The distinction is top top the Desiccant (Surface)

When stating the function the desiccant (a material used to remove moisture native the air throughout storage or move in order to prevent damages to goods) over there is a good deal of man surrounding exactly how it works. In most cases, desiccant adsorbs moisture fairly than absorbs it, and also the distinction can be unclear. However, AGM’s controlling Engineer Pat roadway is below to explain:

This is not a basic subject because the difference between absorption and adsorption is a fuzzy one, and also many materials that perform one also do the other.

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First, let"s take it a look at definitions of the two processes:

From Webster"s Ninth new Collegiate thesaurus (1988. Print):

"Absorption." Def. 1a: the procedure of absorbing or of gift absorbed

“Absorb.” Def. 1: to take in and make part of an currently whole. Def. 2a: come suck up or take it up together as: a sponge absorbs water, charcoal absorbs gas, and plant roots absorb water.

“Adsorption.” Def. 1: The adhesion in really thin class of molecules (as the gases, solutes, or liquids come the surfaces of solid body or liquids with which they room in contact.

From THE CONDENSED chemical Dictionary. (10th ed. 1981. Print.):

“Absorption.” Def. 1: In chemical terminology, the penetration that one substance into the inner structure of another, as identified from adsorption, in i m sorry one substance is attractive to and also held top top the surface of another.

“Adsorption.” Def. 1: adsorption. Adherence of the atoms, ion or molecule of a gas or fluid to the surface ar of an additional substance, called the adsorbent (q.v.) The best-known examples are gas/solid and liquid/solid systems. Finely divided or microporous product presenting a large area of active surface are solid adsorbents, and are offered for removed colors, odors, and water vapor (activated carbon, set off alumina, silica gel.)

The Gist that It

Alright, therefore the two processes sound very similar in regards to definition. To me, however, what distinguish adsorption from absorb is where it occurs, what pressures are involved, and how “thick” the layer is. That is, I think most adsorbed building materials are just a single molecular layer special on the surface ar they room adsorbed onto.

How it Works

Many of us use the analogy that a sponge because that absorption. The sponge conveniently sucks up water and also then conveniently releases it as soon as we mechanically to express the sponge. However, if a totally dry sponge is wetted, climate squeezed out, it still stays damp. This is because at least some of the dampness (although no all) is adsorbed water.



If i wring the end a wet sponge through my hands and also then place it in a press and squeeze it an extremely hard, I deserve to get an ext liquid water to run out the it. At part point, however, no issue how tough I squeeze, ns won’t obtain any more liquid water out – yet the sponge will stay damp. This is the adsorbed portion.

Typically, this part is a single molecular great thick and coats every little bit of the sponge’s surface, consisting of what we don’t check out at the microscopic level. For plenty of materials, consisting of the sponge, they space much much more porous than we see v our eyes. These pores create a much better surface area than we mean – or in many instances can even believe to be present.

In the case of desiccant materials, they show up to our eye as small solids, typically in bead or granule form. However if we were come look in ~ them v a scanning electron microscope, we would check out that castle are incredibly porous with an ext empty room than heavy material, which accounts for your exceptionally expansive surface areas and, therefore, their capability to adsorb significant amounts that moisture.

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Now, if we location the sponge in water and also then lift the out, the will stop dripping ~ a few seconds. But, if we look in ~ it closely, we can see fluid water in the “pores” of the sponge. This represents absorption since we can see the fluid water, which is thousands of molecular class thick.