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(2) Preparation example
①Prepare Al 2 (SO 4 ) 3 into a 6% aqueous solution with activated alumina made from aluminum sulfate and ammonia water, add 20% NH 3 ·H 2 O, and react for 40-60 minutes under vigorous stirring to obtain Al(OH) 3 precipitation.
②In a caustic soda solution with a concentration of 600g/L by nitric acid neutralization method, add Al(OH)3 at 50~80℃, heat up to 110℃, keep the temperature for 3h, dilute and let stand for 1h, filter to remove insoluble impurities, and then Neutralize the clear liquid with 20% HNO 3 , control the temperature at 30-50℃, control the pH value at 7-7.
Figure 4-15 Process flow of activated alumina preparation by nitric acid neutralization method
③The raw material is industrial aluminum sulfate, which is partially neutralized with CaCO 3 -Na 2 CO 3 successively to obtain an intermediate product "basic aluminum sulfate" precipitation, which is completely neutralized in ammonia water to remove sulfate, and aged to obtain the hydration of aluminum oxide.
a.
b.
The reaction formula is as follows:
In the above reaction, the pH value of the reaction with CaCO 3 added should not exceed 4, otherwise the filtrate is easily hydrolyzed in water, causing loss of raw materials
c.
Put the above-mentioned washed qualified filter cake into a porcelain bucket and add 10%-15% ammonia water (volume percentage), control the pH value at 10-11, first beating and then incubating and aging in a constant temperature water bath at 60℃ for 8h before filtering.
The above precipitation conditions are used to ensure the formation of pseudo-boehmite.
d.
The process flow is shown in Figure 4-16
Figure 4-16 Al 2 O 3 preparation process flow
Related links: Physicochemical properties and preparation methods of activated alumina