CN110342582B - Hydroxyl intercalated Mg/Fe type anionic clay material and preparation method thereof based on mechanochemical method - Google Patents

Abstract

The invention discloses a hydroxyl intercalated Mg/Fe type anionic clay material and a preparation method based on a mechanochemical method. According to a method for preparing a hydroxyl-intercalated Mg/Fe type anionic clay material based on a mechanochemical method of the present invention, the mixture of magnesia and ferrihydrite is placed in a grinding device and fully ground, and the color of the mixture is changed from reddish brown to yellow. After browning, an appropriate amount of water and a small amount of anhydrous ethanol were added, and after crystallization, washing, centrifugation and drying, the Mg/Fe-type anionic clay material with interlayer anions only hydroxyl intercalated was obtained. The Mg/Fe type anionic clay of the present invention uses metal (hydroxide) oxides as raw materials to synthesize by mechanochemical method in a ball mill, without heating, the synthetic product yield is high, and has the advantages of simple process, low energy consumption, low cost and the like; The amount of waste water is small, saving resources and protecting the environment; the synthetic product of the present invention is a typical layered double-hydroxyl composite metal hydroxide, but the interlayer only contains hydroxyl and water molecules, and its chemical structural formula is Mg ₆ Fe ₂ (OH) ₁₆ (OH _{) 2.4H2O} .

Description

A hydroxyl-intercalated Mg/Fe-type anionic clay material and its mechanochemical method of preparation

technical field

The invention relates to the technical field of chemical material preparation, in particular to a method for preparing a hydroxyl-intercalated Mg/Fe type anionic clay material based on a mechanochemical method.

Background technique

Mg/Fe type anionic clay (Mg-Fe-LDH) material is a layered double hydroxyl composite metal oxide with a Mg-Fe structure layer. A compound with a layered structure composed of charge-balancing anions, its general structural formula can be expressed as [M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^x+ [(A ^n- ) _x/n ·mH ₂ O], where M ^{2 +} and M ³⁺ are divalent and trivalent metal cations respectively, ^An- is an anion, x=M ³⁺ /(M ²⁺ +M ³⁺ ) and 0.2≤x≤0.33 . The unique chemical structure determines its layered cation adjustability and interlayer anion exchangeability, in which the ion exchange capacity (2-3meq/g) is comparable to that of anion exchange resins, so it is widely used in chemical engineering, ion exchange exchange and adsorption.

In the related field of the present invention, the synthetic methods of anionic clays reported in domestic and foreign literatures and patents are usually co-precipitation methods. The hydrotalcite was prepared by the precipitation method; Huzhou Teachers College "a preparation method of hydrotalcite" (patent number CN101817510A) uses a buffer solution to control the pH value of the reaction on the basis of the traditional co-precipitation method. However, the crystallinity of the particles prepared by the co-precipitation method is low. In order to adapt to the practical application requirements and improve the surface morphology of the synthesized products, East China Jiaotong University "Preparation Method of Hydrotalcite for Treating Phosphorus in Sewage (Patent No. CN106179178A)" uses the hydrothermal method, Wu Xiaohong etc. "a synthetic method of ZnAl-layered double metal hydroxide (patent number CN104445364A)" has obtained Zn/Al type hydrotalcite by nucleation/crystallization isolation method, and the product has high crystallinity and complete structure, However, the synthesis process is relatively complex and energy-intensive. In addition, Shenyang University of Chemical Technology "a kind of preparation method of Mg-Fe layered double metal hydroxide (patent number CN106186080A)", Beijing Normal University "a kind of preparation method of layered double metal hydroxide and its prepared products ( Patent No. CN107128879A)" prepared Mg/Fe layered double metal hydroxide by oxide-salt solution method under specific conditions. Although it can be used for macro preparation, it is still inevitable to introduce other anions between layers. , the potential secondary pollution problem cannot be ignored.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a method for preparing hydroxyl-intercalated Mg/Fe type anionic clay material based on a mechanochemical method with simple process, low energy consumption and low cost, aiming at the above-mentioned deficiencies of the prior art.

According to a method for preparing a hydroxyl-intercalated Mg/Fe type anionic clay material based on a mechanochemical method of the present invention, the mixture of magnesia and ferrihydrite is placed in a grinding device and fully ground, and the color of the mixture is changed from reddish brown to yellow. After browning, an appropriate amount of water and a small amount of anhydrous ethanol were added, and after crystallization, washing, centrifugation and drying, the Mg/Fe-type anionic clay material with interlayer anions only hydroxyl intercalated was obtained.

Preferably, the ferrihydrite is prepared by Fe salt hydrolysis.

Preferably, the molar ratio of MgO to ferrihydrite is 3:1.

Preferably, the grinding device includes grinding balls, and the mass ratio of the grinding balls to the mixture is 20-80:1.

Preferably, grinding is carried out at room temperature.

Preferably, the crystallization temperature is 80-90°C, and the time is 24-48h.

Preferably, the washing is centrifuged until the conductivity of the supernatant liquid is less than 200 μs/cm. If the conductance is very high, it means that the salt and impurities are very high. If it is directly dried without washing, there will be salt precipitation, which will affect the purity of the synthesized product.

A hydroxyl intercalated Mg/Fe type anionic clay material prepared by the above preparation method.

The Mg/Fe type anionic clay of the present invention is synthesized in a ball mill by a mechanochemical method using metal (hydroxide) oxides as raw materials. This method does not require molten state processing of the reagents, and utilizes the high-speed vibration and rotation of the ball mill to strongly strengthen the reactants. The impact, grinding and stirring of the powder particles cause plastic deformation of the powder particles, reduce the diffusion activation energy of the elements, and then induce a chemical reaction to synthesize the target product. Compared with the liquid phase method, no heating is required, and the yield of the synthetic product is higher, and the process is simple and energy-consuming. The invention has the advantages of small size and low cost; the invention only needs a small amount of water to provide liquid-phase environment crystallization, so that the crystallization of the product is complete, the amount of alkaline sewage generated during synthesis is small, resources are saved, and the environment is protected; the synthesis product of the invention is a typical layer 2-hydroxyl composite metal hydroxide, but the interlayer only contains hydroxyl and water molecules, its chemical structural formula is Mg ₆ Fe ₂ (OH) ₁₆ (OH) ₂ ·4H ₂ O, and the interlayer anion is only hydroxyl intercalated. Mg/Fe type anionic clay does not introduce secondary pollution anions, and at the same time increases more hydroxyl active sites, which can effectively improve the adsorption performance of anionic clay in practical applications.

Description of drawings

Fig. 1 is the XRD pattern of the hydroxyl-intercalated Mg/Fe type anionic clay prepared in Example 1 of the present invention;

Fig. 2 is the SEM spectrum of the hydroxyl-intercalated Mg/Fe type anionic clay prepared in Example 1 of the present invention;

Figure 3 is a process flow diagram of the hydroxyl-intercalated Mg/Fe-type anionic clay prepared by mechanochemical method.

Detailed ways

The following are specific embodiments of the present invention and the accompanying drawings to further describe the technical solutions of the present invention, but the present invention is not limited to these embodiments.

Example 1:

At room temperature, 6.564g of light magnesia and 5.810g of amorphous ferrihydrite were added to the nylon grinding jar by using a jar ball mill, and 744g of agate grinding balls (15mm in diameter and 3.9 in average weight per ball) were added. g, a total of 190), the molar ratio of MgO and amorphous ferrihydrite was 3:1, the mass ratio of grinding balls to the mixture was about 60:1, and the grinding was performed for 24 hours. The speed of the pot mill was 90 r/min. The color of the reactant gradually changed from white and reddish-brown mixture to uniform and uniform yellow-brown. Then add deionized water and a small amount of ethanol to the ground product (one is to reduce the agglomeration of the grinding powder after adding an organic solvent, and the other is that the nylon tank wall has a waxy coating, which can be dissolved by adding a little ethanol), at 80 ℃ Under crystallization 24h. Pour the crystallized suspension evenly into centrifuge tubes, place it in a high-speed centrifuge and centrifuge at 4000r/min for 3 minutes, and wash by centrifugation 1-2 times. The conductivity of the supernatant liquid is less than 200μs/cm. The washed product was put into a drying box, dried completely at 45°C, ground and sieved to obtain a hydroxyl-intercalated Mg/Fe type anionic clay material.

It can be seen from Figure 1 that the diffraction peaks of the synthesized products are consistent with the diffraction characteristics of anionic clay, and the components are single and pure.

It can be seen from Figure 2 that the synthesized product has a typical sheet-like structure of anionic clay crystals.

Example 2:

At room temperature, using a planetary ball mill, 0.821g of light magnesia and 0.726g of amorphous ferrihydrite were added to four 100mL agate jars, respectively, and 31g of agate grinding balls, MgO and amorphous water were added. The molar ratio of iron ore is 3:1, and the mass ratio of grinding balls to the mixture is about 20:1. The clockwise and counterclockwise grinding is alternately performed for 1 hour, and the rotation speed of the ball mill is guaranteed to be 400 r/min. The brown gradually changes to a uniform tan. Deionized water and a small amount of ethanol were then added to the ground product, and the suspension was crystallized at 80° C. for 48 h. Pour the crystallized suspension evenly into centrifuge tubes, and wash by centrifugation 1-2 times. The conductivity of the supernatant liquid is less than 200 μs/cm. The washed product was put into a drying box, dried completely at 45°C, ground and sieved to obtain a hydroxyl-intercalated Mg/Fe type anionic clay material.

The parts not covered above are applicable to the prior art.

Although some specific embodiments of the present invention have been described in detail through examples, those skilled in the art should understand that the above examples are only for illustration, not for limiting the scope of the present invention. Various modifications or additions may be made to, or substituted for, the specific embodiments described, without departing from the direction of the invention or going beyond the scope defined by the appended claims. Those skilled in the art should understand that any modification, equivalent replacement, improvement, etc. made to the above embodiments according to the technical essence of the present invention should be included in the protection scope of the present invention.

Claims (8)

1. a method for preparing the Mg/Fe type anionic clay material of hydroxyl intercalation based on mechanochemical method, is characterized in that: the mixture of magnesia and amorphous ferrihydrite is placed in grinding equipment and fully ground, treat mixture After the color changed from red-brown to yellow-brown, an appropriate amount of water and a small amount of anhydrous ethanol were added, and after crystallization, washing, centrifugation and drying, the Mg/Fe-type anionic clay material with interlayer anions only hydroxyl intercalated was obtained. 2 . The method for preparing the Mg/Fe type anionic clay material of hydroxyl intercalation based on a mechanochemical method as claimed in claim 1 , wherein the ferrihydrite is prepared by a Fe salt hydrolysis method. 3 . 3. a kind of method for preparing the Mg/Fe type anionic clay material of hydroxyl intercalation based on mechanochemical method as claimed in claim 2, is characterized in that: the mol ratio of MgO and ferrihydrite is 3:1. 4. a kind of method for preparing the Mg/Fe type anionic clay material of hydroxyl intercalation based on mechanochemical method as claimed in claim 3, is characterized in that: described grinding equipment comprises grinding ball, the quality of described grinding ball and mixture The ratio is 20-80:1. 5. The method for preparing a hydroxyl-intercalated Mg/Fe type anionic clay material based on a mechanochemical method as claimed in claim 1, wherein the method is ground at room temperature. 6 . The method for preparing a hydroxyl-intercalated Mg/Fe type anionic clay material based on a mechanochemical method as claimed in claim 5 , wherein the crystallization temperature is 80-90° C. and the time is 24-48 h. 7 . 7. a kind of method for preparing the Mg/Fe type anionic clay material of hydroxyl intercalation based on mechanochemical method as described in any one of claim 1-6, it is characterized in that: described washing is centrifuged to the electrical conductivity of supernatant liquid less than 200μs/cm. 8. A hydroxyl-intercalated Mg/Fe type anionic clay material prepared by the preparation method of any one of claims 1-7.

Images