Below cmd will retrieve info about persistent disk that belongs to specific user: Test it for a test account before running directly on production:

Get-ProfileDisk –Username <domain>\<username>

Getting list of detached persistent disks only:

Get-ProfileDisk –Username <domain>\<username>  -Status <Detached/InUse/Archiving>

Detaching the PD:

Get-ProfileDisk –Username <domain>\<username> -detachUdd