Method for improving the solid-liquid separation efficiency of hydrochloric acid leaching of monazite optimal-soluble residue pulp

Abstract

The application provides a method for improving the solid-liquid separation efficiency of hydrochloric acid leaching slurry of monazite optimal leaching residue, and belongs to the technical field of hydrometallurgy. The method uses a high molecular polymer as a filter aid, directly adds the filter aid into the slurry after hydrochloric acid leaching of the monazite optimal leaching residue, and improves the solid-liquid separation efficiency of the slurry by improving the filtration performance of the slurry. The method does not have additional requirements for the filtration temperature of the slurry, and the filter aid can be mixed with the slurry and then pumped into a filter press for solid-liquid separation treatment. The filtration speed of the slurry can be easily increased to 100L / (m 2 ·h) or above. The method for adding the filter aid has no side effects, does not produce additional precipitation, does not affect the separation and recovery of valuable elements in the leaching liquid, has no aging waiting time, has simple and continuous process operation, effectively reduces equipment investment and energy power consumption, is low-carbon and environmentally friendly, reduces the production cost of enterprises, and is beneficial to large-scale industrial application.

Description

Technical Field

[0001] This invention relates to the field of hydrometallurgical technology, and in particular to a method for improving the solid-liquid separation efficiency of hydrochloric acid leaching slurry from monazite slag. Background Technology

[0002] Monazite is a rare earth mineral that has been mainly used in my country for extracting rare earth chlorides for many years. Monazite concentrate is processed through alkaline decomposition and hydrochloric acid dissolution to produce rare earth chlorides and trisodium phosphate, yielding a highly soluble residue. This residue mainly contains 7-15% rare earth elements, 15-20% thorium, 0.5-1.5% uranium, as well as iron and zirconium, and has high processing value.

[0003] Currently, the main method for treating monazite leaching residue is complete dissolution with hydrochloric acid, allowing valuable elements such as uranium, thorium, and rare earth elements to enter the leachate. After solid-liquid separation, the leachate is used for stepwise extraction and precipitation to recover uranium, thorium, and rare earth resources. However, because monazite is ground to 300-325 mesh before alkali decomposition, the resulting leaching residue has an even finer particle size. After complete dissolution with high-concentration hydrochloric acid, a large number of dispersed mineral particles and fine, mutually repulsive gel particles are generated in the slurry. This makes it difficult for the leaching residue to settle and filter in the hydrochloric acid leaching slurry, resulting in long solid-liquid separation time, low efficiency, and difficulties in continuous industrial production.

[0004] Jiangxi Jieqiu Environmental Protection Technology Co., Ltd., Hua Rong et al. (CN104775026A) proposed a method for extracting high-purity uranium, thorium, and mixed rare earth elements from high-quality leaching residue. After hydrochloric acid leaching and clarification for 2 hours, the supernatant is siphoned. The slurry after siphoning the supernatant is pumped into a plate and frame filter press and filtered until no solution flows out. The filtrate is then combined with the supernatant. The filter residue from the plate and frame filter press is washed with water until the pH of the filtrate is 2.0–3.0, and the washing liquid is combined with the supernatant. This process requires waiting for clarification before siphoning the supernatant. Furthermore, the hydrochloric acid leaching slurry from high-quality leaching residue itself has poor settling properties, and even after clarification, the solid content of the upper solution remains high, which is unfavorable for subsequent multi-metal separation processes. Although siphoning reduces the water content in the slurry, it does not change its filtration performance, resulting in slow filtration and washing speeds and low efficiency in the solid-liquid separation step.

[0005] Zeng Zhongxian et al. of Hunan CNNC Jinyuan New Materials Co., Ltd. (CN111004920A) proposed a method for smelting and separating uranium, thorium, and rare earth elements from monazite slag. After the slag is completely dissolved in hydrochloric acid and the solution is cooled to below 60°C, hydrogen peroxide is added, and the solution is aged for 8–12 hours. The supernatant is then siphoned to obtain the dissolved liquid. The slurry after siphoning undergoes two-stage countercurrent thickening and sedimentation separation with stirring and washing, followed by a single-stage chamber filter press for solid-liquid separation. This method requires a large amount of reagents, has a long aging period, cannot be used for continuous production, and still requires thickening, sedimentation, stirring, washing, and filter press separation after siphoning. It also involves multiple types of equipment, a complex and lengthy process, high operating costs, and low solid-liquid separation efficiency.

[0006] Su Xuebin et al. of Hunan CNNC Jinyuan New Materials Co., Ltd. (CN114107661A) proposed a method to improve the filtration performance of monazite slurry. The monazite slurry was slurried with water, and a certain amount of oxalic acid was added to the leachate. The mixture was stirred at low speed at 70–90°C for about 30–60 minutes, and then allowed to stand for 3–4 hours to obtain a filter residue and filtrate containing thorium oxalate. The filtrate was then heated to 70°C and subjected to pressure filtration. While this method can effectively improve solid-liquid separation efficiency, the process is complex. It requires a second addition of oxalic acid to the leaching slurry for heating and stirring to induce precipitation. After precipitation, the slurry needs to be left to stand for 3-4 hours, making the process non-continuous. The filtrate after aging needs to be heated again or kept at 70°C, which affects the filtration rate. After adding oxalic acid, some rare earth elements in the leaching solution enter the leaching residue, affecting the subsequent thorium separation. At the same time, the loss rate of rare earth elements increases with the amount of oxalic acid added, which affects the recovery of valuable elements.

[0007] In summary, existing solid-liquid separation processes for monazite slag hydrochloric acid leaching slurry generally suffer from technical problems such as low solid-liquid separation efficiency, complex and lengthy processes, poor continuity, and low recovery rate of valuable elements. Summary of the Invention

[0008] In view of this, the purpose of the present invention is to provide a method for improving the solid-liquid separation efficiency of monazite leaching slurry in hydrochloric acid. The method of the present invention is simple, has good process continuity, low operating cost, does not lose valuable elements, and can effectively improve the solid-liquid separation efficiency of monazite leaching slurry.

[0009] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0010] This invention provides a method for improving the solid-liquid separation efficiency of hydrochloric acid leaching pulp from monazite superior solvent residue, comprising the following steps:

[0011] The monazite slag was acid-leached with hydrochloric acid to obtain a leaching slurry.

[0012] The leaching slurry is mixed with a filter aid, and the resulting mixed slurry is filtered.

[0013] The filter aid includes one or more of polyacrylamide, polyethylene glycol, and polyethyleneimine.

[0014] Preferably, the filter aid is used in the form of an aqueous solution of the filter aid, wherein the mass ratio of the filter aid to water in the aqueous solution is (1-2000):10000.

[0015] Preferably, the mass of the monazite slag is based on dry weight, and the amount of the filter aid is 10-5000 g / t of monazite slag.

[0016] Preferably, the filtration includes plate and frame filtration or vacuum filtration.

[0017] Preferably, the acid leaching temperature is 50–90°C and the time is 1–4 hours.

[0018] Preferably, the solid-liquid ratio of the monazite slag to hydrochloric acid is 1 kg: (2-4) L on a dry weight basis; and the concentration of the hydrochloric acid is 4.5-9 mol / L.

[0019] Preferably, the acid leaching is carried out under stirring conditions, and the stirring speed is 250-600 rpm.

[0020] Preferably, the mixing is carried out under stirring conditions, the stirring speed is 10-30 rpm, and the time is 1-5 min.

[0021] Preferably, the rare earth content in the monazite slag is 7-15% by mass, the thorium content is 15-20%, and the uranium content is 0.5-1.5%.

[0022] Preferably, the temperature of the mixed slurry is 50–90°C.

[0023] This invention provides a method for improving the solid-liquid separation efficiency of hydrochloric acid leaching slurry from monazite slag, comprising the following steps: acid leaching of monazite slag with hydrochloric acid to obtain leaching slurry; mixing the leaching slurry with a filter aid; and filtering the resulting mixed slurry; wherein the filter aid comprises one or more of polyacrylamide, polyethylene glycol, and polyethyleneimine.

[0024] This invention uses a high-molecular polymer as a filter aid, which is directly added to the slurry after the hydrochloric acid leaching of monazite residue. By adding the filter aid, the dispersed mineral particles and electrostatically repulsive gel particles in the slurry combine to form larger flocs, creating a colloid. This reduces the number of microparticles adsorbed on the filter cloth surface, decreasing the degree of clogging of the filter cloth pores by solid particles in the slurry, thereby increasing the filtration speed. There are no additional requirements for the slurry filtration temperature; the filter aid can be pumped into a filter press for solid-liquid separation after mixing with the slurry. The slurry filtration speed can be easily increased to 100 L / (m³). 2 (h) and above. This invention, by adding a filter aid, has no side effects, does not produce additional precipitation, does not affect the separation and recovery of valuable elements in the leachate, requires no aging time, and features simple and continuous process operation. It effectively reduces equipment investment and energy consumption, is low-carbon and environmentally friendly, lowers enterprise production costs, and is suitable for large-scale industrial applications. Attached Figure Description

[0025] Figure 1 This is a flowchart of the method for improving the solid-liquid separation efficiency of hydrochloric acid leaching slurry of monazite superior solvent residue according to the present invention. Detailed Implementation

[0026] This invention provides a method for improving the solid-liquid separation efficiency of hydrochloric acid leaching pulp from monazite superior solvent residue, comprising the following steps:

[0027] The monazite slag was acid-leached with hydrochloric acid to obtain a leaching slurry.

[0028] The leaching slurry is mixed with a filter aid, and the resulting mixed slurry is filtered.

[0029] The filter aid includes one or more of polyacrylamide, polyethylene glycol, and polyethyleneimine.

[0030] Unless otherwise specified, all raw materials used in this invention are commercially available products well known in the art.

[0031] This invention uses hydrochloric acid to leach monazite residue to obtain leaching slurry.

[0032] In this invention, the concentration of the hydrochloric acid is preferably 4.5–9 mol / L, more preferably 5–8 mol / L, and even more preferably 6–7 mol / L. In this invention, based on mass percentage, the rare earth content in the monazite slag is preferably 7–15%, the thorium content is preferably 15–20%, and the uranium content is preferably 0.5–1.5%. In this invention, the solid-liquid ratio of the monazite slag to hydrochloric acid is preferably 1 kg:(2–4) L, more preferably 1 kg:(2.5–3.5) L.

[0033] In this invention, the acid leaching temperature is preferably 50–90°C, more preferably 60–80°C; the acid leaching time is preferably 1–4 hours, more preferably 2–3 hours. In this invention, the acid leaching is preferably carried out under stirring conditions, and the stirring speed is preferably 250–600 rpm, more preferably 350–500 rpm.

[0034] After obtaining the leachate slurry, the present invention mixes the leachate slurry with a filter aid and filters the resulting mixed slurry.

[0035] In this invention, the filter aid preferably includes one or more of polyacrylamide, polyethylene glycol, and polyethyleneimine. When multiple filter aids are used, this invention does not have special requirements on the dosage ratio of each filter aid, and any ratio is acceptable. In this invention, the polyacrylamide preferably includes anionic polyacrylamide, cationic polyacrylamide, nonionic polyacrylamide, or amphoteric polyacrylamide, and more preferably amphoteric polyacrylamide.

[0036] In this invention, the filter aid is preferably used in the form of an aqueous solution. The mass ratio of the filter aid to water in the aqueous solution is preferably (1-2000):10000, more preferably (100-1500):10000, and even more preferably (500-1000):10000. In this invention, the preparation temperature of the aqueous solution is preferably 15-30°C. The aqueous solution is preferably prepared under stirring conditions. This invention does not have special requirements for the stirring time and rate; stirring continues until the filter aid is completely dissolved and no visible particles remain in the solution.

[0037] In this invention, the mass of the monazite slurry is based on dry weight, and the amount of the filter aid is preferably 10-5000 g / t of monazite slurry, more preferably 100-4500 g / t of monazite slurry, further preferably 500-4000 g / t of monazite slurry, and most preferably 1000-3000 g / t of monazite slurry.

[0038] In this invention, the mixing is preferably carried out under stirring conditions, the stirring speed is preferably 10-30 rpm, and the stirring time is preferably 1-5 min. In this invention, the temperature of the leaching slurry during mixing is the post-leaching temperature, i.e., 50-90℃ (no temperature adjustment is required).

[0039] The present invention does not have any special requirements for the filtration method, and any filtration method well known in the art can be used, such as plate and frame filter press or vacuum filtration.

[0040] This invention uses a high-molecular polymer as a filter aid, which is directly added to the slurry after hydrochloric acid leaching of monazite residue. This improves the slurry's solid-liquid separation efficiency by enhancing its filtration performance. No additional requirements are placed on the slurry filtration temperature; the filter aid, after mixing with the slurry, can be pumped into a filter press for solid-liquid separation. The slurry filtration rate can be easily increased to 100 L / (m³). 2 (h) and above. This invention, by adding a filter aid, has no side effects, does not produce additional precipitation, does not affect the separation and recovery of valuable elements in the leachate, requires no aging time, and features simple and continuous operation. It effectively reduces equipment investment and energy consumption, is low-carbon and environmentally friendly, lowers enterprise production costs, and is suitable for large-scale industrial applications.

[0041] The following detailed description, in conjunction with embodiments, illustrates the method for improving the solid-liquid separation efficiency of hydrochloric acid leaching slurry for monazite superior solvent residue provided by the present invention. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0042] Example 1

[0043] The monazite slag has a water content of 35.6%, a uranium content of 1.43%, a thorium content of 20.1%, an iron content of 1.38%, and a rare earth oxide content of 11.6%.

[0044] like Figure 1 As shown, H is prepared using 35% concentrated hydrochloric acid. + A 6 mol / L acidic leaching agent was slowly added to the leaching agent at a dry residue solid-liquid mass-volume ratio of 1 kg: 3 L, while stirring continuously at a speed of 600 rpm. The mixture was then kept in a constant temperature water bath at 70°C and stirred for 4 hours to obtain the leaching slurry.

[0045] Preparation of aqueous solution of filter aid A: Weigh 1g of amphoteric polyacrylamide flocculant using dry and clean weighing paper, and slowly add it to 1L of water while stirring at room temperature. Stir at 500rpm until no solution remains and the solution becomes a clear, transparent, viscous liquid.

[0046] To prepare an aqueous solution of filter aid B: Weigh 5g of polyethylene glycol using a dry, clean weighing paper, and slowly add it to 1L of water while stirring at room temperature. Stir at 500rpm until the solution becomes a clear, transparent liquid.

[0047] Mixing: Take 1.5L of freshly leached slurry, slurry temperature 70℃, leachate H + The concentration was 3.25 mol / L. Filter aid A and filter aid B were added to the slurry in the form of aqueous solution. The mass ratio of filter aid A to the monazite slag before leaching was 60 g / t, and the mass ratio of filter aid B to the monazite slag before leaching was 300 g / t. The mixture was added while stirring slowly at a speed of 10 rpm for 2 min.

[0048] A comparative test of vacuum filtration was conducted on the raw ore slurry and the slurry with added filter aid. The filtration rate of the raw ore slurry ① was 12.4 L / (m). 2 The filtrate concentrations were as follows: uranium 4.71 g / L, thorium 63.60 g / L, rare earth oxides 37.89 g / L; slag concentrations were as follows: uranium 0.095%, thorium 6.70%, rare earth oxides 1.55%; the filtration rate of the slurry ② after adding filter aid was 110.2 L / (m²). 2 ·h), filtrate ② has a uranium concentration of 4.69 g / L, a thorium concentration of 63.22 g / L, and a rare earth oxide concentration of 37.64 g / L, while slag ② has a uranium content of 0.095%, a thorium content of 6.69%, and a rare earth oxide content of 1.54%.

[0049] Example 2

[0050] The monazite slag has a water content of 32.2%, a uranium content of 0.71%, a thorium content of 15.2%, an iron content of 1.02%, and a rare earth oxide content of 10.8%.

[0051] H is prepared using 35% concentrated hydrochloric acid. + Acidic leaching agent with a concentration of 6 mol / L was slowly added to the leaching agent at a dry residue solid-liquid mass-volume ratio of 1 kg: 3 L, while stirring continuously at a stirring speed of 600 rpm. The mixture was then kept in a constant temperature water bath at 60℃ and stirred under sealed conditions for 2 hours.

[0052] To prepare the aqueous solution of the filter aid: Weigh 10g of polyethylene glycol using a dry and clean weighing paper, and slowly add it to 1L of water while stirring at room temperature. Stir at 500rpm until the solution becomes a clear and transparent liquid.

[0053] Mixing: Take 1.5L of freshly leached ore pulp at a temperature of 60℃, and leachate H... + The concentration was 2.64 mol / L. The filter aid was added to the slurry in the form of an aqueous solution at a mass ratio of 990 g / t of filter aid to the monazite residue before leaching, while stirring slowly at a speed of 10 rpm for 2 minutes.

[0054] A comparative vacuum filtration test was conducted on the raw ore slurry and the slurry with added filter aid. The filtration rate of the raw ore slurry (③) was 10.2 L / (m). 2 •h), filtrate ③: uranium concentration 2.34 g / L, thorium concentration 47.62 g / L, rare earth oxide concentration 34.90 g / L; slag ③: uranium content 0.042%, thorium content 5.36%, rare earth oxide content 1.91%; the filtration rate of slurry ④ after adding filter aid is 154.3 L / (m). 2•h) Filtrate ③: Uranium concentration 2.34 g / L, thorium concentration 47.62 g / L, rare earth oxide concentration 34.92 g / L; Slag ④: Uranium content 0.041%, thorium content 5.36%, rare earth oxide content 1.90%.

[0055] Example 3

[0056] The monazite slag has a water content of 38.1%, a uranium content of 0.52%, a thorium content of 18.3%, an iron content of 1.42%, and a rare earth oxide content of 12.8%.

[0057] H is prepared using 35% concentrated hydrochloric acid. + Acidic leaching agent with a concentration of 8 mol / L was slowly added to the leaching agent at a dry residue solid-liquid mass-volume ratio of 1 kg: 4 L, while stirring continuously at a stirring speed of 600 rpm. The mixture was then kept in a constant temperature water bath at 70℃ and stirred under sealed conditions for 3 hours.

[0058] To prepare an aqueous solution of filter aid C: Weigh 0.5g of polyethyleneimine into a dry, clean beaker and slowly add it to 1L of water while stirring at room temperature. Stir at 500rpm until the solution becomes a clear, transparent, viscous liquid.

[0059] To prepare an aqueous solution of filter aid D: Weigh 10g of polyethylene glycol using a dry, clean weighing paper, and slowly add it to 1L of water while stirring at room temperature. Stir at 500rpm until the solution becomes a clear, transparent liquid.

[0060] Mixing: Take 1.5L of freshly leached slurry, slurry temperature 70℃, leachate H + The concentration was 3.86 mol / L. Filter aid C and filter aid D were added to the slurry in water-soluble form, with the mass ratio of filter aid C to the monazite slag before leaching being 7.5 g / t, and the mass ratio of filter aid D to the monazite slag before leaching being 750 g / t. The mixture was added while stirring slowly at a speed of 10 rpm for 2 min.

[0061] A comparative test of vacuum filtration was conducted on the raw ore slurry and the slurry with added filter aid. The filtration rate of the raw ore slurry (⑤) was 14.3 L / (m). 2 ·h), filtrate ⑤: uranium concentration 1.71 g / L, thorium concentration 56.73 g / L, rare earth oxide concentration 40.96 g / L; slag ⑤: uranium content 0.033%, thorium content 8.01%, rare earth oxide content 3.2%; the filtration rate of the slurry ⑥ after adding filter aid is 221.1 L / (m). 2 •h), filtrate ⑥: uranium concentration 1.72 g / L, thorium concentration 56.72 g / L, rare earth oxide concentration 40.95 g / L, slag ⑥ uranium content 0.032%, thorium content 8.00%, rare earth oxide content 3.2%.

[0062] The data from the above examples illustrate that: after the hydrochloric acid leaching of monazite slurry is completed, adding an appropriate amount of filter aid directly, mixing lightly and evenly, and then filtering directly can quickly improve the solid-liquid separation efficiency of the slurry, increasing the filtration rate from 10 L / (m²) to [amount missing]. 2 The volume of water used to increase the ... 2 The process yields (h) or higher, without additional loss of valuable elements. This invention requires no additional equipment, no secondary sedimentation treatment of the leached slurry, no aging or waiting, and no adjustment of slurry temperature and acidity. The operation is continuous, simple, and easy to implement, with a simple and practical process. It effectively reduces equipment investment and energy consumption, meets low-carbon and environmental protection requirements, saves enterprise production costs, and is conducive to industrial application.

[0063] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for improving the solid-liquid separation efficiency of hydrochloric acid leaching slurry from monazite superior solvent residue, characterized in that, The specific steps are as follows: The monazite slag has a moisture content of 38.1%, a uranium content of 0.52%, a thorium content of 18.3%, an iron content of 1.42%, and a rare earth oxide content of 12.8%. The monazite slag is obtained by producing rare earth chlorides and trisodium phosphate from monazite concentrate through alkaline decomposition and hydrochloric acid slurry processes. H is prepared using 35% concentrated hydrochloric acid. + An acidic leaching agent with a concentration of 8 mol / L was slowly added to the leaching agent at a dry residue solid-liquid mass-volume ratio of 1 kg: 4 L, while stirring continuously at a stirring speed of 600 rpm. The mixture was then kept in a constant temperature water bath at 70℃ and stirred under sealed conditions for 3 hours. To prepare an aqueous solution of filter aid C: Weigh 0.5g of polyethyleneimine into a dry and clean beaker, and slowly add it into 1L of water while stirring at room temperature. Stir at 500rpm until the solution becomes a clear, transparent, viscous liquid. To prepare an aqueous solution of filter aid D: Weigh 10g of polyethylene glycol using a dry and clean weighing paper, and slowly add it to 1L of water while stirring at room temperature. Stir at 500rpm until the solution becomes a clear and transparent liquid. Mixing: Take 1.5L of freshly leached slurry, slurry temperature 70℃, leachate H + The concentration was 3.86 mol / L. Filter aid C and filter aid D were added to the slurry in water-soluble form. The mass ratio of filter aid C to the monazite slag before leaching was 7.5 g / t, and the mass ratio of filter aid D to the monazite slag before leaching was 750 g / t. The mixture was added while stirring slowly at a speed of 10 rpm for 2 min.

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