Silica gel is an amorphous and porous form of silicon dioxide (silica), consisting of an irregular tridimensional framework of alternating silicon and oxygen atoms with nanometer-scale voids and pores. The voids may contain water or some other liquids, or may be filled by gas or vacuum. In the last case, the material is properly called silica xerogel.
Silica xerogel with an average pore size of 2.4 nanometers has a strong affinity for water molecules and is widely used as a desiccant. It is hard and translucent, but considerably softer than massive silica glass or quartz; and remains hard when saturated with water.
Silica xerogel is usually commercialized as coarse granules or beads, a few millimeters in diameter. Some grains may contain small amounts of indicator substance that changes color when they have absorbed some water. Small paper envelopes containing silica xerogel pellets, usually with a "do not eat" warning, are often included in dry food packages to absorb any humidity that might cause spoilage of the food.
'Wet' silica gel, as may be freshly prepared from alkali silicate solutions, may vary in consistency from a soft transparent gel, similar to gelatin or agar, to a hard solid, namely a water-logged xerogel. It is sometimes used in laboratory processes, for example to suppress convection in liquids or prevent settling of suspended particles
· Type A – clear pellets, approximate pore diameter: 2.5 nm, drying and moistureproof properties, can be used as catalyst carriers, adsorbents, separators and variable-pressure adsorbent.
· Type B – translucent white pellets, pore diameter: 4.5–7.0 nm, liquid adsorbents, drier and perfume carriers, also may be used as catalyst carriers, cat litter.
· Type C – translucent, micro-pored structure, raw material for preparation of silica gel cat litter. Additionally dried and screened, it forms macro-pored silica gel which is used as drier, adsorbent and catalyst carrier.
Silica alumina gel - light yellow, chemically stable, flame-resistant, insoluble except in alkali or hydrofluoric acid. Superficial polarity, thermal stability, performance greater than fine-pored silica gel.
Stabilizing silica gel - non-crystalline micro-porous solid powder, nontoxic, flame-resisting, used in brewery of grains for beer to improve taste, clearness, color, and foam and for removal of non-micro-organism impurities.
Water Treatment Filter