A method for treating ion-type rare earth ore leaching solution by composite precipitation

Abstract

The present application belongs to the field of hydrometallurgy, and specifically provides a method for treating ion-type rare earth ore leaching solution by composite precipitation, which comprises the following steps: using magnesium oxide to precipitate the rare earth leaching solution in one step, so that the rare earth and impurities are co-precipitated to form an enrichment; treating the rare earth enrichment by acid dissolution, and then separating the solid and liquid, wherein the filter residue is used for covering soil, the filtrate is first neutralized and impurities-removed by using magnesium oxide or the rare earth enrichment, a part of the filtrate after the impurities-removal is used as a precipitant by adjusting the pH and aging sufficiently, and the other part of the filtrate is recovered by using sodium bicarbonate or sodium hydroxide after adjusting the pH by using the above-mentioned precipitant. The method provided by the present application effectively solves the problems of high content of silicon, aluminum, sulfur and magnesium impurities in the rare earth enrichment, low total content of rare earth, poor crystallization of rare earth carbonate product, slow settling, difficult filtration, high loss of rare earth and other problems in the recovery of rare earth by using a single precipitant, and the traditional sodium bicarbonate precipitation, realizes the recycling of magnesium resources in mining and smelting, and improves the overall development and utilization efficiency of ion-type rare earth ore.

Description

Technical Field

[0001] The invention belongs to the field of hydrometallurgy, and relates to a method for enriching ionic rare earth ore leachate, in particular to a composite precipitation treatment method for ionic rare earth leachate. Background Art

[0002] In weathering crust leaching rare earth ores, ionic rare earths are present as electrostatic adsorption on clay minerals such as kaolin. When they encounter more chemically active cations in the leaching agent, the rare earth ions are exchanged and dissociated by the cations in the leaching agent into the leachate. Currently, there are numerous methods for enriching and recovering rare earths from leachates, which can be summarized as traditional inorganic salt precipitation, solvent extraction, ion exchange, liquid membrane separation, and organic precipitation. Precipitation, due to its simplicity and low processing costs, has become a common method for purifying and enriching rare earth mine leachates.

[0003] In terms of precipitation processes and precipitants, mines initially primarily used oxalic acid. This process produces rare earth concentrates with excellent precipitation performance and high product purity, but it requires large amounts of oxalic acid, resulting in high costs and a large amount of toxic oxalic acid remaining in the supernatant after precipitation. Consequently, ammonium bicarbonate precipitation was subsequently developed and widely adopted due to its low-cost, readily available raw materials and high precipitation rate. However, the use of ammonium bicarbonate can easily cause ammonia nitrogen pollution, posing a significant environmental challenge. To completely eliminate ammonia nitrogen pollution, reduce production costs, and achieve efficient and green enrichment of rare earths, research on new ammonium-free precipitants has garnered widespread attention.

[0004] Patent publication number CN119710312A proposes a method for precipitating rare earths from ionic rare earth mother liquors. This method uses sodium bicarbonate to remove impurities and sodium carbonate to precipitate the rare earths. While this method addresses ammonia and nitrogen pollution at the source, it presents the following issues: ① Conventional sodium bicarbonate / sodium carbonate precipitation of low-concentration rare earth leachate results in a low rare earth precipitation rate, with the discharged supernatant still containing only 0.03 g / L of rare earths, resulting in significant rare earth losses; ② sodium ions are introduced into the ecological environment, where their unlimited accumulation increases environmental risks; and ③ the resulting rare earth carbonate precipitate has a non-uniform particle size, often forming a paste-like, amorphous flocculent precipitate. This results in long solid-liquid separation times and is difficult to perform. To address this issue, flocculants are often added to agglomerate the dispersed particles into aggregates, accelerating sedimentation. However, this process introduces impurities such as fluorine into the precipitate, causing fluorine levels to exceed the permitted limit. During the rare earth extraction and separation at the back end, fluoride ions will form chelates with other ions, or form insoluble precipitates that enter the three-phase extraction, thereby affecting the rare earth extraction and separation effect and product quality. The invention patent with publication number CN119240776A discloses a method for ammonium-free enrichment of rare earth mother liquor. The rare earth leachate is precipitated with ultrasound-assisted magnesium oxide. This method completely avoids the introduction of secondary pollution into the mining environment and can achieve the recycling of magnesium ions. However, there are still problems such as low total rare earth content in the precipitate (REO accounts for about 40% after calcination), high impurity content (Mg accounts for about 16% after calcination), and high processing costs. At the same time, the prepared rare earth hydroxide precipitate will contain a large amount of sulfate ions (react to form basic rare earth sulfate), and SO4 in the mixed rare earth oxide after calcination. 2- The content is as high as 14% or more, severely reducing the purity of rare earth materials. Patent publication number CN110484754A proposes a method for removing sulfate from rare earth precipitates. This method involves preparing a solution containing sulfate and rare earth ions from pretreated rare earth precipitates. Oxalate is then added to the solution as a precipitant to initiate a precipitation reaction, resulting in a precipitate. The precipitate is then dissolved with hydrochloric acid, followed by a secondary precipitation reaction using hydroxide as a precipitant. While this method addresses the sulfate content issue, it is complex and costly, making it difficult to implement in mining operations. Summary of the Invention

[0005] In response to the deficiencies in the prior art, the present application provides a composite precipitation treatment method for ionic rare earth ore leachate, which solves the problems of high silicon, aluminum, sulfur and magnesium impurities in rare earth enrichments and low total rare earth content when recovering rare earths using a single precipitant, as well as poor crystallization, slow sedimentation, difficulty in filtration, high ignition cost and excessive fluorine content of rare earth carbonate products during traditional sodium bicarbonate precipitation. This method realizes the recycling of magnesium resource mining and smelting, and improves the overall development and utilization process efficiency of ionic rare earth ores.

[0006] The present invention provides a composite precipitation treatment method for ionic rare earth ore leachate. The method first constructs a hydrometallurgical workshop in an ionic rare earth mine. The hydrometallurgical workshop is equipped with a regulating tank, an acid dissolution tank, an impurity removal tank, an aging tank, a sedimentation tank, a liquid preparation tank, and a filter press. The composite precipitation treatment method includes the following steps:

[0007] (1) In the regulating tank, the pH value of the rare earth leaching solution is adjusted to 7.0-7.5 using magnesium oxide slurry, and rare earth enrichment is obtained by one-step precipitation and enrichment. After the solution is allowed to stand and the precipitation is separated, the enrichment is lowered into the acid dissolution tank;

[0008] (2) Acid dissolution is performed in an acid dissolution tank using dilute sulfuric acid with a mass concentration of ≥10%. The acid dissolution process is continuously stirred. The mixed liquid after acid dissolution is subjected to solid-liquid separation using a plate and frame filter press to obtain a first filter residue and a first filtrate. The first filter residue is used for solid waste well filling or temporary disturbance covering of mining projects;

[0009] (3) The first filtrate is discharged to a decontamination tank, magnesium oxide slurry is added to the decontamination tank to adjust the solution pH to 5.4, and then silicon and aluminum impurities are removed; the obtained mixed solution is subjected to solid-liquid separation using a plate and frame filter press to obtain a second filter residue and a second filtrate, the second filter residue is centrally stored as general solid waste, and the second filtrate is divided into two parts and discharged to an aging tank and a sedimentation tank;

[0010] (4) In the aging tank, continuously add magnesium oxide slurry with a mass concentration of 1% to 10%, adjust the pH of the mixed solution to 7.2 to 7.5 and then stop, stirring continuously during the addition process, and after the addition is completed, control the aging in the tank for more than 18 hours as a precipitant for standby use;

[0011] (5-I) In the sedimentation tank, add the precipitant described in step (4), adjust the solution pH to 6.2, and then add sodium bicarbonate. The amount of sodium bicarbonate added is based on the molar ratio of n(HCO3 - ):n(RE 3+ )=3.5:1~4.5:1, stir continuously during the addition process, control the pH at 7.0~7.5, and age for 0.5 hour~2 hours after the addition is completed;

[0012] (6-Ⅰ) After the mixed liquid in the sedimentation tank is clarified and the sediment is separated into layers, the supernatant is discharged to the liquid preparation tank, the composite rare earth precipitate is placed in the tank, and the second filtrate and the precipitant described in step (4) are then added. After continuous circulation for 3 to 5 times according to step (5-Ⅰ), the mixed liquid is subjected to solid-liquid separation using a plate and frame filter press to obtain a third filter residue and a third filtrate. The third filter residue is a rare earth carbonate and rare earth hydroxide concentrate product, and the third filtrate is reused for leaching;

[0013] or,

[0014] (5-II) In a sedimentation tank, add the precipitant described in step (4), adjust the solution pH to 6.9, then add sodium hydroxide, control the mass concentration of sodium hydroxide in the solution system to 1% to 3%, use hydrochloric acid to control the pH to 10 to 10.5, the reaction time is ≥ 1 hour, and after clarification and precipitation, the liquid is returned to step (4) for use, and the rare earth hydroxide precipitate is placed in the tank;

[0015] (6-Ⅱ) The rare earth hydroxide precipitate described in step (5-Ⅱ) is continuously washed for 1 to 2 hours with the supernatant or clean water in the liquid preparation tank, and is filtered using a plate and frame filter press to obtain a fourth filter residue and a fourth filtrate. The fourth filter residue is the rare earth hydroxide concentrate product, and the fourth filtrate is returned to step (5-Ⅱ) for use.

[0016] As some embodiments of the present application, in step (2), the pH of the acid solution is adjusted to 1.5-2.5.

[0017] As some embodiments of the present application, in step (2), the acid dissolution time is 1 hour to 4 hours, the slurry solid-liquid ratio is 1:7 g / mL to 1:10 g / mL, and the rare earth content in the first filtrate is controlled to be less than 15 g / L.

[0018] As some embodiments of the present application, in step (2), the first filter residue is insoluble silicate mineral residue, and the washing method is countercurrent washing.

[0019] As some embodiments of the present application, in step (2), the first filter residue is washed with clean water until the pH value is 6.0 to 9.0, and the washing water is used for further acid dissolution and slurry adjustment.

[0020] As some embodiments of the present application, in step (3), the second filter residue washing method is countercurrent washing.

[0021] As some embodiments of the present application, in step (3), the second filter residue is first washed with an acid solution having a pH of 4 to 5 and then washed with clean water, and the washing water is reused for acid dissolution and slurry preparation.

[0022] As some embodiments of the present application, in step (6-Ⅰ), the SO4 in the composite rare earth precipitate is detected after continuous circulation 3 to 5 times according to step (5-Ⅰ). 2- Content, when it is burned impurity SO4 2- When the content is ≥2%, first use a sodium hydroxide solution with a mass concentration of 0.3% to 1.5% for continuous washing, and control the washing time to 1 hour to 3 hours until the impurities SO4 are burned. 2- When the content is less than 2%, the mixed liquid is separated into solid and liquid using a plate and frame filter press.

[0023] As some embodiments of the present application, in step (4), rare earth hydroxide concentrate slurry can be used instead of magnesium oxide slurry.

[0024] As some embodiments of the present application, in step (4), the continuous stirring is a kind of mechanical stirring or aeration stirring.

[0025] As some examples of the present application, in (5-II), the reaction time is 1 hour to 3 hours.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. During the mining process, acid dissolution of rare earth concentrates using a superior dissolution method minimizes the dissolution of iron and aluminum impurities, enabling the recycling of aluminosilicate overburden (aluminosilicates account for approximately 15% of the total solid waste residue), thereby reducing the amount of solid waste discharged from the mine. Furthermore, this pH condition delays the polymerization of silicic acid into silica sol, preventing the formation of silica gel. This ensures convenient filtration using a plate and frame filter press during the acid dissolution process, improving solid-liquid separation efficiency. The rare earth concentration in the acid dissolution feed is controlled below 15g / L, preventing the formation of rare earth sulfate complex salts in systems high in sulfate and sodium ions, thereby improving the quality of the rare earth concentrate product.

[0028] 2. Avoid the formation of basic rare earth sulfate (up to about 20%) when a single alkaline oxide precipitates rare earth leachate in a high sulfate system, weakly acidic or neutral conditions. The present invention adopts a method of composite precipitation and sodium hydroxide washing to reduce the formation of basic rare earth sulfate. The main reason is that the carbonate ion concentration in the composite precipitation system is much higher than the hydroxide ion concentration, and the ionic atmosphere around the rare earth ions is mainly carbonate ions. The combination of rare earth ions and carbonate ions has obvious advantages in kinetics. At the same time, washing the rare earth precipitate product with sodium hydroxide will promote the reaction RE2(OH)4SO4+2NaOH = 2RE(OH)3+ Na2SO4, further reducing the SO4 in the rare earth concentrate product. 2- content.

[0029] 3. Because conventional rare earth carbonate is an amorphous flocculent precipitate with a large volume, the resulting slurry is difficult to filter. To address this problem, flocculants are often added during production. On the one hand, the addition of flocculants will cause the fluorine content in the product to exceed the standard, further affecting the extraction and separation effect; on the other hand, the high-temperature incineration method used to remove the flocculant during the smelting and separation process is high in production costs, adding approximately 3,000 yuan to the cost for each ton of oxide produced. The present invention adopts a composite precipitation method, which is conducive to the gradual crystallization of the rare earth carbonate flocculent precipitate after adding magnesium oxide or rare earth hydroxide concentrate, gradually reducing the precipitate volume, gradually increasing the particles, forming crystals, and accelerating precipitation and solid-liquid separation. The main reason is that the rare earth hydroxide concentrate contains a large amount of magnesium oxide. As an alkaline oxide, magnesium oxide has an adsorption effect, which can cause tiny suspended particles in water to aggregate and form larger flocs, facilitating precipitation.

[0030] 4. Increase the total amount of rare earths in traditional magnesium salt enrichments. Using the traditional magnesium oxide method to precipitate rare earth leachate, the enriched product contains high levels of impurities such as silicon, aluminum, magnesium, and sulfur, while the total amount of rare earths is relatively low (approximately 10%). This invention first reduces the silicon, aluminum, and iron impurities through neutralization and impurity removal. Secondly, by extending the aging time and recycling the rare earth hydroxide precipitate, the magnesium oxide content in the product is further reduced. Finally, a composite precipitation method of sodium bicarbonate and sodium hydroxide is used to prevent the formation of basic rare earth sulfate and reduce the sulfate content.

[0031] 5. Reduce rare earth loss and increase rare earth precipitation rate. Relevant research shows that rare earth carbonate can form and exist stably under conditions of pH less than 7. The pH value for the onset of rare earth carbonate precipitation is generally between 4 and 5, and it can form under conditions of pH <4 when the concentration is high. Therefore, the traditional sodium bicarbonate / ammonium bicarbonate impurity removal stage will cause more than 10% rare earth loss. At the same time, when sodium bicarbonate is used as a precipitant to precipitate low-concentration rare earth leachate, the rare earth precipitation rate is low, and the rare earth content in the supernatant discharged after precipitation is still approximately 0.03g / L. The overall rare earth recovery rate is greatly limited by the leachate concentration. In addition, the sodium bicarbonate impurity removal and precipitation process continuously and indirectly introduces a large amount of sodium ions into the ecological environment, which may pose a potential environmental impact risk. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the specific implementation of the present invention or the technical solutions in the prior art, the drawings required for describing the specific implementation or the prior art will be briefly introduced below. Obviously, the drawings described below are only one implementation of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0033] Figure 1 is a process flow chart of the composite precipitation treatment method for ionic rare earth ore leachate of Example 1;

[0034] Figure 2 This is a process flow chart of the composite precipitation treatment method for ionic rare earth ore leachate of Example 4. DETAILED DESCRIPTION

[0035] To make the technical means, creative features, objectives, and effects of the present invention easier to understand, the following is a clear and complete description of the technical solutions in the specific embodiments of the present invention to further illustrate the present invention. Obviously, the specific embodiments described are only part of the embodiments of the present invention, not all of them. Those skilled in the art should understand that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0036] Example 1

[0037] This embodiment provides a Figure 1 The composite precipitation treatment method of ionic rare earth ore leachate is shown.

[0038] First, a hydrometallurgical workshop is built in the ionic rare earth mine. The hydrometallurgical workshop is equipped with a regulating tank, an acid dissolution tank, an impurity removal tank, an aging tank, a sedimentation tank, a liquid preparation tank and a filter press. The composite precipitation treatment method includes the following steps:

[0039] (1) In the regulating tank, the pH value of the rare earth leachate is adjusted to 7.0 using magnesium oxide slurry, and rare earth enrichment is obtained by one-step precipitation and enrichment. After the solution is allowed to stand and the sediment is separated, the enrichment is placed in the acid dissolution tank; the main component of the rare earth leachate is RE 3+ 1015mg / L, Mg 2+ 1655mg / L, Al 3+ 188mg / L, Si 4+ 150mg / L, SO4 2- 3359mg / L, F - 34 mg / L, the leachate compositions of the following examples and comparative examples are the same;

[0040] (2) Acid dissolution is performed in an acid dissolution tank using dilute sulfuric acid with a mass concentration of 10%, the pH of the acid solution is adjusted to 1.5, the acid dissolution time is 1 hour, the slurry solid-liquid ratio is 1:7 g / mL, the acid dissolution process is continuously stirred, and the mixed liquid after acid dissolution is subjected to solid-liquid separation using a plate and frame filter press to obtain a first filter residue and a first filtrate. The rare earth content in the first filtrate is 13.2 g / L. The first filter residue is a sparingly soluble silicate mineral residue. After washing to a residue pH of 6.0, it is used for solid waste well filling or temporary disturbance covering of mining projects, and the washing water is reused for acid dissolution and slurry adjustment;

[0041] (3) The first filtrate is discharged to a decontamination tank, magnesium oxide slurry is added to the decontamination tank to adjust the solution pH to 5.4, and then silicon and aluminum impurities are removed; the obtained mixed solution is subjected to solid-liquid separation using a plate and frame filter press to obtain a second filter residue and a second filtrate, the second filter residue is centrally stored as general solid waste, and the second filtrate is divided into two parts and discharged to an aging tank and a sedimentation tank; the second filter residue is first washed with an acid solution with a pH of 4 and then with clean water, and the washing water is reused for acid dissolution and slurry adjustment;

[0042] (4) In the aging tank, continuously add magnesium oxide slurry with a mass concentration of 5%, adjust the pH of the mixed solution to 7.2 and then stop, stirring continuously during the addition process, and after the addition is completed, control the aging in the tank for 18 hours as a precipitant;

[0043] (5-I) In the sedimentation tank, add the precipitant described in step (4), adjust the solution pH to 6.2, and then add sodium bicarbonate. The amount of sodium bicarbonate added is based on the molar ratio of n(HCO3 - ):n(RE 3+ )=3.5:1, stirring continuously during the addition process, controlling the pH at 7.0, and aging for 2 hours after the addition is completed.

[0044] (6-Ⅰ) After the mixed liquid in the sedimentation tank is clarified and the sediment is separated, the supernatant is discharged to the liquid preparation tank, the composite rare earth precipitate is placed in the tank, and the second filtrate and the precipitant described in step (4) are placed in the tank. After three consecutive cycles according to step (5-Ⅰ), the SO4 content in the composite rare earth precipitate is detected. 2- The content (calculated as oxide) is 3.52%. First, it is washed continuously with a sodium hydroxide solution with a mass concentration of 0.5%. The washing time is controlled to be 1 hour. After washing, it is filtered using a plate and frame filter press. The filtrate is returned to step (5-Ⅰ) for use; until the impurities SO4 are burned 2- When the content is less than 2%, the mixed liquid is separated into solid and liquid by a plate and frame filter press to obtain a third filter residue and a third filtrate. The third filter residue is a rare earth carbonate and rare earth hydroxide concentrate product, and the third filtrate is reused for leaching.

[0045] Example 2

[0046] This embodiment provides a composite precipitation treatment method for ionic rare earth ore leachate. First, a hydrometallurgical workshop is constructed in an ionic rare earth mine. The hydrometallurgical workshop is equipped with a regulating tank, an acid dissolution tank, an impurity removal tank, an aging tank, a sedimentation tank, a liquid preparation tank, and a filter press. The composite precipitation treatment method includes the following steps:

[0047] (1) In the regulating tank, the pH value of the rare earth leaching solution is adjusted to 7.0 using magnesium oxide slurry, and rare earth enrichment is obtained by one-step precipitation and enrichment. After the solution is allowed to stand and the precipitation is separated, the enrichment is lowered into the acid dissolution tank;

[0048] (2) Acid dissolution is performed in an acid dissolution tank using dilute sulfuric acid with a mass concentration of 10%, the pH of the acid solution is adjusted to 1.5, the acid dissolution time is 1 hour, the slurry solid-liquid ratio is 1:7 g / mL, the acid dissolution process is continuously stirred, and the mixed liquid after acid dissolution is subjected to solid-liquid separation using a plate and frame filter press to obtain a first filter residue and a first filtrate. The rare earth content in the first filtrate is 13.2 g / L. The first filter residue is a sparingly soluble silicate mineral residue. After washing to a residue pH of 6.0, it is used for solid waste well filling or temporary disturbance covering of mining projects, and the washing water is reused for acid dissolution and slurry adjustment;

[0049] (3) The first filtrate is discharged to a decontamination tank, magnesium oxide slurry is added to the decontamination tank to adjust the solution pH to 5.4, and then silicon and aluminum impurities are removed; the obtained mixed solution is subjected to solid-liquid separation using a plate and frame filter press to obtain a second filter residue and a second filtrate, the second filter residue is centrally stored as general solid waste, and the second filtrate is divided into two parts and discharged to an aging tank and a sedimentation tank; the second filter residue is first washed with an acid solution with a pH of 4 and then with clean water, and the washing water is reused for acid dissolution and slurry adjustment;

[0050] (4) In the aging tank, continuously add magnesium oxide slurry with a mass concentration of 5%, adjust the pH of the mixed solution to 7.2 and then stop, stirring continuously during the addition process, and after the addition is completed, control the aging in the tank for 18 hours as a precipitant;

[0051] (5-I) In the sedimentation tank, add the precipitant described in step (4), adjust the solution pH to 6.2, and then add sodium bicarbonate. The amount of sodium bicarbonate added is based on the molar ratio of n(HCO3 - ):n(RE 3+ )=4.5:1, stirring continuously during the addition process, controlling the pH at 7.0, and aging for 2 hours after the addition is completed;

[0052] (6-Ⅰ) After the mixed liquid in the sedimentation tank is clarified and the sediment is separated, the supernatant is discharged to the liquid preparation tank, the composite rare earth precipitate is placed in the tank, and the second filtrate and the precipitant described in step (4) are placed in the tank. After three consecutive cycles according to step (5-Ⅰ), the SO4 content in the composite rare earth precipitate is detected. 2- The content (calculated as oxide) is 1.51%. The mixed liquid is separated into solid and liquid by a plate and frame filter press to obtain a third filter residue and a third filtrate. The third filter residue is rare earth carbonate and rare earth hydroxide concentrate products, and the third filtrate is reused for leaching.

[0053] Example 3

[0054] This embodiment provides a composite precipitation treatment method for ionic rare earth ore leachate. First, a hydrometallurgical workshop is constructed in an ionic rare earth mine. The hydrometallurgical workshop is equipped with a regulating tank, an acid dissolution tank, an impurity removal tank, an aging tank, a sedimentation tank, a liquid preparation tank, and a filter press. The composite precipitation treatment method includes the following steps:

[0055] (1) In the regulating tank, the pH value of the rare earth leaching solution is adjusted to 7.0 using magnesium oxide slurry, and rare earth enrichment is obtained by one-step precipitation and enrichment. After the solution is allowed to stand and the precipitation is separated, the enrichment is lowered into the acid dissolution tank;

[0056] (2) Acid dissolution is performed in an acid dissolution tank using dilute sulfuric acid with a mass concentration of 10%, the pH of the acid solution is adjusted to 1.5, the acid dissolution time is 1 hour, the slurry solid-liquid ratio is 1:7 g / mL, the acid dissolution process is continuously stirred, and the mixed liquid after acid dissolution is subjected to solid-liquid separation using a plate and frame filter press to obtain a first filter residue and a first filtrate. The rare earth content in the first filtrate is 13.2 g / L. The first filter residue is a sparingly soluble silicate mineral residue. After washing to a residue pH of 6.0, it is used for solid waste well filling or temporary disturbance covering of mining projects, and the washing water is reused for acid dissolution and slurry adjustment;

[0057] (3) The first filtrate is discharged to a decontamination tank, magnesium oxide slurry is added to the decontamination tank to adjust the solution pH to 5.4, and then silicon and aluminum impurities are removed; the obtained mixed solution is subjected to solid-liquid separation using a plate and frame filter press to obtain a second filter residue and a second filtrate, the second filter residue is centrally stored as general solid waste, and the second filtrate is divided into two parts and discharged to an aging tank and a sedimentation tank; the second filter residue is first washed with an acid solution with a pH of 4 and then with clean water, and the washing water is reused for acid dissolution and slurry adjustment;

[0058] (4) In the aging tank, continuously add magnesium oxide slurry with a mass concentration of 5%, adjust the pH of the mixed solution to 7.2 and then stop, stirring continuously during the addition process, and after the addition is completed, control the aging in the tank for 18 hours as a precipitant;

[0059] (5-I) In the sedimentation tank, add the precipitant described in step (4), adjust the solution pH to 6.2, and then add sodium bicarbonate. The amount of sodium bicarbonate added is based on the molar ratio of n(HCO3 - ):n(RE 3+ )=3.5:1, stirring continuously during the addition process, controlling the pH at 7.0, and aging for 2 hours after the addition is completed;

[0060] (6-Ⅰ) After the mixed liquid in the sedimentation tank is clarified and the sediment is separated, the supernatant is discharged to the liquid preparation tank, the composite rare earth precipitate is placed in the tank, and the second filtrate and the precipitant described in step (4) are placed in the tank. After three consecutive cycles according to step (5-Ⅰ), the SO4 content in the composite rare earth precipitate is detected. 2- The content (calculated as oxide) is 3.52%. First, it is washed continuously with a sodium hydroxide solution with a mass concentration of 1.5%. The washing time is controlled to be 3 hours. After washing, it is filtered using a plate and frame filter press. The filtrate is returned to step (5-Ⅰ) for use; until the impurities SO4 are burned 2-When the content is less than 2%, the mixed liquid is separated into solid and liquid by a plate and frame filter press to obtain a third filter residue and a third filtrate. The third filter residue is a rare earth carbonate and rare earth hydroxide concentrate product, and the third filtrate is reused for leaching.

[0061] Comparative Example 1

[0062] This comparative example provides a method for treating ionic rare earth ore leachate. Compared with Example 1, the sodium bicarbonate composite precipitation and sodium hydroxide washing processes in step (5-Ⅰ) and step (6-Ⅰ) are eliminated.

[0063] Comparative Example 2

[0064] This comparative example provides a composite precipitation treatment method for ionic rare earth ore leachate. Compared with Example 1, the aging time of step (4) is controlled to be 2 hours, and the rest is the same as Example 1.

[0065] Comparative Example 3

[0066] This comparative example provides a composite precipitation treatment method for ionic rare earth ore leachate. Compared with Example 1, the n(HCO3 - ):n(RE 3+ )=2:1, and the rest are the same as in Example 1.

[0067] Comparative Example 4

[0068] This comparative example provides a composite precipitation treatment method for ionic rare earth ore leachate. Compared with Example 1, the number of continuous precipitations in step (6-Ⅰ) is controlled to be 1, and the rest are the same as Example 1.

[0069] Comparative Example 5

[0070] This comparative example provides a composite precipitation treatment method for ionic rare earth ore leachate. Compared with Example 1, after adjusting the pH of the solution to 5.8 in step (5-I), sodium bicarbonate is added. The amount of sodium bicarbonate added is based on the molar ratio of n(HCO3 - ):n(RE 3+ )=4.5:1, and the rest are the same as in Example 1.

[0071] The total amount of REO and impurity content of the concentrate product were determined based on the products obtained in Examples 1 to 3 and Comparative Examples 1 to 5, and the magnesium recycling rate, rare earth recovery rate, and slag production rate were calculated. The results are listed in Table 1.

[0072] Table 1 Product information of Examples 1 to 3 and Comparative Examples 1 to 5

[0073]

[0074] As can be seen from Table 1, the use of magnesium oxide for impurity removal and rare earth precipitation alone will result in a low total amount of REO in the rare earth concentrate product (accounting for only 74.85%), and SO4 2- The content is extremely high (15.39% in terms of SO3). The SO4 content in the concentrate can be significantly reduced by using the method of continuous composite precipitation of sodium bicarbonate. 2- Content, as low as 1.51% and sodium hydroxide washing can further reduce SO4 2- The content of REO was increased to 95.57%, achieving a magnesium recycling rate of 95% (the remaining magnesium was lost by the filter residue and product), and a total rare earth recovery rate of 94% (the remaining rare earth was lost by the filter residue and supernatant). However, after changing the solution pH in step (5-I) to 5.8, although the sulfate content was low and the total REO content was high, the sedimentation rate of the composite precipitate slowed down, and the difficulty of precipitate filtration increased significantly. At the same time, as can be seen from Example 3, increasing the sodium hydroxide concentration during agitation and washing can significantly reduce the sulfate content in the enriched product, but excessive concentrations increase the agitation and washing costs and the amount of sulfuric acid used for leaching.

[0075] Example 4

[0076] This embodiment provides a Figure 2 The composite precipitation treatment method of ionic rare earth ore leachate is shown.

[0077] First, a hydrometallurgical workshop is built in the ionic rare earth mine. The hydrometallurgical workshop is equipped with a regulating tank, an acid dissolution tank, an impurity removal tank, an aging tank, a sedimentation tank, a liquid preparation tank and a filter press. The composite precipitation treatment method includes the following steps:

[0078] (1) In the regulating tank, the pH value of the rare earth leaching solution is adjusted to 7.0 using magnesium oxide slurry, and rare earth enrichment is obtained by one-step precipitation and enrichment. After the solution is allowed to stand and the precipitation is separated, the enrichment is lowered into the acid dissolution tank;

[0079] (2) Acid dissolution is performed in an acid dissolution tank using dilute sulfuric acid with a mass concentration of 10%, the pH of the acid solution is adjusted to 1.5, the acid dissolution time is 1 hour, the slurry solid-liquid ratio is 1:7 g / mL, the acid dissolution process is continuously stirred, and the mixed liquid after acid dissolution is subjected to solid-liquid separation using a plate and frame filter press to obtain a first filter residue and a first filtrate. The rare earth content in the first filtrate is 13.2 g / L. The first filter residue is a sparingly soluble silicate mineral residue. After washing to a residue pH of 6.0, it is used for solid waste well filling or temporary disturbance covering of mining projects, and the washing water is reused for acid dissolution and slurry adjustment;

[0080] (3) The first filtrate is discharged to a decontamination tank, magnesium oxide slurry is added to the decontamination tank to adjust the solution pH to 5.4, and then silicon and aluminum impurities are removed; the obtained mixed solution is subjected to solid-liquid separation using a plate and frame filter press to obtain a second filter residue and a second filtrate, the second filter residue is centrally stored as general solid waste, and the second filtrate is divided into two parts and discharged to an aging tank and a sedimentation tank; the second filter residue is first washed with an acid solution with a pH of 4 and then with clean water, and the washing water is reused for acid dissolution and slurry adjustment;

[0081] (4) In the aging tank, continuously add magnesium oxide slurry with a mass concentration of 5%, adjust the pH of the mixed solution to 7.2 and then stop, stirring continuously during the addition process, and after the addition is completed, control the aging in the tank for 18 hours as a precipitant;

[0082] (5-II) In a sedimentation tank, the precipitant described in step (4) is added, and after adjusting the pH of the solution to 6.9, sodium hydroxide is added to control the mass concentration of sodium hydroxide in the solution system to 3%. Hydrochloric acid is used to control the pH to 10.5. The reaction time is 3 hours. After the clarification and precipitation, the liquid is returned to step (4) for use, and the rare earth hydroxide precipitate is placed in the tank;

[0083] (6-Ⅱ) The supernatant in the liquid preparation tank is used to continuously wash the rare earth hydroxide precipitate described in step (5-Ⅱ) for 1 hour, and a plate and frame filter press is used to filter to obtain a fourth filter residue and a fourth filtrate. The fourth filter residue is the rare earth hydroxide concentrate product, and the fourth filtrate is returned to step (5-Ⅱ) for use.

[0084] Example 5

[0085] This embodiment provides a composite precipitation treatment method for ionic rare earth ore leachate. First, a hydrometallurgical workshop is constructed in an ionic rare earth mine. The hydrometallurgical workshop is equipped with a regulating tank, an acid dissolution tank, an impurity removal tank, an aging tank, a sedimentation tank, a liquid preparation tank, and a filter press. The composite precipitation treatment method includes the following steps:

[0086] (1) In the regulating tank, the pH value of the rare earth leaching solution is adjusted to 7.0 using magnesium oxide slurry, and rare earth enrichment is obtained by one-step precipitation and enrichment. After the solution is allowed to stand and the precipitation is separated, the enrichment is lowered into the acid dissolution tank;

[0087] (2) Acid dissolution is performed in an acid dissolution tank using dilute sulfuric acid with a mass concentration of 10%, the pH of the acid solution is adjusted to 1.5, the acid dissolution time is 1 hour, the slurry solid-liquid ratio is 1:7 g / mL, the acid dissolution process is continuously stirred, and the mixed liquid after acid dissolution is subjected to solid-liquid separation using a plate and frame filter press to obtain a first filter residue and a first filtrate. The rare earth content in the first filtrate is 13.2 g / L. The first filter residue is a sparingly soluble silicate mineral residue. After washing to a residue pH of 6.0, it is used for solid waste well filling or temporary disturbance covering of mining projects, and the washing water is reused for acid dissolution and slurry adjustment;

[0088] (3) The first filtrate is discharged to a decontamination tank, magnesium oxide slurry is added to the decontamination tank to adjust the solution pH to 5.4, and then silicon and aluminum impurities are removed; the obtained mixed solution is subjected to solid-liquid separation using a plate and frame filter press to obtain a second filter residue and a second filtrate, the second filter residue is centrally stored as general solid waste, and the second filtrate is divided into two parts and discharged to an aging tank and a sedimentation tank; the second filter residue is first washed with an acid solution with a pH of 4 and then with clean water, and the washing water is reused for acid dissolution and slurry adjustment;

[0089] (4) In the aging tank, continuously add magnesium oxide slurry with a mass concentration of 5%, adjust the pH of the mixed solution to 7.2 and then stop, stirring continuously during the addition process, and after the addition is completed, control the aging in the tank for 18 hours as a precipitant;

[0090] (5-II) In a sedimentation tank, add the precipitant described in step (4), adjust the solution pH to 6.9, then add sodium hydroxide to control the mass concentration of sodium hydroxide in the solution system to 2%, use hydrochloric acid to control the pH to 10.5, react for 3 hours, and after clarification and precipitation, drain the liquid back to step (4) for use, and place the rare earth hydroxide precipitate in the tank;

[0091] (6) The supernatant in the liquid preparation tank is used to continuously wash the rare earth hydroxide precipitate described in step (5-Ⅱ) for 1 hour, and the filter is filtered using a plate and frame filter press to obtain a fourth filter residue and a fourth filtrate. The fourth filter residue is the rare earth hydroxide concentrate product, and the fourth filtrate is returned to step (5-Ⅱ) for use.

[0092] Example 6

[0093] This embodiment provides a composite precipitation treatment method for ionic rare earth ore leachate. Compared with Example 4, the reaction time of step (5-II) is controlled to be 10 hours, and the rest is the same as Example 4.

[0094] Comparative Example 6

[0095] This comparative example provides a composite precipitation treatment method for an ionic rare earth ore leachate. Compared with Example 4, the mass concentration of sodium hydroxide in step (5-II) is controlled to be 5% and the pH is 13. The rest is the same as Example 4.

[0096] The total amount of REO and impurity content of the concentrate product were determined based on the products obtained in Examples 4 to 6 and Comparative Example 6, and the magnesium recycling rate, rare earth recovery rate, and slag production rate were calculated. The results are listed in Table 2.

[0097] Table 2 Product information of Examples 4 to 6 and Comparative Example 6

[0098]

[0099] It can be seen from Table 1 and Table 2 that the magnesium oxide impurity removal precipitation and sodium hydroxide washing technology disclosed in the present invention can remove SO4 2- The content (as SO3) decreased from 15.39% to 6.64%, and the MgO content decreased from 5.52% to 2.59%. After the reaction time of adding sodium hydroxide was more than 3 hours, the product situation did not change much. However, with the increase of sodium hydroxide concentration and pH, the SO4 content in the concentrate product decreased. 2- The content reduction effect is significant, but the total amount of REO also decreases and the magnesium oxide content increases. But overall, this technical solution can increase the total amount of REO in the concentrate product to 84%, significantly reducing SO4 2- and MgO content, achieving a magnesium recycling rate of 92% and a total rare earth recovery rate of 95%.

[0100] The above describes the main technical features and basic principles of the present invention and the related advantages. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments and that the present invention can be implemented in other specific forms without departing from the concept or essential characteristics of the present invention. Therefore, from all perspectives, the above-mentioned specific embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the appended claims rather than the foregoing description, and it is intended that all changes that come within the meaning and range of equivalents of the claims be included within the present invention.

[0101] In addition, it should be understood that although this specification is described according to various implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each implementation method can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A composite precipitation treatment method for ionic rare earth ore leachate, firstly, a hydrometallurgical workshop is built in an ionic rare earth mine, wherein the hydrometallurgical workshop is equipped with a regulating tank, an acid dissolution tank, an impurity removal tank, an aging tank, a sedimentation tank, a liquid preparation tank and a filter press; characterized in that: The composite precipitation treatment method comprises the following steps: (1) In the regulating tank, the pH value of the rare earth leaching solution is adjusted to 7.0-7.5 using magnesium oxide slurry, and rare earth enrichment is obtained by one-step precipitation and enrichment. After the solution is allowed to stand and the precipitation is separated, the enrichment is lowered into the acid dissolution tank; (2) Acid dissolution is performed in an acid dissolution tank using dilute sulfuric acid with a mass concentration of ≥10%. The acid dissolution process is continuously stirred. The mixed liquid after acid dissolution is subjected to solid-liquid separation using a plate and frame filter press to obtain a first filter residue and a first filtrate. The first filter residue is used for solid waste well filling or temporary disturbance covering of mining projects; (3) The first filtrate is discharged into a decontamination tank, and magnesium oxide slurry is added to the decontamination tank to adjust the pH of the solution to 5.4 and then remove silicon and aluminum impurities; The obtained mixed liquid is subjected to solid-liquid separation using a plate and frame filter press to obtain a second filter residue and a second filtrate. The second filter residue is centrally stored as general solid waste, and the second filtrate is divided into two parts and discharged to an aging tank and a sedimentation tank; (4) In the aging tank, continuously add magnesium oxide slurry with a mass concentration of 1% to 10%, adjust the pH of the mixed solution to 7.2 to 7.5 and then stop, stirring continuously during the addition process, and control the aging time in the tank to be more than 18 hours after the addition is completed before using as a precipitant; (5-I) In the sedimentation tank, add the precipitant described in step (4), adjust the solution pH to 6.2, and then add sodium bicarbonate. The amount of sodium bicarbonate added is based on the molar ratio of n(HCO3 - ):n(RE 3+ )=3.5:1~4.5:1, stir continuously during the addition process, control the pH at 7.0~7.5, and age for 0.5 hour~2 hours after the addition is completed; (6-Ⅰ) After the mixed liquid in the sedimentation tank is clarified and the sediment is separated into layers, the supernatant is discharged to the liquid preparation tank, the composite rare earth precipitate is placed in the tank, and the second filtrate and the precipitant described in step (4) are then added. After continuous circulation for 3 to 5 times according to step (5-Ⅰ), the mixed liquid is subjected to solid-liquid separation using a plate and frame filter press to obtain a third filter residue and a third filtrate. The third filter residue is a rare earth carbonate and rare earth hydroxide concentrate product, and the third filtrate is reused for leaching; or, (5-II) In a sedimentation tank, add the precipitant described in step (4), adjust the solution pH to 6.9, then add sodium hydroxide, control the mass concentration of sodium hydroxide in the solution system to 1% to 3%, use hydrochloric acid to control the pH to 10 to 10.5, the reaction time is ≥ 1 hour, and after clarification and precipitation, the liquid is returned to step (4) for use, and the rare earth hydroxide precipitate is placed in the tank; (6-Ⅱ) The rare earth hydroxide precipitate described in step (5-Ⅱ) is continuously washed for 1 to 2 hours with the supernatant or clean water in the liquid preparation tank, and is filtered using a plate and frame filter press to obtain a fourth filter residue and a fourth filtrate. The fourth filter residue is the rare earth hydroxide concentrate product, and the fourth filtrate is returned to step (5-Ⅱ) to adjust the solution pH.

2. The composite precipitation treatment method for ionic rare earth ore leachate according to claim 1, characterized in that: In step (2), the pH of the acid solution is adjusted to 1.5 to 2.5, the acid dissolution time is 1 to 4 hours, the slurry solid-liquid ratio is 1:7 g / mL to 1:10 g / mL, and the rare earth content in the first filtrate is controlled to be less than 15 g / L.

3. The composite precipitation treatment method for ionic rare earth ore leachate according to claim 1, characterized in that: In step (2), the first filter residue is insoluble silicate mineral residue, and the washing method is countercurrent washing.

4. The composite precipitation treatment method for ionic rare earth ore leachate according to claim 3, characterized in that: In step (2), the first filter residue is washed with clean water until the pH value is 6.0 to 9.0, and the washing water is used for further acid dissolution and slurry preparation.

5. The composite precipitation treatment method for ionic rare earth ore leachate according to claim 1, characterized in that: In step (3), the second filter residue washing method is countercurrent washing.

6. The composite precipitation treatment method for ionic rare earth ore leachate according to claim 5, characterized in that: In step (3), the second filter residue is first washed with an acid solution having a pH of 4 to 5 and then washed with clean water, and the washing water is reused for acid dissolution and slurry preparation.

7. The composite precipitation treatment method for ionic rare earth ore leachate according to claim 1, characterized in that: In step (6-Ⅰ), the SO4 in the composite rare earth precipitate is detected after continuous circulation 3 to 5 times according to step (5-Ⅰ). 2- Content, when it is burned impurity SO4 2- When the content is ≥2%, first use a sodium hydroxide solution with a mass concentration of 0.3% to 1.5% for continuous washing, and control the washing time to 1 hour to 3 hours until the impurities SO4 are burned. 2- When the content is less than 2%, the mixed liquid is separated into solid and liquid using a plate and frame filter press.

8. The composite precipitation treatment method for ionic rare earth ore leachate according to claim 1, characterized in that: In step (4), rare earth hydroxide concentrate slurry is used instead of magnesium oxide slurry.

9. The composite precipitation treatment method for ionic rare earth ore leachate according to claim 1, characterized in that: In step (4), the continuous stirring is a kind of mechanical stirring or ventilation stirring.

10. The composite precipitation treatment method for ionic rare earth ore leachate according to claim 1, characterized in that: In (5-II), the reaction time is 1 to 3 hours.

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