Catalytic effect of Ag+ and Cu2+ on leaching realgar (As2S2)

The catalytic effect of Ag+ and Cu2+ on the dissolution of realgar was studied. In the absence of these catalysis ions, little realgar can be leached by Fe3+ either with or without bacteria. Silver ion can enhance the chemical leaching and bioleaching rate remarkably, while the catalytic effect of copper(II) ion was not so obvious. The catalytic mechanism of Ag+ and Cu2+ was similar: the surface arsenic was replaced by the formation of Ag2S or CuS, which was then dissolved by Fe3+. With Ag+ added, the influences of concentration of Fe3+ and temperature on chemical leaching were also investigated.

Research highlights
► Little realgar can be leached by Fe3+ without catalyst.
► Ag+ can enhance the leaching rate greatly and copper ion was not so obvious.
► High concentration of Ag+ can decrease the leaching rate at lower temperature, but high temperature can eliminate the inhibitory effect.
► Highest leaching fraction was achieved at 60 °C.
► Leaching rate can be increased with increasing Fe3+ concentration.