Can I create 2 different SharePoint farms using the same Active Directory
As mentioned in the above comment, Yes you can, I have already two farm that uses the same shared Active directory ,
but it's preferred to isolate the service accounts for each farm to a specific group.
- Farm1 Service Account Group (that contains for example SP_farm1)
- Farm2 Service Account Group (that contains for example SP_farm2)
Multiple applications can connect to the same Active Directory. This also applies to Sharepoint.
So in short, the answer is yes. But it is advisable to NOT share service accounts across environments/farms.