Apparatus and method for simultaneous concentration and recovery of fluorides using multi-stage semi-fluid electrodes

Abstract

This invention belongs to the field of fluoride wastewater treatment technology, and particularly relates to an apparatus and method for simultaneous concentration and recovery of fluorides using a multi-stage semi-flow electrode, comprising: a fluoride deep removal unit, an electrode slurry preparation tank, and a fluoride resource recovery unit arranged in sequence; the fluoride deep removal unit includes a wastewater inlet, several semi-flow electrochemical adsorption modules, and a purified water outlet arranged in sequence; the semi-flow electrochemical adsorption module includes: an anode, an anion exchange membrane, an ion migration zone, and a solid carbon material cathode arranged in sequence from left to right; several ion migration zones are connected in sequence to form a flow channel, with both ends of the flow channel connected to the wastewater inlet and the purified water outlet, respectively; the anode has a cavity for accommodating a metal composite silicon-based flowing anode slurry, several cavities are connected in series, and the cavities are connected to the ion migration zone through the anion exchange membrane; the electric field formed by energizing the solid carbon material cathode and the anode passes through the ion migration zone.

Description

Technical Field

[0001] This invention belongs to the field of fluoride-containing wastewater treatment technology, and particularly relates to a device and method for simultaneous concentration and recovery of fluorides using a multi-stage semi-fluid electrode. Background Technology

[0002] Fluorides are commonly found in coal resources, and large amounts of fluoride-containing wastewater are generated during coal chemical production processes (such as coal gasification and coking), causing fluorides to enter water bodies and the environment as pollutants. Simultaneously, the explosive growth of renewable energy industries, represented by photovoltaic power generation and energy storage batteries, has led to a surge in demand for fluorine-containing materials, significantly boosting the market demand for fluorine-based chemicals and making fluorine an important strategic resource. Currently, fluorine resources associated with phosphate rock account for over 97.7% of total fluorine resources. Recovering fluorine resources associated with phosphate rock is a crucial source of raw materials for the fluorochemical industry. However, the recovery rate of associated fluorine in wet-process phosphoric acid production is generally below 30%, making the recovery and utilization of fluorine resources and its recovery rate a pressing issue.

[0003] Currently, the mainstream technologies for defluoridation of industrial wastewater mainly include adsorption and chemical precipitation. Adsorption has been widely studied in the treatment of low- to medium-concentration fluoride-containing wastewater, and the process is relatively mature and stable. However, when dealing with low-concentration fluoride-containing wastewater, the efficiency of existing adsorption technologies decreases significantly. This is especially true in applications requiring deep purification of effluent fluoride concentrations to below 1 mg / L, where the technical difficulty increases dramatically. This is mainly due to factors such as a sharp reduction in adsorption capacity of the adsorbent, insufficient mass transfer driving force, limited selective adsorption, and difficulties in desorption and regeneration at extremely low concentrations.

[0004] Therefore, there is an urgent need for a device and method for the simultaneous concentration and recovery of fluorides using a multi-stage semi-fluid electrode to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide an apparatus and method for simultaneous concentration and recovery of fluorides using multi-stage semi-fluid electrodes, in order to solve the above-mentioned problems.

[0006] To achieve the above objectives, the present invention provides the following solution:

[0007] A device for simultaneous concentration and recovery of fluorides using a multi-stage semi-fluid electrode includes a fluoride deep removal unit, an electrode slurry preparation tank, and a fluoride resource recovery unit connected in sequence.

[0008] The fluoride deep removal unit includes a wastewater inlet, several semi-flow electrochemical adsorption modules and a purified water outlet connected in sequence.

[0009] The semi-fluid electrochemical adsorption module includes:

[0010] The anode, anion exchange membrane, ion migration region, and solid carbon material cathode are arranged sequentially from left to right; several of the ion migration regions are connected in sequence to form a flow channel, and the two ends of the flow channel are respectively connected to the sewage inlet and the purified water outlet;

[0011] The anode has a cavity for containing a metal-composite silicon-based flowing anode slurry. Several cavities are connected in series and are connected to each other. The cavities are connected to the ion migration region through the anion exchange membrane. The electric field formed by the current flowing between the solid carbon material cathode and the anode passes through the ion migration region.

[0012] Optionally, the outlet of the electrode slurry mixing tank is connected to the inlet of the anode located near the wastewater inlet, and the inlet of the fluoride resource recovery unit is connected to the outlet of the anode located near the purified water outlet.

[0013] The fluorine resource recovery unit is equipped with a slurry outlet and a sludge collection tank. The slurry outlet is connected to the inlet end of the electrode slurry mixing tank, and the sludge collection tank is used to collect fluorine-containing products.

[0014] Optionally, the flow channel formed by sequentially connecting several of the ion migration regions has a continuously bent structure.

[0015] Optionally, the solid carbon cathode is made of a highly stable and corrosion-resistant carbon-based material.

[0016] Optionally, the fluorine resource recovery unit includes:

[0017] Box;

[0018] A slurry channel is provided at the top of the tank, and the inlet end of the slurry channel is connected to the outlet end of the anode near the purified water outlet;

[0019] A sedimentation zone is located at the bottom of the tank, and a sludge collection trough is located at the bottom of the sedimentation zone;

[0020] A conductive filter membrane is disposed at the bottom of the slurry channel, and the slurry channel is connected to the sedimentation zone through the conductive filter membrane;

[0021] An electrode plate is disposed at the top of the slurry channel, and an electric field is formed between the electrode plate and the conductive filter membrane that passes through the slurry channel;

[0022] The liquid addition section has its inlet end passing through the slurry channel, and its outlet end is located within the sedimentation zone.

[0023] Optionally, a plurality of baffles are fixedly connected inside the slurry channel, and the plurality of baffles form a continuously bent slurry channel inside the slurry channel.

[0024] Optionally, the liquid addition section includes a distributed microporous stirrer, which is fixed inside the tank. The inlet end of the distributed microporous stirrer passes through the slurry channel, and the outlet end of the distributed microporous stirrer is located in the sedimentation zone. The distributed microporous stirrer is used to uniformly disperse the injected solution into the sedimentation zone.

[0025] Optionally, the sludge collection trough has a conical structure.

[0026] Optionally, a drive pump for driving the flow of metal composite silicon-based flowing anode slurry is provided between the electrode slurry preparation tank and the fluoride deep removal unit.

[0027] A method for simultaneous concentration and recovery of fluorides, using the aforementioned multi-stage semi-fluid electrode apparatus for simultaneous concentration and recovery of fluorides, includes the following steps:

[0028] The solid carbon material cathode and anode of the same semi-flow electrochemical adsorption module are electrically connected to the cathode and anode of a DC power supply, respectively, to form a DC electric field between the solid carbon material cathode and anode; and the metal composite silicon-based flowing anode slurry fills and flows through each of the cavities.

[0029] Fluorine-containing wastewater enters the flow channel through the wastewater inlet. In the ion migration zone, fluoride ions are caused by a DC electric field to pass through the anion exchange membrane and flow into the metal composite silicon-based flowing anode slurry in the anode, forming a fluorine-enriched metal composite silicon-based flowing anode slurry.

[0030] The fluorine-enriched metal-composite silicon-based flowing anode slurry flows to the fluorine resource recovery unit for fluorine ion separation and recovery. After the fluorine ions are removed, the fluorine-enriched metal-composite silicon-based flowing anode slurry is returned to each of the semi-flowing electrochemical adsorption modules through the electrode slurry mixing tank.

[0031] Compared with the prior art, the present invention has the following advantages and technical effects:

[0032] This invention innovatively employs an electrode configuration combining a semi-fluid slurry as the anode and a solid carbon cathode. The semi-fluid slurry anode allows for real-time and flexible adjustment of the slurry composition, such as the solid-liquid ratio, active material concentration, or flow rate, based on dynamic changes in the fluoride concentration in the water, significantly improving the system's adaptability to fluctuations in influent fluoride load and its treatment stability. Simultaneously, the use of solid carbon material as the cathode is not only cost-effective and readily available but also convenient to replace and maintain, effectively reducing the operating costs and maintenance complexity of the device. Utilizing the inherent high reactivity and strong affinity between silicon and fluorine, highly selective adsorption and enrichment of fluoride ions are achieved in the anode region. This mechanism effectively suppresses competitive adsorption of coexisting anions, laying the foundation for subsequent recovery of high-purity products. Attached Figure Description

[0033] 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 described 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.

[0034] Figure 1 This is a top view of the structure of the present invention;

[0035] Figure 2 For the present invention Figure 1 Schematic diagram of the cross-sectional structure at point AA;

[0036] Figure 3 This is a schematic diagram of the fluorine resource recovery unit structure of the present invention;

[0037] The unit comprises: 1. Fluoride deep removal unit; 1-1. Inlet; 1-2. Anode; 1-3. Anion exchange membrane; 1-4. Solid carbon cathode; 1-5. Ion migration zone; 1-6. Outlet; 2. Electrode slurry preparation tank; 3. Fluorine resource recovery unit; 3-1. Slurry inlet; 3-2. Electrode plate; 3-3. Conductive filter membrane; 3-4. Distributed microporous stirrer; 3-5. Sedimentation zone; 3-6. Sludge collection tank; 3-7. Baffle; 3-8. Slurry outlet. Detailed Implementation

[0038] The technical solutions of 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.

[0039] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0040] Reference Figures 1 to 3 The present invention discloses a device for simultaneous concentration and recovery of fluoride using a multi-stage semi-fluid electrode, comprising a fluoride deep removal unit 1, an electrode slurry mixing tank 2, and a fluoride resource recovery unit 3 connected in sequence.

[0041] The fluoride deep removal unit 1 includes a wastewater inlet, several semi-flow electrochemical adsorption modules and a purified water outlet connected in sequence.

[0042] The semi-fluid electrochemical adsorption module includes:

[0043] The anode 1-2, anion exchange membrane 1-3, ion migration region 1-5, and solid carbon material cathode 1-4 are arranged sequentially from left to right; several ion migration regions 1-5 are connected in sequence to form a flow channel, and the two ends of the flow channel are connected to the sewage inlet and the clean water outlet, respectively.

[0044] The anode 1-2 is provided with a cavity for containing the metal composite silicon-based flowing anode slurry. Several cavities are connected in series and are connected to each other. The cavities are connected to the ion migration region 1-5 through the anion exchange membrane 1-3. The electric field formed by the current passing through the solid carbon material cathode 1-4 and the anode 1-2 passes through the ion migration region 1-5.

[0045] In use, the metal composite silicon-based flowing anode slurry fills each cavity and flows. Simultaneously, the solid carbon cathode 1-4 and anode 1-2 of the same semi-flowing electrochemical adsorption module are electrically connected to the cathode and anode of a DC power supply, respectively, forming a DC electric field between the solid carbon cathode 1-4 and anode 1-2. Fluorine-containing wastewater enters the flow channel through the wastewater inlet. In the ion migration zone 1-5, under the action of the DC electric field, fluoride ions pass through the anion exchange membrane 1-3 and flow into the metal composite silicon-based flowing anode slurry in the anode 1-2, forming a fluorine-enriched metal composite silicon-based flowing anode slurry. The fluorine-enriched metal composite silicon-based flowing anode slurry flows to the fluorine resource recovery unit 3 for fluorine ion separation and recovery. After the fluorine-enriched metal composite silicon-based flowing anode slurry is separated from the fluoride ions, it flows back to each semi-flowing electrochemical adsorption module through the electrode slurry preparation tank 2.

[0046] This invention innovatively employs an electrode configuration combining a semi-flowing slurry as the anode and solid carbon cathodes 1-4. The semi-flowing slurry anode allows for real-time and flexible adjustment of the slurry composition, such as the solid-liquid ratio, active material concentration, or flow rate, based on dynamic changes in the fluoride concentration in the water, significantly improving the system's adaptability to fluctuations in influent fluoride load and its treatment stability. Simultaneously, the use of solid carbon materials as cathodes is not only cost-effective and readily available but also convenient to replace and maintain, effectively reducing the operating costs and maintenance complexity of the device. Utilizing the inherent high reactivity and strong affinity between silicon and fluorine, highly selective adsorption and enrichment of fluoride ions are achieved in the anode region. This mechanism effectively suppresses competitive adsorption of coexisting anions, laying the foundation for subsequent recovery of high-purity products.

[0047] As an optional implementation, the outlet of the electrode slurry mixing tank 2 is connected to the inlet of the anode 1-2 located near the sewage inlet, and the inlet of the fluorine resource recovery unit 3 is connected to the outlet of the anode 1-2 located near the purified water outlet.

[0048] The fluorine resource recovery unit 3 is equipped with a slurry outlet 3-8 and a sludge collection tank 3-6. The slurry outlet 3-8 is connected to the inlet end of the electrode slurry mixing tank 2, and the sludge collection tank 3-6 is used to collect fluorine-containing products.

[0049] As an optional implementation, the flow channel formed by sequentially connecting several ion migration regions 1-5 has a continuously bent structure.

[0050] The continuously bent flow channel can extend the flow distance of fluoride-containing wastewater, thereby improving the fluoride ion removal efficiency.

[0051] As an optional implementation, the solid carbon cathode 1-4 is made of a highly stable and corrosion-resistant carbon-based material.

[0052] As an optional implementation, the fluorine resource recovery unit 3 includes:

[0053] Box;

[0054] The slurry channel is located at the top of the tank, and the inlet end of the slurry channel is connected to the outlet end of anode 1-2, which is close to the clean water outlet.

[0055] Sedimentation zone 3-5 is located at the bottom of the tank, and sludge collection trough 3-6 is located at the bottom of sedimentation zone 3-5;

[0056] A conductive filter membrane 3-3 is installed at the bottom of the slurry channel, and the slurry channel is connected to the sedimentation zone 3-5 through the conductive filter membrane 3-3;

[0057] Electrode plate 3-2 is set at the top of the slurry channel, and an electric field is formed between electrode plate 3-2 and conductive filter membrane 3-3 that passes through the slurry channel;

[0058] The liquid addition section has its inlet end passing through the slurry channel, and its outlet end is located within the sedimentation zone 3-5.

[0059] As an optional implementation, a number of baffles 3-7 are fixedly connected inside the slurry channel, and the baffles 3-7 form a continuously bent slurry channel inside the slurry channel.

[0060] As an optional implementation, the liquid addition section includes a distributed microporous stirrer 3-4, which is fixed inside the housing. The inlet end of the distributed microporous stirrer 3-4 passes through the slurry channel, and the outlet end of the distributed microporous stirrer 3-4 is located in the sedimentation zone 3-5. The distributed microporous stirrer 3-4 is used to uniformly disperse the injected solution into the sedimentation zone 3-5.

[0061] As an optional implementation, the mud collection troughs 3-6 have a conical structure.

[0062] As an optional implementation, a drive pump for driving the flow of metal composite silicon-based flowing anode slurry is provided between the electrode slurry preparation tank 2 and the fluoride deep removal unit 1.

[0063] The apparatus of this invention mainly comprises a fluoride deep removal unit 1, an electrode slurry preparation tank 2, and a fluoride resource recovery unit 3 connected in series. The fluoride deep removal unit 1 employs a semi-flow electrochemical adsorption module with a specific structure, the core components of which include:

[0064] Anodes 1-2 have an internal cavity containing a flowable anode slurry formulated from a specific metal (aluminum / cobalt / manganese) composite silicon-based material. The electrode material is constructed as a multi-metal and its oxide synergistic system (SiO2, Al2O3, Fe2O3), containing 10.79 wt% silicon, 2.97 wt% aluminum, and 2.06 wt% iron. After high-temperature treatment, the material forms a porous conductive network with SiO2-Al2O3 as its framework, significantly increasing the specific surface area (>1500 μm²). 2 The slurry ( / g) is primarily composed of chemical adsorption, supplemented by ion exchange and physical adsorption to achieve fluoride ion adsorption. The multi-metal mixture ensures good conductivity of the slurry itself. The addition of 5% PVDF further enhances conductivity while improving the slurry's constraint on the electrode material and its attraction to fluoride ions. The cavity is filled with anolyte slurry, thus forming a recyclable conductive slurry layer.

[0065] Solid carbon cathodes 1-4 are static electrodes made of highly stable and corrosion-resistant carbon-based materials.

[0066] Anode 1-2 significantly enhances the adsorption capacity and selectivity of the target anion fluoride ions by doping the silicon substrate with specific metal elements and optimizing its crystal structure. When fluoride-containing wastewater flows through this unit, two synergistic mechanisms are achieved under the action of a low-voltage DC electric field within a preset range:

[0067] Electronic configuration optimization mechanism: The electric field causes the electron cloud distribution of a specific atomic layer of the anode material to be reconstructed, forming a specific empty orbital structure with strong electropositivity;

[0068] Ion-directed enrichment mechanism: Fluoride ions (F-) in wastewater migrate directionally through anion exchange membranes 1-3 under the drive of an electric field and are enriched in the anode region.

[0069] Bonding Stabilization: Fluoride ions enriched in the anode region undergo strong selective bonding with the specific empty orbital structure formed by the reconstruction of the anode material, resulting in highly stable polar covalent bonds. This process utilizes the intrinsic high affinity and bonding stability of silicon-based materials for fluoride ions to achieve efficient and highly selective adsorption of fluoride ions, ensuring that the fluoride concentration in the effluent consistently meets the national discharge standard limit of less than 1 mg / L.

[0070] The specific method is as follows:

[0071] Fluorine-containing wastewater enters the electro-adsorption reactor through inlet 1-1. Under the action of a DC electric field, fluoride ions (F-) in the wastewater migrate directionally towards the anode in ion migration zone 1-5. Driven by the synergistic effect of concentration and potential gradients, F- continuously passes through anion exchange membrane 1-3 and enters the anode chamber. The metal-composite silicon-based flowing anode slurry filled in the anode chamber contains silicon-based active materials. Under the excitation of the electric field, electrons on the surface of the silicon material undergo valence band to conduction band transitions, forming highly active hole sites. Fluoride ions and valence band holes are selectively adsorbed and fixed through strong chemical bonding, achieving deep fluoride removal. The multi-stage series electro-adsorption configuration significantly enhances mass transfer efficiency, shortening the hydraulic retention time (HRT) to ≤60 minutes. The purified water that meets the standards is finally discharged through outlet 1-6.

[0072] Fluorine resource recovery unit 3 is used to treat the anode slurry after adsorption saturation. An alkaline solution with a concentration of 0.5-2 mol / L is injected into the slurry at a preset ratio. Under a controlled weakly acidic reaction environment, the pH value is maintained at 6.0-7.0. The fluorosilicone complexes contained in the slurry react fully with the introduced cations, resulting in directional crystallization to form fluorosilicate crystals with low solubility.

[0073] The specific method is as follows:

[0074] A slurry saturated with fluorine adsorption is injected into the slurry channel from slurry inlet 3-1 via a delivery pump. The slurry flows between electrode plate 3-2 and conductive filter membrane 3-3. Under the influence of the electric field and the combined effects of gravity and concentration diffusion, the hexafluorosilicate (SiF6) ions in the slurry are adsorbed. 2- The solution continuously permeates to the sedimentation zone 3-5 below the membrane; 0.5-2 mol / L NaOH solution is precisely injected through the sodium hydroxide dosing channel using a metering pump, with a dosing ratio of 2.8-3.2:1 to the fluorine content of the slurry; the NaOH solution is instantaneously and globally dispersed by a distributed microporous stirrer 3-4, controlling the local pH to ≤7.0, effectively inhibiting SiO3. 2- Byproduct formation; in a weakly acidic environment (pH 6.0-7.0), Na+ in the reaction zone... + With SiF6 2- The process generates sparingly soluble sodium fluorosilicate Na₂SiF₆, with a room temperature solubility ≤0.78wt%. Crystals undergo directional growth and enrichment in precipitation zone 3-5, and solid-liquid separation is achieved through a conical sludge collection tank 3-6. The periodically recovered high-purity Na₂SiF₆ crystals exhibit a fluorine recovery rate ≥70% and a chemical purity ≥90%, making them suitable for direct use as a fluorochemical raw material. Meanwhile, the metal-composite silicon-based flowing anode slurry continues to flow out from slurry outlet 3-8 and enters the electrode slurry preparation tank for further recycling.

[0075] This invention enables enriched fluorosilicic acid to react efficiently with sodium ions in a weakly acidic environment, crystallizing out high-purity sodium fluorosilicate crystals (purity ≥90%). The process is mild, requiring no strong acid environment or demanding operations, significantly reducing energy consumption and operational complexity.

[0076] Furthermore, another significant advantage of this invention lies in the excellent self-sustaining properties and broad operational adaptability of its reaction system. During the crystallization of Na₂SiF₆, the accompanying dissociation and reaction of fluorosilicic acid naturally releases H₂. + The acidity generated in this process effectively counteracts the alkalinity introduced by the addition of alkali (NaOH), thereby spontaneously maintaining the slurry system in a weakly acidic range conducive to crystallization within a relatively wide range of operating parameters (such as initial pH and reactant ratio). Therefore, this invention significantly reduces or even eliminates the frequent acid-base adjustments required for precise pH control in traditional processes, simplifying the process and improving system stability and operating efficiency.

[0077] This invention employs a specific dispersion and mixing method to effectively promote the selective precipitation and growth of high-purity target fluorosilicate crystals, while preventing the formation of non-target silicate precipitates due to localized over-alkaliness. This method enables the efficient recovery of high-purity target fluorosilicate crystals. The product has low impurity content and can be used directly as a valuable industrial raw material, or further converted into various important fluorochemical products such as sodium fluoride, hydrofluoric acid, and silicon fluoride through conventional chemical processes. This method achieves efficient recovery and resource utilization of the target element fluorine from fluoride-containing wastewater, offering both economic and environmental benefits.

[0078] A method for simultaneous concentration and recovery of fluorides, using the aforementioned multi-stage semi-fluid electrode apparatus for simultaneous concentration and recovery of fluorides, includes the following steps:

[0079] The solid carbon material cathode 1-4 and anode 1-2 of the same half-flow electrochemical adsorption module are electrically connected to the cathode and anode of a DC power supply, respectively, to form a DC electric field between the solid carbon material cathode 1-4 and anode 1-2; and the metal composite silicon-based flowing anode slurry fills each cavity and flows.

[0080] Fluorine-containing wastewater enters the flow channel through the sewage inlet. In the ion migration zone 1-5, the fluoride ions are caused by the DC electric field to pass through the anion exchange membrane 1-3 and flow into the metal composite silicon-based flowing anode slurry in the anode 1-2, forming a fluorine-enriched metal composite silicon-based flowing anode slurry.

[0081] The fluorine-enriched metal-composite silicon-based flowing anode slurry flows to the fluorine resource recovery unit 3 for fluorine ion separation and recovery. After the fluorine ions are removed from the fluorine slurry, it is returned to each semi-flowing electrochemical adsorption module through the electrode slurry preparation tank 2.

[0082] Application example:

[0083] This study treated the deep-treated effluent from a coal chemical plant. The initial fluoride ion concentration was 10-12 mg / L, and the pH was 6.2-6.6. A single-stage reactor with a reaction area of ​​7 cm x 7 cm was used. A DC voltage of 3 V was applied, the wastewater flow rate was 20 ml / min, and the hydraulic retention time was 2 h. The effluent fluoride ion concentration was 0.5-1.0 mg / L, with a removal rate of ≥88%, meeting the Class III fluoride discharge standard in the "Surface Water Environmental Quality Standard" GB3838-2002. Due to the high reactivity of fluoride ions, they react with silicon under normal conditions, while other halide ions, nitrate ions, and sulfate ions under the same conditions rarely react with silicon. Furthermore, the reaction generates H+, effectively reducing the influence of OH-, achieving selective adsorption of fluoride ions. After five adsorption-desorption cycle experiments, the fluoride ion removal rate consistently reached over 85.62%, demonstrating good electrode stability.

[0084] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0085] The above embodiments are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A device for simultaneous concentration and recovery of fluorides using multi-stage semi-fluid electrodes, characterized in that, It includes a fluoride deep removal unit (1), a fluorine resource recovery unit (3), and an electrode slurry preparation tank (2) that are connected in sequence. The fluoride deep removal unit (1) includes a sewage inlet, several semi-flow electrochemical adsorption modules and a purified water outlet connected in sequence. The semi-fluid electrochemical adsorption module includes: The anode (1-2), anion exchange membrane (1-3), ion migration region (1-5), and solid carbon material cathode (1-4) are arranged sequentially from left to right; several of the ion migration regions (1-5) are connected in sequence to form a flow channel, and the two ends of the flow channel are respectively connected to the sewage inlet and the purified water outlet; The anode (1-2) is provided with a cavity for containing a metal composite silicon-based flowing anode slurry. Several cavities are connected in series. The cavities are connected to the ion migration region (1-5) through the anion exchange membrane (1-3). The electric field formed by the energization between the solid carbon material cathode (1-4) and the anode (1-2) passes through the ion migration region (1-5). The outlet of the electrode slurry mixing tank (2) is connected to the inlet of the anode (1-2) located near the sewage inlet, and the inlet of the fluoride resource recovery unit (3) is connected to the outlet of the anode (1-2) located near the purified water outlet. The fluorine resource recovery unit (3) is provided with a slurry outlet (3-8) and a mud collection tank (3-6). The slurry outlet (3-8) is connected to the liquid inlet of the electrode slurry mixing tank (2), and the mud collection tank (3-6) is used to collect fluorine-containing products.

2. The apparatus for simultaneous concentration and recovery of fluorides using a multi-stage semi-fluid electrode according to claim 1, characterized in that: The flow channel formed by the sequential connection of several ion migration regions (1-5) has a continuous bent structure.

3. The apparatus for simultaneous concentration and recovery of fluorides using a multi-stage semi-fluid electrode according to claim 1, characterized in that: The solid carbon cathode (1-4) is made of a highly stable and corrosion-resistant carbon-based material.

4. The apparatus for simultaneous concentration and recovery of fluorides using a multi-stage semi-fluid electrode according to claim 1, characterized in that, The fluorine resource recovery unit (3) includes: Box; A slurry channel is provided at the top of the tank, and the inlet end of the slurry channel is connected to the outlet end of the anode (1-2) near the purified water outlet; A sedimentation zone (3-5) is located at the bottom of the tank, and a sludge collection trough (3-6) is located at the bottom of the sedimentation zone (3-5). A conductive filter membrane (3-3) is disposed at the bottom of the slurry channel, and the slurry channel is connected to the sedimentation zone (3-5) through the conductive filter membrane (3-3); An electrode plate (3-2) is disposed at the top of the slurry channel, and an electric field passing through the slurry channel is formed between the electrode plate (3-2) and the conductive filter membrane (3-3); The liquid addition section has its inlet end passing through the slurry channel, and its outlet end is located within the sedimentation zone (3-5).

5. The apparatus for simultaneous concentration and recovery of fluorides using a multi-stage semi-fluid electrode according to claim 4, characterized in that: Several baffles (3-7) are fixedly connected inside the slurry channel, and the several baffles (3-7) form a continuously bent slurry channel inside the slurry channel.

6. The apparatus for simultaneous concentration and recovery of fluorides using a multi-stage semi-fluid electrode according to claim 4, characterized in that: The liquid addition section includes a distributed microporous stirrer (3-4), which is fixed inside the tank. The inlet end of the distributed microporous stirrer (3-4) passes through the slurry channel, and the outlet end of the distributed microporous stirrer (3-4) is located in the sedimentation zone (3-5). The distributed microporous stirrer (3-4) is used to uniformly disperse the injected solution into the sedimentation zone (3-5).

7. The apparatus for simultaneous concentration and recovery of fluorides using a multi-stage semi-fluid electrode according to claim 4, characterized in that: The mud collection trough (3-6) has a conical structure.

8. The apparatus for simultaneous concentration and recovery of fluorides using a multi-stage semi-fluid electrode according to claim 1, characterized in that: A drive pump for driving the flow of metal composite silicon-based flowing anode slurry is provided between the electrode slurry preparation tank (2) and the fluoride deep removal unit (1).

9. A method for simultaneous concentration and recovery of fluorides, using the apparatus for simultaneous concentration and recovery of fluorides with a multi-stage semi-flow electrode as described in any one of claims 1-8, characterized in that, Includes the following steps: The solid carbon material cathode (1-4) and anode (1-2) of the same semi-flow electrochemical adsorption module are electrically connected to the cathode and anode of a DC power supply, respectively, to form a DC electric field between the solid carbon material cathode (1-4) and the anode (1-2); and the metal composite silicon-based flowing anode slurry fills and flows through each of the cavities. Fluorine-containing wastewater enters the flow channel through the wastewater inlet. In the ion migration zone (1-5), fluoride ions are caused by a DC electric field to pass through the anion exchange membrane (1-3) and flow into the metal composite silicon-based flowing anode slurry in the anode (1-2), forming a fluorine-enriched metal composite silicon-based flowing anode slurry. The fluorine-enriched metal-composite silicon-based flowing anode slurry flows to the fluorine resource recovery unit (3) for fluorine ion separation and recovery. After the fluorine ions are separated, the fluorine-enriched metal-composite silicon-based flowing anode slurry flows back to each of the semi-flowing electrochemical adsorption modules through the electrode slurry preparation tank (2).

Images