Adsorption treatment method for rare earth chloride solution

Abstract

The present invention belongs to the technical field of rare earth solutions, and specifically relates to a method for adsorptive treatment of rare earth chloride solutions. The method includes the following steps: (1) adding a composite adsorbent and a rare earth chloride solution into a container, and performing dynamic adsorption treatment under stirring conditions; filtering and purifying the solution after adsorption to make the suspended solid content ≤ 10 mg / L; (2) detecting the COD value of the solution after adsorption, and if the COD ≥ 200 mg / L, performing microwave pyrolysis regeneration on the composite adsorbent saturated with adsorption; (3) reusing the regenerated composite adsorbent for the dynamic adsorption treatment in step (1); through the "composite adsorption-thermal regeneration synergy" process, organic pollutants in high-salt rare earth chloride solutions can be effectively removed, the COD value of the solution can be significantly reduced, no solid waste is generated during the whole process, and the adsorbent can be recycled, having remarkable economic and environmental benefits.

Description

Technical Field

[0001] The present invention belongs to the technical field of rare earth solutions, and particularly relates to an adsorption treatment method for rare earth chloride solutions. Background Art

[0002] In the rare earth hydrometallurgy process, a large amount of organic phase remains in the rare earth chloride solution due to the extraction process, resulting in a chemical oxygen demand (COD) of up to 800 - 1000 mg / L in the solution. High COD not only forms stable complexes with rare earth ions, inhibits the formation and growth of crystal nuclei during rare earth precipitation, reduces the rare earth recovery rate, but also increases energy consumption in the subsequent calcination process. Traditional adsorption methods have the following defects in the presence of high salinity and heavy metal ions: the adsorption capacity of activated carbon drops sharply due to pore blockage and needs to be replaced with newly purchased activated carbon; diatomite has weak adsorption ability for hydrophobic organic substances and cannot be recycled. In addition, existing adsorption processes are difficult to achieve efficient COD degradation while ensuring the stability of rare earth concentration, and secondary pollution or solid waste is easily generated during the regeneration process. Therefore, there is an urgent need to develop a COD adsorption treatment method for high-salt rare earth chloride solutions to solve problems such as low adsorption efficiency, difficult regeneration, and high environmental load. Summary of the Invention

[0003] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide an adsorption treatment method for rare earth chloride solutions. Through the "composite adsorption - thermal regeneration synergy" process, it can effectively remove organic pollutants in high-salt rare earth chloride solutions, significantly reduce the COD value of the solution, and no solid waste is generated during the whole process. The adsorbent can be recycled, with significant economic and environmental benefits.

[0004] The technical solution adopted by the present invention is as follows:

[0005] The adsorption treatment method for rare earth chloride solutions includes the following steps:

[0006] (1) Add the composite adsorbent and the rare earth chloride solution into a container, adjust the pH of the rare earth chloride solution to 1 - 3 and the temperature to 25 - 40 °C, and perform dynamic adsorption treatment under stirring conditions; filter and purify the adsorbed solution to make the suspended solid content ≤ 10 mg / L;

[0007] (2) Detect the COD value of the adsorbed solution. If its COD ≥ 200 mg / L, perform microwave pyrolysis regeneration on the saturated composite adsorbent;

[0008] (3) Reuse the regenerated composite adsorbent for the dynamic adsorption treatment in step (1).

[0009] Wherein, the COD content of the rare earth chloride solution is 800 - 1000 mg / L, Cl -The concentration is 400 - 600 g / L;

[0010] The preparation method of the composite adsorbent includes the following steps:

[0011] S1. Acidify activated carbon with a nitric acid solution having a concentration of 50 - 70 wt.% to obtain acid-modified activated carbon; calcine diatomite to obtain calcined diatomite;

[0012] S2. Mix the acid-modified activated carbon and the calcined diatomite in a mass ratio of (1 - 5):1, and obtain the composite adsorbent after grinding.

[0013] After the activated carbon is acidified with nitric acid, carboxyl and hydroxyl functional groups are introduced, thereby enhancing the chemical adsorption capacity for polar organic substances.

[0014] The negatively charged property presented on the surface of diatomite after calcination can effectively repel Cl - , thereby reducing the interference of salts on the adsorption process.

[0015] The specific surface area of the activated carbon is 1200 - 1500 m 2 / g, and the pore size is 50 - 80 µm.

[0016] The content of SiO 2 in the diatomite is 70 - 85 wt.%.

[0017] In the step (1), the addition amount of the composite adsorbent is 1 - 2% of the mass of the rare earth oxide.

[0018] In the step (1), the rotation speed of stirring is 100 - 350 r / min, and the adsorption time is 60 - 120 min.

[0019] In the step (1), pressure filtration and purification are carried out using a filter membrane with a pore size of 15 - 20 µm, and the pressure is 0.2 - 0.4 MPa.

[0020] In the step (2), microwave pyrolysis regeneration is carried out under a nitrogen atmosphere, the temperature is 800 - 1000 °C, and the time is 20 - 30 min.

[0021] The rare earth chloride solution is a rare earth chloride solution obtained by decomposing rare earth concentrates by an alkaline method and then performing multi-stage extraction and separation through an extraction tank.

[0022] In the step S1, the mass-volume ratio of the activated carbon to the nitric acid solution is 1:(1 - 2) g / L.

[0023] In the step S1, the conditions for acidification treatment are: impregnation for 1 - 3 h under the condition of 20 - 30 °C.

[0024] In the said step S1, the calcination temperature is 500 - 600 °C and the time is 1 - 3 h.

[0025] In the said step S2, to ensure the uniformity of the material after grinding, it needs to be ground 2 - 3 times, with each grinding time being 10 - 15 min, and ground to a particle size of 20 - 50 µm.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] (1) Through the combined synergistic effect of acid - modified activated carbon and calcined diatomite, the adsorption capacity of the adsorbent of the present invention is significantly improved, and it can be used to treat high - salt solutions with a Cl - concentration ≥ 400 g / L, and the change rate of rare - earth ion concentration is small, which can ensure that the rare - earth recovery rate is not affected;

[0028] (2) The composite adsorbent prepared by the present invention can be recycled multiple times, and has good recycling performance and stability; when the adsorption is saturated, the microwave pyrolysis regeneration technology can be used to decompose the adsorbed organic matter into CO 2 and H 2 O, and there is no secondary pollution during the process. The regenerated adsorbent can still be recycled multiple times, effectively reducing the consumption of raw materials and the generation of solid waste;

[0029] (3) Through the "composite adsorption - thermal regeneration synergistic" process and the supporting regeneration system of the present invention, the recycling of the adsorbent and the deep purification of rare - earth chloride solution are realized, ensuring the continuity and stability of the process. There are no harmful by - products generated during the adsorption process and no solid - waste emissions during the regeneration process, which is green and environmentally friendly. Specific Embodiments

[0030] The following further illustrates the present invention in combination with embodiments, but it does not limit the implementation of the present invention.

[0031] The raw materials used in the embodiments and comparative examples are all conventional commercially available raw materials without special instructions, and the process methods used in the embodiments and comparative examples are all conventional methods in the art without special instructions.

[0032] Some of the raw materials used in the embodiments and comparative examples are described as follows:

[0033] The rare - earth chloride solution is a rare - earth chloride solution obtained by decomposing rare - earth concentrates by the alkali method and then performing multi - stage extraction and separation through an extraction tank.

[0034] The specific surface area of the activated carbon is 1208 m 2 / g, and the pore diameter is 65 µm, purchased from Qingzhou Zengtai Activated Carbon Factory;

[0035] In the diatomite, SiO 2The content is 81 wt.%, purchased from Jiayuan Mineral Products Processing Factory, Lingshou County.

[0036] Example 1

[0037] The preparation method of the composite adsorbent described above includes the following steps:

[0038] S1. Mix activated carbon with a mass-to-volume ratio of 1:1 g / L with nitric acid solution, impregnate at 25 °C for 1 h, and obtain acid-modified activated carbon after suction filtration. The concentration of the nitric acid solution is 69 wt.%; calcine diatomite at 500 °C for 3 h to obtain calcined diatomite;

[0039] S2. Mix the acid-modified activated carbon and the calcined diatomite in a mass ratio of 1:1, grind 3 times to a particle size of 35 ± 15 µm to obtain the composite adsorbent.

[0040] The adsorption treatment method of the rare earth chloride solution described above includes the following steps:

[0041] Add the composite adsorbent and the rare earth chloride solution into a container. The addition amount of the composite adsorbent is 1% of the mass of rare earth oxide. Adjust the pH of the rare earth chloride solution to 1 and the temperature to 25 °C, and perform dynamic adsorption treatment under stirring conditions. The stirring speed is 100 r / min, and the adsorption time is 60 min; use a 15-μm filter membrane to perform pressure filtration purification on the adsorbed solution, control the pressure at 0.2 MPa, and the suspended solid content after pressure filtration purification is 7.5 mg / L;

[0042] Among them, the COD content of the rare earth chloride solution used before adsorption is 890 mg / L, the Cl - concentration is 563.6 g / L, and the rare earth concentration is 347.44 g / L.

[0043] The measured COD content of the rare earth chloride solution after adsorption is 78.1 mg / L, and the Cl - concentration is 563.2 g / L, and the rare earth concentration is 346.7 g / L.

[0044] Example 2

[0045] The preparation method of the composite adsorbent described above includes the following steps:

[0046] S1. Mix activated carbon with a mass ratio of 1:2 with nitric acid solution, impregnate at 30 °C for 2 h, and obtain acid-modified activated carbon after suction filtration. The concentration of the nitric acid solution is 62 wt.%; calcine diatomite at 550 °C for 2 h to obtain calcined diatomite;

[0047] S2. Mix the acid-modified activated carbon and the calcined diatomite in a mass ratio of 3:1, grind 3 times to a particle size of 35 ± 15 µm to obtain the composite adsorbent.

[0048] The adsorption treatment method of the rare earth chloride solution comprises the following steps:

[0049] (1) Add the composite adsorbent and the rare earth chloride solution into a container. The addition amount of the composite adsorbent is 1.5% of the mass of rare earth oxide. Adjust the pH of the rare earth chloride solution to 2 and the temperature to 30 °C, and perform dynamic adsorption treatment under stirring conditions. The stirring speed is 200 r / min, and the adsorption time is 90 min; Use a 15-μm filter membrane to perform pressure filtration purification on the adsorbed solution, control the pressure at 0.2 MPa, and the suspended solid content after pressure filtration purification is 7.6 mg / L;

[0050] Among them, the COD content of the rare earth chloride solution used before adsorption is 886 mg / L, Cl - concentration is 532.4 g / L, and the rare earth concentration is 347.43 g / L.

[0051] It is measured that the COD content of the rare earth chloride solution after adsorption is 79.3 mg / L, Cl - concentration is 531.1 g / L, and the rare earth concentration is 346.89 g / L.

[0052] Example 3

[0053] The preparation method of the composite adsorbent comprises the following steps:

[0054] S1. Mix activated carbon and nitric acid solution with a mass ratio of 1:2, impregnate at 20 °C for 3 h, and obtain acid-modified activated carbon after suction filtration. The concentration of the nitric acid solution is 50 wt.%; Calcinate diatomite at 600 °C for 1 h to obtain calcined diatomite;

[0055] S2. Mix the acid-modified activated carbon and the calcined diatomite at a mass ratio of 5:1, grind 3 times until the particle size is 35 ± 15 µm to obtain the composite adsorbent.

[0056] The adsorption treatment method of the rare earth chloride solution comprises the following steps:

[0057] (1) Add the composite adsorbent and the rare earth chloride solution into a container. The addition amount of the composite adsorbent is 2% of the mass of rare earth oxide. Adjust the pH of the rare earth chloride solution to 3 and the temperature to 40 °C, and perform dynamic adsorption treatment under stirring conditions. The stirring speed is 350 r / min, and the adsorption time is 120 min; Use a 15-μm filter membrane to perform pressure filtration purification on the adsorbed solution, control the pressure at 0.4 MPa, and the suspended solid content after pressure filtration purification is 8.3 mg / L;

[0058] Among them, the COD content of the rare earth chloride solution used before adsorption is 897 mg / L, Cl- The concentration is 531.6 g / L, and the rare earth concentration is 346.8 g / L.

[0059] The measured COD content of the rare earth chloride solution after adsorption is 80.2 mg / L, Cl - The concentration is 530.9 g / L, and the rare earth concentration is 345.9 g / L.

[0060] Example 4

[0061] To evaluate the reusability of the composite adsorbent, the original rare earth chloride solution without adsorption treatment in Example 1 (COD content is 890 mg / L, Cl - The concentration is 563.6 g / L, and the rare earth concentration is 347.44 g / L) is used as the raw material for each repeated experiment. The adsorbent after the first use in step (1) is taken for 5 repeated adsorption experiments. In each repeated adsorption experiment, except for the type of adsorbent, the other dynamic adsorption conditions are the same as those in Example 1.

[0062] The solutions after each repeated adsorption are detected, and the results are as follows:

[0063] First repetition: The COD content of the rare earth chloride solution after adsorption is 91 mg / L, Cl - The concentration is 563.3 g / L, and the rare earth concentration is 346.6 g / L;

[0064] Second repetition: The COD content of the rare earth chloride solution after adsorption is 108.4 mg / L, Cl - The concentration is 563.5 g / L, and the rare earth concentration is 346.7 g / L;

[0065] Third repetition: The COD content of the rare earth chloride solution after adsorption is 151.3 mg / L, Cl - The concentration is 563.4 g / L, and the rare earth concentration is 346.4 g / L;

[0066] Fourth repetition: The COD content of the rare earth chloride solution after adsorption is 179.8 mg / L, Cl - The concentration is 563.3 g / L, and the rare earth concentration is 346.5 g / L.

[0067] Fifth repetition: The COD content of the rare earth chloride solution after adsorption is 249.3 mg / L, Cl - The concentration is 563.4 g / L, and the rare earth concentration is 346.6 g / L.

[0068] It can be seen that with the increase in the number of repetitions, the COD removal efficiency gradually decreases, indicating that the adsorbent has repeatability but there is a trend of performance decay. To ensure that it does not affect the subsequent rare earth precipitation, in the present invention, after detecting that the COD value of the solution after adsorption is ≥200 mg / L, the adsorbent is subjected to microwave regeneration treatment and then continues to be used. During the repeated adsorption process, the Cl - concentration and rare earth concentration fluctuate little, indicating that the adsorbent has no obvious adsorption effect on Cl - and rare earth ions. This selective adsorption mechanism effectively avoids the loss of main components and is crucial for the resource recovery in the rare earth industry.

[0069] Example 5

[0070] The adsorbent after the fifth repetition in Example 4 was taken for microwave pyrolysis regeneration. The microwave pyrolysis regeneration was carried out in a nitrogen atmosphere at a temperature of 900 °C for 30 min.

[0071] The original rare earth chloride solution without adsorption treatment in Example 1 (with a COD content of 890 mg / L, a Cl - concentration of 563.6 g / L, and a rare earth concentration of 347.44 g / L) was used as the raw material for each experiment. The regenerated adsorbent was added for dynamic adsorption treatment. Except for the type of adsorbent, the other dynamic adsorption conditions were the same as those in Example 1. The regenerated adsorbent was used for 5 cyclic adsorption experiments.

[0072] The solutions after each cyclic adsorption were detected, and the results are as follows:

[0073] First cycle: The COD content of the rare earth chloride solution after adsorption was 80.5 mg / L, the Cl - concentration was 563.4 g / L, and the rare earth concentration was 346.7 g / L;

[0074] Second cycle: The COD content of the rare earth chloride solution after adsorption was 94.1 mg / L, the Cl - concentration was 563.5 g / L, and the rare earth concentration was 346.9 g / L;

[0075] Third cycle: The COD content of the rare earth chloride solution after adsorption was 110.4 mg / L, the Cl - concentration was 563.2 g / L, and the rare earth concentration was 346.5 g / L;

[0076] Fourth cycle: The COD content of the rare earth chloride solution after adsorption was 164.1 mg / L, the Cl - concentration was 562.9 g / L, and the rare earth concentration was 346.8 g / L;

[0077] The fifth cycle: The COD content of the rare earth chloride solution after adsorption is 189.6 mg / L, and the Cl - concentration is 563.2 g / L, and the rare earth concentration is 346.8 g / L.

[0078] It can be seen that through microwave pyrolysis regeneration, the activity of the adsorbent can be restored to near the initial state. After the regenerated adsorbent is used for the first time, the COD of the rare earth chloride solution is reduced to 80.5 mg / L, which is close to 78.1 mg / L after the initial adsorbent is used for the first time, indicating that microwave pyrolysis regeneration can effectively desorb the residual organic matter. At the same time, during the recycling process after regeneration, the Cl - and rare earth concentrations change with small fluctuations, indicating that the regeneration process does not damage the selectivity of the adsorbent. In the 5-cycle experiment, after using the regenerated adsorbent for adsorption, the COD content of the rare earth chloride solution gradually increases. This trend is consistent with that when using the non-regenerated adsorbent, but the attenuation rate is slightly faster, indicating that the adsorption capacity of the regenerated adsorbent decreases slightly. This change may be related to the partial collapse of the microporous structure of the adsorbent or the loss of active sites during the microwave pyrolysis process.

[0079] Comparative Example 1

[0080] The difference from Example 1 is that the preparation method of the adsorbent is to mix activated carbon and diatomite in a mass ratio of 1:1 and grind it 3 times to a particle size of 35 ± 15 µm to obtain the adsorbent, and the others are the same as in Example 1.

[0081] The measured COD content of the rare earth chloride solution after adsorption is 212.3 mg / L.

[0082] It shows that when using the adsorbent prepared from unpretreated activated carbon and diatomite for adsorption, its adsorption effect cannot meet the requirement that the COD of the rare earth chloride solution after adsorption is reduced to less than 200 mg / L. After this treatment, the high-COD rare earth chloride will have a certain impact on the subsequent carbon precipitation process.

[0083] Comparative Example 2

[0084] The difference from Example 1 is that during the preparation process of the adsorbent, the concentration of the nitric acid solution used is 30 wt.%, and the others are the same as in Example 1.

[0085] The measured COD content of the rare earth chloride solution after adsorption is 109.8 mg / L.

[0086] It can be seen that the COD value of the adsorbent prepared with a nitric acid solution with a concentration of 30 wt.% is higher than that of Example 1 after being used to adsorb the rare earth chloride solution, because the activated carbon cannot be completely carboxylated and hydroxylated, resulting in a decrease in its chemisorption ability for polar organic substances.

Claims

1. A method for adsorption treatment of rare earth chloride solution, characterized in that: The following steps are involved: (1) Adding the composite adsorbent and rare earth chloride solution into a container, adjusting the pH of the rare earth chloride solution to 1-3 and the temperature to 25-40° C., and performing dynamic adsorption treatment under stirring conditions; The adsorbed solution is filtered and purified to make the suspended matter content ≤10mg / L; (2) Detecting the COD value of the solution after adsorption. If the COD is ≥ 200 mg / L, the saturated composite adsorbent is regenerated by microwave pyrolysis; (3) reusing the regenerated composite adsorbent for the dynamic adsorption treatment in step (1); Wherein, the COD content of the rare earth chloride solution is 800-1000 mg / L, Cl - The concentration is 400-600g / L; The preparation method of the composite adsorbent comprises the following steps: S1, acidifying the activated carbon with a nitric acid solution having a concentration of 50-70wt.% to obtain acid-modified activated carbon; calcining diatomaceous earth to obtain calcined diatomaceous earth; S2. The acid-modified activated carbon and calcined diatomaceous earth are mixed in a mass ratio of (1-5):1, and the composite adsorbent is obtained after grinding.

2. The adsorption treatment method of rare earth chloride solution according to claim 1, characterized in that: In the step (1), the amount of the composite adsorbent added is 1-2% of the mass of the rare earth oxide.

3. The adsorption treatment method of rare earth chloride solution according to claim 1, characterized in that: In the step (1), the stirring speed is 100-350 r / min, and the adsorption time is 60-120 min.

4. The adsorption treatment method of rare earth chloride solution according to claim 1, characterized in that: In the step (1), the filter pressure purification uses a 15-20 μm filter membrane and a pressure of 0.2-0.4 MPa.

5. The adsorption treatment method of rare earth chloride solution according to claim 1, characterized in that: In the step (2), microwave pyrolysis regeneration is carried out in a nitrogen atmosphere at a temperature of 800-1000° C. for 20-30 min.

6. The adsorption treatment method of rare earth chloride solution according to claim 1, characterized in that: In the step S1, the mass volume ratio of activated carbon to nitric acid solution is 1: (1-2) g / L.

7. The adsorption treatment method of rare earth chloride solution according to claim 1, characterized in that: In the step S1, the acidification treatment is carried out under the conditions of: immersion at 20-30° C. for 1-3 hours.

8. The adsorption treatment method of rare earth chloride solution according to claim 1, characterized in that: In the step S1, the calcination temperature is 500-600°C and the calcination time is 1-3h.

9. The adsorption treatment method of rare earth chloride solution according to claim 1, characterized in that: In the step S2, the particles are ground to a particle size of 20-50 μm.