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.
Copper cementation on nickel discs
AbstractThe cementation of copper on various types of nickel discs has been studied in dilute cupric sulphate solutions. Activation of the cathode nickel discs with Te+4 was necessary to achieve reproducible rates, whereas satisfactory results were obtained with mint nickel discs using only a chemical polishing treatment Attempts to cement copper on discs of nickel-copper alloys were unsuccessful.The cementation process on pure nickel takes place by two different rate-controlling mechanisms. At low temperatures the process is probably controlled by a surface reaction, whereas at higher temperatures the process is probably controlled by diffusion through surface layers. When the acidify of the solution is increased, the cementation rate increases. The rate decreases with increasing thickness of the cemented deposit. Resume Le depot de cuivre sur divers types de disques de nickel a ete etudie en solution diluee de sulfate cuivrique. Afin d'obtenir des taux reproductibles il a ete necessaire d'activer les di...
Effect of precipitant surface roughness on cementation kinetics
Abstract Empirical correlation equations for the cementation of cadmium on zinc, of copper on zinc and of copper on cadmium have been developed. For each of the three different systems when the cementation reaction is carried out under an inert atmosphere using a rotating disc geometry under laminar flow conditions, the correlation equation in the initial stage follows the Levich expression written in dimensionless form: Sh = 0.62 (Re)0.5 (Sc)0.333 For the enhanced rate period, the data were correlated by Sh = A (Re)0.74 (Sc)0.29 The constant A depends on the actual deposit morphology and has the values of 0.37, 0.15 and 0.11 for the cadmium/zinc, copper/zinc and copper/cadmium precipitation systems when the deposition is from dilute aqueous solutions.