Page 654 - Materials Chemistry, Second Edition

CAT3525_C22.qxd 1/27/2005 1:00 PM Page 625
Electronics Waste 625
More than 3.2 million tons of electronics discards were disposed in landfills in the United States
in 1997. It is believed that most households and small businesses disposing e-wastes opt to send
them to landfills or incinerators rather than to recyclers. Landfilling and incineration of e-wastes
pose significant health and environmental hazards (see below).
Obsolete electronic equipment is also a concern because electronics are manufactured using
valuable resources such as precious metals, engineered plastics, and glass. The elemental break-
down of a personal desktop computer is listed in Table 22.3. When electronic equipment is disposed

TABLE 22.3
Elemental Breakdown of a Personal Desktop Computer

Element or Content Weight of % Recycling Use Location
Compound (% of Total Material Efficiency
Weight) (lb.) (Current
Recyclability)
Plastics 22.9907 13.8 20 Includes organics and oxides (other than silica)
Lead 6.2988 3.8 5 Metal joining, radiation shield/ CRT, PWB
Aluminum 14.1723 8.5 80 Structural conductivity/ housing, CRT, PWB, connectors
Germanium 0.0016 0.1 0 Semiconductor/ PWB
Gallium 0.0013 0.1 0 Semiconductor/ PWB
Iron 20.4712 12.3 80 Structural, magnetivity/ (steel) housing, CRT, PWB
Tin 1.0078 0.6 70 Metal joining/ PWB, CRT
Copper 6.9287 4.2 90 Conductivity/ CRT, PWB, connectors
Barium 0.0315 0.1 0 Vacuum tube/ CRT
Nickel 0.8503 0.51 80 Structural, magnetivity/ (steel) housing, CRT, PWB
Zinc 2.2046 1.32 60 Battery, phosphor emitter/ PWB, CRT
Tantalum 0.0157 0.1 0 Capacitors/ PWB, power supply
Indium 0.0016 0.1 60 Transistor, rectifiers/ PWB
Vanadium 0.0002 0.1 0 Red phosphor emitter/ CRT
Terbium 0 0 0 Green phosphor activator, dopant/CRT, PWB
Beryllium 0.0157 0.1 0 Thermal conductivity/ PWB, connectors
Gold 0.0016 0.1 99 Connectivity, conductivity/ PWB, connectors
Europium 0.0002 0.1 0 Phosphor activator/ PWB
Titanium 0.0157 0.1 0 Pigment, alloying agent/ (aluminum) housing
Ruthenium 0.0016 0.1 80 Resistive circuit/ PWB
Cobalt 0.0157 0.1 85 Structural, magnetivity/ (steel) housing, CRT, PWB
Palladium 0.0003 0.1 95 Connectivity, conductivity/ PWB, connectors
Manganese 0.0315 0.1 0 Structural, magnetivity/ (steel) housing, CRT, PWB
Silver 0.0189 0.1 98 Conductivity/ PWB, connectors
Antimony 0.0094 0.1 0 Diodes/ housing, PWB, CRT
Bismuth 0.0063 0.1 0 Wetting agent in thick film/ PWB
Chromium 0.0063 0.1 0 Decorative, hardener/ (steel) housing
Cadmium 0.0094 0.1 0 Battery, blue-green phosphor emitter/ housing, PWB, CRT
Selenium 0.0016 0.00096 70 Rectifiers/ PWB
Niobium 0.0002 0.1 0 Welding alloy/ housing
Yttrium 0.0002 0.1 0 Red phosphor emitter/ CRT
Rhodium 0 0 50 Thick film conductor/ PWB
Platinum 0 0 95 Thick film conductor/ PWB
Mercury 0.0022 0.1 0 Batteries, switches/ housing, PWB
Arsenic 0.0013 0.1 0 Doping agents in transistors/ PWB
Silica 24.8803 15 0 Glass, solid-state devices/ CRT, PWB
Source: Reproduced with kind permission of Microelectronics and Computer Technology Corporation, Austin, TX.