Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: scientizscht on 05/09/2018 18:55:41
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Is there adsorbent material for every substance?
Are they extremely selective?
How is desorption can be triggered?
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Yes (probably), though it is hard to define absorption of a solid.,
No.
Generally by heating, or by displacing with something that is more strongly absorbed.
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My knowledge of this comes from my lifelong involvement with surfactants.
For example, I edited "Amphoteric Surfactants" in the Marcel Dekker Surfactant Science Series.
Surfactants work by adsorption. Their hydrophobes can absorb onto hydrophobic surfaces, making them hydrophilic, thus wettable by water. Ionic surfactants can adsorb onto ionic surfaces (charged) making them hydrophobic.
For difficult surfaces, fluorocarbon surfactants may be useful.
If you can detail the problem I may be able to offer more suggestions. In short, surfactants can adsorb onto most surfaces to change their nature, hydrophilic or hydrophobic.
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My knowledge of this comes from my lifelong involvement with surfactants.
For example, I edited "Amphoteric Surfactants" in the Marcel Dekker Surfactant Science Series.
Surfactants work by adsorption. Their hydrophobes can absorb onto hydrophobic surfaces, making them hydrophilic, thus wettable by water. Ionic surfactants can adsorb onto ionic surfaces (charged) making them hydrophobic.
For difficult surfaces, fluorocarbon surfactants may be useful.
If you can detail the problem I may be able to offer more suggestions. In short, surfactants can adsorb onto most surfaces to change their nature, hydrophilic or hydrophobic.
Thanks!
What are the desorption mechanisms please?
How selective can adsorbent be?
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Sorry for the delay in replying. I am new around here and got lost.
What are the desorption mechanisms please?
How selective can adsorbent
be?
Let me start with the second. This seems quite straightforward. Adsorption, in theory, relates directly to the chemical nature of the two items. Substance A should adsorb more selectively onto Substance A than onto Substance B.
I am hanging on here by my shirt tails so someone more qualified may well have a better knowledge of this area.
For the record I have B.Sc. (Hons) Chemical Engineering (B'ham) so my approach is very practical and lacking theoretical foundations. After the above about 40 years experience in surfactants.
I am thinking here of silicon chemistry (in which I have developed a passing interest after my retitement) where you have the substitution of other elements of the same or similar size. There are also electrical considerations.
It really comes back to the old aphorism 'like dissolves like'. I suppose I am postulating 'like adsorbs onto like.
Certainly the opposite should be true. I know from many years or experience that the hydrophobes (e.g., fatty) tails of surfactants adsorb readily onto hydrophobic surfaces rather than the opposite.
As far as desorption mechanisms are concerned, can only suggest that the reverse applies. Substance A should be more readily desorbed from Substance B with which it has less afinity than Substance A.
Hope that provokes some thought,
Catastrophe