What Metal in a Computer Is Recyclable?
Obsolete or broken computers contain significant amounts of various metals, which can be recovered and recycled. In fact, electronic scrap from computer circuit boards has a high precious metal content and contains lower concentrations of harmful elements, such as arsenic, mercury and sulfur, than naturally occurring metal ores.
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Hazardous Metals
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A typical personal computer contains aluminum, cadmium, chromium, copper, gold, iron, lead, mercury and silver, among other metals. Some of these metals, including cadmium, chromium, lead and mercury, are listed as hazardous and cannot, under federal law, be incinerated or disposed of in community landfill sites.
Gold
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The printed circuit boards in a computer -- the flat plastic or fiberglass boards onto which circuits and components are etched and soldered -- contain the highest concentration of precious metals. According to the United States Geological Survey, one metric ton of circuit boards contains between 80 and 1,500 grams of gold, or more gold than that recovered from 17 tons of gold ore. The gold in a single obsolete computer has little intrinsic value, so the gold from many computers must be collected, concentrated and refined. It is typically possible to recover and recycle 99 percent of the gold contained in a printed circuit board, although the process becomes more difficult as electronic products become smaller and smaller.
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Copper
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One metric ton of printed circuits boards also contains between 160 and 210 kilograms of copper, or between 30 and 40 times the concentration of copper contained in the type of copper ore mined in the United States. Copper is typically recovered by smelting it into liquid copper and refining in an electrolytic cell, in which impure copper is used as the positive electrode, or anode, and refined copper is deposited on the negative electrode, or cathode.
Lead
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Lead is found in the soldering of printed circuit boards and in the glass of cathode ray tube, or CRT, computer monitors; a single CRT computer monitor can contain more than 3 kilograms of lead. The glass from CRT computer monitors is typically crushed in a rotating hammer mill, metal is pulled from the mixture with a magnet and the lead-contaminated glass is shipped to a lead smelter, or blast furnace. The glass is used as fluxing agent -- a material used to lower the melting point -- in the processing of lead ore, and the lead becomes part of the raw materials for new products, such as new CRTs, X-ray shielding and batteries.
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References
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