阅读说明：本技术 易分散且增稠性能优异的硅酸镁锂的水热合成方法 (Hydrothermal synthesis method of magnesium lithium silicate with easy dispersion and excellent thickening performance ) 是由 童自强 付绍祥 刘利威 于 2021-01-29 设计创作，主要内容包括：本发明涉及一种易分散且增稠性能优异的硅酸镁锂的水热合成方法,主要包括以下依序进行的步骤：(1)制备LiF溶液；(2)制备MgCl-2溶液；(3)超声环境下制备Mg(OH)-2沉淀；(4)制备混合浆液；(5)Na-2O·nSiO-2缓慢加入步骤(4)获得的混合浆液中,搅拌均匀；(6)将步骤(5)获得的混合液于100-130℃下反应1.5-4h后,过滤、洗涤,干燥至恒重,即得所述易分散且增稠性能优异的硅酸镁锂。该发明克服了现有硅酸镁锂制备过程中存在的水热反应需要高温高压条件、水热反应耗时长、对流体流变性能的调节效果不佳等缺点,通过在氢氧化镁前驱体的制备阶段引入超声处理,即可制备得到高品质、性能优异的硅酸镁锂,该硅酸镁锂颗粒小、分散性好、对流体流变性能的调节效果佳。(The invention relates to a hydrothermal synthesis method of magnesium lithium silicate with easy dispersion and excellent thickening performance, which mainly comprises the following steps of sequentially carrying out: (1) preparing LiF solution; (2) preparation of MgCl 2 A solution; (3) preparation of Mg (OH) in an ultrasonic Environment 2 Precipitating; (4) preparing mixed slurry; (5) na (Na) 2 O·nSiO 2 Slowly adding the mixture into the mixed slurry obtained in the step (4), and uniformly stirring; (6) and (3) reacting the mixed solution obtained in the step (5) at the temperature of 100-130 ℃ for 1.5-4h, filtering, washing and drying to constant weight to obtain the easily-dispersed magnesium lithium silicate with excellent thickening performance. The method overcomes the defects that the hydrothermal reaction needs high-temperature and high-pressure conditions, the hydrothermal reaction consumes long time, the adjusting effect on the rheological property of the fluid is not good and the like in the existing preparation process of the magnesium lithium silicate, and the high-quality magnesium lithium silicate with excellent performance can be prepared by introducing ultrasonic treatment in the preparation stage of the magnesium hydroxide precursor.)

1. A hydrothermal synthesis method of magnesium lithium silicate with easy dispersion and excellent thickening performance is characterized in that: the magnesium lithium silicate with easy dispersion and excellent thickening performance is mainly prepared from the following components in parts by weight:

the hydrothermal synthesis method of the magnesium lithium silicate with easy dispersion and excellent thickening performance mainly comprises the following steps of sequentially carrying out:

(1) adding the LiF into deionized water accounting for 50-71.43% of the total weight of the LiF, and stirring at the rotating speed of 500-1000rpm until the LiF is dissolved to obtain a LiF solution;

(2) adding said MgCl to the remaining deionized water₂·6H₂O, dissolving uniformly to obtain MgCl₂A solution;

(3) mixing MgCl₂Putting the solution in an ultrasonic environment of 90-110W, weighing the alkali liquor with the molar concentration of 2-4mol/L in a constant pressure dropping funnel, and dropping the MgCl at a constant speed within 0.5-1h₂Fully mixing the two in the solution and reacting, centrifuging the obtained reaction solution at the rotating speed of 4000-₂Precipitating;

(4) washing the Mg (OH) with deionized water₂Precipitating at least 3 times to remove the attached ions; mixing the washed Mg (OH)₂Precipitation addition step(1) Stirring the obtained LiF solution for at least 1h to obtain mixed slurry;

(5) starting the stirrer, adjusting the rotation speed to 450-550rpm, and then adding Na₂O·nSiO₂Slowly adding the mixture into the mixed slurry obtained in the step (4), and stirring the mixture until the mixture is uniform;

(6) and (3) transferring the mixed solution obtained in the step (5) into a hydrothermal reaction kettle, reacting at the temperature of 100 ℃ and 130 ℃ for 1.5-4h, filtering and washing, and drying to constant weight to obtain the magnesium lithium silicate with easy dispersion and excellent thickening performance.

2. The hydrothermal synthesis method of magnesium lithium silicate having excellent dispersibility and thickening performance according to claim 1, characterized in that: the alkali liquor is one of an ammonia water solution, a sodium hydroxide solution or a sodium carbonate solution.

3. The hydrothermal synthesis method of magnesium lithium silicate having excellent dispersibility and thickening performance according to claim 1, characterized in that: the ultrasonic condition of the step (3) is 100W.

4. The hydrothermal synthesis method of magnesium lithium silicate having excellent dispersibility and thickening performance according to claim 1, characterized in that: the stirring speed in the step (5) is 500 rpm.

5. The hydrothermal synthesis method of magnesium lithium silicate having excellent dispersibility and thickening performance according to claim 1, characterized in that: the number of washing in step (6) was 1.

Technical Field

The invention relates to a hydrothermal synthesis method of magnesium lithium silicate with easy dispersion and excellent thickening performance, which is applied to the field of preparation of magnesium lithium silicate.

Background

Lithium magnesium silicate (Hectrite) is known as laponite and is first discovered in the Hectrot (Hector) region of California, USA. It is idealChemical composition is Li_0.66[Li_0.66Mg_5.07Si_7.7O₂₀(OH)₄]The crystal structure is a 2:1 type trioctahedral layered structure formed by two silicon-oxygen tetrahedrons and one magnesium-oxygen octahedron sandwiched between the two silicon-oxygen tetrahedrons. In general, the magnesium atoms in the magnesiooctahedron are isomorphously substituted by part of lithium, so that the magnesioxy intermediate layer has a negative charge, which needs to be compensated by adsorption of cations (such as sodium ions, lithium ions, etc.) to achieve electrical neutrality. The degree of substitution of lithium determines the degree of electronegativity of the magnesium-oxygen octahedron, i.e., the cation exchange capacity. Due to the special structure, when the magnesium lithium silicate is dispersed in the aqueous solution, cations between layers are hydrated and migrate to the edges of the lamella, so that the edges are positively charged and the surface of the lamella is negatively charged. Under the electrostatic action of positive and negative charges, a special three-dimensional 'cabin' -shaped gel structure is formed, so that normal migration of water molecules is hindered, and therefore, the aqueous solution becomes viscous. When external shearing force is applied, the structure of the 'cabin' is destroyed, and the aqueous solution returns to a normal low-viscosity state, so that unique rheological and thixotropic regulation effects can be realized, and the 'cabin' can be widely applied to coatings, daily chemicals, agricultural chemicals and other various high-tech products.

Natural lithium magnesium silicate is generally distributed in volcanic ash and tuff with scarce reserves. Therefore, the artificial synthesis of magnesium lithium silicate is a research hotspot of researchers in recent years, and various preparation methods such as hydrothermal synthesis, solid-phase synthesis (fusion synthesis), microwave synthesis, mechanical synthesis and the like are developed successively, wherein the hydrothermal synthesis method is most widely applied. The method uses a high-temperature resistant and high-pressure resistant reaction kettle to artificially simulate the hot water deposit environment in the nature, and uses newly prepared magnesium hydroxide Mg (OH)₂The nano-sheet is a crystal nucleus, and after long-time crystallization growth, the magnesium lithium silicate with high purity and good crystal form can be obtained, and the manufacturers mainly comprise companies such as Laponite, Sudchemie AG in Germany, Elementis specialty and the like in America. The magnesium lithium silicate prepared by these manufacturers almost monopolizes the domestic market, and the price is high, so that the cost of the related products using the magnesium lithium silicate is greatly increased.

It is generally considered that, in the production of lithium magnesium silicate by hydrothermal reaction, nucleation thereof starts from magnesium hydroxide nanosheets as shown in the following equations (1), (2), (3), (4).

Mg²⁺+OH^-→Mg(OH)₂ (1)

SiO₂+H₂O→SiO₃ ^2-+2H⁺ (2)

Mg²⁺Li⁺-OH→Mg-OH-Li (3)

SiO₃ ^2-+Na⁺+Mg-OH-Li→Li_0.66[Li_0.66Mg_5.07Si_7.7O₂₀(OH)₄] (4)

Specifically, the nuclei of lithium magnesium silicate are formed starting from the condensation of silicon-oxygen tetrahedra on magnesium hydroxide nanosheets. During the hydrothermal synthesis, the more magnesium hydroxide nanosheets present, the greater the amount of crystalline magnesium lithium silicate produced. Silicon dioxide (SiO)₂) Lithium fluoride (LiF), magnesium chloride (MgCl)₂) The proper proportion of the components is beneficial to heterogeneous nucleation and growth of the magnesium lithium silicate, and the fluoride ions serve as mineralizers in the hydrothermal reaction process and play an important role in adjusting the dissolution, hydrolysis, condensation and dehydration of reactants and the nucleation and growth of the magnesium lithium silicate. Generally speaking, the composition and purity of the magnesium lithium silicate can be controlled by adjusting the molar ratio of silicon, magnesium and lithium, and the size distribution can be adjusted by changing the hydrothermal reaction conditions such as crystallization time, hydrothermal temperature, pH value and the like. In addition, different heating and stirring modes also influence the overall index of the magnesium lithium silicate product.

The magnesium hydroxide precursor has a crucial influence on the product properties of the prepared lithium magnesium silicate. Because the electronegativity difference between hydrogen atoms and oxygen atoms in the magnesium hydroxide nanosheets is large, the electron cloud density on one side of the oxygen atoms is high, and the hydrogen atoms become semi-naked protons. Therefore, the surface of the magnesium hydroxide nanosheet has strong polarity, and is easy to agglomerate under the action of intermolecular hydrogen bonds. Magnesium hydroxide prepared by a direct precipitation method of adding ammonia water into a magnesium chloride solution under normal pressure is usually flocculent precipitate, the particle size distribution is not concentrated and the agglomeration is serious, so that the monodispersion effect is difficult to achieve.

At present, enterprises, colleges and scientific research institutions in China also actively explore the development and preparation of the lithium magnesium silicate, although the obtained product can meet the market demand to a certain extent, the overall index of the product is poor, the application range is greatly limited, and the main problems and defects are represented in the following three aspects:

(1) the hydrothermal reaction needs to adopt high-temperature (the reaction temperature is about 160-;

(2) the hydrothermal reaction preparation process takes longer time (the reaction time is about 24-48h), and the production efficiency is influenced;

(3) the product has a large particle size (about 30-50 μm) (as shown in fig. 1), and is seriously agglomerated, unfavorable for dispersion, and poor in the effect of adjusting the rheological properties of the fluid.

Therefore, it is desirable to provide a hydrothermal synthesis method of magnesium lithium silicate with excellent thickening performance, easy dispersion, and low energy consumption, which only requires moderate hydrothermal temperature and short reaction time for hydrothermal reaction, and has the advantages of safety, low energy consumption, high efficiency, small particle size, and good adjustment effect of fluid rheological property.

Disclosure of Invention

In order to overcome the defects that the hydrothermal reaction needs high-temperature and high-pressure conditions, the safety is poor, the hydrothermal reaction is long in time consumption, the production efficiency is low, the particle size of a product is large, the agglomeration is serious, the adjusting effect on the rheological property of the fluid is not good and the like in the existing preparation process of the magnesium lithium silicate, the invention provides the hydrothermal synthesis method of the magnesium lithium silicate with easy dispersion and excellent thickening property.

The technical scheme of the invention is as follows:

the hydrothermal synthesis method of the magnesium lithium silicate with the advantages of easy dispersion and excellent thickening performance is characterized in that the magnesium lithium silicate with the advantages of easy dispersion and excellent thickening performance is mainly prepared from the following components in parts by weight:

the hydrothermal synthesis method of the magnesium lithium silicate with easy dispersion and excellent thickening performance mainly comprises the following steps of sequentially carrying out:

(1) adding the LiF into deionized water accounting for 50-71.43% of the total weight of the LiF, and stirring at the rotating speed of 500-1000rpm until the LiF is dissolved to obtain a LiF solution;

(2) adding said MgCl to the remaining deionized water₂·6H₂O, dissolving uniformly to obtain MgCl₂A solution;

(3) mixing MgCl₂Putting the solution in an ultrasonic environment of 90-110W, weighing the alkali liquor with the molar concentration of 2mol/L in a constant-pressure dropping funnel, and dropping the MgCl at a constant speed within 0.5-1h₂Fully mixing the two in the solution and reacting, centrifuging the obtained reaction solution at the rotating speed of 4000-₂Precipitating;

(4) washing the Mg (OH) with deionized water₂Precipitating at least 3 times to remove the attached ions; mixing the washed Mg (OH)₂Adding the precipitate into the LiF solution obtained in the step (1), and stirring for at least 1h to obtain mixed slurry;

(5) starting the stirrer, adjusting the rotation speed to 450-550rpm, and then adding Na₂O·nSiO₂Slowly adding the mixture into the mixed slurry obtained in the step (4), and uniformly stirring;

(6) and (4) transferring the mixed solution obtained in the step (5) into a hydrothermal reaction kettle, reacting at the temperature of 100 ℃ and 130 ℃ for 1.5-4h, filtering, washing and drying to constant weight to obtain the magnesium lithium silicate with easy dispersion and excellent thickening performance.

The hydrothermal synthesis method of the magnesium silicate lithium with easy dispersion and excellent thickening performance starts with the magnesium hydroxide nanosheet with the largest influence on nucleation and growth of the magnesium silicate lithium, ultrasonic treatment is introduced in the process of preparing the magnesium hydroxide precursor by adding alkali liquor into a magnesium chloride solution, and bubbles are alternately increased or reduced to be broken through the change of positive pressure and negative pressure of sound waves, so that high temperature and high pressure in a local range are generated. The water molecules adsorbed on the surface of the magnesium hydroxide particles are evaporated under the conditions of high temperature and high pressure, so that the possibility of forming hydrogen bonds is reduced, the average particle size of the magnesium hydroxide nanosheets is reduced, and the size distribution is more concentrated. In addition, the vibration generated by introducing the ultrasonic can destroy the soft agglomeration among the magnesium hydroxide particles, thereby playing the roles of eliminating the agglomeration and improving the dispersibility. The obtained magnesium hydroxide nanosheet is small in particle size (about 0.5-1 μm, while the particle size of the magnesium hydroxide obtained by the existing preparation process is about 3-5 μm), has a higher specific surface area, exposes a large number of active sites, enables more active surfaces to contact a silicon source, and increases a reaction area. By using the crystal nucleus as the crystal nucleus, the subsequent hydrothermal reaction only needs proper temperature and shorter time (100-. The method is an environment-friendly, safe, efficient and low-cost synthesis method, and the obtained lithium magnesium silicate product is easy to disperse and has excellent thickening performance.

The alkali liquor is one of an ammonia water solution, a sodium hydroxide solution or a sodium carbonate solution.

Ammonia should be the best choice because: the ammonia water solution is a weak base, and when the ammonia water solution is used as a precipitator for preparing magnesium hydroxide, the speed of ionizing out hydroxyl is proper, so that the magnesium hydroxide does not grow too fast, the agglomeration can be reduced, the particle size is reduced, and favorable conditions are created for the subsequent preparation of the magnesium lithium silicate with smaller particle size and concentrated size distribution.

The ultrasonic condition of the step (3) is 100W.

The dispersing effect is preferably optimized by ultrasonic conditions.

The stirring speed in the step (5) is 500 rpm.

The dispersing effect is preferably optimized at the stirring speed.

The number of washing in step (6) was 1.

Preferably, the washing step is carried out with Mg (OH)₂And cleaning the precipitate.

Compared with the prior art, the method has the following advantages:

1) according to the hydrothermal synthesis method of the magnesium lithium silicate with the advantages of easiness in dispersion and excellent thickening performance, ultrasonic treatment is introduced in the preparation stage of the magnesium hydroxide precursor, so that the average particle size of the magnesium lithium silicate can be reduced, the particle size distribution is concentrated, the agglomeration is reduced, the dispersibility is improved, the thickening efficiency is improved, and the more excellent rheological control effect is realized;

2) the hydrothermal synthesis method of the magnesium lithium silicate which is easy to disperse and has excellent thickening performance has moderate reaction temperature and short reaction time, not only improves the production efficiency of a factory, but also saves energy consumption, reduces cost and is beneficial to continuous safe production;

3) the magnesium silicate lithium prepared by the hydrothermal synthesis method of the magnesium silicate lithium which is easy to disperse and excellent in thickening performance is easy to hydrate and disperse, the prepared dispersion liquid is high in light transmittance and excellent in viscosity and thixotropic performance, the effect of adding a large amount of commercially available magnesium silicate lithium in the past can be achieved only by adding a small amount of the dispersion liquid, the cost can be saved, and the performance can be improved.

Drawings

FIG. 1 is a field emission scanning electron micrograph of lithium magnesium silicate prepared by hydrothermal synthesis without the introduction of sonication;

FIG. 2 is a field emission scanning electron microscope image of the magnesium silicate lithium prepared by the hydrothermal synthesis method of the magnesium silicate lithium with easy dispersion and excellent thickening performance.

Detailed Description

The technical solution of the present invention will be described in detail with reference to the embodiments of the specification.

Example 1

The hydrothermal synthesis method of the magnesium lithium silicate with easy dispersion and excellent thickening performance mainly comprises the following steps of sequentially carrying out:

(1) adding 13.5 parts of LiF into 2000 parts of deionized water, and stirring at the rotating speed of 500rpm until the LiF is dissolved to obtain a LiF solution;

(2) adding the 400 parts MgCl to 2000 parts deionized water₂·6H₂O, dissolving uniformly to obtain MgCl₂A solution;

(3) mixing MgCl₂Putting the solution in a 100W ultrasonic environment, weighing 2400 parts of ammonia water solution with the molar concentration of 2mol/L into a constant-pressure dropping funnel, and dropping the MgCl into the solution at a constant speed within 0.5h₂Mixing the two solutions, reacting, centrifuging the obtained reaction solution at 4500rpm for 10 min, and removing supernatant to obtain Mg (OH)₂Precipitating;

(4) washing the Mg (OH) with deionized water₂Precipitating for 3 times to remove attached ions; mixing the washed Mg (OH)₂Adding the precipitate into the LiF solution obtained in the step (1), and stirring for 1h to obtain mixed slurry;

(5) the stirrer was started and the rotation speed was adjusted to 500rpm, after which 370 parts of Na were added₂O·nSiO₂Slowly adding the mixture into the mixed slurry obtained in the step (4), and stirring the mixture until the mixture is uniform;

(6) and (3) transferring the mixed solution obtained in the step (5) into a hydrothermal reaction kettle, reacting for 3h at 120 ℃, filtering, washing for 1 time, and drying to constant weight to obtain the magnesium lithium silicate with easy dispersion and excellent thickening performance.

Example 2

The hydrothermal synthesis method of the magnesium lithium silicate with easy dispersion and excellent thickening performance mainly comprises the following steps of sequentially carrying out:

(1) adding 15 parts of LiF into 2500 parts of deionized water, and stirring at the rotating speed of 800rpm until the LiF is dissolved to obtain a LiF solution;

(2) to 1000 parts of deionized water was added 500 parts of MgCl₂·6H₂O, dissolving uniformly to obtain MgCl₂A solution;

(3) mixing MgCl₂Putting the solution in an ultrasonic environment of 90W, and weighing 2000 parts of the molar concentrationAdding 3mol/L sodium hydroxide solution into a constant pressure dropping funnel, and dropping the MgCl into the solution at constant speed within 1h₂Mixing the two solutions, reacting, centrifuging the obtained reaction solution at 4000rpm for 12 min, and removing supernatant to obtain Mg (OH)₂Precipitating;

(4) washing the Mg (OH) with deionized water₂Precipitating for 4 times to remove attached ions; mixing the washed Mg (OH)₂Adding the precipitate into the LiF solution obtained in the step (1), and stirring for 1.5h to obtain mixed slurry;

(5) the stirrer was started and the rotation speed was adjusted to 550rpm, after which 400 parts of Na were added₂O·nSiO₂Slowly adding the mixture into the mixed slurry obtained in the step (4), and stirring the mixture until the mixture is uniform;

(6) and (3) transferring the mixed solution obtained in the step (5) into a hydrothermal reaction kettle, reacting for 4 hours at 100 ℃, filtering, washing and drying to constant weight to obtain the magnesium lithium silicate with easy dispersion and excellent thickening performance.

Example 3

The hydrothermal synthesis method of the magnesium lithium silicate with easy dispersion and excellent thickening performance mainly comprises the following steps of sequentially carrying out:

(1) adding 22 parts of LiF into 1800 parts of deionized water, and stirring at the rotating speed of 1000rpm until the LiF is dissolved to obtain a LiF solution;

(2) to 1200 parts of deionized water was added 600 parts MgCl₂·6H₂O, dissolving uniformly to obtain MgCl₂A solution;

(3) mixing MgCl₂Placing the solution in a 110W ultrasonic environment, weighing 2500 parts of sodium carbonate solution with the molar concentration of 4mol/L in a constant-pressure dropping funnel, and dropping the MgCl at a constant speed within 0.8h₂Mixing the two solutions, reacting, centrifuging the obtained reaction solution at 5000rpm for at least 18 min, and removing supernatant to obtain Mg (OH)₂Precipitating;

(4) washing the Mg (OH) with deionized water₂Precipitating for 6 times to remove attached ions; mixing the washed Mg (OH)₂Adding the precipitate into the LiF solution obtained in the step (1), and stirring for 3 hours to obtainMixing the slurry;

(5) the stirrer was started and the speed was adjusted to 450rpm, after which 500 parts Na were added₂O·nSiO₂Slowly adding the mixture into the mixed slurry obtained in the step (4), and stirring the mixture until the mixture is uniform;

(6) and (3) transferring the mixed solution obtained in the step (5) into a hydrothermal reaction kettle, reacting at 130 ℃ for 1.5h, filtering, washing and drying to constant weight to obtain the magnesium lithium silicate with easy dispersion and excellent thickening performance.

Experimental data:

control 1: laponite RD, Laponite corporation, uk;

control 2: magnesium lithium silicate prepared by hydrothermal synthesis without introducing ultrasonic treatment (see Direct growth of lithium magnesium silicate nanoparticles on a glass slide, CrystEngComm,2018,20,4695 for details);

the detection method comprises the following steps: the magnesium lithium silicate products of the control sample 1, the control sample 2 and the examples are respectively added into deionized water to prepare a magnesium lithium silicate dispersion liquid with the solid content of 2 wt%, and the dispersion liquid is stirred at a high speed (the stirring speed is 1000-1500rpm) until the dispersion is complete. And standing each dispersion liquid for 24 hours, and then testing the viscosity, the thixotropy, the light transmittance and other properties. Wherein, the viscosity: reference standard ASTM D2196-2018; the thixotropic value is: reference standard GB 50550-; light transmittance: reference is made to the standard GB/T14571.4-2008.

TABLE 1 results of examining the properties of various magnesium lithium silicate dispersions (2 wt.%)

The above table shows that the magnesium silicate lithium product prepared by the hydrothermal synthesis method of the magnesium silicate lithium with easy dispersion and excellent thickening performance is easy to hydrate and disperse, and the prepared dispersion liquid has high light transmittance and excellent viscosity and thixotropic performance, can be widely applied to industries such as building coating, daily chemicals, food, pharmacy and the like, and has wide application prospect. The hydrothermal reaction temperature, the hydrothermal reaction time and the viscosity of the product are all superior to those of a control sample 2 without introducing ultrasonic treatment, and the thickening performance (viscosity and a touch value) and the light transmittance of the product are superior to those of similar imported goods (a control sample 1).

The hydrothermal synthesis method of magnesium lithium silicate with easy dispersion and excellent thickening performance of the present invention is not limited to the above examples, and any modification or replacement according to the principles of the present invention should be within the scope of the present invention.