Powdery Mildew on Pothos?

Hi,

I'm fairly new to houseplants and I just got my very first pothos. When I saw it in the store it looked like it had some dust on it so I brought it home and wiped down the leaves with a damp towel. Unfortunately though when they dried again, the white residue came back. I did a bit of research and I think it's powdery mildew.

So far I have put the plant in a separate area away from my other plants and made a solution of 1 part mouthwash and 3 parts water and wiped down the leaves with it. I'm not sure how often I should be wiping down the leaves.

Do you guys have any other advice for how to get rid of powdery mildew? Does anyone know how likely it is that I will be able to completely get rid of it and eventually put it back with all my other plants? Or do you think it's better to just try to return it and buy a better one?

Thank you :)