Process for preparing ultra-high-purity rare earth oxide by continuous extraction leaching method

Abstract

The invention belongs to the technical field of hydrometallurgy, and particularly relates to a process for preparing ultra-high-purity rare earth oxide by a continuous extraction leaching method. According to the method, rare earth oxides and rare earth chlorides of rare earth elements to be purified are used as raw materials, difficult-to-extract components and easy-to-extract components in target components are removed in a segmented mode through the first-step continuous extraction and elution process and the second-step continuous extraction and elution process, continuous extraction and elution separation of rare earth and impurity ions is achieved, the separation efficiency of an extraction and elution column is improved, and the purity of the rare earth elements is improved. The method is suitable for rare earth impurities and non-rare earth impurities, and the steps of preparing the ultra-pure rare earth compound through the extraction leaching method are simplified.

Description

Technical Field

[0001] The invention belongs to the technical field of hydrometallurgy, and in particular relates to a process for preparing ultra-high purity rare earth oxides by a continuous leaching method. Technical Background

[0002] Rare earth elements have similar chemical properties, and it is very difficult to separate the 15 rare earth elements (except promethium and scandium) into single rare earth compounds one by one. In industry, the tiny properties of rare earth elements are gradually amplified through solvent extraction, leaching resin method, ion exchange method and other methods, so as to achieve separation and purification of rare earth elements.

[0003] Solvent extraction is the most commonly used technology in large-scale industrial production, and it is mainly based on the difference in the distribution coefficients of rare earth elements in the organic phase and the aqueous phase for separation. However, due to the small separation coefficients between some rare earth elements, especially when separating heavy rare earth elements, to obtain a single product with higher purity, it is usually necessary to go through hundreds or even thousands of cascade extractions, which not only increases equipment investment and troughing costs, but also requires complex dust-free workshops when preparing high-purity products, which places extremely high demands on human and material resources. Therefore, although solvent extraction is suitable for large-scale production, it does not have obvious advantages in the purification of small batches and customized high-purity rare earth products.

[0004] The leaching resin method combines the advantages of solvent extraction and ion exchange. It has higher selectivity and separation efficiency by adsorbing and eluting rare earth elements in the extraction column. In the process of high-purity purification of small amounts of rare earth elements, the leaching resin method has the advantages of low cost and high efficiency. However, the leaching operation process provided in the past is intermittent, with a high impurity content during the period. It is necessary to use delayed ions for gradient segmented elution to achieve step-by-step purification of rare earths. The operation process is discontinuous, making the process flow complicated. Especially when separating complex systems containing a large number of non-rare earth impurity ions, the enrichment of target ions in the leaching often depends on the accumulation of a large amount of experimental data and experience, and its applicability is relatively limited. At the same time, the migration and repeated exchange of impurity ions in the column further reduce the separation efficiency of rare earths and impurity ions. Summary of the invention

[0005] Based on the above findings, a process for preparing ultra-high purity rare earth oxides by a continuous leaching method is provided to address the shortcomings of the existing leaching resin method for separating and purifying rare earth elements.

[0006] A process for preparing ultra-high purity rare earth oxides by continuous leaching and extraction, comprising the following steps:

[0007] (1) Using rare earth oxides and rare earth chlorides of rare earth elements to be purified as raw materials, wherein the rare earth elements to be purified refer to main rare earth elements with an element distribution of more than 99%, which are set as component B, and the rare earth oxides are decomposed by hydrochloric acid to obtain rare earth chloride liquid;

[0008] (2) According to the extraction capacity of the leaching resin for rare earth and non-rare earth impurities in the solution, the difficult-to-extract component relative to component B is set as component C, and the easily-extractable component relative to component B is set as component A, that is, the extraction capacity of the leaching resin for components A, B, and C is A>B>C in order;

[0009] (3) The first step of continuous leaching is to achieve complete separation of component A and component BC: In the first step of continuous leaching, the leaching column is divided into three parts: adsorption section, stripping section and water washing section. The leaching columns of each part are connected in series, and the liquid inlet mode is top-in and bottom-out. Among them, there are m columns in the adsorption section and n columns in the stripping section.

[0010] A rare earth feed liquid with a pH value of 3-4.5 is added from the first extraction column of the adsorption section at a linear speed of 2-5 cm / min, and after passing through m extraction columns, the rare earth feed liquid of component BC is collected; hydrochloric acid with a concentration of 4-6 mol / L is added from the first extraction column of the stripping section at a linear speed of 2-5 cm / min, and after passing through n extraction columns, the rare earth feed liquid of component AB is recovered; the extraction column is washed with a weak acid solution with a pH value of 3-4.5 at 2-5 cm / min to obtain a blank extraction column to achieve circulation; every 30-60 minutes, all the extraction columns are stepped once, the blank extraction column is connected to the adsorption section to become the mth adsorption column of the adsorption section, the first adsorption column of the adsorption section is connected to the stripping section to become the nth stripping column of the stripping section, and the first stripping column is changed to the washing section for elution to form a blank extraction column, and the cycle is repeated to achieve complete separation of component A and component BC;

[0011] (4) adjusting the pH value of the BC-containing liquid obtained in step (3) to 3-4.5 with ammonia water and hydrochloric acid, and this solution will be used as the liquid for the second step of continuous leaching to achieve complete separation of the BC component; in the second step of continuous leaching, the leaching column is divided into four parts: an adsorption section, a leaching section, a stripping section, and a water washing section. The leaching columns of the adsorption section and the leaching section are connected in series end to end, and the leaching columns of the stripping section and the water washing section are single columns or multiple columns connected in parallel. The liquid inlet mode is top-in and bottom-out. Among them, there are M columns in the adsorption section and N columns in the leaching section;

[0012] The rare earth feed liquid is added from the first extraction column of the adsorption section at a linear speed of 2-5cm / min, and after passing through M extraction columns, the rare earth feed liquid of component BC is collected; hydrochloric acid with a concentration of 0.1-1.3mol / L is introduced from the upper end of the first extraction column of the elution section at a linear speed of 2-5cm / min to wash a small amount of component C in the extraction column; hydrochloric acid with a concentration of 1-3mol / L is introduced from the upper end of the stripping section at a linear speed of 2-5cm / min to obtain pure component B; the extraction column after stripping is washed with weak acid to obtain a blank extraction column to realize circulation; every 30-60min, all the extraction columns are stepped once, the blank extraction column is connected to the adsorption section to become the Mth adsorption column of the adsorption section, the first adsorption column of the adsorption section becomes the Nth impurity removal column of the elution section, the first impurity removal column of the elution section is connected to the stripping section for stripping, and the extraction column after stripping becomes a water washing section for elution to form a blank extraction column, and the cycle is repeated to realize the complete separation of component pure B;

[0013] (5) The pure B liquid obtained in step (4) is precipitated with high-purity oxalic acid and calcined to prepare ultra-high-purity rare earth oxides.

[0014] Preferably, the non-rare earth impurities in the rare earth oxides and rare earth chlorides in step (1) include one or more of iron, silicon, calcium, magnesium, nickel, cobalt, chromium, zinc, copper, vanadium and manganese.

[0015] Preferably, the leaching resin in step (2) includes one or both of P507 leaching resin and P204 leaching resin.

[0016] Preferably, in step (4), hydrochloric acid with a pH of 4 is used in the water washing section, and the linear speed is 2-5 cm / min.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] 1. The present invention applies fractional extraction to resin separation, removes the difficult-to-extract components and the easily-extracted components in the target components in stages, realizes continuous leaching and separation of rare earth and impurity ions, and improves the separation efficiency of the leaching column. This method is applicable to both rare earth impurities and non-rare earth impurities, and simplifies the steps of preparing ultra-high purity rare earth compounds by leaching;

[0019] 2. The present invention does not limit the number of stages of the leaching column, and the number of stages can be increased or decreased according to the required product purity. The requirements for raw material feed are low, and the products can meet the requirements of high-purity products;

[0020] 3. The raw materials used in the present invention are hydrochloric acid and ammonia water, which avoids the risk of introducing impurity ions by adding delayed ions, and has high impurity removal efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of the first step of the continuous leaching process of the present invention;

[0022] Figure 2 It is a schematic diagram of the second step continuous leaching process of the present invention. DETAILED DESCRIPTION

[0023] The following examples are intended to further illustrate the present invention, rather than to limit the scope of the claims of the present invention.

[0024] Embodiment 1:

[0025] (1) Using 99.99% lanthanum chloride solution as raw material, the pH value of the solution is 4.5, and the rare earth purity and non-rare earth impurity content in the solution are shown in Table 1.

[0026] Table 1 Analysis of the components of lanthanum chloride raw materials and lanthanum oxide products

[0027]

[0028] (2) The first step is to use an extraction column to achieve complete separation of A / BC components. Component A includes easily extractable ions such as Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y, and Fe, component B includes the main component La, and component C includes Ca, Mg, Co, Ni, Cu, Zn, V, Cr, Mn, The P204 leaching resin is loaded into the leaching column, which has 5 adsorption sections, 3 stripping sections, and 1 water washing section. The leaching columns of each section are connected in series, and the liquid inlet mode is from top to bottom. The rare earth feed liquid is added from the first leaching column of the adsorption section at a linear speed of 2cm / min. When the fifth leaching column penetrates, the rare earth feed liquid of component BC is collected. Hydrochloric acid with a concentration of 4mol / L is added from the first leaching column of the stripping section at a linear speed of 4cm / min. After passing through 3 leaching columns, the feed liquid of component AB is recovered. Weak acid water with a pH of 4 is added from the water washing section at a linear speed of 5cm / min to wash and obtain a blank leaching column to achieve circulation. When the fifth leaching column of the adsorption section penetrates, 60 minutes of BC liquid is collected, and then all the leaching columns are stepped once, the blank leaching column is connected to the adsorption section and becomes the fifth adsorption column of the adsorption section, the first adsorption column of the adsorption section is connected to the stripping section and becomes the third stripping column of the stripping section, and the first stripping column of the stripping section is connected to the washing section for water washing to form a blank leaching column, thereby completing the complete separation of component BC and component A.

[0029] (3) The pH value of the BC-containing liquid is adjusted to 4.5 with ammonia and hydrochloric acid. In the second step of the leaching process, the adsorption section has 5 levels and the elution section has 5 levels, and the liquid inlet method is top-in and bottom-out. The rare earth liquid is added from the first elution column of the adsorption section at a linear velocity of 3 cm / min. After passing through 5 elution columns, the rare earth liquid of component BC is collected and recovered. Hydrochloric acid with a concentration of 0.063 mol / L is introduced from the upper end of the elution section 1 at a linear velocity of 3 cm / min, and the elution section 5 enters the adsorption elution column. Hydrochloric acid with a concentration of 1 mol / L is introduced from the upper end of the stripping section at a linear velocity of 3 cm / min to strip the pure lanthanum component in the stripping elution column. After stripping, the stripping column is washed with weak acid water with a pH of 4 to obtain a blank stripping column for circulation. After every 35 minutes, all the leaching columns are stepped once, the blank leaching column is connected to the adsorption section to become the fifth adsorption column, the first adsorption column of the adsorption section is connected to the elution section to become the fifth elution column of the elution section, and the first elution column of the elution section is connected to the stripping section for stripping, thereby obtaining a high-purity lanthanum liquid. The leaching column after stripping is connected to the water washing section, and the first washing column forms a blank leaching column to achieve circulation.

[0030] (4) A solution of 99.999% high-purity oxalic acid was prepared and added to a high-purity lanthanum rare earth solution. The pH value of the precipitation was adjusted to 1.5 with ammonia water. The precipitated lanthanum oxalate was then calcined in a 950°C muffle furnace using a platinum crucible to obtain an ultra-high-purity rare earth oxide product. The impurity detection results of the product are shown in Table 1.

[0031] Embodiment 2:

[0032] (1) Using 99.99% yttrium chloride solution as raw material, the pH value of the solution is 3, and the rare earth purity and non-rare earth impurity content in the solution are shown in Table 2.

[0033] Table 2 Analysis of components of yttrium chloride raw materials and yttrium oxide products

[0034]

[0035] (2) The first step of leaching and extraction is to achieve complete separation of A / BC components, where A components are easily extracted ions such as Er, Tm, Yb, Lu, and Fe, B components are the main component Y, and C components are La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Ca, Mg, Co, Ni, Cu, Zn, V, Cr, Mn, The P507 leaching resin is loaded into the leaching column, which includes 7 adsorption sections, 3 stripping sections, and 1 water washing section. The leaching columns of each section are connected in series, and the liquid inlet is from top to bottom. The rare earth liquid is added from the first leaching column of the adsorption section at a linear speed of 2 cm / min. After the seventh leaching column is penetrated, the rare earth liquid of component BC is collected. Hydrochloric acid with a concentration of 5 mol / L is added from the first leaching column of the stripping section at a linear speed of 4 cm / min. After passing through 3 leaching columns, the liquid of component AB is recovered. Weak acid water with a pH of 4 is added from the water washing section at a linear speed of 5 cm / min to wash and obtain a blank leaching column to achieve circulation. When the 7th leaching column of the adsorption section penetrates, 60 minutes of BC liquid are collected, and then all the leaching columns are stepped once, the blank leaching column is connected to the adsorption section and becomes the 7th adsorption column of the adsorption section, the 1st adsorption column of the adsorption section is connected to the stripping section and becomes the 3rd stripping column of the stripping section, and the 1st stripping column of the stripping section is connected to the washing section for water washing to form a blank leaching column, thereby completing the complete separation of component BC and component A.

[0036] (3) The pH value of the BC-containing liquid is adjusted to 3 with ammonia and hydrochloric acid. The second step of the leaching process has 8 levels of adsorption section and 8 levels of elution section, and the liquid inlet method is top-in and bottom-out. The rare earth liquid is added from the first elution column of the adsorption section at a linear velocity of 2 cm / min. After passing through 8 elution columns, the BC component liquid is collected and recovered. Hydrochloric acid with a concentration of 1.259 mol / L is introduced from the upper end of the elution section 1 at a linear velocity of 2 cm / min, and the 8th elution section enters the adsorption elution column. Hydrochloric acid with a concentration of 3 mol / L is introduced from the upper end of the stripping section at a linear velocity of 2 cm / min to strip the pure yttrium component in the stripping elution column. The stripping elution column is washed with weak acid water with a pH of 4 to obtain a blank elution column for circulation. After every 60 minutes, all the leaching columns are stepped once, the blank leaching column is connected to the adsorption section to become the 8th adsorption column, the 1st adsorption column of the adsorption section is connected to the elution section to become the 8th elution column of the elution section, and the 1st elution column of the elution section is connected to the stripping section for stripping, thereby obtaining a high-purity yttrium liquid. The leaching column after stripping is connected to the water washing section, and the 1st washing column forms a blank leaching column to achieve circulation.

[0037] (4) A solution of 99.999% high-purity oxalic acid was prepared and added to a high-purity yttrium rare earth solution. The pH value of the precipitation was adjusted to 1.5 with ammonia water. The yttrium oxalate obtained by precipitation was then calcined in a 950°C muffle furnace with a platinum crucible to obtain an ultra-high-purity rare earth oxide product. The impurity detection results of the product are shown in Table 2.

[0038] Embodiment 3:

[0039] (1) Using 99.95% praseodymium chloride solution as raw material, the pH value of the solution is 4.5, and the rare earth purity and non-rare earth impurity content in the solution are shown in Table 3.

[0040] Table 3 Analysis of the composition of praseodymium chloride raw materials and praseodymium oxide products

[0041]

[0042] (2) The first step is to use an extraction column to achieve complete separation of A / BC components. Component A includes easily extractable ions such as Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y, and Fe, component B includes the main component of Pr, and component C includes La, Ce, Ca, Mg, Co, Ni, Cu, Zn, V, Cr, Mn, The P204 leaching resin is loaded into the leaching column, which has 10 adsorption sections, 3 stripping sections, and 1 washing section. The leaching columns of each section are connected in series, and the liquid inlet is from top to bottom. The rare earth feed liquid is added from the first leaching column of the adsorption section at a linear speed of 4 cm / min. When the 10th leaching column is penetrated, the rare earth feed liquid of component BC is collected. Hydrochloric acid with a concentration of 5 mol / L is added from the first leaching column of the stripping section at a linear speed of 4 cm / min. After passing through 3 leaching columns, the feed liquid of component AB is recovered. Weak acid water with a pH of 4 is added from the leaching column of the washing section at a linear speed of 5 cm / min to wash and obtain a blank leaching column to achieve circulation. When the 10th leaching column in the adsorption section penetrates, 30 minutes of BC liquid is collected, and then all the leaching columns are stepped once, the blank leaching column is connected to the adsorption section and becomes the 10th adsorption column in the adsorption section, the 1st adsorption column in the adsorption section is connected to the stripping section and becomes the 3rd stripping column in the stripping section, and the 1st stripping column in the stripping section is connected to the washing section for washing to form a blank leaching column, thereby completing the complete separation of component BC and component A.

[0043] (3) The pH value of the BC-containing liquid was adjusted to 4.5 with ammonia and hydrochloric acid. In the second step of the leaching process, there are 8 levels of adsorption section and 8 levels of elution section, and the liquid inlet method is top-in and bottom-out. The rare earth liquid is added from the first elution column of the adsorption section at a linear velocity of 2 cm / min. After passing through 8 elution columns, the BC component liquid is collected and recovered. Hydrochloric acid with a concentration of 0.1047 mol / L is introduced from the upper end of the elution section 1 at a linear velocity of 2 cm / min, and the 8th elution section enters the adsorption elution column. Hydrochloric acid with a concentration of 1 mol / L is introduced from the upper end of the stripping section at a linear velocity of 2 cm / min to strip the pure praseodymium component in the stripping elution column. The stripping elution column is washed with weak acid water with a pH of 4 to obtain a blank elution column for circulation. After every 35 minutes, all the leaching columns are stepped once, the blank leaching column is connected to the adsorption section to become the 8th adsorption column, the 1st adsorption column of the adsorption section is connected to the elution section to become the 8th elution column of the elution section, and the 1st elution column of the elution section is connected to the stripping section for stripping, thereby obtaining a high-purity praseodymium feed liquid. The leaching column after stripping is connected to the water washing section, and the 1st washing column forms a blank leaching column to achieve circulation.

[0044] (4) A solution of 99.999% high-purity oxalic acid was prepared and added to a high-purity praseodymium rare earth solution. The pH value of the precipitation was adjusted to 1.5 with ammonia water. The precipitated lanthanum oxalate was then calcined in a 950°C muffle furnace using a platinum crucible to obtain an ultra-high-purity rare earth oxide product. The impurity detection results of the product are shown in Table 3.

[0045] Embodiment 4:

[0046] (1) Using 99.95% neodymium chloride solution as raw material, the pH value of the solution is 4. The rare earth purity and non-rare earth impurity content in the solution are shown in Table 4.

[0047] Table 4 Composition analysis of raw materials of neodymium chloride and products of neodymium oxide

[0048]

[0049] (2) The first step is to use an extraction column to achieve complete separation of components A / BC. Component A includes easily extractable ions such as Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y, and Fe, component B includes the main component of Nd, and component C includes La, Ce, Pr, Ca, Mg, Co, Ni, Cu, Zn, V, Cr, Mn, The P204 leaching resin is loaded into the leaching column, which has 10 adsorption sections, 3 stripping sections, and 1 washing section. The leaching columns of each section are connected in series, and the liquid inlet is from top to bottom. The rare earth feed liquid is added from the first leaching column of the adsorption section at a linear speed of 3 cm / min. When the 10th leaching column is penetrated, the rare earth feed liquid of component BC is collected. Hydrochloric acid with a concentration of 5 mol / L is added from the first leaching column of the stripping section at a linear speed of 3 cm / min. After passing through 3 leaching columns, the feed liquid of component AB is recovered. Weak acid water with a pH of 4 is added from the washing section at a linear speed of 5 cm / min to wash and obtain a blank leaching column to achieve circulation. When the 10th leaching column in the adsorption section penetrates, 50 minutes of BC liquid is collected, and then all the leaching columns are stepped once, the blank leaching column is connected to the adsorption section and becomes the 10th adsorption column in the adsorption section, the 1st adsorption column in the adsorption section is connected to the stripping section and becomes the 3rd stripping column in the stripping section, and the 1st stripping column in the stripping section is connected to the washing section for water washing to form a blank leaching column, thereby completing the complete separation of component BC and component A.

[0050] (3) The pH value of the BC-containing liquid is adjusted to 4 with ammonia and hydrochloric acid. The second step of the leaching process has 7 levels of adsorption section and 7 levels of elution section, and the liquid inlet method is top-in and bottom-out. The rare earth liquid is added from the first elution column of the adsorption section at a linear velocity of 2 cm / min. After passing through 7 elution columns, the BC component liquid is collected and recovered. Hydrochloric acid with a concentration of 0.1259 mol / L is introduced from the upper end of the elution section 1 at a linear velocity of 2 cm / min, and the elution section 7 enters the adsorption elution column. Hydrochloric acid with a concentration of 1 mol / L is introduced from the upper end of the stripping section at a linear velocity of 2 cm / min to strip the pure neodymium component in the stripping elution column. The stripping elution column is washed with weak acid water with a pH of 4 to obtain a blank elution column for circulation. After every 35 minutes, all the leaching columns are stepped once, the blank leaching column is connected to the adsorption section to become the 7th adsorption column, the 1st adsorption column of the adsorption section is connected to the elution section to become the 7th elution column of the elution section, and the 1st elution column of the elution section is connected to the stripping section for stripping, thereby obtaining a high-purity neodymium liquid. The leaching column after stripping is connected to the water washing section, and the 1st washing column forms a blank leaching column to achieve circulation.

[0051] (4) A solution of 99.999% high-purity oxalic acid was prepared and added to a high-purity neodymium rare earth solution. The pH value of the precipitation was adjusted to 1.5 with ammonia water. The precipitated lanthanum oxalate was then calcined in a 950°C muffle furnace using a platinum crucible to obtain an ultra-high-purity rare earth oxide product. The impurity detection results of the product are shown in Table 4.

[0052] Embodiment 5:

[0053] (1) Using 99.99% samarium chloride solution as raw material, the pH value of the solution is 3.5. The rare earth purity and non-rare earth impurity content in the solution are shown in Table 5.

[0054] Table 5 Analysis of components of samarium chloride raw materials and samarium oxide products

[0055]

[0056] (2) The first step of leaching and extraction is to achieve complete separation of A / BC components, where A components are Eu, Gd, Tb, Dy, Ho, Y, Er, Tm, Yb, Lu, Fe and other easily extractable ions, B components are Sm as the main component, and C components are La, Ce, Pr, Nd, Ca, Mg, Co, Ni, Cu, Zn, V, Cr, Mn, The P507 leaching resin is loaded into the leaching column, which has 12 adsorption sections, 3 stripping sections, and 1 washing section. The leaching columns of each section are connected in series, and the liquid inlet is from top to bottom. The rare earth liquid is added from the first leaching column of the adsorption section at a linear speed of 2 cm / min. After the 12th leaching column is penetrated, the rare earth liquid of component BC is collected. Hydrochloric acid with a concentration of 5 mol / L is added from the first leaching column of the stripping section at a linear speed of 4 cm / min. After passing through 3 leaching columns, the liquid of component AB and non-rare earth impurities is recovered. Weak acid water with a pH of 4 is added from the first leaching column of the washing section at a linear speed of 5 cm / min to wash and obtain a blank leaching column to achieve circulation. When the 12th leaching column in the adsorption section penetrates, 60 minutes of La-Sm liquid is collected, and then all the leaching columns are stepped once, the blank leaching column is connected to the adsorption section and becomes the 12th adsorption column in the adsorption section, the 1st adsorption column in the adsorption section is connected to the stripping section and becomes the 3rd stripping column in the stripping section, and the 1st stripping column in the stripping section is connected to the washing section for washing to form a blank leaching column, thereby completing the complete separation of component BC and component A.

[0057] (3) The pH value of the BC-containing liquid was adjusted to 3.5 with ammonia and hydrochloric acid. The second step of the leaching process has 10 adsorption sections and 10 leaching sections, and the liquid inlet method is top-in and bottom-out. The rare earth liquid is added from the first leaching column of the adsorption section at a linear velocity of 5 cm / min. After passing through 10 leaching columns, the BC component liquid is collected and recovered. Hydrochloric acid with a concentration of 0.138 mol / L is introduced from the upper end of the 1st leaching section at a linear velocity of 5 cm / min, and the 10th leaching section enters the adsorption leaching column. Hydrochloric acid with a concentration of 2 mol / L is introduced from the upper end of the stripping section at a linear velocity of 5 cm / min to strip the pure samarium component in the stripping leaching column. The stripping leaching column is washed with weak acid water with a pH of 4 to obtain a blank leaching column for circulation. After every 40 minutes, all the leaching columns are stepped once, the blank leaching column is connected to the adsorption section to become the 10th adsorption column, the first adsorption column of the adsorption section is connected to the elution section to become the 10th elution column of the elution section, and the first elution column of the elution section is connected to the stripping section for stripping, thereby obtaining a high-purity samarium liquid. The leaching column after stripping is connected to the water washing section, and the first washing column forms a blank leaching column to achieve circulation.

[0058] (4) A solution of 99.999% high-purity oxalic acid was prepared and added to a high-purity samarium rare earth solution. The pH value of the precipitation was adjusted to 1.5 with ammonia water. The samarium oxalate obtained by precipitation was then calcined in a 950°C muffle furnace using a platinum crucible to obtain an ultra-high-purity rare earth oxide product. The impurity detection results of the product are shown in Table 5.

[0059] Embodiment 6:

[0060] (1) Using 99.99% gadolinium chloride solution as raw material, the pH value of the solution is 3, and the rare earth purity and non-rare earth impurity content in the solution are shown in Table 6.

[0061] Table 6 Composition analysis of gadolinium chloride raw materials and gadolinium oxide products

[0062]

[0063]

[0064] (2) The first step of leaching is to use a leaching column to achieve complete separation of components A / BC, where component A is Tb, Dy, Ho, Y, Er, Tm, Yb, Lu, Fe and other easily extractable ions, component B is Gd as the main component, and component C is La, Ce, Pr, Nd, Sm, Eu, Ca, Mg, Co, Ni, Cu, Zn, V, Cr, Mn and other difficultly extractable ions. P507 leaching resin is loaded into the leaching column, which has 11 adsorption sections, 3 stripping sections, and 1 washing section. The leaching columns of each section are connected in series, and the liquid inlet method is top-in and bottom-out. The rare earth feed liquid is added from the first leaching column of the adsorption section at a linear speed of 4 cm / min. When the 11th leaching column penetrates, the rare earth feed liquid of component BC is collected. Hydrochloric acid with a concentration of 6 mol / L is added from the first extraction column of the stripping section at a linear speed of 4 cm / min. After passing through three extraction columns, the components AB and the liquid of non-rare earth impurities are recovered. Weak acid water with pH = 4 is added from the first extraction column of the washing section at a linear speed of 5 cm / min to wash to obtain a blank extraction column to achieve circulation. After the 11th extraction column of the adsorption section penetrates, 30 minutes of BC liquid is collected, and then all extraction columns are stepped once, the blank extraction column is connected to the adsorption section to become the 11th adsorption column of the adsorption section, the 1st adsorption column of the adsorption section is connected to the stripping section to become the 3rd stripping column of the stripping section, and the 1st stripping column of the stripping section is connected to the water washing section to wash to form a blank extraction column, thereby completing the complete separation of components BC and component A.

[0065] (3) The pH value of the BC-containing liquid is adjusted to 3 with ammonia and hydrochloric acid. The second step of the leaching process has 8 levels of adsorption section and 8 levels of elution section, and the liquid inlet method is top-in and bottom-out. The rare earth liquid is added from the first elution column of the adsorption section at a linear velocity of 2 cm / min. After passing through 8 elution columns, the BC component liquid is collected and recovered. Hydrochloric acid with a concentration of 0.251 mol / L is introduced from the upper end of the elution section 1 at a linear velocity of 2 cm / min, and the 8th elution section enters the adsorption elution column. Hydrochloric acid with a concentration of 3 mol / L is introduced from the upper end of the stripping section at a linear velocity of 2 cm / min to strip the pure gadolinium component in the stripping elution column. The stripping elution column is washed with weak acid water with a pH of 4 to obtain a blank elution column for circulation. After every 60 minutes, all the leaching columns are stepped once, the blank leaching column is connected to the adsorption section to become the 8th adsorption column, the 1st adsorption column of the adsorption section is connected to the elution section to become the 8th elution column of the elution section, and the 1st elution column of the elution section is connected to the stripping section for stripping, thereby obtaining a high-purity gadolinium liquid. The leaching column after stripping is connected to the water washing section, and the 1st washing column forms a blank leaching column to achieve circulation.

[0066] (4) A solution of 99.999% high-purity oxalic acid was prepared and added to a high-purity gadolinium rare earth solution. The pH value of the precipitation was adjusted to 2.0 with ammonia water. The precipitated gadolinium oxalate was then calcined in a 950° C. muffle furnace using a platinum crucible to obtain an ultra-high-purity rare earth oxide product. The impurity detection results of the product are shown in Table 6.

Claims

1. A process for preparing ultra-high purity rare earth oxides by continuous leaching, characterized in that: The steps include: (1) Using rare earth oxides and rare earth chlorides of rare earth elements to be purified as raw materials, wherein the rare earth elements to be purified refer to main rare earth elements with an element distribution of more than 99%, which are set as component B, and the rare earth oxides are decomposed by hydrochloric acid to obtain rare earth chloride liquid; (2) According to the extraction capacity of the leaching resin for rare earth and non-rare earth impurities in the solution, the difficult-to-extract component relative to component B is set as component C, and the easily-extractable component relative to component B is set as component A, that is, the extraction capacity of the leaching resin for components A, B, and C is A>B>C in order; (3) The first step of continuous leaching is to achieve complete separation of component A and component BC: In the first step of continuous leaching, the leaching column is divided into three parts: adsorption section, stripping section and water washing section. The leaching columns of each part are connected in series, and the liquid inlet mode is top-in and bottom-out. Among them, there are m columns in the adsorption section and n columns in the stripping section. A rare earth feed liquid with a pH value of 3-4.5 is added from the first extraction column of the adsorption section at a linear speed of 2-5 cm / min, and after passing through m extraction columns, the rare earth feed liquid of component BC is collected; hydrochloric acid with a concentration of 4-6 mol / L is added from the first extraction column of the stripping section at a linear speed of 2-5 cm / min, and after passing through n extraction columns, the rare earth feed liquid of component AB is recovered; the extraction column is washed with a weak acid solution with a pH value of 3-4.5 at 2-5 cm / min to obtain a blank extraction column to achieve circulation; every 30-60 minutes, all the extraction columns are stepped once, the blank extraction column is connected to the adsorption section to become the mth adsorption column of the adsorption section, the first adsorption column of the adsorption section is connected to the stripping section to become the nth stripping column of the stripping section, and the first stripping column is changed to the washing section for elution to form a blank extraction column, and the cycle is repeated to achieve complete separation of component A and component BC; (4) adjusting the pH value of the BC-containing liquid obtained in step (3) to 3-4.5 with ammonia water and hydrochloric acid, and this solution will be used as the liquid for the second step of continuous leaching to achieve complete separation of the BC component; in the second step of continuous leaching, the leaching column is divided into four parts: an adsorption section, a leaching section, a stripping section, and a water washing section. The leaching columns of the adsorption section and the leaching section are connected in series end to end, and the leaching columns of the stripping section and the water washing section are single columns or multiple columns connected in parallel. The liquid inlet mode is top-in and bottom-out. Among them, there are M columns in the adsorption section and N columns in the leaching section; The rare earth feed liquid is added from the first extraction column of the adsorption section at a linear speed of 2-5cm / min, and after passing through M extraction columns, the rare earth feed liquid of component BC is collected; hydrochloric acid with a concentration of 0.1-1.3mol / L is introduced from the upper end of the first extraction column of the elution section at a linear speed of 2-5cm / min to wash a small amount of component C in the extraction column; hydrochloric acid with a concentration of 1-3mol / L is introduced from the upper end of the stripping section at a linear speed of 2-5cm / min to obtain pure component B; the extraction column after stripping is washed with weak acid to obtain a blank extraction column to realize circulation; every 30-60min, all the extraction columns are stepped once, the blank extraction column is connected to the adsorption section to become the Mth adsorption column of the adsorption section, the first adsorption column of the adsorption section becomes the Nth impurity removal column of the elution section, the first impurity removal column of the elution section is connected to the stripping section for stripping, and the extraction column after stripping becomes a water washing section for elution to form a blank extraction column, and the cycle is repeated to realize the complete separation of component pure B; (5) The pure B liquid obtained in step (4) is precipitated with high-purity oxalic acid and calcined to prepare ultra-high-purity rare earth oxides.

2. The process according to claim 1, characterized in that The non-rare earth impurities in the rare earth oxides and rare earth chlorides in step (1) include one or more of iron, silicon, calcium, magnesium, nickel, cobalt, chromium, zinc, copper, vanadium and manganese.

3. The process according to claim 1, characterized in that The leaching resin in step (2) includes one or both of P507 leaching resin and P204 leaching resin.

4. The process according to claim 1, characterized in that In step (4), the washing section uses hydrochloric acid with a pH of 4 and a linear speed of 2-5 cm / min.

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