Recovery of Gold and Silver from an Incinerated Spent Printed Circuit Board Using Chlorination

Abstract

We studied an efficient recovery process for precious metals from secondary resources. The release behaviors of gold and silver were investigated during the heat treatment of an incinerated spent circuit board in a stream of chlorine gas. When the incinerated ash alone was heated in a stream of chlorine, a temperature of 1000°C was required to completely volatilize the gold and silver in the sample. However, the temperature required for the initial release of gold and silver decreased when a mixture of the incinerated spent printed circuit board and carbon particles was heated in a stream of chlorine, and fractions of these metals were captured by the carbon particles. The amounts of gold and silver captured by the carbon particles decreased when the temperature increased above 800°C. To completely volatilize the gold and silver from the sample and to ensure their capture by the carbon particles, the sample was heated to 1000°C in chlorine gas, and the volatilized chlorides were passed through a bed of carbon particles, which was maintained at 800°C. The total amounts of gold and silver from the incinerated printed circuit board were successfully recovered by adjusting the temperature and thickness of the bed of carbon particles.