CN114314619A - Method for preparing high-purity magnesium sulfate by using nickel-iron slag as raw material - Google Patents
Method for preparing high-purity magnesium sulfate by using nickel-iron slag as raw material Download PDFInfo
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Abstract
The invention relates to the field of chemical industry and metallurgy, in particular to a method for preparing high-purity magnesium sulfate by using nickel-iron slag as a raw material. The product has high purity, and can meet the requirements of food-grade and pharmaceutical-grade products, thereby remarkably improving the economic added value. The technology has the advantages of high magnesium recovery rate, low production cost, short flow, low requirement on equipment, easy operation and hopeful improvement of the utilization technology of the nickel-iron slag to a new level.
Description
Technical Field
The invention relates to the field of chemical industry, in particular to a method for preparing high-purity magnesium sulfate by using nickel-iron slag as a raw material.
Background
Magnesium sulfate is an important inorganic chemical product, and has wide application in the fields of medicine, food, agriculture, chemical industry and the like. The high-purity magnesium sulfate is a substance with the magnesium sulfate content of more than 99.9 percent, the quality index is far higher than that of industrial-grade magnesium sulfate, and the application range is wider than that of the industrial-grade magnesium sulfate. At present, the high-purity magnesium sulfate is generally obtained by purifying industrial-grade magnesium sulfate; or after industrial magnesium oxide or high-purity magnesium oxide reacts with sulfuric acid, the magnesium sulfate is prepared by different impurity removal methods, industrial-grade magnesium sulfate contains numerous impurities, such as potassium salt, sodium salt, calcium salt and other metal salt impurities, in the impurity removal process, heavy metal salt is removed by adding alkali to adjust the pH value, a small amount of potassium salt, sodium salt and calcium salt are difficult to remove, calcium and magnesium are homologous elements, chemical properties are very similar, and in the purification process, the calcium salt impurity is difficult to remove, so that the calcium content in the product exceeds the standard. Especially, the calcium ion content of magnesium sulfate used in medicine is not more than 0.02%. For example, patent (CN107935003A) provides a method for preparing high-purity magnesium sulfate from magnesium sulfate waste liquid. The method mainly comprises the steps of roasting magnesium sulfate waste at high temperature, hydrating, and then concentrating and crystallizing twice to prepare the high-purity magnesium sulfate. The preparation process related by the invention is more complicated, and the problem of calcium salt impurities in the prepared magnesium sulfate is not effectively solved. The invention patent (CN103058235A) discloses a method for removing calcium from magnesium sulfate and high-purity magnesium sulfate, wherein calcium ions in magnesium sulfate are precipitated by hydrofluoric acid to obtain high-purity magnesium sulfate, but the hydrofluoric acid belongs to a high-corrosion liquid, so that the production, storage and use processes are extremely dangerous, and precipitates are difficult to treat.
Ferronickel slag is a waste produced by cooling slag in ferronickel production, and generally, ferronickel slag is composed of magnesium, silicon, iron, aluminum and a small amount of harmful elements, such as chromium, which may be converted into toxic water-soluble hexavalent chromium, and poses a threat to the ecological environment and human health. In recent years, the smelting scale of ferronickel alloy in China is continuously enlarged, the discharge amount of ferronickel slag is increased year by year, the ferronickel slag is often limited by factors such as low reaction activity, high content of harmful elements, high operation cost and the like, so that the utilization rate is low, and the ferronickel slag is mainly stockpiled and buried, not only occupies land, but also pollutes the environment and brings a serious challenge to the sustainable development of the ferronickel industry. Therefore, the research of the novel and efficient recycling method of the ferronickel slag is greatly carried out, and the research has great significance for promoting the value-added utilization of the ferronickel slag and the sustainable development of the ferronickel industry.
At present, there are some reports on the recovery of Ni and Cr from ferronickel slag, but it is limited to the treatment of special types of ferronickel slag with high Ni and Cr contents. With the improvement of the smelting technical level and the reduction of the actual content of Ni and Cr in the slag, the economic benefit of recovering Ni and Cr from the nickel-iron slag is not high, and the reduction of the nickel-iron slag cannot be realized. Thus, attention has been shifted to the main magnesium metal in the ferronickel slag. By using a vacuum reduction method, the magnesium oxide in the nickel-iron slag is directly reduced into metal magnesium by taking the mixture of the nickel-iron slag and a reducing agent as raw materials. However, because of the strong stability of magnesium oxide in slag and the high susceptibility of magnesium vapor to oxidation, the separation and recovery under high temperature and high vacuum conditions are required, and therefore, the requirements for equipment, reduction conditions and production safety are high, and thus, the technology is difficult to be applied industrially. The subject group firstly reports orthogonal test and kinetic analysis of magnesium leached from the ferronickel slag at home and abroad in 2020 (see the paper "nonferrous metals, 1: 18-21" for details, which is an important step for recovering magnesium from the ferronickel slag to prepare various magnesium salts; in 2021, the subject group successfully adopts an atmospheric pressure leaching-crystallization method to recover magnesium from the ferronickel slag to prepare magnesium sulfate products with mixed crystal water (see the paper "Journal of Cleaner Production 303(2021) 127049" for details and the patent of a method for recovering magnesium from the ferronickel slag (CN111926193A)), however, the magnesium sulfate products prepared by the methods have low purity and contain MgSO 111926193A)4·nH2The content of O is 99.2 percent, the content of impurity Fe is high (0.5-0.7 percent), Cr and Ni elements (0.02-0.05 percent) are detected, and the magnesium sulfate is possibly suitable for the condition that the requirements on magnesium sulfate products are low, such as agricultural fertilizers, leather additives and the like, but the requirements on food-grade and pharmaceutical-grade magnesium sulfate products are difficult to meet. In addition, the preparation process needs to use more absolute ethyl alcohol for washing so as to remove a large amount of non-volatile sulfuric acid and partial impurities remained in the crystals, thereby increasing the production cost and the complexity of process operation and reducing the production safety.
Disclosure of Invention
The invention aims to solve the technical problems of low product purity, narrow application range, low economic added value, complex process and low production safety of the method for preparing magnesium sulfate by using nickel-iron slag as a raw material in the prior art, thereby providing the method for preparing high-purity magnesium sulfate by using nickel-iron slag as a raw material.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows:
a process for preparing high-purity magnesium sulfate from the nickel-iron dregs includes such steps as ordinary-pressure leaching of nickel-iron dregs in concentrated sulfuric acid, adding crystal seeds, crystallizing to educe out coarse magnesium sulfate, separating solid phase, dissolving in water, neutralizing, hydrolyzing, depositing, purifying, and crystallizing to educe out high-purity magnesium sulfate.
A method for preparing high-purity magnesium sulfate by using nickel-iron slag as a raw material comprises the following steps:
s1, preprocessing: drying, grinding and screening the ferronickel slag to obtain ferronickel slag powder;
s2, leaching: heating, stirring and leaching the nickel-iron slag powder in concentrated sulfuric acid under normal pressure, and filtering to obtain filtrate as primary crystallization stock solution;
s3, primary crystallization: adding seed crystals into the primary crystallization stock solution, separating out the primary crystallization and separating a solid phase to obtain crude magnesium sulfate;
s4, purification: dissolving the crude magnesium sulfate in pure water or dilute sulfuric acid, adding a neutralizing agent, neutralizing, hydrolyzing and precipitating, and purifying to remove impurities to obtain magnesium sulfate refined solution;
s5, secondary crystallization: and (4) carrying out secondary crystallization on the magnesium sulfate fine solution to separate out high-purity magnesium sulfate.
Further, in step S2, the particle size of the ferronickel slag powder is not greater than 38 μm, the concentration of the concentrated sulfuric acid is 5-18N, the liquid-solid ratio of the concentrated sulfuric acid to the ferronickel slag is 5-40: 1L/kg, the leaching temperature is 140-210 ℃, and the stirring speed is 150-1500 rpm.
Further, in step S3, the seed crystal is at least one of anhydrous magnesium sulfate, magnesium sulfate monohydrate, magnesium sulfate dihydrate, magnesium sulfate trihydrate, magnesium sulfate tetrahydrate, magnesium sulfate pentahydrate, magnesium sulfate hexahydrate, and magnesium sulfate heptahydrate; the seed crystal coefficient is 0.2-1.2, the crystallization temperature range is-30-110 ℃, the crystallization time is 2-20 h, and the crystallization stirring speed is 10-500 rpm.
Further, in step S4, stirring at 25-105 deg.C for purification and impurity removal, with a stirring speed of 100-1500 rpm, a reaction time of 30-300 min, and a reaction end point pH of 2-12.
Further, in step S4, the neutralizing agent is at least one of magnesium oxide, magnesium hydroxide, magnesium carbonate, and ammonia water.
Further, in step S5, the crystallization temperature is in the range of-30 to 110 ℃, the crystallization time is 0.5 to 20 hours, and the stirring speed of the crystallization is 10 to 500 rpm.
Furthermore, the primary crystallization and the secondary crystallization can adopt a single variable-temperature cooling crystallization or constant-temperature evaporation crystallization mode, and can also adopt a crystallization mode of cooling and evaporation; the crystallization temperature may be any constant temperature within the temperature range, and may be a crystallization starting temperature and a crystallization finishing temperature.
Further, the high-purity magnesium sulfate is high-purity anhydrous magnesium sulfate and/or high-purity hydrated magnesium sulfate, and the molecular formula of the high-purity anhydrous magnesium sulfate is MgSO4·nH2O, n is more than or equal to 0 and less than or equal to 7, n can be any one of the numerical values of 0-7, and MgSO is contained in high-purity magnesium sulfate4·nH2The content of O is more than or equal to 99.9 percent.
Furthermore, the requirement on the purity of the seeds is not high during primary crystallization, and the pure magnesium sulfate chemical reagent is analyzed; the purity of the seed crystal is required to be high during the secondary crystallization, and the high-purity magnesium sulfate produced in the step S5 can be used as the seed crystal.
Further, in the step S1, the nickel-iron slag is dried at 100 to 105 ℃ for 8 to 12 hours, and then ball-milled on a planetary ball mill, and after ball-milling, the nickel-iron slag is sieved by a 300-mesh sieve, particles larger than 38 μm are returned to the next batch for ball-milling, and the process is repeated, and finally, the materials sieved by all batches are uniformly mixed.
Further, the seed crystal coefficient is preferably 0.4 to 1.
The technical scheme of the invention has the following advantages:
1. the method adopts the all-wet process to convert magnesium in the nickel-iron slag into magnesium sulfate for recycling the magnesium, has simple process, easy operation, low requirement on equipment, high magnesium recycling rate, wide application range of high-purity magnesium sulfate and high added value of products, can be applied to the fields of food, medicine, agriculture and the like, and can obviously improve the utilization rate of the nickel-iron slag.
2. The primary crystallization is carried out in a strong acid environment, and the solution is not neutralized before, so that the aim of ensuring that the crystallized solution has enough acidity and is convenient for recycling the solvent is fulfilled, the acid consumption is reduced, and the production cost is saved. The purification process is arranged between the primary crystallization and the secondary crystallization instead of before the primary crystallization, so as to reduce the consumption of the neutralizer and the production cost.
3. The invention strictly limits the particle size of the ferronickel slag, so that the magnesium can be leached without adding any cosolvent in the leaching process, and the reduction of the purity of the magnesium sulfate product caused by the synchronous crystallization of cosolvent derivatives and magnesium sulfate is avoided. As the production raw materials and the solvent do not contain chlorine, the prepared high-purity magnesium sulfate is chlorine-free magnesium sulfate.
4. The invention limits the technological parameters such as reaction temperature, reaction time, terminal pH value and the like in the process of neutralization, hydrolysis and precipitation, thereby removing impurity elements as much as possible in the purification process, reducing the loss of magnesium element as little as possible, and simultaneously controlling the addition of a neutralizing agent as much as possible to reduce the production cost and foreign impurities, which is the key for preparing high-purity magnesium sulfate products.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments or the prior art descriptions are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained according to the drawings without creative efforts for those skilled in the art.
FIG. 1 is a process flow diagram of the method for preparing high-purity magnesium sulfate by using ferronickel slag as a raw material according to the invention. The figure shows that the nickel-iron slag is used as a raw material to obtain a high-purity magnesium sulfate product, and the method mainly comprises the steps of raw material pretreatment, leaching, primary crystallization and secondary crystallization.
FIG. 2 is an XRD pattern of a ferronickel slag feedstock used in the present invention; the figure shows that the main phase structure of the nickel-iron slag is single forsterite phase (Mg, Fe)2SiO4In which Fe2+With Mg2+The ionic radii are very close and exist in solid solution. The rest of the impurity elementsThe content of the predisposing factor is low and is not shown in XRD.
Figure 3 is an XRD pattern of the high purity magnesium sulfate product of example 1 of this invention. This figure illustrates that magnesium sulfate hexahydrate (MgSO 4), a single phase, can be prepared by the process under suitable reaction conditions4·6H2O) products.
FIG. 4 is an SEM photograph of high purity magnesium sulfate as a product of example 1 of the present invention. The figure illustrates that the magnesium sulfate product prepared by the method is formed by agglomeration of a plurality of micron-sized blocky crystal grains under proper reaction conditions, and the particle size is larger.
Figure 5 is an XRD pattern of the high purity magnesium sulfate product of example 2 of the present invention. The figure illustrates that the magnesium sulfate product prepared by the process under suitable reaction conditions is formed from magnesium sulfate hexahydrate (MgSO 4)4·6H2O) and magnesium sulfate tetrahydrate (MgSO)4·4H2O) two phases.
FIG. 6 is an SEM photograph of high purity magnesium sulfate as a product of example 2 of the present invention. The figure illustrates that the magnesium sulfate product prepared by the method is formed by agglomeration of a plurality of micron-sized blocky crystal grains under proper reaction conditions, and the particle size is small.
Detailed Description
The following examples are provided to further understand the present invention, not to limit the scope of the present invention, but to provide the best mode, not to limit the content and the protection scope of the present invention, and any product similar or similar to the present invention, which is obtained by combining the present invention with other prior art features, falls within the protection scope of the present invention.
The method for preparing the high-purity magnesium sulfate by using the nickel-iron slag as the raw material comprises the following steps of preparing according to the process flow shown in the figure 1. In order to simplify the content of the embodiments, the following descriptions are made for the common content in the embodiments:
(1) the step S1 includes the steps of drying, grinding, screening, weighing and the like of the ferronickel slag. Drying the nickel-iron slag at 105 ℃ for 12h, then carrying out ball milling on a planetary ball mill for 3h, wherein the rotation rate is 300rpm, the revolution rate is 600rpm, the nickel-iron slag is sieved by a 300-mesh sieve after ball milling, particles larger than 38 mu m return to the next batch of ball milling, repeating the process, and finally uniformly mixing the sieved materials of all batches to serve as a solute for subsequent leaching.
(2) In the step S1, the ferronickel slag raw materials have the same components, as shown in table 1, and the phase structure thereof is shown in fig. 2.
TABLE 1 table of main chemical compositions of ferronickel slag raw material
(3) In the leaching process of the step S2, in order to reduce the entrainment of filtrate in the filter cake, after the filtration is finished, the filter cake is washed for 2 times by using a 3N hot sulfuric acid solution to obtain a washing liquid, the washing liquid is mixed with the filtrate, the mixed liquid is adjusted to 400ml by using the hot sulfuric acid solution with the same concentration, and the obtained solution is used as a crystallization stock solution of magnesium sulfate.
(4) If the total solvent evaporation is adopted in the secondary crystallization mode in the step S5 (as in example 1), solid-liquid separation is not needed after the secondary crystallization, and if partial solvent evaporation is adopted, solid-liquid separation is needed subsequently.
(5) The concentration of each element in the solution and the concentration of Mg element in the ferronickel slag are tested by adopting an inductively coupled plasma mass spectrometer (ICP-MS), and the concentration of the rest elements in the ferronickel slag are tested by adopting an X-ray fluorescence spectrometer (XRF).
(6) The crystallization temperature can be any constant temperature in the temperature range, and can also be a crystallization starting temperature and a crystallization finishing temperature, and each embodiment is determined according to actual needs.
The specific embodiment is as follows:
example 1
The embodiment relates to a method for preparing high-purity magnesium sulfate hexahydrate by using nickel-iron slag as a raw material, which comprises the following steps:
s1, preprocessing: drying the nickel-iron slag at 105 ℃ for 12h, then carrying out ball milling on a planetary ball mill for 3h, wherein the rotation rate is 300rpm, the revolution rate is 600rpm, the nickel-iron slag is sieved by a 300-mesh sieve after ball milling, particles larger than 38 mu m return to the next batch of ball milling, repeating the process, and finally uniformly mixing the sieved materials of all batches to serve as a solute for subsequent leaching.
S2, leaching: weighing 20g of fine ferronickel slag powder, placing the fine ferronickel slag powder into a three-neck flask, adding a 15N (Mol/L) sulfuric acid solution under the condition that the liquid-solid ratio is 20:1(ml/g), then transferring the flask into a constant-temperature heating sleeve, heating and stirring the flask, taking out the flask after stirring the solution at a constant temperature for 120min when the temperature of the solution is raised to 180 ℃, standing the solution for 30min, carrying out vacuum filtration on the leached slurry by using a Buchner funnel, and taking the filtrate as a primary crystallization stock solution after constant volume.
S3, primary crystallization: the seed crystal coefficient is 0.5:1 as a seed crystal, to induce crystallization of magnesium sulfate in the magnesium sulfate crystallization stock solution. Firstly, placing primary crystallization stock solution in a big beaker and a water bath kettle, setting the initial crystallization temperature to be 90 ℃, setting the final crystallization temperature to be room temperature (25 ℃), and setting the cooling time to be 10 h. And adding seed crystals into the stock solution while stirring at the speed of 50rpm when the temperature of the solution is reduced, taking out the slurry when the temperature of the solution is reduced to room temperature, and performing vacuum filtration to obtain the primary crystallized crude magnesium sulfate.
S4, purification: magnesium oxide is used as a neutralizing agent. The crude magnesium sulfate obtained by the primary crystallization was dissolved in pure water as a solvent to prepare a crude magnesium sulfate solution. Firstly, placing a crude magnesium sulfate solution obtained by primary crystallization in a big beaker, placing the beaker in a water bath kettle, continuously adding magnesium oxide for neutralization at the reaction temperature of 75 ℃ for 2h, stirring at the same time with the pH end point of 6, taking out the solution and standing for 2h at normal temperature when the reaction is finished, and then carrying out solid-liquid separation by a vacuum suction filtration pump to obtain magnesium sulfate refined solution.
S5, secondary crystallization: the magnesium sulfate fine liquid is used as a crystallization stock solution of secondary crystallization, and the secondary crystallization is carried out in a rotary evaporator. And (3) placing the crystallization stock solution into a distillation flask of a rotary evaporator, and placing the distillation flask into a water bath kettle at a certain temperature for vacuum constant-temperature evaporation crystallization. The crystallization temperature is 35 ℃, the crystallization time is 2h, the stirring speed is 100rpm, and the crystallization is carried out under a certain vacuum degree. And taking out the sample after the solvent is evaporated to dryness, and drying at 40 ℃ for 24h to obtain the final high-purity magnesium sulfate hexahydrate crystal.
Through test analysis, in the embodiment, the leaching rate of magnesium is 95.22%, the main chemical components of the prepared high-purity magnesium sulfate hexahydrate crystal are shown in table 2, wherein the mass percentage of magnesium is 11.35%, and the purity of magnesium sulfate reaches 99.98%.
TABLE 2 Main chemical composition of high purity magnesium sulfate hexahydrate product
Note: the unit of expression is mg/kg
As can be seen from the data in Table 2, the chemical composition of the high purity magnesium sulfate prepared by the method of the present invention meets the requirements of food grade magnesium sulfate and even pharmaceutical grade magnesium sulfate. Wherein the impurity element with the highest content is Ca, but the content of the impurity element does not exceed the requirement of medical-grade magnesium sulfate on the content of Ca (less than or equal to 0.02 percent). The other elements are ppm level and are far lower than the requirements of food-grade and medical-grade magnesium sulfate.
Example 2
The embodiment relates to a method for preparing mixed crystal water type high-purity magnesium sulfate by using nickel-iron slag as a raw material, which comprises the following steps:
s1, preprocessing: the same as in example 1.
S2, leaching: weighing 20g of fine ferronickel slag powder, placing the fine ferronickel slag powder into a three-neck flask, adding a sulfuric acid solution with the concentration of 11N under the condition that the liquid-solid ratio is 10:1(ml/g), then moving the flask into a constant-temperature heating sleeve, heating and stirring the mixture, stirring the mixture at a constant temperature for 180min when the temperature of the solution is raised to 170 ℃, taking out the flask, standing the mixture for 30min, performing vacuum filtration on the leached slurry by using a Buchner funnel, and taking the filtrate as primary crystallization stock solution after constant volume.
S3, primary crystallization: magnesium sulfate heptahydrate with the seed crystal coefficient of 1:1 is used as the seed crystal to induce the crystallization and precipitation of magnesium sulfate in the magnesium sulfate crystallization stock solution. Firstly, placing primary crystallization stock solution in a big beaker and a water bath kettle, setting the initial crystallization temperature to be 85 ℃, setting the final crystallization temperature to be room temperature (25 ℃) and setting the cooling time to be 10 hours. And adding seed crystals into the stock solution while stirring at the speed of 60rpm when the temperature of the solution is reduced, taking out the slurry when the temperature of the solution is reduced to room temperature, and performing vacuum filtration to obtain the primary crystallized crude magnesium sulfate.
S4, purification: magnesium oxide is used as a neutralizing agent. The crude magnesium sulfate obtained by the primary crystallization was dissolved in pure water as a solvent to prepare a crude magnesium sulfate solution. Firstly, placing a primary crystallized magnesium sulfate solution in a big beaker, placing the big beaker in a water bath kettle, stirring at a constant temperature of 75 ℃ at a stirring speed of 500rpm, adding magnesium oxide serving as a neutralizing agent into the big beaker for multiple times, gradually precipitating and separating out impurity precipitates in the reaction process, measuring the pH value of the final point of the solution to be 6 after reacting for 2 hours, taking out the solution, standing for 2 hours at normal temperature, and then carrying out vacuum filtration to obtain the magnesium sulfate refined solution.
S5, secondary crystallization: the magnesium sulfate fine liquid is used as a crystallization stock solution of secondary crystallization, and the secondary crystallization is carried out in a rotary evaporator. And (3) putting the crystallization stock solution into a distillation flask of a rotary evaporator, carrying out vacuum constant-temperature evaporation in a water bath kettle at 50 ℃, simultaneously stirring at the stirring speed of 50rpm, taking out a sample after the solvent is evaporated to dryness, and carrying out vacuum drying at 40 ℃ for 24h to obtain the final high-purity magnesium sulfate crystal.
Through test analysis, the leaching rate of magnesium is 94.31%, the main chemical components of the obtained high-purity magnesium sulfate crystal containing the mixed crystal water are shown in the table 3, the mass percentage of magnesium is 13.39%, and the purity of magnesium sulfate reaches 99.97%.
TABLE 3 main chemical composition of high purity magnesium sulfate crystals containing mixed crystal water
Note: the unit is mg/kg
Example 3
The embodiment relates to a method for preparing high-purity magnesium sulfate by using nickel-iron slag as a raw material, which comprises the following steps:
s1, preprocessing: the same as in example 1.
S2, leaching: weighing 20g of fine ferronickel slag powder, placing the fine ferronickel slag powder into a three-neck flask, adding a 15N (Mol/L) sulfuric acid solution under the condition that the liquid-solid ratio is 20:1(ml/g), then transferring the flask into a constant-temperature heating sleeve, heating and stirring the flask, taking out the flask after stirring the solution at a constant temperature for 120min when the temperature of the solution is raised to 160 ℃, standing the solution for 30min, carrying out vacuum filtration on the leached slurry by using a Buchner funnel, and taking the filtrate as a primary crystallization stock solution after constant volume.
S3, primary crystallization: magnesium sulfate heptahydrate with the seed crystal coefficient of 1:1 is used as the seed crystal to induce the crystallization and precipitation of magnesium sulfate in the magnesium sulfate crystallization stock solution. Firstly, placing a crystallization stock solution in a big beaker and a water bath kettle, setting the initial crystallization temperature to be 90 ℃, setting the final crystallization temperature to be room temperature (25 ℃), and setting the cooling time to be 15 h. And adding seed crystals into the stock solution when the temperature is reduced, stirring at the speed of 90rpm, taking out the slurry when the solution is reduced to room temperature, and performing vacuum filtration to obtain a primary crystallized magnesium sulfate intermediate product.
S4, purification: magnesium oxide is used as a neutralizing agent. The crude magnesium sulfate obtained by the primary crystallization was dissolved in pure water as a solvent to prepare a crude magnesium sulfate solution. Firstly, placing a primary crystallized magnesium sulfate solution in a big beaker, placing the beaker in a water bath kettle, wherein the reaction temperature is 45 ℃, the reaction time is 3 hours, continuously adding magnesium oxide for neutralization, the pH end point of the reaction is 6, simultaneously stirring, the stirring speed is 500rpm, when the reaction is finished, taking out the solution, standing for 2 hours at normal temperature, and then carrying out solid-liquid separation by a vacuum suction filtration pump.
S5, secondary crystallization: the magnesium sulfate fine liquid is used as a crystallization stock solution of secondary crystallization, and the secondary crystallization is carried out in a rotary evaporator. The crystallization stock solution was placed in a distillation flask of a rotary evaporator, and vacuum constant temperature evaporation was carried out in a 25 ℃ water bath while stirring at a stirring speed of 100 rpm. And (4) taking out the slurry after 15h of crystallization, carrying out vacuum filtration, and carrying out vacuum drying on the crystallized product at 40 ℃ for 24h to obtain the final high-purity magnesium sulfate crystal.
Through test analysis, the leaching rate of magnesium is 94.58%, the mass percentage content of magnesium in the obtained high-purity magnesium sulfate crystal is 10.52%, the purity of magnesium sulfate reaches 99.99%, and the content of Ca is only 0.009%.
As can be seen from this example, if the partial solvent evaporation method is used in step S5, the purity of magnesium sulfate can be further improved, mainly because impurities such as Ca are concentrated in the post-crystallization solution during the crystallization process, and the crystallization also plays a role in purification. Impurities in the magnesium sulfate refined solution are completely remained in the magnesium sulfate product by adopting a total solvent evaporation method, and even if the total solvent evaporation method is adopted in secondary crystallization, the product purity still meets the requirement of high-purity magnesium sulfate.
Example 4
The embodiment relates to a method for preparing high-purity magnesium sulfate by using nickel-iron slag as a raw material, which comprises the following steps:
s1, preprocessing: the same as in example 1.
S2, leaching: weighing 20g of fine ferronickel slag powder, placing the fine ferronickel slag powder into a three-neck flask, adding a sulfuric acid solution with the concentration of 13N (Mol/L) under the condition that the liquid-solid ratio is 15:1(ml/g), then moving the flask into a constant-temperature heating sleeve, heating and stirring the flask, taking out the flask after the temperature of the solution rises to 180 ℃, stirring the solution at the constant temperature for 60min, standing the solution for 30min, carrying out vacuum filtration on the leached slurry by using a Buchner funnel, and taking the filtrate as a primary crystallization stock solution after constant volume.
S3, primary crystallization: magnesium sulfate heptahydrate with the seed crystal coefficient of 1:1 is used as the seed crystal to induce the crystallization and precipitation of magnesium sulfate in the magnesium sulfate crystallization stock solution. Firstly, placing a crystallization stock solution in a big beaker and a water bath kettle, setting the initial crystallization temperature to be 80 ℃, setting the final crystallization temperature to be room temperature (25 ℃), and setting the cooling time to be 10 h. And adding seed crystals into the stock solution when the temperature is reduced, stirring at the speed of 60rpm, taking out the slurry when the solution is reduced to room temperature, and performing vacuum filtration to obtain a primary crystallized magnesium sulfate intermediate product.
S4, purification: magnesium oxide is used as a neutralizing agent. The crude magnesium sulfate obtained by the primary crystallization was dissolved in pure water as a solvent to prepare a crude magnesium sulfate solution. Firstly, placing a primary crystallized magnesium sulfate solution in a big beaker, placing the beaker in a water bath, keeping the reaction temperature at 85 ℃, keeping the reaction time at 1.5h, continuously adding magnesium oxide for neutralization, keeping the pH end point of the reaction at 4, simultaneously stirring at the stirring speed of 500rpm, taking out the solution when the reaction is finished, standing the solution at normal temperature for 2h, and then carrying out solid-liquid separation by a vacuum suction filtration pump.
S5, secondary crystallization: the magnesium sulfate fine liquid is used as a crystallization stock solution of secondary crystallization, and the secondary crystallization is carried out in a rotary evaporator. And (3) putting the crystallization stock solution into a distillation flask of a rotary evaporator, carrying out vacuum constant-temperature evaporation in a water bath kettle at 70 ℃, simultaneously stirring at the stirring speed of 100rpm, taking out a sample after the solvent is evaporated to dryness, and carrying out vacuum drying at 40 ℃ for 24 hours to obtain the final high-purity magnesium sulfate crystal.
Through test analysis, the leaching rate of magnesium is 93.26%, the mass percentage content of magnesium in the obtained high-purity magnesium sulfate crystal is 10.45%, and the purity of magnesium sulfate reaches 99.97%.
Example 5
The embodiment relates to a method for preparing high-purity magnesium sulfate by using nickel-iron slag as a raw material, which comprises the following steps:
s1, preprocessing: the same as in example 1.
S2, leaching: weighing 20g of fine ferronickel slag powder, placing the fine ferronickel slag powder into a three-neck flask, adding a sulfuric acid solution with the concentration of 8N (Mol/L) under the condition that the liquid-solid ratio is 8:1(ml/g), then transferring the flask into a constant-temperature heating sleeve, heating and stirring the flask, taking out the flask after the temperature of the solution rises to 170 ℃, stirring the solution at the constant temperature for 60min, standing the solution for 30min, carrying out vacuum filtration on the leached slurry by using a Buchner funnel, and taking the filtrate as a primary crystallization stock solution after constant volume.
S3, primary crystallization: magnesium sulfate heptahydrate with the seed crystal coefficient of 1:1 is used as the seed crystal to induce the crystallization and precipitation of magnesium sulfate in the magnesium sulfate crystallization stock solution. Firstly, placing a crystallization stock solution in a big beaker and a water bath kettle, setting the initial crystallization temperature to be 90 ℃, setting the final crystallization temperature to be room temperature (25 ℃), and setting the cooling time to be 10 h. And adding seed crystals into the stock solution when the temperature is reduced, stirring at the speed of 60rpm, taking out the slurry when the solution is reduced to room temperature, and performing vacuum filtration to obtain a primary crystallized magnesium sulfate intermediate product.
S4, purification: magnesium oxide is used as a neutralizing agent. The crude magnesium sulfate obtained by the primary crystallization was dissolved in pure water as a solvent to prepare a crude magnesium sulfate solution. Firstly, placing a primary crystallized magnesium sulfate solution in a big beaker, placing the beaker in a water bath kettle, wherein the reaction temperature is 55 ℃, the reaction time is 4 hours, continuously adding magnesium oxide for neutralization, the pH end point of the reaction is 5, simultaneously stirring, the stirring speed is 600rpm, when the reaction is finished, taking out the solution, standing for 2 hours at normal temperature, and then carrying out solid-liquid separation by a vacuum suction filtration pump.
S5, secondary crystallization: the magnesium sulfate fine liquid is used as a crystallization stock solution of secondary crystallization, and the secondary crystallization is carried out in a rotary evaporator. And (3) putting the crystallization stock solution into a distillation flask of a rotary evaporator, carrying out vacuum constant-temperature evaporation in a water bath kettle at the temperature of 60 ℃, simultaneously stirring at the stirring speed of 280rpm, crystallizing for 10 hours, carrying out vacuum filtration, and carrying out vacuum drying on a solid-phase product at the temperature of 40 ℃ for 24 hours to obtain the final high-purity magnesium sulfate crystal.
Through test analysis, the leaching rate of magnesium is 95.04%, the mass percentage of magnesium in the obtained high-purity magnesium sulfate crystal is 10.49%, and the purity of magnesium sulfate reaches 99.99%.
Example 6
The embodiment relates to a method for preparing high-purity magnesium sulfate by using nickel-iron slag as a raw material, which comprises the following steps:
s1, preprocessing: the same as in example 1.
S2, leaching: weighing 20g of fine ferronickel slag powder, placing the fine ferronickel slag powder into a three-neck flask, adding a 15N (Mol/L) sulfuric acid solution under the condition that the liquid-solid ratio is 20:1(ml/g), then transferring the flask into a constant-temperature heating sleeve, heating and stirring the flask, taking out the flask after stirring the solution at a constant temperature for 120min when the temperature of the solution is raised to 180 ℃, standing the solution for 30min, carrying out vacuum filtration on the leached slurry by using a Buchner funnel, and taking the filtrate as a primary crystallization stock solution after constant volume.
S3, primary crystallization: magnesium sulfate heptahydrate with a seed crystal coefficient of 0.5:1 is used as a seed crystal to induce crystallization of magnesium sulfate in the magnesium sulfate crystallization stock solution. Firstly, placing a crystallization stock solution in a big beaker and a water bath kettle, setting the initial crystallization temperature to be 90 ℃, setting the final crystallization temperature to be room temperature (25 ℃), and setting the cooling time to be 10 h. And adding seed crystals into the stock solution when the temperature is reduced, stirring at the speed of 50rpm, taking out the slurry when the solution is reduced to room temperature, and performing vacuum filtration to obtain a primary crystallized magnesium sulfate intermediate product.
S4, purification: magnesium oxide is used as a neutralizing agent. The crude magnesium sulfate obtained by the primary crystallization was dissolved in pure water as a solvent to prepare a crude magnesium sulfate solution. Firstly, placing a primary crystallized magnesium sulfate solution in a big beaker, placing the beaker in a water bath kettle, wherein the reaction temperature is 65 ℃, the reaction time is 3 hours, continuously adding magnesium oxide for neutralization, the pH end point of the reaction is 8, simultaneously stirring, the stirring speed is 500rpm, when the reaction is finished, taking out the solution, standing for 2 hours at normal temperature, and then carrying out solid-liquid separation by a vacuum suction filtration pump.
S5, secondary crystallization: the magnesium sulfate fine liquid is used as a crystallization stock solution of secondary crystallization, and the secondary crystallization is carried out in a rotary evaporator. And (3) putting the crystallization stock solution into a distillation flask of a rotary evaporator, carrying out vacuum constant-temperature evaporation in a water bath kettle at the temperature of 80 ℃, simultaneously stirring at the stirring speed of 200rpm, taking out a sample after the solvent is evaporated to dryness, and carrying out vacuum drying at the temperature of 40 ℃ for 24 hours to obtain the final high-purity magnesium sulfate crystal.
Through test analysis, the leaching rate of magnesium is 93.18%, the mass percentage content of magnesium in the obtained high-purity magnesium sulfate crystal is 10.44%, and the purity of magnesium sulfate reaches 99.96%.
Example 7
The embodiment relates to a method for preparing high-purity magnesium sulfate by using nickel-iron slag as a raw material, which comprises the following steps:
s1, preprocessing: the same as in example 1.
S2, leaching: the same as in example 2.
S3, primary crystallization: magnesium sulfate heptahydrate with a seed crystal coefficient of 0.75:1 is used as a seed crystal to induce crystallization of magnesium sulfate in the magnesium sulfate crystallization stock solution. Firstly, placing a crystallization stock solution in a big beaker and a water bath kettle, setting the initial crystallization temperature to be 90 ℃, setting the final crystallization temperature to be room temperature (25 ℃), and setting the cooling time to be 16 h. And adding seed crystals into the stock solution when the temperature is reduced, stirring at the speed of 50rpm, taking out the slurry when the solution is reduced to room temperature, and performing vacuum filtration to obtain a primary crystallized magnesium sulfate intermediate product.
S4, purification: magnesium oxide is used as a neutralizing agent. The crude magnesium sulfate obtained by the primary crystallization was dissolved in pure water as a solvent to prepare a crude magnesium sulfate solution. Firstly, placing a primary crystallized magnesium sulfate solution in a big beaker, placing the beaker in a water bath kettle, wherein the reaction temperature is 55 ℃, the reaction time is 4 hours, continuously adding magnesium oxide for neutralization, the pH end point of the reaction is 8, simultaneously stirring, the stirring speed is 500rpm, when the reaction is finished, taking out the solution, standing for 2 hours at normal temperature, and then carrying out solid-liquid separation by a vacuum suction filtration pump.
S5, secondary crystallization: the magnesium sulfate fine liquid is used as a crystallization stock solution of secondary crystallization, and the secondary crystallization is carried out in a rotary evaporator. And (3) putting the crystallization stock solution into a distillation flask of a rotary evaporator, carrying out vacuum constant-temperature evaporation in a water bath kettle at the temperature of 35 ℃, simultaneously stirring at the speed of 100rpm, taking out a sample after the solvent is evaporated to dryness, and carrying out vacuum drying at the temperature of 40 ℃ for 24 hours to obtain the final high-purity magnesium sulfate crystal.
Through test analysis, the leaching rate of magnesium is 93.18%, the mass percentage content of magnesium in the obtained high-purity magnesium sulfate crystal is 10.43%, and the purity of magnesium sulfate reaches 99.95%.
Example 8
The embodiment relates to a method for preparing high-purity magnesium sulfate by using nickel-iron slag as a raw material, which comprises the following steps:
s1, preprocessing: the same as in example 1.
S2, leaching: weighing 20g of fine ferronickel slag powder, placing the fine ferronickel slag powder into a three-neck flask, adding a sulfuric acid solution with the concentration of 11N (Mol/L) under the condition that the liquid-solid ratio is 8:1(ml/g), then moving the flask into a constant-temperature heating sleeve, heating and stirring simultaneously, taking out the flask after stirring at constant temperature for 80min when the temperature of the solution is raised to 120 ℃, standing for 30min, carrying out vacuum filtration on the leaching slurry by using a Buchner funnel, and taking the filtrate as a primary crystallization stock solution after constant volume.
S3, primary crystallization: magnesium sulfate heptahydrate with a seed crystal coefficient of 0.25:1 is used as a seed crystal to induce crystallization of magnesium sulfate in the magnesium sulfate crystallization stock solution. Firstly, placing a crystallization stock solution in a big beaker and a water bath kettle, setting the initial crystallization temperature to be 85 ℃, setting the final crystallization temperature to be room temperature (25 ℃), and setting the cooling time to be 5 h. And adding seed crystals into the stock solution when the temperature is reduced, stirring at the speed of 60rpm, taking out the slurry when the solution is reduced to room temperature, and performing vacuum filtration to obtain a primary crystallized magnesium sulfate intermediate product.
S4, purification: magnesium oxide is used as a neutralizing agent. The crude magnesium sulfate obtained by the primary crystallization was dissolved in pure water as a solvent to prepare a crude magnesium sulfate solution. Firstly, placing a primary crystallized magnesium sulfate solution in a big beaker, placing the beaker in a water bath kettle, wherein the reaction temperature is 45 ℃, the reaction time is 4 hours, continuously adding magnesium oxide for neutralization, the pH end point of the reaction is 6, simultaneously stirring, the stirring speed is 500rpm, when the reaction is finished, taking out the solution, standing for 2 hours at normal temperature, and then carrying out solid-liquid separation by a vacuum suction filtration pump.
S5, secondary crystallization: the magnesium sulfate fine liquid is used as a crystallization stock solution of secondary crystallization, and the secondary crystallization is carried out in a rotary evaporator. And (3) putting the crystallization stock solution into a distillation flask of a rotary evaporator, carrying out vacuum constant-temperature evaporation in a water bath kettle at the temperature of 80 ℃, simultaneously stirring at the speed of 800rpm, taking out a sample after the solvent is evaporated to dryness, and carrying out vacuum drying at the temperature of 40 ℃ for 24 hours to obtain the final high-purity magnesium sulfate crystal.
Through test analysis, the leaching rate of magnesium is 95.14%, the mass percentage content of magnesium in the obtained high-purity magnesium sulfate crystal is 10.47%, and the purity of magnesium sulfate reaches 99.97%.
Example 9
The embodiment relates to a method for preparing high-purity magnesium sulfate by using nickel-iron slag as a raw material, which comprises the following steps:
s1, preprocessing: the same as in example 1.
S2, leaching: weighing 20g of fine ferronickel slag powder, placing the fine ferronickel slag powder into a three-neck flask, adding a sulfuric acid solution with the concentration of 18N (Mol/L) under the condition that the liquid-solid ratio is 40:1(ml/g), then moving the flask into a constant-temperature heating sleeve, heating and stirring the flask, taking out the flask after stirring the solution at the constant temperature for 30min when the temperature of the solution is raised to 200 ℃, standing the solution for 30min, carrying out vacuum filtration on the leached slurry by using a Buchner funnel, and taking the filtrate as a primary crystallization stock solution after constant volume.
S3, primary crystallization: magnesium sulfate heptahydrate with a seed crystal coefficient of 0.5:1 is used as a seed crystal to induce crystallization of magnesium sulfate in the magnesium sulfate crystallization stock solution. Firstly, placing a crystallization stock solution in a big beaker and a water bath kettle, setting the initial crystallization temperature to be 90 ℃, setting the final crystallization temperature to be room temperature (25 ℃), and setting the cooling time to be 10 h. And adding seed crystals into the stock solution when the temperature is reduced, stirring at the speed of 50rpm, taking out the slurry when the solution is reduced to room temperature, and performing vacuum filtration to obtain a primary crystallized magnesium sulfate intermediate product.
S4, purification: magnesium oxide is used as a neutralizing agent. The crude magnesium sulfate obtained by the primary crystallization was dissolved in pure water as a solvent to prepare a crude magnesium sulfate solution. Firstly, placing a primary crystallized magnesium sulfate solution in a big beaker, placing the beaker in a water bath, keeping the reaction temperature at 65 ℃ for 1.5h, continuously adding magnesium oxide for neutralization, keeping the pH end point of the reaction at 3, simultaneously stirring at the stirring speed of 500rpm, taking out the solution and standing the solution at normal temperature for 2h when the reaction is finished, and then carrying out solid-liquid separation by a vacuum suction filtration pump.
S5, secondary crystallization: the magnesium sulfate fine liquid is used as a crystallization stock solution of secondary crystallization, and the secondary crystallization is carried out in a rotary evaporator. And (3) putting the crystallization stock solution into a distillation flask of a rotary evaporator, carrying out vacuum constant-temperature evaporation in a water bath kettle at 50 ℃, simultaneously stirring at the stirring speed of 400rpm, taking out a sample after the solvent is evaporated to dryness, and carrying out vacuum drying at 40 ℃ for 24 hours to obtain the final high-purity magnesium sulfate crystal.
Through test analysis, the leaching rate of magnesium is 95.14%, the mass percentage content of magnesium in the obtained high-purity magnesium sulfate crystal is 10.51%, and the purity of magnesium sulfate reaches 99.95%.
Example 10
A method for preparing high-purity magnesium sulfate by using nickel-iron slag as a raw material comprises the following steps:
s1, preprocessing: drying the nickel-iron slag at 100 ℃ for 8h, then carrying out ball milling on a planetary ball mill, sieving the nickel-iron slag by using a 300-mesh sieve after ball milling, returning the particles larger than 38 mu m to the next batch of ball milling, repeating the steps, and finally uniformly mixing the sieved materials of all batches to obtain nickel-iron slag powder;
s2, leaching: heating, stirring and leaching the nickel-iron slag powder in concentrated sulfuric acid under normal pressure, and filtering to obtain filtrate as primary crystallization stock solution; the particle size of the ferronickel slag powder is less than or equal to 38 mu m, the concentration of concentrated sulfuric acid is 5N, the liquid-solid ratio of the concentrated sulfuric acid to the ferronickel slag is 5:1L/kg, the leaching temperature is 140 ℃, and the stirring speed is 150 rpm;
s3, primary crystallization: adding seed crystals into the primary crystallization stock solution, separating out the primary crystallization and separating a solid phase to obtain crude magnesium sulfate; the seed crystal is a mixture of anhydrous magnesium sulfate and magnesium sulfate monohydrate; the seed crystal coefficient is 0.2, the crystallization temperature is-30 ℃, the crystallization time is 2h, and the crystallization stirring speed is 10 rpm;
s4, purification: dissolving the crude magnesium sulfate in pure water or dilute sulfuric acid, adding a neutralizing agent, neutralizing, hydrolyzing and precipitating, and purifying to remove impurities to obtain magnesium sulfate refined solution; stirring at 25 deg.C for purification and impurity removal at a stirring speed of 100rpm for 30min, and at a reaction end point pH of 2, wherein the neutralizer is at least one of magnesium oxide, magnesium hydroxide, magnesium carbonate, and ammonia water;
s5, secondary crystallization: and (3) carrying out secondary crystallization on the magnesium sulfate fine solution to separate out high-purity magnesium sulfate, wherein the crystallization temperature is-30 ℃, the crystallization time is 0.5h, and the crystallization stirring speed is 10 rpm.
In this embodiment, the primary crystallization is performed in a crystallization manner in which cooling and evaporation are performed simultaneously; the secondary crystallization adopts a single variable temperature cooling crystallization or constant temperature evaporation crystallization mode.
Example 11
A method for preparing high-purity magnesium sulfate by using nickel-iron slag as a raw material comprises the following steps:
s1, preprocessing: drying the nickel-iron slag at 105 ℃ for 12 hours, then carrying out ball milling on a planetary ball mill, sieving the nickel-iron slag by using a 300-mesh sieve after ball milling, returning the particles larger than 38 mu m to the next batch of ball milling, repeating the steps, and finally uniformly mixing the sieved materials of all batches to obtain nickel-iron slag powder;
s2, leaching: heating, stirring and leaching the nickel-iron slag powder in concentrated sulfuric acid under normal pressure, and filtering to obtain filtrate as primary crystallization stock solution; the particle size of the ferronickel slag powder is less than or equal to 38 mu m, the concentration of the concentrated sulfuric acid is 18N, the liquid-solid ratio of the concentrated sulfuric acid to the ferronickel slag is 40:1L/kg, the leaching temperature is 210 ℃, and the stirring speed is 1500 rpm;
s3, primary crystallization: adding seed crystals into the primary crystallization stock solution, separating out the primary crystallization and separating a solid phase to obtain crude magnesium sulfate; the seed crystal is magnesium sulfate dihydrate; the seed crystal coefficient is 1.2, the crystallization temperature is 110 ℃, the crystallization time is 20h, and the crystallization stirring speed is 500 rpm;
s4, purification: dissolving the crude magnesium sulfate in pure water or dilute sulfuric acid, adding a neutralizing agent, neutralizing, hydrolyzing and precipitating, and purifying to remove impurities to obtain magnesium sulfate refined solution; stirring at 105 deg.C, purifying to remove impurities, stirring at 1500rpm, reacting for 300min, and at the end of reaction pH of 12, wherein the neutralizer is at least one of magnesium oxide, magnesium hydroxide, magnesium carbonate, and ammonia water;
s5, secondary crystallization: and (3) carrying out secondary crystallization on the magnesium sulfate fine solution to separate out high-purity magnesium sulfate, wherein the crystallization temperature is 110 ℃, the crystallization time is 20h, and the crystallization stirring speed is 500 rpm.
In this embodiment, the primary crystallization is a single temperature-variable cooling crystallization or temperature-constant evaporation crystallization, and the secondary crystallization is a crystallization that is performed while cooling and evaporating.
Example 12
A method for preparing high-purity magnesium sulfate by using nickel-iron slag as a raw material comprises the following steps:
s1, preprocessing: drying the nickel-iron slag at 102 ℃ for 10 hours, then carrying out ball milling on a planetary ball mill, sieving the nickel-iron slag by using a 300-mesh sieve after ball milling, returning the particles larger than 38 mu m to the next batch of ball milling, repeating the steps, and finally uniformly mixing the sieved materials of all batches to obtain nickel-iron slag powder;
s2, leaching: heating, stirring and leaching the nickel-iron slag powder in concentrated sulfuric acid under normal pressure, and filtering to obtain filtrate as primary crystallization stock solution; the particle size of the ferronickel slag powder is less than or equal to 38 mu m, the concentration of the concentrated sulfuric acid is 10N, the liquid-solid ratio of the concentrated sulfuric acid to the ferronickel slag is 20:1L/kg, the leaching temperature is 180 ℃, and the stirring speed is 800 rpm;
s3, primary crystallization: adding seed crystals into the primary crystallization stock solution, separating out the primary crystallization and separating a solid phase to obtain crude magnesium sulfate; the seed crystal is magnesium sulfate dihydrate; the seed crystal coefficient is 0.8, the crystallization temperature is 50 ℃, the crystallization time is 12h, and the crystallization stirring speed is 200 rpm;
s4, purification: dissolving the crude magnesium sulfate in pure water or dilute sulfuric acid, adding a neutralizing agent, neutralizing, hydrolyzing and precipitating, and purifying to remove impurities to obtain magnesium sulfate refined solution; stirring at 75 deg.C, purifying to remove impurities, stirring at 800rpm, reacting for 120min, and adjusting pH to 8 at the end of reaction, wherein the neutralizer is at least one of magnesium oxide, magnesium hydroxide, magnesium carbonate, and ammonia water;
s5, secondary crystallization: and (3) carrying out secondary crystallization on the magnesium sulfate fine solution to separate out high-purity magnesium sulfate, wherein the crystallization temperature range is 40 ℃, the crystallization time is 12h, and the crystallization stirring speed is 300 rpm.
In this embodiment, the primary crystallization is a single temperature-variable cooling crystallization or temperature-constant evaporation crystallization, and the secondary crystallization is a crystallization that is performed while cooling and evaporating.
It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are within the scope of the invention.
Claims (10)
1. A method for preparing high-purity magnesium sulfate by using nickel-iron slag as a raw material is characterized by comprising the following steps:
s1, preprocessing: drying, grinding and screening the ferronickel slag to obtain ferronickel slag powder;
s2, leaching: heating, stirring and leaching the nickel-iron slag powder in concentrated sulfuric acid under normal pressure, and filtering to obtain filtrate as primary crystallization stock solution;
s3, primary crystallization: adding seed crystals into the primary crystallization stock solution, separating out the primary crystallization and separating a solid phase to obtain crude magnesium sulfate;
s4, purification: dissolving the crude magnesium sulfate in pure water or dilute sulfuric acid, adding a neutralizing agent, neutralizing, hydrolyzing and precipitating, and purifying to remove impurities to obtain magnesium sulfate refined solution;
s5, secondary crystallization: and (4) carrying out secondary crystallization on the magnesium sulfate fine solution to separate out high-purity magnesium sulfate.
2. The method for preparing high-purity magnesium sulfate by using ferronickel slag as a raw material according to claim 1, wherein in step S2, the particle size of ferronickel slag powder is less than or equal to 38 μm, the concentration of concentrated sulfuric acid is 5-18N, the liquid-solid ratio of concentrated sulfuric acid to ferronickel slag is 5-40: 1L/kg, the leaching temperature is 140-210 ℃, and the stirring speed is 150-1500 rpm.
3. The method for preparing high-purity magnesium sulfate from the ferronickel slag as a raw material according to claim 1, wherein in step S3, the seed crystal is at least one of anhydrous magnesium sulfate, magnesium sulfate monohydrate, magnesium sulfate dihydrate, magnesium sulfate trihydrate, magnesium sulfate tetrahydrate, magnesium sulfate pentahydrate, magnesium sulfate hexahydrate, and magnesium sulfate heptahydrate; the seed crystal coefficient is 0.2-1.2, the crystallization temperature range is-30-110 ℃, the crystallization time is 2-20 h, and the crystallization stirring speed is 10-500 rpm.
4. The method for preparing high-purity magnesium sulfate from ferronickel slag as a raw material according to claim 1, wherein in step S4, the mixture is stirred at a temperature of 25-105 ℃ to remove impurities, the stirring speed is 100-1500 rpm, the reaction time is 30-300 min, and the pH value at the end of the reaction is 2-12.
5. The method for preparing high purity magnesium sulfate using nife slag as raw material according to claim 1, wherein the neutralizing agent is at least one of magnesium oxide, magnesium hydroxide, magnesium carbonate and ammonia water in step S4.
6. The method for preparing high purity magnesium sulfate using ferrocenium nickel slag as a raw material according to claim 1, wherein in step S5, the crystallization temperature is-30 to 110 ℃, the crystallization time is 0.5 to 20 hours, and the stirring speed for crystallization is 10 to 500 rpm.
7. The method for preparing high-purity magnesium sulfate by using the ferronickel slag as a raw material according to any one of claims 1 to 6, wherein the primary crystallization and the secondary crystallization can adopt a single variable temperature cooling crystallization or constant temperature evaporation crystallization mode, or can adopt a crystallization mode of cooling while evaporating; the crystallization temperature may be any constant temperature within the temperature range, and may be a crystallization starting temperature and a crystallization finishing temperature.
8. The method for preparing high-purity magnesium sulfate by using ferronickel slag as a raw material according to any one of claims 1 to 6, wherein the high-purity magnesium sulfate is high-purity anhydrous magnesium sulfate and/or high-purity hydrated magnesium sulfate, and the molecular formula of the high-purity anhydrous magnesium sulfate and/or high-purity hydrated magnesium sulfate is MgSO4·nH2O, n is more than or equal to 0 and less than or equal to 7, n can be any one of the numerical values of 0-7, and MgSO is contained in high-purity magnesium sulfate4·nH2The content of O is more than or equal to 99.9 percent.
9. The method for preparing high-purity magnesium sulfate by using the ferronickel slag as a raw material according to any one of claims 1 to 6, wherein the requirement on the purity of a seed is not high during primary crystallization, and a chemical reagent for pure magnesium sulfate is analyzed; the purity of the seed crystal is required to be high during the secondary crystallization, and the high-purity magnesium sulfate produced in the step S5 can be used as the seed crystal.
10. The method for preparing high-purity magnesium sulfate from ferronickel slag as a raw material according to any one of claims 1 to 6, wherein in step S1, the ferronickel slag is dried at 100 to 105 ℃ for 8 to 12 hours, then ball-milled on a planetary ball mill, the ball-milled ferronickel slag is sieved by a 300-mesh sieve, particles larger than 38 μm are returned to the next batch of ball-milling, and the operation is repeated, and finally, the sieved materials of all batches are mixed uniformly.
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20110110832A1 (en) * | 2008-06-02 | 2011-05-12 | Vale S.A. | Magnesium recycling and sulphur recovery in leaching of lateritic nickel ores |
| US20160137524A1 (en) * | 2013-06-17 | 2016-05-19 | Sumitomo Metal Mining Co., Ltd. | Hematite manufacturing process and hematite manufactured by same |
| CN111017968A (en) * | 2019-12-27 | 2020-04-17 | 河北邢台冶金镁业有限公司 | Method for preparing pure magnesium sulfate by using light burned bitter soil as raw material without adding any impurity removing agent |
| RU2727382C1 (en) * | 2019-11-25 | 2020-07-21 | Акционерное Общество "Группа компаний "Русредмет" (АО "ГК "Русредмет") | Method of producing magnesium sulphate from magnesium-containing raw material |
| CN111926193A (en) * | 2020-07-29 | 2020-11-13 | 广西大学 | Method for recovering magnesium from ferronickel slag |
-
2021
- 2021-08-23 CN CN202110965913.7A patent/CN114314619A/en active Pending
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20110110832A1 (en) * | 2008-06-02 | 2011-05-12 | Vale S.A. | Magnesium recycling and sulphur recovery in leaching of lateritic nickel ores |
| US20160137524A1 (en) * | 2013-06-17 | 2016-05-19 | Sumitomo Metal Mining Co., Ltd. | Hematite manufacturing process and hematite manufactured by same |
| RU2727382C1 (en) * | 2019-11-25 | 2020-07-21 | Акционерное Общество "Группа компаний "Русредмет" (АО "ГК "Русредмет") | Method of producing magnesium sulphate from magnesium-containing raw material |
| CN111017968A (en) * | 2019-12-27 | 2020-04-17 | 河北邢台冶金镁业有限公司 | Method for preparing pure magnesium sulfate by using light burned bitter soil as raw material without adding any impurity removing agent |
| CN111926193A (en) * | 2020-07-29 | 2020-11-13 | 广西大学 | Method for recovering magnesium from ferronickel slag |
Non-Patent Citations (3)
| Title |
|---|
| CAIDUAN ZHANG ET.AL: "Recovery of magnesium sulfate through crystallization in waste liquid after simultaneous desulfurization and denitrification", 《DESALINATION AND WATER TREATMENT》 * |
| FENG GAO ET.AL: "Recovery of magnesium from ferronickel slag to prepare hydrated magnesium sulfate by hydrometallurgy method", 《JOURNAL OF CLEANER PRODUCTION》 * |
| 李晓波: "精炼镁渣制光卤石和硫酸镁工艺研究", 《无机盐工业》 * |
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