Member of the Month: May 2009, Oct 2010, Sept 2017
Generic kitty litter is just clay. Unless your GR smell comes out as a foul liquid, it's probably not the best choice for a filtration material. Besides, unlike your plants, your cats will bury their wastes.
Carbon is king.
There are several DiY carbon filter threads here on this site. Might want to use the Search function (hidden at the top left of every page - under FORUMS).
Don't take chances with odor-filtration or you might come home from work one day, turn onto your street, and smell your grow. Or pull into your driveway and see a couple of your neighbors with flashlights looking for the skunk that they keep smelling, lol.