CN110156061B - Method for preparing micro-nano structure calcium carbonate and ammonium sulfate by using waste phosphogypsum - Google Patents
Method for preparing micro-nano structure calcium carbonate and ammonium sulfate by using waste phosphogypsum Download PDFInfo
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- C01P2004/62—Submicrometer sized, i.e. from 0.1-1 micrometer
Abstract
The invention relates to a method for preparing calcium carbonate and ammonium sulfate with micro-nano structures by using waste phosphogypsum, which is characterized in that the phosphogypsum is ground into powder and then dispersed in water to form phosphogypsum dispersion liquid; sequentially adding a cationic surfactant and ammonium bicarbonate into the phosphogypsum dispersion liquid at the temperature of 25-50 ℃ under the stirring condition, continuously stirring and reacting after uniformly mixing until the obtained mixed liquid is free of bubbles, then carrying out suction filtration on the mixed liquid, and drying the obtained upper-layer solid after the suction filtration is finished to obtain calcium carbonate; and finally, concentrating and crystallizing the filtrate to obtain ammonium sulfate. The product prepared by the method can be used for building materials and fertilizers, can solve the problem of comprehensive utilization of solid waste residue phosphogypsum, can be used for building materials and fertilizers, and has high yield, good application prospect and little environmental damage.
Description
Technical Field
The invention belongs to the technical field of comprehensive utilization of waste resources, and particularly relates to a method for preparing micro-nano structure calcium carbonate and ammonium sulfate by using waste phosphogypsum.
Background
Phosphogypsum refers to the solid waste residue produced when processing phosphorite with sulfuric acid in phosphoric acid production to prepare 1 ton phosphoric acid (100% P)2O5Measured) produces 4.8 to 5.0 tons of phosphogypsum. The phosphogypsum is powdery, is grey white or grey black, is attached with wet powder with 10-30% of water, and has the pH value of 1.9-5.3 and the F value of<0.5 percent, the particle diameter is generally 5 to 50 mu m, the color is offwhite, some are yellow and grayish yellow, the chemical composition is complex, the phosphogypsum contains residual organic phosphorus, inorganic phosphorus, fluoride, fluorine, potassium, sodium and other inorganic substances, and the phosphogypsum is used in the prior artThe material can be widely used as a filling material in the fields of building material market, cement, road repair and the like. An industrial by-product gypsum produced in the production of high-concentration phosphorus compound fertilizer, its main component is calcium sulfate dihydrate (CaSO)4·2H2O), the cumulative inventory exceeds 1 million tons. The production amount of the phosphogypsum in the ten provinces and cities accounts for 91.5 percent of the total production amount of the phosphogypsum in China in Yunnan, Hubei, Guizhou, Shandong, Anhui, Chongqing, Jiangsu, Sichuan, Guangdong and Shanxi. At present, about 2000 million tons of phosphogypsum are discharged every year in China, the accumulated discharge capacity is nearly hundred million tons, the phosphogypsum is one of the largest discharge capacity in gypsum waste residues, and the discharged phosphogypsum residues occupy a large amount of land to form a residue mountain.
The accumulation of a great amount of phosphogypsum occupies a great amount of land resources, namely, the phosphogypsum contains fluoride, free phosphoric acid and P2O5The phosphogypsum is flushed by rainwater, part of soluble impurities are taken away to the underground to pollute soil, in addition, the water quality is also polluted after the soluble impurities enter water or rivers, most people in rural areas in China directly drink underground water, and a water source polluted by the phosphogypsum directly enters human bodies, so that the physical and mental health of people is greatly threatened. In addition, air pollution is caused by wind erosion, the phosphogypsum brings serious 'water, land and air' pollution problems to people, and harmful heavy metal chemical substances such as arsenic, cadmium, mercury and the like contained in the phosphogypsum affect the environment for hundreds of years. In recent years, reports about harming the health of residents by the phosphogypsum are more and more, for example, messages of osteoporosis, kidney lesion, increase of canceration probability and the like caused by long-term drinking of phosphogypsum polluted water source are perceived by people as creeper. Although the relevant regulations about the application of stacking solid wastes are also provided, the stacking of a plurality of phosphogypsum does not meet the national standard, and the civil problem caused by the pollution of the phosphogypsum still exists. Furthermore, the problem of pollution of the phosphogypsum cannot be solved fundamentally even if the standard for stacking the phosphogypsum is established, the phosphogypsum cannot be stacked infinitely, and the problem that the phosphogypsum occupies land resources is solved fundamentally by reducing the stacking quantity of the phosphogypsum from the source of eliminating the stacking quantity of the phosphogypsumThe source and the pollution problem of 'land, water and air', therefore, the center of gravity should be transferred to the comprehensive utilization of the phosphogypsum solid waste while controlling the storage standard of the industrial solid waste.
In recent years, the problems of stockpiling and comprehensive utilization of the phosphogypsum are emphasized at home and abroad, the injection of novel innovation research and the strong support of national policies promote the utilization rate of the phosphogypsum, but the comprehensive utilization rate of the phosphogypsum is still low.
The present application has been made for the above reasons.
Disclosure of Invention
Aiming at the problems in the prior art, the invention aims to provide a method for preparing micro-nano structure calcium carbonate and ammonium sulfate by using waste phosphogypsum. The method uses the solid waste residue phosphogypsum as a raw material, adopts ammonium bicarbonate as a precipitator, and obtains the calcium carbonate and the ammonium sulfate with a micro-nano structure through stirring reaction, so that the problem of comprehensive utilization of the solid waste residue phosphogypsum can be solved, a target product can be used for building materials and fertilizers, the yield is high, the application prospect is good, and the environmental damage is small.
In order to achieve the above object of the present invention, the technical solution adopted by the present invention is specifically as follows:
a method for preparing micro-nano structure calcium carbonate and ammonium sulfate by using waste phosphogypsum comprises the following steps:
grinding phosphogypsum into powder and dispersing the powder in water to form phosphogypsum dispersion liquid; sequentially adding a cationic surfactant and ammonium bicarbonate into the phosphogypsum dispersion liquid at the temperature of 25-50 ℃ under the stirring condition, continuously stirring and reacting after uniformly mixing until the obtained mixed liquid is free of bubbles, then carrying out suction filtration on the mixed liquid, and drying the obtained upper-layer solid after the suction filtration is finished to obtain calcium carbonate; and finally, concentrating and crystallizing the filtrate to obtain ammonium sulfate.
Further, according to the technical scheme, the cationic surfactant is selected from long-chain alkyl ammonium salt containing 12-18 carbon atoms.
Furthermore, in the above technical solution, the long-chain alkyl ammonium salt is preferably any one or more of dodecyl trimethyl ammonium chloride, dodecyl trimethyl ammonium bromide, tetradecyl trimethyl ammonium chloride, tetradecyl trimethyl ammonium bromide, hexadecyl trimethyl ammonium chloride, hexadecyl trimethyl ammonium bromide, octadecyl trimethyl ammonium chloride, and octadecyl trimethyl ammonium bromide.
Preferably, in the above technical solution, the cationic surfactant is dodecyl trimethyl ammonium bromide.
Further, according to the technical scheme, the mass ratio of the cationic surfactant to the phosphogypsum is 1-4: 100.
furthermore, in the above technical scheme, the mass ratio of the cationic surfactant to the phosphogypsum is preferably 2: 100.
further, according to the technical scheme, the molar ratio of the phosphogypsum to the ammonium bicarbonate is 1: 1.5 to 3.
Furthermore, in the above technical solution, the molar ratio of the phosphogypsum to the ammonium bicarbonate is preferably 1: 2.
further, according to the technical scheme, the stirring reaction time is 1-3 hours, and preferably 2 hours.
Further, in the above technical solution, the stirring reaction temperature is preferably 25 ℃.
The invention researches the optimal temperature condition of the reaction of phosphogypsum and ammonium bicarbonate and the optimal addition amount of a proper auxiliary surfactant, and finds that a small amount of surfactant (DTAB) is added, so that higher yield can be obtained under mild conditions. When the addition amount of the surfactant (DTAB) is respectively 0%, 1%, 2%, 3% and 4%, the highest yield is found when the addition amount of the surfactant (DTAB) is 2%, and when the influence of different temperatures (room temperature 25 ℃, 30 ℃, 40 ℃ and 50 ℃) on the yield is screened, the precipitation yield can be higher at the room temperature of 25 ℃ and the precipitation particles are smaller. The patent discusses the principle and regulation of DTAB in the reaction by comparing the effect of different surfactants (DTAB, SDBS, ammonium citrate) on the particle size and yield of the product.
Compared with the prior art, the invention has the following beneficial effects:
the invention has the advantages of simple process, less process flow, higher yield, easy industrialization, less influence on environment, effective and reasonable utilization of the phosphogypsum and better application prospect.
Drawings
FIG. 1 is an X-ray powder diffraction (XRD) spectrum of calcium carbonate as a product of the present invention prepared in example 1.
FIG. 2 is an X-ray powder diffraction (XRD) spectrum of ammonium sulfate, a product obtained in example 1 of the present invention.
FIG. 3 is a Scanning Electron Microscope (SEM) photograph of the product calcium carbonate prepared in example 1 of the present invention.
FIG. 4 is a Scanning Electron Microscope (SEM) photograph of the product ammonium sulfate obtained in example 1 of the present invention.
FIG. 5 is a Scanning Electron Microscope (SEM) photograph of the calcium carbonate product obtained in comparative example 1 of the present invention.
FIG. 6 is a Scanning Electron Microscope (SEM) photograph of the calcium carbonate product obtained in comparative example 2 of the present invention.
FIG. 7 is a Scanning Electron Microscope (SEM) photograph of the calcium carbonate product obtained in comparative example 3 of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the following embodiments and accompanying drawings. The present invention is implemented on the premise of the technology of the present invention, and the detailed embodiments and specific procedures are given to illustrate the inventive aspects of the present invention, but the scope of the present invention is not limited to the following embodiments.
The invention focuses on researching the application in the chemical field, and utilizes simple stirring reaction, suction filtration device and concentration crystallization scheme to react phosphogypsum with cheap and easily available ammonium bicarbonate, and continuously optimizes the scheme to obtain two calcium carbonate and ammonium sulfate compounds with wide application and higher purity.
The reaction equation of the present invention is as follows:
CaSO4+2NH4HCO3＝CaCO3↓+(NH4)2SO4+CO2↑+H2O
the main product is as follows: ammonium sulfate, colorless crystals or white particles, odorless. Decomposing at 280 deg.C or higher. Solubility in water: 70.6g at 0 ℃ and 103.8g at 100 ℃. Insoluble in ethanol and acetone. The pH of the 0.1mol/L aqueous solution was 5.5. The relative density was 1.77. Refractive index 1.521. Ammonium sulfate is an excellent nitrogen fertilizer (commonly called as field fertilizing powder), is suitable for general soil and crops, can make branches and leaves grow vigorously, improve fruit quality and yield, enhance the resistance of the crops to disasters, and can also be used as a base fertilizer, an additional fertilizer and a seed fertilizer. Can produce ammonium chloride by double decomposition reaction with salt, produce ammonium alum by reaction with aluminum sulfate, and produce refractory material together with boric acid. The addition of the plating solution can increase the conductivity. Also a catalyst for food dark brown, a nitrogen source for culturing yeast in the production of fresh yeast, an acid dye dyeing auxiliary agent and a leather deliming agent. In addition, the method is also used for brewing beer, producing chemical reagents and storage batteries and the like. The mining method also has an important function of mining the rare earth, wherein the mining uses ammonium sulfate as a raw material, the rare earth elements in the ore soil are exchanged in an ion exchange mode, and then the rare earth raw ore is obtained after the leachate is collected for impurity removal, precipitation, squeezing and firing, and about 5 tons of ammonium sulfate is needed for each 1 ton of the rare earth raw ore produced by mining. It can also be used in textile, leather, medicine, etc. and the product ammonium sulfate has wide application.
And a second main product: calcium carbonate, also known as calcium powder or limestone. White solid, odorless and tasteless. There are amorphous and crystalline forms. The crystal form can be further divided into orthorhombic and hexagonal crystal forms, and is either columnar or rhombic. The relative density was 2.71. Decomposing at 825-896.6 deg.C, and decomposing into calcium oxide and carbon dioxide at about 825 deg.C. The melting point is 1339 ℃ and the melting point is 1289 ℃ under the pressure of 10.7 MPa. Are poorly soluble in water and alcohols. The calcium carbonate produced by the reaction meets the application requirements of light calcium carbonate, the light calcium carbonate is widely applied to paper making, plastics, plastic films, chemical fibers, rubber, adhesives, sealants, daily chemicals, cosmetics, building materials, coatings, paints, printing ink, putty, sealing wax, putty, carpet packaging, medicines, foods (such as chewing gum and chocolate) and feeds, and has the following functions: increase product volume, reduce cost, improve processing properties (such as viscosity regulation, rheological properties, and vulcanization properties), improve dimensional stability, reinforce or semi-reinforce, improve printing properties, and improve physical properties (such as heat resistance, delustering properties, wear resistance, flame retardancy, whiteness, and gloss). According to the observation of the particle size according to the SEM picture, the particle size can be greatly improved by adding a small amount of cationic surfactant, so that the cationic surfactant becomes a micro-nano structure and can meet the particle size requirement of fine calcium carbonate.
The surfactant is a substance which is added in a small amount and can cause the interface state of a solution system to change obviously. Has fixed hydrophilic and lipophilic groups and can be directionally arranged on the surface of the solution. Surfactant molecules have a unique amphiphilicity: one end of which is a hydrophilic polar group, called hydrophilic group for short, also called oleophobic or oleophobic group, sometimes figuratively called hydrophilic head, e.g. -OH, -COOH, -SO3H、-NH2(ii) a The other end is a lipophilic nonpolar group, called lipophilic group for short, also called hydrophobic group or hydrophobic group, such as R- (alkyl) and Ar- (aryl). The method utilizes the characteristics that the surface tension of water can be changed and the water can react with solute ions, so that the particle size of reaction precipitates is reduced, and the like, and screens out proper surfactant types.
The following examples employ test methods that include: XRD, SEM, weighing and calculating yield.
Calculating the formula: yield is the mass of product obtained by weighing/mass obtained theoretically.
Example 1
The method for preparing the micro-nano structure calcium carbonate and the ammonium sulfate by using the waste phosphogypsum comprises the following steps:
6.807g of phosphogypsum is ground into powder and then dispersed in 100mL of water to form phosphogypsum dispersion liquid; then, sequentially adding 0.136g (accounting for 2 percent of the mass of the phosphogypsum) of dodecyl trimethyl ammonium bromide (cationic surfactant) and 7.9g of ammonium bicarbonate into the phosphogypsum dispersion liquid under the stirring conditions of room temperature (25 ℃) and 1500r/min, uniformly mixing, continuously stirring and reacting for 2 hours at the room temperature (25 ℃), filtering the mixed liquid until no bubbles are generated in the mixed liquid, and baking the obtained upper-layer solid in a 70 ℃ drying oven for 10 hours after the filtering is finished to obtain calcium carbonate; and finally, concentrating and crystallizing the filtrate at 50 ℃ to obtain ammonium sulfate.
The solid product on the upper layer after being baked in the embodiment is characterized by an X powder diffraction (XRD) technology, the XRD characterization result is shown in figure 1, the main diffraction peak is consistent with the standard calcium carbonate spectrum, and the product is confirmed to be calcium carbonate which can be used for building materials.
The product of the concentrated crystallization of the embodiment is characterized by an X powder diffraction (XRD) technology, the XRD characterization result is shown in figure 2, the main diffraction peak is consistent with the standard ammonium sulfate pattern, and the product is proved to be ammonium sulfate, has pure components and can be used as a fertilizer.
Example 2
The method for preparing micro-nano structure calcium carbonate and ammonium sulfate by using waste phosphogypsum is basically the same as the method in the embodiment 1, and the difference is only that: the amount of dodecyltrimethylammonium bromide (DTAB) added was 0.068g (1% of the phosphogypsum mass).
Example 3
The method for preparing micro-nano structure calcium carbonate and ammonium sulfate by using waste phosphogypsum is basically the same as the method in the embodiment 1, and the difference is only that: the addition amount of dodecyl trimethyl ammonium bromide is 0.204g (accounting for 3% of the weight of the phosphogypsum).
Example 4
The method for preparing micro-nano structure calcium carbonate and ammonium sulfate by using waste phosphogypsum is basically the same as the method in the embodiment 1, and the difference is only that: the addition of dodecyl trimethyl ammonium bromide was 0.272g (4% by mass of phosphogypsum).
Example 5
The method for preparing micro-nano structure calcium carbonate and ammonium sulfate by using waste phosphogypsum is basically the same as the method in the embodiment 1, and the difference is only that: the stirring reaction temperature in this example was 30 ℃.
Example 6
The method for preparing micro-nano structure calcium carbonate and ammonium sulfate by using waste phosphogypsum is basically the same as the method in the embodiment 1, and the difference is only that: the stirring reaction temperature in this example was 40 ℃.
Example 7
The method for preparing micro-nano structure calcium carbonate and ammonium sulfate by using waste phosphogypsum is basically the same as the method in the embodiment 1, and the difference is only that: the stirring reaction temperature in this example was 50 ℃.
Example 8
The method for preparing micro-nano structure calcium carbonate and ammonium sulfate by using waste phosphogypsum is basically the same as the method in the embodiment 1, and the difference is only that: the cationic surfactant used in this example was dodecyltrimethylammonium chloride.
Example 9
The method for preparing micro-nano structure calcium carbonate and ammonium sulfate by using waste phosphogypsum is basically the same as the method in the embodiment 1, and the difference is only that: the cationic surfactant used in this example was tetradecyltrimethylammonium bromide.
Example 10
The method for preparing micro-nano structure calcium carbonate and ammonium sulfate by using waste phosphogypsum is basically the same as the method in the embodiment 1, and the difference is only that: the cationic surfactant used in this example was cetyltrimethylammonium chloride.
Example 11
The method for preparing micro-nano structure calcium carbonate and ammonium sulfate by using waste phosphogypsum is basically the same as the method in the embodiment 1, and the difference is only that: the cationic surfactant used in this example was octadecyl trimethyl ammonium bromide.
Comparative example 1
The method for preparing the micro-nano structure calcium carbonate and the ammonium sulfate by using the waste phosphogypsum in the comparative example is basically the same as the method in the example 1, and the difference is only that: this comparative example did not add dodecyltrimethylammonium bromide.
Comparative example 2
The method for preparing the micro-nano structure calcium carbonate and the ammonium sulfate by using the waste phosphogypsum in the comparative example is basically the same as the method in the example 1, and the difference is only that: this comparative example used the anionic surfactant Sodium Dodecylbenzenesulfonate (SDBS) instead of the cationic surfactant dodecyltrimethylammonium bromide of example 1, in a constant amount.
Comparative example 3
The method for preparing the micro-nano structure calcium carbonate and the ammonium sulfate by using the waste phosphogypsum in the comparative example is basically the same as the method in the example 1, and the difference is only that: this comparative example replaces the cationic surfactant dodecyltrimethylammonium bromide of example 1 with the surfactant ammonium citrate, in a constant amount.
The inventors characterize the surface morphologies of the calcium carbonate and ammonium sulfate products obtained in example 1 and comparative examples 1 to 3, wherein the SEM photograph of the calcium carbonate prepared in example 1 is shown in fig. 3, and the SEM photograph of the ammonium sulfate is shown in fig. 4. The SEM photograph of the product calcium carbonate obtained in comparative example 1 is shown in fig. 5, the SEM photograph of the product calcium carbonate obtained in comparative example 2 is shown in fig. 6, and the SEM photograph of the product calcium carbonate obtained in comparative example 3 is shown in fig. 7.
In addition, the surface appearance of the calcium carbonate prepared in the embodiments 8 to 11 of the present invention is substantially the same as that of the calcium carbonate prepared in the embodiment 1, and the calcium carbonate is calcium carbonate with a micro-nano structure.
TABLE 1 comparison of particle size and yield for the products prepared in examples 1-4 and comparative example 1
| (DTAB) addition amount% | The yield of calcium carbonate% | Calcium carbonate particle size (. mu.m) | Yield of ammonium sulfate% | Ammonium sulfate granulesDiameter (mum) | |
| Comparative example 1 | 0 | 70 | 9 | 64 | 2 |
| Example 2 | 1 | 79 | 1.2 | 77 | 1.85 |
| Example 1 | 2 | 90 | 0.55 | 86 | 1.71 |
| Example 3 | 3 | 75 | 1.2 | 80 | 1.80 |
| Example 4 | 4 | 71 | 1.5 | 77 | 1.80 |
As can be seen from Table 1, when the amount of dodecyltrimethylammonium bromide (DTAB) is changed and compared under the condition that other conditions are not changed, the yield is highest when 2% of the surfactant is added, the yield of calcium carbonate is 90%, the yield of ammonium sulfate is 86%, the particle size of the calcium carbonate is not obviously reduced after the addition of 2%, and the appearance of the micron powder with aggregated nanoparticles is obtained from the comparison of 1% to 4%. FIG. 5 shows that the calcium carbonate obtained without adding a surfactant (DTAB) is common light calcium carbonate according to the particle size, and the particle size of the spheres is 10-14 microns. The SEM photograph of the calcium carbonate prepared after adding 2% of the surfactant is shown in figure 3, the particle size is obviously reduced, if the amount of the surfactant is increased, the particle size is not obviously reduced, and some impurities are introduced too much.
TABLE 2 comparison of particle size and yield for the products prepared in example 1 and examples 5-7
| Temperature (. degree.C.) | The yield of calcium carbonate% | Calcium carbonate particle size (. mu.m) | Yield of ammonium sulfate% | Ammonium sulfate particle size (. mu.m) | |
| Example 1 | 25 | 90 | 0.55 | 86 | 1.71 |
| Example 5 | 30 | 83 | 0.57 | 75 | 1.77 |
| Example 6 | 40 | 72 | 0.67 | 69 | 1.85 |
| Example 7 | 50 | 64 | 0.67 | 65 | 1.86 |
From table 2, it can be seen that the yields of calcium carbonate and ammonium sulfate are high at room temperature of 25 ℃, the particle size of calcium carbonate is small, in addition, the temperature is changed without changing other conditions, and it is found that the product obtained by the reaction between room temperature and the conditions of 30 ℃ and 40 ℃ is not significantly improved, i.e. the precipitation effect can be achieved at room temperature.
Under the conditions that the temperature and the number of the surfactants are not changed and the optimal values are used, the sodium dodecyl benzene sulfonate and the ammonium citrate are used as the surfactants for comparison, and the results are shown in the table 3.
Table 3 comparison of particle size and yield of products prepared in example 1 and comparative examples 2 and 3
| Surfactant species | The yield of calcium carbonate% | Calcium carbonate particle size (. mu.m) | Yield of ammonium sulfate% | Ammonium sulfate particle size (. mu.m) | |
| Example 1 | DTAB | 90 | 0.55 | 86 | 1.71 |
| Comparative example 2 | SDBS | 82 | 4 | 70 | 1.82 |
| Comparative example 3 | Ammonium citrate | 91 | 0.67 | 84 | 1.80 |
Tests show that when the addition amount of the surfactant (DTAB) is 2% of the mass of the phosphogypsum, the particle size of the obtained calcium carbonate is smaller. And the yield of the calcium carbonate and the ammonium sulfate is higher, so that the proper proportion of the surfactant is selected, the particle size of the calcium carbonate can be controlled, and the yield of the calcium carbonate and the ammonium sulfate is improved. The temperature contrast experiment shows that the optimum temperature is obtained at room temperature, the difference between the optimum temperature and the result of 30 ℃ is not large, when the temperature is increased again, the hydrolysis of ammonium bicarbonate is accelerated, the yield is obviously influenced, the influence on the yield and the particle size due to the fact that the produced gas is too fast is considered, and the experiment shows that: at room temperature 25 ℃, when the addition of the surfactant is 2% of the mass of the phosphogypsum, the particles of calcium carbonate are smaller and the yields of calcium carbonate and ammonium sulfate are higher.
By comparing the calcium carbonate products of different surfactants, it is found in fig. 6 and 7 that the anionic surfactant (sodium dodecylbenzenesulfonate) SDBS has no effect of reducing the particle size of calcium carbonate particles, while the cationic surfactant has a good effect of adjusting the particle size of calcium carbonate, considering that when the ammonium bicarbonate PH is 8, the cation and bicarbonate anion have a certain attraction to form an anion and a cation pair, and during the reaction, the bicarbonate and ammonium ions are helped to form a buffer system. In the buffer system, sufficient carbonate anion is provided to effectively precipitate calcium carbonate and maintain the solution at a PH of about 8. When the surfactant DTAB is compared with ammonium citrate, the effect on the yield is similar, and the ammonium ions play a role in inhibiting the ionization of bicarbonate radicals in an aqueous solution, but citric acid has chelation and solubilization on calcium ions in calcium carbonate, so that the product calcium carbonate has the phenomena of uneven particle size distribution, easy agglomeration, more difficult drying and the like.
In general, the surfactant DTAB can achieve the best additive effect, but the foaming phenomenon can occur in the reaction system due to the high amount of DTAB, so that the actual production is not facilitated.
Claims (3)
1. A method for preparing micro-nano structure calcium carbonate and ammonium sulfate by using waste phosphogypsum is characterized by comprising the following steps: the method comprises the following steps:
grinding phosphogypsum into powder and dispersing the powder in water to form phosphogypsum dispersion liquid; sequentially adding a cationic surfactant and ammonium bicarbonate into the phosphogypsum dispersion liquid at the temperature of 25-50 ℃ under the stirring condition, continuously stirring and reacting after uniformly mixing until the obtained mixed liquid is free of bubbles, then carrying out suction filtration on the mixed liquid, and drying the obtained upper-layer solid after the suction filtration is finished to obtain calcium carbonate; finally, concentrating and crystallizing the filtrate to obtain ammonium sulfate; wherein: the cationic surfactant is dodecyl trimethyl ammonium bromide; the mass ratio of the cationic surfactant to the phosphogypsum is 2: 100, respectively; the molar ratio of the phosphogypsum to the ammonium bicarbonate is 1: 2.
2. the method for preparing micro-nano structure calcium carbonate and ammonium sulfate by using waste phosphogypsum according to claim 1, which is characterized in that: the stirring reaction time is 1-3 h.
3. The method for preparing micro-nano structure calcium carbonate and ammonium sulfate by using waste phosphogypsum according to claim 1, which is characterized in that: the stirring reaction temperature was 25 ℃.
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