Decomposition of azo dye brilliant red B by radio frequency discharge plasma in aqueous solution

Azo dye is widely used in dyeing and printing industry. Degradation of azo dye Brilliant Red B(ARB) by Radio Frequency Discharge Plasma (RFDP) in aqueous solution under different pH, center dot OH scavengers (methanol, isopropanol) and catalysts (Fe2+, Fe3+) was studied in this paper. Results showed that numerous active species such as center dot OH, H center dot and center dot O were produced in RFDP. Removal of ARB reached 77.89% after 1 hour discharge, and it would be better under acidic conditions. Hydroxyl radicals scavengers had an inhibition effect on ARB removal, while Fe2+ and Fe3+ had catalysis effect on it, with the sequence of Fe2+ > Fe3+. The UV visible absorption spectroscopy illustrated that the main reason for the decolorization of ARB was the break of azo bond which was damaged by center dot OH radicals formed in the discharge process. The main degradation intermediates formed during the process were formic acid, acetic acid, oxalic acid and malonic acid.