A method for extracting, separating and transforming rare earths from marine rare earth sulfuric acid leaching solution

Abstract

The invention discloses a method for extracting, separating and transforming rare earths from marine rare earth sulfuric acid leaching solution. The method uses a secondary carbon primary amine extractant-P350-sulfonated kerosene mixed extractant to extract the marine rare earth sulfuric acid leaching solution to obtain a rare earth-loaded organic phase; and uses a nitrate or chloride solution to strip the rare earth-loaded organic phase to obtain a separated and transformed rare earth nitrate or rare earth chloride stripping solution. The invention cleverly utilizes the N1923-P350-sulfonated kerosene mixed extractant to extract rare earth ions and Fe in sulfate systems, nitrate systems and chloride systems. 3+ and other non-rare earth impurities, and the selective extraction characteristics of rare earth ions and Fe in marine rare earth sulfuric acid leaching solution are achieved. 3+ The complete separation between rare earth ions and other non-rare earth impurity ions, as well as the transformation of rare earth salt systems, has a simple process and no acid or alkali consumption, making it very suitable for subsequent enrichment and recovery.

Description

Technical field:

[0001] The invention relates to the technical field of hydrometallurgy, and in particular to a method for extracting, separating and transforming rare earths from marine rare earth sulfuric acid leaching solution. Background technology:

[0002] Rare earth elements have rich and unique magnetic, optical, and electrical properties. They are indispensable or alternative strategic materials for the development of high-tech and cutting-edge defense technologies and the transformation of traditional industries in countries around the world today. They are non-renewable precious mineral resources. In recent years, as the reserves of rare earth resources on land have gradually decreased, the high-grade rare earth resources that can be developed and utilized are increasingly on the verge of exhaustion, and many countries have begun to look for other ways out. Many researchers have found that deep-sea clay in the international seabed area is rich in rare earth elements, which is expected to be a rare earth resource in the future.

[0003] Studies have shown that among marine rare earth resources, valuable rare earths are mainly stored in apatite in the form of phosphates. Since the solubility product of rare earth phosphates is small, at 25°C, KSP is 10 -23 Based on comprehensive considerations of cost, safety, equipment requirements, etc., sulfuric acid is the preferred acid leaching agent. The marine rare earth sulfuric acid leaching solution obtained has high acidity (pH = -0.5 ~ 1.5), Fe 3+ 、Al 3+ The typical characteristics are high impurity concentration, complete rare earth distribution (including La~Lu, Y and Sc and other rare earth elements) but low concentration. In order to realize the extraction and utilization of rare earth in this system, it is necessary to separate rare earth and non-rare earth impurities. At the same time, since the solubility of rare earth nitrate or chloride is significantly greater than that of rare earth sulfate, the transformation of the rare earth system should be achieved as much as possible to meet the needs of subsequent rare earth recovery and enrichment.

[0004] Although solvent extraction is currently the most studied method for rare earth separation, the existing extractant systems and extraction technologies are difficult to be well applied to the sulfuric acid leaching system to directly extract, separate and transform rare earths, which greatly limits the development and utilization of marine rare earths.

[0005] In view of this, the present invention is proposed. Summary of the invention:

[0006] The purpose of the present invention is to provide a method for extracting, separating and transforming rare earths from marine rare earth sulfuric acid leaching solution.

[0007] The present invention is achieved through the following technical solutions:

[0008] A method for extracting, separating and transforming rare earths from marine rare earth sulfuric acid leaching solution, the method comprising the following steps:

[0009] 1) A secondary carbon primary amine extractant (N1923)-dimethylheptyl methylphosphonate (P350)-sulfonated kerosene mixed extractant is used to extract a marine rare earth sulfuric acid leaching solution to obtain a rare earth-loaded organic phase and a raffinate aqueous phase; wherein the secondary carbon primary amine extractant (N1923)-dimethylheptyl methylphosphonate (P350)-sulfonated kerosene mixed extractant is prepared from a secondary carbon primary amine extractant (N1923), dimethylheptyl methylphosphonate (P350) and sulfonated kerosene in a volume ratio of 1-3:1-3:4-8; the marine rare earth sulfuric acid leaching solution contains 200-500 mg / L rare earth ions, Fe 3+ 0.5~2g / L、Al 3+ 5~10g / L, Mn 2+ 1~5g / L、Mg 2+ 1~10g / L and Ca 2+ 0.5~1.0g / L;

[0010] 2) using a nitrate or chloride solution to strip the rare earth-loaded organic phase obtained in step 1) to obtain a separated and transformed rare earth nitrate or rare earth chloride stripping solution.

[0011] Preferably, the extraction method in step 1) is countercurrent or cross-current extraction; the extraction phase ratio O / A is 1:0.5-2; the extraction stage is 1-3; and the extraction time is 5-10 min.

[0012] Preferably, in step 2), nitrate or chloride solution is used for countercurrent or cross-current stripping of the rare earth-loaded organic phase; the stripping phase ratio O / A is 1:1 to 2.

[0013] Preferably, the concentration of nitrate or chloride is 1 to 3 mol / L.

[0014] Preferably, the nitrate is sodium nitrate; and the chloride is sodium chloride or ammonium chloride.

[0015] Preferably, in step 2), the number of stages of countercurrent or crosscurrent stripping is 3 to 5, and the stripping time is 5 to 10 minutes.

[0016] The pH of the marine rare earth sulfuric acid leaching solution is -0.5 to 1.5.

[0017] The beneficial effects of the present invention are as follows: The present invention ingeniously utilizes the N1923-P350-sulfonated kerosene mixed extractant in the sulfate system, nitrate system and chloride system to extract rare earth ions and Fe 3+ and other non-rare earth impurities, and finally achieve the separation of rare earth ions and Fe in marine rare earth sulfuric acid leaching solution. 3+ The complete separation between rare earth and other non-rare earth impurity ions and the transformation of rare earth salt system is simple and does not consume acid or alkali. In particular, the stripping solution obtained is also weakly acidic, which is very suitable for subsequent enrichment and recovery. Specific implementation method:

[0018] The following is a further description of the present invention, rather than a limitation of the present invention.

[0019] Example 1: A method for extracting, separating and transforming rare earths from marine rare earth sulfuric acid leaching solution

[0020] The composition of marine rare earth sulfuric acid leaching solution is as follows: rare earth ions (including La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y, Sc ions, with concentrations of 38.8, 5.7, 12, 52.6, 12.9, 3, 13.5, 2.2, 11.5, 2.5, 7, 1, 6, 0.9, 99, 5.4 mg / L, respectively) 274 mg / L, Fe 3+ 0.89g / L,Al 3+ 7.69g / L, Mn 2+ 1.12g / L, Mg 2+ 5.83 g / L, Ca 2+ 0.55g / L. pH = 0.68. According to the volume ratio, 10% N1923, 10% P350 and 80% sulfonated kerosene were prepared to form the extraction organic phase. The marine rare earth sulfuric acid leaching solution and the extraction organic phase were subjected to three-stage countercurrent extraction at a ratio of O / A of 1:1.5. The extraction was carried out for 5 minutes, and the rare earth extraction rate was 92.17%, Fe 3+ The extraction rate was 100%, and other non-rare earth impurities were basically not extracted. The rare earth-loaded organic phase was subjected to three-stage cross-current stripping with a 2 mol / L sodium chloride solution at a phase ratio (O / A) of 1:1 for 10 minutes. The rare earth stripping rate was 91.53%, and Fe 3+ It is basically not stripped, and weakly acidic rare earth chloride stripping solution is separated.

[0021] Example 2: A method for extracting, separating and transforming rare earths from marine rare earth sulfuric acid leaching solution

[0022] The composition of marine rare earth sulfuric acid leaching solution is as follows: rare earth ions (including La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y, Sc ions, with concentrations of 38.8, 5.7, 12, 52.6, 12.9, 3, 13.5, 2.2, 11.5, 2.5, 7, 1, 6, 0.9, 99, 5.4 mg / L, respectively) 274 mg / L, Fe 3+ 0.89g / L,Al 3+ 7.69g / L, Mn 2+ 3.12g / L, Mg 2+ 5.83 g / L, Ca 2+0.55g / L. pH = 1.28. According to the volume ratio, 10% N1923, 20% P350 and 70% sulfonated kerosene were prepared to form the extraction organic phase. The marine rare earth sulfuric acid leaching solution and the extraction organic phase were subjected to a first-level countercurrent extraction with an O / A ratio of 1:1. The extraction lasted for 10 minutes, and the rare earth extraction rate was 92.38%, Fe 3+ The extraction rate was 100%, and other non-rare earth impurities were basically not extracted. The rare earth-loaded organic phase was subjected to three-stage cross-current stripping with 2 mol / L sodium nitrate at a phase (O / A) ratio of 1:2 for 10 minutes. The rare earth stripping rate was 85.73%, and Fe 3+ It is basically not stripped, and weakly acidic nitric acid rare earth stripping solution is separated.

[0023] Example 3: A method for extracting, separating and transforming rare earths from marine rare earth sulfuric acid leaching solution

[0024] The composition of marine rare earth sulfuric acid leaching solution is as follows: rare earth ions (including La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y, Sc ions, with concentrations of 70, 10.3, 21.6, 94.7, 23.2, 5.4, 24.3, 3.9, 20.7, 4.5, 12.6, 1.8, 10.8, 1.6, 182.9, 9.7 mg / L, respectively) 498 mg / L, Fe 3+ 1.78g / L,Al 3+ 5.93g / L, Mn 2+ 3.71g / L, Mg 2+ 7.35g / L, Ca 2+ 0.62g / L. pH = 0.68. According to the volume ratio, 30% N1923, 30% P350 and 40% sulfonated kerosene were prepared to form the extraction organic phase. The marine rare earth sulfuric acid leaching solution and the extraction organic phase were subjected to three-stage countercurrent extraction at a ratio of O / A of 1:2. The extraction lasted for 10 minutes, and the rare earth extraction rate was 93.49%, Fe 3+ The extraction rate was 100%, and other non-rare earth impurities were basically not extracted. The rare earth-loaded organic phase was subjected to three-stage countercurrent stripping with 1 mol / L ammonium chloride at a phase (O / A) ratio of 1:2 for 10 minutes. The rare earth stripping rate was 80.49%, and Fe 3+ It is basically not stripped, and weakly acidic rare earth chloride stripping solution is separated.

[0025] Example 4: A method for extracting, separating and transforming rare earths from marine rare earth sulfuric acid leaching solution

[0026] The composition of marine rare earth sulfuric acid leaching solution is as follows: rare earth ions (including La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y, Sc ions, with concentrations of 70, 10.3, 21.6, 94.7, 23.2, 5.4, 24.3, 3.9, 20.7, 4.5, 12.6, 1.8, 10.8, 1.6, 182.9, 9.7 mg / L, respectively) 498 mg / L, Fe 3+ 1.78g / L,Al 3+ 5.93g / L, Mn 2+ 3.71g / L, Mg 2+ 7.35g / L, Ca 2+ 0.62g / L. pH = 0.25. According to the volume ratio, 20% N1923, 20% P350 and 60% sulfonated kerosene were prepared to form the extraction organic phase. The marine rare earth sulfuric acid leaching solution and the extraction organic phase were subjected to three-stage cross-current extraction at a ratio of O / A of 1:2. The extraction lasted for 10 minutes, and the rare earth extraction rate was 93.08%, Fe 3+ The extraction rate was 100%, and other non-rare earth impurities were basically not extracted. The rare earth-loaded organic phase was subjected to 5-stage cross-current stripping with a 3 mol / L ammonium chloride solution at a phase ratio (O / A) of 1:1 for 10 minutes. The rare earth stripping rate was 96.95%, and Fe 3+ It is basically not stripped, and weakly acidic rare earth chloride stripping solution is separated.

[0027] Example 5: A method for extracting, separating and transforming rare earths from marine rare earth sulfuric acid leaching solution

[0028] The composition of marine rare earth sulfuric acid leaching solution is as follows: rare earth ions (including La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y, Sc ions, with concentrations of 70, 10.3, 21.6, 94.7, 23.2, 5.4, 24.3, 3.9, 20.7, 4.5, 12.6, 1.8, 10.8, 1.6, 182.9, 9.7 mg / L, respectively) 498 mg / L, Fe 3+ 1.78g / L,Al 3+ 5.93g / L, Mn 2+ 3.71g / L, Mg 2+ 7.35g / L, Ca 2+ 0.62g / L. pH = -0.5. According to the volume ratio, 30% N1923, 30% P350 and 40% sulfonated kerosene were prepared to form the extraction organic phase. The marine rare earth sulfuric acid leaching solution and the extraction organic phase were subjected to three-stage cross-current extraction with an O / A ratio of 2:1. The extraction lasted for 10 minutes, and the rare earth extraction rate was 92.54%, Fe 3+The extraction rate was 100%, and other non-rare earth impurities were basically not extracted. The rare earth-loaded organic phase was subjected to 5-stage cross-current stripping with a 2.5 mol / L sodium chloride solution at a phase ratio (O / A) of 1:1 for 5 minutes. The rare earth stripping rate was 87.53%, and Fe 3+ It is basically not stripped, and weakly acidic rare earth chloride stripping solution is separated.

[0029] Comparative Example 1

[0030] This comparative example is basically the same as Example 1, except that: P350 is not added when the organic phase is extracted, and 10% N1923 and 90% sulfonated kerosene are used by volume. The rare earth extraction rate is 92%, Fe 3+ The extraction rate is 100%, Al 3+ The extraction rate is 5.31%, and other non-rare earth impurities are basically not extracted. Rare earth, Fe 3+ 、Al 3+ The stripping rates were all 100%, and the transformed rare earth chloride stripping solution could not be separated.

[0031] Comparative Example 2

[0032] This comparative example is basically the same as Example 2, except that: N1923 is not added when the organic phase is extracted, and 20% P350 + 80% sulfonated kerosene is used by volume. 3+ And other non-rare earth impurities are not extracted, and the transformed nitric acid rare earth stripping solution cannot be separated.

[0033] Comparative Example 3

[0034] This comparative example is basically the same as Example 3, except that: N1923 and TBP are not added when the organic phase is extracted, and 100% sulfonated kerosene is used by volume. 3+ And other non-rare earth impurities are not extracted, and the transformed rare earth chloride stripping solution cannot be separated.

[0035] Comparative Example 4

[0036] This comparative example is basically the same as Example 3, except that: the same type of extractant N235 is used to replace N1923, TBP is used to replace P350, 30% N235, 30% TBP and 40% sulfonated kerosene when extracting the organic phase. 3+ The extraction rate is 14.06%, the rare earth extraction rate is 1.27%, other non-rare earth impurities are basically not extracted, and the transformed rare earth chloride stripping solution cannot be separated.

[0037] Comparative Example 5

[0038] This comparative example is basically the same as Example 3, except that: the same type of extractant N263 is used to replace N1923, TBP is used to replace P350, 30% N263, 30% TBP and 40% sulfonated kerosene. 3+ The extraction rate is 8.54%, the rare earth extraction rate is 2.71%, other non-rare earth impurities are basically not extracted, and the transformed rare earth chloride stripping solution cannot be separated.

[0039] Comparative Example 6

[0040] This comparative example is basically the same as Example 4, except that: the same extractant TBP is used to replace P350 when extracting the organic phase, and the volume ratio is 20% N1923, 20% TBP and 60% sulfonated kerosene. The rare earth extraction rate is 97.14%, Fe 3+ The extraction rate is 100%, and other non-rare earth impurities are basically not extracted. Rare earth, Fe 3+ The stripping rates were all 100%, and the transformed rare earth chloride stripping solution could not be separated.

[0041] Comparative Example 7

[0042] This comparative example is basically the same as Example 5, except that: the same type of extractant N235 is used to replace N1923 when extracting the organic phase, and the volume ratio is 30% N235, 30% P350 and 40% sulfonated kerosene. 3+ The extraction rate was 12.79%, the rare earth extraction rate was 0.91%, other non-rare earth impurities were basically not extracted, and the transformed rare earth chloride stripping solution could not be separated.

[0043] Comparative Example 8

[0044] This comparative example is basically the same as Example 5, except that: the same type of extractant N263 is used to replace N1923 when extracting the organic phase, and the volume ratio is 30% N263, 30% P350 and 40% sulfonated kerosene. 3+ The extraction rate is 5.96%, the rare earth extraction rate is 1.47%, other non-rare earth impurities are basically not extracted, and the transformed rare earth chloride stripping solution cannot be separated.

[0045] Comparative Example 9:

[0046] This comparative example is basically the same as Example 1, except that: the same type of extractant N235 is used to replace N1923 when extracting the organic phase, and P507 is added, using 10% N235, 10% P350, 10% P507 and 70% sulfonated kerosene. 3+ The extraction rate is 30.28%, the rare earth extraction rate is 20.81%, and other non-rare earth impurities are basically not extracted; rare earth and Fe 3+None of them are stripped, and it is impossible to separate and obtain the transformed rare earth chloride stripping solution.

[0047] Comparative Example 10:

[0048] This comparative example is basically the same as Example 1, except that: the same extractant N235 is used to replace N1923 when extracting the organic phase, the same extractant TBP is used to replace P350, and P507 is added, and 10% N235, 10% TBP, 10% P507 and 70% sulfonated kerosene are used. 3+ The extraction rate is 33.12%, the rare earth extraction rate is 37.93%, and other non-rare earth impurities are basically not extracted; rare earth and Fe 3+ None of them are stripped, and it is impossible to separate and obtain the transformed rare earth chloride stripping solution.

[0049] By comparing the embodiments and the comparative examples, it can be seen that the extraction, separation and transformation effects of rare earth in the comparative examples are far inferior to those in the embodiments. This shows that the use of N1923-P350-sulfonated kerosene mixed extraction organic phase for extracting and separating rare earth in the sulfuric acid system is not a simple combination of extractants or similar replacement, but has an unexpected significant gain effect.

[0050] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for extracting, separating and transforming rare earths from marine rare earth sulfuric acid leaching solution, characterized in that: The method comprises the following steps: 1) A secondary carbon primary amine extractant-dimethylheptyl methylphosphonate-sulfonated kerosene mixed extractant is used to extract a marine rare earth sulfuric acid leaching solution, and the extraction phase ratio O / A is 1:0.5-2 to obtain a rare earth-loaded organic phase and a raffinate aqueous phase; wherein the secondary carbon primary amine extractant-dimethylheptyl methylphosphonate-sulfonated kerosene mixed extractant is prepared from a secondary carbon primary amine extractant, dimethylheptyl methylphosphonate and sulfonated kerosene in a volume ratio of 1-3:1-3:4-8; the marine rare earth sulfuric acid leaching solution contains 200-500 mg / L rare earth ions, Fe 3+ 0.5~2g / L、Al 3+ 5~10g / L, Mn 2+ 1~5g / L、Mg 2+ 1~10g / L and Ca 2+ 0.5~1.0g / L; pH of the marine rare earth sulfuric acid leaching solution = -0.5~1.5; 2) Using nitrate or chloride solution to strip the rare earth-loaded organic phase obtained in step 1), with the stripping phase ratio O / A being 1:1-2, to obtain a separated and transformed rare earth nitrate or rare earth chloride stripping solution.

2. The method according to claim 1, characterized in that: Step 1) The extraction method is countercurrent or cross-current extraction; the extraction level is 1 to 3; and the extraction time is 5 to 10 minutes.

3. The method according to claim 1, characterized in that Step 2) countercurrent or cross-current stripping of the rare earth-loaded organic phase with a nitrate or chloride solution.

4. The method according to claim 1 or 3, characterized in that: Step 2) The concentration of nitrate or chloride is 1 to 3 mol / L.

5. The method according to claim 4, characterized in that The nitrate is sodium nitrate; the chloride is sodium chloride or ammonium chloride.

6. The method according to claim 1, characterized in that Step 2) The number of countercurrent or crosscurrent stripping stages is 3 to 5; the stripping time is 5 to 10 minutes.