Mount or unmount a sdcard

Hello. My phone is xperia z1 and I wanna unmount my sdcard that has been inserted in the phone via an app,terminal emulator or other option. Note: I dont want to eject the sdcard from the phone physically just I wanna unmount it by keeping inside the phone. Also, I wanna mount it, whenever I need my sdcard to read or write something.
Xperia z1 has an option to unmount or mount a sdcard from the phone but after restarting the phone, the sdcard is mounted automatically by the phone but I dont want this. I wanna control it manually whenever I want.

How can I do it? It is very important. Please, tell me an exact way to do it.

Regards,
Sarkhan