From copper carbonate ores ... The ore can be roasted to concentrate the copper as its oxide. Water is driven off and the carbonate thermally decomposed. copper(II) carbonate ==> copper oxide + carbon dioxide CuCO 3(s) ==> CuO (s) + CO 2(g) The oxide can be smelted by heating with carbon (coke, charcoal) to reduce the oxide to impure copper , though this method isn't really used much these days (the 'bronze age' method archaeologically!). copper(II) oxide + carbon ==> copper + carbon dioxide 2CuO (s) + C (s) ==> 2Cu (s) + CO 2(g) The carbon acts as the reducing agent – the 'oxygen remover'.

From copper sulfide ores ... These include chalcocite /chalcosine = copper(I) sulfide Cu 2 S and covellite = copper(II) sulfide CuS and chalcopyrite CuFeS 2 . which is one of the most important ores for the extraction of copper. This can be roasted in air to produce copper(I) sulfide which is roasted again in a controlled amount of air so as not to form a copper oxide (see below). 2CuFeS 2 + 4O 2 ==> Cu 2 S + 3SO 2 + 2FeO Copper sulfide ores can be rapidly roasted in heated air enriched with oxygen to form impure copper and this extraction process is called ' flash smelting ' and is the most widely used and efficient method of copper extraction. Nasty sulfur dioxide gas is formed, this must be collected to avoid pollution and can be used to make sulfuric acid to help the economy of the process. copper(I) sulfide + oxygen ==> copper + sulfur dioxide Cu 2 S (s) + O 2(g) ==> 2Cu (s) + SO 2(g) or copper(II) sulfide + oxygen ==> copper + sulfur dioxide CuS (s) + O 2(g) ==> Cu (s) + SO 2(g)

It is also possible to dissolve an oxide or carbonate ore in dilute sulfuric acid and extracting copper by .... (1) using electrolysis see purification by electrolysis below, or (2) by adding a more reactive metal to displace it e.g. scrap iron or steel is used by adding it to the resulting copper(II) sulfate solution. iron + copper(II) sulfate ==> iron(II) sulfate + copper Fe (s) + CuSO 4(aq) ==> FeSO 4(aq) + Cu (s) It is possible to spray acid onto copper ore waste and leach out the copper compounds prior to electrolysing the solution or displacing the copper with a cheap metal like iron AND this can also be achieved with the help of bacteria for particular ores – see below.

No industrial process is ever 100% efficient, and metal extraction processes of create lots of waste material AND, crucially, that waste may contain some of the desired metal, or indeed other potentially valuable metals. So, any method that can extract the small percentages of valuable metals from waste will aid the economy of production of the main product. For example, 10% of the copper produced in the US is derived from bacteria which feed of chalcopyrite CuFeS 2 (this could be waste or very low grade ores ??). The bacteria use the Fe 2+ ion and S 2– ion to obtain energy needed to live. The redox chemistry of the bacteria via the oxygen from air involves the ... oxidation of Fe 2+ to Fe 3+ and S 2– to SO4 2– reduction of O 2 to H 2 O overall an energy releasing process to sustain the bacteria. We use sugar, these bacteria use chalcopyrite! – I don't think we'd like the taste! – The bacteria effectively break down the chalcopyrite, releasing copper(II) ions into an acid solution. The optimum conditions for this ' bacterial leaching ' are pH 2–3 and 20 o C–55 o C. Extracting copper in this way is cheaper, quieter, and less polluting than conventional smelting processes. BUT, it is much slower, so it is primarily being used on waste dumps by spraying dilute acid on them and the aerated water slowly percolates through rock fragments and their naturally occurring bacterial colonies. The leached solution of copper(II) ions is very dilute. The solution is concentrated and Cu 2+ ions separated from other ions e.g. Fe 3+ The copper is displaced using cheap scrap iron. The copper is then further purified by electrolysis – described below.

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