Since silica gel adsorbs steams and other organic substances from the media, its adsorption capability declines. After being reclaimed, it can be used again.
The reclaim of silica gel after steam adsorption
After adsorbing moistures, the moistures contained in silica gel can be removed by heating de-adsorption. There are many methods for heating, for example, by electrically heated stove, remaining heat in the flue and hot air drying, etc.
For heating de-adsprption, The temperature should be controlled to be within the range of 120-180℃.For blue gel indicator, chromotropic silica gel and blue silica gel DL, the temperature should be controlled to be within 100-120℃.
When reclaiming industrial silica gels, make sure the highest temperatures are within the following limits:
Macro-pored silica gel no more than 600℃
Fine-pored silica gel no more than 200℃
Blue silica gel and orange silica gel (or chromotropic silica gel) no more than 120℃
Silica alumina gel no more than 350℃
The reclaimed silica gel can be put into use again as long as its moisture content is controlled to be less than 2%.
The reclamation after organic impurities adsorption
1. Roasting
Put macro-pored silica gel into a roaster and gradually rise its temperature to 500-6℃.After about 6-8 hours,the gel grains become white or yellowish-brown. For fine-pored silica gel, the roasting temperature shall be not more than 200℃.
2. Bleaching
Put silica gel into saturated steam to adsorb until it is fully saturated, then drop it into hot water to soak and bleach. Detergent can also be used to remove the waste oil and other organic impurities.After washing it in clean water, dry it to remove the moistures.
3. Solvent Rinsing
Depending on the organic substances adsorbed by silica gel, select the appropriate solvent to dissolve the organic substances adsorbed inside silica gel, then heat up silica gel to get rid of the solvent.
Points for Attention in Silica Gel Reclamation
1. Gradually rise up the temperature in drying reclaim to prevent the gel grains from
exploding and thereby from reducing the recovery ratio as a result of severe drying.
2. In roasting reclaim, excessively high temperature may cause changes to the pore structure of silica gel, thereby substantially reducing its adsorption effect and affecting its usefulness.For blue gel indicator or discoloring silica gel, the temperature for deadsorption reclaim shall be not more than 120℃, otherwise, its developing agent will be gradually oxidized and therefore lose its devdloping effect.
3. The reclaimed silica gel shall usually be sifted out to get rid of the fine grains, thus making the grains well-distributed and uniform.
