A method for inhibiting the formation of tetravalent cerium during rare earth extraction and separation

Abstract

The present invention provides a method for inhibiting the formation of tetravalent cerium during a rare earth extraction and separation process, relating to the field of rare earth separation technology. During the extraction and separation process of a rare earth solution system, while using an environmentally friendly diluent, a certain amount of reducing organic matter is added during the extraction and separation process; the reducing organic matter is used to inhibit the oxidation of trivalent cerium to tetravalent cerium during the extraction and separation process, thereby preventing a shift in the rare earth extraction and separation sequence during the extraction and separation process; the reducing organic matter is an organic matter containing one or more of unsaturated hydrocarbons, aldehydes, and phenols; and the rare earth solution system is at least one of a rare earth chloride solution system, a rare earth sulfuric acid solution system, or a rare earth nitric acid solution system. By using the reducing organic matter during the extraction and separation process, the present invention can inhibit the oxidation of trivalent cerium to tetravalent cerium during the extraction and separation process, thereby preventing a shift in the rare earth extraction and separation sequence during the extraction and separation process.

Description

Technical Field

[0001] The present invention relates to the technical field of rare earth separation, in particular to a method for inhibiting the generation of tetravalent cerium during the rare earth extraction and separation process. Background Art

[0002] An extractant (acidic extractants such as P507, P204, C272, or neutral phosphorus extractants such as C923 and TBP) is first mixed with a diluent to form an organic phase of a certain concentration. This organic phase will be used for rare earth extraction and separation (the rare earth extraction and separation process is mainly divided into organic saponification, rare earth soap preparation, extraction, washing, and stripping). The diluents used in the early days were mostly kerosene or sulfonated kerosene. Kerosene and sulfonated kerosene can cause waste gas generation of volatile organic compounds (VOCs), and the dissolution of the diluent increases the COD (chemical oxygen demand) in the extraction and separation wastewater.

[0003] Therefore, in recent years, rare earth separation companies have generally adopted environmentally friendly diluents such as white oil, hydrogenated kerosene, or aviation kerosene to replace the earlier kerosene or sulfonated kerosene. With the replacement of environmentally friendly diluents, the problem of cerium dislocation in the rare earth extraction and separation process has become prominent. Specifically, trivalent cerium is easily oxidized by oxygen in the air to form tetravalent cerium in the highly alkaline environment of the organic saponification stage, resulting in a dislocation in the rare earth extraction and separation sequence. This is reflected in the cerium distribution (CeO2 / REO) in the praseodymium and neodymium products produced in the field reaching as high as 0.2% and continuing to rise. At the same time, the organic stripping process is difficult to strip tetravalent cerium, and it has the potential to enter the medium and heavy rare earth products.

[0004] In existing production, hydrogen peroxide is often added as a reducing agent during the extraction and separation process to suppress the extraction and separation dislocation caused by the conversion of trivalent cerium to tetravalent cerium during the rare earth extraction and separation process. However, there are the following problems: (1) Hydrogen peroxide has an oxidative degradation effect on the extractant, resulting in the loss of the extractant. The degraded extractant causes the COD and total phosphorus in the extraction wastewater to exceed the standard, making it more difficult to treat, resulting in the reduction of the positive effect of using environmentally friendly diluents that are not easily soluble in water; (2) Hydrogen peroxide is entrained in a small amount by blank organic matter in the stripping section and returns to the organic saponification section. Due to the increase in pH value, hydrogen peroxide exhibits oxidative properties and oxidizes trivalent cerium to tetravalent cerium. After entering the extraction section and washing section, the extraction sequence is dislocated. In order to ensure that there is no extraction dislocation during the extraction and separation process, the amount of hydrogen peroxide used needs to be continuously increased.

[0005] Therefore, in the field of rare earth separation technology, finding a reducing agent that can eliminate the dislocation of the extraction order caused by the widespread use of environmentally friendly diluents, and the reducing agent must avoid oxidative degradation of the extractant, avoid the loss of the extractant and the increase of COD and total phosphorus in the extraction wastewater, has become a technical problem that needs to be solved urgently. Summary of the Invention

[0006] The present invention provides a method for inhibiting the formation of tetravalent cerium during the extraction and separation process of rare earths. During the extraction and separation process of a rare earth solution system, a certain amount of reducing organic matter is added during the extraction and separation process while using an environmentally friendly diluent. The reducing organic matter is used to inhibit the oxidation of trivalent cerium to tetravalent cerium during the extraction and separation process, thereby preventing the rare earth extraction and separation sequence from being dislocated during the extraction and separation process.

[0007] The reducing organic matter is an organic matter containing one or more of unsaturated hydrocarbons, aldehydes and phenols; the rare earth solution system is at least one of a rare earth chloride solution system, a rare earth sulfuric acid solution system or a rare earth nitric acid solution system; and the environmentally friendly diluent is at least one of white oil, hydrogenated kerosene or aviation kerosene.

[0008] Preferably, the reducing organic matter is an organic matter containing unsaturated hydrocarbons.

[0009] Preferably, the carbon number range of the organic matter containing unsaturated hydrocarbons is 6≤C≤16.

[0010] Preferably, the unsaturated hydrocarbon is at least one of pinene and / or aromatic hydrocarbon.

[0011] Preferably, the organic matter containing unsaturated hydrocarbons is at least one of turpentine, kerosene, and sulfonated kerosene.

[0012] Preferably, the amount of the reducing organic matter added is 0.05% to 5% of the total amount of cerium in the rare earth solution system feed liquid.

[0013] Preferably, the cerium content in the rare earth solution system accounts for 1% to 80% of the total amount of rare earth in the rare earth solution system feed liquid.

[0014] Preferably, the extraction and separation process is:

[0015] The rare earth solution system and the refractory rare earth organic phase obtained by rare earth saponification undergo a multi-stage exchange equilibrium reaction in the extraction section and the washing section, and then enter the stripping section; a raffinate containing refractory rare earths is obtained at the front end of the extraction section; and an organic phase containing easily extractable rare earths is obtained at the end of the washing section; wherein the refractory rare earth organic phase is obtained by reacting the saponified organic phase with the raffinate containing refractory rare earths, the saponified organic phase is obtained by reacting a blank organic phase with an alkaline substance in the organic saponification section, and the blank organic phase is obtained by mixing the extractant and the environmentally friendly diluent in proportion;

[0016] Wherein, during the extraction and separation process, the reducing organic matter is gradually added to inhibit the oxidation of trivalent cerium to tetravalent cerium during the rare earth saponification.

[0017] Preferably, the reducing organic matter is added directly and quantitatively during the extraction process, or the reducing organic matter is added after being mixed with the extractant.

[0018] Preferably, the extractant is one of P204, P507, C272, C923, and TBP.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] The present invention provides a method for inhibiting the formation of tetravalent cerium during a rare earth extraction and separation process, relating to the field of rare earth separation technology. During the extraction and separation process of a rare earth solution system, while using an environmentally friendly diluent, a certain amount of reducing organic matter is added; the reducing organic matter is used to inhibit the oxidation of trivalent cerium to tetravalent cerium during the extraction and separation process, thereby preventing a shift in the rare earth extraction and separation sequence during the extraction and separation process; wherein the reducing organic matter is an organic matter containing one or more of unsaturated hydrocarbons, aldehydes, and phenols; the rare earth solution system is at least one of a rare earth chloride solution system, a rare earth sulfuric acid solution system, or a rare earth nitric acid solution system; and the environmentally friendly diluent is at least one of white oil, hydrogenated kerosene, or aviation kerosene. By quantitatively adding the reducing organic matter during the extraction and separation process, the present invention can inhibit the oxidation of trivalent cerium to tetravalent cerium during the extraction and separation process, thereby preventing a shift in the rare earth extraction and separation sequence during the extraction and separation process.

[0021] The embodiment of the present invention, by quantitatively adding reducing organic matter during the extraction process of the rare earth solution system, can inhibit the oxidation of trivalent cerium to tetravalent cerium in the organic phase at the front end of the process. The reducing organic matter can dissolve in the extractant and directly reduce the extracted tetravalent cerium from the extractant, thereby reducing the loss of reducing organic matter and suppressing the phenomenon of dislocation of the extraction order. At the same time, the reducing organic matter used in the present invention can effectively avoid the oxidative degradation of the extractant added to the organic saponification stage, avoiding the degradation loss of the extractant and reducing the COD and total phosphorus content in the extraction wastewater caused by oxidative degradation, thereby avoiding the problem of secondary pollution to the environment. In addition, the method provided by the present invention can also achieve the simultaneous reduction of tetravalent cerium in the organic phase and the aqueous phase.

[0022] The reducing organic matter selected in this embodiment can be mutually soluble with the extractant, and the extracted tetravalent cerium is directly reduced from the extractant, thereby suppressing the oxidation of trivalent cerium to tetravalent cerium in the organic phase. Therefore, the reducing organic matter selected in this embodiment has a more significant reduction effect than the hydrogen peroxide in the prior art. Since the reducing organic matter is also quantitatively added during the rare earth extraction and separation process and is slightly soluble in water, it is beneficial to suppress the oxidation of trivalent cerium to tetravalent cerium in the rare earth aqueous phase. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0024] Figure 1 This is a flow chart of the extraction and separation process provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0025] The following examples are provided for a better understanding of the present invention and are not intended to limit the best mode of implementation. They do not limit the content and scope of protection of the present invention. Any product identical or similar to the present invention obtained by anyone under the guidance of the present invention or by combining the features of the present invention with other prior arts shall fall within the scope of protection of the present invention.

[0026] Where specific experimental steps or conditions are not specified in the examples, the conventional experimental steps or conditions described in the prior art in the art may be used. The reagents and other instruments used, for which the manufacturer is not specified, are all conventional reagent products that can be obtained commercially. Furthermore, the accompanying drawings are merely schematic illustrations of the embodiments of the present disclosure and are not necessarily drawn to scale. Identical reference numerals in the figures represent identical or similar parts, and their repeated descriptions will be omitted. Some block diagrams shown in the accompanying drawings are functional entities and do not necessarily correspond to physically or logically independent entities.

[0027] The present invention provides a method for inhibiting the formation of tetravalent cerium during the extraction and separation process of rare earths. During the extraction and separation process of a rare earth solution system, a certain amount of reducing organic matter is added during the extraction and separation process while using an environmentally friendly diluent. The reducing organic matter is used to inhibit the oxidation of trivalent cerium to tetravalent cerium during the extraction and separation process, thereby preventing the rare earth extraction and separation sequence from being dislocated during the extraction and separation process.

[0028] The reducing organic matter is an organic matter containing one or more of unsaturated hydrocarbons, aldehydes and phenols; the rare earth solution system is at least one of a rare earth chloride solution system, a rare earth sulfuric acid solution system or a rare earth nitric acid solution system; and the environmentally friendly diluent is at least one of white oil, hydrogenated kerosene or aviation kerosene.

[0029] In this embodiment, the addition of a reducing organic compound to the rare earth soap stage and / or the organic saponification stage during the extraction and separation process can inhibit the oxidation of trivalent cerium to tetravalent cerium at the front end of the extraction and separation process. The use of the reducing organic compound provided in this embodiment eliminates the problem of trivalent cerium being oxidized to tetravalent cerium by hydrogen peroxide, a reducing agent, being carried into the organic saponification stage and causing an increase in pH.

[0030] The embodiments of the present invention, by quantitatively adding reducing organic matter during the rare earth soap stage and / or organic saponification stage in the rare earth solution system, can inhibit the oxidation of trivalent cerium to tetravalent cerium in the organic phase at the front end of the process. The reducing organic matter can dissolve in the extractant and directly reduce the extracted tetravalent cerium from the extractant, thereby reducing the loss of reducing organic matter and thus suppressing the phenomenon of dislocation of the extraction sequence. At the same time, the reducing organic matter used in the present invention can effectively avoid oxidative degradation of the extractant added in the organic saponification stage, avoiding degradation loss of the extractant and reducing the COD and total phosphorus content in the extraction wastewater caused by oxidative degradation, thereby reducing the problem of environmental pollution. In addition, the method provided by the present invention can also achieve the simultaneous reduction of tetravalent cerium in the organic phase and the aqueous phase.

[0031] By quantitatively adding reducing organic matter at a specific stage during the extraction and separation process of a rare earth solution system, the oxidation of trivalent cerium to tetravalent cerium can be inhibited, the reaction efficiency of the reducing organic matter with the extractant to reduce the extracted tetravalent cerium can be improved, and the extracted tetravalent cerium in the rare earth solution system can be efficiently reduced to trivalent cerium, thereby greatly reducing the loss of reducing organic matter and effectively avoiding the dislocation of the extraction sequence. This solves the problem of dislocation of the extraction sequence caused by the slow oxidation of trivalent cerium to tetravalent cerium during the rare earth extraction and separation process. At the same time, it effectively avoids the oxidative degradation of the extractant added in the organic saponification stage, avoiding degradation loss of the extractant, and reducing the COD and total phosphorus content in the extraction wastewater caused by oxidative degradation, thereby reducing the problem of environmental pollution caused by increased COD and total phosphorus in the wastewater. In addition, the reducing organic matter selected in the embodiments of the present invention has a large output and a low price, and therefore has the characteristics of high applicability and safety.

[0032] The reducing organic matter selected in this embodiment can be mutually soluble with the extractant, and the extracted tetravalent cerium can be directly reduced from the extractant, thereby suppressing the oxidation of trivalent cerium to tetravalent cerium in the organic phase, and further extracting and separating more trivalent cerium. Therefore, the reducing organic matter selected in this embodiment is more effective in reduction compared with the hydrogen peroxide used in the prior art. Since the reducing organic matter is also quantitatively added during the rare earth extraction and separation process, and the reducing organic matter is slightly soluble in water, the tetravalent cerium in the rare earth solution can be reduced to trivalent cerium, thereby suppressing the oxidation of trivalent cerium to tetravalent cerium in the aqueous phase.

[0033] Preferably, the reducing organic matter is an organic matter containing unsaturated hydrocarbons.

[0034] Furthermore, when the reducing organic matter is an organic matter containing unsaturated hydrocarbons, the carbon number range of the organic matter containing unsaturated hydrocarbons is 6≤C≤16.

[0035] In a specific implementation, when the reducing organic compound is an organic compound containing unsaturated hydrocarbons, the carbon number of the organic compound containing unsaturated hydrocarbons is preferably 16. Since unsaturated hydrocarbons with longer carbon chains are less hydrophilic, they can also act as environmentally friendly diluents, thereby facilitating rare earth extraction and separation while minimizing water pollution.

[0036] Preferably, the unsaturated hydrocarbon is at least one of pinene and / or aromatic hydrocarbon.

[0037] Preferably, the organic matter containing unsaturated hydrocarbons is at least one of turpentine, kerosene, and sulfonated kerosene.

[0038] The reducing organic matter can be turpentine, kerosene, or sulfonated kerosene. Alternatively, the reducing organic matter can be any two or three of these. Turpentine is primarily composed of pinene, meaning it is an organic matter containing pinene. Kerosene and xanthated kerosene are organic matters containing aromatic hydrocarbons. Furthermore, turpentine is preferably used as the reducing organic matter, as it has an inhibition rate of over 92% for tetravalent cerium.

[0039] Turpentine is an essential oil extracted from the resin secreted by plants in the Pinaceae family. It is a highly produced and inexpensive essential oil worldwide. Its excellent properties have led to its widespread use in numerous fields, including medicine, coatings, fragrances, and pesticides. Compared to using hydrogen peroxide as a reducing agent, the inexpensive turpentine used in this embodiment can inhibit the oxidation of trivalent cerium to tetravalent cerium in the rare earth solution system, eliminating the phenomenon of dislocation in the extraction sequence. The use of turpentine in place of hydrogen peroxide can also inhibit further oxidative degradation of the extractant, thereby reducing degradation losses and suppressing increases in COD and total phosphorus in the extraction wastewater, thereby reducing environmental pollution.

[0040] Moreover, the applicability and safety of turpentine are much better than those of hydrogen peroxide: the reducing organic matter uses turpentine, which has a huge output and a low price, and it can replace the purified pinene, which will have a cost advantage; the turpentine used in this embodiment can also serve as an environmentally friendly diluent.

[0041] Preferably, the amount of the reducing organic matter added is 0.05% to 5% of the total amount of cerium in the rare earth solution system feed liquid.

[0042] In a specific implementation, the amount of the further reducing organic matter added is preferably 5%.

[0043] Preferably, the cerium content in the rare earth solution system accounts for 1% to 80% of the total amount of rare earth in the rare earth solution system feed liquid.

[0044] Preferably, the extraction and separation process is:

[0045] The rare earth solution system and the refractory rare earth organic phase obtained by rare earth saponification undergo a multi-stage exchange equilibrium reaction in the extraction section and the washing section, and then enter the stripping section; a raffinate containing refractory rare earths is obtained at the front end of the extraction section; and an organic phase containing easily extractable rare earths is obtained at the end of the washing section; wherein the refractory rare earth organic phase is obtained by reacting the saponified organic phase with the raffinate containing refractory rare earths, the saponified organic phase is obtained by reacting a blank organic phase with an alkaline substance in the organic saponification section, and the blank organic phase is obtained by mixing the extractant and the environmentally friendly diluent in proportion;

[0046] Wherein, during the extraction and separation process, the reducing organic matter is gradually added to inhibit the oxidation of trivalent cerium to tetravalent cerium during the rare earth saponification.

[0047] When implementing it, refer to Figure 1 , Figure 1 The extraction and separation flow chart provided in the embodiment of the present invention takes the rare earth chloride system as an example to describe the entire extraction and separation process in detail, including:

[0048] Organic saponification section: blank organic phase (which will provide H + The organic phase is prepared by mixing an extractant and an environmentally friendly diluent into a certain concentration) and an alkaline substance (such as at least one of sodium hydroxide, ammonia water, magnesium hydroxide or magnesium bicarbonate) for saponification to obtain a saponified organic phase; the mechanism involved is:

[0049] NaOH + HA (blank organic phase) → NaA (saponified organic phase) + H2O.

[0050] Rare earth saponification stage: The saponified organic phase reacts with the hard-to-extract rare earth chloride in the hard-to-extract rare earth to obtain the hard-to-extract rare earth organic phase; the mechanism involved is (taking rare earth chloride as an example):

[0051] RE a Cl3 (difficult-to-extract rare earth chloride) + 3NaA (saponified organic phase) → RE a A3 (difficult-to-extract rare earth organic phase) + 3NaCl (enters wastewater).

[0052] Extraction section and washing section: The mixed rare earth solution to be extracted and separated (it should be noted that since it is a rare earth chloride system, the mixed rare earth solution is a mixed rare earth chloride solution, and the mixed rare earth chloride in the mixed rare earth chloride solution reacts with the difficult-to-extract rare earth organic phase) and the difficult-to-extract rare earth organic phase undergo multi-stage exchange equilibrium reactions in the extraction section and washing section, and then enter the stripping section. The raffinate containing difficult-to-extract rare earths is obtained at the front end of the extraction section, and the organic phase containing easily-extracted rare earths is obtained at the end of the washing section. The mechanism involved is:

[0053] RE a A3 (difficult to extract rare earth organic phase) + (RE a +RE b )Cl3(mixed rare earth chloride)→RE a Cl3 (raffinate containing difficult-to-extract rare earths) + RE b A3 (organic phase containing easily extractable rare earth).

[0054] Stripping section: Entering the stripping section, easy-to-extract rare earth and blank organic phase are obtained; the mechanism involved is:

[0055] RE b A3 (organic phase containing easily extractable rare earth) + HCl (strip acid) → RE b Cl3 (easily extractable rare earth chloride) + 3HA (blank organic phase). For example, the stripping acid can also be sulfuric acid or nitric acid. When hydrochloric acid is used for stripping, the rare earth solution system is a rare earth chloride solution system; when sulfuric acid is used for stripping, the rare earth solution system is a rare earth sulfuric acid solution system; when nitric acid is used for stripping, the rare earth solution system is a rare earth nitric acid solution system.

[0056] In specific implementations, reducing organic matter can also be quantitatively added to the stripping, extraction, and washing stages. Specifically, during the extraction and separation process, quantitatively adding reducing organic matter to one or more stages of the rare earth saponification, extraction, organic saponification, stripping, and washing stages can inhibit the oxidation of trivalent cerium to tetravalent cerium during the extraction and separation process, thereby preventing a mismatch in the extraction and separation sequence. It should be noted that the specific number of stages is not specifically limited herein.

[0057] Specifically, during the entire extraction and separation process, adding reducing organic matter to the rare earth soap section and / or the organic saponification section can inhibit the oxidation of trivalent cerium to tetravalent cerium at the front end of the extraction and separation process. When the reducing organic matter is quantitatively added to the stripping section and / or the washing section, the oxidized tetravalent cerium can be reduced to trivalent cerium at the back end of the process, solving the problem of misalignment in the extraction and separation sequence. If the cerium content in the stripping solution is already high, quantitative addition is performed in the stripping section, the extraction section, and / or the washing section to reduce the oxidized tetravalent cerium to trivalent cerium. Using the reducing organic matter provided in this embodiment eliminates the oxidation problem caused by the entrainment of hydrogen peroxide as a reducing agent into the organic saponification section due to the increased pH value.

[0058] Preferably, the reducing organic matter is added directly and quantitatively during the extraction and separation process, or the reducing organic matter is added after being mixed with an extractant.

[0059] In specific implementation, compared with the form of preparing with the extractant, the quantitative addition method can reduce the loss of the organic reducing agent and simplify the operation steps.

[0060] Preferably, the extractant is one of P204, P507, C272, C923, and TBP.

[0061] In order to enable those skilled in the art to better understand the present invention, the preparation method provided by the present invention is described below through multiple specific examples.

[0062] This example provides a method for characterizing the reducing performance of an organic reducing agent: In a nitrogen-filled, sealed stirring system, a 0.5 mol / L tetravalent cerium nitrate solution with a pH of 1.5 was used as the test agent. Turpentine, kerosene from three different manufacturers, and sulfonated kerosene from three different manufacturers were added as organic reducing agents, respectively. After stirring for a predetermined time at a 1:1 ratio of organic phase to water, the reduction rates of tetravalent cerium were obtained as shown in Table 1. The total cerium content and the tetravalent cerium content can be measured using conventional methods, such as the ferrous ammonium sulfate method, and are not specifically limited in this invention.

[0063] Table 1 Characterization results of reduction performance of organic reducing agents

[0064]

[0065] The reduction rate of tetravalent cerium within a certain period of time obtained based on the above characterization method is used as a criterion for judging the reduction effect, providing a semi-quantitative basis for the use of appropriate organic reducing agents in patent implementation.

[0066] Example 1

[0067] The implementation is carried out in the industrial production line of cerium and praseodymium extraction and separation, and the operating conditions are as follows:

[0068] The flow ratio condition is:

[0069] Organic phase: alkali solution: rare earth soap material: mixed rare earth chloride solution: praseodymium, neodymium and samarium washing solution: back acid: washing water = 450:45:35:40:30:45:5

[0070] Feed solution: concentration 1.5M, wherein the rare earth distribution ratio La:Ce:PNS=25:51:24 (i.e. the cerium distribution ratio in the rare earth solution system is 25% of the total rare earth content)

[0071] Organic phase: concentrated 1.5MP507, diluent is environmentally friendly hydrogenated kerosene

[0072] Liquid caustic soda: concentration 6.0M

[0073] Stripping solution: 5.6M hydrochloric acid

[0074] Number of tank stages in each section:

[0075] Organic saponification section: 3-stage continuous stirring + 2-stage clarification

[0076] Rare earth saponification section: 4-stage continuous stirring + 2-stage clarification

[0077] Extraction stage: 56 levels

[0078] Washing section: 47 levels

[0079] Stripping stage: 12 levels

[0080] The specific implementation content is as follows: adding an extractant and an environmentally friendly diluent to form an organic phase with a certain concentration in the organic saponification section for extraction and separation of cerium and praseodymium; adding turpentine oil quantitatively (0.5%) in the 8th stage of the washing section of rare earth extraction and separation.

[0081] Comparative Example 1

[0082] In Comparative Example 1, no reducing agent was added during the rare earth extraction and separation, and only an environmentally friendly diluent was quantitatively added. The cerium distribution (CeO2 / REO) in the praseodymium-neodymium stripping solution showed a trend of increasing.

[0083] Example 2

[0084] The only difference between this embodiment and embodiment 1 is that kerosene is quantitatively added (2%) to the 8th stage of the washing section for rare earth extraction and separation.

[0085] Example 3

[0086] The only difference between this embodiment and embodiment 1 is that sulfonated kerosene is quantitatively added (2.5%) to the eighth stage of the washing section for rare earth extraction and separation.

[0087] Example 4

[0088] The stripping in this embodiment differs from that in embodiment 1 only in that turpentine is quantitatively added in the 8th stage of the washing section of the rare earth extraction separation, and sulfonated kerosene is added in the 2nd stage of the stripping section; wherein the amount of turpentine added is 1.5% and the amount of sulfonated kerosene added is 2.5%.

[0089] Comparative Example 2

[0090] Comparative Example 2 differed only from Example 1 in that hydrogen peroxide was quantitatively added to the eighth stage of the rare earth extraction and separation wash section. Specifically, the quantitative addition of hydrogen peroxide to the eighth stage of the rare earth extraction and separation wash section (2%) was increased to 2.8% after 40 days of operation.

[0091] The cerium distribution (CeO2 / REO) in the praseodymium-neodymium strip liquor was determined by comparing the experimental test results with those of hydrogen peroxide and the absence of a reducing agent. The test results are shown in Table 2 below. It should be noted that TOC was measured in the extraction wastewater using a TOC analyzer, and total phosphorus (P) was measured using a total phosphorus analyzer.

[0092] Table 2 Example results

[0093]

[0094]

[0095] From the results of Comparative Example 1, it can be seen that the cerium distribution (CeO2 / REO) in the praseodymium-neodymium stripping solution is as high as 1490×10 -6 , there was a serious dislocation in the extraction and separation order, and the separation effect deteriorated, but the COD and total phosphorus contents in the extraction wastewater were low.

[0096] From Examples 1 to 4, it can be seen that as the addition time of the organic reducing agent increases, the reducing agent has an effect on suppressing the phenomenon of dislocation of the extraction and separation order. When the reducing agent is continuously added for more than 40 days, the cerium distribution (CeO2 / REO) in the stripping solution can be reduced to 500×10 -6 Below, and relatively stable operation. Among them, turpentine has the most significant reduction effect, with the lowest cerium distribution in the praseodymium-neodymium strip liquor. This is because turpentine contains a large amount of unsaturated hydrocarbons, which has a good reducing effect on inhibiting the oxidation of trivalent cerium. Sulfonated kerosene has the weakest inhibitory effect and the slowest reduction rate of tetravalent cerium. After stable operation, the cerium distribution in the praseodymium-neodymium strip liquor is high. This is because sulfonated kerosene contains fewer unsaturated bonds, resulting in a weaker ability to inhibit the oxidation of trivalent cerium to tetravalent cerium. The COD and total phosphorus in the wastewater extracted and separated in Examples 1 to 4 were significantly higher than those in Comparative Example 1.

[0097] From Comparative Example 2, it can be seen that hydrogen peroxide can quickly reduce tetravalent cerium to trivalent cerium in the early stage of operation. However, as the operation time increases, part of it is entrained into the blank organic phase. Hydrogen peroxide exhibits oxidizing properties in the saponification organic phase, oxidizing trivalent cerium to tetravalent cerium. After the tetravalent cerium enters the extraction and washing stages, it and praseodymium and neodymium become easily extractable components, causing the extraction order to be dislocated, making it difficult to maintain the cerium distribution (CeO2 / REO) in the stripping solution at 500×10 -6 The following affects the stable operation of the system. At the same time, the strong oxidizing property of hydrogen peroxide also leads to a significant increase in COD and total phosphorus in the wastewater compared with Comparative Example 1 and Examples 1-4. To inhibit its oxidation, the hydrogen peroxide content was increased to 2.8% after 50 days of operation. After another 10 days of operation, the cerium content in the praseodymium-neodymium stripping solution was reduced to 500×10 -6 Below, but COD and total phosphorus in the wastewater further increased.

[0098] Compared to hydrogen peroxide, the turpentine, sulfonated kerosene, and kerosene used in the embodiments of the present invention as reducing agents can effectively inhibit the oxidative degradation of the extractant, thereby resolving the consequences of using hydrogen peroxide, namely, the impact of oxidative degradation of the extractant on costs, and reducing environmental pollution (increased COD and total phosphorus in the extraction wastewater, and oxidative degradation causing loss of the extractant).

[0099] Thus, the embodiments of the present invention select a series of organic reducing substances. According to the method for determining the reducing ability, the inhibitory effect on the dislocation of the extraction order caused by the oxidation of trivalent cerium to tetravalent cerium is verified, as well as the technical problem that the hydrogen peroxide reducing agent will oxidize and degrade the extractant, resulting in the loss of the extractant and the increase of COD and total phosphorus in the extraction wastewater.

[0100] For simplicity of description, the method embodiments are described as a series of actions. However, those skilled in the art should be aware that the present invention is not limited by the order of the actions described, as certain steps can be performed in other orders or simultaneously according to the present invention. Furthermore, those skilled in the art should also be aware that the embodiments described in this specification are preferred embodiments, and the actions and components involved are not necessarily required for the present invention.

[0101] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present disclosure. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification.

[0102] The above is a detailed introduction to a method for inhibiting the formation of tetravalent cerium during the rare earth extraction and separation process provided by the present invention. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the ideas of the present invention, there may be changes in the specific implementation methods and application scopes. In summary, the contents of this specification should not be understood as limiting the present invention.

[0103] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present disclosure, rather than to limit them. Although the present disclosure has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present disclosure.

Claims

1. A method for inhibiting the formation of tetravalent cerium during rare earth extraction and separation, characterized in that: During the extraction and separation process of the rare earth solution system, when an environmentally friendly diluent is used, a certain amount of reducing organic matter is added during the extraction and separation process; the reducing organic matter is used to inhibit the oxidation of trivalent cerium to tetravalent cerium during the extraction and separation process, thereby preventing the rare earth extraction and separation sequence from being dislocated during the extraction and separation process; The reducing organic matter is an organic matter containing one or more of unsaturated hydrocarbons, aldehydes and phenols; the rare earth solution system is at least one of a rare earth chloride solution system, a rare earth sulfuric acid solution system or a rare earth nitric acid solution system; and the environmentally friendly diluent is at least one of white oil, hydrogenated kerosene or aviation kerosene.

2. The method according to claim 1, characterized in that The reducing organic matter is an organic matter containing unsaturated hydrocarbons.

3. The method according to claim 2, characterized in that The carbon number range of the organic matter containing unsaturated hydrocarbons is 6≤C≤16.

4. The method according to claim 1 or 2, characterized in that The unsaturated hydrocarbon is at least one of pinene and / or aromatic hydrocarbon.

5. The method according to claim 3, characterized in that The organic matter containing unsaturated hydrocarbons is at least one of turpentine, kerosene and sulfonated kerosene.

6. The method according to claim 1, characterized in that The amount of the reducing organic matter added is 0.05% to 5% of the total amount of cerium in the rare earth solution system feed liquid.

7. The method according to claim 1, characterized in that The cerium content in the rare earth solution system accounts for 1% to 80% of the total amount of rare earth in the rare earth solution system feed liquid.

8. The method according to claim 1, characterized in that The extraction and separation process is as follows: The rare earth solution system and the rare earth saponification-derived rare earth organic phase obtained by saponifying the rare earths undergo a multi-stage exchange equilibrium reaction in the extraction section and the washing section, and then enters the stripping section; a raffinate containing difficult-to-extract rare earths is obtained at the front end of the extraction section; and an organic phase containing easily-extracted rare earths is obtained at the end of the washing section; wherein the difficult-to-extract rare earth organic phase is obtained by reacting the saponified organic phase with the raffinate containing difficult-to-extract rare earths, the saponified organic phase is obtained by reacting a blank organic phase with an alkaline substance in the organic saponification section, and the blank organic phase is obtained by mixing the extractant and the environmentally friendly diluent in proportion; Wherein, during the extraction and separation process, the reducing organic matter is gradually added to inhibit the oxidation of trivalent cerium to tetravalent cerium during the rare earth saponification.

9. The method according to claim 1 or 8, characterized in that The reducing organic matter is added in a quantitative manner directly during the extraction process, or the reducing organic matter is added after being mixed with the extractant.

10. The method according to claim 8, characterized in that The extractant is one of P204, P507, C272, C923, and TBP.

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