CN-121974363-A - Method for rapidly depolymerizing hectorite nanosheets

Abstract

The invention discloses a method for rapidly depolymerizing hectorite nanosheets, and belongs to the technical field of nano powder preparation. The method comprises the steps of preparing laponite into suspension with the mass concentration of 0.1-wt-wt%, adjusting the pH value to 2-12 by acid and alkali, carrying out high-pressure homogenization treatment under the pressure of 10-100 MPa, and carrying out filter pressing and strong drying to obtain the peeled nano laponite powder with the thickness of 2-10 nm and the water content of less than or equal to 2.0%. The invention realizes the efficient and rapid depolymerization of hectorite under the premise of not damaging the crystal structure by the synergism of pH regulation and high-pressure homogenization, and has the advantages of simple process, low cost and easy amplification.

Inventors

• LU YUSHEN
• WANG AIQIN
• MOU BIN
• ZHANG TIANZHI
• XU JIANG
• ZHANG TIANYI
• WANG QIN

Assignees

• 中国科学院兰州化学物理研究所
• 江苏海明斯新材料科技有限公司

Dates

Publication Date

20260505

Application Date

20260211

Claims (5)

1. 1. A method for rapid depolymerization of hectorite nanoplatelets, comprising the steps of: S1, dispersing laponite in water to prepare a suspension with the mass concentration of 0.1 wt% -5 wt%; S2, adding a pH regulator into the suspension, and regulating the pH value of the system to be within a range of 2-12 so as to change the surface charge state of the end face of the hectorite nano-sheet; S3, carrying out high-pressure homogenization treatment on the suspension subjected to pH adjustment, wherein the treatment pressure is 10-100 MPa, and utilizing the shearing and cavitation effects of fluid generated by the high-pressure homogenization to synergistically weaken the hydrogen bond and electrostatic action between the sheets under the specific pH condition so as to realize the efficient depolymerization of the hectorite aggregate; s4, carrying out filter pressing treatment on the depolymerized suspension to obtain a filter cake; and S5, carrying out strong drying on the filter cake to obtain the peeled nano hectorite powder with the thickness of the slice of 2-10 nm.
2. 2. The method according to claim 1, wherein in step S2, the pH adjuster is a sulfuric acid solution of 0.1 mol/L or a sodium hydroxide solution of 0.1 mol/L.
3. 3. The method according to claim 1, wherein in step S3, the high pressure homogenizing treatment is repeatedly performed or is cyclically performed.
4. 4. The method according to claim 1, wherein in the step S4, the filter pressing treatment adopts a high-pressure diaphragm filter pressing mode, the feeding pressure is 1.5 MPa-2.8 MPa, and the water content of the filter cake is less than 50%.
5. 5. The method according to claim 1, wherein in step S5, the temperature of the strong drying is 90 ℃ to 130 ℃ and the moisture content of the peeled nano lithium soap powder after drying is not more than 2.0% along with the classification function with the frequency of 5Hz to 25 Hz.

Description

Method for rapidly depolymerizing hectorite nanosheets Technical Field The invention belongs to the technical field of nano powder preparation, and particularly relates to a method for rapidly depolymerizing hectorite nano-sheets. Background Hectorite (Laponite) is an artificially synthesized phyllosilicate nanomaterial, the chemical formula of which is generally represented by Na 0.7Si8Mg5.5Li0.3O20(OH)4. The crystal structure of the composite is a typical 2:1 layered unit formed by clamping one layer of magnesia octahedron by two layers of silica tetrahedron, wherein part of Mg 2+ in the octahedron layer is isomorphously substituted by Li +, so that the basal plane of the sheet layer has permanent negative charge, and the interlayer maintains electric neutrality through exchangeable Na+. Meanwhile, the edge (end face) of the hectorite nano-sheet is exposed with a large amount of unsaturated hydroxyl groups such as Si-OH and Mg-OH, the protonation state is regulated by pH, the end face is positively charged under an acidic condition, and the end face tends to be neutral or weakly negatively charged under an alkaline condition. This unique surface charge characteristic not only determines its colloidal behavior in the aqueous phase, such as "card house" structure formation due to edge-to-base electrostatic attraction, but also directly affects the strength and aggregation state of inter-layer hydrogen bonding and electrostatic interactions. The electrostatic effect and the hydrogen bond effect enable the hectorite to easily form a lamellar stacking structure in a natural state, so that the effective stripping of single-layer or few-layer nano sheets is seriously hindered, and the hectorite becomes a key bottleneck for restricting the high-end functional application of the hectorite. Currently, laponite exfoliation relies mainly on chemical intercalation (Langmuir, 2006, 22, 6696-6700;Materials TodayCommunications, 2025, 48, 113548), sonication (APPLIED CLAY SCIENCE, 2010, 49, 21-28), mechanical shearing (CLAY MINERALS, 2012, 47, 341-353) and the like, but there are significant limitations to each type of technique. The chemical intercalation method can realize more sufficient stripping by expanding the interlayer spacing of organic molecules and can regulate and control the surface properties, but the introduced external reagent needs to be removed additionally, and the functional characteristics of the hectorite can be changed. Although ultrasonic stripping can obtain the thin-layer hectorite under laboratory conditions, the problems of long time, high energy consumption, easiness in causing structural defects, breaking of the slices and the like are faced. Mechanical shearing methods such as ball milling are simple to operate and suitable for continuous production, but are not thorough in stripping, and high-proportion single-layer or few-layer sheets are difficult to obtain. The difficulty in exfoliation of laponite is essentially dependent on the balance between interlayer binding energy and external disturbance energy. To achieve efficient exfoliation, the key is to selectively regulate the end-base interaction, rather than simply boost the input energy. There is currently no rational stripping strategy based on the chemical nature of the hectorite surface. Notably, high pressure homogenization techniques have shown significant advantages in the dissociation of one-dimensional nanostructured minerals such as attapulgite bundles as an efficient, continuous, scalable physical dispersion means (CN 201710435267.7). The principle is that the fluid generates strong shearing, cavitation and impact effects under high pressure to effectively destroy the aggregation structure among particles. However, until now, no systematic study or patent report has been made on the application of high pressure homogenization techniques to efficient exfoliation of laponite. Aiming at the problems, the invention provides a novel stripping strategy based on pH regulation and control and high-pressure homogenization. Specifically, the protonation/deprotonation state of lamellar edge groups can be directionally regulated and controlled by accurately regulating the pH value of the hectorite aqueous suspension, so that the terminal surface charge density and the hydrogen bond formation capacity are changed. On the basis, the high-efficiency depolymerization of the hectorite aggregate can be realized by combining the extreme hydrodynamic effect generated by high-pressure homogenization, and the high-dispersion single-layer or few-layer nano-sheet can be obtained. Disclosure of Invention Aiming at the problems of low efficiency, long time consumption, easy damage to the structure, low single layer rate and the like in the existing laponite nano-sheet stripping method, the invention aims to provide a rapid laponite nano-sheet depolymerization method which has simple process and high efficiency and can keep the structural integrity of