Method for producing phosphogypsum sintered ceramsite for water treatment filter

Abstract

The phosphogypsum sintered haydite for water treatment filter material is characterized by comprising the following raw material components in parts: phosphogypsum 35-45, machine-made sand slurry 20-23, graphite tailings 20-25, sludge incineration slag 8-12, 5-7, 5 parts of pore forming agent, and 25-30 parts of water. The phosphogypsum sintered haydite for water treatment filter material prepared by matching various raw materials cannot produce liquid phase and achieve the wrapping effect when the phosphogypsum is too much. As a result, the haydite has low strength and high water absorption. The less the phosphogypsum is, the more the haydite conforms to the traditional haydite, the higher the strength is, and the lower the water absorption is. The reasonable mixing of the phosphogypsum can achieve the effect and consume the phosphogypsum.

Description

Technical Field

[0001] This invention relates to the field of phosphogypsum treatment, especially to the field of phosphogypsum recycling and reuse, and also discloses a method for preparing phosphogypsum sintered ceramsite for water treatment filter media. Background Technology

[0002] Phosphogypsum mainly comes in two colors: grayish-black and grayish-white. The particle diameter is generally 5–50 μm, and the water of crystallization content is 20%–25%. Phosphogypsum is a solid waste generated in the wet-process phosphoric acid production process, and its main component is calcium sulfate dihydrate. The composition of phosphogypsum is relatively complex, containing not only calcium sulfate but also incompletely decomposed phosphate rock, residual phosphoric acid, fluorides, acid-insoluble substances, and organic matter. The presence of fluorine and organic matter has the greatest impact on the resource utilization of phosphogypsum.

[0003] Buildings are a major energy consumer, accounting for 30% of total social energy consumption, ranking alongside industry and transportation as one of the three major energy consumers. There is considerable research on the use of phosphogypsum in non-sintered ceramsite. However, sintered ceramsite is a previously unexplored area for the application of phosphogypsum. Research on sintered phosphogypsum ceramsite will fill this gap in the resource utilization of phosphogypsum, striving to increase its consumption and resource utilization.

[0004] Due to its unique properties, phosphogypsum is generally used as a building material in practical applications, produced as gypsum blocks or phosphogypsum-based non-sintered ceramsite. Research on the production of sintered ceramsite from phosphogypsum is relatively limited. One study found that a sludge:phosphogypsum ratio of 1:4, sintered at 1050℃ for 15 minutes, yielded ceramsite with a bulk density of 685.78 kg / m³, a water absorption rate of 27.34%, and a hydrochloric acid solubility of 11.38%. Further research has focused on the production and modification of sintered ceramsite from phosphogypsum, municipal waste sludge, and red mud for lead ion adsorption.

[0005] Research on phosphogypsum sintered ceramsite is limited. The main component of phosphogypsum is calcium sulfate dihydrate, which also includes some fluorine, phosphorus, and organic matter. This differs significantly from the components required for sintered ceramsite. Therefore, fly ash and clay, as key materials for sintered ceramsite, have been extensively studied, with complete systems and mechanisms established. Graphite tailings contain the basic components of sintered ceramsite, making them a suitable raw material to be combined with phosphogypsum in the production of sintered ceramsite. Summary of the Invention

[0006] The purpose of this invention is to provide sintered phosphogypsum ceramsite for water treatment filter media and its preparation method. By adding other materials, the basic configuration of the ceramsite is achieved. The addition of manufactured sand slurry and graphite tailings aims to consume solid waste and better fix phosphorus and fluorine in the ceramsite. Firstly, phosphogypsum undergoes a calcination process to remove impurities. At 800℃, eutectic phosphorus can be converted into inert pyrophosphate. Of course, organic matter is also removed at high temperatures. However, neither phosphorus nor fluorine can be completely removed. This invention focuses on fixing phosphorus and fluorine, not removal or purification. The presence of fluorine and phosphorus mainly affects the hydration reaction of phosphogypsum as a cementing material, but in this method of sintering ceramsite, the impact of fluorine and phosphorus on the ceramsite is minimal. This invention also provides a method for the resource utilization of phosphogypsum.

[0007] To solve the above problems, the present invention adopts the following technical solution:

[0008] A sintered phosphogypsum ceramsite for water treatment filter media comprises the following raw materials in parts: 35-45 parts phosphogypsum that has passed through a 100-mesh sieve, 20-23 parts manufactured sand slurry, 20-25 parts graphite tailings, 8-12 parts sludge incineration residue, 5-7 parts clay, 5-7 parts pore-forming agent, and 20-25 parts water.

[0009] As a preferred embodiment, the following components are included in parts: phosphogypsum powder: 35 parts; manufactured sand slurry: 23 parts; graphite tailings: 25 parts; sludge incineration residue: 10 parts; clay: 7 parts; plus 5 parts of pore-forming agent and 25 parts of water.

[0010] The phosphogypsum powder is obtained by crushing undisturbed phosphogypsum through a 100-mesh sieve.

[0011] The manufactured sand slurry is the slurry left after washing manufactured sand. The slurry blocks are dried, crushed, and passed through a 100-200 mesh sieve before being put into use.

[0012] The graphite tailings mentioned are a large amount of solid waste generated during graphite mining. Because the required substances are below the minimum extraction content, they are no longer valuable. The tailings are crushed, dried, and passed through a 100-mesh sieve for later use. The graphite tailings are obtained by crushing and passing through a 100-200 mesh sieve. The composition of the graphite tailings is 54%-58% SiO2, 25%-28% Al2O3, 6%-8% Fe2O3, and 4%-6% K2O.

[0013] The pore-forming agent is a ceramic polishing slurry, dried sludge powder, peptone, and starch. It is composed of 30-35 parts ceramic polishing slurry, 25-30 parts dried sludge powder, 15-20 parts peptone, and 20-25 parts starch.

[0014] The method for preparing phosphogypsum sintered ceramsite for water treatment filter media includes the following steps:

[0015] (1) Add phosphogypsum, manufactured sand slurry, graphite tailings, sludge incineration residue, clay, pore-forming agent, and water to a mixer in sequence according to the proportion, and mix the materials thoroughly. (2) Granulate the mixture to obtain raw material pellets (in the conventional method in this field, the mixture is placed in a disc granulator, the disc granulator is started, and water is poured evenly into the granulator for granulation). (3) Place the raw material pellets in an oven to dry at a temperature of 50°C. After drying, place them in a sintering furnace for heating. The preheating temperature is 300°C to 500°C, and the preheating time is maintained for 30 to 60 minutes. Then, continue to heat the mixture at a uniform rate to 1120°C to 1150°C, maintain the temperature for 15 minutes, and the heating rate is 3-8°C / minute. Sinter the raw material pellets. After sintering, wait for cooling and then take them out to obtain phosphogypsum sintered ceramsite for water treatment filter media.

[0016] Phosphogypsum contains over 85% calcium sulfate, as well as fluorine, phosphorus, and some organic matter. This organic matter decomposes at high temperatures. The complete decomposition temperature of pure calcium sulfate is 1350℃ to 1400℃. The presence of impurities lowers the decomposition temperature, leading to premature SO2 release. Therefore, it is crucial to select an appropriate sintering temperature for the ceramsite and to implement effective exhaust gas treatment.

[0017] The decomposition formula for pure calcium sulfate:

[0018] 2CaSO4=2CaO+2SO2+O2, 1350℃-1400℃

[0019] In the presence of carbon, the decomposition temperature of calcium sulfate is lowered. The decomposition process is as follows:

[0020] CaSO4 + 2C = CaS + 2CO2

[0021] CaS + 3CaSO4 = 4CaO + 4SO2

[0022] 2CaSO4 + C = 2CaO + CO2

[0023] In sintered phosphogypsum ceramsite, because phosphogypsum contains a certain amount of organic matter, calcium sulfate will partially decompose at the temperatures used in this technology, such as 1120℃~1150℃. The decomposition temperature of calcium sulfate is 1000℃, which is incomplete. The complete decomposition process requires 1350℃-1400℃ to achieve complete decomposition, thereby generating calcium oxide.

[0024] Calcium sulfate, a major component of phosphogypsum, is also present in sintered phosphogypsum ceramsite, playing a dominant role. Combined with other substances including silica, the solid-state sintering at high temperatures results in high bonding strength. However, the presence of impurities creates internal voids, reducing the bulk density of the ceramsite.

[0025] Fixation reduces the leaching toxicity of phosphorus (F) and phosphorus (P). High temperature only converts eutectic phosphorus into inert pyrophosphate and removes organic matter. The main fixation effect is the liquid-phase encapsulation at high temperature, which reduces the contact between the internal material and water.

[0026] Functions: Except for calcium sulfate, the other substances are the main components of sintered ceramsite. At high temperatures, a liquid phase is generated to encapsulate the ceramsite, and the high-temperature decomposition of organic matter leads to the formation of micropores. Upon further heating, the liquid phase in these micropores continues to expand. Silicon mainly serves a supporting role, enhancing compressive strength, while aluminum and iron mainly generate a liquid phase, creating pores within the ceramsite.

[0027] Undecomposed calcium sulfate and other substances exist in the interlayer, sandwiched between two layers of glaze. The glaze is formed by the solidification of a high-temperature liquid phase at a low temperature. It is hydrophobic, which reduces the contact between the internal substances and water, thus reducing the risk of pollutant release.

[0028] This technical solution has the following beneficial technical effects:

[0029] (1) The raw material used in this invention is solid waste. By combining the components through waste utilization, it is more environmentally friendly and low-cost, thus realizing the effective utilization of resources.

[0030] (2) The water treatment filter material prepared by the present invention uses phosphogypsum sintered ceramsite. If there is too much phosphogypsum, a liquid phase cannot be generated, and the coating effect cannot be achieved. This will result in low strength and high water absorption of the ceramsite. The less phosphogypsum, the more the ceramsite conforms to traditional ceramsite, with higher strength and lower water absorption. Reasonable incorporation of phosphogypsum can achieve the desired effect while also consuming the phosphogypsum.

[0031] A proper formulation involves removing phosphogypsum, and ensuring that the composition of other substances conforms to the Riley ternary phase diagram. Riley proposed a well-known ternary phase diagram for preparing ceramsite with good sintering properties. Specifically, when preparing ceramsite with good sintering properties from clay materials, the basic chemical composition of the raw materials is characterized by 40%-70% SiO2, 10%-25% Al2O3, and 8%-25% Fe2O3. Besides phosphogypsum, manufactured sand slurry, sludge incineration residue, graphite tailings, and clay all have relatively high silicon, aluminum, and iron content, falling within the range suitable for producing sintered ceramsite with good properties. However, the addition of phosphogypsum disrupts the range of the Riley ternary phase diagram, making it unsuitable for sintering high-performance ceramsite. Therefore, a pore-forming agent is added to improve the sintering conditions of the ceramsite and achieve the desired effect.

[0032] (3) By adjusting the raw materials, sintering lightweight ceramic particles at high temperature achieves the effect of purifying organic impurities in phosphogypsum, and the leaching of heavy metal toxicity is lower than the "Integrated Wastewater Discharge Standard". The organic impurities are oxidized and decomposed at high temperature, thus the organic impurities are decomposed by high temperature. The low leaching of heavy metal toxicity is due to the fixation effect; the aluminum-iron materials generate a liquid phase at high temperature to encapsulate the ceramic particles, achieving the effect of fixing heavy metals, not purification. Therefore, this type of ceramic particle can be used as a wastewater filtration material, not a wastewater purification material. Its own toxicity leaching is low, and no other heavy metals or pollutants will enter the wastewater. In addition, the raw materials do not contain a large amount of heavy metals, and there is no heavy metal industrial waste residue. Therefore, the high-temperature sintering liquid phase encapsulation reduces toxicity leaching.

[0033] (4) The processing method provided by the present invention is simple and reasonably reduces the sintering steps, so that operators can easily carry out the preparation of the present invention. Attached Figure Description

[0034] Figure 1 The image shows the expanded clay aggregate from Example 1.

[0035] Figure 2 The image shows the expanded clay aggregate from Example 2.

[0036] Figure 3 The image shows the expanded clay aggregate from Example 3.

[0037] Figure 4 The image shows the expanded clay pellets used in Comparative Example 1.

[0038] Figure 5 The image shows the expanded clay pellets used in Comparative Example 2.

[0039] Figure 6 The image shows the expanded clay pellets used in Comparative Example 3. Detailed Implementation Plan

[0040] The physicochemical properties of each raw material, such as:

[0041] Table 1. Chemical composition analysis (wt%) of the raw materials used.

[0042]

[0043] The chemical composition analysis of the various substances above shows that the main component of phosphogypsum is calcium sulfate, while silicon, aluminum, and iron (Si, A, F) are relatively scarce, resulting in sintered ceramsite composed entirely of phosphogypsum lacking strength. Traditional Si, A, F sintered ceramsite generates a liquid phase at high temperatures, producing internal gas and causing expansion. However, with the addition of phosphogypsum, calcium sulfate is added instead of traditional Si, A, F ceramsite. Nevertheless, the Si, A, F still plays a role at high temperatures, acting as an additive to promote the generation of liquid-phase gas. Undecomposed calcium sulfate is encapsulated between the two liquid phases, reducing the toxic leaching of phosphorus and fluorine.

[0044] Key condition: The amount of phosphogypsum should not be too large. That is, after removing the phosphogypsum, the remaining silicon-aluminum-iron material composition should conform to the actual traditional sintered ceramsite. In order to enhance the formation of pores and liquid phase in the ceramsite at high temperatures, a certain amount of pore-forming agent is added to promote the formation of pores and liquid phase, thereby achieving the desired technical effect.

[0045] Example 1

[0046] A sintered phosphogypsum ceramsite for water treatment filter media comprises the following components:

[0047] Take 35 parts phosphogypsum; 23 parts manufactured sand slurry; 25 parts graphite tailings; 10 parts sludge incineration residue; 7 parts clay; plus 5 parts pore-forming agent; and 25 parts water. Add the phosphogypsum, manufactured sand slurry, graphite tailings, sludge incineration residue, clay, and pore-forming agent (composed of 35 parts ceramic polishing slurry, 30 parts dried sludge powder, 15 parts peptone, and 20 parts starch) and water sequentially to a mixer. Mix at 250 rpm for 15 minutes to thoroughly mix the materials. Place the mixture into a disc granulator, start the granulator, and evenly pour water into it. Run the machine for 20 minutes to obtain raw material pellets. Place the raw material pellets in an oven to dry at 50℃. After drying, the raw material pellets are placed in a sintering furnace for sintering. The preheating temperature is 300℃, and the temperature is maintained for 60 minutes. Then, the temperature is increased to 1120℃ at a constant rate and maintained for 15 minutes. The heating rate is 8℃ / minute. The raw material pellets are sintered. After sintering and cooling, they are taken out to obtain phosphogypsum sintered ceramsite for water treatment filter media.

[0048] According to the requirements of the People's Republic of China Urban Construction Industry Standard CJ / T299-2008 "Artificial Ceramic Abrasive Filter Media for Water Treatment", the measured values ​​of the ceramsite were: a total breakage rate and a grinding rate of 5%; mud content of 0.6%; hydrochloric acid solubility of 1%; porosity of 41.0%; and specific surface area greater than 0.5 × 10⁻⁶. 4 cm 2 / g reached 5206cm 2 / g.

[0049]

[0050] GB / T 17431.1-2010 requires that phosphogypsum be classified as industrial waste residue, and the requirements for lightweight aggregates of industrial waste residue are as follows: different density grades correspond to different requirements.

[0051]

[0052] Toxicity leaching of ceramsite was conducted according to the People's Republic of China National Environmental Protection Standard HJ557-2010 "Solid Waste Leaching Toxicity Leaching Method - Horizontal Oscillation Method". The toxicity leaching of heavy metals was lower than that of the People's Republic of China National Standard GB8978-1996 "Integrated Wastewater Discharge Standard". According to the People's Republic of China National Standard GB 11893-89 "Determination of Total Phosphorus in Water - Ammonium Molybdate Spectrophotometric Method", the phosphorus toxicity leaching was 0.05 mg / L, lower than the Class II water standard of 0.1 mg / L specified in the People's Republic of China National Standard GB3838-2002 "Surface Water Environmental Quality Standard". According to the People's Republic of China National Environmental Protection Standard HJ 873-2017 "Determination of Water-Soluble Fluoride and Total Fluoride in Soil - Ion Selective Electrode Method", the water-soluble fluoride toxicity leaching was 0.4 mg / L, lower than the Class I water standard of 1.0 mg / L specified in the People's Republic of China National Standard GB 3838-2002 "Surface Water Environmental Quality Standard".

[0053]

[0054] Example 2

[0055] A sintered phosphogypsum ceramsite for water treatment filter media comprises the following components:

[0056] Take 40 parts phosphogypsum powder; 20 parts manufactured sand slurry; 24 parts graphite tailings; 11 parts sludge incineration residue; 5 parts clay; plus 5 parts pore-forming agent (pore-forming agent consists of 30 parts ceramic polishing slurry, 30 parts dried sludge powder, 20 parts peptone, and 20 parts starch); and 25 parts water. Add the phosphogypsum, manufactured sand slurry, graphite tailings, sludge incineration residue, clay, pore-forming agent, and water sequentially to a mixer according to the specified ratio. Mix the mixture at 250 rpm for 15 minutes to ensure thorough mixing. Place the mixture into a disc granulator, start the granulator, and evenly pour water into it. Run the machine for 20 minutes to obtain raw pellets. Place the raw pellets in an oven to dry at 50℃. After drying, the raw material pellets are placed in a sintering furnace for sintering. The preheating temperature is 400℃, and the temperature is maintained for 40 minutes. Then, the temperature is increased to 1130℃ at a constant rate and maintained for 15 minutes. The heating rate is 8℃ / minute. The raw material pellets are sintered. After sintering and cooling, they are taken out to obtain phosphogypsum sintered ceramsite for water treatment filter media.

[0057] According to the requirements of the People's Republic of China Urban Construction Industry Standard CJ / T299-2008 "Artificial Ceramic Abrasive Filter Media for Water Treatment", the measured values ​​of the ceramsite were: a total breakage rate and a grinding rate of 4%; a mud content of 0.8%; a hydrochloric acid solubility of 0.9%; a porosity of 41.1%; and a specific surface area greater than 0.5 × 10⁻⁶. 4 cm 2 / g reached 5186cm 2 / g.

[0058]

[0059]

[0060] The ceramsite was subjected to toxicity leaching according to the People's Republic of China National Environmental Protection Standard HJ557-2010 "Solid Waste Leaching Toxicity Leaching Method - Horizontal Oscillation Method". The toxicity leaching of heavy metals was lower than that of the People's Republic of China National Standard GB8978-1996 "Integrated Wastewater Discharge Standard"; the phosphorus toxicity leaching was measured to be 0.06 mg / L according to the People's Republic of China National Standard GB 11893-89 "Determination of Total Phosphorus in Water - Ammonium Molybdate Spectrophotometric Method", which is lower than the Class II water standard of 0.1 mg / L specified in the People's Republic of China National Standard GB3838-2002 "Surface Water Environmental Quality Standard"; the water-soluble fluoride toxicity leaching was measured to be 0.7 mg / L according to the People's Republic of China National Environmental Protection Standard HJ 873-2017 "Determination of Water-Soluble Fluoride and Total Fluoride in Soil - Ion Selective Electrode Method", which is lower than the Class I water standard of 1.0 mg / L specified in the People's Republic of China National Standard GB 3838-2002 "Surface Water Environmental Quality Standard".

[0061]

[0062] Example 3

[0063] A sintered phosphogypsum ceramsite for water treatment filter media comprises the following components:

[0064] Take 45 parts phosphogypsum powder; 22 parts manufactured sand slurry; 20 parts graphite tailings; 8 parts sludge incineration residue; 5 parts clay; plus 5 parts pore-forming agent (pore-forming agent consists of 30 parts ceramic polishing slurry, 25 parts dried sludge powder, 20 parts peptone, and 25 parts starch); and 25 parts water. Add the phosphogypsum, manufactured sand slurry, graphite tailings, sludge incineration residue, clay, pore-forming agent, and water sequentially to a mixer according to the specified ratio. Mix the mixture at 250 rpm for 15 minutes to ensure thorough mixing. Place the mixture into a disc granulator, start the granulator, and evenly pour water into it. Run the machine for 20 minutes to obtain raw pellets. Place the raw pellets in an oven to dry at 50℃. After drying, the raw material pellets are placed in a sintering furnace for sintering. The preheating temperature is 500℃, and the temperature is maintained for 30 minutes. Then, the temperature is increased to 1150℃ at a constant rate and maintained for 15 minutes. The heating rate is 8℃ / minute. The raw material pellets are sintered. After sintering and cooling, the pellets are taken out to obtain phosphogypsum sintered ceramsite for water treatment filter media.

[0065] According to the requirements of the People's Republic of China Urban Construction Industry Standard CJ / T299-2008 "Artificial Ceramic Abrasive Filter Media for Water Treatment", the measured values ​​of the ceramsite were: a total breakage rate and a grinding rate of 3%; a mud content of 0.5%; a hydrochloric acid solubility of 0.6%; a porosity of 41.5%; and a specific surface area greater than 0.5 × 10⁻⁶. 4 cm 2 / g reached 5162cm 2 / g.

[0066]

[0067]

[0068] The ceramsite was subjected to toxicity leaching according to the People's Republic of China National Environmental Protection Standard HJ557-2010 "Solid Waste Leaching Toxicity Leaching Method - Horizontal Oscillation Method". The toxicity leaching of heavy metals was lower than that of the People's Republic of China National Standard GB8978-1996 "Integrated Wastewater Discharge Standard"; the phosphorus toxicity leaching was measured to be 0.08 mg / L according to the People's Republic of China National Standard GB 11893-89 "Determination of Total Phosphorus in Water - Ammonium Molybdate Spectrophotometric Method", which is lower than the Class II water standard of 0.1 mg / L specified in the People's Republic of China National Standard GB3838-2002 "Surface Water Environmental Quality Standard"; the water-soluble fluoride toxicity leaching was measured to be 0.9 mg / L according to the People's Republic of China National Environmental Protection Standard HJ 873-2017 "Determination of Water-Soluble Fluoride and Total Fluoride in Soil - Ion Selective Electrode Method", which is lower than the Class I water standard of 1.0 mg / L specified in the People's Republic of China National Standard GB 3838-2002 "Surface Water Environmental Quality Standard".

[0069]

[0070] Comparative Example 1

[0071] A sintered phosphogypsum ceramsite for water treatment filter media comprises the following components:

[0072] The operation is the same as in Example 1, except that 5 parts of pore-forming agent are not added. Without the addition of pore-forming agent, a liquid phase cannot be generated, resulting in an excessively high breakage rate, making it unsuitable for use as water treatment filter media.

[0073] Comparative Example 2

[0074] A sintered phosphogypsum ceramsite for water treatment filter media comprises the following components:

[0075] Except for setting the sintering temperature to 1100℃, the other operations are the same as in Example 1. If the temperature is too low, the phosphogypsum ceramsite cannot generate a liquid phase, resulting in a high breakage rate and water absorption rate, rendering it unusable.

[0076] Comparative Example 3

[0077] A sintered phosphogypsum ceramsite for water treatment filter media comprises the following components:

[0078] Except for setting the sintering temperature to 1170℃, the other operations were the same as in Example 1. If the temperature is too high, the phosphogypsum ceramsite completely melts and sticks to the crucible. It cannot be removed and is therefore worthless.

Claims

1. A type of phosphogypsum sintered ceramsite for water treatment filter media, characterized in that, The water treatment filter media sintered ceramsite made of phosphogypsum comprises the following raw materials in the following proportions: 35-45 parts phosphogypsum, 20-23 parts manufactured sand slurry, 20-25 parts graphite tailings, 8-12 parts sludge incineration residue, 5-7 parts clay, 5 parts pore-forming agent, and 25-30 parts water. The preparation method of phosphogypsum sintered ceramsite includes the following steps: (1) Add phosphogypsum, manufactured sand slurry, graphite tailings, sludge incineration residue, clay and pore-forming agent into the mixer in sequence according to the proportion, and mix the materials thoroughly; (2) After adding water to the mixture from step (1), the raw material balls are obtained by granulation; (3) The raw material balls are dried and sintered at a preheating temperature of 300℃~500℃ for 30~60 minutes. Then, the temperature is raised to 1120℃~1150℃ at a uniform rate and held for 10-15 minutes. After sintering, the balls are cooled to obtain phosphogypsum sintered ceramsite for water treatment filter media.

2. The phosphogypsum sintered ceramsite for water treatment filter media according to claim 1, characterized in that, The water treatment filter media sintered ceramsite made of phosphogypsum comprises the following raw materials in the following proportions: 35 parts phosphogypsum, 23 parts machine-made sand slurry, 25 parts graphite tailings, 10 parts sludge incineration residue, 7 parts clay, plus 5 parts pore-forming agent and 25 parts water.

3. The phosphogypsum sintered ceramsite for water treatment filter media according to claim 1 or 2, characterized in that, The phosphogypsum mentioned is obtained by crushing undisturbed phosphogypsum and passing it through a 100-200 mesh sieve.

4. The phosphogypsum sintered ceramsite for water treatment filter media according to claim 1 or 2, characterized in that, The slurry remaining after washing the manufactured sand is obtained by filtering, drying, and passing through a 100-200 mesh sieve.

5. The phosphogypsum sintered ceramsite for water treatment filter media according to claim 1 or 2, characterized in that, The graphite tailings are obtained by crushing and passing them through a 100-mesh sieve. The composition of the graphite tailings is 54%-58% SiO2, 25%-28% Al2O3, 6%-8% Fe2O3, and 4%-6% K2O.

6. The phosphogypsum sintered ceramsite for water treatment filter media according to claim 1 or 2, characterized in that, The sludge incineration residue is the waste material left after sludge combustion. The original sludge incineration residue is crushed and passed through a 100-mesh and 0.15mm sieve to obtain the material required by the scheme.

7. The phosphogypsum sintered ceramsite for water treatment filter media according to claim 1 or 2, characterized in that, The pore-forming agent is composed of ceramic polishing slurry, dried sludge powder, peptone, and starch; specifically, ceramic polishing slurry: 30-35 parts, dried sludge powder: 25-30 parts, peptone: 15-20 parts, and starch: 20-25 parts.

8. The phosphogypsum sintered ceramsite for water treatment filter media according to claim 7, characterized in that, The dried sludge powder is obtained by drying wastewater from the secondary sedimentation tank of an urban wastewater treatment plant at 105°C and then crushing it through a 100-mesh and 0.15mm sieve.

9. The phosphogypsum sintered ceramsite for water treatment filter media according to claim 7, characterized in that, The peptone and starch mentioned were purchased as medicine.

10. A method for preparing phosphogypsum sintered ceramsite for water treatment filter media according to any one of claims 1-9, characterized in that, Includes the following steps: (1) Add phosphogypsum, manufactured sand slurry, graphite tailings, sludge incineration residue, clay and pore-forming agent into the mixer in sequence according to the proportion, and mix the materials thoroughly; (2) After adding water to the mixture from step (1), the raw material balls are obtained by granulation; (3) The raw material balls are dried and sintered at a preheating temperature of 300℃~500℃ for 30~60 minutes. Then, the temperature is raised to 1120℃~1150℃ at a uniform rate and held for 10-15 minutes. After sintering, the balls are cooled to obtain phosphogypsum sintered ceramsite for water treatment filter media.

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