Isolation of Metals

Common Terms
Free State

Combined State

Ore

Minerals

Gangue

Metallurgy

General Process of Metallurgy

Metallurgy
Pyrologymetallurgy

Hydrologymetallurgy

Electrometallurgy

Concentration
The process of removal of gangue from the ore is called concentration of ore, also known as dressing or benefaction.

Gravity Separation
Hydraulic Washing using Wilfey Table 

The powdered ore is kept on top of a slating floor of Wilfey's table. A running stream of water is placed across the table. The lighter gangue particles are carried away by the water and heavier particles settle in the wooden cleats on the table.

Hydraulic Classifier

A hydraulic classifier is an inverted conical vessel, filled with water. There is a tube at the top of water level. The powdered ore is then poured into the water. The gangue floats on the surface, while the mineral sinks down. The floating gangue is removed from the tube attached at the top. The or is collected at the bottom of the vessel.

Magnetic Separation
The ore is placed on a magnetic roller. The mineral gets attracted to the magnet, while the gangue remains unattracted. The minerals are then directed to a vessel, and the gangue is directed to another vessel. The gangue and the minerals have different velocities due to attraction of minerals. This property is used to separate them.

Leaching
Leaching is the process of extracting a soluble material from an insoluble solid by dissolving out in a suitable solvent.

Redox
Roasting

Roasting is a process of heating ores to a high temperature in excess of air to convert the metal into volatile metal oxides from their Sulphate forms.

Calcination

Calcination is the process of heating of ores to a high temperature in limited air to convert the metal to volatile oxides from their carbonate forms.

Reduction
Pyrometallurgy

It is a process in which the concentrated ores are reduced to form crude metals at high temperature.

Smelting is the process of extracting the impure molten metal from it's ore at a high temperature using a suitable flux and a reducing agent.

Flux is a chemical substance added to the concentrated ore during in order to remove the gangue to form easily fusible slag.

A slag is a waste product formed by concentration of a flux and gangue during the extraction of metals by smelting process

Hydrometallurgy

It is a process of extraction of metals by converting their ores into aqueous solutions of metal compounds and reduction of these solutions using suitable reducing agents. Mac Arthur Forest Cyanide Process, for extraction of gold and silver is an example of Hydrometallurgy.

Elctrometallurgy

Electrometallurgy is a process of reduction used for highly electropositive elements like Sodium, Potassium. In this method, the metal oxides are fused and electrolyzed. The metal ions are discharged at the cathode.

Alumina Thermite process

Ellingham Diagram
The Ellingham Diagram is a Graph of Gibb's Energy v/s Temperature, which shows the feasibility of a reduction reaction. The Ellingham Diagram is plotted for formation of oxides, thus the reverse is applicable for removal of oxygen.

For a reaction to be spontaneous, the ΔG value should be negative. The ΔG value would become negative at a certain value. If a reaction is spontaneous at low temperature, the reverse reaction is spontaneous at high temperature. Thus, reactions at lower end of the graph (Al,Mg) need low temperatures for oxidation but high temperatures for reduction. The reactions at top of the Graph (Hg,Ag) need a low temperature for reduction.

Refining
Liquation : This method is used when the Metal has a low melting point. The crude metal is heated and the molten metal is collected separately.

Polling : Polling is used for metals with oxide impurities. The crude metal is stirred with Green logs of wood. The heat of molten metals makes the green logs to liberate hydrocarbons which reduces the metal oxide into metal.

Electrolytic refining : This method is used exclusively for highly electropositive metals. The Anode is made up of rods of impure metal and the cathode is made up of pure metal. The pure metal is collected at cathode.

Zone Refining : In Zone refining, a single section of solid metal is heated. Thus, the impurities float on the molten metal. When the next section is heated, the previous section solidifies and the impurities try to migrate to the molten section of the metal. In this way, the impurities are collected in the last section of the metal.

Vapour Phase Refining : Metal is converted into its volatile an easily decomposable form.

Mond Process

van Arkel method : This method is used to remove oxygen and nitrogen completely. The crude metal is heated in a vessel with little iodine to foem iodide of the metal. The metal iodide is volatile.

Chromatography :