Anna, what is the volume of the waste solution? and what were the beads exposed to? Unless the volume is too large, you should dispose it as done for "regular" liquid lab wastes. Ciao!

Thanks, Stefano Amalfitano ! I have 8 beakers 50 mL, hence 400 mL in total. I think it is easiest to let the solution evaporate and then wipe the beaker with paper.

It was also suggested to me to add methylene chloride to redissolve the PS and, yes, as you said, pour it into the organic liquid waste.

There is also the general opinion that these little amounts don't have a sign. effect considering the huge amounts of MP and NP we release alone by our washing machine and other daily processes. But I just wanted to ask what others do.