desalination vs desalinisation

desalination and desalinisation both are nouns.

Word	Noun	Adjective	Verb	Adverb
desalination	Yes	No	No	No
desalinisation	Yes	No	No	No

As nouns, desalination and desalinisation are synonyms defined as:

desalination and desalinisation: the removal of salt (especially from sea water)

Other synonyms of desalination include desalinization.

desalination (noun)	desalinisation (noun)
the removal of salt (especially from sea water)	the removal of salt (especially from sea water)