CN100513600C - Technique for extracting and separating rare earth elements from non-saponification system - Google Patents

Abstract

This invention provides a process for extracting and separating rare earth elements by using non-saponification extractant. The process comprises: utilizing rare earth sulfate solution containing two or more rare earth elements obtained by treating rare earth ore as the raw material, performing Nd/Sm multi-stage fractionation and extraction by using non-saponification extractant P507 to obtain Sm/Eu/Gd enriched product and La/Ce/Pr/Nd extraction raffinate, and further extracting and separating rare earth compounds with non-saponification extractant. The process has such advantages as no emulsification under low-acidity extraction, easy back extraction of medium-molecular-weight rare earth elements, low acid consumption, and high productivity.

Description

A kind of non-saponification system extraction and separation process of rare earth elements

technical field

The invention relates to a process for extracting and separating rare earth elements. Specifically, the rare earth sulfate solution containing at least two rare earth elements obtained from the treatment of rare earth ores is used as a raw material, and non-saponified P507 is used for neodymium/samarium extraction grouping to obtain samarium europium gadolinium enrichment and lanthanum cerium praseodymium neodymium raffinate. Then use non-saponifiable P204 or non-saponifiable P204 and non-saponifiable P507, C272, C301, C302, HEOPPA, P350, TBP one or two of the mixed extraction agent prepared in the lanthanum cerium praseodymium neodymium sulfate and chloride A process for extracting and separating rare earth elements from a mixed solution of rare earth or rare earth nitrate.

Background technique

Lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, yttrium, and scandium are collectively called rare earth elements, and their properties are very similar. In addition to the existence of rare earth minerals, other elements coexist in rare earth minerals. Due to the similar atomic radius and extremely similar chemical properties, separation is difficult. At present, solvent extraction is mainly used for separation in industrial production.

At present, there are many extraction and separation methods for rare earth elements, and the methods commonly used in the industry generally have: 1. Extraction and separation of rare earth elements by saponification P507 hydrochloric acid system ([1] Collected Papers on Rare Earth Chemistry, Changchun Institute of Applied Chemistry, 1982, Science Press); 2. , saponified naphthenic hydrochloric acid system separation and purification of yttrium oxide ([2] Xu Guangxian chief editor, rare earth, second edition (volume 1), Metallurgical Industry Press, 2002, P590); 3, TBP nitric acid system extraction and separation of rare earth elements ([2 ] Xu Guangxian editor-in-chief, Rare Earth, 2nd edition (first volume), Metallurgical Industry Press, 2002, P495); 4, unsaponified P204 extracts and separates rare earth elements from sulfuric acid system ([3] Chinese patent CN 80105043.6). The first and second methods have good separation effects and are widely used, but they must be saponified with ammonia water or ammonium bicarbonate, which will generate a large amount of ammonia nitrogen wastewater and cause great pollution to the environment. The third method is the process adopted by France Rhodia and American Molybdenum Company. It is derived from the rare earth nitrate solution obtained when processing monazite ore to separate rare earth. The concentration of nitric acid in the extraction system of this process is high, so the production cost is high. stop state. The fourth process was invented by Beijing General Research Institute of Nonferrous Metals. It is applied to the extraction and separation of rare earth elements from the sulfuric acid rare earth solution obtained from the sulfuric acid roasting method to treat Baotou rare earth mines. Alkali consumption is small, but due to the low concentration of rare earth in the sulfuric acid system (<45g/L), the investment in equipment extraction agent is large, and P204 has a strong extraction ability under acidic conditions. When the acidity of the feed liquid is low, it is easy to emulsify, and a certain amount of acid, while the medium-heavy rare earth stripping is very difficult, the residual acid in the stripping liquid is high, and the acid consumption is large.

Contents of the invention

The purpose of the present invention is to provide a process for extracting and separating rare earth elements in a non-saponification system. The process extracts under low acidity without emulsification, and the medium and heavy rare earths are easy to strip, reducing acid consumption and cost, increasing production capacity, and reducing investment.

To achieve the above object, the present invention adopts the following technical solutions:

The invention utilizes the characteristic of weak acidity of P507, uses non-saponifiable P507 to carry out Nd/Sm extraction and grouping in rare earth sulfate solution, so as to realize extraction at low acidity without emulsification.

The present invention uses unsaponified P507 as the extractant to reduce residual acid in the stripping liquid, thereby reducing acid consumption and cost.

In order to improve the rare earth concentration in the organic phase and the water phase in the extraction process, the present invention replaces 1N sulfuric acid with high-concentration rare earth chloride or rare earth nitrate stripping liquid as washing liquid, so that the extraction can be carried out in high-concentration rare earth sulfate and rare earth chloride or Rare earth elements are extracted and separated from the mixed solution system of rare earth nitrate to reduce acid consumption, increase production capacity and reduce investment.

Using the rare earth sulfate solution containing at least two rare earth elements obtained from the treatment of rare earth ores as raw materials, non-saponifiable P507 (organic phase) is used for multi-stage fractionation and extraction of neodymium/samarium to obtain samarium europium gadolinium enrichment and lanthanum cerium praseodymium neodymium extraction The remaining liquid is then further extracted and separated from the rare earth compounds with a non-saponifiable extractant

The raw material is a sulfuric acid rare earth solution obtained by sulfuric acid treatment of light rare earth ores. The acidity is pH 1-5, and the rare earth content REO is 10-100g/L. The solution may also contain a small amount of Cl ^- and/or NO ₃ ^- and/or or multiple non-rare earth metal ions; the organic phase used is diluted to 0.1-1.7mol/L with one or more organic solvents in kerosene, solvent naphtha, alkanes, and alcohols.

The sulfuric acid rare earth solution uses 0.5-1.5mol/L unsaponified P507 to carry out neodymium/samarium multi-stage fractionation extraction and grouping, and the washing solution uses 2-7N hydrochloric acid or nitric acid, or rare earth concentration of 100-300gREO/L containing samarium, europium and gadolinium rare earth chloride Or the back-extraction solution of rare earth nitrate, the rare earth-loaded organic phase is back-extracted with 3-7N hydrochloric acid to obtain a samarium-europium-gadolinium enrichment, which can be further extracted and separated from samarium, europium, and gadolinium; The mixed solution of rare earth praseodymium neodymium sulfate and rare earth chloride or rare earth nitrate (water phase), neutralized to PH2-5, and then 0.5—1.7mol/L non-saponifiable P204 (D2EHPA, bis(2-ethylhexyl phosphate) ) or non-saponifiable P204 with non-saponifiable P507 (HEH/EHP, 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester), C272 (di(2,4,4-trimethylpentyl)phosphonic acid) , C301 (bis (2,4,4-trimethylpentyl) thiophosphonic acid), C302 (bis (2,4,4-trimethylpentyl) monothiophosphonic acid), C 923 (HEOPPA Linear alkyl phosphine oxide), P350 (dimethylheptyl methyl phosphate), TBP (tributyl phosphate) or two mixed extractants (organic phase) for extraction transformation or further extraction and separation rare earth compounds.

(1) The raffinate of lanthanum, cerium, praseodymium and neodymium is neutralized to PH2-5, and then all the rare earths are extracted into the organic phase with 0.5-1.7mol/L unsaponified P204, and then prepared by back-extracting with 3-7N hydrochloric acid or nitric acid Lanthanum cerium praseodymium neodymium rare earth chloride or rare earth nitrate.

(2) After neutralizing the raffinate containing lanthanum, cerium, praseodymium and neodymium to pH 2-5, use 0.5-1.7mol/L non-saponifiable P204 or non-saponifiable mixed extractant to carry out praseodymium/neodymium extraction and separation, and the lotion adopts 2- 7N hydrochloric acid or nitric acid, or a rare earth concentration of 100-300g/L REO neodymium-containing rare earth chloride or rare earth nitrate stripping solution; the loaded rare earth organic phase is back-extracted with 2-7N hydrochloric acid or nitric acid to obtain neodymium chloride or neodymium nitrate; After the raffinate containing lanthanum cerium praseodymium is neutralized to PH2-5, lanthanum cerium praseodymium is extracted with 0.5-1.7mol/L non-saponified P204, and 2-7N hydrochloric acid or nitric acid is back-extracted to prepare lanthanum cerium praseodymium chloride or rare earth nitrate .

(3) After the raffinate containing lanthanum, cerium, praseodymium and neodymium is neutralized to pH2-5, 0.5-1.7mol/L non-saponifiable P204 or non-saponifiable mixed extractant is used to carry out cerium/praseodymium extraction grouping, and the lotion is 2- 7N hydrochloric acid or nitric acid, or rare earth concentration of 100-300g/L REO rare earth chloride or rare earth nitrate stripping solution containing praseodymium and neodymium; the loaded rare earth organic phase is back-extracted with 2-7N hydrochloric acid or nitric acid to obtain praseodymium neodymium chloride or nitric acid Praseodymium and neodymium; the obtained raffinate containing lanthanum and cerium is precipitated with ammonium bicarbonate to produce lanthanum and cerium carbonate, or after neutralization to PH2-5, extract lanthanum and cerium with 0.5-1.7mol/L unsaponified P204, 2-7N hydrochloric acid or nitric acid Back extraction is used to prepare lanthanum cerium rare earth chloride or nitrate, praseodymium neodymium and lanthanum cerium compounds can be further extracted to separate a single rare earth compound.

(4) The raffinate containing lanthanum, cerium, praseodymium and neodymium is neutralized to pH2-5, and 0.5-1.7mol/L non-saponifiable P204 or non-saponifiable mixed extractant is used to extract and separate the lanthanum/cerium/praseodymium three outlets, and the 2-7N hydrochloric acid or nitric acid, or praseodymium neodymium chloride rare earth or nitrate rare earth back-extraction solution to wash the loaded rare earth organic phase, open a water phase outlet in the extraction section to output a part of the cerium-rich solution, the content of cerium oxide is >65%, and produce through precipitation Cerium-rich product; the organic phase of NdPr loaded with 2-7N hydrochloric acid or nitric acid is back extracted to obtain NdPr chloride or NdPr nitrate; the obtained raffinate containing lanthanum is precipitated with ammonium bicarbonate to produce lanthanum carbonate or lanthanum oxide, or neutral After the pH is 2-5, it is extracted with 0.5-1.7 mol/L unsaponified P204, back-extracted with hydrochloric acid or nitric acid to prepare 99.9-99.99% lanthanum compounds.

Advantages of the present invention:

1) When non-saponifiable P204 is used for Nd/Sm extraction grouping in rare earth solution, due to the small extraction amount and ratio (organic/aqueous phase, volume ratio), P204 has a strong ability to extract rare earths in low acidic solutions, so it must be Sulfuric acid is added to the feed liquid to adjust the acidity from PH4 to 0.2N, and 0.26 tons of concentrated sulfuric acid needs to be added according to the calculation of each ton of rare earth oxides, so that P204 will not produce supersaturated emulsification. The present invention uses unsaponified P507 rare earth solution for extraction Separation, the extraction liquid does not need to add acid, and the organic extractant loaded with medium and heavy rare earths is easy to strip, which can reduce the residual acid of the stripping liquid by more than 50%, and reduce the acid consumption by about 30%;

2) Replace 1N sulfuric acid with high-concentration rare earth chloride or rare earth nitrate back-extraction liquid as washing solution, extract and separate rare earth elements in the mixed rare earth solution of high-concentration rare earth sulfate and rare earth chloride or rare earth nitrate, and export the organic phase The concentration of rare earth in the water phase of the washing section is increased by 3-4 times, which can improve the efficiency of stripping, reduce the amount of acid by 10%, increase production capacity and reduce investment;

4) Using non-saponified organic phase extraction to separate rare earths, the process is simple, continuous and easy to control, the consumption of main chemical materials is low, and the extraction process does not generate ammonia nitrogen wastewater, which can greatly save the cost of three wastes treatment.

Detailed ways

The process of the present invention will be further described below with examples. The protection scope of the present invention is not limited by these embodiments, and the protection scope of the present invention is determined by the claims.

Example 1

Bastnaesite and monazite mixed rare earth ore (REO 50%) undergoes sulfuric acid roasting, water immersion, neutralization and impurity removal to obtain a pure sulfuric acid rare earth solution with an acidity of pH 4 and main components of REO 40g/L, Fe <0.05g/L, P<0.005g/L, ThO ₂ <0.001g/L, directly use non-saponified 1.0mol/L P507 for Nd/Sm extraction and grouping, use 8-stage extraction, 15-stage washing, and 8-stage stripping , compared to: organic/feed liquid/backwash acid = 0.20/1/0.012, the washing liquid uses a rare earth chloride solution containing 245g/l of samarium, europium and gadolinium, and an acidity of 0.2N, the concentration of rare earth in the washing section is 252g/l, and the loaded rare earth The organic phase contains 15g/l of rare earth, and it is back-extracted with 5N hydrochloric acid to obtain a rare earth chloride solution containing 245g/l of REO and an acidity of 0.2N. Physical products, wherein the Nd ₂ O ₃ content is less than 0.01%.

The obtained lanthanum, cerium, praseodymium and neodymium raffinate (Sm ₂ O ₃ content is less than 0.005%) is neutralized to PH4 with magnesium oxide, fully extracted with 1.5mol/l non-saponified P204, and back-extracted with 5.5N hydrochloric acid to obtain lanthanum-cerium-praseodymium-containing The rare earth chloride solution of 267g/l neodymium is concentrated and crystallized to produce rare earth chloride products of lanthanum cerium praseodymium neodymium, wherein REO>45%, Sm ₂ O ₃ content is less than 0.005%. From the sulfuric acid rare earth solution to the product, the total rare earth yield is 98.2%.

Example 2

Bastnaesite (REO 60%) undergoes sulfuric acid roasting, water immersion, neutralization and impurity removal to obtain a pure rare earth sulfate solution with an acidity of pH 4.5 and a rare earth concentration of REO 36g/L. Carry out Nd/Sm extraction and grouping, use 10-stage extraction, 18-stage washing, and 9-stage back-extraction. The washing solution is a rare earth chloride solution containing 255g/l of samarium, europium, and gadolinium, and an acidity of 0.3N. The rare earth-loaded organic phase contains 12g/l of rare earth , back-extracted with 5.2N hydrochloric acid to obtain a samarium-europium-gadolinium rare-earth chloride solution containing REO 255g/l and an acidity of 0.3N. After precipitation of oxalic acid, precipitation and burning to produce samarium-europium-gadolinium enrichment or further extraction, separation and extraction of samarium, europium, and Gadolinium single rare earth products.

The obtained raffinate containing lanthanum, cerium, praseodymium and neodymium is neutralized to pH4.5 with magnesium oxide, and then 85% (volume percentage, the same below) of 1.3mol/L non-saponifiable P204 and 15% of 1.3mol/L non-saponifiable P204 are used. The mixed extractant of saponified P507 is subjected to praseodymium/neodymium fractional extraction and separation, the lotion is stripped with neodymium-containing rare earth nitrate (REO 240g/L), and the organic phase loaded with rare earth is stripped with 5.5N nitric acid; after 32 stages of extraction, 38 stages of washing , 6-stage stripping to obtain neodymium nitrate (REO 240g/L, Nd ₂ O ₃ purity greater than 99.9%); the raffinate is neutralized to PH4.5, lanthanum cerium praseodymium is extracted with 1.5mol/L non-saponifiable P204, 6N hydrochloric acid reverses Extraction, concentration and crystallization to prepare lanthanum cerium praseodymium rare earth chloride products (REO>45%, Nd ₂ O ₃ content less than 0.05%). From the sulfuric acid rare earth solution to the product, the total rare earth yield is 96.8%.

Example 3

Front part process is the same as embodiment 2

The obtained lanthanum, cerium, praseodymium and neodymium raffinate is neutralized to pH4 with magnesium oxide, then adopts the mixed extractant of 90% 1.5mol/L non-saponification P204 and 10% 1.5mol/L non-saponification C272 (with No. diluted with solvent naphtha) for cerium/praseodymium fractionation extraction grouping. The lotion is stripped with rare earth chloride containing praseodymium and neodymium (REO 258g/L), and the loaded rare earth organic phase is stripped with 6.0N hydrochloric acid; after 23 stages of extraction, 32 stages of washing, and 6 stages of stripping to obtain praseodymium and neodymium chloride (CeO ₂ content is less than 0.05%); the raffinate is neutralized to pH 4.5 with magnesium oxide, lanthanum cerium is extracted with 1.5mol/L unsaponified P204, back-extracted with 5.3N hydrochloric acid, and the obtained lanthanum cerium chloride solution is concentrated and crystallized to prepare lanthanum Cerium rare earth chloride (REO>45%, Pr ₆ O ₁₁ , Nd ₂ O ₃ content less than 0.05%). From the sulfuric acid rare earth solution to the product, the total rare earth yield is 97.3%.

Example 4

Front part operation is with embodiment 2.

The lanthanum, cerium, praseodymium, and neodymium raffinate was neutralized to pH 4 with magnesium oxide, and then the organic phase of 1.2 mol/L non-saponified P204 (diluted with No. 200 solvent oil) was used for extraction and separation of lanthanum/cerium/praseodymium at three outlets. Use praseodymium neodymium rare earth chloride stripping solution (REO 240g/L) to wash the organic phase, open a water phase outlet (the third outlet) at the 22nd stage of the extraction section to discharge a part of the lanthanum cerium solution (cerium>65%), and produce Cerium-enriched product; the loaded rare earth organic phase is back-extracted with 5.5N hydrochloric acid to obtain a praseodymium-neodymium rare earth chloride solution, which is precipitated and burned with oxalic acid to produce a praseodymium-neodymium oxide product (CeO ₂ content is less than 0.05%, Sm ₂ O ₃ content is less than 0.01%) ; The raffinate was precipitated with ammonium bicarbonate to obtain lanthanum carbonate with a purity of 99.9%, and burned to obtain lanthanum oxide. From the sulfuric acid rare earth solution to the product, the total rare earth yield is 97.1%.

Claims (9)

1. A process for extracting and separating rare earth elements with a non-saponifiable extractant is characterized in that: the rare earth sulfate solution containing at least two rare earth elements obtained by processing rare earth ores is used as a raw material, and non-saponifiable P507 is used to carry out neodymium/samarium multi-stage fractional distillation extraction grouping , to obtain samarium europium gadolinium enrichment and lanthanum cerium praseodymium neodymium raffinate, and then use non-saponification extractant to further extract and separate rare earth compounds. 2. The process according to claim 1, characterized in that the raw material is rare earth sulfate solution obtained by treating light rare earth ore with sulfuric acid method, the acidity is pH1-5, the REO content of rare earth is 10-100g/L, and the organic The phase is diluted to 0.1-1.7mol/L with one or more organic solvents in kerosene, mineral spirits, alkanes and alcohols. 3. The process according to claim 1, characterized in that, the sulfuric acid rare earth solution uses 0.5-1.5mol/L unsaponified P507 to carry out multi-stage fractional distillation and grouping of neodymium/samarium, and the lotion uses 2-7N hydrochloric acid or nitric acid, or The stripping solution of samarium europium gadolinium rare earth chloride or rare earth nitrate, the rare earth concentration REO is 100-300g/L; Neutralize the neodymium raffinate to pH2-5, then use 0.5-1.7mol/L unsaponifiable P204 or unsaponifiable P204 and one or both of unsaponifiable P507, C272, C301, C302, HEOPPA, P350, TBP The prepared mixed extractant is used for extraction and separation. 4. The process according to claim 3, characterized in that, said lanthanum cerium praseodymium neodymium raffinate is a mixed solution of lanthanum cerium praseodymium neodymium rare earth sulfate and rare earth chloride or rare earth nitrate, all of which are mixed with 1.0-1.7mol/L P204 The rare earth is extracted into the organic phase, and then back-extracted with 3-7N hydrochloric acid or nitric acid to prepare lanthanum cerium praseodymium neodymium rare earth chloride or rare earth nitrate. 5. The process according to claim 3, characterized in that, after neutralizing the raffinate containing lanthanum, cerium, praseodymium and neodymium to pH 2-5, use 0.5-1.7mol/L non-saponifiable P204 or non-saponifiable mixed extractant to carry out Extraction and separation of praseodymium/neodymium, the washing solution is 2-7N hydrochloric acid or nitric acid, or the stripping liquid containing neodymium rare earth chloride or rare earth nitrate with a rare earth concentration of 100-300g/L REO, and the rare earth organic phase is loaded with 2-7N hydrochloric acid or Nitric acid back extraction to obtain neodymium chloride or neodymium nitrate; after the obtained raffinate containing lanthanum cerium praseodymium is neutralized to PH2-5, use 0.5-1.7mol/L unsaponified P204 to extract lanthanum cerium praseodymium, 2-7N hydrochloric acid or nitric acid Back extraction prepares lanthanum cerium praseodymium rare earth chloride or rare earth nitrate. 6. The process according to claim 3, characterized in that, after neutralizing the raffinate containing lanthanum, cerium, praseodymium and neodymium to pH 2-5, use 0.5-1.7mol/L non-saponifiable P204 or non-saponifiable mixed extractant For cerium/praseodymium extraction and grouping, the washing solution is 2-7N hydrochloric acid or nitric acid, or the back-extraction solution containing praseodymium neodymium rare earth chloride or nitrate with a rare earth concentration of 100-300g/L REO; the loaded rare earth organic phase is 2-7N Back-extract with hydrochloric acid or nitric acid to obtain praseodymium neodymium chloride or praseodymium neodymium nitrate; the obtained raffinate containing lanthanum and cerium is precipitated with ammonium bicarbonate to produce lanthanum cerium carbonate, or after neutralization to PH2-5, use 0.5-1.7mol/L Saponification of P204 to extract lanthanum cerium, 2-7N hydrochloric acid or nitric acid back extraction to prepare lanthanum cerium rare earth chloride or rare earth nitrate. 7. The process according to claim 6, characterized in that the said praseodymium neodymium and lanthanum cerium compounds are further extracted to separate a single rare earth compound. 8. The process according to claim 3, wherein the neutralization of the raffinate containing lanthanum, cerium, praseodymium and neodymium to pH 2-5 is carried out by using 0.5-1.7mol/L non-saponifiable P204 or non-saponifiable mixed extractant. Extraction and separation of lanthanum/cerium/praseodymium three outlets, use 2-7N hydrochloric acid or nitric acid, or praseodymium neodymium rare earth chloride or rare earth nitrate stripping solution to wash the loaded rare earth organic phase, and open a water phase outlet in the extraction section to output a part of the cerium-rich solution , whose cerium oxide content is more than 65%, and the cerium-rich product is produced through precipitation; the loaded praseodymium neodymium organic phase is back-extracted with 2-7N hydrochloric acid or nitric acid to obtain praseodymium neodymium chloride or praseodymium neodymium nitrate; the obtained lanthanum-containing raffinate is treated with bicarbonate Ammonium precipitation produces lanthanum carbonate or lanthanum oxide, or neutralizes to PH2-5, extracts with 0.5-1.7mol/L unsaponified P204, and back-extracts with hydrochloric acid or nitric acid to prepare 99.9-99.99% lanthanum compounds. 9. The process according to claim 1 or 2, characterized in that the samarium europium gadolinium enrichment is further extracted and separated.