Method for preparing Ca-MOF material through two-step mechanochemical treatment of waste phosphogypsum

Abstract

The invention belongs to the field of preparation of a metal-organic framework (MOF) material by upgrading chemical recovery of waste ardealite, and discloses a method for preparing a Ca-MOF material by two-step mechanochemical treatment of waste ardealite, which comprises the following steps: (1) carrying out dry reaction on solid polybasic organic carboxylic acid and a solid strong alkali compound under the mechanochemical action to obtain carboxylate; and (2) carrying out dry reaction on the phosphogypsum and carboxylate under the mechanochemical action again, and then washing and drying the product to obtain the Ca-MOF material. The preparation method comprises the following steps: by taking ardealite as a raw material, carrying out two-step mechanochemical treatment, reacting polybasic organic carboxylic acid with a strong alkali compound to generate polybasic organic carboxylate, and then reacting the polybasic organic carboxylate with ardealite to prepare the Ca-MOF material. The method disclosed by the invention is green and environment-friendly, efficient in reaction and low in cost, and realizes upgrading, recycling and reusing of the phosphogypsum and efficient preparation of the high-added-value MOF material.

Description

Technical Field

[0001] The present invention belongs to the field of upgrading chemical recycling of waste phosphogypsum to prepare metal-organic framework (MOF) materials. More specifically, it relates to a method for preparing Ca-MOF materials by two-step mechanochemical treatment of waste phosphogypsum, and in particular, MOF materials can be prepared using waste phosphogypsum. Background Art

[0002] Phosphogypsum is a by-product of the extraction of phosphoric acid by sulfuric acid decomposition of phosphate rock, mainly from the phosphate fertilizer industry. The main component of phosphogypsum is calcium sulfate dihydrate (CaSO4·2H2O), accounting for more than 90%. The remaining components are complex, mainly including phosphorus, fluorine and organic impurities. At present, the global stockpile of phosphogypsum has reached 6 billion tons and is increasing rapidly at a rate of 200 million tons per year. The global comprehensive utilization rate of phosphogypsum is only about 25%. Most of the unutilized phosphogypsum is disposed of by stacking or discharged into the ocean. The impurities contained in phosphogypsum generate a large amount of hydrogen ions under ionization, which seep into the soil through rain leaching and infiltration, causing acidification of groundwater and soil environment, destroying the ecological environment, and causing the death of a large number of animals and plants exposed to acidified water. At the same time, the phosphorus element in phosphogypsum will enter rivers, lakes and seas with rainwater scouring, causing eutrophication of water bodies. The soluble fluorine substances in phosphogypsum can also be transmitted to humans through the food chain, leading to diseases such as osteoporosis in humans. In this context, how to efficiently recycle and treat waste phosphogypsum and convert it into valuable resources has become the focus of attention of the general public. The traditional application methods for treating waste phosphogypsum mainly include its utilization in four fields: construction, chemical industry, agriculture and environment. The utilization amount of phosphogypsum in building materials accounts for more than 40% of its total application amount. Mainly by using phosphogypsum instead of natural gypsum to prepare cement retarders, but the impurities in phosphogypsum will cause negative effects such as accelerating the early hydration rate of cement. To improve this situation, phosphogypsum was modified by adding appropriate amounts of carbide slag and fly ash, and it was found that the strength of the modified phosphogypsum increased significantly, the contents of soluble phosphorus and fluorine decreased significantly, and the setting time of the prepared portland cement was significantly shorter than that of the original phosphogypsum. In addition, phosphogypsum was made into spheres by chemical modification and physical grinding, and the modified phosphogypsum spheres could significantly shorten the initial and final setting times of cement and improve the degree of hydration in the later stage. However, using phosphogypsum to produce building materials still faces problems such as saturation of the building materials market, reduced demand for phosphogypsum, and low added value of phosphogypsum conversion.

[0003] Converting waste phosphogypsum into high-value-added metal-organic frameworks (MOFs) is a new way for the recycling and reuse of waste phosphogypsum. MOF, also known as coordination polymer or hybrid compound, is a porous crystalline material self-assembled through the metal coordination complexation between organic ligands and metals. Due to its characteristics such as porosity, large specific surface area, presence of unsaturated metal coordination sites, diverse structures, and easy functionalization modification, it has attracted much attention in recent years. The versatility of its crystal structure and the adjustable nature of its porosity properties make MOF materials of interest for various adsorption-related applications and are widely used in fields such as gas storage, catalysis, drug delivery, fluorescence detection, and solar interface photothermal conversion. Currently, there is only one reported article on preparing MOF using waste phosphogypsum. That is, after dissolving phosphogypsum with an alkaline aqueous solution, the silicon dioxide and aluminum components in the filtrate are converted into Cancrinte zeolite through hydrothermal reaction; after the residue is treated with alkali, mainly Ca(OH)2, under solvothermal reactions such as N,N-dimethylformamide (DMF), Ca(OH)2 combines with organic acids to be converted into various Ca-MOF materials (A.M. Yimer, A.H. Assen, I.E. Mghaimimi, O. Lakbita, K. Adil, Y. Belmabkhout, Unlocking the potential of phosphogypsum waste: Unified synthesis of functional metal-organic frameworks and zeolite via a sustainable valorization route, Chem. Eng. J. 479 (2024) 147902). This method has a complex reaction process and requires the use of a large amount of organic solvents, high temperature, and high pressure, making it difficult to achieve large-scale production. Therefore, there is an urgent need for a green, environmentally friendly, highly efficient, and low-cost method to upgrade and recycle waste phosphogypsum to prepare Ca-MOF materials. Summary of the Invention

[0004] Aiming at the above defects or improvement requirements of the prior art, the purpose of the present invention is to provide a method for preparing Ca-MOF materials by two-step mechanochemical treatment of waste phosphogypsum. Using phosphogypsum (especially waste phosphogypsum) as the raw material, through two-step mechanochemical treatment, first react a polycarboxylic acid with a strong base compound to generate a polycarboxylate salt, and then react the polycarboxylate salt with phosphogypsum to prepare Ca-MOF materials. The method of the present invention is green, environmentally friendly, highly efficient, and low-cost, realizing the upgrading, recycling, and reuse of phosphogypsum (especially waste phosphogypsum) and the efficient preparation of high-value-added MOF materials.

[0005] To achieve the above object, according to the present invention, there is provided a method for preparing Ca-MOF material by two-step mechanochemical treatment of phosphogypsum, which is characterized by including the following steps:

[0006] (1) Subject the solid polybasic organic carboxylic acid and the solid strong base compound to a dry reaction under mechanochemical action to obtain carboxylate salt;

[0007] (2) Subject the phosphogypsum and the carboxylate salt obtained in step (1) to a dry reaction again under mechanochemical action, and then wash and dry the product to obtain the Ca-MOF material.

[0008] As a further preference of the present invention, in step (1), the mechanochemical action is ball milling;

[0009] In step (2), the mechanochemical action is ball milling.

[0010] As a further preference of the present invention, in step (1), the polybasic organic carboxylic acid is one or more of terephthalic acid, trimellitic acid and pyromellitic acid.

[0011] ]>As a further preference of the present invention, in step (1), the solid strong base compound is one or more of sodium hydroxide and potassium hydroxide.

[0012] As a further preference of the present invention, in step (1), the molar ratio of the strong base compound to the polybasic organic carboxylic acid is 2-4.

[0013] As a further preference of the present invention, in step (1), the rotation speed of the ball milling treatment is 100-600 r / min, and the time is 0.5-5 h.

[0014] As a further preference of the present invention, in step (2), the molar ratio of calcium sulfate dihydrate contained in the phosphogypsum to the polybasic organic carboxylic acid in step (1) is 2-1.

[0015] As a further preference of the present invention, in step (2), the rotation speed of the ball milling treatment is 100-600 r / min, and the time is 0.5-5 h.

[0016] As a further preference of the present invention, in step (2), the phosphogypsum is waste phosphogypsum, and the mass percentage content of calcium sulfate dihydrate is more than 95%.

[0017] Through the above technical solution conceived by the present invention, compared with the prior art, the present invention reacts phosphogypsum (especially waste phosphogypsum) under mechanochemical action to prepare Ca-MOF materials, including a tandem process of two-step mechanochemical treatment. That is, under mechanochemical action, a polycarboxylic acid is first reacted with a strong base compound to form a polycarboxylate, and then the polycarboxylate is reacted with phosphogypsum to prepare Ca-MOF materials. Specifically analyzed, under mechanochemical action, the polycarboxylic acid reacts with the strong base compound to form a salt; thereafter, the calcium ions in phosphogypsum and the carboxylate ions in the carboxylate salt undergo a coordination reaction under mechanochemical action to form a Ca-MOF material with good crystallinity. Both of these two-step mechanochemical treatment processes are dry processes and do not involve any organic solvents and high temperature and high pressure conditions. The method of the present invention has the advantages of being green and environmentally friendly, simple to operate, highly efficient in reaction, low in cost, etc., and can prepare MOF materials of various crystal forms, and the Ca-MOF materials have good crystallinity.

[0018] Specifically speaking, the method of the present invention can achieve the following beneficial effects:

[0019] (1) Compared with the traditional engineering field recycling methods such as using phosphogypsum as a cement retarder, building gypsum material, filling material, etc., the present invention turns to the chemical field and selects the mechanochemical method to recycle and convert phosphogypsum into high-value-added MOF materials. The field span is large and the recycling results are good, significantly improving the chemical upgrading circular economy, environmental and social benefits of phosphogypsum.

[0020] (2) Compared with the only reported method of preparing MOF materials from phosphogypsum by the solvothermal method, the method used in the present invention is green and environmentally friendly, does not use organic solvents, is at room temperature and normal pressure, is highly efficient, has a high yield, and is easy to realize large-scale production.

[0021] (3) The present invention provides a new way for the upgrading and recycling of phosphogypsum waste. By utilizing this industrial waste phosphogypsum, compared with calcium salts such as calcium nitrate, calcium sulfate, and calcium chloride, which have a purchase cost, the cost of phosphogypsum is extremely low. The present invention uses phosphogypsum as a raw material to prepare high-value-added MOF materials, realizing the high-value utilization of phosphogypsum, turning waste into treasure, reducing resource waste, and conforming to the concept of sustainable development.

[0022] (4) The present invention preferably controls the molar ratio of calcium sulfate dihydrate and organic carboxylic acid ligand contained in phosphogypsum to be 2-1, and preferably controls the ball milling speed to be 100-600 r / min, ensuring that the organic carboxylic acid ligand is fully coordinated with metal calcium ions to form a MOF material with good crystallinity, while avoiding the precipitation of metal oxides.

[0023] In summary, the present invention uses two-step mechanochemical treatment to convert waste phosphogypsum into MOF materials, which has the advantages of environmental friendliness, high reaction efficiency, low cost, etc., and realizes the upgraded chemical recycling and reuse of waste phosphogypsum. This method solves the problem of recycling and reuse of urban and industrial waste phosphogypsum, provides a new green way for the upgraded chemical recycling of a large amount of waste phosphogypsum, realizes "turning waste into treasure", contributes to sustainable development and "carbon neutrality", and has high environmental, economic and social effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 X-ray diffraction pattern of the Ca-MOF material prepared from phosphogypsum and terephthalic acid in Example 1.

[0025] Figure 2 X-ray diffraction pattern and scanning electron microscope image of the Ca-MOF material prepared from phosphogypsum and pyromellitic acid in Example 2; wherein, Figure 2 a in Figure 2 corresponds to the X-ray diffraction pattern,

[0026] Figure 3 X-ray diffraction pattern of the Ca-MOF material prepared from phosphogypsum and trimesic acid in Example 3.

[0027] Figure 4 Scanning electron microscope image and infrared spectrum of the Ca-MOF material prepared from phosphogypsum and terephthalic acid in Example 4; wherein, Figure 4 a in Figure 4 corresponds to the scanning electron microscope image,

[0028] Figure 5 Infrared spectrum of the Ca-MOF material prepared from phosphogypsum and trimesic acid in Example 5.

[0029] Figure 6 Scanning electron microscope image and infrared spectrum of the Ca-MOF material prepared from phosphogypsum and pyromellitic acid in Example 6; wherein, Figure 6 a in Figure 6 corresponds to the scanning electron microscope image,

[0030] Figure 7 Scanning electron microscope image and infrared spectrum of the Ca-MOF material prepared from phosphogypsum and terephthalic acid in Example 7; wherein, Figure 7 a in Figure 7 corresponds to the scanning electron microscope image,

[0031] Figure 8Scanning electron microscope image of the Ca-MOF material prepared using phosphogypsum and pyromellitic acid in Example 8.

[0032] Figure 9 X-ray diffraction pattern of the product prepared using phosphogypsum and terephthalic acid in Comparative Example 1.

[0033] Figure 10 X-ray diffraction pattern of the product prepared using phosphogypsum and terephthalic acid in Comparative Example 2. Detailed implementation manners

[0034] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0035] The phosphogypsum used in the following examples is the waste phosphogypsum powder provided by a phosphogypsum fertilizer production enterprise (phosphogypsum is a by-product of the phosphate fertilizer industry), with a calcium sulfate dihydrate content of 95 wt%, and the main impurities are silicon dioxide, magnesium, phosphoric acid, etc.

[0036] The mechanochemical treatment in the following examples is ball milling treatment, and all ball milling is dry ball milling and is carried out in an air environment at normal temperature and pressure. The two-step ball milling process can be carried out successively in the same ball milling tank. Of course, the ball milling tank can also be replaced.

[0037] Example 1

[0038] (1) After mixing 11.613 g of terephthalic acid and 8.0 g of sodium hydroxide (i.e., the molar ratio of sodium hydroxide to terephthalic acid is 2) evenly, load them into a ball milling tank, add steel balls, and ball mill at a rotation speed of 100 r / min for 0.5 h to collect the product disodium terephthalate.

[0039] (2) Add 18.1 g of phosphogypsum (i.e., the molar ratio of calcium sulfate dihydrate in phosphogypsum to terephthalic acid is 1) to the ball milling tank and ball mill at a rotation speed of 100 r / min for 3 h. The product is washed and dried to obtain the Ca-MOF material, and the yield is 96 wt%. Since terephthalic acid is used as the raw material in this example, the corresponding Ca-MOF material prepared belongs to the Ca-BDC material.

[0040] Figure 1 X-ray diffraction spectrum of the Ca-MOF prepared in Example 1. It can be seen from the X-ray powder diffraction spectrum that the Ca-MOF material has significant characteristic diffraction peaks of Ca-BDC, indicating the successful synthesis of Ca-BDC.

[0041] Example 2

[0042] (1) After mixing 25.415 g of pyromellitic acid and 22.444 g of potassium hydroxide (i.e., the molar ratio of potassium hydroxide to pyromellitic acid is 4) evenly, they are loaded into a ball milling jar, steel balls are added, and ball milling is carried out at a rotation speed of 300 r / min for 1 h to collect the product potassium pyromellitate.

[0043] (2) 36.2 g of phosphogypsum (i.e., the molar ratio of calcium sulfate dihydrate in phosphogypsum to pyromellitic acid is 2) is added to the ball milling jar, and ball milling is carried out at a rotation speed of 300 r / min for 5 h. The product is washed and dried to obtain a Ca-MOF material with a yield of 89 wt%. Since pyromellitic acid is used as the raw material in this example, the prepared Ca-MOF material belongs to the Ca-BTEC material.

[0044] Figure 2 a in [reference] is the X-ray diffraction pattern of the Ca-MOF material prepared in Example 2. It can be seen from the X-ray powder diffraction pattern that the Ca-MOF material has significant characteristic diffraction peaks of Ca-BTEC, indicating the successful synthesis of Ca-BTEC. Figure 2 b in [reference] is the scanning electron microscope image of the Ca-MOF material prepared in Example 2. It can be seen from the scanning electron microscope image that the morphology of the Ca-MOF material is relatively regular, being a block structure with a size of 1 - 2 μm.

[0045] Example 3

[0046] (1) After mixing 21.014 g of trimellitic acid and 12.0 g of sodium hydroxide (i.e., the molar ratio of sodium hydroxide to trimellitic acid is 3) evenly, they are loaded into a ball milling jar, steel balls are added, and ball milling is carried out at a rotation speed of 600 r / min for 2 h to collect the product trisodium trimellitate.

[0047] (2) 27.2 g of phosphogypsum (i.e., the molar ratio of calcium sulfate dihydrate in phosphogypsum to trimellitic acid is 1.5) is added to the ball milling jar, and ball milling is carried out at a rotation speed of 600 r / min for 3 h. The product is washed and dried to obtain a Ca-MOF material with a yield of 98 wt%.

[0048] Figure 3 [reference] is the X-ray diffraction pattern of the Ca-MOF material prepared in Example 3. It can be seen from the X-ray powder diffraction pattern that the Ca-MOF material has significant characteristic diffraction peaks, indicating the successful synthesis of Ca-MOF.

[0049] Example 4

[0050] (1) After mixing 11.613 g of terephthalic acid and 8.0 g of sodium hydroxide (i.e., the molar ratio of sodium hydroxide to terephthalic acid is 2) evenly, load them into a ball mill jar, add steel balls, and ball mill at a speed of 400 r / min for 3 h, then collect the product disodium terephthalate.

[0051] (2) Add 18.1 g of phosphogypsum (i.e., the molar ratio of phosphogypsum to calcium sulfate dihydrate in it to terephthalic acid is 1) into the ball mill jar, and ball mill at a speed of 400 r / min for 2 h. The product is washed and dried to obtain the Ca-MOF material, and the yield is 99 wt%.

[0052] Figure 4 Figure a is the scanning electron microscope image of the Ca-MOF material prepared in Example 4. It can be seen from the scanning electron microscope image that the morphology of the Ca-MOF material is relatively regular, being a straight cylindrical rod-like structure with a size of 1 - 2 μm.

[0053] Figure 4 Figure b is the infrared spectrum of the Ca-MOF prepared in Example 4. The infrared spectrum of Ca-MOF has an obvious Ca-O stretching vibration peak, indicating the successful preparation of Ca-MOF.

[0054] Example 5

[0055] (1) After mixing 21.014 g of trimellitic acid and 16.833 g of potassium hydroxide (i.e., the molar ratio of potassium hydroxide to trimellitic acid is 3) evenly, load them into a ball mill jar, add steel balls, and ball mill at a speed of 200 r / min for 4 h, then collect the product tripotassium trimellitate.

[0056] (2) Add 27.2 g of phosphogypsum (i.e., the molar ratio of calcium sulfate dihydrate in phosphogypsum to trimellitic acid is 1.5) into the ball mill jar, and ball mill at a speed of 200 r / min for 0.5 h. The product is washed and dried to obtain the Ca-MOF material, and the yield is 95 wt%.

[0057] Figure 5 Figure is the infrared spectrum of the Ca-MOF prepared in Example 5. The infrared spectrum of Ca-MOF has an obvious Ca-O stretching vibration peak, indicating the successful preparation of Ca-MOF.

[0058] Example 6

[0059] (1) After mixing 25.415 g of pyromellitic acid and 16.0 g of sodium hydroxide (i.e., the molar ratio of sodium hydroxide to pyromellitic acid is 4) evenly, load them into a ball mill jar, add steel balls, and ball mill at a speed of 500 r / min for 5 h, then collect the product tetrasodium pyromellitate.

[0060] (2) Add 36.2 g of phosphogypsum (i.e., the molar ratio of calcium sulfate dihydrate in phosphogypsum to pyromellitic acid is 2) to the ball milling tank and ball mill for 1 h at a rotation speed of 500 r / min. The product is washed and dried to obtain the Ca-MOF material, and the yield is 97 wt%.

[0061] Figure 6 In a, it is the scanning electron microscope image of the Ca-MOF material prepared in Example 6. It can be seen from the scanning electron microscope image that the morphology of the Ca-MOF material is relatively regular and it is a block structure.

[0062] Figure 6 In b, it is the infrared spectrum of the Ca-MOF prepared in Example 6. The infrared spectrum of Ca-MOF has obvious Ca-O stretching vibration peaks, indicating the successful preparation of Ca-MOF.

[0063] Example 7

[0064] (1) Take 11.613 g of terephthalic acid and 11.222 g of potassium hydroxide (i.e., the molar ratio of potassium hydroxide to terephthalic acid is 2), mix them evenly, put them into the ball milling tank, add steel balls, and ball mill for 2 h at a rotation speed of 300 r / min, and collect the product dipotassium terephthalate.

[0065] (2) Add 18.1 g of phosphogypsum (i.e., the molar ratio of calcium sulfate dihydrate in phosphogypsum to terephthalic acid is 1) to the ball milling tank and ball mill for 3 h at a rotation speed of 300 r / min. The product is washed and dried to obtain the Ca-MOF material, and the yield is 99 wt%.

[0066] Figure 7 In a, it is the infrared spectrum of the Ca-MOF prepared in Example 7. The infrared spectrum of Ca-MOF has obvious Ca-O stretching vibration peaks, indicating the successful preparation of Ca-MOF.

[0067] Figure 7 In b, it is the scanning electron microscope image of the Ca-MOF material prepared in Example 7. It can be seen from the scanning electron microscope image that the morphology of the Ca-MOF material is relatively regular and it is a straight cylindrical rod structure with a size of 1 - 2 μm.

[0068] Example 8

[0069] (1) Take 25.415 g of pyromellitic acid and 16.0 g of sodium hydroxide (i.e., the molar ratio of sodium hydroxide to pyromellitic acid is 4), mix them evenly, put them into the ball milling tank, add steel balls, and ball mill for 1 h at a rotation speed of 400 r / min, and collect the product tetrasodium pyromellitate.

[0070] (2) 36.2 g of phosphogypsum (i.e., the molar ratio of calcium sulfate dihydrate in phosphogypsum to pyromellitic acid is 2) was added to the ball milling tank and ball milled at a rotation speed of 400 r / min for 3 h. The product was washed and dried to obtain the Ca-MOF material with a yield of 97 wt%.

[0071] Figure 8 It is the scanning electron microscope image of the Ca-MOF material prepared in Example 8. It can be seen from the scanning electron microscope image that the morphology of the Ca-MOF material is relatively regular, being a block structure with a size of 1 - 2 μm.

[0072] Comparative Example 1

[0073] 11.613 g of terephthalic acid and 18.1 g of phosphogypsum (i.e., the molar ratio of calcium sulfate dihydrate in phosphogypsum to terephthalic acid is 1) were mixed evenly, loaded into the ball milling tank, steel balls were added, and ball milled at a rotation speed of 400 r / min for 4 h. The product was washed and dried to obtain the product with a yield of 81 wt%.

[0074] Figure 9 It is the X-ray powder diffraction pattern of the product. It can be seen from the X-ray powder diffraction pattern that the product is a mixture of terephthalic acid and phosphogypsum, and no Ca-MOF is formed. Figure 9 What is mainly visible in it is the diffraction peak intensity of terephthalic acid crystals. This is because the diffraction peak intensity of terephthalic acid crystals is high and there is a large amount remaining, resulting in its crystal diffraction peak intensity being much higher than that of phosphogypsum. Therefore, the crystal diffraction peak intensity of phosphogypsum is low, but after local magnification Figure 9 the crystal diffraction peaks of phosphogypsum can be seen (e.g., at 2θ of 25.3°, 31.4°, 38.7°, 40.8°).

[0075] Comparative Example 2

[0076] 11.613 g of terephthalic acid, 8.0 g of sodium hydroxide and 18.1 g of phosphogypsum (i.e., the molar ratio of calcium sulfate dihydrate in phosphogypsum to terephthalic acid is 1) were mixed evenly, loaded into the ball milling tank, steel balls were added, and ball milled at a rotation speed of 400 r / min for 4 h. After washing and drying, the product was obtained with a yield of 72 wt%.

[0077] Figure 10 It is the X-ray powder diffraction pattern of the product. It can be seen from the X-ray powder diffraction pattern that the product is a mixture of terephthalic acid and phosphogypsum, Ca-MOF is formed but the reaction is incomplete, and by-product Ca(OH)2 is formed. Part of the terephthalic acid reacts with sodium hydroxide to form disodium terephthalate which is soluble in water and is washed away, and the remaining terephthalic acid and phosphogypsum remain.

[0078] The above examples are only for illustration. For example, in addition to ball milling treatment, mechanochemical action can also adopt manual grinding.

[0079] Those skilled in the art can easily understand that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing Ca-MOF materials by two-step mechanochemical treatment of phosphogypsum, characterized in that, It includes the following steps: (1) Carry out a dry reaction on the solid polybasic organic carboxylic acid and the solid strong base compound under mechanochemical action to obtain carboxylate; (2) Carry out a dry reaction on phosphogypsum and the carboxylate obtained in step (1) again under mechanochemical action, and then wash and dry the product to obtain the Ca-MOF material.

2. The method according to claim 1, characterized in that In step (1), the mechanochemical action is ball milling; In step (2), the mechanochemical action is ball milling.

3. The method according to claim 1, characterized in that In step (1), the polybasic organic carboxylic acid is one or more of terephthalic acid, trimellitic acid and pyromellitic acid.

4. The method according to claim 1, characterized in that, In step (1), the solid strong base compound is one or more of sodium hydroxide and potassium hydroxide.

5. The method according to claim 1, wherein In step (1), the molar ratio of the strong base compound to the polybasic organic carboxylic acid is 2-4.

6. The method according to claim 2, wherein In step (1), the rotation speed of the ball milling treatment is 100-600 r / min, and the time is 0.5-5 h.

7. The method according to claim 1, wherein In step (2), the molar ratio of calcium sulfate dihydrate contained in the phosphogypsum to the polybasic organic carboxylic acid in step (1) is 2-1.

8. The method according to claim 2, wherein In step (2), the rotation speed of the ball milling treatment is 100-600 r / min, and the time is 0.5-5 h.

9. The method according to claim 1, wherein In step (2), the phosphogypsum is waste phosphogypsum, and the mass percentage content of calcium sulfate dihydrate is more than 95%.

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