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The Kinetics of Chlorine Evolution on Dimensionally Stable Anode (DSA) Used in the Chlor-Alkali Industry

Maryam Vahdati mohaddes, Petrochemical Research & Technology Company, Tehran, Iran, Mandana Akia, chemical engineering department, Iran university of science&technology, Petrochemical Research & Technology Company, Tehran, Iran, and Marzieh Hamidzadeh, Petrochemical Research & Technology Company, Petrochemical Research & Technology Company, Tehran, Iran.

The anodic oxidation of chloride in an acid aqueous media on the DSA leads to the chlorine evolution reaction (ClER) [1]. In our research , we investigate the ClER kinetics by means of Voltammetric curves, Tafel lines and reaction order determinations.

The typical structure of electrodes (DSA) used in kinetic studies consists of a flat support (Ti) Coated with a thick layer of metal oxides from Permascand Company as an industrial electrode. A convenient method with three electrodes system , is used for measuring the ClER rate [2] that is following the change of current density in constant overpotential against the concentration of chloride , using linear sweep voltammetry technique with potentiostat/Galvanostat Autolab (Metrohm) model , PGSTAT 30 .The kinetic experiments of the ClER were carried out in pure chloride solutions and To obtain a value of the ClER rate costant , the concentration of chloride ions were ranged between (0.5 - 5 M) and changes in the pH values were performed by addition of HCl and maintained between 2-4 , because of in the limited range , the ClER is the main electrode reaction . The rest potential of the DSA in solution of (H2O + NaCl + HCl) as electrolyte was measured against a saturated calomel electrode (SCE) and was varried out by sweeping potentioal between (0.51.2 volt). The activation thermodynamic parameters were determined from the ClER rates measured at temperature range of (30 90 C ). The mechanism of the ClER on the DSA is complicated by the specific features of the surface [3] ,but on the basis of the experimental result , we tried to propose the mechanism of the ClER on the DSA .