Fluoride removal from water and wastewater with a bach cylindrical electrode using electrocoagulation

In this study, an electrochemical reactor with a unique design was used for defluoridation. A rotating impeller aluminium cathode and a cylindrical aluminium anode, which until now have not been employed for fluoride removal in the literature, were used, and various operating parameters, such as the electrode material (aluminium and iron), the current density (in the range of 0.5-2 mA/cm(2)), the duration of electrolysis, the supporting electrolyte dosage (in the range of 0.01-0.03 M Na2SO4), the initial pH (in the range of 4-8) and the presence of other ions(Ca2+, Mg2+, PO43-, SO42-), were examined to achieve optimal performance of the process. The experimental results revealed that the fluoride removal could be enhanced at pH 6, higher current density and higher electrocoagulation time using aluminium electrode. The presence of Ca2+ and Mg2+ ions also enhanced the removal efficiency while SO42- and PO43-,ions effected adversely. The fluoride concentration was reduced from the initial value of 5.0-0.12 mg/L, with a removal efficiency of 97.6% after 30 min treatment at the current density of 2 mA/cm(2), pH(i) of 6 and presence of 0.01 M Na2SO4. The required electrocoagulation time to reach the WHO-recommended fluoride limit of 1.2 mg/L at 0.5 mA/cm(2) was 5 min, with an energy consumption of 0.47 kW h/m(3). The obtained results show that this specially designed electrochemical reactor is an efficient alternative for the defluoridation of the water and the wastewater. (C) 2013 Elsevier B.V. All rights reserved.