A high-value recycling method of rare earth oxalic acid precipitation wastewater

Abstract

The application provides a high-value recycling method of rare earth oxalate precipitation wastewater, and the method comprises the following steps: (1) under the condition of field strengthening, mixing the rare earth oxalate precipitation wastewater and an alkaline calcium salt, and obtaining a calcium oxalate precipitation and a calcium salt solution after neutralization reaction; (2) under the condition of field strengthening, mixing the rare earth chloride and the calcium oxalate precipitation, and obtaining a rare earth oxalate precipitation and a calcium chloride solution after displacement reaction; (3) mixing the rare earth sulfate, the calcium salt solution and the calcium chloride solution, and obtaining a calcium sulfate precipitation and a rare earth chloride solution after precipitation reaction. The method provided by the application not only realizes harmless treatment of the rare earth oxalate precipitation wastewater, but also realizes high-value recycling of the oxalic acid resources in the wastewater, and high-value building material calcium sulfate is prepared, waste is turned into treasure, cost is reduced and benefit is increased, and no salt-containing wastewater is discharged, so that the method is a new green and low-cost rare earth oxalate precipitation wastewater resource recycling technology, and promotes green and sustainable development of the rare earth industry.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of resource recycling of rare earth oxalate wastewater, and relates to a high-value recycling method of rare earth oxalate precipitation wastewater, in particular to a high-value recycling method of calcium salt precipitation-rare earth transformation of rare earth oxalate precipitation wastewater. BACKGROUND

[0002] High-purity rare earth oxides are irreplaceable key raw materials for high-tech industries such as national defense, military industry, and intelligent manufacturing, which are mainly prepared by high selectivity precipitation of oxalic acid molecules on rare earth ions, and at the same time, high-acidity rare earth oxalate precipitation wastewater is produced. The preparation of rare earth by selective precipitation of oxalic acid produces toxic and harmful rare earth oxalate precipitation wastewater, which hinders the high-value development and utilization of rare earth resources, so it is urgent to harmless treatment or resource recycling of rare earth oxalate precipitation wastewater.

[0003] According to the characteristics of rare earth oxalate precipitation wastewater, domestic and foreign scholars have carried out a lot of research on its harmless disposal and recycling, and a series of technologies such as neutralization method, extraction method, concentration distillation method, oxidation method, and direct reuse method have been developed. However, there is no industrialized technology that can realize the efficient recycling of oxalic acid resources in wastewater at present, and more is to treat wastewater for reduction and harmless discharge as the main target.

[0004] Among the current various treatment methods, concentration distillation method and electrolysis method (such as CN 112645413A) have the disadvantage of high treatment cost; neutralization method (such as CN 1524841A) and extraction method (such as CN 109252058A) will additionally produce a large amount of salt-containing wastewater; and direct reuse method cannot be continuously scaled up. Therefore, there is still a lack of effective methods for low-cost, zero-emission, and high-value recycling of oxalic acid in wastewater.

[0005] Under the background of ecological civilization construction, the rare earth industry urgently needs to develop new green and low-cost rare earth oxalate wastewater resource recycling technologies. SUMMARY

[0006] In view of the deficiencies of the prior art, the purpose of the present application is to provide a high-value recycling method of rare earth oxalate precipitation wastewater. The method provided by the present application not only realizes the harmless disposal of rare earth oxalate precipitation wastewater, but also realizes the high-value recycling of oxalic acid resources in wastewater, and at the same time, high-value building material calcium sulfate is prepared, which turns waste into treasure, reduces cost and increases efficiency, and does not discharge salt-containing wastewater. It is a green and low-cost new technology for recycling rare earth oxalate wastewater resources, which promotes the green and sustainable development of the rare earth industry.

[0007] To achieve this purpose, the present application adopts the following technical solutions:

[0008] The application provides a high-value recycling method of rare earth oxalate precipitation wastewater, and the high-value recycling method comprises the following steps:

[0009] (1) Under the condition of field strengthening, the mixed rare earth oxalate precipitation wastewater and alkaline calcium salt are neutralized to obtain calcium oxalate precipitation and calcium salt solution;

[0010] (2) Under the condition of field strengthening, the mixed chlorinated rare earth and the calcium oxalate precipitation obtained in step (1) are replaced to obtain rare earth oxalate precipitation and calcium chloride solution;

[0011] (3) The mixed rare earth sulfate, the calcium salt solution obtained in step (1) and the calcium chloride solution obtained in step (2) are precipitated to obtain calcium sulfate precipitation and chlorinated rare earth solution.

[0012] In the application, the low-cost alkaline calcium salt is used as a neutralizing precipitant, then the chlorinated rare earth is used for replacement transformation to obtain rare earth oxalate precipitation and calcium chloride solution, the obtained rare earth oxalate precipitation can be used for preparing high-purity rare earth oxide, the obtained calcium chloride solution is reacted with rare earth sulfate to prepare high-value-added building material calcium sulfate and chlorinated rare earth solution, and the obtained chlorinated rare earth can be used for replacement transformation with calcium oxalate precipitation to prepare rare earth oxalate.

[0013] The application realizes the efficient recycling of oxalic acid in wastewater by the method of “calcium salt precipitation-replacement transformation-replacement precipitation”, completes the additional utilization of calcium ions, not only achieves the harmless disposal purpose of wastewater, but also realizes the high-value recycling of oxalic acid resources in wastewater, and building material calcium sulfate is prepared, waste is turned into treasure, cost is reduced and benefit is increased, and no salt-containing wastewater is discharged, which promotes the green and sustainable development of the rare earth industry.

[0014] As a preferred technical scheme of the application, the field strengthening condition in step (1) and step (2) comprises any one of ultrasonic strengthening, microwave strengthening or magnetic field strengthening, and is preferably ultrasonic strengthening.

[0015] Preferably, the power of the ultrasonic strengthening is 300-1000 W, for example, can be 300 W, 400 W, 500 W, 600 W, 700 W, 800 W, 900 W or 1000 W, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0016] Preferably, the frequency of the ultrasonic strengthening is 25-60 kHz, for example, can be 25 kHz, 30 kHz, 40 kHz, 50 kHz or 60 kHz, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0017] During the process of generating solids through liquid-solid reactions, the precipitate generated by the reaction is easily adsorbed and wrapped on the surface of the solid reactant, thereby hindering the contact between the liquid reactant and the solid reactant, resulting in a low degree of reaction and reduced efficiency. Therefore, the present invention strengthens the vibration or diffusion of the solution components, making it difficult for the generated tiny solid particles to adsorb on the surface of the reaction solid particles. At the same time, it causes cracks in some dense solid reaction particles, promoting the penetration of the reaction liquid into the interior, promoting the reaction and improving efficiency.

[0018] In the present invention, the power of ultrasonic enhancement in the external field enhancement conditions is 300-1000W, and the frequency is 25-60kHz. If the intensity of the external field enhancement is too high, the growth of the generated solid particle nuclei will be restricted, thereby causing difficulties in subsequent solid-liquid separation and affecting the production process. Therefore, the selection of a reasonable external field enhancement intensity is also one of the important factors affecting the reaction.

[0019] As a preferred technical solution of the present invention, the components of the rare earth oxalic acid precipitation wastewater in step (1) include hydrochloric acid, oxalic acid, nitric acid and sulfuric acid.

[0020] Preferably, the oxalic acid content in the rare earth oxalic acid precipitation wastewater is 0.133 to 0.167 mol·L -1 , for example, it can be 0.133 mol·L -1 , 0.14 mol·L -1 , 0.15 mol·L -1 , 0.16 mol·L -1 or 0.167 mol·L -1 , but not limited to the listed values, other values ​​not listed within the numerical range are also applicable;

[0021] Preferably, the hydrochloric acid content in the rare earth oxalic acid precipitation wastewater is 1.5 to 2.0 mol·L -1 , for example, it can be 1.5 mol·L -1 , 1.6 mol·L -1 , 1.7 mol·L -1 , 1.8 mol·L -1 , 1.9 mol·L -1 or 2.0 mol·L -1 , but not limited to the listed values, other values ​​not listed within the numerical range are also applicable;

[0022] Preferably, the nitric acid content in the rare earth oxalate precipitation wastewater is 0 to 0.167 mol·L -1 , for example, it can be 0 mol·L -1 , 0.05mol·L -1 , 0.1 mol·L -1, 0.15 mol·L -1 or 0.167 mol·L -1 , but not limited to the listed values, other values ​​not listed within the numerical range are also applicable;

[0023] Preferably, the sulfuric acid content in the rare earth oxalic acid precipitation wastewater is 0 to 0.167 mol·L -1 , for example, it can be 0mo·L -1 , 0.05mol·L -1 , 0.1 mol·L -1 , 0.15 mol·L -1 or 0.167 mol·L -1 , but not limited to the listed values, other values ​​not listed within the numerical range are also applicable.

[0024] According to the different components in the rare earth oxalic acid precipitation wastewater, the calcium salt solution in step (1) includes calcium chloride solution, calcium sulfate solution and calcium nitrate solution.

[0025] Preferably, the alkaline calcium salt in step (1) comprises any one or a combination of at least two of calcium carbonate, calcium bicarbonate, calcium oxide or calcium hydroxide. Typical but non-limiting combinations include: a combination of calcium carbonate and calcium bicarbonate, a combination of calcium oxide and calcium hydroxide, or a combination of calcium carbonate, calcium bicarbonate, calcium oxide and calcium hydroxide.

[0026] It is worth noting that the alkaline calcium salt of the present invention can be a solid calcium salt or a calcium salt solution.

[0027] Preferably, the molar ratio of the solute to the alkaline calcium salt in the rare earth oxalic acid precipitation wastewater in step (1) is 1:0.9 to 1.7, for example, it can be 1:0.9, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6 or 1:1.7, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0028] Furthermore, the solute in the rare earth oxalic acid precipitation wastewater in step (1) of the present invention refers to the acid solution in the rare earth oxalic acid precipitation wastewater.

[0029] As a preferred technical solution of the present invention, the temperature of the neutralization reaction in step (1) is 25-40°C, for example, it can be 25°C, 30°C, 35°C or 40°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0030] Preferably, the time of the neutralization reaction in step (1) is ≥4h, for example, it can be 4h, 4.2h, 4.4h, 4.6h, 4.8h or 5h, etc., but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0031] Preferably, the stirring speed in the neutralization reaction in step (1) is 300-900r / min, for example, it can be 300r / min, 400r / min, 500r / min, 600r / min, 700r / min, 800r / min or 900r / min, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0032] Preferably, the reaction endpoint of the neutralization reaction in step (1) is that the acidity of the reaction solution is 0.063-0.1mol / L, for example, it can be 0.063mol / L, 0.07mol / L, 0.08mol / L, 0.09mol / L or 0.1mol / L, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0033] In the present application, the acidity of the reaction system at the end of the neutralization reaction in step (1) is 0.063-0.1mol / L (i.e. pH=1-2). If the pH value of the reaction system at the end of the reaction is too high, the solution will be alkaline, thereby causing the rare earth hydroxide to be contained in the rare earth oxalate precipitate obtained in step (2), introducing impurities, and further increasing the difficulty of filtration. If the pH value is too small, the oxalic acid reaction will not be complete, and residual oxalic acid will be left in the wastewater, causing environmental pollution.

[0034] As a preferred technical solution of the present application, the rare earth chloride in step (2) includes any one or a combination of at least two of lanthanum chloride, yttrium chloride or neodymium chloride, for example, it can be a combination of lanthanum chloride and yttrium chloride, a combination of lanthanum chloride and neodymium chloride, a combination of yttrium chloride and neodymium chloride, or a combination of lanthanum chloride, yttrium chloride and neodymium chloride.

[0035] It is worth noting that the rare earth chloride in the present application can be solid rare earth chloride or a rare earth chloride solution.

[0036] Preferably, the molar ratio of the calcium oxalate precipitate to the rare earth chloride in step (2) is 1:1-1.3, for example, it can be 1:1, 1:1.4, 1:1.9, 1:2.3, 1:2.7 or 1:3, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0037] As a preferred technical solution of the present application, the temperature of the displacement reaction in step (2) is 70-90℃, for example, it can be 70℃, 74℃, 78℃, 82℃, 86℃ or 90℃, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0038] Preferably, the time of the displacement reaction in step (2) is 2-4h, for example, it can be 2h, 2.4h, 2.8h, 3.2h, 3.6h or 4h, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0039] Preferably, the stirring speed in the displacement reaction in step (2) is 300-900r / min, for example, it can be 300r / min, 400r / min, 500r / min, 600r / min, 700r / min, 800r / min or 900r / min, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0040] Preferably, the end point of the displacement reaction in step (2) is that the pH value of the reaction solution is 1-3, for example, it can be 1, 1.4, 1.8, 2.2, 2.6 or 3, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0041] As a preferred technical solution of the present application, the rare earth sulfate in step (3) includes any one or a combination of at least two of lanthanum sulfate, yttrium sulfate or neodymium sulfate, and typical but non-limiting combinations include: a combination of lanthanum sulfate and yttrium sulfate, a combination of lanthanum sulfate and neodymium sulfate, a combination of yttrium sulfate and neodymium sulfate, or a combination of lanthanum sulfate, yttrium sulfate and neodymium sulfate.

[0042] It is worth noting that the rare earth sulfate of the present application can be a solid rare earth sulfate or a rare earth sulfate solution.

[0043] Preferably, the molar ratio of calcium ions to rare earth sulfate in the calcium salt solution and the calcium chloride solution is 1:1-1.3, for example, it can be 1:1, 1:1.04, 1:1.08, 1:1.12, 1:1.16, 1:1.2, 1:1.24, 1:1.28 or 1:1.3, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0044] As a preferred technical solution of the present application, the temperature of the precipitation reaction in step (3) is 20-50℃, for example, it can be 20℃, 25℃, 30℃, 35℃, 40℃, 45℃ or 50℃, but is not limited to the listed values, and other values not listed in the value range are also applicable.

[0045] In the present application, the temperature of the precipitation reaction in step (3) is 20-50℃. If the temperature is higher than 50℃, the nucleation rate increases rapidly, and there is not enough solute and time to ensure the growth of calcium sulfate crystal particles, so that the calcium sulfate precipitation particle size is too small, which is difficult to filter, resulting in difficult solid-liquid separation. If the temperature is too low, the precipitation reaction time is too long, which reduces the production efficiency and increases the cost. The suitable temperature (20-50℃) can not only increase the reaction rate and appropriately shorten the precipitation reaction time, but also ensure the growth of crystal particles for a sufficient time, which is beneficial to solid-liquid separation and ensures the production efficiency.

[0046] Preferably, the precipitation reaction in step (3) is performed for 2-8h, for example, 2h, 3h, 4h, 5h, 6h, 7h or 8h, but not limited to the listed values, and other values not listed in the value range are also applicable.

[0047] Preferably, the stirring speed in the precipitation reaction in step (3) is 300-900r / min, for example, 300r / min, 400r / min, 500r / min, 600r / min, 700r / min, 800r / min or 900r / min, but not limited to the listed values, and other values not listed in the value range are also applicable.

[0048] Preferably, the end point of the precipitation reaction in step (3) is that the pH value of the reaction solution is 1-4, for example, 1, 1.5, 2, 2.5, 3, 3.5 or 4, but not limited to the listed values, and other values not listed in the value range are also applicable.

[0049] As a preferred technical solution of the present application, the method further comprises drying the oxalate rare earth precipitate in step (1).

[0050] As a preferred technical solution of the present application, the present application provides a high-value recycling method of rare earth oxalate precipitate wastewater, which comprises the following steps:

[0051] (1) Under the condition of external field strengthening, mixing the rare earth oxalate precipitate wastewater and the alkaline calcium salt, and obtaining calcium oxalate precipitate and calcium salt solution after neutralization reaction;

[0052] The molar ratio of solute in the rare earth oxalate precipitate wastewater to the alkaline calcium salt is 1:0.9-1.7;

[0053] The temperature of the neutralization reaction is 25-40℃, the time is ≥4h, and the stirring speed is 300-900r / min; the end point of the reaction is that the acidity of the reaction solution is 0.063-0.1mol / L;

[0054] (2) under the condition of external field strengthening, the mixed chlorinated rare earth and the calcium oxalate precipitate obtained in step (1) are replaced to obtain a rare earth oxalate precipitate and a calcium chloride solution after the replacement reaction;

[0055] The molar ratio of the calcium oxalate precipitate and the chlorinated rare earth is 1:1-1.3;

[0056] The temperature of the replacement reaction is 70-90℃, the time is 2-4h, and the stirring speed is 300-900r / min; the reaction end point is that the pH value of the reaction solution is 1-3;

[0057] (3) the mixed rare earth sulfate, the calcium salt solution obtained in step (1) and the calcium chloride solution obtained in step (2) are precipitated to obtain a calcium sulfate precipitate and a chlorinated rare earth solution after the precipitation reaction;

[0058] The molar ratio of the calcium ion in the calcium salt solution and the calcium chloride solution to the rare earth sulfate is 1:1-1.3;

[0059] The temperature of the precipitation reaction is 20-50℃, the time is 2-8h, and the stirring speed is 300-900r / min; the reaction end point is that the pH value of the reaction solution is 1-4.

[0060] The numerical range in the application not only includes the point values exemplified above, but also includes any point values between the above numerical ranges which are not exemplified, and the specific point values included in the range are not listed again in the application for the sake of brevity and simplicity.

[0061] Compared with the prior art, the application has the following beneficial effects:

[0062] (1) The method provided by the application not only achieves the harmless disposal purpose of rare earth oxalate wastewater, but also realizes the high-value recycling of oxalic acid resources in the wastewater, and building material calcium sulfate is prepared, waste is turned into treasure, cost is reduced and benefit is increased, no salt-containing wastewater is discharged, it is green and pollution-free, and the ecological and sustainable development of the rare earth separation industry is promoted;

[0063] (2) The application avoids the wrapping of calcium oxalate on the solid particles of the alkaline calcium salt through the external field strengthening effect, and improves the utilization rate of the alkaline calcium salt;

[0064] (3) The application blocks the wrapping of the newly generated rare earth oxalate precipitate on the calcium oxalate through the external field strengthening effect, so that the calcium oxalate is fully reacted with the chlorinated rare earth, and the utilization rate of oxalic acid is improved;

[0065] (4) The method provided by the application does not produce high-salt wastewater, has the characteristics of zero emission, can prepare building material calcium sulfate, and can also obtain a rare earth oxalate precipitate which can be used to prepare high-purity rare earth oxides. BRIEF DESCRIPTION OF DRAWINGS

[0066] Figure 1 A process flow chart of the high-value recycling method of rare earth oxalate precipitation wastewater is provided for Embodiment 1 of the present application. DETAILED DESCRIPTION

[0067] The technical solutions of the present application are further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments are only to help understand the present application and should not be regarded as specific limitations on the present application.

[0068] Embodiment 1

[0069] The present embodiment provides a high-value recycling method of rare earth oxalate precipitation wastewater, as shown in the formula (I): Figure 1 The high-value recycling method comprises the following steps:

[0070] (1) Under the condition of 600W, 45kHz ultrasonic wave intensification, mix the rare earth oxalate precipitation wastewater and calcium oxide, and obtain calcium oxalate precipitation and calcium salt solution after neutralization reaction;

[0071] The molar ratio of solute in the rare earth oxalate precipitation wastewater to calcium oxide is 1:1.4; the concentration of hydrochloric acid in the rare earth oxalate precipitation wastewater is 55g / L, and the concentration of oxalic acid is 13g / L;

[0072] The temperature of the neutralization reaction is 30℃, the time is 5h, and the stirring speed is 600r / min; the reaction end point is that the pH value of the reaction solution is 1.1;

[0073] (2) Under the condition of 500W, 50kHz ultrasonic wave intensification, mix 394.2g / L lanthanum chloride solution and the calcium oxalate precipitation obtained in step (1), and obtain rare earth oxalate precipitation and calcium chloride solution after displacement reaction;

[0074] The molar ratio of the calcium oxalate precipitation to the rare earth chloride is 1:1.2;

[0075] The temperature of the displacement reaction is 80℃, the time is 3h, and the stirring speed is 300r / min; the reaction end point is that the pH value of the reaction solution is 2;

[0076] (3) Mix the lanthanum sulfate solution with a concentration of 16.1g / L, the calcium salt solution obtained in step (1), and the calcium chloride solution obtained in step (2), and obtain calcium sulfate precipitation and rare earth chloride solution after precipitation reaction;

[0077] The molar ratio of calcium ions in the calcium salt solution and the calcium chloride solution to rare earth sulfate is 1:1.2;

[0078] The temperature of the precipitation reaction is 30℃, the time is 5h, and the stirring speed is 500r / min; the reaction end point is that the pH value of the reaction solution is 2.

[0079] Example 2

[0080] The embodiment provides a high-value recycling method of rare earth oxalate precipitation wastewater, and the high-value recycling method comprises the following steps:

[0081] (1) Under the condition of magnetic field strengthening, the rare earth oxalate precipitation wastewater and calcium carbonate are mixed, and after neutralization reaction, calcium oxalate precipitation and calcium salt solution are obtained;

[0082] The molar ratio of solute in the rare earth oxalate precipitation wastewater to calcium carbonate is 1:0.9;

[0083] The temperature of the neutralization reaction is 25 DEG C, the time is 8h, and the stirring speed is 300r / min; the reaction end point is that the pH value of the reaction solution is 1;

[0084] (2) Under the condition of 300W, 60kHz ultrasonic wave strengthening, the yttrium chloride solution and the calcium oxalate precipitation obtained in the step (1) are mixed, and after displacement reaction, rare earth oxalate precipitation and calcium chloride solution are obtained;

[0085] The molar ratio of the calcium oxalate precipitation to the rare earth chloride is 1:1;

[0086] The temperature of the displacement reaction is 70 DEG C, the time is 4h, and the stirring speed is 400r / min; the reaction end point is that the pH value of the reaction solution is 1;

[0087] (3) The yttrium sulfate solution, the calcium salt solution obtained in the step (1) and the calcium chloride solution obtained in the step (2) are mixed, and after precipitation reaction, calcium sulfate precipitation and rare earth chloride solution are obtained;

[0088] The molar ratio of calcium ions in the calcium salt solution and the calcium chloride solution to rare earth sulfate is 1:1;

[0089] The temperature of the precipitation reaction is 20 DEG C, the time is 8h, and the stirring speed is 300r / min; the reaction end point is that the pH value of the reaction solution is 1.

[0090] Example 3

[0091] The embodiment provides a high-value recycling method of rare earth oxalate precipitation wastewater, and the high-value recycling method comprises the following steps:

[0092] (1) Under the condition of 1000W, 25kHz ultrasonic wave strengthening, the rare earth oxalate precipitation wastewater and calcium hydroxide are mixed, and after neutralization reaction, calcium oxalate precipitation and calcium salt solution are obtained;

[0093] The molar ratio of solute in the rare earth oxalate precipitation wastewater to calcium hydroxide is 1:1.7;

[0094] The temperature of the neutralization reaction is 40 DEG C, the time is 4h, and the stirring speed is 900r / min; the reaction end point is that the pH value of the reaction solution is 2;

[0095] (2) Under the microwave intensification condition, the mixed neodymium trichloride and the calcium oxalate precipitate obtained in step (1) are subjected to displacement reaction, and the rare earth oxalate precipitate and the calcium chloride solution are obtained after the displacement reaction;

[0096] The molar ratio of the calcium oxalate precipitate to the rare earth chloride is 1:1.3;

[0097] The temperature of the displacement reaction is 90 DEG C, the time is 2h, and the stirring speed is 900r / min; the reaction end point is that the pH value of the reaction solution is 3;

[0098] (3) The mixed neodymium sulfate, the calcium salt solution obtained in step (1) and the calcium chloride solution obtained in step (2) are subjected to precipitation reaction, and the calcium sulfate precipitate and the rare earth chloride solution are obtained after the precipitation reaction;

[0099] The molar ratio of the calcium ion in the calcium salt solution and the calcium chloride solution to the rare earth sulfate is 1:1.3;

[0100] The temperature of the precipitation reaction is 50 DEG C, the time is 2h, and the stirring speed is 700r / min; the reaction end point is that the pH value of the reaction solution is 4.

[0101] Example 4

[0102] The difference between the high-value recycling method of the rare earth oxalate precipitate wastewater and the example 1 is only that:

[0103] The reaction end point of the neutralization reaction in step (1) is adjusted to pH value 3.5.

[0104] Example 5

[0105] The difference between the high-value recycling method of the rare earth oxalate precipitate wastewater and the example 1 is only that:

[0106] The temperature of the precipitation reaction in step (3) is adjusted to 60 DEG C.

[0107] Example 6

[0108] The difference between the high-value recycling method of the rare earth oxalate precipitate wastewater and the example 1 is only that:

[0109] The power of the ultrasonic intensification in step (1) is adjusted to 1200W, and the frequency is adjusted to 20kHz.

[0110] Example 7

[0111] The embodiment provides a high-value recycling method of rare earth oxalate precipitation wastewater, and the high-value recycling method is different from that of the embodiment 1 only in that:

[0112] In the embodiment, the power of the ultrasonic intensification in the step (1) is adjusted to 200 W, and the frequency is adjusted to 70 kHz.

[0113] Embodiment 8

[0114] The embodiment provides a high-value recycling method of rare earth oxalate precipitation wastewater, and the high-value recycling method is different from that of the embodiment 1 only in that:

[0115] In the embodiment, the power of the ultrasonic intensification in the step (2) is adjusted to 1200 W, and the frequency is adjusted to 20 kHz.

[0116] Embodiment 9

[0117] The embodiment provides a high-value recycling method of rare earth oxalate precipitation wastewater, and the high-value recycling method is different from that of the embodiment 1 only in that:

[0118] In the embodiment, the power of the ultrasonic intensification in the step (2) is adjusted to 200 W, and the frequency is adjusted to 70 kHz.

[0119] Embodiment 10

[0120] The embodiment provides a high-value recycling method of rare earth oxalate precipitation wastewater, and the high-value recycling method is different from that of the embodiment 1 only in that:

[0121] In the embodiment, the ultrasonic intensification in the step (1) and the step (2) is adjusted to microwave intensification.

[0122] Embodiment 11

[0123] The embodiment provides a high-value recycling method of rare earth oxalate precipitation wastewater, and the high-value recycling method is different from that of the embodiment 1 only in that:

[0124] In the embodiment, the ultrasonic intensification in the step (1) and the step (2) is adjusted to magnetic field intensification.

[0125] Comparative example 1

[0126] The comparative example provides a high-value recycling method of rare earth oxalate precipitation wastewater, and the high-value recycling method is different from that of the embodiment 1 only in that:

[0127] In the comparative example, the ultrasonic intensification in the step (1) is omitted.

[0128] Comparative example 2

[0129] The comparative example provides a high-value recycling method of rare earth oxalate precipitation wastewater, which is only different from example 1 in that:

[0130] The comparative example omits the ultrasonic strengthening in step (2).

[0131] Comparative example 3

[0132] The comparative example provides a high-value recycling method of rare earth oxalate precipitation wastewater, which is only different from example 1 in that:

[0133] The comparative example adjusts the chlorinated rare earth in step (2) to nitric acid rare earth, specifically lanthanum nitrate solution.

[0134] The conversion rates of calcium oxalate precipitation, rare earth oxalate precipitation and calcium sulfate precipitation produced during the operation of the method provided in the above examples and comparative examples are detected and calculated, and the results are shown in Table 1.

[0135] Table 1

[0136] Calcium oxalate conversion rate / % Rare earth oxalate conversion rate / % Calcium sulfate conversion rate / % Example 1 99.2 98.5 95.3 Example 2 98.8 97.8 94.2 Example 3 99.0 98.2 94.8 Example 4 95.6 97.2 93.5 Example 5 99.0 98.4 88.6 Example 6 92.3 96.6 90.5 Example 7 91.8 98.0 91.8 Example 8 98.4 92.7 92.6 Example 9 98.2 91.1 90.8 Example 10 92.0 92.3 89.0 Example 11 91.8 91.5 88.5 Comparative Example 1 85.0 88.0 81.6 Comparative Example 2 95.1 84.5 82.5 Comparative Example 3 90.0 92.0 85.0

[0137] According to Table 1, the following points can be known:

[0138] (1) According to the comprehensive analysis of examples 1-3, the high-value recycling method provided by the application can prepare building material calcium sulfate and rare earth oxalate precipitation for preparing high-purity rare earth oxides, and no high-salt wastewater is produced during the reaction process, realizing the high-value recycling of oxalic acid resources in wastewater; and the method provided by the application can further improve the recovery rate and utilization rate of oxalic acid;

[0139] (2) According to the comprehensive analysis of example 1 and examples 4-5, the reaction conditions provided in steps (1)-(3) in the method provided by the application will affect the reaction process;

[0140] When the reaction endpoint pH value of the neutralization reaction in step (1) is too high, the solution will be alkaline, which will cause the rare earth hydroxide in the rare earth oxalate obtained in step (2), introduce impurities, and increase the filtration difficulty;

[0141] When the temperature of the precipitation reaction in step (3) is too high, the calcium sulfate particles will be too fine, the filtration speed will be slow, and the energy consumption will be increased;

[0142] (3) According to the comprehensive analysis of examples 1, examples 6-9 and comparative examples 1-2, external field strengthening is one of the important factors affecting the reaction process;

[0143] More specifically, when the external field strengthening intensity is too low (or the external field strengthening is omitted) in step (1), the vibration or convection degree is not enough, the coating shell cannot be broken, and the reaction efficiency cannot be improved; when the intensity is too high, the energy consumption increases, and the production cost increases.

[0144] When the external field strengthening intensity is too low (or the external field strengthening is omitted) in step (2), the vibration or convection degree is not enough, the coating shell cannot be broken, and the reaction efficiency cannot be improved; when the intensity is too high, the energy consumption increases, and the production cost increases.

[0145] In summary, the method provided by the application not only realizes harmless treatment of rare earth oxalic acid precipitation wastewater, but also realizes high-value recycling of oxalic acid resources in the wastewater, and high-value building material calcium sulfate is prepared, waste is turned into treasure, cost is reduced and benefit is increased, and no salt-containing wastewater is discharged, which is a new green and low-cost rare earth oxalic acid precipitation wastewater resource recycling technology, and promotes the green and sustainable development of the rare earth industry.

[0146] The applicant declares that the above is only a specific embodiment of the application, but the protection scope of the application is not limited thereto, and those skilled in the art should understand that any changes or replacements within the technical scope disclosed by the application can be easily thought of by those skilled in the art, and all fall within the protection scope and disclosure scope of the application.

Claims

1. A method for high-value recycling of rare earth oxalate precipitation wastewater, characterized in that, The high-value recycling method comprises the following steps: (1) Under the condition of external field strengthening, mixed rare earth oxalate precipitation wastewater and alkaline calcium salt, and obtained calcium oxalate precipitation and calcium salt solution after neutralization reaction; (2) Under the condition of external field strengthening, mixed chlorinated rare earth and the calcium oxalate precipitation obtained in step (1), and obtained rare earth oxalate precipitation and calcium chloride solution after displacement reaction; (3) Mixed rare earth sulfate, calcium salt solution obtained in step (1) and calcium chloride solution obtained in step (2), and obtained calcium sulfate precipitation and chlorinated rare earth solution after precipitation reaction; The external field strengthening condition in step (1) and step (2) comprises any one of ultrasonic strengthening, microwave strengthening or magnetic field strengthening.

2. The high-value recycling method according to claim 1, characterized by, The external field strengthening condition in step (1) and step (2) is ultrasonic strengthening; The power of ultrasonic strengthening is 300-1000W; The frequency of ultrasonic strengthening is 25-60kHz.

3. The high-value recycling method according to claim 1, characterized by, The composition of rare earth oxalate precipitation wastewater in step (1) comprises hydrochloric acid, oxalic acid, nitric acid and sulfuric acid; The alkaline calcium salt in step (1) comprises any one or combination of at least two of calcium carbonate, calcium bicarbonate, calcium oxide or calcium hydroxide; The molar ratio of solute in rare earth oxalate precipitation wastewater to alkaline calcium salt in step (1) is 1:0.9-1.

7.

4. The high-value recycling method according to claim 1, characterized by, The temperature of neutralization reaction in step (1) is 25-40℃; The time of neutralization reaction in step (1) is ≥4h; The stirring speed in neutralization reaction in step (1) is 300-900r / min; The reaction end point of neutralization reaction in step (1) is that the acidity of reaction solution is 0.063-0.1mol / L.

5. The high-value recycling method according to claim 1, characterized by, The chlorinated rare earth in step (2) comprises any one or combination of at least two of lanthanum chloride, yttrium chloride or neodymium chloride; The molar ratio of calcium oxalate precipitation to chlorinated rare earth in step (2) is 1:1-1.

3.

6. The high-value recycling method according to claim 1, characterized by, The temperature of displacement reaction in step (2) is 70-90℃; The time of displacement reaction in step (2) is 2-4h; The stirring speed in displacement reaction in step (2) is 300-900r / min; The reaction end point of displacement reaction in step (2) is that the pH value of reaction solution is 1-3.

7. The high-value recycling method according to claim 1, characterized by, The rare earth sulfate in step (3) comprises any one or combination of at least two of lanthanum sulfate, yttrium sulfate or neodymium sulfate; The molar ratio of calcium ion in calcium salt solution and calcium chloride solution to rare earth sulfate is 1:1-1.

3.

8. The high-value recycling method according to claim 1, characterized by, The temperature of precipitation reaction in step (3) is 20-50℃; The time of precipitation reaction in step (3) is 2-8h; The stirring speed in precipitation reaction in step (3) is 300-900r / min; The reaction end point of precipitation reaction in step (3) is that the pH value of reaction solution is 1-4.

9. The high-value recycling method according to claim 1, characterized by, The method further comprises drying treatment on the rare earth oxalate precipitation in step (1).

10. The high-value recycling method according to claim 1, characterized by, The high-value recycling method comprises the following steps: (1) Under the condition of external field strengthening, mixed rare earth oxalate precipitation wastewater and alkaline calcium salt, and obtained calcium oxalate precipitation and calcium salt solution after neutralization reaction; The molar ratio of solute in rare earth oxalate precipitation wastewater to alkaline calcium salt is 1:0.9-1.7; The temperature of the neutralization reaction is 25-40℃, the time is ≥4h, the stirring speed is 300-900r / min; the reaction end point is: the acidity of the reaction solution is 0.063-0.1mol / L; (2) Under the condition of field strengthening, the mixed rare earth chloride and the calcium oxalate precipitate obtained in step (1) are mixed, and after displacement reaction, a rare earth oxalate precipitate and a calcium chloride solution are obtained; The molar ratio of the calcium oxalate precipitate and the rare earth chloride is 1:1-1.3; The temperature of the displacement reaction is 70-90℃, the time is 2-4h, the stirring speed is 300-900r / min; the reaction end point is: the pH value of the reaction solution is 1-3; (3) The rare earth sulfate, the calcium salt solution obtained in step (1) and the calcium chloride solution obtained in step (2) are mixed, and after precipitation reaction, a calcium sulfate precipitate and a rare earth chloride solution are obtained; The molar ratio of calcium ions in the calcium salt solution and the calcium chloride solution to the rare earth sulfate is 1:1-1.3; The temperature of the precipitation reaction is 20-50℃, the time is 2-8h, the stirring speed is 300-900r / min; the reaction end point is: the pH value of the reaction solution is 1-4.

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