Can I return the card at Shanghai Pudong Airport? Where is the refund counter located?

Yes, of course. You can refund it at maglev station in the airport.

I went to Shanghai last year and I asked for return a card (I mean refund) at the airport but the staff said i cannot get the refund but I can still use the card for 20 years.... I have a plan to go Shanghai again next month, do you think I still can use the same card??

Yes, no problem.