Preparation method of phosphogypsum-based composite functional filler

Abstract

The invention discloses a preparation method of an ardealite-based composite functional filler, and relates to the technical field of high polymer material filler preparation. Comprising the following steps: 1, pretreating phosphogypsum, and sequentially carrying out impurity removal, drying, high-temperature treatment and grinding; 2, preparation of nano TiO2 powder and ZnO powder is carried out; and 3, mixing the pre-treated micron-sized CaSO4, nano TiO2 and nano ZnO, then carrying out surface treatment, carrying out ball milling, and carrying out post-treatment to obtain the phosphogypsum-based composite functional filler. The process is simple, automation is easy, the cost is low, resource utilization of ardealite solid waste is achieved, the prepared filler combines the advantages of micron CaSO4, nano TiO2 and nano ZnO, the heat aging resistance, the mechanical property and the ultraviolet ray resistance of the PE pipe can be effectively improved, and the good antibacterial, photocatalytic degradation and thermal stability functions are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer material filler preparation, and in particular to a method for preparing a phosphogypsum-based composite functional filler. Background Art

[0002] Polyethylene (PE) pipes have been the fastest-growing type of pipe in recent years and are currently one of the preferred plastic pipes for municipal water supply systems. While PE pipes offer numerous advantages, they still suffer from deficiencies such as insufficient heat aging resistance, poor environmental weathering resistance, and poor oxidation resistance, which limit their further development. Therefore, modifying PE pipes to enhance mechanical properties and develop diverse functionalities without compromising overall performance is crucial. Inorganic fillers such as carbonates, silicates, sulfates, and metals possess unique physicochemical properties, improving the mechanical, processing, and thermal properties of polymers while also reducing production costs, leading to their widespread application in polymers. While inorganic nanoparticles have achieved some success in enhancing polymer properties, current literature reports suggest that they remain limited and undifferentiated. Therefore, developing multifunctional fillers by combining the characteristics of different inorganic powders is an effective approach to addressing these challenges. Nanosized titanium dioxide (TiO2) and zinc oxide (ZnO) possess high refractive indices and strong UV scattering capabilities, making them widely used as UV shielding agents in building materials, chemical engineering, environmental protection, light industry, metallurgy, and other fields. Adding a certain amount of TiO2 and ZnO to high molecular polymers can greatly improve their thermal insulation properties and effectively improve the aging resistance of the polymer. Moreover, nano-TiO2 and ZnO are white in themselves and can be easily colored. What is particularly valuable is that they have a high visible light transmittance and have a bactericidal and deodorizing effect. The main component of phosphogypsum after high-temperature treatment is calcium sulfate (CaSO4). CaSO4 is added to polymer materials as a filler to improve the strength and brittleness resistance of the material. In summary, in order to solve the problems of poor heat aging resistance and unstable mechanical properties in PE pipes, the present invention focuses on the design and development of new functional fillers. Based on the resource utilization of phosphogypsum solid waste, the present invention designs a preparation method of phosphogypsum-based composite functional fillers.

[0003] At present, the main methods for preparing and modifying composite fillers are in-situ precipitation coating method and impregnation method. The advantage of the in-situ precipitation coating method for preparing composite fillers is that the product has good crystal phase consistency and uniform particle size of the composite filler. The disadvantage is that the production cycle is too long, which is not conducive to large-scale industrial production. The impregnation method for preparing composite fillers has a simple process and simple experimental equipment. The disadvantage is that the choice of carrier is limited by the properties of the solution system and the amount of the load is difficult to control. The above methods are generally limited in meeting the needs of automated production and industrial production. Therefore, the development of a functional filler preparation process that is simple, easy to automate, low-cost, and suitable for the composite of nano-TiO2, ZnO and micron CaSO4 has important research value for enhancing the comprehensive performance of PE pipes. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a method for preparing a phosphogypsum-based composite functional filler, which has a simple process, is easy to automate, and has low cost, and realizes the resource utilization of phosphogypsum solid waste. The prepared filler combines the advantages of micron CaSO4, nano TiO2 and nano ZnO, can effectively improve the heat aging resistance, mechanical and UV resistance of PE pipes, and has good antibacterial, photocatalytic degradation and thermal stability functions.

[0005] In order to achieve the above object, the present invention is implemented by the following technical scheme: a preparation method of phosphogypsum-based composite functional filler, comprising the following steps

[0006] 1. Pre-treat the phosphogypsum by removing impurities, drying, high-temperature treatment and grinding;

[0007] 2. Preparation of nano-TiO2 and ZnO powders;

[0008] 3. The pretreated micron-sized CaSO4, nano-TiO2 and nano-ZnO are mixed and then surface treated, ball milled and post-treated to obtain a phosphogypsum-based composite functional filler.

[0009] Preferably, the step 1 specifically includes:

[0010] 1.1 Impurity Removal: Wash the phosphogypsum raw materials with water to remove surface dirt, sand, and impurities. During the washing process, place the phosphogypsum in a mixing container, add clean water, stir for 15-30 minutes, then let it settle for 30-60 minutes, pour out the supernatant, and repeat the water washing 2-3 times.

[0011] 1.2 Drying: Place the washed phosphogypsum in a drying oven and dry it at 100-120°C for 12-24 hours until constant weight is reached to remove moisture.

[0012] 1.3 High-temperature treatment: The dried phosphogypsum is placed in a muffle furnace and calcined at 600-800°C for 2-4 hours to decompose the organic matter in the phosphogypsum and convert the main component into calcium sulfate (CaSO4). After calcination, it is naturally cooled to room temperature.

[0013] 1.4 Grinding: Use a ball mill to grind the calcined phosphogypsum to a micron-sized particle size, with an average particle size of 10-50 μm. During ball milling, use a ball-to-material ratio of 5:1-10:1, a milling time of 2-6 hours, and a speed of 200-400 rpm.

[0014] Preferably, the step 2 specifically includes:

[0015] 2.1 Preparation of nano-TiO2 powder

[0016] 2.11 Precursor Solution Preparation: Weigh tetrabutyl titanate and dissolve it in anhydrous ethanol to a concentration of 0.1-0.5 mol / L. While stirring, slowly add glacial acetic acid as an inhibitor dropwise at a molar ratio of 1-2:1 to tetrabutyl titanate to control the hydrolysis rate of the tetrabutyl titanate.

[0017] 2.12 Hydrolysis Reaction: Slowly add deionized water dropwise to the above precursor solution while vigorously stirring. Control the hydrolysis temperature at 30-50°C and the reaction time for 2-4 hours. After the addition is complete, continue stirring for 1-2 hours to allow the reaction to proceed fully.

[0018] 2.13 Aging and washing: The reaction solution is allowed to stand for 12-24 hours, then centrifuged and the precipitate is repeatedly washed with deionized water and anhydrous ethanol 3-5 times to remove impurities.

[0019] 2.14 Drying and calcination: Dry the washed precipitate at 60-80°C for 12-24 hours, and then calcine at 400-600°C for 2-4 hours to obtain nano-TiO2 powder with an average particle size controlled at 10-50 nm.

[0020] 2.2 Preparation of nano ZnO powder

[0021] 2.21 Precursor solution preparation: Weigh an appropriate amount of zinc nitrate and dissolve it in deionized water to prepare a solution with a concentration of 0.1-0.3 mol / L. Simultaneously, weigh sodium hydroxide and prepare a solution of the same concentration.

[0022] 2.22 Precipitation Reaction: Slowly add the sodium hydroxide solution dropwise to the zinc nitrate solution while stirring. Control the reaction temperature at 50-70°C for 1-3 hours, and maintain the pH of the solution at 9-11. Continue stirring for 0.5-1 hour after the addition is complete.

[0023] 2.23 Washing and drying: The precipitate after the reaction is centrifuged, washed repeatedly with deionized water for 3-5 times, and then dried at 60-80°C for 12-24 hours.

[0024] 2.24 Calcination: Calcine the dried product at 300-500°C for 2-4 hours to obtain nano ZnO powder with an average particle size of 10-50 nm.

[0025] Preferably, the step 3 specifically includes: 3.1 material mixing: putting the pretreated micron-sized CaSO4, nano-TiO2 and nano-ZnO into a high-speed mixer according to a ratio of 7-8:2-1:1, and mixing for 10-30 minutes to ensure that the materials are fully mixed.

[0026] 3.2 Surface treatment: Add surfactant to the mixture in an amount of 0.5%-2% of the total mass of the material and continue mixing for 10-20 minutes to improve the compatibility of the filler and the polymer.

[0027] 3.3 Ball Milling: Transfer the mixed materials to a ball mill for milling. The ball-to-material ratio should be 5:1-10:1, and the milling time should be 4-8 hours at a speed of 200-400 rpm. During the milling process, nano-TiO2 and ZnO gradually coat the surface of the micron-CaSO4, forming a phosphogypsum-based composite functional filler.

[0028] 3.4 Post-processing: After the ball milling is completed, the ball milled product is sieved to remove large particle impurities, and then dried at 60-80°C for 6-12 hours to obtain the final phosphogypsum-based composite functional filler.

[0029] Preferably, the surfactant in step 3 is a silane coupling agent.

[0030] The present invention has the following beneficial effects: The phosphogypsum-based composite functional filler prepared by the present invention combines the advantages of micronized CaSO₄, nano-TiO₂, and nano-ZnO, effectively improving the heat aging resistance, mechanical properties, and UV resistance of PE pipes. The preparation process is simple, easily automated, and cost-effective. It also achieves resource utilization of phosphogypsum solid waste, resulting in excellent economic and environmental benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments;

[0032] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0033] In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the present invention is further described below in conjunction with specific implementation methods.

[0034] Reference Figure 1 This specific embodiment adopts the following technical solution: a method for preparing a phosphogypsum-based composite functional filler, comprising the following steps:

[0035] 1. Phosphogypsum pretreatment

[0036] 1.1 Impurity Removal: Wash the phosphogypsum raw materials with water to remove impurities such as soil, sand and gravel on the surface. During the washing process, place the phosphogypsum in a mixing container, add an appropriate amount of clean water, stir for 15-30 minutes, then let it settle for 30-60 minutes, pour out the supernatant, and repeat the water washing 2-3 times.

[0037] 1.2 Drying: Place the washed phosphogypsum in a drying oven and dry it at 100-120°C for 12-24 hours until constant weight is reached to remove moisture.

[0038] 1.3 High-temperature treatment: The dried phosphogypsum is placed in a muffle furnace and calcined at 600-800°C for 2-4 hours to decompose the organic matter in the phosphogypsum and convert the main component into calcium sulfate (CaSO4). After calcination, it is naturally cooled to room temperature.

[0039] 1.4 Grinding: Use a ball mill to grind the calcined phosphogypsum to a particle size of micron-level, generally controlling the average particle size to be 10-50 μm. During ball milling, the ball-to-material ratio is 5:1-10:1, the ball milling time is 2-6 hours, and the ball milling speed is 200-400 rpm.

[0040] 2. Preparation of nano-TiO2 and ZnO powders

[0041] 2.1 Preparation of nano-TiO2 powder

[0042] 2.11 Precursor Solution Preparation: Weigh a certain amount of tetrabutyl titanate and dissolve it in anhydrous ethanol to prepare a solution with a concentration of 0.1-0.5 mol / L. While stirring, slowly add glacial acetic acid as an inhibitor dropwise. The molar ratio of glacial acetic acid to tetrabutyl titanate is 1:1-2:1 to control the hydrolysis rate of the tetrabutyl titanate.

[0043] 2.12 Hydrolysis Reaction: Slowly add deionized water dropwise to the above precursor solution while vigorously stirring. Control the hydrolysis temperature at 30-50°C and the reaction time for 2-4 hours. After the addition is complete, continue stirring for 1-2 hours to allow the reaction to proceed fully.

[0044] 2.13 Aging and washing: The reaction solution is allowed to stand for 12-24 hours, then centrifuged and the precipitate is repeatedly washed with deionized water and anhydrous ethanol 3-5 times to remove impurities.

[0045] 2.14 Drying and calcination: Dry the washed precipitate at 60-80°C for 12-24 hours, and then calcine at 400-600°C for 2-4 hours to obtain nano-TiO2 powder with an average particle size controlled at 10-50 nm.

[0046] 2.2 Preparation of nano ZnO powder

[0047] 2.21 Precursor solution preparation: Weigh an appropriate amount of zinc nitrate and dissolve it in deionized water to prepare a solution with a concentration of 0.1-0.3 mol / L. Simultaneously, weigh an appropriate amount of sodium hydroxide and prepare a solution of the same concentration.

[0048] 2.22 Precipitation Reaction: Slowly add the sodium hydroxide solution dropwise to the zinc nitrate solution while stirring. Control the reaction temperature at 50-70°C for 1-3 hours, and maintain the pH of the solution at 9-11. Continue stirring for 0.5-1 hour after the addition is complete.

[0049] 2.23 Washing and drying: The precipitate after the reaction is centrifuged, washed repeatedly with deionized water for 3-5 times, and then dried at 60-80°C for 12-24 hours.

[0050] 2.24 Calcination: Calcine the dried product at 300-500°C for 2-4 hours to obtain nano ZnO powder with an average particle size of 10-50 nm.

[0051] 3. Preparation of composite functional fillers

[0052] 3.1 Material mixing: Place the pretreated micron-sized CaSO4, nano-TiO2 and nano-ZnO in a certain proportion (mass ratio is CaSO4:TiO2:ZnO=7:2:1-8:1:1) into a high-speed mixer for 10-30 minutes to ensure that the materials are fully mixed.

[0053] 3.2 Surface treatment: Add an appropriate amount of surfactant (such as silane coupling agent) to the mixed material, the addition amount of which is 0.5%-2% of the total mass of the material, and continue mixing for 10-20 minutes to improve the compatibility of the filler and the polymer.

[0054] 3.3 Ball Milling: Transfer the mixed materials to a ball mill for milling. The ball-to-material ratio should be 5:1-10:1, and the milling time should be 4-8 hours at a speed of 200-400 rpm. During the milling process, nano-TiO2 and ZnO gradually coat the surface of the micron-CaSO4, forming a phosphogypsum-based composite functional filler.

[0055] 3.4 Post-processing: After the ball milling is completed, the ball milled product is sieved to remove large particle impurities, and then dried at 60-80°C for 6-12 hours to obtain the final phosphogypsum-based composite functional filler.

[0056] The impurity removal efficiency of the phosphogypsum pretreatment stage of this specific embodiment: After three water washes, ICP-MS analysis showed that the impurity content was reduced to below 0.3% (the raw material contained 5.2% impurities), of which Fe2O3 was reduced from 1.8% to 0.05%, and Al2O3 was reduced from 2.1% to 0.07%. The influence of calcination temperature: XRD analysis showed that a small amount of CaSO4·0.5H2O remained after calcination at 600°C; after calcination at 800°C for 2 hours, the CaSO4 purity reached 99.1%. Grinding effect: After 4 hours of ball milling (ball-to-material ratio 8:1, rotation speed 300r / min), the laser particle size analyzer showed D50 = 28μm, and the specific surface area reached 2.5m 2 / g.

[0057] TiO2 hydrolysis control during the preparation of nanopowders in this embodiment: When the molar ratio of glacial acetic acid to tetrabutyl titanate is 1.5:1, TEM shows that the particles are uniformly dispersed, with an average particle size of 25 nm and a BET specific surface area of ​​85 m 2 Optimization of ZnO calcination temperature: ZnO calcined at 400°C for 3 hours has the best crystal form (XRD characteristic peak half-height width 0.12°) and ultraviolet absorption rate 98% (UV-Vis test).

[0058] The performance test data of the composite filler prepared in this specific embodiment are as follows:

[0059] Physical properties

[0060] index Test Method Data range Average particle size Laser particle size analyzer 15-45μm (adjustable) Specific surface area BET nitrogen adsorption <![CDATA[35-50m 2 / g <!-- 4 -->]]> Bulk density GB / T5162-2021 <![CDATA[0.68-0.75g / cm 3 ]]>

[0061] 2. Functional characteristics

[0062] Antibacterial properties (GB / T 31402-2015):

[0063] The antibacterial rate of the filler containing 2% nano-ZnO on Escherichia coli is 99.2% (24 hours contact).

[0064] Photocatalytic degradation (methylene blue solution):

[0065] The filler containing 1.5% TiO2 has a degradation rate of 91.3% (HPLC detection) under UV light for 4 hours.

[0066] Thermal stability (TGA):

[0067] The initial decomposition temperature is raised to 320℃ (280℃ for pure CaSO4).

[0068] Application Example 1:

[0069] 1. Formulation and process

[0070] Basic formulation:

[0071] PVC resin 100 parts, composite filler 20 parts, DOP plasticizer 5 parts, stabilizer 2 parts.

[0072] Processing conditions:

[0073] Twin-screw extruder (temperature 180-200℃), compression molding.

[0074] 2. Performance comparison

[0075]

[0076]

[0077] Synergistic effect of this example: nano-TiO2 / ZnO forms a heterojunction on the surface of CaSO4 (confirmed by SEM-EDS), enhances the separation efficiency of photo-generated carriers (PL spectrum fluorescence intensity decreases by 63%). Interface bonding: silane coupling agent increases the interfacial shear strength of the filler-polymer by 40% (AFM force curve test). Cost accounting: 22% lower than traditional calcium carbonate filler cost (phosphogypsum is an industrial waste). Waste utilization: 1.2 tons of phosphogypsum are consumed per ton of product, reducing solid waste storage by 3.5m 3 .

[0078] The above shows and describes the basic principles and main features of the present application and the advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above examples, and the above examples and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a phosphogypsum-based composite functional filler, characterized in that: The following steps are included (1) Pre-treating the phosphogypsum by removing impurities, drying, high-temperature treatment and grinding; (2) Preparation of nano-TiO2 and ZnO powders; (3) The pretreated micron-sized CaSO4, nano-TiO2 and nano-ZnO are mixed and then surface treated, ball milled and post-treated to obtain a phosphogypsum-based composite functional filler.

2. The method for preparing the phosphogypsum-based composite functional filler according to claim 1, characterized in that: The step (1) specifically includes: (1.1) Impurity Removal: Wash the phosphogypsum raw material with water to remove dirt, sand, and impurities on the surface. During the washing process, place the phosphogypsum in a stirring container, add clean water, stir for 15-30 minutes, then let it settle for 30-60 minutes, pour out the supernatant, and repeat the washing process 2-3 times. (1.2) Drying: Place the washed phosphogypsum in a drying oven and dry it at 100-120°C for 12-24 hours until constant weight is reached to remove moisture; (1.3) High temperature treatment: The dried phosphogypsum is placed in a muffle furnace and calcined at 600-800°C for 2-4 hours to decompose the organic matter in the phosphogypsum and convert the main component into calcium sulfate. After calcination, it is naturally cooled to room temperature. (1.4) Grinding: Use a ball mill to grind the calcined phosphogypsum to a particle size of micron level, with an average particle size controlled at 10-50 μm. During ball milling, the ball-to-material ratio is 5:1-10:1, the ball milling time is 2-6 hours, and the ball milling speed is 200-400 r / min.

3. The method for preparing the phosphogypsum-based composite functional filler according to claim 1, characterized in that: The step (2) specifically includes: (2.1) Preparation of nano-TiO2 powder (2.11) Precursor solution preparation: Weigh tetrabutyl titanate and dissolve it in anhydrous ethanol to a concentration of 0.1-0.5 mol / L. Slowly add glacial acetic acid dropwise as an inhibitor while stirring. The molar ratio of glacial acetic acid to tetrabutyl titanate is 1-2:1 to control the hydrolysis rate of the tetrabutyl titanate. (2.12) Hydrolysis reaction: Deionized water was slowly added dropwise to the precursor solution while stirring vigorously. The hydrolysis temperature was controlled at 30-50°C and the reaction time was 2-4 hours. After the addition was complete, stirring was continued for 1-2 hours to allow the reaction to proceed fully. (2.13) Aging and washing: The reaction solution is allowed to stand for 12-24 hours, then centrifuged and the precipitate is washed repeatedly with deionized water and anhydrous ethanol 3-5 times to remove impurities; (2.14) Drying and calcining: Dry the washed precipitate at 60-80°C for 12-24 hours, and then calcine at 400-600°C for 2-4 hours to obtain nano-TiO2 powder with an average particle size of 10-50 nm; (2.2) Preparation of nano ZnO powder (2.21) Precursor solution preparation: Weigh an appropriate amount of zinc nitrate and dissolve it in deionized water to prepare a solution with a concentration of 0.1-0.3 mol / L. Simultaneously, weigh sodium hydroxide and prepare a solution of the same concentration. (2.22) Precipitation reaction: Slowly add sodium hydroxide solution dropwise to zinc nitrate solution under stirring. Control the reaction temperature at 50-70°C for 1-3 hours, and maintain the pH value of the solution at 9-11. After the addition is complete, continue stirring for 0.5-1 hour. (2.23) Washing and drying: The precipitate after the reaction is centrifuged, washed repeatedly with deionized water 3-5 times, and then dried at 60-80°C for 12-24 hours; (2.24) Calcination: Calcine the dried product at 300-500°C for 2-4 hours to obtain nano ZnO powder with an average particle size of 10-50 nm.

4. The method for preparing the phosphogypsum-based composite functional filler according to claim 1, characterized in that: The step (3) specifically includes: (3.1) Material mixing: Place the pretreated micron-sized CaSO4, nano-TiO2, and nano-ZnO in a high-speed mixer at a ratio of 7-8:2-1:1 and mix for 10-30 minutes to ensure that the materials are fully mixed; (3.2) Surface treatment: Add a surfactant to the mixture at a rate of 0.5% to 2% of the total mass of the material and continue mixing for 10 to 20 minutes to improve the compatibility of the filler and the polymer; (3.3) Ball milling: The mixed materials are transferred to a ball mill for ball milling. During ball milling, the ball-to-material ratio is 5:1-10:1, the milling time is 4-8 hours, and the milling speed is 200-400 rpm. During the ball milling process, nano-TiO2 and ZnO are gradually coated on the surface of micro-CaSO4 to form a phosphogypsum-based composite functional filler. (3.4) Post-processing: After the ball milling is completed, the ball milled product is sieved to remove large particles of impurities, and then dried at 60-80°C for 6-12 hours to obtain the final phosphogypsum-based composite functional filler.

5. The method for preparing the phosphogypsum-based composite functional filler according to claim 4, characterized in that: The surfactant in the step (3) is a silane coupling agent.

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