Method for step-by-step precipitation and linkage impurity removal of ion type rare earth leaching mother liquor

Abstract

The application belongs to the field of rare earth metallurgy, and discloses a method for removing impurities from ion type rare earth leaching mother liquor in a step-by-step and linkage mode, which comprises the following steps: (1) carbonates and hydroxides are respectively precipitated from ion type rare earth mine leaching mother liquor obtained by leaching of a mine, so as to obtain rare earth carbonates and rare earth hydroxides; (2) the rare earth carbonates are acid-dissolved by hydrochloric acid to obtain a rare earth solution to be removed of impurities, and the solution is transferred into a removal reactor; (3) the rare earth hydroxides are slurried by adding water to obtain a rare earth hydroxide slurry; and (4) the rare earth hydroxide slurry is added into the rare earth solution to be removed of impurities to perform a removal cycle mode in a countercurrent exchange mode, until the residual amount of rare earth in the washed residue obtained after water washing of the removal residue is less than 0.5%.

Description

Technical Field

[0001] This invention belongs to the field of rare earth metallurgy and relates to a method for stepwise precipitation and impurity removal of ion-type rare earth leaching mother liquor. Background Technology

[0002] Ionic rare earth elements are typically mined using in-situ leaching. After the leaching agent is injected into the ore body to complete the rare earth leaching, it is collected as a rare earth leaching mother liquor. Since the selective exchange capacity of the leaching agent cations for rare earth ions is not strong, it also has a leaching effect on other non-rare earth ions. Therefore, the rare earth leaching mother liquor obtained from leaching often contains non-rare earth impurity ions such as aluminum, iron, thorium, uranium, and fluorine. These non-rare earth impurity ions will have an adverse effect on the subsequent extraction and separation of rare earth elements. Therefore, the relevant impurity removal work is particularly important.

[0003] Existing purification processes in mining areas are mainly divided into two categories. One is the stepwise precipitation purification method, which involves adding a precipitant to remove most of the non-rare earth impurity ions by utilizing the difference in pH values ​​during rare earth carbonate precipitation. The mother liquor after purification is then further treated with a precipitant to obtain rare earth carbonate concentrate. However, this process requires a large volume of mother liquor and results in significant rare earth loss during purification. The other is the precipitation-then-purification process, which involves using hydroxides to precipitate the rare earth leaching mother liquor. Both rare earth and non-rare earth ions in the mother liquor are precipitated and recovered into rare earth hydroxide. The rare earth feed solution is then obtained by acid dissolution with hydrochloric acid at the smelting and separation plant, followed by purification. The purification process typically uses alkaline reagents to adjust the pH value of the rare earth feed solution, utilizing the difference in pH values ​​between rare earth and non-rare earth ions during hydrolysis to remove impurities. Compared to the stepwise precipitation purification method, this process requires a smaller volume of feed solution to be treated. However, when using hydroxide to precipitate rare earths, the hydrogen-oxygen rare earth concentrate obtained by this process is affected by the precipitation crystal form, which often results in problems such as low total rare earth content and excessive residual precipitant in the hydrogen-oxygen rare earth. In addition, the process of removing impurities also faces the problem of rare earth loss due to non-directional hydrolysis under alkaline conditioning. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a method for stepwise precipitation and subsequent impurity removal of ion-type rare earth leaching mother liquor.

[0005] The technical solution of the present invention is as follows:

[0006] A method for removing impurities from ion-type rare earth leaching mother liquor via stepwise precipitation and subsequent linkage includes the following steps:

[0007] (1) The rare earth leaching mother liquor obtained from ion-type rare earth mine leaching is partially precipitated with carbonates and partially precipitated with hydroxides to obtain rare earth carbonates and rare earth hydroxides, respectively.

[0008] (2) Rare earth carbonate is dissolved in hydrochloric acid to obtain a rare earth solution to be purified, which is then transferred to a purification reaction vessel;

[0009] (3) Hydrogen-oxygen rare earth is mixed with water to form a slurry to obtain hydrogen-oxygen rare earth slurry;

[0010] (4) Add hydrogen-oxygen rare earth slurry to the rare earth liquid to be removed for a countercurrent exchange impurity removal cycle mode until the rare earth residue in the water-washed residue after the impurity removal residue is less than 0.5%. Specifically, the countercurrent exchange means that the hydrogen-oxygen rare earth slurry undergoes multiple impurity removal reactions with the rare earth liquid to be removed, and the rare earth liquid to be removed also undergoes multiple impurity removal reactions with the hydrogen-oxygen rare earth slurry, and finally obtains impurity removal residue with low rare earth residue and impurity removal rare earth liquid with low non-rare earth impurity content.

[0011] Preferably, the precipitant added during carbonate precipitation is one or more of ammonium bicarbonate, sodium carbonate, sodium bicarbonate, and magnesium bicarbonate, and the precipitant added during hydroxide precipitation is one of sodium hydroxide, ammonia, calcium oxide, and magnesium oxide.

[0012] Preferably, the rare earth carbonate is dissolved in hydrochloric acid by adding hydrochloric acid to completely dissolve the rare earth carbonate and then adding rare earth carbonate to adjust the pH value, so as to obtain a rare earth solution to be purified with a pH value of 1.5-3.0, preferably 2.0-2.5.

[0013] Preferably, the solid-liquid ratio of the rare earth hydrogen oxygen slurry when mixed with water is 1:0.2-2, and more preferably 1:0.5-1.

[0014] Preferably, the volume ratio of the hydrogen-oxygen rare earth slurry to the rare earth liquid to be purified is 1:4-1:10, more preferably 1:5-1:8. The slurry is added at a constant rate for 0.5-3 hours, more preferably 1-1.5 hours. After the hydrogen-oxygen rare earth slurry is added, the temperature is raised to a certain level and stirring is continued for the purification reaction. The stirring reaction time is 0.5-3 hours, more preferably 1-1.5 hours, and the reaction temperature is 30-60℃, more preferably 40-50℃.

[0015] Preferably, the impurity removal circulation mode of adding hydrogen-oxygen rare earth slurry to the rare earth liquid to be impurity removed for countercurrent exchange includes the following steps:

[0016] (4.1) Add the hydrogen-oxygen rare earth slurry to the rare earth liquid to be purified;

[0017] (4.2) After impurity removal, the solution and residue are obtained by filtration.

[0018] (4.3) Add new rare earth material solution to the residue to be cleaned for impurity removal;

[0019] (5) Repeat steps (4.2) and (4.3) sequentially until the rare earth residue in the washed residue obtained after removing impurities is less than 0.5%;

[0020] (4.4) Add the impurity removal solution to a new hydrogen-oxygen rare earth slurry for impurity removal;

[0021] (6) Repeat steps (4.2) and (4.4) until the rare earth residue in the washed residue obtained after removing impurities is less than 0.5%.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] This invention utilizes the residual alkali in the rare earth hydroxide solution after hydroxide precipitation to remove impurities from the rare earth carbonate solution after acid dissolution. During this process, not only can the residual alkali of the precipitant in the hydroxide be utilized, increasing the pH of the solution and promoting the hydrolysis of non-rare earth ions, but it can also promote ion exchange between the dissociated rare earth hydroxide and non-rare earth ions. While dissolving rare earth ions from the rare earth hydroxide, non-rare earth ions are hydrolyzed and added to the impurity removal residue. Simultaneously, the added rare earth hydroxide also acts as a carrier for impurity removal, adsorbing smaller, less sediment-prone non-rare earth hydrolysis products, further enhancing the impurity removal effect. Attached Figure Description

[0024] Figure 1 This is a flowchart of the linkage impurity removal process of the present invention;

[0025] Figure 2 This is a flowchart of the multi-stage countercurrent impurity removal process of the present invention. Detailed Implementation

[0026] The following detailed description, in conjunction with embodiments, illustrates a method for stepwise precipitation followed by simultaneous impurity removal from ionic rare earth leaching mother liquor provided by the present invention. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0027] Example 1:

[0028] The analysis results of rare earth leaching mother liquor from a certain ion-type mineral area are shown in Table 1.

[0029] Table 1. Main components of rare earth leaching mother liquor (mg / L)

[0030]

[0031] Magnesium oxide and sodium bicarbonate were added to the rare earth leaching mother liquor to precipitate rare earth hydroxides and rare earth carbonates, respectively. The results of the precipitated rare earth hydroxides and rare earth carbonates are shown in Table 2.

[0032] Table 2. Main components (%) of rare earth hydrogen, rare earth oxides and rare earth carbonates

[0033]

[0034] Rare earth carbonates were dissolved in hydrochloric acid and the pH was adjusted to obtain a rare earth solution with a pH of 2.0 (Table 3). Rare earth hydroxides were mixed with water at a solid-liquid ratio of 1:1 to form a slurry. Then, 20 ml of the slurry was added to the rare earth solution at a volume ratio of 1:5 to carry out the impurity removal reaction. The addition time of the rare earth hydroxide slurry was 1 hour. After the slurry was added, the temperature was raised to 60℃ and the reaction was continued for 1 hour. The mixture was filtered, and the impurity residue was washed with water until no rare earth was detected in the wash water. The analysis results of the solution and the impurity residue before and after impurity removal are shown in Tables 3 and 4 below.

[0035] Table 3. Analysis results of the liquid material before and after impurity removal

[0036]

[0037] Table 4. Analysis results of impurity removal by water washing

[0038]

[0039] As shown in Table 3, the combined impurity removal process achieves a removal rate of over 90% for aluminum, iron, silicon, and fluorine, demonstrating excellent impurity removal performance. Comparing the data from Table 2 (hydrogen-oxygen rare earth) and Table 4 (impurity removal slag), 0.55g of rare earth elements were dissolved from the hydrogen-oxygen rare earth in a single impurity removal process, indicating that the dissociation of hydrogen-oxygen rare earth and the non-rare earth ion exchange reaction can proceed during the impurity removal process.

[0040] Multiple countercurrent impurity removal experiments:

[0041] Rare earth carbonates were dissolved in hydrochloric acid and the pH was adjusted to obtain a rare earth solution with a pH of 2.0 (Table 3). Rare earth hydroxides were mixed with water at a solid-liquid ratio of 1:1 to form a slurry. Then, 20 ml of this slurry was added to 100 ml of the rare earth solution at a volume ratio of 1:5 for the impurity removal reaction. The addition time for the rare earth hydroxide slurry was 1 hour. After the slurry was completely added, the temperature was raised to 60°C and the reaction was continued for 1 hour. The mixture was then filtered to obtain filtrate XH-1 and filter residue. New rare earth hydroxide slurry was added to filtrate XH-1 at a volume ratio of 5:1 for the impurity removal reaction. The addition time for the slurry was 1 hour. After the slurry was completely added, the temperature was raised to 60°C and the reaction was continued for 1 hour. The mixture was then filtered to obtain filtrate XH-2 and filter residue.

[0042] After the XH-1 filter residue was further mixed with water at a 1:1 ratio, it was added to 100ml of the rare earth material solution to be purified under the aforementioned process conditions for purification reaction. The slurry addition time was 1 hour. After the slurry was added, the temperature was raised to 60℃ and the reaction was continued for 1 hour. The residue was then filtered to obtain XH-3 filtrate and filter residue. After the XH-3 filter residue was further mixed with water at a 1:1 ratio, it was added to 100ml of the rare earth material solution to be purified under the aforementioned process conditions for purification reaction. The slurry addition time was 1 hour. After the slurry was added, the temperature was raised to 60℃ and the reaction was continued for 1 hour. The residue was then filtered to obtain XH-4 filtrate and filter residue. The filter residue was washed with water until no rare earth was detected in the wash water. The analysis results of the material solution and the water-washed impurity-removed residue before and after purification are shown in Tables 5 and 6.

[0043] Table 5. Analysis results of the liquid material before and after impurity removal.

[0044]

[0045] Table 6. Analysis results of impurity removal by water washing

[0046]

[0047] As shown in Table 5, after the hydrogen-oxygen rare earth slurry undergoes one impurity removal process, the filter residue, after multiple impurity removal reactions with new rare earth slurry to be removed, still exhibits a certain degree of impurity removal effect on aluminum, iron, silicon, and fluorine. Furthermore, even after the rare earth slurry has undergone one impurity removal process, the concentrations of aluminum, iron, silicon, and fluorine ions continue to decrease when a second impurity removal process is performed with the addition of new hydrogen-oxygen rare earth slurry. Combined with the data in Table 6 regarding the actual rare earth REO content in the impurity-removed residue after three impurity removal processes, this indicates that the impurity removal process conforms to the ion exchange process between rare earth and non-rare earth elements. Using countercurrent impurity removal can yield impurity-removed residue with a rare earth residue content of less than 0.5% and a rare earth slurry with low non-rare earth impurity content.

Claims

1. A method for stepwise precipitation followed by impurity removal from ion-type rare earth leaching mother liquor, characterized in that, Includes the following steps: (1) The rare earth leaching mother liquor obtained from ion-type rare earth mine leaching is partially precipitated with carbonates and partially precipitated with hydroxides to obtain rare earth carbonates and rare earth hydroxides, respectively. (2) Rare earth carbonate is dissolved in hydrochloric acid to obtain a rare earth solution to be purified, which is then transferred to a purification reaction vessel; (3) Hydrogen-oxygen rare earth is mixed with water to form a slurry to obtain hydrogen-oxygen rare earth slurry; (4) Add hydrogen-oxygen rare earth slurry to the rare earth liquid to be cleaned and carry out the cleaned impurity circulation mode of countercurrent exchange until the rare earth residue in the water-washed residue after the cleaned residue is less than 0.5%. Specifically, the countercurrent exchange means that the hydrogen-oxygen rare earth slurry undergoes multiple cleaned impurity reactions with the rare earth liquid to be cleaned, and the rare earth liquid to be cleaned will also undergo multiple cleaned impurity reactions with the hydrogen-oxygen rare earth slurry, and finally obtain the cleaned residue with low rare earth residue and the cleaned rare earth liquid with low non-rare earth impurity content. The impurity removal circulation mode, which involves adding hydrogen-oxygen rare earth slurry to the rare earth liquid to be impurity removed for countercurrent exchange, includes the following steps: (4.1) Add the hydrogen-oxygen rare earth slurry to the rare earth liquid to be purified; (4.2) After impurity removal, the solution and residue are obtained by filtration. (4.3) Add new rare earth material solution to the residue to be cleaned for impurity removal; (5) Repeat steps (4.2) and (4.3) sequentially until the rare earth residue in the washed residue obtained after removing impurities is less than 0.5%; (4.4) Add the impurity removal solution to a new hydrogen-oxygen rare earth slurry for impurity removal; (6) Repeat steps (4.2) and (4.4) until the rare earth residue in the washed residue obtained after removing impurities is less than 0.5%.

2. The method according to claim 1, characterized in that, When precipitating carbonates, the precipitant added is one or more of ammonium bicarbonate, sodium carbonate, sodium bicarbonate, and magnesium bicarbonate. When precipitating hydroxides, the precipitant added is one of sodium hydroxide, ammonia, calcium oxide, and magnesium oxide.

3. The method according to claim 1, characterized in that, The process of adding hydrochloric acid to dissolve rare earth carbonate specifically involves adding hydrochloric acid to completely dissolve the rare earth carbonate, then adding more rare earth carbonate to adjust the pH value, resulting in a rare earth solution with a pH value of 1.5-3.0 to be purified.

4. The method according to claim 1, characterized in that, The solid-liquid ratio of the hydrogen-oxygen rare earth slurry when mixed with water is 1:0.2-2.

5. The method according to claim 1, characterized in that, The volume ratio of the hydrogen-oxygen rare earth slurry to the rare earth liquid to be purified is 1:4-1:

10. The slurry is added at a constant rate for 0.5-3 hours. After the hydrogen-oxygen rare earth slurry is added, the temperature is raised to a certain level and stirring is continued to carry out the purification reaction. The stirring reaction time is 0.5-3 hours and the reaction temperature is 30-60℃.

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