Copper and sodium are two metals that have extremely different physical and chemical properties. Because of this it is relatively easy to separate the copper from a mixture of copper and sodium.
If you want to obtain both metals separated, you just need to recall that all alkaline metals have very low melting points. Because the sodium melting point is just 97.8 degree C (208 degree F) and copper melting point is 1085 degree C (1984 degree F) one just needs to rise the temperature of the mixture at about 100 degree C and the metals will separate in two phases, solid and liquid, that can be easily separated.
If you want to obtain only the copper from the mixture and use an even simpler method, you need to make an appeal to the high chemical reactivity of sodium. Thus, because sodium reacts with water very easily following the reaction
`2*Na + 2*H2O = 2*NaOH + H2`
it is enough to submerge the mixture of copper + sodium under the water, and after short time the entire sodium quantity will form a `NaOH` solution leaving the copper (that is inert in this solution) completely separated.