Method for long-term and stable treatment of lead-containing rare earth waste residues

Abstract

The invention relates to the technical field of lead-containing waste residue treatment, and particularly discloses a method for stably treating lead-containing waste residues for a long time. The citric acid activated phosphorus source is adopted, the phosphorus supply capacity of a phosphorus-containing compound is enhanced, the reaction degree of lead phosphate precipitate generation is improved, meanwhile, the lead-containing rare earth waste residues obtained after treatment of the citric acid activated phosphorus source are treated with sodium molybdate, the surface of a solidified body is coated with unsolidified lead ions, a continuous and compact lead molybdate protection film is formed, and the lead phosphate precipitate generation reaction degree is improved. And secondary dissolution of lead is prevented, and the curing effect is enhanced. The pH value of the lead-containing rare earth waste residues treated through the method is 6-9, the acid leaching amount of lead does not exceed 1.2 mg / L, meanwhile, the lead pollution stabilizing treatment time is greatly shortened, the waste residue treatment efficiency is remarkably improved, the actual requirement for large-scale waste residue rapid treatment is met, the method can be widely applied to waste residue treatment in multiple scenes such as mining and rare earth smelting, and the method has a wide application prospect. The industrial popularization value is extremely high.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lead-containing waste residue treatment, and particularly relates to a method for long-term and stable treatment of lead-containing waste residue. BACKGROUND

[0002] With the rapid development of industrial production and mining activities, the amount of lead-containing waste residue continues to rise, and the environmental pollution problem caused by it is becoming increasingly serious. As a heavy metal with strong toxicity, high mobility and difficult to naturally degrade, lead, once entering the environment, will spread through soil, water and other media, not only seriously threatening the ecological balance, but also possibly enriching through the food chain and causing irreversible damage to human health.

[0003] At present, the treatment technologies for lead-containing waste residue mainly include physical remediation, biological remediation and chemical remediation. Physical remediation technologies, such as soil replacement and electric heating, are not only low in efficiency and high in cost when facing large volume and complex composition of lead-containing waste residue, but are only suitable for small-scale pollution sites. At the same time, the possible associated radioactive substances in the waste residue further increase the safety risk of physical operation. Biological remediation technologies, such as microbial adsorption and hyperaccumulating plant remediation, are severely inhibited by the presence of radioactive elements, high salt content and other toxic substances in lead-containing waste residue, resulting in a long remediation period of several years or even decades and extremely low remediation efficiency, which is difficult to meet the actual remediation demand.

[0004] Traditional chemical remediation technologies also face many challenges in treating lead-containing waste residue. The adsorption capacity of adsorption-type passivator for lead is limited, which is difficult to deal with high concentration of lead pollution in waste residue, and in the case of coexistence of multiple metals, competitive adsorption will significantly reduce the removal efficiency of lead; pH adjuster is difficult to stably adjust the pH value of the system due to the interference of complex acid-base buffer system and salt in waste residue, resulting in unstable passivation effect; conventional phosphorus-containing compounds often need to be added in excess to achieve a certain treatment effect, which not only greatly increases the treatment cost, but also easily causes secondary pollution of phosphorus, such as water eutrophication.

[0005] In addition, lead-containing waste residue usually has the characteristics of associated radioactivity, coexistence of multiple metals, high salt content and complex matrix, which will limit the applicability of existing remediation technologies, interfere with the specific binding of remediation agents and lead ions, and make it difficult to maintain the remediation effect for a long time and stably, which is difficult to fundamentally solve the pollution problem of lead-containing waste residue. Therefore, it is urgent to develop a method for long-term and stable treatment of lead-containing waste residue with low cost, simple operation and environmental friendliness to meet the growing demand for environmental protection. SUMMARY

[0006] In view of the problems of low repair efficiency, high treatment cost, easy secondary pollution, difficulty in adapting to the complex characteristics of rare earth waste residue, and inability to achieve long-term stable treatment of lead-containing waste residue in the existing lead-containing waste residue treatment technology, the present application provides a method for long-term stable treatment of lead-containing rare earth waste residue. The present application selects different passivation agents for rare earth waste residue with different pH and lead content, achieving the purpose of long-term stabilization of leaching state lead in rare earth waste residue with different characteristics, opening up a new path for lead-containing waste residue pollution control, and showing great application potential and significant social and economic value in environmental protection and industrial sustainable development.

[0007] To solve the above technical problems, the technical solution provided by the present application is:

[0008] A method for long-term stable treatment of lead-containing rare earth waste residue, comprising the following steps:

[0009] S1, determining the suitable passivation agent according to the pH and lead acid leaching state content of the lead-containing rare earth waste residue;

[0010] If the pH of the lead-containing rare earth waste residue is ≤5, the suitable passivation agent is citric acid activated phosphorus source, calcium oxide and sodium molybdate;

[0011] If the pH of the lead-containing rare earth waste residue is >5, the suitable passivation agent is citric acid activated phosphorus source and sodium molybdate;

[0012] If the lead acid leaching state content of the lead-containing rare earth waste residue is ≤100 mg / L, the phosphorus source is phosphate rock powder; if the lead acid leaching state content is >100 mg / L, the phosphorus source is superphosphate;

[0013] S2, mixing the substances in the passivation agent except sodium molybdate with the lead-containing rare earth waste residue, adjusting the moisture content to 20%-40%, standing for a first preset time, adding sodium molybdate, mixing uniformly, standing for a second preset time, and obtaining the treated lead-containing rare earth waste residue.

[0014] Compared with the prior art, the method for long-term stable treatment of lead-containing rare earth waste residue provided by the present application uses citric acid activated phosphate rock powder or superphosphate, greatly improves the release efficiency and activity of phosphate radicals in the phosphorus source, promotes rapid reaction with lead ions to form insoluble lead phosphate precipitate, and reduces the mobility of lead from the root; on this basis, the subsequently added sodium molybdate combines with residual lead ions to form a lead molybdate film, which tightly covers the surface of the solidified body, forming a "precipitate-film" double protection structure to effectively block the secondary leaching of lead. At the same time, phosphate rock powder is selected for the treatment of low lead-containing rare earth waste residue, and the slow-release characteristics of phosphate rock powder can ensure the long-term stabilization effect; superphosphate is selected for the treatment of high lead-containing rare earth waste residue, and the rapid precipitation ability of superphosphate can achieve efficient removal of leaching lead ions.

[0015] The processing method of the lead-containing rare earth waste residue provided by the application effectively overcomes the problems of low repair efficiency and unstable effect caused by insufficient adsorption capacity, limited reaction conditions, high risk of secondary pollution and the like in the prior art, and has good applicability to rare earth waste residues with different pH values and different lead pollution degrees, can be widely applied to waste residue treatment in multiple scenes such as mine exploitation and rare earth smelting, and has high industrialization popularization value.

[0016] It should be noted that the pH of the lead-containing rare earth waste residue in the following examples of the lead-containing rare earth waste residue in the application is detected by the following method:

[0017] The lead-containing rare earth waste residue to be treated is placed in a cool and ventilated place for air drying, direct sunlight is avoided, and the air-dried sample is ground to pass through a 2mm nylon screen using a non-metal mortar. 10.0g of the ground sample (accurate to 0.01g) is weighed, 100mL of carbon dioxide-free water (solid-liquid ratio = 1:10) is added into a beaker, a magnetic stirrer is used for continuous stirring for 5min, and then the sample is left to stand for 1min to allow the solid to settle. Then, the electrode is immersed in the supernatant of the residue sample leaching solution (avoiding touching the solid), and the pH value is recorded.

[0018] The lead acid leaching state content in the rare earth waste residue is detected by the following method:

[0019] Step a, sample preparation: the collected rare earth smelting residue sample is air-dried or freeze-dried, ground to pass through a 3mm sieve, mixed uniformly, and 150-200g of the prepared sample is weighed for standby.

[0020] Step b, preparation of leaching solution: mix concentrated H2SO4 and concentrated HNO3 according to a volume ratio of 2:1 to obtain a mixed acid; slowly add the mixed acid into deionized water, and slightly adjust it with a small amount of 0.1mol / L NaOH or 0.1mol / L HNO3 to prepare a leaching solution with pH = 3.20±0.05 (cooled to room temperature);

[0021] Step c, the weighed waste residue sample is placed into a standard specified leaching container (2L wide-mouth polyethylene bottle or glass bottle with a lid), the leaching agent is added according to a solid-liquid ratio of 1:10, the bottle cap is tightly covered to ensure good sealing, and the bottle is fixed on a rolling oscillation device, and is continuously oscillated at a speed of 30±2rpm for 18±2h at a room temperature of 23±2℃;

[0022] Step d, after the oscillation is completed, the sample is left to stand for 10-30min to allow the solid to settle, a 0.45μm microporous filter membrane is used to filter the leaching solution, the filtrate is collected in a clean polyethylene bottle, the volume of the filtrate is recorded, and the lead concentration in the filtrate is measured.

[0023] Further, the lead acid leaching state content in the lead-containing rare earth waste residue is ≤1000mg / L, and the moisture content is ≤40%.

[0024] It should be noted that before the lead-containing rare earth waste residue is treated, it is ground to 5 mesh or less.

[0025] Specifically, the lead-containing rare earth waste residue is a rare earth waste residue with excessive lead content after hydrochloric acid smelting extraction.

[0026] Further, if the pH of the lead-containing rare earth waste residue is ≤5, the mass ratio of the citric acid-activated phosphorus source, calcium oxide and the lead-containing rare earth waste residue is 1:1:(50-100).

[0027] The amount of calcium oxide added can not only neutralize the acidity of the waste residue and adjust the pH of the system to a weak alkaline environment conducive to the reaction of lead and phosphorus, but also avoid the influence of excessive pH on the activity of the phosphorus source. The preferred amount of citric acid-activated phosphorus source can ensure that the phosphate ions and lead ions react rapidly to form stable lead phosphate precipitates, and can also avoid environmental pollution and cost waste caused by excessive phosphorus source.

[0028] Further, if the pH of the lead-containing rare earth waste residue is >5, the mass ratio of the citric acid-activated phosphorus source and the lead-containing rare earth waste residue is 1:(50-100).

[0029] Further, the amount of sodium molybdate added is 1% to 2% of the mass of the lead-containing rare earth waste residue.

[0030] The preferred amount of sodium molybdate added can fully react with the residual lead ions after treatment of the citric acid-activated phosphorus source, forming a continuous and dense lead molybdate protective film on the surface of the solidified material, significantly improving the long-term stability of the waste residue.

[0031] Further, the first predetermined time is 20h-30h.

[0032] Further, the second predetermined time is 2d-4d.

[0033] It should be noted that the water content of the lead-containing rare earth waste residue needs to be maintained at 20%-40% during the above standing process.

[0034] As a specific embodiment of the present application, the preparation method of the citric acid-activated phosphorus source comprises the following steps:

[0035] The phosphorus source is added to the citric acid solution, immersed at 20°C-25°C for 2h-4h, solid-liquid separation, and dried to obtain the citric acid-activated phosphorus source.

[0036] Further, the concentration of the citric acid solution is 0.3mol / L-0.6mol / L.

[0037] Further, the solid-liquid ratio of the citric acid solution to the phosphorus source is 1:(20-50).

[0038] Further, the temperature of the drying is 40-60 DEG C, and the time of the drying is 24-48 hours.

[0039] Specifically, the phosphorus source activated by citric acid is ground to 100 mesh or less after drying for standby.

[0040] To sum up, the present application uses the phosphorus source activated by citric acid to enhance the phosphorus supply capacity of the phosphorus-containing compound, improve the reaction degree of lead phosphate precipitation, and treat the lead-containing rare earth waste residue after the treatment of the phosphorus source activated by citric acid with sodium molybdate, so that the un-solidified lead ions are coated on the surface of the solidified body to form a continuous and dense lead molybdate protective film, prevent the secondary dissolution of lead, and enhance the solidification effect. The pH value of the lead-containing rare earth waste residue treated by the method is 6-9, the acid leaching amount of lead is not more than 1.2 mg / L, which meets the “Hazardous Waste Landfill Pollution Control Standard” (GB / T 18598-2019), the generated lead phosphate is stable in nature, greatly reduces the secondary pollution hidden danger of lead to the surrounding soil and water, at the same time, also greatly shortens the time of lead pollution stabilization treatment, significantly improves the waste residue treatment efficiency, meets the actual needs of large-scale waste residue rapid treatment, can be widely applied to mine exploitation, rare earth smelting and other scene waste residue treatment, and has high industrialization popularization value. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described in detail below in combination with examples. It should be understood that the specific examples described herein are only used to explain the present application, and are not used to limit the present application.

[0042] In order to better illustrate the present application, the following examples are further illustrated by examples.

[0043] The lead-containing rare earth waste residue used in the following examples and comparative examples is the iron-thorium slag and lead-barium slag after rare earth smelting.

[0044] The phosphorus ore powder and superphosphate used in the following examples are industrial grade, and the purity is 60-75%.

[0045] The pH of the lead-containing rare earth waste residue in the following examples is detected by the following method:

[0046] The treated lead-containing rare earth waste residue is placed in a cool and ventilated place for air drying, and direct sunlight is avoided. The air-dried sample is ground to pass through a 2mm nylon screen with a non-metallic mortar. 10.0g of the ground sample (accurate to 0.01g) is weighed, added into 100ml of carbon dioxide-free water (solid-liquid ratio = 1:10) in a beaker, continuously stirred with a magnetic stirrer for 5min, and then placed for 1min to allow the solid to settle. Then, the electrode is immersed in the upper clear liquid of the slag sample leaching solution (avoiding touching the solid), and the pH value is recorded.

[0047] The acid leaching state of lead in rare earth waste is determined by the following method:

[0048] Step a, sample preparation: air-dry or freeze-dry the collected rare earth smelting slag sample, grind it until it can pass through a 3 mm sieve, mix it evenly, and weigh 150-200 g of the prepared sample for use.

[0049] Step b, preparing an extract: mixing concentrated H2SO4 and concentrated HNO3 in a volume ratio of 2:1 to obtain a mixed acid; slowly adding the mixed acid to deionized water, and fine-adjusting with a small amount of 0.1 mol / L NaOH or 0.1 mol / L HNO3 to prepare an extract with a pH of 3.20±0.05 (cooled to room temperature);

[0050] Step c: Place the weighed waste residue sample into a standard leaching container (a 2L wide-mouth polyethylene bottle or glass bottle with a lid), add the leaching agent at a solid-liquid ratio of 1:10, cover the bottle tightly to ensure a good seal, fix the bottle on a flip-type oscillating device, and oscillate continuously at a speed of 30±2 rpm at a room temperature of 23±2°C for 18±2 hours;

[0051] Step d: After the oscillation is completed, the mixture is allowed to stand for 10 to 30 minutes to allow the solid to settle. The leachate is filtered using a 0.45 μm microporous filter membrane, and the filtrate is collected in a clean polyethylene bottle. The volume of the filtrate is recorded, and the lead concentration thereof is determined by atomic absorption spectrometry.

[0052] Example 1

[0053] The embodiment of the present invention provides a method for long-term and stable treatment of lead-containing rare earth waste residue, comprising the following steps:

[0054] S1, the pH of the lead-containing rare earth waste residue to be treated was tested to be 3.65, the acid leaching amount of lead was 90.2 mg / L, and phosphate rock powder activated with citric acid, calcium oxide and sodium molybdate were used as passivation agents;

[0055] S2, citric acid activated phosphate rock powder, calcium oxide and lead-containing rare earth waste slag are mixed in a mass ratio of 1:1:80, water is added to adjust the moisture content to 40%, after standing for 24 hours, sodium molybdate (1% by mass of the lead-containing rare earth waste slag) is added, stirred evenly, and allowed to stand for 3 days.

[0056] The pH of the lead-containing rare earth waste residue after detection was 8.46, the lead acid leaching amount was 0.46 mg / L, and the water content was 30%.

[0057] The preparation method of the citric acid activated phosphate rock powder comprises the following steps:

[0058] Phosphate rock powder is added into 0.5 mol / L aqueous solution of citric acid, the solid-liquid ratio of citric acid to phosphate rock powder is 1:30, and the mixture is placed on a horizontal shaker, the shaking frequency is 250 r / min, and the activation is carried out at 20-25℃ for 3 h. The activated phosphate rock powder is dried at 50℃ for 24 h, ground and passed through a 100 mesh sieve, and is ready for use.

[0059] Comparative Example 1-1

[0060] The present comparative example provides a treatment method of lead-containing rare earth waste residue, which is completely same as Example 1 except that sodium molybdate is not added, and the specific steps are as follows:

[0061] The citric acid-activated phosphate rock powder, calcium oxide and lead-containing rare earth waste residue are mixed according to a mass ratio of 1:1:80, water is added to adjust the moisture content to 40%, and the mixture is left to stand for 4 d.

[0062] The pH of the treated lead-containing rare earth waste residue is 8.20, the lead acid leaching amount is 12.87 mg / L, and the moisture content is 35%.

[0063] Comparative Example 1-2

[0064] The present comparative example provides a treatment method of lead-containing rare earth waste residue, which is completely same as Example 1 except that sodium molybdate is replaced by an equal amount of sodium sulfate, and the specific steps are as follows:

[0065] The citric acid-activated phosphate rock powder, calcium oxide and lead-containing rare earth waste residue are mixed according to a mass ratio of 1:1:80, water is added to adjust the moisture content to 40%, and the mixture is left to stand for 24 h. Then, 1% of sodium sulfate based on the mass of the lead-containing rare earth waste residue is added, the mixture is stirred uniformly, and is left to stand for 3 d.

[0066] The pH of the treated lead-containing rare earth waste residue is 7.85, the lead acid leaching amount is 8.71 mg / L, and the moisture content is 33%.

[0067] Example 2

[0068] The present example provides a method for long-term stable treatment of lead-containing rare earth waste residue, which comprises the following steps:

[0069] S1, the pH of the lead-containing rare earth waste residue to be treated is 2.52, and the acid leaching amount of lead is 385 mg / L. Citric acid-activated superphosphate, calcium oxide and sodium molybdate are used as passivators.

[0070] S2, the citric acid-activated superphosphate, calcium oxide and lead-containing rare earth waste residue are mixed according to a mass ratio of 1:1:50, water is added to adjust the moisture content to 40%, and the mixture is left to stand for 24 h. Then, 2% of sodium molybdate based on the mass of the lead-containing rare earth waste residue is added, the mixture is stirred uniformly, and is left to stand for 4 d.

[0071] The pH of the lead-containing rare earth waste residue after the detection treatment is 7.15, the lead acid leaching amount is 0.35 mg / L, and the water content is 30%.

[0072] The preparation method of the above-mentioned citric acid activated calcium superphosphate comprises the following steps:

[0073] The calcium superphosphate is added into a 0.6 mol / L citric acid aqueous solution, the solid-liquid ratio of the citric acid and the calcium superphosphate is 1:40, the mixture is placed on a horizontal shaker, the shaking frequency is 200 r / min, the activation is carried out at 20-25 DEG C for 4 h, the activated calcium superphosphate is dried at 50 DEG C for 24 h, is ground and passed through a 100 mesh sieve, and is reserved.

[0074] Comparative Example 2-1

[0075] The present comparative example provides a treatment method of lead-containing rare earth waste residue, which is completely same as the example 2 except that no sodium molybdate is added, and the specific steps are as follows:

[0076] The citric acid activated calcium superphosphate, calcium oxide and lead-containing rare earth waste residue are mixed according to the mass ratio of 1:1:50, water is added to adjust the water content to 40%, and the mixture is placed for 5 days.

[0077] The pH of the lead-containing rare earth waste residue after the treatment is 6.80, the lead acid leaching amount is 45.6 mg / L, and the water content is 38%.

[0078] Comparative Example 2-2

[0079] The present comparative example provides a treatment method of lead-containing rare earth waste residue, which is completely same as the example 1 except that the sodium molybdate is replaced by an equal amount of sodium sulfate, and the specific steps are as follows:

[0080] The citric acid activated calcium superphosphate, calcium oxide and lead-containing rare earth waste residue are mixed according to the mass ratio of 1:1:50, water is added to adjust the water content to 40%, and the mixture is placed for 24 h, then 2% of sodium sulfate based on the mass of the lead-containing rare earth waste residue is added, the mixture is stirred uniformly, and is placed for 4 days.

[0081] The pH of the lead-containing rare earth waste residue after the treatment is 6.95, the lead acid leaching amount is 32.1 mg / L, and the water content is 36%.

[0082] Example 3

[0083] The present example provides a method for long-term and stable treatment of lead-containing rare earth waste residue, which comprises the following steps:

[0084] S1, the pH of the lead-containing rare earth waste residue to be treated is 6.50, and the acid leaching amount of lead is 39.5 mg / L, citric acid activated phosphate rock powder and sodium molybdate are used as the passivator;

[0085] S2, the phosphorite powder activated by citric acid and the lead-containing rare earth residue are mixed according to a mass ratio of 1:100, water is added to adjust the moisture content to 40%, and after standing for 24 h, 1.5% of sodium molybdate by mass of the lead-containing rare earth residue is added, stirred uniformly, and stood for 2 d.

[0086] The pH of the lead-containing rare earth residue after the detection treatment is 8.66, the lead acid leaching amount is 0.57 mg / L, and the moisture content is 29%.

[0087] The preparation method of the phosphorite powder activated by citric acid includes the following steps:

[0088] The phosphorite powder is added into a 0.3 mol / L citric acid aqueous solution, the solid-liquid ratio of the citric acid and the phosphorite powder is 1:50, the mixture is placed on a horizontal shaker, the shaking frequency is 250 r / min, the activation is performed at 20-25℃ for 2 h, the activated phosphorite powder is dried at 50℃ for 48 h, is ground and passed through a 100-mesh sieve, and is reserved.

[0089] Comparative Example 3-1

[0090] The present comparative example provides a treatment method of a lead-containing rare earth residue, which is completely same as that of Example 2 except that no sodium molybdate is added, and the specific steps are as follows:

[0091] The phosphorite powder activated by citric acid and the lead-containing rare earth residue are mixed according to a mass ratio of 1:100, water is added to adjust the moisture content to 40%, and after standing for 3 d.

[0092] The pH of the lead-containing rare earth residue after the treatment is 8.30, the lead acid leaching amount is 6.82 mg / L, and the moisture content is 38%.

[0093] Comparative Example 3-2

[0094] The present comparative example provides a treatment method of a lead-containing rare earth residue, which is completely same as that of Example 1 except that the sodium molybdate is replaced by an equal amount of sodium sulfate, and the specific steps are as follows:

[0095] The phosphorite powder activated by citric acid and the lead-containing rare earth residue are mixed according to a mass ratio of 1:100, water is added to adjust the moisture content to 40%, and after standing for 24 h, 1.5% of sodium sulfate by mass of the lead-containing rare earth residue is added, stirred uniformly, and stood for 2 d.

[0096] The pH of the lead-containing rare earth residue after the treatment is 8.22, the lead acid leaching amount is 14.8 mg / L, and the moisture content is 36%.

[0097] Example 4

[0098] The present example provides a method for long-term and stable treatment of a lead-containing rare earth residue, which includes the following steps:

[0099] S1, the pH of the detected lead-containing rare earth waste residue to be treated was 5.61, and the acid leaching amount of lead was 510 mg / L. Citric acid-activated superphosphate and sodium molybdate were used as passivators;

[0100] S2, citric acid-activated superphosphate and lead-containing rare earth waste residue were mixed in a mass ratio of 1:1:70, water was added to adjust the moisture content to 40%, and then the mixture was allowed to stand for 24 h. Then, 2% of sodium molybdate based on the mass of the lead-containing rare earth waste residue was added, and the mixture was stirred uniformly and allowed to stand for 3 d.

[0101] The pH of the treated lead-containing rare earth waste residue was 7.24, the acid leaching amount of lead was 1.09 mg / L, and the moisture content was 31%.

[0102] The preparation method of the citric acid-activated superphosphate includes the following steps:

[0103] The superphosphate was added to a 0.4 mol / L aqueous citric acid solution, and the solid-liquid ratio of citric acid to superphosphate was 1:30. The mixture was placed on a horizontal shaker, and the shaking frequency was 250 r / min. The mixture was activated at 20-25°C for 3 h. The activated superphosphate was dried at 50°C for 24 h, ground to pass through a 100-mesh sieve, and reserved for use.

[0104] Comparative Example 4-1

[0105] This comparative example provides a treatment method for lead-containing rare earth waste residue, which is different from Example 2 only in that sodium molybdate is not added, and the rest is exactly the same. The specific steps are as follows:

[0106] Citric acid-activated superphosphate and lead-containing rare earth waste residue were mixed in a mass ratio of 1:1:70, water was added to adjust the moisture content to 40%, and then the mixture was allowed to stand for 4 d.

[0107] The pH of the treated lead-containing rare earth waste residue was 6.90, the acid leaching amount of lead was 153.0 mg / L, and the moisture content was 39%.

[0108] Comparative Example 4-2

[0109] This comparative example provides a treatment method for lead-containing rare earth waste residue, which is different from Example 1 only in that sodium molybdate is replaced by an equal amount of sodium sulfate, and the rest is exactly the same. The specific steps are as follows:

[0110] Citric acid-activated superphosphate and lead-containing rare earth waste residue were mixed in a mass ratio of 1:1:70, water was added to adjust the moisture content to 40%, and then the mixture was allowed to stand for 24 h. Then, 2% of sodium sulfate based on the mass of the lead-containing rare earth waste residue was added, and the mixture was stirred uniformly and allowed to stand for 3 d.

[0111] The pH of the treated lead-containing rare earth waste residue was 7.02, the acid leaching amount of lead was 68.9 mg / L, and the moisture content was 36%.

[0112] It can be seen by comparison that the addition of sodium molybdate can significantly reduce the acid leaching amount of lead, and the pH and water content meet the standard. Omitting sodium molybdate or replacing sodium molybdate with other sodium salts will increase the acid leaching amount of lead, proving that molybdate ions have an irreplaceable role in the passivation of lead ions in rare earth waste residue.

[0113] In summary, the embodiments of the present application activate the phosphorus source by citric acid, significantly improve the dissolution efficiency of phosphate, and form a dense passivation film with sodium molybdate to realize the "precipitation-wrapping" double stabilization of lead. This method not only overcomes the defects of slow reaction rate and excessive dosage of traditional phosphorus-containing compounds, but also blocks the secondary dissolution of lead through the specific film-forming effect of molybdate ions, especially suitable for rare earth waste residue systems with large pH fluctuations and multiple metal coexistence, providing key technical support for the green and sustainable development of the rare earth industry. It is expected to promote the technological innovation in the field of lead-containing waste residue treatment, fill the gap in the long-term stable treatment of lead-containing waste residue technology, and has a broad application prospect and significant social and economic benefits.

[0114] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modifications, equivalent replacements or improvements made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for long-term and stable treatment of lead-containing rare earth waste residue, characterized in that: The steps include: S1, determining the appropriate passivating agent based on the pH value of the lead-containing rare earth waste residue and the lead acid leaching content; If the pH of lead-containing rare earth waste slag is ≤5, the suitable passivating agent is citric acid activated phosphorus source, calcium oxide and sodium molybdate; If the pH of lead-containing rare earth waste residue is greater than 5, the suitable passivating agent is citric acid activated phosphorus source and sodium molybdate; Wherein, if the lead acid leaching content of the lead-containing rare earth waste slag is ≤100 mg / L, the phosphorus source is phosphate rock powder; if the lead acid leaching content is greater than 100 mg / L, the phosphorus source is superphosphate; S2, mixing the substances in the passivating agent except sodium molybdate with the lead-containing rare earth waste slag, adjusting the moisture content to 20% to 40%, allowing to stand for a first preset time, adding sodium molybdate, mixing evenly, and allowing to stand for a second preset time to obtain treated lead-containing rare earth waste slag.

2. The method for long-term and stable treatment of lead-containing rare earth waste slag according to claim 1, characterized in that: The lead acid leaching content in the lead-containing rare earth waste residue is ≤1000 mg / L, and the water content is ≤40%.

3. The method for long-term and stable treatment of lead-containing rare earth waste slag according to claim 1, characterized in that: If the pH of the lead-containing rare earth waste slag is ≤5, the mass ratio of the citric acid-activated phosphorus source, calcium oxide and the lead-containing rare earth waste slag is 1:1:(50-100).

4. The method for long-term and stable treatment of lead-containing rare earth waste slag according to claim 1, characterized in that: If the pH of the lead-containing rare earth waste residue is greater than 5, the mass ratio of the citric acid-activated phosphorus source to the lead-containing rare earth waste residue is 1:(50-100).

5. The method for long-term and stable treatment of lead-containing rare earth waste slag according to claim 1, characterized in that: The added amount of the sodium molybdate is 1% to 2% of the mass of the lead-containing rare earth waste slag.

6. The method for long-term and stable treatment of lead-containing rare earth waste slag according to claim 1, characterized in that: The first preset time is 20 hours to 30 hours.

7. The method for long-term and stable treatment of lead-containing rare earth waste slag according to claim 1, characterized in that: The second preset time is 2 days to 4 days.

8. The method for long-term and stable treatment of lead-containing rare earth waste slag according to claim 1, characterized in that: The preparation method of the citric acid activated phosphorus source comprises the following steps: The phosphorus source is added to the citric acid solution, immersed at 20° C. to 25° C. for 2 to 4 hours, solid-liquid separation is performed, and drying is performed to obtain the citric acid-activated phosphorus source.

9. The method for long-term and stable treatment of lead-containing rare earth waste slag according to claim 8, characterized in that: The concentration of the citric acid solution is 0.3 mol / L to 0.6 mol / L.

10. The method for long-term and stable treatment of lead-containing rare earth waste slag according to claim 9, characterized in that: The solid-liquid ratio of the citric acid solution to the phosphorus source is 1:(20-50).