A non-hazardous solid waste composite and a method of making the same

Abstract

The present application relates to the technical field of environmental protection, and particularly relates to a harmless solid waste compound and a preparation method thereof, wherein the preparation method of the harmless solid waste compound comprises the following steps: mixing phosphogypsum, sludge and a solidification accelerator to prepare a slurry, mixing a persulfate with a solvent to prepare a persulfate solution, adding the persulfate solution into the slurry to stand and solidify, and finally performing roasting treatment. The present application not only realizes the harmless treatment of the phosphogypsum, thereby greatly improving the mechanical properties and environmental adaptability of the building gypsum prepared from the phosphogypsum, but also realizes the synergistic treatment of the sludge and the phosphogypsum, thereby achieving the purpose of waste treatment by waste.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of environmental protection, in particular to a harmless solid waste compound and a preparation method thereof. BACKGROUND

[0002] Sludge is a paste-like material prone to corruption and stink produced in the process of sewage treatment, and its composition is extremely complex. The physical properties and multi-edge and unstable chemical properties of sludge, such as high water content and loose particle structure, not only make the treatment process consume a huge amount of money, but also make the efficient treatment still have certain technical difficulties. Therefore, the sludge treatment and disposal problem has become a heavy burden of the municipal sewage plant, and even a huge obstacle to the normal operation of some sewage plants.

[0003] Phosphogypsum is a large amount of industrial waste produced in the process of wet-process phosphoric acid production. Every production of 1 ton of phosphoric acid will produce 4.5-5 tons of phosphogypsum. The main component of phosphogypsum is calcium sulfate, although it also contains a small amount of phosphorus and fluorine, but the cost of its regeneration is high, so it is mainly land stored, that is, a phosphogypsum slag field is built by using the principle of engineering. However, land storage of phosphogypsum not only occupies a large amount of land, but also brings great threat to the environment. For example, phosphogypsum will form strong acid wastewater mainly containing phosphoric acid during long-term open-air storage, and carry other dissociated harmful components to penetrate into the ground, eventually leading to leaching pollution of soil, surface water and shallow groundwater, so it is necessary to seek a reasonable harmless treatment approach for phosphogypsum to realize the sustainable development of phosphate fertilizer industry and the high utilization of phosphogypsum.

[0004] Phosphogypsum can be used as raw material for producing building materials to realize resource utilization, but the soluble phosphorus, eutectic phosphorus and soluble fluorine in phosphogypsum will affect the performance of building materials made of phosphogypsum, and easy cracking, weathering, frosting and other phenomena will occur, which will also lead to the decline of the mechanical properties of the products, thereby limiting the resource utilization of phosphogypsum. SUMMARY

[0005] Therefore, the technical problem to be solved by the present application is to overcome the defects that the resource utilization of phosphogypsum and sludge is limited, and to provide a harmless solid waste compound and a preparation method thereof solving the above problems.

[0006] To achieve the above purpose, the present application provides the following technical scheme:

[0007] A preparation method of a harmless solid waste compound, comprising: mixing phosphogypsum, sludge and a solidification accelerator to form a slurry, mixing a persulfate salt with a solvent to prepare a persulfate salt solution, adding the persulfate salt solution to the slurry for standing and solidification, and finally performing calcination treatment.

[0008] Preferably, the mass ratio of the phosphogypsum, sludge and curing accelerator is (50-100):10:(1-5).

[0009] Preferably, the curing accelerator is a Ca / Mg / Al composite material;

[0010] The process for obtaining the Ca / Mg / Al composite material is as follows: aluminum salt, magnesium salt and calcium salt are dissolved in a solvent to form a mixed solution, and then a precipitant is added to carry out a hydrothermal reaction.

[0011] Preferably, in the mixed solution, the mass ratio of the aluminum salt, magnesium salt, calcium salt and solvent is 5:(1-5):(1-5):100;

[0012] And / or, the solvent is water;

[0013] And / or, the precipitant is an alkali; the concentration of the alkali is 2-5 mol / L; the alkali is at least one selected from sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate;

[0014] And / or, the volume ratio of the precipitant to the mixed solution is 1:10;

[0015] And / or, the hydrothermal reaction is carried out at a temperature of 50-80°C for a duration of ≥24 hours.

[0016] Preferably, the aluminum salt is aluminum chloride;

[0017] And / or, the magnesium salt is magnesium chloride;

[0018] And / or, the calcium salt is calcium chloride.

[0019] Preferably, the phosphogypsum, curing agent, and curing accelerator are mixed by wet ball milling;

[0020] And / or, the solid-liquid ratio of the slurry is 1:2.

[0021] Preferably, the wet ball mill has a moisture content of 10%, a ball-to-material ratio of 20:1, a ball mill speed of 600 rpm / min, and a ball milling time of 30-60 min.

[0022] Preferably, the persulfate is sodium persulfate and / or potassium persulfate;

[0023] And / or, the mass ratio of the mixture obtained by mixing the persulfate solution with the phosphogypsum, curing agent, and curing accelerator is 1:5;

[0024] And / or, the solvent of the persulfate solution is water;

[0025] And / or, the concentration of the persulfate solution is 0.1-1 mol / L.

[0026] Preferably, the calcination temperature is 100-150℃ and the calcination time is 1-3 hours.

[0027] Preferably, the phosphogypsum and sludge are dried and ball-milled before mixing.

[0028] Preferably, the drying temperature is 40℃-60℃;

[0029] And / or, in the ball milling process, the ball-to-material ratio of the ball mill is 10:1, the ball milling speed is 400 rpm / min, and the ball milling time is 10-30 min;

[0030] And / or, the ball milling process is followed by sieving, wherein the sieving process uses a 100-mesh sieve.

[0031] Preferably, the sludge is sludge from a water supply plant.

[0032] The present invention also provides a harmless solid waste composite material, which is prepared by the above-described method for preparing harmless solid waste composite material.

[0033] The technical solution of this invention has the following advantages:

[0034] 1. A method for preparing a harmless solid waste composite, comprising: mixing phosphogypsum, sludge, and a solidification accelerator to form a slurry; mixing persulfate with a solvent to prepare a persulfate solution; adding the persulfate solution to the slurry and allowing it to stand and solidify; and finally, calcining the slurry. The main components of sludge are silicon dioxide, aluminum oxide, iron oxide, and silica, which have a solidification and stabilizing effect on soluble phosphorus and fluorine in phosphogypsum; adding a solidification accelerator not only promotes the reaction between phosphogypsum and sludge but also fills the pores of phosphogypsum, thereby increasing its density and strength, which is beneficial for the subsequent resource utilization of phosphogypsum; adding persulfate during calcination can extract impurities from the phosphogypsum crystal lattice, such as eutectic phosphorus and fluorine, and further solidify the released phosphorus and fluorine. In addition, persulfate, through thermal activation, generates sulfate free radicals and hydroxyl free radicals, thereby oxidizing and decomposing organic pollutants in phosphogypsum and sludge.

[0035] In addition, this method not only achieves the harmless treatment of phosphogypsum, thereby greatly improving the mechanical properties and environmental adaptability of the building gypsum prepared from phosphogypsum, but also realizes the synergistic treatment of sludge and phosphogypsum, thus achieving the goal of treating waste with waste.

[0036] 2. In the preparation method of the harmless solid waste composite provided by the present invention, the original structure of the Ca / Mg / Al composite material changes during the ball milling process of mixing with phosphogypsum and sludge, and the surface chemical activity of the composite material increases, which promotes the activity of components in the sludge and thus improves the removal rate of impurities in phosphogypsum. Moreover, the Ca / Mg / Al composite material contains a variety of metals with different valence states, which is more conducive to increasing the surface activity and thus solidifying the impurities in phosphogypsum. In addition, the calcination heating conditions also shorten the aging time required for the solidification and stabilization of phosphogypsum, which is beneficial to practical industrial applications. Attached Figure Description

[0037] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0038] Figure 1 This is a schematic diagram of the process for preparing harmless solid waste composite material according to the present invention;

[0039] Figure 2 This is a scanning electron microscope (SEM) image of the phosphogypsum raw material in Example 1 of the present invention;

[0040] Figure 3 This is a scanning electron microscope (SEM) image of the harmless solid waste composite material in Embodiment 1 of the present invention. Detailed Implementation

[0041] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0042] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0043] Example 1

[0044] This embodiment provides a method for preparing a harmless solid waste composite material, the preparation process is as follows: Figure 1 As shown, it includes the following steps:

[0045] 1) Weigh 100g of phosphogypsum raw material and dry it at 40℃. Then, ball mill it for 10 minutes, with a ball-to-material ratio of 10:1 and a milling speed of 400 rpm / min. Finally, pass it through a 100-mesh sieve to obtain phosphogypsum powder. The phosphogypsum raw material has a plate-like structure and contains small particles formed by phosphorus and fluorine impurities. Its specific microstructure is as follows: Figure 2 As shown;

[0046] 2) Weigh 100g of sludge from the water supply plant and dry it at 40℃. Then, ball mill it for 10 minutes. The ball-to-material ratio of the ball mill is 10:1, the ball mill speed is 400 rpm / min, and finally, pass it through a 100-mesh sieve to obtain sludge powder.

[0047] 3) Weigh out 10g of aluminum chloride, 10g of magnesium chloride and 10g of calcium chloride respectively, then dissolve them in 200mL of deionized water at 50℃, add 20mL of 2mol / L sodium hydroxide, and then carry out a hydrothermal reaction at 50℃ for 24h. Finally, filter and dry in an oven at 50℃ to obtain the Ca / Mg / Al composite material.

[0048] 4) Weigh the phosphogypsum powder obtained in step 1), the sludge powder obtained in step 2), and the Ca / Mg / Al composite material obtained in step 3) according to a mass ratio of 50:10:1. Then, mix them by wet ball milling, wherein the ball-to-material ratio of the ball mill is 20:1, the ball milling speed is 600 rpm / min, and water is added to make the moisture content 10% and the ball milling is carried out for 30 minutes to obtain the mixture.

[0049] 5) Weigh 100g of the mixture obtained in step 4), and then make it into a slurry with a solid-liquid ratio of 1:2. Mix sodium persulfate with water to prepare a 0.5mol / L sodium persulfate solution. Then add 20g of the 0.5mol / L sodium persulfate solution to the slurry and let it stand to solidify, obtaining solidified phosphogypsum. Finally, place it in an oven and calcine at 100℃ for 1 hour to obtain a harmless solid waste composite. Compared with the phosphogypsum raw material, the microstructure of the obtained harmless solid waste composite has changed significantly. The plate-like structure of the phosphogypsum is destroyed, and it has a tendency to recrystallize. Its specific microstructure is as follows: Figure 3 As shown.

[0050] Example 2

[0051] The difference between this embodiment and Embodiment 1 is that in step 4), the mass ratio of phosphogypsum powder, sludge powder, and Ca / Mg / Al composite material is 70:10:3, while other conditions are the same as in Embodiment 1.

[0052] Example 3

[0053] The difference between this embodiment and Embodiment 1 is that in step 4), the mass ratio of phosphogypsum powder, sludge powder, and Ca / Mg / Al composite material is 100:10:5, while other conditions are the same as in Embodiment 1.

[0054] Example 4

[0055] This embodiment provides a method for preparing a harmless solid waste composite, comprising the following steps:

[0056] 1) Weigh 100g of phosphogypsum raw material and dry it at 60℃. Then, ball mill it for 30min. The ball-to-material ratio is 10:1 and the ball milling speed is 400rpm / min. Finally, pass it through a 100-mesh sieve to obtain phosphogypsum powder.

[0057] 2) Weigh 100g of sludge from the water supply plant and dry it at 60℃. Then, ball mill it for 30min. The ball-to-material ratio of the ball mill is 10:1 and the ball mill speed is 400rpm / min. Finally, pass it through a 100-mesh sieve to obtain sludge powder.

[0058] 3) Weigh out 10g of aluminum chloride, 10g of magnesium chloride and 10g of calcium chloride respectively, then dissolve them in 200mL of deionized water at 50℃, add 20mL of 2mol / L sodium hydroxide, and then carry out a hydrothermal reaction at 80℃ for 30h. Finally, filter and dry in an oven at 50℃ to obtain the Ca / Mg / Al composite material.

[0059] 4) Weigh the phosphogypsum powder obtained in step 1), the sludge powder obtained in step 2), and the Ca / Mg / Al composite material obtained in step 3) according to a mass ratio of 50:10:1. Then, mix them by wet ball milling. The ball-to-material ratio of the ball mill is 20:1, the ball milling speed is 600 rpm / min, and water is added to make the moisture content 10%. The mixture is then milled for 60 minutes to obtain the final mixture.

[0060] 5) Weigh 100g of the mixture obtained in step 4), and then make it into a slurry with a solid-liquid ratio of 1:2. Mix sodium persulfate with water to prepare a sodium persulfate solution with a concentration of 0.1mol / L. Then add 20g of 0.1mol / L sodium persulfate solution to the slurry and let it stand to solidify to obtain solidified phosphogypsum. Finally, put it in an oven and calcine at 100℃ for 3h to obtain a harmless solid waste composite.

[0061] Example 5

[0062] The difference between this embodiment and Example 1 is that the concentration of the sodium persulfate solution is 1 mol / L, the calcination temperature is 150°C, the calcination time is 1 h, and other conditions are the same as in Example 1.

[0063] Example 6

[0064] The difference between this embodiment and Embodiment 1 is that in step 3), the amounts of aluminum chloride, magnesium chloride, and calcium chloride are 10g, 6g, and 4g, respectively, while other conditions are the same as in Embodiment 1.

[0065] Example 7

[0066] The difference between this embodiment and Embodiment 1 is that in step 3), the amounts of aluminum chloride, magnesium chloride, and calcium chloride are 10g, 2g, and 2g, respectively, while other conditions are the same as in Embodiment 1.

[0067] Comparative Example 1

[0068] The difference between this comparative example and Example 1 is that quicklime is used instead of sludge, while other conditions are the same as in Example 1.

[0069] Test case

[0070] Soluble phosphorus, eutectic phosphorus, and soluble fluorine in phosphogypsum raw materials and harmless solid waste composites prepared in Examples 1-7 and Comparative Example 1 were tested. Soluble phosphorus was detected by molybdenum antimony spectrophotometry, eutectic phosphorus was detected by phosphogypsum vanadium molybdenum yellow dual-wavelength spectrophotometry, and soluble fluorine was detected by ion-selective electrode method. The test results are shown in Table 1.

[0071] Table 1

[0072]

[0073]

[0074] As shown in Table 1, the soluble phosphate content in the harmless solid waste composite prepared by this invention is <0.5 mg / L and the soluble fluoride content is <10 mg / L, which meets the standard of "Standard for Pollution Control of General Industrial Solid Waste Storage and Landfill" (GB 18599-2020). This invention provides a synergistic treatment method for the harmless treatment of phosphogypsum and sludge.

[0075] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a harmless solid waste composite, characterized in that, include: Phosphogypsum, sludge, and curing accelerator are mixed to form a slurry. Persulfate is mixed with a solvent to prepare a persulfate solution. The persulfate solution is added to the slurry and allowed to stand and solidify. Finally, it is calcined at 100-150℃. The curing accelerator is a Ca / Mg / Al composite material. The Ca / Mg / Al composite material is obtained by dissolving aluminum salt, magnesium salt, and calcium salt in a solvent to form a mixed solution, and then adding a precipitant for hydrothermal reaction.

2. The preparation method according to claim 1, characterized in that, The mass ratio of the phosphogypsum, sludge and solidification accelerator is (50-100):10:(1-5).

3. The preparation method according to claim 1, characterized in that, In the mixed solution, the mass ratio of the aluminum salt, magnesium salt, calcium salt and solvent is 5:(1-5):(1-5):100; And / or, the solvent is water; And / or, the precipitant is an alkali; the concentration of the alkali is 2-5 mol / L; the alkali is at least one selected from sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate; And / or, the volume ratio of the precipitant to the mixed solution is 1:10; And / or, the hydrothermal reaction is carried out at a temperature of 50-80°C for a duration of ≥24 h.

4. The preparation method according to any one of claims 1-3, characterized in that, The phosphogypsum, sludge, and curing accelerator are mixed by wet ball milling. And / or, the solid-liquid ratio of the slurry is 1:

2.

5. The preparation method according to claim 1 or 2, characterized in that, The persulfate is sodium persulfate and / or potassium persulfate; And / or, the mass ratio of the mixture obtained by mixing the persulfate solution with the phosphogypsum, sludge, and solidification accelerator is 1:5; And / or, the solvent of the persulfate solution is water; And / or, the concentration of the persulfate solution is 0.1-1 mol / L.

6. The preparation method according to claim 1 or 2, characterized in that, The roasting process lasts for 1-3 hours.

7. The preparation method according to claim 1 or 2, characterized in that, The phosphogypsum and sludge are dried and ball-milled before being mixed.

8. The preparation method according to claim 1 or 2, characterized in that, The sludge in question is sludge from a water supply plant.

9. A harmless solid waste composite material, characterized in that, It is prepared by the method for preparing the harmless solid waste composite as described in any one of claims 1-8.

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