TiO2-assisted degradation of acid orange 7 textile dye under solar light

Photocatalytic degradation of acid orange 7 (AO7) in aqueous systems was successfully achieved by the combination of TiO2 with potassium persulphate under solar light using a photochemical reactor with recirculation. Degradation of AO7 involves color removal and mineralization. The employment of TiO2 removed ∼85% of color from the 0.2 mM AO7 aqueous solution under solar light; while, ∼66% of color was abated using the persulphate ion as oxidant in the absence of TiO2 under similar conditions in 2 h. However, over 90% of color removal was achieved by combining TiO2 and the persulphate ion for the same solution under similar conditions. Color removal was faster at pH 3. Mineralization of AO7 was followed by measuring chemical oxygen demand (COD). Negligible COD abatement of the textile dye was observed in the absence of persulphate ions (S2O82−) while over 70% of COD abatement was observed for the initial dye concentrations of 0.2–0.7 mM employing a mix of TiO2–S2O82− under solar light.