A method for treating fluorine-containing sludge

Abstract

The application provides a fluorine-containing sediment treatment method, which comprises the following steps: (1) screening and washing the fluorine-containing sediment, and then performing acid leaching and oxidation to leach out the combined fluorine in the fluorine-containing sediment and convert it into free fluorine; (2) performing adsorption on the fluorine-containing sediment treated in step (1) to remove the free fluorine in the sediment; and (3) performing centrifugal dewatering and composting on the fluorine-containing sediment obtained in step (2) to realize the treatment of the fluorine-containing sediment. Through the acid leaching, oxidation and adsorption fluorine removal process, the iron-manganese oxide combined fluorine and organic combined fluorine in the sediment can be effectively leached out into the liquid phase and adsorbed and enriched into the adsorption filler, and the sediment after the adsorption fluorine removal process can be composted to produce greening planting soil, thereby effectively blocking the migration and diffusion of fluorine pollution.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of environmental protection bottom mud treatment technology, in particular to a fluorine-containing bottom mud treatment method. BACKGROUND

[0002] Bottom mud is the sediment of wetland system such as rivers, lakes and seas, and is an important part of natural water areas. When the wetland is polluted, some pollutants are stored in the bottom mud through sedimentation or adsorption by particulate matter. Under appropriate conditions, the pollutants in the bottom mud may be released, becoming a secondary pollution source. Fluorine is a strong oxidizing substance and is one of the indispensable trace elements for life but cannot be too much. High content of fluorine in the human body is harmful to teeth and bones, can form enamel mottling and fluorosis, and cause anemia, leukopenia and other symptoms.

[0003] The bottom mud aerobic composting technology is a derivative method of bottom mud bioremediation, which utilizes the degradation of microorganisms to degrade the contaminated organic matter into inorganic matter during the composting process. The conventional aerobic composting technology has no targeted disposal method for fluorine in fluorine-containing bottom mud. Direct aerobic composting of fluorine-containing bottom mud not only leads to excessive fluorine content in the compost product, but also may affect the growth of microorganisms and the degradation efficiency of pollutants during the composting process. Therefore, it is urgent to develop a green and efficient fluorine-containing bottom mud compost pretreatment process for fluorine-containing bottom mud to reduce the total fluorine mass fraction in the bottom mud compost and inhibit the migration and diffusion of fluorine pollution. SUMMARY

[0004] The purpose of the present application is to provide a green and efficient fluorine-containing bottom mud treatment method to solve the problem of excessive total fluorine mass fraction in the aerobic composting process of fluorine-containing bottom mud.

[0005] To achieve the above-mentioned purpose, the technical scheme adopted by the present application to solve its technical problems is:

[0006] (1) The fluorine-containing bottom mud is screened and washed, and then subjected to acid leaching and oxidation to leach out the combined fluorine in the fluorine-containing bottom mud and convert it into free fluorine;

[0007] (2) The fluorine-containing bottom mud treated in step (1) is further subjected to adsorption to remove the free fluorine in the bottom mud;

[0008] (3) The fluorine-containing bottom mud obtained in step (2) is further subjected to centrifugal dewatering and composting treatment to realize the treatment of the fluorine-containing bottom mud.

[0009] Further, in step (1), the specific steps of acid leaching and oxidation include:

[0010] The fluorine-containing sludge after screening and washing is added into a composite oxidizing agent for acid leaching and oxidation, so that the iron-manganese oxide combined fluorine and organic combined fluorine in the solid phase of the sludge are leached out and converted into free fluorine in the liquid phase; the adding amount of the composite oxidizing agent is 3-5% of the volume of the sludge; and the treatment time of the acid leaching and oxidation is 1-0-4 minutes.

[0011] The main role of the acid leaching and oxidation of the composite oxidizing agent is to extract the combined fluorine in the sludge from the solid phase into the free fluorine ion in the liquid phase through complex decomposition reaction and oxidation-reduction reaction. The iron-manganese oxide combined fluorine is the fluorine combined by adsorption with the iron-manganese oxide particles as the core. By adding 25% dilute hydrochloric acid into the sludge, the complex decomposition reaction occurs between the dilute hydrochloric acid and the iron-manganese oxide particles, the solid phase structure of the iron-manganese oxide particles is destroyed, and thus the adsorbed fluorine is dissolved into the liquid phase in the form of ion. The organic combined fluorine is the fluorine combined by adsorption with the humus and organic particles in the sludge as the core. By adding 20% hydrogen peroxide into the sludge, the oxidation-reduction reaction occurs between the hydrogen peroxide and the humus and organic particles, the molecular structure of the humus and organic particles is effectively destroyed, and thus the adsorption of fluorine is reduced, and the fluorine is dissolved into the liquid phase in the form of ion.

[0012] The composite oxidizing agent is compounded by an acid and an oxidizing agent, and the volume ratio of the acid to the oxidizing agent is 1-3:1; the mass fraction of the acid is 10-30%, and the mass fraction of the oxidizing agent is 10-30%.

[0013] Further, the acid includes dilute hydrochloric acid, dilute nitric acid, dilute sulfuric acid or acetic acid; and the oxidizing agent includes hydrogen peroxide solution, sodium hypochlorite or potassium permanganate.

[0014] Further, the composite oxidizing agent is compounded by dilute hydrochloric acid and hydrogen peroxide; the mass fraction of the hydrochloric acid is 25%, the mass fraction of the hydrogen peroxide is 20%, and the hydrochloric acid and the hydrogen peroxide are compounded according to the volume ratio of 2:1; the 25% mass fraction dilute hydrochloric acid and the 20% mass fraction hydrogen peroxide have weak volatility, strong stability and easy storage; in the composite oxidizing agent compounded according to the ratio of 2:1, the concentration of the hydrochloric acid is about 16.7%, and the concentration of the hydrogen peroxide is about 6.7%; under the concentration conditions, the oxidation-reduction reaction or decomposition reaction does not occur between the two substances; meanwhile, under the ratio and concentration conditions, the hydrochloric acid helps to improve the oxidation reaction efficiency of the hydrogen peroxide on the organic matter in the sludge; meanwhile, the composite oxidizing agent compounded by the dilute hydrochloric acid and the hydrogen peroxide is colorless, has no irritating odor, has high safety in use, has high acid leaching and oxidation efficiency, and does not introduce nitrogen, sulfur and other difficult-to-remove pollutants.

[0015] Further, the fluorine-containing sludge after screening and washing is added into a composite oxidizing agent and placed in an acid leaching and oxidation device for acid leaching and oxidation.

[0016] The acid leaching oxidation device includes a first shell, a first feed inlet sequentially arranged on the first shell, a first polytetrafluoroethylene liner arranged inside the shell, a Venturi jet dosing device, a first support leg, a first discharge port, a first air inlet, a first dosing port, a first impeller, a first rotating shaft, a first manhole, and a first rotary motor. A composite oxidant is added to the fluorine-containing sediment in the acid leaching oxidation device through the Venturi jet dosing device. At the same time, the high-speed fluid shear force generated by the Venturi jet dosing device achieves full mixing of the composite oxidant and the sediment. The mixing is further achieved by a stirring device.

[0017] Furthermore, the specific steps for adsorption in step (2) include:

[0018] The fluoride-containing bottom mud that has been acid-leached and oxidized is placed in an adsorption defluorination device for adsorption defluorination, and the reaction time is 30-50 minutes.

[0019] The adsorption and defluorination device includes a carbon steel shell, a second inlet arranged sequentially on the carbon steel shell, a second polytetrafluoroethylene liner arranged inside the carbon steel shell, a second support leg, a second outlet, a second manhole, a second rotary motor, a second rotating shaft connected to the second rotary motor, a component connecting device connected to the second rotating shaft, a component fixing device connected to the component connecting device, and an adsorption component connected to the component fixing device.

[0020] The adsorption component is an adsorption bag, which is composed of an inner layer, a middle layer and an outer layer, and the inner layer is filled with adsorption filler.

[0021] Furthermore, the adsorption filler is made of calcium chloride, fly ash and coal gangue particles with a particle size of 5-10 mm in a mass ratio of 1-1:2-5:5-8; the bag body is woven from meltblown nonwoven fabric with a pore size of 2-3 μm.

[0022] Furthermore, in step (1), the specific steps for screening and washing include:

[0023] Fluorine-containing sediment is screened through a grid or mechanical screen to separate animal and plant remains, as well as plastic and fabric debris. Biodegradable animal and plant remains are retained, mixed with aquatic plants, crushed, and used as composting feedstock. Non-biodegradable plastic and fabric debris are dehydrated and disposed of by waste treatment units.

[0024] The fluorinated sediment, after initial screening by a mechanical bar screen, is conveyed to a vibrating screen for further screening to separate large particles of gravel and sand. These gravel and sand are then stored as raw materials for the preparation of building materials. The fluorinated sediment, after being screened by the vibrating screen, is conveyed to a sand washing machine for further separation of small-diameter fine sand. This fine sand is then stored as raw materials for the preparation of building materials.

[0025] Furthermore, the specific steps for centrifuging and dewatering the fluoride-containing sediment obtained in step (2) include:

[0026] The bottom sludge after adsorption and defluorination is transported to a sludge-water separation device. After concentration and pressure filtration, wet sludge cake and filtrate with a water content of 55% to 65% are obtained. The filtrate is then discharged after being treated by a wastewater treatment device.

[0027] Furthermore, the specific steps for composting the fluoride-containing sediment obtained in step (2) include:

[0028] The wet mud cake with a moisture content of 55% to 65% is mixed with urban sewage sludge, auxiliary materials and biological agents, and subjected to aerobic composting treatment to obtain greening planting soil; the perfluorinated mass fraction of the greening planting soil is less than 10 mg / kg.

[0029] The beneficial effects of this invention are as follows:

[0030] (1) High-efficiency defluorination of sediment: This invention targets fluoride-containing sediment with a perfluoride mass fraction of up to 500 mg / kg. Through acid leaching, oxidation and adsorption defluorination processes, it can effectively leach iron and manganese oxide-bound fluoride and organic-bound fluoride in the sediment into the liquid phase and adsorb and enrich them into the adsorption packing. After the sediment is defluorinated by adsorption, the perfluoride mass fraction in the greening planting soil produced after composting is reduced to below 10 mg / kg, effectively blocking the migration and diffusion of fluoride pollution.

[0031] (2) Resource recycling: A systematic resource recycling process is formed for various components mixed in the sediment. Large pieces of animal and plant remains mixed in the sediment are crushed and mixed with regularly harvested aquatic plants for crushing and conditioning, and then prepared as composting auxiliary materials to provide organic matter supplementation for the composting process. Inorganic components such as gravel and sand mixed in the sediment are screened and washed and can be used as building materials. The adsorption packing used in the fluoride removal section includes solid waste components such as fly ash and coal gangue, which fully realizes waste utilization. After the adsorption packing is saturated, it is enriched with fluorine and can also be used as building materials after treatment, which not only realizes waste recycling, but also inhibits the spread of fluoride pollution. Attached Figure Description

[0032] Figure 1 This is a process flow diagram of the fluoride-containing sediment treatment method of the present invention;

[0033] Figure 2 This is a schematic diagram of the structure of the acid leaching and oxidation apparatus of the present invention;

[0034] Figure 3 This is a schematic diagram of the adsorption and defluorination device of the present invention.

[0035] Figure label:

[0036] 1-1: First feed inlet; 1-2: First housing; 1-3: First PTFE liner; 1-4: Venturi jet dosing device; 1-401: First air inlet; 1-402: First dosing port; 1-5: First rotary motor; 1-6: First shaft; 1-7: First blade; 1-8: First manhole; 1-9: First support leg; 1-10: First discharge port; 2-1: Second feed inlet; 2-2: Carbon steel housing; 2-3: Second PTFE liner; 2-4: Second rotary motor; 2-5: Second shaft; 2-6: Component connecting device; 2-7: Adsorption component; 2-8: Component fixing device; 2-9: Second discharge port; 2-10: Second manhole; 2-11: Second support leg. Detailed Implementation

[0037] 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 only for explaining the invention and are not intended to limit the invention; that is, the described embodiments are merely some embodiments of the invention, and not all embodiments.

[0038] Therefore, the following detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0039] It should be noted that relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes the element.

[0040] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0041] Example 1

[0042] According to one embodiment of the present invention, such as Figure 1As shown, a method for treating fluoride-containing sediment is provided. This method combines a series of technologies, including stirring, screening, acid leaching, oxidation, adsorption, concentration, pressure filtration, and composting, to achieve the harmless and resource-based disposal of the fluoride-containing sediment. Fluorides are separated for use in manufacturing building materials, and the perfluoride content in the compost products is reduced to below 10 mg / kg. Specifically, the method includes the following steps:

[0043] Step 1: Vacuum suction mechanical dredging is used to obtain fluoride-containing wetland sediment with a water content of over 95%, which is then discharged into a mixing tank for thorough mixing; the perfluoride mass fraction in the fluoride-containing wetland sediment is over 500 mg / kg.

[0044] Step 2: The fluoride-containing wetland sediment, after being stirred and mixed, is screened and washed through a grid, mechanical bar screen, vibrating screen, and sand washing machine to obtain mud, fine sand, gravel, and animal and plant residues. The gravel and fine sand are further sorted and washed and used as building materials. The animal and plant residues are further crushed and used as aerobic composting additives.

[0045] Step 3: The fluorine-containing sludge, after screening and washing, is transported to the acid leaching oxidation unit via a sludge pump. Hydrochloric acid-hydrogen peroxide composite oxidant is added to the unit for acid leaching and oxidation. The amount of hydrochloric acid-hydrogen peroxide composite oxidant added is 3% to 5% of the sludge volume. This process extracts the iron-manganese oxide-bound fluorine and organic-bound fluorine in the solid phase of the sludge and converts them into free fluorine in the liquid phase.

[0046] The composite oxidant is composed of a low concentration of acid and oxidant. In this embodiment, it is a hydrochloric acid-hydrogen peroxide composite oxidant. The composite oxidant composed of dilute hydrochloric acid and hydrogen peroxide is colorless, has no irritating odor, is highly safe to use, has high acid leaching oxidation efficiency, and does not introduce pollutants such as nitrogen and sulfur that are difficult to remove.

[0047] The hydrochloric acid-hydrogen peroxide composite oxidant is prepared by mixing 25% by mass dilute hydrochloric acid and 20% by mass hydrogen peroxide in a volume ratio of 2:1. At this concentration, the 25% by mass dilute hydrochloric acid and 20% by mass hydrogen peroxide exhibit low volatility, high stability, and are easy to store. In the composite oxidant prepared in a 2:1 ratio, the hydrochloric acid concentration is approximately 16.7%, and the hydrogen peroxide concentration is approximately 6.7%. Under these concentration conditions, the two substances will not undergo redox reactions or decomposition reactions. Furthermore, under these ratio and concentration conditions, hydrochloric acid helps to enhance the oxidation efficiency of hydrogen peroxide on organic matter in the sediment.

[0048] The main mechanism of action of composite oxidants is to extract bound fluorine from the solid phase in sediment through metathesis and redox reactions, transforming it into free fluoride ions in the liquid phase. Iron-manganese oxide bound fluorine is fluorine bound to iron-manganese oxide particles through adsorption. Adding 25% dilute hydrochloric acid to the sediment triggers a metathesis reaction with the iron-manganese oxide particles, disrupting their solid-phase structure and allowing the adsorbed fluorine to redissolve in ionic form into the liquid phase. Organic bound fluorine is fluorine bound to humic and organic matter particles in the sediment through adsorption. Adding 20% ​​hydrogen peroxide to the sediment triggers a redox reaction with these particles, effectively disrupting their molecular structure and reducing their adsorption, allowing the fluorine to redissolve in ionic form into the liquid phase.

[0049] According to one embodiment of this application, such as Figure 2 As shown, the acid leaching oxidation device consists of a first housing 1-2, a first feed port 1-1 sequentially arranged on the first housing 1-2, a first polytetrafluoroethylene liner 1-3 arranged inside the housing, a Venturi jet dosing device 1-401, a first support leg 1-9, a first discharge port 1-10, a first air inlet 1-401, a first dosing port 1-402, a first impeller 1-7, a first rotating shaft 1-6, a first manhole 1-8, and a first rotary motor 1-5. The designed reaction residence time is not less than 15 minutes.

[0050] Step four: After acid leaching and oxidation, the fluorine-containing sludge is transported to the adsorption and defluorination device via a sludge pump to fully adsorb and remove free fluorine from the liquid phase of the sludge.

[0051] like Figure 3 As shown, the adsorption and defluorination device consists of a carbon steel shell 2-2, a second inlet 2-1 sequentially arranged on the carbon steel shell 2-2, a second polytetrafluoroethylene liner 2-3 arranged inside the carbon steel shell, a second support leg 2-11, a second outlet 2-9, a second manhole 2-10, a second rotary motor 2-4, a second rotating shaft 2-5 connected to the second rotary motor 2-4, a component connecting device 2-6 connected to the second rotating shaft 2-5, a component fixing device 2-8 connected to the component connecting device 2-6, and an adsorption component 2-7 connected to the component fixing device 2-8. The designed residence time is not less than 30 minutes.

[0052] The adsorption component adopts an adsorption bag structure. The bag body is made of meltblown nonwoven fabric with a pore size of 2-3μm, and is composed of three layers, with the innermost layer of the bag body filled with adsorption filler.

[0053] The adsorption filler is made by compounding calcium chloride, fly ash and coal gangue particles with a particle size of 5-10 mm in a mass ratio of 1:2:5.

[0054] After the adsorption filler is fully adsorbed and saturated, it is mixed with the crushed stone and fine sand mentioned in step two to prepare building materials.

[0055] Step 5: The bottom sludge after adsorption and defluorination is transported to a mud-water separation device, and after concentration and pressure filtration, wet mud cake and filtrate with a water content of 55% to 65% are obtained.

[0056] The filtrate is discharged after being treated by a wastewater treatment device to meet the standards.

[0057] Step 6: The wet mud cake with a moisture content of 55% to 65% is mixed with urban sewage sludge, auxiliary materials, and biological agents for aerobic composting to produce green planting soil.

[0058] The auxiliary material is made by mixing and crushing the animal and plant residues mentioned in step two with aquatic plants harvested regularly in the wetland. The particle size of the auxiliary material is 30-50mm.

[0059] The perfluoride content in the greening planting soil is less than 10 mg / kg.

[0060] Example 2

[0061] According to one embodiment of the present invention, such as Figure 1 As shown, a method for treating fluoride-containing sediment is provided. This method combines a series of technologies, including stirring, screening, acid leaching, oxidation, adsorption, concentration, pressure filtration, and composting, to achieve the harmless and resource-based disposal of the fluoride-containing sediment. Fluorides are separated for use in manufacturing building materials, and the perfluoride content in the compost products is reduced to below 10 mg / kg. Specifically, the method includes the following steps:

[0062] Vacuum suction dredging machinery uses a mechanical arm to agitate and a suction pipe to pump fluoride-containing wetland sediment into a mixing tank, where rotating blades thoroughly mix the fluoride-containing wetland sediment.

[0063] The mixed fluoride-containing wetland sediment is transported to the mechanical screen well through the bottom pipe of the mixing tank. The mechanical screen separates large pieces of animal and plant remains, as well as plastics, fabrics and other debris. The biodegradable animal and plant remains are retained, mixed with the regularly harvested aquatic plants from the wetland, crushed and used as composting feedstock. The non-biodegradable plastics, fabrics and other debris are dehydrated and sent to the waste disposal unit for disposal.

[0064] After initial screening by mechanical bar screen, the fluorine-containing wetland sediment is transported to a vibrating screen, where large particles of gravel and sand are further screened out. The gravel and sand are retained as raw materials for the preparation of building materials.

[0065] After being screened by a vibrating screen, the fluorine-containing wetland sediment is transported to a sand washing machine, where it is further separated into small-diameter fine sand. The fine sand is retained as raw material for the preparation of building materials.

[0066] After being sorted by the sand washing machine, the fluorine-containing wetland sediment is transported to the acid leaching and oxidation unit by the sludge pump for acid leaching and oxidation treatment;

[0067] like Figure 2 As shown, the acid leaching oxidation device consists of a first housing 1-2, a first feed inlet 1-1 sequentially arranged on the first housing 1-2, a first polytetrafluoroethylene liner 1-3 arranged inside the housing, a Venturi jet dosing device 1-401, a first support leg 1-9, a first discharge port 1-10, a first air inlet 1-401, a first dosing port 1-402, a first impeller 1-7, a first rotating shaft 1-6, a first manhole 1-8, and a first rotary motor 1-5. The designed reaction residence time is not less than 15 seconds. Minutes; 3% to 5% of the volume of hydrochloric acid-hydrogen peroxide composite oxidant is added to the fluoride-containing wetland sediment in the acid leaching oxidation device through the Venturi jet dosing device 1-401; the hydrochloric acid-hydrogen peroxide composite oxidant is prepared by mixing 25% by mass of dilute hydrochloric acid and 20% by mass of hydrogen peroxide in a volume ratio of 2:1; the hydrochloric acid-hydrogen peroxide composite oxidant is fully mixed with the sediment by means of the high-speed fluid shear force generated by the Venturi jet dosing device, and further stirred and mixed by the stirring device;

[0068] After acid leaching and oxidation treatment, the fluorine-containing wetland sediment enriched in iron-manganese oxide-bound fluorine and organic-bound fluorine in the solid phase is extracted into the liquid phase and becomes free fluorine. The acid-leached and oxidized fluorine-containing wetland sediment is then transported to an adsorption defluorination device for adsorption defluorination treatment.

[0069] like Figure 3 As shown, the adsorption and defluorination device comprises a carbon steel shell 2-2, a second inlet 2-1 sequentially arranged on the carbon steel shell 2-2, a second polytetrafluoroethylene liner 2-3 arranged inside the carbon steel shell, a second support leg 2-11, a second outlet 2-9, a second manhole 2-10, a second rotary motor 2-4, a second rotating shaft 2-5 connected to the second rotary motor 2-4, a component connecting device 2-6 connected to the second rotating shaft 2-5, a component fixing device 2-8 connected to the component connecting device 2-6, and an adsorption component 2-7 connected to the component fixing device 2-8. The design residence time is no less than 30 minutes. Adsorption components 2-7 employ an adsorption bag structure. The bag body is made of meltblown nonwoven fabric with a pore size of 2-3 μm, composed of three layers, with the innermost layer filled with adsorption packing material. The adsorption packing material is made of calcium chloride, fly ash, and coal gangue particles with a particle size of 5-10 mm in a mass ratio of 1:2:5. The fly ash and coal gangue particles in the adsorption packing material contain CaO, MgO, and other components, which react with the hydrochloric acid remaining after acid leaching and oxidation treatment of the bottom sediment, increasing the pH value of the bottom sediment liquid phase and generating CaO. 2+ Mg 2+The adsorption packing material, along with calcium chloride in the adsorption packing, combines with free fluorine in the liquid phase of the sediment to form solid precipitates such as CaF2 and MgF2. These precipitates are deposited and adsorbed into the porous structure of fly ash and coal gangue particles, thus removing fluorine. The adsorption packing material, after being fully adsorbed and saturated, is enriched with free fluorine in the sediment and can be used as a raw material for the preparation of building materials after being discarded.

[0070] After defluorination, the sediment is transported to a thickening unit to reduce its moisture content to about 90%, and then to a high-pressure plate and frame filter press to further reduce its moisture content to about 65%. The clear liquid and filtrate produced by sediment thickening and filtration are transported to a wastewater treatment plant and discharged after treatment to meet standards. The sediment after thickening and filtration is transported to an aerobic composting unit, where it is fully mixed with municipal sewage sludge, biological agents, and composting additives in a specific ratio for aerobic composting. The aerobic compost product is greening planting soil, in which the perfluorinated content is reduced to below 10 mg / kg.

[0071] The above content is merely an example and illustration of the structure of the present invention. Any modifications or additions to the specific embodiments described, or substitutions made by those skilled in the art without creative effort, shall still fall within the scope of protection of this patent.

Claims

1. A method for treating fluoride-containing sediment, characterized in that, Includes the following steps: (1) The fluorine-containing sediment is screened, washed, and then acid-leached and oxidized to extract the bound fluorine in the fluorine-containing sediment and convert it into free fluorine; (2) The fluorine-containing sediment treated in step (1) is then adsorbed to remove the free fluorine in the sediment; (3) Then, the fluorine-containing sediment obtained in step (2) is centrifuged and dehydrated, and then composted to achieve the treatment of the fluorine-containing sediment; In step (1), the specific steps for acid leaching and oxidation include: The fluorine-containing sludge, after screening and washing, is transported to the acid leaching oxidation unit by a sludge pump. Hydrochloric acid-hydrogen peroxide composite oxidant is added to the unit for acid leaching and oxidation. The amount of hydrochloric acid-hydrogen peroxide composite oxidant added is 3% to 5% of the sludge volume. The fluorine in the iron-manganese oxide bound state and organic bound state in the sludge solid phase is leached out and converted into free fluorine in the liquid phase. The specific steps for adsorption in step (2) include: The fluoride-containing bottom mud that has been acid-leached and oxidized is placed in an adsorption defluorination device for adsorption defluorination, and the reaction time is 30-50 minutes. The adsorption and defluorination device includes a carbon steel shell, a second inlet arranged sequentially on the carbon steel shell, a second polytetrafluoroethylene liner arranged inside the carbon steel shell, a second support leg, a second outlet, a second manhole, a second rotary motor, a second rotating shaft connected to the second rotary motor, a component connecting device connected to the second rotating shaft, a component fixing device connected to the component connecting device, and an adsorption component connected to the component fixing device. The adsorption component is an adsorption bag, which is composed of an inner layer, a middle layer and an outer layer, and the inner layer is filled with adsorption filler. The adsorption filler is made of calcium chloride, fly ash and coal gangue particles with a particle size of 5-10 mm in a mass ratio of 1:2-5:5-8; the bag body is woven from meltblown nonwoven fabric with a pore size of 2-3 μm.

2. The method for treating fluoride-containing sediment according to claim 1, characterized in that, In step (1), the specific steps for screening and washing include: Fluorine-containing sediment is screened through a grid or mechanical screen to separate animal and plant remains, as well as plastic and fabric debris. Biodegradable animal and plant remains are retained, mixed with aquatic plants, crushed, and used as composting feedstock. Non-biodegradable plastic and fabric debris are dehydrated and disposed of by waste treatment units. The fluorinated sediment, after preliminary screening by mechanical bar screen, is conveyed to a vibrating screen to separate large particles of gravel and sand. The gravel and sand are retained as raw materials for the preparation of building materials. The fluorinated sediment after screening by the vibrating screen is conveyed to a sand washing machine to separate small-diameter fine sand. The fine sand is retained as raw materials for the preparation of building materials.

3. The method for treating fluoride-containing sediment according to claim 1, characterized in that, The specific steps for centrifuging and dewatering the fluoride-containing sediment obtained in step (2) include: The bottom sludge after adsorption and defluorination is transported to a sludge-water separation device. After concentration and pressure filtration, wet sludge cake and filtrate with a water content of 55% to 65% are obtained. The filtrate is then discharged after being treated by a wastewater treatment device.

4. The method for treating fluoride-containing sediment according to claim 3, characterized in that, The specific steps for composting the fluoride-containing sediment obtained in step (2) include: The wet mud cake with a moisture content of 55%~65% is mixed with urban sewage sludge, auxiliary materials and biological agents, and subjected to aerobic composting treatment to obtain greening planting soil; the perfluorinated mass of the greening planting soil is less than 10mg / kg.

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