PRESENTATION OF ALUMINIUM: FROM ITS EXTRACTION TO ITS USE IN THE MANUFACTURING OF SMARTPHONES - Video commentary

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PRESENTATION OF ALUMINIUM:
FROM ITS EXTRACTION TO ITS USE
IN THE MANUFACTURING OF
SMARTPHONES
Video commentary

Presentation of aluminium: from its extraction to its use in the
               manufacturing of smartphones
Link to the video
https://www.youtube.com/watch?v=aE1lkxu4BBY

Content
This paper is aimed at teachers as a tool to be incorporated into lessons. It consists of a video and
supporting commentary. Teachers can use them as a prompt to introduce the principal aspects of aluminium
production, following its journey from how it is extracted from the ground, through to how it can be used to
manufacture a smartphone.

Source
Maxime Evrard, GeMMe Laboratory at the University of Liège, December 2017

Duration: 1 minute 54

General introduction
This video could be shown during a geography or chemistry class. It looks at the question of aluminium and
in particular how it is extracted and produced.

This activity constitutes a good introduction to a more in-depth study of different materials, whether as part
of geography, physics, chemistry or geology.

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Aluminium: from its extraction to its use in the manufacturing of smartphones           February 2018

Teacher’s Guide
Presentation of the video before watching
You are about to watch a short video about aluminium which follows a typical journey for aluminium
(although there are other possible journeys) from being extracted through to how it can be used to
manufacture mobile phones.

Nowadays, aluminium is considered an everyday product which can be used, for example, to keep food
fresh. It has not always been seen this way. The first time aluminium was produced was in the mid-19th
century. At the time, it was considered on a par with silver; a precious metal which could be used to make
jewellery, for example. It was only after the Second World War that it began to be used to manufacture
products on an industrial scale. Despite being used very widely, aluminium extraction and processing are
still extremely energy-intensive practices. Therefore, we cannot afford to misuse them.

Video commentary
Timing: 0 to 25 seconds. Presentation of aluminium and the Weipa Mine (Australia).
Aluminium is not as such found in nature but appears in the form of aluminium hydroxide (AIOOH) which is
a dominant mineral in a rock known as bauxite. For a deposit to be economically viable, the rock extracted
from the mine must be made up of at least 45% alumina (Al2O3).

These conditions are mainly found in tropical soils (abundant rainfall and humidity result in a higher residual
concentration of aluminium in rocks due to the leaching of other chemical elements such as Mg, Na, K, Si…
composing the initial rock) like in Weipa, in Northern Australia. At the mine, the bauxite is crushed and rinsed
before being transported.

Timing: 26 to 42 seconds. Processing of aluminium concentrate.

                              Figure 1: Process of turning bauxite into aluminium

The crushed bauxite is then sent to Western Australia to be treated using the Bayer Process which turns
aluminium hydroxide into an alumina concentrate.

The bauxite rock containing aluminium hydroxides is dissolved using caustic soda (NaOH) under high
pressure (5 bars) and temperature (140°C). The mixture is then filtered to remove any impurities that have
not been dissolved. The residue is called red mud because it contains mostly iron oxides and it is stored in
huge dams which are formed and monitored by the plant (= artificial red lakes on the satellite imagery).

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Aluminium: from its extraction to its use in the manufacturing of smartphones         February 2018

Timing: 43 seconds to 1 minute 07. To the aluminium ingot.
At this stage, aluminium is in the form of a soluble compound (NaAlO2). The solution is heated up and
transferred into large cells where the warm solution cools down and precipitates in the form of very fine
aluminium oxide crystals (Al2O3). These are then filtered and sent to electrolysis to make metallic aluminium.

 To delve even further – electrolysis
 The process consists of reducing by electrolysis the alumina dissolved in a cryolite bath (aluminium and
 sodium double fluoride – AlF3, 3NaF) melted to approximately 950°C, in a tank through which a strong
 electric current is passed.
 When subjected to this constant electric charge (always travelling in the same direction), the ions are
 transported between the two electrodes.
 The positive electrode, the anode, where the current comes in, attracts the negative ions, the oxygen (O2-
 ). The anode is placed at the top of the tank where the electrolysis takes place; this releases the oxygen in
 the form of gaseous CO2, after having burned off the carbon which forms the anode.
 The negative electrode, the cathode, where the current goes out, attracts the positive ions, the (Al3+). The
 cathode is located at the bottom of the tank where the aluminium that is heavier than the bath is deposited
 and stays in the form of a liquid layer.
 The global phenomenon can be translated by the reaction: 2 Al2O3 + 3 C = 4 Al + 3CO2

This is an extremely energy-intensive process (15kWh per kg of Al) which is why the aluminium electrolysis
is operated in countries where energy is less expensive because of abundant oil and gas reserves (the plant
in this case is in Dubai) or renewable energies (ex. Iceland).

Timing: 1 minute 07 to 1 minute 32. From the aluminium ingot to its use in industry.
Once transformed into ingots, aluminium is shipped to the four corners of the globe to the various
factories where it is used as a raw material. Aluminium has broad and varied uses. Here it is being used
in the manufacturing of smartphone casing in a Chinese factory.

Timing: 1 minute 33 to 1 minute 54. The smartphone.
From the moment of its extraction to the time the phone arrives on the European market, aluminium has
travelled across almost 4 continents.

Furthermore, it is just one of several elements that go into making our phones. It is estimated that about
forty extraction sites in the four corners of the planet are needed to extract the elements that make up our
smartphones.

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Aluminium: from its extraction to its use in the manufacturing of smartphones             February 2018

To delve even further. The formation of aluminium.
Aluminium ore (bauxite) is formed by intense atmospheric weathering of a “lambda” rock which naturally
contains aluminium. This source rock may be a granite, a sandstone or even an impure limestone. This type
of alteration is unique to the humid climates of tropical areas, alternating between dry seasons and very
humid seasons.

This is how granite is made up of several minerals such as orthoclase (KAlSi3O8), anorthosite (Ca Al2Si2O8),
quartz (SiO2), biotite K(Mg,Fe)3(OH,F)2(Si3AlO10) or muscovite KAl2(AlSi3O10)(OH,F)2.

The intense alteration (or total hydrolysis) of orthoclase translates into the leaching of minerals less resistant
to dissolution such as those containing K and Si, thus increasing the residual concentration of Al-hydroxides
(Gibbsite, Boehmite, Diaspore). This is the reaction:

  (Si3Al)O8K       +       16 H2O          ----------------------->     Al(OH)3      +           (K+, OH-)

      orthose      +         water                                       gibbsite             scrubbing solution

The same reasoning can be applied for anorthosite and muscovite.

The leaching of a rock causes many different soil horizons (= “layers” in the soil) to appear in which the soil
is the uppermost layer (figure 1). In the case of lateritic profiles of aluminium deposits, the bauxite is the
“rock layer” found between the initial source rock (= our granite, for example) and the ferricrete crust found
underneath the soil (figure 1). This horizon can run to over 100m deep in places.

          Figure 2: 3 alteration profiles causing deposits of bauxite (Al) and nickel to form

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Aluminium: from its extraction to its use in the manufacturing of smartphones   February 2018

 This activity has received funding from the European Institute of Innovation and
                                   Technology (EIT),
   a body of the European Union, under the Horizon 2020, the EU Framework
                      Programme for Research and Innovation.

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