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CN-117660787-B - Method for recovering thorium and rare earth elements from rare earth waste residues

CN117660787BCN 117660787 BCN117660787 BCN 117660787BCN-117660787-B

Abstract

The invention discloses a method for recovering thorium and rare earth elements from rare earth waste residues, which comprises the steps of (S1) roasting the rare earth waste residues for the first time, mixing the rare earth waste residues with inorganic acid for the second time, roasting and leaching by heating to obtain a raw material liquid containing thorium and rare earth elements, (S2) extracting the raw material liquid containing thorium and rare earth elements by adopting an organic phase containing extractant, S3) washing an organic phase obtained after the extraction of the step (S2) by using a washing liquid to enable the rare earth elements to be in an aqueous phase, and S4) back-extracting the organic phase containing thorium obtained in the step (S3) by using a back-extraction liquid to recover thorium, wherein the washing liquid in the step (S3) is NH 4 HCO 3 . The invention is subjected to 10 rows of cascade extraction, so that the content of thorium in an aqueous phase outlet is lower than 0.5mg/L, the final rare earth yield is more than 95%, and the loss of cerium is at most 3%.

Inventors

  • SUN XIAOQI
  • Bie Chao
  • WU SHAN

Assignees

  • 厦门稀土材料研究所

Dates

Publication Date
20260505
Application Date
20220831

Claims (15)

  1. 1. A method for recovering thorium and rare earth elements from rare earth waste residues, the method comprising the steps of: (S1) after the first roasting of the rare earth waste residue, mixing the rare earth waste residue with ammonium sulfate for the second roasting, and carrying out heating leaching to obtain a raw material liquid containing thorium and rare earth elements; In the step (S1), the rare earth waste residue is mixed with calcium hydroxide for roasting in the first roasting, wherein the temperature of the first roasting is 800-1000 ℃, and the temperature of the second roasting is 350-600 ℃; (S2) extracting organic phase containing thorium and rare earth elements by adopting a raw material liquid containing an extracting agent, wherein the extracting agent is ionic liquid [ N 1888 ] [ DEAO ], and the structural formula is shown as follows: ; (S3) washing the organic phase obtained after the extraction in step (S2) with a washing liquid so that the rare earth element is incorporated into the aqueous phase and thorium remains in the organic phase; (S4) stripping the organic phase containing thorium obtained in the step (S3) by using stripping liquid to recover thorium; Wherein in the step (S3), the washing liquid is NH 4 HCO 3 , and the concentration of NH 4 HCO 3 is 0.01-mol/L-0.1 mol/L; In the step (S4), the strip liquor is at least one of Na 2 C 2 O 4 solution and NaOH solution.
  2. 2. The method according to claim 1, wherein in step (S1), the rare earth element is selected from at least one of La, ce, pr, nd, pm, sm, eu, sc, Y, gd, tb, dy, ho, er, tm, yb, lu.
  3. 3. The method according to claim 1, wherein in the step (S1), at least one of Al, ca, mg, and Fe is further included in the raw material liquid.
  4. 4. The method according to claim 1, wherein in the step (S1), the mass of the calcium hydroxide is 15 to 30wt% of the rare earth slag.
  5. 5. The method according to claim 1, wherein in step (S1), the time for the first firing is 3 to 6 hours.
  6. 6. The method according to claim 1, wherein the concentration of ammonium sulfate is 2-7mol/L.
  7. 7. The method according to claim 1, wherein in step (S1), the time for the second firing is 3 to 7 hours.
  8. 8. The method according to claim 1, wherein in step (S1), water is added for heat leaching.
  9. 9. The method according to claim 1, wherein in the step (S1), the temperature of the heat leaching is 70-110 ℃, and the time of the heat leaching is 1-4 hours.
  10. 10. The method according to claim 1, wherein in the step (S1), the mass ratio of the rare earth waste residue to the ammonium sulfate is 1 (1-10).
  11. 11. The process according to claim 1, wherein in step (S2), the ratio by volume of the starting solution containing thorium and rare earth elements to the organic phase is 1 (2-5).
  12. 12. The method according to claim 1, wherein in step (S2), the concentration of the extractant is 0.01-0.1 mol/L.
  13. 13. The method according to claim 1, wherein in step (S3), the volume ratio of the washing liquid to the organic phase in step (S2) is 1 (1-3).
  14. 14. The process according to claim 1, wherein in step (S4), the volume ratio of the stripping solution to the organic phase in step (S2) is (1-3): 1.
  15. 15. The method according to claim 1, further comprising the step (S5) of adding the alkaline liquid produced in the method to the rare earth slag leachate.

Description

Method for recovering thorium and rare earth elements from rare earth waste residues Technical Field The invention belongs to the technical field of rare earth extraction separation, and particularly relates to a method for recovering thorium and rare earth elements from rare earth waste residues. Background The problem group Wu Wenyuan of the university of northeast studied the valence state change of Ce baked at different temperatures, and the method is obtained by means of TG, DTA and the like, and part of Ce (III) is converted into Ce (IV) by baking at a certain temperature. In industry, ce (IV) separation can be facilitated by oxidizing roasting or adding an oxidant after roasting is completed to convert Ce (III) into Ce (IV) as completely as possible. However, some cerium is lost from the waste residues produced in industry, and the selective extraction of Th (IV) and Ce (IV) by common extractants is not obvious. Thus, it is common to separate Th (IV) and Ce (IV) after their total leaching and to selectively strip Th (IV) and Ce (IV). For example, a reductive back extraction method is adopted, cerium, thorium, fluorine and the like are extracted and separated by adopting P507, then the Ce (IV) is back extracted by adopting hydrogen peroxide and hydrochloric acid, and after cerium oxide is recovered, the Th (IV) is back extracted by adopting sulfuric acid, so that the ThO 2 is finally obtained. Cerium and thorium separation can be achieved by using different stripping agents. The Beijing square rare earth science and technology research shows that the bastnaesite is oxidized and roasted, then mixed with the coordination precipitant for solid-liquid separation to realize the separation of Ce (IV), the precipitate is calcined to obtain cerium oxide, and thorium is remained in the filtrate. At present, there are mainly two extraction and separation methods, namely, firstly, extraction and separation are carried out by utilizing different extraction capacities of organic relative Ce (IV) and Ce (III), ce (IV) is reduced into Ce (III) by utilizing a reducing agent, the Ce (III) is back extracted from an organic phase, and secondly, ceO 2 is separated by utilizing that the Ce (IV) is difficult to dissolve in dilute acid compared with other rare earth elements. However, the separation efficiency of thorium and rare earth elements in the prior art is still not high. Disclosure of Invention In order to improve the technical problems, the invention provides a method for recovering thorium and rare earth elements from rare earth waste residues, which is characterized in that after the rare earth waste residues are calcined with calcium hydroxide, inorganic acid (such as ammonium sulfate) is used for roasting and leaching, and ionic liquid is used for thorium removal cascade operation to separate thorium and rare earth elements. The technical scheme of the invention is as follows: A method for recovering thorium and rare earth elements from rare earth waste residues, the method comprising the steps of: (S1) after the first roasting of the rare earth waste residue, mixing the rare earth waste residue with inorganic acid to carry out second roasting, and carrying out heating leaching to obtain a raw material liquid containing thorium and rare earth elements; (S2) extracting organic phase containing thorium and rare earth elements by adopting a raw material liquid containing an extracting agent; (S3) washing the organic phase obtained after the extraction in step (S2) with a washing liquid so that the rare earth element is incorporated into the aqueous phase and thorium remains in the organic phase; (S4) stripping the organic phase containing thorium obtained in the step (S3) by using stripping liquid to recover thorium; In the step (S3), the washing solution is NH 4HCO3. In the present invention, the organic phase containing an extractant means kerosene containing an extractant. In the invention, the raw material liquid containing thorium and rare earth elements is rare earth waste residue leaching liquid. According to the present invention, in step (S1), the rare earth element is selected from at least one of La, ce, pr, nd, pm, sm, eu, sc, Y, gd, tb, dy, ho, er, tm, yb, lu. According to the present invention, in the step (S1), the raw material liquid further includes at least one of Al, ca, mg, fe, and the like. According to the invention, in the step (S1), the rare earth waste residue can be mixed with calcium hydroxide for roasting in the first roasting process so as to stabilize fluorine in the rare earth waste residue. Preferably, the mass of calcium hydroxide is 15-30wt%, for example 25wt%, of the rare earth waste residue. According to the invention, in step (S1), the first calcination is carried out at a temperature of 800-1000 ℃, illustratively 900 ℃, and the time for the first calcination is 3-6 hours, for example 4 hours. According to the present invention, in the step (S1), the inorganic acid is selected