Kinetic mechanisms of cementation of cadmium ions by zinc powder from sulphate solutions
2006 (English)In: Hydrometallurgy, ISSN 0304-386X, Vol. 84, no 3–4, 155-164 p.Article in journal (Refereed) Published
The cementation of cadmium ions by zinc powder was studied in a batch reactor at low and high concentrations at pH 5.2–5.4 and it is shown that the reaction is first-order. XRD and SEM analysis confirm that the deposited layer is metallic with no evidence of basic zinc sulphate or re-dissolution of cadmium. Dependence of the reaction constant on initial cadmium concentration proves the reaction mechanism. Different possible kinetic controlling models of cadmium ion (Cd2+) cementation from aqueous solution by zinc powder were studied with respect to initial cadmium concentration, temperature, zinc powder size and stoichiometric ratio. The experiments demonstrate that at initial cadmium concentrations > 1000 ppm, the ash diffusion control model prevails, while at concentrations < 500 ppm, the data has good agreement with the film diffusion model. For concentrations between 500 ppm and 1000 ppm, a combination of ash diffusion and film diffusion models controls the reaction rate. Based on numerical analysis, the calculated activation energies at high and low concentrations are 9.6 and 7.2 kJ/mol, respectively. Statistical data analysis was performed and different reaction rate constants were estimated from the equations for high and low initial cadmium concentrations.
Place, publisher, year, edition, pages
2006. Vol. 84, no 3–4, 155-164 p.
Cadmium cementation, Kinetics, Zinc powder, Mechanism
Metallurgy and Metallic Materials
IdentifiersURN: urn:nbn:se:uu:diva-242775DOI: 10.1016/j.hydromet.2006.05.005OAI: oai:DiVA.org:uu-242775DiVA: diva2:785037