Why are silica gel desiccant discoloration?

Fully after washing, silicic acid congealed gel silica gel is made to remove soluble salts, dry and dehydration In the future, constitute a kind of porous solids. Silica gel to the polar molecules such as water has strong adsorption effect, on the job, life is often appointed a prevent mildew and rust. Now in the silicone products is soaked the silica gel with cobalt oxide solution, drying after activation Made a desiccant.

Using silica gel desiccant can make the person centering. If the storage environment humidity is big, silica gel desiccant will become blue, notice everyone takes care of the environment humidity is big, become wet, should lead to consider. Why after the silica gel desiccant moisture absorption will change color?

Silica gel desiccant is color change when using cobalt oxide water absorption and dehydration attack temper, to indicate the status of the silica gel moisture absorption. Cobalt metal wave is a Swedish chemist, grant found in 2345. The cobalt oxide is a kind of important compounds of cobalt. It temper perverse: cobalt oxide under anhydrous conditions is blue, in the humid air, 2 how much oxygen of cobalt with suction, so that it is not the same as the number of crystal water and appear different colours, gradually form monohydrate, two water...... Until six water cobalt oxide; Colors from blue progressive into blue purple, purple, pink, red. Cobalt oxide, cobalt oxide is six water became red powder, it will inform you it has been drinking enough water, never to water absorption. If the silica gel desiccant is powder red, indicates the hygroscopic degree of it has become full, at the moment, the drying ability is very poor, needs a change, perhaps from the beginning.

Silica gel absorption effect is mainly physical adsorption, drying to variation of silica gel to try to make its resurrection; and use again. Dry concrete practice: will be lost to the silicon glue into the oven about 2167, its water transpiration, step by step, red water six cobalt oxide powder will be dehydrated, become blue anhydrous cobalt oxide, again make it attach to recover, absorption can be sustained for all to use.

Inorganic silica gel is a highly active adsorption data, the general is to use sodium silicate and sulfuric acid reaction, and the aging, acid soak and a series of post-treatment process and system. Silica gel is amorphous material, its chemical formula is mSiO2. NH2O. Insoluble in water and any solvents, non-toxic tasteless, chemical stability, in addition to the strong alkali, hydrofluoric acid and no physical attacks. The various types of silica gel for its production method is different form different microporous structure. Silicone chemical components and physical structure, determines it has a lot of other similar data irreplaceable characteristics: high adsorption function, good thermal stability, chemical stability, has high mechanical strength, etc. Silica gel according to the range of the aperture can be divided into: the macroporous silica gel, coarse pore silica gel, b-type silica gel, silica. Because the pore structure is different, so their adsorption function.

Silica gel desiccant technology goal:

(1) the particle standard: 2-4 mm 4-8 mm 2-5 mm

(2) 95% or greater mechanical strength

At 25 ℃ and relative humidity of water quantity (%) of the following:

In relative humidity 20%, % 8.0 or higher

In relative humidity 50%, % 20.0 or higher

In relative humidity 90%, % 30.0 or higher

This product avirulent insipidity, removing the outer packing in the future that can directly use (except directly touch the food, pharmaceutical), generally do not need to make any processing.

Color silica gel regeneration process:

Color silica gel in the process of applying for the medium water vapor adsorption or other organic matter, adsorption ability is reduced, can be regenerated through repeated use.

1. After the adsorption of water vapor.

Silica gel after moisture absorption, stripping method to water through heat away, there are multiple ways of heating, such as electric heating furnace, flue waste heat heating and hot air drying, etc. Stripping heating temperature control in the 120-180 ℃ advisable, for the blue gel indicator, allochroic silica gel, DL blue silica gel is controlled in 100-120 ℃ advisable. All kinds of industrial silica gel regeneration when the highest temperature should not be more than the following limits: coarse silica gel is not higher than 600 ℃; Of fine silica shall not be higher than 200 ℃; Blue glue target agent (or color silica gel) shall not be higher than 120 ℃; Silicon aluminum adhesive shall not be higher than 350 ℃. After the regeneration of silica gel, its general control moisture below 2% can be put into use from the beginning.

Color silica gel is adding some inorganic salt with water of crystallization in silica gel, a few dichloride silicon, such as cobalt salt. When no water is lost at the time of crystallization water is blue, water is the water of crystallization for the condition of red powder. Color silicone cycle use. After the color change, can be baked in the oven, to make it back to the condition of no water can continue to use. Blue blue gel indicator, allochroic silica gel and blue silica gel points glue, appearance is blue or light blue glass particles. Generally as the indicator to use, its characteristic is to become the red after moisture absorption. When not hygroscopic particles appear blue, when be affected with damp be affected with damp, colloidal particles moisture absorption and gradually become a light blue, after continuous moisture absorption will become pink red to show demand change using new silicone or regeneration. Cooperate with general silica gel desiccant is applied, indicates the degree of moisture absorption and desiccant discriminant environment relative humidity.