Composite filler, preparation method and application thereof

Abstract

The application belongs to the technical field of sewage treatment fillers, and particularly relates to a composite filler and a preparation method and application thereof. The iron-carbon micro powder is loaded in a hydrophilic polyurethane biological filler with a three-dimensional interpenetrating network structure and high pore connectivity in a physical mixing manner, so that the iron-carbon micro powder is stably distributed on the surface and in the internal pores of the filler. The problems of easy loss and easy deposition of traditional direct addition of iron-carbon materials are avoided, the enrichment and protection of the polyurethane carrier on microorganisms are fully played, and the system biomass and operation stability are significantly improved.

Description

Technical Field

[0001] This application belongs to the field of wastewater treatment packing technology, specifically relating to a composite packing with polyurethane as the skeleton and iron-carbon powder as the attached material. Background Technology

[0002] With the advancement of urbanization and the continuous improvement of wastewater discharge standards, wastewater treatment systems are facing increasingly stringent requirements for the removal of pollutants such as nitrogen and phosphorus. Among existing wastewater treatment processes, biological methods are widely used due to their stable operation and relatively low treatment costs.

[0003] To enhance the treatment capacity of biochemical treatment units, biological packing materials are typically added to the reactor in engineering practice to increase the biomass within the system and improve the growth environment for microorganisms. Among these, polyurethane biological packing materials are widely used in wastewater treatment due to their lightweight structure, high porosity, large specific surface area, and good hydrolysis resistance. Meanwhile, iron-carbon materials possess unique micro-electrolysis characteristics (they can spontaneously form Fe / C galvanic cells in the aqueous phase, continuously releasing Fe). 2+ Active substances such as ·OH not only enhance the degradation of organic pollutants but also promote denitrification, chemical phosphorus removal, and act as nuclei to induce the formation of granular sludge. Therefore, they are introduced into polyurethane filler systems to achieve synergistic effects of physicochemical and biochemical processes. Currently, research mainly focuses on how to effectively composite inorganic iron-carbon materials with organic polyurethane matrices. For example, patent application number 202510765048.X discloses a method for preparing elastic microcarriers by mixing iron-carbon powder with thermoplastic polyurethane through a melt blending process; patent application number 202110906328.X directly incorporates iron powder and biochar powder during the polyurethane foaming process. While these methods can firmly embed the iron-carbon components within the polyurethane framework, they inevitably result in a large number of iron-carbon particles being coated by the dense polymer, making it difficult to fully contact with wastewater, significantly weakening its micro-electrolysis activity, and limiting the synergistic effect. On the other hand, given that pure iron powder is easily lost and has poor long-term stability, some solutions use larger iron shavings as a substitute. As shown in patents with application numbers 202410356848.1 and 202511983271.8, while iron shavings are sandwiched inside or attached to the surface of polyurethane fillers to some extent, new technical bottlenecks are introduced: the specific surface area of ​​iron shavings is extremely small, the reaction interface is limited, and the micro-electrolysis efficiency is low; its macroscopic size does not match the micron-sized pores of polyurethane, making it difficult to form an effective composite structure; the carbon content in iron shavings is uncontrollable and unevenly distributed, making it difficult to construct an efficient Fe-C micro battery network.

[0004] In summary, how to ensure the high exposure and high reactivity of iron-carbon materials while achieving stable anchoring in polyurethane porous structures, thereby balancing efficient pollutant removal and long-term operational stability, remains a key technical challenge that urgently needs to be overcome in the field of wastewater treatment packing materials. Summary of the Invention

[0005] The purpose of this application is to provide a composite packing material that balances efficient pollutant removal with long-term operational stability, specifically achieved through the following technical solution:

[0006] A method for preparing a composite filler includes the following steps: placing hydrophilic polyurethane biofiller and iron-carbon micro powder in a mixing container at a mass ratio of 1:(0.05~0.5), and using a physical mixing method to distribute the iron-carbon micro powder on the surface of the polyurethane biofiller and in its internal interconnected pore structure; wherein, the mass fraction of iron powder in the iron-carbon micro powder is 60%~80%.

[0007] Preferably, the carbon powder in the iron-carbon micro powder includes one or more of activated carbon powder, graphite powder, coke powder, and biomass carbon powder.

[0008] Preferably, the iron-carbon micro powder can be obtained by mixing iron powder and carbon powder in a certain proportion, and then pressing, sintering, crushing or grinding, and its particle size range is 150-250 mesh.

[0009] Preferably, the hydrophilic polyurethane biofiller is a porous elastomer material with a three-dimensional interpenetrating network structure and high pore connectivity.

[0010] Preferably, the physical mixing method employs one or more of mechanical stirring, drum mixing, or centrifugal dispersion.

[0011] Preferably, the iron powder in the iron-carbon micro powder has a mass fraction of 70% to 80%.

[0012] A composite filler is prepared using any of the above-mentioned preparation methods.

[0013] The above-mentioned composite packing material is used in wastewater treatment.

[0014] Compared with the prior art, this application has the following beneficial effects:

[0015] This application loads iron-carbon micropowder into a hydrophilic polyurethane biofiller with a three-dimensional interpenetrating network structure and high porosity through a physical mixing method. This ensures that the iron-carbon micropowder is stably distributed on its surface and within its internal pores, avoiding the problems of easy loss and deposition associated with traditional direct addition of iron-carbon materials. It also fully leverages the enrichment and protection effects of the polyurethane carrier on microorganisms, significantly improving the system's biomass and operational stability. Furthermore, by limiting the iron powder mass fraction in the iron-carbon micropowder to 60%~80% (preferably 70%~80%), this application ensures that the material forms a moderate and continuous micro-electrolysis effect in the aquatic environment, effectively promoting nitrification. The selective reduction of acid salts and the chemical precipitation of phosphates achieve synergistic and efficient removal of nitrogen and phosphorus pollutants. Furthermore, by controlling the particle size of iron-carbon micropowder to 150–250 mesh and matching it with the macroscopic pore size of polyurethane filler, the micropowder can be fully embedded without clogging the pores, thus extending the service life of functional components while ensuring mass transfer efficiency. Furthermore, this application adopts a physical composite process that does not require chemical binders or high-temperature in-situ synthesis. It is simple to operate, environmentally friendly, and easy to scale up in engineering. It is applicable to urban sewage, rural domestic sewage, and various industrial wastewater treatment scenarios, combining technological advancement with industrial feasibility. Attached Figure Description

[0016] The attached diagram will be briefly described below:

[0017] Figure 1 This is a schematic diagram of a polyurethane-supported iron-carbon micropowder composite filler, where 1 is the polyurethane skeleton and 2 is the iron-carbon micropowder.

[0018] Figure 2 SEM-EDS images of polyurethane before loading iron-carbon micropowder (a) and after loading iron-carbon micropowder (b);

[0019] Figure 3 These are photos of the polyurethane-supported iron-carbon micropowder composite filler before (a) and after (b) use. Detailed Implementation

[0020] The present application will now be further described by way of specific embodiments. Those skilled in the art will be able to implement the present application based on these descriptions. Furthermore, the embodiments of the present application described below are generally only a part of the embodiments of the present application, and not all of the embodiments. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present application without inventive effort should fall within the scope of protection of the present application.

[0021] Example 1

[0022] A method for preparing a composite filler specifically includes the following steps:

[0023] Polyurethane biofiller is selected as the carrier. Specifically, a hydrophilically modified open-cell polyurethane foam material is chosen, which has a three-dimensional interpenetrating and interconnected network structure with a pore size ranging from 200 to 1000 μm and a large specific surface area, which is conducive to microbial attachment and biofilm formation. This material also has good biocompatibility, hydrolysis resistance, mass transfer performance, and elastic recovery ability, and can maintain structural integrity under aeration or water flow disturbance conditions, and is not easy to collapse or break. In this embodiment, the polyurethane biofiller is preferably a cubic block structure with a side length of 20-50 mm to balance filling efficiency and hydraulic flow.

[0024] Iron-carbon micro powder is selected as a functional filler. Specifically, the iron-carbon micro powder is a powder composed of elemental metallic iron as the main phase and one or more carbon materials. The mass fraction of iron powder is controlled at 80%, and the carbon component is selected from activated carbon powder. The particle size range of the micro powder is 150~250 mesh, which can effectively embed into the pore structure of the polyurethane carrier while avoiding pore blockage.

[0025] Pretreatment of polyurethane biofiller: The selected cubic hydrophilic open-cell polyurethane biofiller is rinsed with deionized water or low-concentration cleaning solution to remove surface dust and processing residues. Then it is placed in a ventilated environment to drain, or air-dried at a low temperature of 40~60℃ until there is no visible free water on the surface, ensuring that its pores are in an open and slightly moist state, which is conducive to the effective penetration and adhesion of iron and carbon micro powders.

[0026] Weigh out the appropriate amount of iron-carbon micropowder according to a mass ratio of polyurethane bio-filler to iron-carbon micropowder of 1:0.1. Add the pretreated polyurethane filler and iron-carbon micropowder together into a mixing container and use a drum mixer to tumble and mix at a low speed of 60 rpm for 30 minutes. During this process, the polyurethane material undergoes reversible deformation under rolling pressure due to its elastic properties, resulting in periodic compression and rebound of the pores. This causes the iron-carbon micropowder to gradually penetrate into the internal interconnected channels under the action of gravity, friction, and micro-airflow, and stably adhere to the pore walls and surface through van der Waals forces, electrostatic adsorption, and physical interlocking.

[0027] After mixing, the resulting material is allowed to stand or placed on a screen and gently tapped or vibrated, or swept with a low-pressure airflow to remove loose powder that is not firmly bonded, thus preventing system blockage or loss of functional components due to powder shedding during the initial operation. To further improve the uniformity and stability of the load, the powder addition-tumbling-shaking operation can be repeated 1-2 times, adding a small amount of fresh iron-carbon micro powder each time, but the total amount added should still be controlled within the above-mentioned mass ratio range to prevent overfilling from causing pore blockage, a decrease in specific surface area, or an increase in mass transfer resistance. In the final composite filler, the iron-carbon micro powder is uniformly distributed on the inner and outer surfaces of the polyurethane three-dimensional porous network, which not only retains the original high porosity and biocompatibility of the carrier, but also successfully introduces micro-electrolysis active sites, laying a structural foundation for subsequent biodegradation and electrochemical synergistic purification in wastewater treatment.

[0028] The structural diagram of the composite packing is shown below. Figure 1 As shown, the distribution of iron-carbon micropowder in the three-dimensional framework of polyurethane is clearly demonstrated. Figure 2 The SEM-EDS images are shown in (a) and (b) before and after loading iron-carbon micropowder onto polyurethane filler. In (b), a significant enhancement of Fe and C element signals can be clearly observed, confirming that the iron-carbon micropowder has been successfully loaded onto the surface and pore walls of the polyurethane matrix.

[0029] Example 2

[0030] The difference between this embodiment and Embodiment 1 is that the mass fraction of carbon powder in the iron-carbon micro powder is controlled at 60%, and the mass ratio of polyurethane biofiller to iron-carbon micro powder is 1:0.5.

[0031] Example 3

[0032] The difference between this embodiment and Embodiment 1 is that the mass fraction of carbon powder in the iron-carbon micro powder is controlled at 70%.

[0033] Comparative Example 1

[0034] The difference between this comparative example and Example 1 is that the mass fraction of iron powder is controlled at 50%.

[0035] Comparative Example 2

[0036] The difference between this comparative example and Example 1 is that the mass fraction of iron powder is controlled at 98%.

[0037] Performance testing

[0038] To evaluate the actual performance of the composite packing material of this invention in wastewater treatment, comparative experiments were conducted on the composite packing materials prepared in Example 1, Comparative Example 1, and Comparative Example 2. The experiments used a simulated wastewater system and conducted a continuous flow pilot test under the same hydraulic retention time (HRT = 6 h), temperature (25 °C), and initial pollutant concentration conditions to examine its pollutant removal performance. The simulated wastewater quality was as follows: COD 20 mg / L, nitrate content 10 mg / L, and total phosphorus content 2 mg / L. Experimental apparatus and operating conditions: Three sets of continuous flow reactors of the same specifications were used, each with an effective volume of 4 L, filled with an equal volume (4 L) of the composite packing material from Example 1, Comparative Example 1, and Comparative Example 2, respectively. The system was inoculated with recycled sludge from a municipal wastewater treatment plant, and after 7 days of biofilm formation acclimatization, it entered a stable operation phase, running continuously for 30 days, with influent and effluent water quality samples taken every 5 days. Detection indicators and methods: COD was measured using the potassium dichromate method, total nitrogen using the alkaline potassium persulfate digestion-ultraviolet spectrophotometry method, and total phosphorus using the ammonium molybdate spectrophotometry method. The results are summarized in the table below:

[0039] Table 1. Wastewater Treatment Effect of Composite Packing Material sample Iron powder mass fraction (%) Nitrate removal rate (%) Total nitrogen removal rate (%) Total phosphorus removal rate (%) Example 1 80% 58% 50% 70% Comparative Example 1 50% 66% 22% 57% Comparative Example 2 98% 23% 23% 33% .

[0040] In summary, by optimizing the iron mass fraction in the iron-carbon micro powder to 60%~80% (preferably 70%~80%), this invention maintains suitable micro-electrolysis activity while better balancing biocompatibility, reaction selectivity, and structural stability. This not only effectively improves the removal efficiency of total nitrogen and total phosphorus but also avoids the problem of excessive reduction of nitrate to ammonia nitrogen due to excessive reducing power, thus achieving more efficient and stable wastewater treatment performance.

Claims

1. A method for preparing a composite filler, characterized in that, Includes the following steps: Hydrophilic polyurethane biofiller and iron-carbon micro powder are placed in a mixing container at a mass ratio of 1:(0.05~0.5). The iron-carbon micro powder is distributed on the surface of the polyurethane biofiller and in its internal interconnected pore structure by physical mixing. The mass fraction of iron powder in the iron-carbon micro powder is 60%~80%.

2. The method for preparing a composite filler according to claim 1, characterized in that, The carbon powder in the iron-carbon micro powder includes one or more of activated carbon powder, graphite powder, coke powder, and biomass carbon powder.

3. The method for preparing a composite filler according to claim 2, characterized in that, The iron-carbon micro powder can be obtained by mixing iron powder and carbon powder in a certain proportion, and then pressing, sintering, crushing or grinding, and its particle size range is 150-250 mesh.

4. The method for preparing a composite filler according to claim 1, characterized in that, The hydrophilic polyurethane biofiller is a porous elastomer material with a three-dimensional interpenetrating network structure and high pore connectivity.

5. The method for preparing a composite filler according to claim 1, characterized in that, The physical mixing method employs one or more of the following: mechanical stirring, drum mixing, or centrifugal dispersion.

6. The method for preparing a composite filler according to claim 1, characterized in that, The iron-carbon micro powder contains 70% to 80% iron powder by mass.

7. A composite filler, characterized in that, It is prepared by any one of the preparation methods of claims 1 to 6.

8. The application of the composite filler according to claim 7 in wastewater treatment.

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