The pulley is held in place by a 13mm nut

Using a ratchet and socket to remove it.

Since the pulley will easily turn when using the ratchet, it is best to tap the ratchet handle by hand instead of trying a continues motion. It is common thread (Lefty Loosey). Of course, an impact wrench would be simpler :-)

The nut does come of fairly easy once it is loose.