A calcium oxide composite agent, its preparation method and application

Abstract

The application discloses a calcium oxide composite medicament and a preparation method and application thereof, and relates to the field of environmental protection, and in particular to a calcium oxide composite medicament and a preparation method and application thereof. The calcium oxide composite emulsion can be used for harmless treatment of phosphogypsum, can effectively remove phosphates and fluorine ions, and the treated phosphogypsum meets relevant environmental pollution standards. The preparation conditions of the composite emulsion are simple, the removal effect of the composite emulsion on pollutants is stable, and the composite emulsion has little environmental pollution.

Description

Technical Field

[0001] This invention belongs to the field of environmental protection technology, specifically relating to a calcium oxide composite agent, its preparation method, and its application. Background Technology

[0002] my country is rich in phosphate rock resources, and the phosphate chemical industry, mainly producing phosphate fertilizers, plays a significant role in the national economy, resulting in a large output of phosphogypsum. During rainfall and long-term accumulation, phosphogypsum not only occupies land resources, but some components in its leachate can also impact the ecological environment. Mechanical operations at phosphogypsum stockpiles and dry, windy weather can generate dust, leading to dust pollution. Harmful impurities in phosphogypsum, such as phosphorus, mercury, cadmium, and radioactive elements, can enter the atmosphere with water vapor, also harming the atmospheric environment. Excessive or high stockpiles of phosphogypsum at construction sites can cause serious collapses and landslides during stormy weather. For a long time, people have used stockpiling to dispose of phosphogypsum, which not only wastes land resources but also causes a series of environmental problems. Enterprises are now more urgently demanding solutions to the stockpiling problem of phosphogypsum and its comprehensive utilization.

[0003] Phosphogypsum mainly originates from general industrial solid waste generated during the wet-process phosphoric acid production. Producing 1 ton of phosphoric acid yields 5 tons of phosphogypsum, of which over 90% is CaSO4·2H2O. It also contains small amounts of phosphorus, fluorine, organic matter, oxides, and trace amounts of heavy metals and radioactive substances. Furthermore, it contains a large amount of insoluble impurities, such as quartz, undecomposed apatite, insoluble P2O5, eutectic P2O5, fluorides, and phosphates and sulfates of fluorine, aluminum, and magnesium. It also contains soluble impurities, including water-soluble P2O5, and trace amounts of radioactive elements. The fluorides, free phosphoric acid, P2O5, and phosphates contained in phosphogypsum are the main factors causing water, air, and soil pollution during its storage. When phosphogypsum is discharged, it typically contains unfiltered and washed residues of water-soluble phosphorus and free fluorine. If the slag heap is poorly managed or soaked by rainwater for extended periods, these harmful components can seep into nearby rivers through underground karst caves at the bottom of the slag heap, polluting the environment. Treating this polluted water is not only technically challenging but also extremely costly. Furthermore, the presence of residual water-soluble phosphorus and free fluorine in phosphogypsum significantly restricts its comprehensive utilization and increases the pressure on its storage.

[0004] Soluble phosphorus has a significant impact on phosphogypsum. Lime neutralization involves adding quicklime to phosphogypsum, which reacts with soluble phosphorus, fluoride, residual acid, and other impurities to form insoluble phosphates and fluorides, thus removing impurities. Lime neutralization solidification is the preferred process for non-water-washing pretreatment of phosphogypsum. It is effective, simple, and requires low investment, making it a practical and effective pretreatment method. For large-scale phosphogypsum treatment, it is a very simple, efficient, and low-investment harmless treatment process. However, traditional lime agents have some significant drawbacks in the phosphogypsum solidification process. First, the reaction rate is relatively slow, requiring a long solidification time, which is inefficient in industrial applications. Second, the solidified product may have unstable morphology, potentially leading to structural changes during long-term storage or under specific environmental conditions. Furthermore, the solidified phosphogypsum may dissolve excessive phosphorus contaminants in the leachate, causing the leachate quality to fail to meet environmental standards. Therefore, to overcome these technical bottlenecks, it is necessary to develop a more stable and efficient composite lime agent for phosphogypsum solidification. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide a calcium oxide composite agent, its preparation method and application, so as to solve the technical problem that the current prior art cannot harmlessly treat phosphogypsum.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] This invention discloses a method for preparing a calcium oxide composite agent, comprising: ball milling calcium oxide, adding organic dispersant polyethylene glycol and 1,2-ethylene glycol monoacetate, stirring evenly, then adding water and retarder polyacrylamide, continuing to stir evenly, and allowing to stand to obtain the calcium oxide composite agent.

[0008] Preferably, the mass ratio of calcium oxide, polyethylene glycol and 1,2-ethylene glycol monoacetate is (40-50):(8-12):(5-8).

[0009] Preferably, the ratio of water to calcium oxide is (400-600) mL: (40-50) g:.

[0010] Preferably, the retarder polyacrylamide used is a 20% polyacrylamide solution, and the mass ratio of the polyacrylamide solution to calcium oxide is (2-5):(50-65).

[0011] Preferably, the ball milling is dry milling, with a rotation speed of 240 rpm and a milling time of 2 to 2.5 hours.

[0012] Preferably, both stirring treatments are carried out at 20–40°C for 0.5–1 hour.

[0013] Preferably, the settling time is 0.5 to 1 hour.

[0014] Preferably, the calcium oxide used in this invention is an industrially produced product with an effective ingredient content of 80%-90%.

[0015] The present invention also discloses a calcium oxide composite agent prepared by the above preparation method, characterized in that the viscosity of the calcium oxide composite agent is less than 0.5 mPa·s and the average particle size of calcium oxide is less than 5 μm, and it has high rheological properties and dispersibility.

[0016] The present invention also discloses the application of the above-mentioned calcium oxide composite agent in the harmless treatment of phosphogypsum.

[0017] Preferably, the calcium oxide composite agent is added to the phosphogypsum powder to be treated, stirred evenly, and then cured for 6-24 hours, followed by stacking for 1-14 days; wherein the mass of calcium oxide is 1% of the dry basis mass fraction of phosphogypsum.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] This invention discloses a method for preparing a calcium oxide composite agent. The method involves ball-milling calcium oxide and mixing it with an organic dispersant (polyethylene glycol and 1,2-ethylene glycol monoacetate) and a gelling agent (polyacrylamide). First, the use of ball-milled calcium oxide powder in the composite emulsion reduces the particle size and dispersion resistance of the solid material, increasing the stability and rheological properties of the composite agent. Second, the use of polyethylene glycol and 1,2-ethylene glycol monoacetate significantly increases the dispersibility of calcium oxide, promoting thorough mixing and reaction with the phosphogypsum to be treated, and mitigating the exothermic hydration reaction of calcium oxide upon contact with water, resulting in stable treatment effects. Third, the addition of the gelling agent PAM allows for long-term storage of the calcium oxide composite agent, reducing the occurrence of stratification or deterioration. Therefore, this compounding method significantly improves the emulsification degree of lime powder, enhances the stability of the composite agent, and reduces adverse environmental impacts. This novel preparation method successfully produces a calcium oxide composite agent, providing an effective, economical, and stable solution for the harmless disposal of phosphogypsum.

[0020] The calcium oxide composite agent prepared by the method described above in this invention has several characteristics, including high rheological properties, high activity, and high dispersibility. This means that during the release of Ca from the agent... 2+During the process, it can fully react with substances such as phosphorus and fluorine and precipitate. This characteristic enables the calcium oxide composite agent to efficiently treat phosphogypsum. This treatment method can completely solve the environmental pollution problem caused by phosphogypsum and has broad application prospects. On the other hand, the new calcium oxide composite agent is economical. The agent prepared using new materials has a relatively low cost, and the preparation process only requires simple mixing of different components according to the corresponding steps. The preparation difficulty is low and the energy consumption is small, which can reduce the economic burden of phosphogypsum disposal. In addition, the stability of the composite agent can ensure the persistence and reliability of the treatment effect. Experiments have shown that the phosphogypsum after solidification reaches the Class I solid waste index within 3 days, and the data shows no rebound after two weeks. In summary, the calcium oxide composite agent prepared by this invention has broad application prospects.

[0021] The calcium oxide composite agent of this invention has a good removal effect on phosphorus and fluorine pollutants in phosphogypsum, effectively solving the problems of traditional wet treatment of calcium oxide and improving the treatment effect and speed. Experimental verification shows that the calcium oxide composite agent of this invention, when used in the treatment of phosphogypsum, employs a direct dry mixing method, with an addition amount of 1% of the dry weight of the phosphogypsum. After a 6-24 hour curing reaction and 14 days of stacking, it thoroughly removes harmful substances such as soluble phosphorus, soluble fluorine, and ammonia nitrogen from the phosphogypsum, achieving a removal rate of over 98%. Attached Figure Description

[0022] Figure 1 A photograph of the calcium oxide composite agent prepared in Example 1;

[0023] Figure 2 The image shows the actual product of the calcium oxide composite agent prepared in Example 1.

[0024] Figure 3 This is a graph showing the changes in soluble phosphorus concentration in different phosphogypsum leachates at different reaction times in Example 4.

[0025] Figure 4 This is a graph showing the changes in soluble fluoride concentration in different phosphogypsum leachates at different reaction times in Example 4.

[0026] Figure 5 The graph shows the pH value changes of different phosphogypsum leachates at different reaction times in Example 4. Detailed Implementation

[0027] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0028] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0029] The present invention will now be described in further detail with reference to the accompanying drawings:

[0030] The present invention provides a method for preparing a calcium oxide composite agent, comprising the following steps:

[0031] 1) Under normal temperature and pressure conditions, a certain mass ratio of calcium oxide is ball-milled in a dry powder state;

[0032] Among them, calcium oxide is a commercially available industrial-grade product with an effective calcium content of 80%-90%. The ball milling method is dry milling, and the grinding balls are 5mm diameter agate balls. The speed is set to 240rpm, and the milling time is 2.0-2.5h.

[0033] 2) Add a certain mass of polyethylene glycol and 1,2-ethylene glycol monoacetate as organic dispersants to the ball-milled solid powder in sequence, stir thoroughly and let stand for a certain time before adding water;

[0034] The mass ratio of calcium oxide to organic dispersant polyethylene glycol to 1,2-ethylene glycol monoacetate is (40-50) g: (8-12) g: (5-8) g.

[0035] The ratio of water to calcium oxide is 400-600 mL: 40-50 g, and the standing time is 0.5-1 h.

[0036] 3) Next, add a certain amount of gelling agent polyacrylamide (PAM) and stir again until fully mixed. After standing for a certain period of time, the calcium oxide composite agent is obtained.

[0037] Preferably, in steps 2) and 3), a magnetic stirrer is used to ensure thorough mixing, with the temperature of the magnetic stirrer adjusted to 20-40°C and the mixing time to 0.5-1h.

[0038] Preferably, in step 3), the gelling agent added is a PAM solution with a mass fraction of 20%; the mass ratio of the gelling agent solution to calcium oxide is (2-5) g: (50-65) g.

[0039] This invention relates to the application of a calcium oxide composite agent in the treatment of phosphogypsum and phosphorus- and fluoride-containing wastewater. The agent uses calcium oxide as the main component, with the addition of organic dispersants and gelling agents. This composite agent can effectively solidify soluble phosphorus and fluoride elements in phosphogypsum, enabling the phosphogypsum to meet harmless treatment standards.

[0040] The harmful components in the phosphogypsum include soluble phosphorus content of 20-150 mg / L and soluble fluoride content of 15-500 mg / L, with a leachate pH value below 7. After conversion and addition, the total mass of CaO and MgO in the agent (i.e., the calcium oxide composite agent prepared in this invention) is 1% of the dry weight of the phosphogypsum. The curing reaction time is 6-24 hours, and the phosphogypsum is then left to stand for 3-14 days. After curing, the phosphogypsum is tested and found to have a soluble phosphorus content below 0.5 mg / L, a soluble fluoride content below 10 mg / L, and a pH of 6-9. The calcium oxide composite agent achieves an average removal rate of 99.8% for soluble phosphorus and 97.6% for soluble fluoride in the phosphogypsum. Furthermore, after 14 days of standing, the treated phosphogypsum leachate still meets these requirements.

[0041] Example 1

[0042] The reagent was prepared under ambient temperature and pressure conditions using the following steps:

[0043] (1) 50g of calcium oxide with a mass fraction of 85% was dry-milled with 5mm diameter agate beads, the speed was set to 240rpm, and the milling time was 2.0h.

[0044] (2) After mixing polyethylene glycol and 1,2-ethylene glycol monoacetate at a ratio of 12g:8g, add the mixture to the ground mixture, stir with a magnetic stirrer at 25°C for 0.5h, and then add 600mL of pure water.

[0045] (3) Add 5g of PAM solution with a mass fraction of 20% to the solution, stir again with a magnetic stirrer at 25°C for 0.5h, and let stand for 1h to obtain calcium oxide composite agent.

[0046] Photographs of the prepared pharmaceutical preparation are shown below. Figure 1 and Figure 2 As shown.

[0047] Example 2

[0048] (1) 45g of calcium oxide with a mass fraction of 83% was dry-milled with 5mm diameter agate beads, the speed was set to 240rpm, and the milling time was 2.0h.

[0049] (2) After mixing polyethylene glycol and 1,2-ethylene glycol monoacetate at a ratio of 10g:6g, add the mixture to the ground mixture, stir with a magnetic stirrer at 30°C for 0.5h, and then add 550mL of pure water.

[0050] (3) Add 4g of PAM solution with a mass fraction of 20% to the solution, stir again with a magnetic stirrer at 30°C for 0.5h, and let stand for 0.5h to obtain calcium oxide composite agent.

[0051] Example 3

[0052] (1) 40g of calcium oxide with a mass fraction of 90% was dry-milled with 5mm diameter agate beads, the speed was set to 240rpm, and the milling time was 2.0h.

[0053] (2) Mix polyethylene glycol and 1,2-ethylene glycol monoacetate at a ratio of 8g:5g and add them to the ground mixture. Stir with a magnetic stirrer at 40°C for 1 hour, and then add 500mL of pure water.

[0054] (3) Add 3g of PAM solution with a mass fraction of 20% to the solution, stir again with a magnetic stirrer at 40℃ for 1h, and let stand for 1h to obtain calcium oxide composite agent.

[0055] Example 4

[0056] The application of calcium oxide composite agents in the treatment of phosphogypsum under room temperature and atmospheric pressure conditions follows these steps:

[0057] (1) Under laboratory conditions, eight phosphogypsum powders with different initial concentrations were selected for batch experiments. Different phosphogypsum powders (about 100 grams on dry basis) were added to a 500 ml beaker. The calcium oxide composite agent prepared in Example 1 was added at a dosage of 1% (i.e., the mass of calcium oxide in the agent is 1% of the dry basis mass of the phosphogypsum powder) and stirred thoroughly for 0.5 h to make it evenly dispersed. The mixture was allowed to stand for 6 to 24 hours and then left to stand for 14 days.

[0058] (2) After the solidified phosphogypsum was taken, samples were leached with pure water at different times. According to the national standard for determination of total phosphorus in water (GB 11893~1989), the initial concentration and the concentration of soluble phosphorus in the phosphogypsum after treatment were detected by spectrophotometer.

[0059] (3) According to the national standard for the detection of fluoride ions in water (GB 11894~2014), the initial concentration and the concentration of soluble fluoride in the leachate were detected by ion chromatography.

[0060] (4) Use a pH meter to monitor the pH changes of the leachate at different times. After 3 days, place the phosphogypsum in the experiment for a longer period of time and test the above three indicators again at different times until the solidification reaction is completed two weeks later.

[0061] Figure 3 For this embodiment, the data on the changes in soluble phosphorus concentration in different phosphogypsum leachates on day 3 and day 14 are presented. Figure 4 For this embodiment, the data on the changes in soluble fluoride concentration in different phosphogypsum leachates on day 3 and day 14 are presented. Figure 5 This embodiment presents data on the pH changes of different phosphogypsum leachates on days 3 and 14. The experimental results show that the calcium oxide composite agent reacts fully with the soluble phosphorus and soluble fluorine in the phosphogypsum, reaching the national standard within 3 days, and the data stabilizes after two weeks.

[0062] The concentrations of relevant substances in the leachates of different phosphogypsum raw materials before the reaction are shown in Table 1 below:

[0063] Table 1

[0064]

[0065] According to the "GB 8978~1996 Integrated Wastewater Discharge Standard" and the "GB 18599~2020 Pollution Control Standard for Storage and Filling of General Industrial Solid Waste", the soluble phosphorus concentration was below 0.5 mg / L, the soluble fluoride concentration was below 10 mg / L, and the pH value was between 6 and 9. Two weeks later, the soluble phosphorus, soluble fluoride, and pH value remained within the acceptable range, with no rebound in the data.

[0066] In summary, this invention renders phosphogypsum harmless at the source of potential pollution by adding alkaline lime to chemically solidify the water-soluble phosphorus and free fluorine in the phosphogypsum and neutralize the H+ in the phosphogypsum. +This method ensures that the indicators in the phosphogypsum leachate meet the standards of "GB 8978~1996 Integrated Wastewater Discharge Standard" and "GB 18599~2020 Pollution Control Standard for Storage and Landfill of General Industrial Solid Waste," specifically meeting the standards of soluble phosphorus below 0.5 mg / L, soluble fluoride below 10 mg / L, and pH value between 6 and 9. Simultaneously, it reduces the damage to the anti-corrosion layer at the bottom of the slag yard caused by seepage, extends the service life of the slag yard, and reduces the risk of phosphogypsum leachate entering the external environment.

[0067] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for preparing a calcium oxide composite agent, characterized by, Comprise: After the calcium oxide is ball milled, the organic dispersant polyethylene glycol and 1,2-ethylene glycol monoacetate are added, stirred uniformly, then the water and the retarder polyacrylamide are added, continue to stir uniformly, and the calcium oxide composite agent is prepared after standing; The mass ratio of calcium oxide, polyethylene glycol and 1,2-ethylene glycol monoacetate is (40-50):(8-12):(5-8); the ratio of the amount of water and calcium oxide is (400-600)mL:(40-50)g; the retarder polyacrylamide used is a polyacrylamide solution with a mass fraction of 20%, and the mass ratio of the polyacrylamide solution and calcium oxide is (2-5):(50-65).

2. The method of claim 1, wherein the calcium oxide composite agent is prepared by the steps of: The dry grinding is used for ball milling, the rotating speed is 240 rpm, and the ball milling time is 2-2.5 h.

3. The method of claim 1, wherein the calcium oxide composite agent is prepared by the steps of: Both the stirring treatments are carried out at 20-40℃, and the stirring treatment time is 0.5-1 h.

4. The method of claim 1, wherein the calcium oxide composite agent is prepared by the steps of: The standing treatment time is 0.5-1 h.

5. The calcium oxide composite agent prepared by the method according to any one of claims 1 to 4, characterized in that, The viscosity value of the calcium oxide composite agent is lower than 0.5 mPa·s, and the average particle size value of calcium oxide is lower than 5 μm.

6. The application of the calcium oxide composite agent in claim 5 in the harmless treatment of phosphogypsum.

7. Use according to claim 6, characterized in that, The calcium oxide composite agent is added to the phosphogypsum powder to be treated, stirred uniformly, and then the solidification reaction is carried out for 6-24 h, and then the product is stacked for 1-14 days; wherein the mass of calcium oxide is 1% of the mass fraction of the dry basis of phosphogypsum.

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