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GCSE Chemistry Notes: Explaining why there are different methods of metal extraction

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blast furnace

1. Introduction to methods of extracting metals from their ores

METALS ARE VERY IMPORTANT MATERIALS IN OUR EVERYDAY LIVES this page is an introduction to the theory and practice of extracting metals from their naturally occurring ores

 Doc Brown's Chemistry GCSE/IGCSE/O Level Revision Notes - Mining of Minerals, Methods of Extracting of Metals from Ores These revision notes on the extraction of copper and the electrolytic refining of copper, useful for the new AQA, Edexcel and OCR GCSE (9–1) chemistry science courses.

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Metal extraction index


1. Introduction to Metal Extraction (this page)

2. Extraction of Iron and Steel Making

3. Extraction of Aluminium and Sodium

4. Extraction and Purification of Copper, phytomining & bioleaching

5. Extraction of Lead, Zinc, Titanium and Chromium

6. Economic & environmental Issues and recycling of various materials

For more on the reactivity series of metals and oxidation-reduction (redox) reaction see

Detailed notes on the 'Reactivity Series of Metals'

Detailed notes on oxidation and reduction and rusting

Detailed notes on metal reactivity series experiments

Summary for this page

Rocks are a mixture of minerals and from these minerals extremely useful metals can be extracted. How are metals extracted from mineral ores? What methods to be use? How do we extract and make iron, steel, other alloys, aluminium, sodium, copper, zinc, titanium and chromium? The six linked pages include an introduction to metal extraction or metal manufacture and production. There are detailed notes on the extraction of iron and its conversion to steel. The extraction and manufacture of aluminium and sodium are described. The extraction, smelting and purification of copper is covered and similarly notes on the extraction of zinc, titanium and chromium. How to extract a metal is one technological issue, but finally some economic and environmental Issues and metal recycling are discussed as a result of metal extraction. Below is the index of revision notes on extraction procedures and theory, so, scroll down for revision notes on the theory of extraction procedures which should prove useful for school/college assignments/projects on ways of extracting metals from their ores.

Equation note:

The equations are sometimes written three times: (i) word equation, (ii) balanced symbol equation without state symbols, and, (iii) with the state symbols (g), (l), (s) or (aq) to give the complete balanced symbol equation.

A summary diagram of important ideas to do with the reactivity series of metals!

Reactivity series of metals - method of metal extraction - relative ease of oxidation reaction with acids

1. Introduction to the extraction of metals - the theoretical and practical background ideas

What methods can be used in extracting metals from mineral ores?

Why can one method be used to extract one metal, but not another?

  • The Earth's crust contains many different rocks.

  • Rocks are a mixture of minerals and from some we can make useful substances.

  • A mineral can be a solid metallic or non–metallic element or a compound found naturally in the Earth's crust.

  • Mineral ores are naturally occurring rocks that provide an economic starting point for the extraction and manufacture of metals for a huge variety of purposes ie a metal ore is rock containing sufficient metal to be worth extracting the metal from it.

  • The simplest definition of an ore is a mixture of a metal containing mineral and other materials ('minerals') from the surrounding rocks, which can be described as impurities with respect to what you want from the ore.

  • Metal ores are obtained by mining and that this may involve digging up and processing large amounts of rock.

    • Most ores are mined have to be concentrated before the metal is extracted and purified.

    • This often results in lots of waste material that must be dealt with from an environment of view.

    • The social, economic and environmental impacts of exploiting metal ores are discussed on a separate page.

    • The rock must contain enough of the metal compound, hence enough of the metal, to be worth exploiting the ore reserve and extract the metal by physical and chemical processes.

    • Low grade ores are usually uneconomic to mine and process, but high grade ores have a high enough metal content to be worth mining and extracting the metal.

  • The metal ore, a mineral or mixture of minerals from which economically viable amounts of metal can be extracted, i.e. its got to have enough of the metal, or one of its compounds, in it to be worth digging out!

    • Ores are often oxides, carbonates or sulphides because these non-metals readily combine with many metals.

      • e.g. iron  +  oxygen  ===> iron oxide ores

        • Fe  +  O2(air)  ===> Fe2O3 or Fe3O4    (not balanced equations, just the idea!)

        • This the typical chemistry involved in metal ore formation.

      • In extracting metals from ores you have to reverse the process e.g. by heating the ore with carbon (coke or charcoal) in a very hot smelting furnace e.g. in a blast furnace to make iron ...

        • iron oxide ore  +  carbon  ===> free iron  +  carbon dioxide waste gas

        • Fe3O4  +  2C  ===>  3Fe  +  2CO2

        • The iron oxide is reduced (oxygen loss) and the carbon reducing agent is oxidised (oxygen gain).

        • This is typical extraction chemistry for less reactive metals.

      • For details see sections 2. Extraction of Iron and Steel Making and 4. Extraction and Purification of Copper

    • These ores are all finite resources so we should use them wisely!

    • Any ore must contain enough of the metal to make it worthwhile to mine and then extract the metal.

    • High grade ores will therefore be the most economical to exploit BUT over time the better quality–richer sources will decrease, especially with the power of the global economy and powerful and growing economies of Brazil, China, India and other Asian economies.

    • The economics of metal extraction are not only dependent on the quality of the ore and the cost of extraction (ie richer ores lead to cheaper production), but also depend on the market price and demand.

      • If demand is high the metal price rises and may off–set the price of mining lower grade ores, but if demand is low, the metal price falls and inefficient mines and smelters will go out of business ie its not worth extracting the metal.

      • Of course it is possible to improve the technology of metal extraction and enable companies to produce more metal from the ore than was previously possible and even utilise low grade ores previously discarded and not considered worthwhile mining or processing waste from mining

    • Since the majority of metals are found combined with non–metals like oxygen (oxide ion) or sulfur (sulfide ion) or the carbonate ion, chemical reactions are needed to free the metal from its mineral source.

  • In order to extract a metal, the ore or compound of the metal must undergo a process called REDUCTION to free the metal i.e.

    • The oxide/sulfide loses oxygen/sulfur, to form the free metallic atoms, or

    • the positive metal ion gains negative electrons to form the neutral metal atom.

    • The chemical that removes the oxygen from an oxide is called the reducing agent i.e. carbon, carbon monoxide or sometimes hydrogen.

  • (c) doc bOrder of decreasing reactivity related to the earliest know date of extraction and use:

    • (BP means before present time)

    • francium (1939, very radioactive), caesium (1860, ?), rubidium (1861, ?)

    • potassium (1807, 1855 from electrolysis), sodium (1807, from electrolysis)

    • lithium (1817, electrolysis?), calcium (1808, from electrolysis)

    • magnesium (1755, 1808 from electrolysis), aluminium (1825, by electrolysis)

    • zinc (before 1500, ), iron (extracted with charcoal before 3000 BP)

    • tin (~4500 BP, used to make bronze)

    • lead (over 9000 BP, archaeologist have found lead beads 9000 years old, used by the Romans for plumbing well over 2000 years ago)

    • copper (~11000 BP extracted via charcoal from ores >4000 years ago, found 'native' and was beaten out of rocks and into a useful shape!)

    • silver (~7000 BP, used by ancient civilisations)

    • gold (~8000 BP, used by ancient civilisations, e.g. Egyptian civilisations, found 'native' in streams and extracted by 'panning')

    • platinum (~1735, recognised as a rare metal but known to ancient South American civilisations before Europeans arrived in the 15th century, brought to Europe ~1750)

    • I've tried to indicate the earliest date of extraction and use, however impure the metal might be, like bronze age copper and iron age iron!).

    • The less reactive metals could be found as the element or relatively easily extracted using charcoal (like coke, it has a high % of carbon in it).

    • The date is quoted as the 'normal' year (BCE/AD) or BP meaning years before present year (I've not used BC).

    • 'native' seems a politically incorrect term, but it is a term that means finding the element in its free chemically uncombined state e.g. gold in alluvial deposits washed into mountain streams or 'native' copper was beaten out of rocks over 6000 years ago.

    • The understanding of electricity and the development of d.c. electrical supplies e.g. using simple voltaic batteries meant that reactive metals could then be extracted by electrolysis.

    • Once more reactive metals could be produced in larger quantities by electrolysis, these metals themselves were (and still are) used to extract other metals e.g. chromium, which were often difficult to extract by conventional smelting furnaces using carbon.

    • Generally speaking the more reactive the metal the later it is extracted and used as the technology of metal extraction improves.

    • Detailed notes on the 'Reactivity Series of Metals'

  • As described above, historically as technology and science have developed the methods of extraction have improved to the point were all metals can be produced. The reactivity is a measure of the ease of compound formation and stability. The more reactive the metal, the more readily the metal forms a stable compound eg with oxygen or sulfur, and therefore because of this greater compound stability, the more difficult it is to reduce the compound to the metal.

    • (c) doc bThe position of a metal in the reactivity series of metals (right diagram) has important implications for the method used to extract metals.

      • In 'general' to summarise before a more general discussion and detailed notes page:

      • The most reactive metals K, Na, Ca, Mg and Al cannot be extracted using carbon or hydrogen, as the reducing agent and must be obtained by costly electrolysis.

      • You should realise that in order to extract a metal from its oxide, you have to remove the oxygen!

        • The more reactive a metal, the strongly it is chemically bound to oxygen (or sulfur) in its oxide (or sulfide).

        • Therefore, the more reactive the metal, the more difficult it is to extract the metal and usually more energy is needed, and up go the costs too!

      • Metals below aluminium can be extracted using carbon or carbon monoxide as the reducing agents, those above zinc can't.

        • The carbon displaces the metal and is cheaper than electricity!

        • Charcoal is made by baking wood at a high temperature in an oven with a limited oxygen supply.

        • Coke is made by heat coal to a high temperature. Both contain a high % of the element carbon.

      • A reducing agent is a chemical agent that typically removes oxygen from a metal oxide ore to leave the free metallic element.

        • In the process the metal oxide is reduced by oxygen loss, which also equates to the metal ion gaining electrons - reduction e.g. CuO ==> Cu  or  Cu2+ + 2e-  ==> Cu

        • A reducing agent like carbon (C) or carbon monoxide (CO) can remove the oxygen from the oxide to leave the free metal (and forming carbon dioxide, CO2, in the process)

        • i.e. the reducing agent is oxidised by oxygen gain - so C ==> CO or CO2, or CO ==> CO2.

      • Metals below lead can be extracted using hydrogen as the reducing agent, those above copper can't.

    • The least reactive (unreactive) metals such as gold, silver and copper have been used for the past 10000 years because the pure metal was found naturally.

      • Their lack of chemical reactivity allows them to exist as the uncombined element.

      • Conversely, the more reactive a metal, the stronger it bonds to other elements like oxygen and sulfur. Therefore it is far less likely such a metal is found as the uncombined element AND the more reactive a metal the more difficult it is to extract from its ores AND more costly to extract it from the compounds the metal had formed over geological time.

    • blast furnaceModerately reactive metals like copper, iron, lead, tin have been extracted using carbon based smelting for the past 2000–4000 years.

      • This is possible because carbon is sufficiently reactive to displace these less reactive metals.

      • Any metal below carbon can theoretically be extracted from its oxide by heating with carbon (coke or charcoal).

      • Compounds of these less reactive are reduced by heating with carbon e.g. copper and silver.

      • Reduction is the loss of oxygen from a compound.

    • BUT it is only in the last 200 years that very reactive metals like sodium or aluminium have been extracted by electrolysis.

      • Electrolysis is required because carbon is NOT sufficiently reactive to displace these more reactive metals. Electrolysis doesn't even require a high voltage to split a metal from its molten ore.

    • In other words, our exploitation of metal mineral resources as developed and expanded as the technology of metal extraction has also developed and improved.

      • Therefore the economics of extraction may change over time with eg reduced costs by technological advances or increased by depletion of high grade ore reserves.

      • The depletion of high grade ore reserves has resulted in technology research  increasingly looking at ways of extracting metals from low grade ores which were previously uneconomic to use.

  • The crucial point is that generally speaking, the method of extraction depends on the metals position in the reactivity series.

  • The reactivity series of metals can be presented to include two non–metals, carbon and hydrogen, to help predict which method could be used to extract the metal.

    • lower Pt Au Ag Cu (H) Pb Sn Fe Zn (C) Al Mg Ca Na K higher in series

    • RULE: Any element higher in the series can displace any other lower element

    • reactivity

    • Notes on Reactivity Series of Metals & Metal Reactivity Experiments–Observations

    • Generally speaking, the more reactive a metal, the more difficult it is to extract.

      • This is because the more reactive a metal, the more strongly it combines with another non–metallic element like as oxygen or sulfur and therefore the oxide or sulfide is more difficult to reduce to the metal.

  • Although most metals occur as compounds, some metals are so unreactive that they do not readily combine with oxygen in the air or any other element present in the Earth's crust, and so can be found as the metal itself (sometimes referred to as 'native' metal).

    • For example, a metal, most frequently found as the uncombined metal is gold (and sometimes copper and silver) and no chemical separation is needed.

    • In fact all the metals below hydrogen can be found as the 'free' or 'native' element, though they occur mainly as compounds combined with non–metals like oxygen (oxide ion) or sulfur (sulfide ion) or the carbonate ion in their ores.

      • Therefore, for most metals, their naturally occurring compounds require processing via chemical reactions to obtain the free metals.


A summary diagram of important ideas to do with the reactivity series of metals!

Reactivity series of metals - method of metal extraction - relative ease of oxidation reaction with acids

  • At this point we need to say more about oxidation and reduction and redox reactions.

    • One definition of oxidation is oxygen gain.

      • Somewhere in the past aluminium combined with oxygen to form aluminium oxide, the main compound in bauxite ore from which aluminium is extracted.

      • aluminium + oxygen ==> aluminium oxide.

      • We would therefore say the aluminium was oxidised by oxygen gain.

      • Therefore to extract aluminium we must reduce it and remove the oxygen.

    • One definition of reduction is oxygen loss.

      • Copper ores are processed to give copper oxide from which copper may be obtained by a reduction process to remove the oxygen (reduction). This can be done by heating with carbon.

      • copper oxide + carbon ==> copper + carbon dioxide.

      • Here the copper oxide is reduced by oxygen loss, and the carbon is the 'oxygen remover' and is referred to as the reducing agent.

    • Similarly in a blast furnace, the iron oxide is reduced with carbon to free the iron from oxygen.

      • iron oxide + carbon ==> iron + carbon dioxide.

    • The method employed to extract a metal by a reduction process largely depends on its reactivity

    • See a separate page for a detailed discussion of oxidation - reduction ('redox') reactions

  • (c) doc bMetals below carbon in the reactivity series (see table on right) can be extracted by heating the oxide with carbon or carbon monoxide. The non–metallic elements carbon will displace the metals less reactive than carbon in a smelter or  blast furnace e.g. iron or zinc and metals lower in the series.

    • Therefore metals like iron, copper, tin, lead, zinc can readily be extracted by reaction–reduction of their e.g. oxides using cheap carbon (i.e. coke made from coal).

      • As described above, the carbon removes the oxygen from the metal oxide.

    • Iron ore is used to make iron and steel and iron is produced in a blast furnace by reducing iron oxides with carbon and it is the carbon that removes the oxygen from the iron oxides – the carbon is known as the reducing agent.

    • The metal copper can be easily extracted BUT copper–rich ores are becoming scarce so new methods of extracting copper are being developed to exploit low grade ores.

      • A low grade ore is one with low concentrations of copper and research is going on to try and exploit waste material left over from processing high grade ores.

    • Metals below hydrogen will not displace hydrogen from acids. Their oxides are easily reduced to the metal by heating in a stream of hydrogen, though this is an extraction method rarely used in industry.

    • In fact most metal oxides below carbon can be reduced when heated in hydrogen, even if the metal reacts with acid.

  • Metals above carbon in the reactivity series cannot usually be extracted with carbon or carbon monoxide.

  • So, metals more reactive than carbon are usually extracted by electrolysis of the purified molten ore or other suitable compound.

    • Electrolysis is the process of breaking down a compound using electrical energy and is needed to extract the most reactive metals.

    • The process of electrolysis uses of large amounts of energy in the extraction of these reactive metals and makes them expensive to produce.

    • The metal ions in the ore compound are forced by electrical energy into accepting electrons and producing free metal atoms.

      • Another definition of reduction is electron gain.

      • e.g. during the electrolysis of molten aluminium oxide the following reaction happens ..

        • aluminium ion (3+) + 3 electrons (–) ==> neutral and free aluminium atoms

        • Al3+ + 3e ==> Al

        • so, once again the metal ore compound is reduced to the metal, that is the positive metal ion in the ore is reduced to the metal by electron gain.

    • Aluminium is a very useful metal but expensive to produce.

    • e.g. aluminium from molten aluminium oxide or sodium from molten sodium chloride.

    • The ore or compound must be molten or dissolved in a solution in an electrolysis cell to allow free movement of ions (electrical current). The conducting melt or solution is called the electrolyte.  Theory given in the appropriate sections.

    • Because these reactive metals cannot be obtained by relatively cheap carbon reduction methods, their extraction tends to be more costly due to more specialised stages in the extraction process, more energy is needed (maybe costly electricity) and more costly specialist chemicals like a more reactive metal or chlorine (remember carbon–coke is relatively cheap e.g. as used in the blast furnace extraction of iron).

  • Other methods are used in special cases using the displacement rule.

    • A more reactive metal can be used to displace and extract a less reactive metal but these are costly processes since the more reactive metal also has to be produced in the first place!

    • Titanium is another very useful metal but expensive to produce.

  • Sometimes electrolysis is used to purify less reactive metals which have previously been extracted using carbon or hydrogen (e.g. see extraction of copper or zinc). Electrolysis is also used to plate one metal with another.

  • The demand for raw materials does have social, economic and environmental implications e.g. conservation of mineral resources by recycling metals, minimising pollution etc.

  • Metals can be mixed together to make alloys to improve the metal's properties to better suit a particular purpose.


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