Method for inhibiting oxidation of variable valence rare earth ions in rare earth ion extraction and separation process

Abstract

The invention provides a method for inhibiting oxidation of variable valence rare earth ions in the rare earth ion extraction and separation process, and belongs to the technical field of rare earth hydrometallurgy. In the extraction and separation process of a rare earth solution system, under the condition that an environment-friendly diluent is used, a certain amount of composite liquid inhibitor is added in the extraction and separation process. The composite liquid inhibitor is insensitive to the acid-base property of a rare earth extraction system, and the problem that cerium (III) is oxidized into cerium (IV) by oxygen in air in a saponification-rare earth soap section high-pH environment can be effectively avoided.

Description

Technical Field

[0001] The invention relates to the technical field of rare earth hydrometallurgy, and in particular to a method for inhibiting oxidation of valence-varying rare earth ions during the rare earth ion extraction and separation process. Background Art

[0002] Rare earth elements are one of the few key elements in my country with certain strategic advantages. For the extraction and purification of rare earth elements, the conventional method is solvent extraction. For the entire rare earth separation and extraction system, it is generally composed of two phases, namely, organic phase and aqueous phase. The organic phase is composed of an extractant that reacts with metal ions and a diluent that only improves the physical properties of the extractant. The aqueous phase is composed of rare earth feed liquid, washing liquid, acid and other aqueous solutions.

[0003] In recent years, with the strict control of volatile organic compounds (VOCs) emissions, rare earth companies can only use environmentally friendly diluents to reduce VOCs waste gas emissions from the source to improve the production environment. However, this also leads to the problem of excessive cerium in rare earth chloride solutions in the process of separating and purifying praseodymium-neodymium series compounds by cascade extraction technology in most separation companies. The rare earth impurity CeO2 / TREO in praseodymium-neodymium series products is greater than 0.05%.

[0004] For the praseodymium-neodymium series of elements, as the core raw materials of permanent magnet materials, the stability of their quality is crucial to achieving corporate benefits, supporting the country's strategic emerging industries and the development of modern society.

[0005] Therefore, how to obtain a method for inhibiting oxidation during the extraction and separation process of rare earth ions is a technical problem that needs to be solved at present. Summary of the invention

[0006] The purpose of the present invention is to provide a method for inhibiting the oxidation of variable-valence rare earth ions during the extraction and separation process of rare earth ions, so as 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, thereby affecting the purity of the product.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

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

[0009] In the process of extracting and separating the rare earth solution system, a certain amount of composite liquid inhibitor is added to the organic phase when an environmentally friendly diluent is used, and then the organic phase is added to the rare earth solution system for reaction;

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

[0011] The composite liquid inhibitor comprises a main inhibitor, an auxiliary inhibitor and a diluent;

[0012] The main inhibitor comprises a hindered phenol compound, and the auxiliary inhibitor comprises a polyphenolic hydroxyl compound.

[0013] Further, the hindered phenol 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 polyphenol hydroxy compound includes one or more of 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-butylpyrogallol, 4-allylpyrogallol, 2-methyl-4-pentylpyrogallol and phenethylpyrogallol.

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

[0016] Furthermore, the addition amount of the composite liquid inhibitor in 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-environmentally friendly diluent.

[0020] Beneficial effects of the present invention:

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

[0022] (2) The present invention can replace the current process of adding reducing agents VC and hydroxylamine hydrochloride in the industry, and solve the problems of complicated solid agent addition process, increased labor cost and high production cost caused by the high price of reducing agents.

[0023] (3) After the implementation of the technology of the present invention, the process flow is simplified, and the hydrogen peroxide or ascorbic acid, hydroxylamine hydrochloride feeding process is no longer set. The generation of tetravalent cerium can be inhibited only by regularly adding a composite liquid inhibitor to the extraction production line, thereby avoiding the damage of the traditional hydrogen peroxide dripping to the structure of the rare earth extraction organic phosphorus extractant and diluent, which leads to a series of problems such as decreased organic extraction capacity, increased organic consumption, increased phosphorus content in rare earth feed liquid, and high phosphorus content in subsequent products; it also avoids the high price of ascorbic acid, which requires an additional dissolving process before it can be used, resulting in a time-consuming and laborious production process and increased costs. While ensuring the quality of the product, the production process is simplified and the production cost is reduced, which is a green, efficient and low-cost process. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is the graph showing the inhibitory effect of the amount of composite liquid inhibitor added on the Ce(Ⅳ) content in the organic phase;

[0025] Figure 2 This is the inhibitory effect of reaction temperature on the Ce(Ⅳ) content in the organic phase;

[0026] Figure 3 This is the effect diagram of the addition amount of composite liquid inhibitor on the elimination of Ce(Ⅳ) content in the organic phase;

[0027] Figure 4 This is the effect diagram of the addition amount of composite liquid inhibitor on the elimination of Ce(Ⅳ) content in the organic phase;

[0028] Figure 5 This is a graph showing the effect of reaction temperature on the elimination of Ce(Ⅳ) content in the organic phase. DETAILED DESCRIPTION

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

[0030] In the process of extracting and separating the rare earth solution system, a certain amount of composite liquid inhibitor is added to the organic phase when an environmentally friendly diluent is used, and then the organic phase is added to the rare earth solution system for reaction;

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

[0032] The composite liquid inhibitor comprises a main inhibitor, an auxiliary inhibitor and a diluent;

[0033] The main inhibitor comprises a hindered phenol compound, and the auxiliary inhibitor comprises a polyphenolic hydroxyl compound.

[0034] In the present invention, the mass ratio of the main inhibitor, the auxiliary 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 more preferably 20-25:12-18:90.

[0035] In the present invention, the hindered phenol compound comprises one or more of tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate] pentaerythritol, 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), 4,4'-thiobis(6-tert-butyl-2-methylphenol) Several, preferably one or more of tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] pentaerythritol ester, β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate octadecyl ester, 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, further preferably one or more of tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] pentaerythritol ester, β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate octadecyl ester and 2,2'-methylenebis(6-tert-butyl-4-methylphenol).

[0036] In the present invention, the polyphenol hydroxy compound comprises one or more of 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-butylpyrogallol, 4-allylpyrogallol, 2-methyl-4-pentylpyrogallol and phenethylresorcinol, preferably 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-butylpyrogallol, 4-allylpyrogallol, 2-methyl-4-pentylpyrogallol and phenethylresorcinol. One or more of 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, and 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 the present invention, the diluent comprises one or more of kerosene, sulfonated kerosene, aviation kerosene, hydrogenated enhanced kerosene, No. 200 solvent oil, No. 260 solvent oil, synthetic solvent oil, IP80, white oil, light white oil, white wax oil, n-hexane, cyclohexane, cyclohexanone and n-hexane, preferably one or more of kerosene, sulfonated kerosene, hydrogenated enhanced kerosene, cyclohexane, cyclohexanone and n-hexane, and more preferably one or more of kerosene, No. 260 solvent oil, sulfonated kerosene and hydrogenated enhanced kerosene. In the present invention, the addition amount of the composite liquid inhibitor in the organic phase is 0.1-20 g / L, preferably 1-10 g / L, and more preferably 2-5 g / L.

[0038] In the present 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 the present invention, the environmentally friendly diluent is preferably P507-environmentally friendly diluent.

[0040] In the present 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 are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0042] Example 1

[0043] The composite liquid inhibitor is made of the following raw materials in proportion by mass:

[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: Mix the main inhibitor, auxiliary inhibitor and solvent oil in a reactor, stir for 0.5h, then heat to 40°C and continue stirring for 50min. After blending, transfer the mixed material to a storage tank through an insulated pipe, cool to 20°C to obtain a composite liquid inhibitor.

[0048] Example 2

[0049] The composite liquid inhibitor is made of the following raw materials in proportion by mass:

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

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

[0052] Diluent No. 260 solvent oil 90 parts

[0053] Preparation method: Mix the main inhibitor, auxiliary inhibitor and solvent oil in a reactor, stir for 0.5h, then heat to 50°C and continue stirring for 50min. After blending, transfer the mixed material to a storage tank through an insulated pipe, cool to 25°C to obtain a composite liquid inhibitor.

[0054] Example 3

[0055] The composite liquid inhibitor is made of the following raw materials in proportion by mass:

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

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

[0058] Kerosene 100 parts

[0059] Preparation method: Mix the main inhibitor, auxiliary inhibitor and solvent oil in a reactor, stir for 0.5h, then heat to 60°C and continue stirring for 50min. After blending, transfer the mixed material to a storage tank through an insulated pipe, cool to 30°C to obtain a composite liquid inhibitor.

[0060] Example 4

[0061] The composite liquid inhibitor is made of the following raw materials in proportion by mass:

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

[0063] 15 parts of phenethyl resorcinol

[0064] Cyclohexane 100 parts

[0065] Preparation method: Mix the main inhibitor, auxiliary inhibitor and solvent oil in a reactor, stir for 0.5h, then heat to 40°C and continue stirring for 50min. After blending, transfer the mixed material to a storage tank through an insulated pipe, cool to 20°C to obtain a composite liquid inhibitor.

[0066] Example 5

[0067] The composite liquid inhibitor is made of the following raw materials in proportion by mass:

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

[0069] 2-Methyl-4-pentyl phloroglucinol 22 parts

[0070] Cyclohexanone 100 parts

[0071] Preparation method: Mix the main inhibitor, auxiliary inhibitor and solvent oil in a reactor, stir for 0.5h, then heat to 40°C and continue stirring for 50min. After blending, transfer the mixed material to a storage tank through an insulated pipe, cool to 20°C to obtain a composite liquid inhibitor.

[0072] Example 6

[0073] The composite liquid inhibitor is made of the following raw materials in proportion by mass:

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

[0075] 20 parts of 4-allyl pyrogallol

[0076] 90 parts of No. 200 solvent oil

[0077] Preparation method: Mix the main inhibitor, auxiliary inhibitor and solvent oil in a reactor, stir for 0.5h, then heat to 50°C and continue stirring for 50min. After blending, transfer the mixed material to a storage tank through an insulated pipe, cool to 20°C to obtain a composite liquid inhibitor.

[0078] Example 7

[0079] During the extraction and separation process of the rare earth solution system, the composite liquid inhibitor obtained in Example 1 and P507-environmentally friendly diluent are prepared in a volume ratio of 5:95 to form an organic phase with a composite liquid inhibitor concentration of 5 g / L, which is added to the last stage of the stripping section. At 30°C, a cycle is completed through the saponification-rare earth soap section, the extraction section, the washing section, and the stripping section. During the reciprocating cycle of the organic phase to which the inhibitor is added, a significant inhibitory and elimination effect can be exerted on cerium (IV) in the extraction system, 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 the 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 the 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 the 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] Embodiment 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 the 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 the 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 separation wastewater with the addition of the composite liquid inhibitor after running for 30 days was tested, and the test results are shown in Table 1:

[0091] Table 1 Test results

[0092]

[0093]

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

[0095] A certain volume of newly configured organic phase was measured, and the organic phase was saponified with sodium hydroxide. The saponification value was controlled to 0.5 mol / L, the reaction temperature was set to 50 °C, the rare earth liquid was a mixed rare earth chloride solution, and the reaction phase ratio (O / A) was determined to be 10:1. The inhibitory effect of the addition amount of the composite liquid inhibitor 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 detecting the generation of Ce(Ⅳ) in the organic phase during the reaction process is prolonged, and the growth rate of Ce(Ⅳ) in the organic phase with the reaction time is different under different agent addition amounts. When the agent concentration is 0.5g / L, the inhibition time of Ce(Ⅳ) production in the organic phase is only 40h, and in the later period, with the extension of reaction time, the linear growth rate of Ce(Ⅳ) generation in the organic phase is higher. When the concentration of Ce(Ⅳ) inhibitor is 2.0g / L, the inhibition time of Ce(Ⅳ) generation in the organic phase is extended to 120h, and in the later period, with the extension of reaction time, the linear growth rate of Ce(Ⅳ) generation in the organic phase is lower. The reason for the above changes is that with the increase of the amount of agent added, the thicker the reducing atmosphere of the extraction system, the stronger its inhibitory effect on the oxidation of air wrapped in the extraction stirring process. When the reaction time reaches a certain period, the effective agent concentration decreases, the inhibitory effect of the agent on the generation of Ce(Ⅳ) in the organic phase decreases, and the Ce(Ⅳ) content in the organic phase slowly increases.

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

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

[0099] Depend on Figure 2It can be seen that with the increase of reaction temperature, its inhibitory effect on Ce(Ⅳ) in the organic phase decreases. The higher the temperature, the greater the growth trend of Ce(Ⅳ) in the organic phase. Under the condition of reaction temperature of 30℃, its inhibition time on the generation of Ce(Ⅳ) in the organic phase is as long as more than 200h and the linear growth rate is small, increasing by about 0.0008g / L every 20h on average. Under the condition of reaction temperature of 60℃, its inhibition time on the generation of Ce(Ⅳ) in the organic phase is only 80h and the linear growth rate increases sharply, increasing by about 0.005g / L every 20h on average. 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 generation of tetravalent cerium in the organic phase tends to increase. At the same time, the chemical reaction rate of hindered phenol antioxidants and oxygen is faster, which accelerates the consumption of antioxidant inhibitors, thereby shortening the time to inhibit the oxidation generation of Ce(Ⅳ).

[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 taken, the reaction temperature was controlled at 50℃, the beaker was sealed, and the effect of adding hindered phenol antioxidant on the elimination of Ce(Ⅳ) in the Ce(Ⅳ)-containing organic phase was investigated under a certain stirring intensity. Figure 3 and Figure 4 .

[0102] Depend on Figure 3 It can be seen that when the amount of hindered phenol antioxidant added is within the range of 0.5-2.0 g / L and the reaction time is within 0-30 min, the Ce(Ⅳ) content in the organic phase rapidly decreases from 0.2879 g / L to below 0.01 g / L. When the reaction time is extended, the Ce(Ⅳ) content in the organic phase is eliminated as shown in Figure 4 When the hindered phenolic antioxidant was added at a concentration of 0.5 g / L, a trace amount of Ce(Ⅳ) could still be detected in the organic phase at 90 minutes of reaction, indicating that the concentration of the agent was insufficient and could not completely eliminate Ce(Ⅳ) in the organic phase. When the hindered phenolic antioxidant was added at a concentration of 1.0-2 g / L, as the concentration of the agent increased, the time for eliminating Ce(Ⅳ) in the organic phase was shortened. When the hindered phenolic antioxidant was added at a concentration of 1.0 g / L, the Ce(Ⅳ) in the organic phase was completely eliminated at 70 minutes of reaction. When the hindered phenolic antioxidant was added at a concentration of 2.0 g / L, the Ce(Ⅳ) in the organic phase was completely eliminated at 75 minutes of reaction, indicating that the concentration of the agent was sufficient and could completely eliminate Ce(Ⅳ) in the organic phase.

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

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

[0105] Depend on Figure 5 It can be seen that when the added concentration of hindered phenol antioxidant is fixed at 2g / L, with the extension of reaction time, the Ce(Ⅳ) content in the organic phase at different reaction temperatures shows a decreasing trend. With the increase of the reaction temperature of the system, the time for the Ce(Ⅳ) content in the organic phase to be completely eliminated is shortened. Under the condition of reaction temperature of 20℃, the time for the Ce(Ⅳ) content in the organic phase to be completely eliminated is 120min. Under the condition of reaction temperature of 60℃, the time for the Ce(Ⅳ) content in the organic phase to be completely eliminated is only 60min. This is because under the condition of low temperature, the viscosity of the organic phase is large, the extraction reaction kinetics decreases, and the probability of the inhibitor contacting with Ce(Ⅳ) in the organic phase decreases. The increase of high temperature can increase the contact opportunity between Ce(Ⅳ) in the organic phase and the inhibitor, and promote 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 the extraction and separation of rare earth ions. The composite liquid inhibitor of the present invention is insensitive to the acidity and alkalinity of the rare earth extraction system, and can effectively avoid the oxidation of cerium (III) to cerium (IV) by oxygen in the air under 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, adds a certain amount of the above organic phase to the head of the extraction production line, and completes a cycle through the saponification-rare earth soap section, the extraction section, the washing section, and the stripping section. The organic phase to which the inhibitor is added can play a significant inhibitory and elimination role on cerium (IV) in the extraction system during the reciprocating cycle. Through the method of the present invention, the cerium content in the final output extraction and separation wastewater is ≤300ppm, ensuring the qualification of cerium in the praseodymium-neodymium series products.

[0107] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for inhibiting the oxidation of variable-valence rare earth ions during the extraction and separation process of rare earth ions, characterized in that: The following steps are involved: In the process of extracting and separating the rare earth solution system, a certain amount of composite liquid inhibitor is added to the organic phase when an environmentally friendly diluent is used, and then the organic phase is added to the rare earth solution system for reaction; The composite liquid inhibitor is used to inhibit the oxidation of trivalent cerium to tetravalent cerium during the extraction and separation process to prevent the presence of tetravalent cerium from affecting the purity of the product; The composite liquid inhibitor comprises a main inhibitor, an auxiliary inhibitor and a diluent; The main inhibitor comprises a hindered phenol compound, and the auxiliary inhibitor comprises a polyphenolic hydroxyl compound.

2. The method for inhibiting oxidation of variable-valence rare earth ions during rare earth ion extraction and separation according to claim 1, characterized in that: The hindered phenol 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).

3. The method for inhibiting oxidation of variable-valence rare earth ions during rare earth ion extraction and separation according to claim 1 or 2, characterized in that: The polyphenol hydroxy compound comprises one or more of 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-butylpyrogallol, 4-allylpyrogallol, 2-methyl-4-pentylpyrogallol and phenethylpyrogallol.

4. The method for inhibiting oxidation of variable-valence rare earth ions during rare earth ion extraction and separation according to claim 3, characterized in that: The diluent comprises one or more of kerosene, sulfonated kerosene, aviation kerosene, hydrogenated enhanced kerosene, No. 200 solvent oil, No. 260 solvent oil, synthetic solvent oil, IP80, white oil, light white oil, white wax oil, cyclohexane, cyclohexanone and n-hexane.

5. The method for inhibiting oxidation of variable-valence rare earth ions during rare earth ion extraction and separation according to claim 1, 2 or 4, characterized in that: The addition amount of the composite liquid inhibitor in the organic phase is 0.1-20 g / L.

6. The method for inhibiting oxidation of variable-valence rare earth ions during rare earth ion extraction and separation according to claim 5, characterized in that: The volume ratio of the composite liquid inhibitor to the environmentally friendly diluent is 0.1-20:80-99.

9.

7. The method for inhibiting oxidation of variable-valence rare earth ions during rare earth ion extraction and separation according to claim 1 or 6, characterized in that: The environmentally friendly diluent comprises P507-environmentally friendly diluent.

8. The method for inhibiting oxidation of variable-valence rare earth ions during rare earth ion extraction and separation according to claim 7, characterized in that: The reaction temperature is 30-50° C., and the reaction time is 20-120 hours.

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