Is there any way to save disk brake pads once they've gotten even a little bit of mineral oil on them? I did a frame swap recently and my front brakes are now screeching loud and not as powerful as they were on the other frame. This leads me to believe that I must have gotten some mineral oil or other contaminant on them during the frame swap process. 

The problem is that the pads are expensive and they still have a lot of life left on them. But just wondering if it's a lost cause this point to try to clean or salvage them
The best approach I've seen in terms of producing non-mediocore results is heat them up with a heat gun until you can see the oil smoking up and maintain that heat until the smoke stops. You want to heat it through and minimize peak temperature, so let that inform your setting and distance.

This can work pretty well but I make no promises what the metallurgical side effects may be. It's an at your own risk thing only. That said it's a pretty common trick and I doubt there's much risk. And of course do this with good ventilation and with the pads in a vise, hanging on a cable, or some other way where they won't need to be handled until cool.

Things like sanding, degreasing etc really don't work because the whole problem is the material has some porosity.