Coprecipitation of Au(III) Complex Ions with Iron(III) Hydroxide and Their Spontaneous Reduction

For recovery of gold from wastes of electronic products, it is necessary to concentrate Au(III) complex ions from solution and to reduce them to elemental Au (Au(0)). To develop the recovery system, the coprecipitation of Au(III) complex ions with iron(III) hydroxide as a concentration procedure and their spontaneous reduction to elemental gold (Au(0)) were investigated as a function of iron concentration, pH and electrolyte concentration at ambient temperature. Most of the Au(III) complex ions were coprecipitated with iron(III) hydroxide around neutral pH, at low Cl concentration and even at low iron concentration. Under the condition, the coprecipitated Au(III) complex ions were spontaneously reduced to Au(0) even in the absence of a specific reducing agent, and 1 - 5 μm gold particles in size were formed. Finally this method was applied to recover gold from electronic devices of cellular phone.