it is simple. The water evaporates and the salt remains as a solid.
This is the way the world makes salt from sea water.
in salt water sodium and chloride dissociate as ions. so salt dissolves well. The boiling point of salt water increases by some degrees.
the water molecules absorb heat and change state to gaseous state. Sodium and chlorine ions combine back to solid crystalline form. The boiling point of salt is very high compared to that of water. So salt remains as white powder.
