DC - is my domain sandboxed?

Hi!

I have an internet project which is hosted on two different domains and advertised with ppc thats why i didnt care about any SEO criterias. So on domain 1 and on domain 2 are exactly the same pages 1:1 uploaded. I think that both urls are now sandboxed because of duplicate content. I would like to use one domain for SEO purposes. How can I check if a domain is sandboxed or blacklisted and how long does it take till the domain is "clean" again for google.

cheers

Use backlinks from one site to the other and include google's canonical tag. Then submit for review in webmaster tools.