Silica gel can be reused after regeneration due to its adsorption of water vapor or other organic substances in the medium.
1、 Regeneration of silica gel after adsorption of water vapor
After silica gel adsorbs water, it can be removed by thermal desorption. There are many heating methods, such as electric furnace, flue waste heat heating and hot air drying.
The temperature of desorption heating should be controlled at 120-180 ℃, while for blue glue indicator, discolored silica gel and DL type blue silica gel, it should be controlled at 100-120 ℃. The * high temperature of various industrial silica gel regeneration should not exceed the following limits:
The macroporous silica gel should not be higher than 600 ℃;
The pore silica gel should not be higher than 200 ℃;
The blue glue index agent (or discolored silica gel) shall not be higher than 120 ℃;
The temperature of silicone aluminum adhesive shall not be higher than 350 ℃.
The regenerated silica gel can be reused if its moisture content is controlled below 2%.
2、 Regeneration of silica gel after adsorption of organic impurities
1. Roasting method
For coarse porous silica gel, it can be heated gradually to 500-600 ℃ in a baking furnace, and the colloidal particles will be white or yellowish brown after about 6-8 hours. The calcination temperature should not exceed 200 ℃.
2. Rinsing method
After the silica gel is adsorbed in saturated steam, it is soaked and rinsed in hot water, combined with detergent to remove waste oil or other organic impurities, and then washed with purified water, dried and dehydrated.
3. Solvent washing method
According to the types of organics adsorbed on silica gel, the appropriate solvent is selected to dissolve the organics adsorbed in the silica gel, and then the silica gel is heated to remove the solvent.
3、 Problems in regeneration of silica gel
1. During drying and regeneration, attention should be paid to gradually increasing the temperature, so as to avoid severe drying causing rubber particles to burst and reduce the recovery rate.
2. When the silica gel is roasted and regenerated, the pore structure of silica gel will change when the temperature is too high, which will obviously reduce the adsorption effect and affect the use value. For blue glue indicator or discolored silica gel, the temperature of desorption and regeneration should not exceed 120 ℃, otherwise, the chromogenic effect will be lost due to the gradual oxidation of chromogenic reagent.
3. The regenerated silica gel should be sieved to remove the fine particles to make the particles uniform.