Effects of chloride ions on electro-coagulation-flotation process with aluminum electrodes for algae removal

Electro-coagulation-flotation (ECF) is one of the most promising technologies that offers an attractive alternative to conventional coagulation and flotation. In this study, the effectiveness and mechanisms of algae removal by ECF process using aluminum electrodes was investigated in the presence of Cl- ions. The results showed that the addition of Cl- ions (1.0, 3.0, 5.0 and 8.0 mM) had a promoting effect on the algae removal in terms of both the cell density and chlorophyll-a, which could be attributed to the following two reasons. Firstly, active chlorine could be generated in the ECF when Cl- ions were present. The electrochemically generated active chlorine was demonstrated to be effective for the inactivation of algae cells with the aid of the electric field in the ECF. Secondly, the Cl- ions in the algae solution could enhance the release of Al3+ from the aluminum electrodes in the ECF. Through SEM-EDX analysis, pitting corrosion and alleviated formation of oxide film by Cl- ions were observed on the anode surface. When considering that Cl- ions are universally present in natural waters, the effects of Cl- on ECF process for algae removal are of great significance. (c) 2010 Elsevier B.V. All rights reserved.