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Zinc: High Demand Metals

Decent Essays
The world’s future metal, Zinc.

Half of the world's top ten worst pollution problems are mining related. This report will investigate the extraction processes of high demand metals, such as zinc, iron and aluminium, and the energy demands, chemical processes and costs of each metal. It will also discuss which metal is the most environmentally healthy, and find possible alternative extraction techniques.

Zinc
Zinc is used in many everyday objects, such as batteries. Zinc uses two main methods to extract from the ore, electrolytic refining and smelting, but electrolytic refining is a much more widely used method.

Electrolysis
The electrolysis of zinc is the process of purifying the ore. The electrolysis speeds up the decomposition of zinc
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Many chemical reactions take place in this furnace, and allowing the iron to be tapped. Iron ores are mainly iron oxides, allowing them to be extracted by heating them with carbon in the form of coke.

At the high temperatures at the bottom of the furnace, carbon reacts with carbon dioxide to produce carbon monoxide. This is the main reducing agent in the furnace.

In higher temperatures, the carbon itself can also act as a reducing agent.

The temperature of the furnace is hot enough to melt the iron which trickles down to the bottom where it can be tapped off.

As the iron oxide is not purely iron, there are other minerals in the ore, which would not melt in the temperatures of the furnace, resulting in a clog. Limestone is added to convert this into slag, which melts and runs to the bottom. The furnace’s temperatures decomposes the limestone to create calcium oxide. (ChemGuide,
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Endothermic Reactions
Endothermic reactions take energy in from its surrounding. (BBC, 2014) The opposite reaction, an exothermic reaction, releases heat due to a chemical reaction and gives energy. For a reaction to be endothermic, the enthalpy of the product must be higher than that of the reactants. (ChemWiki, 2015)

Aluminium
Aluminium is the most plentiful metal on earth. Despite its abundance, it is one of the most expensive, due to the large amount of electricity used in the extraction process. As aluminium’s melting point is 2000°C, molten cryolite is used to melt the aluminium in preparation for electrolysis. Aluminium ore is called bauxite ore, and for the bauxite ore to be prepared for extraction, it must be processed into aluminium oxide for pure aluminium to be extracted. This uses the Bayer process, where the crushed bauxite ore is treated with a moderately concentrated sodium hydroxide solution. (ChemGuide, 2014)

(Cell for Aluminium Extraction)

The electrolysis process is a redox reaction. The aluminium is reduced, leaving behind pure aluminium at the cathode. The oxygen laced in the aluminium ore is then harvested at the anode, and it is oxidised. This redox reaction is what allows the aluminium to be processed to be ready for casting. (BBC,
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