Page 209 - Materials Chemistry, Second Edition

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Sustainable Industrial Design and Waste Management
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material is mainly indirectly heated by a combination of radiation and
conduction.
For both techniques a low density, very fluffy, crumbled aluminum foil
material is obtained. The decoated aluminum material is then remelted in
an electrically heated crucible furnace. High quality remelted aluminum is
produced which is suitable for the production of thin gauge foil.

Recycling of aluminum and polyethylene
A chemical process can be used to recover the aluminum content in the
aluminum/polyethylene residual obtained from the repulping process dis-
cussed in the previous section. The process involves the addition of toluene or
xylene solvents to the residual mixture contained in a crucible. The crucible is
then heated to a temperature of about 80°C. As the mixture is heated, the
toluene or xylene contained in the crucible causes the PE layer to separate from
the aluminum foil. The resulting aluminum and polyethylene materials can
be used further for recycling and the remaining solvent can be recovered.

Recycling of polyethylene
Alternative chemical processes are used to recover the polyethylene content
in the aluminum/polyethylene residual obtained from the repulping process
from milk packaging materials and produce aluminum compounds. The
obtained polyethylene material is washed and repelletized to be suitable for
producing recycled polyethylene products while the aluminum compounds
can be used in different industries. Three different chemicals will be used
independently to recycle polyethylene: hydrochloric acid, sulfuric acid or
sodium hydroxide.

Using hydrochloric acid
This process involves the addition of hydrochloric acid (HCl) to the residual
mixture. Diluted HCl is added to the PE/Al mixture. Hydrogen gas is pro-
duced as the aluminum content reacts with hydrochloric acid forming alu-
minum chloride. Polyethylene remains suspended in the resulting aqueous
solution of aluminum chloride. The polyethylene is obtained by filtering the
solution using filter paper.

Aluminum Hydrochloric acid : Aluminum chloride Hydrogen

2Al (s) 6HCl (aq) : 2AlCl 3(aq) 3H 2(g)

Using sulfuric acid
This process involves the addition of sulfuric acid (H 2 SO 4 ) to the residual mix-
ture. Diluted H 2 SO 4 is added to the PE/Al mixture. Hydrogen gas is produced