Special phosphorus removal agent for deep phosphorus removal as well as preparation method and application of special phosphorus removal agent

Abstract

The invention discloses a special phosphorus removal agent for deep phosphorus removal and a preparation method and application thereof, and relates to the field of phosphorus removal agents and preparation methods thereof.The phosphorus removal agent is prepared from a porous precursor, an activating agent and a dispersing agent, and the porous precursor comprises at least one of aluminum oxide, iron oxide, calcium oxide and magnesium oxide; the activating agent comprises at least one of lanthanum salt, cerium salt, zircon salt, magnesium salt and ferric salt. By optimizing the composition of the porous precursor and activating treatment, the phosphorus adsorption capacity is remarkably improved, the phosphorus removal agent also plays a role in micro-flocculation in the process of mixed adsorption with sewage, a wet adding mode is adopted, the adding amount can be flexibly adjusted according to the phosphorus concentration condition of inlet water and outlet water, and the phosphorus removal efficiency is improved. The phosphorus removal agent can reduce the total phosphorus concentration in tail water of a sewage treatment plant to 0.5 mg / L or below.

Description

Technical Field

[0001] The present invention relates to the field of phosphorus removal agents and their preparation methods, and particularly to a special phosphorus removal agent for deep phosphorus removal, its preparation method and application. Background Art

[0002] Water resources are one of the most important substances for human survival, but the current water shortage crisis is becoming increasingly serious. Water pollution is an important factor causing the water shortage crisis. Water eutrophication is one of the main causes of water pollution, and phosphorus is the most critical limiting factor for water eutrophication. Therefore, the national effluent standards for sewage treatment plants are getting higher and higher. The current first-class A standard requires that the total phosphorus concentration ≤ 0.5 mg / L. Many sewage treatment plants face the problem of not meeting this effluent standard. The total phosphorus in the tail water of most sewage treatment plants is about 1 mg / L. To achieve up-to-standard discharge, deep phosphorus removal is required.

[0003] Since the total phosphorus content in the tail water is already very low, it is not suitable for biological phosphorus removal; it is generally difficult to reduce the total phosphorus to below 0.5 mg / L by chemical precipitation method, and a large amount of chemical sludge will be produced, causing secondary pollution; the adsorption method is simple in operation and has relatively less sludge production, so it is highly efficient, environmentally friendly, and it is very necessary to develop and apply low-cost adsorption materials. Summary of the Invention

[0004] The purpose of the present invention is to provide a special phosphorus removal agent for deep phosphorus removal, its preparation method and application. By adding an activator and a dispersant to a porous precursor for reaction, an activated phosphorus removal agent is obtained to solve the problem that it is difficult to deeply remove phosphorus from tail water with a relatively low total phosphorus content in the prior art.

[0005] First, an embodiment of the present invention provides a special phosphorus removal agent for deep phosphorus removal, including a material prepared from the following raw materials: a porous precursor, an activator, and a dispersant. The porous precursor includes at least one of alumina, iron oxide, calcium oxide, and magnesium oxide. The activator includes at least one of lanthanum salt, cerium salt, zirconium salt, magnesium salt, and iron salt.

[0006] It should be noted that the porous precursor (such as alumina, iron oxide, calcium oxide, and magnesium oxide) itself has a certain adsorption capacity, but by adding an activator (such as lanthanum salt, cerium salt, zirconium salt, magnesium salt, and iron salt), its adsorption performance can be significantly improved. Specifically, the activator can promote the development of the pore structure of the precursor during the reaction, increase the specific surface area, thereby providing more adsorption sites, and at the same time can form a more stable chemical bond with phosphorus, enhancing the ability of the adsorbent to fix phosphorus.

[0007] During the adsorption process, metal oxides in the porous precursor (such as alumina, iron oxide) can adsorb phosphate ions through ion exchange reactions. For example, alumina (Al2O3) can react with phosphate ions to form insoluble aluminum phosphate (AlPO4); metal ions in the activator (such as lanthanum ions, zirconium ions) can react with phosphate ions to form stable complexes. For example, lanthanum ions (La 3+ 3+

[0008] The porous precursor and the activator work together to increase the adsorption sites and activity on the adsorbent surface, thereby enhancing the surface adsorption capacity for phosphorus. Lanthanum salts and zirconium salts can also react with the hydroxyl groups (-OH) on the surface of the porous precursor to generate surface functional groups with higher adsorption activity.

[0009] As an alternative embodiment, the dispersant includes at least one of polyvinylpyrrolidone and polyethylene glycol.

[0010] It should be noted that polyethylene glycol interacts with metal ions during the pH adjustment process, that is, polyethylene glycol attaches to the surface of metal hydroxy complexes through weak physical actions, avoiding the agglomeration of metal ions and precursor particles, and facilitating the uniform distribution of metal oxides on the porous precursor. Polyvinylpyrrolidone has a certain stabilizing effect and can attach to the surface of the porous precursor, reducing the surface tension between the precursors, preventing the aggregation of precursor particles, improving the stability of the precursors in the solution, extending the stable time of the precursor dispersion, facilitating the activation of the precursors, and improving the activation efficiency.

[0011] The two dispersants can be used alone, but the best effect is achieved when used in combination. Because the use of polyethylene glycol facilitates the entry of metal ions into the precursor pores, and polyvinylpyrrolidone facilitates the stable and uniform dispersion of the precursors in the solution. The preferred mass ratio range is 0.5~1:1, because too much polyvinylpyrrolidone will cause it to densely coat the surface of the precursor particles, preventing the attachment of metal ions on the surface and in the pores of the precursor.

[0012] As an alternative embodiment, the porous precursor comprises alumina, iron oxide, calcium oxide and magnesium oxide, and their mass fractions in the porous precursor are respectively: 10-40%, 5-30%, 3-20% and 1-7%.

[0013] Both alumina, iron oxide, calcium oxide and magnesium oxide can react with phosphate ions through chemical precipitation to form insoluble phosphates, thereby removing phosphorus in water. A relatively high alumina content can provide a large number of adsorption sites, while iron oxide, calcium oxide and magnesium oxide enhance the adsorption effect through surface adsorption and chemical precipitation. The mixed use of calcium oxide and magnesium oxide can adjust the pH value of water, provide a suitable environment for the adsorption reaction, and further improve the phosphorus removal efficiency of the adsorbent.

[0014] Secondly, in order to better solve the above problems, the embodiment of the present invention also provides a preparation method of a special phosphorus removal agent for deep phosphorus removal, comprising the following steps: S1: Dry the sludge and reserve it for later use; S2: Calcinate the dried sludge to obtain a porous precursor; S3: Dissolve the activator in water to obtain a salt solution, and add a dispersant solution to the salt solution to obtain a mixed liquid; S4: Add the porous precursor to the mixed liquid, adjust the pH and then carry out the reaction; S5: After the reaction is completed, carry out solid-liquid separation, washing and drying in sequence to obtain the phosphorus removal agent.

[0015] In this preparation method, the porous precursor can be directly prepared from sludge, which can realize the high-value conversion of waste. Municipal sludge is generally selected, and the specific source of the sludge is not limited here, as long as a porous precursor containing at least one of alumina, iron oxide, calcium oxide and magnesium oxide can be prepared in S2.

[0016] As an alternative embodiment, the calcination temperature in S2 is 700-1100 °C, and the calcination time is 4-8 h.

[0017] High-temperature calcination can fully decompose the organic matter in the sludge, and at the same time promote the formation and crystallization of metal oxides. During this process, the specific surface area of the sludge gradually increases. However, too high a temperature will cause the sludge ash to melt, which is instead not conducive to the development of the pore structure. Therefore, a suitable temperature range needs to be selected. An appropriate holding time can ensure the complete decomposition of the organic matter in the sludge and the full crystallization of the metal oxides.

[0018] In the embodiments of the present invention, by selecting appropriate calcination temperature and time, the pore structure of the sludge can be optimized, the specific surface area can be increased, thereby improving the adsorption capacity. The calcination temperature and time within this range can ensure the stable existence of metal oxides (such as aluminum oxide, iron oxide, calcium oxide, and magnesium oxide) in the sludge, and avoid composition changes caused by excessive temperature.

[0019] As an alternative embodiment, the atmosphere for calcination in S2 includes introducing nitrogen gas into a sealed reactor for protection.

[0020] During the calcination process, the metal oxides (such as aluminum oxide, iron oxide, calcium oxide, and magnesium oxide) in the sludge may react with oxygen, resulting in changes in composition and structure. To prevent the sludge from losing its pore structure due to oxidation during calcination.

[0021] As an alternative embodiment, the concentration of a single metal ion in the salt solution in S3 is 0.05 - 0.5 wt%, and the concentration of the dispersant in the mixed liquid is 0.2 - 2 wt%.

[0022] Too high a salt concentration will cause excessive aggregation of metal ions in the pore channels, forming larger particles, thereby blocking the pore channels, reducing the adsorption area and adsorption capacity. An appropriate salt concentration can ensure the uniform distribution of metal ions on the surface and in the pore channels of the phosphorus removal agent precursor, contribute to the formation of more active sites, and improve the adsorption performance. Too high a dispersant concentration will hinder the distribution of metal ions on the surface of the phosphorus removal agent precursor and in the pore channels. An appropriate dispersant concentration can prevent the aggregation of metal ions and ensure their uniform distribution. This range of dispersant concentration can optimize the pore structure of the phosphorus removal agent precursor, increase the specific surface area, thereby improving the adsorption performance. At the same time, it can improve the stability of the phosphorus removal agent precursor, prevent particle agglomeration, and ensure uniform reaction. An appropriate volume ratio can balance the effects of the dispersant and the salt solution, ensure the uniform distribution of metal ions on the surface and in the pore channels of the phosphorus removal agent precursor, and prevent pore channel blockage.

[0023] As an alternative embodiment, the activator is nitrate and / or chloride salt.

[0024] As an alternative embodiment, the addition amount of the porous precursor in S4 is 2.5 - 10 wt%, and it also includes adjusting the pH to 7.5 - 9.5, the reaction temperature is 80 - 140 °C, and the reaction time is 8 - 16 h. An appropriate amount of the precursor is beneficial to its dispersion in the solution and is beneficial to attaching sufficient metal ions.

[0025] In the preparation process of the special phosphorus remover for deep phosphorus removal, the control of pH value is crucial for the formation of metal oxides or hydroxides. Exemplarily, when the pH value is too low, the solution is acidic, and metal ions mainly exist in the free state, making it difficult to form metal oxides or hydroxides. When the pH value is too high, the solution is strongly alkaline, and metal ions will rapidly form hydroxide precipitates, but these precipitates may not be stable enough to achieve the purpose of activating the precursor. Within this pH range, metal ions can gradually form stable hydroxides or oxides while maintaining a certain solubility, thereby achieving the purpose of activating the precursor. This pH range can optimize the pore structure of the porous precursor, increase the specific surface area, and thus improve the adsorption performance.

[0026] Finally, the embodiment of the present invention also provides an application of the special phosphorus remover for deep phosphorus removal, including using the phosphorus remover in the tail water of a sewage treatment plant to make the total phosphorus concentration in the tail water of the sewage treatment plant ≤ 0.5 mg / L.

[0027] Compared with the prior art, the embodiment of the present invention has the following advantages and beneficial effects: 1. The phosphorus remover of the present invention significantly improves the phosphorus adsorption capacity by optimizing the composition of the porous precursor and the activation treatment. The phosphorus remover also plays a role in micro-flocculation during the process of mixing and adsorbing with sewage. In the wet feeding method, the dosage can be flexibly adjusted according to the phosphorus concentration of the influent and effluent. Compared with the traditional chemical precipitation method, the dosage method of the phosphorus remover in the embodiment of the present invention is simple, the operation is flexible, and it is not necessary to change the original water treatment process or add large-scale water treatment structures. It enables the sewage treatment plant to quickly achieve deep phosphorus removal without large-scale transformation.

[0028] 2. The activator and dispersant used in the embodiment of the invention can ensure the uniform distribution of metal ions on the surface and in the pores of the porous precursor at a specific concentration and volume ratio, avoid pore blockage, and at the same time increase the specific surface area of the adsorbent. Compared with the traditional chemical precipitation method, the consumption of chemical agents is significantly reduced.

[0029] 3. In the preparation process of the embodiment of the present invention, by controlling the pH value within the range of 7.5 - 9.5, the formation of metal oxides or hydroxides is promoted, and these substances can react with phosphate ions to form stable precipitates. The phosphorus remover can reduce the total phosphorus concentration in the tail water of the sewage treatment plant to less than 0.5 mg / L. Detailed Embodiments

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention.

[0031] Therefore, the following detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0032] An embodiment of the present invention provides a preparation method of a special phosphorus removal agent for deep phosphorus removal, comprising the following steps: S1: Dry the sludge and set it aside, where the drying temperature is 80~100 °C; S2: Calcinate the dried sludge to obtain a porous precursor. The calcination temperature is 700~1100 °C, the calcination time is 4~8 h, and the calcination atmosphere includes introducing nitrogen into a sealed reactor for protection; S3: Dissolve the activator in water to obtain a salt solution, and add a dispersant solution to the salt solution to obtain a mixed liquid, where the concentration of a single metal ion in the salt solution is 0.05~0.5 wt%, and the concentration of the dispersant in the mixed liquid is 0.2~2 wt%. S4: Add the porous precursor to the mixed liquid, adjust the pH and then carry out the reaction. The addition amount of the porous precursor is 2.5~10 wt%, and it also includes adjusting the pH to 7.5~9.5. The reaction temperature is 80~140 °C, and the reaction time is 8~16 h; S5: After the reaction is completed, carry out solid-liquid separation, washing, and drying in sequence to obtain the phosphorus removal agent.

[0033] Among them, the porous precursor includes at least one of alumina, iron oxide, calcium oxide, and magnesium oxide; the activator includes at least one of lanthanum salt, cerium salt, zirconium salt, magnesium salt, and iron salt; the dispersant includes at least one of polyvinylpyrrolidone and polyethylene glycol; and the activator is a nitrate and / or a chloride salt.

[0034] Example 1 An embodiment of the present invention provides a preparation method of a special phosphorus removal agent for deep phosphorus removal, comprising the following steps: Add alumina and / or iron oxide and / or calcium oxide and / or magnesium oxide to the sludge for ingredient blending and mixing. After mixing evenly, spread it out in a tray, place it in an oven, set the oven temperature at 90 °C, and dry the sludge for standby.

[0035] (1) Place the dried sludge in a tubular furnace for calcination. The calcination temperature is 800 °C, the calcination time is 8 hours, and nitrogen is introduced for protection during the firing process. After calcination, a phosphorus removal agent precursor is obtained (containing alumina, iron oxide, calcium oxide, and magnesium oxide, and the mass fractions are 25%, 20%, 15%, and 5% respectively).

[0036] (2) Preparation of the activator: Dissolve lanthanum nitrate, zirconium nitrate, cerium nitrate, magnesium nitrate, and iron nitrate in water to obtain a salt solution. The mass concentrations of each metal element are 0.25% for lanthanum, 0.1% for zirconium, 0.1% for cerium, 0.25% for magnesium, and 0.1% for iron. Then, add the wetting and dispersing agent polyvinylpyrrolidone to the salt solution. The mass fraction after adding polyvinylpyrrolidone is 0.6%. After stirring evenly, the activator is obtained.

[0037] (3) Mix the phosphorus removal agent precursor and the activator evenly (the mass ratio of the phosphorus removal agent precursor to the activator is 2.5:97.5). Adjust the pH to 9 with sodium hydroxide solution, and then transfer the solution to a high-pressure reaction kettle for activation. The activation conditions are: activation temperature 100 °C, activation time 16 h. After activation, centrifuge to separate the solid, wash the solid with water until neutral, and dry to obtain the phosphorus removal agent.

[0038] Example 2 The embodiment of the present invention provides a preparation method of a special phosphorus removal agent for deep phosphorus removal, including the following steps: Add alumina and / or iron oxide and / or calcium oxide and / or magnesium oxide to the sludge for ingredient blending and mixing. After mixing evenly, spread it out in a tray, place it in an oven, set the oven temperature to 90 °C, and dry the sludge for later use.

[0039] (1) Calcinate the dried sludge in a tubular furnace at a calcination temperature of 900 °C for 6 hours. Nitrogen is passed through during the calcination process. After calcination, a phosphorus removal agent precursor is obtained (containing alumina, iron oxide, calcium oxide, and magnesium oxide, and the mass fractions are 40%, 5%, 3%, and 1% respectively).

[0040] (2) Preparation of the activator: Dissolve lanthanum chloride, zirconium chloride, cerium chloride, magnesium chloride, and iron chloride in water to obtain a salt solution. The mass concentrations of each metal element are 0.3% for lanthanum, 0.1% for zirconium, 0.1% for cerium, 0.3% for magnesium, and 0.05% for iron. Then, add the wetting and dispersing agent polyvinylpyrrolidone to the salt solution. The mass fraction after adding polyvinylpyrrolidone is 0.8%. After stirring evenly, the activator is obtained.

[0041] (3) Mix the phosphorus removal agent precursor and the activator evenly (the mass ratio of the phosphorus removal agent precursor to the activator is 5:95). Adjust the pH to 8 with sodium hydroxide solution, and then transfer the solution to a high-pressure reaction kettle for activation. The activation conditions are: activation temperature 120 °C, activation time 12 h. After activation, centrifuge to separate the solid, wash the solid with water until neutral, and dry to obtain the phosphorus removal agent.

[0042] Example 3 The embodiment of the present invention provides a preparation method of a special phosphorus removal agent for deep phosphorus removal, including the following steps: Add alumina and / or iron oxide and / or calcium oxide and / or magnesium oxide to the sludge for ingredient blending and mixing. After mixing evenly, spread it out in a tray and place it in an oven. Set the oven temperature to 90°C and dry the sludge for later use.

[0043] (1) Place the dried sludge in a tube furnace for calcination. The calcination temperature is 900°C and the calcination time is 6 hours. Nitrogen is passed through during the firing process for protection. After calcination, a phosphorus removal agent precursor is obtained (containing alumina, iron oxide, calcium oxide, and magnesium oxide, and the mass fractions are 10%, 30%, 20%, and 7% respectively).

[0044] (2) Preparation of the activator: Dissolve lanthanum nitrate, zirconium nitrate, cerium nitrate, magnesium nitrate, and iron nitrate in water to obtain a salt solution. The mass concentrations of each metal element are 0.3% for lanthanum, 0.1% for zirconium, 0.1% for cerium, 0.3% for magnesium, and 0.1% for iron. Then add the wetting and dispersing agent polyethylene glycol to the salt solution. The mass fraction of polyethylene glycol after addition is 1.2%. Stir evenly to obtain the activator.

[0045] (3) After mixing the phosphorus removal agent precursor and the activator evenly (the mixing mass ratio of the phosphorus removal agent precursor to the activator is 5:95), adjust the pH to 8 with sodium hydroxide solution, and then transfer the solution to a high-pressure reactor for activation. The activation conditions are: activation temperature 120°C, activation time 12 h. After activation, centrifuge to separate the solid, wash the solid with water until neutral, and dry to obtain the phosphorus removal agent.

[0046] Example 4 The embodiment of the present invention provides a preparation method of a special phosphorus removal agent for deep phosphorus removal, including the following steps: Add alumina and / or iron oxide and / or calcium oxide and / or magnesium oxide to the sludge for ingredient blending and mixing. After mixing evenly, spread it out in a tray and place it in an oven. Set the oven temperature to 90°C and dry the sludge for later use.

[0047] (1) Place the dried sludge in a tube furnace for calcination. The calcination temperature is 900°C and the calcination time is 6 hours. Nitrogen is passed through during the firing process for protection. After calcination, a phosphorus removal agent precursor is obtained (containing alumina, iron oxide, calcium oxide, and magnesium oxide, and the mass fractions are 25%, 20%, 15%, and 5% respectively).

[0048] (2) Preparation of the activator: Dissolve lanthanum nitrate, zirconium nitrate, cerium nitrate, magnesium nitrate, and iron nitrate in water to obtain a salt solution. The mass concentrations of each metal element are 0.3% for lanthanum, 0.1% for zirconium, 0.15% for cerium, 0.2% for magnesium, and 0.15% for iron. Then add the wetting and dispersing agents polyethylene glycol and polyvinylpyrrolidone to the salt solution. The mass ratio of polyethylene glycol to polyvinylpyrrolidone is 3:2. The mass fraction of the wetting and dispersing agent after addition is 1%. Stir evenly to obtain the activator.

[0049] (3) After uniformly mixing the phosphorus removal agent precursor and the activator (the mass ratio of the phosphorus removal agent precursor to the activator is 5:95), adjust the pH to 8 with sodium hydroxide solution, then transfer the solution to an autoclave for activation. The activation conditions are: activation temperature 120 °C, activation time 12 h. After activation, centrifuge to separate the solid, wash the solid with water until neutral, and dry to obtain the phosphorus removal agent.

[0050] Comparative Example 1 Provide a preparation method of a phosphorus removal agent, including the following steps: Add alumina and / or iron oxide and / or calcium oxide and / or magnesium oxide to the sludge for composition blending and mixing. After mixing evenly, spread it out in a tray, place it in an oven, set the oven temperature to 90 °C, and dry the sludge for later use.

[0051] (1) Calcinate the dried sludge in a tube furnace at a calcination temperature of 900 °C for 6 hours. During the calcination process, pass nitrogen for protection. After calcination, obtain the phosphorus removal agent precursor (containing alumina, iron oxide, calcium oxide, and magnesium oxide, and the mass fractions are: 25%, 20%, 15%, and 5% respectively).

[0052] (2) Preparation of the activator: Dissolve lanthanum nitrate, zirconium nitrate, cerium nitrate, magnesium nitrate, and iron nitrate in water to obtain a salt solution. The mass concentrations of each metal element are 0.3% for lanthanum, 0.1% for zirconium, 0.1% for cerium, 0.3% for magnesium, and 0.1% for iron. After stirring evenly, obtain the activator.

[0053] (3) After uniformly mixing the phosphorus removal agent precursor and the activator (the mass ratio of the phosphorus removal agent precursor to the activator is 5:95), adjust the pH to 8 with sodium hydroxide solution, then transfer the solution to an autoclave for activation. The activation conditions are: activation temperature 120 °C, activation time 12 h. After activation, centrifuge to separate the solid, wash the solid with water until neutral, and dry to obtain the phosphorus removal agent.

[0054] Comparative Example 2 Provide a preparation method of a phosphorus removal agent, including the following steps: Add alumina and / or iron oxide and / or calcium oxide and / or magnesium oxide to the sludge for composition blending and mixing. After mixing evenly, spread it out in a tray, place it in an oven, set the oven temperature to 90 °C, and dry the sludge for later use.

[0055] Place the dried sludge in a tube furnace for calcination at a calcination temperature of 900 °C for 6 hours. During the calcination process, pass nitrogen for protection. After calcination, wash it with water and then dry to obtain the phosphorus removal agent (containing alumina, iron oxide, calcium oxide, and magnesium oxide, and the mass fractions are: 25%, 20%, 15%, and 5% respectively).

[0056] Example 5 An embodiment of the present invention provides a preparation method of a special phosphorus remover for deep phosphorus removal. The difference from Example 1 is that during the preparation of the bifunctional activator, lanthanum nitrate and zirconium nitrate are dissolved in water to obtain a salt solution, and the mass concentrations of each metal element are 0.25% for lanthanum and 0.1% for zirconium; the remaining steps remain unchanged.

[0057] Example 6 An embodiment of the present invention provides a preparation method of a special phosphorus remover for deep phosphorus removal. The difference from Example 1 is that during the preparation of the bifunctional activator, cerium nitrate, magnesium nitrate, and iron nitrate are dissolved in water to obtain a salt solution, and the mass concentrations of each metal element are 0.1% for cerium, 0.25% for magnesium, and 0.1% for iron; the remaining steps remain unchanged.

[0058] Example 7 An embodiment of the present invention provides a preparation method of a special phosphorus remover for deep phosphorus removal. The difference from Example 1 is that sodium dodecylbenzenesulfonate is used as the dispersant, and the remaining steps remain unchanged.

[0059] Example 8 An embodiment of the present invention provides a preparation method of a special phosphorus remover for deep phosphorus removal. The difference from Example 1 is that the mass concentrations of each metal element are 0.6% for lanthanum, 0.6% for zirconium, 0.6% for cerium, 0.6% for magnesium, and 0.6% for iron, and the remaining steps remain unchanged.

[0060] Example 9 An embodiment of the present invention provides a preparation method of a special phosphorus remover for deep phosphorus removal. The difference from Example 1 is that the mass concentrations of each metal element are 0.04% for lanthanum, 0.04% for zirconium, 0.04% for cerium, 0.04% for magnesium, and 0.04% for iron, and the remaining steps remain unchanged.

[0061] Example 10 An embodiment of the present invention provides a preparation method of a special phosphorus remover for deep phosphorus removal. The difference from Example 1 is that the mass fraction of polyvinylpyrrolidone is 0.1%, and the remaining steps remain unchanged.

[0062] Example 11 An embodiment of the present invention provides a preparation method of a special phosphorus remover for deep phosphorus removal. The difference from Example 1 is that the mass fraction of polyvinylpyrrolidone is 2.1%, and the remaining steps remain unchanged.

[0063] Example 12 An embodiment of the present invention provides a preparation method of a special phosphorus remover for deep phosphorus removal. The difference from Example 1 is that the calcination temperature is 650 °C, and the remaining steps remain unchanged.

[0064] Example 13 The embodiment of the present invention provides a preparation method of a special phosphorus remover for deep phosphorus removal. The difference from Example 1 is that the calcination temperature is 1200 °C, and the remaining steps remain unchanged.

[0065] Example 14 The embodiment of the present invention provides a preparation method of a special phosphorus remover for deep phosphorus removal. The difference from Example 1 is that the pH is adjusted to 6 with sodium hydroxide solution, and the remaining steps remain unchanged.

[0066] Example 15 The embodiment of the present invention provides a preparation method of a special phosphorus remover for deep phosphorus removal. The difference from Example 1 is that the pH is adjusted to 11 with sodium hydroxide solution, and the remaining steps remain unchanged.

[0067] Example 16 The embodiment of the present invention provides a preparation method of a special phosphorus remover for deep phosphorus removal. The difference from Example 1 is that the addition amount of the porous precursor is 2 wt%, and the remaining steps remain unchanged.

[0068] Example 17 The embodiment of the present invention provides a preparation method of a special phosphorus remover for deep phosphorus removal. The difference from Example 1 is that the addition amount of the porous precursor is 12 wt%, and the remaining steps remain unchanged.

[0069] It should be noted that the above sludge is all municipal sludge, all from the Qingbaijiang Sludge Treatment Plant in Chengdu. The sampling time is January 2024. In other embodiments, the sludge can also be sampled from other sludge treatment plants or at other times, which is not limited here. During the preparation process, the composition ratios of alumina, iron oxide, calcium oxide, and magnesium oxide can be adjusted according to actual needs.

[0070] Test results The phosphorus removers prepared in Examples 1-17 and Comparative Examples 1-2 were detected. Specifically, the above phosphorus removers were added to the water with a total phosphorus content of 1.2 mg / L at dosages of 50 mg / L, 80 mg / L, and 100 mg / L respectively to adsorb phosphorus in the water, and finally the phosphorus content (mg / L) in the water after adsorption treatment was detected. The results are shown in Table 1 below.

[0071] Table 1

[0072] Referring to Table 1, it can be seen from Examples 1-4 that the phosphorus remover prepared in the embodiment of the present invention can make the total phosphorus content in the water less than 0.5 mg / L when the addition amount is 50 mg / L, and can make the total phosphorus content in the water less than 0.1 mg / L when the addition amount is 100 mg / L.

[0073] As can be seen from Comparative Example 1, when the dispersant is not added, metal ions will aggregate during the reaction to form larger particles, thereby blocking the pores, reducing the adsorption area, resulting in a decrease in the number of adsorption sites, and thus reducing the adsorption performance.

[0074] As can be seen from Comparative Example 2, the calcined sludge has a certain adsorption effect on phosphorus, but the adsorption capacity of the unactivated sludge is limited. Since the total phosphorus content in the tail water is only 1.2 mg / L, the phosphorus adsorption amount of the dispersant added in Comparative Example 2 can be ignored and cannot meet the requirement of ≤0.5 mg / L.

[0075] As can be seen from the comparison between Example 5 and Example 1, when only lanthanum nitrate and zirconium nitrate are added as the activator, although there is a certain phosphorus removal effect, the effect is limited and not as good as that when multiple metal salts are added as the activator.

[0076] As can be seen from the comparison between Example 6 and Example 1 and Example 5, when only cerium nitrate, magnesium nitrate, and iron nitrate are added as the activator, the effect is similar to that when lanthanum nitrate and zirconium nitrate are added, but not as good as that when five salts are added as the activator.

[0077] As can be seen from the comparison between Example 7 and Example 1, when sodium dodecylbenzenesulfonate is used as the dispersant, the effect is poor because sodium dodecylbenzenesulfonate has a poor dispersing effect on metal hydroxides, and the hydroxides aggregate severely and cannot effectively adhere to the precursor.

[0078] As can be seen from the comparison between Example 8 and Example 1, when the concentration of metal ions in the activator is too high, the metal hydroxides aggregate into large particles, which is not conducive to their adhesion to the precursor, and the phosphorus removal agent has a poor phosphorus removal effect.

[0079] As can be seen from the comparison between Example 9 and Example 1, when the concentration of metal ions in the activator is too low, too few metal hydroxides or oxides can adhere to the precursor, and there are few effective sites that can bind phosphorus, resulting in a poor phosphorus removal effect.

[0080] As can be seen from the comparison between Example 10 and Example 1, when the amount of the dispersant is too small, the precursor and metal hydroxides cannot be effectively dispersed, which is not conducive to the metal adhering to the precursor, the effective sites of the phosphorus removal agent decrease, and the phosphorus removal effect on phosphorus is not good.

[0081] As can be seen from the comparison between Example 11 and Example 1, when the amount of the dispersant is too large, the dispersant wraps around the precursor, hindering the effective activation of the precursor, resulting in a poor phosphorus removal effect of the phosphorus removal agent on phosphorus.

[0082] As can be seen from the comparison between Example 12 and Example 1, when the sludge calcination temperature is too low, the precursor structure is unstable, and stable granular phosphorus removal agent cannot be formed during the hydrothermal process.

[0083] Comparing Example 13 with Example 1, it can be seen that when the sludge calcination temperature is too high, the effective sites on the surface of the precursor that bind metal hydroxides will be damaged, and the amount of metal ions that can be bound will decrease, resulting in a poor effect of the final phosphorus removal agent.

[0084] Comparing Example 14 with Example 1, it can be seen that during the hydrothermal process, when the pH value is too small, too little metal hydroxide is formed, which is not conducive to the fixation of metal hydroxides or oxides during the hydrothermal synthesis process, and finally results in a poor effect of the phosphorus removal agent.

[0085] Comparing Example 15 with Example 1, it can be seen that during the hydrothermal process, when the pH value is too large, large particle precipitates of metal hydroxide are formed, making it impossible for metal oxides or hydroxides to adhere to the precursor, resulting in a poor phosphorus removal effect of the phosphorus removal agent.

[0086] Comparing Example 16 with Example 1, it can be seen that during the hydrothermal process, when the addition amount of the porous precursor is too small, the precursor can be evenly dispersed, and metal ions can also effectively adhere to the surface and pores of the precursor. Therefore, the effect of the phosphorus removal agent is better, but the activator is wasted.

[0087] Comparing Example 17 with Example 1, it can be seen that during the hydrothermal process, when the addition amount of the porous precursor is too large, the precursor cannot be effectively and evenly dispersed in the solution, and the amount of metal ions that can adhere to each precursor particle decreases, resulting in a poor effect of the final phosphorus removal agent.

[0088] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above description is only the specific embodiments of the present invention and is not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A special phosphorus remover for deep phosphorus removal, characterized in that, A material prepared from the following raw materials: a porous precursor, an activator, and a dispersant, wherein the porous precursor includes at least one of alumina, iron oxide, calcium oxide, and magnesium oxide, and the activator includes at least one of lanthanum salt, cerium salt, zirconium salt, magnesium salt, and iron salt.

2. The phosphorus removal agent dedicated to deep phosphorus removal according to claim 1, characterized in that, The dispersant includes at least one of polyvinylpyrrolidone and polyethylene glycol.

3. The special phosphorus remover for deep phosphorus removal according to claim 2, characterized in that The porous precursor includes alumina, iron oxide, calcium oxide, and magnesium oxide, and their mass fractions in the porous precursor are respectively: 10 - 40%, 5 - 30%, 3 - 20%, and 1 - 7%.

4. A preparation method of a special phosphorus remover for deep phosphorus removal as described in any one of claims 1 to 3, characterized in that, It includes the following steps: S1: Dry the sludge and reserve it for later use; S2: Calcinate the dried sludge to obtain a porous precursor; S3: Dissolve the activator in water to obtain a salt solution, and add a dispersant solution to the salt solution to obtain a mixed liquid; S4: Add the porous precursor to the mixed liquid, adjust the pH, and then carry out the reaction; S5: After the reaction is completed, carry out solid-liquid separation, rinsing, and drying in sequence to obtain a phosphorus remover.

5. The preparation method of a special phosphorus remover for deep phosphorus removal according to claim 4, characterized in that, In S2, the calcination temperature is 700 - 1100 °C, and the calcination time is 4 - 8 h.

6. The preparation method of a special phosphorus remover for deep phosphorus removal according to claim 5, characterized in that, The calcination atmosphere in S2 includes introducing nitrogen into a sealed reactor for protection.

7. The preparation method of a special phosphorus-removing agent for deep phosphorus removal according to claim 4, characterized in that, In S3, the concentration of a single metal ion in the salt solution is 0.05 - 0.5 wt%, and the concentration of the dispersant in the mixed liquid is 0.2 - 2 wt%.

8. The preparation method of a special phosphorus remover for deep phosphorus removal according to claim 4, characterized in that, The activator is a nitrate and / or a chloride.

9. The preparation method of a special phosphorus remover for deep phosphorus removal according to claim 4, characterized in that, In S4, the addition amount of the porous precursor is 2.5 - 10 wt%, and it also includes adjusting the pH to 7.5 - 9.5, the reaction temperature is 80 - 140 °C, and the reaction time is 8 - 16 h.

10. Use of a special phosphorus remover for deep phosphorus removal as described in any one of claims 1 to 3, characterized in that, It includes using the phosphorus remover in the tail water of a sewage treatment plant to make the total phosphorus concentration in the tail water of the sewage treatment plant ≤ 0.5 mg / L.

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