Method for preparing hydrotalcite by adopting brucite

Abstract

The invention relates to the technical field of hydrotalcite preparation, in particular to a method for preparing hydrotalcite by using brucite. The present invention uses brucite as the magnesium source and aluminum hydroxide as the aluminum source, including two main process steps of amorphization of brucite and aluminum hydroxide and recrystallization of the amorphous material. First, brucite and hydroxide are oxidized The aluminum is mixed with a magnesium-aluminum molar ratio of 2 to 4, and then the mixed material and zirconia balls are mixed evenly at a ball-to-material ratio of 50:1, and they are put into a zirconia ball mill jar for ball milling, and then the mass fraction of water magnesium is added. Continue ball milling with deionized water with 10% to 20% of the total amount of stone and aluminum hydroxide; then mix the ball milled material with sodium carbonate solution at a molar ratio of Mg2+:CO32-=1.5 to 6, and stir in a water bath at 60 to 80°C Crystallize for 1-5 hours, the stirring speed is 500r / min, and finally wash and dry to obtain the final product hydrotalcite.

Description

technical field [0001] The invention relates to the technical field of hydrotalcite preparation, in particular to a method for preparing hydrotalcite by using brucite. Background technique [0002] Hydrotalcite is a layered double hydroxyl compound metal oxide (Layered double hydroxides, referred to as LDHs), which is a type of anionic clay that has developed rapidly in recent years. Its ideal molecular formula is Mg 6 al 2 (OH) 16 CO 3 4H 2 O. The structure of hydrotalcite is similar to brucite Mg(OH) 2 , by MgO 6 Octahedrons share edges to form a unit layer, and the Mg on the layer 2+ Can be replaced by Al with similar radius within a certain range 3+ Isomorphic substitution, resulting in Mg 2+ 、Al 3+ , OH - The layers are positively charged, and the interlayer anion CO 3 2- The positive charge balance with the laminate makes the whole structure electrically neutral. In addition, there are some water molecules between the layers, which can be removed without d...

AI Technical Summary

Problems solved by technology

However, these existing preparation methods have the following deficiencies: (1) Nucleation and crystallization are carried out simultaneously in the entire preparation process of the co-precipitation method, which makes the particle size distribution of the product wide and non-uniform, and there are many factors that affect the precipitation conditions. Factors, such as pH value, dropping method, ingredient Mg / Al ratio, etc., are difficult to control in operation and take a long time

(2) The nucleation / crystallization isolation method requires a special "full back-mixing explosive nucleation reactor" and "constant temperature reflux crystallization process equipment", which increases the complexity of the process, is time-consuming and laborious, and the reaction concentration is too high. Causes phase separation, seriously affecting the purity of the hydrotalcite

The process is cumbersome and has many influencing factors, making it difficult to control

(4) The roasting reduction method requires high-temperature calcination, which requires a large investment in equipment, and it is necessary to select a suitable calcination temperature according to the composition of the matrix. If the temperature is too high, it will cause the formation of a spinel phase and make the structure impossible to rebuild.

(5) The hydrothermal synthesis method has a small yield and is not suitable for large-scale production

(6) The sol-gel method requires the use of metal alkoxides, which are expensive and their hydrolysis is difficult to control

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