Will we be able to purchase Shanghai Transport card at Hongqiao airport?

Yes, you can buy the card at the Ticketing Window of the metro stations at SHA.

However, you cannot return it at South Railway Station. You need to return the card at Customer Service Center, Card Vending Machines inside some metro stations, SPD Banks, All days convenience stores, etc. For example, you can return it the Card Vending Machines at Xujiahui Metro Station. Good luck!

To get a card, you need to pay CNY 20 as the deposit, and add some value to it.