The Catalytic Effect of Metal Ions on the Degradation of 4-Chlorophenol Induced by an Aqueous Pulsed Discharge Plasma

The influence of metal ions, such as Fe2+, Fe3+, Cu2+ and Mn2+, on 4-CP degradation was investigated in an aqueous pulsed discharge plasma system with or without the addition of a TiO2 photo-catalyst. From an analysis of the pseudo first-order rate constant (k(CP)) and energy efficiency (G(50%)) for 4-CP degradation, the experimental results show that the degradation of 4-CP is much enhanced in the presence of ferrous ions at the optimal concentration of 0.2 similar to 0.8 mmol/L or 0.2 mmol/L in an aqueous pulsed discharge plasma without or with the TiO2 system, respectively, and the enhancement is ascribed to plasma induced Fenton and photo-Fenton reactions. Meanwhile, the rank of such metal ions for catalytic effect on 4-CP degradation was Fe2+ > Fe3+ > Cu2+ > Mn2+ and Fe2+ > Fe3+ > Mn2+ > Cu2+ for the former and the latter systems, respectively, and the reasons behind this were discussed through the analysis of active species, especially hydrogen peroxide.