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

Abstract

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•
) in the UV-C
system was demonstrated using tert-butyl alcohol as a hydroxyl radical scavenger. Then, the effects of bicarbonate (HCO3
-
)
carbonate (CO3
2-
) 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, [CO3
2-
] = 1000 mg/L and
[Br-
] = 3000 mg/L) inhibited the degradation process through consuming HO•
, despite the formation of other radicals
(carbonate and bromide radicals) which are probably less reactive than HO• 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.