Cipher is a Windows utility that can be used clean the free space on a volume

cipher /W:D:\

Get-Date

cipher /w:D:\

Get-Date

Important: I'm a bit concerned by the cipher help for /W which seems to say if you specify a mount mount e.g. D: the data is removed so I'm assuming specifying D:\ is critical so you don't lose data but I haven't tested this.

This might allay my concerns: https://learn.microsoft.com/en-us/troubleshoot/windows-server/certificates-and-public-key-infrastructure-pki/use-cipher-to-overwrite-deleted-data

I wish they would modify the help to say "the data existing in unallocated space on that volume will be removed"

cipher.exe /?

# .... snippage ...
/W        Removes data from available unused disk space on the entire
          volume. If this option is chosen, all other options are ignored.
          The directory specified can be anywhere in a local volume. If it
          is a mount point or points to a directory in another volume, the
          data on that volume will be removed.

# .... snippage ....