Is there any way to remove the Sandbox study?

No, the Sandbox study is a default study available to all who have access to it to practice and see the impact of entries in the system without affecting your "real" studies.

If access to the Sandbox study will cause confusion, you can manually remove a user's access (ie, their ability to see it among the list of studies) by taking the following steps:

• An Administrator user should navigate to ADMINSTRATION < USER MANAGEMENT
• Click on the name of the user whose access to the Sandbox you would like to remove
• Click on the "Account Actions" button and select the "Edit User Details" option
• In the resulting window, untick the check mark next to Allow Sandbox Access
• Click Save to retain the change