Admins in the platform can remove other users from the workspace:
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​1. Go to settings (on the front page in the upper left corner, when you click on the name a menu pops up)

2. In settings, click on "Users"
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3. Click on the three dots on the person you wish to remove from the workspace, and choose "Delete user".

Note that removing a user from a business workspace doesn't delete a user's personal workspace, it just removes them from the business one.