Oxidation of S(IV) in Seawater by Pulsed High Voltage Discharge Plasma with TiO ^₂ /Ti Electrode as Catalyst

Oxidation of S(IV) to S(VI) in the effluent of a flue gas desulfurization(FGD) sys- tem is very critical for industrial applications of seawater FGD. This paper reports a pulsed corona discharge oxidation process combined with a TiO 2 photocatalyst to convert S(IV) to S(VI) in artificial seawater. Experimental results show that the oxidation of S(IV) in artificial seawater is enhanced in the pulsed discharge plasma process through the application of TiO ₂ coating electrodes. The oxidation rate of S(IV) using Ti metal as a ground electrode is about 2.0×10 ⁻⁴ mol·L ⁻¹ ·min ⁻¹, the oxidation rate using TiO ₂ /Ti electrode prepared by annealing at 500 ^? C in air is 4.5×10 ⁻⁴ mol·L ⁻¹ ·min ⁻¹, an increase with a factor 2.25. The annealing temper- ature for preparing TiO ₂ /Ti electrode has a strong effect on the oxidation of S(IV) in artificial seawater. The results of in-situ emission spectroscopic analysis show that chemically active species (i.e. hydroxyl radicals and oxygen radicals) are produced in the pulsed discharge plasma process. Compared with the traditional air oxidation process and the sole plasma-induced oxidation process, the combined application of TiO ₂ photocatalysts and a pulsed high-voltage electrical discharge process is useful in enhancing the energy and conversion efficiency of S(IV) for the seawater FGD system.