Recovery of base and precious metals from computer circuit board scrap

Scrap generated from the manufacture of electronic hardware and the discarding of obsolete computers, printed circuit boards or connectors can provide a source of precious metals. These metals are recovered by exposing the scrap to a leaching solution to separate the chips from the boards. The chips are crushed to liberate the metals. The base metals are dissolved by leaching. The remaining solid constituents are leached with aqua regia. The impure gold sponge is precipitated by adding ferrous sulfate, while platinum is recovered as ammonium chloroplatinate.; The metal nitrate filtrate from the first two leach stages is treated to precipitate an impure silver chloride product which is dissolved and reprecipitated as silver chloride. After copper cementation, sulfuric acid is added to precipitate metal sulfates. Water washing the precipitate leaves high purity lead sulfate. Iron is removed as a crystalline, coarse hydroxide. After filtration, the purified solution is treated to precipitate nickel oxalate. Finally, the remaining contaminants are precipitated as hydroxides. (Abstract shortened by UMI.)...