A flotation agent and method for selectively extracting cesium ions in a competing ion system

Abstract

The application discloses a flotation agent and method for selectively extracting cesium ions in a competitive ion system, and belongs to the technical field of ion flotation. In view of the problem of low selective extraction efficiency of the existing flotation agent on cesium ions in a competitive alkali metal ion system, the flotation agent comprises alkyl gallate and lecithin, and the mass ratio of the alkyl gallate and the lecithin is 7-13:3-6, and the length of the alkyl carbon chain is 6-18. The method comprises the following steps: adding the flotation agent into an aqueous solution containing cesium and competitive alkali metal ions to perform ion flotation, so that the cesium ions are selectively enriched in a foam phase. According to the application, the two natural amphiphilic molecules are synergistically compounded to construct a flotation system with selective recognition ability for the cesium ions at a gas-liquid interface, and the flotation system does not need a precipitant or an adsorbent, and the process is simple; the extraction rate of the cesium ions can reach more than 80% in the presence of competitive ions, and the application is suitable for radioactive wastewater treatment and hydrometallurgy.

Description

Technical Field

[0001] This invention belongs to the field of ion flotation technology, specifically, it relates to a flotation agent and a method for selectively extracting cesium ions from an aqueous solution containing competing alkali metal ions. Background Technology

[0002] Ion flotation involves adding surfactants to the system to enrich the target ions at the gas-liquid interface, and then separating them by bubble flotation. It has advantages such as simple process flow, fast processing speed and low cost, and has promising applications in radioactive wastewater treatment, hydrometallurgy and seawater resource utilization.

[0003] However, existing ionic flotation reagents have significant limitations in extracting cesium ions. For example, when using monorhamnolipid as a flotation reagent to treat radioactive wastewater, the extraction rate of cesium ions is only about 40%. Other studies have used sodium tetraphenylborate as an adsorbent to remove cesium ions from radioactive wastewater via adsorption flotation, but this requires additional iron oxide coating to achieve separation, making the process complex and costly. More importantly, in complex aqueous solutions containing competing alkali metal ions such as potassium and sodium ions, existing flotation reagents struggle to construct a flotation system with selective recognition capabilities for cesium ions at the gas-liquid interface, resulting in low selective extraction efficiency and failing to meet practical application requirements. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a flotation agent and method for selectively extracting cesium ions from aqueous solutions containing competing alkali metal ions, aiming to solve the technical problem that existing technologies cannot achieve efficient and selective extraction of cesium ions from complex aqueous solutions containing a large number of competing alkali metal ions.

[0005] The technical solution of the present invention is as follows: A flotation agent for selectively extracting cesium ions from an aqueous solution containing competing alkali metal ions comprises an alkyl gallate and lecithin, wherein the mass ratio of the alkyl gallate to lecithin is 7-13:3-6, and the alkyl carbon chain length of the alkyl gallate is 6-18.

[0006] Preferably, the alkyl carbon chain length of the gallic acid alkyl ester is 10-16.

[0007] Preferably, the mass ratio of the alkyl gallate to lecithin is 8-10:3-5.

[0008] Preferably, the active ingredients of the flotation agent are alkyl gallate and lecithin.

[0009] Preferably, the flotation agent further comprises an alcohol solvent, wherein the alcohol solvent is ethanol and / or methanol, and the mass fraction of the alcohol solvent in the flotation agent is 40%-90%.

[0010] A method for selectively extracting cesium ions from an aqueous solution containing competing alkali metal ions, the method comprising: adding a flotation agent to an aqueous solution containing cesium ions and competing alkali metal ions and performing ion flotation, thereby selectively enriching cesium ions in the foam phase at the gas-liquid interface; wherein the flotation agent comprises alkyl gallate and lecithin, the mass ratio of alkyl gallate to lecithin being 7-13:3-6, and the alkyl carbon chain length of the alkyl gallate being 6-18.

[0011] Preferably, the pH of the aqueous solution is 8-12.

[0012] Preferably, the competing alkali metal ions include potassium ions and / or sodium ions, and the molar concentration ratio of the competing alkali metal ions to cesium ions is less than or equal to 10:1.

[0013] Preferably, the aqueous solution is stirred for 30 minutes before adding the flotation agent.

[0014] Preferably, the amount of flotation agent used is 2.5-40 mg / L.

[0015] Beneficial Effects: This invention constructs a flotation system with selective recognition capability for cesium ions by compounding alkyl gallate and lecithin in a specific mass ratio and limiting the alkyl carbon chain length of the alkyl gallate to 6-18. Utilizing the synergistic self-assembly of these two natural amphiphilic molecules at the gas-liquid interface, this compound system can form a stable selective adsorption layer at the gas-liquid interface in complex aqueous solutions containing a large number of competing alkali metal ions. Through the synergistic effect of the phenolic hydroxyl recognition site of the alkyl gallate and the zwitterionic head group of lecithin, highly efficient selective capture and enrichment of cesium ions are achieved, resulting in the selective enrichment of cesium ions in the foam phase. Compared with existing technologies, this invention eliminates the need for precipitants or adsorbents and additional coating steps, simplifying the process. Furthermore, it achieves effective selective enrichment of cesium ions in mixed systems containing competing alkali metal ions, with an extraction rate exceeding 80%, significantly improving the selective extraction efficiency of cesium ions and reducing extraction costs. Detailed Implementation

[0016] Specific embodiments of the present invention will now be described in detail. However, the present invention can be implemented in many different forms, and should not be construed as limiting itself to the specific embodiments set forth herein. Rather, these embodiments are provided to explain the principles of the invention and its practical application, thereby enabling others skilled in the art to understand the various embodiments of the invention and various modifications suitable for particular intended applications.

[0017] As described in the background section, existing ion flotation agents struggle to construct a flotation system with selective recognition capability for cesium ions at the gas-liquid interface in complex aqueous solutions containing competing alkali metal ions such as potassium and sodium ions. This results in low selective extraction efficiency of cesium ions, failing to meet practical application requirements. To address this technical problem, the present invention employs the following inventive concept: in complex aqueous solutions containing a large number of competing alkali metal ions, a gas-liquid interface flotation system with selective recognition capability for cesium ions is constructed through the synergistic compounding of specific natural amphiphilic molecules—alkyl gallic acid esters and lecithin.

[0018] This invention provides a flotation agent for the selective extraction of cesium ions from aqueous solutions containing competing alkali metal ions. The flotation agent comprises alkyl gallate and lecithin, wherein the mass ratio of alkyl gallate to lecithin is 7-13:3-6, and the alkyl carbon chain length of the alkyl gallate is 6-18. The competing alkali metal ions refer to other alkali metal ions such as potassium and sodium ions that coexist with cesium ions in the aqueous solution.

[0019] For flotation agents, the alkyl carbon chain length of the alkyl gallate is further limited to 10-16. This limitation aims to address the following: if the carbon chain is too short, the hydrophobicity is insufficient, making stable anchoring at the gas-liquid interface difficult; if the carbon chain is too long, the steric hindrance of the molecules increases significantly, hindering the formation of a synergistic selective recognition conformation for cesium ions between the alkyl gallate and lecithin at the interfacial layer. By limiting the alkyl carbon chain length to 10-16, an optimal balance between interfacial adsorption capacity and selective recognition accuracy is achieved.

[0020] The mass ratio of alkyl gallate to lecithin is further limited to 8-10:3-5. This limitation aims to prevent the following: if the ratio deviates from this range, an excess of alkyl gallate will cause the gas-liquid interface to become too dense, shielding the zwitterionic head groups of lecithin and weakening its charge repulsion against competing alkali metal ions; conversely, an excess of lecithin will dilute the phenolic hydroxyl recognition sites provided by the alkyl gallate. By limiting the mass ratio to 8-10:3-5, the synergistic effect of the two is maximized.

[0021] The active ingredients of the flotation agent are further limited to alkyl gallate and lecithin. This limitation is intended to prevent the introduction of a third component (such as additional surfactants, auxiliaries, or inorganic salts) from disrupting the self-assembly and coordinated arrangement of the two natural amphiphilic molecules at the gas-liquid interface, leading to a decrease in the purity and recognition specificity of the selective recognition layer. By limiting it to a binary complex system, the molecular basis for the selective recognition of cesium ions is ensured to be free from interference by external components.

[0022] The flotation agent further comprises an alcohol solvent, wherein the alcohol solvent is ethanol and / or methanol, and the mass fraction of the alcohol solvent in the flotation agent is 40%-90%. This configuration aims to prevent the solid compound from agglomerating or dispersing unevenly when directly added to the aqueous phase, resulting in excessively high or low local concentrations and an inability to form a uniform selective adsorption layer on the bubble surface. By using an alcohol solution of a specific concentration as a dispersion carrier, it is ensured that the amphiphilic molecules are in a molecular-level dispersed state before being added to the aqueous phase, thereby rapidly reconstructing a uniform selective recognition system at the gas-liquid interface.

[0023] The present invention also provides a method for selectively extracting cesium ions from an aqueous solution containing competing alkali metal ions. The method comprises: adding a flotation agent to an aqueous solution containing cesium ions and competing alkali metal ions and performing ion flotation, thereby selectively enriching cesium ions in the foam phase at the gas-liquid interface; wherein the flotation agent comprises alkyl gallate and lecithin, the mass ratio of alkyl gallate to lecithin being 7-13:3-6, and the alkyl carbon chain length of the alkyl gallate being 6-18.

[0024] For the flotation method, the pH of the aqueous solution is further limited to 8-12. The purpose of this limitation is that if the pH is too low, the phenolic hydroxyl groups of the gallic acid alkyl ester will not dissociate sufficiently, weakening its electrostatic and coordination interactions with cesium ions; if the pH is too high, the strongly alkaline environment will alter the charge distribution and hydrophilic-lipophilic balance of the zwitterionic head groups of lecithin, disrupting the charge-matched structure of the selective recognition layer that they synergistically construct. By limiting the pH to 8-12, the optimal state of the charge environment and spatial conformation of this recognition layer is maintained.

[0025] The competing alkali metal ions are further defined as including potassium ions and / or sodium ions, and the molar concentration ratio of the competing alkali metal ions to cesium ions is less than or equal to 10:1. This limitation aims to clarify the applicability boundaries of this method under the most stringent scenario of high-rate coexistence of competing ions, thus demonstrating the selectivity robustness of the flotation system under complex system conditions approaching those of real nuclear wastewater and salt lake brine. By limiting the types and upper limits of the competing ions, the effectiveness of the flotation system in a highly competitive environment is verified.

[0026] Before adding the flotation agent, the aqueous solution is further stirred for 30 minutes. This is to prevent uneven distribution of competing alkali metal ions and cesium ions in the solution, creating local concentration gradients. In such cases, the flotation agent is more likely to preferentially form non-selective adsorption in regions rich in non-target ions, leading to a significant decrease in the overall selective extraction accuracy of the flotation process. Pre-stirring and homogenization ensures the necessary conditions for accurate construction of the subsequent selective recognition layer.

[0027] The dosage of the flotation agent is further limited to 2.5-40 mg / L. This limitation aims to address the following: if the dosage is too low, there are insufficient active sites for selective recognition at the gas-liquid interface, leading to a decrease in cesium ion capture rate; if the dosage is too high, excessive surfactant forms non-selective micelles or an overly stable foam phase, causing non-specific mechanical entrainment of competing alkali metal ions, thus reducing selectivity. By limiting the dosage to 2.5-40 mg / L, an optimal balance between high selectivity and high extraction rate is achieved.

[0028] The technical solution and beneficial effects of the present invention will be further illustrated below through specific embodiments and comparative examples.

[0029] Example 1 Alkyl gallate (alkyl carbon chain length of 10) and lecithin are mixed at a mass ratio of 7:3 and placed in a beaker. An ethanol solution with a mass fraction of 40%-90% is added and stirred continuously at room temperature to obtain a flotation agent solution.

[0030] Prepare a cesium-containing aqueous solution with a cesium ion concentration of 2 mmol / L. After stirring for 30 min, transfer the solution to a flotation machine. Adjust the pH of the solution to 7-13, and add the above-mentioned flotation reagent solution to make the flotation reagent dosage 5 mg / L (based on the total mass of alkyl gallate and lecithin). Stir the reagent and solution at a stirring speed of 300-700 rpm for 0.5-2 h. After stirring, aerate and begin skimming the foam. After the foam is completely skimmed off, the remaining solution is the water sample after cesium ion removal. The cesium ion extraction rate was found to be 81.45%.

[0031] Example 2 Alkyl gallate (alkyl carbon chain length of 12) and lecithin are mixed at a mass ratio of 10:5 and placed in a beaker. An ethanol solution with a mass fraction of 40%-90% is added and stirred continuously at room temperature to obtain a flotation agent solution.

[0032] Prepare a cesium-containing aqueous solution with a cesium ion concentration of 2 mmol / L. After stirring for 30 min, transfer the solution to a flotation machine. Adjust the pH of the solution to 7-13, and add the above-mentioned flotation reagent solution to make the flotation reagent dosage 2.5 mg / L. Stir the reagent and solution at a stirring speed of 300-700 rpm for 0.5-2 h. After stirring, aerate and skim off the foam. After skimming off all the foam, the remaining solution is the water sample after cesium ion removal. The cesium ion extraction rate was found to be 82.14%.

[0033] Example 3 Alkyl gallate (alkyl carbon chain length of 6) and lecithin were mixed at a mass ratio of 13:3 and placed in a beaker. An ethanol solution with a mass fraction of 40%-90% was added and stirred continuously at room temperature to obtain a flotation agent solution.

[0034] Prepare a cesium-containing aqueous solution with a cesium ion concentration of 2 mmol / L. After stirring for 30 min, transfer the solution to a flotation machine. Adjust the pH of the solution to 7-13, and add the above-mentioned flotation reagent solution to make the flotation reagent concentration 80 mg / L. Stir the reagent and solution at a stirring speed of 300-700 rpm for 0.5-2 h. After stirring, aerate and skim off the foam. After skimming off all the foam, the remaining solution is the water sample after cesium ion removal. The cesium ion extraction rate was found to be 84.52%.

[0035] Example 4 Alkyl gallate (alkyl carbon chain length of 18) and lecithin were mixed at a mass ratio of 8:3 and placed in a beaker. An ethanol solution with a mass fraction of 40%-90% was added and stirred continuously at room temperature to obtain a flotation agent solution.

[0036] Prepare a cesium-containing aqueous solution with a cesium ion concentration of 2 mmol / L. After stirring for 30 min, transfer the solution to a flotation machine. Adjust the pH of the solution to 7-13, and add the aforementioned flotation reagent solution to achieve a flotation reagent concentration of 80 mg / L. Stir the reagent and solution at a stirring speed of 300-700 rpm for 0.5-2 h. After stirring, aerate and skim off the foam. Once the foam is completely skimmed off, the remaining solution is the water sample after cesium ion removal. The cesium ion extraction rate was measured to be 85.46%.

[0037] Example 5 Alkyl gallate (alkyl carbon chain length of 16) and lecithin were mixed at a mass ratio of 8:3 and placed in a beaker. An ethanol solution with a mass fraction of 40%-90% was added and stirred continuously at room temperature to obtain a flotation agent solution.

[0038] Prepare a mixed aqueous solution with cesium and potassium ion concentrations of 2 mmol / L. After stirring for 30 min, transfer the solution to a flotation machine. Adjust the pH of the solution to 7-13, and add the aforementioned flotation reagent solution to a concentration of 80 mg / L. Stir the reagent and solution at a speed of 300-700 rpm for 0.5-2 h. After stirring, aerate and skim off the foam. Once the foam is removed, the remaining solution is the water sample after cesium ion removal. The cesium ion extraction rate was found to be 80.21%.

[0039] Example 6 Alkyl gallate (alkyl carbon chain length of 16) and lecithin were mixed at a mass ratio of 8:3 and placed in a beaker. An ethanol solution with a mass fraction of 40%-90% was added and stirred continuously at room temperature to obtain a flotation agent solution.

[0040] Prepare a mixed aqueous solution with cesium and sodium ion concentrations of 2 mmol / L. After stirring for 30 min, transfer the solution to a flotation machine. Adjust the pH of the solution to 7-13, and add the aforementioned flotation reagent solution to a concentration of 80 mg / L. Stir the reagent and solution at 300-700 rpm for 0.5-2 h. After stirring, aerate and skim off the foam. Once the foam is removed, the remaining solution is the water sample after cesium ion removal. The cesium ion extraction rate was found to be 81.36%.

[0041] Comparative Example 1 Alkyl gallate (alkyl carbon chain length of 16) was used as a flotation agent alone, i.e., the mass ratio of alkyl gallate to lecithin was 1:0. It was placed in a beaker, and an ethanol solution with a mass fraction of 40%-90% was added. The mixture was stirred continuously at room temperature to obtain the flotation agent solution.

[0042] Prepare a mixed aqueous solution with cesium and potassium ion concentrations of 2 mmol / L. After stirring for 30 min, transfer the solution to a flotation machine. Adjust the pH of the solution to 7-13, and add the aforementioned flotation reagent solution to a concentration of 80 mg / L. Stir the reagent and solution at 300-700 rpm for 0.5-2 h. After stirring, aerate and skim off the foam. Once the foam is removed, the remaining solution is the water sample after cesium ion removal. The cesium ion extraction rate was found to be 60.21%.

[0043] Comparative Example 2 Lecithin was used alone as a flotation agent, with a mass ratio of alkyl gallate to lecithin of 0:1. It was placed in a beaker, and an ethanol solution with a mass fraction of 40%-90% was added. The mixture was stirred continuously at room temperature to obtain a flotation agent solution.

[0044] Prepare a mixed aqueous solution with cesium and potassium ion concentrations of 2 mmol / L. After stirring for 30 min, transfer the solution to a flotation machine. Adjust the pH of the solution to 7-13, and add the aforementioned flotation reagent solution to a concentration of 80 mg / L. Stir the reagent and solution at a stirring speed of 300-700 rpm for 0.5-2 h. After stirring, aerate and skim off the foam. Once the foam is removed, the remaining solution is the water sample after cesium ion removal. The cesium ion extraction rate was found to be 26.56%.

[0045] As can be seen from the above examples and comparative examples, the extraction rate of cesium ions by combining alkyl gallate and lecithin in a specific ratio is significantly higher than that when either component is used alone, indicating a significant synergistic effect between the two. Furthermore, in mixed solutions containing competing alkali metal ions such as potassium and sodium ions, the flotation agent of this invention still maintains a high extraction rate for cesium ions, demonstrating good selectivity.

[0046] In summary, this invention constructs a flotation system with selective recognition capability for cesium ions by compounding alkyl gallate and lecithin in a specific mass ratio and limiting the alkyl carbon chain length of the alkyl gallate. This is achieved through the synergistic self-assembly of the two natural amphiphilic molecules at the gas-liquid interface. In complex aqueous solutions containing a large number of competing alkali metal ions, this compound system can form a stable selective adsorption layer at the gas-liquid interface. Through the synergistic effect of the phenolic hydroxyl recognition site of the alkyl gallate and the zwitterionic head group of lecithin, highly efficient selective capture and enrichment of cesium ions are achieved, resulting in the selective enrichment of cesium ions in the foam phase. Compared with existing technologies, this invention eliminates the need for precipitants or adsorbents and additional coating steps, simplifying the process. Furthermore, it achieves effective selective enrichment of cesium ions in mixed systems containing competing alkali metal ions, with an extraction rate exceeding 80%, significantly improving the selective extraction efficiency of cesium ions and reducing extraction costs.

[0047] The optional embodiments of the present invention have been described in detail above. However, the embodiments of the present invention are not limited to the specific details in the above embodiments. Within the scope of the technical concept of the embodiments of the present invention, various simple modifications can be made to the technical solutions of the embodiments of the present invention, and these simple modifications all fall within the protection scope of the embodiments of the present invention.

Claims

1. A flotation agent for selectively extracting cesium ions from an aqueous solution containing competing alkali metal ions, characterized in that, It contains alkyl gallate and lecithin, wherein the mass ratio of alkyl gallate to lecithin is 7-13:3-6, and the alkyl carbon chain length of the alkyl gallate is 6-18.

2. The flotation agent according to claim 1, characterized in that, The alkyl carbon chain length of the gallic acid alkyl ester is 10-16.

3. The flotation agent according to claim 1, characterized in that, The mass ratio of the alkyl gallate to lecithin is 8-10:3-5.

4. The flotation agent according to claim 1, characterized in that, The active ingredients of the flotation agent are alkyl gallate and lecithin.

5. The flotation agent according to claim 1, characterized in that, The flotation agent further comprises an alcohol solvent, wherein the alcohol solvent is ethanol and / or methanol, and the mass fraction of the alcohol solvent in the flotation agent is 40%-90%.

6. A method for selectively extracting cesium ions from an aqueous solution containing competing alkali metal ions, characterized in that, The method includes: adding a flotation agent to an aqueous solution containing cesium ions and competing alkali metal ions and performing ion flotation, so that cesium ions are selectively enriched in the foam phase at the gas-liquid interface; the flotation agent comprises alkyl gallate and lecithin, wherein the mass ratio of alkyl gallate to lecithin is 7-13:3-6, and the alkyl carbon chain length of the alkyl gallate is 6-18.

7. The method according to claim 6, characterized in that, The pH of the aqueous solution is 8-12.

8. The method according to claim 6, characterized in that, The competing alkali metal ions include potassium ions and / or sodium ions, and the molar ratio of the competing alkali metal ions to cesium ions is less than or equal to 10:

1.

9. The method according to claim 6, characterized in that, The aqueous solution was stirred for 30 minutes before the flotation agent was added.

10. The method according to claim 6, characterized in that, The amount of the flotation agent used is 2.5-40 mg / L.