Effect of water matrices on the photochemical degradation of orange G in aqueous solution

In this study, we assessed the effect of aqueous matrices nature in the degradation of an azo dye Orange G (OG), using a UV Process at a wavelength of 254 nm. First of all, the effect of initial dye concentration was investigated and found to follow pseudo-first order kinetic. The apparent reaction rate constant (kapp) was decreased from 0.622 to 0.034 min-1 with increasing initial OG concentration from 2 to 50 mg/L respectively. The implication of hydroxyl radical (HO center dot) in the UV-C system was demonstrated using tert-butyl alcohol as a hydroxyl radical scavenger. Then, the effects of bicarbonate (HCO3-) carbonate (CO32-) and bromide (Br-) ions on the efficiency of the photodegradation of OG (50 mg/L) were investigated. It was found that the presence of these ions, especially at high concentration ([HCO3-] = 1000 mg/L, [CO32-] = 1000 mg/L and [Br-] = 3000 mg/L) inhibited the degradation process through consuming HO center dot, despite the formation of other radicals (carbonate and bromide radicals) which are probably less reactive than HO center dot towards OG. Finally, five types of water: ultra -pure water, tap water, mineral bottled water, Mediterranean Sea water and Dead Sea water, were used as target matrices for the photodegradation process and compared with that used distilled water, the removal efficiency was as follow: 99.8%, 84.5%, 64.4%, 57.4% and 17% respectively.