ion exchange vs natural action

ion exchange and natural action both are nouns.

Word	Noun	Adjective	Verb	Adverb
ion exchange	Yes	No	No	No
natural action	Yes	No	No	No

As nouns, natural action is a hypernym of ion exchange; that is, natural action is a word with a broader meaning than ion exchange:

ion exchange: a process in which ions are exchanged between a solution and an insoluble (usually resinous) solid; widely used in industrial processing
natural action: a process existing in or produced by nature (rather than by the intent of human beings)

Other hypernyms of ion exchange include action, activity, natural process.

ion exchange (noun)	natural action (noun)
a process in which ions are exchanged between a solution and an insoluble (usually resinous) solid; widely used in industrial processing	a process existing in or produced by nature (rather than by the intent of human beings)