Chemsheets AS006 (Electron arrangement) 21/04/2017 www.CHEMSHEETS.co.uk METAL EXTRACTION © www.chemsheets.co.uk AS 080 10-Jul-12

ORES Most metals are found in compounds in the Earth’s crust. A rock containing enough of the metal for extraction to be profitable is called an ore. iron ore haematite Fe2O3 copper ore malchite CuCO3 titanium ore rutile TiO2 aluminium ore bauxite Al2O3 lead ore galena PbS

EARTH’S CRUST Metals have to be extracted by chemical reactions from compounds found in the crust.

EXTRACTION METHODS Methods 1) Reduction by heating with carbon 2) Reduction by electrolysis of melt 3) Reduction by active metal 4) Reduction by hydrogen Which method is used depends on 1) Energy requirements (heat, electricity) 2) Cost of reductants (C / active metal / electricity) 3) Purity of metal required © www.chemsheets.co.uk AS 080 10-Jul-12

ROASTING SULPHIDE ORES Ore is roasted in air e.g. ZnS + 3/2 O2  ZnO + SO2 Produces SO2 – causes acid rain To prevent this, SO2 is collected to stop it entering the atmosphere (and then used to make some H2SO4) © www.chemsheets.co.uk AS 080 10-Jul-12

ACID RAIN Damages plants

Branches from a tree in Germany's Black Forest show needle loss and yellowed boughs caused by acid rain

Kills fish

Damages some stones (e.g. limestone)

REDUCTION WITH CARBON Most metals can be extracted by heating with carbon. Many are not because: 1) Metal carbides may be formed (e.g. with Ti, W, Al) 2) Temperature required is excessively high (energy costs) © www.chemsheets.co.uk AS 080 10-Jul-12

BLAST FURNACE 1) C + O2 → CO2 2) C + CO2 → 2 CO Fe2O3 + 3 CO → 2 Fe + 3 CO2 Fe2O3 + 3 C → 2 Fe + 3 CO 4) CaCO3 → CaO + CO2 5) CaO + SiO2 → CaSiO3

BLAST FURNACE Pollution issues 1) CO2 formed – greenhouse gas 2) CO formed – toxic 3) SO2 formed (roasting of sulphide ores) – acid rain © www.chemsheets.co.uk AS 080 10-Jul-12

STEEL MAKING Impurities: C, P, S, Si 1) Inject powdered Mg to remove S (forms MgS – floats on surface and scraped off) 2) Scrap steel added to recycle 3) O2 blown through molten metal (converts C, P, Si to oxides, CO2 bubbles off) 4) Limestone added (decomposes to CaO) which reacts with P4O10 and SiO2 to form slag 5) Other metals and/or C added to make steel © www.chemsheets.co.uk AS 046 10-Jul-12

REDUCTION WITH CARBON Mn MnO2 + C  Mn + CO2 Cu 2 CuO + C  2 Cu + CO2 Malachite ore CuCO3  CuO + CO2

ELECTROLYSIS OF MELTS © www.chemsheets.co.uk AS 046 10-Jul-12

ACTIVE METAL REDUCTION Titanium is Low density Strong Corrosion resistant Replacement hip joints Nuclear reactors Aircraft

ACTIVE METAL REDUCTION Titanium must be very pure. Reduction with C forms TiC which is brittle. Electrolysis does not make it pure enough. © www.chemsheets.co.uk AS 080 10-Jul-12

Ti EXTRACTION 1) TiO2 + 2 Cl2 + 2 C → TiCl4 + 2 CO 2) Purify TiCl4 by fractional distillation TiCl4 + 4 Na → Ti + 4 NaCl TiCl4 + 2 Mg → Ti + 2 MgCl2 Expensive due to: High temperatures (high energy) Use of Ar Cost of Na/Mg (made by electrolysis) © www.chemsheets.co.uk AS 080 10-Jul-12

Wolframite (contains WO3) HYDROGEN REDUCTION Wolframite (contains WO3) Tungsten WO3 + 3 H2  W + 3 H2O C reduction would form WC (tungsten carbide)

RECYCLING METALS Advantages Disadvantages Lower energy cost Saves resources Less waste Less pollutants (e.g. CO2, SO2, CO) Preventing people throwing away Transport cost © www.chemsheets.co.uk AS 080 10-Jul-12

COPPER RECYCLING & EXTRACTION 1) Covert waste Cu to Cu2+(aq) – add H2SO4 or enzyme 2) Extract Cu from solution with Fe: Cu2+(aq) + Fe(s)  Cu(s) + Fe2+(aq) Useful for recycling scrap extraction from low grade ores