Coal gangue non-magnetic iron full-fluorine film forming sorting removal process

Abstract

The application designs a coal gangue non-magnetic iron full-fluorine film forming separation and removal process, which comprises the following steps: (1) ore pulp pretreatment; (2) selective coordination film forming modification: adding short-chain degradable full-fluorine coordination agent into the pretreated ore pulp, and then adding fluorine modified resin emulsion dropwise to form a hydrophobic coating film on the surface of iron minerals; (3) micro-bubble coupled heavy medium separation: using inert heavy medium suspension, the modified ore pulp is sent into a separation device, and air is synchronously introduced to generate micro-bubbles for separation; (4) reagent circulation and subsequent treatment: collecting the floated iron concentrate, and recycling the full-fluorine reagent through weak alkali elution; collecting the sunk aluminum ore pulp and sending it into a subsequent aluminum extraction process. By utilizing the coordination characteristic difference of the hydroxyl sites on the surfaces of iron and aluminum minerals, the functionalization differentiation of adsorption forms, film forming ability and surface hydrophobicity is realized, and by combining micro-bubble loading with regulation and control of the effective separation density of particles, the efficient physical separation of non-magnetic iron and aluminum minerals is realized.

Description

Technical Field

[0001] This invention belongs to the field of coal gangue solid waste resource utilization and mineral sorting and purification technology, specifically involving a perfluorinated film-forming sorting and removal process for non-magnetic iron in coal gangue. Background Technology

[0002] Coal gangue is a large-scale industrial solid waste generated during coal mining and processing. Rich in aluminum-containing minerals such as kaolinite and boehmite, it is an important low-cost raw material for the preparation of alumina and aluminum salt products. In the industrial production of aluminum extraction from coal gangue, iron-based impurities are the core harmful impurities that restrict the purity of aluminum products, increase production energy consumption, and increase solid waste output.

[0003] Iron impurities in coal gangue are mainly divided into two categories: magnetic iron and non-magnetic iron. Non-magnetic iron primarily consists of goethite, hematite, amorphous iron hydroxide, and finely embedded iron. These impurities are non-magnetic or weakly magnetic and are the most difficult to remove during aluminum extraction from coal gangue. Existing sorting and impurity removal processes have significant technical shortcomings. Traditional physical separation processes have poor applicability. Conventional magnetic separation and gravity separation processes rely on the differences in the inherent magnetic properties and primary density of minerals to achieve mineral separation. However, non-magnetic iron in coal gangue is mostly ultrafine particles smaller than 20μm, and is often finely embedded on the surface of aluminosilicate minerals and inside grain fissures. Some iron elements replace aluminum lattice sites in a isomorphic manner. In an aqueous medium, ultrafine particles are dominated by viscous resistance, and the differences in primary density and physical properties are offset by fluid resistance. Conventional physical separation processes have a non-magnetic iron removal rate of less than 55%, and cannot achieve deep impurity removal.

[0004] Traditional chemical iron removal processes are not economically or environmentally friendly. Currently, the mainstream industrial methods for iron removal include the goethite method, neutralization-hydrolysis precipitation method, and solvent extraction method. Although these methods have high iron removal efficiency, they generally suffer from problems such as requiring high-temperature and high-pressure reactions, large consumption of acid and alkali reagents, large output of hazardous iron sludge, high aluminum resource entrainment loss rate, and the potential for secondary pollution from organic reagents. These issues significantly increase the production cost and environmental pressure of aluminum extraction from coal gangue.

[0005] In summary, existing technologies cannot simultaneously meet the requirements of efficient removal of ultrafine embedded nonmagnetic iron, low aluminum resource loss, low cost, and green production. Therefore, it is necessary to develop an efficient, low-loss, and recyclable process for sorting and removing nonmagnetic iron from coal gangue. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a perfluorinated film-forming sorting and removal process for non-magnetic iron in coal gangue. This solves the technical problems of difficulty in sorting ultrafine non-magnetic iron and the high energy consumption, significant aluminum loss, and large hazardous waste production associated with fluorine-modified iron-aluminum sorting in the prior art.

[0007] This invention is implemented as follows: a perfluorinated film-forming sorting and removal process for non-magnetic iron in coal gangue, characterized by comprising the following steps: (1) Slurry pretreatment: After crushing and grinding coal gangue, prepare slurry with a solid content of 15%~25%, adjust the pH value of the slurry to 4.5~5.5, and stir and disperse; (2) Selective coordination film-forming modification: Add short-chain degradable perfluorinated ligand to the pretreated slurry, stir at a constant temperature, and then add fluorinated modified resin emulsion to form a hydrophobic coating film on the surface of iron minerals. (3) Microbubble-coupled heavy medium sorting: Prepared with a density of 2.55~2.59 g / cm³ 3 An inert heavy medium suspension is used to feed the modified slurry into the sorting equipment, and air is simultaneously introduced to generate microbubbles for sorting. (4) Reagent recycling and subsequent treatment: Collect the floating iron concentrate and recover the perfluorinated reagent by elution with a weak alkali with pH≥8; collect the sinking aluminum slurry and send it to the subsequent aluminum extraction process.

[0008] More preferably, in step (1), the particle size of the coal gangue grinding is controlled to be ≤20μm.

[0009] More preferably, in step (1), 10wt%~20wt% dilute hydrochloric acid is used to adjust the pH value, the stirring speed is 300~500r / min, and the stirring and dispersion time is 5~10min.

[0010] More preferably, in step (2), the temperature of the constant temperature stirring reaction is 25~35℃ and the reaction time is 15~25min.

[0011] More preferably, in step (2), the short-chain degradable perfluorinated ligand is a degradable short-chain perfluorinated carboxylic acid with a carbon chain length of C4~C6.

[0012] More preferably, in step (2), the fluorinated resin emulsion is a modified PVDF / PTFE aqueous emulsion with a solid content of 8%~12%.

[0013] More preferably, in step (2), the thickness of the hydrophobic coating film formed on the surface of the iron mineral is 80~300nm.

[0014] More preferably, in step (3), the particle size of the microbubbles is 50~200μm.

[0015] More preferably, in step (3), the sorting device is a hydrocyclone or a microbubble flotation separator.

[0016] More preferably, in step (4), the weak base is a sodium carbonate or sodium bicarbonate solution with a mass concentration of 1% to 3%.

[0017] The advantages and technical effects of this invention are as follows: Compared with the prior art, the present invention has the following beneficial effects: (1) It adopts a functionally differentiated sorting mechanism. The present invention relies on the differentiated characteristics of adsorption morphology, film-forming function and hydrophobic properties to achieve efficient sorting of ultrafine embedded nonmagnetic iron. (2) It is suitable for ultrafine and difficult-to-sort iron impurities and has high impurity removal efficiency. The present invention effectively solves the industry problem of traditional gravity separation and magnetic separation failure of ultrafine nonmagnetic iron and surface embedded iron below 20μm. It can remove 83%~90% of free nonmagnetic iron and surface micro-embedded iron in coal gangue, and greatly reduce the pressure of the downstream iron removal process. (3) It has low aluminum resource loss and significant economic benefits. In the present invention, aluminum minerals only undergo weak non-specific adsorption, without hydrophobic film formation and bubble adhesion behavior. The aluminum ore entrainment and floating loss rate is ≤2%, which is far lower than the 5%~15% aluminum loss rate of the traditional chemical iron removal process. At the same time, the pre-physical iron removal can reduce the consumption of downstream acid and alkali agents by more than 60%, eliminate the production of a large amount of iron sludge hazardous waste, and greatly reduce production and environmental protection costs. (4) Green and recyclable, with strong industrial adaptability. This invention can use short-chain degradable perfluorinated agents or recyclable and pollution-free perfluorinated suspension emulsions to avoid the environmental risks of traditional long-chain PFAS agents. The agent recycling rate is ≥90%, and no high-salt or organic waste liquid is generated. The process is carried out at room temperature and pressure, without the need for high-temperature and high-pressure equipment. It can be adapted to complex coal gangue raw materials with high silicon, high iron, and low grade, and has broad prospects for industrial application. Attached Figure Description

[0018] In the picture Figure 1 The contact angle test is performed on the powder tablets after Example 1.

[0019] Figure 2 This is a TEM image of the hydrophobic modified section from Example 1.

[0020] Figure 3 The contact angle test was performed on the powder tablets of Comparative Example 4. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0022] The sorting approach of this invention utilizes the differences in coordination characteristics of hydroxyl sites on the surfaces of iron and aluminum minerals to achieve functional differentiation based on adsorption morphology, film-forming ability, and surface hydrophobicity. Combined with microbubble loading to regulate the effective sorting density of particles, it achieves efficient physical separation of non-magnetic iron and aluminum minerals. At the same time, it constructs a segmented iron removal system, taking into account both sorting efficiency and process economy.

[0023] To achieve the above objectives, the present invention provides a perfluorinated film-forming separation and removal process for non-magnetic iron in coal gangue, comprising the following steps: (1) Slurry pretreatment: After crushing and grinding coal gangue, prepare slurry with a solid content of 15%~25%. Adjust the pH of the slurry to 4.5~5.5 with dilute acid, stir and disperse for 5~10 min to remove impurities on the mineral surface, expose the active hydroxyl sites on the surface of iron minerals, and inhibit the dissolution and non-specific adsorption of aluminum minerals. Detailed Mechanism: After ultrafine grinding, coal gangue can fully dissociate the micro-embedded non-magnetic iron particles encapsulated on the surface and in the fissures of aluminum minerals, exposing a large number of ≡Fe-OH active sites on the surface of the iron minerals, providing sufficient reaction sites for subsequent selective complexation reactions. By precisely controlling the weakly acidic pH range, the surface potential of the minerals can be precisely controlled, avoiding excessive dissolution of aluminum minerals and the generation of free Al due to excessively low pH. 3+ Eliminate free AI 3+ It preferentially complexes with perfluorinated reagents to compete for active agents, while avoiding premature hydrolysis and passivation of iron minerals and failure of active sites caused by excessively high pH. At the same time, stirring and dispersing can eliminate the agglomeration of ultrafine particles, break the clustered structure of iron and aluminum minerals, reduce the probability of physical entrainment of aluminum minerals from the source, and distinguish the subsequent reaction interface of iron and aluminum minerals to the greatest extent.

[0024] Different minerals in coal gangue possess inherent fixed isoelectric points. The isoelectric point of non-magnetic iron-bearing minerals (hematite, iron-bearing silicates, etc.) is pH 6.0–7.0, while that of aluminum minerals such as gibbsite and alumina is pH 8.0–9.0. By adjusting the pH of the coated and modified slurry to the range above the isoelectric points of these two types of minerals, the surface charge of particles can be precisely controlled using the difference between the slurry pH and the mineral isoelectric points. After adjustment, the slurry pH is significantly lower than the isoelectric points of iron-bearing and aluminum-bearing minerals, resulting in a uniform negative charge on the surfaces of both non-magnetic iron-bearing and aluminum-bearing mineral particles. Utilizing the electrostatic effect of like charges repelling each other, the heterogeneous adsorption, interfacial adhesion, and agglomeration of iron and aluminum mineral particles in the wet slurry system can be completely suppressed at the source. This effectively avoids the formation of aluminum-iron composite mixed particles, ensuring the degree of individual dissociation of mineral particles throughout the separation system and eliminating problems such as decreased separation accuracy, increased aluminum entrainment, and incomplete iron separation caused by particle adhesion.

[0025] (2) Selective coordination film-forming modification: Add short-chain degradable perfluorinated ligands to the pretreated slurry and stir at a constant temperature for 15-25 min to allow the perfluorinated ligands to preferentially form internal spherical complexes and anchor with the exposed ≡Fe-OH sites on the surface of the iron mineral; then add fluorinated modified resin emulsion dropwise and deposit and polymerize in situ to form a continuous hydrophobic coating film with a thickness of 80-300 nm on the surface of the iron mineral; Detailed Mechanism: Under a pre-set weakly acidic system, the ≡Fe-OH sites on the iron mineral surface have high charge density and strong coordination activity, enabling irreversible inner-sphere complexation reactions with the carboxyl and sulfonic acid anionic end groups of the perfluorinated ligand to form stable Fe-OC(F) covalent bonds. This allows the perfluorinated molecules to be monolayered and orderly anchored on the iron mineral surface, forming a modified substrate. In contrast, the ≡Al-OH sites on the aluminum mineral surface have weak coordination activity, only undergoing reversible electrostatic outer-sphere adsorption without stable covalent bond formation. Only sporadic weak adsorption occurs, failing to form a continuous modified substrate. Subsequently, the fluorinated modified resin uses the anchored perfluorinated molecules as growth sites, undergoing in-situ deposition and polymerization, growing layer by layer, ultimately forming a uniform, dense, and continuous hydrophobic fluorine film on the iron mineral surface. Because the aluminum mineral lacks continuous anchoring sites, resin film coating cannot be achieved, resulting in differentiated surface characteristics: hydrophobic film formation on the iron mineral and hydrophilic exposure on the aluminum mineral, providing the core functional basis for subsequent sorting.

[0026] (3) Microbubble-coupled heavy medium sorting: Prepared with a density of 2.55~2.59 g / cm³ 3 An inert heavy medium suspension is used to feed the modified slurry into the sorting equipment, while a small amount of air is simultaneously introduced to generate 50-200 μm micron-sized bubbles. The modified iron mineral surface is strongly hydrophobic and the microbubbles adhere stably, effectively reducing the sorting density to 2.2-2.5 g / cm³. 3 It floats and accumulates; the aluminum mineral has no continuous hydrophobic film and does not adhere to microbubbles, maintaining an effective density of 2.60~2.65 g / cm³. 3 And settle and separate; Detailed Mechanism: Based on the surface functional differences formed in step S2, the dense fluorocarbon film on the surface of the modified iron mineral possesses extremely strong hydrophobicity and high interfacial tension with the water medium. It can spontaneously and stably adsorb micron-sized bubbles in the system. These bubbles fill the pores on the particle surface and the gaps in the coating film, significantly reducing the overall effective sorting density of the particles and overcoming the viscous resistance limitation of ultrafine particles in water. The surface of the aluminum mineral is hydrophilic and lacks a continuous hydrophobic structure, making it unable to adsorb microbubbles. The effective density of the particles is basically consistent with that of the original mineral. By precisely matching the density range of the heavy medium suspension, a density sorting threshold is constructed: the effective density of the modified iron mineral is less than the density of the heavy medium, and it continues to float and enrich under the action of the flow field; the effective density of the aluminum mineral is greater than the density of the heavy medium, and it settles stably under the action of gravity. This completely breaks through the industry bottleneck of insufficient density difference of natural minerals and the inability to sort ultrafine particles, achieving precise reverse stratification of iron and aluminum minerals.

[0027] (4) Reagent recycling and subsequent treatment: Collect the floating iron concentrate, and recover the perfluorinated resin and perfluorinated complexing agent by weak alkali washing and desorption, and reuse them; collect the sinking aluminum slurry and send it to the subsequent roasting-acid leaching aluminum extraction process to remove isomorphous iron impurities inside the aluminum mineral lattice.

[0028] Detailed Mechanism: The Fe-OC(F) coordination bonds on the surface of iron minerals can undergo controlled hydrolytic breakage under a weakly alkaline and mild environment, causing fluoropolymers and perfluorinated coordinators to desorb and dissociate from the iron mineral surface, achieving efficient separation of the reagents from the iron slag. The desorbed perfluorinated reagents retain their structural integrity and activity, and can be directly recycled for the next round of modification reactions, achieving closed-loop utilization of the reagents. For isomorphous iron completely encapsulated within the aluminum mineral lattice without exposed hydroxyl active sites, this invention does not perform physical sorting and removal. This part of the iron impurities cannot participate in the surface complexation film reaction and enters the subsequent process with the aluminum minerals for deep removal through traditional roasting-acid leaching. This forms a segmented coupled iron removal system of "pre-physical removal of free / embedded non-magnetic iron + post-chemical removal of lattice iron", which avoids the technical problem of physical sorting of lattice iron and significantly reduces the reagent load and aluminum resource loss of post-chemical iron removal.

[0029] More preferably, in step (1), the particle size of the coal gangue is controlled to be ≤20μm, the solid content of the slurry is preferably 18%~22%, and the optimal solid content is 20%; dilute hydrochloric acid is used as a pH adjuster, and the stirring speed is controlled to be 300~500r / min; the optimal process conditions are: pH=5.0, stirring time 8min, stirring speed 400r / min. This parameter range can maximize the exposure of active sites of iron minerals, while suppressing the non-specific adsorption of aluminum minerals to the lowest level.

[0030] Further preferably, the isothermal reaction temperature in step (2) is controlled within the range of 25~35℃, the preferred reaction time is 18~22min, and the optimal reaction time is 20min; the perfluorinated ligand is preferably a biodegradable short-chain perfluorinated carboxylic acid with a carbon chain length of C4~C6, avoiding the risk of long-chain PFAS pollutant control; the fluorinated modified resin emulsion is preferably a modified PVDF / PTFE aqueous emulsion, with a solid content controlled at 8%~12%; the optimal coating film thickness is controlled at 120~180nm, with 150nm being the most preferred. This thickness can take into account the integrity of hydrophobic film formation, reagent utilization rate and sorting stability, avoiding the problems of discontinuous film formation due to excessively thin film and waste of reagents due to excessively thick film.

[0031] Cost reduction options include: reducing the amount of biodegradable short-chain perfluorocarboxylic acids added and increasing the amount of modified PVDF / PTFE aqueous emulsion, depending on the actual situation.

[0032] More preferably, the heavy medium suspension in step (3) is preferably an inert silica sol heavy medium, with its density optimally controlled at 2.56~2.57 g / cm³. 3 The optimal microbubble particle size is controlled to be 80~150μm, and the optimal air volume is 0.08~0.12m³. 3 / (m 3 ·min), the optimal value is 0.1m 3 / (m 3•min); The sorting equipment uses hydrocyclones or microbubble flotation separators, and the sorting is carried out at normal temperature and pressure. These optimized parameters can maximize the effective density difference between iron and aluminum minerals, improve the sorting accuracy, and further control the aluminum entrainment loss to within 2%.

[0033] More preferably, the weak alkaline solution used for desorption in step (4) is a low-concentration sodium carbonate or sodium bicarbonate solution, the mass concentration of the alkaline solution is controlled at 1%~3%, the desorption stirring time is 10~15min, and the desorption temperature is 25~30℃; the optimal desorption conditions are: sodium carbonate solution mass concentration 2%, desorption time 12min, which can achieve a perfluorinated reagent desorption rate ≥92%, and the number of cycles is ≥8 times, greatly reducing the reagent usage cost; the settled aluminum ore slurry is directly sent to the subsequent roasting and acid leaching process, only removing lattice-like isomorphic iron, retaining the effective aluminum component, and maximizing the aluminum resource recovery rate.

[0034] The core differentiating mechanism of this invention lies in: not ignoring the weak adsorption behavior of aluminum minerals on perfluorinated compounds, but strictly distinguishing the adsorption nature and functional differences between iron and aluminum minerals. The ≡Fe-OH sites on the surface of iron minerals can undergo irreversible inner-sphere complexation reactions with the terminal functional groups of perfluorinated compounds, forming stable Fe-OC(F) covalent bonds and assembling to form a continuous and dense hydrophobic functional film; the ≡Al-OH sites on the surface of aluminosilicate minerals only undergo reversible weak electrostatic outer-sphere adsorption, without the formation of stable covalent bonds, resulting only in sporadic point adsorption and failing to constitute a hydrophobic functional film.

[0035] Based on the above differences, modified iron minerals can selectively adhere to microbubbles to achieve effective density control, while aluminum minerals are hydrophilic on the surface and their density does not change significantly. Relying on a precisely controlled heavy medium density system, efficient reverse stratification and sorting of iron and aluminum minerals can be achieved. For lattice-like isomorphic iron without exposed active sites, this invention uses a downstream wet process for deep removal, forming a segmented coupled process of pre-physical impurity removal and downstream chemical purification.

[0036] Example 1: A perfluorinated film-forming separation and removal process for non-magnetic iron in coal gangue, comprising the following steps: (1) Slurry pretreatment: The coal gangue is crushed and ground to a particle size ≤20μm, a slurry with a solid content of 20% is prepared, the pH value of the slurry is adjusted to 5.0 with dilute hydrochloric acid, and the mixture is stirred and dispersed for 8min to remove floating dust and soluble impurities on the mineral surface and expose the active sites of iron minerals; (2) Selective coordination film-forming modification: A short-chain perfluorocarboxylic acid coordination agent is added to the pretreated slurry, and the mixture is stirred and reacted at a constant temperature for 20min to complete the anchoring of iron mineral surface sites; then a concentrated PTFE dispersion is added dropwise to form a continuous hydrophobic coating film with a thickness of 150nm; (3) Microbubble coupling heavy media separation: A slurry with a density of 2.57g / cm³ is prepared. 3 An inert heavy medium suspension is used to feed the modified slurry into the sorting equipment, with the aeration rate controlled at 0.1 m³ / s. 3 / (m 3·min), generating 50~200μm microbubbles for reverse stratification and sorting; (4) reagent recycling and subsequent treatment: the floating iron concentrate is desorbed and the perfluorinated reagent is recovered by weak alkaline solution and recycled; the sinking aluminum slurry is sent to the subsequent aluminum extraction process to remove residual lattice-like isomorphic iron.

[0037] Example test results: Overall removal rate of non-magnetic iron 87.2%, aluminum mineral entrainment loss rate 1.8%, fluorine reagent recycling rate 92.5%, and downstream iron removal alkali consumption reduced by 63%. Key data: Contact angle 111°, coating thickness 100~200nm; the contact angle is hydrophobic, which increases flotation efficiency. Please refer to [link / reference]. Figure 1 and Figure 2 Example 2: This example is basically the same as Example 1 in terms of process, except that: the pH value of the slurry is adjusted to 4.5, the coating film thickness is controlled to 80 nm, and the density of the heavy medium is set to 2.55 g / cm³. 3 Test results: The overall removal rate of non-magnetic iron was 83.5%, the loss rate of aluminum mineral entrainment was 1.5%, and the recycling rate of fluorine reagent was 90.1%.

[0038] Example 3: This example is basically the same as the process in Example 1, except that the pH of the slurry is adjusted to 5.5 and the density of the heavy medium is set to 2.59 g / cm³. 3 Test results: The overall removal rate of non-magnetic iron was 89.6%, the loss rate of aluminum mineral inclusions was 1.9%, and the recycling rate of fluorine reagents was 91.3%.

[0039] Comparative Example 1: Conventional High-Gradient Magnetic Separation Process: A conventional industrial high-gradient magnetic separation process was used to treat coal gangue slurry with the same particle size and grade. The slurry solid content was 20%, and separation was performed at room temperature and pressure with a magnetic field strength of 1.2T. The separation time was consistent with the embodiment of this invention. Test results showed that the overall removal rate of non-magnetic iron was 52.3%, ultrafine embedded non-magnetic iron was almost impossible to remove, and the aluminum mineral entrainment loss rate was 4.6%. Deep removal of ultrafine non-magnetic iron could not be achieved, and the impurity removal accuracy was far lower than that of the process of this invention.

[0040] Comparative Example 2: Traditional Gravity Heavy Medium Separation Process: Using an inert heavy medium suspension of the same density as in this invention, traditional gravity separation was performed directly without perfluorinated compound modification or microbubble coupling. Test results showed that relying on the original density difference of minerals for separation, the overall removal rate of non-magnetic iron was 38.7%. Ultrafine (diameter ≤20μm) non-magnetic iron basically settled synchronously with the aluminum minerals, with no separation effect. The specificity of iron-aluminum separation was extremely poor, completely failing to meet the requirements of industrial impurity removal.

[0041] Comparative Example 3: Traditional Neutralization Hydrolysis Chemical Iron Removal Process: The mainstream industrial neutralization hydrolysis precipitation iron removal process was used to treat the same coal gangue slurry, adjusting the pH to 3.5-4.0 to hydrolyze and precipitate iron ions. Test results showed that the overall removal rate of non-magnetic iron was 95.1%, indicating high iron removal efficiency. However, the aluminum resource entrainment loss rate was as high as 11.3%, the consumption of acid and alkali reagents increased significantly, and a large amount of hazardous iron sludge was generated. The process's economic and environmental performance was significantly inferior to that of this invention.

[0042] Comparative Example 4: Blank Control Process Without Perfluorinated Modification: The complete process flow of this invention was adopted, except that short-chain perfluorinated ligands and fluorinated modified resins were not added; only slurry pretreatment and microbubble-coupled heavy media separation were performed. Test results showed that the surface of the iron minerals without fluorinated modification was hydrophilic, preventing the adhesion of microbubbles. The sedimentation behavior of iron and aluminum minerals was basically the same, and the removal rate of non-magnetic iron was only 29.5%, with almost no separation effect. This proves that perfluorinated selective film-forming modification is the core key to achieving efficient iron-aluminum separation. Figure 3 With a contact angle of 60°, it is a hydrophilic surface, resulting in poor flotation performance.

[0043] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A perfluorinated film-forming separation and removal process for non-magnetic iron in coal gangue, characterized in that, Includes the following steps: (1) Slurry pretreatment: After crushing and grinding coal gangue, prepare slurry with a solid content of 15%~25%, adjust the pH value of the slurry to 4.5~5.5, and stir and disperse; (2) Selective coordination film-forming modification: Add short-chain degradable perfluorinated ligand to the pretreated slurry, stir at a constant temperature, and then add fluorinated modified resin emulsion to form a hydrophobic coating film on the surface of iron minerals. (3) Microbubble-coupled heavy medium sorting: Prepared with a density of 2.55~2.59 g / cm³ 3 An inert heavy medium suspension is used to feed the modified slurry into the sorting equipment, and air is simultaneously introduced to generate microbubbles for sorting. (4) Reagent recycling and subsequent treatment: Collect the floating iron concentrate and recover the perfluorinated reagent by elution with a weak alkali with pH≥8; collect the sinking aluminum slurry and send it to the subsequent aluminum extraction process.

2. The perfluorinated film-forming separation and removal process for non-magnetic iron in coal gangue according to claim 1, characterized in that, In step (1), the particle size of the coal gangue is controlled to be ≤20μm.

3. The perfluorinated film-forming separation and removal process for non-magnetic iron in coal gangue according to claim 1, characterized in that, In step (1), 10wt%~20wt% dilute hydrochloric acid is used to adjust the pH value, the stirring speed is 300~500r / min, and the stirring and dispersion time is 5~10min.

4. The perfluorinated film-forming separation and removal process for non-magnetic iron in coal gangue according to claim 1, characterized in that, In step (2), the temperature of the constant temperature stirring reaction is 25~35℃, and the reaction time is 15~25min.

5. The perfluorinated film-forming separation and removal process for non-magnetic iron in coal gangue according to claim 1, characterized in that, In step (2), the short-chain degradable perfluorinated ligand is a degradable short-chain perfluorinated carboxylic acid with a carbon chain length of C4~C6.

6. The perfluorinated film-forming separation and removal process for non-magnetic iron in coal gangue according to claim 1, characterized in that, In step (2), the fluorinated resin emulsion is a modified PVDF / PTFE aqueous emulsion with a solid content of 8%~12%.

7. The perfluorinated film-forming separation and removal process for non-magnetic iron in coal gangue according to claim 1, characterized in that, In step (2), the thickness of the hydrophobic coating film formed on the surface of the iron mineral is 80~300nm.

8. The perfluorinated film-forming separation and removal process for non-magnetic iron in coal gangue according to claim 1, characterized in that, In step (3), the particle size of the microbubbles is 50~200μm.

9. The perfluorinated film-forming separation and removal process for non-magnetic iron in coal gangue according to claim 1, characterized in that, In step (3), the sorting equipment is a hydrocyclone or a microbubble flotation separator.

10. The perfluorinated film-forming separation and removal process for non-magnetic iron in coal gangue according to claim 1, characterized in that, In step (4), the weak base is a sodium carbonate or sodium bicarbonate solution with a mass concentration of 1% to 3%.

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