A method for suppressing the oxidation of variable-valence rare earth ions during rare earth ion extraction and separation.

Abstract

This invention provides a method for suppressing the oxidation of variable-valence rare earth ions during rare earth ion extraction and separation, belonging to the field of rare earth hydrometallurgical technology. In the extraction and separation process of a rare earth solution system, this invention adds a certain amount of composite liquid inhibitor while using an environmentally friendly diluent. The composite liquid inhibitor of this invention is insensitive to the acidity or alkalinity of the rare earth extraction system, effectively avoiding the problem of oxygen in the air oxidizing cerium(III) to cerium(IV) in the high pH environment of the saponification-rare earth soap stage.

Description

Technical Field

[0001] This invention relates to the field of rare earth hydrometallurgy technology, and in particular to a method for suppressing the oxidation of variable valence rare earth ions during rare earth ion extraction and separation. Background Technology

[0002] Rare earth elements are among the few key elements in my country that possess certain strategic advantages. The conventional method for extracting and purifying rare earth elements is solvent extraction. The entire rare earth separation and extraction system generally consists of two phases: an organic phase and an aqueous phase. The organic phase comprises the extractant that undergoes a complexation reaction with metal ions and a diluent that only improves the physical properties of the extractant. The aqueous phase consists of rare earth feed solution, washing solution, and back acid, among other aqueous solutions.

[0003] In recent years, with the strict control of volatile organic compound (VOC) emissions, rare earth enterprises have had to use environmentally friendly diluents to reduce VOC emissions at the source to improve the production environment. However, this has also led to a widespread problem of excessive cerium content in rare earth chloride solutions during the separation and purification of praseodymium-neodymium series compounds by most separation enterprises using cascade extraction processes. The rare earth impurity CeO2 / TREO in praseodymium-neodymium series products is >0.05%.

[0004] For praseodymium and neodymium series elements, as the core raw materials of permanent magnet materials, the stability of their quality is crucial for achieving corporate benefits, supporting national strategic emerging industries and modern social development.

[0005] Therefore, finding a method to suppress oxidation during rare earth ion extraction and separation is a technical problem that needs to be solved. Summary of the Invention

[0006] The purpose of this invention is to provide a method for suppressing the oxidation of variable-valence rare earth ions during rare earth ion extraction and separation, in order to solve the problem of excessive rare earth cerium impurities caused by the conversion of trivalent cerium to tetravalent cerium during the extraction and separation process, which affects the purity of the product.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0008] This invention provides a method for suppressing the oxidation of variable-valence rare earth ions during rare earth ion extraction and separation, comprising the following steps:

[0009] In the extraction and separation process of rare earth solution system, when using environmentally friendly diluent, a certain amount of composite liquid inhibitor is added to the organic phase, and then the organic phase is added to the rare earth solution system for reaction.

[0010] The composite liquid inhibitor is used to suppress the oxidation of trivalent cerium to tetravalent cerium during the extraction and separation process, so as to prevent the presence of tetravalent cerium from affecting the purity of the product;

[0011] The composite liquid inhibitor comprises a primary inhibitor, a secondary inhibitor, and a diluent;

[0012] The primary inhibitor comprises a hindered phenolic compound, and the secondary inhibitor comprises a polyphenolic hydroxyl compound.

[0013] Furthermore, the hindered phenolic compound comprises one or more of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 2,2'-methylenebis(6-tert-butyl-4-methylphenol), 2,6-di-tert-butyl-p-cresol, 2,2'-methylenebis(4-tert-butyl-4-ethylphenol), 2,4,6-tri-tert-butylphenol, 4-hydroxy-3-tert-butyl-anisole, 2,6-di-tert-butyl-4-(dimethylaminomethyl)phenol, 4,4'-thiobis(2-tert-butyl-5-methylphenol), and 4,4'-thiobis(6-tert-butyl-2-methylphenol).

[0014] Furthermore, the polyphenolic hydroxyl compounds include one or more of the following: propyl gallate, pyrogallol, 1,3-di-tert-butyl-4,6-benzene, 3-butylcatechol, 4-butylcatechol, n-octylresorcinol, 5-pentylresorcinol, 4-propylresorcinol, tert-butylhydroquinone, 2,5-di-tert-butylhydroquinone, 2-methyl-5-sec-octadecyl-1,4-benzene, 4,6-di-tert-butylcatechol, 4-allylpyrogallol, 2-methyl-4-pentylresorcinol, and phenylethylresorcinol.

[0015] Furthermore, the diluent comprises one or more of the following: kerosene, sulfonated kerosene, aviation kerosene, hydrotreated kerosene, No. 200 solvent oil, No. 260 solvent oil, synthetic solvent oil, IP80, white oil, light white oil, paraffin oil, cyclohexane, cyclohexanone, and n-hexane.

[0016] Furthermore, the amount of the composite liquid inhibitor added to the organic phase is 0.1–20 g / L.

[0017] Furthermore, the volume ratio of the composite liquid inhibitor to the environmentally friendly diluent is 0.1–20:80–99.9.

[0018] Furthermore, the reaction temperature is 30–50°C, and the reaction time is 20–120 h.

[0019] Furthermore, the environmentally friendly diluent includes P507 - an environmentally friendly diluent.

[0020] The beneficial effects of this invention are:

[0021] (1) This invention can replace the current process method of adding reducing agent H2O2 in the industry, and solves the environmental problems caused by the destruction of organic structure, such as increased organic cost, product quality fluctuation and increased difficulty in wastewater treatment.

[0022] (2) This invention can replace the existing process of adding reducing agent VC and hydroxylamine hydrochloride in the industry, and solves the problems of complex solid agent addition process, increased labor costs and high production costs caused by the high price of reducing agent.

[0023] (3) After the implementation of the present invention, the process flow is simplified. The addition of hydrogen peroxide, ascorbic acid, or hydroxylamine hydrochloride is no longer required. The formation of tetravalent cerium can be inhibited simply by periodically adding a composite liquid inhibitor to the extraction production line. This avoids the damage to the structure of rare earth extractants and diluents caused by traditional hydrogen peroxide dripping, which leads to decreased organic extraction capacity, increased organic consumption, higher phosphorus content in the rare earth solution, and higher phosphorus content in subsequent products. It also avoids the problems of expensive ascorbic acid requiring an additional dissolving process, resulting in time-consuming and costly production. While ensuring product quality, the production process is simplified and production costs are reduced, making it a green, efficient, and low-cost process. Attached Figure Description

[0024] Figure 1 The effect of the amount of compound liquid inhibitor added on the inhibition of Ce(Ⅳ) content in the organic phase is shown in the figure.

[0025] Figure 2 The graph shows the effect of reaction temperature on the inhibition of Ce(Ⅳ) content in the organic phase.

[0026] Figure 3 Graph showing the effect of the amount of composite liquid inhibitor added on the elimination of Ce(Ⅳ) content in the organic phase;

[0027] Figure 4 Graph showing the effect of the amount of composite liquid inhibitor added on the elimination of Ce(Ⅳ) content in the organic phase;

[0028] Figure 5 The graph shows the effect of reaction temperature on the elimination of Ce(Ⅳ) content in the organic phase. Detailed Implementation

[0029] This invention provides a method for suppressing the oxidation of variable-valence rare earth ions during rare earth ion extraction and separation, comprising the following steps:

[0030] In the extraction and separation process of rare earth solution system, when using environmentally friendly diluent, a certain amount of composite liquid inhibitor is added to the organic phase, and then the organic phase is added to the rare earth solution system for reaction.

[0031] The composite liquid inhibitor is used to suppress the oxidation of trivalent cerium to tetravalent cerium during the extraction and separation process, so as to prevent the presence of tetravalent cerium from affecting the purity of the product;

[0032] The composite liquid inhibitor comprises a primary inhibitor, a secondary inhibitor, and a diluent;

[0033] The primary inhibitor comprises a hindered phenolic compound, and the secondary inhibitor comprises a polyphenolic hydroxyl compound.

[0034] In this invention, the mass ratio of the main inhibitor, the co-inhibitor and the diluent is 5-40:1-30:80-110, preferably 10-35:5-25:85-105, more preferably 15-30:10-20:90-100, and even more preferably 20-25:12-18:90.

[0035] In this invention, the hindered phenolic compound comprises one or more of the following: pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 2,2'-methylenebis(6-tert-butyl-4-methylphenol), 2,6-di-tert-butyl-p-cresol, 2,2'-methylenebis(4-tert-butyl-4-ethylphenol), 2,4,6-tri-tert-butylphenol, 4-hydroxy-3-tert-butyl-anisole, 2,6-di-tert-butyl-4-(dimethylaminomethyl)phenol, 4,4'-thiobis(2-tert-butyl-5-methylphenol), and 4,4'-thiobis(6-tert-butyl-2-methylphenol). Several, preferably one or more of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 2,2'-methylenebis(6-tert-butyl-4-methylphenol), 2,6-di-tert-butyl-p-cresol, 2,2'-methylenebis(4-tert-butyl-4-ethylphenol), and 2,4,6-tri-tert-butylphenol, more preferably one or more of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, and 2,2'-methylenebis(6-tert-butyl-4-methylphenol).

[0036] In this invention, the polyphenolic hydroxyl compounds comprise one or more of the following: propyl gallate, pyrogallol, 1,3-di-tert-butyl-4,6-benzenehydrin, 3-butylcatechol, 4-butylcatechol, n-octylresorcinol, 5-pentylresorcinol, 4-propylresorcinol, tert-butylhydroquinone, 2,5-di-tert-butylhydroquinone, 2-methyl-5-sec-octadecyl-1,4-benzenehydrin, 4,6-di-tert-butylcatechol, 4-allylpyrogallol, 2-methyl-4-pentylresorcinol, and phenylethylresorcinol, preferably propyl gallate. Propyl gallate, pyrogallol, 1,3-di-tert-butyl-4,6-benzene, 3-butylcatechol, 4-butylcatechol, n-octylresorcinol, 5-pentylresorcinol, 4-propylresorcinol, tert-butylhydroquinone, 2,5-di-tert-butylhydroquinone, and 2-methyl-5-sec-octadecyl-1,4-benzene, more preferably one or more of propyl gallate, pyrogallol, 1,3-di-tert-butyl-4,6-benzene, 3-butylcatechol, 4-butylcatechol, and n-octylresorcinol.

[0037] In this invention, the diluent comprises one or more of kerosene, sulfonated kerosene, aviation kerosene, hydrotreated kerosene, No. 200 solvent oil, No. 260 solvent oil, synthetic solvent oil, IP80, white oil, light white oil, paraffin oil, n-hexane, cyclohexane, cyclohexanone, and n-hexane, preferably one or more of kerosene, sulfonated kerosene, hydrotreated kerosene, cyclohexane, cyclohexanone, and n-hexane, and more preferably one or more of kerosene, No. 260 solvent oil, sulfonated kerosene, and hydrotreated kerosene. In this invention, the amount of the composite liquid inhibitor added to the organic phase is 0.1–20 g / L, preferably 1–10 g / L, and more preferably 2–5 g / L.

[0038] In this invention, the volume ratio of the composite liquid inhibitor to the environmentally friendly diluent is 0.1-20:80-99.9, preferably 1-15:85-99, and more preferably 5-10:95-90.

[0039] In this invention, the environmentally friendly diluent is preferably P507-environmentally friendly diluent.

[0040] In this invention, the reaction temperature is 30-50°C, preferably 40°C; the reaction time is 20-120 h, preferably 40-100 h.

[0041] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0042] Example 1

[0043] The compound liquid inhibitor is made from the following raw materials in the specified mass ratio.

[0044] 5 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]

[0045] 5 parts of propyl gallate

[0046] 90 parts of diluent No. 260 solvent oil

[0047] Preparation method: The main inhibitor, auxiliary inhibitor and solvent oil are mixed in a reaction vessel and stirred for 0.5 h. Then the temperature is raised to 40 °C and stirred for another 50 min. After the mixing is completed, the mixture is transferred to a storage tank through an insulated pipe and cooled to 20 °C to obtain the composite liquid inhibitor.

[0048] Example 2

[0049] The compound liquid inhibitor is made from the following raw materials in the specified mass ratio.

[0050] 5 parts of β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate stearyl alcohol ester

[0051] 5 parts of 1,3-di-tert-butyl-4,6-benzenediol

[0052] 90 parts of diluent No. 260 solvent oil

[0053] Preparation method: The main inhibitor, auxiliary inhibitor and solvent oil are mixed in a reaction vessel and stirred for 0.5 h. Then the temperature is raised to 50 °C and stirred for another 50 min. After the mixing is completed, the mixture is transferred to a storage tank through an insulated pipe and cooled to 25 °C to obtain the composite liquid inhibitor.

[0054] Example 3

[0055] The compound liquid inhibitor is made from the following raw materials in the specified mass ratio.

[0056] 8 parts of β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate stearyl ester

[0057] 12 parts of 2,5-di-tert-butylhydroquinone

[0058] 100 parts kerosene

[0059] Preparation method: The main inhibitor, auxiliary inhibitor and solvent oil are mixed in a reaction vessel and stirred for 0.5 h. Then the temperature is raised to 60 °C and stirred for another 50 min. After the mixing is completed, the mixture is transferred to a storage tank through an insulated pipe and cooled to 30 °C to obtain the composite liquid inhibitor.

[0060] Example 4

[0061] The compound liquid inhibitor is made from the following raw materials in the specified mass ratio.

[0062] 20 parts of β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate stearyl ester

[0063] 15 parts of phenylethyl resorcinol

[0064] 100 parts of cyclohexane

[0065] Preparation method: The main inhibitor, auxiliary inhibitor and solvent oil are mixed in a reaction vessel and stirred for 0.5 h. Then the temperature is raised to 40 °C and stirred for another 50 min. After the mixing is completed, the mixture is transferred to a storage tank through an insulated pipe and cooled to 20 °C to obtain the composite liquid inhibitor.

[0066] Example 5

[0067] The compound liquid inhibitor is made from the following raw materials in the specified mass ratio.

[0068] 2,2'-Methylenebis(6-tert-butyl-4-methylphenol) 18 parts

[0069] 22 parts of 2-methyl-4-pentylphloroglucinol

[0070] 100 parts of cyclohexanone

[0071] Preparation method: The main inhibitor, auxiliary inhibitor and solvent oil are mixed in a reaction vessel and stirred for 0.5 h. Then the temperature is raised to 40 °C and stirred for another 50 min. After the mixing is completed, the mixture is transferred to a storage tank through an insulated pipe and cooled to 20 °C to obtain the composite liquid inhibitor.

[0072] Example 6

[0073] The compound liquid inhibitor is made from the following raw materials in the specified mass ratio.

[0074] 15 parts of 2,6-di-tert-butyl-p-cresol

[0075] 20 parts of 4-allylpyrogallol

[0076] 90 parts of No. 200 solvent oil

[0077] Preparation method: The main inhibitor, auxiliary inhibitor and solvent oil are mixed in a reaction vessel and stirred for 0.5 h. Then the temperature is raised to 50 °C and stirred for another 50 min. After the mixing is completed, the mixture is transferred to a storage tank through an insulated pipe and cooled to 20 °C to obtain the composite liquid inhibitor.

[0078] Example 7

[0079] During the extraction and separation process in the rare earth solution system, the composite liquid inhibitor obtained in Example 1 was mixed with P507-environmentally friendly diluent at a volume ratio of 5:95 to form an organic phase with a composite liquid inhibitor concentration of 5 g / L. This organic phase was added to the last stage of the back-extraction section. The process was completed at 30°C through a saponification-rare earth soaping section, an extraction section, a washing section, and a back-extraction section. During the repeated circulation of the organic phase with added inhibitor, cerium(IV) in the extraction system could be significantly inhibited and eliminated, thereby ensuring the qualification of cerium in the praseodymium-neodymium series products.

[0080] Example 8

[0081] Same as Example 7, except that: the concentration of the composite liquid inhibitor in the rare earth solution system is 2 g / L, the volume ratio of the composite liquid inhibitor to P507-environmentally friendly diluent is 2:98, the composite liquid inhibitor obtained in Example 2 is used, and the reaction temperature is 40°C.

[0082] Example 9

[0083] Same as Example 7, except that: the concentration of the composite liquid inhibitor in the rare earth solution system is 1.5 g / L, the volume ratio of the composite liquid inhibitor to P507-environmentally friendly diluent is 1.5:98.5, the composite liquid inhibitor obtained in Example 3 is used, and the reaction temperature is 50°C.

[0084] Example 10

[0085] Same as Example 7, except that: the concentration of the composite liquid inhibitor in the rare earth solution system is 0.5 g / L, the volume ratio of the composite liquid inhibitor to P507-environmentally friendly diluent is 0.5:99.5, the composite liquid inhibitor obtained in Example 4 is used, and the reaction temperature is 30°C.

[0086] Example 11

[0087] Same as Example 7, except that: the concentration of the composite liquid inhibitor in the rare earth solution system is 1 g / L, the volume ratio of the composite liquid inhibitor to P507-environmentally friendly diluent is 1:99, the composite liquid inhibitor obtained in Example 5 is used, and the reaction temperature is 40°C.

[0088] Example 12

[0089] Same as Example 7, except that: the concentration of the composite liquid inhibitor in the rare earth solution system is 2.5 g / L, the volume ratio of the composite liquid inhibitor to P507-environmentally friendly diluent is 2.5:97.5, the composite liquid inhibitor obtained in Example 6 is used, and the reaction temperature is 50°C.

[0090] The extraction and separation wastewater containing a compound liquid inhibitor was tested after 30 days of operation. The test results are shown in Table 1 below:

[0091] Table 1 Test Results

[0092]

[0093]

[0094] Experimental Example 1: Verifying the effect of the amount of composite liquid inhibitor added on the formation of Ce(Ⅳ) in the organic phase:

[0095] A certain volume of freshly prepared organic phase was measured and saponified with sodium hydroxide, with the saponification value controlled to 0.5 mol / L. The reaction temperature was set at 50℃. A mixed rare earth chloride solution was used as the rare earth feed solution, and the reaction ratio (O / A) was determined to be 10:1. The inhibitory effect of the amount of composite liquid inhibitor added on Ce(Ⅳ) in the organic phase was investigated under a certain stirring intensity. The results are shown in […]. Figure 1 .

[0096] Depend on Figure 1 It can be seen that with the increase of the amount of composite liquid inhibitor added, the time for Ce(Ⅳ) to be detected in the organic phase during the reaction process is prolonged, and the increase of Ce(Ⅳ) in the organic phase with reaction time varies with different reagent addition amounts. When the reagent concentration is 0.5 g / L, the inhibition time of Ce(Ⅳ) production in the organic phase is only 40 h, and the linear increase of Ce(Ⅳ) in the organic phase with the extension of reaction time is relatively high in the later stage. When the Ce(Ⅳ) inhibitor concentration is 2.0 g / L, the inhibition time of Ce(Ⅳ) formation in the organic phase is extended to 120 h, and the linear increase of Ce(Ⅳ) in the organic phase with the extension of reaction time is relatively low in the later stage. The reason for the above variation is that with the increase of reagent addition, the reducing atmosphere of the extraction system is stronger, and its inhibitory effect on the oxidation of air incorporated in the extraction stirring process is stronger. When the reaction time reaches a certain period, the effective reagent concentration decreases, the inhibitory effect of the reagent on the formation of Ce(Ⅳ) in the organic phase decreases, and the Ce(Ⅳ) content in the organic phase slowly increases.

[0097] Experimental Example 2: Verifying the effect of reaction temperature on the formation of Ce(Ⅳ) in the organic phase:

[0098] A certain volume of freshly prepared organic phase was measured. The concentration of hindered phenolic antioxidant was fixed at 2 g / L. The organic phase was saponified with sodium hydroxide, and the saponification value was controlled to 0.5 mol / L. A mixed rare earth chloride solution was used for the rare earth feed solution. The reaction ratio (O / A) was determined to be 10:1. The effect of reaction temperature on the inhibition of Ce(IV) in the organic phase was investigated under a certain stirring intensity. The results are shown in [Figure Number]. Figure 2 .

[0099] Depend on Figure 2It can be seen that the inhibitory effect on Ce(Ⅳ) in the organic phase decreases with increasing reaction temperature. The higher the temperature, the greater the growth trend of Ce(Ⅳ) in the organic phase. Under the condition of reaction temperature of 30℃, the inhibition time of Ce(Ⅳ) formation in the organic phase is longer than 200h and the linear growth rate is small, with an average increase of about 0.0008 g / L every 20h. Under the condition of reaction temperature of 60℃, the inhibition time of Ce(Ⅳ) formation in the organic phase is only 80h and the linear growth rate increases sharply, with an average increase of about 0.005 g / L every 20h. This is because in an aerobic atmosphere, the higher the temperature, the more activated molecules in the system. With the increase of reaction temperature, the amount of tetravalent cerium generated in the organic phase shows an increasing trend. At the same time, the chemical reaction rate of hindered phenolic antioxidants with oxygen is also faster, which accelerates the consumption of antioxidant inhibitors, thereby shortening the time for inhibiting Ce(Ⅳ) oxidation.

[0100] Experimental Example 3: Effect of the amount of composite liquid inhibitor added on the elimination of Ce(Ⅳ) in the organic phase:

[0101] A certain volume of Ce(IV)-containing organic phase was measured, and the reaction temperature was controlled at 50℃. The beaker was sealed, and the effect of the amount of hindered phenolic antioxidant added on the elimination of Ce(IV) in the Ce(IV)-containing organic phase was investigated under a certain stirring intensity. (See figure...) Figure 3 and Figure 4 .

[0102] Depend on Figure 3 It can be seen that within the range of 0.5–2.0 g / L of hindered phenolic antioxidant, and within a reaction time of 0–30 min, the Ce(Ⅳ) content in the organic phase rapidly decreased from 0.2879 g / L to below 0.01 g / L. The elimination pattern of Ce(Ⅳ) content in the organic phase with further extended reaction time is shown in [the table / document / reference needed]. Figure 4 When the concentration of hindered phenolic antioxidant added is 0.5 g / L, trace amounts of Ce(IV) can still be detected in the organic phase after 90 min of reaction, indicating that the concentration of the agent is insufficient to completely eliminate Ce(IV) in the organic phase. When the concentration of hindered phenolic antioxidant added is 1.0–2 g / L, the elimination time of Ce(IV) in the organic phase decreases with increasing agent concentration. When the concentration of hindered phenolic antioxidant added is 1.0 g / L, the Ce(IV) in the organic phase is completely eliminated after 70 min of reaction. When the concentration of hindered phenolic antioxidant added is 2.0 g / L, the Ce(IV) in the organic phase is completely eliminated after 75 min of reaction, indicating that the agent concentration is sufficient to completely eliminate Ce(IV) in the organic phase.

[0103] Experimental Example 4: Effect of reaction temperature on the elimination of Ce(Ⅳ) from the organic phase by a composite liquid inhibitor:

[0104] A certain volume of Ce(IV)-containing organic phase was measured, and the concentration of hindered phenolic antioxidant was fixed at 2 g / L. The beaker was sealed, and the effect of different temperatures on the elimination of Ce(IV) from the Ce(IV)-containing organic phase was investigated under a certain stirring intensity. The results are shown in [Figure number missing]. Figure 5 .

[0105] Depend on Figure 5 It can be seen that when the concentration of hindered phenolic antioxidant is fixed at 2 g / L, the Ce(Ⅳ) content in the organic phase at different reaction temperatures shows a decreasing trend with the extension of reaction time. As the reaction temperature increases, the time for complete elimination of Ce(Ⅳ) in the organic phase shortens. At a reaction temperature of 20℃, the time for complete elimination of Ce(Ⅳ) in the organic phase is 120 min, while at a reaction temperature of 60℃, the time is only 60 min. This is because at lower temperatures, the viscosity of the organic phase is higher, the extraction reaction kinetics decrease, and the probability of contact between the inhibitor and Ce(Ⅳ) in the organic phase decreases. Higher temperatures increase the contact opportunities between Ce(Ⅳ) and the inhibitor in the organic phase, promoting the reduction of Ce(Ⅳ).

[0106] As can be seen from the above embodiments, the present invention provides a method for inhibiting the oxidation of variable valence rare earth ions during rare earth ion extraction and separation. The composite liquid inhibitor of the present invention is insensitive to the acidity or alkalinity of the rare earth extraction system, and can effectively avoid the oxidation of cerium(III) to cerium(IV) by oxygen in the air in the high pH environment of the saponification-rare earth soap section, as well as the oxidation of variable valence rare earth ions by oxygen in the air during the rare earth extraction and separation process. The present invention mixes the composite liquid inhibitor with an environmentally friendly diluent in an organic phase, and adds a certain amount of the above organic phase to the tank head of the extraction production line. After passing through the saponification-rare earth soap section, extraction section, washing section, and back-extraction section to complete one cycle, the organic phase with added inhibitor can play a significant role in inhibiting and eliminating cerium(IV) in the extraction system during the repeated circulation process. The method of the present invention ensures that the cerium content in the final extraction and separation wastewater is ≤300ppm, ensuring the qualification of cerium in praseodymium-neodymium series products.

[0107] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for suppressing the oxidation of variable-valence rare earth ions during rare earth ion extraction and separation, characterized in that, Includes the following steps: In the extraction and separation process of rare earth solution system, a certain amount of composite liquid inhibitor is added to environmentally friendly diluent to form an organic phase, and then the organic phase is added to rare earth solution system for reaction. The composite liquid inhibitor is used to suppress the oxidation of trivalent cerium to tetravalent cerium during the extraction and separation process, so as to prevent the presence of tetravalent cerium from affecting the purity of the product; The composite liquid inhibitor consists of a primary inhibitor, a secondary inhibitor, and a diluent; The mass ratio of the main inhibitor, the co-inhibitor, and the diluent is 5~40:1~30:80~110; The main inhibitor is a hindered phenolic compound, and the co-inhibitor is a polyphenolic hydroxyl compound; The hindered phenolic compounds include one or more of the following: pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 2,2'-methylenebis(6-tert-butyl-4-methylphenol), 2,6-di-tert-butyl-p-cresol, 2,2'-methylenebis(4-tert-butyl-4-ethylphenol), 2,4,6-tri-tert-butylphenol, 4-hydroxy-3-tert-butyl-anisole, 2,6-di-tert-butyl-4-(dimethylaminomethyl)phenol, 4,4'-thiobis(2-tert-butyl-5-methylphenol), and 4,4'-thiobis(6-tert-butyl-2-methylphenol); The polyphenolic hydroxy compounds include one or more of the following: propyl gallate, pyrogallol, 1,3-di-tert-butyl-4,6-benzene, 3-butylcatechol, 4-butylcatechol, n-octylresorcinol, 5-pentylresorcinol, 4-propylresorcinol, tert-butylhydroquinone, 2,5-di-tert-butylhydroquinone, 2-methyl-5-sec-octadecyl-1,4-benzene, 4,6-di-tert-butylcatechol, 4-allylpyrogallol, 2-methyl-4-pentylresorcinol, and phenylethylresorcinol. The amount of the composite liquid inhibitor added to the organic phase is 0.1~20 g / L; The reaction temperature is 30~50℃.

2. The method for suppressing the oxidation of variable-valence rare earth ions during rare earth ion extraction and separation according to claim 1, characterized in that, The diluent comprises one or more of kerosene, No. 200 solvent oil, synthetic solvent oil, white oil, cyclohexane, cyclohexanone, and n-hexane.

3. The method for suppressing the oxidation of variable-valence rare earth ions during rare earth ion extraction and separation according to claim 2, characterized in that, The volume ratio of the composite liquid inhibitor to the environmentally friendly diluent is 0.1~20:80~99.

9.

4. The method for suppressing the oxidation of variable-valence rare earth ions during rare earth ion extraction and separation according to claim 1 or 3, characterized in that, The environmentally friendly diluent includes P507 - environmentally friendly diluent.

5. The method for suppressing the oxidation of variable-valence rare earth ions during rare earth ion extraction and separation according to claim 4, characterized in that, The reaction time is 20-120 hours.

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