A method and device for the purification and separation of purified metal from a metal mother liquid having a specific density and comprising one or more foreign element(s). The method includes: providing in a column device a starting material including metal crystals and a metal mother liquid including at least one foreign element; applying a temperature difference between a relatively hot zone at the upper end of the column and a relatively cool zone at the lower end of the column; a separation step wherein at least a part of the metal crystals is separated from the metal mother liquid by rising of the metal crystals to the upper surface of the metal mother liquid; and a further separation step wherein purified metal floating on the upper surface of the metal mother liquid is discharged from the column device.