Adsorption treatment method of rare earth chloride solution

Abstract

The invention belongs to the technical field of rare earth solutions, and particularly relates to an adsorption treatment method of a rare earth chloride solution. Comprising the following steps: (1) adding a composite adsorbent and a rare earth chloride solution into a container, and carrying out dynamic adsorption treatment under a stirring condition; carrying out filter pressing purification on the solution after adsorption to enable the content of suspended matters to be less than or equal to 10mg / L; (2) detecting the COD (Chemical Oxygen Demand) value of the solution after adsorption, and if the COD is more than or equal to 200mg / L, performing microwave pyrolysis regeneration on the composite adsorbent which is saturated by adsorption; (3) reusing the regenerated composite adsorbent for the dynamic adsorption treatment in the step (1); through the composite adsorption-thermal regeneration cooperation technology, organic pollutants in the high-salt rare earth chloride solution can be effectively removed, the COD value of the solution is remarkably reduced, no solid waste is generated in the whole technological process, the adsorbent can be recycled, and remarkable economic benefits and environmental protection benefits are achieved.

Description

Technical Field

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

[0002] In the rare earth hydrometallurgical process, the rare earth chloride solution has a large amount of organic phase remaining in the extraction process, resulting in a chemical oxygen demand (COD) of up to 800-1000 mg / L. High COD will not only form a stable complex with rare earth ions, inhibit the formation and growth of crystal nuclei during rare earth precipitation, reduce the recovery rate of rare earths, but also increase energy consumption in the subsequent calcination process. The traditional adsorption method has the following defects under the conditions of high salt 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; diatomaceous earth has weak adsorption capacity for hydrophobic organic matter and cannot be recycled. In addition, the existing adsorption process is difficult to achieve efficient COD degradation under the premise of ensuring the stability of rare earth concentration, and secondary pollution or solid waste is easily generated during the regeneration process. Therefore, it is urgent to develop a COD adsorption treatment method suitable for high-salt rare earth chloride solution to solve the problems of low adsorption efficiency, difficult regeneration and high environmental load. Summary of the invention

[0003] In view of the shortcomings of the prior art, the purpose of the present invention is to provide an adsorption treatment method for rare earth chloride solution. Through the "composite adsorption-thermal regeneration synergistic" process, the organic pollutants in the high-salt rare earth chloride solution can be effectively removed, and the COD value of the solution can be significantly reduced. No solid waste is generated during the entire process, and the adsorbent can be recycled, which has significant economic and environmental benefits.

[0004] The technical solution adopted by the present invention is as follows: The adsorption treatment method of the rare earth chloride solution comprises the following steps: (1) Add the composite adsorbent and 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; perform filter press purification on the adsorbed solution 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) The regenerated composite adsorbent is reused in the dynamic adsorption treatment of step (1).

[0005] 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.

[0006] After the activated carbon is treated with nitric acid, carboxyl and hydroxyl functional groups are introduced, thereby enhancing the chemical adsorption capacity for polar organic matter.

[0007] The negative charge on the surface of diatomite after calcination can effectively repel Cl - , thereby reducing the interference of salt on the adsorption process.

[0008] The specific surface area of ​​the activated carbon is 1200-1500m 2 / g, pore size is 50-80µm.

[0009] The content of SiO2 in the diatomaceous earth is 70-85wt.%.

[0010] In the step (1), the amount of the composite adsorbent added is 1-2% of the mass of the rare earth oxide.

[0011] In the step (1), the stirring speed is 100-350 r / min, and the adsorption time is 60-120 min.

[0012] In the step (1), the filter pressure purification uses a 15-20 μm filter membrane and a pressure of 0.2-0.4 MPa.

[0013] 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.

[0014] The rare earth chloride solution is a rare earth chloride solution obtained by decomposing rare earth concentrate by alkali method and then performing multi-stage extraction and separation in an extraction tank.

[0015] In the step S1, the mass volume ratio of activated carbon to nitric acid solution is 1: (1-2) g / L.

[0016] In the step S1, the acidification treatment is carried out under the conditions of: immersion at 20-30° C. for 1-3 hours.

[0017] In the step S1, the calcination temperature is 500-600°C and the calcination time is 1-3h.

[0018] In the step S2, in order to ensure the uniformity of the material after grinding, it is necessary to grind 2-3 times, each grinding time is 10-15 minutes, and grind to a particle size of 20-50μm.

[0019] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention significantly improves the adsorption capacity of the adsorbent through the composite synergistic effect of acid-modified activated carbon and calcined diatomite, and can be used to treat Cl - High salt solution with concentration ≥400g / L and small change rate of rare earth ion concentration can ensure that the rare earth recovery rate is not affected; (2) The composite adsorbent prepared by the present invention can be recycled for many times and has good recycling performance and stability. When the adsorption is saturated, microwave pyrolysis regeneration technology can be used to decompose the adsorbed organic matter into CO2 and H2O, and there is no secondary pollution in the process. The regenerated adsorbent can still be recycled for many times, effectively reducing the consumption of raw materials and the generation of solid waste; (3) The present invention realizes the recycling of adsorbent and deep purification of rare earth chloride solution through the "composite adsorption-thermal regeneration synergy" process and the supporting regeneration system, ensuring the continuity and stability of the process. No harmful by-products are generated during the adsorption process, and no solid waste is discharged during the regeneration process, which is green and environmentally friendly. DETAILED DESCRIPTION

[0020] The present invention is further described below with reference to the embodiments, but they do not limit the implementation of the present invention.

[0021] The raw materials used in the examples and comparative examples are conventional commercially available raw materials unless otherwise specified, and the process methods used in the examples and comparative examples are conventional methods in the art unless otherwise specified.

[0022] Some of the raw materials used in the examples and comparative examples are described as follows: Rare earth chloride solution is a rare earth chloride solution obtained by alkaline decomposition of rare earth concentrate and then multi-stage extraction and separation in an extraction tank.

[0023] The specific surface area of ​​activated carbon is 1208m 2 / g, pore size 65µm, purchased from Qingzhou Zengtai Activated Carbon Factory; The SiO2 content in diatomite is 81wt.%, which was purchased from Jiayuan Mineral Products Processing Plant in Lingshou County.

[0024] Example 1 The preparation method of the composite adsorbent comprises the following steps: S1. Mix activated carbon with a nitric acid solution at a mass volume ratio of 1:1 g / L, immerse 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; S2. The acid-modified activated carbon and calcined diatomaceous earth were mixed in a mass ratio of 1:1, and ground three times to a particle size of 35±15µm to obtain a composite adsorbent.

[0025] The adsorption treatment method of the rare earth chloride solution comprises the following steps: The composite adsorbent and rare earth chloride solution are added into a container, the amount of the composite adsorbent added is 1% of the mass of the rare earth oxide, the pH of the rare earth chloride solution is adjusted to 1, the temperature is adjusted to 25°C, and dynamic adsorption treatment is carried out under stirring conditions, the stirring speed is 100r / min, and the adsorption time is 60min; the adsorbed solution is filtered by pressure purification using a 15μm filter membrane, the pressure is controlled at 0.2MPa, and the suspended matter content after filter pressure purification is 7.5mg / L; Among them, the COD content of the rare earth chloride solution used before adsorption was 890 mg / L, and Cl - The concentration is 563.6g / L and the rare earth concentration is 347.44g / L.

[0026] The COD content of the rare earth chloride solution after adsorption was measured to be 78.1 mg / L, and Cl - The concentration is 563.2g / L and the rare earth concentration is 346.7g / L.

[0027] Example 2 The preparation method of the composite adsorbent comprises the following steps: S1. Mix activated carbon and nitric acid solution in a mass ratio of 1:2, immerse at 30°C for 2h, and obtain acid-modified activated carbon after suction filtration. The concentration of the nitric acid solution is 62wt.%; calcine diatomite at 550°C for 2h to obtain calcined diatomite; S2. The acid-modified activated carbon and calcined diatomaceous earth were mixed in a mass ratio of 3:1, and ground three times to a particle size of 35±15µm to obtain a composite adsorbent.

[0028] The adsorption treatment method of the rare earth chloride solution comprises the following steps: (1) Adding a composite adsorbent and a rare earth chloride solution into a container, the amount of the composite adsorbent added is 1.5% of the mass of the rare earth oxide, adjusting the pH of the rare earth chloride solution to 2 and the temperature to 30°C, and performing dynamic adsorption treatment under stirring conditions, the stirring speed is 200 r / min, and the adsorption time is 90 min; using a 15 μm filter membrane to filter the adsorbed solution for purification, the pressure is controlled at 0.2 MPa, and the suspended matter content after filter pressure purification is 7.6 mg / L; Among them, the COD content of the rare earth chloride solution used before adsorption was 886 mg / L, and Cl - The concentration is 532.4g / L and the rare earth concentration is 347.43g / L.

[0029] The COD content of the rare earth chloride solution after adsorption was measured to be 79.3 mg / L, and Cl - The concentration is 531.1g / L and the rare earth concentration is 346.89g / L.

[0030] Example 3 The preparation method of the composite adsorbent comprises the following steps: S1. Mix activated carbon and nitric acid solution in a mass ratio of 1:2, immerse at 20°C for 3 hours, and obtain acid-modified activated carbon after suction filtration. The concentration of the nitric acid solution is 50wt.%; calcine diatomite at 600°C for 1 hour to obtain calcined diatomite; S2. The acid-modified activated carbon and calcined diatomaceous earth were mixed in a mass ratio of 5:1, and ground three times to a particle size of 35±15µm to obtain a composite adsorbent.

[0031] The adsorption treatment method of the rare earth chloride solution comprises the following steps: (1) Adding a composite adsorbent and a rare earth chloride solution into a container, the amount of the composite adsorbent added is 2% of the mass of the rare earth oxide, adjusting the pH of the rare earth chloride solution to 3 and the temperature to 40°C, and performing dynamic adsorption treatment under stirring conditions, the stirring speed is 350r / min, and the adsorption time is 120min; using a 15μm filter membrane to filter the adsorbed solution for purification, the pressure is controlled at 0.4MPa, and the suspended matter content after filter pressure purification is 8.3mg / L; Among them, the COD content of the rare earth chloride solution used before adsorption was 897 mg / L, and Cl - The concentration is 531.6g / L and the rare earth concentration is 346.8g / L.

[0032] The COD content of the rare earth chloride solution after adsorption was measured to be 80.2 mg / L, and Cl - The concentration is 530.9g / L and the rare earth concentration is 345.9g / L.

[0033] Example 4 In order to evaluate the reusability of the composite adsorbent, the original rare earth chloride solution (COD content of 890 mg / L, Cl - The concentration of 563.6 g / L and the rare earth concentration of 347.44 g / L were used as the raw materials for each repeated experiment. The adsorbent used for the first time in step (1) was used for 5 repeated adsorption experiments. In each repeated adsorption experiment, except for the type of adsorbent, the other dynamic adsorption conditions were consistent with those in Example 1.

[0034] The solutions after each repeated adsorption were tested, and the results were as follows: First repetition: COD content of rare earth chloride solution after adsorption was 91 mg / L, Cl - The concentration is 563.3 g / L, and the rare earth concentration is 346.6 g / L; Second repetition: COD content of rare earth chloride solution after adsorption was 108.4 mg / L, Cl - The concentration is 563.5 g / L, and the rare earth concentration is 346.7 g / L; The third repetition: COD content of rare earth chloride solution after adsorption was 151.3 mg / L, Cl - The concentration is 563.4 g / L, and the rare earth concentration is 346.4 g / L; The fourth repetition: the COD content of the rare earth chloride solution after adsorption was 179.8 mg / L, Cl - The concentration is 563.3g / L and the rare earth concentration is 346.5g / L.

[0035] The fifth repetition: COD content of rare earth chloride solution after adsorption was 249.3 mg / L, Cl - The concentration is 563.4g / L and the rare earth concentration is 346.6g / L.

[0036] It can be seen that with the increase of the number of repetitions, the COD removal efficiency gradually decreases, which shows that the adsorbent is repeatable, but there is a trend of performance attenuation. In order to ensure that it does not affect the subsequent rare earth precipitation, the present invention performs microwave regeneration on the adsorbent after detecting that the COD value of the adsorbed solution is ≥200 mg / L, and continues to use it after regeneration. In the repeated adsorption process, Cl - The concentration and rare earth concentration fluctuated slightly, indicating that the adsorbent had a good effect on Cl - There is no obvious adsorption effect on rare earth ions. This selective adsorption mechanism effectively avoids the loss of main components and is crucial for resource recovery in the rare earth industry.

[0037] Example 5 The adsorbent after the fifth repetition in Example 4 was regenerated by microwave pyrolysis. The microwave pyrolysis regeneration was carried out under a nitrogen atmosphere at a temperature of 900° C. for 30 min.

[0038] The original rare earth chloride solution (COD content of 890 mg / L, Cl - The concentration was 563.6 g / L and the rare earth concentration was 347.44 g / L as the raw material for each experiment. A regenerated adsorbent was added for dynamic adsorption treatment. Except for the type of adsorbent, the other dynamic adsorption conditions were consistent with Example 1. The regenerated adsorbent was used for 5 cyclic adsorption experiments.

[0039] The solution after each cycle of adsorption was tested, and the results are as follows: First cycle: COD content of rare earth chloride solution after adsorption is 80.5mg / L, Cl - The concentration is 563.4 g / L, and the rare earth concentration is 346.7 g / L; Second cycle: COD content of rare earth chloride solution after adsorption is 94.1mg / L, Cl - The concentration is 563.5 g / L, and the rare earth concentration is 346.9 g / L; The third cycle: COD content of rare earth chloride solution after adsorption is 110.4 mg / L, Cl - The concentration is 563.2 g / L, and the rare earth concentration is 346.5 g / L; The fourth cycle: the COD content of the rare earth chloride solution after adsorption was 164.1 mg / L, Cl - The concentration is 562.9 g / L, and the rare earth concentration is 346.8 g / L; The fifth cycle: COD content of rare earth chloride solution after adsorption is 189.6 mg / L, Cl - The concentration is 563.2g / L and the rare earth concentration is 346.8g / L.

[0040] It can be seen that microwave pyrolysis regeneration can restore the activity of the adsorbent to a state close to the initial state. After the first use of the regenerated adsorbent, the COD of the rare earth chloride solution decreased to 80.5 mg / L, which is close to the 78.1 mg / L of the initial adsorbent after the first use. This shows that microwave pyrolysis regeneration can effectively desorb the residual organic matter. At the same time, in the recycling process after regeneration, Cl -The fluctuations with the change of rare earth concentration were small, indicating that the regeneration process did not damage the selectivity of the adsorbent. In the 5 cycle experiments, the COD content of the rare earth chloride solution gradually increased after adsorption using the regenerated adsorbent. This trend was consistent with the trend when the unregenerated adsorbent was used, but the decay rate was slightly faster, indicating that the adsorption capacity of the regenerated adsorbent decreased slightly. This change may be related to the partial collapse of the adsorbent microporous structure or the loss of active sites during microwave pyrolysis.

[0041] Comparative Example 1 The difference from Example 1 is that the preparation method of the adsorbent is to mix activated carbon and diatomaceous earth in a mass ratio of 1:1, grind 3 times to a particle size of 35±15µm, and obtain the adsorbent. The rest is the same as Example 1.

[0042] The COD content of the rare earth chloride solution after adsorption was measured to be 212.3 mg / L.

[0043] It shows that when the adsorbent made of activated carbon and diatomaceous earth without pretreatment is used for adsorption, its adsorption effect cannot meet the requirement of reducing the COD of rare earth chloride solution to below 200 mg / L after adsorption. The high COD rare earth chloride after this treatment will have a certain impact on the subsequent carbon precipitation process.

[0044] Comparative Example 2 The difference from Example 1 is that, in the preparation process of the adsorbent, the concentration of the nitric acid solution used is 30 wt.%, and the rest is the same as Example 1.

[0045] The COD content of the rare earth chloride solution after adsorption was measured to be 109.8 mg / L.

[0046] It can be seen that the COD value of the adsorbent prepared by using a nitric acid solution with a concentration of 30wt.% is higher than that of Example 1 after being used to adsorb rare earth chloride solution. This is because the activated carbon has not been completely carboxylated and hydroxylated, resulting in a decrease in its chemical adsorption capacity for polar organic matter.

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.