Particle size grading method of high-purity titanium dioxide particles
By combining composite dispersants and density gradient solutions, along with ultrasonic-assisted dispersion and real-time monitoring, the problems of low particle size classification efficiency and contamination in titanium dioxide were solved, achieving high-purity and high-efficiency particle size classification.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- PANZHIHUA IRON & STEEL RES INST OF PANGANG GROUP
- Filing Date
- 2025-12-31
- Publication Date
- 2026-04-21
AI Technical Summary
Existing technologies are inefficient and prone to introducing contamination during titanium dioxide particle size classification. Traditional centrifugation requires repeated operations, while membrane filtration is difficult to handle high-concentration slurries, and agglomeration interference leads to deviations in particle size detection.
The suspension was treated with a composite dispersant to depolymerize it. The process involved combining density gradient solution and dynamic density gradient centrifugation, ultrasonic-assisted dispersion, real-time monitoring of particle size distribution, and adjustment of centrifugation parameters to precisely control particle size. A second centrifugation was then performed to remove particles smaller than the target size.
By increasing the slurry concentration and reducing the viscosity, precise control over the settling position of particles of different sizes is achieved, avoiding agglomeration, shortening the grading cycle by 30%, and increasing the purity to over 99%, thus avoiding the contamination problem of membrane filtration.
Smart Images
Figure CN121892318A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of high-purity titanium dioxide production technology, and particularly to a method for particle size classification of high-purity titanium dioxide particles. Background Technology
[0002] The particle size distribution of titanium dioxide (titanium dioxide) directly affects its optical properties and applications. For example, particles of 140-240 nm have the best hiding power in coatings and plastics. Currently, titanium dioxide is mainly processed using centrifugal classification and membrane filtration. Centrifugal classification is a process that uses centrifugal force to separate and purify titanium dioxide particles of different sizes. Its core principle is based on the difference in sedimentation velocity of particles under centrifugal force, achieving the classification of coarse, qualified, and ultrafine particles. It is widely used for particle size control in finished titanium dioxide products to meet the particle size requirements of different fields such as coatings, plastics, and papermaking. Traditional centrifugation requires multiple repeated operations (e.g., 4-stage centrifugation), resulting in low efficiency and a high risk of contamination. Membrane filtration still suffers from membrane fouling and flux decay problems, making it difficult to handle high-concentration slurries. Furthermore, the agglomeration of titanium dioxide can lead to particle size detection errors; for example, 80 nm particles may be misclassified as 150 nm after agglomeration.
[0003] Therefore, existing technologies still need improvement. Summary of the Invention
[0004] To address the aforementioned technical problems, this invention proposes a particle size classification method for high-purity titanium dioxide particles, thereby resolving the technical issues existing in the particle size classification of titanium dioxide in the prior art.
[0005] To address the aforementioned technical problems, some embodiments of the present invention disclose a particle size classification method for high-purity titanium dioxide particles, comprising: Step 1: Depolymerize the initial titanium dioxide using a composite dispersant to prepare a suspension; Step 2: Perform dynamic density gradient centrifugation on the suspension using a density gradient solution to collect the precipitated particles at the predetermined density solution. Step 3: After redispersing the precipitated particles, perform a second centrifugation to remove particles smaller than the target size from the precipitated particles, and obtain titanium dioxide particles within the predetermined particle size range.
[0006] In some embodiments, the composite dispersant is an isopropanolamine-sodium hexametaphosphate-alkylphenol polyoxyethylene ether-polyethylene glycol fatty acid ester composite dispersant; The slurry concentration of the suspension is 1100-1300 g / L, and the viscosity is less than 500 mPa·s.
[0007] In step two of some embodiments, the dynamic density gradient centrifugation classification of the suspension using a density gradient solution includes: using the non-equilibrium density gradient of the solution in conjunction with Stokes' law to control the sedimentation position of particles of different sizes.
[0008] In some embodiments, the non-equilibrium density gradient ranges from 1.1 to 1.2 g / cm³. 3 Alternatively, during the dynamic density gradient centrifugation grading process, pulsed ultrasound may be applied simultaneously.
[0009] In some embodiments, the pulsed ultrasound employs a working procedure of 2-4 seconds on and 0.5-1.5 seconds off.
[0010] In some embodiments, during the secondary centrifugation process, a laser particle size analyzer is used to detect the particle size distribution of the supernatant in real time, and the centrifuge speed and density gradient solution density are adjusted based on the detection results.
[0011] In some embodiments, during the dynamic density gradient centrifugation grading process, the centrifuge speed range is 4000-12000 rpm, and the centrifugation time is 20-50 minutes. Alternatively, the density gradient solution may be a sucrose solution, a xylose solution, or a glucose solution, and the gradient concentration range may be 5wt%-55wt%.
[0012] In some embodiments, the depolymerization treatment of the initial titanium dioxide using a composite dispersant includes: Dissolve 2.8-3.2 parts by weight of isopropanolamine, 1.8-2.2 parts by weight of sodium hexametaphosphate, 0.8-1.2 parts by weight of alkylphenol polyoxyethylene ether and 0.2-0.5 parts by weight of polyethylene glycol fatty acid ester in deionized water to prepare a dispersant stock solution with a mass concentration of 60%. After mixing the initial titanium dioxide with the dispersant mother liquor at a mass ratio of 1:(0.2-0.4), add glycerol-water solution to prepare a preliminary suspension with a concentration of 1100-1300 g / L. The suspension was treated with ultrasonic pulses for 15-25 minutes under stirring to obtain a suspension with an absolute zeta potential value ≥40mV.
[0013] In some embodiments, the suspension is subjected to dynamic density gradient centrifugation fractionation using a density gradient solution, and the collection of precipitated particles includes: Inject a solution at a density of 1.18-1.22 g / cm³ into the bottom of the centrifuge tube. 3 A density gradient solution was injected in the middle with a density of 1.08-1.12 g / cm³. 3 A density gradient solution, topped with the suspension; Centrifuge at 3500-4500 rpm for 15-25 minutes, and simultaneously use ultrasonic pulse treatment during centrifugation. Extract the middle density gradient solution layer and collect the bottom precipitate as the first separated particles. Transfer the extracted middle density gradient solution layer to a new centrifuge tube, and add a solution with a density of 1.03-1.07 g / cm³. 3 The density gradient solution was centrifuged at 11500-12500 rpm for 45-55 minutes, with simultaneous ultrasonic pulse treatment during centrifugation, and the bottom precipitate was collected as the precipitate particles.
[0014] In some embodiments, after the precipitated particles are redispersed, a second centrifugation is performed to remove particles smaller than the target size, resulting in titanium dioxide particles within a predetermined particle size range, including: The precipitated particles were redispersed in deionized water containing 0.08-0.12 wt% dispersant, and ultrasonically treated for 8-12 minutes to obtain a redispersed solution. The redispersed solution was prepared using a solution with a density of 1.08-1.12 g / cm³. 3 The density gradient solution was centrifuged twice for 35-45 minutes at a speed of 9000-11000 rpm, and the precipitate was collected to obtain titanium dioxide particles with a particle size of 140-240 nm and a particle size of ≥99%. Furthermore, during the second centrifugation, a laser particle size analyzer is used to detect the particle size distribution of the supernatant in real time. If a peak of 140-240 nm is detected, the centrifuge speed is increased in the next round of centrifugation; if a peak smaller than 140 nm is detected and the peak intensity is greater than 1%, the concentration of the dispersant is increased to 0.35-0.45 wt% in the next round of centrifugation.
[0015] By adopting the above technical solution, the present invention has at least the following beneficial effects: This invention provides a method for particle size classification of high-purity titanium dioxide particles. By using a composite dispersant, the slurry concentration is greatly increased while the viscosity of the slurry is kept below 500 mPa. The method employs a density gradient solution to achieve precise control over the sedimentation position of particles of different sizes; ultrasonic-assisted dispersion effectively avoids particle agglomeration during centrifugation and enhances dispersion stability. Attached Figure Description
[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0017] Figure 1 This is a flowchart of a particle size classification method for high-purity titanium dioxide particles disclosed in some embodiments of the present invention. Detailed Implementation
[0018] The embodiments of this disclosure will be further described in detail below with reference to the accompanying drawings and examples. The detailed description of the embodiments and the accompanying drawings are used to illustrate the principles of this disclosure by way of example, but should not be used to limit the scope of this disclosure. This disclosure can be implemented in many different forms and is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.
[0019] These embodiments are provided to make the disclosure thorough and complete, and to fully express the scope of the disclosure to those skilled in the art. It should be noted that, unless otherwise specifically stated, the relative arrangement of components and steps, material composition, numerical expressions, and values set forth in these embodiments should be interpreted as exemplary only and not as limiting.
[0020] It should be noted that, in the description of this disclosure, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," and "outer," etc., indicating orientation or positional relationship, are only for the convenience of describing this disclosure and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this disclosure. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.
[0021] Furthermore, the terms "first," "second," and similar terms used in this disclosure do not indicate any order, quantity, or importance, but are merely used to distinguish different parts. "Vertical" is not strictly vertical, but within the permissible margin of error. "Parallel" is not strictly parallel, but within the permissible margin of error. Terms such as "including" or "contains" mean that the element preceding the word encompasses the element listed after the word, and do not exclude the possibility of encompassing other elements as well.
[0022] It should also be noted that, in the description of this disclosure, unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this disclosure depending on the specific circumstances. When a particular device is described as being located between a first device and a second device, an intermediary device may or may not be present between the particular device and the first or second device.
[0023] All terms used in this disclosure have the same meaning as understood by one of ordinary skill in the art to which this disclosure pertains, unless otherwise specifically defined. It should also be understood that terms defined in general dictionaries should be interpreted as having meanings consistent with their meanings in the context of the relevant art, and not as idealized or highly formalized, unless expressly defined herein.
[0024] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, they should be considered part of the specification.
[0025] like Figure 1 As shown, some embodiments of the present invention disclose a method for particle size classification of high-purity titanium dioxide particles, including: Step 1: Depolymerize the initial titanium dioxide using a composite dispersant to prepare a suspension. The composite dispersant can be an isopropanolamine-sodium hexametaphosphate-alkylphenol polyoxyethylene ether-polyethylene glycol fatty acid ester composite dispersant, preferably with a weight ratio of 3:2:2:(0.2-0.5). The resulting suspension should have a slurry concentration of 1100-1300 g / L and a viscosity of less than 500 mPa·s.
[0026] Step 2: Perform dynamic density gradient centrifugation on the suspension using a density gradient solution, collecting the precipitated particles at the predetermined density. The non-equilibrium density gradient of the solution, combined with Stokes' law, can be used to control the settling position of particles of different sizes. During dynamic density gradient centrifugation, pulsed ultrasound can be applied simultaneously to avoid agglomeration during centrifugation, which would affect the particle size classification results. The pulsed ultrasound can operate for 2-4 seconds and then pause for 0.5-1.5 seconds. The centrifuge speed range is 4000-12000 rpm, and the centrifugation time is 20-50 minutes. The density gradient solution can be a sucrose solution, xylose solution, or glucose solution, and the gradient concentration range is preferably 5wt%-55wt%.
[0027] Step 3: After redispersing the precipitated particles, perform a second centrifugation to remove particles smaller than the target size, obtaining titanium dioxide particles within the predetermined particle size range. During the second centrifugation, a laser particle size analyzer can be used to monitor the particle size distribution of the supernatant in real time, and the centrifuge speed and density gradient solution density can be adjusted based on the monitoring results.
[0028] The above embodiments of the present invention, through the use of a composite dispersant, significantly increase the slurry concentration while maintaining the slurry viscosity below 500 mPa. The system employs a density gradient solution to precisely control the sedimentation position of particles of different sizes. Ultrasonic-assisted dispersion effectively prevents particle agglomeration during centrifugation and enhances dispersion stability. During secondary centrifugation, an integrated laser particle size analyzer monitors the particle size distribution of the supernatant in real time, automatically adjusting centrifugation parameters (such as rotation speed and gradient concentration) to effectively shorten the fractionation cycle and reduce purity fluctuations.
[0029] Some embodiments of the present invention also disclose a method for particle size classification of high-purity titanium dioxide particles, comprising: Dissolve 2.8-3.2 parts by weight of isopropanolamine, 1.8-2.2 parts by weight of sodium hexametaphosphate, 0.8-1.2 parts by weight of alkylphenol polyoxyethylene ether and 0.2-0.5 parts by weight of polyethylene glycol fatty acid ester in deionized water to prepare a dispersant stock solution with a mass concentration of 60%. After mixing the initial titanium dioxide with the dispersant mother liquor at a mass ratio of 1:(0.2-0.4), add glycerol-water solution to prepare a preliminary suspension with a concentration of 1100-1300 g / L. The suspension was treated with ultrasonic pulses for 15-25 minutes under stirring to obtain a suspension with an absolute zeta potential value ≥40mV.
[0030] Inject a solution at a density of 1.18-1.22 g / cm³ into the bottom of the centrifuge tube. 3 A density gradient solution was injected in the middle with a density of 1.08-1.12 g / cm³. 3 A density gradient solution, topped with the suspension; Centrifuge at 3500-4500 rpm for 15-25 minutes, and simultaneously use ultrasonic pulse treatment during centrifugation. Extract the middle density gradient solution layer and collect the bottom precipitate as the first separated particles. Transfer the extracted middle density gradient solution layer to a new centrifuge tube, and add a solution with a density of 1.03-1.07 g / cm³. 3 The density gradient solution was centrifuged at 11500-12500 rpm for 45-55 minutes, with simultaneous ultrasonic pulse treatment during centrifugation. The bottom precipitate was collected and recorded as precipitate particles.
[0031] The precipitated particles were redispersed in deionized water containing 0.08-0.12 wt% dispersant, and ultrasonically treated for 8-12 minutes to obtain a redispersed solution. The redispersed solution was prepared using a solution with a density of 1.08-1.12 g / cm³. 3 The density gradient solution was centrifuged twice for 35-45 minutes at a speed of 9000-11000 rpm, and the precipitate was collected to obtain titanium dioxide particles with a particle size of 140-240 nm and a particle size of ≥99%. Furthermore, during the second centrifugation, a laser particle size analyzer is used to detect the particle size distribution of the supernatant in real time. If a peak of 140-240 nm is detected, the centrifuge speed is increased in the next round of centrifugation; if a peak smaller than 140 nm is detected and the peak intensity is greater than 1%, the concentration of the dispersant is increased to 0.35-0.45 wt% in the next round of centrifugation.
[0032] The above embodiments, through depolymerization of composite dispersants, gradient centrifugation classification, and online monitoring feedback, can increase the proportion of 140-240nm particles from 60-70% to over 99%. This method overcomes the bottleneck of traditional centrifugation efficiency, shortens the classification cycle by 30%, and avoids the contamination problems of membrane filtration, making it suitable for the production of high-purity titanium dioxide in coatings, plastics, and other fields.
[0033] Example 1: Dynamic density gradient centrifugation fractionation using sucrose solution as the gradient medium I. Pretreatment: Depolymerization of composite dispersant Dispersant preparation: Dissolve isopropanolamine (3 parts by weight), sodium hexametaphosphate (2 parts by weight), alkylphenol polyoxyethylene ether (1 part by weight) and polyethylene glycol fatty acid ester (0.3 parts by weight) in deionized water to prepare a dispersant stock solution with a mass concentration of 60%. Slurry preparation: Mix the initial titanium dioxide (80-400 nm, 140-240 nm content 60-70%) with the dispersant stock solution at a mass ratio of 1:0.3, and add 5% glycerol-water solution (viscosity 0.0015 Pa). (s), prepared into a suspension with a concentration of 1200 g / L; Ultrasonic pretreatment: 300W pulsed ultrasound treatment for 20 minutes (3 seconds working / 1 second stopping), combined with stirring at 500 rpm, so that the absolute value of zeta potential is ≥40mV.
[0034] II. Dynamic density gradient centrifugation classification (1) Gradient medium preparation: 10 mL of 50% sucrose solution (density 1.2 g / cm³) was injected into the bottom of the centrifuge tube, 15 mL of 30% sucrose solution (density 1.1 g / cm³) was injected into the middle, and the pretreated suspension was covered on top; (2) Coarse removal of large particles: Parameters: 4000 rpm, centrifugation for 20 minutes (particles larger than 240 nm completely settle to the bottom sucrose layer, and particles smaller than 140 nm remain in the 30% sucrose layer). Collection: Extract the middle 30% sucrose layer (containing 140-240 nm particles), and also collect the bottom particles larger than 240 nm.
[0035] (3) Removal of small particles: Parameters: Transfer the middle solution to a new centrifuge tube, add 10% sucrose solution (density 1.05 g / cm³), centrifuge at 12000 rpm for 50 minutes (particles larger than 140 nm settle to the bottom of the 10% sucrose layer, and particles of 80 nm remain in the supernatant). Collection: The bottom precipitate consists of 140-240 nm particles (the proportion increased to 95%).
[0036] The centrifugation and fractionation process is combined with pulsed ultrasound (300W-500W, 3 seconds on, 1 second off) to improve dispersibility and control the sucrose solution concentration accuracy within ±0.5%.
[0037] III. Ultrasonic Enhanced Purification (1) Redispersion: The precipitate was redispersed in deionized water containing 0.1% dispersant and ultrasonically treated for 10 minutes; (2) Second centrifugation: Using a sucrose gradient with a density of 1.1 g / cm³, centrifuge at 10,000 rpm for 40 minutes to remove residual 80-140 nm particles; Final purity: SEM detection and statistics showed that the proportion of 140-240 nm particles was ≥99%, with no obvious agglomeration.
[0038] IV. Online Monitoring System Integrate a laser particle size analyzer (such as the Malvern Mastersizer 3000) at the centrifuge outlet to monitor the particle size distribution of the supernatant in real time (resolution 0.1-3000 μm): If a peak in the 240-400nm range is detected, the centrifugation speed will be automatically increased to 4500rpm in the next round. If the peak intensity of 80-140nm is >1%, increase the amount of dispersant to 0.4%.
[0039] Example 2: Dynamic density gradient centrifugation fractionation using xylose solution as the gradient medium I. Pretreatment: Depolymerization of composite dispersant Dispersant preparation: Dissolve isopropanolamine (3 parts by weight), sodium hexametaphosphate (2 parts by weight), alkylphenol polyoxyethylene ether (1 part by weight) and polyethylene glycol fatty acid ester (0.3 parts by weight) in deionized water to prepare a dispersant stock solution with a mass concentration of 60%.
[0040] Slurry preparation: Mix the initial titanium dioxide (80-400 nm, 140-240 nm content 60-70%) with the dispersant stock solution at a mass ratio of 1:0.3, and add 5% glycerol-water solution (viscosity 0.0015 Pa). (s), prepared into a suspension with a concentration of 1200 g / L.
[0041] Ultrasonic pretreatment: 300W pulsed ultrasound treatment for 20 minutes (3 seconds working / 1 second stopping), combined with stirring at 500 rpm, so that the absolute value of zeta potential is ≥40 mV.
[0042] II. Dynamic density gradient centrifugation classification (1) Gradient medium preparation: 10 mL of 55% xylose solution (density 1.2 g / cm³) was injected into the bottom of the centrifuge tube, 15 mL of 35% xylose solution (density 1.1 g / cm³) was injected into the middle, and the pretreated suspension was covered on top.
[0043] (2) Coarse removal of large particles: Parameters: 4000 rpm, centrifugation for 20 minutes (particles larger than 240 nm completely settle to the bottom xylose layer, and particles smaller than 140 nm remain in the 35% xylose layer).
[0044] Collection: Extract the middle 35% xylose layer (containing 140-240 nm particles), and also collect the bottom particles larger than 240 nm.
[0045] (3) Removal of small particles: Parameters: Transfer the middle solution to a new centrifuge tube, add 12% xylose solution (density 1.05 g / cm³), centrifuge at 12000 rpm for 50 minutes (particles larger than 140 nm settle to the bottom of the 12% xylose layer, and 80 nm particles remain in the supernatant).
[0046] Collection: The bottom precipitate consists of 140-240 nm particles (the proportion increased to 95%).
[0047] The centrifugation and fractionation process is combined with pulsed ultrasound (300W-500W, 3 seconds on, 1 second off) to improve dispersibility and control the xylose solution concentration accuracy within ±0.5%.
[0048] III. Ultrasonic Enhanced Purification (1) Redispersing: The precipitate is redispersed in deionized water containing 0.1% dispersant and ultrasonically treated for 10 minutes.
[0049] (2) Second centrifugation: Using a xylose gradient of density 1.1 g / cm³ (35% xylose solution), centrifuge at 10000 rpm for 40 minutes to remove residual 80-140 nm particles.
[0050] Final purity: SEM detection and statistics showed that the proportion of 140-240 nm particles was ≥99%, with no obvious agglomeration.
[0051] IV. Online Monitoring System Integrate a laser particle size analyzer (such as the Malvern Mastersizer 3000) at the centrifuge outlet to monitor the particle size distribution of the supernatant in real time (resolution 0.1-3000 μm): If a peak in the 240-400 nm range is detected, the centrifugation speed will be automatically increased to 4500 rpm in the next round. If the peak intensity of 80-140 nm is >1%, increase the amount of dispersant to 0.4%.
[0052] Example 3: Dynamic density gradient centrifugation fractionation using glucose solution as the gradient medium I. Pretreatment: Depolymerization of composite dispersant Dispersant preparation: Dissolve isopropanolamine (3 parts by weight), sodium hexametaphosphate (2 parts by weight), alkylphenol polyoxyethylene ether (1 part by weight) and polyethylene glycol fatty acid ester (0.3 parts by weight) in deionized water to prepare a dispersant stock solution with a mass concentration of 60%.
[0053] Slurry preparation: Mix the initial titanium dioxide (80-400 nm, 140-240 nm content 60-70%) with the dispersant stock solution at a mass ratio of 1:0.3, and add 5% glycerol-water solution (viscosity 0.0015 Pa). (s), prepared into a suspension with a concentration of 1200 g / L.
[0054] Ultrasonic pretreatment: 300W pulsed ultrasound treatment for 20 minutes (3 seconds working / 1 second stopping), combined with stirring at 500 rpm, so that the absolute value of zeta potential is ≥40 mV.
[0055] II. Dynamic density gradient centrifugation classification (1) Gradient medium preparation: 10 mL of 48% glucose solution (density 1.2 g / cm³) was injected into the bottom of the centrifuge tube, 15 mL of 28% glucose solution (density 1.1 g / cm³) was injected into the middle, and the pretreated suspension was covered on top.
[0056] (2) Coarse removal of large particles: Parameters: 4000 rpm, centrifugation for 20 minutes (particles larger than 240 nm completely settle to the bottom glucose layer, and particles smaller than 140 nm remain in the 28% glucose layer).
[0057] Collection: Extract the middle 28% glucose layer (containing 140-240 nm particles), and also collect the bottom particles larger than 240 nm.
[0058] (3) Removal of small particles: Parameters: Transfer the middle solution to a new centrifuge tube, add 8% glucose solution (density 1.05 g / cm³), centrifuge at 12000 rpm for 50 minutes (particles larger than 140 nm settle to the bottom of the 8% glucose layer, while 80 nm particles remain in the supernatant).
[0059] Collection: The bottom precipitate consists of 140-240 nm particles (the proportion increased to 95%).
[0060] The centrifugation and fractionation process is combined with pulsed ultrasound (300W-500W, 3 seconds on, 1 second off) to improve dispersibility and control the glucose solution concentration accuracy within ±0.5%.
[0061] III. Ultrasonic Enhanced Purification (1) Redispersing: The precipitate is redispersed in deionized water containing 0.1% dispersant and ultrasonically treated for 10 minutes.
[0062] (2) Second centrifugation: A glucose gradient of density of 1.1 g / cm³ (28% glucose solution) was used, and centrifuged at 10,000 rpm for 40 minutes to remove residual 80-140 nm particles.
[0063] Final purity: SEM detection and statistics showed that the proportion of 140-240 nm particles was ≥99%, with no obvious agglomeration.
[0064] IV. Online Monitoring System Integrate a laser particle size analyzer (such as the Malvern Mastersizer 3000) at the centrifuge outlet to monitor the particle size distribution of the supernatant in real time (resolution 0.1-3000 μm): If a peak in the 240-400 nm range is detected, the centrifugation speed will be automatically increased to 4500 rpm in the next round. If the peak intensity of 80-140 nm is >1%, increase the amount of dispersant to 0.4%.
[0065] In summary, the particle size classification method for high-purity titanium dioxide particles disclosed in this invention is the first to apply a non-equilibrium sucrose, xylose, and glucose gradient to titanium dioxide classification, achieving a particle size resolution of ±5nm through density differences (1.05-1.2g / cm³). Simultaneous ultrasonication (300W, pulse mode) during centrifugation improves the deagglomeration efficiency of agglomerates by 40%, avoiding secondary agglomeration after traditional centrifugation. Automatic adjustment of centrifugation parameters based on particle size data shortens the classification cycle by 30%, with purity fluctuation <0.5%. It overcomes the concentration limitations of traditional single dispersants, increasing the slurry concentration from 600g / L to 1200g / L while reducing viscosity by 80%.
[0066] The embodiments of this disclosure have now been described in detail. To avoid obscuring the concept of this disclosure, some details known in the art have not been described. Those skilled in the art can fully understand how to implement the technical solutions disclosed herein based on the above description.
[0067] While specific embodiments of this disclosure have been described in detail by way of examples, those skilled in the art should understand that the examples are for illustrative purposes only and not intended to limit the scope of this disclosure. Those skilled in the art should understand that modifications can be made to the above embodiments or equivalent substitutions can be made to some technical features without departing from the scope and spirit of this disclosure. In particular, as long as there is no structural conflict, the technical features mentioned in the various embodiments can be combined in any manner.
Claims
1. A method for particle size classification of high-purity titanium dioxide particles, characterized in that, include: Step 1: Depolymerize the initial titanium dioxide using a composite dispersant to prepare a suspension; Step 2: Perform dynamic density gradient centrifugation on the suspension using a density gradient solution to collect the precipitated particles at the predetermined density solution. Step 3: After redispersing the precipitated particles, perform a second centrifugation to remove particles smaller than the target size from the precipitated particles, and obtain titanium dioxide particles within the predetermined particle size range.
2. The particle size classification method according to claim 1, characterized in that, The composite dispersant is an isopropanolamine-sodium hexametaphosphate-alkylphenol polyoxyethylene ether-polyethylene glycol fatty acid ester composite dispersant. The slurry concentration of the suspension is 1100-1300 g / L, and the viscosity is less than 500 mPa·s.
3. The particle size classification method according to claim 1, characterized in that, In step two, the dynamic density gradient centrifugation classification of the suspension using a density gradient solution includes: using the non-equilibrium density gradient of the solution, combined with Stokes' law, to control the sedimentation position of particles of different sizes.
4. The particle size classification method according to claim 3, characterized in that, The non-equilibrium density gradient ranges from 1.1 to 1.2 g / cm³. 3 Alternatively, during the dynamic density gradient centrifugation grading process, pulsed ultrasound may be applied simultaneously.
5. The particle size classification method according to claim 4, characterized in that, The pulsed ultrasound uses a working procedure of 2-4 seconds on and 0.5-1.5 seconds off.
6. The particle size classification method according to claim 1, characterized in that, During the secondary centrifugation process, a laser particle size analyzer is used to detect the particle size distribution of the supernatant in real time, and the centrifuge speed and density gradient solution density are adjusted based on the detection results.
7. The particle size classification method according to claim 6, characterized in that, During the dynamic density gradient centrifugation grading process, the centrifuge speed range is 4000-12000 rpm, and the centrifugation time is 20-50 minutes. Alternatively, the density gradient solution may be a sucrose solution, a xylose solution, or a glucose solution, and the gradient concentration range may be 5wt%-55wt%.
8. The particle size classification method according to claim 1, characterized in that, The deagglomeration treatment of initial titanium dioxide using composite dispersants includes: Dissolve 2.8-3.2 parts by weight of isopropanolamine, 1.8-2.2 parts by weight of sodium hexametaphosphate, 0.8-1.2 parts by weight of alkylphenol polyoxyethylene ether and 0.2-0.5 parts by weight of polyethylene glycol fatty acid ester in deionized water to prepare a dispersant stock solution with a mass concentration of 60%. After mixing the initial titanium dioxide with the dispersant mother liquor at a mass ratio of 1:(0.2-0.4), add glycerol-water solution to prepare a preliminary suspension with a concentration of 1100-1300 g / L. The suspension was treated with ultrasonic pulses for 15-25 minutes under stirring to obtain a suspension with an absolute zeta potential value ≥40mV.
9. The particle size classification method according to claim 1, characterized in that, The suspension was subjected to dynamic density gradient centrifugation fractionation using a density gradient solution, and the collected precipitated particles included: Inject a solution at a density of 1.18-1.22 g / cm³ into the bottom of the centrifuge tube. 3 A density gradient solution was injected in the middle with a density of 1.08-1.12 g / cm³. 3 A density gradient solution, topped with the suspension; Centrifuge at 3500-4500 rpm for 15-25 minutes, and simultaneously use ultrasonic pulse treatment during centrifugation. Extract the middle density gradient solution layer and collect the bottom precipitate as the first separated particles. Transfer the extracted middle density gradient solution layer to a new centrifuge tube, and add a solution with a density of 1.03-1.07 g / cm³. 3 The density gradient solution was centrifuged at 11500-12500 rpm for 45-55 minutes, with simultaneous ultrasonic pulse treatment during centrifugation, and the bottom precipitate was collected as the precipitate particles.
10. The particle size classification method according to claim 1, characterized in that, After redispersing the precipitated particles, a second centrifugation is performed to remove particles smaller than the target size, resulting in titanium dioxide particles within a predetermined particle size range, including: The precipitated particles were redispersed in deionized water containing 0.08-0.12 wt% dispersant, and ultrasonically treated for 8-12 minutes to obtain a redispersed solution. The redispersed solution was prepared using a solution with a density of 1.08-1.12 g / cm³. 3 The density gradient solution was centrifuged twice for 35-45 minutes at a speed of 9000-11000 rpm, and the precipitate was collected to obtain titanium dioxide particles with a particle size of 140-240 nm and a particle size of ≥99%. Furthermore, during the second centrifugation, a laser particle size analyzer is used to detect the particle size distribution of the supernatant in real time. If a peak of 140-240 nm is detected, the centrifuge speed is increased in the next round of centrifugation; if a peak smaller than 140 nm is detected and the peak intensity is greater than 1%, the concentration of the dispersant is increased to 0.35-0.45 wt% in the next round of centrifugation.