Chromium ions (Cr6+ & Cr3+) removal from synthetic wastewater by electrocoagulation using vertical expanded Fe anode

Abstract

The performance of an innovative batch cell design in removing chromium ions (Cr6+ & Cr3+) from synthetic wastewater solutions by electrocoagulation has been investigated. The cell consists of two concentric vertical cylindrical Fe-electrodes; the outer electrode is a cylindrical solid Fe-cathode which is supported in the vessel wall, whereas the inner electrode is an expanded cylindrical Fe-anode. The distance between the two electrodes is 0.5cm apart. The performance of the present cell has been expressed in terms of % removal of (Cr6+ & Cr3+). The effect of key parameters such as electrolysis time, current density, pH, initial (Cr6+ & Cr3+) ions concentration, NaCl concentration and electrode connection on the % removal (Cr6+ & Cr3+) has been investigated. The study revealed that as current density increases, % Cr3+ removal slightly increases, whereas % Cr6+ removal slightly decreases. As NaCl concentration increases, % Cr6+ removal increases gradually, while % Cr3+ removal increases up to 1g/l and decreases beyond this value. Maximum % Cr6+ removal occurs at pH 4.5, whereas maximum % Cr3+ removal occurs at pH 8. As the initial concentration of Cr ions increases, % Cr removal decreases. Monopolar parallel electrode connection is the optimum electrode connection. Power consumption evaluation of the present cell design reveals that power consumption increases as current density increases, while it decreases as NaCl concentration increases. Power consumption calculations show that at optimum conditions of Cr3+ removal by Electrocoagulation (EC) a 10.98kWh/kg (1.09kWh/m3) is required whereas at optimum conditions of Cr6+ removal by Electrocoagulation (EC) a 16.14kWh/kg (2.299kWh/m3) is required.