کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
213647 | 462120 | 2006 | 10 صفحه PDF | دانلود رایگان |
![عکس صفحه اول مقاله: Kinetic mechanisms of cementation of cadmium ions by zinc powder from sulphate solutions Kinetic mechanisms of cementation of cadmium ions by zinc powder from sulphate solutions](/preview/png/213647.png)
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.
Journal: Hydrometallurgy - Volume 84, Issues 3–4, November 2006, Pages 155–164