Describe a method for refining nickel?

Mond process for refining of Nickel:-It is base on the principle that nickel is heated in presence of carbon monoxide to form tetranickel carbonyl which is a volatile complex Ni +4CO-----Ni(CO)4 Column chromatography for purification of rare elements.It is based on the priciple that different components of the mixture are differently adsorbed on the adsorbent.In it there are two phases-mobile phase and stationary phase.The moble phase is gas,liquid or supercritical liquid and the stationary phase is immobile and immiscible.Al2O3 is commonly used as a stationary phase