How do you do things?

If this is a question concerning industry, there are various methods. With size as a sorting factor, wire mesh is often used or openings of various size. Optical sensors placed on a diverging conveyor with a pushing "arm" can be used to sort by color. High strength magnets can be used to sort magnetic materials from nonmagnetic. Hall effect sensors may also be used for this purpose, with the same diverging conveyor system that I mentioned with optical sensors.

Different fluids can be separated by centrifuge, or by a distillation process. Particulates are separated from fluids by filtration.

I hope this helps.