A method for removing aluminum and purifying rare earth liquid

Abstract

The present invention discloses a method for removing aluminum from a rare earth feed liquid and purifying the rare earth feed liquid, comprising: allowing the rare earth feed liquid containing aluminum ions to enter an ion exchange column filled with a high molecular polymer having a selective coordination function for aluminum ions from above, and the aqueous phase flowing out of the outlet at the lower end of the ion exchange column is the rare earth feed liquid after aluminum removal. In the present invention, the used ion exchange column can also be regenerated and reused multiple times. After the rare earth feed liquid of the present invention is subjected to the aluminum removal purification method of the present invention, the aluminum ions in the rare earth feed liquid are reduced, and the aluminum content in the extracted organic phase in the subsequent extraction process is also reduced, thereby improving the extraction capacity of the organic phase for rare earths and saving acid and alkali consumption. The rare earth carbonate prepared by the rare earth feed liquid obtained by the present invention has a low aluminum content and high purity, and the precipitation particles of the rare earth carbonate are good, the washing time is short, and water can be saved.

Description

Technical Field

[0001] The invention belongs to the technical field of separation and purification of rare earth elements, and in particular relates to a method for removing aluminum and purifying a rare earth liquid. Background Art

[0002] Ion adsorption rare earth ores and NFB rare earth wastes contain high levels of aluminum. After being treated with hydrochloric acid dissolution, aluminum dissolves into aluminum ions and enters the rare earth solution. In the P507-kerosene-hydrochloric acid system separation process, when the aluminum ion content reaches 1000-10000ppm, it will occupy the load of the extractant, thereby reducing the extraction capacity of organic phases for rare earths, resulting in increased rare earth extraction acid and alkali consumption and reduced rare earth separation effect. After aluminum ions are extracted and enriched by the P507-kerosene-hydrochloric acid system, the aluminum ion content in the Nd and Sm rare earth solutions is as high as 1-10g / L. When using this rare earth liquid as a raw material to prepare rare earth carbonates such as praseodymium-neodymium carbonate, neodymium carbonate, and samarium carbonate, the colloidal aluminum hydroxide formed by aluminum precipitation greatly affects the nucleus formation of praseodymium-neodymium carbonate, neodymium carbonate, and samarium carbonate, resulting in finer particles of precipitated praseodymium-neodymium carbonate, neodymium carbonate, and samarium carbonate, which is not conducive to the washing of impurities such as chloride ions, and the residual aluminum hydroxide affects the purity of praseodymium-neodymium carbonate, neodymium carbonate, and samarium carbonate. Therefore, in order to improve the purity of rare earth carbonate prepared from rare earth liquid, the dissolved rare earth liquid must be purified by removing aluminum.

[0003] At present, the commonly used aluminum removal method in the production of neodymium chloride and praseodymium-neodymium chloride is the 25% cyclohexane acid-20% isooctyl alcohol-55% kerosene system extraction method. This method has a general aluminum removal effect. Cyclohexane acid is easily hydrolyzed and has poor phase separation. In addition, the pH value of the rare earth liquid must be strictly controlled, otherwise it is easy to cause the system to emulsify and the extraction process cannot be carried out. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for removing aluminum from a rare earth liquid to solve the shortcomings of the current method for removing aluminum from a rare earth liquid. The method has good aluminum removal effect, low cost, high rare earth recovery rate and convenient operation and control.

[0005] A method for removing aluminum from a rare earth liquid of the present invention comprises the following steps:

[0006] The pH value of the rare earth solution containing aluminum ions is adjusted to 2.5-3.5, and then enters from the top into an ion exchange column filled with a high molecular polymer having a selective coordination function for aluminum ions. The aqueous phase flowing out from the outlet at the lower end of the ion exchange column is the rare earth solution after aluminum removal.

[0007] Preferably, the aluminum ion content in the rare earth liquid containing aluminum ions is 1000-10000 ppm.

[0008] Preferably, after the ion exchange column is saturated with aluminum adsorption, the rare earth solution containing aluminum ions is switched into another ion exchange column filled with a high molecular polymer having a selective coordination function for aluminum ions to obtain a rare earth solution after aluminum is removed.

[0009] Take the water phase from the outlet of the lower end of the ion exchange column, precipitate with oxalic acid and take the precipitation supernatant, adjust the pH value to 5.0-6.0. If there is flocculation precipitation in the supernatant, it means that the resin adsorption is saturated.

[0010] Preferably, the high molecular polymer is HP2000 aluminum removal adsorbent purchased from Jiangsu Haipu Functional Materials Co., Ltd. The product appearance is white to milky white spherical particles, and was originally used for aluminum removal from wastewater.

[0011] Preferably, the ratio of the diameter to the height of the ion exchange column is D:H=1:3.5-1:5.

[0012] Preferably, the filling ratio of the high molecular polymer in the ion exchange column is 50-90%.

[0013] Preferably, the aluminum ion content in the rare earth liquid containing aluminum ions is 1000-10000 ppm.

[0014] Preferably, the flow rate of the rare earth solution containing aluminum ions entering the ion exchange column is 2-10 BV / H.

[0015] Preferably, the used ion exchange column is regenerated by:

[0016] (1) Use clean water to rinse the ion exchange column until the pH value of the outlet water phase is greater than 3.0-5.0;

[0017] (2) the acid solution is introduced into the ion exchange column from the top of the ion exchange column until the aluminum ion in the outlet water phase is less than 200 ppm;

[0018] (3) Rinse the ion exchange column with clean water until the pH value of the outlet water phase is greater than 3.0-5.0;

[0019] (4) introducing alkali solution from the top of the ion exchange column until the pH value of the outlet water phase is greater than 8.0-12.0;

[0020] (5) Finally, the ion exchange column is rinsed with clean water until the pH value of the outlet water phase is less than 7.0-9.0, and the regeneration is completed and it is ready for use.

[0021] Preferably, the acid solution in step (2) is a 1-4 mol / L hydrochloric acid solution, and its flow rate is 1-2 BV / H.

[0022] Preferably, the concentration of the alkali solution in step (4) is 1-4 mol / L, and its flow rate is 1-2 BV / H.

[0023] The above-mentioned rapid detection method for aluminum ions in the outlet water phase being less than 200 ppm is as follows: when the pH value of the outlet water phase is adjusted to 5.5-6.5 with liquid alkali, there is no flocculation precipitation.

[0024] The rare earth feed liquid containing aluminum ions used in the present invention is a rare earth ion feed liquid of pH=0.5-1.0, which is extracted and separated by a saponified P507-HCl-kerosene system and contains praseodymium-neodymium chloride, neodymium chloride, samarium chloride, etc., and has a separation coefficient close to that of aluminum ions.

[0025] The present invention creatively applies the polymer aluminum removal adsorbent HP 2000 used in the field of wastewater aluminum removal to the field of rare earth aluminum removal. Compared with the 25% cyclohexane acid-20% isooctyl alcohol-55% kerosene system extraction method, this method has the advantages of small investment, small footprint, stable aluminum removal effect, etc. Compared with the traditional wastewater aluminum removal treatment method. The present invention adjusts the pH value of the rare earth feed liquid to 2.5-3.5 in advance, improves the adsorption capacity of the resin to aluminum, takes samples of the outlet water phase on site, and adopts the method of first precipitating the rare earth with oxalic acid, adjusting the pH value of the precipitation supernatant to 5.5-6.5 and then observing the aluminum precipitation. In order to judge the aluminum removal effect of the resin on site, there is no need to wait for the test results of professional analytical instruments, and ensure the continuity of production.

[0026] The aluminum removal adsorbent HP 2000 has a weak adsorption capacity for rare earth elements. In the regeneration process of the ion exchange column, the content of rare earth elements in the hydrochloric acid eluent is detected to be less than 10g / L. After elution, the aqueous phase is directly precipitated with oxalic acid to obtain pure rare earth oxalate, thus avoiding the loss of rare earth.

[0027] Beneficial effects:

[0028] (1) After the rare earth liquid is purified by the aluminum removal method of the present invention, the aluminum ions in the rare earth liquid are reduced to below 150 ppm, which also reduces the aluminum content in the extracted organic phase in the subsequent extraction process, improves the extraction capacity of the organic phase for rare earths, and saves acid and alkali consumption.

[0029] (2) After the rare earth liquid is purified by the aluminum removal method of the present invention, the aluminum ions in the rare earth liquid such as Nd and Sm are reduced, and the precipitated particles of rare earth carbonates such as praseodymium carbonate, neodymium carbonate, and samarium carbonate prepared by using the rare earth liquid as raw materials are good, the washing time is short, and water can be saved.

[0030] (3) The method for removing aluminum from rare earth liquid and purifying the rare earth liquid of the present invention reduces the aluminum ion content in the rare earth liquid; the precipitated crystals of rare earth carbonates such as praseodymium carbonate, neodymium carbonate, and samarium carbonate prepared by using the method as raw materials are good and large in size, which is convenient for washing and filtering. The burning rate after filtration is high, and the burning cost is saved by 10-30%. DETAILED DESCRIPTION

[0031] The embodiments of the present invention are further described below.

[0032] Example 1

[0033] A method for removing aluminum from a rare earth liquid and purifying the same, comprising:

[0034] (1) Two sets of acid-base corrosion-resistant ion exchange columns with a D:H ratio of 1:3.5 were prepared, namely, column ① and column ②;

[0035] (2) filling the above ion exchange column with 80% of a macroporous polymer HP2000 aluminum removal adsorbent having a selective coordination function for aluminum ions;

[0036] (3) 100 ml of praseodymium-neodymium chloride rare earth solution with an aluminum content of 100-500 ppm and a pH of 2.5 is introduced into column ① from the top of the ion exchange column at a flow rate of 8-10 BV / H;

[0037] (4) The feed liquid is leached through column ①, and a water phase flows out from the outlet at the lower end of the exchange column. The water phase is the rare earth feed liquid after aluminum removal;

[0038] (5) When column ① is saturated with aluminum adsorption, the feed liquid is switched to column ② at the same flow rate to execute steps (3) and (4).

[0039] The aluminum ion content in the rare earth liquid after aluminum removal is 45 ppm.

[0040] Example 2

[0041] On the basis of Example 1, 100 ml of praseodymium-neodymium chloride rare earth solution with a pH of 2.5, the aluminum ion content in the rare earth solution is 1000-5000 ppm, and the flow rate of the rare earth solution is 4-6 BV / H.

[0042] The aluminum ion content in the rare earth liquid after aluminum removal is 135 ppm.

[0043] Example 3

[0044] On the basis of Example 1, 100 ml of praseodymium-neodymium chloride rare earth solution with a pH of 2.5, the aluminum ion content in the rare earth solution is 5000-10000 ppm, and the rare earth solution flow rate is 1-5 BV / H.

[0045] The aluminum ion content in the rare earth liquid after aluminum removal is 158 ppm.

[0046] Example 4

[0047] Ion exchange column regeneration:

[0048] (1) Use clean water to rinse the exchange column until the pH of the outlet water phase is 4.5;

[0049] (2) A 1-4 mol / L hydrochloric acid solution is introduced into column ① from the top of the ion exchange column at a flow rate of 1-2 BV / H until the aluminum ion in the outlet water phase is less than 200 ppm (no flocculation or precipitation occurs when the pH is adjusted to 5-6 with liquid caustic soda);

[0050] (3) Use clean water to rinse the exchange column until the pH of the outlet water phase is 5.0;

[0051] (4) A 1-4 mol / l liquid alkali solution is introduced into column ① from the top of the ion exchange column at a flow rate of 1-2 BV / H until the pH value of the outlet water phase is 9.

[0052] (5) Use clean water to rinse the exchange column until the pH of the outlet water phase reaches 8, and then regeneration is completed and set aside.

[0053] Comparative Example 1

[0054] (1) Prepare 1000 ml of 25% cyclohexane acid-20% isooctyl alcohol-55% kerosene extractant.

[0055] (2) Add the extractant obtained in step (1) into liquid alkali and mix thoroughly to obtain a saponified extractant with a saponification value of 0.3 mol / L.

[0056] (3) 100 ml of praseodymium-neodymium rare earth chloride solution with an aluminum content of 5000-10000 ppm and a pH of 0.5 is fully mixed with the saponified extractant obtained in step (2), and after standing for stratification, an aqueous phase after aluminum removal is obtained.

[0057] (4) The aluminum ion content in the rare earth liquid after aluminum removal is 342 ppm.

[0058] The specific embodiments of the present invention are described in detail above, but they are only examples, and the present invention is not limited to the specific embodiments described above. For those skilled in the art, any equivalent modifications and substitutions made to the present invention are also within the scope of the present invention. Therefore, the equalization changes and modifications made without departing from the spirit and scope of the present invention are all within the scope of the present invention.

Claims

1. A method for removing aluminum from a rare earth liquid, comprising: The pH value of the rare earth feed solution containing aluminum ions is adjusted to 2.5-3.5, wherein the rare earth feed solution containing aluminum ions is a rare earth ion feed solution with a pH value of 0.5-1.0 obtained by extraction and separation by a saponified P507-HCl-kerosene system, and the separation coefficient of praseodymium-neodymium chloride, neodymium chloride, and samarium chloride is close to that of aluminum ions; Then, the liquid enters an ion exchange column filled with a polymer having a selective coordination function for aluminum ions from above. After the ion exchange column is saturated with aluminum, the rare earth liquid containing aluminum ions is switched to another ion exchange column filled with a polymer having a selective coordination function for aluminum ions, wherein the polymer is HP2000 aluminum removal adsorbent; The water phase flowing out from the outlet of the lower end of the ion exchange column is the rare earth feed liquid after aluminum removal; Among them, the standard for switching different ion exchange columns is to take on-site samples of the water phase flowing out of the lower outlet of the ion exchange column, use oxalic acid to precipitate the rare earth, adjust the pH value of the precipitation supernatant to 5.5-6.5, and switch when flocculation precipitation is observed in the supernatant.

2. The method for removing aluminum from a rare earth liquid according to claim 1, characterized in that: The aluminum ion content in the rare earth liquid containing aluminum ions is 1000-10000ppm.

3. The method for removing aluminum from a rare earth liquid according to claim 1, characterized in that: The ratio of the diameter to the height of the ion exchange column is D:H=1:3.5-1:

5.

4. The method for removing aluminum from a rare earth liquid according to claim 1, characterized in that: The filling ratio of the high molecular polymer in the ion exchange column is 50-90%.

5. The method for removing aluminum from a rare earth liquid according to claim 1, characterized in that: The flow rate of the rare earth liquid containing aluminum ions entering the ion exchange column is 2-10 BV / H.

6. The method for removing aluminum from a rare earth liquid according to claim 1, characterized in that: Regenerate the used ion exchange column. The specific operation is as follows: (1) Use clean water to rinse the ion exchange column until the pH value of the outlet water phase is greater than 3.0-5.0; (2) the acid solution is introduced into the ion exchange column from the top of the ion exchange column until the aluminum ion in the outlet water phase is less than 200 ppm; (3) Rinse the ion exchange column with clean water until the pH value of the outlet water phase is greater than 3.0-5.0; (4) introducing alkali solution from the top of the ion exchange column until the pH value of the outlet water phase is greater than 8.0-12.0; (5) Finally, the ion exchange column is rinsed with clean water until the pH value of the outlet water phase is less than 7.0-9.0, and the regeneration is completed and it is ready for use.

7. The method for removing aluminum from a rare earth liquid according to claim 6, characterized in that: The acid solution in step (2) is a 1-4 mol / L hydrochloric acid solution, and its flow rate is 1-2 BV / H.

8. The method for removing aluminum from a rare earth liquid according to claim 6, characterized in that: The concentration of the alkali solution in step (4) is 1-4 mol / L, and its flow rate is 1-2 BV / H.