Carbothermal recovery of zinc from brass ash

Brass ash of composition (wt-%) 59-67Zn-9-22Cu-1.45Pb-2-61SiO ₂-0-36Cl was treated by carbothermal reduction in a temperature controlled tube furnace. The aim of the work was to collect zinc in the form of metal and/or zinc oxide in the gaseous phase. Treatment temperature (950-1200°C) and time (15-180 min) were varied. At 1200°C and 60 min, recovery of zinc was 92.5% and zinc content in the remaining residue was found to be 12.8 wt-%. Kinetic analysis of the experimental results showed that initially the reaction was under chemical control with an activation energy of 90.1 kJ mol^-1. Subsequently the development of a sintering structure caused the reaction mechanism to change to diffusion control.