WO2015089777A1

WO2015089777A1 - Method for preparing light, ball-flower shaped nanometer magnesium hydroxide with high specific surface area

Info

Publication number: WO2015089777A1
Application number: PCT/CN2013/089902
Authority: WO
Inventors: 林璋; 陈伦泰; 王永好; 吴智诚; 洪杨平; 黄嘉魁
Original assignee: 中国科学院福建物质结构研究所
Priority date: 2013-12-18
Filing date: 2013-12-18
Publication date: 2015-06-25

Abstract

The present invention relates a method for preparing light, ball-flower shaped nanometer magnesium hydroxide with high specific surface area, comprising the following steps of: (1) preparing a magnesium salt aqueous solution with a certain concentration in a reaction vessel; (2) preparing an alkali solution with a certain concentration in a vessel; (3) adding a certain amount of dispersant into the solution of step (1) or the solution of step (2) before reaction; (4) dropping the solution of step (2) into the solution of step (1) slowly, or dropping the solution of step (1) into the solution of step (2) slowly, reacting and obtaining a white precipitate, centrifuging and cleaning the white precipitate (magnesium hydroxide) after aging to remove other impurity ions, thereby obtaining a white gelatinous solid. The method of the present invention provides a method for preparing a special morphological magnesium hydroxide, and the method has the characteristic of simple operation, nonpollution for environment, easy of enlarging scale production and low requirements for apparatus. The magnesium hydroxide synthesized by the method is mainly used for treatment of dyeing waste water, adsorption of heavy metal ion and desulphurizer of flue gas.

Description

Method for producing lightweight, high specific surface area, flower-sphere type nanometer magnesium hydroxide

The invention belongs to the technical field of inorganic material preparation. Specifically, it is a method of producing a nano-magnesium hydroxide having a special morphology by reacting a base and a magnesium salt with the addition of a dispersant.

Background technique

Magnesium hydroxide has advantages that other inorganic materials do not have, because of its good thermal stability, high decomposition temperature, non-toxicity, and smoke suppression, it has been traditionally used as a high-performance inorganic flame retardant in polymer materials. It is a recognized environmentally friendly green chemical product with varying degrees of application in acid rain soil treatment, food and feed additives, and biological and pharmaceutical preparations. At present, magnesium hydroxide has been valued by all countries and is one of the products favored and respected by developed countries in the implementation of sustainable development strategies, environmental protection and beneficial ecological development. It is called green safe neutralizer and environmentally friendly. The fuel and the third alkali are very active in research and production activities. In addition to this, magnesium hydroxide is also used in:

1. Neutralizer for environmentally friendly acidic wastewater: Green safe, pH is not more than 9, after adsorption, with heavy metal ions adsorbed;

2. Printing and dyeing wastewater treatment: The decolorization effect is obvious;

3. Flue gas desulfurizer or coal-fired sulfur-fixing agent: Desulfurization rate is as high as 95%-98%, higher than other Reagent

4. Heavy metal ion remover: It can adsorb As ³⁺ , M ²⁺ , Pb ²⁺ , Cd ²⁺ , Mn ²⁺ , Cr ³⁺ , Cr ⁶⁺ , U ^{3+ ,} etc .

In addition, magnesium hydroxide is an important inorganic chemical raw material, and nano-magnesium hydroxide with specific morphology can be used as a specific functional material. The excellent performance of nano-magnesium hydroxide has attracted wide attention in the field of material chemistry. Since the morphology and size of magnesium hydroxide particles have a great influence on their application, it is necessary to explore the synthesis of magnesium hydroxide with special morphology and fine size. Among them, nanometer magnesium hydroxide has many unique effects due to its small size. For example, small size effect, quantum size effect, surface effect, macroscopic quantum tunneling, etc., make nanometer magnesium hydroxide have excellent chemical and physical properties, and expand its Application range.

At present, nanometer magnesium hydroxide powder preparation methods mainly include precipitation synthesis method, hydrothermal method, reverse precipitation method, precipitation-azeotropic distillation method, etc., but there are still many problems:

1. If the product is large in particle size, the purity is not high, and the particle size distribution is not uniform;

2. Shortcomings such as high equipment requirements, harsh conditions, complicated operation, and low product yield.

3. Industrialization is difficult, production is low, and cost is high.

4. The process of producing magnesium hydroxide in most enterprises is the brine ammonia process. The by-product ammonia nitrogen content is high. Ammonia nitrogen is a substance that is strictly restricted by the state, and emissions will cause environmental problems. Secondly, the production process produces a pungent odor due to the volatility of ammonia. Summary of the invention

The object of the present invention is to overcome the shortcomings of the prior art for preparing nanometer magnesium hydroxide, and to provide a method for easily producing magnesium hydroxide with special morphology, which is easy to operate and easy to use. Industrial amplification, no pollution to the environment, nano magnesium hydroxide can be obtained at room temperature, the final product is easy to clean, does not agglomerate after drying, and has high purity. The magnesium hydroxide prepared by the method is a light-weight magnesium hydroxide having a micro-nano structure, and the magnesium hydroxide nanosheets are self-assembled to form a globular structure, and the product has a large specific surface area.

To achieve the above object, the present invention is achieved by the following technical solutions:

A method for preparing nanometer magnesium hydroxide, comprising the steps of:

(1) preparing a certain concentration of magnesium salt aqueous solution in a reaction vessel;

(2) preparing a certain concentration of an alkali solution in the container;

(3) before the reaction, adding a certain amount of the agent in the step (1) solution or the step (2) solution, or adding a dispersing agent in both solutions;

(4) slowly dropping the solution in the step (2) into the solution of the step (1), or slowly dropping the solution of the step (1) into the solution of the step (2) to obtain a white precipitate, and after aging, The white precipitate (magnesium hydroxide) was washed by centrifugation, and other impurity ions were removed by washing to obtain a white gelatinous solid.

According to the invention, the step (3) preferably adds a certain amount of a dispersing agent to the solution of the step (1), or adds a certain amount of a dispersing agent to the solution of the step (2), or adds both solutions. Dispersant.

According to the present invention, it is preferred to uniformly mix the agent with the solution of the step (1) or (2).

According to the present invention, the dispersing agent according to the step (3) is selected from a lower diol or a lower triol, for example, a diol or a trihydric alcohol having 2 to 6 carbon atoms, preferably ethylene glycol or propylene glycol. Glycerol, butanediol, butyltriol or butanol; most preferred is ethylene glycol or glycerol.

According to the invention, the dispersing agent is added in an amount of from 1 to 50% by weight, preferably from 5 to 40% by weight, more preferably from 10 to 30% by weight, most preferably from 20 to 30% by weight of the solution in the step (1) or (2) weight.

Preferred technical solution according to the invention:

A method for preparing nanometer magnesium hydroxide, comprising the steps of:

(1) arranging a certain amount of dispersant solution, then adding a certain concentration of magnesium salt aqueous solution, optionally adding a certain amount of the agent, and mixing uniformly;

(2) preparing a certain concentration of an alkali solution in the container;

(4) slowly dropping the solution in the step (2) into the solution of the step (1), or slowly dropping the solution of the step (1) into the solution of the step (2) to obtain a white precipitate, and after aging, The white precipitate (magnesium hydroxide) was washed by centrifugation, and other impurity ions were removed by washing to obtain a white dish-like solid.

Preferred technical solution according to the invention:

A method for preparing nanometer magnesium hydroxide, comprising the steps of:

(1) arranging a certain concentration of magnesium salt aqueous solution;

(2) arranging a certain amount of dispersant solution, and then preparing a certain concentration of alkali solution in the container, optionally adding a certain amount of the agent, and mixing uniformly;

(4) slowly dropping the solution in the step (2) into the solution of the step (1), or slowly dropping the solution of the step (1) into the solution of the step (2) to obtain a white precipitate, and after aging, The white precipitate (magnesium hydroxide) was washed by centrifugation, and other impurity ions were removed by washing to obtain a white dish-like solid. Preferred technical solution according to the invention:

A method for preparing nanometer magnesium hydroxide, comprising the steps of:

(1) Configuring a certain amount of dispersant solution, and then adding a certain concentration of magnesium salt aqueous solution, optionally adding a certain amount of the agent, and mixing uniformly;

(2) Configuring a certain amount of dispersant solution, and then preparing a certain concentration of alkali solution in the container, optionally adding a certain amount of the agent, and mixing uniformly;

(4) The solution in the step (2) is slowly dropped into the solution of the step (1), or the solution of the step (1) is slowly dropped into the solution of the step (2), and the reaction is white precipitated, and after aging, The white precipitate (magnesium hydroxide) was washed by centrifugation, and other impurity ions were removed by washing to obtain a white dish-like solid.

According to the present invention, the magnesium salt in the step (1) may be magnesium sulfate (anhydrous magnesium sulfate or magnesium sulfate heptahydrate), magnesium chloride (anhydrous magnesium chloride or magnesium chloride hexahydrate), magnesium nitrate (anhydrous magnesium nitrate or six). Water magnesium nitrate). Preferably, the magnesium salt is selected from magnesium sulfate or magnesium chloride.

According to the invention, the concentration of the aqueous magnesium salt solution is preferably from 0.1 to 4 mol/L, preferably from 0.3 to 1.5 mol/L; more preferably from 0.5 to 1 mol/L.

According to the invention, the alkali solution described in the step (2) is selected from the group consisting of lithium hydroxide, sodium hydroxide, potassium hydroxide or ammonia water. Preferably, the alkali solution is sodium hydroxide or potassium hydroxide.

According to the invention, the concentration of the alkali solution is preferably from 0.5 to 20 mol/L, preferably from 1 to 10 mol/L.

According to the present invention, the following steps are further included before the step (4): optionally adding other organic auxiliary solvent, and mixing is uniform. According to the invention, the organic auxiliary solvent can also be added to the reactor before the dispersant is mixed with the solution of step (1) or (2).

According to the present invention, the organic auxiliary solvent is selected from the group consisting of: a lower monohydric alcohol, an ether or a lower ketone organic auxiliary solvent, for example, a monohydric alcohol of 1 to 6 carbon atoms or an ether of 1 to 6 carbon atoms or 1 The lower ketone of -6 carbon atoms is preferably decyl alcohol, ethanol or acetone, more preferably ethanol.

According to the invention, the organic auxiliary solvent is preferably added to the reactor in the form of a solution, for example, an aqueous solution of a lower alcohol having a volume ratio of 1:1-1:4, for example 1:2:3, such as an aqueous ethanol solution. The form is added to the reactor.

According to the invention, in the step (4), the solution in the step (2) is preferably slowly dropped into the solution of the step (1).

According to the invention, the addition is at 20-60. C, for example, at room temperature.

According to the invention, the reaction is carried out at room temperature at a certain agitation rate. The agitation rate is from 100 to 5,000 rpm, preferably from 700 to 3,000 rpm. The stirring time is 5-48 hours, preferably 10-24 hours.

According to the invention, in the step (4), the aging time is from 1 to 8 hours, preferably from 2 to 6 hours.

According to the invention, in the step (4), the white precipitate after centrifugation washing is washed with deionized water, preferably several times, for example, from 1 to 4 times.

According to the present invention, in the step (4), after washing and washing until no other impurity ions are present, it is washed with anhydrous ethanol and once, to obtain a white gelatinous solid.

According to the invention, in the step (4), the white solid is dried to a constant temperature at a constant temperature. Heavy, that is, magnesium hydroxide powder is obtained. Preferably, the drying temperature is from 30 ^e C to 340 ^e C, preferably from 60 to 200. C.

According to the present invention, the prepared magnesium hydroxide is in the form of a gel before drying; the finally obtained magnesium hydroxide is a nano-magnesium hydroxide having a micro-nano structure, a light weight, a high specific surface area, and a flower ball type. Preference is given to a bulk density of magnesium hydroxide: < 0.15 _g /mL and a large specific surface area: > 50 m ² /g, preferably > 100 m ² /g.

The beneficial effects of the present invention compared with the prior art are: in the production process, by using glycerol or ethylene glycol as an additive, the product obtained by the reaction at room temperature is nano-flower-type magnesium hydroxide, dried. After the agglomeration, powdered magnesium hydroxide was obtained. The equipment required for the reaction is simple, easy to operate, easy to amplify, and environmentally friendly. The magnesium hydroxide synthesized by the method of the invention has uniform particle size, good dispersibility, high purity and easy synthesis in a large amount. If it is desired to produce a large amount of magnesium hydroxide production, simply scale up as described in the examples below. Magnesium hydroxide synthesized by this method is mainly used for printing and dyeing wastewater treatment, heavy metal ion adsorption, and flue gas desulfurizing agent.

DRAWINGS

Figure 1 is a schematic view of a scanning electron micrograph (X2000) of the product of Example 1.

2 is a schematic view of a scanning electron micrograph (x100) of the product of Example 1.

Figure 3 is a schematic view of a scanning electron micrograph (X30000) of the product of Example 1.

4 is a powder diffraction pattern of a nanometer magnesium hydroxide sample prepared in Example 2.

detailed description: Phase analysis: Using JXOL's model JSM-6700F scanning electron microscope analysis, the particle size of the self-assembled polymer of magnesium hydroxide nanosheets of this product is around ΙΟμιη (as shown in Figure 1), and the thickness of nanosheets is 15 Nm (as shown in Figure 2 and Figure 3). The specific surface area of magnesium hydroxide measured by the BET method was 110 m ² / _g . Due to the nanocrystallization of the magnesium hydroxide powder, the diffraction peak on the magnesium hydroxide diffraction pattern is broadened, and no other impurity peaks are observed on the powder diffraction pattern, indicating that the obtained magnesium hydroxide has high purity (as shown in FIG. 4).

Example 1:

A. Prepare a mixed solution of ethanol and water in a ratio of 1:1 in the reaction vessel, prepare a 0.5 mol/L magnesium sulfate solution in the mixed solution, and add 30% (mass fraction) of glycerin to mix well.

B. Prepare a mixed solution of ethanol and water in a ratio of 1:4 in a container, and prepare a 1 mol/L sodium hydroxide solution in the mixed solution.

C. 1 L of the solution of B was slowly dropped into 1 L of the solution of A at room temperature, while stirring at a stirring speed of 700 rpm for 20 h, a white precipitate was obtained in the reaction vessel A, and after aging for 2 h. The white precipitate was filtered, washed with deionized water and washed several times until there was no sulfate ion, and then washed with anhydrous ethanol to give a white solid. Drying to constant weight at C temperature gives a light weight, high specific surface area (90 m ² / _g ), and nano-magnesium hydroxide.

Example 2:

A. Prepare a 0.5 mol/L aqueous solution of magnesium sulfate in the reaction vessel and add 30% The amount of glycerol is mixed evenly.

B. Prepare a 1 mol/L sodium hydroxide solution in the container.

C. 1 L of the solution of B was slowly dropped into 1 L of the solution of A at room temperature, while stirring at a stirring speed of 700 rpm for 15 h, a white precipitate was obtained in the reaction vessel A, and aged for 1.5 h. The white precipitate was filtered, washed with deionized water and dried several times until no sulfate ion was taken and washed with anhydrous ethanol to give a white solid. Drying to constant weight at C temperature gives a light, high specific surface area (110 m ² / _g ), and a nano-magnesium hydroxide.

Example 3:

A. Prepare a 0.5 mol/L aqueous solution of magnesium chloride in a reaction vessel and add 15% (mass fraction) of glycerol. Mix well.

B. Prepare a 1 mol/L potassium hydroxide solution in a container and add 15% (mass fraction) of glycerol. Mix well.

C. 1 L of the solution of B was slowly dropped into 1 L of the solution of A at room temperature, while stirring at 800 rpm for 8 h, a white precipitate was obtained in the reaction vessel A, and after aging for 3 h, The white precipitate was washed by centrifugation, washed with deionized water, and washed several times until there was no chloride ion, and then washed with anhydrous ethanol and washed once to obtain a white gelatinous solid. Drying to constant weight under C gives a light weight, high specific surface area (70 m ² / _g ), and a spherical nano-magnesium hydroxide.

Example 4:

A. Prepare a mixed solution of ethanol and water in a ratio of 1:1 in the reaction vessel, in which the solution is Prepare a 0.5 mol/L magnesium sulfate solution.

B. Prepare a mixed solution of ethanol and water in a ratio of 1:1 in the container, prepare a 1 mol/L sodium hydroxide solution in this solution, and add 30% (mass fraction) of glycerin, and mix well.

C. 1 L of the solution of B was slowly dropped into 1 L of the solution of A, while stirring at a stirring speed of 700 rpm for 18 h, a white precipitate was obtained in the reaction vessel A, and after aging for 2.5 h, The white precipitate was washed by centrifugation, washed with deionized water, and washed several times until there was no sulfate ion, and washed with absolute ethanol to obtain a white gelatinous solid with a white solid at 60. Drying to constant weight under C gives a light weight, high specific surface area (80 m ² / _g ), and a nano-magnesium hydroxide.

Example 5

A. Prepare a 1 mol/L aqueous solution of magnesium chloride in the reaction vessel.

B. Prepare a 2 mol/L sodium hydroxide solution in a container and add 30% (mass fraction) of glycerol. Mix well.

C. 1 L of the solution of B was slowly dropped into 1 L of the solution of A at room temperature, while stirring at 700 rpm for 10 h, a white precipitate was obtained in the reaction vessel A, and aged for 2 h. The white precipitate was washed by centrifugation, washed with deionized water, and washed several times until there was no chloride ion, and then washed once with absolute ethanol to obtain a white dish-like solid with a white solid at 60. Drying to constant weight under C gives a light weight, high specific surface area (72 m ² / _g ), and a spherical nano-magnesium hydroxide. A. Prepare a 1 mol/L aqueous solution of magnesium chloride in the reaction vessel. Add 30% (mass fraction) of ethylene glycol and mix well.

B. Prepare a 2 mol/L sodium hydroxide solution in a container.

C. 1 L of the solution of B was slowly dropped into 1 L of the solution of A at room temperature, while stirring at a stirring speed of 700 rpm for 10 h, a white precipitate was obtained in the reaction vessel A, and aged for 2.5 h. The white precipitate was washed by centrifugation, washed with deionized water, and washed several times until there was no chloride ion, and then washed once with absolute ethanol to obtain a white dish-like solid with a white solid at 60. Drying to constant weight at C gives a light weight, high specific surface area (68 m ² / _g ), and a spherical nano-magnesium hydroxide.

Example 7

A. Prepare a 0.5 mol/L aqueous solution of magnesium sulfate in a reaction vessel and add 30% (mass fraction) of glycerol. Mix well.

B. Prepare a 1 mol/L sodium hydroxide solution in the container.

C. 37.5 L of the solution of B was slowly dropped into 30 L of the solution of A at room temperature, while stirring at a stirring speed of 700 rpm for 24 h, a white precipitate was obtained in the reaction vessel A, aged 6 After h, the white precipitate was washed by centrifugation, washed with deionized water and washed several times until no sulfate ions were used, and then washed with absolute ethanol to obtain a white gelatinous solid with a white solid at 60. Drying to constant weight under C gives a kilogram of light weight, high specific surface area (56 m ² / _g ), and nano-magnesium hydroxide. Finally, it should be noted that the above-described embodiments are merely preferred embodiments of the present invention and are not intended to limit the present invention, although the present invention has been described in detail with reference to the foregoing embodiments, Those skilled in the art can still modify the schemes recorded in the foregoing embodiments, or modify or replace some of the technical features. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and scope of the present invention are intended to be included within the scope of the present invention.

Claims

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A method for preparing nanometer magnesium hydroxide, comprising the steps of:

(2) preparing a certain concentration of an alkali solution in the container;

The method according to claim 1, characterized in that the step (3) preferably adds a certain amount of a dispersing agent to the solution of the step (1), or adds a certain amount of a dispersing agent to the solution of the step (2). , or add a dispersant to both solutions.

Preferably, the agent is uniformly mixed with the solution of step (1) or (2).

Preferably, the dispersing agent described in the step (3) is selected from a lower diol or a lower triol, for example, a diol or a trihydric alcohol having 2 to 6 carbon atoms, preferably ethylene glycol, propylene glycol, or propylene glycol. Alcohol, butylene glycol, butyl triol or tetramethylene alcohol; ethylene glycol or glycerol is most preferred.

The dispersing agent is preferably a mixed solution of a lower alcohol and water. Preferably, the volume ratio is 1:1-1:4, for example, 1: 2-1: 3 aqueous solution of a lower alcohol, such as an aqueous ethanol solution.

The method according to claim 1 or 2, wherein the dispersing agent is added in an amount of 1 to 50% by weight, preferably 5 to 40% by weight, more preferably 10 to 30% by weight, most preferably 20 to 30% by weight of the solution in the step (1) or (2).

The method according to any one of claims 1 to 3, characterized in that it comprises the following steps:

(2) preparing a certain concentration of an alkali solution in the container;

(1) arranging a certain concentration of magnesium salt aqueous solution;

(1) Configuring a certain amount of dispersant solution, and then adding a certain concentration of magnesium salt aqueous solution, optionally adding a certain amount of the agent, and mixing uniformly; (2) arranging a certain amount of dispersant solution, and then preparing a certain concentration of alkali solution in the container, optionally adding a certain amount of the agent, and mixing uniformly;

The method according to any one of claims 1 to 6, wherein the magnesium salt in the step (1) may be magnesium sulfate (anhydrous magnesium sulfate or magnesium sulfate heptahydrate), magnesium chloride (anhydrous magnesium chloride or magnesium chloride hexahydrate). , magnesium nitrate (anhydrous magnesium nitrate or magnesium nitrate hexahydrate). Preferably, the magnesium salt is selected from magnesium sulfate or magnesium chloride.

Preferably, the concentration of the aqueous magnesium salt solution is preferably from 0.1 to 4 mol/L, preferably from 0.3 to 1.5 mol/L; more preferably from 0.5 to 1 mol/L.

Preferably, the alkali solution described in the step (2) is selected from the group consisting of lithium hydroxide, sodium hydroxide, potassium hydroxide or ammonia water. Preferably, the alkali solution is sodium hydroxide or potassium hydroxide. Preferably, the concentration of the solution is preferably from 0.5 to 20 mol/L, preferably from 1 to 10 mol/L.

Preferably, before the step (4), the following steps are further included: optionally adding other organic auxiliary solvent, and mixing is uniform. More preferably, the organic auxiliary solvent may also be added to the reactor before the dispersant is mixed with the solution of step (1) or (2).

The method according to any one of claims 1 to 7, wherein in the step (4), the dropping is at 20-60. C, for example, at room temperature.

Preferably, the reaction is carried out at room temperature at a certain agitation rate. Stirring rate It is 100-5000 rpm, preferably 700-3000 rpm. The stirring time is from 5 to 48 hours, preferably from 10 to 24 hours.

Preferably, the aging time is from 1 to 8 hours, preferably from 2 to 6 hours.

Preferably, the white precipitate after centrifugation is washed with deionized water, preferably several times, for example 1-4 times.

Preferably, after washing and scrubbing to no other impurity ions, it is washed and washed once with absolute ethanol to obtain a white dish-like solid.

Preferably, the white solid is dried to a constant weight at a certain temperature to obtain a magnesium hydroxide powder. Preferably, the drying temperature is from 30 ^e C to 340 ^e C, preferably from 60 to 200. (

The method according to any one of claims 1-8, characterized in that the prepared magnesium hydroxide is in the form of a gel before drying; the finally obtained magnesium hydroxide has a micro-nano structure, light weight, high Specific surface area, flower sphere type nano magnesium hydroxide. The bulk density of magnesium hydroxide is preferably < 0.15 _g /mL, and has a large specific surface area: >100 m ² /g.