How to remove the duplicate records from primary filegroup after partitioning?
Once SQL Server acquires disk space from the operating system and allocates it to a database it will not voluntarily give it back.  It takes time and effort to allocate this space so it is more efficient for the database to hang onto it once it has acquired it.  If you genuinely have moved the data and not copied it (you would have to post your SQL for us to be sure) there will be a lot of free space in the files of the PRIMARY filegroup. Have a look at this post for hints how to find the free space in a file.

To force SQL Server to hand back this free space to the operating system you will have to uses a SHRINK command.  This is well documented in Books Online.  There are potential performance problems with SHRINK, so use it after proper consideration.