A method for surface pretreatment to promote the full-scale flotation separation of lepidolite and feldspar.

Abstract

This invention discloses a method for promoting the flotation separation of lepidolite and feldspar across the entire particle size range through surface pretreatment. The method involves adding an alkaline solution to a slurry of lepidolite ore and gangue minerals, followed by alkaline etching under the combined action of mechanical stirring and ultrasound to obtain a surface-pretreated mineral sample. After adjusting the slurry pH to neutral, a metal ion activator and an anionic collector are added to the pretreated mineral sample for flotation, yielding lepidolite concentrate and tailings. This invention targets the flotation of lepidolite across the entire particle size range, including conventional flotation sizes of -74μm and +38μm, as well as the fine-grained size of -38μm. It effectively achieves the flotation separation of lepidolite and gangue minerals, reduces collector costs, minimizes the loss of fine-grained lepidolite, and ultimately yields a high-grade lepidolite concentrate. This invention features an innovative process flow, extremely low reagent usage, and high economic efficiency, making it significant for the separation and recovery of lepidolite and gangue minerals.

Description

Technical Field

[0001] This invention belongs to the field of mineral processing technology and relates to a method for surface pretreatment to promote the flotation separation of lepidolite and feldspar across all particle sizes. In particular, it relates to a method for surface pretreatment that utilizes the synergistic effects of alkaline solution, mechanical stirring, and ultrasonic waves to promote the flotation separation of lepidolite and feldspar across all particle sizes. Background Technology

[0002] Lithium is considered a metal of significant strategic importance globally. With increasing emphasis on environmental protection, there is an urgent need to improve lithium extraction technology to achieve clean and comprehensive resource utilization. Currently, lithium is mainly extracted from salt lake brines and hard-rock lithium deposits. Although lithium extraction technology from salt lake brines in China has developed rapidly in recent years, lithium salt production remains primarily based on ore extraction due to resource and technological limitations. Lepidolite is the main source of hard-rock lithium deposits, with the chemical formula K{Li}. 2-x Al 1+x [Al 2x Si 4-2x O 10 Feldspar (F,OH)2 is the main aluminosilicate gangue mineral in lepidolite ore. Its crystal structure is also mainly [SiO4] and [AlO6]. This makes its surface properties very similar to lepidolite, which makes it easy to be collected by lepidolite collectors, resulting in difficulties in flotation separation.

[0003] Existing research on the flotation separation of lepidolite and feldspar mainly focuses on the development of collectors and depressants. Currently, lepidolite collectors primarily include cationic and anionic / cationic mixed collectors. Traditional amine cationic collectors require an acidic environment, which can cause severe corrosion to equipment. Currently, lepidolite flotation typically uses anionic / cationic mixed collectors because these collectors are less expensive and suitable for neutral pH values. However, the mechanism of action of this method remains unclear. To improve the floatability difference between lepidolite and gangue silicate minerals, targeted depressants are needed to prevent gangue from entering the lepidolite concentrate. Currently, the main types of depressants are inorganic, organic, and combined depressants.

[0004] Besides collectors and depressants, methods for lepidolite activation are limited, and methods for flotation pretreatment are even fewer. Weathering of lepidolite ore forms primary and secondary slime. Typically, desliming methods are used before flotation to reduce the influence of slime, but this leads to significant loss of fine-grained lepidolite minerals. The O, Si, and Al content on the surface of lepidolite and feldspar directly affects their flotation performance. Effectively addressing these issues during flotation is very challenging. Therefore, a surface pretreatment method is needed to promote the flotation separation of lepidolite and feldspar across the entire particle size range. Summary of the Invention

[0005] In view of the problems of severe loss of fine-grained lepidolite, small difference in floatability, and low flotation index in the existing technology of lepidolite and feldspar flotation separation process, the purpose of this invention is to provide an efficient surface pretreatment method to promote the flotation separation of lepidolite and feldspar across all particle sizes.

[0006] To achieve the above-mentioned technical objectives, the present invention provides a method for surface pretreatment to promote the full-scale flotation separation of lepidolite and feldspar. The method involves adding an alkaline solution to the slurry of lepidolite ore and gangue minerals, and then subjecting the mixture to an alkaline etching reaction under the combined action of mechanical stirring and ultrasound to obtain a surface-pretreated mineral sample. After adjusting the pH of the slurry to neutral, a metal ion activator and an anion collector are added to the surface-pretreated mineral sample for flotation to obtain lepidolite concentrate and tailings.

[0007] The principle of this invention is as follows:

[0008] Weathering of lepidolite ore forms primary and secondary slime. The content of O, Si, and Al on the surface of lepidolite and feldspar directly affects their flotation performance. Effectively addressing these issues during the flotation process is very challenging.

[0009] This invention employs alkaline corrosion pretreatment to utilize the chemical reaction between hydroxide ions in an alkaline solution and oxides and contaminants on the metal surface, thereby removing contaminants, oxide layers, and other undesirable surface features. On mineral surfaces, alkaline corrosion exhibits a certain selectivity; some components on the surface of lepidolite are more easily dissolved, leading to the relative accumulation of the remaining components on the surface, while the dissolution of feldspar is not selective. This results in differences in the surface properties of the two minerals, providing a basis for the separation of the two minerals.

[0010] This invention incorporates mechanical stirring and ultrasonic synergy in the alkaline etching process. Mechanical stirring ensures uniform mixing of lepidolite, feldspar, and the alkaline solution, promotes solution circulation and heat transfer, reduces side reactions, and shortens reaction time. However, mechanical stirring alone is insufficient to etch the surface of fine lepidolite particles. Ultrasonic stimulation generates tiny high-energy bubbles (cavitation), which significantly agitate the liquid during formation and bursting, enhancing mass transfer in the alkaline solution. Furthermore, ultrasonic waves agitate the slurry at the microscopic level, breaking down or weakening micro-agglomerates, thus ensuring alkaline etching of even fine lepidolite particles. This promotes more uniform distribution of reactants in the solution and accelerates the alkaline etching reaction. Therefore, mechanical stirring accelerates selective alkaline etching of lepidolite surfaces, and the combined effect of ultrasonic waves and mechanical stirring further promotes the alkaline etching process.

[0011] The flotation performance of lepidolite can then be improved by adding appropriate activators, such as metal ions or organic molecules. These activators can chemically react with or adsorb onto the surface of lepidolite, altering its surface properties and making the lepidolite particles more readily interact with bubbles and float. The inventors have experimentally demonstrated that calcium ions have the strongest activating effect on lepidolite, followed by magnesium, copper, and lead ions. However, due to a lack of selectivity, ion activation is rarely used for the flotation of lepidolite and its gangue minerals (feldspar). The surface pretreatment of this invention enhances the surface differences between the two minerals, giving ion activation a certain selectivity on the mineral surface and enabling separation.

[0012] In the flotation process of lepidolite, anionic collectors typically struggle to achieve satisfactory flotation results. This is because lepidolite carries a negative charge on its surface, while anionic collectors usually react chemically or adsorb onto the surfaces of cationic minerals, rather than interacting readily with the lepidolite surface. However, through the combined effects of surface pretreatment and metal ion activation, the surface properties of lepidolite change, allowing anionic collectors to adsorb onto its surface or onto metal ions on its surface. This alters the wettability of the lepidolite surface, enabling its flotation and recovery.

[0013] As a preferred embodiment, the pulp concentration of the lepidolite ore and gangue minerals is 35-70%.

[0014] As a preferred embodiment, the lithium mica ore is of all particle sizes, including conventional flotation particle sizes of -74μm and +38μm, as well as fine particle size flotation of -38μm.

[0015] As a preferred embodiment, the concentration of the alkaline solution is 1000–1500 mg / L.

[0016] As a preferred embodiment, the alkaline solution is an aqueous solution of NaOH and / or KOH.

[0017] As a preferred embodiment, the mechanical stirring speed is 500-800 rpm.

[0018] As a preferred embodiment, the intensity of the ultrasonic wave is 50–80 Hz.

[0019] As a preferred embodiment, the alkaline etching reaction time is 5 to 15 minutes.

[0020] In this invention, the rotational speed of the mechanical agitation and the intensity of the ultrasonic waves jointly affect mass transfer during the alkaline etching process, thereby influencing the grade of lepidolite separated from feldspar in flotation. If the rotational speed of the mechanical agitation or the intensity of the ultrasonic waves is too low, the alkaline etching effect is low, the surface modification of lepidolite is incomplete, and the flotation effect is poor. Within a certain range, increasing the rotational speed of the mechanical agitation and the intensity of the ultrasonic waves will increase the alkaline etching effect, but after reaching a certain value, the flotation indicators reach their limit. Further increases will not only lead to energy and resource waste but also reduce the grade of lepidolite.

[0021] As a preferred embodiment, the metal ion activator is Ca. 2+ and / or Mg 2+ The metal ion activator selected in this invention can selectively react chemically with or adsorb onto the treated lepidolite surface, altering its surface properties and making the lepidolite particles more readily interact with bubbles and float.

[0022] As a preferred embodiment, the anionic collector is a compound of sodium oleate and sodium dodecyl sulfonate in a mass ratio of (1-3):(3-1). The present invention uses sodium oleate and sodium dodecyl sulfonate as a compound anionic collector because sodium oleate has a carbon chain structure, which allows it to form a stable molecular layer at the oil-water interface, resulting in good collection performance. Furthermore, sodium oleate can selectively adsorb onto the surface of droplets or bubbles containing the target component, thereby achieving effective collection of the target component. Compared to other collectors, sodium oleate has lower toxicity and relatively less impact on the environment and human health. In addition, during flotation, sodium oleate causes mineral flocs, which helps in their collection. However, the foam it produces under neutral conditions has poor stability. Sodium dodecyl sulfonate, on the other hand, has a good foaming effect under neutral conditions, and its combination with sodium oleate compensates for the foam-suppressing effect of sodium oleate, further enhancing the flotation performance of the minerals. Furthermore, like sodium oleate, sodium dodecyl sulfonate has a relatively small environmental impact under proper use and treatment conditions. It can rapidly degrade in water and does not accumulate in the environment. At the same time, a better flotation effect can be achieved by rationally adjusting the mass ratio of sodium oleate and sodium dodecyl sulfonate.

[0023] As a preferred embodiment, the concentration of the metal ion activator is: 1.1 × 10⁻⁶ for conventional flotation particle sizes. -5 ~15×10 -4 mol / L; Fine-grained flotation: 2×10 -4 ~5×10 -3 mol / L.

[0024] As a preferred embodiment, the concentration of the anionic collector is: 1×10⁻⁶ for conventional flotation particle sizes. -5 ~8×10 -5 mol / L; Fine-grained flotation: 8×10-5 ~8×10 -4 mol / L.

[0025] This invention provides a method for surface pretreatment to promote the flotation separation of lepidolite and feldspar across the entire particle size, specifically including the following steps:

[0026] 1) Alkali etching: Alkali solution is added to the slurry of lepidolite ore and gangue minerals. After the reaction is fully carried out under the combined action of mechanical stirring and ultrasound, solid-liquid separation is performed to obtain a mineral sample with surface pretreatment.

[0027] 2) Flotation: The product obtained in step 1) is placed in a flotation cell, the pH of the pulp is adjusted to neutral, a metal ion activator is added and stirred thoroughly, and then a combination of anionic collectors is added for flotation to obtain lepidolite concentrate and tailings.

[0028] As a preferred embodiment, the sample needs to be washed multiple times (3 to 5 times) during the solid-liquid separation process.

[0029] As a preferred embodiment, the pulp concentration in the flotation cell is 35-50%.

[0030] As a preferred embodiment, the stirring time after adding the metal ion activator is 2 to 3 minutes.

[0031] As a preferred embodiment, the stirring time after adding the combined anionic collector is 2 to 3 minutes.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1) The alkaline etching pretreatment process in this invention is selective for lepidolite and feldspar, activating the lepidolite surface without affecting the feldspar surface activity; the difference in activation effect of metal ions on the lepidolite and feldspar surfaces is enhanced under the alkaline etching pretreatment; the combined anionic collector, with low dosage and low price, plays a key role in the flotation separation of lepidolite and feldspar. This invention uses a surface pretreatment method combined with metal ion activation, under the action of an anionic collector, to effectively achieve the flotation separation of lepidolite and feldspar.

[0034] 2) This invention enhances the flotation recovery of fine-grained lepidolite minerals. The process is simple, the reagent dosage is low, and the economic benefits are high. It is of great significance for the efficient separation and recovery of lithium resources.

[0035] 3) In the alkaline etching pretreatment process of the present invention, the synergistic effect of alkaline solution, mechanical stirring and ultrasound can greatly improve the recovery rate of lepidolite in the flotation process of lepidolite and feldspar, while ensuring a high grade of lepidolite. Detailed Implementation

[0036] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments. Obviously, the embodiments described below are only a part of the embodiments, and all other embodiments obtained by those skilled in the art without creative effort are still within the scope of protection of the present invention.

[0037] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0038] Example 1

[0039] This embodiment uses an artificially mixed lepidolite and feldspar ore, with a mineral particle size of conventional flotation size (-74μm, +38μm), and a lepidolite to feldspar ore mass ratio of 1:1. The metal ion used in this embodiment is Mg. 2+ The combined collector is composed of sodium oleate and sodium dodecyl sulfonate in a mass ratio of 1:1. The specific steps and formulation are as follows:

[0040] 1) Alkali etching: Add 1500 mg / L NaOH to the slurry of lepidolite and gangue minerals (1.5 g mineral sample, 40 ml water). After reacting for 5 min under the combined action of mechanical stirring at 700 rpm and 60 Hz ultrasound, the solid and liquid are separated. The solid sample is washed 3 times to obtain the mineral sample after surface pretreatment.

[0041] 2) Flotation: Surface-pretreated samples (1.5g per group) are placed in the flotation cell. The flotation pulp concentration is 35%. The pulp pH is adjusted to 8, and 10.5 × 10⁻⁶ g of ore is added. -4 mol / L Mg 2+ After stirring thoroughly for 3 minutes, add 4×10 of the combined anionic collector. -5 After stirring thoroughly for 3 minutes with mol / L solution, a roughing process was performed to obtain lepidolite concentrate and tailings.

[0042] The experimental results are shown in Table 1. It can be seen that the final Li₂O grade in the lepidolite concentrate was 5.84%, with a recovery rate of 90.85%. The Li₂O loss rate in the tailings was only 9.15%.

[0043] Table 1. Experimental Results

[0044] Product Name Yield / % Li2O grade / % Li2O recovery rate / % Concentrate 87.84 5.840 90.85 Tailings 12.16 4.250 9.15 raw ore 100.00 5.647 100.00

[0045] Comparative Example 1

[0046] Using the artificial mixed ore from Example 1 as the raw ore, and employing the same reagent system and flotation process as in Example 1, the influence of pretreatment methods on the flotation indicators of lepidolite was investigated.

[0047] The experimental results are shown in Table 2. It can be seen that under alkaline treatment alone, lepidolite showed no enrichment; under stirring pretreatment + alkaline treatment alone, the Li2O recovery rate of lepidolite concentrate improved, but remained low; under ultrasonic pretreatment + alkaline treatment alone, the Li2O recovery rate of lepidolite concentrate improved, but remained lower than that under the combined effect of ultrasonic and stirring + alkaline treatment. Under the combined pretreatment of ultrasonic and stirring + alkaline treatment, the Li2O grade in the lepidolite concentrate was 5.84%, with a recovery rate of 90.85%.

[0048] Table 2. Experimental results of different pretreatment methods

[0049]

[0050] Under alkaline treatment alone, the surface of lepidolite does not undergo selective dissolution, and cannot expose more active sites. Consequently, it cannot synergistically promote the adsorption of anionic collectors with metal ions, and therefore cannot float in the anionic collector system, resulting in extremely low recovery rate.

[0051] The intensity of both stirring treatment + alkali treatment and ultrasonic treatment + alkali treatment was low, and under the same time, the limit value of pretreatment was not reached, resulting in poor effect.

[0052] The synergistic effect of stirring and ultrasonic treatment combined with alkali treatment enables the minerals to achieve a good alkali etching pretreatment effect in a relatively short time (5 minutes).

[0053] Comparative Example 2

[0054] Using the artificially mixed ore from Example 1 as the raw ore, and employing the same pretreatment method, collector regime, and flotation process as in Example 1, the influence of parameter changes during the pretreatment process on the flotation index of lepidolite was investigated.

[0055] The experimental results are shown in Table 3. As the concentration of alkali solution increases, the flotation recovery rate increases, but remains constant after reaching a certain level. As the rotation speed increases, the flotation recovery rate increases, but remains constant after reaching a certain level. As the ultrasonic intensity increases, the flotation recovery rate increases, but remains constant after reaching a certain level. In other words, as these variables increase, the effect of alkali etching will increase, but after reaching the limit value, the recovery rate will remain constant, but the grade will decrease.

[0056] Table 3. Parameter test results during pretreatment.

[0057]

[0058]

[0059] Comparative Example 3

[0060] Using the artificial mixed ore from Example 1 as the raw ore, and employing the same pretreatment method, collector system, and flotation process as in Example 1, the influence of metal ion species on the flotation index of lepidolite was investigated.

[0061] The experimental results are shown in Table 4. It can be seen that, without the action of metal ions, the recovery rate of Li₂O in lepidolite concentrate is low, and the recovery rate of Mg is also low. 2 + and Ca 2+ Both methods can achieve a Li₂O recovery rate of over 90% in the concentrate, while Fe... 3+ And Al 3+ The activation of lepidolite and gangue mineral feldspar is not selective, resulting in no enrichment of lepidolite.

[0062] Table 4 Results of metal ion type tests

[0063]

[0064]

[0065] Comparative Example 4

[0066] Using the artificial mixed ore from Example 1 as the raw ore, and employing the same pretreatment method, reagent system, and flotation process as in Example 1, the influence of the type of collector on the flotation index of lepidolite was investigated.

[0067] The experimental results are shown in Table 5. It can be seen that when sodium oleate is used alone as the collector, the Li₂O recovery rate in lepidolite concentrate is low, with almost no enrichment. When sodium dodecyl sulfate or sodium dodecyl sulfonate is used alone as the collector, the Li₂O recovery rate in lepidolite concentrate is improved, but still low. When using a combined inhibitor (sodium oleate:sodium dodecyl sulfonate = 1:1), the Li₂O recovery rate in lepidolite concentrate can reach 90.85%.

[0068] Table 5. Test results of different types of collectors

[0069]

[0070]

[0071] Example 2

[0072] This embodiment uses an artificially mixed pure lepidolite and feldspar ore, with a mineral particle size of conventional flotation size (-74μm, +38μm), and a lepidolite to feldspar ore mass ratio of 1:1.5. The metal ion used in this embodiment is Ca. 2+ The combined collector is composed of sodium oleate and sodium dodecyl sulfonate in a mass ratio of 1:2. The specific steps and formulation are as follows:

[0073] 1) Alkali etching: 1300 mg / L NaOH was added to the slurry of lepidolite and gangue minerals (1.5 g mineral sample, 40 ml water). After the mixture was stirred at 800 rpm and subjected to 75 Hz ultrasound for 5 min, the solid and liquid were separated. The solid sample was washed 3 times to obtain the mineral sample after surface pretreatment.

[0074] 2) Flotation: Surface-pretreated samples (1.5g per group) are placed in a flotation cell. The flotation pulp concentration is 35%. The pulp pH is adjusted to 8, and 1.1 × 10⁻⁶ ppm is added. -5 mol / L metal ion Ca 2+ After stirring thoroughly for 3 minutes, add 3.5 × 10⁻⁶ of the combined anionic collector. -5 After stirring thoroughly for 3 minutes with mol / L solution, a roughing process was performed to obtain lepidolite concentrate and tailings.

[0075] The experimental results are shown in Table 6. It can be seen that the final Li₂O grade in the lepidolite concentrate was 5.14%, with a recovery rate of 92.52%. The Li₂O loss rate in the tailings was only 7.48%.

[0076] Table 6. Experimental Results

[0077] Product Name Yield / % <![CDATA[Li2O grade / %]]> <![CDATA[Li2O recovery rate / %]]> Concentrate 88.66 5.140 92.52 Tailings 11.34 3.250 7.48 raw ore 100.00 4.926 100.00

[0078] Example 3

[0079] This embodiment uses an artificially mixed lepidolite and feldspar ore, with a fine-grained particle size (-38μm) and a lepidolite to feldspar ore mass ratio of 1:1. The metal ion used in this embodiment is Mg. 2+ The combined collector is composed of sodium oleate and sodium dodecyl sulfonate in a mass ratio of 1:1. The specific steps and formulation are as follows:

[0080] 1) Alkali etching: Add 1500 mg / L NaOH to the slurry of lepidolite and gangue minerals (1.5 g mineral sample, 40 ml water). After reacting for 5 min under the combined action of mechanical stirring at 700 rpm and 60 Hz ultrasound, the solid and liquid are separated. The solid sample is washed 3 times to obtain the mineral sample after surface pretreatment.

[0081] 2) Flotation: Surface-pretreated samples (1.5g per group) are placed in the flotation cell. The flotation pulp concentration is 35%. The pulp pH is adjusted to 8, and 5×10⁻⁶ mol / L is added. -3 mol / L Mg 2+ After stirring thoroughly for 3 minutes, add 4×10 of the combined anionic collector. -4 After stirring thoroughly for 3 minutes with mol / L solution, a roughing process was performed to obtain lepidolite concentrate and tailings.

[0082] The experimental results are shown in Table 7. It can be seen that the final Li₂O grade in the lepidolite concentrate was 5.75%, with a recovery rate of 80.29%.

[0083] Table 7 Experimental Results

[0084] Product Name Yield / % <![CDATA[Li2O grade / %]]> <![CDATA[Li2O recovery rate / %]]> Concentrate 76.16 5.750 80.29 Tailings 23.84 4.510 19.71 raw ore 100.00 5.454 100.00

[0085] Example 4

[0086] This embodiment uses actual lepidolite mineral from Jiangxi Province, with a Li₂O grade of 0.30%. The main gangue minerals include quartz and feldspar. The main valuable metallic mineral is lepidolite. The main grain size distribution is approximately: +75μm 10%, -74μm to +38μm 50%, and -38μm 40%.

[0087] In this embodiment, the metal ion is Mg. 2+ The combined collector is composed of sodium oleate and sodium dodecyl sulfonate in a mass ratio of 1:2. The specific steps and formulation are as follows:

[0088] 1) Alkali etching: 1500 mg / L NaOH was added to the slurry of lepidolite and gangue minerals (slurry concentration 35%). After the reaction was carried out for 10 min under the combined action of mechanical stirring at 800 rpm and ultrasonic waves at 80 Hz, the solid and liquid were separated. The solid sample was washed 3 times to obtain the mineral sample after surface pretreatment.

[0089] 2) Flotation: The surface-pretreated sample is placed in the flotation cell. The flotation pulp concentration is 35%. The pulp pH is adjusted to 8, and 2×10⁻⁶ mol / L is added. -4 mol / L Mg 2+ After stirring thoroughly for 3 minutes, add 8×10 of the combined anionic collector. -5 After stirring thoroughly for 3 minutes with mol / L solution, one roughing, two cleaning, and two scavenging processes were performed to obtain lepidolite concentrate and tailings.

[0090] The results of the closed-loop test of the entire process are shown in Table 8. It can be seen that the final Li₂O grade in the lepidolite concentrate was 1.84%, with a recovery rate of 77.02%.

[0091] Table 8. Test Results

[0092] Product Name Yield / % <![CDATA[Li2O grade / %]]> <![CDATA[Li2O recovery rate / %]]> Concentrate 12.72 1.840 77.02 Tailings 87.28 0.080 22.98 raw ore 100.00 0.304 100.00

Claims

1. A method for surface pretreatment to promote the full-scale flotation separation of lepidolite and feldspar, characterized in that: Alkali solution is added to the slurry of lepidolite ore and gangue minerals, and an alkaline etching reaction is carried out under the combined action of mechanical stirring and ultrasound to obtain a mineral sample with surface pretreatment. After adjusting the pH of the slurry to neutral, metal ion activator and anion collector are added to the surface pretreatment mineral sample for flotation to obtain lepidolite concentrate and tailings. The lepidolite ore is of all particle sizes, including conventional flotation particle sizes of -74μm and +38μm, as well as fine particle size flotation of -38μm. The intensity of the ultrasonic wave is 50~80Hz; the metal ion activator is Ca. 2+ and / or Mg 2+ ; The anionic collector is composed of sodium oleate and sodium dodecyl sulfonate in a mass ratio of (1~3):(3~1); The mechanical stirring speed is 500~800 rpm; The concentration of the alkaline solution is 1000~1500 mg / L.

2. The method for surface pretreatment to promote the full-scale flotation separation of lepidolite and feldspar according to claim 1, characterized in that: The pulp concentration of the lepidolite ore and gangue minerals is 35-70%.

3. The method for surface pretreatment to promote the full-scale flotation separation of lepidolite and feldspar according to claim 1, characterized in that: The alkaline solution is an aqueous solution of NaOH and / or KOH.

4. The method for surface pretreatment to promote the full-scale flotation separation of lepidolite and feldspar according to claim 1, characterized in that: The alkaline etching reaction time is 5-15 minutes.

5. The method for surface pretreatment to promote the full-scale flotation separation of lepidolite and feldspar according to claim 4, characterized in that: The concentration of the metal ion activator is: 1.1 × 10⁻⁶ for conventional flotation particle sizes. -5 ~15×10 -4 mol / L; Fine-grained flotation: 2×10 -4 ~5×10 -3 mol / L; The concentration of the anionic collector is: 1×10⁻⁶ for conventional flotation particle sizes. -5 ~8×10 -5 mol / L; Fine-grained flotation: 8×10 -5 ~8×10 -4 mol / L.

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