Method for preparing modified calcium carbonate from phosphogypsum and application thereof

Abstract

The application provides a method for preparing modified calcium carbonate from phosphogypsum and application thereof, and the preparation method comprises the following steps: S1, uniformly mixing phosphogypsum, POF (Porous Organic Frameworks) material and water to prepare a slurry; S2, adding ammonia water into the slurry, and controlling the sulfur-nitrogen ratio to be 40-50%; S3, introducing carbon dioxide gas into the slurry of S2 to react, and after the reaction is completed, filtering and washing are performed, and the filter residue is dried to obtain POF material modified calcium carbonate. The method uses phosphogypsum as raw material, modifies the calcium carbonate in the preparation process of the calcium carbonate, and uses the modified calcium carbonate for plastic products, so that the compatibility problem of the calcium carbonate and plastic polymers can be solved, the strength and toughness of the plastic products are significantly improved, the cost is low, the process is simple, and the method is also helpful for resource utilization of the phosphogypsum.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of phosphogypsum resource utilization, and particularly relates to a method for preparing modified calcium carbonate from phosphogypsum and application thereof. BACKGROUND

[0002] Phosphogypsum is a by-product of the process of producing phosphoric acid by the wet method. Calcium carbonate is used as a filler for plastic products, which can improve the tensile strength, elongation at break, bending strength and Brinell hardness of the products and reduce the unit cost of the plastic products. The traditional preparation of calcium carbonate is prepared by calcining and carbonizing limestone or marble, so that the preparation of nano calcium carbonate from phosphogypsum, which is a solid waste rich in calcium ions, not only reduces the consumption of natural mineral resources such as limestone and marble, but also provides a new way for the resource utilization of phosphogypsum.

[0003] Generally, calcium carbonate products have strong alkalinity and are hydrophilic and oleophobic, and have poor affinity with polymers, which makes it difficult to disperse in polymers and easily form interface defects with polymers. With the increase of the filling amount of calcium carbonate, these shortcomings are more obvious, and even the products lose their use value. In recent years, nanotechnology has emerged, and nano calcium carbonate and ultrafine calcium carbonate are widely used in various fields. However, due to the smaller particle size of ultrafine calcium carbonate, the number of surface atoms increases, the surface energy increases, and the adsorption effect increases, so the particles tend to agglomerate with each other, which leads to poor dispersion of the particles in the polymer matrix. In order to improve the dispersibility of nano calcium carbonate and ultrafine calcium carbonate and the affinity with polymers, it is necessary to modify nano and ultrafine calcium carbonate to play its nano effect and make it a functional modified material, so as to broaden its application field.

[0004] CN113372618A discloses a modified calcium carbonate, a preparation method thereof, a PVC pipe material containing the modified calcium carbonate, and a PVC pipe material. The modified calcium carbonate is prepared by grafting maleic anhydride on the surface of calcium carbonate, and then using the unsaturated bond in fatty acid glycerol diester to react with maleic anhydride to form free radicals, so that fatty acid glycerol diester is further grafted on the surface of calcium carbonate. Compared with unmodified calcium carbonate, the tensile yield strength of the modified calcium carbonate can be increased by about 1.5 times, and the elongation at break can be increased by about 2.1 times. However, the preparation process is complex, and the raw materials used for preparing calcium carbonate are not environmentally friendly.

[0005] CN110951116A discloses a modified calcium carbonate and a high-performance plastic prepared from the modified calcium carbonate. The calcium carbonate is mixed and ground with a grinding aid, and then a modifier is added to prepare the modified calcium carbonate. The modified calcium carbonate has good dispersibility, processing fluidity, chemical stability and weather resistance. However, there is a compatibility problem between the modifier and the calcium carbonate, and the utilization rate of the modifier is low. SUMMARY

[0006] The application provides a method for preparing modified calcium carbonate from phosphogypsum and application thereof, which is prepared from phosphogypsum and modified in the process of preparing calcium carbonate, can solve the problem of compatibility of calcium carbonate and plastic polymer, is low in cost, simple in process and helpful to resource utilization of phosphogypsum.

[0007] In order to achieve the above-mentioned target, the application adopts the following technical scheme: a method for preparing modified calcium carbonate from phosphogypsum, comprising the following steps:

[0008] S1, using phosphogypsum as raw material, adding POF material and water to mix uniformly to prepare slurry;

[0009] S2, adding ammonia water to the slurry, and controlling the sulfur-nitrogen ratio to be 40-50%;

[0010] S3, passing carbon dioxide gas into the slurry of S2 to react, after the reaction is completed, filtering and washing, and drying the filter residue to obtain POF material modified calcium carbonate.

[0011] Further, the content of calcium sulfate in the phosphogypsum is 80-90wt%.

[0012] Further, the POF material is hydrophobic and oleophilic POF, such as covalent organic framework (COF) and conjugated microporous polymer (CMP).

[0013] Further, the addition amount of the POF material is 0.1-0.5% of the mass of the phosphogypsum.

[0014] Further, the solid-liquid mass ratio is controlled to be 5%-20% when adding water in S1.

[0015] Further, the temperature is controlled to be 20-50℃ in S2.

[0016] Further, the amount of carbon dioxide passed in S3 is 50-500 PL / Pin.

[0017] Further, the drying temperature of the filter residue is 80℃-120℃, and the drying time is 8-12h.

[0018] The application also relates to modified calcium carbonate prepared by the method and application of the modified calcium carbonate in plastic products.

[0019] The application has the following beneficial effects:

[0020] 1. The application uses phosphogypsum as raw material to prepare calcium carbonate by using calcium sulfate in phosphogypsum, and POF material is added in the preparation process, which can form a micro-phase reaction system in the aqueous solution, provide a micro-phase reaction space for the phosphogypsum complex decomposition reaction, effectively reduce the agglomeration phenomenon in the synthesis process of calcium carbonate, make the reaction proceed in a direction more conducive to the nucleation of calcium carbonate, and more easily obtain nano calcium carbonate with smaller particle size, and the porous characteristics of the POF material can store carbon dioxide in the reaction process, reduce the release of carbon dioxide in the reaction system, and reduce the amount of carbon dioxide.

[0021] 2. The preparation method is simple in process operation, can realize the full utilization of phosphogypsum, effectively alleviate the problem of phosphogypsum stockpiling, and meet the green development requirements of enterprises. The modified calcium carbonate obtained is used for plastic products, can toughen and reinforce the plastic products, significantly improve the strength and toughness of the plastic products, and the nano calcium carbonate is mixed with hydrophobic and oleophilic POF, which improves the affinity of calcium carbonate in the polymer matrix and effectively reduces the interface defect seam between calcium carbonate and the polymer.

[0022] 3. The impurities of phosphogypsum contain SiO2, and the synthesized nano calcium carbonate contains a small amount of silicon substances. Since nano calcium carbonate has strong surface activity and is easy to agglomerate, it is difficult to disperse in the polymer. The presence of silicon slag can effectively improve the dispersibility of calcium carbonate in the polymer. DETAILED DESCRIPTION

[0023] The embodiments of the application will be described in detail below with reference to the examples, but those skilled in the art will understand that the following examples are only for illustration of the application and should not be regarded as limiting the scope of the application.

[0024] Example 1

[0025] 1kg of phosphogypsum was weighed, mixed uniformly with 1g of POF material (COF-LZU1), and then added into a reaction kettle. 12.5L of aqueous solution was added, when the temperature reached 40℃, ammonia water with a sulfur-nitrogen ratio of 40% (the mass concentration of ammonia water was 26%) was added, and carbon dioxide gas with a flow rate of 300PL / Pin was introduced. When the content of sulfate in the reaction solution reached the maximum value, the reaction was completed, and the filter cake was dried in an oven at 80℃. After drying, the modified nano calcium carbonate was prepared.

[0026] According to the detection standard of GB / T 19590-2011, the activation rate of the product was 96%, the oil absorption value (DOP) was about 14g / 100g CaCO3, the average particle size was 60nm, and the viscosity was 21.3Pa·s.

[0027] Example 2

[0028] Take 1 kg of phosphogypsum, mixed with 2.5 g of POF material (COF-LZU1) uniformly after adding into the reactor, add aqueous solution, when the aqueous solution 10L, the temperature reaches 30℃, with sulfur nitrogen ratio of 41% ammonia water (concentration 26%) is added, and the flow rate of 140PL / Pin carbon dioxide gas is introduced, after the reaction, washing, filter cake in 80℃ oven drying, drying is completed after the preparation of modified nano calcium carbonate. The activation rate of the product is 96%, oil absorption value (DOP) about 13g / 100g CaCO3, particle size 57nm, viscosity 21.7Pa·s.

[0029] Example 3

[0030] Take 1 kg of phosphogypsum, mixed with 3.5 g of POF material (COF-LZU1) uniformly after adding into the reactor, add aqueous solution 6.5L, the temperature reaches 40℃, with sulfur nitrogen ratio of 43% ammonia water (concentration 26%) is added, and the flow rate of 140PL / Pin carbon dioxide is introduced, after the reaction, washing, filter cake in 80℃ oven drying, drying is completed after the preparation of modified nano calcium carbonate. The activation rate of the product is 99%, oil absorption value (DOP) about 12g / 100g CaCO3, particle size 53nm, viscosity 23.6Pa·s.

[0031] Example 4

[0032] Take 1 kg of phosphogypsum, mixed with 5 g of POF material (COF-LZU1) uniformly after adding into the reactor, add aqueous solution 10L, the temperature reaches 50℃, with sulfur nitrogen ratio of 43% ammonia water (concentration 26%) is added, and the flow rate of 100PL / Pin carbon dioxide gas is introduced, after the reaction, washing, filter cake in 80℃ oven drying, drying is completed after the preparation of modified nano calcium carbonate, the activation rate of the product is 97%, oil absorption value (DOP) about 11g / 100g CaCO3, particle size 58nm, viscosity 22.3Pa·s.

[0033] Example 5

[0034] Take 1 kg of phosphogypsum, mixed with 4 g of POF material (COF-LZU1) uniformly after adding into the reactor, add aqueous solution 6.5L, the temperature reaches 30℃, with sulfur nitrogen ratio of 44% ammonia water (concentration 26%) is added, and the flow rate of 250PL / Pin carbon dioxide gas is introduced, after the reaction, washing, filter cake in 80℃ oven drying, drying is completed after the preparation of modified nano calcium carbonate, the activation rate of the product is 98%, oil absorption value (DOP) about 15g / 100g CaCO3, particle size 54nm, viscosity 23.1Pa·s.

[0035] Example 6

[0036] Example 1 1 kg of phosphogypsum was weighed into a reactor, and 5 g of POF material (COF-LZU1) was added thereto. Then, 6.5 L of an aqueous solution was added, and when the temperature reached 50°C, ammonia water (concentration 26%) was added at a sulfur-nitrogen ratio of 45%, and carbon dioxide gas was introduced at a rate of 100 PL / Pin. After the reaction was completed, the product was washed and filtered, and the filter cake was dried in an oven at 80°C. The modified nano calcium carbonate was prepared after drying, and the activation rate of the product was 96%, the oil absorption value (DOP) was about 12 g / 100 g CaCO3, the particle size was 61 nm, and the viscosity was 22.7 Pa·s.

[0037] Example 7

[0038] Example 3 was used as a basis, and the only difference was that the amount of POF added was 0.51%. The modified nano calcium carbonate was prepared, and the activation rate of the product was 99%, the oil absorption value (DOP) was about 12 g / 100 g CaCO3, the particle size was 126 nm, and the viscosity was 23.7 Pa·s.

[0039] Example 8

[0040] Example 3 was used as a basis, and the only difference was that the amount of POF added was 0.09%. The modified nano calcium carbonate was prepared, and the activation rate of the product was 91%, the oil absorption value (DOP) was about 19 g / 100 g CaCO3, the particle size was 213 nm, and the viscosity was 19.7 Pa·s.

[0041] Example 9

[0042] Example 3 was used as a basis, and the only difference was that the sulfur-nitrogen ratio was 35%. The modified nano calcium carbonate was prepared, and the activation rate of the product was 99%, the oil absorption value (DOP) was about 12 g / 100 g CaCO3, the particle size was 122 nm, and the viscosity was 23.1 Pa·s.

[0043] Example 10

[0044] Example 3 was used as a basis, and the only difference was that the sulfur-nitrogen ratio was 55%. The modified nano calcium carbonate was prepared, and the activation rate of the product was 86%, the oil absorption value (DOP) was about 23 g / 100 g CaCO3, the particle size was 458 nm, and the viscosity was 17.2 Pa·s.

[0045] Example 11

[0046] Example 3 was used as a basis, and the only difference was that the temperature was 55°C. The modified nano calcium carbonate was prepared, and the activation rate of the product was 98%, the oil absorption value (DOP) was about 12 g / 100 g CaCO3, the particle size was 176 nm, and the viscosity was 22.7 Pa·s.

[0047] Comparative Example 1

[0048] Based on Example 3, the only difference is that no POF material is added. Nano calcium carbonate is prepared, the activation rate of the product is 0%, the oil absorption value (DOP) is about 53.2 g / 100 g CaCO3, the particle size is 576 nm, and the viscosity is 3.7 Pa·s.

[0049] The calcium carbonate prepared in the above examples and comparative examples is used as a filler for the production of plastics, and the raw material formula is: PVC-SG5 resin 100 parts, calcium carbonate 50 parts, stearic acid 1 part, composite stabilizer 4 parts, ACR-401 5 parts, and titanium dioxide 1 part. The finished plastic product is detected, and the specific conditions are shown in Table 1 below, wherein the control group is a commercially available nano calcium carbonate.

[0050] Table 1

[0051]

[0052] From the experimental data of Examples 1-6 and the control group, it can be seen that the modified nano calcium carbonate prepared in Examples 1-6 applied to plastic products has excellent tensile strength, elongation at break, bending strength, and Brinell hardness compared to the control group. In Examples 7-8, the amount of POF exceeds the limited range, resulting in an increase in particle size, so the strength of the plastic parts prepared from the modified nano calcium carbonate prepared in Examples 1-6 is significantly reduced. In Example 9, the sulfur-nitrogen ratio is lower than the limit, resulting in a too fast reaction and large particles, so the tensile strength, elongation at break, and bending strength are significantly reduced. In Example 10, the sulfur-nitrogen ratio exceeds the limit, resulting in incomplete reaction and the presence of calcium sulfate particles, which have large particles, low activity, high oil absorption value, and low viscosity, so the strength of the parts is reduced. In Example 11, the reaction temperature is lower than the limit, resulting in a too fast reaction and large particles, so the tensile strength, elongation at break, and bending strength are significantly reduced. In Comparative Example 1, there is no POF, resulting in large particles, low activity, high oil absorption value, and low viscosity, so the plastic reinforcing effect is reduced.

[0053] It should be noted that the above examples are only used to illustrate the technical solutions of the present application, and are not limited thereto; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that they can modify the technical solutions described in the foregoing examples, or make equivalent substitutions for part or all of the technical features; and these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing modified calcium carbonate using phosphogypsum, characterized by, The method comprises the following steps: S1, taking phosphogypsum as raw material, adding COF-LZU1 and water to mix uniformly to prepare slurry; S2, adding ammonia water to the slurry, and controlling the sulfur-nitrogen ratio to be 40-50%; S3, passing carbon dioxide gas into the slurry of S2 to react, filtering and washing after the reaction is completed, and drying the filter residue to obtain POF material modified calcium carbonate.

2. The method of claim 1, wherein: The content of calcium sulfate in the phosphogypsum is 80-90 wt%.

3. The method of claim 1, wherein: The added amount of COF-LZU1 is 0.1-0.5% of the mass of the phosphogypsum.

4. The method of claim 1, wherein: The solid-liquid mass ratio is controlled to be 5%-20% when water is added in S1.

5. The method of claim 1, wherein: The temperature is controlled to be 20-50℃ in S2.

6. The method of claim 1, wherein: The drying temperature of the filter residue is 80℃-120℃, and the drying time is 8~12h.

7. Modified calcium carbonate prepared by the method according to any one of claims 1-6.

8. Application of the modified calcium carbonate according to claim 7 in plastic products.

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