Question: [Sunday 4th Tamuz, 5780]
I redeemed a pair of Pasul Tefillin from a gentile. What am I to do with it?
You must place it in Geniza. There are special boxes of Geniza for Tefillin in the general Geniza drop offs.
The reason: Pasul Tefillin are to be placed in Geniza and not held at home, in order so someone does not come to by mistake wear them, thinking that they are Kosher.
Sources: See Igros Moshe 4:12; Piskeiy Teshuvos 32:36; 154:10-11