Sulfur-metal synergistic porous nitrogen and phosphorus removal active carrier and preparation method thereof

Abstract

The invention provides a sulfur-metal synergistic porous nitrogen and phosphorus removal active carrier and a preparation method thereof. The carrier comprises the following components in percentage by mass: 25%-85% of elemental sulfur, 5%-30% of sulfur-iron compound particles, 1%-30% of a synergistic phosphorus removal strengthening component and 1%-30% of a composite pore forming agent, the sulfur-iron compound particles comprise at least one of pyrite, hemite, pyrrhotite and maquinol ore, and have a standard sulfur-iron crystal structure; the synergistic dephosphorization strengthening component comprises a compound of one or more than two elements of aluminum, magnesium, calcium, lanthanum and zirconium; the composite pore-forming agent comprises a water-soluble inorganic salt pore-forming agent and a thermal decomposition pore-forming agent, and the thermal decomposition pore-forming agent accounts for 5-50% of the total mass of the composite pore-forming agent. According to the technical scheme, the sulfur-metal synergistic porous carrier has stable electrochemical driving and multiple synergistic phosphorus removal functions.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to a sulfur-metal synergistic porous denitrification and phosphorus removal active carrier and its preparation method. Background Technology

[0002] In the field of advanced wastewater treatment, existing technologies for the synergistic removal of nitrogen and phosphorus from water with low carbon-to-nitrogen ratios mainly focus on the following materials, but all of them have inherent drawbacks: (1) Traditional sulfur-based denitrification materials (such as solid sulfur particles) rely on sulfur autotrophic denitrification, but they have a dense structure, small specific surface area, extremely low mass transfer efficiency, and the reaction only occurs on the surface. The utilization rate of internal sulfur sources is low, and it is easy to cause a local pH decrease.

[0003] (2) The sulfur-iron simple composite material aims to combine denitrification and chemical phosphorus removal functions by physically mixing sulfur and iron powder. However, the simple mixing results in insufficient contact between sulfur and iron, making it difficult to form an effective micro-electrolysis synergy effect; the iron component is unevenly distributed, resulting in limited phosphorus removal efficiency and easy dissolution, causing secondary pollution and rapid material consumption.

[0004] (3) Although conventional porous biological carriers (such as porous ceramics and activated carbon) can provide a high specific surface area to facilitate microbial attachment, they are inert materials and cannot provide the electron donors required for denitrification. When treating wastewater with a low carbon-to-nitrogen ratio, it is still necessary to add an external carbon source, which increases the cost and complexity.

[0005] Chinese patent CN116969606A discloses a porous denitrification packing material prepared using molten sulfur mixed with pyrite powder and sodium bicarbonate as a pore-forming agent. While this technology introduces a porous structure and iron, the pyrite powder used has a complex composition and uneven activity, and its interaction with elemental sulfur is merely physical doping, failing to construct an efficient and stable microscopic electrochemical coupling system, resulting in low electron transfer efficiency. Secondly, the packing material exists in the form of pyrite, and phosphorus removal mainly relies on limited chemical precipitation, resulting in low capacity, slow rate, and no other enhanced phosphorus removal mechanism, making it difficult to meet the requirements for deep removal of low-concentration phosphorus. Finally, this carrier uses only sodium bicarbonate as a pore-forming agent, resulting in a relatively uniform pore structure, making it difficult to simultaneously meet the dual requirements of macropore mass transfer and micropore adhesion, and the functional components are easily encapsulated and deactivated. Summary of the Invention

[0006] To address the above technical problems, this invention discloses a sulfur-metal synergistic porous denitrification and phosphorus removal active carrier and its preparation method. By improving the composition ratio and preparation process, a composite functional material with a well-developed pore structure and multiple active components is constructed, which accelerates the denitrification process, improves phosphorus removal capacity, rate and long-term effectiveness, and has better water treatment effect; it solves the technical defects of existing sulfur-based carriers, such as limited specific surface area, low mass transfer efficiency and single function.

[0007] The technical solution adopted by this invention is as follows: A sulfur-metal synergistic porous denitrification and phosphorus removal active carrier comprises the following components and their mass percentages: elemental sulfur 25%-80%, sulfur-iron compound particles 5%-30%, synergistic phosphorus removal enhancement component 1%-30%, and composite pore-forming agent 1%-30%; The sulfur-iron compound particles include pyrite (FeS2), marcasite (FeS2, allomorphous), and pyrrhotite (Fe... 1-x It contains at least one of sulfur (S) and makinoite (FeS), and has a standard sulfur-iron crystal structure; when the sulfur-iron compound particles come into contact with the elemental sulfur matrix, they can form a uniformly distributed and stable reaction interface. The synergistic phosphorus removal enhancement component includes compounds of one or more elements selected from aluminum, magnesium, calcium, lanthanum, and zirconium. The composite pore-forming agent includes a water-soluble inorganic salt pore-forming agent and a thermally decomposable pore-forming agent, wherein the thermally decomposable pore-forming agent accounts for 5% to 50% of the total mass of the composite pore-forming agent.

[0008] Elemental sulfur serves as the carrier framework and the main electron donor for sulfur autotrophic denitrification.

[0009] This technical solution introduces a sulfur-iron compound with a regular crystal structure to replace simple iron powder mixing, forming a stable and efficient reaction system within the carrier, greatly promoting electron transfer and accelerating the denitrification process. Building upon iron-based phosphorus removal, one or more reinforcing components selected from aluminum (Al), lanthanum (La), zirconium (Zr), calcium (Ca), and magnesium (Mg) are introduced. These components complement and synergize with the chemical precipitation of iron through different mechanisms such as specific adsorption, coordination precipitation, or co-precipitation, significantly improving phosphorus removal capacity, rate, and long-term effectiveness. A composite pore-forming agent is used to construct an interconnected network with both micropores (<10 μm, for microbial attachment) and macropores (≥10 μm, for rapid mass transfer), enabling efficient transport and colonization of pollutants and microorganisms within the carrier, effectively solving the mass transfer bottleneck and ensuring that every phosphorus removal active site is fully utilized. The three-dimensional gradient porous composite material obtained by this technical solution possesses stable electrochemical driving and multiple synergistic phosphorus removal functions.

[0010] As a further improvement of the present invention, the synergistic phosphorus removal enhancing component is an oxide, hydroxide, hydroxyl oxide, or a sparingly soluble salt. The synergistic phosphorus removal enhancing component works synergistically with the iron component through mechanisms such as adsorption, coordination, or precipitation, significantly improving the ability and stability of phosphate ion capture.

[0011] As a further improvement of the present invention, the water-soluble inorganic salt is at least one of sodium chloride, potassium chloride, sodium sulfate, and ammonium sulfate, used to dissolve and leach the main through-hole.

[0012] As a further improvement of the present invention, the thermally decomposable pore-forming agent is at least one of ammonium bicarbonate, ammonium carbonate, ammonium oxalate, and citric acid, which decomposes to produce gas when heated, forming micropores inside the carrier.

[0013] As a further improvement of the present invention, the particle size of the water-soluble inorganic salt is ≤200 μm.

[0014] As a further improvement of the present invention, the average particle size of the sulfur-iron compound particles is ≤100 μm.

[0015] As a further improvement of the present invention, the sulfur-metal synergistic porous denitrification and phosphorus removal active carrier is spherical, cylindrical, sheet-like, or amorphous particles. More preferably, the sulfur-metal synergistic porous denitrification and phosphorus removal active carrier is spherical with a particle size of 0.5~10 mm. Preferably, the particle size of the sulfur-metal synergistic porous denitrification and phosphorus removal active carrier is 3~5 mm.

[0016] As a further improvement of the present invention, the sulfur-metal synergistic porous denitrification and phosphorus removal active carrier comprises the following components and their mass percentages: elemental sulfur 50%-60%, sulfur-iron compound particles 10%-20%, synergistic phosphorus removal enhancement component 15%-20%, and composite pore-forming agent 5%-15%.

[0017] As a further improvement of the present invention, the synergistic phosphorus removal enhancing component includes at least two of alumina, magnesium carbonate, and calcium carbonate. Further, the synergistic phosphorus removal enhancing component is a mixture of alumina and magnesium carbonate or a mixture of magnesium carbonate and calcium carbonate. When the synergistic phosphorus removal enhancing component is a mixture of alumina and magnesium carbonate, the mass ratio of alumina to magnesium carbonate is 3:1. When the synergistic phosphorus removal enhancing component is a mixture of magnesium carbonate and calcium carbonate, the mass ratio of calcium carbonate to magnesium carbonate is 3:1. Further, the alumina is nano-γ-Al₂O₃.

[0018] This invention discloses a method for preparing the sulfur-metal synergistic porous denitrification and phosphorus removal active carrier as described above, comprising the following steps: Step S1: Place elemental sulfur in a reaction vessel and heat until completely melted; Step S2: Add sulfur-iron compound particles to molten sulfur and stir to make them evenly dispersed and coated with sulfur; Step S3: Add the synergistic phosphorus removal enhancement component, continue stirring, and mix thoroughly. Step S4: Add the composite pore-forming agent, stir evenly, and then granulate to obtain solidified particles; Step S5: Wash the solidified particles with water to dissolve water-soluble inorganic salts, and heat (e.g., 60-100℃) to decompose and release the thermally decomposing pore-forming agent, thereby obtaining a composite carrier with a gradient pore structure, namely a sulfur-metal synergistic porous denitrification and phosphorus removal active carrier.

[0019] As a further improvement of the present invention, in step S1, the heating temperature is 120-150°C. The melting temperature of sulfur is approximately 119°C. By using this heating temperature, which is above the melting temperature, the sulfur is completely melted to form liquid sulfur.

[0020] As a further improvement of the present invention, in step S4, the granulation includes forming the slurry by dripping, extrusion or molding and then placing it in a cooling medium for curing.

[0021] As a further improvement of the present invention, in steps S1 to S3, the stirring rate is 250-350 rpm, and in step S4, the stirring rate is 500-700 rpm.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: First, functional synergy and enhanced efficiency. By introducing pre-fabricated iron-sulfur compounds with regular crystalline structures, a highly efficient and stable built-in electron transport network is constructed, fundamentally improving denitrification kinetics. The introduction of multi-metal components such as aluminum, magnesium, and calcium achieves synergistic phosphorus removal through multiple mechanisms (such as adsorption, coordination, precipitation, and bioreaction processes), with particularly impressive results in deep phosphorus removal. Experiments demonstrate a breakthrough improvement in TP removal rate. Furthermore, it explicitly proposes and implements a synergistic coupling of iron and phosphorus within the carrier, rather than a simple functional superposition. Experimental data proves that this synergistic effect results in a qualitative leap in total phosphorus removal efficiency (e.g., from 24% to 81%), far exceeding the effects expected by those skilled in the art when using only iron components or adding aluminum, calcium, magnesium, or other metal components alone. The pre-fabricated FeS2 unit ensures a highly efficient and stable denitrification electron flow; iron and other metal components synergistically achieve deep phosphorus removal within the same carrier space. By sharing the "acidic microenvironment activation (i.e., sulfur autotrophic denitrification reaction producing acid to promote metal ion dissolution)" step, the optimal synergy between denitrification and phosphorus removal processes in time and space is achieved.

[0023] Second, mass transfer efficiency is significantly improved. By using a composite pore-forming agent system to create a gradient interconnected pore structure, a controllable, interconnected micron-scale pore network is introduced into the active support, completely changing the dense structural morphology of traditional sulfur-based supports. This structure provides efficient channels for the diffusion of pollutants and nutrients, eliminates mass transfer bottlenecks, and allows for full utilization of internal active sites, thereby significantly improving reaction kinetics and the overall utilization efficiency of the support.

[0024] Third, the microbial habitat is optimized. The multi-layered pores formed by the composite pore-forming agent solve the mass transfer bottleneck of traditional materials, enabling the aforementioned synergistic reactions to fully occur within the entire carrier. Furthermore, the porous structure effectively increases the specific surface area and surface roughness of the carrier, providing a superior attachment and colonization environment for functional microorganisms (such as sulfur-oxidizing bacteria and denitrifying bacteria), which is conducive to the formation of high-density, highly active biofilms, further enhancing the stability and efficiency of the biological denitrification process.

[0025] Fourth, it offers long-term stability and wide adaptability. The functional components in the packing carrier exist in a solid composite form, releasing their activity through slow interfacial reactions, thus avoiding rapid loss of active components and ensuring a long service life. The carrier's morphology and particle size can be flexibly designed to meet the needs of various wastewater treatment processes such as fluidized beds and fixed beds.

[0026] Fifth, the preparation process is simple and low-cost. The preparation process adopted by the technical solution of this invention is based on mature hot-melt blending and granulation technology, which has low equipment requirements. Complex functions can be achieved through optimized component and sequence control. Raw material costs are controllable, and it is very easy to scale up industrial production. Moreover, the raw materials are widely available and economical, making this carrier have broad application prospects and significant competitive advantages in wastewater treatment, especially in the deep treatment of wastewater with low carbon-to-nitrogen ratios. Attached Figure Description

[0027] Figure 1 These are the appearance morphology images of the sulfur-metal synergistic porous denitrification and phosphorus removal active carrier of Embodiment 1 of the present invention; wherein (a), (b), and (c) are appearance morphology images at different magnifications.

[0028] Figure 2 These are the appearance morphology images of the porous elemental sulfur support in Comparative Example 1; where (a), (b), and (c) are appearance morphology images at different magnifications.

[0029] Figure 3 This is a diagram showing the surface morphology of the sulfur-iron composite support in Comparative Example 2.

[0030] Figure 4The following are the surface elemental analysis results of the sulfur-metal synergistic porous denitrification and phosphorus removal active carrier of Example 1 of the present invention, wherein (a) is a scanning electron microscope image; (b) is a sulfur element distribution mapping image; (c) is an iron element distribution mapping image; (d) is an aluminum element distribution mapping image; and (e) is a magnesium element distribution mapping image.

[0031] Figure 5 The results are X-ray energy dispersive spectroscopy analysis results of the sulfur-metal synergistic porous denitrification and phosphorus removal active carrier of Example 1 of the present invention.

[0032] Figure 6 These are comparative images of the morphological characteristics of microorganisms colonized on different carrier surfaces in Example 1 and Comparative Example 2 of the present invention; wherein, (a) and (b) are morphological characteristic images of microorganisms colonized on the surface of the sulfur-metal synergistic porous denitrification and phosphorus removal active carrier of Example 1 at different magnifications, and (c) and (d) are morphological characteristic images of microorganisms colonized on the surface of the conventional sulfur-iron composite carrier of Comparative Example 2 at different magnifications.

[0033] Figure 7 These are surface analysis diagrams of the carrier after reaction according to an embodiment of the present invention; wherein, (a) is a SEM image, (b) is a P distribution mapping image, and (c) is the distribution data of each element.

[0034] Figure 8 This is an elemental analysis diagram of the surface of the sulfur-metal synergistic porous denitrification and phosphorus removal active carrier in Embodiment 4 of the present invention; wherein, (a) is a sulfur element distribution mapping diagram, (b) is an iron element distribution mapping diagram, (c) is a calcium element distribution mapping diagram, (d) is a magnesium element distribution mapping diagram, and (e) is the distribution data of each element. Detailed Implementation

[0035] The preferred embodiments of the present invention will be described in further detail below. Example 1

[0036] A method for preparing a spherical sulfur-metal synergistic porous denitrification and phosphorus removal active carrier, wherein the spherical sulfur-metal synergistic porous denitrification and phosphorus removal active carrier is a spherical sulfur-iron-aluminum synergistic porous carrier, which adopts a synergistic system of pre-prepared pyrite and aluminum-enhanced phosphorus removal.

[0037] The raw materials and proportions (by mass percentage) are as follows: Continuous matrix: Elemental sulfur (industrial grade), 55%; Nitrogen and phosphorus removal active component: pyrite (FeS2) particles (average particle size ≤100 μm), 15%; Synergistic phosphorus removal enhancement components: nano-alumina (γ-Al2O3), 15%; magnesium carbonate (MgCO3, which provides both alkalinity and magnesium source), 5%; Composite pore-forming agent: Sodium chloride (NaCl, particle size ≤200 μm), 5%; Ammonium bicarbonate (NH4HCO3), 5%.

[0038] The preparation steps include: (1) Melting: Place elemental sulfur in a reaction vessel and heat it in an oil bath at 145°C until it is completely melted.

[0039] (2) Sequential mixing: a. Add the pre-made pyrite particles to the molten sulfur and mechanically stir at 300 rpm for 10 minutes to fully disperse and coat them with sulfur.

[0040] b. Add nano-alumina and magnesium carbonate powder, and continue stirring for 5 minutes to ensure a uniform mixture.

[0041] c. Finally, add the mixed pore-forming agent of sodium chloride and ammonium bicarbonate, stir quickly for 3 minutes, and immediately proceed to the next step to prevent the pore-forming agent from decomposing prematurely.

[0042] (3) Granulation and solidification: The above uniform slurry is transferred to the granulation device and the droplets are dropped into a cold water bath at 5-10℃, which quickly solidifies to form spherical particles.

[0043] (4) Post-treatment: Remove the granules, soak and wash them in deionized water for 48 hours to completely dissolve the sodium chloride. Then, place the granules in a 60°C oven to dry for 12 hours. During this process, ammonium bicarbonate decomposes upon heating (NH4HCO3→NH3↑+ CO2↑+H2O), producing gas that escapes and forms micropores.

[0044] The obtained sulfur-metal synergistic porous denitrification and phosphorus removal active support was characterized. The support consisted of spherical particles with a diameter of 3-5 mm and a rough surface. Its internal SEM morphology was as follows. Figure 1 As shown, it exhibits a rich and interconnected gradient pore structure with uniform element distribution, such as... Figure 4 As shown.

[0045] Comparative Example 1 (Porous elemental sulfur carrier): Based on Example 1, only elemental sulfur and sodium chloride were used as pore-forming agents, without adding any metal components or ammonium bicarbonate. Granulation, washing, and drying were performed using a similar basic process. The resulting carrier structure had poor density, with large and uneven pores. Figure 2 As shown.

[0046] Comparative Example 2 (Traditional Sulfur-Iron Composite Carrier): Based on Example 1, equal masses of ordinary sulfur powder and siderite powder (FeCO3) were used to replace the pre-prepared pyrite and alumina in Example 1, and no pore-forming agents (sodium chloride, ammonium bicarbonate) were added. The mixture was simply hot-melted and then cooled to form the substrate. The resulting carrier had a relatively dense surface with virtually no visible pore structure, such as... Figure 3 As shown. Example 2

[0047] The spherical sulfur-iron-aluminum synergistic porous denitrification and phosphorus removal active carriers, porous elemental sulfur carriers, and sulfur-iron composite carriers prepared in Example 1, Comparative Example 1, and Comparative Example 2, respectively, should be characterized using scanning electron microscopy images such as... Figure 1 , Figure 2 , Figure 3 As shown, their appearance morphological features are revealed respectively.

[0048] As can be seen from the comparison, the carrier in Example 1 (such as...) Figure 1 The example shown exhibits an optimal pore structure, with pore sizes ranging from several micrometers to tens of micrometers, forming a connected network. Compared to Comparative Example 1 (… Figure 2 Compared to the macroporous structure of the carrier in Example 1, the proportion of micropores is significantly increased. This is due to the pore-refining effect of insoluble functional particles (FeS2, Al2O3) and the additional micropores generated by the decomposition of ammonium bicarbonate. During water treatment, the carrier in Example 1 exhibits increased sulfur autotrophic denitrification, producing acid (H+). + The acid promotes the dissolution of solid minerals and the release of metal elements. Iron and aluminum chemically precipitate to form Fe-P compounds and Al-P compounds, thus simultaneously removing phosphorus. (Comparative Example 2) Figure 3 Compared to the dense structure of ), its advantages are more obvious.

[0049] Elemental distribution and composition, such as Figure 4 and Figure 5 As shown, Figure 4 The EDS surface mapping results clearly show that S, Fe, and Al elements are uniformly distributed within the cross-section of the carrier in Example 1, without obvious agglomeration, proving the effectiveness of the "sequential hot melt blending" process. Figure 5 The energy-dispersive X-ray spectral mapping (i.e., EDS energy dispersive spectroscopy) provides the relative abundance of each element, confirming the successful introduction of the designed components.

[0050] After conducting microbial colonization experiments on various carriers under identical conditions, the results of the microbial colonization effect are as follows: Figure 6 As shown. Figure 6 As shown in (a) and (b), a dense and intact biofilm is visible on the surface of the carrier in Example 1, indicating active microbial morphology. Figure 6As shown in (c) and (d), the biofilm on the surface of the carrier in Comparative Example 2 is sparse and uneven. This directly proves that the carrier of the present invention, due to its optimized pore structure and abundant functional sites, can create a superior microbial habitat environment.

[0051] The SEM image of the carrier after the above reaction is shown below. Figure 7 As shown, secondary phosphorus-containing minerals are formed on the surface of the carrier in Example 1 after the reaction, confirming that it can effectively remove phosphorus. Example 3

[0052] Wastewater treatment effect verification experiment.

[0053] To quantitatively evaluate the actual effectiveness of the sulfur-metal synergistic porous denitrification and phosphorus removal active carrier of Example 1 of this invention, a rigorous parallel comparative experiment was designed in this example. Specifically, two sets of packed bed reactors were constructed simultaneously, with three parallel reactors in each set. One set of reactors was filled with the sulfur-metal synergistic porous denitrification and phosphorus removal active carrier of Example 1, while the other set of reactors was filled with a conventional sulfur-iron composite carrier (Comparative Example 2). The inner diameter of each reactor was 4 cm, and the empty bed volume (effective working volume) was 163.28 mL. For each packed bed reactor, from bottom to top, it consisted of a water distribution zone (5 cm), a support layer (3 cm), a carrier filling layer (13 cm), and a clear water zone (4 cm). The particle size of the carrier was 3.00~6.00 mm. In addition to the reactor body, the experiment was also equipped with an inlet tank, an outlet tank, a peristaltic pump, and pipelines. The inlet peristaltic pump was used to transport the synthetic wastewater into the bottom of the reactor. A continuous flow operation mode was adopted to introduce synthetic wastewater to start the reactor. All reactors are equipped with a circulating water insulation layer on the outer layer, and circulating water is introduced through an intelligent circulating water bath to control the experimental temperature to be constant at 27±3 ℃.

[0054] The formulation for the synthetic wastewater is as follows: 20 mg / L NO3 - -N (provided by NaNO3), 1.0 mg / L PO4 3--P (provided by KH2PO4), 100 mg / L NaHCO3 (combined with the background alkalinity of tap water ~50 mg / L and the total alkalinity of the synthetic wastewater ~150 mg / L, which is within the typical range of secondary effluent from a wastewater treatment plant), and 1 mL / L Wolf's trace element solution. The synthetic wastewater underwent pre-deoxygenation treatment, maintaining dissolved oxygen (DO) content below 0.5 mg / L. All reactors operated in an upward continuous flow mode, with an empty bed retention time (EBCT) constantly set at 0.5 hours, which is close to the hydraulic retention time in actual operation of denitrification deep bed filters in wastewater treatment plants. All reactors operated continuously for 30 days to compare and examine the differences in nitrogen and phosphorus removal efficiency of the reaction systems. When the effluent nitrate nitrogen concentration and effluent phosphate concentration stabilized and remained at low levels, the reactors were considered to be in a stable operating period. Key water quality indicators were monitored and statistically analyzed during the stable operating period.

[0055] The results are shown in Table 1. During the stable operation period (based on average values ​​calculated from data collected over 10-30 days), the reactor loaded with the carrier of Example 1 exhibited significantly better treatment performance than the control system. Specifically, under the condition that the total nitrogen concentration in the influent was 20.0 ± 0.7 mg / L, the average total nitrogen concentration in the effluent was 3.72 ± 0.35 mg / L, which was 44.89% lower than that of Comparative Example 2 (6.75 ± 0.51 mg / L). Correspondingly, the total nitrogen removal reached 16.28 mg / L, and the average total nitrogen removal rate was 81.40%, representing increases of 1.23 times and 22.87 percentage points, respectively, compared to Comparative Example 2.

[0056] In terms of phosphorus removal performance, the carrier in Example 1 demonstrates a more significant advantage. Under the condition that the total phosphorus concentration in the influent was 1.0 ± 0.1 mg / L, the average total phosphorus concentration in the effluent of the reactor loaded with the carrier of Example 1 was 0.19 ± 0.05 mg / L, a 75.00% reduction compared to the 0.76 ± 0.18 mg / L of the reactor loaded with the carrier of Comparative Example 2. The total phosphorus removal capacity of the carrier in Example 1 reached 0.81 mg / L, with an average total phosphorus removal rate of 81.00%, representing an improvement of 3.38 times and 237.50 percentage points compared to Comparative Example 2.

[0057] Overall, the experimental group corresponding to the carrier in Example 1 outperformed Comparative Example 2 in terms of denitrification, phosphorus removal efficiency, and system stability, demonstrating its superior simultaneous denitrification and phosphorus removal performance. In particular, the significant improvement in TP removal rate (more than 3 times higher than the previous example) far exceeds the expected results of simple iron phosphorus removal or increased porosity.

[0058] The aforementioned performance improvement can be attributed to the unique structural characteristics of the carrier in Example 1. By introducing a soluble salt pore-forming agent and allowing it to dissolve after molding, a well-developed, interconnected microporous structure is formed within the carrier. This porous structure significantly increases the specific surface area, providing a superior habitat for microbial attachment and growth, while also greatly improving the mass transfer efficiency of pollutants within the carrier. Elemental distribution analysis shows that sulfur and iron are evenly distributed within the carrier, ensuring the effective utilization of functional components. The synergistic effect of the porous structure and the evenly distributed active components not only promotes the sulfur autotrophic denitrification process but also enhances the chemical phosphorus removal effect by increasing the contact reaction opportunities between iron, aluminum, and other metal elements and phosphates, ultimately achieving a simultaneous improvement in nitrogen and phosphorus removal efficiency.

[0059] The rigorous comparative experiments demonstrated that the sulfur-metal synergistic porous denitrification and phosphorus removal active carrier in Example 1 exhibits significantly superior performance compared to traditional sulfur-iron composite carriers in both denitrification and phosphorus removal when treating wastewater with a low carbon-to-nitrogen ratio, fully verifying its effectiveness and advanced nature in practical applications. Example 4

[0060] Based on Example 1, the difference in this example is that it uses a spherical sulfur-iron-calcium synergistic porous carrier, and the raw materials and proportions (mass percentage) are as follows: Continuous matrix: Elemental sulfur (industrial grade), 55%; Electrochemical active unit: pre-fabricated pyrite (FeS2) particles (average particle size ≤100 μm), 15%; Synergistic phosphorus removal enhancement components: Calcium carbonate (CaCO3, providing both alkalinity and calcium source), 15%; Magnesium carbonate (MgCO3, providing both alkalinity and magnesium source), 5%; Composite pore-forming agent: Sodium chloride (NaCl, particle size ≤200μm), 5%; Ammonium bicarbonate (NH4HCO3), 5%.

[0061] The preparation steps are the same as in Example 1.

[0062] The surface elemental analysis diagram of the sulfur-metal synergistic porous denitrification and phosphorus removal active carrier in this embodiment is shown below. Figure 8 As shown, the EDS surface scanning (mapping) results clearly show that S, Fe, and Ca elements are uniformly distributed within the cross-section of the carrier, with no obvious agglomeration. Example 5

[0063] Based on Example 1, the difference in this example is that it uses a spherical sulfur-iron synergistic porous carrier, and the raw materials and proportions (mass percentage) are as follows: Continuous matrix: Elemental sulfur (industrial grade), 55%; Electrochemical active unit: pre-fabricated pyrite (FeS2) particles (average particle size ≤100 μm), 30%; Synergistic phosphorus removal enhancement component: Magnesium carbonate (MgCO3, which provides both alkalinity and magnesium source), 5%; Composite pore-forming agent: Sodium chloride (NaCl, particle size ≤200μm), 5%; Ammonium bicarbonate (NH4HCO3), 5%.

[0064] The preparation steps are the same as in Example 1. Example 6

[0065] Based on Example 1, the difference in this example is that it uses a spherical sulfur-aluminum synergistic porous denitrification and phosphorus removal active carrier, and the raw materials and proportions (mass percentage) are as follows: Continuous matrix: Elemental sulfur (industrial grade), 55%; Synergistic phosphorus removal enhancement components: nano-alumina (γ-Al2O3), 30%; magnesium carbonate (MgCO3, which provides both alkalinity and magnesium source), 5%; Composite pore-forming agent: Sodium chloride (NaCl, particle size ≤200μm), 5%; Ammonium bicarbonate (NH4HCO3), 5%.

[0066] The carriers of Examples 1, 4, 5, and 6 were loaded into the reactor and tested according to the steps of Example 3. The results are shown in Table 1.

[0067] Table 1 Comparison of key operational data during stable operation of the examples and comparative examples

[0068] Under the condition of a constant EBCT setting of 0.5 h, the comparison of Examples 1, 4-6, and Comparative Example 2 in Table 1 shows that the sulfur-iron-aluminum synergistic porous denitrification and phosphorus removal active carrier of Example 1 has better performance in TN and TP removal than the sulfur-iron synergistic porous denitrification and phosphorus removal active carrier of Example 5 and the sulfur-aluminum synergistic porous denitrification and phosphorus removal active carrier of Example 6. For example, the TN removal amount of Example 5 is only 14.39 mg / L, and the corresponding TN removal load is 690.72 gN / m³. 3 / d; Example 6 was 14.05 mg / L, corresponding to a TN removal load of 674.40 gN / m 3 / d; however, Example 1 achieved 16.28 mg / L, corresponding to a TN removal load as high as 781.44 gN / m 3 / d. In Example 5, the TP removal amount was only 0.51 mg / L, corresponding to a TP removal load of 24.48 gP / m³. 3 / d; Example 6 was 0.58 mg / L, corresponding to a TP removal load of 27.84 gP / m 3 / d; however, Example 1 achieved 0.81 mg / L, corresponding to a TP removal load as high as 38.88 gP / m 3 / d. It is evident that sulfur-iron-aluminum produced a stronger synergistic effect in nitrogen and phosphorus removal.

[0069] As can be seen from the data in Table 1, the sulfur-iron-aluminum synergistic porous denitrification and phosphorus removal active carrier of Example 1 and the sulfur-iron-calcium synergistic porous denitrification and phosphorus removal active carrier of Example 4 both have superior TN removal and TP removal effects compared with the sulfur-iron composite carrier of Example 2. Example 7

[0070] Implementation examples of carrier physical morphology variants.

[0071] The carrier of the technical solution of the present invention is not limited to a sphere, and its shape can be adjusted according to the application scenario.

[0072] (1) Columnar carrier: Using the slurry of Example 1, it is extruded into short cylinders with a diameter of 3 mm and a length of 5-10 mm, and then cut, cooled and post-processed. It is suitable for fixed bed reactors and has high crushing strength.

[0073] (2) Sheet / block carrier: The slurry is injected into the mold and cooled and shaped into a specific shape (such as a disc or a block), which is suitable for modular packing units or reactors with specific configurations.

[0074] (3) Irregular particles: obtained by crushing, screening and forming large pieces of material, which is economical.

[0075] All morphological variants retain the core components and gradient porous structure features described in Example 1.

[0076] The synergistic phosphorus removal enhancing components involved in this invention are not limited to aluminum and calcium; other metals that can produce similar coupling synergistic effects with iron (such as lanthanum (La) and zirconium (Zr)) can also achieve similar effects. For example, hydrated lanthanum oxide (La₂O₃·xH₂O) can be used instead of alumina, utilizing La… 3+ With PO4 3- By forming LaPO4 with a smaller solubility product and working synergistically with iron-based precipitates, deep removal of ultra-low concentrations of phosphorus can be achieved.

[0077] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A sulfur-metal synergistic porous denitrification and phosphorus removal active carrier, characterized in that: Its components and their mass percentages are as follows: elemental sulfur 25% - 80%, sulfur-iron compound particles 5% - 30%, synergistic phosphorus removal and strengthening components 1% - 30%, and composite pore-forming agent 1% - 30%; The sulfur-iron compound particles include at least one of pyrite, marcasite, pyrrhotite, and makinoite, and have a standard sulfur-iron crystal structure; The synergistic phosphorus removal enhancement component includes compounds of one or more elements selected from aluminum, magnesium, calcium, lanthanum, and zirconium. The composite pore-forming agent includes a water-soluble inorganic salt pore-forming agent and a thermally decomposable pore-forming agent, wherein the thermally decomposable pore-forming agent accounts for 5% to 50% of the total mass of the composite pore-forming agent.

2. The sulfur-metal synergistic porous denitrification and phosphorus removal active carrier according to claim 1, characterized in that: The synergistic phosphorus removal enhancement component is an oxide, hydroxide, hydroxy oxide, or insoluble salt.

3. The sulfur-metal synergistic porous denitrification and phosphorus removal active carrier according to claim 1, characterized in that: The water-soluble inorganic salt is at least one of sodium chloride, potassium chloride, sodium sulfate, and ammonium sulfate; the thermally decomposable pore-forming agent is at least one of ammonium bicarbonate, ammonium carbonate, ammonium oxalate, and citric acid; and the particle size of the water-soluble inorganic salt is ≤200 μm.

4. The sulfur-metal synergistic porous denitrification and phosphorus removal active carrier according to claim 1, characterized in that: The sulfur-metal synergistic porous denitrification and phosphorus removal active carrier is a spherical, cylindrical, sheet-like, or amorphous particle.

5. The sulfur-metal synergistic porous denitrification and phosphorus removal active carrier according to claim 4, characterized in that: The sulfur-metal synergistic porous denitrification and phosphorus removal active carrier is spherical with a particle size of 0.5~10 mm.

6. The sulfur-metal synergistic porous denitrification and phosphorus removal active carrier according to claim 1, characterized in that: Its components and their mass percentages are as follows: elemental sulfur 50% - 60%, sulfur-iron compound particles 10% - 20%, synergistic phosphorus removal and strengthening components 15% - 20%, and composite pore-forming agent 5% - 15%; The synergistic phosphorus removal enhancement component includes at least two of alumina, magnesium carbonate, and calcium carbonate.

7. The method for preparing the sulfur-metal synergistic porous denitrification and phosphorus removal active carrier according to any one of claims 1 to 6, characterized in that: Includes the following steps: Step S1: Place elemental sulfur in a reaction vessel and heat until completely melted; Step S2: Add sulfur-iron compound particles to molten sulfur and stir to make them evenly dispersed and coated with sulfur; Step S3: Add the synergistic phosphorus removal enhancement component, continue stirring, and mix thoroughly. Step S4: Add the composite pore-forming agent, stir evenly, and then granulate to obtain solidified particles; Step S5: The solidified particles are washed with water to dissolve water-soluble inorganic salts, and heated to decompose and release the thermally decomposing pore-forming agent, thereby obtaining a sulfur-metal synergistic porous denitrification and phosphorus removal active carrier.

8. The method for preparing the sulfur-metal synergistic porous denitrification and phosphorus removal active carrier according to claim 7, characterized in that: In step S1, the heating temperature is 120-150℃.

9. The method for preparing the sulfur-metal synergistic porous denitrification and phosphorus removal active carrier according to claim 7, characterized in that: In step S4, the granulation includes forming the slurry by dripping, extrusion or molding, and then placing it in a cooling medium for curing.

10. The method for preparing the sulfur-metal synergistic porous denitrification and phosphorus removal active carrier according to claim 7, characterized in that: In steps S1 to S3, the stirring speed is 250-350 rpm, and in step S4, the stirring speed is 500-700 rpm.

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