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Sat 6 Mar, 2010 08:59 pm
(1) CHEMISORPTION -- why do ions exchange happen in chromatography, for eg. why molybdenum in form MoO4 replace some other ion with less adsorption potential(but also bounded by chemisorption) on the surface of alumina? How does the MoO4 break the other ion's chemical bond with the surface of alumina without coming into contact with the alumina molecule as it is blocked by the ion on it?
(2) VAN DER WAALS FORCE -- in a situation where an atom of element A sticks to the surface of alumina by physisorption, and another atom of element B adheres to A by Van der waals force, and then another atom of element A comes along and touches element B (by van der waals) but could not touch atom element A because blocked by other atoms of element B from other angles , (distance from all angles for atom A to reach the other atom A is only one diameter of element B),
QUESTION : will the second atom A have higher affinity for the first atom A on the surface of alumina and thus kick the atom B out of the way to get to first atom A, even though the outer (second) atom A has never come into contact with the inner atom A before.?
(also replace word "atom" above by "molecule" if appropriate as i am unsure)
Thank you so very much.
@achris,
there are several sites on the derivation of Langmuir and Freundlich isotherms. Id try looking at these derivation sites because the mechanics of sorption (and most surface chemistry reactions) are contained therein
thank you farmerman, i am trying to understand this : if a molecule of plutonium (say plutonium oxide, PuO2) sticks on surface of alumina(prob. by van der waals force) inside a narrow channel, and while the fluid mixture flows through, another PuO2 molecule brushes and touch the first PuO2 molecule adhered to the alumina, taking into account say gravitational flow rate which means about 1 million molecules (if similar size to PuO2) brushes past the first PuO2,
Question : (1) is it likely that the 2nd PuO2 will stick by the attractive force of normal PuO2 compound as PuO2 is solid at room temp.?
(2) is it true that the moment the 2nd PuO2 touches the 1st one which is adhered to the surface of the channel, regardless of the flow rate, the two PuO2 will form their normal intermolecular bond that bonds them to be solid at room temp.? Isnt that easy for solids to form or crystalise in this manner of passing through a very narrow channel in adsorption scenario? Wouldn't this clog up the system as all liquid has to flow through the initial openings at the top of the alumina which are small, only about 10 to 30 micrometers diameter because alumina is in powder form in column, at 150 mesh.
i am trying to understand how easy for solids like metallic or mixed like PuO2 to form through aggregation in this manner. Thank you so much.
@achris,
youve hit upon the concept pof "breakthrough" in sorption kinetics. Do you have a good source on adsorption /desorption kinetics?
i cant seem to find the answers i seek from the net. you know, just like the concept of : if you pour some fluid with sticky sediments into a narrow channel, they mouth of it will get clogged, ie. aggregates form at the initial openings and there is less adsorption the further away from the mouth you get. hope you can shed some light.
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