Fig. 7. Percentages of COD reduction (black bars) and CI reduction (light grey bars), decolorization (dark grey bars) and EC (white bars) of WW with Fe-AC at different constant potential drops: 15 V, 10 V and 5 V after 24 hours of electro-Fenton treatment of WW at an air flow of 1 L/min and PD173074 3.2.Figure optionsDownload full-size imageDownload as PowerPoint slide
According to Martínez and Bahena  the low applied potential differences reduce the electrolytic reactions, thus the reagents of electro-Fenton are in low concentration to react with pollutant molecules reducing the degradation rate. However, the energy consumptions per amount of destroyed COD showed in Fig. 7, indicate that it is possible to obtain a good degradation degree with low energy cost (0.5 kWh/kgCOD) when the applied potential difference is 5 V.
3.3. Reaction mechanisms
The heterogeneous electro-Fenton treatment with Fe-AC is a complex system where several reactions (Table 1) are responsible of HO generation, and consequently, of decolorization and degradation of organic compounds as a result of HO reactive action (Eq. 8).