How to remove Sn from Sn60Cu40 alloy?
You can remove tin from bronze (copper-tin alloys) and leave behind the copper. However, doing so may not leave you with copper in an easy to use form. 

Tin is a less reactive metal than copper. Tin reacts with all acids, like $\ce{HCl}$, while copper only reacts with oxidizing acids, like $\ce{HNO3}$.

$$\ce{Sn(s) +2H+(aq) -&gt; Sn^{2+}(aq) + H2 (g)^ }$$
$$\ce{Cu(s) + 2H+ (aq) -&gt; No \ Reaction}$$
$$\ce{Cu(s) + 4H+(aq) + 2NO3- (aq) -&gt; Cu^{2+} (aq) + 2H2O (l) + 2NO2 (g) ^}$$

Soaking your bronze in acid (even vinegar might work) will eventually dissolve the tin away from the copper. Heating, or using a stronger acid like the $\ce{HCl}$ in muriatic acid, will likely increase the rate. However, since the composition of the alloy is uniform throughout, the copper will likely come out of solution as a fine powder.