How would I separate a mixture of salt and sand using hexane?

Actually, what you are asking for is simply not possible.  Both salt (sodium chloride) and sand are powdery solids.  As a result, they cannot be mechanically separated by simply picking the individual grains apart.  So you must perform some kind of physical change to one of them that makes the two able to be separated.  Normally, that would be to freeze, dissolve, boil, melt, or a similar physical change process one of the two chemicals in the mixture without changing the other one.  Sand is basically a mineral and therefore cannot be melted or changed without incredibly extreme conditions.  That means that the salt is the chemical that must be changed.  Normally that would mean to dissolve the salt in water to separate the two.  Hexane is an organic solvent and is incredibly non-polar.  A polar solvent like water is required to dissolve a salt.  If you put salt in hexane, even hot hexane, non of the salt will dissolve, nor or course will the sand.  So adding hexane to the mixture will do absolutely nothing and will not allow you to separate the two components.