12th January 2003, 12:02 AM
The characteristics and safety perfomance of silica gel
Characteristis: 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 aftertreatment processes such as aging, picking, 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, nonodor and chemically stable. Except for alkali and hydrofluoric acid, it does not react with any other substance. Owing to their different manufacturing methods. the various types of silica gels are formulated with different pore structures. Thanks to its unique chemical composition and physical structure, silica gel possesses a 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 the different pore diameters of silica gels, they are categorized into large pore silica gel, macro-pored silica gel, B type silica gel and fine-pored silica gel. Owing to their different pore structure, their adsorptive performances are variable. Under the dircumstance where there is a high relative humidity, macro-pored silica gel has a relatively high adsorption capacity. Whereas, under the circumstance where there is a low relative humidity, fine-pored silica gel has a higher adsorption capacity than macro-pored silica gel. The pore structure of silica gel Type B lies between macro-pored and fine-pored silica gel, so its adsorption amount is also between those of macro-pored and fine-pored silica gel. 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: The main component of silica gel is silica, which is chemical stable and flame-resisting. Silica get is a kind of non-crystalline silica. The dust content inside thw workshop should be controlled to be no more than 10mg/m3. The workshop shall be well-ventilated. Operators should wear mouth-muffles when processing.
The strong adsorption capability of silica gel may cause drying effects on human skins. Therefore, operators should be instructed to wear working clothes when processing. If silica gel accidentally comes into one's eyes, be sure to wash them using large amount of water and seek for medical care as soon as possible.
Containing small amount of cobalt chloride and being toxic, blue silica gel should be kept form contacting the foods and inhaling into one's mouth. Seek medical care as soon as possible once there is a poisoning accident.