Photolytic Degradation of Organic AZO Dye in Aqueous Solution using Xe-Excimer Lamp

Abstract

The photodegradation of organic azo dye C.I. Food Yellow 4 (FY-4) in aqueous solution was achieved, without the addition of oxidants, by 172 nm vacuum ultraviolet (VUV) radiation emitted from the planar Xe-excimer lamp. The degradation was mainly attributed to the impact of HO^˙ radicals produced by water absorbing VUV radiation. The dye decolorization followed pseudo-first order kinetics. The initial quantum yields of FY-4 decolorization in O₂-saturated solution and N₂-saturated solution were respectively 0.151±0.003 and 0.103±0.002. Dissolved oxygen in the solution contributed to the increase of the decolorization rate and chemical oxygen demand (COD) removal rate while KCl added as HO^. radical scavenger decreased the efficiency of the decolorization and COD removal. It was found from the change of the UV-Vis spectra that the degradation of FY-4 was accompanied by both the cleavage of chromophoric group and the opening of aromatic ring. Major intermediates detected were aromatic compounds, some low molecular weight by-products and several organic acids and inorganic ions.

Keywords:

• 172 NM VUV RADIATION
• HO RADICALS
• DECOLORIZATION
• COD REMOVAL