The Difference is on the Desiccant (Surface)

When stating the function of desiccant (a product supplied to rerelocate moisture from the air during storage or carry in order to prevent damages to goods) tbelow is an excellent deal of confusion neighboring exactly how it works. In most cases, desiccant adsorbs moisture rather than absorbs it, and the difference have the right to be unclear. However before, AGM’s Managing Engineer Pat Lane is below to explain:

This is not a basic subject because the distinction in between absorption and also adsorption is a fuzzy one, and also many kind of products that carry out one additionally carry out the other.

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First, let"s take a look at interpretations of the 2 processes:

From Webster"s Ninth New Collegiate Dictionary (1988. Print):

"Absorption." Def. 1a: the process of absorbing or of being absorbed

“Absorb.” Def. 1: to take in and make component of an existing whole. Def. 2a: To suck up or take up such as: a sponge absorbs water, charcoal absorbs gas, and plant roots absorb water.

“Adsorption.” Def. 1: The adhesion in a really thin layer of molecules (as of gases, solutes, or liquids to the surfaces of solid bodies or liquids through which they are in contact.

From THE CONDENSED Chemical Thesaurus. (10th ed. 1981. Publish.):

“Absorption.” Def. 1: In chemical terminology, the penetration of one substance into the inner structure of one more, as distinguished from adsorption, in which one substance is attracted to and held on the surconfront of an additional.

“Adsorption.” Def. 1: adsorption. Adherence of the atoms, ions or molecules of a gas or liquid to the surchallenge of one more substance, called the adsorbent (q.v.) The best-well-known examples are gas/solid and also liquid/solid devices. Finely divided or microporous material presenting a huge area of energetic surchallenge are solid adsorbents, and are used for rerelocating colors, odors, and water vapor (activated carbon, caused alumina, silica gel.)

The Gist of It

Alright, so the 2 procedures sound exceptionally similar in regards to meaning. To me, however, what distinguishes adsorption from absorption is wbelow it occurs, what pressures are involved, and also how “thick” the layer is. That is, I believe the majority of adsorbed substances are just a single molecular layer thick on the surface they are adsorbed onto.

How It Works

Many of us use the analogy of a sponge for absorption. The sponge conveniently sucks up water and also then easily releases it as soon as we mechanically squeeze the sponge. However, if a completely dry sponge is wetted, then squeezed out, it still remains damp. This is because at least some of the dampness (although not all) is adsorbed water.



If I wring out a damp sponge via my hands and then place it in a press and squeeze it exceptionally difficult, I can obtain more liquid water to run out of it. At some suggest, yet, no issue exactly how hard I squeeze, I won’t obtain any type of more liquid water out – yet the sponge will reprimary damp. This is the adsorbed portion.

Typically, this portion is a single molecular layer thick and also coats eincredibly bit of the sponge’s surchallenge, consisting of what we don’t see at the microscopic level. For many kind of materials, including the sponge, they are much even more porous than we view through our eyes. These pores develop a much better surface area than we suppose – or in many type of cases can also think to be present.

In the case of desiccant products, they show up to our eyes as little solids, usually in bead or granule form. But if we were to look at them with a scanning electron microscope, we would see that they are incredibly porous through even more empty room than solid product, which accounts for their exceptionally expansive surchallenge locations and also, therefore, their ability to adsorb substantial amounts of moisture.

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Now, if we place the sponge in water and then lift it out, it will speak dripping after a couple of secs. But, if we look at it carefully, we deserve to view liquid water in the “pores” of the sponge. This represents absorption bereason we deserve to check out the liquid water, which is countless molecular layers thick.