Naked Science Forum
Non Life Sciences => Chemistry => Topic started by: scientizscht on 08/03/2024 11:30:11
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Hello!
I am quite confused with the so-called solid hydrogels. These are supposed to be quite solid materials but with very high water content. These are also not swellable which I suppose it means they do not absorb additional water like sponges. However they don't seem to behave the way I am expecting.
Let's say, we take a solid hydrogel material and put it contact with a water solution of a solute. Upon contact, the solute should migrate via diffusion from the water solution to the hydrogel right since both contain water and since they touch each other.
However, for some strange reason this does not seem to be the case. It may be that the mere contact of the solid hydrogel and the water solution is not enough to allow the solute to migrate via diffusion. Or some other reason, I don't know.
I am basically looking for a solid-like material that when I put it in contact with a water solution, it will get filled by the solute via diffusion without having to absorb water. So basically, I want to migrate the solute from the solution to the material without bulk migrating any solvent (of course the solvent can still migrate via diffusion as the solute but the net bulk move would be nil, i.e. the material will not increase its water content).
Any idea on that?
Thanks!
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Gels and colloids are an area about which I know very little, unfortunately. I would imagine that in the situation described that water would migrate out of the gel due to osmotic effects- I could be totally wrong on this.
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Did Harry Potter ever find the Philosophers' Stone?
As a rugby coach, I used to have a magic sponge that drew all the pain out of a collision. Try your local sports club!
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If the solutes are ions then, yes it's relatively easy.
https://www.thenakedscientists.com/forum/index.php?topic=81640.0
If not then it might still be possible.
https://www.sciencedirect.com/science/article/abs/pii/S221415882200040X
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Back in the days when I wanted to be a chemist, I used methylene blue to extract anionic surfactants from water into soution in chloroform. Not quite what the OP requested but it is certainly possible to tailor a reagent or structure to extract specific solutes, just as the liver and kidneys do.
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That's an interesting procedure, Alan. I would have thought that methylene blue would lead to an ionic product with anionic surfactants and hence be insoluble in chloroform?, a sulphonium sulphate or sulphonate, depending on the type of surfactant. Late edit: having thought about it further the large hydrophobic sections of the two molecules would shield the ionic centre and render it chloroform soluble, I think.
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It's the basis for the measurement of anionic detergents in water by "old school" chemistry.
As opposed to Mass spectroscopy which is about a million times more sensitive.
https://en.wikipedia.org/wiki/MBAS_assay