Basic Silica Gel

General Characteristics
Silica gel is a kind of highly active adsorption material. It is usually formulated by sodium silicate and sulphuric acid reaction and through a series of after treatment processes such as aging, pickling, etc. Silica gel is amorphous substance. Its chemical molecular formula is SiO2.nH2O. It is insoluble in water and any other solvent. It is nontoxic, non-odor and chemically stable. Except for alkali and hydrofluoric acid, it does not react with any other substance. Owing to their different manufacturing methods, silica gel can be formulated with different pore structures. Because of its unique chemical composition and physical structure, silica gel possesses a great number of characteristics with which other similar materials are incomparable, such as high adsorption feature, stable thermal performance, stable physical property and relatively high mechanical strength, etc.

According to pore diameters, the silica gel can be classified into macro-pored, fine-pored and type B ones. The pore size of silica gel type B lies between macro-pored and fine-pored ones, and its adsorption capability is also between them. When there is a low relative humidity, fine-pored silica gel has a higher adsorption capacity than macro-pored one. Otherwise, macro-pored ones may have higher capacity. Large pored silica gel is usually used as catalyst carrier, matting agent and toothpaste abrasive, etc. Therefore, the appropriate type is to be selected according to your specific field of application.

Safety Performance
1. The main component of silica gel is silica, which is chemically stable and flame resistant. Silica gel is a kind of non-crystalline silica. During manufacturing process, the dust content inside the workshop should be no more than 10mg/m3, and the workshop should be well ventilated. Meanwhile, operators should wear mouth-muffles.
2. The strong moisture adsorption capability of silica gel may cause drying of human skin. Therefore, operators should be instructed to wear working clothes while processing. If silica gel accidentally comes into one's eyes, be sure to wash them using a large amount of clean water and seek for medical care as soon as possible.
3. Containing small amount of cobalt chloride and being toxic, blue and orange silica gel should be kept from contacting the foods and inhaling into one's mouth. Seek for medical care as soon as possible once there is a poisoning accident.
4. Colloidal silica or silica sol's main composition is silicon dioxide and water. It is also non-toxic. However, its main application is not absorption.

Reclamation
Since silica gel adsorbs steams and other organic substances from the media, so its adsorption capability declines. After being reclaimed, it can be used again.
1. The reclaim of silica gel after steam adsorption
After adsorbing moistures, the moistures contained in silica gel can be removed by heating. 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-adsorption, 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, please 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%.

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, and 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 during heating process 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 de-adsorption shall be not more than 120℃, otherwise, its developing agent will be gradually oxidized and therefore lose its developing 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.

Storage and Packing
Silica gel is strong in moisture adsorption; therefore, it should be stored in dry places. Shelf racks should be put between the container and the floor. The containers can be steel drums, paper bags, cardboard boxes, plastic bottles, polyethylene plastic compound bags and flexible container bags, etc. Please refer to the categorized product descriptions for detailed packing specifications.

All silica gel products should be kept from rain, moisture and sun.
The colloidal silica or silica sol should be kept between 0-40℃.

Sinchem is a China basic silica gel manufacturer and supplier. We offer basic silica gel, and cat litter, drying indicator silica gel. Our high quality products are offered at competitive prices. Sinchem is located in China, and the full chain of manufacturing tiny power silica gel, silicide can be completed in China, even in one city. Lower manufacturing cost saves your purchasing cost. The more details of each product are shown on the page with description.