close to vs about

close to is not an adjective while about is an adjective.

Word	Noun	Adjective	Verb	Adverb
close to	No	No	No	Yes
about	No	Yes	No	Yes

As adverbs, close to and about are synonyms defined as:

close to and about: (of quantities) imprecise but fairly close to correct

Other synonyms of close to include approximately, around, just about, more or less, or so, roughly, some.

close to (adjective)	about (adjective)
	on the move

close to (adverb)	about (adverb)
(of quantities) imprecise but fairly close to correct	(of quantities) imprecise but fairly close to correct
	in the area or vicinity
	in or to a reversed position or direction
	in rotation or succession
	used of movement to or among many different places or in no particular direction
	(of actions or states) slightly short of or not quite accomplished; all but
	all around or on all sides