While in Hong Kong, I'm planning to get an Octopus card to use on public transport to get about the city. As with a lot of these stored value, contactless public transport cards around the world, there's a refundable deposit that you pay when you get the card.
When I come to leave Hong Kong, I'll likely want to use the Octopus card to get to the airport. Once at the airport, the card'll have a little bit of money on it, along with the deposit, less the $9 admin fee for short duration returns.
Is it possible to get a refund of the deposit and un-used balance on an Octopus card at the airport? And if so, where?