CN112110469A - Method for preparing vaterite type calcium carbonate - Google Patents
Method for preparing vaterite type calcium carbonate Download PDFInfo
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- CN112110469A CN112110469A CN202011096534.0A CN202011096534A CN112110469A CN 112110469 A CN112110469 A CN 112110469A CN 202011096534 A CN202011096534 A CN 202011096534A CN 112110469 A CN112110469 A CN 112110469A
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Abstract
The present invention relates to a method for preparing vaterite-type calcium carbonate, which comprises: (1) mixing limestone and ammonium chloride, and then sequentially grinding and roasting to obtain roasted sand; (2) leaching the calcine obtained in the step (1), and performing solid-liquid separation to obtain a calcium chloride leaching solution; (3) mixing a surfactant with the calcium chloride leaching solution obtained in the step (2), then introducing carbon dioxide and ammonia gas for carbonization treatment, and carrying out solid-liquid separation after complete carbonization to obtain the vaterite type calcium carbonate. According to the invention, limestone and ammonium chloride are used as raw materials to produce the vaterite type calcium carbonate, and the surfactant is added in the carbonization process, so that on one hand, a large amount of accumulated ammonium chloride byproducts in the soda industry can be treated, and high-value utilization of surplus resources is realized; on the other hand, the produced vaterite type calcium carbonate has controllable shape, uniform particle size of the obtained calcium carbonate and good hydrophobicity on the surface of the crystal, thereby greatly widening the application field of the calcium carbonate.
Description
Technical Field
The invention belongs to the technical field of inorganic salt materials, relates to a preparation method of calcium carbonate, and particularly relates to a method for preparing vaterite-type calcium carbonate.
Background
Calcium carbonate is used as a basic chemical raw material, is mainly divided into three crystal forms of calcite, aragonite and vaterite, and is widely applied to the industries of cement, coating, plastics, paper making and the like. In particular, the vaterite type calcium carbonate has larger specific surface area, higher solubility and dispersion performance and smaller specific gravity, so that the coating performance of paper and the filling performance of plastics, coatings, printing ink, paper and the like can be effectively improved, and the physical property, the glossiness, the flowability and the printing performance of target products are improved.
Many researchers have conducted research on the preparation of the vaterite-type calcium carbonate at present, and the methods adopted include a gas-liquid mixing method, a monomolecular film method, a template method and the like. But basically has the problems of high raw material cost, complex preparation conditions, difficult control of product form, non-uniform particle size, strong crystal surface hydrophilicity and the like.
In addition, with the continuous development of the soda ash industry in recent years, the yield of the by-product ammonium chloride is increased year by year, and the development of soda ash enterprises is severely restricted by the large amount of accumulated cheap ammonium chloride. Therefore, the method has important significance for treating a large amount of accumulated ammonium chloride and producing high value-added products by adopting a proper process. The problem of the accumulation of the ammonium chloride at present can be relieved to a certain extent by using limestone and the ammonium chloride as raw materials to produce calcium carbonate products with different properties and different purposes, so that the waste is changed into valuable, and the method has great industrial research value and theoretical significance.
CN101823729A discloses a method for preparing common activated calcium carbonate series products and co-producing ammonium chloride. By utilizing an ammonium carbonization method, products of the front reaction and the back reaction are recycled as reactants, so that the investment is small, the cost is low, the production is simple, and the yield is high; the method can produce active calcium carbonate with various fineness while co-producing ammonium chloride, and has higher economic benefit. However, the specific conditions of the reaction are not described in detail in the preparation method, and the types of the prepared calcium carbonate products are mixed, so that the selective production of the vaterite-type calcium carbonate cannot be realized.
CN1025555C discloses a method for producing crystalline calcium carbonate by decomposing limestone with saturated solution of ammonium chloride and solid ammonium chloride, purifying the produced calcium chloride and recovering ammonium bicarbonate and ammonium hydroxide converted by the reaction of the reaction products ammonia, carbon dioxide and water. Finally, the purified calcium chloride reacts with the ammonium bicarbonate and the ammonium hydroxide absorbed in the ammonium chloride solution to generate a crystal calcium carbonate product. In order to ensure that the reaction is complete, the reaction temperature of the ammonium chloride and the limestone is increased to 600 ℃, and the production control is very complicated in the practical industrial application, thereby causing resource waste to a certain extent. In addition, the calcium carbonate product is also not high in vaterite content.
CN102267713A discloses a method for producing high-quality light calcium carbonate by ammonium salt circulation method, which comprises calcining calcium raw material to convert calcium compound in the raw material into calcium oxide, hydrating to generate calcium hydroxide, reacting with ammonium salt to generate calcium salt solution, and finally feeding the calcium salt solution into a carbonization tank for carbonization treatment to produce light calcium carbonate. The calcium carbonate produced by the method has complete and uniform crystal structure and high utilization rate of calcium raw materials, and is not only suitable for limestone, but also suitable for various calcium waste residues in industry. However, the process of calcining the calcium raw material in the early stage to obtain calcium oxide is energy-consuming and not very high in economic benefit. There is also a problem that the vaterite type calcium carbonate cannot be produced in a targeted manner.
CN103922378A discloses a method for preparing high-purity metastable vaterite calcium carbonate by using gypsum. The method takes the gypsum as the raw material, can provide technical support for solving the problem of resource utilization of industrial solid waste gypsum, and realizes changing waste into valuable. In addition, the prepared vaterite calcium carbonate has high crystal form purity and simple preparation process, the yield of the vaterite calcium carbonate is improved by the high-concentration ammonium bicarbonate concentration reaction, and the production cost of the vaterite calcium carbonate can be greatly reduced. However, the surface of the vaterite calcium carbonate crystal prepared by the method does not have hydrophobicity, and the problem that the particle size of the calcium carbonate product is not uniform due to particle agglomeration cannot be avoided.
Therefore, the problems of complex process, high cost, low vaterite selectivity in the product, non-uniform particle size, low crystal surface hydrophobicity and the like generally exist in the preparation of the vaterite type calcium carbonate in the prior art. How to produce high-quality vaterite-type calcium carbonate by using cheap and easily available raw materials, realize the high-value utilization of surplus resources and simultaneously improve the market supply of high-quality vaterite-type calcium carbonate becomes a problem which needs to be solved urgently at present.
Disclosure of Invention
The invention aims to provide a method for preparing vaterite type calcium carbonate, which utilizes limestone and ammonium chloride as raw materials to produce the vaterite type calcium carbonate, and adds a surfactant in the carbonization process, so that on one hand, a large amount of accumulated ammonium chloride byproducts in the soda industry can be treated, and the high-value utilization of surplus resources is realized; on the other hand, the produced vaterite type calcium carbonate has controllable shape, uniform particle size of the obtained calcium carbonate and good hydrophobicity on the surface of the crystal, thereby greatly widening the application field of the calcium carbonate.
In order to achieve the purpose, the invention adopts the following technical scheme:
the present invention provides a method for preparing vaterite-type calcium carbonate, which comprises:
(1) mixing limestone and ammonium chloride, and then sequentially grinding and roasting to obtain roasted sand;
(2) leaching the calcine obtained in the step (1), and performing solid-liquid separation to obtain a calcium chloride leaching solution;
(3) mixing a surfactant with the calcium chloride leaching solution obtained in the step (2), then introducing carbon dioxide and ammonia gas for carbonization treatment, and carrying out solid-liquid separation after complete carbonization to obtain the vaterite type calcium carbonate.
According to the invention, ammonium chloride is used as a raw material in the step (1), and a large amount of accumulated cheap ammonium chloride byproducts in the soda ash industry can be fully utilized, so that the production cost is reduced; in addition, the limestone and the ammonium chloride are ground and then roasted, so that a large amount of waste of water resources can be avoided.
Adding a surfactant into the calcium chloride leaching solution in the step (3) of the invention can influence the density, viscosity, surface tension and dielectric constant of the solution; the surfactant can reduce the surface tension of water, so that the solution is concentrated; in addition, the surfactants can affect the solubility of the substrate and product in aqueous solution, and thus affect the interparticle interactions.
Preferably, the molar ratio of limestone to ammonium chloride in step (1) is (2.0-3.0):1, and may be, for example, 2.0:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1 or 3.0: 1; further preferably (2.6-3.0):1, but the values listed are not limited thereto, and other values not listed in the numerical range are also applicable.
The mol ratio has obvious influence on the conversion rate of the ammonium chloride, and when the mol ratio is in the range of (2.0-3.0):1, the conversion rate of the ammonium chloride can reach more than 93 percent. However, when the molar ratio is below 2.0:1, the conversion of ammonium chloride is below 90%; when the molar ratio is higher than 3.0:1, the conversion rate of ammonium chloride is not increased obviously, but limestone is wasted.
Preferably, the grinding method of step (1) comprises: mortar grinding and/or grinder grinding. The mortar can be a quartz mortar or an agate mortar; the grinder may be a 125 mm lightweight bench grinder.
Preferably, the step (1) further comprises a screening step between grinding and roasting.
The screening of the invention can remove the larger particles left after grinding, so that the limestone and the ammonium chloride are fully contacted and reacted in the roasting process, thereby further improving the conversion rate of the limestone and the ammonium chloride.
Preferably, the mesh number of the screen used for screening is 50 to 80 mesh, for example, 50 mesh, 55 mesh, 60 mesh, 65 mesh, 70 mesh, 75 mesh or 80 mesh, and more preferably 60 mesh, but not limited to the enumerated values, and other unrecited values within the numerical range are also applicable.
Preferably, the temperature of the calcination in step (1) is 300-.
The calcination temperature of the invention has a significant effect on the conversion of ammonium chloride. When the roasting temperature is in the range of 300-380 ℃, the conversion rate of the ammonium chloride is in a trend of increasing and then decreasing along with the increase of the roasting temperature, and the conversion rate can reach a maximum value close to 97% in the temperature range of 320-360 ℃. However, when the calcination temperature is lower than 300 ℃ and higher than 380 ℃, the conversion rate of ammonium chloride is not sufficient to 85%.
Preferably, the temperature rise rate of the calcination in step (1) is 1-5 deg.C/min, such as 1 deg.C/min, 2 deg.C/min, 3 deg.C/min, 4 deg.C/min or 5 deg.C/min, and more preferably 2-4 deg.C/min, but not limited to the values listed, and other values not listed in the range of values are also applicable.
When the heating rate is lower than 1 ℃/min, the roasting time is excessively prolonged, and resources are wasted; when the temperature rise rate is higher than 5 ℃/min, the raw materials are heated unevenly at the initial stage of roasting, so that the conversion rate of the raw materials is adversely affected.
Preferably, the calcination time in step (1) is 20-100min, such as 20min, 40min, 60min, 80min or 100min, and more preferably 40-60min, but not limited to the recited values, and other values not recited in the range of values are also applicable.
The roasting time of the invention has a significant influence on the conversion rate of ammonium chloride. When the roasting time is within the range of 20-100min, the conversion rate of the ammonium chloride shows a trend of changing stably after rising along with the prolonging of the roasting time, and the conversion rate can reach a stable value which is close to 83 percent within the range of 40-60min of the roasting time. Excessive extension of the calcination time beyond 100min increases energy consumption, while calcination times below 20min results in insufficient reaction between limestone and ammonium chloride.
Preferably, the leach solution used in the leaching of step (2) comprises water;
preferably, the liquid-solid ratio of the leaching solution to the calcine in the step (2) is (1-3):1, and for example, may be 1:1, 1.5:1, 2:1, 2.5:1 or 3:1, but is not limited to the recited values, and other values not recited in the numerical range are also applicable.
The liquid-solid ratio of the invention has obvious influence on the leaching rate of calcium ions. When the liquid-solid ratio is in the range of (1-3):1, the leaching rate of calcium ions is increased and then reduced along with the increase of the liquid-solid ratio, and the leaching rate can reach more than 98 percent at most. However, when the liquid-solid ratio is less than 1:1 and more than 3:1, the leaching rate of calcium ions is less than 95%.
Preferably, the temperature of the leaching in step (2) is 20-60 ℃, for example 20 ℃, 30 ℃, 40 ℃, 50 ℃ or 60 ℃, more preferably 30-50 ℃, but not limited to the recited values, and other values not recited in the numerical range are equally applicable.
The leaching temperature of the invention has obvious influence on the leaching rate of calcium ions. When the leaching temperature is in the range of 20-60 ℃, the leaching rate of calcium ions shows a change trend that the calcium ions rise first and then tend to be stable along with the rising of the leaching temperature, and the stable value of the leaching rate is close to 99 percent within the range of 30-50 ℃. However, the leaching temperature higher than 60 ℃ increases the energy consumption, and the leaching temperature lower than 20 ℃ causes the leaching rate of calcium ions to be less than 95%.
Preferably, the leaching time in step (2) is 30-180min, such as 30min, 50min, 100min, 150min or 180min, and more preferably 60-120min, but is not limited to the recited values, and other values not recited in the range of values are equally applicable.
The leaching time of the invention has obvious influence on the leaching rate of calcium ions. When the leaching time is within the range of 30-180min, the leaching rate of calcium ions shows a change trend of increasing firstly and then tending to be stable along with the prolonging of the leaching time, and the stable value of the leaching rate can be close to 100% within the range of 60-120 min. However, the leaching time exceeding 180min increases the energy consumption, and the leaching time below 30min results in a leaching rate of calcium ions of less than 90%.
Preferably, the surfactant of step (3) comprises a nonionic surfactant.
Preferably, the nonionic surfactant comprises coconut oil fatty acid diethanolamide,
preferably, the amount of the nonionic surfactant is 0.1-10% of the calcium chloride leachate obtained in step (2), for example, 0.1%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%, but not limited to the recited values, and other values not recited in the range of the values are also applicable.
The dosage of the nonionic surfactant has obvious influence on the crystal form variety of the calcium carbonate product. When the amount of the nonionic surfactant is in the range of 0.1 to 10%, the content of calcite-type calcium carbonate in the product gradually decreases and the content of vaterite-type calcium carbonate gradually increases with increasing amount of the nonionic surfactant, and the content of the vaterite-type calcium carbonate is up to approximately 90%. However, when the amount of the nonionic surfactant is less than 0.1%, the carbonized product obtained after the calcium chloride leachate is carbonized is only calcite-type calcium carbonate; when the amount of the nonionic surfactant is more than 10%, the increase in the content of the vaterite-type calcium carbonate in the product is no longer significant.
Preferably, the flow rate of the carbon dioxide in step (3) is 8-24mL/min, such as 8mL/min, 10mL/min, 12mL/min, 14mL/min, 16mL/min, 18mL/min, 20mL/min, 22mL/min or 24mL/min, but not limited to the values listed, and other values not listed in the numerical range are also applicable.
Preferably, the flow rate of the ammonia gas in the step (3) is 16-54mL/min, such as 16mL/min, 20mL/min, 24mL/min, 28mL/min, 32mL/min, 36mL/min, 40mL/min, 44mL/min, 48mL/min or 54mL/min, but not limited to the enumerated values, and other non-enumerated values in the numerical range are also applicable.
The flow rate of the carbon dioxide and the flow rate of the ammonia gas in the present invention significantly affect the yield of the vaterite-type calcium carbonate. When the flow of carbon dioxide is less than 8mL/min and/or the flow of ammonia is less than 16mL/min, the concentration of reactants in the calcium chloride leaching solution is low, the reaction is insufficient, and calcium ions do not completely participate in the reaction. When the flow of the carbon dioxide is within the range of 8-24mL/min and the flow of the ammonia gas is within the range of 16-54mL/min, the concentration of reactants in the calcium chloride leaching solution is gradually increased along with the gradual increase of the gas flow, the reaction rate is gradually increased, and calcium ions and carbonate ions are fully combined to generate calcium carbonate. In addition, when the flow rate of the carbon dioxide is in the range of 8-24mL/min and the flow rate of the ammonia gas is in the range of 16-54mL/min, the particle size of the product calcium carbonate is gradually reduced along with the gradual increase of the gas flow rate. However, when the flow rate of carbon dioxide is more than 24mL/min and/or the flow rate of ammonia is more than 54mL/min, aragonite calcium carbonate aggregated together in a rod shape is generated in the calcium chloride leaching solution, and the product is mainly mixed crystals of aragonite calcium carbonate and calcite calcium carbonate.
Preferably, the carbonization treatment in step (3) is performed under stirring.
The stirring of the invention can promote the full reaction of carbon dioxide and ammonia gas with the calcium chloride leaching solution so as to improve the yield of calcium carbonate. In addition, the stirring can also make the leaching temperature distribution uniform, thereby promoting the carbonization reaction.
Preferably, the stirring speed is 200-800rpm, such as 200rpm, 300rpm, 400rpm, 500rpm, 600rpm, 700rpm or 800rpm, and more preferably 400-600rpm, but not limited to the enumerated values, and other unrecited values within the numerical range are also applicable.
The stirring speed of the invention is lower than 200rpm, which causes uneven distribution of reactants and temperature in the solution, thereby influencing the reaction progress; the rotation speed of the stirring higher than 800rpm can cause the solution to splash on one hand and can cause energy waste on the other hand.
Preferably, the stirring paddles used for stirring are: two-blade spiral stirring paddle with 10cm blade area2
Preferably, the carbon dioxide in the step (3) is bubbled into the calcium chloride leaching solution. For example, a microporous aeration tray may be provided at the bottom of the calcium chloride leachate vessel so that carbon dioxide bubbles into the solution from the bottom of the calcium chloride leachate through the microporous aeration tray. In this way, the contact area between the carbon dioxide gas and the calcium chloride leaching solution can be increased, and the reaction is promoted.
Preferably, the ammonia gas in the step (3) is introduced into the calcium chloride leachate above the liquid level of the reactor. For example, a conduit may be provided above the reactor level for the introduction of ammonia.
Preferably, the solid-liquid separation of step (3) comprises filtration, washing and drying.
Preferably, the filtration comprises any one or a combination of at least two of gravity filtration, pressure filtration, vacuum filtration or centrifugal filtration.
Preferably, the washing liquid comprises water and/or absolute ethanol.
Preferably, the drying includes any one of atmospheric drying, reduced pressure drying, or microwave drying, or a combination of at least two thereof.
Compared with the prior art, the invention has the following beneficial effects:
1) according to the invention, a large amount of accumulated cheap ammonium chloride byproducts in the soda ash industry are selected as raw materials, and the conversion rate of ammonium chloride is up to 97%, so that the cost can be greatly saved, and high-valued utilization of surplus resources can be realized;
2) the calcium ion leaching rate in the method adopted by the invention can reach more than 99 percent at most, and the produced vaterite type calcium carbonate has controllable shape, the obtained calcium carbonate has uniform particle size, and the crystal surface has good hydrophobicity, thereby greatly widening the application field of the calcium carbonate.
Drawings
FIG. 1 is a flow chart of a process for preparing vaterite-type calcium carbonate;
FIG. 2 is a schematic view of a carbonization process in a method for preparing vaterite-type calcium carbonate;
FIG. 3 is an XRD spectrum of the vaterite-type calcium carbonate prepared in example 1;
FIG. 4 is a FT-IR spectrum of the vaterite-type calcium carbonate prepared in example 1;
FIG. 5 is an SEM image of the vaterite-type calcium carbonate prepared in example 1;
FIG. 6 is the particle size distribution of the vaterite-type calcium carbonate prepared in example 1;
FIG. 7 is the contact angle of the vaterite-type calcium carbonate prepared in example 1;
FIG. 8 is an SEM image of the vaterite-type calcium carbonate prepared in example 2;
FIG. 9 is an SEM image of the non-vaterite-type calcium carbonate prepared in comparative example 1;
FIG. 10 is a particle size distribution of the vaterite-type calcium carbonate prepared in comparative example 1;
FIG. 11 is the contact angle of the non-vaterite calcium carbonate prepared in comparative example 1.
Detailed Description
The technical solution of the present invention is further explained by the following embodiments. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.
Example 1
This example provides a process for preparing vaterite-type calcium carbonate, which is carried out according to the process scheme shown in fig. 1, comprising the following steps:
(1) mixing limestone and ammonium chloride according to a molar ratio of 2.8:1, fully and uniformly grinding in a quartz mortar, screening by a 60-mesh screen, and roasting in an intermittent rotary atmosphere resistance furnace, wherein the atmosphere is argon, the atmosphere flow is 100mL/min, the roasting temperature is 340 ℃, the heating rate is 3 ℃/min, and the roasting time is 50min, so as to finally obtain roasted sand;
(2) leaching the calcine obtained in the step (1) by using distilled water as a leaching solution, wherein the leaching process is carried out in a magnetic stirring thermostatic bath, the stirring speed is set to be 500rpm, the liquid-solid ratio of the distilled water to the calcine is 2:1, the leaching temperature is 40 ℃, the leaching time is 90min, and finally, a calcium chloride leaching solution is subjected to suction filtration by using a vacuum pump;
(3) mixing coconut oil fatty acid diethanolamide with the calcium chloride leaching solution obtained in the step (2), wherein the mass fraction of the coconut oil fatty acid diethanolamide in the calcium chloride leaching solution is 1%, and then introducing carbon dioxide with the gas flow rate of 16mL/min and ammonia with the gas flow rate of 35mL/min into the solution to carry out carbonization treatment.
As shown in figure 2, carbon dioxide is introduced into the solution in a bubbling mode through a microporous aeration disc at the bottom of the container, ammonia gas is directly introduced into the solution through a conduit arranged above the liquid level, and the area of a blade is selected to be 10cm2The two-blade screw type stirring paddle stirs the mixture, and the set rotating speed is 500 rpm.
And after complete carbonization, filtering, washing and drying to obtain the vaterite type calcium carbonate product.
Wherein the filtration is vacuum filtration, and the feed liquid is subjected to suction filtration by using a vacuum pump; the washing liquid is absolute ethyl alcohol, and the obtained solid is placed in the absolute ethyl alcohol for ultrasonic dispersion for 10 min; the drying is normal pressure drying, and the obtained solid is put into an oven at 80 ℃ for drying for 2 h.
The conversion of ammonium chloride during calcination and the leaching of calcium ions during leaching in this example are shown in Table 1.
The XRD pattern of the vaterite-type calcium carbonate obtained in this example is shown in FIG. 3; the FT-IR spectrum of the resulting vaterite-type calcium carbonate is shown in FIG. 4; the SEM image of the resulting vaterite-type calcium carbonate is shown in FIG. 5; the particle size distribution of the obtained vaterite-type calcium carbonate is shown in FIG. 6; the contact angle of the resulting vaterite-type calcium carbonate is shown in FIG. 7.
Example 2
The steps of this example are the same as those of example 1 except that the surfactant coconut oil fatty acid diethanolamide is replaced by sodium dodecyl sulfate, and thus the description is omitted here.
The conversion of ammonium chloride during calcination and the leaching of calcium ions during leaching in this example are shown in Table 1.
The XRD spectrum and FT-IR spectrum of the vaterite-type calcium carbonate obtained in this example were substantially the same as those of example 1; the SEM image of the resulting vaterite-type calcium carbonate is shown in fig. 8.
Example 3
The present example provides a method for preparing vaterite-type calcium carbonate, the method comprising:
(1) mixing limestone and ammonium chloride according to a molar ratio of 2.6:1, fully and uniformly grinding in a quartz mortar, screening by a 60-mesh screen, and roasting in an intermittent rotary atmosphere resistance furnace, wherein the atmosphere is argon, the atmosphere flow is 100mL/min, the roasting temperature is 320 ℃, the heating rate is 2 ℃/min, and the roasting time is 40min, so as to finally obtain roasted sand;
(2) leaching the calcine obtained in the step (1) by using distilled water as a leaching solution, wherein the leaching process is carried out in a magnetic stirring thermostatic bath, the stirring speed is set to be 500rpm, the liquid-solid ratio of the distilled water to the calcine is 2:1, the leaching temperature is 30 ℃, the leaching time is 60min, and finally, a calcium chloride leaching solution is subjected to suction filtration by using a vacuum pump;
(3) mixing coconut oil fatty acid diethanolamide with the calcium chloride leaching solution obtained in the step (2), wherein the mass fraction of the coconut oil fatty acid diethanolamide in the calcium chloride leaching solution is 0.5%, and then introducing carbon dioxide with the gas flow rate of 12mL/min and ammonia with the gas flow rate of 25mL/min into the solution to carry out carbonization treatment.
Wherein, the carbon dioxide is introduced into the solution in a bubbling mode through a microporous aeration disc at the bottom of the container, the ammonia gas is directly introduced into the solution through a conduit arranged above the liquid level, and simultaneously, the area of a blade is selected to be 10cm2The two-blade screw type stirring paddle stirs the mixture, and the set rotating speed is 400 rpm.
The rest of the steps are the same as those in embodiment 1, and thus are not described herein.
The conversion of ammonium chloride during calcination and the leaching of calcium ions during leaching in this example are shown in Table 1.
The shape, particle size, surface hydrophobicity, and other characteristics of the vaterite-type calcium carbonate obtained in this example are substantially the same as those of the vaterite-type calcium carbonate obtained in example 1, and thus, the description thereof will not be repeated.
Example 4
The present example provides a method for preparing vaterite-type calcium carbonate, the method comprising:
(1) mixing limestone and ammonium chloride according to the molar ratio of 3.0:1, fully and uniformly grinding in a quartz mortar, screening by a 60-mesh screen, and roasting in an intermittent rotary atmosphere resistance furnace, wherein the atmosphere is argon, the atmosphere flow is 100mL/min, the roasting temperature is 360 ℃, the heating rate is 4 ℃/min, and the roasting time is 60min, so that roasted sand is finally obtained;
(2) leaching the calcine obtained in the step (1) by using distilled water as a leaching solution, wherein the leaching process is carried out in a magnetic stirring thermostatic bath, the stirring speed is set to be 500rpm, the liquid-solid ratio of the distilled water to the calcine is 2:1, the leaching temperature is 50 ℃, the leaching time is 120min, and finally, a calcium chloride leaching solution is subjected to suction filtration by using a vacuum pump;
(3) mixing coconut oil fatty acid diethanolamide with the calcium chloride leaching solution obtained in the step (2), wherein the coconut oil fatty acid diethanolamide accounts for 5% by mass of the calcium chloride leaching solution, and then introducing carbon dioxide with the gas flow rate of 20mL/min and ammonia with the gas flow rate of 45mL/min into the solution to carry out carbonization treatment.
Wherein, the carbon dioxide is introduced into the solution in a bubbling mode through a microporous aeration disc at the bottom of the container, the ammonia gas is directly introduced into the solution through a conduit arranged above the liquid level, and simultaneously, the area of a blade is selected to be 10cm2The two-blade screw type stirring paddle stirs the mixture, and the set rotating speed is 600 rpm.
The rest of the steps are the same as those in embodiment 1, and thus are not described herein.
The conversion of ammonium chloride during calcination and the leaching of calcium ions during leaching in this example are shown in Table 1.
The shape, particle size, surface hydrophobicity, and other characteristics of the vaterite-type calcium carbonate obtained in this example are substantially the same as those of the vaterite-type calcium carbonate obtained in example 1, and thus, the description thereof will not be repeated.
Example 5
The present example provides a method for preparing vaterite-type calcium carbonate, the method comprising:
(1) mixing limestone and ammonium chloride according to a molar ratio of 2.0:1, fully and uniformly grinding in a quartz mortar, screening by a 50-mesh screen, and roasting in an intermittent rotary atmosphere resistance furnace, wherein the atmosphere is argon, the atmosphere flow is 100mL/min, the roasting temperature is 300 ℃, the heating rate is 1 ℃/min, and the roasting time is 20min, so as to finally obtain roasted sand;
(2) leaching the calcine obtained in the step (1) by using distilled water as a leaching solution, wherein the leaching process is carried out in a magnetic stirring thermostatic bath, the stirring speed is set to be 500rpm, the liquid-solid ratio of the distilled water to the calcine is 1:1, the leaching temperature is 20 ℃, the leaching time is 30min, and finally, a calcium chloride leaching solution is subjected to suction filtration by using a vacuum pump;
(3) mixing coconut oil fatty acid diethanolamide with the calcium chloride leaching solution obtained in the step (2), wherein the mass fraction of the coconut oil fatty acid diethanolamide in the calcium chloride leaching solution is 0.1%, and then introducing carbon dioxide with the gas flow rate of 8mL/min and ammonia with the gas flow rate of 16mL/min into the solution to carry out carbonization treatment.
Wherein, the carbon dioxide is introduced into the solution in a bubbling mode through a microporous aeration disc at the bottom of the container, the ammonia gas is directly introduced into the solution through a conduit arranged above the liquid level, and simultaneously, the area of a blade is selected to be 10cm2The two-blade screw type stirring paddle stirs the mixture, and the set rotating speed is 600 rpm.
The rest of the steps are the same as those in embodiment 1, and thus are not described herein.
The conversion of ammonium chloride during calcination and the leaching of calcium ions during leaching in this example are shown in Table 1.
The shape, particle size, surface hydrophobicity, and other characteristics of the vaterite-type calcium carbonate obtained in this example are substantially the same as those of the vaterite-type calcium carbonate obtained in example 1, and thus, the description thereof will not be repeated.
Example 6
The present example provides a method for preparing vaterite-type calcium carbonate, the method comprising:
(1) mixing limestone and ammonium chloride according to a molar ratio of 2.3:1, fully and uniformly grinding in a quartz mortar, screening by using a 80-mesh screen, and roasting in an intermittent rotary atmosphere resistance furnace, wherein the atmosphere is argon, the atmosphere flow is 100mL/min, the roasting temperature is 380 ℃, the heating rate is 5 ℃/min, and the roasting time is 100min, so that roasted sand is finally obtained;
(2) leaching the calcine obtained in the step (1) by using distilled water as a leaching solution, wherein the leaching process is carried out in a magnetic stirring thermostatic bath, the stirring speed is set to be 500rpm, the liquid-solid ratio of the distilled water to the calcine is 3:1, the leaching temperature is 60 ℃, the leaching time is 180min, and finally, a calcium chloride leaching solution is subjected to suction filtration by using a vacuum pump;
(3) mixing coconut oil fatty acid diethanolamide with the calcium chloride leaching solution obtained in the step (2), wherein the mass fraction of the coconut oil fatty acid diethanolamide in the calcium chloride leaching solution is 10%, and then introducing carbon dioxide with the gas flow rate of 24mL/min and ammonia with the gas flow rate of 54mL/min into the solution to carry out carbonization treatment.
Wherein, the carbon dioxide is introduced into the solution in a bubbling mode through a microporous aeration disc at the bottom of the container, the ammonia gas is directly introduced into the solution through a conduit arranged above the liquid level, and simultaneously, the area of a blade is selected to be 10cm2The two-blade screw type stirring paddle stirs, and the set rotating speed is 800 rpm.
The rest of the steps are the same as those in embodiment 1, and thus are not described herein.
The conversion of ammonium chloride during calcination and the leaching of calcium ions during leaching in this example are shown in Table 1.
The shape, particle size, surface hydrophobicity, and other characteristics of the vaterite-type calcium carbonate obtained in this example are substantially the same as those of the vaterite-type calcium carbonate obtained in example 1, and thus, the description thereof will not be repeated.
Example 7
In this embodiment, the steps are the same as those in embodiment 1 except that the molar ratio of limestone to ammonium chloride is changed to 1.7:1, and thus the description is omitted here.
The conversion of ammonium chloride during calcination and the leaching of calcium ions during leaching in this example are shown in Table 1.
Example 8
The process of this embodiment is the same as that of embodiment 1 except that the calcination temperature of limestone and ammonium chloride is changed to 280 ℃, and thus the description thereof is omitted.
The conversion of ammonium chloride during calcination and the leaching of calcium ions during leaching in this example are shown in Table 1.
Example 9
The process of this embodiment is the same as that of embodiment 1 except that the calcination temperature of limestone and ammonium chloride is changed to 400 ℃, and thus the description thereof is omitted.
The conversion of ammonium chloride during calcination and the leaching of calcium ions during leaching in this example are shown in Table 1.
Example 10
In this embodiment, the steps are the same as those in embodiment 1 except that the calcination time of limestone and ammonium chloride is changed to 10min, and thus the description is omitted here.
The conversion of ammonium chloride during calcination and the leaching of calcium ions during leaching in this example are shown in Table 1.
Example 11
The steps of this example are the same as those of example 1 except that the liquid-solid ratio of the distilled water to the calcine is changed to 0.75:1, and therefore, the description thereof is omitted.
The conversion of ammonium chloride during calcination and the leaching of calcium ions during leaching in this example are shown in Table 1.
Example 12
The remaining steps of this example are the same as those of example 1 except that the liquid-solid ratio of the distilled water to the calcine is changed to 3.25:1, and therefore, the description thereof is omitted.
The conversion of ammonium chloride during calcination and the leaching of calcium ions during leaching in this example are shown in Table 1.
Example 13
The same procedure as in example 1 was repeated except that the leaching temperature of the calcine with distilled water was changed to 15 deg.C, and thus the description thereof is omitted.
The conversion of ammonium chloride during calcination and the leaching of calcium ions during leaching in this example are shown in Table 1.
Example 14
The same procedure as in example 1 was repeated except that the leaching time of the calcine with distilled water was changed to 20min, and thus the description thereof is omitted.
The conversion of ammonium chloride during calcination and the leaching of calcium ions during leaching in this example are shown in Table 1.
Comparative example 1
This comparative example is the same as example 1 except that no surfactant is added, and thus, the description thereof is omitted.
The conversion of ammonium chloride during roasting and the leaching of calcium ions during leaching in this comparative example are shown in Table 1.
The SEM image of the product calcium carbonate obtained in the comparative example is shown in FIG. 9; the particle size distribution of the obtained product calcium carbonate is shown in figure 10; the contact angle of the obtained calcium carbonate product is shown in FIG. 11.
TABLE 1
Note: the formula for calculating the conversion of ammonium chloride is as follows:
in the formula: η — conversion of ammonium chloride,%;
m0-initial ammonium chloride mass, g;
m1the mass of ammonium chloride consumed by the reaction, g.
The leaching rate of calcium ions is calculated as follows:
in the formula: etaCa-leaching rate of calcium ions,%;
CCa-concentration of calcium ions in the leachate, g/L;
VL-volume of leachate, L;
m-mass of calcine, g;
omega-mass fraction of calcium ions in the calcine,%.
From the above results, it can be seen that: the setting range of relevant experimental parameters has obvious influence on the conversion rate of ammonium chloride in the roasting process and the leaching rate of calcium ions in the carbonization process, the conversion rate of the ammonium chloride in the parameter setting range of the invention can be up to 97 percent, and the leaching rate of the calcium ions can be up to more than 99 percent; furthermore, in comparison with examples 1 to 14, the surfactant was not added in comparative example 1, which resulted in that no vaterite-type calcium carbonate was present in the carbonized product and the obtained calcium carbonate product had a broad particle size distribution and no hydrophobicity on the crystal surface, and thus it was found that the addition of the surfactant during the carbonization process was critical for the production of a high-quality vaterite-type calcium carbonate.
In conclusion, the method selects a large amount of accumulated cheap ammonium chloride byproducts in the soda ash industry as raw materials, and adds the surfactant in the carbonization process, so that the cost can be greatly saved, and high-value utilization of surplus resources can be realized; the produced vaterite type calcium carbonate has controllable shape, uniform particle size of the obtained calcium carbonate and good hydrophobicity on the surface of the crystal, thereby greatly widening the application field of the calcium carbonate.
The applicant declares that the above description is only a specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and it should be understood by those skilled in the art that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are within the scope and disclosure of the present invention.
Claims (10)
1. A method for preparing vaterite-type calcium carbonate, comprising:
(1) mixing limestone and ammonium chloride, and then sequentially grinding and roasting to obtain roasted sand;
(2) leaching the calcine obtained in the step (1), and performing solid-liquid separation to obtain a calcium chloride leaching solution;
(3) mixing a surfactant with the calcium chloride leaching solution obtained in the step (2), then introducing carbon dioxide and ammonia gas for carbonization treatment, and carrying out solid-liquid separation after complete carbonization to obtain the vaterite type calcium carbonate.
2. The method according to claim 1, wherein the molar ratio of limestone to ammonium chloride in step (1) is (2.0-3.0):1, more preferably (2.6-3.0): 1;
preferably, the grinding method of step (1) comprises: mortar grinding and/or grinder grinding.
3. The method of claim 1 or 2, further comprising the step of sieving between the grinding and roasting of step (1);
preferably, the mesh number of the screen used for screening is 50 to 80 mesh, and more preferably 60 mesh.
4. The method according to any one of claims 1 to 3, wherein the temperature for the roasting in step (1) is 300-380 ℃, preferably 320-360 ℃;
preferably, the temperature rise rate of the roasting in the step (1) is 1-5 ℃/min, and further preferably 2-4 ℃/min;
preferably, the roasting time in the step (1) is 20-100min, and more preferably 40-60 min.
5. The process according to any one of claims 1 to 4, wherein the leach liquor used in the leach of step (2) comprises water;
preferably, the liquid-solid ratio of the leaching solution to the calcine in the step (2) is (1-3): 1;
preferably, the temperature of the leaching in the step (2) is 20-60 ℃, and further preferably 30-50 ℃;
preferably, the leaching time in step (2) is 30-180min, more preferably 60-120 min.
6. The method according to any one of claims 1 to 5, wherein the surfactant of step (3) comprises a nonionic surfactant;
preferably, the nonionic surfactant comprises coconut oil fatty acid diethanolamide;
preferably, the dosage of the nonionic surfactant accounts for 0.1-10% of the mass fraction of the calcium chloride leaching solution obtained in the step (2).
7. The method according to any one of claims 1 to 6, wherein the flow rate of the carbon dioxide in the step (3) is 8 to 24 mL/min;
preferably, the flow rate of the ammonia gas in the step (3) is 16-54 mL/min.
8. The method according to any one of claims 1 to 7, wherein the carbonization treatment in the step (3) is performed under stirring conditions;
preferably, the rotation speed of the stirring is 200-800rpm, and more preferably 400-600 rpm;
preferably, the stirring paddles used for stirring are: two-blade spiral stirring paddle with 10cm blade area2。
9. The process according to any one of claims 1 to 8, wherein the carbon dioxide in step (3) is bubbled through the calcium chloride leach solution;
preferably, the ammonia gas in the step (3) is introduced into the calcium chloride leachate above the liquid level of the reactor.
10. The process of any one of claims 1 to 9, wherein the solid-liquid separation of step (3) comprises filtration, washing and drying;
preferably, the filtration comprises any one or a combination of at least two of gravity filtration, pressure filtration, vacuum filtration or centrifugal filtration;
preferably, the washing liquid comprises water and/or absolute ethanol;
preferably, the drying includes any one of atmospheric drying, reduced pressure drying, or microwave drying, or a combination of at least two thereof.
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| CN116119701A (en) * | 2023-03-16 | 2023-05-16 | 河北工业大学 | Method for preparing nano calcium carbonate from carbide slag |
| CN116395729A (en) * | 2022-12-22 | 2023-07-07 | 浙江大学 | Fly ash building material utilization method based on vaterite dissolution and recrystallization |
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| CN115504497A (en) * | 2022-10-09 | 2022-12-23 | 陕西安东兴阳岗石科技有限公司 | Preparation method and application of low-oil-absorption-value nano calcium carbonate |
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