If donating doesn't work, I'm sure you'll be able to get rid of it on Craigslist. There is a free section if you don't want anything for it.
What is the size and where are you located? One of us might want it for a project, etc.
There are also places like Freecycle where you can drop things off for pickup by someone else.
People with reptiles love leaking tanks for their critters.
Best of luck,
Roy