Purchase transport smart card on Beijing South Station and its return at Capital Intl Airport.

In September I am arriving to the city by train (G-Train from Shanghai to the South Railway Station) and leaving the city by plane from PEK Airport. Could you please advise if I can buy Transportation Smart Card on the South Station and return the card at the airport.
Please also advise the easiest way (by metro and/ or other public transport like bus) to get from the South Station to Jingtailong Intl Hotel on Zhushikou W. Street.
Thanks in advance,
Andrzej from Poland