Preparation method of functionalized rare earth mineral-based autotrophic denitrification material and application thereof in purification of fluorine-rich black and odorous water body

Abstract

The application discloses a preparation method of a functionalized rare earth mineral-based autotrophic denitrification material and application of the material in purification of fluorine-rich black and odorous water bodies. The application adopts cement as a binder and a pH buffer, and uses waste fruit kernels as inner cores, and the waste fruit kernels have a carbon source slow-release effect; nano zero-valent iron composite material and nano zero-valent aluminum composite material are used as pore-forming agents, and are mixed with nano zero-valent sulfur composite material and nano rare earth composite material to prepare a porous rare earth / sulfur mineral biological carrier material. The composite material has a large specific surface area and high porosity. The porous rare earth / sulfur mineral biological carrier material is added into a fluorine-rich black and odorous water body which needs to be deeply purified, and is used as an electron donor in a filter tank of the fluorine-rich black and odorous water body to reduce nitrate nitrogen into nitrogen gas to achieve denitrification. Meanwhile, lanthanum ions, cerium ions, calcium ions, iron ions and aluminum ions are complexed with phosphate ions and fluorine ions in the black and odorous water body to simultaneously remove fluorine and phosphorus.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment, specifically relating to a method for preparing a functionalized rare earth mineral autotrophic denitrification material and its application in the purification of fluoride-rich black and odorous water bodies. Background Technology

[0002] Black and odorous water bodies refer to water bodies where a large amount of exogenous organic pollutants enter, causing the proliferation of heterotrophic microorganisms and algae, reducing dissolved oxygen and transforming the water into an anoxic or anaerobic state. Subsequently, the substances in the water undergo a series of physicochemical and biochemical reactions to produce blackening and odor-causing substances. The main cause of black and odorous water bodies is that after nitrogen and phosphorus enter the water body, autotrophic algae proliferate and cover the water surface, inhibiting the reoxygenation process. The decomposition of algal residues by anaerobic microorganisms releases a large amount of blackening and odor-causing substances. Pollutants such as iron and manganese that enter the water body combine with sulfides to form black, insoluble substances, causing the water body to turn black. On the other hand, organic pollutants, algae, and plant residues in the water are transferred to the bottom sediment through sedimentation, adsorption, and biochemical reactions. When encountering hydraulic scouring, human disturbance, or environmental changes, pollutants are released from the bottom sediment, causing water quality deterioration. In recent years, the rapid development of my country's integrated circuit, lithium battery, and photovoltaic industries has led to the presence of large amounts of ammonia nitrogen, phosphorus, and fluoride ions in black and odorous water bodies. Ammonia nitrogen and phosphorus are the main causes of eutrophication in water bodies, while fluoride ion concentrations exceeding 1 mg / L in water can lead to dental fluorosis and skeletal fluorosis in humans. Therefore, effectively removing ammonia nitrogen, phosphorus, and fluoride ions from polluted water bodies is an urgent and crucial public welfare project. Commonly used methods for purifying fluoride-rich polluted water bodies include sediment dredging, aeration and reoxygenation, biological methods, and chemical methods. However, these methods often cannot deeply treat polluted water bodies. A combination of chemical and biological methods is an effective way to deeply purify fluoride-rich polluted water bodies. Therefore, developing novel technologies for simultaneous nitrogen, phosphorus, and fluoride removal to achieve deep purification of polluted water bodies is imperative.

[0003] Sulfate autotrophic denitrification removes nitrogen by using sulfur autotrophic denitrifying bacteria and denitrifying thiobacilli as electron donors to reduce nitrate nitrogen to nitrogen gas under anaerobic conditions, achieving efficient nitrogen removal and reducing sludge production during denitrification. The packing material is the core component of a sulfur autotrophic denitrification filter. Currently, expanded clay is used as a carrier for sulfur autotrophic denitrifying bacteria and denitrifying thiobacilli, providing them with a growth space. However, current sulfur autotrophic denitrification packing materials suffer from drawbacks such as low open porosity, low biomass loading, high density, and slow sulfur mass transfer rate, hindering the widespread adoption of sulfur autotrophic denitrification biotechnology. Therefore, developing novel functionalized nano-mineral biological carrier materials to achieve efficient purification of fluoride-rich, black, and odorous water bodies is an urgent technical problem to be solved.

[0004] Currently, materials for the deep purification of fluoride-rich, black, and odorous water bodies have the following prominent problems:

[0005] 1. Currently, sulfur autotrophic denitrification materials suffer from slow denitrification rates in biochemical denitrification processes. Sulfur autotrophic denitrification materials include iron sulfide minerals (pyrite, pyrrhotite, and nanostructured pyrrhotite obtained from pyrolytic pyrite) and sulfur paste, all of which can be used as electron donors by sulfur autotrophic denitrifying bacteria and denitrifying thiobacterium for autotrophic denitrification. However, the main problem is the slow kinetic reaction rate and excessively long hydraulic retention time (>10 hours) in anaerobic biological filters, affecting the denitrification efficiency of the anaerobic biological filter reactor and imposing an economic burden on municipal wastewater treatment plants. This is because the interaction between iron sulfide minerals and microorganisms requires electron shuttles to transfer electrons during the metabolism of denitrifying thiobacterium. However, iron sulfide minerals are generally poorly soluble, leading to low denitrification efficiency. Although sodium acetate has a short hydraulic retention time, its high cost prevents large-scale application. Sulfur minerals, due to their dense structure, have low solubility (<5 μg / L), severely limiting their biodegradability. Therefore, how to improve the biochemical reaction rate of denitrifying thiobacilli and shorten the hydraulic retention time through the modification of packing materials is a key engineering and technical application problem that urgently needs to be solved.

[0006] 2. Regarding the large amount of H produced during the sulfur autotrophic denitrification process induced by iron sulfide minerals... + This causes pH instability within the anaerobic biological filter reactor, reducing the metabolic activity of sulfur autotrophic denitrifying bacteria and denitrifying thiobacilli, severely impacting denitrification efficiency. Currently, the most popular methods on the market are constructing sulfur autotrophic denitrification systems using elemental sulfur-limestone composite materials and sulfur-siderite composite materials. In these reaction systems, the H2 produced during the sulfur autotrophic denitrification process... + It can react with carbonate minerals to form soluble HCO3. - Carbonate and CO2 provide inorganic carbon sources for microbial denitrification. However, carbonate minerals do not directly participate in the denitrification process, and these combined packing materials occupy the volume of electron donors for denitrification, leading to increased treatment costs. Using a mixture of elemental sulfur and sawdust as packing material, while reducing sulfate formation in the reactor under synergistic effects, causes abrasion during mixing due to the different bulk densities of elemental sulfur and sawdust. This leads to material stratification during backwashing, affecting denitrification efficiency.

[0007] 3. Backwashing of sulfur autotrophic denitrification packing causes filter bed clogging. Currently, commercially available sulfur autotrophic denitrification packing is in powder or granular form. Due to biofilm aging, anaerobic biological filters require regular backwashing, which can cause packing material loss, leading to the shedding of the biofilm formed by sulfur autotrophic denitrifying bacteria and denitrifying thiobacilli. Anaerobic biofilm recovery takes a long time, affecting effluent quality during the recovery phase. Therefore, preventing packing clogging is a key issue for the widespread application of this technology. On the other hand, sulfur mineral particles have low strength and density; the strong water and air flow generated during backwashing can cause sulfur mineral wear, increasing sulfur mineral loss and depletion, and also causing sulfur mineral segregation. Currently, functional materials for denitrification, phosphorus removal, and fluoride removal suffer from small specific surface area, low porosity, and low biomass loading, resulting in low removal efficiency. Commercially available materials only focus on denitrification and phosphorus removal, neglecting fluoride removal. Therefore, the development of functionalized nanomaterials for simultaneous denitrification, phosphorus removal, and fluoride removal is urgently needed, representing a key engineering technology problem that needs to be solved for black and odorous water bodies. Summary of the Invention

[0008] This invention addresses the shortcomings of existing technologies by using cement as a binder and pH buffer, and discarded fruit pits as the core material, which also have a slow-release carbon source effect. Nano-zero-valent iron composite materials and nano-zero-valent aluminum composite materials are used as pore-forming agents, and are mixed and granulated with nano-sulfur composite materials and nano-rare earth composite materials to prepare porous rare earth / sulfur mineral biocarrier materials.

[0009] Nano-mineral resources consist of various nano-minerals, mineral nanoparticles, and non-nano-mineral particles. They are characterized by large reserves and environmental friendliness, and have been widely used in water purification in recent years. The main chemical components of natural rare earth minerals are cerium group rare earth elements and lanthanum group rare earth elements. Rare earth elements exist in an ion-adsorbed state between the particles of natural nano-minerals, possessing rich complex structures that form various rare earth oxidation states, exhibiting non-metallic chemical properties. In recent years, rare earth minerals have often been used as adsorbents in water pollution control. Bauxite, mainly composed of gibbsite and boehmite, is an important nano-mineral resource with large reserves. Aluminum is a metallic element with a 1s electron configuration. 2 2s 2 2p 6 3s 2 3p 1 When aluminum is in its free state, it has a valence of 0. When aluminum loses its three outermost electrons, it exhibits a valence of +3, so aluminum has valence states of 0 and +3. Limonite is a nano-mineral resource with goethite as its main component. It is abundant, environmentally friendly, and uses inexpensive raw materials. It contains metal elements with variable valences. Hydrogen reduction roasting can nanostructure limonite, transforming it into environmentally functional materials with multiple valence states.

[0010] Our research group discovered that nano-rare earth mineral composite materials obtained by hydrogen reduction roasting of rare earth minerals can effectively fix phosphate and fluoride ions in water. The roasting products obtained by hydrogen reduction roasting of bauxite and limonite also exhibit an affinity for fluoride and phosphate ions. Therefore, leveraging the synergistic effect of these natural nano-minerals is an effective method for purifying fluoride-rich, black, and odorous water bodies.

[0011] The present invention discloses a method for preparing functionalized rare earth mineral-based autotrophic denitrification materials, comprising the following steps:

[0012] Step 1: Crush the rare earth minerals and pass them through a 200-mesh sieve to obtain powder with a particle size of 0.075 mm. Then, calcine the powder at 100-1000℃ under a hydrogen atmosphere for 2-4 hours to obtain nano-rare earth mineral composite materials.

[0013] Step 2: Crush the limonite and pass it through a 200-mesh sieve to obtain powder with a particle size of 0.075 mm. Then, calcine it at 100-1000℃ in a hydrogen atmosphere for 2-4 hours to obtain nano-zero-valent iron composite material.

[0014] Step 3: Crush the bauxite and pass it through a 200-mesh sieve to obtain powder with a particle size of 0.075 mm. Then, calcine it at 100-1000℃ in a hydrogen atmosphere for 2-4 hours to obtain nano-zero-valent aluminum composite material.

[0015] Step 4: Crush the sulfur minerals and pass them through a 200-mesh sieve to obtain particles with a particle size of 0.075 mm. Then, calcine them at 100-1000℃ in a hydrogen atmosphere for 2-4 hours to obtain nano-sulfur composite materials.

[0016] Step 5: Mix the nano-sulfur composite material, nano-rare earth mineral composite material and cement in a mass ratio of 10:1-8:2-6 to obtain a mixture; crush the waste fruit pits to obtain 1-10mm particles, add the crushed waste fruit pit particles to the obtained mixture, with a mass ratio of mixture to fruit pits of 2:1, and spray a certain amount of water during the rolling granulation process to obtain composite particles.

[0017] Step 6: Add nano-zero-valent iron composite material and nano-zero-valent aluminum composite material to the obtained composite particles in a mass ratio of 10:2-5:1-7. Hydrogen gas is generated at this time, and a multi-level porous structure is rapidly formed. Allow it to cure naturally for 10-30 days at a humidity of 15-20℃. Spray a certain amount of water every day during the curing process to obtain porous nano-rare earth / sulfur biocarrier material.

[0018] The rare earth minerals contain lanthanum at a content of 25%-45% and cerium at a content of 40%-55%.

[0019] The particle size of the porous nano-rare earth / sulfur biocarrier material is 4-10 mm.

[0020] The present invention relates to the application of porous nano-rare earth / sulfur biocarrier material in the deep treatment of fluoride-rich black and odorous water bodies.

[0021] The porous nano-rare earth / sulfur biological carrier material is added to the anaerobic biological filter that requires deep purification of fluoride-rich black and odorous water. In the denitrification, phosphorus removal and fluoride removal filter, it acts as an electron donor to reduce nitrate nitrogen to nitrogen gas. At the same time, lanthanum ions, cerium ions, calcium ions, and aluminum ions complex with fluoride ions and phosphate ions in the fluoride-rich black and odorous water, so as to achieve the simultaneous removal of nitrogen, fluoride and phosphorus.

[0022] The porous nano-rare earth / sulfur biocarrier material serves as an anaerobic microbial carrier, an electron donor for anaerobic microorganisms, an electron shuttle for anaerobic microorganisms, and an adsorbent for fluoride and phosphorus removal. Nano-sulfur composite materials and nano-zero-valent iron composite materials can act as electron donors for microorganisms to reduce nitrate nitrogen, while the pits of discarded fruits serve as a slow-release carbon source. In situations where wastewater lacks carbon sources, this synergistic effect of sulfur autogenous denitrification achieves deep, simultaneous nitrogen, fluoride, and phosphorus removal.

[0023] This invention achieves sulfur autotrophic denitrification and nitrogen removal by adding porous nano-rare earth / sulfur biological carrier materials, while simultaneously enhancing the removal of fluoride and phosphorus. It can prevent the packing material from breaking during backwashing, thus solving the problem of existing urban sewage treatment plants lacking functional materials for treating fluoride-rich black and odorous water bodies, and achieving the goal of upgrading and transforming the technology.

[0024] The beneficial effects of this invention are reflected in the following aspects:

[0025] 1. This invention is the first to utilize rare earth minerals, limonite, sulfur minerals, and bauxite as raw materials, which are reduced and roasted under a hydrogen atmosphere to prepare nano-rare earth mineral composite materials, nano-sulfur composite materials, nano-zero-valent iron composite materials, and nano-zero-valent aluminum composite materials. The nano-zero-valent iron composite material and the nano-zero-valent aluminum composite material, due to their high activity, generate a large amount of hydrogen gas in an alkaline environment, forming a porous nano-rare earth / sulfur biocarrier material with a highly open pore structure. This provides space for microbial growth, promotes the activity of sulfur-autotrophic denitrifying bacteria and denitrifying thiobacilli, increases the bioload of microorganisms, and achieves deep purification of fluoride-rich black and odorous water bodies. Currently, actual fluoride-rich black and odorous water bodies contain complex competing ions, while commercially available defluorination and phosphorus removal materials are all single metals, easily affected by anions and cations. The porous nano-rare earth / sulfur biocarrier material of this invention is rich in nano-rare earth composite materials, nano-zero-valent calcium composite materials, cement hydration silicate, nano-sulfur composite materials, nano-zero-valent iron composite materials, and nano-zero-valent aluminum composite materials. The nanocomposite contains lanthanum ions, cerium ions, calcium ions, iron ions, aluminum ions, and other multi-metal ions, which can effectively and selectively remove fluoride ions and phosphate ions from water, with effluent fluoride ion and phosphate ion concentrations of less than 0.1 mg / L and 0.02 mg / L, respectively.

[0026] 2. Nano-sulfur composite materials and nano-zero-valent iron composite materials can serve as carbon sources for sulfur-autotrophic denitrifying bacteria and denitrifying thiobacteria, while waste fruit pits can act as slow-release carbon sources, promoting the activity of sulfur-autotrophic denitrifying bacteria and denitrifying thiobacteria. Porous nano-rare earth / sulfur biocarrier materials are preferentially metabolized by microorganisms during autotrophic deep denitrification, thus promoting microbial denitrification. The sulfur minerals, nano-zero-valent iron composite materials, and fruit pits present in the porous nano-rare earth / sulfur biocarrier materials can serve as electron transport mediators in sulfur-autotrophic denitrifying bacteria and denitrifying thiobacteria, or enhance protease synthesis as electron shuttles, thereby increasing the denitrification biological activity of sulfur-autotrophic denitrifying bacteria and denitrifying thiobacteria and significantly shortening the hydraulic retention time of filters for deep purification of fluoride-rich black and odorous water bodies.

[0027] 3. This invention adds porous nano-rare earth / sulfur biological carrier materials to the filter bed of fluoride-rich black and odorous water bodies, reducing energy consumption and costs. It has practical significance for wastewater with a low carbon / nitrogen ratio (<3). Compared with traditional heterotrophic denitrification, phosphorus removal, and defluorination processes using chemical agents, the cost is reduced by 90%. The porous nano-rare earth / sulfur biological carrier material can directly transfer electrons with microorganisms, effectively increasing the denitrification rate compared to sulfur minerals. The porous nano-rare earth / sulfur biological carrier material, whose main components are silicates after cement hydration, nano-rare earth mineral composite materials, nano-zero-valent iron composite materials, nano-sulfur composite materials, and nano-zero-valent aluminum composite materials, serves as a neutralizing material for acid produced during biochemical reactions. It effectively provides the inorganic carbon source and alkalinity required for the autotrophic metabolism of sulfur-autotrophic denitrifying bacteria and denitrifying thiobacilli, achieving deep purification of fluoride-rich black and odorous water bodies.

[0028] Chemical equation for the autotrophic denitrification reaction of porous nano-rare earth / sulfur biocarrier materials to produce acid (1):

[0029] (1) 2H₂O + 5S + 6NO₃ - =3N2+4H + +5SO4 2-

[0030] Chemical equations (2)-(6) for neutralizing acids using porous rare earth / sulfur biocarrier materials:

[0031] (2)3CaO·SiO2+H2O→CaO·SiO2·YH2O+Ca(OH)2

[0032] (3)2CaO·SiO2+H2O→CaO·SiO2·YH2O+Ca(OH)2

[0033] (4)3CaO·Al2O3+6H2O→3CaO·Al2O3·6H2O

[0034] 3CaO·Al2O3+3CaSO4·2H2O+26H2O→3CaO·Al2O3·3CaSO4·32H2O

[0035] 3CaO·Al2O3·3CaSO4·32H2O+2(3CaO·Al2O3)+4H2O→3(3CaO·Al2O3·CaSO4·12H2O)

[0036] (5)4CaO·Al2O3·Fe2O3+7H2O→3CaO·Al2O3·6H2O+CaO·Fe2O3·H2O

[0037] (6) CaCO3 + 2H+ + =Ca 2++CO2+H2O Attached Figure Description

[0038] Figure 1 Images of various materials are shown. Among them: (A) cherry pit; (B) pistachio pit; (C) almond pit; (D) loquat pit; (E) sulfur mineral; (F) cement; (G) limonite; (H) bauxite; (I) porous nano-rare earth / sulfur mineral biocarrier material.

[0039] Figure 2 This is the XRD pattern of cement. Figure 2 It can be seen that the characteristic diffraction peaks of cement are tricalcium aluminate (C3A), tetracalcium aluminoferrite (C4AF), tricalcium silicate (C3S), dicalcium silicate (C2S), gypsum dihydrate, anhydrite, and calcite.

[0040] Figure 3 XRD pattern of hydrated cement. Figure 3 It can be seen that the characteristic diffraction peaks of hydrated cement are CSH and Ca(OH)2. These chemical substances can neutralize the acids produced during the biochemical process of sulfur minerals.

[0041] Figure 4 The image shows the XRD pattern of the nano-zero-valent aluminum composite material prepared in Material Preparation Example 1. Figure 4 The characteristic diffraction peaks of elemental aluminum can be observed, indicating that the reduction roasting of bauxite under a hydrogen atmosphere produces nano-zero-valent aluminum composite materials.

[0042] Figure 5 XRD pattern of porous rare earth / sulfur biocarrier material for Example 1. Figure 5 It can be seen that the porous nano-rare earth / sulfur biocarrier material mainly consists of nano-lanthanum, nano-cerium, nano-zero-valent aluminum, nano-zero-valent iron, and nano-sulfur, indicating that the porous nano-rare earth / sulfur biocarrier material has been successfully synthesized.

[0043] Figure 6 This is an XRD pattern of a rare earth mineral. Figure 6 The characteristic diffraction peaks of lanthanum oxide and cerium oxide can be observed, indicating that rare earth minerals are mainly composed of lanthanum oxide and cerium oxide.

[0044] Figure 7 The image shows the XRD pattern of material preparation example 2. Figure 7 It can be seen that the main phase composition of the porous nano-rare earth / sulfur biocarrier material is nano-lanthanum, nano-cerium, nano-zero-valent aluminum, nano-zero-valent iron, nano-sulfur, etc., indicating that the porous nano-rare earth / sulfur biocarrier material has been successfully synthesized.

[0045] Figure 8 The XRD pattern is shown for material preparation example 3. Figure 8It can be seen that the main phase composition of the porous nano-rare earth / sulfur biocarrier material is nano-lanthanum, nano-cerium, nano-zero-valent aluminum, nano-phosphorus iron, nano-sulfur, etc., indicating that the porous nano-rare earth / sulfur biocarrier material was successfully synthesized.

[0046] Figure 9 The image shows the XRD pattern of material preparation example 4. Figure 9 It can be seen that the main phase composition of the porous nano-rare earth / sulfur biocarrier material is nano-lanthanum, nano-cerium, nano-zero-valent aluminum, nano-zero-valent iron, nano-sulfur, etc., indicating that the porous nano-rare earth / sulfur biocarrier material has been successfully synthesized.

[0047] Figure 10 The XRD pattern for material preparation example 5. Figure 10 It can be seen that the main phase composition of the porous nano-rare earth / sulfur biocarrier material is nano-lanthanum, nano-cerium, nano-zero-valent aluminum, nano-zero-valent iron, nano-sulfur, etc., indicating that the porous nano-rare earth / sulfur biocarrier material has been successfully synthesized.

[0048] Figure 11 The XRD pattern for material preparation example 6. Figure 11 It can be seen that the main phase composition of the porous nano-rare earth / sulfur biocarrier material is nano-lanthanum, nano-cerium, nano-zero-valent aluminum, nano-zero-valent iron, nano-sulfur, etc., indicating that the porous nano-rare earth / sulfur biocarrier material has been successfully synthesized.

[0049] Figure 12 SEM images of porous rare earth / sulfur biocarrier material from Example 1, where AI represents SEM images at different magnifications. Figure 12 It can be seen that its surface and interior have a porous petal-like morphology, with a macroporous structure, a large specific surface area and porosity. This structural characteristic can provide space for microorganisms to grow.

[0050] Figure 13 Material Preparation Example 2: SEM image of porous rare earth / sulfur nanomaterials used as biological carriers. (The image shows...) Figure 13 (A, B, C, E, F) It can be seen that there are porous petal-like morphologies on its surface and inside. This macroporous structure can provide space for microorganisms to grow. Figure 13 (D and N) are point scan energy dispersive spectroscopy (DSS) spectra of porous nano-rare earth / sulfur biocarrier material. As can be seen from the figure, the composite material mainly contains Mg, Al, Si, O and S elements, with O content of 61%, Si content of 22%, Mg content of 10%, Al content of 4% and S content of 3%. Figure 13(G, H, I, J, K, L, M) are surface scan images of the porous rare earth / sulfur biocarrier material. In Figure (G), the yellow particles represent the distribution trend of sulfur (S); in Figure (H), the green particles represent the distribution trend of silicon (Si); in Figure (I), the purple particles represent the distribution trend of magnesium (Mg); in Figure (J), the light green particles represent the distribution trend of al (Al); in Figure (K), the red particles represent the distribution trend of silicon (Si); in Figure (L), the light gray particles represent the distribution trend of calcium (Ca); and in Figure (M), the white particles represent the distribution trend of laium (La). The point scan and surface scan images of the porous rare earth / sulfur biocarrier material show inconsistent elemental distributions. This may be due to the uneven distribution of elements in natural nano-minerals and differences in their chemical composition, leading to uneven elemental distribution in the synthesized porous rare earth / sulfur biocarrier material. The above analysis shows that the porous nano-rare earth / sulfur biocarrier material is composed of elements such as Ca, Al, Mg, Si, S, La, and O, indicating that the porous nano-rare earth / sulfur biocarrier material has been successfully synthesized.

[0051] Figure 14 SEM image of porous rare earth / sulfur biocarrier material, Example 3. Figure 14 (A) It can be seen that its surface and interior have a porous, petal-like morphology, and this macroporous structure can provide space for microorganisms to grow. Figure 14 (B) is a point energy spectrum scan of the porous nano-rare earth / sulfur biocarrier material. As can be seen from the figure, the elemental composition of the composite material is Ca, Mg, Fe, Cl, C, O and Si. Figure 14 (C, D, E, F, G, H, I) are the surface scan energy dispersive spectroscopy (ESD) spectra of the porous rare earth / sulfur biocarrier material. Figure (C) shows the distribution trend of sulfur (S) in the yellow particles, Figure (D) shows the distribution trend of silicon (Si) in the green particles, Figure (E) shows the distribution trend of iron (Fe) in the orange-red particles, Figure (F) shows the distribution trend of aluminum (Al) in the red particles, Figure (G) shows the distribution trend of magnesium (Mg) in the light green particles, Figure (H) shows the distribution trend of ce (Ce) in the white particles, and Figure (I) shows the distribution trend of oxygen (O) in the purple particles. The point scan and surface scan spectra of the porous rare earth / sulfur biocarrier material show inconsistent elemental distributions. This may be due to the uneven distribution of elements in natural nano-minerals and differences in their chemical composition, leading to uneven elemental distribution in the synthesized porous rare earth / sulfur biocarrier material. Based on the analysis of the point scan and area scan images above, it can be seen that the porous nano-rare earth / sulfur biocarrier material is composed of elements such as Ca, Mg, Fe, Cl, C, Al, O, Si, S, and Ce.

[0052] Figure 15 SEM images of sulfur minerals, where AD represents SEM images of sulfur minerals at different magnifications. Figure 15 It can be seen that sulfur minerals have a small amount of nanoporous structure, which is because they are formed under natural geological conditions.

[0053] Figure 16 SEM images of the nano-zero-valent iron composite material, where AD represents SEM images of the nano-zero-valent iron composite material at different magnifications. Figure 16 It can be seen that it has a nanoporous structure. This is because the limonite is reduced and roasted in a hydrogen atmosphere to form a nanostructure. The composite material has a large porosity and high activity.

[0054] Figure 17 SEM images of nano-zero-valent aluminum composite materials, where AC represents SEM images of the nano-zero-valent aluminum composite materials at different magnifications. Figure 17 It can be seen that it has a nanoporous structure. This is because the bauxite is reduced and roasted in a hydrogen atmosphere to form a nanostructure. The composite material has a large porosity and high activity.

[0055] Figure 18 SEM images of rare earth minerals, where AC represents images of rare earth minerals at different magnifications. Figure 18 It can be seen that it has a dense structure, low porosity, and small specific surface area, which is because it was formed under natural geological conditions.

[0056] Figure 19 SEM images of nano-zero-valent rare earth mineral composite materials, where AC represents images of the nano-rare earth mineral composite materials at different magnifications. Figure 19 It can be seen that it has a porous layered structure with nanopores. This is because rare earth minerals are reduced and roasted in a hydrogen atmosphere, resulting in a large porosity and high activity.

[0057] Figure 20 SEM images of the nano-sulfur mineral composite material, where AB represents SEM images of the nano-sulfur mineral composite material at different magnifications. Figure 20 It can be seen that the nano-sulfur mineral composite material contains nanoparticles. These nanoparticles are nanostructured structures generated by calcining sulfur minerals under hydrogen. This nano-sulfur mineral composite material has high porosity and high activity. Detailed Implementation

[0058] The technical solution of the present invention will be further analyzed and explained through specific embodiments below.

[0059] Material Preparation Example 1

[0060] (1) The rare earth minerals, limonite, bauxite, and sulfur minerals were crushed and passed through a 200-mesh sieve to obtain rare earth mineral powder, limonite powder, bauxite powder, and sulfur mineral powder, respectively. The loquat kernels were crushed to obtain particles with a diameter of about 2 mm.

[0061] (2) Rare earth mineral powder, sulfur mineral powder, limonite powder and bauxite powder were calcined at 500°C and under a hydrogen atmosphere for 2 hours to obtain nano-rare earth mineral composite material, nano-sulfur composite material, nano-zero-valent iron composite material and nano-zero-valent aluminum composite material, respectively.

[0062] (3) Nano-zero-valent sulfur composite material, nano-rare earth mineral composite material and cement are mixed in a certain mass ratio of 10:5:2 to obtain the mixed material. Then, loquat kernels are added in a mass ratio of 2:1 to the mixed material, and the mixture is rolled and granulated. A certain amount of water is sprayed to obtain composite particles.

[0063] (4) Nano-zero-valent aluminum composite material and nano-zero-valent iron composite material were added to the obtained composite particles as pore-forming agents in a mass ratio of 10:2:1, generating H2. This rapidly generated a multi-level porous structure. After natural curing for 10 days, a porous nano-rare earth / sulfur biocarrier material was obtained. The specific surface area of ​​this composite material was 219 m². 2 / g, with a porosity of 93%.

[0064] Material Preparation Example 2

[0065] (1) The rare earth minerals, limonite, sulfur minerals and bauxite are crushed and passed through a 200-mesh sieve to obtain rare earth mineral powder, limonite powder, sulfur mineral powder and bauxite powder respectively.

[0066] (2) Rare earth mineral powder, sulfur mineral powder, limonite powder and bauxite powder were calcined at 600℃ and under hydrogen atmosphere for 3 hours to obtain nano rare earth mineral composite material, nano sulfur composite material, nano zero-valent iron composite material and nano zero-valent aluminum composite material.

[0067] (3) Mix nano-sulfur composite material, nano-rare earth mineral composite material and cement in a certain mass ratio of 10:3:2 to obtain the mixed material. Then add cherry pits in a mass ratio of 2:1 to the mixed material and cherry pits, roll granulation, and spray a certain amount of water to obtain composite particles.

[0068] (4) Nano-zero-valent aluminum composite material and nano-zero-valent iron composite material were added to the obtained composite particles as pore-forming agents in a mass ratio of 10:3:1, generating H2. This rapidly generated a multi-level porous structure. After natural curing for 15 days, a porous nano-rare earth / sulfur biocarrier material was obtained. The specific surface area of ​​this composite material was 308 m². 2 / g, with a porosity of 96%.

[0069] Material preparation example 3

[0070] (1) The rare earth minerals, limonite, sulfur minerals and bauxite are crushed and passed through a 200-mesh sieve to obtain rare earth mineral powder, limonite powder, bauxite powder and sulfur mineral powder; the pistachio kernels are crushed to obtain particles with a particle size of 3 mm.

[0071] (2) Rare earth mineral powder, limonite powder, sulfur mineral powder and bauxite powder were calcined at 700℃ and under hydrogen atmosphere for 4 hours to obtain nano rare earth mineral composite material, nano zero-valent iron composite material, nano sulfur composite material and nano zero-valent aluminum composite material.

[0072] (3) Mix nano-sulfur composite material, nano-rare earth mineral composite material and cement in a certain mass ratio of 10:1:2 to obtain the mixed material. Then add pistachio kernels in a mass ratio of 2:1 to the mixed material and pistachio kernels, roll granulation, and spray a certain amount of water to obtain composite particles.

[0073] (4) Nano-zero-valent aluminum composite material and nano-zero-valent iron composite material were added to the obtained composite particles as pore-forming agents in a mass ratio of 10:2:7, generating H2. This rapidly generated a multi-level porous structure. After natural curing for 17 days, a porous nano-rare earth / sulfur biocarrier material was obtained. The specific surface area of ​​this composite material was 211 m². 2 / g, with a porosity of 90%.

[0074] Material preparation example 4

[0075] (1) The rare earth minerals, limonite, sulfur minerals, and bauxite are crushed and passed through a 200-mesh sieve to obtain rare earth mineral powder, limonite powder, sulfur mineral powder, and bauxite powder; the peach shell is relatively large. The peach pit is crushed to obtain particles with a particle size of 4 mm;

[0076] (2) Rare earth mineral powder, sulfur mineral powder, limonite powder and bauxite powder were calcined at 800℃ and under hydrogen atmosphere for 4 hours to obtain nano rare earth mineral composite material, nano sulfur mineral material, nano zero-valent iron composite material and nano zero-valent aluminum composite material.

[0077] (3) Mix nano-sulfur mineral materials, nano-rare earth mineral composite materials and cement in a certain mass ratio of 10:3:6 to obtain the mixed material. Then add peach kernels in a mass ratio of 2:1 to the mixed material and peach kernels, roll granulation, and spray a certain amount of water to obtain composite particles.

[0078] (4) Nano-zero-valent aluminum composite material and nano-zero-valent iron composite material were added to the obtained composite particles as pore-forming agents in a mass ratio of 10:2:5, generating H2. This rapidly generated a multi-level porous structure. After natural curing for 19 days, a porous nano-rare earth / sulfur biocarrier material was obtained. The specific surface area of ​​this composite material was 334 m². 2 / g, with a porosity of 98%.

[0079] Material preparation example 5

[0080] (1) The rare earth minerals, limonite, sulfur minerals and bauxite are crushed and passed through a 200-mesh sieve to obtain rare earth mineral powder, limonite powder, sulfur mineral powder and bauxite powder.

[0081] (2) Rare earth mineral powder, sulfur mineral powder, limonite powder and bauxite powder were calcined at 900℃ and under hydrogen atmosphere for 4 hours to obtain nano rare earth mineral composite material, nano sulfur mineral material, nano zero-valent iron composite material and nano zero-valent aluminum composite material.

[0082] (3) Mix nano-sulfur mineral materials, nano-rare earth mineral composite materials and cement in a certain mass ratio of 10:8:3 to obtain the mixed material. Then add cherry pits in a mass ratio of 2:1 to the mixed material and cherry pits, roll granulation, and spray a certain amount of water to obtain composite particles.

[0083] (4) Nano-zero-valent aluminum composite material and nano-zero-valent iron composite material were added to the obtained composite particles as pore-forming agents in a mass ratio of 10:3:3, generating H2. This rapidly generated a multi-level porous structure. After natural curing for 18 days, a porous nano-rare earth / sulfur biocarrier material was obtained. The specific surface area of ​​this composite material was 378 m². 2 / g, with a porosity of 89%.

[0084] Material preparation example 6

[0085] (1) The rare earth minerals, limonite, sulfur minerals and bauxite are crushed and passed through a 200-mesh sieve to obtain rare earth mineral powder, limonite powder, sulfur mineral powder and bauxite powder; the loquat kernels are crushed to obtain particles with a particle size of about 3 mm.

[0086] (2) Rare earth mineral powder, sulfur mineral powder, limonite powder and bauxite powder were calcined at 1000℃ and under hydrogen atmosphere for 3 hours to obtain nano rare earth mineral composite material, nano zero-valent iron composite material, nano sulfur mineral material and nano zero-valent aluminum composite material.

[0087] (3) Mix nano-sulfur mineral materials, nano-rare earth mineral composite materials and cement in a certain mass ratio of 10:5:2 to obtain the mixed material. Then add loquat kernels in a mass ratio of 2:1 to the mixed material and loquat kernels, roll granulation, and spray a certain amount of water to obtain composite particles.

[0088] (4) Nano-zero-valent aluminum composite material and nano-zero-valent iron composite material were added to the obtained composite particles as pore-forming agents in a mass ratio of 10:5:4, generating H2. This rapidly generated a multi-level porous structure. After natural curing for 20 days, a porous nano-rare earth / sulfur biocarrier material was obtained. The specific surface area of ​​this composite material was 413 m². 2 / g, with a porosity of 97%.

[0089] Preparation of comparative materials

[0090] Comparative Example 1:

[0091] Rare earth mineral filler: Rare earth minerals are crushed to obtain particles with a diameter of 4-9 mm. The specific surface area of ​​this composite material is 12 m². 2 / g, with a porosity of 17%.

[0092] Comparative Example 2:

[0093] Sulfur paste granules: Sulfur paste is granulated into 4-9mm particles. The specific surface area of ​​this composite material is 0m². 2 / g, with a porosity of 3%.

[0094] Comparative Example 3:

[0095] Sulfur mineral particles: Sulfur minerals are crushed to obtain particles of 4-9 mm. The specific surface area of ​​this composite material is 0 m². 2 / g, with a porosity of 4%.

[0096] Comparative Example 4:

[0097] Pyrite particles: Pyrite is crushed to obtain particles of 4-9 mm. The specific surface area of ​​this composite material is 0 m². 2 / g, with a porosity of 2%.

[0098] Comparative Example 5:

[0099] Pyrrhotite particles: Pyrrhotite is crushed to obtain particles of 4-9 mm. The specific surface area of ​​this composite material is 0 m².2 / g, with a porosity of 9%.

[0100] Comparative Example 6:

[0101] Nanostructured pyrrhotite particles: Pyrite was crushed to obtain 4-9 mm particles, and then pyrolyzed at 700℃ for 3 hours under a nitrogen protective atmosphere. The specific surface area of ​​this composite material is 0 m². 2 / g, with a porosity of 8%.

[0102] Comparative Example 7:

[0103] Low-density zeolite aerated biological filter packing: Zeolite powder, cement, and polystyrene particles are granulated in a mass ratio of 7:3:1 and naturally cured for 20 days. The specific surface area of ​​this composite material is 13 m². 2 / g, with a porosity of 18%.

[0104] Comparative Example 8:

[0105] Commercially available sulfur-based autotrophic denitrification packing material has a specific surface area of ​​21 m². 2 / g, with a porosity of 15%.

[0106] Comparative Example 9:

[0107] Hematite-hematite composite pyrolysis: Pyrite and hematite were mixed in a mass ratio of 7:2 and pyrolyzed at 700℃ for 2 hours under nitrogen atmosphere. The specific surface area of ​​the composite material was 0 m². 2 / g, with a porosity of 27%.

[0108] Static systematic experiment:

[0109] Fifteen 500mL IV bottles were used as static test reactors. Simulated wastewater was prepared using sodium nitrate, sodium fluoride, and potassium dihydrogen phosphate, respectively. At this time, the NO3 in the water... - The concentrations of nitrogen (N) and phosphorus (P) were 70 mg / L, and the concentration of fluoride (F) was 10 mg / L. 200 mL of laboratory-prepared water was added to each vial. 1 g of the materials used in Examples 1-6 and Comparative Examples 1-9 were added to each of the 15 vials. Nitrogen gas was bubbled through a nitrogen cylinder for 30 min. Approximately 20 mL of anaerobic sludge rich in sulfur-autotrophic denitrifying bacteria and denitrifying thiobacilli was added to each vial. The vials were placed in a constant-temperature water bath shaker, with the water bath temperature set to 30℃-35℃ and the shaking speed to 60 r / min. The static shaking time was 30 days. Samples were taken daily and filtered through a 0.45 μm aqueous phase filter membrane. The total nitrogen, total phosphorus, and fluoride ion concentrations were then monitored.

[0110] As shown in Tables 1-3, the static experimental results of Material Preparation Examples 1-6 show that the removal efficiency of total nitrogen, total phosphorus and fluoride ions is higher. This is because, compared with Tables 4-6 (Comparative Examples 1-9), the porous nano-rare earth / sulfur biocarrier materials prepared in Material Preparation Examples 1-6 have higher activity, larger specific surface area and higher porosity.

[0111] Table 1. Static experiments on total nitrogen removal rate in material preparation examples 1-6

[0112]

[0113] Table 2. Fluoride ion removal rate in static experiments of material preparation examples 1-6

[0114]

[0115] Table 3. Static experiments on total phosphorus removal rate in material preparation examples 1-6

[0116]

[0117] Table 4 Comparative Examples 1-9: Static Experiments on Total Nitrogen Removal Rate

[0118]

[0119] Table 5 shows the fluoride ion removal rate in static experiments of Comparative Examples 1-9.

[0120]

[0121] Table 6 Comparative Examples 1-9: Phosphorus Removal Rate in Static Experiments

[0122]

[0123] Dynamic running experiment:

[0124] (1) Sodium nitrate, sodium fluoride and potassium dihydrogen phosphate were used to prepare fluoride-rich black and odorous water bodies, with nitrate nitrogen at 70 mg / L, fluoride ion concentration at 10 mg / L and phosphorus ion concentration at 1 mg / L.

[0125] (2) Fill the fluoride-rich black and odorous water body with a self-made reaction device, in which an anaerobic biological filter reactor simulating denitrification, defluorination and dephosphorization is made of plexiglass plastic with a diameter of 15 cm and a height of 2 m.

[0126] (3) The same mass (approximately 50 kg) of sample packing material was packed into the anaerobic biological filter reactor. The sample packing materials were material preparation examples 1-6 and comparative examples 1-9, respectively.

[0127] (4) Use a high-power peristaltic pump to inject anaerobic sludge rich in denitrifying bacteria and sulfur autotrophic denitrifying bacteria into the inlets at the bottom of the 15 anaerobic biological filter reactors.

[0128] (5) The water flowing out of the outlet of the 15 biological filter reactors is transported to the inlet by a peristaltic pump and the water is circulated according to a hydraulic retention time of 10h to promote the loading and reproduction of denitrifying bacteria and sulfur autotrophic denitrifying bacteria on the surface of material preparation examples 1-6 and comparative examples 1-9.

[0129] (6) Monitor the TN concentration at the inlet and outlet during the microbial biofilm formation process. Microbial biofilm formation is completed when the TN concentration in the water in the 15 biofilter reactors is <1 mg / L.

[0130] (7) After successful biofilm formation, a peristaltic pump is used to continuously feed water for anaerobic denitrification, defluorination and dephosphorization. The pump flow rate is adjusted to make the hydraulic residence time 1 hour. The system is run continuously for 70 days at an ambient temperature above 25°C, and the concentrations of total nitrogen, total phosphorus and fluoride ions in the effluent are monitored.

[0131] The dynamic experimental results show that Tables 7-9, which are material preparation examples 1-6, exhibit high removal efficiencies for total nitrogen, total phosphorus, and fluoride ions. This is because, compared to Tables 10-12, which are comparative examples 1-9, the porous nano-rare earth / sulfur biocarrier materials prepared in material preparation examples 1-6 have higher activity, larger specific surface area, and higher porosity.

[0132] Table 7. Material Preparation Examples 1-6: Dynamic Experiments on Total Nitrogen Removal Rate

[0133]

[0134] Table 8 shows the fluoride ion removal efficiency of dynamic experiments in material preparation examples 1-6.

[0135]

[0136] Table 9. Material Preparation Examples 1-6: Dynamic Experiments on Total Phosphorus Removal Efficiency

[0137]

[0138]

[0139] Table 10 compares the total nitrogen removal rate in dynamic experiments of Examples 1-9.

[0140]

[0141] Table 11 Comparison of Fluoride Ion Removal Efficiency in Dynamic Experiments of Examples 1-9

[0142]

[0143]

[0144] Table 12 Comparison of phosphorus removal efficiency in dynamic experiments of Examples 1-9

[0145]

Claims

1. A method for preparing a functionalized rare earth mineral-based autotrophic denitrification material, characterized in that... Includes the following steps: Step 1: Crush the rare earth minerals and pass them through a 200-mesh sieve, then calcine them under a hydrogen atmosphere to obtain nano-rare earth mineral composite materials. Step 2: Crush the limonite and pass it through a 200-mesh sieve, then roast it under a hydrogen atmosphere to obtain a nano-zero-valent iron composite material. Step 3: Crush the bauxite and pass it through a 200-mesh sieve, then calcine it under a hydrogen atmosphere to obtain nano-zero-valent aluminum composite material; Step 4: Crush the sulfur minerals and pass them through a 200-mesh sieve, then calcine them under a hydrogen atmosphere to obtain nano-zero-valent sulfur composite materials; Step 5: Mix the nano-zero-valent sulfur composite material, the nano-rare earth mineral composite material, and cement to obtain a mixture; crush waste fruit pits to obtain 1-10mm particles, add the crushed waste fruit pit particles to the obtained mixture, and spray a certain amount of water during the rolling granulation process to obtain composite particles. Step 6: Add nano-zero-valent iron composite material and nano-zero-valent aluminum composite material to the obtained composite particles. Hydrogen gas is generated at this time, and multi-level porous structure is rapidly formed. Natural curing for 10-30 days with a curing humidity of 15-20℃, and a certain amount of water is sprayed every day during curing to obtain porous nano-rare earth / sulfur biocarrier material. In steps 1-4, the roasting temperature is 100-1000℃ and the roasting time is 2-4 hours; In step 5, the nano-zero-valent sulfur composite material, the nano-rare earth mineral composite material, and cement are mixed in a mass ratio of 10:1-8:2-6; the mass ratio of the mixture to the fruit pit is 2:

1. In step 6, the mass ratio of the composite particles, the nano-zero-valent iron composite material, and the nano-zero-valent aluminum composite material is 10:2-5:1-7.

2. The preparation method according to claim 1, characterized in that: The particle size of the porous nano-rare earth / sulfur biocarrier material is 4-10 mm.

3. The application of porous nano-rare earth / sulfur biocarrier materials prepared by any one of the preparation methods in claims 1-2 in the deep treatment of fluoride-rich black and odorous water bodies.

4. The application according to claim 3, characterized in that: The porous nano-rare earth / sulfur biocarrier material is added to the anaerobic biological filter that requires deep purification of fluoride-rich black and odorous water. In the denitrification, phosphorus removal, and fluoride removal filter, it acts as an electron donor to reduce nitrate nitrogen to nitrogen gas. At the same time, lanthanum ions, cerium ions, calcium ions, iron ions, and aluminum ions complex with fluoride ions and phosphate ions in the fluoride-rich black and odorous water, achieving the simultaneous removal of nitrogen, fluoride, and phosphorus.

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