A method for recovering valuable rare earths from lead- barium slag

Abstract

The application discloses a method for recycling valuable rare earth in lead-barium slag, and the method for recycling valuable rare earth in lead slag comprises the following steps: A, slurry of the lead slag is prepared by using water, the slurry water is heated, and then sulfuric acid is added for acid dissolution; B, the slurry water is cooled and filtered, the filter residue is temporarily stored in a warehouse, the filter liquor is heated, then barium chloride is added and stirred to precipitate, then the mixture is cooled and filtered, the filter residue is temporarily stored in a warehouse, and the filter liquor is a rare earth chloride solution; the method for recycling valuable rare earth from barium slag comprises the following steps: (1), the acid washing solution is mixed with the barium slag, the reaction system is heated, and then the mixture is washed and left to stand; (2), the reaction system is filtered, the filter residue is temporarily stored in a warehouse, and the filter liquor is a rare earth chloride solution. According to the method, the recovery rate of the valuable rare earth can be increased to more than 95%, the barium slag reduction amount can be more than 15%, and the lead slag reduction amount can be more than 45%, so that the yield of the valuable rare earth is effectively improved, the storage amount of the lead-barium slag is reduced, and the industrial practicability is high.

Description

Technical Field

[0001] This invention relates to the field of rare earth separation technology, and in particular to a method for recovering valuable rare earth elements from lead-barium slag. Background Technology

[0002] Currently, most of the rare earth minerals used in Sichuan Province come from the Maoniuping Rare Earth Mine in Mianning County, Liangshan Prefecture, and are mostly fluorocarbon cerium rare earth concentrates. Inevitably, lead is carried into the fluorocarbon cerium ore, with a PbO content of about 0.2%. After oxidation roasting, hydrochloric acid leaching, alkali conversion, and acid dissolution again, some lead exists in the form of lead ions in the mixed rare earth chloride. In the extraction section, in order to improve the quality of single rare earth chloride, the concentration of mixed rare earth chloride entering the tank is required to be above 250 g / L, and the PbO content should be less than 0.025 g / L. Before impurity removal, the PbO content in the mixed rare earth chloride is generally about 2.5 g / L. After impurity removal, 0.8% of valuable rare earth is carried into the lead-barium slag. The inclusion of valuable rare earth elements in lead-barium slag not only increases the slag inventory but also results in the loss of valuable rare earth elements. Therefore, in order to reduce the inventory of lead-barium slag and increase the yield of valuable rare earth elements, how to recover valuable rare earth elements from lead-barium slag is a technical problem that technicians need to solve.

[0003] Currently, there are two main mature processes for recovering valuable rare earth elements from lead-barium slag: One method involves calcining the lead slag, dissolving it in sulfuric acid, followed by double salt precipitation, and then alkali-to-acid dissolution. For example, existing patent CN103572064A discloses a method for enriching lead and recovering rare earth elements from rare earth lead slag, which employs calcination, sulfuric acid leaching, solid-liquid separation, alkali-to-acid dissolution of the supernatant, and extraction of rare earth elements. This recovery process is lengthy, costly, and results in a high loss of valuable rare earth elements, with a maximum recovery rate of only 91.7%, indicating room for improvement. The other method involves recovering rare earth elements through carbon precipitation of the sulfate solution obtained after calcination and sulfuric acid leaching, followed by dissolution with hydrochloric acid. This method also suffers from drawbacks such as a long recovery process, high cost, and a high loss of valuable rare earth elements.

[0004] Chinese patent CN113604672A discloses a method for recovering lead chloride from lead-barium slag. The method involves dissolving the dechlorinated lead-barium slag with nitric acid, adding a flocculant, performing solid-liquid separation, cooling the resulting liquid, adding hydrochloric acid, and performing solid-liquid separation to obtain a mixed solution of lead chloride crystals, nitric acid, and rare earth nitrates. A saturated chloride salt solution is then added to the mixed solution of lead nitrates and rare earth nitrates obtained after multiple dissolutions of the lead-barium slag to obtain lead chloride. The rare earth solution containing nitric acid obtained from solid-liquid separation is then extracted to obtain a single rare earth element. The method claims that the yield of both lead and rare earth elements is above 96%, demonstrating high recovery efficiency. However, nitric acid is highly volatile and easily volatilizes during the dissolution of lead slag, increasing the difficulty of recovering waste gas. At the same time, after the introduction of nitric acid, lead nitrate is a soluble nitrate under acidic conditions. During the enrichment of lead chloride, some lead nitrate inevitably coexists. After extraction and separation in the nitric acid system, the lead content in the final rare earth product exceeds the standard, which will affect the quality of the rare earth product. In addition, this method has strict requirements for equipment (for example, it requires the use of highly corrosive nitric acid), resulting in high equipment investment costs and limited practicality. Summary of the Invention

[0005] The purpose of this invention is to provide a method for recovering valuable rare earth elements from lead-barium slag, thereby addressing the shortcomings of existing technologies and solving the problems mentioned above.

[0006] The technical solution adopted in this invention is as follows: A method for recovering valuable rare earth elements from lead-barium slag, wherein the lead-barium slag is lead slag and barium slag produced after acid-base leaching of fluorocarbon cerium ore, and the method for recovering valuable rare earth elements from the lead slag includes:

[0007] A. Use water to slurry the lead slag, then heat the slurry to above 80°C, and then add sulfuric acid for acid dissolution;

[0008] B. After the acid dissolution reaction is completed, the slurry is cooled and filtered. The filter residue is transferred to the warehouse for temporary storage. The filtrate is heated to above 60°C, and then barium chloride is added and stirred to precipitate. Then it is cooled and filtered. The filter residue is transferred to the warehouse for temporary storage. The filtrate is the rare earth chloride solution.

[0009] Methods for recovering valuable rare earth elements from barium slag include:

[0010] (1) Mix the acidic washing solution with the barium slag, heat the reaction system to 40-60℃ (preferably 50℃, mainly related to the solubility of rare earth), wash for a period of time, and let stand to clarify;

[0011] (2) Filter the reaction system, transfer the filter residue to the warehouse for temporary storage, and the filtrate is a rare earth chloride solution.

[0012] Furthermore, in step A, when the lead slag is slurried, the solid-liquid ratio is 1:7-15, and the specific solid-liquid ratio is selected according to actual needs.

[0013] Furthermore, in step A, the sulfuric acid is concentrated sulfuric acid, and the acid dissolution reaction time is 1-3 hours, preferably 2 hours.

[0014] Furthermore, in step A, during the acid dissolution process, the acid dissolution operation is stopped when the residual acid concentration reaches 0.2±0.1 mol / L.

[0015] Furthermore, in step B, barium chloride is added and stirred to precipitate. Then, during cooling and filtration, the filter residue is washed with hydrochloric acid solution with a pH of 3-4, and the washing liquid generated is added to the filtrate.

[0016] Furthermore, in step B, the first filter residue produced is lead slag, the second filter residue produced is barium slag, and the obtained rare earth chloride solution is used as the bottom water of the acid leaching tank for acid dissolution of roasted ore or alkali cake.

[0017] Furthermore, in step (1), the pH value of the acidic washing solution is 3-4, and the liquid-solid ratio of the acidic washing solution to the barium slag is 1:3-7, preferably 1:5.

[0018] Furthermore, in step (1), the barium slag is repeatedly washed with acidic washing solution until the REO concentration in the supernatant after standing reaches below 0.3 g / L.

[0019] Furthermore, in step (2), the obtained filter residue is the barium residue after rare earth recovery, and the obtained rare earth chloride solution is used as the slurry water for roasting ore.

[0020] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0021] 1. Based on the different formation principles of lead slag and barium slag, this invention designs different methods to recover valuable rare earth elements. Specifically, barium slag is recovered by washing with acidic washing solution, while lead slag is recovered by dissolving it in concentrated sulfuric acid and then using barium chloride to convert the sulfuric acid system into a hydrochloric acid system. Compared with existing lead slag recovery processes, this invention directly dissolves lead slag in dilute sulfuric acid and then directly converts it with barium chloride. This process has fewer steps, avoids the loss of valuable rare earth elements due to long process steps, ensures the recovery rate of valuable rare earth elements, and saves the cost of rare earth recovery.

[0022] 2. The method of the present invention can increase the recovery rate of valuable rare earths to over 95%, reduce barium slag by over 15%, and reduce lead slag by over 45%. It not only effectively improves the recovery rate of valuable rare earths, but also reduces the inventory of lead and barium slag. It has strong industrial applicability and is worthy of promotion and application. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the existing acid-base combined method for producing mixed rare earth chlorides from bastnaesite.

[0024] Figure 2 This is a schematic diagram of the process flow for a method of recovering valuable rare earth elements from lead-barium slag according to the present invention. Detailed Implementation

[0025] The present invention will now be described in detail with reference to the accompanying drawings.

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0027] The mixed rare earth chloride solution obtained from bastnaesite through an acid-base leaching process has a concentration of approximately 140 g / L. After conditioning and concentration, the concentration of the mixed rare earth chloride solution can reach over 250 g / L. Following further removal of lead and barium / radium impurities and aging for approximately 48 hours, the mixed rare earth chloride solution can be fed into the extraction process for rare earth extraction. Please refer to the acid-base leaching process details. Figure 1 It includes the following steps:

[0028] S1. Oxidative roasting of fluorocarbon cerium concentrate (REO≥68.5%) at a temperature of 580-600℃;

[0029] S2. Roasted ore is leached with hydrochloric acid (C / R ≤ 8%). + (≤0.3mol / L), resulting in a leaching residue and a leachate, with the leaching residue being transferred to the alkali conversion process;

[0030] S3. Alkali conversion (OH-) of the leaching residue. - (≥1.5mol / L), washed with water until pH=7-8, to obtain alkali-converted residue and alkali-converted solution. The alkali-converted solution is used as leachate, and after conditioning, evaporation, impurity removal and filtration, mixed rare earth chloride is obtained.

[0031] S4. The alkali-converted slag is acid-washed and water-washed. The water-washed slag is cerium-rich slag. The water-washed liquid is then carbonized to obtain conditioning water.

[0032] In the above process, the main steps for filtering the leachate to remove impurities are as follows:

[0033] 1. The slag produced after removing barium and radium is called barium slag. Generally, the rare earth content in barium slag is around 13%. The reaction equation for producing barium slag is:

[0034] Ba 2+ +SO4 2- =BaSO4↓

[0035] During the barium removal process, the temperature is raised to above 60°C, and soluble salts containing sulfate are added. Concentrated sulfuric acid is generally used for barium removal in this case, and it produces the least amount of rare earth sulfate complex salts. Therefore, concentrated sulfuric acid is used for barium removal in this case.

[0036] In actual production, due to the low BaO content in bastnaesite, the BaO content in the mixed rare earth chlorides produced after acid leaching is relatively low. 2+ The content of rare earth elements is relatively low. Currently, processing 800 tons of fluorocarbon cerium ore with 70% REO per month yields approximately 6 tons of barium slag, with a moisture content of about 30%. Rare earth elements generally exist in the barium slag as rare earth chlorides, and partly as sodium rare earth sulfate double salts. Based on the principle of barium slag formation, this invention innovatively recovers valuable rare earth elements from the barium slag as follows (e.g., Figure 2 As shown):

[0037] Add the barium slag to the reaction vessel, then add the prepared acidic washing solution (e.g., a dilute sulfuric acid solution) with a pH of 3-4 at a liquid-to-solid ratio of 1:5 (1:3-7 can be selected) to the reaction vessel. Start stirring and heat to about 50℃ (40-60℃). Wash with water for about 0.5 hours, then stop stirring and clarify. Then, siphon the supernatant to the acid leaching tank for use in the pulping of the roasted ore. Repeat this washing process several times until the REO concentration of the supernatant is below 0.3g / L. Then, filter with a plate and frame filter and transfer the barium sulfate slag to the hazardous waste warehouse for temporary storage. The filtrate is added to the acid leaching tank.

[0038] 2. In the extraction of valuable rare earth elements from bastnaesite, the slag produced after removing lead impurities from the mixed rare earth chloride is called lead slag. The lead removal process is as follows: A certain amount of mixed rare earth chloride is transferred to a reaction vessel, heated to 80°C, and stirred. Then, a weighed amount of sodium sulfide is slowly added. After stirring for 0.5 hours, stirring is stopped, the mixture is clarified, and samples are sent for testing. If the PbO content is less than 0.025 g / L, the liquid is filtered; otherwise, sodium sulfide is added to remove lead. The amount of sodium sulfide added each time should not exceed 5 kg. The reaction equation for lead removal is:

[0039] Pb 2+ +S 2- =PbS↓

[0040] RE 3+ +S 2- =RE2S3↓

[0041] S 2- +H2O+H + =H2S↑ + OH -

[0042] 3OH - +RE 3+=RE(OH)3↓

[0043] As can be seen from the above reaction principle, the valuable rare earth elements in lead slag mainly exist in the form of rare earth sulfides and rare earth hydroxides. Based on the principle of lead slag formation, this invention innovatively recovers the valuable rare earth elements in lead slag as follows (e.g.) Figure 2 As shown):

[0044] After the lead slag is slurried (at a solid-liquid ratio of 1:7-15), the temperature is raised to above 80℃, and then concentrated sulfuric acid (98% by mass) is added for acid dissolution. The reaction is carried out for 2 hours, and the residual acid concentration is maintained at 0.2±0.1 mol / L. The reaction equation for dissolving rare earth elements is as follows:

[0045] 2RE(OH)3+3H2SO4=RE2(SO4)3+6H2O

[0046] 12H + +RE2S3+3SO4 2- =RE2(SO4)3 + 6H2O + 3S↓

[0047] H + +HS - =H2S↑

[0048] In actual production, after lead slag is dissolved in sulfuric acid, the lead sulfate is difficult to dissolve, while the solubility of rare earth sulfate is about 20g / L. Therefore, the lead slag (transferred to the hazardous waste warehouse for temporary storage) and rare earth sulfate can be separated by filtration.

[0049] The rare earth sulfate solution is heated to above 60℃, and then barium chloride is added according to the concentration of sulfate ions in the solution. This causes the sulfate ions to combine with the barium ions to form barium sulfate precipitate, which can then be separated by filtration using a plate and frame filter press. The filter residue is washed with hydrochloric acid solution with a pH of 3-4 (the washing liquid can be combined with the filtrate) to obtain barium sulfate residue. The barium sulfate residue is stored in a slag pool for resale. The resulting filtrate is a rare earth chloride solution with a concentration of about 20-25 g / L, which can be transferred to an acid leaching tank as bottom water for acid dissolution of roasted ore or alkali cake.

[0050] To better illustrate the present invention, some embodiments are listed below:

[0051] Example 1

[0052] A method for recovering rare earth elements from lead slag produced by an acid-base combined process includes the following steps:

[0053] S1. Add 500 kg of lead slag with a moisture content of 30% and a rare earth content of 24% into the reaction tank, and then add 5 cubic meters of clean water to carry out slurrying.

[0054] S2. Pour 85L of concentrated sulfuric acid (98% by mass) into the reaction vessel, then heat it to above 80℃. After reacting for 2 hours, stop stirring and, after clarification, extract 4.5 cubic meters of the supernatant into a spare reaction vessel (i.e., rare earth sulfuric acid solution). The concentration of rare earth in the supernatant was found to be 24.70 g / L and the acidity was 0.23 mol / L.

[0055] S3. Add 2 cubic meters of clean water to the reaction tank, add 10L of concentrated sulfuric acid and react. Wash with water for 0.5 hours, then filter directly using a plate and frame filter. The REO concentration in the filtrate was found to be 2.81g / L. The filtrate was left in the reaction tank as bottom water for the first leaching of lead slag. The filter residue (lead slag) weighed 262kg, with a moisture content of 18.5% and a rare earth REO content of 0.83%. The filter residue was transferred to the hazardous waste warehouse for temporary storage.

[0056] S4. Heat the supernatant in the standby reaction tank to above 60°C, and then slowly add 220 kg of industrial-grade barium chloride with a content of over 98% (add within 1 hour). After reacting for 0.5 hours, let it stand and extract the supernatant to the acid leaching reaction tank. The supernatant can be used as the bottom water for acid leaching of rare earth roasted ore.

[0057] S5. Filter using a plate and frame filter press. The filtrate is a rare earth chloride solution, and the filter residue is barium sulfate residue. Add acidified water with a pH of 3.5 to the barium sulfate residue, wash with water for 0.5 hours, let stand, and then filter. Use the filtrate as the bottom water for acid leaching of rare earth roasted ore. The total weight of the washed barium sulfate residue is 295.5 kg, with a rare earth content of 0.31%, which is directly resold as a barite product.

[0058] A method for recovering rare earth elements from barium slag produced by an acid-base combined process includes the following steps:

[0059] S1. Weigh 500 kg of barium slag produced from the acid leaching combined treatment of fluorocarbon cerium ore into a reaction vessel. The slag has an REO content of 13.5% and a moisture content of 38%.

[0060] S2. Add 3 cubic meters of water acidified with hydrochloric acid to the barium slag. The pH value of the acidified water is 3.5. After slurrying, heat to 50°C and stir for 0.5 hours.

[0061] S3. Allow the supernatant to stand and extract it (the supernatant can be used as the bottom water for acid leaching of rare earth roasted ore), then add acid washing solution and repeatedly acid wash until the REO concentration in the supernatant is below 0.3g / L.

[0062] S4. Plate and frame filtration, the filtrate and pickling solution are used as bottom water for acid leaching of rare earth roasted ore, to obtain 420 kg of filter residue (barium residue), with a moisture content of 40.12% and a rare earth content of 0.26%, and then the barium residue is resold.

[0063] Example 2

[0064] A method for recovering rare earth elements from lead slag produced by an acid-base combined process includes the following steps:

[0065] S1. Take 300 kg of lead slag that has been dried for a period of time into a reaction vessel. Its moisture content is 15.2% and rare earth content is 29.8%. Add 4 cubic meters of clean water to make slurry.

[0066] S2. Inject 50L of concentrated sulfuric acid (98% by mass), heat to above 80℃, react for 2 hours and then stop stirring. Draw 3.4 cubic meters of supernatant into a spare reaction tank (i.e. rare earth sulfuric acid solution). The concentration of rare earth in the supernatant was found to be 24.3 g / L.

[0067] S3. Add 3L of concentrated sulfuric acid (98% by mass) and 1 cubic meter of clean water to the remaining acid-leached lead slag, wash with water for 0.5 hours, and after plate and frame filtration, obtain 1200L of filtrate with a rare earth concentration of 3.34g / L. Use the filtrate as bottom water for the next batch. The filter residue (lead slag) weighs 164.1kg, with a moisture content of 20.05% and a rare earth content of 2.74%.

[0068] S4. Heat the supernatant in the standby reaction vessel to above 60°C, then stir and slowly add 192 kg of barium chloride (to be completed within 1 hour). After reacting for 0.5 hours, clarify and extract the supernatant. The supernatant is used as the bottom water for acid leaching of rare earth roasted ore.

[0069] S5. Filter using a plate and frame filter press. The filtrate is a rare earth chloride solution, and the filter residue is barium sulfate residue. Add 1 cubic meter of acidified water (hydrochloric acid acidification) with a pH of 3.5-4.0 to the barium sulfate residue. After washing with water for 0.5 hours, let it stand and then filter. Use the filtrate as the bottom water for acid leaching of rare earth roasted ore. The weight of the filter residue (barium sulfate residue) is 254.20 kg, and the rare earth content in the filter residue is 0.24%. It is directly resold as barite.

[0070] A method for recovering rare earth elements from barium slag produced by an acid-base combined process includes the following steps:

[0071] S1. Weigh 300 kg of barium slag produced by the acid-base combined method (the barium slag has been dried for a period of time), with a moisture content of 20.23% and an REO content of 15.2%. Then add 1.5 cubic meters of hydrochloric acid-acidified water to make slurry. The pH value of the acidified water is 3.5.

[0072] S2. After heating the slurry to 50℃, stir for 0.5h, then let it stand and extract the supernatant (the supernatant can be used as the bottom water for acid leaching of rare earth roasted ore), then add acidic water and repeatedly acid wash until the REO concentration in the supernatant is below 0.3g / L.

[0073] S3. Plate and frame filtration. The filtrate and pickling solution are used as bottom water for acid leaching of rare earth roasted ore, yielding 254.7 kg of filter residue with a moisture content of 36.77% and a rare earth content of 0.47%, which can be directly resold.

[0074] Example 3

[0075] A method for recovering rare earth elements from lead slag produced by an acid-base combined process includes the following steps:

[0076] S1. In a laboratory environment, take 250g of lead slag with a moisture content of 27% and a REO content of 33% into a 5L beaker, add 2.5L of water to slurry it, then add 50mL of concentrated sulfuric acid (mass fraction 98%), heat to above 80℃, and stop stirring after reacting for 2 hours.

[0077] S2. After standing, collect the supernatant into a spare beaker to obtain 2530ml of supernatant. The REO content of the supernatant was analyzed and found to be 27.66g / L.

[0078] S3. Add 1L of water and 5mL of sulfuric acid to the beaker, acid wash for 0.5h, then stop stirring, filter the lead slag, and obtain 137.25g of lead slag with a moisture content of 19.34% and a rare earth content of 1.74%; obtain 1110mL of filtrate with a rare earth concentration of 2.54g / L.

[0079] S4. Mix the supernatant and filtrate and transfer them to a 5L beaker. Heat to above 60°C and start stirring. Then slowly add 220g of barium chloride (add it all within 1 hour). After reacting for 0.5 hours, let it stand and extract the supernatant into a spare 5L beaker.

[0080] S5. Add acidified water (hydrochloric acid acidification) with pH 3.5 to the beaker, wash with water for 0.5 hours, let stand and filter, and combine the filtrate with the supernatant in the spare beaker (i.e. rare earth chloride solution) to obtain 282.33g of filter residue (barium residue) with a rare earth content of 0.43%.

[0081] A method for recovering rare earth elements from lead slag produced by an acid-base combined process includes the following steps:

[0082] S1. In the laboratory, weigh 250g of barium slag produced by acid leaching combined treatment of fluorocarbon cerium ore into a 5L beaker. The slag has an REO content of 15.62% and a moisture content of 33%. Then add 2.5L of hydrochloric acid-acidified water to make a slurry. The pH value of the acidified water is 3.5.

[0083] S2. Heat the slurry to 50℃, stir for 0.5h, let it stand, extract the supernatant, add acidified water and wash repeatedly until the REO concentration in the supernatant is below 0.3g / L.

[0084] S3. Filter the barium residue, combine the filtrate with the supernatant to obtain 208g of filter residue (barium residue), with a moisture content of 40.12% and a rare earth content of 0.31%.

[0085] Comparative Example 1

[0086] Comparative Example 1 is the same as Example 1, except that in step S5 of the barium slag rare earth recovery process, the pH of the acidified water was adjusted to 1 before acid washing of the barium slag. The BaO content in the filtrate was then measured, and it was found to be 0.27%, which is greater than the process requirement of BaO ≤ 0.1%. Correspondingly, the filtrate from step S5 of Example 1 was tested, and the BaO content was found to be ≤ 0.1%. This shows that when the pH of the acidified water (i.e., the acid washing solution) is too high, the barium sulfate slag will dissolve into BaO in the strongly acidic acidified water. 2+ Ions and SO4 2- This increases the solubility of barium slag under high acidity conditions, leading to excessive barium content. Therefore, controlling the pH value of the acidification water used to wash the barium slag within 3-4 can not only wash out the rare earth elements entrained in the barium slag but also prevent the barium content from exceeding the standard.

[0087] Comparative Example 2

[0088] Comparative Example 2 is the same as Example 1, except that after dissolving the lead slag with hydrochloric acid, it was filtered and the filtrate was tested. The REO concentration was 126.37 g / L and the PbO content was 0.35%, which is higher than the quality requirement of PbO ≤ 0.01% for mixed rare earth chlorides. Therefore, when using hydrochloric acid to dissolve the lead slag, the lead content in the mixed rare earths exceeded the standard because lead chloride is only slightly soluble. Therefore, this invention does not use hydrochloric acid to dissolve the lead slag.

[0089] Comparative Example 3

[0090] Comparative Example 3 is the same as Example 1, except that the residual acid concentration is controlled at 0.4 mol / L during acid dissolution of lead slag, and the amount of concentrated sulfuric acid used is about 160 L. Simultaneously, to convert rare earth sulfate, 599.04 kg of barium chloride is required. The amounts of sulfuric acid and barium chloride used are essentially doubled. Therefore, excessively high residual acidity will lead to waste of auxiliary materials and increase the cost of treating lead slag.

[0091] Comparative Example 4

[0092] Comparative Example 4 was the same as Example 1, except that concentrated sulfuric acid was replaced with concentrated nitric acid (98% by mass) in the treatment of lead slag. After filtration, concentrated hydrochloric acid was added to the filtrate, and after no new precipitate was formed, filtration was performed. The resulting filtrate was rare earth nitrate, with a rare earth concentration of 127.88 g / L and a PbO content of 0.58%, which is higher than the requirement of PbO ≤ 0.01% in the mixed rare earth. Meanwhile, nitric acid is highly volatile, and some nitrogen oxides volatilize during the production process, increasing the cost of environmentally friendly waste gas recovery and treatment. The resulting lead nitrate is a soluble salt, while lead chloride is only slightly soluble in aqueous solution. Therefore, adding hydrochloric acid to remove lead will result in a higher lead content in the mixed rare earth.

[0093] Furthermore, the effects of the above Examples 1-3 on the recovery rate of valuable rare earth elements and the reduction of lead-barium slag are shown in Table 1.

[0094] Table 1. Effects of use in Examples 1-3

[0095]

[0096]

[0097] As shown in Table 1, the method of this invention can increase the recovery rate of valuable rare earth elements to over 95%, reduce barium slag by over 15%, and reduce lead slag by over 45%. This not only effectively improves the recovery rate of valuable rare earth elements but also reduces the inventory of lead and barium slag. Furthermore, based on Comparative Examples 1-4, sulfuric acid is the optimal solvent for acid dissolution of lead slag, allowing for a more scientific and cost-effective recovery of valuable rare earth elements from waste slag (lead and barium slag).

[0098] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for recovering valuable rare earth elements from lead-barium slag, characterized in that, The lead-barium slag is the lead or barium slag produced after leaching bastnaesite using a combined acid-base method. Methods for recovering valuable rare earth elements from the lead slag include: A. Use water to slurry the lead slag, then heat the slurry to above 80°C, and then add sulfuric acid for acid dissolution. The sulfuric acid is concentrated sulfuric acid with a mass fraction of 98%. The acid dissolution reaction time is 1-3 hours. When slurrying the lead slag, the solid-liquid ratio is 1:7-15. During the acid dissolution process, when the residual acid concentration reaches 0.2±0.1mol / L, the acid dissolution operation is stopped. B. After the acid dissolution reaction is completed, the slurry is cooled and filtered. The filter residue is transferred to the warehouse for temporary storage. The filtrate is heated to above 60°C, and then barium chloride is added and stirred to precipitate. Then it is cooled and filtered. The filter residue is transferred to the warehouse for temporary storage. The filtrate is the rare earth chloride solution. Methods for recovering valuable rare earth elements from barium slag include: (1) Mix the acidic washing solution with the barium slag, heat the reaction system to 40-60℃, wash for a period of time, and let it stand to clarify; the pH value of the acidic washing solution is 3-4, and the solid-liquid ratio of the acidic washing solution to the barium slag is 1:3-8. (2) Filter the reaction system, transfer the filter residue to the warehouse for temporary storage, and the filtrate is a rare earth chloride solution.

2. The method for recovering valuable rare earth elements from lead-barium slag as described in claim 1, characterized in that, In step B, barium chloride is added and stirred to precipitate. Then, during cooling and filtration, the filter residue is washed with hydrochloric acid solution with a pH of 3-4, and the resulting washing liquid is added to the filtrate.

3. The method for recovering valuable rare earth elements from lead-barium slag as described in claim 2, characterized in that, In step B, the first filter residue produced is lead slag, and the second filter residue produced is barium slag. The obtained rare earth chloride solution is used as the bottom water of the acid leaching tank for acid dissolution of roasted ore or alkali cake.

4. The method for recovering valuable rare earth elements from lead-barium slag as described in claim 3, characterized in that, In step (1), the barium slag is repeatedly washed with acidic washing solution until the REO concentration in the supernatant after standing reaches below 0.3 g / L.

5. The method for recovering valuable rare earth elements from lead-barium slag as described in claim 4, characterized in that, In step (2), the filter residue obtained is the barium residue after rare earth recovery, and the rare earth chloride solution obtained is used as the slurry water for roasting ore.

6. The method for recovering valuable rare earth elements from lead-barium slag as described in any one of claims 1-5, characterized in that, The recovery rate of valuable rare earth elements in lead-barium slag is over 95%, the amount of barium slag is reduced by over 15%, and the amount of lead slag is reduced by over 40%.

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