Photo-catalytic degradation of toxic dye amaranth on TiO₂/UV in aqueous suspensions

The photo-catalytic degradation of an azo dye - Amaranth (AM) - has been investigated in TiO₂/UV aqueous suspensions. The results obtained from the experiments during H₂O₂/TiO₂ addition show that the highest decolorization rate is provided by the combination of (UV + TiO₂ + H₂O₂). The decolorization efficiencies were 17%, 26%, 38% and 64% in the runs UV, UV + H₂O₂, UV + TiO₂ and (UV + TiO₂ + H₂O₂) after approximately 100 min illumination periods, respectively. The observed dye degradation rates followed pseudo-first order kinetics with respect to the substrate concentration under the experimental conditions used. Different experimental conditions, such as temperature, pH and presence of electron acceptor were investigated. The temperature effect was investigated at the range of 293-313 K and it was observed that decolorization rate increased by the increase in temperature. Chemical oxygen demand and dye absorbance of the photodegraded dye solution substantially decreased. Effect of pH was also investigated and it was observed that the lower the pH the higher the degradation. In addition, an enhancement in the photodegradation rate was observed by the addition of hydrogen peroxide as an electron acceptor. The adsorption trends of Amaranth at various initial concentrations followed the Langmuir isotherm trend. This work adds to the global discussion on the role of the advanced oxidation processes in water treatment.