Environment-friendly material taking phosphogypsum as filler and used for ecological green plant system and preparation method of environment-friendly material

Abstract

The invention discloses an environment-friendly material using phosphogypsum as filler for an ecological green plant system, which is prepared from the following raw materials in parts by weight: 60 to 70 parts of polylactic acid, 50 to 60 parts of modified phosphogypsum, 10 to 20 parts of poly (butylene succinate), 5 to 10 parts of polyvinyl alcohol, 3 to 5 parts of epoxidized soybean oil, 2 to 3 parts of calcium stearate and 0.5 to 1 part of antioxidant. The environment-friendly material has good mechanical properties, also has good degradability, not only solves the problem of high cost of a biodegradable material, but also solves the problem of resource utilization of phosphogypsum, expands the application range of solid waste phosphogypsum, and has good application prospects.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer materials, and particularly relates to an environmentally friendly material for (desert) ecological greening systems using phosphogypsum as a filler and a preparation method thereof. Background Art

[0002] Phosphogypsum is a solid waste generated in the wet-process production of phosphoric acid. Its main component is calcium sulfate dihydrate, and there are also small amounts of impurities such as phosphorus, fluorine, organic matter, oxides, heavy metals, and radioactive substances. Usually, for every 1t of phosphoric acid produced, 4 - 6t of phosphogypsum is generated. Nearly 300 million tons of phosphogypsum are newly generated globally every year. In 2021, about 80 million tons of phosphogypsum were generated in China, and the recovery rate is less than 27%. In China, a small amount of phosphogypsum is used in the production of building materials, and most of it is stored in stacks. Long-term large-scale stacking may pollute the soil, surface water, and groundwater. In addition, phosphogypsum storage yards also cause dust pollution. Phosphogypsum contains harmful impurities such as phosphorus, mercury, cadmium, and radioactive elements. If it enters the atmosphere with steam, it may pose a hazard to human health. Thus, phosphogypsum stacking not only occupies a large amount of land resources but also poses potential risks to the ecological environment. Therefore, the harmless treatment and comprehensive utilization of phosphogypsum have become key research projects in solid waste treatment and resource utilization.

[0003] Currently, the comprehensive utilization of phosphogypsum mainly focuses on the following aspects: (1) Building materials field: used as a cement retarder, gypsum building materials (such as gypsum boards, gypsum blocks), subgrade materials, etc. This is the main application route of phosphogypsum, but the added value is low and it is limited by the market capacity. (2) Agricultural field: used as a soil conditioner, mineralized compound fertilizer, etc. However, phosphogypsum may contain heavy metals and radioactive elements, which limit its application in the agricultural field. (3) Chemical industry field: used to prepare chemical products such as sulfuric acid and ammonium sulfate. This method has high technical difficulty, high cost, and low economic benefits.

[0004] In recent years, there have also been studies on using phosphogypsum as a filler for polymer materials. For example, phosphogypsum is directly added to common plastics such as polypropylene and polyethylene to reduce costs and improve certain properties of the materials. However, these studies usually have the following technical defects: (1) The phosphogypsum is untreated or insufficiently treated: directly using untreated phosphogypsum, impurities therein (such as undecomposed phosphate rock, organic matter, fluoride, soluble phosphorus, etc.) will seriously affect the properties of polymer materials, such as mechanical properties, optical properties, weather resistance, etc. (2) Poor compatibility: The surface of phosphogypsum is hydrophilic and has poor compatibility with most hydrophobic polymer materials, resulting in defects inside the material and reducing the mechanical properties. (3) Poor thermal stability: Gypsum dihydrate will lose its crystal water at a relatively low temperature, affecting the thermal stability of the material. Therefore, in order to obtain polymer composites with excellent properties, it is usually necessary to treat phosphogypsum to produce anhydrous gypsum and conduct surface modification, which can significantly improve the compatibility between phosphogypsum and polymer materials, improve the mechanical properties, thermal stability, etc. of the composites, and reduce the negative impacts brought by impurities.

[0005] Chinese patent application CN111592691A discloses a phosphogypsum-filled plastic modified particle and its preparation method. The phosphogypsum-filled plastic modified particle includes phosphogypsum powder, polyolefin carrier plastic raw material, polyethylene wax, coupling agent, paraffin wax, antioxidant, anti-ultraviolet additive, and color masterbatch. The preparation method includes Step 1, preparing phosphogypsum powder, Step 2, surface activation treatment of phosphogypsum powder, and Step 3, granulating to obtain phosphogypsum-filled plastic modified particles. The preparation method of the phosphogypsum-filled plastic modified particle of this invention improves the utilization value of phosphogypsum, turns waste into treasure, and can reduce environmental pollution. The plastic products manufactured with this material have good quality and strong antioxidant property. However, this patent only treats the phosphogypsum raw material by calcination, and cannot effectively remove the impurities in the phosphogypsum. The quality of the pretreated phosphogypsum obtained is not good, thus affecting the comprehensive properties of the plastic. And when it is applied to degradable materials, it is impossible to know whether it will affect the degradation performance of the materials.

[0006] Therefore, it is of great significance to develop an environmentally friendly material using phosphogypsum as a filler for ecological green plant systems in this field. Summary of the Invention

[0007] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide an environmentally friendly material using phosphogypsum as a filler for ecological green plant systems and its preparation method. This environmentally friendly material has good mechanical properties and also has good degradability. It not only solves the problem of high cost of biodegradable materials, but also solves the problem of resource utilization of phosphogypsum, expands the use range of solid waste phosphogypsum, and has good application prospects.

[0008] To achieve the above purpose, the present invention provides the following technical solutions:

[0009] An environmentally friendly material using phosphogypsum as a filler for an ecological green plant system, by weight, comprises the following raw materials:

[0010] 60 - 70 parts of polylactic acid, 50 - 60 parts of modified phosphogypsum, 10 - 20 parts of polybutylene succinate, 5 - 10 parts of polyvinyl alcohol, 3 - 5 parts of epoxy soybean oil, 2 - 3 parts of calcium stearate, 0.5 - 1 part of antioxidant.

[0011] Preferably, an environmentally friendly material using phosphogypsum as a filler for an ecological green plant system, by weight, comprises the following raw materials:

[0012] 60 - 65 parts of polylactic acid, 50 - 55 parts of modified phosphogypsum, 10 - 15 parts of polybutylene succinate, 5 - 8 parts of polyvinyl alcohol, 4 - 5 parts of epoxy soybean oil, 2 - 2.5 parts of calcium stearate, 0.7 - 1 part of antioxidant.

[0013] Preferably, the preparation method of the modified phosphogypsum comprises the following steps:

[0014] S1. Grind the phosphogypsum and pass it through a 100 - mesh sieve, then add it to deionized water. After dispersing evenly, add calcium oxide and disodium EADA, stir. After stirring is completed, add sulfuric acid solution to adjust the pH to 7, then centrifuge and filter to obtain pretreated phosphogypsum;

[0015] S2. Add the pretreated phosphogypsum in step S1 to deionized water, adjust the pH to 8 - 10, then add a flotation agent and conduct flotation treatment. After flotation is completed, perform solid - liquid separation to obtain a flotation phosphogypsum slurry;

[0016] S3. Add a composite additive to the flotation phosphogypsum slurry in step S2, mix evenly and then conduct calcination. After calcination is completed, obtain anhydrous gypsum;

[0017] S4. Mix the anhydrous gypsum in step S3 evenly with a silane coupling agent ethanol solution, conduct ball milling. After ball milling is completed, dry and grind to obtain the modified phosphogypsum.

[0018] Preferably, in step S1, the solid - liquid ratio of the phosphogypsum to deionized water is 1:3 - 5, the addition amount of calcium oxide is 2 - 3% of the mass of the phosphogypsum, the addition amount of disodium EADA is 0.5 - 1% of the mass of the phosphogypsum, the stirring speed is 60 - 80 r / min, the temperature is 40 - 50 °C, the time is 50 - 80 min, and the mass fraction of the sulfuric acid solution is 5 - 10%.

[0019] In the present invention, first, the phosphogypsum is pretreated by washing with water, and calcium oxide and disodium EADA are added simultaneously, which can react with impurities such as soluble phosphates and organic matters in the phosphogypsum, and can remove soluble P2O5 and fluorine impurities in the phosphogypsum, reduce the impurity content in the phosphogypsum, and create favorable conditions for subsequent flotation.

[0020] Preferably, in step S2, the mass ratio of the pretreated phosphogypsum to deionized water is 1:4 - 5, the addition amount of the flotation agent is 1 - 1.5% of the mass of the pretreated gypsum, the aeration amount of the flotation treatment is 0.4 - 0.5 L / min, the time is 20 - 30 min, and the rotation speed is 1500 - 1800 r / min; the water content of the phosphogypsum slurry is controlled to be 30 - 40%.

[0021] Preferably, the preparation method of the flotation agent in step S2 is as follows:

[0022] Tween 80 is added to deionized water, and after stirring evenly, a Tween solution with a mass concentration of 2 - 3% is obtained; 4 - 6 g of dodecylamine is added to 80 - 100 g of the Tween solution, and emulsified for 8 - 12 min under the conditions of an ultrasonic frequency of 30 - 40 kHz and a power of 50 - 100 W to obtain a dodecylamine emulsion; 2 - 3 g of terpineol is added to 70 - 80 g of the Tween solution, and emulsified for 8 - 12 min under the conditions of an ultrasonic frequency of 30 - 40 kHz and a power of 50 - 100 W to obtain a terpineol emulsion; 80 - 100 g of the dodecylamine emulsion and 70 - 80 g of the terpineol emulsion are mixed evenly, and then 3 - 4 g of sodium oleate and 1 - 2 g of carboxymethyl cellulose are added and stirred evenly to obtain the flotation agent.

[0023] In the present invention, by adding a specific flotation agent and performing flotation treatment on the phosphogypsum, the content of impurities such as organic matters in the phosphogypsum can be effectively reduced, thereby improving the purity of the phosphogypsum and improving the interfacial bonding force between the phosphogypsum and the polymer.

[0024] Preferably, the preparation method of the composite additive in step S3 is as follows:

[0025] 5 - 7 g of potassium sulfate is added to 100 - 120 g of deionized water, and after stirring evenly, 2 - 3 g of sodium citrate, 1 - 2 g of sodium polyacrylate, and 3 - 5 g of silica sol are added, and stirred at a constant temperature of 40 - 50 °C for 50 - 60 min. After the stirring is completed, the composite additive is obtained.

[0026] Preferably, the content of silicon dioxide in the silica sol is 40 - 45%.

[0027] Preferably, the addition amount of the composite additive in step S3 is 12-16% of the mass of the flotation phosphogypsum slurry, the temperature of the pre-calcination treatment is 200-220 °C, and the time is 1.5-2 h; the roasting process is to raise the temperature to 460-500 °C at a heating rate of 7-10 °C / min and keep it warm for 3-3.5 h.

[0028] In the present invention, a specific composite additive is added during the pre-calcination treatment. Through the four-component synergistic mechanism of potassium sulfate - sodium citrate - sodium polyacrylate - silica sol, the gypsum crystal phase transformation process is effectively regulated. Potassium sulfate acts as a mineralizer to promote the directional growth of anhydrite, sodium citrate chelates calcium ions to delay the dehydration rate, and sodium polyacrylate prevents particle aggregation through electrostatic repulsion; during the roasting process, silica sol forms a SiO2 network coating layer when roasted at 460-500 °C, and by controlling the heating rate, crystal explosion and structural defects caused by rapid heating are avoided; keeping warm in the temperature range of 460-500 °C ensures that the phosphogypsum is fully dehydrated and transformed into anhydrite, improves the purity of anhydrite in the modified gypsum, and improves the interfacial shear strength between anhydrite and the polylactic acid matrix, thereby increasing the comprehensive performance of the environmental protection material.

[0029] Preferably, the mass concentration of the silane coupling agent in the silane coupling agent ethanol solution in step S4 is 4-7%, the mass ratio of the anhydrite to the silane coupling agent ethanol solution is 100:70-80, the rotation speed of the ball milling is 800-900 r / min, and the time is 20-30 min.

[0030] In the present invention, by ball milling and modifying the anhydrite with a silane coupling agent, the dispersibility of the anhydrite is further improved, and at the same time, the compatibility between the modified phosphogypsum and the polymer is improved, and the comprehensive performance of the environmental protection material is enhanced.

[0031] The present invention also protects a preparation method of an environmental protection material using phosphogypsum as a filler for an ecological green plant system as described above, including the following steps:

[0032] Weigh the raw materials according to the formula, add polylactic acid, modified phosphogypsum, polybutylene succinate, polyvinyl alcohol, calcium stearate, epoxy soybean oil, and antioxidant into a high-speed mixer and mix evenly, then carry out twin-screw granulation to obtain masterbatch; dry the masterbatch and add it into an extruder for sheet extrusion to obtain a sheet, and then punch holes in the sheet to obtain the environmental protection material.

[0033] In the present invention, the environmentally friendly material can be applied to a desert ecological greening system. The ecological greening system is composed of multiple pieces of environmentally friendly materials, which form a honeycomb cell after being unfolded. In desert areas, the wind is strong and sand grains are easily blown away by the wind, leading to the aggravation of land desertification. The honeycomb restraint system can fix the sand grains in the cells, restrict the lateral movement of the sand grains, and effectively prevent wind erosion. In desert areas, precipitation is scarce and the water retention capacity of the soil is poor. The honeycomb cells can reduce water evaporation, improve the water retention of the soil, and create favorable conditions for plant growth. Moreover, the honeycomb structure has good air permeability, which is conducive to the air circulation in the soil and promotes the growth of plant roots. This environmentally friendly material can not only meet the requirements of the honeycomb system for mechanical strength but also has good degradability, providing an innovative solution for desertification control.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] (1) The environmentally friendly material provided by the present invention using phosphogypsum as a filler for the ecological greening system realizes the high-value utilization of phosphogypsum through a multi-stage synergistic modification process. First, a synergistic water washing pretreatment with calcium oxide - disodium EADA is carried out to effectively remove soluble phosphorus, fluorine, and organic impurities. Subsequently, a special flotation agent is used to achieve deep removal of organic matter. Combined with a composite additive-assisted roasting process, the purity and crystal stability of anhydrous gypsum are significantly improved. Finally, surface modification with a silane coupling agent optimizes the interfacial compatibility. This system enables the modified phosphogypsum addition amount to reach a relatively high content (35 - 40%) while still maintaining excellent mechanical properties of the material (tensile strength ≥ 35 MPa, flexural modulus ≥ 3.5 GPa). At the same time, due to the degradable characteristics of the polylactic acid and polybutylene succinate matrices, the environmentally friendly material has degradability, successfully converting and recycling large amounts of phosphogypsum-based solid waste, improving the utilization value of solid waste under the premise of reducing environmental pollution, realizing the efficient resource utilization of phosphogypsum, and simultaneously solving the dual problems of performance deterioration and insufficient ecological compatibility of traditional phosphogypsum filler composites.

[0036] (2) The environmentally friendly material provided by the present invention using phosphogypsum as a filler for the ecological greening system, through the addition of a specific flotation agent prepared with a specific formula and method, the dodecylamine and sodium oleate added can selectively adsorb on the surface of impurities and have a good collecting effect on impurities such as silicate under acidic conditions. The added terpineol as a foaming agent can reduce the surface tension of water. Compared with short-chain alcohols and long-chain alcohols, it has better foaming properties, generating a large number of small and stable bubbles. It can not only ensure that the bubbles stay in the pulp for enough time to enable mineral particles to fully adhere but also break on the surface of the flotation cell, which is beneficial to the control of the foam layer, thereby improving the flotation effect, increasing the purity of phosphogypsum. Removing these impurities can improve the interfacial bonding force between the modified gypsum and the polymer, thereby improving the mechanical properties such as the tensile strength and flexural strength of the composite material.

[0037] (3) The environmental protection material provided by the present invention, which uses phosphogypsum as a filler for the ecological green plant system, adds a specific composite additive during the pre-calcination treatment. Through the quadruple synergistic mechanism of potassium sulfate - sodium citrate - sodium polyacrylate - silica sol, the crystal phase transformation process of gypsum is effectively regulated. Potassium sulfate, as a mineralizer, promotes the directional growth of anhydrite. Sodium citrate chelates calcium ions to delay the dehydration rate. Sodium polyacrylate prevents particle aggregation through electrostatic repulsion. During the calcination process, silica sol forms a SiO2 network coating layer when calcined at 460 - 500 °C. Silica particles can form a porous structure between phosphogypsum particles, increasing the specific surface area and improving the contact area with the polymer material. This composite action mechanism significantly improves the crystal form, morphology, and specific surface area of anhydrite, enhancing its reinforcement effect as a filler. And by controlling the heating rate, crystal bursting and structural defects caused by rapid heating are avoided. Insulating at a temperature range of 460 - 500 °C ensures that phosphogypsum is fully dehydrated and converted into anhydrite, improving the purity of anhydrite in the modified gypsum and increasing the interfacial shear strength between anhydrite and the polymer matrix, thereby enhancing the comprehensive performance of the environmental protection material. Description of the Drawings

[0038] Figure 1 It is a physical diagram of the environmental protection material prepared in Example 1 of the present invention. Detailed Embodiments

[0039] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0040] In the present invention, the molecular weight of the polylactic acid is 50,000; the polybutylene succinate is Bionolle1020MD, and the melt mass flow rate (2.16 kg, 190 °C) is 25 g / 10 min; the grade of the polyvinyl alcohol is PVA1788; the phosphogypsum used in the present invention is an industrial solid waste material generated by the phosphoric acid manufacturing industry during the wet production of phosphoric acid after preliminary aging treatment through recycling; the content of dihydrate gypsum and the main impurity composition in the phosphogypsum are as follows:

[0041]

[0042] Example 1

[0043] An environmental protection material using phosphogypsum as a filler for the ecological green plant system, by weight, includes the following raw materials:

[0044] 65 parts of polylactic acid, 55 parts of modified phosphogypsum, 15 parts of polybutylene succinate, 8 parts of polyvinyl alcohol, 4 parts of epoxidized soybean oil, 2.5 parts of calcium stearate, 0.8 part of antioxidant.

[0045] The preparation method of the modified phosphogypsum comprises the following steps:

[0046] S1. Grind the phosphogypsum and sieve it through a 100-mesh sieve, then add it into deionized water. The solid-liquid ratio of phosphogypsum to deionized water is 1:4. After dispersing evenly, add calcium oxide and disodium EADA. The addition amount of calcium oxide is 2.5% of the mass of phosphogypsum, and the addition amount of disodium EADA is 0.8% of the mass of phosphogypsum. Stir at a stirring speed of 70 r / min and a temperature of 45 °C for 70 min. After stirring, add a sulfuric acid solution with a mass fraction of 5% to adjust the pH to 7, then centrifuge and filter to obtain pretreated phosphogypsum;

[0047] S2. Add the pretreated phosphogypsum in step S1 into deionized water. The mass ratio of pretreated phosphogypsum to deionized water is 1:4.5. Adjust the pH to 9, then add a flotation agent. The addition amount of the flotation agent is 1.3% of the mass of pretreated gypsum. Carry out flotation for 25 min under the conditions of an air inflow rate of 0.45 L / min and a rotation speed of 1700 r / min. After flotation, carry out solid-liquid separation to obtain a flotation phosphogypsum slurry (with a water content of 35%);

[0048] S3. Add a composite additive to the flotation phosphogypsum slurry in step S2. The addition amount of the composite additive is 15% of the mass of the flotation phosphogypsum slurry. After mixing evenly, carry out pre-calcination. The pre-calcination temperature is 210 °C and the time is 1.5 h. After pre-calcination, carry out roasting. The roasting process is to rise to 480 °C at a heating rate of 8 °C / min and keep warm for 3.5 h. After roasting, anhydrous gypsum is obtained;

[0049] S4. Mix 100 g of the anhydrous gypsum in step S3 evenly with 75 g of a γ-aminopropyltriethoxysilane ethanol solution (the mass concentration of γ-aminopropyltriethoxysilane is 6%). Ball mill at a rotation speed of 850 r / min for 25 min. After ball milling, dry and grind to obtain the modified phosphogypsum.

[0050] The preparation method of the flotation agent described in step S2 is as follows:

[0051] Tween 80 was added to deionized water, and after stirring evenly, a Tween solution with a mass concentration of 2.5% was obtained; 5 g of dodecylamine was added to 90 g of the Tween solution, and emulsification was carried out for 10 min under the conditions of an ultrasonic frequency of 35 kHz and a power of 80 W to obtain a dodecylamine emulsion; 2.5 g of terpineol was added to 75 g of the Tween solution, and emulsification was carried out for 10 min under the conditions of an ultrasonic frequency of 35 kHz and a power of 80 W to obtain a terpineol emulsion; 90 g of the dodecylamine emulsion and 75 g of the terpineol emulsion were mixed evenly, and then 3.5 g of sodium oleate and 1.5 g of carboxymethyl cellulose were added and stirred evenly to obtain the flotation agent.

[0052] The preparation method of the composite additive described in step S3 is as follows:

[0053] 6 g of potassium sulfate was added to 110 g of deionized water, and after stirring evenly, 2.5 g of sodium citrate, 1.5 g of sodium polyacrylate, and 4 g of silica sol (the content of silicon dioxide was 45%) were added, and stirring was carried out at a constant temperature of 45 °C for 55 min. After the stirring was completed, the composite additive was obtained.

[0054] A preparation method of an environmentally friendly material using phosphogypsum as a filler for an ecological green plant system includes the following steps:

[0055] Weigh the raw materials according to the formula, add polylactic acid, modified phosphogypsum, polybutylene succinate, polyvinyl alcohol, calcium stearate, epoxy soybean oil, and antioxidant into a high-speed mixer and mix evenly, and then carry out twin-screw granulation. Control the temperature of the twin-screw conveying section to be 155 °C, the melting section temperature to be 185 °C, the kneading section temperature to be 195 °C, and the head section temperature to be 185 °C to obtain masterbatch; after drying the masterbatch, add it into an extruder for sheet extrusion. Control the temperature of the feed section of the extruder to be 165 °C, the compression section temperature to be 190 °C, the homogenization section temperature to be 195 °C, and the die head section temperature to be 185 °C to obtain a sheet, and then punch holes in the sheet to obtain the environmentally friendly material.

[0056] Example 2

[0057] An environmentally friendly material using phosphogypsum as a filler for an ecological green plant system, by weight, includes the following raw materials:

[0058] 65 parts of polylactic acid, 55 parts of modified phosphogypsum, 15 parts of polybutylene succinate, 7 parts of polyvinyl alcohol, 4 parts of epoxy soybean oil, 2.5 parts of calcium stearate, and 0.7 part of antioxidant.

[0059] The preparation method of the modified phosphogypsum includes the following steps:

[0060] S1. Grind the phosphogypsum and sieve it through a 100-mesh sieve. Then add it to deionized water. The solid-liquid ratio of phosphogypsum to deionized water is 1:4. After dispersing evenly, add calcium oxide and disodium EADA. The addition amount of calcium oxide is 2.5% of the mass of phosphogypsum, and the addition amount of disodium EADA is 0.7% of the mass of phosphogypsum. Stir at a stirring speed of 70 r / min and a temperature of 45 °C for 60 min. After stirring, add a 10% sulfuric acid solution to adjust the pH to 7, and then centrifuge and filter to obtain pretreated phosphogypsum;

[0061] S2. Add the pretreated phosphogypsum in step S1 to deionized water. The mass ratio of pretreated phosphogypsum to deionized water is 1:4.5. Adjust the pH to 9, and then add a flotation agent. The addition amount of the flotation agent is 1.2% of the mass of pretreated gypsum. Carry out flotation for 25 min under the conditions of an air inflow rate of 0.45 L / min and a rotation speed of 1600 r / min. After flotation, carry out solid-liquid separation to obtain a flotation phosphogypsum slurry (with a water content of 35%);

[0062] S3. Add a composite additive to the flotation phosphogypsum slurry in step S2. The addition amount of the composite additive is 14% of the mass of the flotation phosphogypsum slurry. After mixing evenly, carry out pre-calcination. The pre-calcination temperature is 210 °C and the time is 2 h. After pre-calcination, carry out roasting. The roasting process is to raise the temperature to 480 °C at a heating rate of 9 °C / min and hold for 3 h. After roasting, anhydrous gypsum is obtained;

[0063] S4. Mix 100 g of the anhydrous gypsum in step S3 evenly with 75 g of a γ-aminopropyltriethoxysilane ethanol solution (the mass concentration of γ-aminopropyltriethoxysilane is 5%). Ball mill at a rotation speed of 850 r / min for 25 min. After ball milling, dry and grind to obtain modified phosphogypsum.

[0064] The preparation method of the flotation agent described in step S2 is as follows:

[0065] Add Tween 80 to deionized water and stir evenly to obtain a Tween solution with a mass concentration of 2.5%. Add 5 g of dodecylamine to 90 g of the Tween solution and emulsify for 10 min under the conditions of an ultrasonic frequency of 35 kHz and a power of 70 W to obtain a dodecylamine emulsion. Add 2.5 g of terpineol to 75 g of the Tween solution and emulsify for 10 min under the conditions of an ultrasonic frequency of 35 kHz and a power of 70 W to obtain a terpineol emulsion. Mix 9 g of the dodecylamine emulsion and 75 g of the terpineol emulsion evenly, and then add 3.5 g of sodium oleate and 1.5 g of carboxymethyl cellulose and stir evenly to obtain the flotation agent.

[0066] The preparation method of the composite additive described in step S3 is as follows:

[0067] Add 6 g of potassium sulfate to 110 g of deionized water. After stirring evenly, add 2.5 g of sodium citrate, 1.5 g of sodium polyacrylate, and 4 g of silica sol (the content of silicon dioxide is 40%). Stir at a constant temperature of 45 °C for 55 min. After the stirring is completed, the composite additive is obtained.

[0068] A preparation method of an environmentally friendly material using phosphogypsum as a filler for an ecological green plant system, comprising the following steps:

[0069] Weigh the raw materials according to the formula. Add polylactic acid, modified phosphogypsum, polybutylene succinate, polyvinyl alcohol, calcium stearate, epoxy soybean oil, and antioxidant into a high-speed mixer and mix evenly. Then, perform twin-screw granulation. Control the temperature of the twin-screw feeding section at 160 °C, the melting section at 180 °C, the kneading section at 195 °C, and the head section at 185 °C to obtain masterbatch; After drying the masterbatch, add it into an extruder for sheet extrusion. Control the temperature of the extruder feeding section at 160 °C, the compression section at 185 °C, the homogenization section at 195 °C, and the die head section at 185 °C to obtain a sheet. Then, punch holes in the sheet to obtain the environmentally friendly material.

[0070] Example 3

[0071] An environmentally friendly material using phosphogypsum as a filler for an ecological green plant system, by weight, comprises the following raw materials:

[0072] 60 parts of polylactic acid, 50 parts of modified phosphogypsum, 10 parts of polybutylene succinate, 5 parts of polyvinyl alcohol, 3 parts of epoxy soybean oil, 2 parts of calcium stearate, and 0.5 part of antioxidant.

[0073] The preparation method of the modified phosphogypsum comprises the following steps:

[0074] S1. Grind the phosphogypsum and pass it through a 100-mesh sieve. Then, add it into deionized water. The solid-liquid ratio of phosphogypsum to deionized water is 1:3. After dispersing evenly, add calcium oxide and disodium EADA. The addition amount of calcium oxide is 2% of the mass of phosphogypsum, and the addition amount of disodium EADA is 0.5% of the mass of phosphogypsum. Stir at a stirring speed of 60 r / min and a temperature of 40 °C for 80 min. After the stirring is completed, add a sulfuric acid solution with a mass fraction of 5% to adjust the pH to 7. Then, centrifuge and filter to obtain pretreated phosphogypsum;

[0075] S2. Add the pretreated phosphogypsum in step S1 into deionized water. The mass ratio of pretreated phosphogypsum to deionized water is 1:4. Adjust the pH to 8. Then, add a flotation agent. The addition amount of the flotation agent is 1% of the mass of pretreated gypsum. Perform flotation for 30 min under the conditions of an air inflow rate of 0.4 L / min and a rotation speed of 1500 r / min. After the flotation is completed, perform solid-liquid separation to obtain a flotation phosphogypsum slurry (with a water content of 30%);

[0076] S3. Add a composite additive to the flotation phosphogypsum slurry in step S2. The addition amount of the composite additive is 12% of the mass of the flotation phosphogypsum slurry. After mixing evenly, perform pre-calcination at a temperature of 200 °C for 2 h. After the pre-calcination is completed, perform roasting. The roasting process is to raise the temperature to 460 °C at a heating rate of 7 °C / min and hold for 3.5 h. After the roasting is completed, anhydrous gypsum is obtained;

[0077] S4. Mix 100 g of the anhydrous gypsum in step S3 evenly with 70 g of γ-aminopropyltriethoxysilane ethanol solution (the mass concentration of γ-aminopropyltriethoxysilane is 4%). Ball mill for 30 min at a rotation speed of 800 r / min. After the ball milling is completed, dry and grind to obtain the modified phosphogypsum.

[0078] The preparation method of the flotation agent described in step S2 is as follows:

[0079] Add Tween 80 to deionized water and stir evenly to obtain a Tween solution with a mass concentration of 2%. Add 4 g of dodecylamine to 80 g of the Tween solution and emulsify for 12 min under the conditions of an ultrasonic frequency of 30 kHz and a power of 50 W to obtain a dodecylamine emulsion. Add 2 g of terpineol to 70 g of the Tween solution and emulsify for 12 min under the conditions of an ultrasonic frequency of 30 kHz and a power of 50 W to obtain a terpineol emulsion. Mix 80 g of the dodecylamine emulsion and 70 g of the terpineol emulsion evenly, then add 3 g of sodium oleate and 1 g of carboxymethyl cellulose, and stir evenly to obtain the flotation agent.

[0080] The preparation method of the composite additive described in step S3 is as follows:

[0081] Add 5 g of potassium sulfate to 100 g of deionized water, stir evenly, then add 2 g of sodium citrate, 1 g of sodium polyacrylate, and 3 g of silica sol (the content of silicon dioxide is 40%), and stir at a constant temperature of 40 °C for 60 min. After the stirring is completed, the composite additive is obtained.

[0082] A preparation method of an environmentally friendly material using phosphogypsum as a filler for an ecological green plant system, comprising the following steps:

[0083] Weigh the raw materials according to the formula. Add polylactic acid, modified phosphogypsum, polybutylene succinate, polyvinyl alcohol, calcium stearate, epoxidized soybean oil, and antioxidant into a high-speed mixer and mix them evenly. Then, perform twin-screw granulation. Control the temperature of the twin-screw conveying section at 150 °C, the melting section at 180 °C, the kneading section at 190 °C, and the head section at 180 °C to obtain the masterbatch. After drying the masterbatch, add it into an extruder for sheet extrusion. Control the temperature of the extruder feeding section at 160 °C, the compression section at 185 °C, the homogenization section at 190 °C, and the die head section at 180 °C to obtain the sheet. Then, punch holes in the sheet to obtain the environmentally friendly material.

[0084] Example 4

[0085] An environmentally friendly material using phosphogypsum as a filler for an ecological green plant system, by weight, comprises the following raw materials:

[0086] 70 parts of polylactic acid, 60 parts of modified phosphogypsum, 20 parts of polybutylene succinate, 10 parts of polyvinyl alcohol, 5 parts of epoxidized soybean oil, 3 parts of calcium stearate, and 1 part of antioxidant.

[0087] The preparation method of the modified phosphogypsum comprises the following steps:

[0088] S1. Grind the phosphogypsum and pass it through a 100-mesh sieve. Then, add it into deionized water. The solid-liquid ratio of phosphogypsum to deionized water is 1:5. After dispersing evenly, add calcium oxide and disodium EADA. The addition amount of calcium oxide is 3% of the mass of phosphogypsum, and the addition amount of disodium EADA is 1% of the mass of phosphogypsum. Stir at a stirring speed of 80 r / min and a temperature of 50 °C for 50 min. After stirring, add a 10% sulfuric acid solution to adjust the pH to 7. Then, centrifuge and filter to obtain the pretreated phosphogypsum.

[0089] S2. Add the pretreated phosphogypsum obtained in step S1 into deionized water. The mass ratio of the pretreated phosphogypsum to deionized water is 1:5. Adjust the pH to 10. Then, add a flotation agent. The addition amount of the flotation agent is 1.5% of the mass of the pretreated gypsum. Perform flotation for 20 min under the conditions of an air inflow rate of 0.5 L / min and a rotation speed of 1800 r / min. After flotation, perform solid-liquid separation to obtain the flotation phosphogypsum slurry (with a water content of 40%).

[0090] S3. Add a composite additive to the flotation phosphogypsum slurry obtained in step S2. The addition amount of the composite additive is 16% of the mass of the flotation phosphogypsum slurry. After mixing evenly, perform pre-calcination. The pre-calcination temperature is 220 °C, and the time is 1.5 h. After pre-calcination, perform roasting. The roasting process is to raise the temperature to 500 °C at a heating rate of 10 °C / min and hold for 3 h. After roasting, anhydrous gypsum is obtained.

[0091] S4. Mix 100 g of anhydrous gypsum in step S3 with 80 g of γ-aminopropyltriethoxysilane ethanol solution (the mass concentration of γ-aminopropyltriethoxysilane is 7%), mix evenly, ball mill at a rotation speed of 900 r / min for 20 min, and after the ball milling is completed, dry and grind to obtain modified phosphogypsum.

[0092] The preparation method of the flotation agent described in step S2 is as follows:

[0093] Add Tween 80 to deionized water, and after stirring evenly, obtain a Tween solution with a mass concentration of 2 - 3%; add 6 g of dodecylamine to 100 g of the Tween solution, and emulsify for 8 min under the conditions of an ultrasonic frequency of 40 kHz and a power of 100 W to obtain a dodecylamine emulsion; add 3 g of terpineol to 80 g of the Tween solution, and emulsify for 8 min under the conditions of an ultrasonic frequency of 40 kHz and a power of 100 W to obtain a terpineol emulsion; mix 100 g of the dodecylamine emulsion and 80 g of the terpineol emulsion evenly, then add 4 g of sodium oleate and 2 g of carboxymethyl cellulose, and stir evenly to obtain the flotation agent.

[0094] The preparation method of the composite additive described in step S3 is as follows:

[0095] Add 7 g of potassium sulfate to 120 g of deionized water, stir evenly, then add 3 g of sodium citrate, 2 g of sodium polyacrylate, and 5 g of silica sol (the content of silicon dioxide is 45%), and stir at a constant temperature of 50 °C for 50 min. After the stirring is completed, obtain the composite additive.

[0096] A preparation method of an environmentally friendly material using phosphogypsum as a filler for an ecological green plant system, comprising the following steps:

[0097] Weigh the raw materials according to the formula, add polylactic acid, modified phosphogypsum, polybutylene succinate, polyvinyl alcohol, calcium stearate, epoxy soybean oil, and antioxidant into a high-speed mixer and mix evenly, then carry out twin-screw granulation, control the temperature of the twin-screw conveying section at 160 °C, the melting section at 190 °C, the kneading section at 200 °C, and the head section at 190 °C to obtain masterbatch; dry the masterbatch and then add it into an extruder for sheet extrusion, control the temperature of the extruder feeding section at 170 °C, the compression section at 195 °C, the homogenization section at 200 °C, and the die head section at 190 °C to obtain a sheet, and then punch holes in the sheet to obtain the environmentally friendly material.

[0098] Comparative Example 1

[0099] An environmentally friendly material using phosphogypsum as a filler for an ecological green plant system, by weight, comprises the following raw materials:

[0100] 65 parts of polylactic acid, 55 parts of modified phosphogypsum, 15 parts of polybutylene succinate, 8 parts of polyvinyl alcohol, 4 parts of epoxidized soybean oil, 2.5 parts of calcium stearate, 0.8 part of antioxidant.

[0101] The preparation method of the modified phosphogypsum includes the following steps:

[0102] S1. Grind the phosphogypsum and pass it through a 100-mesh sieve, then add it to deionized water. The solid-liquid ratio of phosphogypsum to deionized water is 1:4. After dispersing evenly, add calcium oxide and disodium EADA. The addition amount of calcium oxide is 2.5% of the mass of phosphogypsum, and the addition amount of disodium EADA is 0.8% of the mass of phosphogypsum. Stir at a stirring speed of 70 r / min and a temperature of 45 °C for 70 min. After stirring, add a 5% sulfuric acid solution to adjust the pH to 7, then centrifuge and filter to obtain pretreated phosphogypsum;

[0103] S2. Add the pretreated phosphogypsum in step S1 to deionized water. The mass ratio of pretreated phosphogypsum to deionized water is 1:4.5. Adjust the pH to 9, then add a flotation agent. The addition amount of the flotation agent is 1.3% of the mass of pretreated gypsum. Carry out flotation for 25 min under the conditions of an air inflow rate of 0.45 L / min and a rotation speed of 1700 r / min. After flotation, carry out solid-liquid separation to obtain a flotation phosphogypsum slurry (water content is 35%);

[0104] S3. Add a composite additive to the flotation phosphogypsum slurry in step S2. The addition amount of the composite additive is 15% of the mass of the flotation phosphogypsum slurry. After mixing evenly, carry out pre-calcination. The pre-calcination temperature is 210 °C and the time is 1.5 h. After pre-calcination, carry out roasting. The roasting process is to rise to 480 °C at a heating rate of 8 °C / min and keep the temperature for 3.5 h. After roasting, anhydrous gypsum is obtained;

[0105] S4. Mix 100 g of the anhydrous gypsum in step S3 evenly with 75 g of a γ-aminopropyltriethoxysilane ethanol solution (the mass concentration of γ-aminopropyltriethoxysilane is 6%). Ball mill at a rotation speed of 850 r / min for 25 min. After ball milling, dry and grind to obtain the modified phosphogypsum.

[0106] The preparation method of the flotation agent described in step S2 is as follows:

[0107] Add Tween 80 to deionized water, and after stirring evenly, obtain a Tween solution with a mass concentration of 2.5%; add 2.5 g of terpineol to 75 g of the Tween solution, and emulsify for 10 min under the conditions of an ultrasonic frequency of 35 kHz and a power of 80 W to obtain a terpineol emulsion; stir 75 g of the terpineol emulsion evenly with 5 g of carboxymethyl cellulose to obtain the flotation agent.

[0108] The preparation method of the composite additive described in step S3 is as follows:

[0109] Add 6 g of potassium sulfate to 110 g of deionized water. After stirring evenly, add 2.5 g of sodium citrate, 1.5 g of sodium polyacrylate, and 4 g of silica sol (the content of silicon dioxide is 45%). Stir at a constant temperature of 45 °C for 55 min. After the stirring is completed, the composite additive is obtained.

[0110] A preparation method of an environmentally friendly material using phosphogypsum as a filler for an ecological green plant system includes the following steps:

[0111] Weigh the raw materials according to the formula. Add polylactic acid, modified phosphogypsum, polybutylene succinate, polyvinyl alcohol, calcium stearate, epoxy soybean oil, and antioxidant into a high-speed mixer and mix evenly. Then, perform twin-screw granulation. Control the temperature of the twin-screw feeding section at 155 °C, the melting section at 185 °C, the kneading section at 195 °C, and the head section at 185 °C to obtain masterbatch. After drying the masterbatch, add it into an extruder for sheet extrusion. Control the temperature of the extruder feeding section at 165 °C, the compression section at 190 °C, the homogenization section at 195 °C, and the die head section at 185 °C to obtain a sheet. Then, punch holes in the sheet to obtain the environmentally friendly material.

[0112] Compared with Example 1, dodecylamine and sodium oleate were not added to the flotation agent in this comparative example.

[0113] Comparative Example 2

[0114] An environmentally friendly material using phosphogypsum as a filler for an ecological green plant system, by weight, includes the following raw materials:

[0115] 65 parts of polylactic acid, 55 parts of modified phosphogypsum, 15 parts of polybutylene succinate, 8 parts of polyvinyl alcohol, 4 parts of epoxy soybean oil, 2.5 parts of calcium stearate, and 0.8 part of antioxidant.

[0116] The preparation method of the modified phosphogypsum includes the following steps:

[0117] S1. Grind the phosphogypsum and pass it through a 100-mesh sieve. Then, add it into deionized water. The solid-liquid ratio of phosphogypsum to deionized water is 1:4. After dispersing evenly, add calcium oxide and EADA disodium. The addition amount of calcium oxide is 2.5% of the mass of phosphogypsum, and the addition amount of EADA disodium is 0.8% of the mass of phosphogypsum. Stir at a stirring speed of 70 r / min and a temperature of 45 °C for 70 min. After the stirring is completed, add a sulfuric acid solution with a mass fraction of 5% to adjust the pH to 7. Then, centrifuge and filter to obtain pretreated phosphogypsum;

[0118] S2. Add the pre-treated phosphogypsum in step S1 to deionized water. The mass ratio of the pre-treated phosphogypsum to deionized water is 1:4.5. Adjust the pH to 9. Then add a flotation agent. The addition amount of the flotation agent is 1.3% of the mass of the pre-treated gypsum. Carry out flotation for 25 min under the conditions of an air inflow rate of 0.45 L / min and a rotation speed of 1700 r / min. After flotation is completed, carry out solid-liquid separation to obtain a flotation phosphogypsum slurry (with a water content of 35%);

[0119] S3. Add a composite additive to the flotation phosphogypsum slurry in step S2. The addition amount of the composite additive is 15% of the mass of the flotation phosphogypsum slurry. After mixing evenly, carry out pre-calcination. The temperature of the pre-calcination is 210 °C and the time is 1.5 h. After pre-calcination is completed, carry out roasting. The roasting process is to raise the temperature to 480 °C at a heating rate of 8 °C / min and keep the temperature for 3.5 h. After roasting is completed, anhydrous gypsum is obtained;

[0120] S4. Mix 100 g of the anhydrous gypsum in step S3 evenly with 75 g of a γ-aminopropyltriethoxysilane ethanol solution (the mass concentration of γ-aminopropyltriethoxysilane is 6%). Carry out ball milling for 25 min at a rotation speed of 850 r / min. After ball milling is completed, dry and grind to obtain the modified phosphogypsum.

[0121] The preparation method of the flotation agent described in step S2 is as follows:

[0122] Add Tween 80 to deionized water. After stirring evenly, obtain a Tween solution with a mass concentration of 2.5%. Add 5 g of dodecylamine to 90 g of the Tween solution. Emulsify for 10 min under the conditions of an ultrasonic frequency of 35 kHz and a power of 80 W to obtain a dodecylamine emulsion. Add 2.5 g of terpineol to 75 g of the Tween solution. Emulsify for 10 min under the conditions of an ultrasonic frequency of 35 kHz and a power of 80 W to obtain a terpineol emulsion. Mix 90 g of the dodecylamine emulsion and 75 g of the terpineol emulsion evenly. Then add 3.5 g of sodium oleate and 1.5 g of carboxymethyl cellulose and stir evenly to obtain the flotation agent.

[0123] The preparation method of the composite additive described in step S3 is as follows:

[0124] Add 10 g of potassium sulfate to 110 g of deionized water. After stirring evenly, add 4 g of sodium citrate and stir at a constant temperature of 45 °C for 55 min. After stirring is completed, obtain the composite additive.

[0125] A preparation method of an environmentally friendly material using phosphogypsum as a filler for an ecological green plant system, comprising the following steps:

[0126] Weigh the raw materials according to the formula. Add polylactic acid, modified phosphogypsum, polybutylene succinate, polyvinyl alcohol, calcium stearate, epoxy soybean oil, and antioxidant into a high-speed mixer and mix evenly. Then, perform twin-screw granulation. Control the temperature of the twin-screw conveying section at 155 °C, the melting section at 185 °C, the kneading section at 195 °C, and the head section at 185 °C to obtain the masterbatch. After drying the masterbatch, add it into an extruder for sheet extrusion. Control the temperature of the feeding section of the extruder at 165 °C, the compression section at 190 °C, the homogenization section at 195 °C, and the die head section at 185 °C to obtain the sheet. Then, punch holes in the sheet to obtain the environmentally friendly material.

[0127] Compared with Example 1, sodium polyacrylate and silica sol were not added to the composite additive in this comparative example.

[0128] Comparative Example 3

[0129] An environmentally friendly material using phosphogypsum as a filler for an ecological green plant system, by weight, includes the following raw materials:

[0130] 65 parts of polylactic acid, 55 parts of modified phosphogypsum, 15 parts of polybutylene succinate, 8 parts of polyvinyl alcohol, 4 parts of epoxy soybean oil, 2.5 parts of calcium stearate, and 0.8 part of antioxidant.

[0131] The preparation method of the modified phosphogypsum includes the following steps:

[0132] S1. Grind the phosphogypsum and pass it through a 100-mesh sieve. Then, add it into deionized water. The solid-liquid ratio of phosphogypsum to deionized water is 1:4. After dispersing evenly, add calcium oxide and EADA disodium. The addition amount of calcium oxide is 2.5% of the mass of phosphogypsum, and the addition amount of EADA disodium is 0.8% of the mass of phosphogypsum. Stir at a stirring speed of 70 r / min and a temperature of 45 °C for 70 min. After stirring, add a sulfuric acid solution with a mass fraction of 5% to adjust the pH to 7. Then, centrifuge and filter to obtain the pretreated phosphogypsum.

[0133] S2. Add the pretreated phosphogypsum obtained in step S1 into deionized water. The mass ratio of the pretreated phosphogypsum to deionized water is 1:4.5. Adjust the pH to 9. Then, add a flotation agent. The addition amount of the flotation agent is 1.3% of the mass of the pretreated gypsum. Perform flotation for 25 min under the conditions of an air inflow rate of 0.45 L / min and a rotation speed of 1700 r / min. After flotation, perform solid-liquid separation to obtain the flotation phosphogypsum slurry (with a water content of 35%).

[0134] S3. Add a composite additive to the flotation phosphogypsum slurry in step S2. The addition amount of the composite additive is 15% of the mass of the flotation phosphogypsum slurry. After mixing evenly, perform pre-calcination. The pre-calcination temperature is 210 °C and the time is 1.5 h. After the pre-calcination is completed, perform roasting. The roasting process is to raise the temperature to 480 °C at a heating rate of 8 °C / min and hold for 3.5 h. After the roasting is completed, anhydrous gypsum is obtained.

[0135] S4. Mix 100 g of the anhydrous gypsum in step S3 evenly with 75 g of γ-aminopropyltriethoxysilane ethanol solution (the mass concentration of γ-aminopropyltriethoxysilane is 6%). Ball mill at a rotation speed of 850 r / min for 25 min. After the ball milling is completed, dry and grind to obtain the modified phosphogypsum.

[0136] The preparation method of the flotation agent described in step S2 is as follows:

[0137] Add Tween 80 to deionized water. After stirring evenly, obtain a Tween solution with a mass concentration of 2.5%. Add 2.5 g of terpineol to 75 g of the Tween solution and emulsify for 10 min under the conditions of an ultrasonic frequency of 35 kHz and a power of 80 W to obtain a terpineol emulsion. Stir 75 g of the terpineol emulsion evenly with 5 g of carboxymethyl cellulose to obtain the flotation agent.

[0138] The preparation method of the composite additive described in step S3 is as follows:

[0139] Add 10 g of potassium sulfate to 110 g of deionized water. After stirring evenly, add 4 g of sodium citrate and stir at a constant temperature of 45 °C for 55 min. After the stirring is completed, obtain the composite additive.

[0140] A preparation method of an environmentally friendly material using phosphogypsum as a filler for an ecological green plant system, comprising the following steps:

[0141] Weigh the raw materials according to the formula. Add polylactic acid, modified phosphogypsum, polybutylene succinate, polyvinyl alcohol, calcium stearate, epoxy soybean oil, and antioxidant into a high-speed mixer and mix evenly. Then perform twin-screw granulation. Control the temperature of the twin-screw feeding section at 155 °C, the melting section at 185 °C, the kneading section at 195 °C, and the head section at 185 °C to obtain masterbatch. After drying the masterbatch, add it into an extruder for sheet extrusion. Control the temperature of the extruder feeding section at 165 °C, the compression section at 190 °C, the homogenization section at 195 °C, and the die head section at 185 °C to obtain a sheet. Then punch holes in the sheet to obtain the environmentally friendly material.

[0142] Compared with Example 1, in this comparative example, dodecylamine and sodium oleate are not added to the flotation agent, and sodium polyacrylate and silica sol are not added to the composite additive.

[0143] The masterbatches prepared in Examples 1-4 and Comparative Examples 1-3 were dried and then made into specimens on an injection molding machine. The mechanical properties were tested using a universal mechanical testing machine. The tensile strength and elongation at break were tested according to GB / T 1040.1-2018. The standard sample was of Type 1A, and the test speed was 10 mm / min. Three specimens were tested in each group, and the average value was calculated to obtain the tensile strength and elongation at break. The notched impact strength was tested according to GB / T 1043.1-2008. It was tested at room temperature using a simply supported beam impact testing machine. The pendulum energy was 5 J, the notch type was Type A, and the impact speed was 2.9 m / s. Five parallel specimens were tested, and the results were averaged. The biodegradation rate was tested according to GB / T 19811-2005, and the test time was 180 days. The test results are shown in Table 1 below.

[0144] Table 1

[0145]

[0146] As can be seen from Table 1, the environmentally friendly material prepared in the present invention using phosphogypsum as a filler for the ecological green plant system has good mechanical properties and good degradability. It not only solves the problem of high cost of biodegradable materials but also solves the problem of resource utilization of phosphogypsum, and has good application prospects.

[0147] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An environmentally friendly material using phosphogypsum as a filler for an ecological green plant system, characterized in that, By weight parts, it includes the following raw materials: 60 - 70 parts of polylactic acid, 50 - 60 parts of modified phosphogypsum, 10 - 20 parts of polybutylene succinate, 5 - 10 parts of polyvinyl alcohol, 3 - 5 parts of epoxidized soybean oil, 2 - 3 parts of calcium stearate, 0.5 - 1 part of antioxidant.

2. The environmental protection material using phosphogypsum as a filler for an ecological green plant system according to claim 1, characterized in that, By weight parts, it includes the following raw materials: 60 - 65 parts of polylactic acid, 50 - 55 parts of modified phosphogypsum, 10 - 15 parts of polybutylene succinate, 5 - 8 parts of polyvinyl alcohol, 4 - 5 parts of epoxidized soybean oil, 2 - 2.5 parts of calcium stearate, 0.7 - 1 part of antioxidant.

3. The environmentally friendly material using phosphogypsum as a filler for an ecological green plant system according to claim 1, characterized in that The preparation method of the described modified phosphogypsum includes the following steps: S1. Grind the phosphogypsum and pass it through a 100 - mesh sieve, then add it to deionized water. After dispersing evenly, add calcium oxide and disodium EADA, and stir. After stirring is completed, add sulfuric acid solution to adjust the pH to 7, then centrifuge and filter to obtain pretreated phosphogypsum; S2. Add the pretreated phosphogypsum in step S1 to deionized water, adjust the pH to 8 - 10, then add a flotation agent and carry out flotation treatment. After flotation is completed, carry out solid - liquid separation to obtain a flotation phosphogypsum slurry; S3. Add a composite additive to the flotation phosphogypsum slurry in step S2, mix evenly and then carry out pre - calcination. After pre - calcination is completed, carry out roasting. After roasting is completed, obtain anhydrous gypsum; S4. Mix the anhydrous gypsum in step S3 evenly with a silane coupling agent ethanol solution, carry out ball - milling. After ball - milling is completed, dry and grind to obtain the modified phosphogypsum.

4. The environmentally friendly material using phosphogypsum as a filler for an ecological green plant system according to claim 3, characterized in that, In step S1, the solid - liquid ratio of the phosphogypsum to deionized water is 1:3 - 5, the addition amount of calcium oxide is 2 - 3% of the mass of phosphogypsum, the addition amount of disodium EADA is 0.5 - 1% of the mass of phosphogypsum, the stirring speed is 60 - 80 r / min, the temperature is 40 - 50 °C, the time is 50 - 80 min, and the mass fraction of the sulfuric acid solution is 5 - 10%.

5. The environmentally friendly material according to claim 3, which uses phosphogypsum as a filler for an ecological green plant system, is characterized in that, In step S2, the mass ratio of the pretreated phosphogypsum to deionized water is 1:4 - 5, the addition amount of the flotation agent is 1 - 1.5% of the mass of the pretreated gypsum, the aeration amount of the flotation treatment is 0.4 - 0.5 L / min, the time is 20 - 30 min, and the rotation speed is 1500 - 1800 r / min.

6. The environmentally friendly material using phosphogypsum as a filler for an ecological green plant system according to claim 3, characterized in that, The preparation method of the flotation agent in step S2 is as follows: Add Tween 80 to deionized water, and after stirring evenly, obtain a Tween solution with a mass concentration of 2 - 3%; add 4 - 6 g of dodecylamine to 80 - 100 g of the Tween solution, and emulsify for 8 - 12 min under the conditions of an ultrasonic frequency of 30 - 40 kHz and a power of 50 - 100 W to obtain a dodecylamine emulsion; add 2 - 3 g of terpineol to 70 - 80 g of the Tween solution, and emulsify for 8 - 12 min under the conditions of an ultrasonic frequency of 30 - 40 kHz and a power of 50 - 100 W to obtain a terpineol emulsion; mix 80 - 100 g of the dodecylamine emulsion and 70 - 80 g of the terpineol emulsion evenly, then add 3 - 4 g of sodium oleate and 1 - 2 g of carboxymethyl cellulose, and stir evenly to obtain the flotation agent.

7. The environmentally friendly material according to claim 3, which uses phosphogypsum as a filler for an ecological green plant system, is characterized in that, The preparation method of the composite additive in step S3 is as follows: Add 5 - 7 g of potassium sulfate to 100 - 120 g of deionized water. After stirring evenly, add 2 - 3 g of sodium citrate, 1 - 2 g of sodium polyacrylate, and 3 - 5 g of silica sol. Stir at a constant temperature of 40 - 50 °C for 50 - 60 min. After the stirring is completed, the composite additive is obtained.

8. The environmentally friendly material according to claim 3, which uses phosphogypsum as a filler for an ecological green plant system, is characterized in that In step S3, the addition amount of the composite additive is 12 - 16% of the mass of the flotation phosphogypsum slurry. The temperature of the pre - calcination is 200 - 220 °C, and the time is 1.5 - 2 h. The roasting process is to rise to 460 - 500 °C at a heating rate of 7 - 10 °C / min and hold for 3 - 3.5 h.

9. The environmentally friendly material according to claim 1, which uses phosphogypsum as a filler for an ecological green plant system, is characterized in that In step S4, the mass concentration of the silane coupling agent in the ethanol solution of the silane coupling agent is 4 - 7%. The mass ratio of the anhydrous gypsum to the ethanol solution of the silane coupling agent is 100:70 - 80. The rotation speed of the ball mill is 800 - 900 r / min, and the time is 20 - 30 min.

10. A preparation method of an environmentally friendly material using phosphogypsum as a filler for an ecological green plant system according to any one of claims 1-9, characterized in that, It includes the following steps: Weigh the raw materials according to the formula. Add polylactic acid, modified phosphogypsum, polybutylene succinate, polyvinyl alcohol, calcium stearate, epoxy soybean oil, and antioxidant into a high - speed mixer and mix evenly. Then, perform twin - screw granulation to obtain masterbatch. After drying the masterbatch, add it into an extruder for sheet extrusion to obtain a sheet. Then, punch holes in the sheet to obtain the environmental protection material.

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