 ml of highly polar organic phase containing 80 vol% PEG 200. Weigh 0.0897 g of neodymium chloride hexahydrate and 0.0758 g of yttrium chloride hexahydrate, heat and stir to dissolve them in the highly polar organic phase to prepare a mixed rare earth solution containing 0.025 mol / L neodymium and 0.025 mol / L yttrium.

[0085] The high-polarity organic phase and the low-polarity organic phase were mixed in a 1:1 ratio and extracted in a constant-temperature water bath shaker at 25°C, 300 rpm, and for 30 min. After extraction, the mixture was centrifuged at 2500 rpm for 15 min and then transferred to a 60 ml separatory funnel for separation to obtain a yttrium-rich organic phase and raffinate. The ion concentrations in the raffinate were collected and determined using ICP-OES to calculate the extraction efficiency and separation coefficients of yttrium and neodymium. The yttrium-rich organic phase was then washed with HCl and back-extracted 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, the extraction efficiency of yttrium increases with increasing Cyanex 272 concentration. At a Cyanex 272 concentration of 0.4 mol / L, the extraction efficiency reaches 97.99%, at which point the separation coefficient between yttrium and neodymium reaches its maximum (3520). When the Cyanex 272 concentration continues to increase, the extraction efficiency of yttrium remains essentially unchanged, while the extraction efficiency of neodymium continuously increases, and the separation coefficient between yttrium and neodymium continuously decreases. Therefore, the optimal Cyanex 272 concentration for separating yttrium and neodymium is 0.4 mol / L.

[0086] Example 7

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

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

[0089] Take 2 ml of water and 8 ml of PEG 200 and mix them evenly to prepare 10 ml of highly polar organic phase containing 80 vol% PEG 200. Weigh 0.0897 g of neodymium chloride hexahydrate and 0.0758 g of yttrium chloride hexahydrate, heat and stir to dissolve them in the highly polar organic phase to prepare a mixed rare earth solution containing 0.025 mol / L neodymium and 0.025 mol / L yttrium.

[0090] The high-polarity organic phase and low-polarity organic phase were mixed in a 1:1 ratio and extracted in a constant-temperature water bath shaker at 25°C for 30 min at a shaking speed of 300 rpm. After extraction, the mixture was centrifuged at 2500 rpm for 15 min and then transferred to a 60 ml separatory funnel for separation to obtain a yttrium-rich organic phase and a neodymium-rich raffinate. The ion concentrations in the raffinate were collected and determined using ICP-OES to calculate the extraction efficiency and separation coefficients of yttrium and neodymium. The yttrium-rich organic phase was washed with 0.01–4 mol / L HCl, HNO3, and H2SO4, respectively. The concentration of neodymium after washing was determined using ICP-OES to calculate the washing effect of neodymium. The washing effect of different inorganic acid concentrations on neodymium in the supported organic phase is shown in the figure. Figure 7 As shown: Calculations show that in this embodiment, approximately 1.37% of neodymium is extracted into the organic phase. HCl, HNO3, and H2SO4 can all effectively wash neodymium from the LP phase with similar results. We chose HCl because it is safer and more economical, minimizing environmental impact. Using 0.01 mol / L HCl, 96.31% of neodymium can be quantitatively washed out of the yttrium-rich organic phase; therefore, 0.01 mol / L HCl is the preferred inorganic acid for washing neodymium.

[0091] Example 8

[0092] The effect of different inorganic acid concentrations on the back-extraction of 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 solvent oil No. 260, is a low-polarity organic phase;

[0094] Take 2 ml of water and 8 ml of PEG 200 and mix them evenly to prepare 10 ml of highly polar organic phase containing 80 vol% PEG 200. Weigh 0.0897 g of neodymium chloride hexahydrate and 0.0758 g of yttrium chloride hexahydrate, heat and stir to dissolve them in the highly polar organic phase to prepare a mixed rare earth solution containing 0.025 mol / L neodymium and 0.025 mol / L yttrium.

[0095] The high-polarity organic phase and low-polarity organic phase were mixed in a 1:1 ratio and extracted in a constant-temperature water bath shaker at 25°C for 30 min at a shaking speed of 300 rpm. After extraction, the mixture was centrifuged at 2500 rpm for 15 min and then transferred to a 60 ml separatory funnel for separation to obtain a yttrium-rich organic phase and a neodymium-rich raffinate. The ion concentrations in the raffinate were collected and determined using ICP-OES to calculate the extraction efficiency and separation coefficient of yttrium and neodymium. The yttrium-rich organic phase was then washed with 0.01 mol / L HCl to remove co-extracted neodymium, followed by back-extraction with 0.01–4 mol / L HCl, HNO3, and H2SO4. The concentration of yttrium after back-extraction was determined using ICP-OES to calculate the back-extraction efficiency. The effects of different inorganic acid concentrations on the back-extraction of yttrium in the yttrium-rich organic phase are shown in the figure. Figure 8 As shown: Calculations show that in this embodiment, approximately 97.99% of the yttrium is extracted into the organic phase. HCl, HNO3, and H2SO4 can all effectively back-extract yttrium from the LP phase, with little difference in back-extraction efficiency. We chose HCl because it is safer and more economical, minimizing environmental impact. Furthermore, the back-extraction efficiency increases with increasing HCl concentration, remaining essentially constant after reaching 1 mol / L. Using 1 mol / L HCl for yttrium back-extraction achieves an efficiency of 95.88%, yielding a high-purity yttrium chloride solution. Therefore, the preferred inorganic acid for yttrium back-extraction is 1 mol / L HCl.

[0096] Example 9

[0097] This embodiment describes a method for separating yttrium and neodymium from waste generated during the processing of neodymium-doped yttrium aluminum garnet crystals by a company in Chengdu using a non-aqueous solvent extraction method. The method includes the following steps:

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

[0099] According to the method described in the paper "Recovering Rare Earths from Neodymium-Doped Yttrium Aluminum Garnet Crystals [J]. Journal of Rare Earths, 2017, Vol. 35 (2): 225-230", a mixed rare earth solution containing 1.778 g / L yttrium and 0.027 g / L neodymium was obtained by crushing, alkali melting, water washing, acid dissolution and impurity removal of neodymium-doped yttrium aluminum garnet crystal waste. PEG 200 containing 80 vol% was added as a highly polar organic phase.

[0100] The high-polarity organic phase and low-polarity organic phase were mixed in a 1:1 ratio and extracted in a constant-temperature water bath shaker at 25°C, 300 rpm, and for 30 min. After extraction, the mixture was centrifuged at 2500 rpm for 15 min and then transferred to a separatory funnel for separation to obtain a yttrium-rich organic phase and a neodymium-rich raffinate. The ion concentrations in the raffinate were collected and determined using ICP-OES to calculate the extraction efficiency and separation coefficients of yttrium and neodymium. The yttrium-rich organic phase was then washed with 0.01 mol / L HCl to remove co-extracted neodymium, and then back-extracted with 1 mol / L HCl to obtain a high-purity yttrium chloride solution. Three parallel experiments were conducted to obtain a non-aqueous solvent extraction method for separating yttrium and neodymium from neodymium-doped yttrium aluminum garnet crystal waste. The results are as follows. Figure 9 As shown: According to calculations, in this embodiment, the extraction efficiency of yttrium reached 98.46%, 98.58%, and 98.60%, respectively, and the separation coefficients of yttrium and neodymium reached 991, 1050, and 1010, respectively.

Claims

1. A method for separating yttrium and neodymium from neodymium-doped yttrium aluminum garnet crystal waste using non-aqueous solvent extraction, characterized in that: Includes the following steps: (1) Cyanex 272 was diluted with solvent oil No. 260 to obtain a low polarity organic phase, wherein the concentration of Cyanex 272 in the low polarity organic phase was 0.4 mol / L; (2) Dissolve polyethylene glycol 200 in pure water according to the specified ratio, mix well, and obtain a highly polar organic phase. The volume fraction of polyethylene glycol 200 in the highly polar organic phase is 80 vol%. (3) The rare earth chloride solution obtained by sequentially crushing, alkali melting, water washing, acid dissolution and impurity removal of neodymium-doped yttrium aluminum garnet crystal waste is added to the highly polar organic phase to obtain a highly polar organic phase containing rare earth ions; (4) Mix the high polarity organic phase containing rare earth ions with the low polarity organic phase at a volume ratio of 1:1, and then extract the resulting mixture at 20~45℃ under shaking conditions for 5~60 min; after extraction, centrifuge to obtain the yttrium-rich organic phase and the neodymium-rich extract residue. (5) The yttrium-rich organic phase is washed with a 0.01 mol / L dilute hydrochloric acid solution to remove a small amount of co-extracted neodymium, and then the washed yttrium-rich organic phase is back-extracted with a 1 mol / L dilute hydrochloric acid solution to obtain a high-purity yttrium solution. The neodymium in the raffinate was extracted using a Cyanex 272 extractor, and then back-extracted using a dilute hydrochloric acid solution to obtain a high-purity neodymium solution; thus completing the separation of yttrium and neodymium.

2. The method according to claim 1, characterized in that: The extraction time in step (4) is 30 min; the extraction temperature is 25℃.

3. The method according to claim 1, characterized in that: Step (5) The neodymium in the raffinate is extracted using Cyanex 272 and then back-extracted using dilute hydrochloric acid solution to obtain a high-purity neodymium solution with a concentration of 0.01~4 mol / L.

Images