Views:248 Author:Site Editor Publish Time: 2020-03-27 Origin:Site
Silica gel can be reused. Water-absorbing silica gel can be regenerated by heating at 120°C for two hours. The silica gel is immersed in a solution of cobalt chloride or ammonium chlorocobalate ((NH4) 2CoCl4), and then dried and activated to obtain color-changing silica gel, which can be used to indicate the degree of water absorption of the silica gel. This is because anhydrous cobalt chloride (CoCl2) is blue and cobalt chloride hexahydrate (CoCl2 · 6H2O) is red. The silica gel absorbs water vapor or other organic substances in the medium during use, the adsorption capacity decreases, and it can be reused after regeneration.
After the silica gel adsorbs moisture, it can be removed by thermal desorption. There are many heating methods, such as electric furnace, flue waste heat heating and hot air drying. It is appropriate to control the temperature of de-addition heat at 120-180℃. For blue gel indicator, discoloration silica gel, and blue silica gel, it is appropriate to control 100-120℃. The maximum temperature for various industrial silica gel regeneration should not exceed the following limits:
The coarse-pored silica gel should not be higher than 600℃;
Fine-pored silica gel should not be higher than 200 ℃;
Blue glue indicator (or discolored silica gel) should not be higher than 120 ℃;
Silicon aluminum glue must not be higher than 350 ℃.
After regeneration, the moisture content of silica gel is generally controlled below 2%, and then it can be put back into use.
For coarse-pored silica gel, it can be gradually heated to 500-600℃ in a baking furnace, and the rubber particles can be white or yellow-brown in about 6-8 hours. For fine-pored silica gel, the firing temperature cannot exceed 200℃.
After the silica gel is saturated with saturated water vapor to reach saturation, it can be soaked and rinsed in hot water, and can be combined with detergent to remove waste oil or other organic impurities, and then washed with clean water and dried and dehydrated.
According to the type of the organic substance adsorbed by the silica gel, an appropriate solvent is selected to dissolve the organic substances adsorbed in the silica gel, and then the silica gel is heated to remove the solvent.
When drying the regenerating silica gel, you should pay attention to gradually increasing the temperature, so as not to cause the rubber particles to burst due to drastic drying and reduce the recovery rate.
When the silica gel is roasted and regenerated, the excessive temperature will cause the pore structure of the silica gel to change, which will obviously reduce its adsorption effect and affect the use value. For blue gel indicator or color-changing silica gel, the temperature for desorption regeneration should not exceed 120 °C, otherwise the color development effect will be lost due to the gradual oxidation of the color developer.
The regenerated silica gel should generally be sieved to remove fine particles to make the particles uniform. Although we understand the principle of silicone regeneration, at the same time we should also recognize that silicone is harmful and we should not rely too much on silicone. For example, it is often encountered in daily life that silica gel is packed in certain paper bags or bags made of semi-permeable membrane resin to absorb water, control humidity, and prevent the deterioration of certain items. Silicone bags are generally marked "Do Not Eat". It can cause irritation to the respiratory system, digestive system, skin and eyes. Some discolored silica gels also contain humidity indicators such as cobalt chloride. Cobalt chloride is a toxic substance and belongs to the IARC second carcinogen cancer.
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