launch Disk Utility
Select New Image
Give the image a name, size and select AES for encryption.
Then set a password for the disk. Make sure you do not select the Remember Password option as this means the partition can be automatically mounted.
The drive image will then be created.
To mount the drive select the image in finder and double click it - enter the password and the driver is then available.
Simply select the eject icon to then remover the image.
would work well in this env.