Aluminum-containing sludge resourceful treatment method and application thereof

Abstract

The invention provides an aluminum-containing sludge resourceful treatment method and application thereof, and belongs to the technical field of environmental protection. The resourceful treatment method for the aluminum-containing sludge comprises the following steps: dehydrating the aluminum-containing sludge; adding a magnesium source and a rare earth compound into the dehydrated sludge, and mixing; carrying out pre-activation treatment on the mixed material by using a substance containing phosphate radicals; carrying out granulation reaction on the pre-activated material and a sodium silicate solution to obtain a granular product; and aging, curing and drying the granular product to obtain the granular phosphorus removal agent. Through the steps of phosphoric acid pre-activation, rare earth element addition, appropriate sodium silicate granulation, core-shell structure construction and the like, the synergistic effect of all the components and the structure is achieved, the adsorption capacity and the adsorption speed of the phosphorus removal agent are remarkably improved, and the phosphorus removal agent has wide application prospects and actual value in the deep phosphorus removal field of sewage treatment.

Description

Technical Field

[0001] The present application relates to the field of environmental protection technology, and in particular to a method for resource-based treatment of aluminum-containing sludge and its application. Background Art

[0002] Surface treatment is essential in aluminum processing. Polishing, pickling, oxidation, and coloring consume large amounts of cleaning water, with each square meter of aluminum consumed 65-180L of water. This water consumption is the primary source of industrial wastewater in aluminum plants. After neutralization, coagulation, and sedimentation, wastewater sludge is obtained. This sludge primarily consists of colloidal aluminum hydroxide and some amorphous forms. Traditional disposal methods involve stockpiling or landfilling, which not only occupies land but also poses environmental risks. Existing resource recovery methods include: Preparation of building materials: such as brick making and cement additives, but the added value is low and may cause salt accumulation.

[0003] Recovery of aluminum salts: Aluminum sulfate or polyaluminum chloride (PAC) is regenerated through acid leaching, but the process is complex, the cost is high, and the acid mist pollution is serious.

[0004] Directly used as a phosphorus removal agent: Studies have attempted to use dried aluminum sludge directly for phosphorus removal, but its phosphorus removal capacity is low, the rate is slow, and it is easy to become compacted, and the effect is far inferior to commercial agents.

[0005] Patent CN201610775907.4 discloses a method for preparing wear-resistant and refractory castables from aluminum-containing sludge. The method involves adding aluminum-containing sludge, lime, and filler to water glass in sequence while stirring to form a suspension. The pH is adjusted to 8-10, and the suspension is homogenized by microwave radiation. The suspension is then removed, heated, and dried to produce a raw meal. The raw meal is then calcined for 4-8 hours, cooled, and ground to produce a wear-resistant and refractory castable with excellent wear resistance and thermal conductivity. Patent CN202010047250.6 discloses a method for recovering resources from aluminum-containing sludge. The steps include ore blending, roasting, leaching, solid-liquid separation, carbon separation, and physical separation. The present invention controls the molar ratio of calcium oxide to aluminum oxide in the raw material, converts aluminum oxide into calcium sulfoaluminate and calcium aluminate during the clinker roasting process, and subsequently separates aluminum and calcium through leaching with a sodium carbonate solution. The obtained sodium aluminate solution can be used to prepare aluminum hydroxide through a carbon separation process, and the sodium carbonate solution can be returned to the clinker leaching step for recycling. At the same time, the leached residue is physically sorted to obtain a calcium carbonate concentrate, which can be returned to the ore blending step for recycling or used for sewage treatment.

[0006] The products obtained by these methods cannot be used for wastewater phosphorus removal because they fail to effectively activate the chemical activity of aluminum in the sludge and reconstruct its physical structure to meet the needs of efficient phosphorus removal. Summary of the Invention

[0007] The present application is made in view of the above-mentioned problems, and its purpose is to provide a method for resource processing of aluminum-containing sludge and its application. The present invention has a simple process flow, low cost, high product added value, and an environmentally friendly method for resource processing of aluminum-containing sludge, which converts it into a granular and efficient phosphorus removal agent with high phosphorus adsorption capacity and rapid kinetic performance, turning waste into treasure.

[0008] Specifically, the first aspect of the present application provides a method for resource-based treatment of aluminum-containing sludge, comprising the following steps: Dewatering the aluminum-containing sludge; adding a magnesium source and a rare earth compound to the dehydrated sludge and mixing the mixture; Pre-activating the mixed materials using a phosphate-containing substance; The pre-activated material is subjected to a granulation reaction with a sodium silicate solution to obtain a granular product; The granular product is aged, cured and dried to obtain a granular phosphorus removal agent.

[0009] Furthermore, the rare earth compound is one or more of nitrates, chlorides or oxides of cerium or lanthanum; and / or the added amount of the rare earth compound is 0.5%-3% of the mass of Al2O3 in the dry basis of the aluminum-containing sludge.

[0010] Furthermore, the magnesium source is light-burned magnesium oxide; and / or the amount of the magnesium source added satisfies the molar ratio: n(Al): n(Mg) = (5-10): 1, wherein n(Al) is derived from the aluminum content in the dry basis of the aluminum-containing sludge.

[0011] Furthermore, the phosphate-containing substance is one or more of phosphoric acid, dihydrogen phosphate, and hydrogen phosphate.

[0012] Furthermore, the pre-activation treatment is to add a phosphate-containing substance to the mixed material, control the pH value of the reaction system to 6.0-7.5, and react at 50-70° C. for 0.5-2 hours.

[0013] Furthermore, the granulation reaction is carried out at a temperature of 70-95° C., with a reaction residence time of 30-70 min; and / or the modulus of the sodium silicate solution is 2.0-2.4, and the concentration is 5%-10%.

[0014] Furthermore, the aging and curing conditions are curing at 50-65°C and humidity greater than 70% for 12-36 hours; the drying temperature is not higher than 120°C.

[0015] Furthermore, the phosphorus removal agent is a composite particle containing rare earth elements, magnesium, aluminum, silicon and phosphate.

[0016] Furthermore, the particle size of the phosphorus removal agent is 1-5 mm, and the bulk density is 0.8-1.1 g / cm 3 ; The static saturated adsorption capacity for phosphate is not less than 30 mg PO4 3- -P / g.

[0017] The second aspect of the present application provides an application of the dephosphorization agent in sewage treatment, wherein the dephosphorization agent is used to deeply remove phosphates from water bodies.

[0018] The present invention has the following beneficial effects: The present invention first adds magnesium source and rare earth compound to the dehydrated sludge. The addition of magnesium source and rare earth compound plays a key role in improving the performance of aluminum-containing sludge. Magnesium source can change the chemical composition and structure of sludge and enhance its ability to bind with phosphorus. Rare earth compound has unique electronic structure and chemical properties, which accelerates the hydrolysis of MgO and OH through catalytic effect. - Release, making the activation reaction efficient and thorough; at the same time, rare earth ions act as structure-directing agents, guiding the formation of an ordered and stable mesoporous structure, increasing the specific surface area and active sites, which can not only improve the activity of aluminum in the sludge, but also promote chemical reactions on the sludge surface, thereby significantly improving the phosphorus removal effect. In the pre-activation treatment step, the mixed material is treated with a phosphate-containing substance, which can form sites with special activity on the surface of the sludge particles. These sites can interact more strongly with phosphorus ions, laying the foundation for subsequent efficient phosphorus removal. The trace rare earth elements loaded by the phosphorus removal agent produce a ternary synergistic effect with aluminum and magnesium, significantly improving the adsorption capacity for ultra-low concentration phosphorus. In the granulation reaction, the pre-activated material is reacted with a sodium silicate solution, and the sodium silicate plays a role of bonding and structural support during the reaction. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solutions and advantages of this application more clearly understood, the present application is described and illustrated below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are merely used to explain this application and are not intended to limit this application. Based on the embodiments provided in this application, all other embodiments obtained by those of ordinary skill in the art without making any creative work are within the scope of protection of this application.

[0020] Obviously, the following descriptions are merely some examples or embodiments of the present application. Those skilled in the art can apply the present application to other similar scenarios without inventive effort. Furthermore, it is also understood that, although the effort involved in such a development process may be complex and lengthy, for those skilled in the art related to the content disclosed in the present application, changes in design, manufacturing, or production based on the technical content disclosed in the present application are merely conventional technical means and should not be construed as an insufficiency of the content disclosed in the present application.

[0021] An embodiment of the first aspect of the present invention provides a method for resource-based treatment of aluminum-containing sludge, comprising the following steps: Dewatering the aluminum-containing sludge; adding a magnesium source and a rare earth compound to the dehydrated sludge and mixing the mixture; Pre-activating the mixed materials using a phosphate-containing substance; The pre-activated material is subjected to a granulation reaction with a sodium silicate solution to obtain a granular product; The granular product is aged, cured and dried to obtain a granular phosphorus removal agent.

[0022] The dehydration treatment in the above treatment method can reduce the water content of aluminum-containing sludge, making it easier to handle later. Adding magnesium source and rare earth compound, on the one hand, magnesium source can change the chemical composition and structure of sludge, making it more conducive to combining with phosphorus; on the other hand, the unique electronic structure and chemical properties of rare earth compound can not only accelerate the hydrolysis of MgO and OH - It can release aluminum and make the activation reaction more efficient. It can also serve as a structure-directing agent to guide the formation of an ordered and stable mesoporous structure, increase the specific surface area and active sites, and greatly improve the activity of aluminum in the sludge and the chemical reaction activity of the sludge surface.

[0023] During the pre-activation step, the mixture is treated with a phosphate-containing substance, which forms specific active sites on the surface of the sludge particles. These sites interact more strongly with phosphorus ions, ensuring efficient phosphorus removal. Furthermore, the trace rare earth elements loaded into the phosphorus removal agent create a ternary synergistic effect with aluminum and magnesium, significantly enhancing the adsorption capacity for ultra-low concentrations of phosphorus.

[0024] During the granulation process, the sodium silicate solution reacts with the pre-activated material, providing a binding and structural support, giving the granules excellent physical properties. The aging, curing, and drying steps further stabilize the structure and properties of the granules, ensuring the quality of the resulting granular phosphorus removal agent.

[0025] The granular phosphorus remover prepared by this treatment method has a particle size of 1-5 mm and a bulk density of 0.8-1.1 g / cm 3The static saturated adsorption capacity of phosphate is not less than 30 mg PO4 3- -P / g, with high phosphorus adsorption capacity and rapid kinetics. In wastewater treatment applications, it can deeply remove phosphates from water bodies, realizing resource utilization of aluminum-containing sludge. This not only solves the difficult problem of aluminum-containing sludge treatment, but also produces high-value-added products with good economic and environmental benefits. Furthermore, this method achieves waste treatment through the synergistic treatment of aluminum sludge and high-phosphorus digestate, forming a closed-loop waste flow, eliminating the cost of purchasing phosphoric acid, and further enhancing its application value and market competitiveness. In this example, the aluminum-containing sludge was dehydrated using a high-pressure diaphragm plate-and-frame filter press, with the addition of 0.3% (by weight of dry sludge) of an anionic PAM flocculant. The pressure was maintained at 1.8 MPa for 40 minutes to reduce the sludge moisture content to 60%-65%. This moisture content represents the optimal viscosity range for the subsequent mixing reaction.

[0026] In this embodiment, the rare earth compound is one or more of cerium or lanthanum nitrate, chloride or oxide, such as cerium nitrate (Ce(NO3)3) or lanthanum chloride (LaCl3), which can be dissolved in a diluted sodium silicate solution and sprayed together; the amount of the rare earth compound added is 0.5%-3% of the mass of Al2O3 in the dry basis of the aluminum-containing sludge. 4+ / Ce 3+ or La 3+ It has a unique electronic structure and can catalyze the hydrolysis of MgO and OH at low temperature. - The release process makes the activation reaction faster and more thorough. Rare earth ions act as nucleation sites, guiding the magnesium-aluminum-silica gel to form a more ordered and stable mesoporous structure, greatly increasing the specific surface area and active sites. The trace rare earth elements loaded in the final product are themselves excellent phosphorus removers, creating a ternary synergistic effect with aluminum and magnesium, further significantly improving the adsorption capacity and speed of ultra-low concentration phosphorus.

[0027] Furthermore, the magnesium source is light-burned magnesium oxide; the amount of the magnesium source added satisfies the following molar ratio: n(Al): n(Mg) = (5-10): 1, preferably 8:1, wherein n(Al) is derived from the aluminum content in the dry basis of the aluminum-containing sludge. The amount of magnesium source added has a significant effect on the performance of the dephosphorization agent. When n(Al): n(Mg) is in the range of (5-10): 1, the activity of aluminum in the sludge can be fully activated, while ensuring that the dephosphorization agent has good structural stability and adsorption properties. If the amount of magnesium source added is too small, that is, n(Al): n(Mg) is greater than 10: 1, then the chemical composition and structural changes of the sludge are limited, the binding ability with phosphorus is not significantly improved, and the dephosphorization effect of the dephosphorization agent is difficult to achieve an ideal state. However, if the addition of too much magnesium source, with an n(Al):n(Mg) ratio less than 5:1, not only will this increase costs, but it may also lead to an overly dense structure, reducing the specific surface area and covering the active sites, which is detrimental to phosphorus adsorption. When the n(Al):n(Mg) ratio is 8:1, the phosphorus removal agent's various properties reach a relatively balanced state, ensuring sufficient active sites for phosphorus binding while maintaining a good physical structure, thereby achieving high phosphorus adsorption capacity and rapid kinetic performance.

[0028] The present invention adopts phosphate preactivation, and the specific operation is as follows: The dehydrated sludge cake was conveyed to a twin-shaft differential speed mixer, where light-burned magnesium oxide (MgO, active content ≤40s, 200 mesh) powder was added at a molar ratio of n(Al) : n(Mg) = 7:1. Cerium nitrate (Ce(NO3)3·6H2O) powder was also added at a rate of 1.5% by mass of the Al2O3 content in the dry sludge. During the mixing process, a 2% phosphoric acid (H3PO4) solution was sprayed at a low speed. The spray rate was controlled by an online pH meter to maintain a stable pH of 6.5-7.0 (slightly acidic to neutral). The total mixing time was 20 minutes. The preactivated material was transferred to a sealed aging bin and aged at 60°C for 1 hour to ensure a thorough and uniform preactivation reaction.

[0029] Under these conditions, MgO is partially hydrolyzed to provide OH - , H3PO4 provides PO4 3- , Ce 30 As catalysts, the three react rapidly with the active aluminum in the sludge to generate trace amounts of amorphous aluminum phosphate / magnesium phosphate complexes in situ, providing a large number of highly active crystal nuclei for subsequent steps.

[0030] In this embodiment, the phosphate-containing substance is one or more of phosphoric acid, dihydrogen phosphate, and hydrogen phosphate. This invention adds a "pre-reaction" step before the "activation granulation" step. The sludge material mixed with MgO is aged at 50-70°C for 0.5-2 hours. During this time, a dilute phosphoric acid solution (concentration 1-3%) is sprayed to adjust the pH of the material to 6.0-7.5. These conditions ensure the formation of specifically active sites on the surface of the sludge particles. When the pH is below 6.0, the reaction system becomes too acidic, potentially destroying the sludge structure and hindering the formation of active sites. When the pH is above 7.5, the alkalinity may cause some aluminum precipitation, reducing its activity. Controlling the reaction temperature between 50-70°C accelerates the reaction rate and ensures more complete formation of active sites. A reaction time between 0.5-2 hours ensures sufficient reaction progress without being too long, which would waste energy.

[0031] Pre-added PO4 3- It preferentially reacts with the most active aluminum and magnesium sites in the material, pre-forming an extremely thin, insoluble, amorphous primary active layer of aluminum / magnesium phosphate within the particles. This active layer becomes a more powerful "crystal nucleus" during the subsequent sodium silicate granulation process, attracting more active gel to coat it, ultimately forming a "core-shell" active site structure with a phosphate core and a hydroxyl gel shell. This structure is far more active than randomly formed gels. When this product is placed in phosphorus-containing water, the phosphate groups in its core produce a "common ion effect," more strongly "attracting" phosphates in the water to its surface for enrichment and exchange reactions, with extremely rapid kinetics. This product, produced by this method, has an extremely rapid phosphorus adsorption rate and is particularly suitable for deep treatment filters with short hydraulic retention times.

[0032] In this example, the granulation reaction is carried out at a temperature of 70-95°C, with a reaction residence time of 30-70 minutes. The sodium silicate solution has a modulus of 2.0-2.4 and a concentration of 5%-10%. During the granulation reaction, the reaction residence time is 30-70 minutes. This temperature range allows the sodium silicate solution to better perform its bonding and structural support functions, promoting the formation of granular products. Too low a temperature will result in insufficient viscosity and reactivity of the sodium silicate, making it difficult to form a good granular structure. Too high a temperature may cause excessive water evaporation, affecting granule uniformity. Controlling the reaction residence time is also critical. Too short a time will result in incomplete reaction and poor granule strength and stability. Too long a time will increase energy consumption and costs. The sodium silicate solution has a modulus of 2.0-2.4 and a concentration of 5%-10%. The modulus reflects the molar ratio of silicon dioxide to sodium oxide in the sodium silicate. A modulus between 2.0 and 2.4 indicates excellent bonding and stability. The solution concentration is 5%-10%, which can ensure that during the granulation process, sodium silicate can effectively bond the materials without making the particles too wet, affecting the subsequent aging, curing and drying processes.

[0033] Specifically, the low-temperature activation granulation process involves diluting an industrial sodium silicate solution with a modulus of 2.2 to a working concentration of 6%. A rotary drum granulator equipped with a steam-heated jacket and a two-fluid atomizing spray gun is used. The preactivated material is continuously fed into the granulator. The prepared 6% sodium silicate solution is atomized using a spray gun (at an atomizing pressure of 0.4 MPa) and sprayed onto the tumbling material bed. Simultaneously, 0.3 MPa steam is introduced into the granulator jacket to precisely control the material temperature at 85±2°C. The total residence time of the material in the granulator is 50 minutes. Under the synergistic effects of temperature and sodium silicate, the crystal nuclei generated during the preactivation stage grow rapidly. Silicate ions crosslink with aluminum, magnesium, and cerium ions to form a "Ce-magnesium-aluminum-silicon" multi-component composite hydrated gel, which encapsulates the preformed phosphate core, initially building a "phosphate core-hydroxyl gel shell" composite structure.

[0034] In this embodiment, the granulated particles are sent to a curing bin for 12-36 hours at a temperature of 50-65°C and a humidity greater than 70%. The drying temperature is no higher than 120°C. This allows the gel network to further condense and solidify, forming a stable mesoporous structure and achieving sufficient mechanical strength.

[0035] More specifically, the drying process utilizes a three-layer belt dryer, with Zone 1 (preheating zone): 105°C for 10 minutes; Zone 2 (main drying zone): 118°C (strictly controlled to <120°C) for 35 minutes; and Zone 3 (cooling zone): ambient air cooling. The final product moisture content is ≤ 4%.

[0036] Through vibration screening, particles of 1-5mm are taken as qualified products.

[0037] In this embodiment, the dephosphorization agent is a composite particle containing rare earth elements, magnesium, aluminum, silicon and phosphate. The particle size of the dephosphorization agent is 1-5 mm and the bulk density is 0.8-1.1 g / cm 3 ; The static saturated adsorption capacity for phosphate is not less than 30mg PO4 3- -P / g.

[0038] The second aspect of the present application provides an application of the dephosphorization agent in sewage treatment, wherein the dephosphorization agent is used to deeply remove phosphates from water bodies.

[0039] The aluminum and magnesium elements in the phosphorus removal agent react chemically with phosphate to form insoluble phosphate precipitates. Aluminum ions combine with phosphate to form aluminum phosphate precipitates, while magnesium ions react with phosphate to form ammonium magnesium phosphate or magnesium phosphate precipitates, thereby removing phosphate from the solution. The presence of rare earth elements further enhances the effectiveness of this chemical reaction. Their unique electronic structure and chemical properties promote the binding of aluminum and magnesium with phosphate, increasing the reaction rate and efficiency.

[0040] The mesoporous structure of the phosphate remover also plays a significant role. Its abundant surface area and active sites provide ample space for phosphate adsorption. When phosphorus-containing water comes into contact with the phosphate remover, phosphate ions rapidly diffuse into the pores of the phosphate remover and are adsorbed on the active sites. This physical adsorption, in synergy with the chemical reaction, significantly enhances the phosphate removal effect.

[0041] The phosphorus remover's "core-shell" active site possesses unique advantages. The phosphate groups within the core create a "common ion effect," strongly attracting phosphate groups in the water to its surface. This enrichment increases the concentration of phosphate groups on the phosphorus remover's surface, further promoting chemical reactions and adsorption processes. Furthermore, this structure provides the phosphorus remover with excellent adsorption capacity even at ultra-low concentrations of phosphorus, enabling deep phosphate removal from water, reducing phosphorus levels to extremely low levels.

[0042] In practical wastewater treatment applications, this dephosphorizer exhibits rapid response, achieving efficient phosphate removal in a short period of time. Its rapid kinetics make it particularly suitable for use in deep treatment filters with short hydraulic retention times. When treating high-phosphorus wastewater, the dephosphorizer rapidly reduces phosphorus content, ensuring that the effluent meets stringent discharge standards. Furthermore, its high phosphorus adsorption capacity extends the dephosphorizer's service life, reducing replacement frequency and operating costs.

[0043] This phosphorus remover also exhibits excellent physical properties and stability. Its compact particle structure and moderate bulk density make it resistant to breakage and loss under water impact. It maintains stable phosphorus removal performance under varying water quality conditions and ambient temperatures, demonstrating strong adaptability and reliability. Example The following examples describe the present disclosure in more detail and are intended to be illustrative only, as various modifications and variations within the scope of the present disclosure will be apparent to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are by weight. Unless otherwise stated, all reagents used in the examples are available through conventional commercial sources or synthesized according to conventional methods and can be used directly without further processing. Unless otherwise stated, all instruments used in the examples are available through conventional commercial sources.

[0044] Example 1 A method for recycling aluminum-containing sludge comprises the following steps: A high-pressure diaphragm plate and frame filter press was used, with 0.3% (dry sludge mass ratio) of anionic PAM flocculant added. The pressure was maintained at 1.8 MPa for 40 minutes to reduce the sludge moisture content to 60%. The dehydrated sludge was conveyed to a twin-shaft differential speed mixer, where light-burned magnesium oxide powder was added at a molar ratio of n(Al):n(Mg) = 7:1. Simultaneously, cerium nitrate (Ce(NO3)3·6H2O) powder was added at a rate of 1.5% of the mass of Al2O3 in the dry sludge. During the mixing process, a 2% phosphoric acid (H3PO4) solution was sprayed at a low speed to stabilize the pH of the mixture at 6.5. The total mixing time was 60 minutes, yielding a preactivated material. A 6% sodium silicate solution was sprayed onto the tumbling material bed through a spray gun (atomization pressure 0.4 MPa). Simultaneously, 0.3 MPa steam was introduced into the granulator jacket. The material temperature was precisely controlled at 85°C. The total residence time of the material in the granulator was 50 minutes. The granular product was cured at 55° C. and 72% humidity for 20 hours, and then dried to obtain a granular phosphorus removal agent.

[0045] Example 2 This embodiment is basically the same as embodiment 1, except that cerium nitrate (Ce(NO3)3·6H2O) powder is added at 1% of the mass of Al2O3 in the dry sludge.

[0046] Example 3 This embodiment is basically the same as embodiment 1, except that cerium nitrate (Ce(NO3)3·6H2O) powder is added at 2% of the mass of Al2O3 in the dry sludge.

[0047] Example 4 This embodiment is substantially the same as embodiment 1, except that cerium nitrate is replaced by an equal molar amount of lanthanum chloride (LaCl 3 ).

[0048] Comparative Example 1 Aluminum sludge with 80% water content was dried at 105°C to constant weight, crushed and ground to pass through a 100-mesh sieve.

[0049] Comparative Example 2 Aluminum sludge was acid-leached with 20% sulfuric acid at 90°C for 2 h, and the filtrate was filtered and concentrated to obtain liquid polyaluminum chloride (PAC).

[0050] Comparative Example 3 This comparative example is basically the same as Example 1, except that MgO is added according to n(Al):n(Mg)=7:1, granulation is performed with 8% sodium silicate solution (85°C, 50 min), and curing and drying are carried out.

[0051] Comparative Example 4 On the basis of Comparative Example 3, 1.5% cerium nitrate was added, but the phosphoric acid pre-activation step was not performed.

[0052] Comparative Example 5 This comparative example is basically the same as Example 1, except that the pH of the material mixed with MgO is adjusted to 6.5 with 2% H3PO4, pre-activated for 1 hour, and then granulated with 8% sodium silicate, without adding rare earth.

[0053] Experimental Case Place 100 mL of a 10.0 mg / L (P) potassium dihydrogen phosphate solution in a conical flask. Accurately weigh 0.100 g (dry weight) of the adsorbent sample to be tested (samples prepared in Examples 1-4 and Comparative Examples 1-5) and add it to the flask. Oscillate the flask in a thermostatic oscillator (25°C, 150 rpm) for 24 hours to ensure adsorption equilibrium. After sampling and filtration, determine the residual phosphorus concentration in the filtrate using ammonium molybdate spectrophotometry.

[0054] Adsorption capacity Qe (mg / g) Calculation formula: Qe = (C o -C e ) * V / m Where: C o , Ce are the initial and equilibrium phosphorus concentrations in mg / L, respectively; V is the volume of the solution in L; and m is the mass of the adsorbent in g. The experimental results are shown in Table 1.

[0055] Table 1 Test results of Examples 1-4 and Comparative Examples 1-5

[0056] As shown in Table 1, the adsorption capacity and time required to reach 90% Qe of Examples 1-5 were significantly superior to those of Comparative Examples 1-5. In the examples, variations in additives and operating conditions also had a certain impact on the phosphorus removal effect. In Example 3, cerium nitrate was added at 2% of the mass of Al2O3 in the dry sludge, resulting in an adsorption capacity of 40.5 mg / g and a time required to reach 90% Qe of only 10 minutes. This indicates that appropriately increasing the amount of cerium nitrate added can further improve the adsorption performance and adsorption rate of the phosphorus removal agent. Comparing Examples 1 and 4, after replacing cerium nitrate with an equimolar amount of lanthanum chloride, the adsorption capacity decreased and the time required to reach 90% Qe increased, indicating that cerium nitrate is more effective in phosphorus removal than lanthanum chloride in this system.

[0057] Among the comparative examples, Comparative Example 1, which simply dried and ground aluminum sludge, yielded extremely low adsorption capacity and a very long time to reach 90% Qe. This may be due to the lack of any chemical modification or structural adjustment. The aluminum sludge itself has few active sites and a small specific surface area, resulting in very limited phosphate adsorption capacity and rate. Comparative Example 2, which used sulfuric acid to acid-leach aluminum sludge to prepare liquid polyaluminum chloride, improved phosphorus removal to some extent. However, since it primarily removed phosphorus through the hydrolysis and polymerization of aluminum ions, it lacked the core-shell structure and synergistic effect of the rare earth elements as in the examples. Therefore, the adsorption capacity and rate were still far inferior to those in the examples. Comparative Example 3, which used an 8% sodium silicate solution for granulation, while forming a certain granular structure, lacked the phosphoric acid preactivation step, preventing the formation of effective crystal nuclei and core-shell structures, resulting in inferior adsorption performance compared to the examples. Comparative Example 4, based on Comparative Example 3, added cerium nitrate but without phosphoric acid preactivation, preventing the rare earth elements from fully exerting their synergistic effect, resulting in insufficient active crystal nuclei and still poor adsorption. Comparative Example 5 does not add rare earth elements, and only relies on phosphoric acid preactivation and sodium silicate granulation. The rare earth elements lack the promoting effect on the chemical reaction, and the adsorption capacity and adsorption rate are also significantly lower than those in the examples.

[0058] In summary, the dephosphorus remover prepared by the resource utilization method of aluminum-containing sludge provided by the present invention realizes the synergistic effect between the various components and structures through the steps of phosphoric acid pre-activation, rare earth element addition, appropriate sodium silicate granulation and core-shell structure construction, significantly improves the adsorption capacity and adsorption rate of the dephosphorus remover, and has broad application prospects and practical value in the field of deep dephosphorization in sewage treatment. It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A method for resource treatment of aluminum-containing sludge, characterized in that: The following steps are involved: Dewatering the aluminum-containing sludge; adding a magnesium source and a rare earth compound to the dehydrated sludge and mixing the mixture; Pre-activating the mixed materials using a phosphate-containing substance; The pre-activated material is subjected to a granulation reaction with a sodium silicate solution to obtain a granular product; The granular product is aged, cured and dried to obtain a granular phosphorus removal agent.

2. The method for resource recovery of aluminum-containing sludge according to claim 1, characterized in that: The rare earth compound is one or more of cerium or lanthanum nitrate, chloride or oxide; and / or the added amount of the rare earth compound is 0.5%-3% of the mass of Al2O3 in the dry basis of the aluminum-containing sludge.

3. The method for resource recovery of aluminum-containing sludge according to claim 1, characterized in that: The magnesium source is light-burned magnesium oxide; and / or the amount of the magnesium source added satisfies the molar ratio: n(Al): n(Mg) = (5-10): 1, wherein n(Al) is derived from the aluminum content in the aluminum-containing sludge dry basis.

4. The method for resource recovery of aluminum-containing sludge according to claim 1, characterized in that: The phosphate-containing substance is one or more of phosphoric acid, dihydrogen phosphate, and hydrogen phosphate.

5. The method for recycling aluminum-containing sludge according to claim 1, characterized in that: The pre-activation treatment is to add a phosphate-containing substance to the mixed material, control the pH value of the reaction system to 6.0-7.5, and react at 50-70° C. for 0.5-2 hours.

6. The method for recycling aluminum-containing sludge according to claim 1, characterized in that: The granulation reaction is carried out at a temperature of 70-95° C., with a reaction residence time of 30-70 min; and / or the modulus of the sodium silicate solution is 2.0-2.4, and the concentration is 5%-10%.

7. The method for recycling aluminum-containing sludge according to claim 1, characterized in that: The aging curing conditions are curing at 50-65°C and humidity greater than 70% for 12-36 hours; the drying temperature is not higher than 120°C.

8. The method for recycling aluminum-containing sludge according to claim 1, characterized in that: The phosphorus removal agent is composite particles containing rare earth elements, magnesium, aluminum, silicon and phosphate.

9. The method for resource recovery of aluminum-containing sludge according to claim 1, characterized in that: The particle size of the phosphorus removal agent is 1-5 mm, and the bulk density is 0.8-1.1 g / cm 3 ; The static saturated adsorption capacity for phosphate is not less than 30 mg PO4 3- -P / g.

10. Use of the phosphorus removal agent according to any one of claims 1 to 9 in sewage treatment.

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