Recycling critical raw materials from waste electronic equipment

Recycling critical raw materials
from waste electronic equipment
obtained, some with good recovery rates, other critical metals such as tantalum are lost in
this process (see Section 6.1). Successful recovery of tantalum would require a prior
separation and removal of the tantalum capacitors which is currently only carried out on a
pilot scale by a very few companies (see Section 6.5).
For the mechanical pre-treatment and sorting processes in general it should be noted that
these are only able to separate the complex intermix of materials in a very inadequate
manner, so that many components containing important resources are only partially sorted
into the correct fractions. This leads to high losses of critical raw materials 27 . For one
shredding company which can be viewed as fairly representative, Chancerel & Rotter (2009)
have shown that, in the mechanical treatment process, 74.4% of the gold and palladium and
88.5% of the silver end up in fractions from which precious metals cannot be recovered. If it
is assumed that more careful pre-treatment methods are used in some plants (e.g. manual
removal of the motherboard), then losses of precious metals can be estimated at
approximately 70%.
Due to their data content, special attention is often paid to the disposal of hard disk drives
which are of particular importance for raw materials. Customers often make a guaranteed
deletion of data as one of the terms of contract for the waste disposal company. Data can be
deleted either using software, with strong magnetic fields or by physical destruction
(shredding) of the storage media. However, it can be assumed that a certain percentage of
hard disk drives are treated as a separate waste stream.
A significant point concerning the recovery of critical raw materials from hard disk drives is
that the fractions of importance for raw materials (incl. PCBs and magnets) are difficult to
separate from the other material (incl. stainless steel and aluminum). This is mainly due to
the very compact design and the use of a wide variety of different screws. In addition, as well
as the screw connections, the cover on the hard disk drive (usually made from stainless
steel) is firmly glued to the aluminum housing. The consequence of this is that it is very labor
intensive to manually open the hard disks and separate the components containing important
raw materials into different types, and the process can only be mechanized to a certain
extent. The PCBs are the easiest to remove as in most cases these are screwed onto the
underside of the hard disk drive from outside and can therefore be dismantled without
opening the cover.
Possible stages which could be mechanized include the following measures:
27 Losses occur primarily at the interface between the pre-treatment and the refining processes. If raw material
fractions of importance such as fragments of assembled PCBs are sorted into other fractions (e.g. aluminum
or steel), then the precious or special metals in them are lost by dissipation in the downstream refining
process.
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