A pegmatite-based quartz purification pre-treatment process

Abstract

This invention relates to the field of non-metallic mineral processing and purification technology, and discloses a quartz purification pretreatment process based on pegmatite, comprising: crushing the raw ore and calcining it at 1000℃, then directly water quenching it after heat preservation to induce microcracks at the grain boundaries by utilizing the difference in thermal expansion; performing multi-stage crushing and screening on the pretreated ore, collecting fine powder with a particle size between 38.5 micrometers and 74 micrometers as flotation feed; adding water to adjust the slurry and adding sulfuric acid to adjust the pH to 4, then adding hydrofluoric acid as a modifier for stirring reaction; adding dodecylamine, which has been dissolved in hydrochloric acid beforehand, as a collector to the slurry, and starting reverse flotation to float and remove gangue minerals; and washing and drying the tailings in the bottom tank to obtain quartz concentrate. This process destroys the dense embedded structure through phase transformation and eliminates the physical encapsulation effect of over-grinding slime through narrow particle size control, ultimately achieving effective separation and purification of refractory pegmatite in an acidic fluorine-containing system.

Description

Technical Field

[0001] This invention relates to the field of non-metallic mineral processing and purification technology, specifically a quartz purification pretreatment process based on pegmatite. Background Technology

[0002] Quartz is a basic raw material for industries such as semiconductors, photovoltaics, and optical fiber communication. With the gradual depletion of high-quality natural crystal resources, the purification of quartz using silicon-based mineral resources such as pegmatite has become a current industry trend. Pegmatite ore has a complex composition, in which quartz is mixed and interlocked with gangue minerals such as potassium feldspar, sodium feldspar, and mica. In conventional mineral processing, it is difficult to destroy this dense symbiotic structure by simply relying on mechanical external force, resulting in low individual liberation of quartz and feldspar gangue minerals, and a large number of impurity minerals exist in the form of intergrowths.

[0003] To improve the liberation of minerals, conventional processes typically involve extending the grinding time or increasing the grinding intensity. However, this easily leads to over-grinding and mud formation in gangue minerals such as feldspar. The fine mud has a large specific surface area and adheres to the surface of quartz particles, forming a physical coating that alters the physicochemical properties of the quartz surface. In subsequent flotation separation, this mud coating severely interferes with the selective adsorption of the collector. Furthermore, if conventional alkaline or neutral flotation systems are used, both quartz and feldspar have negatively charged surfaces. Conventional collectors in the pulp are unable to differentiate the hydrophobic surface modification of feldspar minerals due to electrostatic repulsion. These problems, including liberation difficulties, over-grinding and mud formation, and electrostatic repulsion of reagents, cause quartz and feldspar to co-float during flotation. The final product contains high levels of impurities such as aluminum, potassium, and sodium, and the purification effect of silica is insufficient to meet the requirements of subsequent industrial processing. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a quartz purification and pretreatment process based on pegmatite, which solves the problems of the dense embedding of quartz and gangue minerals in existing pegmatite ore, making it difficult to achieve single-unit separation, and the tendency of feldspar to become muddy and form encapsulation during the crushing process, resulting in poor separation selectivity and high impurity content in the product in conventional flotation systems.

[0005] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a quartz purification and pretreatment process based on pegmatite, comprising the following steps: S100 ore pretreatment: The pegmatite ore is initially crushed, then calcined at a constant temperature of 1000 degrees Celsius for 1.5 hours; after the heat preservation is completed, it is taken out and put into pure water for cooling and water quenching, and then dried to obtain pretreated ore; S200 crushing and screening: Multi-stage mechanical crushing and vibrating screening of pre-treated ore to collect fine-grained pegmatite powder with a particle size between 38.5 micrometers and 74 micrometers as flotation feed; S300 Slurry Preparation and Reagent Activation: Add water to the flotation feed and stir to prepare the slurry. Add sulfuric acid to adjust the pH of the slurry to 4, and then add hydrofluoric acid as a modifier and stir to react for 3 minutes. S400 reverse flotation separation: Add a pre-prepared dodecylamine acidic solution dissolved in hydrochloric acid to the slurry as a collector, and control the amount of dodecylamine active ingredient to be 600 grams per ton; after stirring and reacting for 3 minutes, start the flotation machine to perform reverse flotation, so that gangue minerals float to the surface with the foam and are removed, and quartz minerals are enriched in the bottom tailings. S500 Solid-Liquid Separation and Drying: The tailings slurry in the bottom tank is filtered, and the filter cake is neutralized and washed with a pH adjuster, and then dried to obtain quartz concentrate.

[0006] As a preferred embodiment of the above scheme, the pegmatite ore is composed of quartz, potassium feldspar, sodium feldspar, and mica in a mixed and interlocking state.

[0007] As a preferred embodiment of the above scheme, in step S100, a jaw crusher is used to initially crush the pegmatite ore to a size of 5 mm, and then it is pushed into the central area of ​​a double-tube heating furnace for constant temperature calcination.

[0008] As a preferred embodiment of the above scheme, in step S200, the crushing particle size of the multi-stage mechanical crushing is set to 5 mm, 3 mm, 1 mm, 0.5 mm and 0.3 mm respectively.

[0009] As a preferred embodiment of the above scheme, in step S200, the 0.3 mm pulverized ore is recycled into the crusher and crushed three times.

[0010] As a preferred embodiment of the above scheme, in the vibrating screening of step S200, intergrowth particles larger than 74 micrometers and fine mud particles smaller than 38.5 micrometers are removed by a sieve to collect fine-grained pegmatite mineral powder.

[0011] As a preferred embodiment of the above scheme, in step S300, water is added to adjust the slurry concentration to 30%.

[0012] As a preferred embodiment of the above scheme, in step S300, the mass fraction of hydrofluoric acid added is 10%.

[0013] As a preferred embodiment of the above scheme, in step S400, the time for starting the flotation machine to scrape bubbles and perform reverse flotation is 5 minutes.

[0014] As a preferred embodiment of the above scheme, in step S500, the rinsed filter cake is placed in a forced-air drying oven at 105 degrees Celsius and dried for 24 hours.

[0015] This invention provides a quartz purification and pretreatment process based on pegmatite. It has the following beneficial effects: 1. In the pretreatment stage, this invention employs a constant-temperature calcination process at 1000 degrees Celsius followed by cooling and water quenching. By utilizing the difference in thermal expansion coefficients between quartz and feldspar gangue minerals, thermal stress is generated at the interface between different mineral phases, and microcracks are induced at the grain boundaries. This microcrack structure disrupts the dense mosaic symbiotic state of the pegmatite ore, reduces the mechanical energy consumption of monomer dissociation, and provides a physical channel for the subsequent penetration of hydrofluoric acid into the ore, thereby increasing the contact area between the reagent and the mineral.

[0016] 2. This invention controls the particle size of the flotation feed to between 38.5 micrometers and 74 micrometers. After high-temperature treatment, the mechanical strength of gangue minerals in pegmatite ore decreases, and they are prone to excessive grinding during multi-stage mechanical crushing, forming fine sludge. By removing fine sludge particles smaller than 38.5 micrometers, the sludge is prevented from adhering to the surface of quartz particles and forming a coating layer. This eliminates the alteration of the physicochemical properties of the quartz surface by fine particles and ensures the selective adsorption efficiency of the collector on feldspar minerals in subsequent flotation operations.

[0017] 3. This invention specifies a low-concentration, short-time flotation pretreatment process, employing an acidic slurry conditioning environment in conjunction with a hydrofluoric acid modifier and a dodecylamine collector system. Under these specific conditions, hydrofluoric acid can slightly etch the Al sites on the feldspar surface and expose the active region, while simultaneously reacting on the quartz surface to form a hydrophilic silica-fluorine complex, effectively avoiding the continuous dissolution and loss of quartz under high-concentration hydrofluoric acid or prolonged immersion. Subsequently, dodecylamine undergoes protonation in the acidic slurry at pH 4, selectively adsorbing onto the modified feldspar surface through electrostatic attraction, making it hydrophobic, while the quartz surface maintains a stable hydrophilic state thanks to the silica-fluorine complex. This mechanism allows feldspar to be effectively floated and removed with the bubbles, achieving efficient separation of quartz and gangue minerals in pegmatite and significantly improving the silica grade in the quartz concentrate. Attached Figure Description

[0018] Figure 1 This is a flowchart of the method of the present invention. Detailed Implementation

[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Please see Figure 1This invention provides a quartz purification and pretreatment process based on pegmatite.

[0021] raw material: The pegmatite ore used in the following embodiments and comparative examples of this invention is a natural ore. Optical microscopy and X-ray diffraction energy dispersive spectroscopy analysis revealed that it is mainly composed of gangue minerals such as quartz, potassium feldspar, sodium feldspar, and mica in a mixed and interlocking state. Quantitative chemical composition analysis showed that the batch of ore contained 70.84% ​​silica, 14.66% alumina, 7.76% potassium oxide, and 5.55% sodium oxide by mass.

[0022] The reagents used include hydrofluoric acid (10% by mass), dodecylamine (DDA), hydrochloric acid, and sulfuric acid, all of which are commercially available industrial grade or analytical grade products. The dodecylamine collector was pre-dissolved in hydrochloric acid to prepare an acidic solution for later use, ensuring its effective dispersion and collecting activity in the slurry.

[0023] Example 1:

[0024] This embodiment provides a quartz purification pretreatment process based on pegmatite, which is performed entirely according to the following specific parameters: S100 Ore Pretreatment: Weigh the pegmatite ore and use a jaw crusher to initially crush it to a size of 5mm; then push the crushed pegmatite ore into the central area of ​​a double-tube heating furnace and calcine it at a constant temperature of 1000℃ for 1.5h; after the heat preservation is completed, immediately take out the ore and put it directly into a container filled with pure water for cooling and water quenching. Utilizing the difference in thermal expansion coefficients between quartz and feldspar gangue minerals, thermal stress is induced at the mineral phase contact interface and microcracks are formed. After drying, the pretreated ore is obtained.

[0025] S200 Crushing and Screening: The pre-treated ore is subjected to multi-stage mechanical crushing using a jaw crusher, with crushed particle sizes of 5mm, 3mm, 1mm, 0.5mm, and 0.3mm respectively. The 0.3mm particle size is recycled back into the crusher for repeated crushing three times. The crushed ore is then subjected to vibrating screening through a double screen to remove intergrowth particles larger than 74μm and fine mud particles smaller than 38.5μm. Fine-grained pegmatite powder with a particle size range of 38.5μm to 74μm is strictly collected as flotation feed.

[0026] S300 Slurry Preparation and Reagent Activation: Place the collected flotation feed into a standard flotation cell, add water to adjust the slurry concentration to 30%, add sulfuric acid to adjust the pH of the slurry to 4, and then add 10% hydrofluoric acid as a modifier and stir for 3 minutes.

[0027] S400 reverse flotation separation: A dodecylamine acidic solution, pre-dissolved in hydrochloric acid, is added to the slurry as a collector, with the effective dodecylamine content controlled at 600 g / t. After stirring and reacting for 3 minutes, the flotation machine is turned on to perform reverse flotation for 5 minutes, causing the surface-modified gangue minerals to float and be removed, while the quartz minerals are enriched in the bottom tank.

[0028] S500 Solid-Liquid Separation and Drying: The tailings slurry is filtered, and the filter cake is neutralized and washed with a pH adjuster. Then it is placed in a 105℃ forced-air drying oven for 24 hours to obtain quartz concentrate.

[0029] Comparative Example 1: Compared with Example 1, the difference is that step S100 ore pretreatment is omitted, and the pegmatite ore is directly subjected to multi-stage mechanical crushing and screening in step S200. The rest are the same.

[0030] Comparative Example 2: Compared with Example 1, the difference is that in step S200, ultrafine pegmatite powder with a particle size of less than 38.5 μm is collected as flotation feed, while the rest are the same.

[0031] Comparative Example 3: Compared with Example 1, the difference lies in the change of the flotation reagent system. Specifically, in step S300, sodium hydroxide is added to adjust the pH of the pulp to 10.5, and hydrofluoric acid is not added; in step S400, a mixed collector composed of sodium oleate and dodecylamine in a mass ratio of 3:1 is directly added at a dosage of 1200g / t, and the rest are the same.

[0032] Test example: Quartz concentrates prepared in Example 1 and Comparative Examples 1 to 3 were placed in a forced-air drying oven and dried to constant weight at 105°C. After cooling, the samples were ground in an agate mortar until the particle size completely passed through a 200-mesh standard sieve, and used as samples for chemical analysis. Simultaneously, pegmatite ore from the same batch was collected and prepared as raw ore analysis samples under the same grinding conditions. Principal component elemental quantitative scanning of the raw ore samples and each group of concentrate samples was performed using X-ray fluorescence spectrometry to determine and record the mass fractions of silicon dioxide, aluminum oxide, potassium oxide, and sodium oxide in the samples.

[0033] The test results are recorded in Table 1: Table 1. Test results of main chemical components of quartz concentrate in the examples and comparative examples.

[0034] According to the test results in Table 1, the silica mass fraction of the product in Example 1 was 79.24%, which showed improved impurity removal compared to the raw ore and the comparative examples. The technical mechanism of this process was clarified through data comparison.

[0035] Regarding mineral liberation, Comparative Example 1, without calcination and water quenching, was directly mechanically crushed and then floated, resulting in a silica mass fraction of 73.52%. This is because the quartz and feldspar in the pegmatite ore are closely associated, making it difficult to achieve grain boundary liberation solely through mechanical force. Example 1, through calcination at 1000℃ and cold water quenching, utilized the difference in thermal expansion coefficients between quartz and feldspar to generate thermal stress at the interface between different mineral phases, thereby inducing microcracks at the grain boundaries. These microcracks disrupt the intercrystalline mosaic structure, reducing the difficulty of monomer liberation and providing a channel for the subsequent penetration of the hydrofluoric acid modifier, thus expanding the reaction contact area.

[0036] Regarding particle size control, Comparative Example 2 used ultrafine particles with a diameter less than 38.5 micrometers as flotation feed, resulting in a final product with a silica mass fraction of only 71.87%. After high-temperature treatment, the mechanical strength of gangue minerals decreases. If the lower limit of the feed particle size is not controlled, the gangue is prone to over-grinding during crushing, forming slime. Fine slime has a large specific surface area and adheres to the surface of quartz particles, forming a coating layer that alters the physicochemical properties of the quartz surface, hindering the selective adsorption of collectors and feldspar, leading to a decrease in separation efficiency. Example 1 controlled the lower particle size at 38.5 micrometers, eliminating ultrafine particles and the adverse effects of physical slime coating.

[0037] Regarding the compatibility of the reagent system, Comparative Example 3 used an alkaline slurry conditioning environment combined with a mixture of sodium oleate and dodecylamine. The final product had a silica mass fraction of 70.31%, showing virtually no purification effect. In an alkaline slurry with a pH of 10.5, both quartz and feldspar surfaces carried negative charges. The mixed collector micelles and mineral surfaces experienced electrostatic repulsion, making selective collection impossible. Example 1 introduced hydrofluoric acid as a modifier in an acidic environment. Hydrofluoric acid selectively eroded the aluminosilicate structure on the feldspar surface and exposed active sites. Protonated dodecylamine was adsorbed onto the feldspar surface through electrostatic attraction, causing it to float hydrophobically. Quartz remained in a hydrophilic state in the bottom tailings, thus achieving the separation of quartz and gangue minerals in the pegmatite.

[0038] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A quartz purification and pretreatment process based on pegmatite, characterized in that, Includes the following steps: S100 ore pretreatment: The pegmatite ore is initially crushed and then calcined at a constant temperature of 1000 degrees Celsius for 1.5 hours; After the heat preservation is completed, the ore is taken out and immersed in pure water for cooling and quenching, and then dried to obtain the pretreated ore. S200 crushing and screening: Multi-stage mechanical crushing and vibrating screening of pre-treated ore to collect fine-grained pegmatite powder with a particle size between 38.5 micrometers and 74 micrometers as flotation feed; S300 Slurry Preparation and Reagent Activation: Add water to the flotation feed and stir to prepare the slurry. Add sulfuric acid to adjust the pH of the slurry to 4, and then add hydrofluoric acid as a modifier and stir to react for 3 minutes. S400 reverse flotation separation: Add a pre-prepared dodecylamine acidic solution dissolved in hydrochloric acid to the slurry as a collector, and control the amount of dodecylamine active ingredient to be 600 grams per ton; after stirring and reacting for 3 minutes, start the flotation machine to perform reverse flotation, so that gangue minerals float to the surface with the foam and are removed, and quartz minerals are enriched in the bottom tailings. S500 Solid-Liquid Separation and Drying: The tailings slurry in the bottom tank is filtered, and the filter cake is neutralized and washed with a pH adjuster, and then dried to obtain quartz concentrate.

2. The quartz purification and pretreatment process based on pegmatite according to claim 1, characterized in that, The pegmatite ore is composed of quartz, potassium feldspar, sodium feldspar, and mica in a mixed and interlocking manner.

3. The quartz purification and pretreatment process based on pegmatite according to claim 1, characterized in that, In step S100, a jaw crusher is used to initially crush the pegmatite ore to a size of 5 mm, and then it is pushed into the central area of ​​a double-tube heating furnace for constant temperature calcination.

4. The quartz purification and pretreatment process based on pegmatite according to claim 1, characterized in that, In step S200, the particle size of the multi-stage mechanical crushing is set to 5 mm, 3 mm, 1 mm, 0.5 mm and 0.3 mm in sequence.

5. The quartz purification and pretreatment process based on pegmatite according to claim 4, characterized in that, In step S200, the 0.3 mm pulverized ore is recycled into the crusher and crushed three times.

6. The quartz purification and pretreatment process based on pegmatite according to claim 1, characterized in that, In the vibrating sieving process of step S200, intergrowth particles larger than 74 micrometers and fine mud particles smaller than 38.5 micrometers are removed by a sieve, and the fine-grained pegmatite mineral powder is collected.

7. The quartz purification and pretreatment process based on pegmatite according to claim 1, characterized in that, In step S300, water is added to adjust the slurry concentration to 30%.

8. The quartz purification and pretreatment process based on pegmatite according to claim 1, characterized in that, In step S300, the added hydrofluoric acid has a mass fraction of 10%.

9. The quartz purification and pretreatment process based on pegmatite according to claim 1, characterized in that, In step S400, the time for starting the flotation machine to scrape bubbles and perform reverse flotation is 5 minutes.

10. The quartz purification and pretreatment process based on pegmatite according to claim 1, characterized in that, In step S500, the rinsed filter cake is placed in a forced-air drying oven at 105 degrees Celsius and dried for 24 hours.

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