Electro activation of persulfate using iron sheet as low-cost electrode: the role of the operating conditions.

This work assesses the role of the operational conditions upon the electro-activation of persulfate (PS) using sacrificed iron electrode as a continuous low-cost Fe source. An aqueous phenol solution (100 mg L) was selected as model effluent. The studied variables include current density (1-10 mA cm), persulfate concentration (0.7-2.85 g L), temperature (30-90°C) and the solution conductivity (2.7-20.7 mS cm) using NaSO and NaCl as supporting electrolyte. A mineralization degree of around 80% with NaSO and 92% in presence of NaCl was achieved at 30°C using 2.15 g L PS at the lowest current density tested (1 mA cm). Besides PS concentration, temperature was the main variable affecting the process. In the range of 30-70°C, it showed a positive effect, achieving TOC conversion above 95% (using NaSO under the previous conditions) along with a significant increase in iron sludge, which adversely affects the economy of the process. A lumped and simplified kinetic model based on persulfate consumption and TOC mineralization is suggested. The activation energy obtained for the TOC decay was 29 kJ mol. An estimated operating cost of US$ 3.00 per m was obtained, demonstrating the economic feasibility of this process.