Definition Of Extraction Of Metals
Metals, save for a few, do not occur free on the earth. They are always in their combined state.
More About Extraction of Metals
- An ore is a source of metal from which you can economically extract the metal
- Metals are generally extracted by the following steps:
- Ore concentration: an ore is never completely pure compound and is found with several other impurities which need to be removed hence increasing the availability of metal for the extraction process
- Extracting the required metal using a suitable process: After choosing a suitable process based on the reactivity of the required metal several precautions need to be taken since many ores do not contain just one metal hence a suitable process in which the metals can be separated needs to be used. For example, extracting magnesium from dolomite (an ore containing magnesium and calcium) one needs to make sure that calcium is not precipitated at the electrodes by maintaining the optimum voltage
- Aluminum is found as its silicates which are first converted to aluminum oxide by heating with calcium carbonate and it is extracted by electrolysis
- Metals including iron and copper are usually found as sulfides and are heated in the presence of carbon (coke) to give pure metal
- Zinc is found as its carbonate or sulfate which is converted to oxide by heating and then reduced to zinc by heating in the presence of carbon
- Reactive metals like sodium and other alkali metals and alkaline earth metals are found usually as chlorides or silicates (ex. Rock salt (Na), magnesite (Mg)) and they can be extracted by electrolysis of the salts. Sometimes they also occur as carbonates (Dolomite (Ca, Mg)) however they cannot be extracted by converting the carbonates into oxides as they are too stable and also they cannot be reduced by carbon
- Lanthanides occur principally as their phosphates and carbonates and are separated using electrolysis and fractional crystallization as they are very reactive and have salts soluble in water with almost equal solubility for all metal salts. These days solvent separation is used
- Some of the actinides occur due to radioactive decay of other elements but most of the other elements are quite similar to lanthanides and are separated the same way
- Metals which are found mostly free in nature are called noble metals, they include ruthenium, rhodium, palladium, silver, osmium, iridium, platinum, and gold. They are extracted using macro cyclic compounds which form a complex with it and the metal can be recovered later
