A method for reducing lead and rare earth loss in rare earth concentrate
By reacting the dimethoate solution with the rare earth concentrate to form a complex precipitate, and then adjusting it with magnesium chloride, the problems of low lead removal rate and large rare earth loss in the rare earth concentrate are solved. This achieves a highly efficient and environmentally friendly lead removal process for rare earth concentrate, which is suitable for the rare earth smelting industry.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SICHUAN JIANGTONG RARE EARTH CO LTD
- Filing Date
- 2023-11-10
- Publication Date
- 2026-06-30
AI Technical Summary
Existing lead removal processes for rare earth concentrates suffer from problems such as low lead removal rates, large rare earth losses, severe environmental pollution, and complex processes. In particular, the sulfide precipitation method results in high rare earth loss rates and a poor operating environment.
The pH value was adjusted by using dimethoate solution and reacted with rare earth concentrate to form a lead complex precipitate. Then, a low-lead rare earth solution was obtained by solid-liquid separation. Magnesium chloride was used to adjust the residual amount of dimethoate and the reaction conditions were controlled to achieve selective lead removal.
While ensuring low rare earth loss, it achieves efficient lead removal, simplifies the process, reduces environmental pollution risks and production costs, and is suitable for the rare earth smelting industry.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of rare earth hydrometallurgical technology, specifically a method for reducing the loss of lead and rare earth elements in rare earth concentrate. Background Technology
[0002] my country is a major rare earth resource country, ranking first in the world in both reserves and production. Its resources are mainly distributed in Inner Mongolia, Panzhihua-Xichang region of Sichuan, Jiangxi, and Shandong. Among them, the Panzhihua-Xichang region of Sichuan is primarily composed of light rare earth fluorocarbon cerium ore, with reserves reaching 4.86 million tons, second only to Inner Mongolia, making it my country's second largest light rare earth resource area.
[0003] Rare earth concentrates obtained through beneficiation contain approximately 60%–70% REO and 0.05%–0.2% lead impurities. Currently, the mainstream smelting process for this type of rare earth concentrate is “concentrate oxidative roasting – hydrochloric acid leaching – atmospheric pressure alkali conversion – hydrochloric acid dissolution – impurity removal and concentration – extraction and separation”. The acid leaching solution is obtained through two acid dissolution steps. As the smelting process progresses, most of the lead is eventually enriched in the concentrate, which seriously affects the product quality. Therefore, lead removal is required before the concentrate enters the extraction stage to ensure the purity of the rare earth product.
[0004] Currently, the main methods for lead removal from rare earth solutions both domestically and internationally include chemical precipitation (such as neutralization precipitation and sulfide precipitation), electrochemical methods, ion exchange, and extraction. Given that lead is an amphoteric metal, and rare earth ion precipitation requires a high pH value, neutralization precipitation can only remove a portion of the lead impurities, thus limiting its practicality. Electrochemical lead removal uses a stainless steel mesh cathode and a graphite plate anode. Air is introduced during electrolysis for agitation, achieving a lead removal rate of 99%. The process results in almost no loss of rare earth elements, and the cathode can be recycled, minimizing impact on subsequent rare earth smelting and separation. However, this method requires strict process parameters and is costly, currently only in the laboratory research stage. Ion exchange primarily achieves targeted lead removal by designing specific lead-removing groups on the ion exchange resin. While resin production technology is mature, this method is rarely used in rare earth industrial production. The main reason is the extremely stringent requirements for the purity of the feed solution; even a small amount of suspended particles can cause severe resin blockage and failure. Taking into account both economic costs and lead removal efficiency, sulfide precipitation is currently the most common lead removal method both domestically and internationally.
[0005] Currently, most rare earth smelting enterprises in Sichuan Province use sodium sulfide to remove lead from rare earth concentrates, which utilizes Pb... 2+The sulfide in lead slag forms PbS precipitate. However, industrial sodium sulfide contains impurities such as sodium sulfate and is strongly alkaline. During lead removal, high concentrations of rare earth ions inevitably undergo hydroxide precipitation and double salt precipitation reactions, causing rare earth elements to enter the lead slag, resulting in a rare earth loss rate of 1% to 2%. To reduce this rare earth loss, some companies recycle the lead slag. Common recycling methods include hydrochloric acid dissolution and sulfuric acid double salt precipitation. The hydrochloric acid dissolution method directly uses high-concentration hydrochloric acid to dissolve the lead slag. This method has a rare earth recovery rate of only about 70%, resulting in a low recovery rate, a poor operating environment, severe hydrogen sulfide pollution, and certain safety hazards. In addition, the sulfuric acid double salt precipitation method also has some applications. That is, sulfuric acid is used to dissolve lead slag, and lead precipitates in the form of lead sulfate. After solid-liquid separation, sodium salt is introduced into the supernatant containing rare earth elements, so that the rare earth elements precipitate in the form of double salt. The rare earth sulfate double salt is then converted by alkali to obtain rare earth hydroxide, and acid dissolution is used to obtain rare earth acid leaching solution. This method has a relatively high rare earth recovery rate, but the process is complicated, the solid-liquid conversion is frequent, the consumption of auxiliary materials is large, and the production cost is high, so its industrial application is also limited.
[0006] To address the problems in lead removal from rare earth concentrates and lead slag recovery mentioned above, it is urgent to develop a green and low-pollution lead removal process that is simple to operate, has a high lead removal rate, and a low rare earth loss rate. This will alleviate the environmental pressure on enterprises and reduce production costs. Summary of the Invention
[0007] The purpose of this invention is to address the problems existing in the prior art, such as the low lead removal rate, large rare earth co-precipitation loss, and the easy generation of toxic hydrogen sulfide gas, resulting in serious environmental pollution, in the current rare earth acid leaching lead removal process. Furthermore, the REO recovery process in lead slag suffers from complex operation, low recovery rate, high auxiliary material consumption, and low equipment utilization. This invention provides a method to reduce rare earth loss during lead removal from rare earth concentrate. This method achieves selective lead removal while ensuring a low rare earth loss rate during the lead removal process. It features good lead removal effect, low rare earth loss, simple process, no generation of toxic or harmful gases, and low economic cost, making it highly promising for industrial application.
[0008] To achieve the above-mentioned objectives, the specific technical solution of this invention is as follows:
[0009] A method for reducing lead and rare earth loss in rare earth concentrates includes the following steps:
[0010] S1) Prepare a 5wt% to 40wt% solution of dichlorvos and adjust the pH of the solution to 1 to 9 using hydrochloric acid;
[0011] S2) Add the lead-containing rare earth concentrate to the stirring tank. The concentration of rare earth oxides (REO) in the concentrate is 200-350 g / L.
[0012] S3) Add the dimethoate solution to the lead-containing rare earth concentrate, and control the mass ratio of dimethoate in the added dimethoate solution to PbO in the lead-containing rare earth concentrate to be W1, where W1 is 1.9 to 3.5. Stir for 5 to 120 minutes to promote full reaction and selectively form lead complex precipitates.
[0013] S4) Detect the mass concentration ratio of dichlorvos / REO in the rare earth concentrate after lead removal. If it is greater than 0.03%, add solid anhydrous magnesium chloride and control the mass ratio of the added magnesium chloride to the residual dichlorvos in the rare earth concentrate to W2. If it is less than or equal to 0.03%, proceed to the next step.
[0014] S5) Solid-liquid separation was performed to obtain low-lead rare earth solution and lead slag. The lead slag was washed and dried, and the composition of the low-lead rare earth solution and lead slag was analyzed.
[0015] In a preferred embodiment of this application, hydrochloric acid is used in step S1) to adjust the pH of the solution to 3-7.
[0016] In a preferred embodiment of this application, in step S2), the pH value of the lead-containing rare earth concentrate is controlled to be 1-5 and the temperature is controlled to be 20-70°C.
[0017] In a preferred embodiment of this application, the pH value of the lead-containing rare earth concentrate and the temperature of the concentrate can also be controlled to be 1-5 and 40-50°C in step S2).
[0018] In a preferred embodiment of this application, W1 in step S3) is 2.3 to 2.6, and the reaction is stirred for 10 to 30 minutes.
[0019] In a preferred embodiment of this application, W2 in step S4) is 0.5 to 2.0, or it can be 0.5 to 1.0; under this condition, the reaction needs to be carried out at 20 to 60°C for 30 minutes with stirring.
[0020] In a preferred embodiment of this application, the PbO / REO mass concentration ratio in the low-lead rare earth solution in step S5) is <0.01%, and the REO content in the lead slag is <2wt%.
[0021] Unless otherwise specified, all raw materials and reagents used in this invention are commercially available products well known to those skilled in the art.
[0022] Due to manufacturing processes, commercially available dichlorvos typically contains residual impurities such as sodium hydroxide, and it also forms a stable (CH3)2NCSS. -The anionic group, this sulfur-containing ligand, belongs to the Lewis soft base category, making the solution of dichlorvos strongly alkaline. Therefore, directly adding dichlorvos to rare earth concentrate will cause precipitation loss of rare earth hydroxide. By applying the technical solution of this invention, a 5wt%–40wt% dichlorvos solution is prepared, and the pH value of the solution is adjusted to 1–9 using hydrochloric acid, thus avoiding the precipitation loss of rare earth hydroxide caused by the strong alkalinity of dichlorvos.
[0023] According to the Lewis acid-base theory, (CH3)2NCSS - The anionic group has a strong affinity for Lewis soft acids and some boundary acids, therefore (CH3)2NCSS - With Pb in solution 2+ Ni 2+ Co 3+ Cu 2+ Zn 2+ Both can form complexes, resulting in the precipitation of metal complexes. However, by controlling appropriate temperature and acidity conditions, (CH3)2NCSS can be precipitated. - It has a weak complexing ability with rare earth ions, thus achieving the purpose of selective lead removal from rare earth concentrate.
[0024] Because dichlorvos contains sulfur and nitrogen, excessive dichlorvos content in low-lead rare earth slurry can adversely affect the quality of subsequent rare earth products. This invention addresses this by adding magnesium chloride to precipitate the residual dichlorvos in the slurry, thus avoiding the adverse effects of excessive dichlorvos content on subsequent processes and rare earth products. This method is simple to operate, low in cost, and the added magnesium chloride has no adverse effect on rare earth smelting.
[0025] Compared with the prior art, the positive effects of the present invention are reflected in:
[0026] Compared to the existing lead removal process using rare earth concentrate sulfidation, this invention achieves selective lead removal while ensuring a low rare earth loss rate. Furthermore, the lead slag produced by this method has no recycling value due to its low rare earth content, eliminating the need for lead slag recovery in traditional rare earth smelting. Additionally, the technical solution employed in this invention does not generate toxic or harmful gases during the lead removal process, improving the operating environment and reducing safety risks. The lead removal method using rare earth concentrate involved in this invention features a short process flow, simple operation, and environmental friendliness, resulting in significant social and economic benefits and making it highly suitable for industry promotion. Detailed Implementation
[0027] All features disclosed in this specification, or all steps in all disclosed methods or processes, may be combined in any way, except for mutually exclusive features and / or steps.
[0028] Any feature disclosed in this specification (including the claims and abstract) may be replaced by other equivalent or similar features, unless specifically stated otherwise. That is, unless specifically stated otherwise, each feature is merely one example of a series of equivalent or similar features.
[0029] Example 1:
[0030] A 5 wt% trichlorfon solution was prepared, and the pH was adjusted to 1 using hydrochloric acid. 1 L of lead-containing rare earth concentrate was added to a beaker and stirred. The REO concentration of the concentrate was 211.75 g / L, and the PbO concentration was 1.149 g / L. The pH was adjusted to 1 using hydrochloric acid, and the solution was kept at a constant temperature of 20°C in a water bath, maintaining a relatively constant solution volume throughout the reaction. 43.7 g of trichlorfon solution was uniformly added to the lead-containing rare earth concentrate, and the reaction was allowed to proceed for 5 minutes. No special odor was observed during the reaction. The trichlorfon concentration in the rare earth concentrate after lead removal was measured to be 0.009 g / L, and the trichlorfon / REO mass concentration ratio was <0.03%. Solid-liquid separation yielded a low-lead rare earth solution and lead slag. The lead slag was washed and dried. The PbO / REO mass concentration ratio in the low-lead rare earth solution was 0.066%, and the REO content in the lead slag was 2.00 wt%. The praseodymium-neodymium oxide loss rate during the lead removal process was 0.03%.
[0031] Example 2
[0032] A 20wt% trichlorfon solution was prepared, and the pH was adjusted to 3 using hydrochloric acid. 1L of lead-containing rare earth concentrate was added to a beaker and stirred. The concentration of REO in the concentrate was 211.75g / L, and the concentration of PbO was 1.149g / L. The pH was adjusted to 3 using hydrochloric acid, and the solution was kept at a constant temperature of 40℃ in a water bath, maintaining a relatively constant volume throughout the reaction. 13.2g of trichlorfon solution was added uniformly to the lead-containing rare earth concentrate, and the reaction was allowed to proceed for 10 minutes. No special odor was observed during the reaction. The concentration of trichlorfon in the rare earth concentrate after lead removal was measured to be 0.035g / L, and the mass concentration ratio of trichlorfon / REO was <0.03%. Solid-liquid separation yielded a low-lead rare earth solution and lead slag. The lead slag was washed and dried. The mass concentration ratio of PbO / REO in the low-lead rare earth solution was <0.001%, and the REO content in the lead slag was 1.08wt%. The praseodymium-neodymium oxide loss rate during the lead removal process was 0.02%.
[0033] Example 3
[0034] A 30wt% trichlorfon solution was prepared, and the pH of the solution was adjusted to 4 using hydrochloric acid. 1L of lead-containing rare earth concentrate was added to a beaker and stirred. The concentration of REO in the concentrate was 289.85g / L, the concentration of PbO was 1.435g / L, and the pH was 5. The solution was kept at a constant temperature of 50℃ in a water bath, and the volume of the solution was kept essentially constant by adding water during the reaction. 12.4g of trichlorfon solution was added evenly to the lead-containing rare earth concentrate, and the reaction was carried out for 30 minutes. No special odor was observed during the reaction. The concentration of trichlorfon in the rare earth concentrate after lead removal was measured to be 0.041g / L, and the mass concentration ratio of trichlorfon / REO was <0.03%. Solid-liquid separation was performed to obtain a low-lead rare earth solution and lead slag. The lead slag was washed and dried. The mass concentration ratio of PbO / REO in the low-lead rare earth solution was <0.001%, the REO content in the lead slag was 0.73wt%, and the praseodymium-neodymium oxide loss rate during the lead removal process was 0.01%.
[0035] Example 4
[0036] A 40wt% trichlorfon solution was prepared, and the pH was adjusted to 7 using hydrochloric acid. 1L of lead-containing rare earth concentrate was added to a beaker and stirred. The concentration of REO in the concentrate was 289.85g / L, and the concentration of PbO was 1.435g / L. The pH was adjusted to 1 using hydrochloric acid, and the solution was kept at a constant temperature of 60℃ in a water bath. Water was added during the reaction to maintain a relatively constant solution volume. 9.3g of trichlorfon solution was added evenly to the lead-containing rare earth concentrate, and the reaction was allowed to proceed for 60 minutes. No special odor was observed during the reaction. The concentration of trichlorfon in the rare earth concentrate after lead removal was measured to be 0.052g / L, and the mass concentration ratio of trichlorfon / REO was <0.03%. Solid-liquid separation yielded a low-lead rare earth solution and lead slag. The lead slag was washed and dried. The mass concentration ratio of PbO / REO in the low-lead rare earth solution was <0.001%, and the REO content in the lead slag was 1.40wt%. The praseodymium-neodymium oxide loss rate during the lead removal process was 0.02%.
[0037] Example 5
[0038] A 40wt% trichlorfon solution was prepared, and the pH was adjusted to 9 using hydrochloric acid. 1L of lead-containing rare earth concentrate was added to a beaker and stirred. The concentrate had a REO concentration of 344.06g / L and a PbO concentration of 1.700g / L. The pH was adjusted to 3 using hydrochloric acid, and the solution was kept at a constant temperature of 60℃ in a water bath. Water was added during the reaction to maintain a relatively constant solution volume. 12.3g of trichlorfon solution was added evenly to the lead-containing rare earth concentrate, and the reaction was allowed to proceed for 120 minutes. No special odor was observed during the reaction. The concentration of rare earth concentrate after lead removal was measured. The concentration of dichlorvos was 0.688 g / L, and the mass concentration ratio of dichlorvos / REO was 0.20%. The concentrate was heated to 60°C in a water bath, and 0.344 g of anhydrous magnesium chloride was added. After reacting for 30 minutes, the residual dichlorvos was 0.015 g / L, which met the standard. Solid-liquid separation was performed to obtain a low-lead rare earth solution and lead slag. The lead slag was washed and dried. The mass concentration ratio of PbO / REO in the low-lead rare earth solution was <0.001%, and the REO content in the lead slag was 2.66 wt%. The loss rate of praseodymium-neodymium oxide during the lead removal process was 0.04%.
[0039] Example 6
[0040] A 40wt% trichlorfon solution was prepared, with a pH value >14, without using hydrochloric acid to adjust the pH. 1L of lead-containing rare earth concentrate was added to a beaker and stirred. The concentration of REO in the concentrate was 289.85g / L, the concentration of PbO was 1.435g / L, and the pH was 5. The solution was kept at a constant temperature of 50℃ in a water bath, and the volume of the solution was kept essentially constant by adding water during the reaction. 9.3g of trichlorfon solution was added evenly to the lead-containing rare earth concentrate, and the reaction was allowed to proceed for 60 minutes. No special odor was observed during the reaction. The concentration of trichlorfon in the rare earth concentrate after lead removal was measured to be 0.040g / L, and the mass concentration ratio of trichlorfon / REO was <0.03%. Solid-liquid separation yielded a low-lead rare earth solution and lead slag. The lead slag was washed and dried. The mass concentration ratio of PbO / REO in the low-lead rare earth solution was <0.001%, and the REO content in the lead slag was 9.06wt%. The praseodymium-neodymium oxide loss rate during the lead removal process was 0.16%.
[0041] Example 7
[0042] A 30wt% trichlorfon solution was prepared, and the pH of the solution was adjusted to 4 using hydrochloric acid. 1L of lead-containing rare earth concentrate was added to a beaker and stirred. The concentration of REO in the concentrate was 289.85g / L, the concentration of PbO was 1.435g / L, and the pH was 5. The solution was kept at a constant temperature of 70℃ in a water bath, and the volume of the solution was kept essentially constant by adding water during the reaction. 12.4g of trichlorfon solution was added evenly to the lead-containing rare earth concentrate, and the reaction was carried out for 30 minutes. No special odor was observed during the reaction. The concentration of trichlorfon in the rare earth concentrate after lead removal was measured to be 0.025g / L, and the mass concentration ratio of trichlorfon / REO was <0.03%. Solid-liquid separation was performed to obtain a low-lead rare earth solution and lead slag. The lead slag was washed and dried. The mass concentration ratio of PbO / REO in the low-lead rare earth solution was 0.013%, and the REO content in the lead slag was 15.60wt%. The loss rate of praseodymium-neodymium oxide during the lead removal process was 0.37%.
[0043] Example 8
[0044] A 40wt% trichlorfon solution was prepared, and the pH was adjusted to 4 using hydrochloric acid. 1L of lead-containing rare earth concentrate was added to a beaker and stirred. The concentrate had a REO concentration of 344.06g / L, a PbO concentration of 1.700g / L, and a pH of 5. The solution was kept at a constant temperature of 70℃ in a water bath, and the volume was maintained by adding water during the reaction. 14.9g of trichlorfon solution was added evenly to the lead-containing rare earth concentrate, and the reaction was allowed to proceed for 30 minutes. No special odor was observed during the reaction. The concentration of trichlorfon in the rare earth concentrate after lead removal was measured. The concentration was 0.172 g / L, and the mass concentration ratio of dimethoate / REO was 0.05%. The concentrate was kept at a constant temperature of 20°C in a water bath, and 0.172 g of anhydrous magnesium chloride was added. After reacting for 30 minutes, the residual dimethoate was 0.026 g / L, which met the content standard. Solid-liquid separation was performed to obtain low-lead rare earth solution and lead slag. The lead slag was washed and dried. The mass concentration ratio of PbO / REO in the low-lead rare earth solution was 0.008%, and the REO content in the lead slag was 21.22 wt%. The praseodymium-neodymium oxide loss rate during the lead removal process was 0.56%.
[0045] Example 9
[0046] Prepare a 10wt% trichlorfon solution and adjust the pH to 4 using hydrochloric acid. Take 1L of lead-containing rare earth concentrate into a beaker, stir, and the concentrate has a REO concentration of 344.06g / L, a PbO concentration of 1.700g / L, and a pH of 5. Maintain a constant water bath temperature of 40℃, adding water during the reaction to keep the solution volume essentially constant. Add 59.5g of trichlorfon solution evenly to the lead-containing rare earth concentrate and react for 30 minutes. No special odor is observed during the reaction. The concentration of trichlorfon in the rare earth concentrate after lead removal is measured. The concentration per mu was 1.120 g / L, and the mass concentration ratio of dimethoate / REO was 0.33%. The concentrate was heated to 40℃ in a water bath, and 2.24 g of anhydrous magnesium chloride was added. After reacting for 30 minutes, the residual dimethoate was 0.032 g / L, which met the standard. Solid-liquid separation was performed to obtain low-lead rare earth solution and lead slag. The lead slag was washed and dried. The mass concentration ratio of PbO / REO in the low-lead rare earth solution was <0.001%, and the REO content in the lead slag was 1.21 wt%. The loss rate of praseodymium-neodymium oxide during the lead removal process was 0.02%.
[0047] Comparative Example 1
[0048] Take 1L of lead-containing rare earth concentrate into a beaker and stir. The concentration of REO in the concentrate is 245.55g / L, the concentration of PbO is 1.259g / L, and the pH value is 5. Maintain a constant temperature of 70℃ in a water bath. During the reaction, add water to keep the solution volume basically constant. Prepare a 100g / L industrial sodium sulfide solution with a pH value >14. Take 44ml of this sodium sulfide solution and slowly add it to the lead-containing rare earth concentrate. React for 30 minutes. During the reaction, there is a rotten egg smell. Flocculate and filter to obtain low-lead rare earth feed solution and lead slag. Wash and dry the lead slag. The mass concentration ratio of PbO / REO in the low-lead rare earth feed solution is 0.002%, the REO content of the lead slag is 33.31wt%, and the loss rate of praseodymium and neodymium oxides in the lead removal process is 1.55%.
[0049] Comparative Example 2
[0050] Prepare a 100 g / L industrial sodium sulfide solution with a pH > 14. Take 31 ml of this sodium sulfide solution to remove lead from the lead-containing rare earth concentrate, with other conditions the same as in Comparative Example 1. The detection and calculation results are listed in Table 2.
[0051] Comparative Example 3
[0052] Prepare a 100 g / L industrial sodium sulfide solution with a pH > 14. Take 25 ml of this sodium sulfide solution to remove lead from the lead-containing rare earth concentrate, with other conditions the same as in Comparative Example 1. The detection and calculation results are listed in Table 2.
[0053] Comparative Example 4
[0054] Take 1L of lead-rare earth concentrate into a beaker, stir, and the concentrate has a REO concentration of 245.55g / L, a PbO concentration of 1.259g / L, and a pH of 5. Maintain a constant water bath temperature of 50℃, and keep the solution volume essentially constant by adding water during the reaction. Prepare a 100g / L industrial sodium sulfide solution with a pH >14, and slowly add 31ml of this sodium sulfide solution to the lead-rare earth concentrate. React for 30 minutes. Filter through flocculation to obtain a low-lead rare earth solution and lead slag. Wash and dry the lead slag. The test and calculation results are listed in Table 2.
[0055] Comparative Example 5
[0056] Take 1 L of lead-containing rare earth concentrate into a beaker, stir, the concentration of REO in the concentrate is 245.55 g / L, the concentration of PbO is 1.259 g / L, the pH value is 5, and the sodium sulfide is used to remove lead in a water bath at 30℃. Other conditions are the same as those in Comparative Example 4. The detection and calculation results are listed in Table 2.
[0057] Comparative Example 6
[0058] Take 1L of lead-rare earth concentrate into a beaker, stir, and the concentrate has a REO concentration of 245.55g / L, a PbO concentration of 1.259g / L, and a pH of 5. Maintain a constant water bath temperature of 70℃, and keep the solution volume essentially constant by adding water during the reaction. Prepare a 100g / L industrial sodium sulfide solution, adjust its pH to approximately 9 using hydrochloric acid, and slowly add 44ml of this sodium sulfide solution to the lead-rare earth concentrate. React for 30 minutes. Filter through flocculation to obtain a low-lead rare earth solution and lead slag. Wash and dry the lead slag. The detection and calculation results are listed in Table 2.
[0059] Comparative Example 7
[0060] Prepare a 100 g / L industrial sodium sulfide solution, adjust its pH to approximately 7 using hydrochloric acid, and use this sodium sulfide solution to remove lead from a lead-containing rare earth concentrate. Other conditions are the same as in Comparative Example 6. The detection and calculation results are listed in Table 2.
[0061] Table 1:
[0062]
[0063] Table 2:
[0064]
[0065]
[0066] As shown in Tables 1 and 2, in Examples 2, 3, 4, 5, and 9, the PbO / REO ratio of the low-lead rare earth solution was <0.01%, indicating a qualified lead content. Simultaneously, the rare earth loss rate in the lead slag was low, with the REO content in the lead slag ranging from 0.73 wt% to 2.66 wt%, and the praseodymium-neodymium loss rate from 0.01% to 0.04%. This achieved selective lead removal from the lead-containing rare earth concentrate, and the low rare earth loss rate in the lead slag eliminated the need for rare earth recovery. Comparing Examples 3 and 6, it can be seen that by lowering the pH value of the dimethoate solution using hydrochloric acid, the praseodymium-neodymium loss rate in the lead slag was reduced from 0.16% to 0.01%. In Examples 5, 8, and 9, the use of magnesium chloride effectively reduced the residual dimethoate concentration in the low-lead rare earth solution. Comparing Examples 4, 7, 8, and 9, it can be seen that controlling the appropriate lead removal temperature is a crucial factor in achieving selective lead removal and reducing rare earth loss in the lead slag. Overall, the suitable lead removal temperature should be less than or equal to 60℃.
[0067] In Comparative Examples 1–7, lead removal from lead-containing rare earth concentrates was performed using sodium sulfide solution. However, selective lead removal could not be achieved by adjusting the removal temperature, sodium sulfide dosage, and pH value of the sodium sulfide solution. Furthermore, a gas with a rotten egg odor was observed to be generated during the sodium sulfide lead removal process, necessitating attention to safety risk prevention measures.
[0068] The examples described above are merely preferred embodiments of this patent, but the scope of protection of this patent is not limited thereto. It should be noted that, for those skilled in the art, without departing from the principles of this patent, based on the technical solution and patent concept of this patent, several improvements and modifications can be made, and these improvements and modifications should also be considered within the scope of protection of this patent.
Claims
1. A method for reducing lead and rare earth loss in rare earth concentrate, characterized in that, The process includes the following steps: S1) Prepare a 5wt%~40wt% solution of dichlorvos and adjust the pH of the solution to 1~9 using hydrochloric acid; S2) Add the lead-containing rare earth concentrate to the mixing tank. The concentration of rare earth oxides (REO) in the concentrate is 200~350 g / L. S3) Add the dimethoate solution to the lead-containing rare earth concentrate, and control the mass ratio of dimethoate in the added dimethoate solution to PbO in the lead-containing rare earth concentrate to be W1. Stir for 5 to 120 minutes to promote full reaction and selectively form lead complex precipitates; W1 is 1.9 to 3.
5. S4) After the lead removal reaction is completed, the mass concentration ratio of dichlorvos / REO in the rare earth concentrate after lead removal is detected; if it is greater than 0.03%, solid anhydrous magnesium chloride is added, and the mass ratio of the added magnesium chloride to the residual dichlorvos in the rare earth concentrate is controlled to be W2, where W2 is 0.5~2.0; the reaction is stirred at 20~60℃ for 30 minutes; if it is less than or equal to 0.03%, the next step is performed. S5) Solid-liquid separation was performed to obtain low-lead rare earth solution and lead slag. The lead slag was washed and dried, and the composition of the low-lead rare earth solution and lead slag was analyzed.
2. The method according to claim 1, characterized in that, In S1), hydrochloric acid is used to adjust the pH of the solution to 3-7.
3. The method according to claim 1, characterized in that, The pH value of the lead-containing rare earth concentrate in S2 is 1~5, and the temperature is 20~70℃.
4. The method according to claim 3, characterized in that, The pH value of the lead-rare earth concentrate in S2) is 1~5, and the temperature is 40~50℃.
5. The method according to claim 1, characterized in that, The stirring reaction time in S3) is 10-30 minutes.
6. The method according to claim 1, characterized in that, In S3), W1 is 2.3~2.
6.
7. The method according to claim 1, characterized in that, In S4), W2 is 0.5~1.
0.
8. The method according to claim 1, characterized in that, The PbO / REO mass concentration ratio in the low-lead rare earth feed solution in S5) is <0.01%, and the REO content in the lead slag is <2wt%.