Deleting An Apple ID

i have 2 iphones. they both use different id's but i would like to get rid of the apple id linked to the older phone, i have already factory reset the older phone and i set up an id since i didnt want to link it to my current phone. now i have deleted the email associated with my current iphone and am trying to use my primary email but ive already used it on the older phone and i really regret that. now i just want to delete my apple id so i can use my primary email on my current phone instead of risking losing all my stuff by switching id's..