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Author Topic: What is the difference betwenn chemcal absorption and chemical reaction?  (Read 3755 times)

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nchristedem

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Hi,
I am not a specialist in chemistry but I deal with sorption processes (so called!) for example water vapour absorption by lithium bromide solution. This is said to be a physical absorption. I read that there are also chemical absorption and I would like to know what is the difference between a chemical reaction and a chemical absorption. Is a chemical soption a chemical reaction?
Thanks
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DevaDevil

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chemisorbed vs physisorbed:

the difference is indeed that in physisorption the molecules are not reacting, but held close to the sorbent by physical interaction, such as van der waals forces. In chemisorption a reaction takes place, such as electron transfer (for example, protons adsorbing on platinum in watery solutions near 0V), which then means the sorbents chemically interact

chemisorption is often an intermediate state in a full chemical reaction, and is usually reversible
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nchristedem

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Thank you DevaDevil. Your last sentence allow me to understand a little what is involved, as my question is focused on the difference between CHEMICAL absorption and CHEMICAL reaction.

For example, why the absorbing of CO2 and H2S with aqueous solution of monoethanolamine (MEA), diethanolamine (DEA), diethyleneglycol (DEG) or triethyleneglycol (TEG) are call chemical absorption and not chemical reaction? what is the particularity of a chemical sorption?

Another example: Here is a chemisorption (chemical adsorption): how do I know that is is a chemical adsoption and not a chemical reaction?

SrBr2.6H2O
SrBr2.1H2O + 5H2O

thank you.
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CrazyCh3m

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Thank you DevaDevil. Your last sentence allow me to understand a little what is involved, as my question is focused on the difference between CHEMICAL absorption and CHEMICAL reaction.

For example, why the absorbing of CO2 and H2S with aqueous solution of monoethanolamine (MEA), diethanolamine (DEA), diethyleneglycol (DEG) or triethyleneglycol (TEG) are call chemical absorption and not chemical reaction? what is the particularity of a chemical sorption?

Another example: Here is a chemisorption (chemical adsorption): how do I know that is is a chemical adsoption and not a chemical reaction?

SrBr2.6H2O
SrBr2.1H2O + 5H2O

thank you.

A chemical absorption depends by the structure of the material. If you take something like clays or zeolite they have a cage structure which can absorb atoms or small molecule. There is not a real chemical reaction meaning that there is no bond involved, instead you can have a charge stabilization or a sterical stabilization.
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ad0rian423

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Re: What is the difference betwenn chemcal absorption and chemical reaction?
« Reply #4 on: January 09, 2012, 11:59:38 PM »

Quantachrome UK have a handy dictionary on their site:
http://www.quantachrome.co.uk/en/Particle-Characterisation-Dictionary.asp

adsorption (noun) - the adhesion of atoms, gases, solutes or liquids (the adsorbate) to the surface of a solid or liquid (the adsorbent). Note the difference with absorption where one fluid permeates into the other material.

chemisorption (noun) - Type of adsorption where the monolayer adhesion results from a chemical bond formation between the adsorbent and the adsorbate. Abbreviated from "chemical adsorption."


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