الفهرس 
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Abstract
The prese~t work is concemed with the removal of chromium ions ( Cr+3 & Cr+6) from simulated wastewater by electrocoagulation using an electrolytic cell with vertical cylindrical expanded iron electrodes. Removal efficiency and rate of removal were studied under different c•onditions, which are: I. Electrolysis time:2. Current density.3.Electrolyte (NaCl) concentration.4. Initial chromium ions concentration.5.Initial solution pH .6.Electrode connections. The study revealed the following results: I.As current density increases, % C/3 removal increases, whereas % Cr+6 removal decreases.2.As NaCl concentration increases, % Cr+6 removal increases gradually, while % Cr+3 removal increases up to 1 g/l and decreases beyond this value.3. Maximum Cr+6 removal occurs at pH 4.5, whereas maximum Cr+3 removal occurs at pH 8. 4.As the initial concentration of Cr ions increases, % Cr removal decreases.
5. Monopolar parallel electrode connection is the optimum electrode connection.6.Kinetic study of EC of Cr+6 reveals that the reaction can be described by first order kinetic model. 7.Power consumption evaluation of the present cell design reveals that power consumption increases as current density increases, while it decreases as NaCl concentration increases. 8.Power consumption calculations show that at optimum conditions of Cr+3 removal by EC a 10.98 kV{.h/kg is required whereas at optimum conditions of C/6 removal by EC a 16.14 kW.h/kgis required.9.The difference in the behaviour ofEC of Cr+3 & Cr+6 can be explained in terms of their different removal mechanism.