Can I use ferrites for the ground connections?
Increasing the impedance of the system ground between various devices is a bad idea.  Decouple the power supply feed points, filter signals between blocks as necessary, but keep the ground connections as solid as you can.

If you do manage to decouple the ground, like by adding inductance in series, then the noise will be even larger on all the signals coming out of that block.  By allowing the ground to float at high frequencies, you make everything common mode noise, so it will show up on all signals too.