Carbothermal recovery of zinc from brass ash

Brass ash of composition (wt-%) 59(.)67Zn-9(.)22-Cu-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 (950-1200degreesC) and time (15-180 min) were varied. At 1200degreesC 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 all activation energy of 90(.)1 kJ mol(-1). Subsequently the development of a sintering structure caused the reaction mechanism to change to diffusion control.