Question:
I am a student researching for a chemistry assignment which involves the study of a chemical separation process used to obtain a substance from either the biosphere, lithosphere, hydrosphere or atmosphere.

My first thought was the use of reverse osmosis to extract NaCl from sea water, however I now feel that choice might be a bit too popular.

Answer: I can't believe thats the case. If someone wanted table salt from sea water, they would just evaporate it, poor countries do it that way, and so does the San Francisco bay area for some reason.

It's usually more cost effective to get sodium chloride from saline brines pumped from underground, or even to mine it as a solid. Reverse osmosis sounds unique enough to me.

Copper electrorefining anode muds for selenium and tellurium. Bauxite to metallic aluminum. Lithium from granite pegmatites. Separated rare earths plus thorium from monazite and whatever. Uranium isotope enrichment starting with ore. (Diamonds from kimberlite and lamproite is strictly physical separation