A study of factors influencing the kinetics of copper cementation during atmospheric leaching of converter matte
The kinetics of copper cementation during atmosphere leaching of a Ni-Cu matte in CuSO4-H2SO4 solution was studied as a function of initial copper ion concentration, initial acid concentration, temperature, stirring rate, particle size distribution and pulp density. It was found that all these process variables influenced the rate of cementation. A two-stage rate of reaction was observed in most of the experiments, with the rate of cementation in the initial stage being slower than that of the subsequent second stage. The increased rate of cementation in the second stage was attributed to the enhancing effect of the surface deposit. The cementation process was found to take place by two different rate-controlling mechanisms. At a temperature range of 50i?½70i?½C, an activation energy of 74.6 kJ/mol was obtained, indicating a surface reaction controlled process. At higher temperatures (70i?½80i?½C) a lower value of activation energy was observed (18.2 kJ/mol), indicative of a process controlled by diffusion through surface layers. The structural characteristics of the cemented deposit could not be determined in the investigated system where the deposit was mixed with the leach solid residue.
A kinetic study of the cementation of copper from sulphate solutions onto a rotating aluminum disc
Abstract The cementation kinetics of copper deposition from sulphate solutions onto aluminum was studied using a rotating disc electrode system. The effect of temperature, Cu++ ion concentration, rotational speed of the aluminum disc and pH was investigated. The activation energy was found to be 14.1 kJ mol−1, confirming that the rate of reaction was controlled by diffusion.
Silver cementation from chloride solution using rotating disks of copper and lead
Abstract The kinetics of silver cementation from 3.0 M NaCl-0.3 M HCl solution on to rotating discs of lead and copper were examined. Comparison of the experimental data with a convective diffusion model of rate control incorporating reactant depletion indicated that the copper system behaved nearly as predicted whereas the lead system showed an enhanced rate of silver cementation under the same conditions. Optical microscopy and SEM analysis of the cement products suggests that the different silver morphologies obtained on copper and lead may be responsible for the differences in the rate behaviours.