Method for continuous in-situ removal of impurities from neodymium iron boron waste hydrochloric acid optimum solution and application

Abstract

The application provides a method for continuously removing impurities in a neodymium-iron-boron waste hydrochloric acid optimum solution in situ and application thereof, and the method comprises the following steps: adding the oxidized hydrochloric acid optimum solution into an overflow reactor, controlling the adding speed to make the oxidized hydrochloric acid optimum solution mix with the bottom liquid in the overflow reactor, adjusting the pH of the mixed solution of the hydrochloric acid optimum solution and the bottom liquid in the overflow reactor to a set value by using a neutralizing agent, so that the content of free iron ions in the mixed solution is lower than a set concentration, thereby obtaining a neutralized solution, and the obtained neutralized solution is aged to obtain a rare earth solution from which impurity elements are removed. The method realizes the hydrolysis and co-precipitation of iron and aluminum elements, and realizes the in-situ adsorption of impurity elements such as fluorine and boron by using the strong adsorption capacity of the hydrolysis product to fluorine and boron, thereby realizing the efficient removal of impurities such as iron, aluminum, fluorine and boron in the hydrochloric acid optimum solution. The method also reduces the entrainment loss of rare earth elements in the process of removing impurity elements, and improves the filtration performance of the impurity removal residue.

Description

Technical Field

[0001] This invention belongs to the field of rare earth secondary resource technology, and relates to a method and application for continuous in-situ removal of impurities from NdFeB waste hydrochloric acid solution. Background Technology

[0002] Neodymium iron boron (NdFeB) waste is an important secondary resource in the rare earth resource recycling process, characterized by its wide range of sources, diverse types, and complex composition. In response to the ever-increasing demand for rare earth resources, recovering rare earth elements from NdFeB waste can effectively alleviate the persistent structural contradictions in the supply side of rare earth resources. NdFeB waste contains 20-30% rare earth elements (mainly including Pr, Nd, Tb, and Dy). In my country alone, the amount of waste generated during processing and that reaches the end of its service life is approximately 200,000 tons annually, and this figure continues to increase.

[0003] Currently, the oxidative roasting-hydrochloric acid preferential dissolution process is the mainstream technology for recycling NdFeB waste. After oxidative roasting, rare earth elements and iron in the NdFeB waste are oxidized into their corresponding oxides. Based on the pH-dependent solubility characteristics of different oxides, the roasted products are added to hydrochloric acid for preferential dissolution, allowing rare earth oxides to preferentially dissolve and leach into the solution. During this process, some iron is released as Fe. 2+ Fe 3+ The rare earth elements are introduced into the leachate in the form of oxidants. Iron impurities are removed by adding oxidants and adjusting the pH. The purified rare earth solution is then extracted, precipitated, and calcined to produce rare earth oxides. However, the process of removing impurities has several drawbacks: poor filtration performance of the residue, high water content, and a large loss rate of rare earth elements (approximately 1% of rare earth elements enter the residue); incomplete removal (currently only iron impurities in the leachate are treated, while aluminum is not), which seriously affects the production efficiency of subsequent processes and the quality of rare earth products; and the leaching-removal process is intermittent, resulting in low production efficiency and low automation, which is not conducive to large-scale industrial production.

[0004] CN108559845A discloses a method for removing iron and organic matter from NdFeB waste using a room-temperature wet ultrasonic-ozone oxidation process. The steps are as follows: NdFeB waste is mixed with acid under stirring, and the pH of the solution is adjusted to 4.0–4.5; the pH is controlled between 4.8 and 5.3, and organic matter in the solution is removed by ultrasonic ozone aeration oxidation, converting ferrous ions to ferric ions; the pH is further adjusted to allow the ferric ions to hydrolyze and precipitate, and after solid-liquid separation, ferric hydroxide filter residue and a purified rare earth solution are obtained. This method directly mixes and dissolves NdFeB waste with acid, requiring a large amount of acid and generating hydrogen gas that is prone to combustion and explosion, posing a high risk. Room-temperature aeration oxidation is inefficient and unsuitable for large-scale industrial production; furthermore, the high pH of the solution during the process causes rare earth elements to precipitate into the residue, resulting in rare earth element loss.

[0005] CN116083723A discloses a method for separating and recovering rare earth elements and iron from NdFeB waste. This method involves crushing the NdFeB waste and then leaching it with phosphoric acid solution, utilizing the difference in solubility products between rare earth elements and ferrous elements. The rare earth elements combine with phosphate ions to form precipitates that remain in the residue, while the iron dissolves in the phosphoric acid solution as ferrous ions, thus achieving the separation of rare earth elements and iron. However, this method requires a large amount of phosphoric acid as a leaching agent (precipitant), and phosphoric acid reagents are expensive, resulting in high costs for subsequent treatment of phosphorus-containing wastewater. Therefore, it is not suitable for large-scale industrial production.

[0006] CN116004988A discloses a method for removing ferrous ions from NdFeB waste recovery liquid. This method involves adding calcium magnesium carbonate as a removal agent to the NdFeB waste recovery liquid, followed by solid-liquid separation to obtain a filter residue containing ferric hydroxide and calcium magnesium carbonate, as well as a purified rare earth solution. However, at high temperatures, the added calcium magnesium carbonate can cause localized over-alkaliness, resulting in significant losses of rare earth elements; while at low temperatures, the removal efficiency of this method decreases significantly. Furthermore, the synthesis cost of calcium magnesium carbonate is high, making it unsuitable for large-scale industrial applications.

[0007] Currently available methods for removing impurities from rare earth waste recovery solutions all have certain drawbacks. These include difficulty in simultaneously and efficiently removing impurities such as iron, aluminum, fluorine, and boron; high rare earth element loss rates; poor filtration performance of the residue; and complex operation that hinders large-scale industrial production. Therefore, developing a novel method for removing impurities from hydrochloric acid solutions is crucial. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention aims to provide a method and application for continuous in-situ removal of impurities from NdFeB waste hydrochloric acid solutions. This method achieves the hydrolysis and co-precipitation of iron and aluminum, and utilizes the strong adsorption capacity of the hydrolysis products for impurities such as fluorine and boron. By controlling the morphology and structure of the hydrolysis products, in-situ adsorption of impurities such as fluorine and boron is achieved, thereby realizing the efficient removal of impurities such as iron, aluminum, fluorine, and boron from hydrochloric acid solutions. The method also improves the filtration performance of the impurity removal residue and reduces the entrainment loss of rare earth elements during the impurity removal process. Furthermore, the method has the advantage of simple operation and is suitable for large-scale industrial production.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a method for continuous in-situ removal of impurities from NdFeB waste hydrochloric acid solution, the method comprising:

[0011] The oxidized hydrochloric acid solution is added to the overflow reactor, and the addition rate is controlled to mix the oxidized hydrochloric acid solution with the bottom liquid in the overflow reactor. The pH of the mixed solution of hydrochloric acid solution and bottom liquid in the overflow reactor is adjusted to a set value using a neutralizing agent, so that the free iron ion content in the mixed solution is lower than the set concentration, thereby obtaining a neutralized solution. The obtained neutralized solution is then aged to obtain a rare earth solution with impurity elements removed.

[0012] The method provided by this invention achieves co-precipitation of iron and aluminum through hydrolysis by controlling the content of free iron ions in the mixed solution and adjusting the pH of the mixed solution to a set value. The hydrolysis products have a strong adsorption capacity for impurity elements such as fluorine and boron, realizing in-situ adsorption of impurity elements. This achieves efficient removal of impurities such as iron, aluminum, fluorine, and boron from hydrochloric acid solutions, with removal rates of over 99%, 90%, 50%, and 75% for iron, aluminum, fluorine, and boron, respectively. The method also improves the filtration performance of the impurity removal slag, reduces the entrainment loss of rare earth elements during the removal of impurity elements, and lowers the rare earth content in the slag to below 0.20%, achieving efficient recovery of rare earth elements. In addition, the method has the advantages of simple operation, fewer process steps, and low cost of removing impurity elements, making it suitable for large-scale industrial production.

[0013] In this invention, by removing impurity elements from the oxidized hydrochloric acid solution in the overflow reactor, the continuous feeding of the oxidized hydrochloric acid solution is achieved, ensuring the continuous operation of the method and thus realizing the continuous and automated removal of impurity elements.

[0014] In the method provided in this invention, the impurity residue is a solid obtained by solid-liquid separation after aging the neutralized solution; the filtration performance of the impurity residue is examined by a positive pressure filter, and its filtration performance is examined by calculating the ratio of the volume of the filtered liquid to the filtration time under constant pressure conditions; generally, the faster the average filtration speed, the better the filtration performance of the impurity residue.

[0015] Preferably, the method for preparing the oxidized hydrochloric acid solution includes: mixing the hydrochloric acid solution with an oxidizing agent.

[0016] Preferably, the hydrochloric acid solution comprises a solution obtained by leaching NdFeB waste oxidized roasting residue with hydrochloric acid.

[0017] Preferably, the oxidant includes any one or a combination of at least two of chlorate, hypochlorite, persulfate, or hydrogen peroxide. Typical but non-limiting combinations include combinations of chlorate and hypochlorite, hypochlorite and persulfate, persulfate and hydrogen peroxide, chlorate, hypochlorite and persulfate, or chlorate, hypochlorite, persulfate and hydrogen peroxide, preferably sodium chlorate.

[0018] Preferably, the amount of oxidant used in the mixture is 1 to 1.5 times the theoretically calculated amount of oxidant used to oxidize all ferrous ions in the hydrochloric acid solution to ferric ions. For example, it can be 1, 1.1, 1.2, 1.3, 1.4 or 1.5 times, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0019] Preferably, the mixing temperature is 40 to 90°C, for example, 40°C, 50°C, 60°C, 70°C, 80°C or 90°C, but not limited to the listed values. Other unlisted values ​​within this range are also applicable, preferably 60 to 80°C.

[0020] Preferably, the mixing time is 20 to 40 minutes, for example, 22 minutes, 25 minutes, 28 minutes, 30 minutes, 32 minutes, 35 minutes, 38 minutes or 40 minutes, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0021] Preferably, the temperature during mixing remains constant.

[0022] Preferably, the oxidized hydrochloric acid solution is added to the overflow reactor in the following manner:

[0023] Water is added to the overflow reactor as a base liquid, and an oxidized hydrochloric acid solution is added to the overflow reactor. As the oxidized hydrochloric acid solution is added, the overflow reactor overflows synchronously.

[0024] Preferably, the temperature inside the overflow reactor is 30 to 90°C, for example, it can be 30°C, 40°C, 50°C, 60°C, 70°C, 80°C or 90°C, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable, preferably 70 to 90°C.

[0025] The overflow reactor described in this invention is a device known to those skilled in the art.

[0026] In this invention, by removing impurity elements from the oxidized hydrochloric acid solution in the overflow reactor, the continuous feeding of the oxidized hydrochloric acid solution is achieved, ensuring the continuous operation of the method and thus realizing the continuous and automated removal of impurity elements.

[0027] In this invention, the oxidized hydrochloric acid solution is added to water dropwise by a pump. To control the free iron ion content in the overflow reactor to be lower than the set concentration, the addition rate of the oxidized hydrochloric acid solution is calculated based on the amount of iron ions in the added solution.

[0028] Preferably, the addition rate is 0.05–1.5 g Fe·min-1 For example, it could be 0.05g Fe·min -1 0.8g Fe·min -1 0.1g Fe·min -1 0.3g Fe·min -1 0.5g Fe·min -1 0.7g Fe·min -1 0.9gFe·min -1 Or 1.5g Fe·min -1 However, it is not limited to the listed values; other unlisted values ​​within this range also apply. The addition rate corresponds to the residence time of the hydrochloric acid solution.

[0029] Preferably, the oxidized hydrochloric acid is added to the water while the mixture is stirred simultaneously at a speed of 50–600 r / min. -1 For example, it could be 50 r·min -1 100r·min -1 200 r·min -1 300r·min -1 400r·min -1 Or 500 r·min -1 However, this does not apply to all values ​​listed; other unlisted values ​​within the same range also apply.

[0030] Preferably, the neutralizing agent comprises any one or a combination of at least two of sodium, potassium, calcium, or ammonium hydroxides, bicarbonates, or carbonates. Typical but non-limiting combinations include combinations of sodium hydroxide and sodium bicarbonate, combinations of sodium carbonate and potassium hydroxide, combinations of potassium bicarbonate and potassium carbonate, or combinations of ammonium hydroxide and ammonium bicarbonate, or combinations of sodium hydroxide, potassium hydroxide, calcium hydroxide, and ammonium hydroxide.

[0031] Preferably, the neutralizing agent is any one or a combination of at least two of calcium hydroxide, sodium hydroxide, or ammonia. Typical but non-limiting combinations include a combination of calcium hydroxide and sodium hydroxide, a combination of sodium hydroxide and ammonia, or a combination of calcium hydroxide, sodium hydroxide, and ammonia, preferably ammonia.

[0032] Preferably, the concentration of the neutralizing agent is 0.5–15 mol·L⁻¹. -1 For example, it could be 0.5 mol·L⁻¹ -1 1 mol·L -1 3 mol·L -1 5 mol·L -1 7 mol·L -19 mol·L -1 10 mol·L -1 12 mol·L -1 14 mol·L -1 or 15 mol·L -1 However, this is not limited to the listed values; other unlisted values ​​within this range also apply, preferably 1–10 mol·L⁻¹. -1 .

[0033] Preferably, the set value is 2.5 to 4.0, for example, it can be 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9 or 4.0, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0034] Preferably, the aging time is 30 to 360 minutes, for example, it can be 30 minutes, 50 minutes, 70 minutes, 90 minutes, 100 minutes, 120 minutes, 140 minutes, 160 minutes, 180 minutes, 200 minutes, 220 minutes, 240 minutes, 260 minutes, 280 minutes, 300 minutes, 320 minutes, 340 minutes or 360 minutes, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable, preferably 120 minutes to 240 minutes.

[0035] Preferably, the aging temperature is 40 to 90°C, for example, 40°C, 50°C, 60°C, 70°C, 80°C or 90°C, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable, preferably 60 to 80°C.

[0036] Preferably, the aging process is carried out simultaneously with stirring, and the stirring speed is 50-300 r / min. -1 For example, it could be 50 r·min -1 70 r·min -1 90r·min -1 100r·min -1 130 r·min -1 150 r·min -1 180 r·min -1 200 r·min -1 220 r·min -1 250 r·min -1 280 r·min -1 Or 300 r·min -1However, this does not apply to all values ​​listed; other unlisted values ​​within the same range also apply.

[0037] Preferably, the method further includes solid-liquid separation after aging.

[0038] The solid-liquid separation described in this invention includes any one or a combination of at least two of vacuum filtration, plate and frame filtration, vertical filtration, or centrifugation. Typical but non-limiting combinations include a combination of vacuum filtration and plate and frame filtration, a combination of plate and frame filtration and vertical filtration, a combination of vertical filtration and centrifugation, a combination of vacuum filtration, plate and frame filtration and vertical filtration, or a combination of vacuum filtration, plate and frame filtration, vertical filtration and centrifugation.

[0039] As a preferred embodiment of the method described in this invention, the method includes:

[0040] (1) Mix hydrochloric acid solution and oxidant at a constant temperature of 40-90℃ for 20-40 min to obtain oxidized hydrochloric acid solution; the amount of oxidant used in the mixture is 1-1.5 times the theoretically calculated amount to oxidize all ferrous ions in hydrochloric acid solution to ferric ions;

[0041] (2) Add water as a base liquid to the overflow reactor, and add 0.05–1.5 g Fe·min to the overflow reactor. -1 The oxidized hydrochloric acid solution obtained in step (1) is added at a rate that ensures the free iron ion content in the mixture of the oxidized hydrochloric acid solution and water is below 0.5–1 g / L. The oxidized hydrochloric acid solution is added to the water while simultaneously being stirred at a speed of 50–600 r / min. -1 Simultaneously use concentrations of 0.5–15 mol·L⁻¹ -1 The pH of the mixed solution is adjusted to 2.5–4.0 using a neutralizing agent. As the oxidized hydrochloric acid solution is added, the overflow reactor simultaneously overflows. The temperature inside the overflow reactor is 30–90°C, and the residence time of the hydrochloric acid solution in the overflow reactor is 30–600 min, resulting in a neutralized solution.

[0042] (3) The neutralized solution obtained in step (2) is aged at a temperature of 40–90°C for 30–360 min, wherein the aging is carried out at a speed of 50–300 r·min. -1 The stirring is performed synchronously at the rotation speed, and after solid-liquid separation, a rare earth solution with impurity elements removed is obtained.

[0043] In a second aspect, the present invention provides a rare earth solution for removing impurity elements, wherein the rare earth solution is obtained by the method described in the first aspect.

[0044] Thirdly, the present invention provides an application of the method described in the first aspect, the method being used for the removal of impurity elements from NdFeB waste.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] (1) The method provided by the present invention controls the content of free iron ions in the mixed solution and adjusts the pH of the mixed solution to a set value, thereby achieving the co-precipitation of iron and aluminum elements by hydrolysis. The hydrolysis products have a strong adsorption capacity for impurity elements such as fluorine and boron, realizing the in-situ adsorption of impurity elements, thus achieving the efficient removal of impurities such as iron, aluminum, fluorine, and boron from hydrochloric acid solution. The removal rates of iron, aluminum, fluorine, and boron reach 99%, 90%, 50%, and 75% or more, respectively. The method also reduces the entrainment loss of rare earth elements during the removal of impurity elements, and the rare earth content in the slag is reduced to below 0.20%, realizing the efficient recovery of rare earth elements. The method also improves the filtration performance of the impurity slag. In addition, the method has the advantages of simple operation, fewer process steps, and low cost of removing impurity elements, and is suitable for large-scale industrial production.

[0047] (2) In this invention, by removing impurity elements from the oxidized hydrochloric acid solution in the overflow reactor, the continuous feeding of the oxidized hydrochloric acid solution is achieved, ensuring the continuous operation of the method, thereby realizing the continuous and automated removal of impurity elements. Attached Figure Description

[0048] Figure 1 This is a flowchart of the method for removing impurity elements from hydrochloric acid solution provided in Examples 1 to 19 of the present invention. Detailed Implementation

[0049] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0050] In the embodiments provided by this invention, the hydrochloric acid solution is obtained by oxidative roasting and hydrochloric acid dissolution of NdFeB waste, and its main component is: RE 3+ 125g·L -1 Fe 3+ 8g·L -1 Fe 2+ 37g·L -1 Al 3+ 1.5g·L -1 F - 0.62 g·L -1 B 1.5g·L -1 The pH value is 0.50.

[0051] Example 1

[0052] This embodiment provides a method for removing impurity elements from hydrochloric acid solutions, such as... Figure 1 As shown, the method includes:

[0053] (1) Mix 5L of hydrochloric acid solution with 87.87g of sodium chlorate at a constant temperature of 80℃ for 30min to obtain oxidized hydrochloric acid solution; the amount of sodium chlorate used in the mixture is 1.5 times the theoretically calculated amount to oxidize all ferrous ions in the hydrochloric acid solution to ferric ions;

[0054] (2) Add 3L of water to the overflow reactor as a base liquid, and add 0.5g of iron ions (Fe·min) to the overflow reactor. -1 The oxidized hydrochloric acid solution obtained in step (1) is added at a rate that ensures the free iron ion content in the mixture of the oxidized hydrochloric acid solution and water is below 1 g / L; the oxidized hydrochloric acid solution is added to the water while simultaneously being stirred at a speed of 350 r·min. -1 Simultaneously using a concentration of 4 mol·L -1 The pH of the mixed solution is adjusted to 3.5 with ammonia water. As the oxidized hydrochloric acid solution is added, the overflow reactor overflows simultaneously. The temperature inside the overflow reactor is 80°C, and the residence time of the hydrochloric acid solution in the overflow reactor is 180 min, resulting in a neutralized solution.

[0055] (3) The neutralized solution obtained in step (2) is aged at 80°C for 150 min, wherein the aging is carried out at 200 r·min. -1 The stirring is performed synchronously at the rotation speed, and after solid-liquid separation, a rare earth solution with impurity elements removed is obtained.

[0056] Example 2

[0057] This embodiment provides a method for removing impurity elements from a hydrochloric acid solution, the method comprising:

[0058] (1) Mix 5L of hydrochloric acid solution with 58.58g of sodium chlorate at a constant temperature of 80℃ for 30min to obtain oxidized hydrochloric acid solution; the amount of sodium chlorate used in the mixture is 1 times the theoretically calculated amount to oxidize all ferrous ions in the hydrochloric acid solution to ferric ions;

[0059] (2) Water is added to the overflow reactor as a bottom liquid, and iron ions are added to the overflow reactor at a rate of 0.5 g Fe·min. -1The oxidized hydrochloric acid solution obtained in step (1) is added at a rate that ensures the free iron ion content in the mixture of the oxidized hydrochloric acid solution and water is below 1 g / L; the oxidized hydrochloric acid solution is added to the water while simultaneously being stirred at a speed of 350 r·min. -1 Simultaneously using a concentration of 4 mol·L -1 The pH of the mixed solution is adjusted to 4.0 with ammonia water. As the oxidized hydrochloric acid solution is added, the overflow reactor overflows simultaneously. The temperature inside the overflow reactor is 80°C, and the residence time of the hydrochloric acid solution in the overflow reactor is 180 min, resulting in a neutralized solution.

[0060] (3) The neutralized solution obtained in step (2) is aged at 80°C for 150 min, wherein the aging is carried out at 200 r·min. -1 The stirring is performed synchronously at the rotation speed, and after solid-liquid separation, a rare earth solution with impurity elements removed is obtained.

[0061] Example 3

[0062] This embodiment provides a method for removing impurity elements from a hydrochloric acid solution, the method comprising:

[0063] (1) Mix 5L of hydrochloric acid solution with 58.58g of sodium chlorate at a constant temperature of 90℃ for 30min to obtain oxidized hydrochloric acid solution; the amount of sodium chlorate used in the mixture is 1 times the theoretically calculated amount to oxidize all ferrous ions in the hydrochloric acid solution to ferric ions;

[0064] (2) Water is added to the overflow reactor as a bottom liquid, and iron ions are added to the overflow reactor at a rate of 0.5 g Fe·min. -1 The oxidized hydrochloric acid solution obtained in step (1) is added at a rate that ensures the free iron ion content in the mixture of the oxidized hydrochloric acid solution and water is below 1 g / L; the oxidized hydrochloric acid solution is added to the water while simultaneously being stirred at a speed of 350 r·min. -1 Simultaneously using a concentration of 4 mol·L -1 The pH of the mixed solution is adjusted to 3.5 with ammonia water. As the oxidized hydrochloric acid solution is added, the overflow reactor overflows simultaneously. The temperature inside the overflow reactor is 80°C, and the residence time of the hydrochloric acid solution in the overflow reactor is 180 min, resulting in a neutralized solution.

[0065] (3) The neutralized solution obtained in step (2) is aged at 80°C for 150 min, wherein the aging is carried out at 200 r·min. -1 The stirring is performed synchronously at the rotation speed, and after solid-liquid separation, a rare earth solution with impurity elements removed is obtained.

[0066] Example 4

[0067] This embodiment provides a method for removing impurity elements from a hydrochloric acid solution, the method comprising:

[0068] (1) Mix 5L of hydrochloric acid solution with 58.58g of sodium chlorate at a constant temperature of 80℃ for 30min to obtain oxidized hydrochloric acid solution; the amount of sodium chlorate used in the mixture is 1 times the theoretically calculated amount to oxidize all ferrous ions in the hydrochloric acid solution to ferric ions;

[0069] (2) Water is added to the overflow reactor as a bottom liquid, and iron ions are added to the overflow reactor at a rate of 0.5 g Fe·min. -1 The oxidized hydrochloric acid solution obtained in step (1) is added at a rate that ensures the free iron ion content in the mixture of the oxidized hydrochloric acid solution and water is below 1 g / L; the oxidized hydrochloric acid solution is added to the water while simultaneously being stirred at a speed of 350 r·min. -1 Simultaneously using a concentration of 4 mol·L -1 The pH of the mixed solution is adjusted to 3.5 with ammonia water. As the oxidized hydrochloric acid solution is added, the overflow reactor overflows simultaneously. The temperature inside the overflow reactor is 75°C, and the residence time of the hydrochloric acid solution in the overflow reactor is 180 min, resulting in a neutralized solution.

[0070] (3) The neutralized solution obtained in step (2) is aged at 80°C for 150 min, wherein the aging is carried out at 200 r·min. -1 The stirring is performed synchronously at the rotation speed, and after solid-liquid separation, a rare earth solution with impurity elements removed is obtained.

[0071] Example 5

[0072] This embodiment provides a method for removing impurity elements from a hydrochloric acid solution, the method comprising:

[0073] (1) Mix 5L of hydrochloric acid solution with hydrogen peroxide at a constant temperature of 40℃ for 40min to obtain oxidized hydrochloric acid solution; the amount of hydrogen peroxide used in the mixing is 1.2 times the theoretically calculated amount to oxidize all ferrous ions in the hydrochloric acid solution to ferric ions;

[0074] (2) Water is added to the overflow reactor as a base liquid, and iron ions are added to the overflow reactor at a rate of 0.05 g Fe·min. -1 The oxidized hydrochloric acid solution obtained in step (1) is added at a rate that ensures the free iron ion content in the mixture of the oxidized hydrochloric acid solution and water is below 0.5 g / L. The oxidized hydrochloric acid solution is added to the water while simultaneously being stirred at a speed of 50 r / min.-1 Simultaneously using a concentration of 0.5 mol·L -1 The pH of the mixed solution is adjusted to 2.5 with ammonia water. As the oxidized hydrochloric acid solution is added, the overflow reactor overflows simultaneously. The temperature inside the overflow reactor is 30°C, and the residence time of the hydrochloric acid solution in the overflow reactor is 600 min, resulting in a neutralized solution.

[0075] (3) The neutralized solution obtained in step (2) is aged at 40°C for 360 min, wherein the aging is carried out at 50 r·min. -1 The stirring is performed synchronously at the rotation speed, and after solid-liquid separation, a rare earth solution with impurity elements removed is obtained.

[0076] Example 6

[0077] This embodiment provides a method for removing impurity elements from a hydrochloric acid solution, the method comprising:

[0078] (1) Mix hydrochloric acid solution and sodium hypochlorite at a constant temperature of 90℃ for 20 min to obtain oxidized hydrochloric acid solution; the amount of sodium hypochlorite used in the mixture is 1.3 times the theoretically calculated amount to oxidize all ferrous ions in hydrochloric acid solution to ferric ions;

[0079] (2) Water is added to the overflow reactor as a base liquid, and iron ions are added to the overflow reactor at a rate of 1 g Fe·min. -1 The oxidized hydrochloric acid solution obtained in step (1) is added at a rate that ensures the free iron ion content in the mixture of the oxidized hydrochloric acid solution and water is below 0.8 g / L; the oxidized hydrochloric acid solution is added to the water while simultaneously being stirred at a speed of 600 r·min. -1 Simultaneously using a concentration of 15 mol·L -1 The pH of the mixed solution is adjusted to 4.0 with ammonia water. As the oxidized hydrochloric acid solution is added, the overflow reactor overflows simultaneously. The temperature inside the overflow reactor is 70°C, and the residence time of the hydrochloric acid solution in the overflow reactor is 30 minutes, resulting in a neutralized solution.

[0080] (3) The neutralized solution obtained in step (2) is aged at 90°C for 30 min, wherein the aging is carried out at 300 r·min. -1 The stirring is performed synchronously at the rotation speed, and after solid-liquid separation, a rare earth solution with impurity elements removed is obtained.

[0081] Example 7

[0082] This embodiment provides a method for removing impurity elements from a hydrochloric acid solution. Except for adjusting the pH of the mixed solution to 2 in step (2), the rest is the same as in embodiment 4.

[0083] Example 8

[0084] This embodiment provides a method for removing impurity elements from a hydrochloric acid solution. Except for adjusting the pH of the mixed solution to 5 in step (2), the rest is the same as in embodiment 4.

[0085] Example 9

[0086] This embodiment provides a method for removing impurity elements from hydrochloric acid solutions, except that in step (2), the amount of iron ions added is 0.05 g Fe·min -1 Except for the addition of the oxidized hydrochloric acid solution at a certain rate, everything else is the same as in Example 4.

[0087] Example 10

[0088] This embodiment provides a method for removing impurity elements from hydrochloric acid solutions, except that in step (2), the amount of iron ions added is 1.2 g Fe·min -1 Except for the addition of the oxidized hydrochloric acid solution at a certain rate, everything else is the same as in Example 4.

[0089] Example 11

[0090] This embodiment provides a method for removing impurity elements from hydrochloric acid solution. Except for the temperature of 20°C in the overflow reactor mentioned in step (2), the rest is the same as in embodiment 4.

[0091] Example 12

[0092] This embodiment provides a method for removing impurity elements from hydrochloric acid solution. Except for the temperature of 95°C in the overflow reactor mentioned in step (2), the rest is the same as in embodiment 4.

[0093] Example 13

[0094] This embodiment provides a method for removing impurity elements from a hydrochloric acid solution. Except for step (2), in which sodium hydroxide of the same concentration is used as a neutralizing agent to adjust the pH of the mixed solution, the rest is the same as in Example 4.

[0095] Example 14

[0096] This embodiment provides a method for removing impurity elements from a hydrochloric acid solution, except that the concentration of ammonia in step (2) is 0.5 mol·L⁻¹. -1 Except for the above, everything else is the same as in Example 4.

[0097] Example 15

[0098] This embodiment provides a method for removing impurity elements from hydrochloric acid solution, except that the concentration of ammonia in step (2) is 15 mol·L⁻¹. -1Except for the above, everything else is the same as in Example 4.

[0099] Example 16

[0100] This embodiment provides a method for removing impurity elements from hydrochloric acid solution. Except for aging at 30°C in step (3), the rest is the same as in embodiment 4.

[0101] Example 17

[0102] This embodiment provides a method for removing impurity elements from hydrochloric acid solution. Except for aging at 100°C in step (3), the rest is the same as in embodiment 4.

[0103] Example 18

[0104] This embodiment provides a method for removing impurity elements from hydrochloric acid solution. Except for the 20-minute aging in step (3), the rest is the same as in embodiment 4.

[0105] Example 19

[0106] This embodiment provides a method for removing impurity elements from hydrochloric acid solution. Except for the aging process of 400 min in step (3), the rest is the same as in embodiment 4.

[0107] Comparative Example 1

[0108] This comparative example provides a method for removing impurity elements from a hydrochloric acid solution. The method is as follows:

[0109] (1) Mix 5L of hydrochloric acid solution with 87.87g of sodium chlorate at a constant temperature of 80℃ for 30min to obtain oxidized hydrochloric acid solution; the amount of sodium chlorate used in the mixture is 1.5 times the theoretically calculated amount to oxidize all ferrous ions in the hydrochloric acid solution to ferric ions;

[0110] (2) Add 5L of the oxidized hydrochloric acid solution obtained in step (1) to the reactor, and add a 4mol·L⁻¹ solution to the reactor. -1 The pH of the hydrochloric acid solution was adjusted to 3.5 with ammonia water. Stirring was performed simultaneously with the addition of ammonia water at a speed of 350 r / min. -1 ;

[0111] (3) The neutralized solution obtained in step (2) is aged at 80°C for 150 min, wherein the aging is carried out at 200 r·min. -1 The stirring is performed synchronously at the rotation speed, and after solid-liquid separation, a rare earth solution with impurity elements removed is obtained.

[0112] After removing impurity elements from the hydrochloric acid solution using the methods provided in Examples 1-19 and Comparative Example 1, the removal rates of iron, aluminum, fluorine, and boron were tested. The impurity element content was measured using ICP-OES and ion chromatography. The method for calculating the Fe removal rate is as follows:

[0113]

[0114] In the formula V 前 The volume of the solution before treatment, Fe 前 V represents the iron concentration before treatment. 后 The volume of the treated solution, Fe 后 The iron concentration after treatment.

[0115] The removal rates of Al, F and B are calculated using the same formula as above, and the test results are shown in Table 1.

[0116] After removing impurities from the hydrochloric acid solution using the methods provided in Examples 1-19 and Comparative Example 1, the filtration rate of the removed residue was tested. The test method was as follows: the solution was filtered at 0.3 MPa using a positive pressure filter, and the filtration time t and filtration volume V were recorded. The test results are shown in Table 1.

[0117] After removing impurity elements from the hydrochloric acid solution using the methods provided in Examples 1-19 and Comparative Example 1, rare earth inclusions were tested. The test method was to use XRF analysis to determine the percentage content of various elements in the impurity removal residue to obtain the amount of rare earth inclusions. The test results are shown in Table 1.

[0118] Table 1

[0119]

[0120]

[0121] From Table 1, we can obtain:

[0122] (1) The methods provided in Examples 1 to 6 achieve efficient removal of impurities such as iron, aluminum, fluorine, and boron from hydrochloric acid solutions, with removal rates of iron, aluminum, fluorine, and boron reaching 99%, 90%, 50%, and 75% or more, respectively; the methods also reduce the entrainment loss of rare earth elements during the removal of impurity elements, reducing the rare earth content in the slag to below 0.20%, thus achieving efficient recovery of rare earth elements; the methods also improve the filtration performance of the impurity-removed slag;

[0123] (2) By comparing Example 4 with Examples 7 and 8, it can be seen that the pH value of the mixed solution adjusted by the neutralizing agent in this invention will affect the effect of the method. When the pH value of the mixed solution is adjusted to be too small by the neutralizing agent, the degree of co-precipitation of iron and aluminum elements will be reduced, and the phase and morphology of the hydrolysis product will be unsatisfactory. As a result, the adsorption capacity of fluorine and boron elements will be significantly reduced, resulting in incomplete removal of impurity elements. The filtration performance of the hydrolysis product and the loss of rare earth elements will also be unsatisfactory. When the pH value of the mixed solution is adjusted to be too large by the neutralizing agent, the nucleation rate of the hydrolysis product will be significantly faster than its growth rate, which will make it easier to cause co-precipitation loss of rare earth elements, resulting in a higher content of rare earth inclusions.

[0124] (3) By comparing Example 4 with Examples 9 and 10, it can be seen that the addition rate of hydrochloric acid solution in this invention will affect the effectiveness of the method. When the addition rate of hydrochloric acid solution is too slow, although it can achieve efficient removal of impurities such as iron, aluminum, fluorine, and boron in hydrochloric acid solution, reduce the entrainment loss of rare earth elements during the removal of impurity elements, and improve the filtration performance of the slag, it will lead to a longer time for the method, resulting in a decrease in removal efficiency and an increase in labor costs. When the addition rate of hydrochloric acid solution is too fast, the concentration gradient of impurity ions in the mixed solution in the overflow reactor changes greatly, the iron and aluminum hydrolysis process is not thorough, the hydrolysis product has a small particle size, the adsorption capacity decreases, the overall removal efficiency of impurity elements decreases, the filtration performance of the slag deteriorates, and the entrainment loss of rare earth increases.

[0125] (4) By comparing Example 4 with Examples 11 and 12, it can be seen that the temperature inside the overflow reactor in this invention will affect the effectiveness of the method. When the temperature inside the overflow reactor is low, the hydrolysis of iron and aluminum will be incomplete, the removal rate will be reduced, and the adsorption efficiency of the hydrolysis products on fluorine and boron impurities will decrease, resulting in a low removal efficiency of fluorine and boron. When the temperature inside the overflow reactor is high, the hydrolysis of iron and aluminum will be complete, the growth rate of the hydrolysis products obtained in the co-precipitation process will be too large, thereby reducing the adsorption efficiency of fluorine and boron impurities, improving the filtration performance of impurity removal residue, and reducing the loss of rare earth entrainment. However, high temperature will consume a lot of energy and increase the production cost.

[0126] (5) By comparing Example 4 and Example 13, it can be seen that the type of neutralizing agent described in this invention will affect the effect of the method. When sodium hydroxide with the same concentration as ammonia is used, the rare earth content in the residue is significantly higher and the average filtration performance is worse. This is because the added sodium hydroxide is a strong alkaline substance, the nucleation rate of the hydrolysis product is significantly faster than its growth rate, and it is easier to cause co-precipitation loss of rare earth elements.

[0127] (6) By comparing Example 4 with Examples 14 and 15, it can be seen that the concentration of the neutralizing agent in this invention affects the effect of the method. When the concentration of the neutralizing agent is too low, a large amount of neutralizing agent is required to adjust the pH of the mixed solution, which significantly reduces the concentration of rare earth solution obtained by the method and increases the subsequent production cost. When the concentration of the neutralizing agent is too high, the pH adjustment process of the mixed solution becomes more difficult. Due to the increase in supersaturation, the nucleation rate of hydrolysis products is accelerated, resulting in smaller product particle size. At this time, the co-precipitation process of iron and aluminum hydrolysis is more complete, but the morphology and structure of the hydrolysis products are poor, the adsorption capacity for fluorine and boron is weakened, the filtration performance of the slag is significantly reduced, and the rare earth entrainment loss in the slag is significantly increased.

[0128] (7) By comparing Example 4 with Examples 16 and 17, it can be seen that the aging temperature in this invention affects the effect of the method. When the aging temperature is too low, the adsorption efficiency of the hydrolysis products obtained from the co-precipitation process of iron and aluminum for fluorine and boron impurities will decrease, resulting in a low removal efficiency of fluorine and boron. When the aging temperature is too high, the growth rate of the hydrolysis products obtained from the co-precipitation process of iron and aluminum will be too fast, resulting in a decrease in the adsorption efficiency of fluorine and boron impurities, and also resulting in a large amount of energy loss, thereby increasing the production cost.

[0129] (8) By comparing Example 4 with Examples 18 and 19, it can be seen that the aging time in this invention affects the effectiveness of the method. When the aging time is too short, the removal efficiency of fluorine and boron elements is significantly reduced due to insufficient reaction time, and the hydrolysis product particles do not have enough growth time, resulting in smaller particle size, poorer filtration performance, and increased rare earth element entrainment loss. When the aging time is too long, the method will take too long, resulting in a decrease in removal efficiency and an increase in labor costs.

[0130] (9) By comparing Example 4 with Comparative Example 1, it can be seen that the method provided by the present invention achieves the co-precipitation of iron and aluminum elements by controlling the content of free iron ions in the mixed solution and adjusting the pH of the mixed solution to a set value. The hydrolysis products have a strong adsorption capacity for impurity elements such as fluorine and boron, realizing the in-situ adsorption of impurity elements, thereby achieving the efficient removal of impurities such as iron, aluminum, fluorine, and boron from hydrochloric acid solution. The removal rates of iron, aluminum, fluorine, and boron reach 99%, 90%, 50%, and 75% or more, respectively. The method also reduces the amount of rare earth elements in the process of removing impurity elements. The method reduces the entrainment loss of rare earth elements, lowering the rare earth content in the slag to below 0.20%, thus achieving efficient recovery of rare earth elements. It also improves the filtration performance of the impurity-removing slag. Furthermore, the method is simple to operate, has fewer process steps, and lower cost for removing impurity elements, making it suitable for large-scale industrial production. In this invention, by removing impurity elements from the oxidized hydrochloric acid solution within the overflow reactor, continuous feeding of the oxidized hydrochloric acid solution is achieved, ensuring the continuous operation of the method and thus realizing the continuous and automated removal of impurity elements.

[0131] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for continuous in-situ removal of impurities from NdFeB waste using hydrochloric acid solution, characterized in that, The method includes: The oxidized hydrochloric acid solution was added to the overflow reactor at a rate of 0.05–1.5 g Fe·min⁻¹. -1 The oxidized hydrochloric acid solution is mixed with the bottom liquid in the overflow reactor. The pH of the mixed solution of hydrochloric acid solution and bottom liquid in the overflow reactor is adjusted to a set value of 2.5~4.0 using a neutralizing agent, so that the free iron ion content in the mixed solution is lower than a set concentration of 0.5~1 g / L. The temperature in the overflow reactor is 75~80℃ to obtain a neutralized solution. The obtained neutralized solution is then aged to obtain a rare earth solution with removed impurities. The aging time is 140~360 min, and the aging temperature is 60~80℃.

2. The method according to claim 1, characterized in that, The method for preparing the oxidized hydrochloric acid solution includes: mixing the hydrochloric acid solution with an oxidizing agent.

3. The method according to claim 2, characterized in that, The hydrochloric acid solution comprises a solution obtained by leaching NdFeB waste oxidized roasting residue with hydrochloric acid.

4. The method according to claim 2, characterized in that, The oxidant includes any one or a combination of at least two of chlorate, hypochlorite, persulfate, or hydrogen peroxide.

5. The method according to claim 2, characterized in that, The amount of oxidant used in the mixture is 1 to 1.5 times the theoretically calculated amount needed to oxidize all ferrous ions in the hydrochloric acid solution to ferric ions.

6. The method according to claim 2, characterized in that, The mixing temperature is 40~90℃.

7. The method according to claim 6, characterized in that, The mixing temperature is 60~80℃.

8. The method according to claim 2, characterized in that, The mixing time is 20-40 minutes.

9. The method according to claim 2, characterized in that, The temperature during mixing remains constant.

10. The method according to claim 1, characterized in that, The method for adding the oxidized hydrochloric acid solution to the overflow reactor includes: Water is added to the overflow reactor as a base liquid, and an oxidized hydrochloric acid solution is added to the overflow reactor. As the oxidized hydrochloric acid solution is added, the overflow reactor overflows synchronously.

11. The method according to claim 10, characterized in that, The oxidized hydrochloric acid solution is added to water while being stirred simultaneously at a speed of 50-600 r / min. -1 .

12. The method according to claim 1, characterized in that, The neutralizing agent includes any one or a combination of at least two of the following: hydroxides of sodium, potassium, calcium or ammonium, bicarbonates or carbonates.

13. The method according to claim 12, characterized in that, The neutralizing agent is any one or a combination of at least two of calcium hydroxide, sodium hydroxide, or ammonia.

14. The method according to claim 13, characterized in that, The neutralizing agent is ammonia.

15. The method according to claim 1, characterized in that, The concentration of the neutralizing agent is 0.5~15 mol·L⁻¹ -1 .

16. The method according to claim 15, characterized in that, The concentration of the neutralizing agent is 1~10 mol·L⁻¹ -1 .

17. The method according to claim 1, characterized in that, The aging process is carried out simultaneously with stirring, and the stirring speed is 50~300 r·min. -1 .

18. The method according to claim 1, characterized in that, The method also includes solid-liquid separation after aging.

19. The method according to claim 1, characterized in that, The method includes: (1) Mix hydrochloric acid solution and oxidant at a constant temperature of 40~90 ℃ for 20~40 min to obtain oxidized hydrochloric acid solution; the amount of oxidant used in the mixture is 1~1.5 times the theoretically calculated amount to oxidize all ferrous ions in hydrochloric acid solution to ferric ions; (2) Add water as a bottom liquid to the overflow reactor, and add 0.05~1.5 g Fe·min to the overflow reactor. -1 The oxidized hydrochloric acid solution obtained in step (1) is added at a rate that ensures the free iron ion content in the mixture of the oxidized hydrochloric acid solution and water is below 0.5~1 g / L; the oxidized hydrochloric acid solution is added to the water while stirring simultaneously at a speed of 50~600 r·min. -1 Simultaneously use concentrations of 0.5~15 mol·L⁻¹ -1 The pH of the mixed solution is adjusted to 2.5-4.0 by a neutralizing agent. As the oxidized hydrochloric acid solution is added, the overflow reactor overflows simultaneously. The temperature inside the overflow reactor is 75-80°C, and the residence time of the hydrochloric acid solution in the overflow reactor is 30-600 min, resulting in a neutralized solution. (3) The neutralized solution obtained in step (2) is aged at a temperature of 60~80 °C for 140~360 min, wherein the aging is carried out at a speed of 50~300 r·min. -1 The stirring is performed synchronously at the rotation speed, and after solid-liquid separation, a rare earth solution with impurity elements removed is obtained.

Images