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Aluminum is the most abundant metal of earth's crust (8.3%) and exist as oxide and fluoride ores. The metal is extracted from bauxite ore (Al 2 O 3 .2H 2 O). The extraction process involve three stages or steps step 1 Purification of bauxite step 2 Electrolytic reduction of Al 2 O 3 step 3 Electrolytic purification of aluminium 1. Purification of bauxite The bauxite ore contain iron oxide and silicon dioxide as impurities. It is purified by leaching method using concentrated sodium hydroxide solution in which bauxite dissolve forming sodium meta aluminate. On agitating this solution with freshly precipitated Al(OH) 3 for several hours Al(OH) 3 is precipitated. NaAlO 2   +  2H 2 O  ------------>  NaOH  +  Al(OH) 3  The precipitate is filtered and dried and NaOH is concentrated and used again for leaching . The aluminium hydroxide precipitate is calcined at 1500 o C to obtain pure alumina. 2. Electrolytic reduction of pure alumina ...

Concentration Beneficiation by Forth flotation This method is used for the concentration of sulphide ores which are lighter than the impurities. The powdered ore is added to water containing pine oil (frothing agent) and sodium ethyl xanthate (collecting agent). The mixture is strongly agitated by passing compressed air. The sulphide particles stick to the oil droplets forming a forth which rises to the surface. The heavier gangue particles settle to the bottom of the vessel. The forth is skimmed off and heated to separate the oil and the sulphide. Related post Leaching: metallurgy

The extraction of aluminium involves two steps that is, purification of bauxite by Baeyer's process and electrolysis of alumina . 1. Purification of bauxite by Baeyer's process In the Baeyer's process, the bauxite ore is heated with concentrated NaOH solution under pressure ( Aluminum is purified by leaching method ). The alumina dissolves as sodium meta aluminate. The other materials present in the ore are left as insoluble part. This solution is filtered in ore are left as insoluble part. This solution is filtered off. From the solution Al(OH)3 is precipitated by adding freshly prepared Al(OH)3 to the cold dilute solution and agitating. Al2O3 + 2NaOH -------> 2NaAlO2 + H2O NaAlO2 + 2h2o -------> NaOH + Al(OH)3 The precipitated Al(OH)3 is dried and ignited to get pure alumina. 2Al(OH)3 --------> Al2O3 + 3H2O 2. Electrolysis of alumina The alumina is dissolved in a mixture of molten cryolite and fluorspar which lowers the melting point. It is then elect...

Leaching is a chemical method for the concentration of the ore. Here the powdered ore is treated with a suitable reagent in which the ore alone dissolves. The impurities are filtered off and from the solution the ore is regenerated by precipitation. Thus bauxite (Al 2 O 3 .2H 2 O), the ore of aluminum , contain silicon dioxide and oxides of iron and titanium as impurities. The powdered ore is digested with 45% sodium hydroxide solution at 500K and 35 atmosphere pressure. Al 2 O 3 forms soluble sodium aluminate (SiO 2 form soluble sodium silicate). The solution is filtered to remove insoluble impurities, diluted with water and seeded with some freshly precipitated Al(OH) 3 which induce the precipitation of Al(OH) 3 from the solution. The precipitate is filtered and heated to get pure alumina (Sodium silicate remain in solution). Al 2 O 3 .2H 2 O + 2NaOH ----------> 2NaAlO 2 + 3H 2 O NaAlO 2 + 2H 2 O -----------> Al(OH) 3 + NaOH 2Al(OH) 3 ------^-----> Al 2 O ...

 Iron is extracted from its oxide ores. The ores are crushed and concentrated by gravity method. Magnetite is further concentrated by magnetic method. The concentrated ore is calcined to remove volatile impurities and make the ore porous. The calcined ore contains SiO 2 as the chief impurity. It is mixed with lime stone (CaCO 3 ) as flux and coke as reducing agent and the mixture is charged into a blast furnace (a very tall steel tower lined inside with fire bricks). The charge is heated by a hot blast of air preheated at 1000 K blown in through narrow pipes (tuyers) at the base of the furnace. Here coke burns producing heat and temperature rise to 2100 K. C + O 2 --------------> CO 2 + heat The temperature falls to 500 K towards the top of the furnace due to the endothermic reaction. CO 2 + C ---------------> 2CO - heat Carbon monoxide reduces iron oxide to iron in the middle and upper regions of the furnace. 3Fe 2 O 3 + CO -----------------> 2Fe 3 O 4...

 As sodium is a highly electro positive metal it cannot be prepared by the usual methods of reduction. The metal is extracted by the electrolysis of a molten mixture of NaCl, CaCl 2 and KF in a Downs cell at 600 degree Celsius. The cell has a graphite anode and a circular iron cathode, both covered and with proper outlets. Chlorine liberated at the cathode rises up through a pipe and gets collected in a receiver in the molten state. NaCl ------> Na + + Cl - Na + + e - -------> Na (At cathode)  2Cl - --------> Cl 2 + 2e - (At anode) The electrolysis of NaCl presents some difficulties. The fusion temperature of pure NaCl is 803 degree celsius. At this temperature both Na and Cl 2 are highly corrosive. Addition of CClCl 2 and KF reduce the fusion temperature to 600 degree celsius. Did you Know how the extraction of aluminum is done ? visit for more details extraction of aluminum

Copper is extracted from its principal ore copper pyrites (CuFeS 2 ). The ore is concentrated by froth flotation process. The concentrated ore is roasted in a reverberatory furnace when the following reactions occur.  1. The volatiles like sulphur and arsenic escape as gases     S + O 2 --------------> SO 2 4AS + 3O 2 --------------->2AS 2 O 3  2. Copper pyrites is converted to a mixture of Cu 2 S and FeS     2CuFeS 2 + O 2 ---------------> Cu 2 S + 2FeS + SO 2 3. The sulphides of Cu and Fe are partially oxidized  2Cu 2 S + 3O 2 <=======> 2Cu 2 O + 2SO 2  2FeS + 3O 2 <========> 2FeO + 2SO 2 Smelting in extraction of copper   The roasted ore mixed with silica as flux is heated in a blast furnace by a blast of hot air. Most of the FeO is removed as a slag and a molten mixture of Cu 2 S and FeS called matte, get collected in the hearth of the furnace.     ...

Sulphur occurs in nature in the elemental forms, as metal sulphides and as sulphates. Sulphur also occurs as H2S present in natural gas. Sulphur is extracted by the following methods 1. Frasch process In this process, sulphur is extracted from underground deposits by pumping super heated steam down the beds to melt the sulphur and then blown out the molten sulphur with compressed air. 2. Extraction of sulphur from natural gas Natural gas contains a large amount of hydrogen sulphides (H2S). Hydrogen sulphide is first absorbed in monomethanolamine and then converts H2S into sulphur by the following reactions. 2H2S + 3O2 ------------> 2SO2 + 2H2O 2H2S + SO2 ------------> 3/8 S8 + 2H2O (at 673K and Fe2O3 as catalyst) Related article extraction of aluminium extraction of copper