Out line the principles of refining metals by the following method:
Zone refining
Electrolytic refining
Vapour phase refining
Out line the principles of refining metals by the following method:
Zone refining
Electrolytic refining
Vapour phase refining
Zone refining: This method is based on the principle that impurities are more soluble in the molten state of metal (the melt) than in the solid state. In the process of zone refining, a circular mobile heater is fixed at one end of a rod of impure metal. As the heater moves, the molten zone of the rod also moves along with it. As a result, pure metal crystallizes out of the melt and the impurities pass to the adjacent molten zone.
Electrolytic refining; Electrolytic refining is the process of refining impure metals by using electricity. In this process, impure metal is made the anode and a strip of pure metal is made the cathode. A solution of a soluble salt of the same metal is taken as the electrolyte. When an electric current is passed, metal ions from the electrolyte are deposited at the cathode as pure metal and the impure metal from the anode dissolves into the electrolyte in the form of ions. The impurities present in the impure metal gets collected below the anode. This is known as anode mud.
Electrolytic refining it is used for less reactive metals like Cu, Ag, Au, Al etc, In it, the anode is made by impure metal and a thin strip of pure metal acts as a cathode. On passing electricity, metal dissolves from the anode and pure metal get deposited at the cathode.
At anode MImpuremetal⟶Mn++ne−
At cathode Mn++ne−⟶MPuremethod
Impurities settle down below anode in the form fo anode mud.
Vapour phase refining Vapour phase refining is the process of refining metal by converting it into its volatile compound and then, decomposing it to obtain a pure metal. To carry out this process,
(i) the metal should form a volatile compound with an available reagent, and
(ii) the volatile compound should be easily decomposable so that the metal can be easily recovered. Nickel, zirconium, and titanium are refined using this method.
Zone refining: This method is based on the principle that impurities are more soluble in the molten state of metal (the melt) than in the solid state. In the process of zone refining, a circular mobile heater is fixed at one end of a rod of impure metal. As the heater moves, the molten zone of the rod also moves along with it. As a result, pure metal crystallizes out of the melt and the impurities pass to the adjacent molten zone.
Electrolytic refining; Electrolytic refining is the process of refining impure metals by using electricity. In this process, impure metal is made the anode and a strip of pure metal is made the cathode. A solution of a soluble salt of the same metal is taken as the electrolyte. When an electric current is passed, metal ions from the electrolyte are deposited at the cathode as pure metal and the impure metal from the anode dissolves into the electrolyte in the form of ions. The impurities present in the impure metal gets collected below the anode. This is known as anode mud.
Electrolytic refining it is used for less reactive metals like Cu, Ag, Au, Al etc, In it, the anode is made by impure metal and a thin strip of pure metal acts as a cathode. On passing electricity, metal dissolves from the anode and pure metal get deposited at the cathode.
At anode MImpuremetal⟶Mn++ne−
At cathode Mn++ne−⟶MPuremethod
Impurities settle down below anode in the form fo anode mud.
Vapour phase refining Vapour phase refining is the process of refining metal by converting it into its volatile compound and then, decomposing it to obtain a pure metal. To carry out this process,
(i) the metal should form a volatile compound with an available reagent, and
(ii) the volatile compound should be easily decomposable so that the metal can be easily recovered. Nickel, zirconium, and titanium are refined using this method.
