High-activity lime milk, its preparation method and application

Abstract

The application discloses high-activity lime milk and a preparation method and application thereof, and comprises the following steps: performing ball milling treatment on calcium oxide, adding organic dispersant butyl formate and n-propanol into the calcium oxide powder after the ball milling treatment, performing first stirring, adding a retarder glycerol drop by drop under the stirring condition, standing for 1.5-2.5 hours, adding water into the reaction system to continue stirring uniformly, and naturally cooling to prepare the high-activity lime milk. The experiment proves that the high-activity lime milk can be used for harmless disposal of phosphogypsum and treatment of phosphorus and fluorine-containing wastewater, can effectively remove phosphates and fluorine ions, and the treated phosphogypsum and phosphorus and fluorine-containing wastewater meet relevant environmental pollution standards. The high-activity lime milk has simple preparation conditions, stable pollutant removal effect and small environmental pollution.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of industrial solid waste treatment and environmental protection, and particularly relates to a high-activity lime milk as well as a preparation method and application thereof. BACKGROUND

[0002] Phosphogypsum is a by-product of the phosphoric acid industry. Generally, 4.5-5.5 tons of phosphogypsum are produced for each ton of phosphoric acid. Phosphogypsum belongs to solid waste, and its appearance is fine-particle powder or block-shaped material in yellowish white, grayish white or blackish gray. China is a large country in the production of phosphate fertilizer in the world, and the total stock of phosphogypsum has exceeded 800 million tons, with an annual increase of about 50 million tons. However, most of the phosphogypsum is treated by stacking, which not only occupies land resources, but also causes serious environmental threat. Therefore, it is very urgent to solve the environmental problems caused by phosphogypsum, which not only contributes to the sustainable development of the wet-process phosphoric acid industry, but also promotes the economic prosperity of the surrounding areas of enterprises. At present, there are mainly two ways to treat phosphogypsum in engineering: one is to discharge and abandon it, i.e. to stack it; the other is to utilize it after harmless treatment. At present, most of the phosphogypsum is treated by open-air stacking in the slag yard of each phosphoric acid enterprise. Phosphogypsum has high water content and fine particles, and has strong fluidity and migration. Specifically, the soluble phosphorus, fluorine and metal sulfides in phosphogypsum are easily formed into percolate containing harmful substances through the action of precipitation, which will seriously pollute the groundwater and the surrounding soil. Lime neutralization and solidification is the preferred process for the pretreatment of non-water-washing phosphogypsum. The lime neutralization method has remarkable effect, simple process route and low investment, and is a practical and effective method in the pretreatment mode, especially suitable for phosphogypsum with low organic matter content and stable quality. However, the commonly used traditional lime reagents (such as quicklime, slaked lime and composite alkali) have problems of low effective calcium content and weak alkalinity. In the harmless process of phosphogypsum, these problems will lead to poor solidification effect of harmful components, and it is difficult to convert them from the second-class solid waste to the first-class solid waste. Therefore, the development of new functional lime reagents to solve the above technical problems is a hot research issue at present.

[0003] Phosphorus and fluorine are common pollutants in water bodies. Excessive phosphorus in water bodies will lead to water eutrophication, which will destroy the water ecological environment. The copper green microalgae that can easily grow in eutrophic water bodies and the red tide water bodies caused by eutrophication will cause great harm to human health and the aquaculture industry. Excessive fluorine in water will enter the human body through the food chain, leading to fluorosis, and even harming the nervous system. China has strict control on these two pollutants. In the first level standard of the "Integrated Wastewater Discharge Standard" (GB 8978-1996), the limits of total phosphorus and fluorine (calculated as fluoride) are 0.5 mg / L and 10 mg / L, respectively.

[0004] At present, the methods for removing phosphorus and fluorine from wastewater mainly include biological method, chemical precipitation method, adsorption method, membrane technology treatment method, etc., and the methods for removing fluorine mainly include adsorption, precipitation, ion exchange and membrane separation technology, etc. Among them, the adsorption method is concerned due to its simple process, easy-to-control condition, reliable operation and ability to achieve deep treatment level. The adsorbent is the core of the adsorption method, and some metal oxide adsorbents are increasingly paid attention to due to their ability to form coordination complexes with phosphorus and fluorine ions and good adsorption selectivity. A large number of studies have proved that when the pH is higher than 6, F generally exists in the form of F-; when the pH is higher than 10, P exists in the form of (PO4) 3- Adding calcium base into wastewater can adjust the pH value, so that F and P are converted into ion forms that can be treated, and Ca can react with F and P to generate CaF2 and Ca(PO4)3, etc. which are difficult to dissolve in water, so as to be precipitated and separated from the water body, so as to achieve the effect of removing phosphorus and fluorine from wastewater. If the pH value is too high, the pH value of the water body can be adjusted by using sulfuric acid, and at the same time, the excess calcium ions can be removed. Therefore, calcium base has obvious advantages in wastewater treatment. However, the solubility of traditional calcium base (such as quicklime and slaked lime) in water is not high, and the dispersing performance is poor, so a large amount of calcium cannot be utilized, causing waste and secondary pollution. Therefore, the performance improvement of calcium treatment agent is an important problem in the treatment of water body by calcium base method.

[0005] However, in the existing research, most adsorbents can only have good adsorption effect on one of the pollutants of phosphorus or fluorine, and do not have the ability to simultaneously and efficiently remove phosphorus and fluorine. In fact, phosphorus and fluorine often exist simultaneously in natural water or groundwater. Therefore, it is necessary to develop and prepare a new type of composite alkaline precipitator, which combines the specific adsorption ability of metal oxides for phosphorus and fluorine and the excellent hydrodynamic performance of large particle carriers, so as to achieve the purpose of simultaneously removing phosphorus and fluorine. SUMMARY

[0006] In order to overcome the shortcomings of the prior art, the purpose of the present application is to provide a high-activity lime milk and a preparation method and application thereof, so as to solve the technical problem that the existing adsorbents cannot simultaneously and efficiently remove phosphorus and fluorine.

[0007] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0008] The present application discloses a preparation method of high-activity lime milk, which comprises: ball milling calcium oxide, adding organic dispersant butyl formate and n-propanol to the calcium oxide powder after ball milling, stirring for the first time, and adding gelling retarder glycerol dropwise under stirring condition, standing for 1.5-2.5 h, then adding water into the reaction system and stirring uniformly, and naturally cooling, so as to obtain high-activity lime milk.

[0009] Preferably, the ball milling adopts dry milling, the ball milling beads adopt agate beads with a diameter of 5mm, the rotating speed is set to 200rpm, and the ball milling time is 1.5-2.5h, so that 85% of the calcium oxide has a particle size of less than 200 mesh.

[0010] Preferably, the mass ratio of the organic dispersing agent butyl formate and n-propanol is (2-3):(1-2).

[0011] Preferably, the mass ratio of the calcium oxide, butyl formate and n-propanol is 20:(2-3):(1-2).

[0012] Preferably, the addition amount of the glycerol is 2-5g per 100g of the calcium oxide.

[0013] More preferably, the glycerol is used as a retarder to control the viscosity of the composite emulsion. The glycerol is a commercially available product with a purity of 99%.

[0014] Preferably, the calcium oxide is a commercially available product with an effective calcium content of ≥80%, and the butyl formate and n-propanol are commercially available products with a purity of 99%.

[0015] Preferably, the amount of water added is 100g of water per 11g of the calcium oxide.

[0016] Preferably, the first stirring time is controlled to be 10-20min, and the second stirring time is at least 2h to reduce the temperature of the reaction system to below 40℃.

[0017] The application discloses a high-activity lime milk prepared by the preparation method.

[0018] The application further discloses application of the high-activity lime milk in harmless treatment of phosphogypsum.

[0019] The application further discloses application of the high-activity lime milk in treatment of phosphorus-containing and fluorine-containing wastewater.

[0020] Compared with the prior art, the present application has the following beneficial effects:

[0021] The preparation method of the high-activity lime milk disclosed by the present application breaks through the technical defects of traditional lime medicaments, mixes the calcium oxide after dry ball milling with different types of water reducing agents, surfactants and active components to improve the emulsification degree of lime powder. The calcium oxide powder after ball milling is selected in the composite emulsion, which reduces the particle size and dispersion resistance of solid materials and increases the stability and rheological property of the composite emulsion. Meanwhile, the use of some ester and alcohol organic matters greatly increases the dispersibility of metal oxides, promotes the full mixing and reaction of the metal oxides in the phosphogypsum to be treated or wastewater, and the effect after treatment is stable. The organic components are volatile, the addition of the retarder glycerol enables the medicament to be stored for a long time and reduces the stratification phenomenon. Some organic matters and other medicaments in the high-activity lime milk can improve the treatment effect and reduce the influence on the environment.

[0022] Further, the prepared calcium-based high-activity lime milk with high alkalinity and high rheological property is applied to the harmless disposal of phosphogypsum and the adsorption treatment of wastewater containing phosphorus and fluorine, and the effectiveness, economy and stability are guaranteed.

[0023] In the wastewater removal process, the high-activity lime milk has the characteristics of high rheological property, high activity and high dispersity, can be fully dispersed and release calcium ions in the water body; the pH value adjustment takes effect quickly and the dosage is small, does not contain other pollution components and does not cause the problems of ordinary lime, such as difficult solubility, excessive addition leading to high pH value, easy caking and heat release. After the high-activity lime milk is put into the water body, the high rheological property of the degradable organic components wrapped with alkaline components can be fully dispersed in the water body, and Ca 2+ , P and F are fully reacted and precipitated, so that the present calcium alkali realizes the efficient treatment of the polluted water body. As described above, the high-activity lime milk prepared by the present application has very wide application prospects. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The actual photo of the high-activity lime milk prepared for Example 1 is shown in the figure.

[0025] Figure 2 The actual photo of the high-activity lime milk prepared for Example 1 is shown in the figure.

[0026] Figure 3 The actual photo of the phosphogypsum solidified by adding the high-activity lime milk in Example 2 is shown in the figure. DETAILED DESCRIPTION

[0027] In the following, the technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application, so that those skilled in the art can better understand the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work should fall within the scope of protection of the present application.

[0028] It should be noted that the terms "first", "second" and the like in the description and claims of the present application and the above drawings are used to distinguish similar objects, and do not necessarily indicate a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0029] The present application will be described in further detail below in combination with the drawings:

[0030] Embodiment 1

[0031] 30g of calcium oxide was ball milled under room temperature and normal pressure, dry milling was adopted, agate beads with a diameter of 5mm were used, the rotation speed was set to 200rpm, and the ball milling time was 2h;

[0032] After ball milling, 3g of butyl formate and 1.5g of n-propanol were added to the calcium oxide powder as organic dispersants, 1.1g of glycerol was added dropwise while being fully stirred on a magnetic stirrer, and the stirring was continued for 15min, followed by standing for 2h;

[0033] After adding 272g of water, the stirring was continued for another 4h, and the high-activity lime milk was prepared when the temperature dropped to room temperature.

[0034] Embodiment 2

[0035] 30g of calcium oxide was ball milled under room temperature and normal pressure, dry milling was adopted, agate beads with a diameter of 5mm were used, the rotation speed was set to 200rpm, and the ball milling time was 2h;

[0036] After ball milling, 3g of butyl formate and 1.5g of n-propanol were added to the calcium oxide powder as organic dispersants, 0.7g of glycerol was added dropwise while being fully stirred on a magnetic stirrer, and the stirring was continued for 15min, followed by standing for 2h;

[0037] After adding 272 g of water, continuously stirring for 4 h again, and waiting for the temperature to drop to room temperature, a high-activity lime milk is prepared.

[0038] Example 3

[0039] At room temperature and normal pressure, 30 g of calcium oxide is ball milled, the ball milling mode is dry milling, the ball milling beads are 5 mm diameter agate beads, the rotation speed is set to 200 rpm, and the ball milling time is 2 h;

[0040] To the ball-milled calcium oxide powder, 3.5 g of butyl formate and 1.7 g of n-propanol as an organic dispersant are sequentially added, while fully stirring on a magnetic stirrer, 1.0 g of glycerol is added dropwise, continuously stirring for 15 min, and then standing for 2 h;

[0041] After adding 272 g of water, continuously stirring for 4 h again, and waiting for the temperature to drop to room temperature, a high-activity lime milk is prepared.

[0042] Example 4

[0043] At room temperature and normal pressure, 30 g of calcium oxide is ball milled, the ball milling mode is dry milling, the ball milling beads are 5 mm diameter agate beads, the rotation speed is set to 200 rpm, and the ball milling time is 2 h;

[0044] To the ball-milled calcium oxide powder, 4.0 g of butyl formate and 2.0 g of n-propanol as an organic dispersant are sequentially added, while fully stirring on a magnetic stirrer, 1.2 g of glycerol is added dropwise, continuously stirring for 15 min, and then standing for 2 h;

[0045] After adding 272 g of water, continuously stirring for 4 h again, and waiting for the temperature to drop to room temperature, a high-activity lime milk is prepared.

[0046] Example 5

[0047] At room temperature and normal pressure, 30 g of calcium oxide is ball milled, the ball milling mode is dry milling, the ball milling beads are 5 mm diameter agate beads, the rotation speed is set to 200 rpm, and the ball milling time is 2 h;

[0048] To the ball-milled calcium oxide powder, 4.5 g of butyl formate and 2.2 g of n-propanol as an organic dispersant are sequentially added, while fully stirring on a magnetic stirrer, 1.5 g of glycerol is added dropwise, continuously stirring for 15 min, and then standing for 2 h;

[0049] After adding 272 g of water, continuously stirring for 4 h again, and waiting for the temperature to drop to room temperature, a high-activity lime milk is prepared.

[0050] Example 6

[0051] Under the condition of room temperature and normal pressure, the reaction steps are as follows: ①Under laboratory conditions, a kind of phosphogypsum powder (dry basis about 100 grams) is added into a 500ml beaker, the high-activity lime milk prepared in Example 1 is added at a dosage of 1%, and is fully stirred for 0.5h to make it uniformly dispersed, and is placed for 6-24h. ②The solidified phosphogypsum is leached with pure water, and the initial concentration and the concentration after treatment of the soluble phosphorus in the phosphogypsum are detected by using a spectrophotometer according to the national standard for determination of total phosphorus in water (GB 11893-1989). ③The initial concentration and the concentration after treatment of the soluble fluorine in the phosphogypsum are detected by using ion chromatography according to the national standard for determination of fluorine ions in water (GB 11894-2014). ④The initial pH value of the leaching solution is monitored by using a pH meter, and the phosphogypsum in the experiment is further placed, and the above three indicators are detected again at different times until two weeks after the solidification reaction. The experimental results show that the reaction is fully occurred within 0.5h, and the concentrations of the related substances in the leaching solution before and after 24h are shown in Table 1:

[0052] Table 1

[0053] Measured parameters Before treatment After treatment Initial pH value 2.5 7.8 Soluble phosphorus (mg / L) 226.55 mg / L 0.23 F - Concentration (mg / L) 586.74 mg / L 6.87 mg / L

[0054] According to the national standard for comprehensive discharge of wastewater (GB 8978-1996) and the national standard for pollution control of general industrial solid waste storage and filling (GB 18599-2020), the soluble phosphorus is lower than 0.5mg / L, the soluble fluorine is lower than 10mg / L, and the pH value is between 6-9. After two weeks, the detection of soluble phosphorus is lower than the detection limit, the detection value of soluble fluorine is 5.38mg / L, and the pH value is stable between 7.3-7.5.

[0055] Example 7

[0056] In the laboratory, simulated wastewater is configured for treatment to observe the effect of the high-activity lime milk prepared in the application. The first group of simulated wastewater contains F - =400mg / L, (PO4) 3 =120mg / L, and pH=7. According to the calculation results of chemical equilibrium, the high-activity lime milk prepared in Example 1 is added at a dosage of 1% of the water body, and after 24h of standing reaction, it is detected that F 3- =6.14mg / L, (PO4) 3- =0.26mg / L, and pH=9.52. The second group of simulated wastewater contains F 3-= 0.44 mg / L, pH = 7.72. The P removal effect is over 99%, the F removal effect is over 90%, the pH is controlled below 10, the dosage is very small, and the performance is excellent. Both groups of data meet the first level standard of "Integrated Wastewater Discharge Standard - GB 8978-1996".

[0057] The above merely illustrates the technical idea of the present application, and cannot limit the protection scope of the present application. Any modification made according to the technical idea of the present application on the basis of the technical scheme falls within the protection scope of the present application.

Claims

1. A method for preparing highly active lime slurry, characterized in that, include: Calcium oxide was ball-milled to reduce the particle size of 85% of the calcium oxide to less than 200 mesh. The ball-milled calcium oxide powder was then mixed with butyl formate and n-propanol, and stirred for 10-20 minutes. Glycerol was added dropwise as a retarder under stirring conditions. The mixture was allowed to stand for 1.5-2.5 hours. Water was then added to the reaction system for a second stirring, which lasted at least 2 hours to allow the temperature of the reaction system to drop below 40°C. The mixture was then allowed to cool naturally to obtain a highly active lime slurry. The mass ratio of the organic dispersant butyl formate to n-propanol is (2~3):(1~2); The mass ratio of calcium oxide to butyl formate and n-propanol is 20:(2~3):(1~2).

2. The method for preparing highly active lime slurry according to claim 1, characterized in that, Dry grinding was used in the ball mill, with 5mm diameter agate beads as the grinding balls. The rotation speed was set to 200 rpm, and the grinding time was 1.5-2.5 hours.

3. The method for preparing highly active lime slurry according to claim 1, characterized in that, The dosage of glycerol is 2-5 g per 100 g of calcium oxide.

4. The method for preparing highly active lime slurry according to claim 1, characterized in that, The amount of water added is: 100 g of water for every 11 g of calcium oxide.

5. A highly active lime slurry prepared by the preparation method according to any one of claims 1 to 4, characterized in that, This highly active lime slurry exhibits high rheological properties, with a viscosity of 0.24~0.37 mPa·s.

6. The application of the highly active lime slurry according to claim 5 in the harmless treatment of phosphogypsum, characterized in that, For phosphogypsum with soluble phosphorus of 20-400 mg / kg and soluble fluoride of 100-7000 mg / kg, adding highly active lime slurry with an effective calcium content of 1% of the dry weight of the phosphogypsum and performing a curing reaction for 6-24 hours resulted in an average removal rate of 99.5% and 98.3% for soluble phosphorus and fluoride, respectively. After one month of exposure to air and subsequent stacking, the removal rates of soluble phosphorus and fluoride remained at 99.6% and 99.1%, respectively.

7. The application of the highly active lime slurry according to claim 5 in the treatment of phosphorus- and fluoride-containing wastewater, characterized in that, For phosphorus and fluoride-containing wastewater with phosphate concentration of 10-120 mg / L, fluoride ion concentration of 10-400 mg / L, and pH value below 5, adding highly active lime slurry to raise the pH value to >8 and reacting for 0.5-1.5 h resulted in an average removal rate of 99.2% for phosphate and 97.5% for fluoride ions.

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