you could do that, i usually leave my pentagram necklace in the full moon light once a month to charge.
what path do you follow? there are different purification for different paths. when i purified my athame [the first time] i anointed it with sesame oil, said a little change, then charged it. now i use the dragon purification.
try my friends purification, it works wonders for us. start by meditating holding the item [in this case your athame] when you're ready, take some salt water [you can also use solar water or lunar water] and lightly sprinkle it over your athame. close your eyes and charge it. visualize it first as black, then as energy flows from you it become white and glows. you can say a little something if you want, then kiss the blade and pass it through some frankincense smoke.