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Purification of aluminium from Bauxite

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Introduction

Purification of aluminium from Bauxite http://upload.wikimedia.org/wikipedia/commons/thumb/b/bf/Bayer-process-en.svg/500px-Bayer-process-en.svg.png Key features of the production process * First, we have the crushing stage which enables people to separate the metal-rich ore from the other rocks that are attached to it * The ore is roasted sometimes which helps remove sulphur * The metal goes through electrolysis to be able to extract the aluminium. But first is melted through molten cryolite so that the electricity can be able to pass through it. This is done to in order to ease the melting of the aluminium because it has a really high melting point of 660.3 °C because of the strong bonds between atoms. If it was to by processed without cryolite if would take too much electricity which would be a waste. * The metal is finally extracted; it can be cast and rolled. Sometimes other metals are added to it while it is molten in order to make alloys with useful properties. ...read more.

Middle

So the temperature increases very quickly. The carbon dioxide then reacts with hot carbon to make carbon monoxide. The carbon monoxide is really important because it is this chemical that reduces the iron to the final iron metal. Iron Iron is not a very reactive metal, so, because its position in the reactivity series of metals, iron can be extracted using carbon in a blast furnace because iron is below carbon (iron is less reactive than carbon). Therefore, iron can be displaced from its e.g. its oxides, by heating with the theoretically 'more reactive' carbon in a sort of displacement reaction. Iron is a good electricity and heat conductor with a boiling point of 2861° and a melting of 1,538° at this melting point, the iron is soft enough to be turned into many other objects with the help alloys. When mixed with alloy, it can be used to manufacture things like metal pans, scissors etc... ...read more.

Conclusion

We purify the solution by filtering off the solid impurities. Originally, the alkaline solution was cooled and treated by bubbling carbon dioxide into it, through which aluminium hydroxide precipitates: 2 NaAlO2 + CO2 → 2 Al (OH)3 + Na2CO3 + H2O But later, this gave way to seeding the supersaturated solution with high-purity aluminium hydroxide (Al(OH)3) crystal, which helped removed the need for cooling the liquid and was more economically feasible: 2 H2O + NaAlO2 → Al(OH)3 + NaOH Then, when heated to 980°C (calcined), the aluminium hydroxide decomposes to aluminium oxide, giving off water vapour in the process: 2 Al(OH)3 → Al2O3 + 3 H2O The left-over NaOH solution is then recycled. This, however, allows gallium and vanadium impurities to build up in the liquors, so these are extracted. For bauxites having more than 10% silica, Bayer process becomes infeasible due to insoluble sodium aluminium silicate being formed, which reduces yield, and another process must be chosen. A large amount of the aluminium oxide so produced is then subsequently smelted in the Hall–Héroult process in order to produce aluminium. http://www.webqc.org/balance.php?reaction https://answers.yahoo.com/question/index?qid=20100616195013AAo9hQb ...read more.

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