Both "cannot" and "can not" are acceptable spellings, but the first is much more usual. http://www.oxforddictionaries.com/words/cannot-or-can-not
From the link you provided.
Both cannot and can not are acceptable spellings, but the first is much more usual. You would use can not when the "not" forms part of another construction such as "not only." For example:
These green industries can not only create more jobs, but also promote sustainable development of the land.