A perlite-based adsorbent material and a method for preparing the same

Abstract

This invention relates to a method for preparing a perlite-based adsorbent material, the resulting material, and its applications. The preparation method includes: pretreating expanded perlite particles; mixing polyaluminum chloride and urea in water to obtain an impregnation solution; subjecting the pretreated perlite to vacuum impregnation followed by atmospheric pressure soaking, allowing the impregnation solution to enter the open pores; then subjecting it to staged heating treatment to decompose the urea and release alkaline components, promoting the confined transformation and immobilization of aluminum species in the open pores and pore openings of the perlite; subsequently washing, aging, and drying to obtain the perlite-based adsorbent material. The obtained material is a granular material with a particle size of 2–6 mm, containing an aluminum-based immobilization layer on its surface and within its open pores, and can be used for the treatment of phosphorus-containing water.

Description

Technical Field

[0001] This invention relates to the technical field of water treatment adsorption materials, and in particular to a perlite-based adsorption material and its preparation method. Background Technology

[0002] Phosphorus-containing water bodies are widely found in domestic sewage, agricultural drainage, aquaculture wastewater, and some industrial wastewater. Excessive phosphorus content in water bodies can easily lead to eutrophication, resulting in abnormal algal growth, decreased dissolved oxygen, and imbalance of the aquatic ecosystem. Therefore, how to effectively remove phosphorus from water bodies has always been a crucial technical issue in the field of water treatment.

[0003] Currently, chemical precipitation, biological methods, and adsorption are commonly used techniques for treating phosphorus-containing water. Among these, adsorption is particularly suitable for the advanced treatment of low-concentration phosphorus-containing water and for applications under continuous flow conditions due to its relatively low equipment requirements, simple operation, and wide applicability. One existing adsorption material approach involves loading active components such as aluminum, iron, and calcium onto the surface of porous minerals or particulate carriers to remove phosphorus through the interaction between the active components and phosphorus.

[0004] However, existing supported adsorbent materials still suffer from a significant problem in practical applications: the distribution and binding stability of the active components on the support are often difficult to balance. If the active components are mainly concentrated on the outer surface of the particles, although initial contact sites are easier to form, insufficient utilization of the active components and inadequate stability under flowing water scouring can easily occur during continuous use. If the active components form localized accumulations or coverage during loading, it may also affect the original pore structure of the particles and the mass transfer process in the water, thereby reducing the treatment effect of the material under actual operating conditions. Therefore, how to prepare a particulate adsorbent material with both good phosphorus removal capacity and good operational stability remains a technical problem that needs to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to overcome the problem that the distribution of active components and the binding stability of the existing supported phosphorus removal materials are difficult to balance, and to provide a method for preparing perlite-based adsorbent materials, perlite-based adsorbent materials and their application in the treatment of phosphorus-containing water.

[0006] To achieve the above objectives, the first aspect of the present invention provides a method for preparing a perlite-based adsorbent material, comprising the following steps:

[0007] S1: Pre-treat expanded perlite particles to obtain pre-treated perlite;

[0008] S2: Polyaluminum chloride and urea are mixed in water to obtain an impregnation solution;

[0009] S3: The pretreated perlite is placed in the impregnation solution for vacuum impregnation treatment, and then immersed at normal pressure to allow the impregnation solution to enter the open pores of the pretreated perlite; wherein, step S3 satisfies the following relationship:

[0010] ;

[0011] In the formula, K1 is the infiltration driving coefficient; P v The absolute value of the vacuum is expressed in MPa; t v The duration of a single vacuuming cycle is in minutes; N is the number of vacuuming-restoration cycles; d is the average particle size of the pretreated perlite in mm; K1 is 0.08–1.50.

[0012] S4: The perlite treated in step S3 is subjected to segmented heating treatment to decompose urea and release alkaline components, thereby promoting the confined transformation and fixation of aluminum species in the open pores and pore mouth regions of the pretreated perlite; wherein, steps S2 and S4 satisfy the following relationship:

[0013] ;

[0014] In the formula, K2 is the conversion control coefficient; R u t is the molar ratio of urea to aluminum; t is the second stage heat preservation time in step S4, in hours; T is the second stage heat preservation temperature in step S4, in degrees Celsius; K2 is 0.8 to 4.5.

[0015] And K1 and K2 satisfy 1.2≤K2 / K1≤4;

[0016] S5: The particles obtained in step S4 are washed, matured and dried to obtain the perlite-based adsorbent material.

[0017] This invention focuses on the open pore structure of expanded perlite, and continuously controls the infiltration process of aluminum-containing precursors and the subsequent transformation and fixation process within the pores. This allows the aluminum-containing components to first enter the surface layer and open pores of the carrier, and then complete the confined transformation and stable fixation under controlled conditions. As a result, the aluminum-based active components are further expanded from being loaded on the outer surface of the particles to being synergistically fixed on the particle surface and inside the open pores, which is more conducive to balancing the loading of active components, pore accessibility and stability in use.

[0018] In this invention, expanded perlite undergoes pretreatment to optimize its surface and open pore state. Polyaluminum chloride and urea are then combined to prepare an impregnation solution, which is used to introduce aluminum-containing precursors into the open pores via vacuum impregnation. Subsequently, staged heating causes the urea to gradually decompose and release alkaline components, allowing the aluminum species already in the pores to undergo confined hydrolysis and fixation within and near the pore openings. The resulting aluminum-based components can be distributed on the particle surface and within the open pores, thereby improving the utilization rate of effective sites during phosphorus removal while maintaining particle mass transfer pathways.

[0019] This invention further establishes a K1 relationship in the infiltration stage to comprehensively control the process of aluminum-containing precursors entering open pores. K1 incorporates the absolute value of vacuuming, vacuuming duration, number of cycles, and particle size into a unified constraint. The absolute value of vacuuming, vacuuming duration, and number of cycles collectively affect the ability of the impregnating liquid to expel gas from the pores and enter the pore channels, while the particle size affects the path length and infiltration resistance of the impregnating liquid into the particle interior. By restricting these factors in a correlated manner, a better matching relationship can be formed between the infiltration driving force and the particle size, allowing the aluminum-containing precursor to be distributed at an appropriate depth and in an appropriate amount on the particle surface and in the open pore region. This provides a uniform and effective precursor foundation for subsequent in-pore fixation and facilitates the formation of a particle structure that balances the loading of active components and the degree of pore openness.

[0020] This invention further establishes a K2 relationship for the transformation stage to comprehensively control the transformation process of aluminum species from an infiltrated state to a fixed state after entering the pores. K2 incorporates the molar ratio of urea to aluminum, the second-stage holding time, and the second-stage holding temperature into a unified constraint. The molar ratio of urea to aluminum affects the local alkalization capacity of the system; the second-stage holding time affects the degree of aluminum species transformation; and the second-stage holding temperature affects the urea decomposition rate and the extent of aluminum species hydrolysis, hydroxylation, and fixation. During heating, urea gradually releases alkaline components, creating a progressively alkalized environment within the pores, which is more conducive to the restricted transformation of aluminum species within and near the pore openings. By synergistically constraining the above factors, aluminum species entering the pores can be fixed at an appropriate rate and location, improving the binding stability of the active components and the carrier structure, and helping to maintain the dispersion of active sites within the pores.

[0021] In this invention, K2 and K1 are further controlled in a coordinated manner, satisfying 1.2 ≤ K2 / K1 ≤ 4, to ensure that the degree of infiltration introduction is coordinated with the subsequent degree of in-pore transformation. K1 primarily characterizes the degree to which the precursor enters the open pores, while K2 primarily characterizes the ability of the precursor to complete fixation within the pores after entry. Both factors work together to influence the final distribution of the aluminum-based component on the particle surface and within the open pores. By controlling their ratio within the aforementioned range, the precursor's entry depth, in-pore distribution, and subsequent confined transformation rhythm can be kept consistent. This allows the aluminum-based fixation layer to effectively enter the open pores to form usable sites while maintaining structural coordination between the particle surface and the pore region, thereby further improving the mass transfer performance and fixation stability of the material under fixed-bed operating conditions.

[0022] Through the above technical solution, the obtained particulate material forms a relatively stable aluminum-based immobilized layer on the surface and within the open pores. When the phosphorus-containing water to be treated flows through the fixed bed, phosphorus can not only contact the active sites on the outer surface of the particles, but also enter the near-surface interior along the retained open pores, continuously interacting with the dispersed sites within the pores, thereby improving the effective adsorption and utilization rate per unit particle. Simultaneously, because the aluminum species undergo restricted transformation within the pores and are fixed after washing and aging, their binding state is more stable, thus making it easier to control aluminum leaching during use and suitable for treating phosphorus-containing water under continuous flow conditions.

[0023] Preferably, the pretreatment in step S1 includes pickling, washing with water, and drying.

[0024] Preferably, in step S2, the concentration of polyaluminum chloride, calculated as Al2O3, is 0.5–5.0 wt%, and the concentration of urea is 0.5–8.0 wt%.

[0025] In this invention, controlling the concentration of polyaluminum chloride within the aforementioned range helps maintain a suitable precursor supply level for aluminum species entering the perlite surface and open pores, thereby providing a material basis for the subsequent formation of an aluminum-based support layer with a certain degree of dispersion and continuity on the particle surface and within the pores. This concentration range is beneficial for balancing the source of active component loading with the structural coordination of the pore openings and open pore regions, enabling the aluminum-based components formed by subsequent thermal conversion to achieve a relatively balanced spatial distribution on the surface and within the pores, thus facilitating the mass transfer and accessibility of the open pores of the particles.

[0026] Meanwhile, controlling the urea concentration within the aforementioned range facilitates the formation of gradual alkalization conditions adapted to the distribution of precursors within the pores during heat treatment. This allows aluminum species already inside the open pores to complete hydrolysis, hydroxylation, and immobilization transformation within a suitable time and space. Since urea serves as the source of slow-release alkalization within the pores in this scheme, its concentration within the aforementioned range is more conducive to promoting the gradual, restricted transformation of aluminum species within and near the pore openings, and improving the binding stability between the active component and the carrier structure. Consequently, the resulting aluminum-based immobilized layer possesses both good dispersibility and stability.

[0027] Furthermore, controlling the concentrations of polyaluminum chloride and urea within the aforementioned ranges essentially ensures that the amount of aluminum precursor infiltrated and the sustained-release alkalization capacity available during subsequent heat treatment remain within a suitable range for confined conversion, thus achieving a good match between the introduction of aluminum-containing components and the subsequent intrapore immobilization capacity. Based on this fundamental matching relationship, aluminum species can form a dispersed and stable aluminum-based immobilization layer on the particle surface and inside the open pores while maintaining pore openness. This is beneficial for improving the actual adsorption and utilization efficiency of phosphorus by the particulate material and enhancing the stability of the active components during use in water.

[0028] Preferably, the molar ratio R of urea to aluminum in step S2 is... u The ratio is 3:1 to 15:1.

[0029] R u Controlling the ratio within the aforementioned range is beneficial for ensuring that each aluminum species corresponds to a suitable alkalization source, allowing the local environment within the pores to gradually develop alkalization conditions adapted to the transformation of aluminum species during heat treatment. This promotes the hydrolysis, hydroxylation, and immobilization transformation of aluminum species within the open pores, and improves the retention of aluminum-based active components in the carrier structure. Based on this molar ratio range, the aluminum-containing precursor entering the pores can achieve a smooth transformation from an infiltrated state to an immobilized state within a suitable time and space range, thus facilitating the formation of more stable aluminum-based active sites.

[0030] At the same time, R u Within the aforementioned range, it is also beneficial to maintain coordination between the transformation process of aluminum species and the spatial distribution within the pores, allowing the formed aluminum-based immobilization layer to achieve a more reasonable distribution on the particle surface and inside the open pores. Thus, the aluminum-based component can not only obtain better immobilization conditions within the pores but also maintain structural coordination and active site dispersion in the open pore region, thereby balancing effective loading rate, pore accessibility, and the utilization degree of active components.

[0031] Preferably, the absolute value P of the vacuum pumping in step S3 v The pressure is 0.04–0.09 MPa, and the duration of a single vacuum pumping is t. vThe time is 5 to 25 minutes, the number of vacuuming-restoring atmospheric pressure cycles N is 1 to 3 times, and the average particle size d is 2.5 to 5.0 mm.

[0032] By adopting the above technical solution, the driving force, action time and particle size of the infiltration liquid entering the open pores of perlite can be synergistically adjusted, so that the aluminum-containing precursor can be distributed in the open pore region on the surface and near the surface of the particles with appropriate entry depth and amount, thereby providing a suitable precursor distribution basis for subsequent in-pore confined transformation.

[0033] Expanded perlite is a porous granular material. Its internal open pores are typically occupied by gas before impregnation. The process of the impregnating liquid entering the pores is related not only to the magnitude of the negative pressure but also to the duration of the negative pressure, the opportunity for liquid backfilling upon restoration to normal pressure, and the length of the particle's own infiltration path. By using P... v t v The coordinated control of N and d helps to maintain a balance between the degree of original gas discharge in the pores, the degree of impregnation liquid backfilling, and the difficulty of particle penetration. This allows aluminum-containing precursors to enter open pores and form a more reasonable spatial distribution under different particle size conditions, thereby improving the stability and consistency of the impregnation process.

[0034] Furthermore, P v Controlling the pressure within the above range is beneficial for creating a suitable negative pressure driving force, allowing the gas in the open pores of the perlite to be effectively released, and providing conditions for the infiltrate to enter the pores after restoring normal pressure; t v Controlling the pressure within the aforementioned range allows for a suitable duration of negative pressure during venting, promoting the penetration of the impregnating fluid into the open pore areas on the particle surface and near the surface. Maintaining nitrogen (N) at 1-3 times facilitates repeated vacuuming and atmospheric pressure restoration, increasing the chances of the impregnating fluid backfilling the pore space and ensuring a more thorough and balanced introduction of the aluminum-containing precursor into the open pores of the particles. Based on the synergistic effect of these parameters, the impregnation driving force and the process can be kept at an appropriate level, thus facilitating the formation of a precursor suitable for subsequent solidification.

[0035] Meanwhile, controlling the average particle size d of the pretreated perlite within the range of 2.5–5.0 mm helps to adapt the difficulty of entering the internal pores of the particles to the vacuum infiltration conditions. This particle size range is beneficial for the distribution of aluminum-containing precursors along the particle surface to the near-surface open pore region, and also helps to maintain the stability of the particle structure and good fluid access under fixed-bed operation conditions. Particle size parameters and P v t vThe combined action of nitrogen and phosphorus can maintain good coordination in the process of the impregnating liquid entering the internal open pores at different particle sizes, thereby enabling the aluminum precursor to form a more suitable penetration depth and distribution state on the particle surface and in the open pores.

[0036] Furthermore, P v t v Controlling N and d within the aforementioned ranges essentially aims to create a matching relationship between the driving force, action time, repeated entry opportunities, and internal penetration path of the leachate into the open pores, resulting in a more coordinated distribution of the aluminum-containing precursor on the particle surface and in the open pores. Based on this synergistic control, the resulting material is better able to balance the effective loading of aluminum-based active sites, the degree of pore openness, and mass transfer performance under fixed-bed operating conditions, thereby improving the actual treatment effect on phosphorus-containing water and the stability of the material in use.

[0037] Preferably, the segmented heating treatment in step S4 includes a first stage of heat preservation and a second stage of heat preservation. The first stage heat preservation temperature is 55-70°C and the heat preservation time is 0.5-2 h. The second stage heat preservation temperature is 75-95°C and the heat preservation time is 1-5 h.

[0038] By adopting the above technical solution, the transformation process of aluminum species in the pores can be regulated in stages, so that the precursors that infiltrate into the open pores of perlite can first complete the distribution stabilization and preliminary transformation, and then further complete a more sufficient solidification transformation, thereby promoting the formation of a coordinated solidification structure of aluminum-based components on the particle surface and inside the open pores.

[0039] For the polyaluminum chloride and urea system entering the pores, temperature conditions not only affect the rate of urea decomposition and release of alkaline components, but also the hydrolysis, hydroxylation, aggregation, and immobilization processes of aluminum species. By adopting a segmented heating method, it is beneficial to gradually advance the alkalization process and the aluminum species transformation process within the pores from slow to strong, ensuring that the spatial distribution of the precursors within the pores is coordinated with the subsequent immobilization rhythm, thereby providing suitable heat treatment conditions for the formation of a dispersed and stable aluminum-based immobilized layer.

[0040] Furthermore, controlling the first-stage heat preservation temperature at 55–70℃ and the heat preservation time at 0.5–2 h is beneficial for promoting a more stable distribution of the impregnating liquid in the pore and orifice areas under relatively mild thermal conditions, and for allowing urea to begin to decompose gradually, providing conditions for the formation of a progressively alkaline environment within the pores. During this stage, aluminum species can smoothly transition from the impregnated state to the initial transformation state, thereby improving the coordination of precursor distribution within the pores and near the surface, and laying the foundation for subsequent further fixation.

[0041] Meanwhile, controlling the second-stage holding temperature at 75–95℃ and the holding time at 1–5 h is beneficial for further promoting the hydrolysis, hydroxylation, and immobilization transformation of aluminum species based on the distribution state and preliminary alkalization conditions established in the previous stage. This ensures that the aluminum-based components are stably distributed on the particle surface and inside the open pores. This stage, in conjunction with the first stage, helps maintain consistency between the degree of aluminum species transformation and the distribution state within the pores, thereby improving the binding stability between the active components and the carrier structure and maintaining good structural coordination in the open pore region.

[0042] Furthermore, controlling the temperature and time in the above two stages within appropriate ranges essentially involves continuously regulating the urea decomposition rate, the local alkalization process within the pores, and the aluminum species immobilization rhythm. This allows the aluminum species to gradually transform from precursors to immobilized active components under suitable heat treatment conditions. Based on this segmented heating control, the resulting aluminum-based immobilized layer is more conducive to maintaining a stable distribution on the particle surface and within the open pores, while also maintaining good pore accessibility. This facilitates continuous contact between phosphorus in the water and the particle surface and near-surface internal sites under fixed-bed operation conditions, improving the actual phosphorus removal efficiency and operational stability of the material.

[0043] Preferably, the ripening temperature in step S5 is 30–60°C, the relative humidity is 60%–95%, and the ripening time is 6–24 h.

[0044] By adopting the above technical solution, after washing and before final drying, an environment is provided for further stabilizing and adjusting the bonding state of the aluminum-based components formed on the surface of perlite and in open pores, thereby promoting a more coordinated and stable interfacial bonding relationship between the aluminum-based solid layer and the carrier structure.

[0045] After staged heating, the aluminum species have undergone major transformation within the pores and at the pore openings, forming a preliminary fixed state on the particle surface and inside the open pores. By setting the above-mentioned maturation conditions, it is beneficial for the aluminum-based components to continue to undergo local structural adjustment, surface hydroxyl state optimization, and interfacial bonding stabilization in a relatively mild temperature and humidity environment. This makes the bond between the aluminum and the perlite pore walls and surface areas more stable, thus providing conditions for maintaining the structure during the subsequent drying process.

[0046] Furthermore, controlling the curing temperature at 30–60°C helps provide a suitable structural adjustment environment for the aluminum-based components, allowing the substrate layer, which is still evolving after washing, to achieve further stabilization under relatively mild conditions. Controlling the relative humidity at 60%–95% helps maintain suitable and moderate water loss conditions during the curing process, promoting balanced adjustment of the aluminum-based components within the pores and on the surface. Controlling the curing time at 6–24 h helps ensure that the above stabilization process has a suitable duration, thereby improving the adhesion stability and structural compatibility of the aluminum-based substrate layer.

[0047] Furthermore, controlling the curing temperature, humidity, and time within the aforementioned range essentially allows the aluminum-based immobilized layer to undergo a moderate, gradual stabilization phase after washing, enabling it to form a relatively stable bonded and dispersed state before subsequent drying. Based on this curing process, the aluminum-based component in the resulting particulate material is more likely to maintain stable adhesion on the surface and within open pores, while maintaining a good degree of pore openness. This facilitates the maintenance of the mass transfer pathway from phosphorus to near-surface internal sites of the particles under fixed-bed operation conditions, and improves the stability of the adsorption process and resistance to leaching during use.

[0048] The second aspect of the present invention provides a perlite-based adsorbent material prepared by the preparation method described above, wherein the perlite-based adsorbent material is a particulate material with a particle size of 2 to 6 mm, and its surface and open pores contain an aluminum-based support layer.

[0049] In this invention, the obtained material is a particulate material with a particle size of 2-6 mm, and its particle surface and open pores contain an aluminum-based support layer. These limitations adapt the material structure to the fixed-bed application method, enabling the particulate material to maintain good packing stability and water permeability while possessing the structural characteristic of the surface layer and open pores synergistically participating in adsorption.

[0050] The particle size is controlled between 2 and 6 mm, which is beneficial for the stable loading and continuous operation of the material in the fixed bed, while also taking into account particle strength, bed water flow conditions, and mass transfer performance. The aluminum-based support layer is distributed on the particle surface and inside the open pores, which allows the phosphorus-containing water to not only contact the active sites on the outer surface of the particles when flowing through the particle bed, but also to enter the near-surface interior along the open pores and interact with the sites inside the pores, thereby improving the utilization of the active components.

[0051] Meanwhile, the aluminum-based component is bonded to the particle surface and open pores in the form of a solid support layer, which helps to improve the binding stability between the active component and the carrier, enabling the material to maintain good structural stability and adsorption stability under continuous use conditions.

[0052] Preferably, the aluminum loading (calculated as Al2O3) in the perlite-based adsorbent material is 1.5–12 wt%, and after soaking the perlite-based adsorbent material in deionized water for 24 h, the leachate contains Al2O3. 3+ The calculated leaching amount is no higher than 8% of the total aluminum content in the material.

[0053] By adopting the above technical solution, the loading level of aluminum-based active components in the material and their ability to maintain stability in the aquatic environment are defined, so that the resulting material has both good phosphorus removal foundation and use stability.

[0054] Controlling the aluminum loading to 1.5–12 wt% is beneficial for forming an aluminum-based immobilization layer with appropriate content on the surface of perlite particles and within open pores, thereby providing sufficient active sites for phosphorus removal. This loading range is conducive to balancing the quantity, spatial distribution, and pore structure coordination of active components, allowing aluminum-based components to be distributed in a suitable state on the particle surface and within open pores, thus improving the actual utilization rate of active sites per unit particle.

[0055] Meanwhile, after 24 hours of soaking, use A l3+ The leaching amount is controlled to be no more than 8% of the total aluminum content in the material. This is beneficial for characterizing the immobilization stability of the aluminum-based components in the aquatic environment, indicating that the aluminum-based components in the material can be stably bound to the perlite surface and open pores. Based on this limitation, the aluminum-based active sites can still maintain good adhesion stability and structural integrity after contact with water, thus helping to maintain the material's activity retention capacity during use.

[0056] A third aspect of the present invention provides a method for treating phosphorus-containing water, wherein the perlite-based adsorbent material described above is filled into a fixed bed, and the water to be treated flows through the fixed bed to remove phosphorus from the water.

[0057] The present invention, by adopting the above technical solution, has the following beneficial effects:

[0058] (1) Based on the open pore structure of expanded perlite, this invention connects the pretreatment, vacuum impregnation, segmented heating conversion, washing and maturation steps one after another, so that the aluminum-containing precursor first enters the particle surface and open pores, and then completes the restricted conversion and stable fixation in the pores and near the pore openings. The aluminum-based components formed in this way no longer mainly stay in the outermost layer of the particles, but are distributed in a coordinated manner in the surface and the interior of the open pores, so that the material can increase the utilization of effective sites that can participate in the phosphorus removal process while maintaining the water permeability and pore accessibility of the particles.

[0059] (2) This invention uses K1, K2, and their ratio to control the degree of infiltration and subsequent in-pore conversion, ensuring that the precursor's entry depth, in-pore distribution, and loading rhythm are matched. This avoids the problem of low in-pore loading due to insufficient infiltration and also suppresses surface enrichment, pore blockage, and localized deposition thickening due to excessively rapid conversion. Consequently, the resulting material more easily achieves a suitable aluminum loading, good pore openness, and a stable dispersion of active sites. Therefore, under fixed-bed operation conditions, the material is more conducive to maintaining the mass transfer path of phosphorus in water to near-surface internal sites of particles, thus improving the actual adsorption efficiency.

[0060] (3) The material obtained by this invention is a particulate material suitable for fixed bed packing, and the aluminum-based component in the material has good stability in the aquatic environment. By comprehensively limiting the aluminum loading, aluminum leaching level, particle size, and aging conditions, the material not only has good phosphorus removal capacity, but also reduces the tendency of aluminum loss during use and maintains the stability of particle structure and bed operation. Therefore, this solution is more suitable for the treatment of phosphorus-containing water under continuous flow conditions, taking into account both treatment effect and reliability. Attached Figure Description

[0061] Figure 1 This is a line scan curve of Al element in the particle cross section of Example 1;

[0062] Figure 2 Line scan curves of Al element in the cross-section of particles in Comparative Example 3;

[0063] Figure 3 The image shows the Al element line scan curve of the particle cross section in Comparative Example 7. Detailed Implementation

[0064] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0065] Unless otherwise defined, all scientific and technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art.

[0066] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0067] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0068] The present invention will now be described in detail with reference to specific embodiments, which are intended to understand rather than limit the invention.

[0069] Unless otherwise specified, the polyaluminum chloride used in the following examples and comparative examples is industrial-grade liquid polyaluminum chloride with an effective content of 30% based on Al2O3; the urea is analytical grade; the expanded perlite is commercially available expanded perlite granules; and the deionized water is laboratory-made deionized water.

[0070] Example 1

[0071] This embodiment discloses a method for preparing a perlite-based adsorbent material, including the following steps:

[0072] S1: Take 1000 g of commercially available expanded perlite granules, and select granules with an average particle size of 4.0 mm after sieving. Add the expanded perlite granules to 4000 mL of a 3% hydrochloric acid solution, soak at 25°C for 30 min, and stir at 200 rpm for 10 min during the soaking process. After acid washing, discard the acid solution and rinse repeatedly with deionized water until the pH of the washing solution reaches 6.8. Place the washed granules in a 105°C forced-air drying oven and dry for 4 h to obtain pretreated perlite.

[0073] S2: Polyaluminum chloride was added to deionized water to prepare 3000 mL of a polyaluminum chloride solution with a concentration of 2.5 wt% (Al2O3). Then, 75 g of urea was added to this solution, and the mixture was stirred at 300 rpm for 20 min at 25°C to obtain the impregnation solution. In step S2, the molar ratio R of urea to aluminum is... u The ratio is controlled at 6:1.

[0074] S3: Place all the pretreated perlite obtained in step S1 into the impregnation solution obtained in step S2, ensuring the liquid level is 30 mm above the perlite particles. Place the container holding the system in a vacuum device and evacuate to an absolute value P. v The pressure is controlled at 0.07 MPa, and the duration of a single vacuum pumping is t. v Soaking time is 15 minutes, then the pressure is restored to normal and soaking continues for another 15 minutes, repeating this cycle twice. After soaking is complete, the particles are removed and drained at 25°C for 10 minutes.

[0075] In this step, K1 = 0.07 × 15 × 2 ÷ 4.0 = 0.525.

[0076] S4: Spread the perlite granules processed in step S3 evenly on a stainless steel tray and place it in a forced-air drying oven for segmented heating treatment. The first stage heat treatment temperature is 65℃, and the heat treatment time is 1 hour; the second stage heat treatment temperature T is 85℃, and the heat treatment time t is 2 hours. After the heat treatment is completed, allow it to cool naturally to 25℃.

[0077] In this step, K2 = 6 × 2 × 10 ÷ 85 = 1.41;

[0078] K2 / K1 = 1.41 ÷ 0.525 = 2.69.

[0079] S5: Wash the particles obtained in step S4 with deionized water 3 times, using 3000 mL of deionized water each time, and filter after washing for 5 min; then place the washed particles in an environment of 45℃ and 80% relative humidity for 12 h to mature; finally dry at 80℃ for 5 h to obtain perlite-based adsorbent material.

[0080] Example 2

[0081] This embodiment discloses a method for preparing a perlite-based adsorbent material, including the following steps:

[0082] S1: Take 1000 g of commercially available expanded perlite granules, and select granules with an average particle size of 3.2 mm after sieving. Add the granules to 4000 mL of a 4% hydrochloric acid solution, soak at 25°C for 25 min, and stir at 250 rpm for 10 min during the soaking process. After acid washing, discard the acid solution, wash repeatedly with deionized water until the pH of the washing solution reaches 6.7, and then dry at 100°C for 5 h to obtain pretreated perlite.

[0083] S2: Polyaluminum chloride was added to deionized water to prepare 3000 mL of a polyaluminum chloride solution with a concentration of 3.8 wt% (Al2O3). Then, 114 g of urea was added to this solution, and the mixture was stirred at 300 rpm for 25 min at 25°C to obtain the impregnation solution. In step S2, the molar ratio R of urea to aluminum is... u The ratio is controlled at 8:1.

[0084] S3: Place the pretreated perlite obtained in step S1 into the impregnation solution obtained in step S2, and treat it under vacuum conditions, with the absolute value of the vacuum being P. v The pressure is 0.08 MPa, and the duration of a single vacuum pumping operation is t. v The soaking time was 16 min, followed by 20 min at normal pressure, and this cycle was repeated twice. After soaking, the particles were removed and drained at 25°C for 10 min.

[0085] In this step, K1 = 0.08 × 16 × 2 ÷ 3.2 = 0.80.

[0086] S4: Place the particles obtained in step S3 into a forced-air drying oven for segmented heating treatment. The first stage of heat treatment is held at 68℃ for 1.5 h; the second stage of heat treatment is held at 90℃ for 2 h. After the heat treatment is completed, allow the particles to cool naturally to 25℃.

[0087] In this step, K2 = 8 × 2 × 10 ÷ 90 = 1.78;

[0088] K2 / K1 = 1.78 ÷ 0.80 = 2.23.

[0089] S5: Wash the particles obtained in step S4 with deionized water 3 times, each time using 3000 mL of deionized water, and filter after washing for 5 min; then mature at 50℃ and 85% relative humidity for 18 h, and then dry at 85℃ for 5 h to obtain perlite-based adsorbent material.

[0090] Example 3

[0091] This embodiment discloses a method for preparing a perlite-based adsorbent material, including the following steps:

[0092] S1: Take 1000 g of commercially available expanded perlite granules, and select granules with an average particle size of 4.6 mm after sieving. Add the granules to 4000 mL of a 2% hydrochloric acid solution, soak at 25°C for 20 min, and stir at 200 rpm for 8 min during the soaking process. After acid washing, discard the acid solution, wash repeatedly with deionized water until the pH of the washing solution reaches 6.9, and then dry at 110°C for 3 h to obtain pretreated perlite.

[0093] S2: Polyaluminum chloride was added to deionized water to prepare 3000 mL of a polyaluminum chloride solution with a concentration of 1.2 wt% (Al2O3). Then, 36 g of urea was added to this solution, and the mixture was stirred at 300 rpm for 15 min at 25°C to obtain the impregnation solution. In step S2, the molar ratio R of urea to aluminum is... u The ratio is 4:1.

[0094] S3: Place the pretreated perlite obtained in step S1 into the impregnation solution obtained in step S2, and apply a vacuum with an absolute value P. v The pressure is controlled at 0.05 MPa, and the duration of a single vacuum pumping operation is t. v The soaking time was 12 min, followed by 10 min at normal pressure, and this cycle was repeated twice. After soaking, the particles were removed and drained at 25°C for 10 min.

[0095] In this step, K1 = 0.05 × 12 × 2 ÷ 4.6 = 0.261.

[0096] S4: The particles obtained in step S3 are subjected to segmented heating treatment. The first stage is held at a temperature of 58℃ for 0.8 h; the second stage is held at a temperature of 78℃ for 2 h. After the treatment, the particles are allowed to cool naturally to 25℃.

[0097] In this step, K2 = 4 × 2 × 10 ÷ 78 = 1.03;

[0098] K2 / K1 = 1.03 ÷ 0.261 = 3.95.

[0099] S5: Wash the particles obtained in step S4 with deionized water 3 times, each time using 3000 mL of deionized water, and filter after washing for 5 min; then mature in an environment of 35℃ and 70% relative humidity for 8 h, and then dry at 75℃ for 4 h to obtain perlite-based adsorbent material.

[0100] Comparative Example 1

[0101] This comparative example discloses a method for preparing a perlite-based adsorbent material, comprising the following steps:

[0102] S1: Take 1000 g of commercially available expanded perlite granules, and select granules with an average particle size of 4.0 mm after sieving. Do not perform acid washing, water washing and drying pretreatment.

[0103] S2: Polyaluminum chloride was added to deionized water to prepare 3000 mL of a polyaluminum chloride solution with a concentration of 2.5 wt% (Al2O3). Then, 75 g of urea was added to this solution, and the mixture was stirred at 300 rpm for 20 min at 25°C to obtain the impregnation solution. In step S2, the molar ratio R of urea to aluminum is... u The ratio is controlled at 6:1.

[0104] S3: Place all the perlite particles obtained in step S1 into the impregnation solution obtained in step S2, and apply a vacuum with an absolute value P. v The pressure is 0.07 MPa, and the duration of a single vacuum pumping operation is t. v The soaking time is 15 minutes, followed by 15 minutes of restoring normal pressure immersion, and this cycle is repeated twice.

[0105] S4: The particles obtained in step S3 are subjected to segmented heating treatment. The first stage heat treatment temperature is 65℃ and the heat treatment time is 1 h; the second stage heat treatment temperature T is 85℃ and the heat treatment time t is 2 h.

[0106] S5: After washing the particles obtained in step S4 three times, they are aged in an environment of 45℃ and 80% relative humidity for 12 h, and then dried at 80℃ for 5 h to obtain perlite-based adsorbent material.

[0107] Comparative Example 2

[0108] This comparative example discloses a method for preparing a perlite-based adsorbent material, comprising the following steps:

[0109] S1: The expanded perlite particles were pretreated according to the method of Example 1 to obtain pretreated perlite with an average particle size d of 4.0 mm.

[0110] S2: Prepare the impregnation solution according to the method in Example 1. In step S2, the molar ratio R of urea to aluminum is... u The ratio is controlled at 6:1.

[0111] S3: Place the pretreated perlite obtained in step S1 into the impregnation solution obtained in step S2, and apply a vacuum with an absolute value P. v The pressure is 0.03 MPa, and the duration of a single vacuum pumping operation is t. v For 5 minutes, restore normal pressure and soak for 10 minutes, repeat once.

[0112] In this step, K1 = 0.03 × 5 × 1 ÷ 4.0 = 0.0375.

[0113] S4: Perform segmented heating treatment according to the method of Example 1. The second stage heat preservation temperature is 85°C and the heat preservation time is 2 hours.

[0114] S5: Wash, mature and dry according to the method of Example 1 to obtain perlite-based adsorbent material.

[0115] Comparative Example 3

[0116] This comparative example discloses a method for preparing a perlite-based adsorbent material, comprising the following steps:

[0117] S1: The expanded perlite particles were pretreated according to the method of Example 1 to obtain pretreated perlite with an average particle size d of 4.0 mm.

[0118] S2: Prepare the impregnation solution according to the method in Example 1. In step S2, the molar ratio R of urea to aluminum is... u The ratio is controlled at 6:1.

[0119] S3: Place the pretreated perlite obtained in step S1 into the impregnation solution obtained in step S2, and apply a vacuum with an absolute value P. v The pressure is 0.09 MPa, and the duration of a single vacuum pumping operation is t. v The soaking time is 25 minutes, followed by 20 minutes of restoring normal pressure immersion, and this cycle is repeated 3 times.

[0120] In this step, K1 = 0.09 × 25 × 3 ÷ 4.0 = 1.6875.

[0121] S4: Perform segmented heating treatment according to the method of Example 1. The second stage heat preservation temperature is 85°C and the heat preservation time is 2 hours.

[0122] S5: Wash, mature and dry according to the method of Example 1 to obtain perlite-based adsorbent material.

[0123] Comparative Example 4

[0124] This comparative example discloses a method for preparing a perlite-based adsorbent material, comprising the following steps:

[0125] S1: Preprocess according to the method of Example 1.

[0126] S2: Polyaluminum chloride was added to deionized water to prepare 3000 mL of a polyaluminum chloride solution with a concentration of 2.5 wt% (Al2O3). Then, 37.5 g of urea was added to this solution, and the mixture was stirred at 300 rpm for 20 min at 25°C to obtain the impregnation solution. In step S2, the molar ratio R of urea to aluminum is... u The ratio is controlled at 3:1.

[0127] S3: Perform vacuum impregnation treatment according to the method of Example 1.

[0128] In this step, K1 = 0.525.

[0129] S4: The particles obtained in step S3 are subjected to segmented heating treatment. The first stage heat treatment temperature is 60℃ and the heat treatment time is 0.5 h; the second stage heat treatment temperature T is 95℃ and the heat treatment time t is 1 h.

[0130] In this step, K2 = 3 × 1 × 10 ÷ 95 = 0.316.

[0131] S5: Wash, mature and dry according to the method of Example 1 to obtain perlite-based adsorbent material.

[0132] Comparative Example 5

[0133] This comparative example discloses a method for preparing a perlite-based adsorbent material, comprising the following steps:

[0134] S1: Preprocess according to the method of Example 1.

[0135] S2: Polyaluminum chloride was added to deionized water to prepare 3000 mL of a polyaluminum chloride solution with a concentration of 2.5 wt% (Al2O3). Then, 187.5 g of urea was added to this solution, and the mixture was stirred at 300 rpm for 20 min at 25°C to obtain the impregnation solution. In step S2, the molar ratio R of urea to aluminum is... u The ratio is 15:1.

[0136] S3: Perform vacuum impregnation treatment according to the method of Example 1.

[0137] In this step, K1 = 0.525.

[0138] S4: The particles obtained in step S3 are subjected to segmented heating treatment. The first stage heat treatment temperature is 70℃ and the heat treatment time is 2 h; the second stage heat treatment temperature T is 75℃ and the heat treatment time t is 3 h.

[0139] In this step, K2 = 15 × 3 × 10 ÷ 75 = 6.0.

[0140] S5: Wash, mature and dry according to the method of Example 1 to obtain perlite-based adsorbent material.

[0141] Comparative Example 6

[0142] This comparative example discloses a method for preparing a perlite-based adsorbent material, comprising the following steps:

[0143] S1: Pre-treatment was performed according to the method of Example 1 to obtain pre-treated perlite with an average particle size d of 3.0 mm.

[0144] S2: Polyaluminum chloride was added to deionized water to prepare 3000 mL of a polyaluminum chloride solution with a concentration of 2.5 wt% (Al2O3). Then, 100 g of urea was added to this solution, and the mixture was stirred at 300 rpm for 20 min at 25°C to obtain the impregnation solution. In step S2, the molar ratio R of urea to aluminum is... u The ratio is controlled at 8:1.

[0145] S3: Place the pretreated perlite obtained in step S1 into the impregnation solution obtained in step S2, and apply a vacuum with an absolute value P. v The pressure is 0.09 MPa, and the duration of a single vacuum pumping operation is t. v The soaking time is 20 minutes, followed by 15 minutes of restoring normal pressure immersion, and this cycle is repeated twice.

[0146] In this step, K1 = 0.09 × 20 × 2 ÷ 3.0 = 1.20.

[0147] S4: The particles obtained in step S3 are subjected to segmented heating treatment. The first stage heat treatment temperature is 60℃ and the heat treatment time is 1 h; the second stage heat treatment temperature T is 90℃ and the heat treatment time t is 1 h.

[0148] In this step, K2 = 8 × 1 × 10 ÷ 90 = 0.889;

[0149] K2 / K1 = 0.889 ÷ 1.20 = 0.74.

[0150] S5: Wash, mature and dry according to the method of Example 1 to obtain perlite-based adsorbent material.

[0151] Comparative Example 7

[0152] This comparative example discloses a method for preparing a perlite-based adsorbent material, comprising the following steps:

[0153] S1: Pre-treatment was performed according to the method of Example 1 to obtain pre-treated perlite with an average particle size d of 4.0 mm.

[0154] S2: Polyaluminum chloride was added to deionized water to prepare 3000 mL of a polyaluminum chloride solution with a concentration of 2.5 wt% (Al2O3). Then, 150 g of urea was added to this solution, and the mixture was stirred at 300 rpm for 20 min at 25°C to obtain the impregnation solution. In step S2, the molar ratio R of urea to aluminum is... u The ratio is controlled at 12:1.

[0155] S3: Place the pretreated perlite obtained in step S1 into the impregnation solution obtained in step S2, and apply a vacuum with an absolute value P. v The pressure is 0.04 MPa, and the duration of a single vacuum pumping operation is t. v The soaking time is 8 minutes, followed by 10 minutes of restoring normal pressure immersion, and this cycle is repeated once.

[0156] In this step, K1 = 0.04 × 8 × 1 ÷ 4.0 = 0.08.

[0157] S4: The particles obtained in step S3 are subjected to segmented heating treatment. The first stage heat treatment temperature is 60℃ and the heat treatment time is 1 h; the second stage heat treatment temperature T is 80℃ and the heat treatment time t is 2 h.

[0158] In this step, K2 = 12 × 2 × 10 ÷ 80 = 3.0;

[0159] K2 / K1 = 3.0 ÷ 0.08 = 37.5.

[0160] S5: Wash, mature and dry according to the method of Example 1 to obtain perlite-based adsorbent material.

[0161] Comparative Example 8

[0162] This comparative example discloses a method for preparing a perlite-based adsorbent material, comprising the following steps:

[0163] S1: Preprocess according to the method of Example 1.

[0164] S2: Prepare the impregnation solution according to the method in Example 1. In step S2, the molar ratio R of urea to aluminum is... u The ratio is controlled at 6:1.

[0165] S3: Perform vacuum impregnation treatment according to the method of Example 1.

[0166] In this step, K1 = 0.525.

[0167] S4: Perform segmented heating treatment according to the method of Example 1.

[0168] In this step, K2 = 1.41.

[0169] S5: After washing the particles obtained in step S4 with deionized water three times, without aging, they are directly dried at 80℃ for 5 h to obtain perlite-based adsorbent material.

[0170] Performance testing

[0171] 1. Aluminum Load Detection Method

[0172] Approximately 0.2000 g of perlite-based adsorbent material sample, dried to constant weight, was weighed, pulverized, and placed in a polytetrafluoroethylene digestion vessel. 8 mL of nitric acid, 2 mL of hydrochloric acid, and 2 mL of hydrofluoric acid were added. The vessel was sealed and placed in a microwave digester for digestion. The digestion program was set to heat to 180℃ and maintain for 30 min. After digestion, the solution was cooled to room temperature, transferred to a volumetric flask, and diluted to 100 mL with deionized water. The Al content in the solution was determined using inductively coupled plasma atomic emission spectrometry (ICP-AES), and the aluminum loading in the sample, expressed as Al2O3, was calculated. Each sample was measured in triplicate, and the average value was taken as the final result. The aluminum loading was calculated using the following formula:

[0173] Aluminum loading (wt%) = m1 / m0 × 100%

[0174] In the formula, m1 is the mass of aluminum in the sample as Al2O3, in g; m0 is the mass of the sample to be tested, in g.

[0175] 2. 24-hour aluminum leaching ratio detection method

[0176] Weigh 5.000 g of the dried perlite-based adsorbent material sample and place it in a 250 mL polyethylene bottle. Add 100 mL of deionized water and allow it to soak at 25 °C for 24 h. After soaking, filter the supernatant through a 0.45 μm filter membrane and determine the Al content in the filtrate using inductively coupled plasma atomic emission spectrometry. 3+ Concentration. The total aluminum content of another sample from the same batch was determined using the aluminum loading detection method, and then converted to the total aluminum content of the 5.000 g sample. The Al content in the leachate was used as the basis for the determination. 3+ The proportion of total aluminum in the sample to the total aluminum content represents the aluminum leaching rate over 24 hours. Each sample was measured in triplicate, and the average value was taken as the final result. The aluminum leaching rate was calculated using the following formula:

[0177] Aluminum leaching rate (%) = m² / m³ × 100%

[0178] In the formula, m2 represents the Al content in the leachate over 24 hours. 3+ Total amount, in mg; m3 is the total aluminum in the sample, in mg.

[0179] 3. Static adsorption capacity detection method

[0180] A phosphorus-containing simulated water with an initial total phosphorus concentration of 20.0 mg / L was prepared, using potassium dihydrogen phosphate as the phosphorus source, with concentration expressed as elemental phosphorus. 0.500 g of dried perlite-based adsorbent material was weighed and placed in a 250 mL Erlenmeyer flask. 100 mL of the above-mentioned phosphorus-containing simulated water was added, and the mixture was shaken at 25℃ and 150 rpm for 24 h. After shaking, the suspension was filtered, and the remaining total phosphorus concentration in the filtrate was determined using ammonium molybdate spectrophotometry. The static adsorption capacity was calculated based on the difference in phosphorus concentration before and after adsorption and the amount of material added. Each sample was measured in triplicate, and the average value was taken as the final result. The static adsorption capacity was calculated using the following formula:

[0181] q = (C0 - C e )×V / m

[0182] In the formula, q is the static adsorption capacity, in mg / g; C0 is the initial total phosphorus concentration, in mg / L; C e The total phosphorus concentration after equilibration is expressed in mg / L; V is the solution volume in L; and m is the sample mass in g.

[0183] 4. Method for detecting dynamic water volume treated by fixed bed

[0184] A fixed bed column made of plexiglass with an inner diameter of 20 mm and a height of 300 mm was selected. Quartz sand and glass fiber wool were laid at the bottom of the column as a support layer. 100 mL of perlite-based adsorbent material with a particle size of 2–6 mm was weighed and filled into the fixed bed, and the bed volume was recorded. Phosphorus-containing simulated water with a total phosphorus concentration of 5.0 mg / L was prepared and fed from bottom to top using a peristaltic pump. The empty bed contact time was controlled at 15 min, and the operating temperature was maintained at 25℃. Effluent samples were collected periodically, and the total phosphorus concentration in the effluent was determined using the ammonium molybdate spectrophotometric method. When the total phosphorus concentration in the effluent reached 0.5 mg / L, the cumulative treated water volume was recorded, and the ratio of this volume to the bed volume was expressed as the fixed bed treated water volume, expressed in BV. Each sample was measured once, with two parallel sets packed into the column, and the average value was taken as the final result. The fixed bed treated water volume was calculated using the following formula:

[0185] Water treatment capacity (BV) = V1 / V b

[0186] In the formula, V1 is the cumulative treated water volume when the total phosphorus concentration in the effluent reaches 0.5 mg / L, in mL; V b The volume of the packed bed is expressed in mL.

[0187] 5. Cyclic Use Performance Testing Method

[0188] After completing one fixed-bed dynamic adsorption experiment, the material in the fixed bed was removed, rinsed with deionized water to remove surface residue, and then immersed in 0.1 mol / L sodium hydroxide solution for 4 h for desorption treatment. Afterward, it was washed with deionized water until neutral and dried at 60℃ to constant weight. The regenerated sample was repacked into the fixed bed, and the next round of operation was performed according to the fixed-bed dynamic adsorption capacity detection method, repeated three times in total. The treated water volume at which the total phosphorus concentration in the effluent reached 0.5 mg / L was recorded in each round, and the retention rate of treated water volume in the third run relative to the first run was calculated. The retention rate was calculated using the following formula:

[0189] Retention rate (%) = V3 / V1 × 100%

[0190] In the formula, V3 is the fixed bed water volume processed in the third operation, in BV; V1 is the fixed bed water volume processed in the first operation, in BV.

[0191] 6. Material breakage rate testing methods

[0192] Weigh 100.00 g of the dried perlite-based adsorbent material sample and place it in a cylindrical rolling tester, rolling it at 25 rpm for 30 min. After the test, remove the sample, sieve it through a 2 mm sieve, and weigh the mass of the broken particles that pass through the sieve. The material breakage rate is expressed as the ratio of the mass of the particles passing through the sieve to the total mass of the sample before the test. Each sample is measured in triplicate, and the average value is taken as the final result. The breakage rate is calculated using the following formula:

[0193] Breakage rate (%) = m4 / m5 × 100%

[0194] In the formula, m4 is the mass of the particles that pass through the 2 mm sieve after rolling, in g; m5 is the total mass of the sample before the test, in g.

[0195] 7. BET Specific Surface Area Testing Method

[0196] After pulverizing the perlite-based adsorbent material sample, approximately 0.300 g was placed in the sample tube of a surface area analyzer and degassed under vacuum at 120℃ for 6 h to remove adsorbed water and volatile impurities from the sample surface. Following degassed, adsorption-desorption tests were performed using nitrogen adsorption at liquid nitrogen temperature. The specific surface area of ​​the sample was calculated based on the BET model. Each sample was measured twice, and the average value was taken as the final result.

[0197] 8. Total Porosity Detection Method

[0198] Using the same sample pretreatment and nitrogen adsorption-desorption test conditions as BET specific surface area detection, adsorption data were read when the relative pressure was close to 1, and the total pore volume of the sample was calculated according to the instrument software. Each sample was measured twice, and the average value was taken as the final result.

[0199] 9. Methods for detecting total phosphorus concentration

[0200] Total phosphorus concentration was determined using the ammonium molybdate spectrophotometric method. An appropriate amount of water sample was taken, and if necessary, digestion was performed first to convert all forms of phosphorus in the sample into orthophosphate. Then, ammonium molybdate colorimetric reagent and reducing agent were added. After the colorimetric reaction was completed within a specified time, the absorbance was measured at a wavelength of approximately 700 nm, and the total phosphorus concentration was calculated using a pre-plotted standard working curve. All water samples were measured twice in parallel, and the average value was taken as the final result.

[0201] The test results are shown in Tables 1 and 2.

[0202] Table 1 Example 1 6.8 3.2 18.6 165 1.8 14.2 0.112 Example 2 9.1 5 19.8 156 2 13.4 0.105 Example 3 3.2 6.6 11.3 95 1.6 12.7 0.101 Comparative Example 1 4.1 9.7 10.1 81 2.7 10.4 0.083 Comparative Example 2 1.2 12.8 5.6 39 1.9 12 0.095 Comparative Example 3 7.4 8.8 9.5 66 3.3 8.6 0.065 Comparative Example 4 4.7 14 8.3 55 2.2 11.8 0.092 Comparative Example 5 10.4 9.3 11.8 69 3.2 7.8 0.057 Comparative Example 6 6 11.4 8.9 61 2.5 10.7 0.088 Comparative Example 7 5.8 8.9 8.6 58 2.4 10.5 0.07 Comparative Example 8 6.5 7.8 14.8 116 2.8 13.7 0.108

[0203] Table 2 Example 1 165 154 146 88.5 Comparative Example 4 55 42 30 54.5 Comparative Example 8 116 94 72 62.1

[0204] As shown in Table 1, the aluminum loading (based on Al2O3) of the materials obtained in Examples 1 to 3 is at a suitable level. The aluminum loadings in Examples 1 and 2 are 6.8 wt% and 9.1 wt%, respectively, significantly higher than both Example 3 and the insufficiently impregnated Comparative Example 2. This indicates that under the combined conditions of pretreatment, vacuum impregnation, and segmented heating conversion, the aluminum-containing precursor can effectively penetrate the perlite surface and open pores, forming a stable solid load in subsequent treatment. Meanwhile, the aluminum dissolution rate after 24 h of soaking in deionized water in Examples 1 to 3 is no higher than 8%, indicating that the aluminum-based component is not simply attached to the outermost layer of the particles, but rather combined in a relatively stable state with the perlite surface and the inner walls of the open pores. Among these, Example 1 has the best overall performance with an aluminum dissolution rate of only 3.2%, demonstrating a good match between its impregnation degree and subsequent conversion degree. In contrast, the aluminum leaching ratios of Comparative Examples 1, 2, 4, 6, and 8 were significantly increased, indicating that when there is a lack of pretreatment, insufficient infiltration, insufficient conversion, imbalance in the matching relationship, or insufficient subsequent stabilization, the aluminum-based components in the material are more likely to migrate and be lost during washing and soaking.

[0205] From the perspectives of static adsorption capacity and fixed-bed water treatment capacity, Examples 1 and 2 exhibited higher levels. Specifically, Example 1 had a static adsorption capacity of 18.6 mg / g and a fixed-bed water treatment capacity of 165 BV; Example 2 had a slightly higher static adsorption capacity of 19.8 mg / g, but its fixed-bed water treatment capacity was slightly lower than Example 1. This indicates that simply increasing the aluminum loading does not necessarily lead to better dynamic treatment results. Only when the aluminum-based components maintain a relatively coordinated distribution on the surface and within the open pores can the unit loading be more fully utilized. Although Example 3 had a lower static adsorption capacity and dynamic water treatment capacity than Examples 1 and 2 due to its lower overall loading, its performance was still significantly better than most comparative examples. This demonstrates that near the lower parameter boundaries, as long as the infiltration drive, conversion intensity, and their matching relationship are within a reasonable range, materials with practical phosphorus removal capabilities can still be formed.

[0206] The comparative results further illustrate the role of each key technical feature. In Comparative Example 1, no pretreatment was performed, resulting in a decrease in aluminum loading, an increase in aluminum leaching, and significantly lower static adsorption capacity and fixed-bed treatment water volume compared to Example 1. This indicates that acid washing, water washing, and drying pretreatment are beneficial for cleaning pores, improving the surface condition of the carrier, and enhancing the effectiveness of subsequent infiltration and fixation. In Comparative Example 2, K1 was below the limit range, with an aluminum loading of only 1.2 wt%. Both static adsorption capacity and fixed-bed treatment water volume decreased significantly, indicating that insufficient infiltration driving force makes it difficult for precursors to effectively enter open pores, ultimately resulting in a low level of surface loading. In Comparative Example 3, K1 was above the limit range. Although its aluminum loading was not low, the BET specific surface area and total pore volume decreased significantly, and the fixed-bed treatment water volume was also lower than in Example 1. This indicates that an excessively strong infiltration process will cause more precursors to accumulate in local pores and macropore regions, easily forming a thicker deposition layer after subsequent conversion, thus compressing the effective mass transfer pathway.

[0207] Comparative Examples 4 and 5 correspond to cases where K2 is too low and too high, respectively. In Comparative Example 4, due to the low molar ratio of urea to aluminum and the low intensity of the second-stage heat treatment, the aluminum species that had entered the pores could not be fully converted and immobilized, resulting in an aluminum dissolution rate of 14.0%, indicating significant insufficient immobilization. In Comparative Example 5, due to excessive conversion, aluminum species were more likely to preferentially precipitate at the pore openings and surface areas. Although the aluminum loading was high, the specific surface area and total pore volume decreased significantly, and the dynamic water treatment volume did not increase accordingly, but was lower than that of Examples 1 and 2. This indicates that excessive conversion leads to surface enrichment and pore channel confinement, weakening the effective utilization of active sites.

[0208] Comparative Examples 6 and 7 further demonstrate that simply setting K1 and K2 to certain levels is insufficient to achieve good results; a proper match between them is also necessary. In Comparative Example 6, the K2 / K1 ratio is below 1.2, indicating a relatively high degree of precursor penetration into open pores, but insufficient subsequent conversion and immobilization capacity. This leads to the unstable retention of aluminum species already in the pores, resulting in an increased aluminum dissolution rate and decreased adsorption performance. In Comparative Example 7, K... 2 / A K1 value higher than 4 indicates that the subsequent transformation process is too strong relative to the infiltration degree, making aluminum species more likely to precipitate preferentially at the pore openings and surface, resulting in surface deposition and reduced pore openness. These results are consistent with the microstructure observations of representative samples.

[0209] As shown in Table 2, after three cycles of fixed-bed use, Example 1 maintained a water treatment capacity retention rate of 88.5%, significantly higher than Comparative Examples 4 and 8. This indicates that under reasonable conditions of infiltration introduction, conversion and fixation, and subsequent curing, the aluminum-based active components in the material can maintain high stability during cyclic operation. In contrast, the retention rates of Comparative Examples 4 and 8 were significantly lower, indicating that when conversion is insufficient or curing is omitted, although the material still has a certain phosphorus removal capacity in the initial stage, its performance is more prone to degradation under continuous use due to the loss of aluminum-based components or insufficient stability of the fixation layer.

[0210] The results above demonstrate that the pretreatment, vacuum infiltration, segmented heating conversion, and aging drying steps employed in this application are not isolated conventional processes, but rather form a continuous and interconnected regulatory system centered around the open pore structure of perlite and the intrapore fixation process of the aluminum-based components. By coordinating and controlling K1, K2, and the K2 / K1 ratio, the aluminum-containing precursor can penetrate the perlite surface and open pores to an appropriate extent, and complete the confined conversion and stable fixation at an appropriate pace in subsequent processing. This results in a material that simultaneously possesses a high effective aluminum loading, a low aluminum leaching tendency, and good dephosphorization capabilities.

[0211] Example 1, Comparative Example 3, and Comparative Example 7 were selected as representative samples. Several intact particles were randomly selected from each sample, with those showing relatively intact shape and no obvious breakage chosen for testing. The selected particles were embedded in epoxy resin. After the resin cured, the embedded samples were cut and ground to prepare a cross-section extending through the outer surface and into the interior of the particles. Subsequently, the samples were progressively sanded and polished to obtain a relatively smooth particle cross-section. If necessary, the sample surface was treated with carbon or gold spraying to improve conductivity and reduce the impact of charge accumulation on signal stability during testing.

[0212] Aluminum elemental linear scanning analysis was performed on the cross-sections of the aforementioned particles using a scanning electron microscope equipped with an energy dispersive spectroscopy (EDS) system. During testing, a path perpendicular to the outer surface and pointing inwards was selected as the scanning direction on the particle cross-section, focusing on the aluminum elemental distribution from the particle surface to the near-surface region. The linear scanning length was set to 60 μm. To minimize the influence of local microscopic fluctuations and individual anomalous regions on the results, three different particles were selected for each sample, and one to two representative scanning paths were chosen for testing on each particle cross-section. During the testing process, the accelerating voltage, working distance, beam current conditions, and integration time were kept consistent. The characteristic signal intensity of Al elemental signal at different depths along the scanning path was recorded. The outer surface of the particle where the scanning start point is located was defined as 0 μm, and a linear scanning curve was plotted with the depth from the outer surface as the x-axis and the relative signal intensity of Al elemental signal as the y-axis.

[0213] In the results analysis, the initial signal intensity of the surface layer of the Al element linear scan curves of each sample was mainly compared, as well as the attenuation trend from the surface inwards, the presence of local peaks or enhanced fluctuations in the 10–20 μm range, and the signal retention after 20 μm. If the curve is relatively flat overall and gradually decreases with depth, it indicates that the aluminum-based component is distributed relatively evenly in the surface and near-surface regions of the particles. If the curve shows a significant peak in a local depth range, it indicates that the aluminum-based component is locally enriched in the corresponding region. If the curve shows a high signal at the surface layer followed by rapid attenuation, it indicates that the aluminum-based component tends to concentrate on the outermost layer of the particles, exhibiting a more obvious surface deposition. The test results are as follows: Figure 1-3 As shown.

[0214] The results show that in Example 1, the Al element exhibits a relatively gentle variation trend from the outer surface of the particles inward, indicating that the distribution of aluminum-based components in the particle surface and near-surface regions is relatively coordinated. In Comparative Example 3, the local fluctuations in the Al element line scan curve are more pronounced, indicating a certain degree of local enrichment of aluminum-based components in this sample. In Comparative Example 7, the Al element signal is mainly concentrated on the outer surface of the particles, while the distribution inward is relatively weak, indicating that this sample is more prone to surface deposition. In summary, the distribution of aluminum-based components in Example 1 is more conducive to balancing the utilization of active sites on the particle surface and the mass transfer needs of the near-surface region, while Comparative Examples 3 and 7 show either enhanced local enrichment or a heavier emphasis on surface deposition, respectively. These results are consistent with the findings in Table 1 that Example 1 has a higher fixed-bed water treatment capacity, while Comparative Examples 3 and 7 show a decrease in dynamic treatment capacity.

[0215] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a perlite-based adsorbent material, characterized in that, Includes the following steps: S1: Pre-treat expanded perlite particles to obtain pre-treated perlite; S2: Polyaluminum chloride and urea are mixed in water to obtain an impregnation solution; S3: The pretreated perlite is placed in the impregnation solution for vacuum impregnation treatment, and then immersed at normal pressure to allow the impregnation solution to enter the open pores of the pretreated perlite; wherein, step S3 satisfies the following relationship: ； In the formula, K1 is the infiltration driving coefficient; P v The absolute value of the vacuum is expressed in MPa; t v The duration of a single vacuuming cycle is in minutes; N is the number of vacuuming-restoration cycles; d is the average particle size of the pretreated perlite in mm; K1 is 0.08–1.

50. S4: The perlite treated in step S3 is subjected to segmented heating treatment to decompose urea and release alkaline components, thereby promoting the confined transformation and fixation of aluminum species in the open pores and pore mouth regions of the pretreated perlite; wherein, steps S2 and S4 satisfy the following relationship: ； In the formula, K2 is the conversion control coefficient; R u t is the molar ratio of urea to aluminum; t is the second stage heat preservation time in step S4, in hours; T is the second stage heat preservation temperature in step S4, in degrees Celsius; K2 is 0.8 to 4.

5. And K1 and K2 satisfy 1.2≤K2 / K1≤4; S5: The particles obtained in step S4 are washed, matured and dried to obtain the perlite-based adsorbent material.

2. The method for preparing a perlite-based adsorbent material according to claim 1, characterized in that, The pretreatment described in step S1 includes pickling, washing, and drying.

3. The method for preparing a perlite-based adsorbent material according to claim 1, characterized in that, In step S2, the concentration of polyaluminum chloride, calculated as Al2O3, is 0.5–5.0 wt%, and the concentration of urea is 0.5–8.0 wt%.

4. The method for preparing a perlite-based adsorbent material according to claim 1, characterized in that, The molar ratio R of urea to aluminum in step S2 u The ratio is 3:1 to 15:

1.

5. The method for preparing a perlite-based adsorbent material according to claim 1, characterized in that, The absolute value of vacuum P mentioned in step S3 v The pressure is 0.04–0.09 MPa, and the duration of a single vacuum pumping is t. v The time is 5 to 25 minutes, the number of vacuuming-restoring atmospheric pressure cycles N is 1 to 3 times, and the average particle size d is 2.5 to 5.0 mm.

6. The method for preparing a perlite-based adsorbent material according to claim 1, characterized in that, The segmented heating treatment in step S4 includes a first stage of heat preservation and a second stage of heat preservation. The first stage heat preservation temperature is 55-70℃ and the heat preservation time is 0.5-2 h. The second stage heat preservation temperature is 75-95℃ and the heat preservation time is 1-5 h.

7. The method for preparing a perlite-based adsorbent material according to claim 1, characterized in that, The aging temperature in step S5 is 30–60°C, the relative humidity is 60%–95%, and the aging time is 6–24 h.

8. A perlite-based adsorbent material prepared by the preparation method according to any one of claims 1 to 7, characterized in that, The perlite-based adsorbent material is a particulate material with a particle size of 2 to 6 mm, and its surface and open pores contain an aluminum-based support layer.

9. The perlite-based adsorbent material according to claim 8, characterized in that, The perlite-based adsorbent material has an aluminum loading of 1.5–12 wt% (based on Al2O3), and after soaking the perlite-based adsorbent material in deionized water for 24 h, the leachate contains Al2O3. 3+ The calculated leaching amount is no higher than 8% of the total aluminum content in the material.

10. A method for treating phosphorus-containing water, characterized in that, The perlite-based adsorbent material as described in claim 8 or 9 is filled into a fixed bed, and the water to be treated flows through the fixed bed to remove phosphorus from the water.

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