A club statement read: "Izzy Iriekpen is out of contract at the end of this season and will not be offered a new contract.
"In light of this and in the best interests of both the club and the player, Izzy will be placed on the transfer list in the January transfer window."
Cliff Byrne has been given the armband permanently, with the Iron manager Nigel Adkins saying he "epitomizes the standards and values which I demand at this football club".
Byrne will begin his reign as captain when Hartlepool United visit Glanford Park on Boxing Day.