Removal of azo dye C.I. acid red 14 from contaminated water using fenton, UV/H₂O₂, UV/H₂O₂/Fe(II), UV/H ₂O₂/Fe(III) and UV/H₂O₂/Fe(III)/ oxalate processes: A comparative study

The decolorization of the solution containing a common textile and leather dye, C.I. Acid Red 14 (AR14), at pH 3 by hydrogen peroxide photolysis, Fenton, Fenton-like and photo-Fenton processes was studied. The dark and light reactions were carried out in stirred batch photoreactor equipped with an UV-C lamp (30 W) as UV light source. The experiments showed that the dye was resistant to the UV illumination, but was oxidized when one of Fe(II), Fe(III) and H ₂O₂ compounds was present. It was also found that UV light irradiation can accelerate significantly the rate of AR14 decolorization in the presence of Fe(III)/H₂O₂ or Fe(II)/H₂O ₂, comparing to that in the dark. The effect of different system variables like initial concentration of the azo dye, effect of UV light irradiation, initial concentration of Fe(II) or Fe(III) and added oxalate ion has been investigated. The results showed that the decolorization efficiency of AR14 at the reaction time of 2 min follows the decreasing order: UV/H ₂O₂/Fe(III)/oxalate > UV/H₂O ₂/Fe(III) > UV/H₂O₂/Fe(II) > UV/H ₂O₂. Our results also showed that the UV/H ₂O₂/Fe(III)/oxalate process was appropriate as the effective treatment method for decolorization of a real dyeing and finishing. The mechanism for each process is also discussed and linked together for understanding the observed differences in reactivity.