Don't seperate them, this is completely natural. its simply them trying to figure out whose the dominant ferret. ALL fuzzbutts do this. It can take a few hours to a few months for them to completely accept one another but usually maybe two weeks tops. Just let them be, they may hiss, squeak snarl and they will grab at each other's necks and either drag or alligator roll each other around. (the dominant one is the one that does all the grabbing and rolling lol) the only reason you need to seperate them is if blood is drawn or if one ferret literally poops itself from fear. Otherwise let them be it might sound painful and whatnot but no blood no foul.