Recycling critical raw materials from waste electronic equipment

Recycling critical raw materials
from waste electronic equipment
Based on these data, the following quantitative estimates can be made:
Table 6: Estimated mean weights of rare earth metals in LCD displays with CCFL background
illumination
Yttrium
[mg]
Europium
[mg]
Lanthanum
[mg]
Cerium
[mg]
Terbium
[mg]
Gadolinium
[mg]
Notebooks 1.8 0.13 0.11 0.076 0.038 0.011
Monitors 16.0 1.20 1.00 0.680 0.340 0.095
Televisions 110.0 8.10 6.80 4.500 2.300 0.630
Newer LCD monitors are sometimes already fitted with background illumination based on
white LEDs (see Section 5). In 2010 the market share of LCD monitors and LCD televisions
fitted with LEDs was around 30% whereas around 90% of all new notebooks were already
equipped with LED background illumination (Young 2011). Like CCFL tubes, white LEDs
also make use of a luminescent substance which converts the short-wave light produced in
the LED into the visible spectrum. The support matrix is usually made from yttrium aluminum
garnet (YAG) with substantial admixtures of gadolinium. The doping consists of a few
percent by weight of cerium and sometimes europium. The actual LED semiconductor chip
which produces the light is composed of indium gallium nitride (see also Section 5.1). This
results in a somewhat different composition for the rare earths in LCD monitors, LCD
televisions and notebooks with LED background illumination in comparison to Table 6, as
shown in Table 8 (indium and gallium are included in this list). This table makes use of the
proportions of critical metals in white LEDs specified in Table 7 (see also Table 30 in Section
5.1). The number of white LEDs in a monitor required for the projection is a quantity which
varies depending on the manufacturer and can therefore only be estimated for a general
survey. Based on model data in Young (2011), estimates of 100 LEDs for an LCD PC
monitor, 150 LEDs for an LCD television and 50 LEDs for a notebook display have been
made (see Table 7).
7