Method for extracting cesium by roasting pollucite

Abstract

The invention provides a method for extracting cesium by roasting pollucite, and belongs to the technical field of cesium ore smelting. The method comprises the following steps: mixing pollucite, a composite chlorinating agent and a chlorine fixing agent, roasting to obtain clinker, mixing the clinker with water, and leaching to obtain leaching residues and a leaching solution; step-by-step crystallization is conducted on the leachate, precipitated salt and primary purified liquid are obtained, and the precipitated salt serves as a composite chlorinating agent and returns to the front end to be roasted; calcium and magnesium are removed from the primary purification liquid, calcium and magnesium removed slag and secondary purification liquid are obtained, and the calcium and magnesium removed slag returns to the front end to be roasted; and adjusting the pH value of the secondary purified liquid, and extracting and separating lithium, rubidium and cesium. According to the method, the high cesium extraction rate is achieved, no chlorine tail gas is generated, and meanwhile recycling of waste residues generated in the process is achieved; meanwhile, the method disclosed by the invention is simple in process flow, safe, simple and convenient to operate and small in dosage of auxiliary materials, and has a wide application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of cesium ore smelting, and particularly relates to a method for roasting and extracting cesium from pollucite. BACKGROUND

[0002] Cesium is widely used in traditional fields such as chemical industry, biology, medicine, physics, electronic devices and special glass, and emerging fields such as aerospace, new energy and information science due to its unique properties.

[0003] The existing process for extracting cesium from pollucite generally uses acid to treat cesium ore to obtain cesium alum. CN 102659145 B and CN 103241750 B use 35wt% concentrated sulfuric acid to leach cesium at 130℃ for 4h. CN 118684249 B uses sulfuric acid to leach pollucite concentrate under heating. However, the acid treatment changes pollucite (2Cs2O·2Al2O3·9SiO2·H2O) into cesium alum (CsAl(SO4)2·12H2O), which not only leaches cesium but also leaches a large amount of aluminum, resulting in a large amount of acid consumption. Then, the aluminum needs to be removed in the form of aluminum hydroxide by adding alkali. This scheme generates aluminum hydroxide which is difficult to filter, and the amount of auxiliary materials such as acid and alkali is large.

[0004] In addition, CN 113174480 B proposes that lithium, rubidium and cesium silicate ore, calcium chloride and solid chlorine agent are mixed in a certain proportion and then roasted, and then leached to extract lithium, rubidium and cesium. However, the roasting temperature of this scheme is high.

[0005] In summary, it is of great significance to develop a method for extracting cesium from pollucite which can fully utilize auxiliary materials, reduce energy consumption and reduce the leaching of difficult-to-filter impurities such as aluminum. SUMMARY

[0006] The present application aims to provide a method for roasting and extracting cesium from pollucite to solve the problems of generating difficult-to-filter aluminum hydroxide and large amount of auxiliary materials such as acid and alkali in the acid treatment of pollucite, and to solve the problem of high roasting temperature in the single chlorinating agent roasting method.

[0007] In order to achieve the above-mentioned application purposes, the present application provides the following technical scheme: The present application provides a method for roasting and extracting cesium from pollucite, comprising the following steps: 1) mixing pollucite, a composite chlorinating agent and a solid chlorine agent, roasting to obtain clinker, crushing the clinker and mixing with water, leaching to obtain leaching residue and leaching solution; 2) step-by-step crystallization of the leaching solution to obtain precipitated salt and primary purified solution; 3) calcium and magnesium removal of the primary purified solution to obtain calcium and magnesium removal residue and secondary purified solution; 4) After adjusting the pH of the secondary purification solution, lithium, rubidium and cesium are separated by extraction.

[0008] Further, the mass ratio of the cesium spar, the composite chlorination agent and the solid chlorine agent is 1:0.6-2.0:0.05-0.3.

[0009] Further, the temperature of the roasting is 500-950℃, and the roasting time is 15-180 min.

[0010] Further, the liquid-solid ratio of the water and the clinker is 1-5 mL / g, the leaching temperature is 10-95℃, and the leaching time is 30-90 min.

[0011] Further, the composite chlorination agent comprises two or more of sodium chloride, potassium chloride, calcium chloride and magnesium chloride, and the solid chlorine agent comprises one or more of calcium oxide, magnesium oxide, calcium hydroxide, magnesium hydroxide, calcium carbonate, magnesium carbonate, calcium bicarbonate and magnesium bicarbonate.

[0012] Further, in the step 2), the fractional crystallization is two-step evaporation concentration.

[0013] Further, in the step 3), the calcium and magnesium removal uses sodium carbonate reagent, and the stirring is performed at 80-100℃ for 20-40 min; the calcium and magnesium removal residue is returned to the step 1) as the solid chlorine agent.

[0014] The present application has the following beneficial effects: The method of the present application solves the problems of large amount of auxiliary materials such as aluminum hydroxide and acid and alkali in the acid method for treating cesium spar, by precipitating the salt and recycling the calcium and magnesium removal residue, and only a small amount of composite chlorination agent needs to be supplemented periodically. Not only the auxiliary material cost can be effectively reduced, but also the generation of difficult-to-filter aluminum hydroxide is avoided.

[0015] The composite chlorination compound has a low eutectic point, and the melting point of the composite chlorination compound is lower than that of the single chlorination compound, which can effectively reduce the roasting temperature; the viscosity of the composite chlorination compound is lower than that of the single chlorination compound at the same temperature, and the flowability is better, which is more conducive to the contact and reaction of the chlorination agent with the surface layer of the cesium spar. Through the use of the composite chlorination compound, the problem of high roasting temperature in the single chlorination agent roasting method is solved.

[0016] The method of the present application has the advantages of simple process flow, safe and simple operation, small amount of auxiliary materials, significant economic value and environmental friendliness, and wide application prospect. DETAILED DESCRIPTION

[0017] The present application provides a method for roasting cesium spar to extract cesium, comprising the following steps: 1) Cesium garnet, composite chlorinating agent and chlorine-fixing agent are mixed and roasted to obtain clinker. The clinker is crushed and mixed with water for leaching to obtain leaching residue and leaching solution. 2) The leachate is crystallized stepwise to obtain precipitated salt and primary purified solution; 3) Remove calcium and magnesium from the primary purification solution to obtain calcium and magnesium-removed slag and secondary purification solution; 4) After adjusting the pH of the secondary purification solution, lithium, rubidium and cesium are extracted and separated.

[0018] In this invention, the mass ratio of cesium garnet, composite chlorinating agent and solid chlorinating agent is 1:0.6~2.0:0.05~0.3, preferably 1:0.6-1.6:0.05~0.2, and more preferably 1:0.7-1.2:0.05~0.15.

[0019] In this invention, the calcination temperature is 500~950℃, preferably 600~920℃, more preferably 700~900℃, and even more preferably 750~900℃; the calcination time is 15~180min, preferably 20~100min, more preferably 35~60min, and even more preferably 45~55min.

[0020] In this invention, during the roasting of the composite chlorinating agent described in step 1), the valuable metal ions in the composite chlorinating agent undergo ion exchange with the valuable metal ions in cesium garnet. Subsequently, the clinker is crushed and leached, causing lithium, rubidium, and cesium in the cesium garnet to leach out as chloride salts. Simultaneously, unreacted composite chlorinating agent is also leached out, while aluminum and silicon in the cesium garnet remain in the leaching residue and cannot be leached. The cesium garnet also contains a large amount of alumina and silicon dioxide. According to thermodynamic calculations, the Gibbs free energy of the ion exchange reaction is lower in the presence of alumina and silicon dioxide, thus promoting the ion exchange reaction and achieving the extraction of valuable metals from the cesium garnet.

[0021] In this invention, the liquid-to-solid ratio of water to clinker is 1-5 mL / g, preferably 1-4 mL / g, more preferably 1-3 mL / g, and even more preferably 2-3 mL / g; the leaching temperature is 10-95℃, preferably 10-65℃, more preferably 15-55℃, and even more preferably 15-45℃; the leaching time is 30-90 min, preferably 30-80 min, more preferably 30-75 min, and even more preferably 30-55 min.

[0022] In this invention, the composite chlorinating agent comprises two or more of sodium chloride, potassium chloride, calcium chloride, and magnesium chloride; the solid chlorinating agent comprises one or more of calcium oxide, magnesium oxide, calcium hydroxide, magnesium hydroxide, calcium carbonate, magnesium carbonate, calcium bicarbonate, and magnesium bicarbonate.

[0023] In this invention, step 2) involves step-by-step crystallization, which is achieved through two-step evaporation and concentration.

[0024] In this invention, in step 3), sodium carbonate is used to remove calcium and magnesium, and the mixture is stirred at 80-100°C for 20-40 minutes, preferably at 95°C for 30 minutes; the calcium and magnesium slag is returned to step 1) as a chlorine-fixing agent.

[0025] In this invention, by recycling the precipitated salt and the calcium-magnesium slag, only a small amount of composite chlorinating agent needs to be added periodically, thus solving the problem of large quantities of acid and alkali auxiliary materials required in the acid process for treating cesium garnet. This not only effectively reduces the cost of auxiliary materials but also achieves the recycling of waste residue.

[0026] In this invention, the use of composite chlorides solves the problem of high roasting temperatures in single-chlorination roasting methods. Through roasting, valuable metals such as lithium, rubidium, and cesium in cesium garnet are leached out in the form of chlorides with high solubility, while impurities such as aluminum and silicon, which are difficult to filter, remain in the leaching residue and are not extracted. This solves the problem of generating difficult-to-filter aluminum hydroxide in acid treatment of cesium garnet.

[0027] The composite chloride has a low eutectic point, which is lower than that of the single chloride, effectively reducing the roasting temperature. At the same temperature, the composite chloride has lower viscosity and better fluidity than the single chloride, making it more conducive to the contact and reaction between the chlorinating agent and the cesium garnet surface. The composite chloride effectively lowers the roasting temperature because its low melting point causes it to melt during roasting; both cesium garnet and the chlorinating agent have higher melting points (above the roasting temperature) and do not melt during roasting. Therefore, the molten chlorinating agent "flows" within the voids of the cesium garnet, accelerating the reaction process and lowering the roasting temperature. The cesium garnet and chlorinating agent provide a kind of "skeletal support" for the easily fusible chlorinating agent, effectively preventing the chlorinating agent from melting (during roasting, unmelted cesium garnet and chlorinating agent can fix the molten chlorinating agent within the voids of the cesium garnet and chlorinating agent).

[0028] In this invention, by adding a chlorination-fixing agent, the acidic chlorine-containing gas generated during the roasting process reacts with the chlorination-fixing agent to generate a chlorinating agent. This reduces the use of chlorinating agents and avoids the generation of acidic chlorine-containing tail gas.

[0029] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0030] Example 1

[0031] 1) Cesium garnet, composite chlorinating agent (sodium chloride to calcium chloride mass ratio 1:1), and chlorinating agent (calcium carbonate to magnesium hydroxide mass ratio 1:1) are mixed in a mass ratio of 1:1:0.1 and then compressed into tablets. The tablets are calcined at 850℃ for 45 min to obtain clinker. The clinker is crushed, and water is added to the clinker with a liquid-solid ratio of 2 mL / g. The tablets are then leached at 20℃ for 30 min to obtain leaching residue and leaching solution. 2) The leachate is evaporated and concentrated, and then filtered while hot to obtain precipitated salt 1 and concentrated solution 1. The main component of precipitated salt 1 is sodium chloride. Concentrated solution 1 is further evaporated and concentrated, and then cooled to room temperature and filtered to obtain precipitated salt 2 and primary purified solution. The main components of precipitated salt 2 are potassium chloride, calcium chloride and magnesium chloride. Precipitated salts 1 and 2 are mixed and returned to the front end as a composite chlorinating agent, and the primary purified solution goes to the next process. 3) Add 1.1 equivalents of sodium carbonate to the primary purification liquid, stir at 95°C for 30 minutes, and filter while hot to obtain calcium- and magnesium-removed slag and secondary purification liquid. The calcium- and magnesium-removed slag is returned to the front end as a chlorine-fixing agent. 4) After adjusting the pH of the secondary purification solution, lithium, rubidium, and cesium are extracted and separated.

[0032] The extraction rate of cesium in this embodiment was found to be 98%.

[0033] Example 2

[0034] 1) Cesium garnet, a composite chlorinating agent (potassium chloride, sodium chloride, and calcium chloride in a mass ratio of 1:2:3), and a chlorinating agent (calcium oxide) are mixed evenly in a mass ratio of 1:0.8:0.15. After compression into tablets, the mixture is calcined at 800℃ for 50 minutes to obtain clinker. The clinker is then crushed, and the liquid-to-solid ratio of water to clinker is controlled at 3 mL / g. The mixture is then leached at 40℃ for 40 minutes to obtain leaching residue and leachate. 2) The leachate undergoes a two-step evaporation and concentration process: First, the leachate is evaporated to half its original volume and filtered while hot to obtain precipitated salt 1 (mainly sodium chloride). Second, the leachate is further evaporated and concentrated to one-quarter of its original volume, cooled to room temperature, and then filtered to obtain precipitated salt 2 (mainly potassium chloride and calcium chloride) and a primary purified solution. Precipitated salt 1 and precipitated salt 2 are mixed and returned to step 1) for use as a composite chlorinating agent. 3) Add 1.05 equivalents of sodium carbonate to the primary purification liquid, stir at 90°C for 25 minutes, and filter while hot to obtain calcium- and magnesium-removed slag and secondary purification liquid. The calcium- and magnesium-removed slag is returned to step 1) as a chlorine-fixing agent. 4) Adjust the pH of the secondary purification solution and use an extractant to extract and separate lithium, rubidium, and cesium.

[0035] The extraction rate of cesium in this embodiment was found to be 95%.

[0036] Example 3

[0037] 1) Cesium garnet, a composite chlorinating agent (potassium chloride to calcium chloride in a mass ratio of 1:1.2), and a chlorinating agent (calcium carbonate) were mixed evenly in a mass ratio of 1:0.9:0.11. After being compressed into tablets, the mixture was calcined at 900℃ for 55 minutes to obtain clinker. After the clinker was crushed, the liquid-to-solid ratio of water to clinker was controlled at 2.5 mL / g, and the mixture was leached at 45℃ for 40 minutes to obtain leaching residue and leachate. 2) The leachate undergoes a two-step evaporation and concentration process: First, the leachate is evaporated to 2 / 3 of its original volume and filtered while hot to obtain precipitated salt 1 (mainly potassium chloride). Second, the leachate is further evaporated and concentrated to 1 / 3 of its original volume, cooled to room temperature, and then filtered to obtain precipitated salt 2 (mainly calcium chloride) and a primary purified solution. Precipitated salt 1 and precipitated salt 2 are mixed and returned to step 1) as a composite chlorinating agent. 3) Add 1.1 equivalents of sodium carbonate to the primary purification liquid, stir at 85°C for 35 minutes, and filter while hot to obtain calcium- and magnesium-removed slag and secondary purification liquid. The calcium- and magnesium-removed slag is returned to step 1) as a chlorine-fixing agent. 4) Adjust the pH of the secondary purification solution and perform extraction to separate lithium, rubidium, and cesium.

[0038] The extraction rate of cesium in this embodiment was found to be 96%.

[0039] Example 4

[0040] 1) Cesium garnet, a composite chlorinating agent (sodium chloride, magnesium chloride, and calcium chloride in a mass ratio of 1:1:3), and a chlorinating agent (calcium hydroxide) were mixed evenly in a mass ratio of 1:1.1:0.12. After being compressed into tablets, the mixture was calcined at 800℃ for 45 minutes to obtain clinker. After the clinker was crushed, the liquid-to-solid ratio of water to clinker was controlled at 3 mL / g, and the mixture was leached at 25℃ for 45 minutes to obtain leaching residue and leachate. 2) The leachate undergoes a two-step evaporation and concentration process: First, the leachate is evaporated to half its original volume and filtered while hot to obtain precipitated salt 1 (mainly composed of sodium chloride and potassium chloride); second, it is further evaporated and concentrated to one-quarter of its original volume, cooled to room temperature, and then filtered to obtain precipitated salt 2 (mainly composed of magnesium chloride and calcium chloride) and a primary purified solution. Precipitated salt 1 and precipitated salt 2 are mixed and returned to step 1) as a composite chlorinating agent. 3) Add 1.1 equivalents of sodium carbonate to the primary purification liquid, stir at 95°C for 30 minutes, and filter while hot to obtain calcium- and magnesium-removed slag and secondary purification liquid. The calcium- and magnesium-removed slag is returned to step 1) as a chlorine-fixing agent. 4) Adjust the pH of the secondary purification solution and perform extraction to separate lithium, rubidium, and cesium.

[0041] The extraction rate of cesium in this embodiment was found to be 97%.

[0042] As can be seen from the above embodiments, the present invention provides a method for cesium extraction from cesium garnet by roasting. The method of the present invention, through the recycling of precipitated salt and calcium-magnesium slag, only requires periodic replenishment of a small amount of composite chlorinating agent, solving the problems of generating difficult-to-filter aluminum hydroxide and the large amount of auxiliary materials such as acids and alkalis in acid treatment of cesium garnet. This not only effectively reduces auxiliary material costs but also avoids the generation of difficult-to-filter aluminum hydroxide. This method not only achieves a high cesium extraction rate and no chlorine tail gas generation but also realizes the recycling of waste residue generated in the process; furthermore, the method of the present invention has a simple process flow, is safe and easy to operate, and requires less auxiliary materials, thus having broad application prospects.

[0043] 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 calcining cesium garnet to extract cesium, characterized in that, Includes the following steps: 1) Cesium garnet, composite chlorinating agent and chlorine-fixing agent are mixed and roasted to obtain clinker. The clinker is crushed and mixed with water for leaching to obtain leaching residue and leaching solution. 2) The leachate is crystallized stepwise to obtain precipitated salt and primary purified solution; 3) Remove calcium and magnesium from the primary purification solution to obtain calcium and magnesium-removed slag and secondary purification solution; 4) After adjusting the pH of the secondary purification solution, lithium, rubidium and cesium are extracted and separated.

2. The method for calcining cesium garnet to extract cesium according to claim 1, characterized in that, The mass ratio of the cesium garnet, the composite chlorinating agent, and the solid chlorinating agent is 1:0.6~2.0:0.05~0.

3.

3. The method for calcining cesium garnet to extract cesium according to claim 1 or 2, characterized in that, The roasting temperature is 500~950℃, and the roasting time is 15~180min.

4. The method for calcining cesium garnet to extract cesium according to claim 3, characterized in that, The liquid-to-solid ratio of water to clinker is 1~5 mL / g, the leaching temperature is 10~95℃, and the leaching time is 30~90 min.

5. The method for calcining cesium garnet to extract cesium according to claim 1, 2, or 4, characterized in that, The composite chlorinating agent contains two or more of sodium chloride, potassium chloride, calcium chloride, and magnesium chloride, and the solid chlorinating agent contains one or more of calcium oxide, magnesium oxide, calcium hydroxide, magnesium hydroxide, calcium carbonate, magnesium carbonate, calcium bicarbonate, and magnesium bicarbonate.

6. The method for calcining cesium garnet to extract cesium according to claim 1, characterized in that, In step 2), the stepwise crystallization is a two-step evaporation and concentration process.

7. The method for calcining cesium garnet to extract cesium according to claim 5, characterized in that, In step 3), sodium carbonate is used to remove calcium and magnesium, and the mixture is stirred at 80-100°C for 20-40 minutes; the calcium and magnesium slag is returned to step 1) as a chlorine-fixing agent.