$ sudo apt-get remove libqhull6 

Uninstall libqhull6 including dependent package

If you would like to remove libqhull6 and it's dependent packages which are no longer needed from Ubuntu,

$ sudo apt-get remove --auto-remove libqhull6 

Use Purging libqhull6

If you use with purge options to libqhull6 package all the configuration and dependent packages will be removed.

$ sudo apt-get purge libqhull6 

If you use purge options along with auto remove, will be removed everything regarding the package, It's really useful when you want to reinstall again.

$ sudo apt-get purge --auto-remove libqhull6 

See Also,