A synergistic reagent system for separating rubidium, cesium and lithium from mica and its application

Abstract

This invention discloses a synergistic reagent system for neutral flotation separation of rubidium and cesium lepidolite and its application. The reagent system comprises 20-50 mg / L tetradecyl dimethyl glycidyl chloride collector and 600-1200 mg / L sodium hexametaphosphate. Within a pulp pH range of 6-8, it achieves highly efficient and selective separation of rubidium and cesium-containing lepidolite from quartz and potassium feldspar, yielding a lepidolite concentrate with a Li₂O grade of 3.87% and a recovery rate of 88.32%. Simultaneously, the recovery rates of Rb₂O and Cs₂O also reach over 86%, achieving synergistic enrichment of lithium, rubidium, and cesium in lepidolite. This avoids the corrosion of equipment and wastewater treatment problems associated with traditional strongly acidic flotation processes such as dodecylamine. Furthermore, the tetradecyl dimethyl glycidyl chloride synthesis raw materials are widely available, the process is simple, the product has good water solubility, and the foaming amount is moderate, demonstrating good industrial application prospects and economic benefits, and thus possessing significant value for widespread application.

Description

Technical Field

[0002] This invention relates to mineral processing flotation technology, and more particularly to a synergistic reagent system for neutral flotation separation of rubidium-cesium-lithium mica and its application in the flotation of rubidium-cesium-lithium mica ore. Background Technology

[0003] Lithium, rubidium, and cesium are all important strategic rare metals with wide and irreplaceable applications in high-tech fields such as new energy, optoelectronic displays, aerospace, and catalysis. my country is rich in rubidium- and cesium-bearing lepidolite resources, which are important raw materials for the synergistic recovery of lithium, rubidium, and cesium. However, lepidolite is closely associated with silicate gangue minerals such as quartz and potassium feldspar, and their surface physicochemical properties are similar, making flotation separation a persistent technical challenge in the mineral processing field.

[0004] Currently, the industrial flotation of lepidolite mainly uses cationic amine collectors such as dodecylamine under strongly acidic conditions. This process has several prominent problems: First, the strongly acidic pulp severely corrodes the flotation equipment, resulting in high maintenance costs; second, it requires large amounts of acid, placing a heavy burden on wastewater treatment and creating significant environmental pressure; third, conventional amine collectors lack selectivity, often resulting in gangue mineral inclusions in the concentrate, affecting product grade. More critically, when the pulp pH rises to neutral or near-neutral, the collecting capacity of existing amine collectors decreases significantly, leading to a substantial reduction in lithium recovery. Simultaneously, rubidium and cesium, present in the lepidolite lattice, are lost along with the gangue minerals, making it difficult to achieve synergistic recovery of lithium, rubidium, and cesium.

[0005] This invention addresses the aforementioned technical problems by providing a method for preparing tetradecyl dimethyl glycidyl chloride (TEDAC) collector and its application in the synergistic flotation of rubidium-cesium-bearing lepidolite with sodium hexametaphosphate under neutral conditions (pH=6-8). TEDAC possesses a suitable carbon chain length and optimized molecular structure, exhibiting excellent selective collection ability for rubidium-cesium-bearing lepidolite under neutral pH conditions, while showing weaker collection ability for gangue minerals such as quartz and potassium feldspar. Combined with sodium hexametaphosphate inhibitors to selectively inhibit gangue minerals, efficient simultaneous enrichment of lithium, rubidium, and cesium can be achieved under neutral conditions, significantly reducing equipment corrosion and wastewater treatment costs, providing a novel technical solution for the green, efficient, and comprehensive recovery of rubidium-cesium-bearing lepidolite resources. Summary of the Invention

[0006] The purpose of this invention is to address the problems of poor selectivity, the need for strong acidic media leading to equipment corrosion and high wastewater treatment costs, and the difficulty in simultaneously and efficiently enriching associated rubidium and cesium in the flotation of lepidolite-potassium feldspar-quartz type lepidolite ores. This invention provides a tetradecyl quaternary ammonium salt collector containing glycidylene oxide and its application in the flotation of rubidium and cesium-containing lepidolite ores under neutral conditions (pH=6-8). The collector TEDAC provided by this invention, used synergistically with sodium hexametaphosphate under neutral conditions, can selectively float rubidium and cesium-containing lepidolite, while exhibiting weak collecting ability for gangue minerals such as quartz and potassium feldspar. This achieves efficient separation of lepidolite and gangue minerals, significantly improving the concentrate quality and recovery rate of rubidium and cesium-containing lepidolite, and simultaneously enriching rubidium and cesium, solving the problem of difficult co-recovery of lithium, rubidium, and cesium. It can also be used for the flotation collection of other rubidium and cesium-containing or similar silicate gangue lepidolite ores.

[0007] This invention provides a reagent system for neutral flotation separation of rubidium, cesium, and lithium mica, comprising tetradecyl dimethyl glycidyl chloride collector and sodium hexametaphosphate.

[0008] Preferably, the amount of sodium hexametaphosphate is 600-1200 mg / L, and the amount of tetradecyl dimethyl glycidyl chloride collector is 20-50 mg / L.

[0009] Preferably, the structural formula of the tetradecyl dimethyl glycidyl ammonium chloride collector is: .

[0010] Preferably, the preparation method of the tetradecyl dimethyl glycidyl ammonium chloride collector includes the following steps: Using epichlorohydrin as both reactant and solvent, N,N-dimethyltetradecyl tertiary amine and epichlorohydrin were mixed at a molar ratio of 1:1.3-4.0 and heated to react. After the reaction was completed, unreacted epichlorohydrin was removed by vacuum distillation, and the mixture was recrystallized, washed, and dried under vacuum to obtain tetradecyldimethylepoxypropylammonium chloride.

[0011] Preferably, the stirring speed is 200-600 rpm, the heating temperature is 50-80℃, and the reaction time is 4-8h.

[0012] Preferably, the conditions for vacuum distillation are: vacuum degree 0.08~0.095MPa, temperature 40~80℃.

[0013] Preferably, the recrystallization is carried out using a mixed solution of ethanol and ethyl acetate in a mass ratio of 5-8:1. Preferably, the washing is performed using ethyl acetate 2-3 times.

[0014] Preferably, the vacuum drying temperature is 30-60℃ and the drying time is 36-72h.

[0015] Furthermore, the present invention also provides a reagent system for neutral flotation separation of rubidium and cesium lepidolite in the flotation of rubidium and cesium lepidolite ore. This reagent system can efficiently recover lepidolite during the flotation process of rubidium and cesium lepidolite ore, while having selective collection capabilities for potassium feldspar and quartz, thereby achieving synergistic enrichment of lithium, rubidium, and cesium.

[0016] The present invention also provides a flotation method for rubidium-cesium lepidolite ore, comprising the following steps: grinding lepidolite, potassium feldspar, and quartz ore, feeding them into a flotation machine and stirring and adjusting the slurry for 2-5 minutes, adjusting the pH of the slurry to 6-8 with a pH adjuster and stirring for 1-5 minutes, adding sodium hexametaphosphate and continuing to stir for 2-5 minutes, finally adding the collector TEDAC and stirring for 2-5 minutes, and then aerating and skimming.

[0017] Preferably, the particle size of the lepidolite ore, potassium feldspar, and quartz ore is 38-74 μm.

[0018] Preferably, the pH adjuster comprises hydrochloric acid and sodium hydroxide.

[0019] Preferably, the amount of sodium hexametaphosphate is 600-1200 mg / L, and the amount of tetradecyl dimethyl glycidyl chloride collector is 20-50 mg / L.

[0020] The synergistic reagent system for neutral flotation separation of rubidium-cesium lepidolite disclosed in this invention has the following innovative features and technical effects compared with conventional lepidolite collectors such as dodecylamine: (1) The TEDAC collector provided by this invention, when used in conjunction with sodium hexametaphosphate under neutral conditions (pH=6-8), can achieve highly efficient and selective separation of rubidium- and cesium-containing lepidolite from quartz and potassium feldspar. When the dosage of TEDAC is 40 mg / L and the dosage of sodium hexametaphosphate is 1000 mg / L, the Li2O grade in the flotation concentrate of the artificial mixed ore (lepidolite:potassium feldspar:quartz = 1:1:1) reaches 3.87%, with a recovery rate of 88.32%; at the same time, associated rubidium and cesium are efficiently and simultaneously enriched, with Rb2O grade of 0.87% and recovery rate of 86.38%, and Cs2O grade of 0.15% and recovery rate of 86.73%. In contrast, the traditional dodecylamine significantly reduces its ability to collect lepidolite under neutral conditions, with a lithium recovery rate of less than 60%. This indicates that TEDAC has excellent selective collecting ability in a neutral synergistic system and can achieve synergistic enrichment of lithium, rubidium, and cesium.

[0021] (2) This invention avoids the corrosion of equipment and wastewater treatment problems caused by strong acid flotation process. Conventional amine collectors need to be in strong acid (pH=2~3) conditions to obtain good indicators, while TEDAC of this invention can achieve efficient separation under neutral conditions. The reagent is less corrosive, the operating environment is friendly, and the wastewater treatment is simple, which significantly reduces production costs and environmental pressure.

[0022] (3) TEDAC collector has excellent water solubility and can be directly prepared into working solutions of any concentration with water, making it convenient to use. In contrast, traditional amine collectors such as dodecylamine have poor water solubility, require acid to dissolve, and are prone to precipitation and significant decrease in solubility at low temperatures, which seriously affects the flotation effect and industrial production stability. TEDAC's excellent solubility effectively avoids the above problems, improving the convenience of reagent use and the reliability of the process.

[0023] (4) Compared with traditional amine collectors, TEDAC has a wide range of raw material sources, a simple synthesis process, good water solubility of the product, and moderate foaming amount. In addition, it is more environmentally friendly during use. In particular, the neutral synergistic flotation system avoids the corrosion of equipment and wastewater treatment problems caused by strong acid conditions, and has good industrial application prospects and economic benefits.

[0024] (5) This invention has broad applicability to rubidium-cesium-bearing lepidolite deposits. Artificial mixed ore tests show that, under the typical ratio of lepidolite:potassium feldspar:quartz = 1:1:1, the co-flotation of TEDAC and sodium hexametaphosphate can yield high-grade, high-recovery mixed lithium, rubidium, and cesium concentrates, providing a new technical approach for the efficient, green, and comprehensive utilization of rubidium-cesium-bearing lepidolite resources. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 The infrared spectrum of tetradecyl dimethyl glycidyl ammonium chloride prepared in Example 1 of this invention.

[0027] Figure 2 The nuclear magnetic resonance spectrum of tetradecyldimethylepoxypropylammonium chloride prepared in Example 1 of this invention.

[0028] Figure 3 This is the mass spectrum of tetradecyldimethylepoxypropylammonium chloride prepared in Example 1 of the present invention.

[0029] Figure 4The above are flowcharts of single mineral flotation provided in Embodiments 2 and 3 of the present invention. Detailed Implementation

[0030] The present invention will be further described below with reference to embodiments, but is not limited to the limitations of the embodiments.

[0031] The lepidolite, potassium feldspar, and quartz minerals manually selected from the mine were washed with distilled water and air-dried. They were then ground finely using a ceramic ball mill, and the conventional particle size of -74 to +38 μm was sieved and dried at low temperature in an oven for use in the flotation test study of the example.

[0032] Example 1 Preparation of tetradecyl dimethyl glycidyl ammonium chloride: 24.15 parts of N,N-dimethyltetradecyl tertiary amine were placed in a three-necked flask, and then 13.89 parts of epichlorohydrin were slowly added dropwise over a period of 1 h at a temperature of 25 °C. After the addition was complete, the system was heated to 50 °C and the reaction was continued for 4.5 h. After the reaction was completed, the crude product was distilled under reduced pressure and recrystallized from the crude product with a mixture of ethanol and ethyl acetate. The recrystallized product was washed with ethyl acetate and then dried under vacuum at 35 °C for 48 h to obtain a white powder. The purified product was characterized by infrared spectroscopy; the infrared spectrum is shown below. Figure 1 Infrared spectral analysis is shown in Table 1; 1H NMR spectrum is shown in Table 1. Figure 2 Mass spectrometry (see) Figure 3 .

[0033] Table 1. Infrared spectral analysis of tetradecyl dimethyl epioxypropyl ammonium chloride ; according to Figure 1 As shown in the infrared spectral analysis in Table 1, the infrared spectral characterization results are highly consistent with the structure of the target product, tetradecyldimethylepoxypropylammonium chloride. (965 cm⁻¹) -1 CN at the location + The stretching vibration absorption peak indicates that the tertiary amine nitrogen atom has been successfully converted into quaternary ammonium nitrogen, forming the characteristic structure of a quaternized cationic surfactant; while the 904 cm⁻¹ peak indicates that the tertiary amine nitrogen atom has been successfully converted into quaternary ammonium nitrogen, forming the characteristic structure of a quaternized cationic surfactant; -1 The characteristic vibrational peaks of the epoxy ring at 2921 cm⁻¹ confirm that while the chlorine atom in epichlorohydrin participates in the quaternization reaction, its three-membered epoxy ring does not undergo ring-opening, and the reactive sites of the glycidyl side chain are fully preserved in the molecule. The presence of the long-chain alkyl skeleton is indicated by the peak at 2921 cm⁻¹. -1 2853cm -1 1471 cm -1 1371 cm -1 and 721 cm -1The combined peaks of CH stretching and deformation vibrations at that location further corroborate this. Additionally, at 1225 cm⁻¹... -1 The COC stretching vibration at the position further confirmed the existence of the ether oxygen structure, corresponding to the COC bond in the epoxypropyl group. In summary, this product integrates a tetradecyl hydrophobic chain, a quaternary ammonium cationic hydrophilic group, and an epoxypropyl reactive group, which is highly consistent with the structure of the target product tetradecyldimethylepoxypropylammonium chloride, and the product structure is well defined.

[0034] according to Figure 2 of 1 The 1H NMR spectrum shows that the chemical shifts and integral values ​​of each proton signal precisely correspond to the target molecule structure: δ 0.88 ppm (3H) corresponds to the terminal methyl group, δ 1.26 ppm (22H) corresponds to the tetradecyl long-chain methylene group, and δ 1.62 ppm (2H) and δ 3.35–3.50 ppm (13H) belong to the methylene group adjacent to the quaternary ammonium nitrogen, respectively. N+- Dimethyl and glycidyl hydrogen. No tertiary amine nitrogen methyl signal (δ 2.2–2.3 ppm) or hydroxyl signal after epoxy ring opening was observed in the spectrum, indicating that the tertiary amine has been completely converted into a quaternary ammonium salt, and the three-membered epoxy ring did not undergo ring opening while the chlorine atom of epichlorohydrin participated in the quaternization reaction, thus the product structure is clear.

[0035] according to Figure 3 ESI-MS mass spectrometry further confirmed the product structure at the molecular weight level: the base peak at m / z 298.31 corresponds to the quaternary ammonium cation. [M-Cl]+ The molecular weight is highly consistent with the theoretical molecular weight, confirming the molecular composition of tetradecyldimethylepoxypropylammonium chloride. m / z 316.32 and m / z 631.59 are the water addition peak and dimer ion peak, respectively, consistent with the mass spectrometric behavior of surfactants. No other molecular weight series impurity peaks were observed in the mass spectrum, and the absence of unassigned hydrogen signals in the NMR indicates high product purity.

[0036] Comprehensive infrared spectroscopy, 1 The triple spectral analysis results of H NMR and ESI-MS confirmed the successful preparation of tetradecyl dimethyl glycidyl ammonium chloride containing a tetradecyl hydrophobic chain, a quaternary ammonium cationic hydrophilic group, and a glycidyl reactive group, with complete quaternization and intact epoxy ring retention.

[0037] Example 2 Single-mineral flotation tests were conducted using an XFG-II5 hanging-tank flotation machine at room temperature (25℃). The main shaft speed of the flotation machine was fixed at 1992 r / min. The specific test procedure is as follows: Figure 4As shown in the figure. First, 2g of pure mineral was added to the flotation cell, followed by 30ml of distilled water and stirring for 2 minutes to adjust the slurry pH. The pH of the slurry was then adjusted to 7 with HCl or NaOH, followed by the addition of the collector and stirring for 2 minutes, and then skimming for 3 minutes. After the flotation test, the froth product was filtered, dried, weighed, analyzed, and the recovery rate was calculated. The collecting effects of tetradecyl dimethyl glycidyl ammonium chloride and dodecylamine on lepidolite, potassium feldspar, and quartz are shown in Tables 2 and 3, respectively.

[0038] Table 2. Flotation test results of tetradecyldimethylepoxypropylammonium chloride ; Table 3. Flotation test results of dodecylamine ; Table 2-3 shows that under neutral (pH=7) slurry conditions, within a collector concentration gradient of 20-50 mg / L, tetradecyl dimethyl glycidyl chloride exhibits significantly better collecting ability for lepidolite than dodecylamine. However, both reagents show high recoveries of 94%-97% for potassium feldspar and quartz, indicating unsatisfactory selective separation. Effective separation requires the use of depressants.

[0039] Compared to dodecylamine, tetradecyl dimethyl glycidyl ammonium chloride, as a quaternary ammonium salt-type cationic collector, has a stronger hydrophobic tail of its long C14 chain than that of dodecylamine's C12 chain. The dimethyl quaternary ammonium head group has a higher positive charge density, which is conducive to electrostatic adsorption with the negative potential of the lepidolite layered silicate surface. The glycidyl side chain in the molecule can form hydrogen bonds or coordination with the lepidolite surface, providing a chemical adsorption auxiliary mechanism, thereby enhancing the adsorption strength and bubble mineralization efficiency at low concentrations.

[0040] Example 3: The flotation test of the floating minerals was conducted using an XFG-II5 hanging tank flotation machine at room temperature (25℃). The spindle speed of the flotation machine was fixed at 1992 r / min. The specific test procedure is as follows: Figure 4 As shown in Table 4, 2g of pure mineral was first added to the flotation cell, followed by 30ml of distilled water and stirring for 2 minutes. The pH of the pulp was adjusted to 7 with HCl or NaOH. Then, 1000mg / L of sodium hexametaphosphate inhibitor was added and stirred for 2 minutes, followed by 40mg / L of TEDAC collector and stirring for 2 minutes. The froth was then skimmed for 3 minutes. After the flotation test, the froth product was filtered, dried, weighed, analyzed, and the recovery rate was calculated. The test results are shown in Table 4.

[0041] Table 4. Flotation test results of TEDAC on ternary mixed minerals of lepidolite-potassium feldspar-quartz. ; Under neutral (pH=7) pulp conditions, based on the flotation test results of TEDAC on a ternary mixture of lepidolite-potassium feldspar-quartz, it can be concluded that: Combining sodium hexametaphosphate as a depressant for gangue such as quartz, TEDAC exhibits excellent separation performance in ternary mixed ores of lepidolite-potassium feldspar-quartz under neutral conditions (pH=7): at a concentrate yield of 43.48%, a lepidolite concentrate with a Li₂O grade of 3.87% and a recovery rate of 88.32% was obtained, while the recovery rates of Rb₂O and Cs₂O also reached over 86%, achieving synergistic enrichment of valuable elements in lepidolite. This process avoids the need to adjust the strong acid environment when using dodecylamines and has significant potential for industrial application. Further optimization should focus on two stages: fine-grained upgrading and scavenging loss reduction, to further improve the concentrate grade and total recovery rate, bringing it up to industrial production standards. A reagent system for neutral flotation separation of rubidium-cesium lepidolite is also described.

[0042] The above experimental results fully demonstrate that the reagent system for neutral flotation separation of rubidium and cesium-containing lepidolite prepared in this invention has significant advantages: First, the reagent system has a significant synergistic recovery effect on associated rubidium and cesium, with the recovery rate of the three valuable elements simultaneously reaching over 86%, which is conducive to the comprehensive development and utilization of resources; Second, it can be directionally adsorbed onto the surface of lepidolite in a neutral medium of pH=7 by electrostatics and hydrogen bonding, avoiding the strong acid environment required for conventional lepidolite flotation such as dodecylamine, and has good compatibility with the neutral slurry system in industrial settings. It also exhibits strong repulsion ability against gangue minerals such as potassium feldspar and quartz, combining excellent selectivity and environmental friendliness, and has promotional application value.

[0043] It should be clarified that the above embodiments are only used to illustrate specific implementations of the present invention and do not constitute a limitation on the scope of protection of the present invention. Based on the technical content disclosed in the present invention, those skilled in the art can make various modifications, adjustments or equivalent substitutions within its basic principles and design concepts; although these modifications and improvements do not need to be listed one by one, they should all fall within the scope of protection of the present invention.

Claims

1. A reagent system for the separation of rubidium, cesium and lithium mica by neutral flotation, characterized in that, Including tetradecyl dimethyl glycidyl ammonium chloride collector and sodium hexametaphosphate; The structural formula of the tetradecyldimethylepoxypropylammonium chloride collector is: 。 2. The reagent system for neutral flotation separation of rubidium, cesium, and lithium mica as described in claim 1, characterized in that, The dosage of sodium hexametaphosphate is 600-1200 mg / L, and the dosage of tetradecyl dimethyl glycidyl chloride collector is 20-50 mg / L.

3. The reagent system for neutral flotation separation of rubidium, cesium, and lithium mica as described in claim 1, characterized in that, The preparation method of the tetradecyl dimethyl glycidyl ammonium chloride collector includes the following steps: Using epichlorohydrin as both reactant and solvent, N,N-dimethyltetradecyl tertiary amine and epichlorohydrin were mixed at a molar ratio of 1:1.3-4.0 and heated to react. After the reaction was completed, unreacted epichlorohydrin was removed by vacuum distillation, and the mixture was recrystallized, washed, and dried under vacuum to obtain tetradecyldimethylepoxypropylammonium chloride.

4. The reagent system for neutral flotation separation of rubidium, cesium, and lithium mica as described in claim 3, characterized in that, The stirring speed is 200-600 rpm, the heating temperature is 50-80℃, and the reaction time is 4-8h.

5. The reagent system for neutral flotation separation of rubidium, cesium, and lithium mica as described in claim 3, characterized in that, The conditions for vacuum distillation are: vacuum degree 0.08~0.095MPa, temperature 40~80℃.

6. The reagent system for neutral flotation separation of rubidium, cesium, and lithium mica as described in any one of claims 3-5, characterized in that, The recrystallization is carried out using a mixed solution of ethanol and ethyl acetate in a mass ratio of 5-8:1; and / or, the washing is performed using ethyl acetate 2-3 times.

7. The reagent system for neutral flotation separation of rubidium, cesium, and lithium mica as described in any one of claims 3-5, characterized in that, The vacuum drying temperature is 30-60℃, and the drying time is 36-72h.

8. The application of the reagent system for neutral flotation separation of rubidium-cesium-lithium mica as described in any one of claims 1-7 in the flotation of rubidium-cesium-lithium mica ore, characterized in that, The reagent system efficiently recovers lepidolite in the flotation of rubidium-cesium-bearing lepidolite ore, while also selectively collecting potassium feldspar and quartz, achieving synergistic enrichment of lithium, rubidium, and cesium.

9. A flotation method for rubidium-cesium-lithium mica ore, characterized in that, Includes the following steps: The lepidolite, potassium feldspar, and quartz ore are ground and fed into the flotation machine and stirred for 2-5 minutes. The pH of the slurry is adjusted to 6-8 with a pH adjuster and stirred for 1-5 minutes. Sodium hexametaphosphate is then added and stirred for another 2-5 minutes. Finally, tetradecyl dimethyl glycidyl ammonium chloride collector is added and stirred for 2-5 minutes, followed by aeration and foam removal.

10. The flotation method for rubidium-cesium-lithium mica ore as described in claim 9, characterized in that, The lepidolite ore, potassium feldspar, and quartz ore are ground to a particle size of 38-74 μm; and / or, the pH adjuster includes hydrochloric acid and sodium hydroxide; and / or, the amount of sodium hexametaphosphate is 600-1200 mg / L, and the amount of tetradecyl dimethyl glycidyl chloride collector is 20-50 mg / L.

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