A method for efficiently recovering rare earth oxides from rare earth wastewater

Abstract

The present application belongs to the technical field of wastewater treatment and rare earth recovery, and discloses a method for efficiently recovering rare earth oxides from rare earth wastewater. The method comprises the following steps: (1) adding an alkali solution and a polyacrylamide solution into the rare earth wastewater and stirring to react, filtering the reacted solution, washing and drying the precipitate to obtain a precipitate product; (2) calcining the precipitate product obtained in step (1) under an air atmosphere and at a temperature of 400-900 DEG C to obtain a rare earth oxide material. The method uses alkali solution and polyacrylamide solution to cooperatively precipitate and treat the rare earth wastewater, and combines with subsequent high-temperature calcination under an air atmosphere to obtain a rare earth oxide material with high purity and high yield. The above method is simple and efficient, has low treatment cost, and has good application prospect.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of wastewater treatment and rare earth recovery, and particularly relates to a method for efficiently recovering rare earth oxides from rare earth wastewater. BACKGROUND

[0002] Due to the special atomic structure, rare earth elements can endow materials with excellent physical properties such as light, electricity, magnetism, superconductivity, catalysis, etc., and thus are widely used in various fields of national economy and national defense industry, and are known as "industrial MSG". With the entry of human society into the information age, various types of rare earth materials (such as rare earth permanent magnet materials, rare earth superconducting materials, rare earth fluorescent materials, rare earth laser materials, and rare earth hydrogen storage materials) play an increasingly important role, and have become key materials for developing new-generation information technology, energy saving and environmental protection, new energy materials, and high-end equipment manufacturing, etc. The application of rare earth materials in traditional fields also has a significant impact on the technological progress and optimization and upgrading of traditional industries.

[0003] With the development of rare earth resources, the problem of resource loss caused by production is also increasingly prominent. According to incomplete statistics in the industry, the extraction rate of rare earths can only reach 96% to 97% at most, that is, as many as thousands of tons of rare earths are lost in low-concentration state with wastewater every year. The discharge of these wastewater containing rare earths not only causes environmental pollution but also causes the loss of valuable resources. Therefore, it is of great significance for the sustainable and healthy development of the rare earth industry and environmental protection to enrich and extract and recover rare earth elements from wastewater.

[0004] The chemical precipitation method refers to adding a reagent that can form a precipitate with rare earth ions. This method can be used for the treatment of a large amount of wastewater containing high-concentration rare earth metal pollutants. The most commonly used chemicals include hydroxides, carbonates, sulfides, etc. The addition of these chemicals not only can efficiently remove rare earth ions in pollutants but also can adjust the pH value of the solution, so as to meet the discharge standard. The alkali precipitation method has the advantages of simplicity and low cost, and has become one of the most widely used methods for treating rare earth ions. This method mainly utilizes the formation of a precipitate with small solubility by alkali and rare earth ions, and the main feature of this method is that it can better realize the treatment of rare earth ions in wastewater. For example, patent CN 104878201 A discloses a method for recovering rare earths from wastewater containing rare earths, wherein the method comprises: (1) contacting the wastewater containing rare earths with an alkali precipitant capable of precipitating rare earth metal elements, and after settling, solid-liquid separation is performed to obtain a first solution and a rare earth precipitate; (2) contacting the rare earth precipitate with a hydrofluoric acid-containing aqueous solution, and after settling, solid-liquid separation is performed to obtain a second solution and a fluorinated rare earth.

[0005] However, the recovery rate of rare earth wastewater treated by simple alkali precipitation method is limited, and the addition of other auxiliary reagents will increase the impurity content of rare earth recovery products, affecting the subsequent treatment process and application. Polyacrylamide flocculant is widely used in wastewater treatment to improve the efficiency of sedimentation, clarification, filtration, centrifugation and other processes in wastewater treatment process. However, there is no report on the use of polyacrylamide to improve the recovery rate of rare earth wastewater by alkali precipitation method, and how to obtain high-purity rare earth recovery material is also a technical problem to be solved by those skilled in the art. SUMMARY

[0006] In view of the shortcomings and deficiencies of the prior art, the primary object of the present application is to provide a method for efficiently recovering rare earth oxides from rare earth wastewater. The method of the present application uses sodium hydroxide solution and polyacrylamide solution for co-precipitation treatment of rare earth wastewater, and can obtain high-purity and high-yield rare earth oxide materials by subsequent air atmosphere high temperature calcination treatment. The above method is simple, efficient and low in processing cost, and has good application prospect.

[0007] Another object of the present application is to provide a rare earth oxide material obtained by the above method.

[0008] The object of the present application is achieved by the following technical solutions:

[0009] A method for efficiently recovering rare earth oxides from rare earth wastewater, comprising the following steps:

[0010] (1) adding an alkali solution and a polyacrylamide solution to the rare earth wastewater and stirring to react, filtering the reacted solution, washing and drying the precipitate to obtain a precipitate product;

[0011] (2) calcining the precipitate product obtained in step (1) at an air atmosphere and a temperature of 400-900℃ to obtain a rare earth oxide material.

[0012] Further, the alkali solution in step (1) refers to at least one of sodium hydroxide solution, potassium hydroxide solution, sodium carbonate solution, sodium bicarbonate solution, potassium carbonate solution, potassium bicarbonate solution and ammonia.

[0013] Further preferably, the amount of alkali solution added is to adjust the pH of the rare earth wastewater to 0.1-13.

[0014] Further, the amount of polyacrylamide added is 0.1-5 times the amount of alkali added.

[0015] Further, the rare earth wastewater in step (1) refers to wastewater containing at least one of Eu, Dy and Tb rare earth ions.

[0016] Further preferably, the concentration of rare earth ions in the rare earth wastewater is 0.01-300 mg / L.

[0017] Further, the stirring reaction in step (1) is stirring reaction at 10-30 ℃ for 1-30 min.

[0018] Further, the washing in step (1) is washing with deionized water, and the drying is drying at 100-140 ℃.

[0019] Further, the time for the calcination treatment in step (2) is 5-500 min.

[0020] A rare earth oxide material prepared by the above method, the rare earth oxide material has a two-dimensional sheet structure with a diameter of 10-50 μm, and the purity is >99%.

[0021] The principle of the present application is: using alkali to combine with rare earth organic complex or rare earth ions in rare earth wastewater to form flocculation suspended particles, then using the active acyl on the polyacrylamide main chain to bridge and adsorb the suspended particles dispersed in the solution to perform flocculation precipitation, through the synergistic effect of the two, the rare earth ions are converted to solid phase, then the solid product after reaction is filtered, washed and dried; then the obtained solid product is subjected to calcination treatment of organic matter under air atmosphere and at a temperature of 400-900 ℃, to obtain a rare earth oxide material, the recovery efficiency of Eu, Dy, Tb and other rare earth ions can all reach 99% or more, and the purity of the obtained rare earth oxide can reach 99% or more.

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

[0023] (1) The method of the present application uses alkali solution and polyacrylamide solution to cooperatively treat rare earth wastewater, the rare earth ions in the solution can be quickly settled, and the recovery efficiency of the rare earth ions can all reach 99% or more. The solid product is subjected to calcination treatment under air atmosphere, and the purity of the rare earth oxide can reach 99% or more.

[0024] (2) The application method of the present application in rare earth recovery has the advantages of high recovery efficiency and low cost compared with the conventional adsorption method, chemical precipitation method, ion exchange method and membrane separation method. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 The scanning electron microscope image of the rare earth oxide Dy2O3 obtained in Example 1;

[0026] Figure 2 The XRD and XRF images of the rare earth oxide Dy2O3 obtained in Example 1;

[0027] Figure 3This is a scanning electron microscope image of the rare earth oxide Eu2O3 obtained in Example 2;

[0028] Figure 4 The XRD and XRF patterns of the rare earth oxide Eu2O3 obtained in Example 2 are shown below.

[0029] Figure 5 This is a scanning electron microscope image of the rare earth oxide Tb4O7 obtained in Example 3;

[0030] Figure 6 The XRD and XRF patterns of the rare earth oxide Tb4O7 obtained in Example 3 are shown below.

[0031] Figure 7 The graph shows the recovery efficiency of rare earth ions in Examples 1-3.

[0032] Figure 8 The recovery efficiency of rare earth ions is shown in the diagrams for comparative examples 1 to 3.

[0033] Figure 9 The graph shows the recovery efficiency of rare earth ions in Comparative Examples 4–6. Detailed Implementation

[0034] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0035] Example 1

[0036] This embodiment of a method for efficiently recovering rare earth oxide Dy2O3 from Dy-containing wastewater includes the following steps:

[0037] (1) A 6 mol / L sodium hydroxide solution and a polyacrylamide solution were sequentially added to a wastewater solution containing Dy rare earth elements (samples taken from actual production, containing DyCl3, oxalic acid, hydrochloric acid, P507, naphthenic acid, kerosene, isooctyl alcohol, etc.). 3+ The concentration was 92.5 mg / L, and the solution pH was < 0. The reaction was carried out under magnetic stirring at 25°C for 20 min until the pH of the solution was 1. The amount of polyacrylamide added was 3 times the mass of sodium hydroxide. The product after the reaction was filtered, washed with deionized water, and dried at 120°C to obtain the precipitate.

[0038] (2) The obtained precipitate is placed in a tube furnace and heated and roasted in an air atmosphere. The heating and roasting treatment is carried out at a temperature of 500°C for 120 minutes to obtain the rare earth metal oxide Dy2O3 of this embodiment.

[0039] The scanning electron microscope image of the rare earth metal oxide Dy2O3 obtained in this embodiment is as follows: Figure 1 As shown, its XRD and XRF plots are as follows:Figure 2 As shown, the rare earth oxide Dy2O3 obtained in this embodiment is composed of a two-dimensional sheet structure with a diameter of 10-50 μm, and the purity of the corresponding rare earth oxide Dy2O3 is 99.96%.

[0040] The solution treated in this embodiment was tested by ICP-OES to calculate the rare earth ion recovery rate. The test results are as follows: Figure 7 As shown. By Figure 7 The results show that the recovery rate of Dy rare earth ions in this embodiment is 99.83%.

[0041] Example 2

[0042] This embodiment of a method for efficiently recovering rare earth oxide Eu2O3 from Eu-containing wastewater includes the following steps:

[0043] (1) A 6 mol / L sodium hydroxide solution and a polyacrylamide solution were sequentially added to a wastewater solution containing Eu rare earth elements (samples taken from actual production, containing EuCl3, oxalic acid, hydrochloric acid, P507, naphthenic acid, kerosene, isooctyl alcohol, etc.). 3+ The concentration was 86.9 mg / L, and the solution pH was < 0. The reaction was carried out under magnetic stirring at 30°C for 15 min until the pH of the solution was 1. The amount of polyacrylamide added was twice the mass of sodium hydroxide. The product after the reaction was filtered, washed with deionized water, and dried at 120°C to obtain the precipitate.

[0044] (2) The obtained precipitate is placed in a tube furnace and heated and roasted in an air atmosphere. The heating and roasting treatment is carried out at a temperature of 600°C for 90 minutes to obtain the rare earth metal oxide Eu2O3 of this embodiment.

[0045] The scanning electron microscope image of the rare earth metal oxide Eu2O3 obtained in this embodiment is as follows: Figure 3 As shown, its XRD and XRF plots are as follows: Figure 4 As shown, the rare earth oxide Eu2O3 obtained in this embodiment is composed of a two-dimensional sheet structure with a diameter of 10-50 μm, and the purity of the corresponding rare earth oxide Eu2O3 is 99.95%.

[0046] The solution treated in this embodiment was tested by ICP-OES to calculate the rare earth ion recovery rate. The test results are as follows: Figure 7 As shown. By Figure 7 The results show that the recovery rate of Eu rare earth ions in this embodiment is 99.99%.

[0047] Example 3

[0048] The method for efficiently recovering rare earth oxide Tb4O7 from Tb-containing rare earth wastewater comprises the following steps:

[0049] (1) 6 mol / L sodium hydroxide solution and polyacrylamide solution are sequentially added to the Tb-containing rare earth wastewater solution (sample taken from actual production, containing TbCl3, oxalic acid, hydrochloric acid, P507, naphthenic acid, kerosene, isooctanol and other components, Tb 3+ The concentration is 102.7 mg / L, the solution pH is less than 1, and the solution is magnetically stirred at 20°C for 30 min. The addition amount of polyacrylamide is 4 times the mass of sodium hydroxide. The product after reaction is filtered, washed with deionized water, and dried at 120°C to obtain a precipitate product.

[0050] (2) The obtained precipitate product is placed in a tube furnace and subjected to heating calcination treatment in an air atmosphere, the heating calcination treatment temperature is 700°C, and the time is 60 min, to obtain the rare earth metal oxide Tb4O7 of the embodiment.

[0051] The scanning electron microscope image of the rare earth metal oxide Tb4O7 obtained in the embodiment is shown in Figure 5 , and the XRD and XRF images are shown in Figure 6 . It can be seen that the rare earth oxide Tb4O7 obtained in the embodiment is composed of two-dimensional sheet structure with a diameter of 10-50 μm, and the purity of the corresponding rare earth oxide Tb4O7 is 99.90%.

[0052] The solution after treatment in the embodiment is tested by ICP-OES, and the rare earth ion recovery rate is calculated, and the test results are shown in Figure 7 . From the Figure 7 results, it can be seen that the recovery rate of Tb rare earth ions in the embodiment is 99.92%.

[0053] Examples 4-6

[0054] Examples 4-6 respectively compared with Examples 1-3, respectively using sodium carbonate solution instead of sodium hydroxide solution to adjust the pH of the solution to 3, and the rest of the parameters are the same.

[0055] The purity of the obtained rare earth oxides Dy2O3, Eu2O3 and Tb4O7 is 99.87%, 99.90% and 99.85%, respectively. The solution after treatment is tested by ICP-OES, and the rare earth ion recovery rate is calculated, and the results show that the recovery rates of Dy, Eu and Tb rare earth ions are 99.90%, 99.93% and 99.86%, respectively.

[0056] Examples 7-9

[0057] Compared with Examples 1 to 3, Examples 7 to 9 use ammonia solution instead of sodium hydroxide solution to adjust the pH of the solution to 5, while the other parameters are the same.

[0058] The purities of the obtained rare earth oxides Dy₂O₃, Eu₂O₃, and Tb₄O₇ were tested to be 99.91%, 99.82%, and 99.95%, respectively. The treated solution was analyzed by ICP-OES, and the rare earth ion recoveries were calculated. The results showed that the recoveries of Dy, Eu, and Tb rare earth ions were 99.78%, 99.81%, and 99.75%, respectively.

[0059] Comparative Examples 1-3

[0060] Comparative Examples 1-3 describe a method for recovering rare earth oxides from rare earth wastewater. Compared with Examples 1-3, the method does not involve the addition of polyacrylamide solution, but is otherwise identical.

[0061] The solutions treated with comparative examples 1-3 were tested by ICP-OES, and the rare earth ion recovery rate was calculated. The test results are as follows: Figure 8 As shown. By Figure 8 The results show that the recovery efficiencies of rare earth ions Dy, Eu, and Tb in Comparative Examples 1–3 were 95.72%, 95.83%, and 95.76%, respectively.

[0062] A comparison with the results of Examples 1-3 shows that the recovery rate of rare earth ions was significantly reduced when no polyacrylamide solution was added during the alkaline solution treatment.

[0063] By further adjusting the stepwise treatment of sodium hydroxide solution and polyacrylamide solution in Examples 1-3, an equal volume of sodium hydroxide solution was first added and stirred for 20 min, then filtered. The filtrate was then added again to an equal volume of polyacrylamide solution and stirred for 20 min, filtered again, and the precipitates were combined, washed with deionized water, and dried at 120°C to obtain the precipitates. The treated solutions were tested by ICP-OES, and the rare earth ion recovery rates were calculated. The recovery efficiencies for Dy, Eu, and Tb rare earth ions were 95.96%, 96.22%, and 96.15%, respectively.

[0064] The results above show that treating with sodium hydroxide solution and polyacrylamide solution in steps did not significantly improve the recovery rate of rare earth ions compared to treating with sodium hydroxide solution alone. This indicates that simultaneous treatment with alkaline solution and polyacrylamide solution is key to improving the recovery rate of rare earth ions.

[0065] Comparative Examples 4-6

[0066] The method for recovering rare earth oxides from rare earth wastewater of Comparative Examples 4-6 is compared with Examples 1-3 respectively, and no sodium hydroxide solution is added in the treatment process, and the pH of the solution is adjusted by adjusting the amount of polyacrylamide, and the rest is the same.

[0067] The solution treated by Comparative Examples 4-6 is tested by ICP-OES to calculate the recovery rate of rare earth ions, and the test results are shown in Table 2. Figure 9 Figure 9 It can be seen from the results that the recovery efficiency of Dy, Eu and Tb rare earth ions in Comparative Examples 4-6 is 55.67%, 52.79% and 53.68% respectively.

[0068] By comparing the results of Examples 1-3, it can be seen that the rare earth wastewater is treated by a single polyacrylamide solution, and it is difficult for rare earth ions to form flocculent suspended colloidal particles and precipitate under strong acidic conditions, and the recovery rate of rare earth ions is significantly reduced.

[0069] By further adjusting the step-by-step treatment of sodium hydroxide solution and polyacrylamide solution in Examples 1-3, i.e. adding the same amount of polyacrylamide solution and stirring for 20 minutes, filtering, then adding the same amount of sodium hydroxide solution to the filtrate and stirring for 20 minutes, filtering, and washing the precipitate with deionized water, drying at 120°C to obtain the precipitate. The solution treated is tested by ICP-OES to calculate the recovery rate of rare earth ions, and the recovery efficiency of Dy, Eu and Tb rare earth ions is 91.32%, 91.57% and 92.06% respectively.

[0070] From the above results, it can be seen that the recovery rate of rare earth ions is significantly improved by using polyacrylamide solution and sodium hydroxide solution for step-by-step treatment compared with single polyacrylamide solution treatment. However, compared with the recovery rate of rare earth ions in Examples 1-3 and Comparative Examples 1-3, the recovery rate of rare earth ions is significantly reduced. It is shown that the use of polyacrylamide solution for treatment has an adverse effect on the subsequent treatment of sodium hydroxide solution. It is further proved that the use of alkali solution and polyacrylamide solution for simultaneous treatment is the key to improving the recovery rate of rare earth ions.

[0071] The above examples are the preferred embodiments of the present application, but the embodiments of the present application are not limited by the above examples, and any changes, modifications, substitutions, combinations and simplifications made without departing from the spirit and principles of the present application shall be equivalent replacement methods, and all shall be within the scope of protection of the present application.​

Claims

1. A method for efficiently recovering rare earth oxides from rare earth waste water, characterized by, It comprises the following steps: (1) adding alkali solution and polyacrylamide solution into rare earth wastewater to stir and react, filtering the reacted solution, washing and drying the precipitate to obtain a precipitate product; (2) calcining the precipitate product obtained in step (1) in air atmosphere at a temperature of 400-900 ℃ to obtain a rare earth oxide material; The alkali solution is added in an amount to adjust the pH of the rare earth wastewater to 0.1-13; the polyacrylamide is added in an amount of 0.1-5 times the mass of the alkali; the rare earth wastewater refers to wastewater containing at least one kind of rare earth ion of Eu, Dy and Tb, and the concentration of the rare earth ion in the rare earth wastewater is 0.01-300 mg / L.

2. The method for efficiently recovering rare earth oxides from rare earth wastewater according to claim 1, characterized by, The alkali solution in step (1) refers to at least one of sodium hydroxide solution, potassium hydroxide solution, sodium carbonate solution, sodium bicarbonate solution, potassium carbonate solution, potassium bicarbonate solution and ammonia water.

3. The method for efficiently recovering rare earth oxides from rare earth wastewater according to claim 1, characterized by, The stirring reaction in step (1) refers to stirring and reacting at a temperature of 10-30 ℃ for 1-30 min.

4. The method for efficiently recovering rare earth oxides from rare earth wastewater according to claim 1, characterized by, The washing in step (1) refers to washing with deionized water, and the drying refers to drying at a temperature of 100-140 ℃.

5. The method for efficiently recovering rare earth oxides from rare earth wastewater according to claim 1, characterized by, The calcining in step (2) is performed for 5-500 min.

6. A rare earth oxide material, characterized by, The rare earth oxide material prepared by the method of any one of claims 1-5 has a two-dimensional sheet structure with a diameter of 10-50 μm, and the purity is >99%. The rare earth oxide material prepared by the method of any one of claims 1-5 has a two-dimensional sheet structure with a diameter of 10-50 μm, and the purity is >99%.

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