Iodine
Expensive Compound!
Iodine may be disposed in a separate bottle. Since it is very expensive you should try to find a subsequent user instead.
Iodine with poor quality may be purified by sublimation. If this is too much effort if you are doing a research job, maybe this could be performed as an extra-experiment in a lab-course?
Small quantities typical for lab work may be reduced with sulfite and then flushed down the drain.