documentary vs documental

documentary is a noun but documental is not a noun.

Word	Noun	Adjective	Verb	Adverb
documentary	Yes	Yes	No	No
documental	No	Yes	No	No

As adjectives, documentary and documental are synonyms defined as:

documentary and documental: relating to or consisting of or derived from documents

documentary (noun)	documental (noun)
a film or TV program presenting the facts about a person or event

documentary (adjective)	documental (adjective)
relating to or consisting of or derived from documents	relating to or consisting of or derived from documents
(of film, television, radio, or photography) depicting a real-life event using images or interviews with people involved in the event