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 Fe ²⁺, Fe ³⁺, Cu ²⁺ and Mn ²⁺, on 4-CP degrada tion was investigated in an aqueous pulsed discharge plasma system with or without the addition of a TiO ₂ 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 degrada- tion of 4-CP is much enhanced in the presence of ferrous ions at the optimal concentration of 0.2∼0.8 mmol/L or 0.2 mmol/L in an aqueous pulsed discharge plasma without or with the TiO ₂ 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 Fe ²⁺ > Fe³⁺ > Cu ²⁺ > Mn²⁺ and Fe ²⁺ > Fe ³⁺ > Mn ²⁺ > Cu ²⁺ for the former and the latter systems, respectively, and the reasons behind this were discussed through the analysis of active species, especially hydrogen peroxide.