WO2016106732A1 - 分步萃取回收稀土的方法 - Google Patents

分步萃取回收稀土的方法 Download PDF

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WO2016106732A1
WO2016106732A1 PCT/CN2014/096023 CN2014096023W WO2016106732A1 WO 2016106732 A1 WO2016106732 A1 WO 2016106732A1 CN 2014096023 W CN2014096023 W CN 2014096023W WO 2016106732 A1 WO2016106732 A1 WO 2016106732A1
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rare earth
organic phase
extraction
solution
reo
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PCT/CN2014/096023
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English (en)
French (fr)
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黄小卫
王良士
冯宗玉
董金诗
王猛
肖燕飞
崔大立
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有研稀土新材料股份有限公司
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Priority to MYPI2015001702A priority Critical patent/MY189476A/en
Priority to PCT/CN2014/096023 priority patent/WO2016106732A1/zh
Priority to BR112017001370-3A priority patent/BR112017001370B1/pt
Publication of WO2016106732A1 publication Critical patent/WO2016106732A1/zh

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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B59/00—Obtaining rare earth metals
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling

Definitions

  • the invention relates to the field of rare earth hydrometallurgy technology, in particular to a method for fractional extraction and recovery of rare earth.
  • Ion-adsorbed rare earth ore is a rare resource rich in medium and heavy rare earths in the world.
  • the rare earth is adsorbed on the aluminosilicate minerals such as kaolin and mica.
  • the ion-adsorbed rare earth ore has a low content of rare earth, generally less than one thousandth, and contains lanthanum, cerium, lanthanum, cerium, lanthanum, cerium, lanthanum, cerium, lanthanum, cerium, lanthanum, cerium, lanthanum, cerium, lanthanum, cerium, More than ten kinds of rare earth elements, ( ⁇ , ⁇ , ⁇ , ⁇ are called “light rare earths”, ⁇ , ⁇ , ⁇ , ⁇ , ⁇ , ⁇ , ⁇ , ⁇ , ⁇ and ⁇ are called “medium weight” Rare earth”), wherein the content of medium and heavy rare earth is 40% or more.
  • the ionic rare earth ore is usually leached with ammonium sulfate, and the obtained rare earth content is a low concentration sulfuric acid rare earth solution of about 2 g/L in terms of REO, and the rare earth content is recovered by ammonium hydrogencarbonate or oxalic acid precipitation, and then calcined to obtain a rare earth content to REO.
  • the rare earth separation plant dissolves the above rare earth oxide concentrate with hydrochloric acid, removes impurities and filters to obtain a high concentration mixed rare earth chloride solution, and then uses P507 or naphthenic acid for multi-step cascade extraction to obtain a purity of 2N-5N rare earth chloride.
  • the solution is further precipitated with ammonium hydrogencarbonate, oxalic acid or sodium carbonate to obtain a rare earth salt, and finally calcined to obtain various pure rare earth oxide products.
  • the above rare earth oxide concentrate contains 10% of impurities such as iron, aluminum, calcium, silicon and trace radionuclides, after the hydrochloric acid is dissolved, the impurities are enriched in the slag, resulting in the radioactive specific activity of the slag exceeding the standard, and the radioactive activity is required.
  • the waste slag disposal regulations are built in storage, and the slag also contains about 5% rare earth, which causes partial rare earth loss.
  • the rare earth recovery rate of the existing rare earth recovery process has high recovery rate of chemical reagents, and there are problems such as high-salt wastewater discharge such as ammonia nitrogen.
  • the rare earth concentration in the tailings and leachate of the southern ion mine tail mine is even lower.
  • the effective enrichment and recovery of the rare earth resources of the tailings liquid is still very difficult, and the loss will not only cause the rare earth resources of the rare southern ion ore. The loss, more serious, poses a serious threat to the safety of water resources in the surrounding areas.
  • the rare earth separation and purification method mainly has a solvent extraction method, which has the characteristics of continuous and easy control, low cost, and easy realization of large-scale production, and is widely used.
  • An acidic phosphorus extraction system for industrial application in the rare earth industry There are mainly P507, P204, naphthenic acid and the like.
  • the extraction separation and purification of rare earths are carried out in a high concentration of rare earth chloride solution. Since the extraction ability of the acidic extractant for the rare earth is inversely proportional to the third power of the extracted aqueous phase, the saponification of the organic phase (acidic extractant) is generally carried out by using an inorganic base such as ammonia or sodium hydroxide.
  • the organic phase containing ammonium or sodium is obtained, and then the rare earth extraction and separation are carried out. This process not only consumes a large amount of alkali, but also increases the production cost, and produces a large amount of high salinity wastewater such as ammonia nitrogen, which causes serious pollution to water resources.
  • the invention aims to provide a method for fractional extraction and recovery of rare earth, so as to solve the problems of low rare earth recovery rate, high cost and easy pollution of the environment in the rare earth leaching solution of the existing ionic ore rare earth leaching solution.
  • the present invention provides a method for fractional extraction and recovery of rare earth, using a rare earth solution containing medium and heavy rare earth as a raw material liquid, the pH of the raw material liquid is 2.5-5.5, and the rare earth solution is stepwise extracted and recovered to recover rare earth.
  • the method comprises the following steps: using a first organic relative raw material liquid containing a non-saponified acidic phosphorus extracting agent with a PKa value of >4 for the first extraction, and controlling the equilibrium aqueous acidity of the extracted aqueous phase to be 1 ⁇ pH ⁇ 3, to obtain a primary loaded organic phase.
  • a primary raffinate containing light rare earth the first raffinate containing light rare earth is subjected to a second extraction with a second organic phase containing a non-saponified acidic phosphorus extractant having a PKa value of ⁇ 3.5 to control the equilibrium acidity of the extracted aqueous phase
  • the secondary loaded organic phase and the secondary raffinate are obtained; the rare earth in the primary organic phase and the secondary loaded organic phase are separately recovered by reverse stripping to obtain a heavy chloride rare earth solution and a chlorinated light rare earth. Solution.
  • the pH of the raw material liquid is 4-5, wherein the rare earth content is less than 10 g/L in terms of REO, and the medium-weight rare earth mass percentage in the raw material liquid is between 10% and 85%, preferably the raw material liquid.
  • the medium-weight rare earth mass percentage is between 15% and 50%.
  • the rare earth solution is a rare earth sulfate solution and/or a rare earth chloride solution
  • the preferred rare earth solution is made of ionic rare earth ore by magnesium sulfate, ammonium sulfate, ferrous sulfate, magnesium chloride, ammonium chloride, and chloride.
  • magnesium sulfate magnesium sulfate
  • ammonium sulfate ferrous sulfate
  • magnesium chloride magnesium chloride
  • ammonium chloride and chloride
  • One or more inorganic salt solutions of iron, calcium chloride and sodium chloride are obtained as leaching solution.
  • the acidic phosphorus extracting agent having a PKa value of >4 in the above method is one or more of P507, P229, C302 and C272, preferably P507; and the acidic phosphorus extracting agent having a PKa value of ⁇ 3.5 is P204, P215 One or more of P406 and C301, preferably P204.
  • the first organic phase and the second organic phase further contain a diluent, and the concentration of the acidic phosphorus extractant in the first organic phase and the second organic phase is 0.5 to 1.5 mol/L.
  • the first extraction step in the above method more than 95% of the medium and heavy rare earth in the raw material liquid is extracted into the primary supported organic phase, and more than 98% of the medium and heavy rare earth in the preferred raw material liquid is extracted to the primary loaded rare earth. In the organic phase.
  • the rare earth content in the primary supported organic phase is 5-28 g/L, preferably 10-25 g/L in terms of REO; and the rare earth content in the secondary loaded organic phase is 4-25 g/L in terms of REO, preferably 8 ⁇ 20g/L.
  • the rare earth content in the secondary raffinate is less than 0.1 g/L, preferably less than 0.02 g/L, in terms of REO, and more preferably, the secondary raffinate may be mixed with the leaching agent and returned to the ion. Leaching of the mine.
  • the first extraction and the second extraction are respectively carried out by using 2 to 10 stages of extraction, preferably 2 to 5 stages of countercurrent or cross-flow extraction, and more preferably, the extraction process is performed by using a centrifugal extractor or a pulse sieve. Plate tower equipment.
  • the above method further comprises the steps of degreasing the primary raffinate and the secondary raffinate, and preferably the step of degreasing adopts static degreasing, kerosene washing and degreasing, air flotation degreasing, ultrasonic degreasing, filtering
  • degreasing adopts static degreasing, kerosene washing and degreasing, air flotation degreasing, ultrasonic degreasing, filtering
  • One or several methods of degreasing, chemical oxidation and biochemical degreasing are used for degreasing.
  • the step of separately extracting and recovering the rare earth in the primary organic phase and the secondary loaded organic phase in the above method comprises: stripping the primary loaded organic phase with 3.5-6 mol/L hydrochloric acid to obtain a chlorinated heavy rare earth solution, preferably The rare earth content in the chlorinated heavy rare earth solution is greater than 150 g/L in REO, preferably greater than 230 g/L; and the secondary supported organic phase is back-extracted with 3.5-6 mol/L hydrochloric acid to obtain a chlorinated light rare earth solution, preferably The rare earth content in the chlorinated light rare earth solution is greater than 150 g/L, preferably greater than 230 g/L, in terms of REO.
  • the second to tenth stage stripping is used, preferably the third to sixth stage countercurrent or semi-countercurrent stripping, and the more preferable stripping process.
  • the method for recovering rare earth by the stepwise extraction method of the present invention comprises the stepwise extraction of the rare earth solution by using a non-saponified acidic phosphorus extracting agent to realize pre-grouping of the heavy rare earth and the light rare earth, and the recycling method of the present invention is compared with the conventional method.
  • the invention eliminates the precipitation, filtration, calcination and acid dissolution process of ammonium bicarbonate, which not only shortens the process flow, but also greatly reduces the consumption of chemical materials, and has the advantages of improving rare earth recovery rate, reducing production cost, and eliminating ammonia-nitrogen wastewater discharge;
  • the saponification extractant is extracted under weakly acidic conditions, the organic phase dissolution loss is greatly reduced, and the three-phase substance is not easy to be produced, the extraction process is ensured smoothly, the rare earth solution is efficiently cleaned, the utilization of rare earth resources is improved, and the pollutant emission is reduced. And the consumption of chemical raw materials to effectively protect the environment.
  • 1 is a schematic flow chart showing a method for fractional extraction of rare earth solution to recover rare earth according to an embodiment of the present invention.
  • the method for recovering rare earth from the ionic ore rare earth leaching solution is complicated, the rare earth recovery rate is low, the cost is high, and the environment is easily polluted.
  • a stepwise extraction and recovery of rare earth is provided.
  • the method wherein the rare earth solution has a pH of from 2.5 to 5.5, preferably from 4 to 5, and has a REO content of less than 10 g/L.
  • the method for recovering rare earth provided by the present invention is preferably made of a rare earth solution leached from an ionic rare earth ore containing a medium and heavy rare earth.
  • the rare earths include lanthanum, cerium, lanthanum, cerium, lanthanum, cerium, lanthanum, cerium, lanthanum, cerium, lanthanum, cerium, lanthanum, cerium, lanthanum, cerium, lanthanum, cerium, lanthanum, cerium, lanthanum, cerium, lanthanum, cerium, lanthanum, cerium, lanthanum, cerium, lanthanum, cerium, lanthanum, cerium, lanthanum, cerium, lanthanum, cerium, lanthanum , ⁇ and ⁇ are medium and heavy rare earths; ⁇ , ⁇ , ⁇ , ⁇ are light rare earths.
  • the above-mentioned recovery method of the present invention directly extracts rare earth ions in the rare earth solution into the organic phase by using a non-saponified acidic extracting agent without saponification treatment such as ammonia water or liquid alkali, and controls the extraction ratio (organic phase/aqueous phase is O) /A)
  • a supported organic phase having a high rare earth content is obtained, and after the reverse stripping, the high concentration of the rare earth chloride solution is obtained by controlling the stripping, so that the rare earth in the low concentration rare earth solution is enriched by 100 to 500 times.
  • the rare earth recovery rate is over 98%, so that the rare earth is efficiently cleaned and recycled.
  • the method for extracting rare earth by stepwise extraction of the rare earth solution comprises using a rare earth solution containing a medium and heavy rare earth as a raw material liquid, and adjusting the pH of the raw material liquid by a basic compound to be 2.5-5.5, preferably 4-5.
  • the iron, aluminum and the like in the raw material liquid are removed to avoid affecting the extraction of the subsequent rare earth, and on the other hand, the rare earth is extracted completely.
  • the process comprises the following steps: using a first organic relative raw material liquid containing a non-saponified acidic phosphorus extractant having a PKa value of >4 for the first extraction, and controlling the equilibrium aqueous acidity of the extracted aqueous phase to be 1 ⁇ pH ⁇ 3, to obtain a primary loaded organic phase.
  • a light rare earth primary raffinate the first raffinate containing the light rare earth is subjected to a second extraction with a second organic phase containing a non-saponified acidic phosphorus extractant having a PKa value of ⁇ 3.5, and the equilibrium acidity of the extracted aqueous phase is controlled to 0.5 ⁇ pH ⁇ 2.5, the secondary loaded organic phase and the secondary raffinate are obtained, and the rare earth in the primary organic phase and the secondary loaded organic phase are separately recovered by reverse stripping to obtain a chlorinated medium rare earth solution and a chlorinated light rare earth solution.
  • the PKa value -lg[Ka]
  • Ka is the dissociation equilibrium constant of the acid.
  • the organic phase concentration is adjusted according to the medium and heavy rare earth element content in the raw material liquid, and the equilibrium acidity of the extracted aqueous phase is controlled to be 1 ⁇ pH ⁇ 3, which will make more than 95% of the medium and heavy rare earth in the rare earth solution.
  • the organic phase type and concentration, the extraction method and the extraction are selected according to the concentration and composition of the rare earth in the primary raffinate Controlling the extracted aqueous phase to have an equilibrium acidity of 0.5 ⁇ pH ⁇ 2.5 will allow almost all of the remaining rare earth to be extracted into the organic phase.
  • the acidic phosphorus extracting agent with PKa value >4 alone is weak in acidity. Although it can effectively extract medium and heavy rare earths and the stripping is relatively easy, there is limited ability to extract light rare earth, especially the organic phase loaded rare earth concentration is high.
  • the rare earth extraction is incomplete, the purpose of complete enrichment and recovery of rare earth cannot be achieved, and the organic phase needs to be saponified with ammonia or liquid alkali; while the acidic phosphorus extractant with PKa value ⁇ 3.5 is relatively strong, and the rare earth is relatively strong.
  • the extraction ability is strong, but heavy rare earths are difficult to strip and cannot be industrially applied.
  • two different Ka organic phases are simultaneously used for extraction, firstly extracting medium and heavy rare earths in the raw material liquid by using an acidic phosphorus extracting agent such as P507 with a PKa value of >4, and then adopting an acidity such as P204 having a PKa value of ⁇ 3.5.
  • Phosphorus extractant extracts light rare earth, which solves the problem that P507 has weak extraction ability for light rare earth and P204 is difficult to strip back rare earth, and realizes the effect of pre-group separation of heavy rare earth and light rare earth.
  • FIG. 1 a schematic flow chart of a method for fractional extraction and recovery of rare earth of the present invention is given in FIG. 1, and the preferred embodiments and advantageous effects of the present invention will be further described below in conjunction with the flow chart.
  • a rare earth solution containing a medium-heavy rare earth is used as a raw material liquid, and the medium-heavy rare earth content is more than 10%.
  • the rare earth solution is preferably a rare earth sulfate solution and/or a rare earth chloride solution, and the rare earth solution is particularly preferably an ionic rare earth mineral by magnesium sulfate, ammonium sulfate, ferrous sulfate, magnesium chloride, ammonium chloride, ferrous chloride, chlorination.
  • One or more inorganic salts of calcium and sodium chloride are obtained as leaching agents.
  • the rare earth solution particularly preferably has a REO content of less than 10 g/L, and a medium to heavy rare earth mass ratio in the raw material liquid is between 10% and 85%, preferably the medium and heavy rare earth mass percentage in the raw material liquid is 15% to 50%. %between.
  • the method of the invention is also applicable, but the extraction effect is worse than the low concentration rare earth solution, and a certain amount of water can be added in the extraction process to adjust the rare earth concentration of the solution, thereby reducing the extraction water.
  • the phase equilibrium acidity allows the rare earth in the solution to be completely extracted into the organic phase for efficient recovery.
  • the first organic relative raw material liquid containing a non-saponified acidic phosphorus extractant having a PKa value of >4 is subjected to a first extraction to obtain a primary supported organic phase and a primary raffinate.
  • the concentration of the organic phase can be adjusted according to the content of the medium and heavy rare earth elements in the raw material liquid, and the equilibrium acidity of the extracted aqueous phase is controlled to be 1 ⁇ pH ⁇ 3, and the appropriate rare earth extraction rate is ensured, so that the medium and heavy rare earth extraction rate is greater than 98. %.
  • O/A extraction ratio
  • increasing the content of rare earth in the primary loaded organic phase is beneficial to the enrichment of the rare earth, and then increasing the concentration of the rare earth in the stripping solution compared with increasing the stripping, thereby facilitating the subsequent steps.
  • the organic phase type and concentration, the extraction method and the extraction ratio can be selected according to the concentration of the raw material liquid and the composition of the light and medium heavy rare earth, thereby ensuring the obtained organic phase with a higher rare earth concentration, and the organic phase is once loaded.
  • the high content of rare earth in the phase is beneficial to the enrichment of rare earth.
  • the rare earth content in the primary supported organic phase is 5 to 28 g/L in terms of REO.
  • the rare earth content in the primary loaded organic phase is 10 to 25 g/L in terms of REO.
  • a second extraction of the raffinate is carried out, and a second organic phase containing a non-saponified acidic phosphorus extractant having a PKa value of ⁇ 3.5 is used in the second extraction.
  • the organic phase type and concentration, the extraction mode and the extraction ratio can be selected according to the concentration and composition of the rare earth in the primary raffinate, and the equilibrium acidity of the extracted aqueous phase is controlled to be 0.5 ⁇ pH ⁇ 2.5 to ensure the rare earth. All of the organic phase is extracted into the organic phase, and the organic phase with higher rare earth concentration is obtained.
  • the rare earth content in the secondary loaded organic phase is high, which is beneficial to the enrichment of rare earth and the concentration of rare earth in the stripping solution, which facilitates the subsequent steps.
  • the rare earth content in the secondary supported organic phase is 4 to 25 g/L in terms of REO.
  • the rare earth content in the secondary loaded rare earth organic phase is 8-20 g/L in terms of REO, but the concentration of the supported organic phase is too high, and the rare earth extraction recovery rate is decreased.
  • the rare earth content in the secondary raffinate is less than 0.1 g/L in terms of REO.
  • the first raffinate is extracted with an acidic phosphorus extractant having a PKa value of ⁇ 3.5, and the remaining rare earth is extracted by using a smaller PKa extractant, which has higher acidity and strong extraction ability, and the remaining raffinate is left.
  • the rare earth extraction is complete, and the rare earth content in the secondary raffinate is less than 0.1 g/L, preferably less than 0.02 g/L.
  • the method further comprises the steps of degreasing the primary raffinate and the secondary raffinate, more preferably degreasing.
  • the step is to statically remove oil,
  • One or several methods of kerosene washing and degreasing, air flotation deoiling, ultrasonic degreasing, filtration adsorption degreasing, chemical oxidation and biochemical degreasing are used for degreasing.
  • the secondary raffinate obtained in the second extraction step is made of magnesium oxide, magnesium hydroxide or calcium oxide.
  • At least one of the calcium hydroxides is adjusted to have a pH greater than 2, and is supplemented with a leaching agent to be used as a leaching solution to return to leaching of the ion ore.
  • leaching agents which may be used therein include, but are not limited to, one or more of magnesium sulfate, ammonium sulfate, magnesium chloride, ammonium chloride, calcium chloride, and sodium chloride.
  • the first organic phase used in the first extraction step and the second organic phase used in the second extraction step may contain at least a diluent in addition to the acidic phosphorus extractant, and a diluent that can be used includes It is not limited to one or more of kerosene, sulfonated kerosene, n-hexane, n-heptane, octane, decane, decane, and the like, which are well known in the art.
  • the concentration of the acidic phosphorus extractant in the first organic phase and the second organic phase is 0.1 to 1.5 mol/L, preferably 0.5 to 1.5 mol/L.
  • the concentration of the rare earth in the rare earth solution is selected according to the concentration of the rare earth, that is, the rare earth can be effectively extracted into the organic phase and reduced by the extraction.
  • (O/A) increases the concentration of rare earth in the supported organic phase, which is beneficial to the stripping of the rare earth in the primary-loaded organic phase and the secondary-loaded organic phase, and then by increasing the concentration of the stripped hydrochloric acid and adjusting the large stripping Back extraction, obtaining a rare earth chloride rare earth solution, is beneficial to improve the efficiency and productivity of subsequent single rare earth extraction separation and purification.
  • the present invention adopts 2 to 10 stages of extraction, and the extraction method includes However, it is not limited to countercurrent, semi-reverse flow, cross-flow, etc., wherein 2 to 5 countercurrent extraction is preferred, and cross-flow extraction is used in the case of very low rare earth concentration, which can increase the concentration of rare earth in the supported organic phase, but the ratio of rare earth recovery is higher. And low in countercurrent extraction.
  • a semi-reverse flow method is used to self-circulate the organic phase in the same stage, thereby increasing the mixing effect of the two phases and obtaining a better mixing effect.
  • Equipment that may be employed in the above extraction process includes, but is not limited to, a centrifugal extractor or a pulsed sieve column.
  • the method for fractional extraction and recovery of rare earth provided by the invention has the advantages that the extraction process does not need to be saponified, the discharge of ammonia nitrogen wastewater or high salinity wastewater is eliminated, and the pre-group separation effect of heavy rare earth and light rare earth in the process of rare earth recovery is achieved. And solve the problems of low rare earth yield and small organic loading of acidic phosphorus extractant with PKa value >4.
  • the acidic phosphorus extractant with PKa value ⁇ 3.5 under low acidity condition is easy to be emulsified and the medium and heavy rare earth is difficult to reverse.
  • the effect of the problem Preferably, a first organic phase comprising P507 is employed in the first extraction and a second organic phase comprising P204 is employed in the secondary extraction.
  • the method for the stepwise extraction and recovery of rare earth by the rare earth solution of the present invention comprises the steps of separately recovering the rare earth in the supported organic phase and the secondary supported organic phase by using the inorganic acid back extraction separately after the first extraction and the second extraction are completed.
  • the step of loading the rare earth in the organic phase and the secondary loading organic phase is preferably carried out by hydrochloric acid stripping.
  • the stripping acid can also be used for nitric acid, sulfuric acid, etc., but the solubility of the rare earth sulfate is lower, in order to better connect
  • the present invention uses hydrochloric acid for stripping.
  • stripping with 2mol/L hydrochloric acid can also achieve the purpose of stripping.
  • 3.5 ⁇ 6mol/L hydrochloric acid stripping to obtain a heavy chloride solution in chlorination, and then extracting and purifying to prepare a single rare earth or precipitate crystal to recover medium heavy rare earth, more preferably, the chlorinated medium heavy rare earth solution obtained by stripping The weight content of the medium rare earth is more than 150g/L, preferably more than 230g/L, in terms of REO.
  • the rare earth concentration in the heavy rare earth solution in the chlorination can be increased to 250g/L.
  • the medium-heavy rare earth solution can be directly sent to a rare earth separation plant as a raw material for extracting and separating and purifying a single rare earth.
  • the medium and heavy rare earths and the light rare earths can be separated and extracted as much as possible, but the process cannot directly separate the two completely, and a part of the chlorination is inevitable in the heavy rare earth solution in the above chlorination.
  • Light rare earth solution but in order to facilitate understanding of the main intention of the present invention, it is still referred to as a chlorinated medium heavy rare earth solution.
  • the light rare earth content in the chlorinated heavy rare earth solution accounts for 5-20 wt.% of the total rare earth content, and controlling the light rare earth content in the heavy chloride solution in the chlorination is beneficial to achieve the pre-group separation effect, effectively Reduce investment operating costs.
  • stripping with 2mol/L hydrochloric acid can also achieve the purpose of stripping, but in order to obtain a higher concentration of mixed chlorinated light rare earth solution, preferably, for secondary loading organic
  • the phase is stripped with 3.5 ⁇ 6mol/L hydrochloric acid to obtain a chlorinated light rare earth solution.
  • the medium rare earth content/total rare earth content in the chlorinated light rare earth solution is ⁇ 5%, preferably ⁇ 1%, and then purified by extraction and purification. Rare earth or precipitated crystallization recovers light rare earth.
  • the rare earth weight content in the chlorinated heavy rare earth solution obtained by stripping is greater than 150 g/L, preferably greater than 230 g/L, in terms of REO, by increasing the stripping acid concentration and stripping (O/A)
  • the concentration of rare earth in the chlorinated light rare earth solution can be increased to more than 250g/L.
  • the chlorinated light rare earth solution can be directly sent to the rare earth separation plant as a raw material for extracting and separating and purifying a single rare earth.
  • the medium and heavy rare earths and the light rare earths can be separated and extracted as much as possible, but the process cannot directly separate the two completely, and a part of the chlorination is inevitable in the heavy rare earth solution in the above chlorination.
  • Light rare earth solution but in order to facilitate understanding of the main intention of the present invention, it is still referred to as a chlorinated medium heavy rare earth solution.
  • each stripping process preferably adopts multi-stage stripping, and the more the number of rare earths, the higher the stripping rate of rare earth, but in order to save cost And investment, etc.
  • the present invention uses 2 to 10 stages of stripping, preferably 3 to 6 stages, and the stripping method includes but is not limited to the use of countercurrent or semi-reverse flow, in the above-mentioned one stripping step and the second stripping step,
  • the volume ratio of organic phase to aqueous phase (O/A) is 50:1 ⁇ 1:1, optimized to 30:1 to 3:1.
  • the present invention preferably employs a 3-6 stage countercurrent or semi-countercurrent stripping.
  • Equipment that may be employed in the above stripping process includes, but is not limited to, centrifugal extractors or pulsed sieve trays.
  • the organic phase i.e., the first organic phase
  • the organic phase i.e., the second organic phase
  • REO rare earth content
  • TREO total rare earth oxide
  • magnesium sulfate as a leaching agent to leach the ion-adsorbed rare earth ore to obtain a rare earth solution containing rare earth REO 0.30g/L as a raw material liquid (where the medium-heavy rare earth REO/TREO is 50% and the light rare earth REO/TREO is 50). %), adjust the pH of the raw material liquid to 3.5.
  • the first raffinate is further extracted with 1.0 mol/L C301 as the second organic phase (diluent is kerosene), and the 5th-stage cross-flow extraction is adopted.
  • the volume ratio of the organic phase to the aqueous phase is 1:40, and the extracted aqueous phase is controlled.
  • the rare earth content in the secondary raffinate was 0.005 g/L, and the rare earth recovery rate was 98.3%.
  • the obtained primary organic phase was back-extracted with 3.5 mol/L hydrochloric acid, and the second-stage countercurrent stripping was carried out.
  • the volume ratio of organic phase to aqueous phase (O/A) was 30:1, and chlorination of rare earth REO 151 g/L was obtained.
  • the obtained secondary supported organic phase was back-extracted with 3.5 mol/L hydrochloric acid, and the second-stage countercurrent stripping was carried out.
  • the volume ratio of organic phase to aqueous phase (O/A) was 32:1, and the rare earth-containing REO was obtained at a high concentration of 153 g/L.
  • the extraction and stripping process adopts a centrifugal extractor, and the obtained rare earth chloride solution is used as a raw material for extracting and separating and purifying a single rare earth.
  • the mixture of magnesium sulfate and magnesium chloride is used as a leaching agent to leach the ion-adsorbed rare earth ore to obtain a rare earth solution containing rare earth REO 0.35 g/L as a raw material liquid (where the medium-heavy rare earth REO/TREO is 60%, light rare earth REO) /TREO is 40%), and the pH of the raw material liquid is adjusted to 3.2.
  • the raffinate is further extracted with 0.5 mol/L of the second organic phase containing P204 (the diluent is n-hexane), and the 8th-order error extraction is used.
  • the recovery rate was 98.6%.
  • the obtained primary organic phase was back-extracted with 3.8 mol/L hydrochloric acid, and the third-stage countercurrent stripping was carried out.
  • the volume ratio of organic phase to aqueous phase (O/A) was 25:1, and a high concentration of rare earth REO 167 g/L was obtained.
  • the obtained secondary supported organic phase was back-extracted with 3.6 mol/L hydrochloric acid, and the third-stage semi-countercurrent stripping was carried out.
  • the volume ratio of organic phase to aqueous phase (O/A) was 30:1, and the rare earth-containing REO 158 g/L was obtained.
  • the extraction and stripping process uses a pulsed sieve column, and the obtained rare earth chloride solution is used as a raw material for extracting and separating and purifying a single rare earth.
  • the ion-adsorbed rare earth ore is leached by using a magnesium sulfate solution as a leaching agent to obtain a rare earth solution containing rare earth REO 0.5 g/L as a raw material liquid (where the medium-heavy rare earth REO/TREO is 40%, and the light rare earth REO/TREO is 60%), adjust the pH of the raw material liquid to 5.5.
  • the medium-weight rare earth in the raw material liquid was extracted with 0.6 mol/L of the first organic phase containing P507 (the diluent was kerosene), and the volume ratio of the organic phase to the aqueous phase (O/A) was 1:25 by the second-stage countercurrent extraction.
  • the raffinate is further extracted with 0.7 mol/L of the second organic phase containing P204 (the diluent is kerosene), and the second-stage countercurrent extraction is used.
  • the volume ratio of the organic phase to the aqueous phase (O/A) is 1: 30.
  • the secondary raffinate is degreased by filtration and adsorption method, adding magnesium oxide or magnesium hydroxide, adjusting the pH value to more than 2, and returning to the leaching of the ion ore after supplementing the magnesium sulfate.
  • the obtained primary organic phase was back-extracted with 3.5 mol/L hydrochloric acid, and the third-stage semi-countercurrent stripping was carried out.
  • the volume ratio of organic phase to aqueous phase (O/A) was 25:1, and the rare earth-containing REO was obtained at 156 g/L.
  • the concentration of chlorinated heavy rare earth solution was 25:1, and the rare earth-containing REO was obtained at 156 g/L.
  • the obtained secondary supported organic phase was back-extracted with 3.5 mol/L hydrochloric acid, and the countercurrent extraction was carried out by a 4-stage countercurrent extraction.
  • the volume ratio of the organic phase to the aqueous phase (O/A) was 25:1, and the rare earth-containing REO 151 g/L was obtained.
  • the extraction and stripping process adopts a centrifugal extractor, and the obtained rare earth chloride solution is used as a raw material for extracting and separating and purifying a single rare earth.
  • the ion-adsorbed rare earth ore is leached by using a calcium chloride solution as a leaching agent to obtain a rare earth chloride solution containing rare earth REO 0.8 g/L as a raw material liquid (in which the medium and heavy rare earth REO/TREO is 85%, light rare earth REO/ TREO is 15%), and the pH of the raw material liquid is adjusted to 2.5.
  • the raffinate is further extracted with 0.6 mol/L of the second organic phase containing P204 (the diluent is kerosene), and the 5th-stage cross-flow extraction is used.
  • the rate is 98.7%.
  • the obtained primary organic phase was back-extracted with 5.0 mol/L hydrochloric acid, and the 3-stage countercurrent stripping was carried out.
  • the volume ratio of organic phase to aqueous phase (O/A) was 15:1, and a high concentration of rare earth REO 216 g/L was obtained.
  • the obtained secondary supported organic phase was back-extracted with 3.8 mol/L hydrochloric acid, and the third-stage semi-countercurrent stripping was carried out.
  • the volume ratio of organic phase to aqueous phase (O/A) was 40:1, and the rare earth-containing REO 159 g/L was obtained.
  • the extraction and stripping process adopts a centrifugal extractor, and the obtained rare earth chloride solution is used as a raw material for extracting and separating and purifying a single rare earth.
  • the ion-adsorbed rare earth ore is leached by using a magnesium sulfate solution as a leaching agent to obtain a rare earth chloride solution containing rare earth REO 1 g/L as a raw material liquid (where the medium and heavy rare earth REO/TREO is 40%, and the light rare earth REO/TREO is 60%), adjust the pH of the raw material liquid to 3.
  • the medium organic rare earth in the raw material was extracted with 0.8 mol/L of the first organic phase containing P507 (the diluent was kerosene), and the volume ratio of the organic phase to the aqueous phase (O/A) was 1:20.
  • the first raffinate is further extracted with 1.0 mol/L of the second organic phase containing P204 (the diluent is kerosene), and the fourth-stage countercurrent extraction is used.
  • the rate was 99.0%, and the secondary raffinate was added with magnesium oxide or magnesium hydroxide to adjust the pH to more than 2, and the magnesium sulfate was added to return to the leaching of the ion ore.
  • the obtained primary organic phase was back-extracted with 4.5 mol/L hydrochloric acid, and the 3-stage countercurrent stripping was carried out.
  • the volume ratio of organic phase to aqueous phase (O/A) was 20:1, and a high concentration of rare earth REO 192 g/L was obtained.
  • the obtained secondary supported organic phase was back-extracted with 4.8 mol/L hydrochloric acid, and the countercurrent extraction was carried out by a 4-stage countercurrent extraction.
  • the volume ratio of the organic phase to the aqueous phase (O/A) was 20:1, and the rare earth-containing REO was obtained at a height of 208 g/L.
  • the extraction and stripping process adopts a centrifugal extractor, and the obtained rare earth chloride solution is used as a raw material for extracting and separating and purifying a single rare earth.
  • the ion-adsorbed rare earth ore was leached by using a magnesium sulfate solution as a leaching agent to obtain a rare earth solution containing rare earth REO 1.5 g/L as a raw material liquid (the medium-heavy rare earth REO/TREO was 65%, and the light rare earth REO/TREO was 35%), adjust the pH of the raw material liquid to 3.2.
  • the medium-weight rare earth in the raw material liquid was extracted with 1.3 mol/L organic phase containing P507 (diluent as kerosene), and the volume ratio of organic phase to water phase (O/A) was 1:20.
  • the raffinate is further extracted with 0.9 mol/L of P204-containing organic phase (diluent is kerosene), and the residual rare earth is extracted by a three-stage countercurrent extraction.
  • the volume ratio of organic phase to aqueous phase (O/A) is 1:18.
  • the rare earth content in the secondary raffinate was 0.009 g/L, and the rare earth recovery rate was greater than 99.4. %.
  • magnesium oxide or magnesium hydroxide is added to adjust the pH value to more than 2, and the magnesium sulfate is added to return to the leaching of the ion ore. .
  • the obtained primary organic phase was back-extracted with 5.5 mol/L hydrochloric acid, and the third-stage countercurrent stripping was carried out.
  • the volume ratio of organic phase to aqueous phase (O/A) was 13:1, and a high concentration of rare earth REO 268 g/L was obtained.
  • the obtained secondary supported organic phase was back-extracted with 4.0 mol/L hydrochloric acid, and the third-stage countercurrent stripping was carried out.
  • the volume ratio of the organic phase to the aqueous phase (O/A) was 20:1, and the rare earth-containing REO 160 g/L was obtained.
  • the concentration of the chlorinated light rare earth solution, wherein the medium heavy rare earth content / total rare earth content is 3.5%.
  • the extraction and stripping process adopts a centrifugal extractor, and the obtained rare earth chloride solution is used as a raw material for extracting and separating and purifying a single rare earth.
  • the ionic ore leaching solution containing rare earth REO 2g/L was used as a raw material liquid (where the medium and heavy rare earth REO/TREO was 50%, and the light rare earth REO/TREO was 50%), and the pH of the raw material liquid was adjusted to 4.
  • the raffinate is further extracted with 1.2 mol/L of the second organic phase containing P204 (the diluent is decane), and the fourth-stage countercurrent extraction is used.
  • the obtained primary organic phase was back-extracted with 5.5 mol/L hydrochloric acid, and the countercurrent extraction was carried out by a 4-stage countercurrent extraction.
  • the volume ratio of the organic phase to the aqueous phase (O/A) was 12:1, and a high concentration of rare earth REO 230 g/L was obtained.
  • the obtained secondary loaded organic phase was back-extracted with 5.5 mol/L hydrochloric acid, and the countercurrent extraction was carried out by a 4-stage countercurrent extraction.
  • the volume ratio of the organic phase to the aqueous phase (O/A) was 15:1, and the rare earth-containing REO 238 g/L was obtained.
  • the extraction and stripping process adopts a centrifugal extractor, and the obtained rare earth chloride solution is used as a raw material for extracting and separating and purifying a single rare earth.
  • the ion-adsorbed rare earth ore is leached by using a magnesium chloride solution as a leaching agent to obtain a rare earth solution containing rare earth REO 2.5 g/L as a raw material liquid (the medium-heavy rare earth REO/TREO is 35%, and the light rare earth REO/TREO is 65%). Adjust the pH of the raw material liquid to 4.2).
  • the medium organic rare earth in the raw material liquid was extracted with 1.3 mol/L of the first organic phase containing P507 (the diluent was kerosene), and the 8-phase countercurrent extraction was used.
  • the volume ratio of the organic phase to the aqueous phase (O/A) was 1:20.
  • the first raffinate is extracted with 1.4 mol/L of the second organic phase containing P204 (the diluent is sulfonated kerosene), and the residual rare earth is extracted by a 5-stage countercurrent extraction.
  • the recovery rate is 99.6%.
  • magnesium oxide is added to adjust the pH value to more than 2
  • the magnesium chloride is added to return to the leaching of the ion ore.
  • the obtained primary organic phase was back-extracted with 5.7 mol/L hydrochloric acid, and the countercurrent extraction was carried out by a 4-stage countercurrent extraction.
  • the volume ratio of the organic phase to the aqueous phase (O/A) was 13:1, and a high concentration of rare earth REO 258 g/L was obtained.
  • the obtained secondary supported organic phase was back-extracted with 5.7 mol/L hydrochloric acid, and the countercurrent extraction was carried out by a 5-stage countercurrent extraction.
  • the volume ratio of the organic phase to the aqueous phase (O/A) was 13:1, and the rare earth-containing REO was obtained at a height of 267 g/L.
  • the concentration of the chlorinated light rare earth solution, wherein the medium heavy rare earth content / total rare earth content is 0.8%.
  • the extraction and stripping process adopts a centrifugal extractor, and the obtained rare earth chloride solution is used as a raw material for extracting and separating and purifying a single rare earth.
  • the ion-adsorbed rare earth ore was leached by using a magnesium sulfate solution as a leaching agent to obtain a rare earth solution containing rare earth REO 3.5 g/L as a raw material liquid (in which the medium-heavy rare earth REO/TREO was 18% and the light rare earth REO/TREO was 82). %, adjust the pH of the raw material liquid to 5.5).
  • the medium-weight rare earth in the raw material liquid was extracted with 1.5 mol/L of the first organic phase containing P507 (the diluent was kerosene), and the volume ratio of the organic phase to the aqueous phase (O/A) was 1:30.
  • the first raffinate is extracted with 1.4 mol/L of the second organic phase containing P204 (the diluent is sulfonated kerosene), and the 6-stage countercurrent extraction is used.
  • the recovery rate was 99.4%.
  • the obtained primary organic phase was back-extracted with 5.6 mol/L hydrochloric acid, and the 6-stage countercurrent stripping was carried out.
  • the volume ratio of organic phase to aqueous phase (O/A) was 9:1, and a high concentration of rare earth REO 247 g/L was obtained.
  • the obtained secondary supported organic phase was back-extracted with 6 mol/L hydrochloric acid, and the 5-stage countercurrent stripping was carried out.
  • the volume ratio of organic phase to aqueous phase (O/A) was 14:1, and a high concentration of rare earth REO 271 g/L was obtained.
  • the extraction and stripping process adopts a centrifugal extractor, and the obtained rare earth chloride solution is used as a raw material for extracting and separating and purifying a single rare earth.
  • the ionic ore leaching solution containing rare earth REO 5.2 g/L was used as a raw material liquid (in which the medium-heavy rare earth REO/TREO was 30% and the light rare earth REO/TREO was 70%), and the pH of the raw material liquid was adjusted to 5.
  • the medium-weight rare earth in the raw material liquid was extracted with 1.4 mol/L of the first organic phase containing P507 (the diluent was kerosene), and the volume ratio of the organic phase to the aqueous phase (O/A) was 1:10.
  • the raffinate is further extracted with 1.0 mol/L of the second organic phase containing P204 (the diluent is kerosene), and the 5-stage countercurrent extraction is used.
  • the volume ratio of the organic phase to the aqueous phase (O/A) is 1: 3, control the extraction of water phase balance
  • the rare earth content in the secondary raffinate was 0.03 g/L, and the rare earth recovery was 99.4%.
  • the obtained primary organic phase was back-extracted with 5.4 mol/L hydrochloric acid, and the countercurrent extraction was carried out by a 4-stage countercurrent extraction.
  • the volume ratio of the organic phase to the aqueous phase (O/A) was 12:1, and a high concentration of rare earth REO 249 g/L was obtained.
  • the obtained secondary supported organic phase was back-extracted with 5.5 mol/L hydrochloric acid, and the countercurrent extraction was carried out by a 4-stage countercurrent extraction.
  • the volume ratio of the organic phase to the aqueous phase (O/A) was 25:1, and the rare earth-containing REO was obtained at a high concentration of 230 g/L.
  • the extraction and stripping process adopts a centrifugal extractor, and the obtained rare earth chloride solution is used as a raw material for extracting and separating and purifying a single rare earth.
  • the ionic ore leaching solution containing rare earth REO 6g/L was used as a raw material liquid (in which the medium and heavy rare earth REO/TREO was 20% and the light rare earth REO/TREO was 80%), and the pH of the raw material liquid was adjusted to 4.5.
  • the medium-weight rare earth in the raw material liquid was extracted with 1.3 mol/L of the first organic phase containing P507 (diluent as kerosene), and the volume ratio of organic phase to water phase (O/A) was 1:11 by 4-stage countercurrent extraction.
  • the raffinate is further extracted with 1.5 mol/L of the second organic phase containing P204 (the diluent is kerosene), and the 6-stage countercurrent extraction is used.
  • the volume ratio of the organic phase to the aqueous phase (O/A) is 1: 4.7.
  • Control the equilibrium acidity of the extracted aqueous phase to pH 1.0, and obtain the secondary loaded organic phase and the secondary raffinate containing rare earth REO 20g/L.
  • the rare earth content in the secondary raffinate is 0.05g/L, and the rare earth recovery rate It is 99.2%.
  • the obtained primary organic phase was back-extracted with 4.5 mol/L hydrochloric acid, and the countercurrent extraction was carried out by a 4-stage countercurrent extraction.
  • the volume ratio of the organic phase to the aqueous phase (O/A) was 10:1, and a high concentration of rare earth REO 188 g/L was obtained.
  • the obtained secondary supported organic phase was back-extracted with 5 mol/L hydrochloric acid, and the 8-stage countercurrent stripping was carried out.
  • the volume ratio of organic phase to aqueous phase (O/A) was 10:1, and the high concentration of rare earth-containing REO 197 g/L was obtained.
  • the extraction and stripping process adopts a centrifugal extractor, and the obtained rare earth chloride solution is used as a raw material for extracting and separating and purifying a single rare earth.
  • the ionic ore leaching solution containing rare earth REO 8 g/L was used as a raw material liquid (in which the medium and heavy rare earth REO/TREO was 20%, and the light rare earth REO/TREO was 80%), and the pH of the raw material liquid was adjusted to 5.5.
  • the medium-weight rare earth in the raw material liquid was extracted with 1.5 mol/L of the first organic phase containing P507 (the diluent was kerosene), and the volume ratio of the organic phase to the aqueous phase (O/A) was 1:12.
  • the raffinate is further extracted with 1.5 mol/L of the second organic phase containing P204 (the diluent is kerosene), and the 6-stage countercurrent extraction is used.
  • the volume ratio of the organic phase to the aqueous phase (O/A) is 1: 4.
  • Control the equilibrium acidity of the extracted aqueous phase to pH 0.7, and obtain the secondary loaded organic phase and the secondary raffinate containing the rare earth REO 24.2g/L.
  • the rare earth content in the secondary raffinate is 0.1g/L, and the rare earth is recovered. The rate is 98.7%.
  • the obtained primary organic phase was back-extracted with 5.5 mol/L hydrochloric acid, and the 10-phase semi-countercurrent stripping was carried out.
  • the volume ratio of organic phase to aqueous phase (O/A) was 11:1, and the rare earth-containing REO was obtained at 256 g/L.
  • the concentration of chlorinated heavy rare earth solution was 11:1, and the rare earth-containing REO was obtained at 256 g/L.
  • the obtained secondary supported organic phase was back-extracted with 5.5 mol/L hydrochloric acid, and the countercurrent extraction was carried out by 10 stages.
  • the volume ratio of the organic phase to the aqueous phase (O/A) was 10:1, and the rare earth-containing REO was obtained at a high concentration of 240 g/L.
  • the extraction and stripping process adopts a centrifugal extractor, and the obtained rare earth chloride solution is used as a raw material for extracting and separating and purifying a single rare earth.
  • the ionic ore leaching solution containing rare earth REO 10 g/L was used as a raw material liquid (in which the medium and heavy rare earth REO/TREO was 11%, and the light rare earth REO/TREO was 89%), and the pH of the raw material liquid was adjusted to 5.
  • the medium-weight rare earth in the raw material liquid was extracted with 1.4 mol/L of the first organic phase containing P507 (the diluent was kerosene), and the volume ratio of the organic phase to the aqueous phase (O/A) was 1:15.
  • the raffinate is further extracted with 1.3 mol/L of the second organic phase containing P204 (the diluent is kerosene), and the residual rare earth is extracted by a 5-stage countercurrent extraction.
  • the volume ratio of the organic phase to the aqueous phase (O/A) is 1: 2.
  • Control the equilibrium acidity of the extracted aqueous phase to pH 0.5, and obtain the secondary loaded organic phase and the secondary raffinate containing rare earth REO 17g/L.
  • the rare earth content in the secondary raffinate is 0.1g/L, and the rare earth recovery rate It is 99%.
  • the obtained primary organic phase was back-extracted with 5.0 mol/L hydrochloric acid, and the 5-stage countercurrent stripping was carried out.
  • the volume ratio of organic phase to aqueous phase (O/A) was 10:1, and a high concentration of rare earth REO 218 g/L was obtained.
  • the obtained secondary supported organic phase was back-extracted with 4.7 mol/L hydrochloric acid, and the countercurrent extraction was carried out by a 4-stage countercurrent extraction.
  • the volume ratio of the organic phase to the aqueous phase (O/A) was 12:1, and the rare earth-containing REO was 202 g/L.
  • the extraction and stripping process adopts a centrifugal extractor, and the obtained rare earth chloride solution is used as a raw material for extracting and separating and purifying a single rare earth.
  • magnesium sulfate as a leaching agent to leach the ion-adsorbed rare earth ore to obtain a rare earth solution containing rare earth REO 0.30g/L as a raw material liquid (where the medium-heavy rare earth REO/TREO is 50% and the light rare earth REO/TREO is 50). %), adjust the pH of the raw material liquid to 3.5.
  • the first raffinate is further extracted with 1.0 mol/L P215 as the second organic phase (diluent is kerosene), and the residual rare earth is extracted by 5-stage cross-flow extraction.
  • the volume ratio of organic phase to aqueous phase is 1:40, and the extracted aqueous phase is controlled.
  • the rare earth content in the secondary raffinate was 0.005 g/L, and the rare earth recovery rate was 98.3%.
  • the obtained primary organic phase was back-extracted with 3.5 mol/L hydrochloric acid, and the second-stage countercurrent stripping was carried out.
  • the volume ratio of organic phase to aqueous phase (O/A) was 30:1, and chlorination with rare earth REO 150 g/L was obtained.
  • the obtained secondary supported organic phase was back-extracted with 3.5 mol/L hydrochloric acid, and the second-stage countercurrent stripping was carried out.
  • the volume ratio of organic phase to aqueous phase (O/A) was 35:1, and the rare earth-containing REO was obtained at a height of 157 g/L.
  • the extraction and stripping process adopts a centrifugal extractor, and the obtained rare earth chloride solution is used as a raw material for extracting and separating and purifying a single rare earth.
  • the invention aims at pre-extracting medium-heavy rare earth by using an acidic phosphorus extracting agent with a PKa value of >4 for the lower rare earth concentration and acidity of the ionic ore rare earth leaching solution, and the high-concentration rare earth chloride solution is obtained by back-collecting the organic phase with a primary loading organic phase.
  • the liquid has a rare earth concentration of more than 230 g/L; the primary raffinate is extracted and recovered by an acidic phosphorus extractant having a PKa value of ⁇ 3.5, and the second loaded organic phase is subjected to hydrochloric acid stripping to obtain a high concentration rare earth chloride solution, and the rare earth concentration thereof More than 230g / L, rare earth enrichment 100 ⁇ 500 times, the preferred solution in rare earth recovery can be greater than 98%.
  • the extraction process does not require saponification, nor does it use ammonium bicarbonate to precipitate rare earths, eliminates the discharge of ammonia nitrogen wastewater or high salinity wastewater, and at the same time achieves the pre-separation separation effect of heavy rare earth and light rare earth in the rare earth recovery process, and solves the PKa Acidic phosphorus extractant with value >4 extracts low rare earth yield and small organic loading. Under the condition of low acidity, the acidic phosphorus extractant with PKa value ⁇ 3.5 is easy to be emulsified and the medium and heavy rare earth is difficult to strip.
  • the invention replaces the existing ammonium bicarbonate or oxalic acid precipitation-baking process, and the obtained high concentration rare earth chloride solution can be directly supplied to the rare earth separation plant for separation and purification of the rare earth, and the rare earth oxide concentrate hydrochloric acid dissolution process is eliminated, and the rare earth recovery rate is greatly increased. Improve, production costs are greatly reduced, and no radioactive waste residue is produced, eliminating high-salt wastewater discharge such as ammonia nitrogen, calcium, sodium and magnesium, promoting efficient development and utilization of ionic rare earth resources, rapid development of green environmental protection technology, and solving rare earth resources
  • the problems of low recovery rate, large amount of wastewater discharge, high salt or ammonia nitrogen and other pollutants exceeding the standard will promote the healthy and sustainable development of the rare earth industry.

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Abstract

本申请公开了一种分步萃取回收稀土的方法。该方法包括以下步骤：以含有中重稀土的稀土溶液作为原料液，原料液的pH值为2.5-5.5，采用含PKa值>4的酸性磷类萃取剂的第一有机相对原料液进行第一次萃取，控制萃取水相平衡酸度为1<pH<3，得到一次负载有机相和含轻稀土的一次萃余液；将含轻稀土的一次萃余液用含PKa值<3.5的酸性磷类萃取剂的第二有机相进行第二次萃取，控制萃取水相平衡酸度为0.5<pH<2.5，得到二次负载有机相和二次萃余液；分别反萃回收一次负载有机相和二次负载有机相中的稀土，得到氯化中重稀土溶液和氯化轻稀土溶液。本方法具有工艺流程短、稀土回收率高、成本低及清洁高效等优点。

Description

分步萃取回收稀土的方法 技术领域
本发明涉及稀土湿法冶金技术领域，具体而言，涉及一种分步萃取回收稀土的方法。
背景技术
离子吸附型稀土矿是世界罕见的富含中重稀土的宝贵资源，其中稀土以离子态吸附在高岭土和云母等铝硅酸盐矿物上。这种离子吸附型稀土矿中稀土含量很低，一般在千分之一以下，含有镧、铈、镨、钕、钐、铕、钆、铽、镝、钬、铒、铥、镱、镥、钇十多种稀土元素，(镧、铈、镨、钕被称为“轻稀土”，钐、铕、钆、铽、镝、钬、铒、铥、镱、镥和钇被称为“中重稀土”)，其中中重稀土的含量为40％以上。目前，离子型稀土矿通常采用硫酸铵浸出，得到的稀土含量以REO计为2g/L左右的低浓度硫酸稀土溶液，采用碳酸氢铵或草酸沉淀回收稀土，再经过焙烧，得到稀土含量以REO计为90％的混合稀土氧化物精矿。稀土分离厂将上述稀土氧化物精矿用盐酸溶解，除杂过滤，得到高浓度混合氯化稀土溶液，再采用P507或环烷酸进行多步串级萃取分离，得到纯度2N～5N稀土氯化物溶液，再采用碳酸氢铵、草酸或碳酸钠沉淀得到稀土盐，最后经过焙烧，得到各种纯稀土氧化物产品。由于上述稀土氧化物精矿含有10％的铁、铝、钙、硅及微量放射性核素等杂质，盐酸溶解后，上述杂质富集到渣中，导致该渣放射性比活度超标，需按放射性废渣处置规定建库堆存，另外渣中还含有5％左右的稀土，导致部分稀土损失。
由于离子矿稀土浸出液稀土浓度低，一般在2g/L左右，杂质含量高，现有沉淀回收稀土工艺存在稀土回收率较低，化工试剂消耗大，存在氨氮等高盐度废水排放等问题。而南方离子矿尾矿山的浸矿尾液和淋滤液中稀土浓度甚至更低，目前该尾矿液稀土资源的有效富集与回收还很困难，其流失不仅会造成宝贵南方离子矿稀土资源的损失，更严重的是对周边区域水资源的安全构成严重威胁。因此，如何实现低浓度南方离子矿稀土浸出液的低成本绿色高效富集回收，以及矿山浸矿尾液和尾矿渗滤液中低浓度稀土的高效经济提取回收，是提高离子型稀土资源利用率，解决资源流失等问题的关键。
目前，稀土分离提纯方法主要有溶剂萃取法，具有连续易控制，成本低、易实现大规模生产的特点而得到广泛应用。其中稀土行业中工业化应用的酸性磷类萃取体系 主要有P507、P204、环烷酸等。为了提高生产效率、减少设备投资，稀土的萃取分离提纯均在高浓度的氯化稀土溶液中进行。由于酸性萃取剂对稀土的萃取能力与萃取水相平衡酸度的3次方成反比，因此，稀土萃取分离时，普遍采用氨水、氢氧化钠等无机碱先对有机相(酸性萃取剂)进行皂化，得到含铵或含钠的有机相，然后再进行稀土萃取分离，该过程不但消耗大量的碱，造成生产成本增加，而且产生大量的氨氮等高盐度废水，对水资源造成严重的污染。
发明内容
本发明旨在提供一种分步萃取回收稀土的方法，以解决现有离子矿稀土浸出液中回收稀土工艺存在的稀土回收率低、成本高、且易污染环境等问题。
为了实现上述目的，本发明提供了一种分步萃取回收稀土的方法，以含有中重稀土的稀土溶液作为原料液，原料液的pH值为2.5-5.5，稀土溶液分步萃取回收稀土的方法包括如下步骤：采用含PKa值>4的非皂化酸性磷类萃取剂的第一有机相对原料液进行第一次萃取，控制萃取水相平衡酸度为1<pH<3，，得到一次负载有机相和含轻稀土的一次萃余液；将含轻稀土的一次萃余液用含PKa值<3.5的非皂化酸性磷类萃取剂的第二有机相进行第二次萃取，控制萃取水相平衡酸度为0.5<pH<2.5，得到二次负载有机相和二次萃余液；分别反萃回收一次负载有机相和二次负载有机相中的稀土，得到氯化中重稀土溶液和氯化轻稀土溶液。
进一步地，上述方法中原料液的pH值为4-5，其中稀土含量以REO计小于10g/L，原料液中的中重稀土质量百分含量为10％～85％之间，优选原料液中的中重稀土质量百分含量为15％～50％之间。
进一步地，上述方法中稀土溶液为硫酸稀土溶液和/或氯化稀土溶液，优选的稀土溶液为由离子型稀土矿经硫酸镁、硫酸铵、硫酸亚铁、氯化镁、氯化铵、氯化亚铁、氯化钙、氯化钠中的一种或多种无机盐溶液作为浸矿液浸出得到。
进一步地，上述方法中PKa值>4的酸性磷类萃取剂为P507、P229、C302和C272中的一种或多种，优选为P507；PKa值<3.5的酸性磷类萃取剂为P204、P215、P406、C301中的一种或多种，优选为P204。
进一步地，上述方法中第一有机相和第二有机相中均还含有稀释剂，第一有机相和第二有机相中酸性磷类萃取剂浓度为0.5～1.5mol/L。
进一步地，上述方法中第一次萃取步骤中，原料液中大于95％的中重稀土被萃取到一次负载有机相中，优选的原料液中大于98％的中重稀土被萃取到一次负载稀土有机相中。
进一步地，上述方法中一次负载有机相中稀土含量以REO计为5～28g/L，优选10～25g/L；二次负载有机相中稀土含量以REO计为4～25g/L，优选8～20g/L。
进一步地，上述方法中二次萃余液中稀土含量以REO计小于0.1g/L，优选小于0.02g/L，更优选地，二次萃余液可与浸矿剂混合后返回用于离子矿的浸出。
进一步地，上述方法中第一次萃取和第二次萃取过程中分别采用2～10级萃取，优选为2～5级逆流或错流萃取，更优选的萃取的过程采用离心萃取器或脉冲筛板塔设备。
进一步地，上述方法中还包括一次萃余液和二次萃余液进行除油的步骤，优选除油的步骤采用静置除油、煤油洗涤除油、气浮除油、超声波除油、过滤吸附除油、化学氧化和生化除油中的一种或几种方法进行除油。
进一步地，上述方法中分别反萃回收一次负载有机相和二次负载有机相中稀土的步骤包括：对一次负载有机相采用3.5～6mol/L盐酸反萃，得到氯化中重稀土溶液，优选地，氯化中重稀土溶液中稀土含量以REO计大于150g/L，优选大于230g/L；对二次负载有机相采用3.5～6mol/L盐酸反萃，得到氯化轻稀土溶液，优选地，氯化轻稀土溶液中稀土含量以REO计大于150g/L，优选大于230g/L。
进一步地，上述方法中对一次负载有机相和二次负载有机相进行反萃时，采用2～10级反萃，优选采用3～6级逆流或半逆流反萃，更优选的反萃的过程采用离心萃取器或脉冲筛板塔设备。
应用本发明的上述分步萃取回收稀土的方法，通过采用非皂化酸性磷类萃取剂对稀土溶液进行分步萃取，实现重稀土与轻稀土的预分组，本发明的回收方法与传统方法相比，省去了碳酸氢铵沉淀、过滤、煅烧、酸溶工序，不仅缩短了工艺流程，而且化工材料消耗大幅降低，而且具有提高稀土回收率、降低生产成本、无氨氮废水排放等优点；采用非皂化萃取剂在弱酸性条件下进行萃取，有机相溶解损失大幅度降低，而且不容易产生三相物，保证萃取过程顺利进行，实现稀土溶液高效清洁提取，提高稀土资源利用率，减少污染物排放及化工原材料消耗，有效保护环境。
附图说明
构成本申请的一部分的说明书附图用来提供对本发明的进一步理解，本发明的示意性实施例及其说明用于解释本发明，并不构成对本发明的不当限定。在附图中：
图1示出了一种根据本发明实施例的稀土溶液分步萃取回收稀土的方法的流程示意图。
具体实施方式
需要说明的是，在不冲突的情况下，本申请中的实施例及实施例中的特征可以相互组合。下面将参考附图并结合实施例来详细说明本发明。
为了克服背景技术所指出现有从离子矿稀土浸出液中回收稀土的方法操作流程复杂、稀土回收率低、成本高且易污染环境的不足，在本发明中提供了一种分步萃取回收稀土的方法,其中稀土溶液pH值为2.5-5.5，优选为4-5，其REO含量小于10g/L。而且，本发明所提供的这种回收稀土的方法优选以含中重稀土的离子型稀土矿浸出的稀土溶液为原料。其中稀土包括镧、铈、镨、钕、钐、铕、钆、铽、镝、钬、铒、铥、镱、镥和钇；钐、铕、钆、铽、镝、钬、铒、铥、镱、镥和钇为中重稀土；镧、铈、镨、钕为轻稀土。
本发明上述回收方法通过采用非皂化酸性萃取剂，不经过氨水或液碱等皂化处理，直接将稀土溶液中的稀土离子全部萃取到有机相中，通过控制萃取相比(有机相/水相即O/A)在上述范围内，得到稀土含量高的负载有机相，经过反萃，控制反萃相比得到高浓度的氯化稀土溶液，使低浓度稀土溶液中的稀土富集100～500倍，稀土回收率达到98％以上，使稀土得到高效清洁回收利用。
本发明所提供的稀土溶液分步萃取回收稀土的方法，以含有中重稀土的稀土溶液作为原料液，采用碱性化合物调节原料液pH值为2.5-5.5，优选为4-5，一方面能够将原料液中的铁、铝等去除，避免影响后续稀土的萃取，另一方面有利于稀土被萃取完全。工艺包括以下步骤：采用含PKa值>4的非皂化酸性磷类萃取剂的第一有机相对原料液进行第一次萃取，控制萃取水相平衡酸度为1<pH<3，得到一次负载有机相和含轻稀土一次萃余液；将含轻稀土的一次萃余液用含PKa值<3.5的非皂化酸性磷类萃取剂的第二有机相进行第二次萃取，控制萃取水相平衡酸度为0.5<pH<2.5，得到二次负载有机相和二次萃余液，分别反萃回收一次负载有机相和二次负载有机相中的稀土，得到氯化中重稀土溶液和氯化轻稀土溶液。其中PKa值＝-lg[Ka]，Ka为酸的离解平衡常数。控制萃取水相平衡pH值，一是为了将稀土萃取完全，二是保持酸性，有机相 溶解损失大幅度降低，而且不容易形成三相物。第一次萃取中，根据原料液中的中重稀土元素含量调整有机相浓度和相比，控制萃取水相平衡酸度为1<pH<3，将使稀土溶液中的95％以上的中重稀土萃取到有机相中，优选98％以上的中重稀土萃取到有机相中；第二次萃取中，根据一次萃余液中稀土浓度及组成来选择有机相种类和浓度、萃取方式及萃取相比，控制萃取水相平衡酸度为0.5<pH<2.5，将使剩余的稀土几乎全部萃取到有机相中。
按常规工艺，单独采用PKa值>4的酸性磷类萃取剂酸性较弱，虽然能够有效萃取中重稀土，且反萃相对容易，但存在萃取轻稀土能力有限、特别是有机相负载稀土浓度高时稀土萃取不完全等问题，无法达到稀土完全富集回收的目的，需要用氨水或液碱等对有机相进行皂化；而采用PKa值<3.5的酸性磷类萃取剂酸性相对较强，对稀土的萃取能力较强，但重稀土很难反萃，无法实现工业应用。在本发明中同时采用了两种不同Ka的有机相进行萃取，首先利用PKa值>4的P507等酸性磷类萃取剂萃取原料液中的中重稀土，再采用PKa值<3.5的P204等酸性磷类萃取剂萃取轻稀土，解决了P507对轻稀土萃取能力弱，P204对重稀土难反萃的难题，而且实现了重稀土与轻稀土的预分组分离的效果。
如图1所示，在图1中给出一种本发明分步萃取回收稀土的方法的流程示意图，以下将结合该流程图进一步说明本发明的优选方案以及有益效果。
如图1所示，在本发明分步萃取回收稀土的方法中，以含有中重稀土的稀土溶液作为原料液，中重稀土含量大于10％。其中稀土溶液优选为硫酸稀土溶液和/或氯化稀土溶液，稀土溶液特别优选为由离子型稀土矿经硫酸镁、硫酸铵、硫酸亚铁、氯化镁、氯化铵、氯化亚铁、氯化钙和氯化钠中的一种或多种无机盐作为浸矿剂浸出得到。稀土溶液尤其优选为REO含量为小于10g/L，原料液中的中重稀土质量比为10％～85％之间，优选所述原料液中的中重稀土质量百分含量为15％～50％之间。对于稀土REO含量高于10g/L的稀土溶液，本发明方法同样适用，只是萃取效果比低浓度的稀土溶液要差，可以在萃取过程中加入一定量的水调整溶液稀土浓度，从而降低萃取水相平衡酸度，使溶液中的稀土能够完全被萃入有机相中得到有效回收。
采用含PKa值>4的非皂化酸性磷类萃取剂的第一有机相对原料液进行第一次萃取，得到一次负载有机相和一次萃余液。在第一次萃取过程中，第一有机相中PKa值>4的酸性磷类萃取剂包括但不限于P507(2－乙基己基膦酸单2－乙基己基酯，pKa＝4.10)、P229(二(2-乙基己基)膦酸，pKa＝4.98)、C302(二(2，4，4-三甲基戊基)单硫代膦酸(HDTMPTP)，pKa＝5.63)和C272(二(2，4，4-三甲基戊基)膦酸(HDTMPP)，pKa＝6.37)中的一种或多种，优选使用P507；在上述第一次萃取步骤中，采用碱性化 合物调节原料液pH值为2.5-5.5，优选为4-5，原料液中的大部分中重稀土被萃取到一次负载有机相中，中重稀土萃取率大于95％。进一步地，可根据原料液中的中重稀土元素含量调整有机相浓度和相比，控制萃取水相平衡酸度为1<pH<3，保证合适的稀土萃取率，使中重稀土萃取率大于98％。通过降低萃取相比(O/A)，提高一次负载有机相中稀土的含量，有利于稀土的富集，然后增大反萃相比，提高反萃液中稀土浓度，方便衔接后续工序。
在上述第一次萃取步骤中，可根据原料液浓度及轻、中重稀土组成来选择有机相种类和浓度、萃取方式及萃取相比，保证获得较高稀土浓度的负载有机相，一次负载有机相中稀土含量高，有利于稀土的富集。优选一次负载有机相中稀土含量以REO计为5～28g/L。结合原料特点以及设备、投资及运行成本等经济因素，更优选一次负载有机相中稀土含量以REO计为10～25g/L。
在完成第一次萃取后，对一次萃余液进行第二次萃取，第二次萃取过程中采用含PKa值<3.5的非皂化酸性磷类萃取剂的第二有机相。其中第二有机相中PKa值<3.5的酸性磷类萃取剂包括但不限于P204(二(2-乙基己基磷酸)、磷酸二异辛酯(HDEHP、D2EHPA)，pKa＝3.32)、P215(二(1-甲基庚基)磷酸、磷酸二仲辛酯，pKa＝3.22)、P406(苯基膦酸单2-乙基己基脂，pKa＝3.12)、C301(二(2，4，4-三甲基戊基)二硫代膦酸(HDTMPDTP)，pKa＝2.61)中的一种或多种，优选使用P204。
在上述第二次萃取步骤中，可根据一次萃余液中稀土浓度及组成来选择有机相种类和浓度、萃取方式及萃取相比，控制萃取水相平衡酸度为0.5<pH<2.5，保证稀土全部被萃取到有机相中，获得较高稀土浓度的负载有机相，二次负载有机相中稀土含量高，有利于稀土的富集，提高反萃液中稀土浓度，方便衔接后续工序。优选二次负载有机相中稀土含量以REO计为4～25g/L。结合设备、投资及运行成本等经济因素，更优选二次负载稀土有机相中稀土含量以REO计为8～20g/L，但负载有机相浓度太高，稀土萃取回收率会有所下降。
在上述第二次萃取步骤中，二次萃余液中稀土含量以REO计小于0.1g/L。将一次萃余液再采用PKa值<3.5的酸性磷类萃取剂进行萃取剩余的稀土，利用较小的PKa值萃取剂，其酸性较高，萃取能力强的特点，把一次萃余液中剩余的稀土萃取完全，能够保证二次萃余液中稀土含量小于0.1g/L，优选小于0.02g/L。
在完成上述第一次萃取和第二次萃取步骤后，在本发明一种优选的实施例中，还包括对一次萃余液和二次萃余液进行除油的步骤，更优选除油的步骤采用静置除油、 煤油洗涤除油、气浮除油、超声波除油、过滤吸附除油、化学氧化和生化除油中的一种或几种方法进行除油。
在完成上述第一次萃取和第二次萃取步骤后，在本发明另一种优选的实施例中，将第二次萃取步骤获得的二次萃余液采用氧化镁、氢氧化镁、氧化钙、氢氧化钙中的至少一种调节pH值大于2，并补充浸矿剂调配后作为浸矿液，返回用于离子矿的浸出。实现二次萃余液循环利用以及提高稀土收率的效果。其中可以使用的浸矿剂包括但不限于硫酸镁、硫酸铵、氯化镁、氯化铵、氯化钙和氯化钠中的一种或多种。
在上述第一次萃取步骤中使用的第一有机相和第二次萃取步骤中使用的第二有机相中除了酸性磷类萃取剂以外，至少还可以含有稀释剂，可以使用的稀释剂包括但不限于煤油、磺化煤油、正己烷、正庚烷、辛烷、壬烷、癸烷等本领域熟知的有机溶剂中的一种或多种。为了确保稀土的高萃取收率，在第一有机相和第二有机相中酸性磷类萃取剂浓度为0.1～1.5mol/L，优选为0.5～1.5mol/L。有机相浓度增加，稀土萃取能力提高，但反萃能力下降，要根据稀土溶液中稀土的浓度选择合适的有机相浓度，即要保证稀土能够有效被萃取到有机相中，并通过降低萃取相比(O/A)提高负载有机相中的稀土浓度，进而有利于对一次负载有机相和二次负载有机相中稀土的反萃，再通过提高反萃盐酸浓度及调节大的反萃相比进行反萃，获得稀土含量较高的氯化稀土溶液，有利于提高后续单一稀土萃取分离提纯效率和生产能力。
在上述第一次萃取步骤和第二次萃取步骤中优选采用多级萃取，级数越多萃取分离效果越好，但为了节约成本及投资等，本发明采用2～10级萃取，萃取方式包括但不限于逆流、半逆流、错流等方式，其中优选采用2～5级逆流萃取，稀土浓度很低的情况下采用错流萃取，可以提高负载有机相中稀土浓度，但稀土回收率比多及逆流萃取的低。在上述第一次萃取步骤和第二次萃取步骤中相比(O/A)为5:1～1:50，优化为1:1～1:30，在相比较小(O/A＝1:5以下)的情况下，为了保证有机相与水相的混合效果，采用半逆流的方式即将同级部分有机相自循环，从而增大两相的混合相比，获得更好的混合效果。在上述萃取过程中可以采用的设备包括但不限于离心萃取器或脉冲筛板塔等。
本发明所提供的分步萃取回收稀土的方法具有萃取过程不需要进行皂化，消除了氨氮废水或高盐度废水的排放，同时达到了稀土回收过程中的重稀土与轻稀土的预分组分离效果，并解决PKa值>4的酸性磷类萃取剂萃取稀土收率低及有机负载量小等问题，低酸度条件下PKa值<3.5的酸性磷类萃取剂萃取稀土易乳化以及中重稀土难反萃等问题的效果。优选地，在第一次萃取中采用含P507的第一有机相，在二次萃取中采用含P204的第二有机相。
本发明稀土溶液分步萃取回收稀土的方法在完成第一次萃取和第二次萃取后，还包括分别采用无机酸反萃回收一次负载有机相和二次负载有机相中稀土的步骤，在回收一次负载有机相和二次负载有机相中稀土的步骤优选采用盐酸反萃的方式，在反萃步骤中反萃酸也可采用硝酸、硫酸等，但硫酸稀土溶解度较低，为了更好衔接后续工序并降低成本，本发明采用盐酸进行反萃。
在对一次负载有机相进行反萃的过程中，采用2mol/L盐酸反萃也能达到反萃目的，但为了得到更高浓度的氯化中重稀土溶液，优选地，对一次负载有机相采用3.5～6mol/L盐酸反萃，得到氯化中重稀土溶液，再经过萃取分离提纯制备单一稀土或沉淀结晶回收中重稀土，更为优选地，经反萃所得到的氯化中重稀土溶液中稀土重量含量以REO计大于150g/L，优选大于230g/L，通过提高反萃酸浓度和反萃相比(O/A)，氯化中重稀土溶液中稀土浓度可以提高到250g/L以上，这种中重稀土溶液可直接输送到稀土分离厂作为萃取分离提纯单一稀土的原料。
经本发明所提供的方法，能够尽量将中重稀土与轻稀土进行分离提取，但该过程无法直接将两者完全分离，在上述氯化中重稀土溶液中不可避免的还会存在一部分氯化轻稀土溶液，但为了便于理解本发明的主要意图，依然将其称为氯化中重稀土溶液。优选地，该氯化中重稀土溶液中轻稀土含量占总稀土含量的5～20wt.％，控制氯化中重稀土溶液中轻稀土含量有利于在达到预分组分离效果的前提下，有效地降低投资运行成本。在对二次负载有机相进行反萃的过程中，采用2mol/L盐酸反萃也能达到反萃目的，但为了得到更高浓度的混合氯化轻稀土溶液，优选地，对二次负载有机相采用3.5～6mol/L盐酸反萃，得到氯化轻稀土溶液，氯化轻稀土溶液中的中重稀土含量/总稀土含量<5％，优选为<1％，再经过萃取分离提纯制备单一稀土或沉淀结晶回收轻稀土。更为优选地，经反萃所得到的氯化中重稀土溶液中稀土重量含量以REO计大于150g/L，优选大于230g/L，通过提高反萃酸浓度和反萃相比(O/A)，氯化轻稀土溶液中稀土浓度可以提高到250g/L以上，这种氯化轻稀土溶液可直接输送到稀土分离厂作为萃取分离提纯单一稀土的原料。
经本发明所提供的方法，能够尽量将中重稀土与轻稀土进行分离提取，但该过程无法直接将两者完全分离，在上述氯化中重稀土溶液中不可避免的还会存在一部分氯化轻稀土溶液，但为了便于理解本发明的主要意图，依然将其称为氯化中重稀土溶液。
在上述对一次负载有机相进行反萃和对二次负载有机相进行反萃的过程中，各反萃过程优选采用多级反萃，级数越多稀土反萃率越高，但为了节约成本及投资等，本发明采用2～10级反萃，优选采用3～6级，反萃方式包括但不限于采用逆流或半逆流等方式，在上述一次反萃步骤和二次反萃步骤中，有机相和水相体积比(O/A)为50:1～ 1:1，优化为30:1～3:1。本发明优选采用3～6级逆流或半逆流反萃。在相比较大(O/A＝5:1以上)的情况下，为了保证有机相与水相的混合效果，采用半逆流的方式即将同级部分水相自循环，从而减少两相的混合相比，获得更好的混合效果。在上述反萃过程中可以采用的设备包括但不限于离心萃取器或脉冲筛板塔等。
在对上述一次负载有机相反萃后有机相(即第一有机相)返回用于第一次萃取，对上述二次负载有机相反萃后有机相(即第二有机相)返回用于第二次萃取。
以下将结合实施例1～14进一步说明本发明的有益效果，在如下实施例中稀土含量以REO计，简称为含稀土REO。REO代表稀土氧化物，TREO代表稀土氧化物总量。
实施例1：
采用硫酸镁为浸矿剂浸取离子吸附型稀土矿，得到含稀土REO 0.30g/L的硫酸稀土溶液，作为原料液(其中中重稀土REO/TREO为50％，轻稀土REO/TREO为50％)，调节原料液的pH值为3.5。
用1.0mol/L的含C272的第一有机相(稀释剂为煤油)萃取原料液中的中重稀土，采用4级错流萃取，第一有机相和水相体积比(O/A)为1：35，控制萃取水相平衡酸度为pH＝2.8，原料液中中重稀土萃取率为98.5％，得到含稀土REO 5.1g/L的一次负载有机相和一次萃余液。
一次萃余液再用1.0mol/L C301为第二有机相(稀释剂为煤油)萃取剩余的稀土，采用5级错流萃取，有机相和水相体积比为1：40，控制萃取水相平衡酸度为pH＝2.5，得到含稀土REO 4.8g/L的二次负载有机相和二次萃余液，二次萃余液中稀土含量为0.005g/L，稀土回收率98.3％。
将得到的一次负载有机相用3.5mol/L盐酸反萃，采用2级逆流反萃，有机相和水相体积比(O/A)为30：1，得到含稀土REO 151g/L的氯化中重稀土溶液。
将得到的二次负载有机相用3.5mol/L盐酸反萃，采用2级逆流反萃，有机相和水相体积比(O/A)为32：1，得到含稀土REO 153g/L的高浓度氯化轻稀土溶液，其中中重稀土含量/总稀土含量为5％。
萃取、反萃过程采用离心萃取器，得到的氯化稀土溶液作为萃取分离提纯单一稀土的原料。
实施例2：
采用硫酸镁和氯化镁的混合液为浸矿剂浸取离子吸附型稀土矿，得到含稀土REO0.35g/L的稀土溶液，作为原料液(其中中重稀土REO/TREO为60％，轻稀土REO/TREO为40％)，调节原料液的pH值为3.2。
用0.50mol/L的含P507的第一有机相(稀释剂为磺化煤油)萃取原料液中的中重稀土，采用10级错流萃取，有机相和水相体积比(O/A)为1：30，控制萃取水相平衡酸度为pH＝2.5，原料液中中重稀土萃取率为98.2％，得到含稀土REO 6.8g/L的一次负载有机相和一次萃余液。
一次萃余液再用0.5mol/L的含P204的第二有机相(稀释剂为正己烷)萃取剩余的稀土，采用8级错萃取，有机相和水相体积比(O/A)为1：40，控制萃取水相平衡酸度为pH＝2.3，得到含稀土REO 4.9g/L的二次负载有机相和二次萃余液，二次萃余液中稀土含量为0.005g/L，稀土回收率为98.6％。
将得到的一次负载有机相用3.8mol/L盐酸反萃，采用3级逆流反萃，有机相和水相体积比(O/A)为25：1，得到含稀土REO 167g/L的高浓度氯化中重稀土溶液。
将得到的二次负载有机相用3.6mol/L盐酸反萃，采用3级半逆流反萃，有机相和水相体积比(O/A)为30：1，得到含稀土REO 158g/L的高浓度氯化轻稀土溶液，其中中重稀土含量/总稀土含量为4％。
萃取、反萃过程采用脉冲筛板塔，得到的氯化稀土溶液作为萃取分离提纯单一稀土的原料。
实施例3：
采用硫酸镁溶液为浸矿剂浸取离子吸附型稀土矿，得到含稀土REO 0.5g/L的硫酸稀土溶液，作为原料液(其中中重稀土REO/TREO为40％，轻稀土REO/TREO为60％)，调节原料液的pH值为5.5。
用0.6mol/L的含P507的第一有机相(稀释剂为煤油)萃取原料液中的中重稀土，采用2级逆流萃取，有机相和水相体积比(O/A)为1：25，控制萃取水相平衡酸度为pH＝3，原料液中中重稀土萃取率为99.2％，得到含稀土REO 6.25g/L的一次负载有机相和一次萃余液。
一次萃余液再用0.7mol/L的含P204的第二有机相(稀释剂为煤油)萃取剩余的稀土，采用2级逆流萃取，有机相和水相体积比(O/A)为1：30，控制萃取水相平衡酸度为pH＝2.2，得到含稀土REO 6g/L的二次负载有机相和二次萃余液，二次萃余液中稀土含量为0.006g/L，稀土回收率为98.8％，二次萃余液采用过滤吸附方法进行除油后添加氧化镁或氢氧化镁，调节pH值大于2，补充硫酸镁后返回用于离子矿的浸出。
将得到的一次负载有机相用3.5mol/L盐酸反萃，采用3级半逆流反萃，有机相和水相体积比(O/A)为25：1，得到含稀土REO 156g/L的高浓度氯化中重稀土溶液。
将得到的二次负载有机相用3.5mol/L盐酸反萃，采用4级逆流反萃，有机相和水相体积比(O/A)为25：1，得到含稀土REO 151g/L的高浓度氯化轻稀土溶液，其中中重稀土含量/总稀土含量为4％。
萃取、反萃过程采用离心萃取器，得到的氯化稀土溶液作为萃取分离提纯单一稀土的原料。
实施例4：
采用氯化钙溶液为浸矿剂浸取离子吸附型稀土矿，得到含稀土REO 0.8g/L的氯化稀土溶液，作为原料液(其中中重稀土REO/TREO为85％，轻稀土REO/TREO为15％)，调节原料液的pH值为2.5。
用1.0mol/L的含P507的第一有机相(稀释剂为磺化煤油)萃取原料液中的中重稀土，采用3级逆流萃取，有机相和水相体积比(O/A)为1：20，控制萃取水相平衡酸度为pH＝2.2，原料液中中重稀土萃取率为96.5％，得到含稀土REO 14.4g/L的一次负载有机相和一次萃余液。
一次萃余液再用0.6mol/L的含P204的第二有机相(稀释剂为煤油)萃取剩余的稀土，采用5级错流萃取，有机相和水相体积比(O/A)为1：50，控制萃取水相平衡酸度为pH＝1.8，得到含稀土REO 4g/L的二次负载有机相和二次萃余液，二次萃余液中稀土含量为0.01g/L，稀土回收率为98.7％。
将得到的一次负载有机相用5.0mol/L盐酸反萃，采用3级逆流反萃，有机相和水相体积比(O/A)为15：1，得到含稀土REO 216g/L的高浓度氯化中重稀土溶液。
将得到的二次负载有机相用3.8mol/L盐酸反萃，采用3级半逆流反萃，有机相和水相体积比(O/A)为40：1，得到含稀土REO 159g/L的高浓度氯化轻稀土溶液，其中中重稀土含量/总稀土含量为1.5％。
萃取、反萃过程采用离心萃取器，得到的氯化稀土溶液作为萃取分离提纯单一稀土的原料。
实施例5：
采用硫酸镁溶液为浸矿剂浸取离子吸附型稀土矿，得到含稀土REO 1g/L的氯化稀土溶液，作为原料液(其中中重稀土REO/TREO为40％，轻稀土REO/TREO为60％)，调节原料液的pH值为3。
用0.8mol/L的含P507的第一有机相(稀释剂为煤油)萃取原料中的中重稀土，采用2级逆流萃取，有机相和水相体积比(O/A)为1：20，控制萃取水相平衡酸度为pH＝2.3，原料液中中重稀土萃取率为98.5％，得到含稀土REO 9.6g/L的一次负载有机相和一次萃余液。
一次萃余液再用1.0mol/L的含P204的第二有机相(稀释剂为煤油)萃取剩余的稀土，采用4级逆流萃取，有机相和水相体积比(O/A)为1：20，控制萃取水相平衡酸度为pH＝1.7，得到含稀土REO 10.4g/L的二次负载有机相和二次萃余液，二次萃余液中稀土含量为0.01g/L，稀土回收率为99.0％，二次萃余液添加氧化镁或氢氧化镁调节pH值大于2，补充硫酸镁后返回用于离子矿的浸出。
将得到的一次负载有机相用4.5mol/L盐酸反萃，采用3级逆流反萃，有机相和水相体积比(O/A)为20：1，得到含稀土REO 192g/L的高浓度氯化中重稀土溶液。
将得到的二次负载有机相用4.8mol/L盐酸反萃，采用4级逆流反萃，有机相和水相体积比(O/A)为20：1，得到含稀土REO 208g/L的高浓度氯化轻稀土溶液，其中中重稀土含量/总稀土含量为2.5％。
萃取、反萃过程采用离心萃取器，得到的氯化稀土溶液作为萃取分离提纯单一稀土的原料。
实施例6：
采用硫酸镁溶液为浸矿剂浸取离子吸附型稀土矿，得到含稀土REO 1.5g/L的硫酸稀土溶液，作为原料液(其中中重稀土REO/TREO为65％，轻稀土REO/TREO为35％)，调节原料液的pH值为3.2。
用1.3mol/L的含P507的有机相(稀释剂为煤油)萃取原料液中的中重稀土，采用2级逆流萃取，有机相和水相体积比(O/A)为1：20，控制萃取水相平衡酸度为 pH＝2，原料液中中重稀土萃取率为98.2％，得到含稀土REO 21g/L的一次负载有机相和一次萃余液。
一次萃余液再用0.9mol/L的含P204的有机相(稀释剂为煤油)萃取剩余的稀土，采用3级逆流萃取，有机相和水相体积比(O/A)为1：18，控制萃取水相平衡酸度为pH＝1.6，得到含稀土REO 8.1g/L的二次负载有机相和二次萃余液，二次萃余液中稀土含量0.009g/L，稀土回收率大于99.4％。二次萃余液采用气浮方法除油后，添加氧化镁或氢氧化镁调节pH值大于2，补充硫酸镁后返回用于离子矿的浸出。。
将得到的一次负载有机相用5.5mol/L盐酸反萃，采用3级逆流反萃，有机相和水相体积比(O/A)为13:1，得到含稀土REO 268g/L的高浓度氯化中重稀土溶液。
将得到的二次负载有机相用4.0mol/L盐酸反萃，采用3级逆流反萃，有机相和水相体积比(O/A)为20：1，得到含稀土REO 160g/L的高浓度氯化轻稀土溶液，其中中重稀土含量/总稀土含量为3.5％。
萃取、反萃过程采用离心萃取器，得到的氯化稀土溶液作为萃取分离提纯单一稀土的原料。
实施例7：
以含稀土REO 2g/L的离子矿浸出液作为原料液(其中中重稀土REO/TREO为50％，轻稀土REO/TREO为50％)，调节原料液的pH值为4。
用1.2mol/L的含P507的第一有机相(稀释剂为磺化煤油)萃取原料液中的中重稀土，采用3级逆流萃取，有机相和水相体积比(O/A)为1：16，控制萃取水相平衡酸度为pH＝1.8，原料液中中重稀土萃取率为98％，得到含稀土19.2g/L的一次负载有机相和一次萃余液。
一次萃余液再用1.2mol/L的含P204的第二有机相(稀释剂为癸烷)萃取剩余的稀土，采用4级逆流萃取，有机相和水相体积比(O/A)为1：20，控制萃取水相平衡酸度为pH＝1.5，得到含稀土16g/L的二次负载有机相和二次萃余液，二次萃余液中稀土含量为0.01g/L，稀土回收率为99.5％。
将得到的一次负载有机相用5.5mol/L盐酸反萃，采用4级逆流反萃，有机相和水相体积比(O/A)为12：1，得到含稀土REO 230g/L的高浓度氯化中重稀土溶液。
将得到的二次负载有机相用5.5mol/L盐酸反萃，采用4级逆流反萃，有机相和水相体积比(O/A)为15：1，得到含稀土REO 238g/L的高浓度氯化轻稀土溶液，其中中重稀土含量/总稀土含量为1％。
萃取、反萃过程采用离心萃取器，得到的氯化稀土溶液作为萃取分离提纯单一稀土的原料。
实施例8：
采用氯化镁溶液为浸矿剂浸取离子吸附型稀土矿，得到含稀土REO 2.5g/L的稀土溶液，作为原料液(其中中重稀土REO/TREO为35％，轻稀土REO/TREO为65％，调节原料液的pH值为4.2)。
用1.3mol/L的含P507的第一有机相(稀释剂为煤油)萃取原料液中的中重稀土，采用8级逆流萃取，有机相和水相体积比(O/A)为1：20，控制萃取水相平衡酸度为pH＝2，原料液中中重稀土萃取率为99％，得到含稀土REO 20g/L的一次负载有机相和一次萃余液。
一次萃余液用1.4mol/L的含P204的第二有机相(稀释剂为磺化煤油)萃取剩余的稀土，采用5级逆流萃取，有机相和水相体积比(O/A)为1：15，控制萃取水相平衡酸度为pH＝1.4，得到含稀土REO 22.3g/L的二次负载有机相和二次萃余液，二次萃余液中稀土含量为0.01g/L，稀土回收率为99.6％，二次萃余液采用静置除油后，添加氧化镁调节pH值大于2，并补充氯化镁后返回用于离子矿的浸出。
将得到的一次负载有机相用5.7mol/L盐酸反萃，采用4级逆流反萃，有机相和水相体积比(O/A)为13：1，得到含稀土REO 258g/L的高浓度氯化中重稀土溶液，其中轻稀土含量/总稀土含量为9％。
将得到的二次负载有机相用5.7mol/L盐酸反萃，采用5级逆流反萃，有机相和水相体积比(O/A)为13：1，得到含稀土REO 267g/L的高浓度氯化轻稀土溶液，其中中重稀土含量/总稀土含量为0.8％。
萃取、反萃过程采用离心萃取器，得到的氯化稀土溶液作为萃取分离提纯单一稀土的原料。
实施例9：
采用硫酸镁溶液为浸矿剂浸取离子吸附型稀土矿，得到含稀土REO 3.5g/L的稀土溶液，作为原料液(其中中重稀土REO/TREO为18％，轻稀土REO/TREO为82％，调节原料液的pH值为5.5)。
用1.5mol/L的含P507的第一有机相(稀释剂为煤油)萃取原料液中的中重稀土，采用10级逆流萃取，有机相和水相体积比(O/A)为1：30，控制萃取水相平衡酸度为pH＝1.9，原料液中中重稀土萃取率为99％，得到含稀土REO 27.3g/L的一次负载有机相和一次萃余液。
一次萃余液用1.4mol/L的含P204的第二有机相(稀释剂为磺化煤油)萃取剩余的稀土，采用6级逆流萃取，有机相和水相体积比(O/A)为1：10，控制萃取水相平衡酸度为pH＝1.3，得到含稀土REO 19.5g/L的二次负载有机相和二次萃余液，二次萃余液中稀土含量为0.02g/L，稀土回收率为99.4％。
将得到的一次负载有机相用5.6mol/L盐酸反萃，采用6级逆流反萃，有机相和水相体积比(O/A)为9：1，得到含稀土REO 247g/L的高浓度氯化中重稀土溶液，其中轻稀土含量/总稀土含量为6％。
将得到的二次负载有机相用6mol/L盐酸反萃，采用5级逆流反萃，有机相和水相体积比(O/A)为14：1，得到含稀土REO 271g/L的高浓度氯化轻稀土溶液，其中中重稀土含量/总稀土含量为0.7％。
萃取、反萃过程采用离心萃取器，得到的氯化稀土溶液作为萃取分离提纯单一稀土的原料。
实施例10：
以含稀土REO 5.2g/L的离子矿浸出液作为原料液，(其中中重稀土REO/TREO为30％，轻稀土REO/TREO为70％)调节原料液的pH值为5。
用1.4mol/L的含P507的第一有机相(稀释剂为煤油)萃取原料液中的中重稀土，采用4级逆流萃取，有机相和水相体积比(O/A)为1：10，控制萃取水相平衡酸度为pH＝1.6，原料液中中重稀土萃取率为99％，得到含稀土REO 20.8g/L的一次负载有机相和一次萃余液。
一次萃余液再用1.0mol/L的含P204的第二有机相(稀释剂为煤油)萃取剩余的稀土，采用5级逆流萃取，有机相和水相体积比(O/A)为1：3，控制萃取水相平衡 酸度为pH＝1.1，得到含稀土REO 9.3g/L的二次负载有机相和二次萃余液，二次萃余液中稀土含量为0.03g/L，稀土回收率为99.4％。
将得到的一次负载有机相用5.4mol/L盐酸反萃，采用4级逆流反萃，有机相和水相体积比(O/A)为12:1，得到含稀土REO 249g/L的高浓度氯化中重稀土溶液。
将得到的二次负载有机相用5.5mol/L盐酸反萃，采用4级逆流反萃，有机相和水相体积比(O/A)为25：1，得到含稀土REO 230g/L的高浓度氯化轻稀土溶液，其中中重稀土含量/总稀土含量为0.6％。
萃取、反萃过程采用离心萃取器，得到的氯化稀土溶液作为萃取分离提纯单一稀土的原料。
实施例11：
以含稀土REO 6g/L的离子矿浸出液作为原料液(其中中重稀土REO/TREO为20％，轻稀土REO/TREO为80％)，调节原料液的pH值为4.5。
用1.3mol/L的含P507的第一有机相(稀释剂为煤油)萃取原料液中的中重稀土，采用4级逆流萃取，有机相和水相体积比(O/A)为1：11，控制萃取水相平衡酸度为pH＝1.5，原料液中中重稀土萃取率为99.7％，得到含稀土REO 19g/L的一次负载有机相和一次萃余液。
一次萃余液再用1.5mol/L的含P204的第二有机相(稀释剂为煤油)萃取剩余的稀土，采用6级逆流萃取，有机相和水相体积比(O/A)为1：4.7，控制萃取水相平衡酸度为pH＝1.0，得到含稀土REO 20g/L的二次负载有机相和二次萃余液，二次萃余液中稀土含量为0.05g/L，稀土回收率为99.2％。
将得到的一次负载有机相用4.5mol/L盐酸反萃，采用4级逆流反萃，有机相和水相体积比(O/A)为10:1，得到含稀土REO 188g/L的高浓度氯化中重稀土溶液。
将得到的二次负载有机相用5mol/L盐酸反萃，采用8级逆流反萃，有机相和水相体积比(O/A)为10：1，得到含稀土REO 197g/L的高浓度氯化轻稀土溶液，其中中重稀土含量/总稀土含量为2％。
萃取、反萃过程采用离心萃取器，得到的氯化稀土溶液作为萃取分离提纯单一稀土的原料。
实施例12：
以含稀土REO 8g/L的离子矿浸出液作为原料液(其中中重稀土REO/TREO为20％，轻稀土REO/TREO为80％)，调节原料液的pH值为5.5。
用1.5mol/L的含P507的第一有机相(稀释剂为煤油)萃取原料液中的中重稀土，采用5级逆流萃取，有机相和水相体积比(O/A)为1：12，控制萃取水相平衡酸度为pH＝1.4，原料液中中重稀土萃取率为99.3％，得到含稀土REO 23.5g/L的一次负载有机相和一次萃余液。
一次萃余液再用1.5mol/L的含P204的第二有机相(稀释剂为煤油)萃取剩余的稀土，采用6级逆流萃取，有机相和水相体积比(O/A)为1：4，控制萃取水相平衡酸度为pH＝0.7，得到含稀土REO 24.2g/L的二次负载有机相和二次萃余液，二次萃余液中稀土含量为0.1g/L，稀土回收率为98.7％。
将得到的一次负载有机相用5.5mol/L盐酸反萃，采用10级半逆流反萃，有机相和水相体积比(O/A)为11:1，得到含稀土REO 256g/L的高浓度氯化中重稀土溶液。
将得到的二次负载有机相用5.5mol/L盐酸反萃，采用10级逆流反萃，有机相和水相体积比(O/A)为10：1，得到含稀土REO 240g/L的高浓度氯化轻稀土溶液，其中中重稀土含量/总稀土含量为1％。
萃取、反萃过程采用离心萃取器，得到的氯化稀土溶液作为萃取分离提纯单一稀土的原料。
实施例13：
以含稀土REO 10g/L的离子矿浸出液作为原料液(其中中重稀土REO/TREO为11％，轻稀土REO/TREO为89％)，调节原料液的pH值为5。
用1.4mol/L的含P507的第一有机相(稀释剂为煤油)萃取原料液中的中重稀土，采用5级逆流萃取，有机相和水相体积比(O/A)为1：15，控制萃取水相平衡酸度为pH＝1.1，原料液中中重稀土萃取率为99.5％，得到含稀土REO 22g/L的一次负载有机相和一次萃余液。
一次萃余液再用1.3mol/L的含P204的第二有机相(稀释剂为煤油)萃取剩余的稀土，采用5级逆流萃取，有机相和水相体积比(O/A)为1：2，控制萃取水相平衡酸度为pH＝0.5，得到含稀土REO 17g/L的二次负载有机相和二次萃余液，二次萃余液中稀土含量为0.1g/L，稀土回收率为99％。
将得到的一次负载有机相用5.0mol/L盐酸反萃，采用5级逆流反萃，有机相和水相体积比(O/A)为10:1，得到含稀土REO 218g/L的高浓度氯化中重稀土溶液。
将得到的二次负载有机相用4.7mol/L盐酸反萃，采用4级逆流反萃，有机相和水相体积比(O/A)为12：1，得到含稀土REO 202g/L的高浓度氯化轻稀土溶液，其中中重稀土含量/总稀土含量为0.5％。
萃取、反萃过程采用离心萃取器，得到的氯化稀土溶液作为萃取分离提纯单一稀土的原料。
实施例14：
采用硫酸镁为浸矿剂浸取离子吸附型稀土矿，得到含稀土REO 0.30g/L的硫酸稀土溶液，作为原料液(其中中重稀土REO/TREO为50％，轻稀土REO/TREO为50％)，调节原料液的pH值为3.5。
用1.0mol/L的含C302的第一有机相(稀释剂为煤油)萃取原料液中的中重稀土，采用5级错流萃取，第一有机相和水相体积比(O/A)为1：35，控制萃取水相平衡酸度为pH＝2.7，原料液中中重稀土萃取率为98.5％，得到含稀土REO 5g/L的一次负载有机相和一次萃余液。
一次萃余液再用1.0mol/L P215为第二有机相(稀释剂为煤油)萃取剩余的稀土，采用5级错流萃取，有机相和水相体积比为1：40，控制萃取水相平衡酸度为pH＝2.5，得到含稀土REO 4.5g/L的二次负载有机相和二次萃余液，二次萃余液中稀土含量为0.005g/L，稀土回收率98.3％。
将得到的一次负载有机相用3.5mol/L盐酸反萃，采用2级逆流反萃，有机相和水相体积比(O/A)为30：1，得到含稀土REO 150g/L的氯化中重稀土溶液。
将得到的二次负载有机相用3.5mol/L盐酸反萃，采用2级逆流反萃，有机相和水相体积比(O/A)为35：1，得到含稀土REO 157g/L的高浓度氯化轻稀土溶液，其中中重稀土含量/总稀土含量为5％。
萃取、反萃过程采用离心萃取器，得到的氯化稀土溶液作为萃取分离提纯单一稀土的原料。
本发明针对离子矿稀土浸取液较低的稀土浓度及酸度，直接采用PKa值>4的酸性磷类萃取剂预先萃取中重稀土，一次负载有机相采用盐酸反萃获得高浓度氯化稀土溶 液，其稀土浓度大于230g/L；一次萃余液采用PKa值<3.5的酸性磷类萃取剂萃取回收轻稀土，二次负载有机相采用盐酸反萃获得高浓度氯化稀土溶液，其稀土浓度大于230g/L，稀土富集100～500倍，优选方案中稀土回收率可大于98％。萃取过程不需要进行皂化，也不采用碳酸氢铵沉淀稀土，消除了氨氮废水或高盐度废水的排放，同时达到了稀土回收过程中的重稀土与轻稀土的预分组分离效果，并解决PKa值>4的酸性磷类萃取剂萃取稀土收率低及有机负载量小等问题，低酸度条件下PKa值<3.5的酸性磷类萃取剂萃取稀土易乳化以及中重稀土难反萃等问题。
本发明取代现有碳酸氢铵或草酸沉淀-焙烧工艺，得到的高浓度氯化稀土溶液可以直接供给稀土分离厂进行稀土的分离提纯，取消了稀土氧化物精矿盐酸溶解工序，稀土回收率大幅提高，生产成本大幅降低，而且不产生放射性废渣，消除了氨氮、钙、钠、镁等高盐度废水排放，推动离子型稀土资源的高效开发利用、绿色环保工艺技术的快速发展，解决稀土资源回收率低、废水排放量大、高盐或氨氮等污染物超标等问题，促进稀土行业的健康可持续发展。
以上所述仅为本发明的优选实施例而已，并不用于限制本发明，对于本领域的技术人员来说，本发明可以有各种更改和变化。凡在本发明的精神和原则之内，所作的任何修改、等同替换、改进等，均应包含在本发明的保护范围之内。

Claims (12)

  1. 一种分步萃取回收稀土的方法，其特征在于，所述方法包括如下步骤：
    以含有中重稀土的稀土溶液作为原料液，所述原料液的pH值为2.5-5.5，采用含PKa值>4的酸性磷类萃取剂的第一有机相对所述原料液进行第一次萃取，控制萃取水相平衡酸度为1<pH<3，得到一次负载有机相和含轻稀土的一次萃余液；
    将所述含轻稀土的一次萃余液用含PKa值<3.5的酸性磷类萃取剂的第二有机相进行第二次萃取，控制萃取水相平衡酸度为0.5<pH<2.5，得到二次负载有机相和二次萃余液；
    分别反萃回收所述一次负载有机相和二次负载有机相中的稀土，得到氯化中重稀土溶液和氯化轻稀土溶液。
  2. 根据权利要求1所述的方法，其特征在于，所述原料液的pH值为4-5，其中稀土含量以REO计小于10g/L，所述原料液中的中重稀土质量百分含量在10％～85％之间，优选所述原料液中的中重稀土质量百分含量在15％～50％之间。
  3. 根据权利要求1所述的方法，其特征在于，所述稀土溶液为硫酸稀土溶液和/或氯化稀土溶液，优选所述稀土溶液为由离子型稀土矿经硫酸镁、硫酸铵、硫酸亚铁、氯化镁、氯化铵、氯化亚铁、氯化钙或氯化钠中的一种或多种无机盐溶液作为浸矿液,浸出得到。
  4. 根据权利要求1所述的方法，其特征在于，所述PKa值>4的酸性磷类萃取剂为P507、P229、C302和C272中的一种或多种，优选为P507；所述PKa值<3.5的酸性磷类萃取剂为P204、P215、P406、C301中的一种或多种，优选为P204。
  5. 根据权利要求1至4中任一项所述的方法，其特征在于，所述第一有机相和所述第二有机相中均还含有稀释剂，所述第一有机相和所述第二有机相中酸性磷类萃取剂浓度为0.5～1.5mol/L。
  6. 根据权利要求1至4中任一项所述的方法，其特征在于，所述第一次萃取步骤中，所述原料液中大于95％的中重稀土被萃取到所述一次负载有机相中，优选所述原料液中大于98％的中重稀土被萃取到所述一次负载稀土有机相中。
  7. 根据权利要求1至4中任一项所述的方法，其特征在于，所述一次负载有机相中稀土含量以REO计为5～28g/L，优选10～25g/L；所述二次负载有机相中稀土含量以REO计为4～25g/L，优选8～20g/L。
  8. 根据权利要求1至4中任一项所述的方法，其特征在于，所述二次萃余液中稀土含量以REO计小于0.1g/L，优选小于0.02g/L，更优选地，所述二次萃余液可返回用于离子矿的浸出。
  9. 根据权利要求1至4中任一项所述的方法，其特征在于，所述第一次萃取和第二次萃取过程中分别采用2～10级萃取，优选为2～5级逆流或错流萃取，更优选第一次萃取和第二次萃取过程采用离心萃取器或脉冲筛板塔设备。
  10. 根据权利要求1至3中任一项所述的方法，其特征在于，所述方法中还包括对所述一次萃余液和二次萃余液进行除油的步骤，优选所述除油的步骤为静置除油、煤油洗涤除油、气浮除油、超声波除油、过滤吸附除油、化学氧化、生化除油中一种或几种方法进行除油。
  11. 根据权利要求1至4中任一项所述的方法，其特征在于，分别反萃回收所述一次负载有机相和二次负载有机相中稀土的步骤包括：
    对所述一次负载有机相采用3.5～6mol/L盐酸反萃，得到所述氯化中重稀土溶液，所述氯化中重稀土溶液中稀土含量以REO计大于150g/L，优选大于230g/L；
    对所述二次负载有机相采用3.5～6mol/L盐酸反萃，得到所述氯化轻稀土溶液，所述氯化轻稀土溶液中稀土含量以REO计大于150g/L，优选大于230g/L。
  12. 根据权利要求11所述的方法，其特征在于，对所述一次负载有机相和二次负载有机相进行反萃时，采用2～10级反萃，优选采用3～6级逆流或半逆流反萃，更优选的所述反萃过程采用离心萃取器或脉冲筛板塔设备。
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