Kinetics of copper and cadmium cementation by zinc powder.

Abstract

The cementation of copper and cadmium by zinc powder was investigated in order to assess the influence of different parameters in the process. The results showed that the process follows a first order reaction with two stages in both systems. In the system Cu/Zn, the second stage is faster than the first while in the system Cd/Zn the second stage is slower than the first. In the system Cu/Zn, the variation on the surface area of copper cement followed a power law and a straight line was obtained by plotting –ln([Cu2+]/[Cu2+] 0 ) against t3/2, the activation energy was calculated as 16.3kJ. In the system Zn/Cd the surface area available for reaction decreased as a result of the cement agglomeration. On the experiments carried out with ions Cu2+ and Cd2+ in solution, purer copper cement was obtained when the experiments were carried out in the presence of less than stoichiometric amount of zinc powder and longer reaction times.