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

• Published in: Environmental technology Vol. 39; no. 9; pp. 1208 - 1216
• Main Authors: Silveira, Jefferson E., Cardoso, Tais O., Barreto-Rodrigues, Marcio, Zazo, Juan A., Casas, José A
• Format: Journal Article
• Language: English
• Published: England Taylor & Francis 03-05-2018; Taylor & Francis Ltd
• Subjects: Current density; Decay; Economics; electro-activation; Electrodes; Feasibility studies; intensification; Iron; iron electrode; Low cost; Mineralization; Operating costs; Persulfate; Phenols; Sludge; Sodium chloride; Sodium sulfate; sulfate radical; Temperature; iron electrode; intensification; electro-activation; Persulfate; sulfate radical
• ISSN: 0959-3330; 1479-487X
• DOI: 10.1080/09593330.2017.1323960

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
2+
source. An aqueous phenol solution (100 mg L
−1
) was selected as model effluent. The studied variables include current density (1-10 mA cm
−2
), persulfate concentration (0.7-2.85 g L
−1
), temperature (30-90°C) and the solution conductivity (2.7-20.7 mS cm
−1
) using Na
2
SO
4
and NaCl as supporting electrolyte. A mineralization degree of around 80% with Na
2
SO
4
and 92% in presence of NaCl was achieved at 30°C using 2.15 g L
−1
PS at the lowest current density tested (1 mA cm
−2
). 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 Na
2
SO
4
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
−1
. An estimated operating cost of US$ 3.00 per m
3
was obtained, demonstrating the economic feasibility of this process.