Liquation is used to purify the metal whose melting point is lower than that of impurities like $\mathrm{Sn}, \mathrm{Bi},\mathrm{Pb}$ etc.
Mond’s process The impure nickle is heated in presence of carbon monoxide. 

${\mathrm{Ni}}_{\left(\mathrm{s}\right)} + {\mathrm{CO}}_{\left(\mathrm{g}\right)} \to {\left[\mathrm{Ni}{\left(\mathrm{CO}\right)}_4\right]}_{\left(\mathrm{g}\right)} \to {\mathrm{Ni}}_{\left(\mathrm{s}\right)} + 4{\mathrm{CO}}_{\left(\mathrm{g}\right)}$
Zone refining is based on the principle that impurities are more soluble in melt that in the pure solid metal. The metals like $\mathrm{Ga}, \mathrm{Ge}$ etc. are purified by this method.
Van Arkell method  is used for those metals which are very difficult to obtain in pure state like $\mathrm{Zr}$.