Method for preparing monodisperse nano calcium carbonate from calcium-containing industrial solid waste

Abstract

The invention provides a method for preparing monodisperse nano calcium carbonate from calcium-containing industrial solid waste. The method for preparing the monodisperse nano calcium carbonate by using the calcium-containing industrial solid waste comprises the following steps: S1, mixing the calcium-containing solid waste and an ammonium salt solution, reacting, and filtering to obtain a calcium-containing filtrate; s2, mixing the calcium-containing filtrate, CO2-containing gas and a crystal form control agent, reacting, and filtering to obtain nano calcium carbonate; and S3, mixing the nano calcium carbonate with the aqueous solution containing the surfactant, reacting, centrifuging, washing and drying to obtain the monodisperse nano calcium carbonate. According to the method, the leaching rate of calcium in the calcium-containing solid waste is increased, explosive nucleation and rapid growth of calcium carbonate are achieved, the reaction capacity and reaction timeliness between a surfactant and nano calcium carbonate particles are enhanced, and the dispersion degree and the surface modification degree of the calcium carbonate nano particles are improved.

Description

Technical Field

[0001] The invention relates to the technical field of nano calcium carbonate preparation, in particular to a method for preparing monodisperse nano calcium carbonate by utilizing calcium-containing industrial solid waste. Background Art

[0002] Calcium-containing alkaline solid wastes such as steel slag, red mud, and carbide slag are difficult to use directly and have low value due to their complex composition, high alkalinity, and high content of heavy metals. They are mostly used in low-end fields such as the preparation of cement and building base materials, resulting in a waste of valuable resources.

[0003] Calcium carbonate is an important chemical raw material with the advantages of low price, non-toxicity, non-irritation, good color, high whiteness, excellent mechanical properties, etc. It is widely used in rubber, plastics, ink, papermaking, medicine, food, cosmetics and other industries. Nano calcium carbonate is a new industry that has been continuously upgraded and developed from light calcium products. It has advantages that ordinary calcium carbonate does not have, such as fine particle size, large specific surface area, and high activity. The particle size, dispersibility, structural morphology, and surface properties of nano calcium carbonate products affect and determine their functionality and application areas.

[0004] At present, the methods for producing calcium carbonate mainly include carbonization method (Ca(OH) 2 -H 2 O-CO 2 ), ammonium chloride (CaCl 2 -NH 4 Cl) and calcium chloride method (CaCl 2 -Na 2 CO 3 ), Solvay process (CaCl 2 -NaHCO 3 ), etc., all of the above methods involve complex processes such as gas-liquid-solid multiphase mass transfer, heat transfer, crystal nucleus formation, crystal growth, agglomeration, etc., and there are problems such as large calcium carbonate particle size, uneven particle size distribution, poor dispersion effect, and separation difficulty.

[0005] In view of this, the present invention is proposed. Summary of the invention

[0006] The object of the present invention is to provide a method for preparing monodisperse nano-calcium carbonate by utilizing calcium-containing industrial solid waste, which improves the leaching rate of calcium in the calcium-containing solid waste, realizes the explosive nucleation and rapid growth of calcium carbonate, strengthens the reaction ability and reaction time efficiency between surfactant and nano-calcium carbonate particles, and improves the dispersion degree and surface modification degree of calcium carbonate nano-particles.

[0007] The present invention provides a method for preparing monodisperse nano-calcium carbonate by using calcium-containing industrial solid waste, comprising the following steps:

[0008] S1: mixing the calcium-containing solid waste and the ammonium salt solution and reacting them, and filtering to obtain a calcium-containing filtrate;

[0009] S2: The calcium-containing filtrate and CO 2 The gas and the crystal form control agent are mixed and reacted, and nano calcium carbonate is obtained by filtration;

[0010] S3: mixing the nano-calcium carbonate with an aqueous solution containing a surfactant and reacting the mixture, and then centrifuging, washing and drying to obtain monodispersed nano-calcium carbonate.

[0011] In step S1, the calcium-containing solid waste is selected from at least one of red mud, carbide slag, steel slag and yellow phosphorus slag; the mass content of ammonium salt in the ammonium salt solution is 9-20%, and the ammonium salt is selected from at least one of ammonium nitrate, ammonium chloride and ammonium acetate, preferably ammonium chloride; the mass ratio of the calcium-containing solid waste to the ammonium salt solution is (0.05-0.2):1, for example (0.086-0.170):1; the temperature during mixing is 20-50°C, for example 25°C, and the time is 5-10min, for example 10min; the temperature during reaction is 60-120°C, for example 120°C, and the time is 1-6h, for example 1-3h; the mass content of calcium chloride in the calcium-containing filtrate is 5-14%, for example 7.18-13.3%.

[0012] In step S2, the crystal form control agent is selected from at least one of glucose, sodium polyphosphate, dodecylbenzene sulfonic acid, sodium dodecyl sulfate, polyethylene glycol, sodium sulfate, citric acid and oxalic acid; the mass ratio of the crystal form control agent to the nano calcium carbonate is (0.002-0.005):1, preferably (0.003-0.005):1; the CO 2 The gas is N 2 and CO 2 Mixed gas containing CO 2 CO in gas 2 The mass content is 2-100%, for example 10-80%, containing CO 2 The gas can be introduced by self-priming, for example, a venturi tube can be used to introduce CO 2 gas; the reaction temperature is 20-50°C, such as 25°C, and the reaction time is 1-10min, such as 3-10min.

[0013] In step S3, the surfactant is selected from at least one of stearic acid, dodecylbenzene sulfonic acid, silane coupling agent, aluminate coupling agent and titanate coupling agent; the mass ratio of the surfactant to the nano-calcium carbonate is (0.03-0.05): 1; the temperature during the reaction is 20-50°C, for example, 50°C, and the time is 5-10min, for example, 10min; the temperature during drying is 60-100°C, and the time is 6-12h.

[0014] In the above steps S1-S3, a mixing device can be used for mixing; the mixing device includes a shell, a feed chamber is provided at the upper part of the shell, the feed chamber is connected with the feed port, a stator is fixedly provided at the lower part of the shell, the stator has a hollow cavity, a rotor is provided in the hollow cavity, an adjustable gap is provided between the rotor and the stator, the top of the gap is connected with the feed chamber, a plurality of guide grooves are provided at intervals along the circumferential direction on the inner wall of the stator and the outer wall of the rotor, the rotor is connected with the driving shaft of the driving mechanism through a rotating shaft, a reflux port is provided at the top of the shell, two ends of the reflux port are connected with the feed chamber and the reflux pipe respectively, an outlet connected with the bottom of the gap is provided at the bottom of the shell, the outlet is connected with the lower part of the reflux pipe through a three-way valve, a venturi tube is provided in the middle of the reflux pipe, the throat of the venturi tube is connected with the air inlet, and an air inlet valve is provided on the air inlet.

[0015] Furthermore, the feed cavity is in the shape of an inverted truncated cone, and the bottom of the feed cavity is flush with the top of the stator. The hollow cavity of the stator and the rotor are both in the shape of a truncated cone, and the rotor is connected to a lifting mechanism, which can drive the rotor to move up and down relative to the stator to adjust the gap size. The gap size is adjustable in the range of 20-500μm, and the gap size is, for example, 50-200μm. The speed of the rotor is adjustable in the range of 1000-6000r / min, and the CO content is adjusted by the intake valve. 2 Gas intake volume.

[0016] In step S1, the speed of mixing is 1000-5000 r / min, and the time is 5-10 min; in step S2, the speed of mixing is 2000-6000 r / min, and the time is 1-10 min; in step S3, the speed of mixing is 1000-3000 r / min, and the time is 5-10 min.

[0017] The monodisperse nano calcium carbonate prepared above has regular morphology, purity>98.2%, chlorine content<0.006%, alkalinity of 7.5-7.8, sedimentation volume of 2.8-3.8mL / g, particle size of 10-100nm, narrow particle size distribution, the product is white, and no impurities are visible visually.

[0018] The present invention provides a method for preparing monodisperse nano calcium carbonate by using calcium-containing industrial solid waste. In the calcium-containing solid waste ammonium salt leaching stage, the high-pressure liquid film shearing and high-frequency oscillation effect formed by the stator and rotor of the mixing reaction device during the high-speed rotation process is used to strengthen the crushing and reaction ability of the calcium-containing solid waste particles, thereby improving the contactability and reactivity between the calcium-containing solid waste and the ammonium salt solution. 2 The gas enters the reaction system precisely and controllably through the air inlet and air inlet valve at the throat of the venturi tube to form nano-micro bubbles, which accelerate the release of ammonia during the reaction and improve the leaching rate and timeliness of calcium in calcium-containing solid waste. In the carbonization stage of the calcium-containing filtrate, the Bernoulli principle is used to convert CO 2The gas and the calcium-containing filtrate are pre-mixed to obtain a first gas-liquid mixed flow containing large bubbles, which enters the inverted cone reaction chamber through the liquid inlet set on the top of the shell, and then enters the micrometer-scale dynamic confined micro-reaction space formed by the stator and the rotor. The large bubbles are sheared into extremely small bubbles by the extrusion and shearing effect of the high-speed rotation of the rotor to form a second gas-liquid mixed flow of micrometer scale, which increases the CO 2 The gas-liquid contact area with the calcium-containing filtrate improves the gas-liquid mass transfer process and micro-mixing efficiency, suppresses the heterogeneity of mass, temperature and concentration in the system, and makes CO 2 The reaction time of the calcium-containing filtrate and the mixing time between the gas and liquid materials are matched to accurately control the CO 2 The absorption rate and supersaturation of the reaction system achieve explosive nucleation and rapid growth of calcium carbonate, thereby obtaining nano-calcium carbonate with small particle size and narrow particle size distribution; in the surface functionalization treatment stage, the shearing, crushing, and depolymerization capabilities of the high-speed rotating liquid film in the micrometer scale can break up the soft agglomeration during the preparation and storage of nano-calcium carbonate, and strengthen the reaction ability and reaction timeliness between the surfactant and the nano-calcium carbonate particles, thereby obtaining monodisperse nano-calcium carbonate. Compared with the existing kettle / tank reactor and related processes, the present invention is simple to operate, has a short process flow, is easy to batch stabilized production, has low cost and low energy consumption for the preparation of monodisperse nano-calcium carbonate, and has good industrialization prospects, providing an important way for large-scale, low-cost, resource utilization of industrial solid waste, quality improvement and efficiency improvement of nano-calcium carbonate products, and technological progress in calcium carbonate and its related application industries. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 This is the scanning electron microscope photo and energy spectrum scan of steel slag;

[0021] Figure 2 This is a scanning electron microscope photo and energy spectrum scan of red mud;

[0022] Figure 3 The scanning electron microscope photo and energy spectrum scan of the steel slag after ammonium salt calcium leaching in Example 1;

[0023] Figure 4 This is the XRD pattern of the monodisperse nano-calcium carbonate prepared in Example 1;

[0024] Figure 5This is a scanning electron microscope photo of the monodisperse nano-calcium carbonate prepared in Example 1;

[0025] Figure 6 The scanning electron microscope photo and energy spectrum scan of the red mud ammonium salt after calcium leaching in Example 2;

[0026] Figure 7 This is a scanning electron microscope photo of the monodisperse nano-calcium carbonate prepared in Example 2;

[0027] Figure 8 This is a scanning electron microscope photo of the monodisperse nano-calcium carbonate prepared in Example 3;

[0028] Fig. 9 The particle size distribution curve of the monodisperse nano-calcium carbonate prepared in Example 4;

[0029] Fig.10 The particle size distribution curve of the monodisperse nano-calcium carbonate prepared in Example 5;

[0030] Fig.11 This is a schematic diagram of the structure of the mixing and reaction device of Example 6;

[0031] Fig.12 This is a schematic diagram of the structure of the rotor of the mixing and reaction device of Example 6;

[0032] Fig.13 This is a scanning electron microscope photograph of the calcium carbonate prepared in Example 7;

[0033] Fig.14 The particle size distribution curve of calcium carbonate prepared in Example 7;

[0034] Fig.15 This is a scanning electron microscope photograph of the calcium carbonate prepared in Control Example 1.

[0035] Description of reference numerals:

[0036] 1: Shell; 2: Feed chamber; 3: Feed port; 4: Stator; 5: Rotor; 6: Guide groove; 7: Guide groove; 8: Rotating shaft; 9: Reflux port; 10: Reflux pipe; 11: Outlet; 12: Three-way valve; 13: Venturi tube; 14: Air inlet; 15: Air inlet valve; 16: Air escape port; 17: Discharge port. DETAILED DESCRIPTION

[0037] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0038] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form also includes the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this description, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0039] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] The calcium-containing solid waste used in each embodiment is as follows:

[0041] Steel slag: It is a micron-scale irregular block, mainly containing calcium, silicon, iron, aluminum, magnesium, phosphorus and other components. The distribution of calcium, silicon and phosphorus is consistent, and the distribution of iron, magnesium, manganese and other elements is consistent. The content of calcium in steel slag is 47.95% in terms of CaO, and the content of silicon in terms of SiO 2 The content is 10.92%, iron is Fe 2 O 3 The content of manganese is 27.45%, the content of manganese is 4.23% as MnO, and the content of phosphorus is 4.23% as P 2 O 5 The content is 2.33%; the morphology and element distribution are as follows Figure 1 shown.

[0042] Red mud: It is a micron-sized irregular block, mainly containing calcium, silicon, iron, titanium, aluminum and other elements. The content of calcium in red mud is 48.21% in terms of CaO, and the content of silicon in red mud is 48.21% in terms of SiO. 2 The content is 15.51, iron is Fe 2 O 3 The content is 16.75%, titanium in the form of TiO 2 The content is 6.52%, aluminum is Al 2 O 3 The content is 5.76%; the morphology and element distribution are as follows Figure 2 shown.

[0043] Example 1

[0044] The method of preparing monodisperse nano-calcium carbonate using calcium-containing industrial solid waste in this embodiment comprises the following steps:

[0045] (I) Calcium-containing solid waste ammonium salt leaching

[0046] 50 g of ammonium chloride was dissolved in 200 mL of water to form a clear ammonium chloride solution, wherein the mass content of ammonium chloride in the ammonium chloride solution was 20%.

[0047] Weigh 40 g of steel slag and disperse it in the above ammonium chloride solution to form a stable suspension, and control the mass ratio of steel slag to ammonium chloride solution to be 0.160:1.

[0048] The above suspension was added to the mixing reactor of Example 6, the rotor speed of the mixing reactor was 5000 r / min, the gap between the stator and the rotor was set to 100 μm, and the reaction was carried out at 25° C. for 10 min. Then, it was transferred to a reactor and reacted at 120° C. for 3 h. The insoluble slag phase and the calcium-containing filtrate were obtained by filtration.

[0049] (II) Carbonization of calcium-containing filtrate

[0050] The calcium-containing filtrate obtained in step (a) was mixed with N 2 and CO 2 The mixed gas is simultaneously introduced into the mixed reactor of Example 6 for carbonization reaction. 2 The mass content is 80%, and sodium polyphosphate is added as a crystal form control agent. 2 The gas intake volume is 500 mL / min, the mass ratio of ammonium polyphosphate to calcium carbonate is 0.005:1, the rotor speed of the mixing reaction device is 6000 r / min, and the reaction is carried out at 25°C for 3 minutes. After centrifugation and washing, it is dried at 60°C for 12 hours to obtain nano calcium carbonate.

[0051] (III) Surface functionalization treatment

[0052] The nano-calcium carbonate obtained in step (ii) is dispersed in an aqueous solution containing dodecylbenzenesulfonic acid, and the surface is rapidly functionalized in the mixing device of Example 6, wherein the mass ratio of dodecylbenzenesulfonic acid to calcium carbonate is 0.05:1, the rotor speed of the mixing device is 3000 r / min, and the reaction is carried out at 50° C. for 10 min. After centrifugation and washing, the mixture is dried at 60° C. for 12 h to obtain monodisperse nano-calcium carbonate.

[0053] The mass ratio of calcium oxide dissolved in steel slag to total calcium oxide in steel slag was calculated, and the calcium extraction rate of steel slag was 81.2%. Figure 3 As shown, the content of calcium element is significantly reduced, and the content of iron element is significantly increased. The percentage of calcium chloride in the obtained calcium-containing filtrate is 13.3%, and the yield of monodisperse nano-calcium carbonate is 93.8%.

[0054] The monodispersed nano-calcium carbonate prepared in this embodiment has a regular morphology, a purity of 98.4%, a chlorine content of 0.004%, an alkalinity of 7.5, and a sedimentation volume of 3.4 mL / g; the average particle size measured by the particle size distribution is 50 nm, the particle size distribution is narrow, the product is white, and there is no visible impurity. Figure 4 It can be seen from the XRD diagram that the monodispersed nano-calcium carbonate has a vaterite crystal structure, and its scanning electron microscope photo is as follows Figure 5 As shown, from Figure 5 It can be seen that the monodisperse nano-calcium carbonate is spherical particles with a narrow particle size distribution and a particle size of about 55nm.

[0055] Example 2

[0056] The method of preparing monodisperse nano-calcium carbonate using calcium-containing industrial solid waste in this embodiment comprises the following steps:

[0057] (I) Calcium-containing solid waste ammonium salt leaching

[0058] 35 g of ammonium chloride was dissolved in 200 mL of water to form a clear ammonium chloride solution, wherein the mass content of ammonium chloride in the ammonium chloride solution was 14.9%.

[0059] Weigh 40 g of red mud and disperse it in the above ammonium chloride solution to form a stable suspension, and control the mass ratio of red mud to ammonium chloride solution to be 0.170:1.

[0060] The above suspension was added to the mixing reactor of Example 6, the rotor speed of the mixing reactor was 3000 r / min, the gap between the stator and the rotor was set to 100 μm, and the reaction was carried out at 25° C. for 10 min. Then, it was transferred to a reactor and reacted at 120° C. for 1 h. The insoluble slag phase and the calcium-containing filtrate were obtained by filtration.

[0061] (II) Carbonization of calcium-containing filtrate

[0062] The calcium-containing filtrate obtained in step (a) was mixed with N 2 and CO 2 The mixed gas is simultaneously introduced into the mixed reactor of Example 6 for carbonization reaction. 2 The mass content of calcium carbonate is 60%, and sodium sulfate is added simultaneously as a crystal control agent. The mass ratio of sodium sulfate to calcium carbonate is 0.005:1. The rotor speed of the mixing reaction device is 3000r / min. The reaction is carried out at 25°C for 3min. After centrifugation and washing, it is dried at 60°C for 12h to obtain nano calcium carbonate.

[0063] (III) Surface functionalization treatment

[0064] The nano-calcium carbonate obtained in step (ii) is dispersed in an aqueous solution containing stearic acid, and the surface is rapidly functionalized in the mixing device of Example 6, wherein the mass ratio of stearic acid to calcium carbonate is 0.03:1, the rotor speed of the mixing device is 2000 r / min, and the reaction is carried out at 50° C. for 10 min. After centrifugation and washing, the mixture is dried at 60° C. for 12 h to obtain monodisperse nano-calcium carbonate.

[0065] The mass ratio of calcium oxide dissolved in red mud to total calcium oxide in red mud was calculated, and the calcium extraction rate of red mud was 72.1%. Figure 6 As shown, the content of calcium element is significantly reduced, and the content of iron element is significantly increased. The percentage of calcium chloride in the obtained calcium-containing filtrate is 12.1%, and the yield of monodisperse nano-calcium carbonate is 95.2%.

[0066] The monodispersed nano-calcium carbonate prepared in this embodiment has a regular morphology, a purity of 98.6%, a chlorine content of 0.005%, an alkalinity of 7.6, a sedimentation volume of 3.6 mL / g, an average particle size of 80 nm, a narrow particle size distribution, a white product, and no visible impurities. The scanning electron microscope photo is as shown in FIG. Figure 7 As shown, from Figure 7 It can be seen that the monodisperse nano-calcium carbonate is a nanoparticle with an aspect ratio of about 1.2, a narrow particle size distribution, and an average particle size of about 90nm.

[0067] Example 3

[0068] The method of preparing monodisperse nano-calcium carbonate using calcium-containing industrial solid waste in this embodiment comprises the following steps:

[0069] (I) Calcium-containing solid waste ammonium salt leaching

[0070] 25 g of ammonium chloride was dissolved in 250 mL of water to form a clear ammonium chloride solution, wherein the mass content of ammonium chloride in the ammonium chloride solution was 9%.

[0071] Weigh 40 g of red mud and disperse it in the above ammonium chloride solution to form a stable suspension, and control the mass ratio of red mud to ammonium chloride solution to be 0.145:1.

[0072] The above suspension was added to the mixing reactor of Example 6, the rotor speed of the mixing reactor was 6000 r / min, the gap between the stator and the rotor was set to 50 μm, and the reaction was carried out at 25° C. for 10 min. Then, the suspension was transferred to a reactor and reacted at 120° C. for 3 h. The insoluble slag phase and the calcium-containing filtrate were obtained by filtration.

[0073] (II) Carbonization of calcium-containing filtrate

[0074] The calcium-containing filtrate obtained in step (a) was mixed with N2 and CO 2 The mixed gas is simultaneously introduced into the mixed reactor of Example 6 for carbonization reaction. 2 The mass content is 20%, and citric acid is added as a crystal form control agent, containing CO 2 The gas intake volume is 1000 mL / min, the mass ratio of citric acid to calcium carbonate is 0.003:1, the rotor speed of the mixing device is 4000 r / min, and the reaction is carried out at 25°C for 3 minutes. After centrifugation and washing, it is dried at 60°C for 12 hours to obtain nano calcium carbonate.

[0075] (III) Surface functionalization treatment

[0076] The nano-calcium carbonate obtained in step (ii) is dispersed in an aqueous solution containing stearic acid, and the surface is rapidly functionalized in the mixing reaction device of Example 6, the mass ratio of stearic acid to calcium carbonate is 0.05:1, the rotor speed of the mixing reaction device is 2000r / min, and the reaction is carried out at 50°C for 10min. After centrifugation and washing, it is dried at 60°C for 12h to obtain monodisperse nano-calcium carbonate.

[0077] The mass ratio of calcium oxide dissolved in red mud to total calcium oxide in red mud was calculated, and the red mud calcium extraction rate was 52.6%; the percentage of calcium chloride in the obtained calcium-containing filtrate was 9.7%; and the yield of monodisperse nano-calcium carbonate was 96.4%.

[0078] The monodispersed nano calcium carbonate prepared in this example has a regular morphology, a purity of 98.3%, a chlorine content of 0.005%, an alkalinity of 7.6, a sedimentation volume of 3.8 mL / g, an average particle size of 40 nm, a narrow particle size distribution, a white product, and no visible impurities. The scanning electron microscope photo is as shown in FIG. Figure 8 As shown, from Figure 8 It can be seen that the monodisperse nano-calcium carbonate is spherical nanoparticles with a narrow particle size distribution and a particle size of about 40nm.

[0079] Example 4

[0080] The method of preparing monodisperse nano-calcium carbonate using calcium-containing industrial solid waste in this embodiment comprises the following steps:

[0081] (I) Calcium-containing solid waste ammonium salt leaching

[0082] 30 g of ammonium chloride was dissolved in 200 mL of water to form a clear ammonium chloride solution, wherein the mass content of ammonium chloride in the ammonium chloride solution was 13%.

[0083] Weigh 20 g of steel slag and disperse it in the above ammonium chloride solution to form a stable suspension, and control the mass ratio of steel slag to ammonium chloride solution to be 0.086:1.

[0084] The above suspension was added to the mixing reactor of Example 6, the rotor speed of the mixing reactor was 4000 r / min, the gap between the stator and the rotor was set to 200 μm, and the reaction was carried out at 25° C. for 10 min. Then, it was transferred to a reactor and reacted at 120° C. for 3 h. The insoluble slag phase and the calcium-containing filtrate were obtained by filtration.

[0085] (II) Carbonization of calcium-containing filtrate

[0086] The calcium-containing filtrate obtained in step (a) was mixed with N 2 and CO 2 The mixed gas is simultaneously introduced into the mixed reactor of Example 6 for carbonization reaction. 2 The mass content is 20%, polyethylene glycol is added as a crystal form control agent, and CO 2 The gas intake volume is 500 mL / min, the mass ratio of polyethylene glycol to calcium carbonate is 0.003:1, the rotor speed of the mixing device is 6000 r / min, and the reaction is carried out at 25°C for 3 minutes. After centrifugation and washing, it is dried at 60°C for 12 hours to obtain nano calcium carbonate.

[0087] (III) Surface functionalization treatment

[0088] The nano-calcium carbonate obtained in step (ii) is dispersed in an aqueous solution containing stearic acid, and the surface is rapidly functionalized in the mixing device of Example 6, wherein the mass ratio of stearic acid to calcium carbonate is 0.05:1, the rotor speed of the mixing device is 3000 r / min, and the reaction is carried out at 50° C. for 10 min. After centrifugation and washing, the mixture is dried at 60° C. for 12 h to obtain monodisperse nano-calcium carbonate.

[0089] The mass ratio of calcium oxide dissolved in the steel slag to the total calcium oxide in the steel slag was calculated, and the calcium extraction rate of the steel slag was 79.5%; the percentage of calcium chloride in the obtained calcium-containing filtrate was 7.18%; and the yield of monodisperse nano-calcium carbonate was 95.8%.

[0090] The monodispersed nano-calcium carbonate prepared in this example has a regular morphology, a purity of 98.7%, a chlorine content of 0.005%, an alkalinity of 7.8, a sedimentation volume of 2.8 mL / g, and a particle size distribution curve as shown in FIG. Fig. 9 As shown, the average particle size is 98nm, the particle size distribution is narrow, the product is white, and there is no visible impurity. The average particle size observed by scanning electron microscopy is 90nm.

[0091] Example 5

[0092] The method of preparing monodisperse nano-calcium carbonate using calcium-containing industrial solid waste in this embodiment comprises the following steps:

[0093] (I) Calcium-containing solid waste ammonium salt leaching

[0094] 40 g of ammonium chloride was dissolved in 200 mL of water to form a clear ammonium chloride solution, wherein the mass content of ammonium chloride in the ammonium chloride solution was 20%.

[0095] Weigh 40 g of steel slag and disperse it in the above ammonium chloride solution to form a stable suspension, and control the mass ratio of steel slag to ammonium chloride solution to be 0.167:1.

[0096] The above suspension was added to the mixing reactor of Example 6, the rotor speed of the mixing reactor was 6000 r / min, the gap between the stator and the rotor was set to 200 μm, and the reaction was carried out at 25° C. for 10 min. Then, it was transferred to a reactor and reacted at 120° C. for 3 h. The insoluble slag phase and the calcium-containing filtrate were obtained by filtration.

[0097] (II) Carbonization of calcium-containing filtrate

[0098] The calcium-containing filtrate obtained in step (a) was mixed with N 2 and CO 2 The mixed gas is simultaneously introduced into the mixed reactor of Example 6 for carbonization reaction. 2 The mass content is 10%, glucose is added simultaneously as a crystal control agent, the mass ratio of glucose to calcium carbonate is 0.003:1, the rotor speed of the mixing reaction device is 5000r / min, and the reaction is carried out at 25°C for 10min. After centrifugation and washing, it is dried at 60°C for 12h to obtain nano calcium carbonate.

[0099] (III) Surface functionalization treatment

[0100] The nano-calcium carbonate obtained in step (ii) is dispersed in an aqueous solution containing stearic acid, and the surface is rapidly functionalized in the mixing device of Example 6, wherein the mass ratio of stearic acid to calcium carbonate is 0.05:1, the rotor speed of the mixing device is 3000 r / min, and the reaction is carried out at 50° C. for 10 min. After centrifugation and washing, the mixture is dried at 60° C. for 12 h to obtain monodisperse nano-calcium carbonate.

[0101] The mass ratio of calcium oxide dissolved in the steel slag to the total calcium oxide in the steel slag was calculated, and the calcium extraction rate of the steel slag was 68.7%; the percentage of calcium chloride in the obtained calcium-containing filtrate was 11.5%; and the yield of monodisperse nano-calcium carbonate was 95.8%.

[0102] The monodispersed nano-calcium carbonate prepared in this example has a regular morphology, a purity of 98.8%, a chlorine content of 0.004%, an alkalinity of 7.7, a sedimentation volume of 3.1 mL / g, and a particle size distribution curve as shown in FIG. Fig.10 As shown, the average particle size is 94nm, the particle size distribution is narrow, the product is white, and there is no visible impurity. The average particle size observed by scanning electron microscopy is 89nm.

[0103] Example 6

[0104] Combination Fig.11 , Fig.12 As shown, this embodiment provides a mixing and reaction device for embodiments 1-5, the mixing and reaction device includes a shell 1, a feed chamber 2 is provided at the upper part of the shell 1, the feed chamber 2 is connected to the feed port 3, a stator 4 is fixedly provided at the lower part of the shell 1, the stator 4 has a hollow cavity, a rotor 5 is provided in the hollow cavity, an adjustable gap is provided between the rotor 5 and the stator 4, the top of the gap is connected to the feed chamber 2, and a plurality of guide grooves 6 are provided at intervals along the circumferential direction on the inner wall of the stator 4 and the outer wall of the rotor 5. and a plurality of guide grooves 7, the rotor 5 is connected to the driving shaft of the driving mechanism through a rotating shaft 8, a reflux port 9 is provided at the top of the shell body 1, and the two ends of the reflux port 9 are respectively connected to the feed chamber 2 and the reflux pipe 10, an outlet 11 connected to the bottom of the gap is provided at the bottom of the shell body 1, the outlet 11 is connected to the lower part of the reflux pipe 10 through a three-way valve 12, a venturi tube 13 is provided in the middle of the reflux pipe 10, the throat of the venturi tube 13 is connected to the air inlet 14, and an air inlet valve 15 is provided on the air inlet 14.

[0105] The shell 1 can be a cylindrical closed shell, and a feed port 3, a reflux port 9 and an exhaust port 16 are independently provided on the top. The feed port 3, the reflux port 9 and the exhaust port 16 are respectively connected to the feed chamber 2. The feed port 3 is used to deliver the material to the feed chamber 2, the reflux port 9 is used to make the material in the gap reflux to the feed chamber 2, and the exhaust port 16 is used for exhaust.

[0106] A feed chamber 2 is provided at the upper part of the shell 1. The feed chamber 2 is in the shape of an inverted truncated cone. The bottom of the feed chamber 2 is flush with the top of the stator 4, so that the material in the feed chamber 2 can enter the gap between the stator 4 and the rotor 5 for mixing and reaction. A stator 4 and a rotor 5 are provided at the lower part of the shell 1. The stator 4 is provided in the hollow cavity of the rotor 5. There is a gap between the stator 4 and the rotor 5. The gap forms a dynamic confined micro-reaction space of micrometer scale, which is conducive to the formation of high-pressure liquid film shear and high-frequency oscillation during high-speed rotation, so as to enhance the crushing and reaction ability of calcium-containing solid waste particles, and improve the contactability and reactivity between the calcium-containing solid waste and the ammonium salt solution.

[0107] There is no strict restriction on the adjustable method of the gap size, as long as the gap size can be adjusted within the range of 20-500μm. Specifically, the hollow cavity of the stator 4 and the rotor 5 are in a mutually matching truncated cone shape, the hollow cavity and the truncated cone side of the rotor 5 have the same inclination angle, and the upper and lower bottom sizes of the hollow cavity truncated cone are larger than the upper and lower bottom sizes of the rotor 5 truncated cone, and the stator 4 and the rotor 5 are coaxially arranged. When the stator 4 and the rotor 5 are relatively fixed, there is a fixed gap between the stator 4 and the rotor 5.

[0108] Furthermore, the rotor 5 can be connected to a lifting mechanism, which can drive the rotor 5 to move up and down relative to the stator 4 to adjust the gap size, and the gap size can be adjusted within the range of 20-500 μm according to actual process requirements. It can be understood that when the rotor 5 moves upward relative to the stator 4, the gap between the stator 4 and the rotor 5 becomes smaller; when the rotor 5 moves downward relative to the stator 4, the gap between the stator 4 and the rotor 5 becomes larger.

[0109] In addition, a plurality of guide grooves 6 are provided at intervals along the circumferential direction on the inner wall of the stator 4, and the depth of the guide grooves 6 is 1-2 mm; a plurality of guide grooves 7 are provided at intervals along the circumferential direction on the outer wall of the rotor 5, and the depth of the guide grooves 7 is 1-2 mm. The guide grooves 6 and 7 can be provided through from top to bottom along the inner wall of the stator 4 and the outer wall of the rotor 5; at the same time, the guide grooves 6 and 7 can be provided at an angle of 45-75 degrees, and the spacing between adjacent guide grooves 6 is 1-2 mm, and the spacing between adjacent guide grooves 7 is 1-2 mm.

[0110] The rotor 5 is connected to the driving shaft of the driving mechanism through the rotating shaft 8. The driving mechanism drives the rotor 5 to rotate through the driving shaft and the rotating shaft 8. The speed of the rotor 5 is adjustable within the range of 1000-6000r / min. The stator 4 and the rotor 5 form high-pressure liquid film shearing and high-frequency oscillation during high-speed rotation, thereby enhancing the crushing and reaction capabilities of calcium-containing solid waste particles, and improving the contactability and reactivity between calcium-containing solid waste and ammonium salt solution; at the same time, the gap between the stator 4 and the rotor 5 is a micrometer-scale dynamic confined micro-reaction space, which uses the extrusion and shearing effects of the rotor 5 during high-speed rotation to move CO 2 Large bubbles are sheared into extremely small bubbles to form a second gas-liquid mixed flow at the micrometer scale, increasing the CO 2 The gas-liquid contact area with the calcium-containing filtrate improves the gas-liquid mass transfer process and micro-mixing efficiency, suppresses the heterogeneity of mass, temperature and concentration in the system, and makes CO 2 The reaction time of the calcium-containing filtrate and the mixing time between the gas and liquid materials are matched to accurately control the CO 2 The absorption rate and supersaturation of the reaction system achieve explosive nucleation and rapid growth of calcium carbonate, thereby obtaining nano-calcium carbonate with small particle size and narrow particle size distribution; in addition, the shearing, crushing and deagglomeration capabilities of the high-speed rotating liquid film within the micron scale can break up the soft agglomerates during the preparation and storage of nano-calcium carbonate, enhance the reaction ability and reaction timeliness between the surfactant and the nano-calcium carbonate particles, and thereby obtain monodisperse nano-calcium carbonate.

[0111] One end of the reflux pipe 10 is connected to the reflux port 9, and the other end of the reflux pipe 10 forms a discharge port 17; when the mixing reaction effect of the mixing reaction device does not meet the preset requirements, the material can be refluxed to the mixing reaction device through the reflux pipe 10 through the outlet 11 to continue the mixing reaction; when the mixing reaction effect of the mixing reaction device meets the preset requirements, the material can be discharged through the discharge port 17.

[0112] A venturi tube 13 is provided in the middle of the return pipe 10, containing CO 2 The gas can be self-absorbed into the mixing reactor through the venturi tube 13. The outlet 11 is connected to the venturi tube 13, and the gas containing CO is introduced through the venturi tube 13. 2 The gas is then fed to the rotor 4 to obtain a preliminary gas-liquid mixed flow, and then a second gas-liquid mixed flow is obtained in the micrometer-scale dynamic confined microenvironment formed by the gap between the stator 4 and the rotor 5, thereby enhancing the mixing and reaction ability between the gas and the liquid. 2 The gas enters the reaction system precisely and controllably through the air inlet 14 and the air inlet valve 15 at the throat of the venturi tube 13 to form nano-micro bubbles to accelerate the escape of ammonia during the reaction, thereby improving the leaching rate and leaching timeliness of calcium in calcium-containing solid waste. In addition, the Bernoulli principle is used to leach CO 2 The gas and the calcium-containing filtrate are preliminarily premixed to obtain a first gas-liquid mixed flow containing large bubbles, which enters the inverted truncated cone-shaped feed chamber 2 through the feed port 3 set on the top of the shell 1, and then enters the micrometer-scale dynamic confined micro-reaction space formed by the stator 4 and the rotor 5 to shear the large bubbles into extremely small bubbles to form a micrometer-scale second gas-liquid mixed flow, thereby improving the gas-liquid mass transfer process and the microscopic mixing efficiency.

[0113] Example 7

[0114] Except for using the existing mixing reaction device (ZJRIII-4 three-stage emulsification pump of Anhui Zhongjinghuasheng Technology Co., Ltd.) to replace the mixing reaction device of Example 1, the rest is the same as Example 1.

[0115] The mass ratio of calcium oxide dissolved in the slag to the total calcium oxide in the slag was calculated, and the calcium extraction rate of the slag was 68.3%; the percentage of calcium chloride in the obtained calcium-containing filtrate was 10.56%, and the yield of monodisperse nano-calcium carbonate was 89.2%.

[0116] Combination Fig.13 , Fig.14 The nano calcium carbonate prepared in this embodiment has a spherical secondary agglomerate composed of 50nm primary particles. The average particle size of the agglomerate measured by the particle size distribution curve is 3μm, the purity of calcium carbonate is 97.3%, the chlorine content is 0.083%, the alkalinity is 7.9, the sedimentation volume is 2.6mL / g, and the average particle size is 2.7μm.

[0117] Comparative Example 1

[0118] Except that a conventional mechanical stirring device is used to replace the mixing device in the carbonization step of the calcium-containing filtrate, the rest is the same as Example 1; that is, this reference example carries out the rotation reaction in the carbonization step of the calcium-containing filtrate under mechanical stirring conditions, followed by centrifugation, washing, and drying to obtain nano calcium carbonate.

[0119] The calcium carbonate prepared in this example has an irregular morphology, and is a spherical particle agglomerate composed of primary particles of about 10 nm, accompanied by irregular blocks of about 300 nm. The average particle size measured by the particle size distribution curve is 1.8 μm, the purity of calcium carbonate is 97.4%, the chlorine content is 0.065%, the alkalinity is 7.6, the sedimentation volume is 2.3 mL / g, and the scanning electron microscope photo is as follows: Fig.15 As shown, from Fig.15 It can be seen that spherical particles and irregular blocks appear at the same time, and the particle size of spherical agglomerates is about 1.5μm.

[0120] Comparative Example 2

[0121] Except that a conventional mechanical stirring device is used to replace the mixing device in the calcium-containing solid waste ammonium salt leaching step, the rest is the same as Example 1; that is, in this control example, the rotational mixing in the calcium-containing solid waste ammonium salt leaching step is carried out under mechanical stirring conditions, and then the mixture is transferred to the reactor for reaction.

[0122] The mass ratio of the calcium oxide dissolved in the steel slag to the total calcium oxide in the steel slag was calculated, and the calcium extraction rate of the steel slag was 56.3%. The percentage of calcium chloride in the obtained calcium-containing filtrate was 8.5%.

[0123] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing monodisperse nano-calcium carbonate using calcium-containing industrial solid waste, characterized in that: The steps include: S1: mixing the calcium-containing solid waste and the ammonium salt solution and reacting them, and filtering to obtain a calcium-containing filtrate; S2: mixing the calcium-containing filtrate, the CO2-containing gas and the crystal form control agent, reacting them, and filtering to obtain nano calcium carbonate; S3: mixing the nano-calcium carbonate with an aqueous solution containing a surfactant and reacting the mixture, and then centrifuging, washing and drying to obtain monodispersed nano-calcium carbonate.

2. The method according to claim 1, characterized in that In step S1, the calcium-containing solid waste is selected from at least one of red mud, carbide slag, steel slag and yellow phosphorus slag; the mass content of ammonium salt in the ammonium salt solution is 9-20%, and the ammonium salt is selected from at least one of ammonium nitrate, ammonium chloride and ammonium acetate.

3. The method according to claim 1, characterized in that In step S1, the mass ratio of calcium-containing solid waste to ammonium salt solution is (0.05-0.2):1; the temperature during the reaction is 60-120°C, and the time is 1-6h.

4. The method according to claim 1, characterized in that: In step S2, the crystal form control agent is selected from at least one of glucose, sodium polyphosphate, dodecylbenzene sulfonic acid, sodium dodecyl sulfate, polyethylene glycol, sodium sulfate, citric acid and oxalic acid; the mass ratio of the crystal form control agent to the nano calcium carbonate is (0.002-0.005):

1.

5. The method according to claim 1, characterized in that In step S2, the mass content of CO2 in the CO2-containing gas is 2-100%; the temperature during the reaction is 20-50°C, and the time is 1-10 minutes.

6. The method according to claim 1, characterized in that In step S3, the surfactant is selected from at least one of stearic acid, dodecylbenzene sulfonic acid, silane coupling agent, aluminate coupling agent and titanate coupling agent; the mass ratio of the surfactant to the nano-calcium carbonate is (0.03-0.05):

1.

7. The method according to claim 1, characterized in that In step S3, the reaction temperature is 20-50°C and the reaction time is 5-10 minutes.

8. The method according to claim 1, characterized in that A mixing and reaction device is used for mixing; the mixing and reaction device comprises a shell, a feed chamber is arranged at the upper part inside the shell, the feed chamber is connected with the feed port, a stator is fixedly arranged at the lower part inside the shell, the stator has a hollow cavity, a rotor is arranged in the hollow cavity, an adjustable gap is arranged between the rotor and the stator, the top of the gap is connected with the feed chamber, a plurality of guide grooves are arranged at intervals along the circumferential direction on the inner wall of the stator and the outer wall of the rotor, the rotor is connected with the driving shaft of the driving mechanism through a rotating shaft, a reflux port is arranged at the top of the shell, the two ends of the reflux port are connected with the feed chamber and the reflux pipe respectively, an outlet connected with the bottom of the gap is arranged at the bottom of the shell, the outlet is connected with the lower part of the reflux pipe through a three-way valve, a venturi tube is arranged in the middle part of the reflux pipe, the throat of the venturi tube is connected with the air inlet, and an air inlet valve is arranged on the air inlet.

9. The method according to claim 8, characterized in that In step S1, the speed of mixing is 1000-5000 r / min, and the time is 5-10 min; in step S2, the speed of mixing is 2000-6000 r / min, and the time is 1-10 min; in step S3, the speed of mixing is 1000-3000 r / min, and the time is 5-10 min.

10. The method according to claim 1, characterized in that The particle size of monodisperse nano calcium carbonate is 10-100nm.

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