A.A.Taha*

Department of Chemistry, Faculty of Science, University of Alexandria, Alexandria, Egypt.

Received 12 December 2002; accepted in revised form 2 March 2004

Abstract

The rate of copper II/zinc cementation from copper sulphate solutions in the absence and in the presence of methanol (CH₃OH) and dimethyl sulphoxide (DMSO) has been studied and the reaction was found to follow first-order kinetics. The influence of several parameters on the course of the reaction, such as cylinder rotation speed, initial concentration of Cu²⁺ ions, temperature and concentration of organic solvent, was investigated. In the case of CH₃OH, rotating zinc cylinder was used, while in the presence of DMSO stationary zinc sheet and rotating zinc cylinder were used. It was found that (1) the percentage inhibition caused by methanol ranged from 10.70 to 58.38 depending on the concentration of the alcohol used; (2) the rate of cementation in the presence of DMSO using rotating zinc cylinder > the rate of cementation in the presence of DMSO using stationary zinc sheet; (3) the rate of cementation on zinc cylinder in the presence of DMSO < the rate of cementation in the presence of CH₃OH. Different reaction conditions, and the physical properties of solutions are studied to obtain dimensionless correlation among all these parameters. Thermodynamic parameters ΔS*, ΔH* and ΔG* were studied.

Keywords: Cementation, methanol, dimethyl sulphoxide, rotating zinc cylinder.

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*Corresponding author. E-mail address: vegfruexp@yahoo.com