Visible light assisted photocatalytic mineralization of Reactive Red 180 using colloidal TiO2 and oxone

The photocatalytic degradation of Reactive Red 180 (RR180), a mono-azo textile dye, has been investigated using aqueous suspensions of titanium dioxide (TiO2) under visible light irradiation. The photocatalytic degradation is monitored by measuring the decolorization rate and the total organic carbon (TOC) content reduction during the course of the reaction. The effect of catalyst concentration, substrate concentration, pH of the solution and addition of electron acceptors, such as hydrogen peroxide (H2O2), potassium peroxodisulfate (K2S2O8) and potassium peroxomonosulfate (PMS or oxone), on the photocatalytic degradation of RR180 in the presence of colloidal titanium dioxide is also studied. The photocatalytic degradation rate is found to be depending on the ratio of TiO2 to dye. Addition of oxone in the TiO2–RR180 system increases the degradation rate by about 10 fold and is found to be promising for the degradation of Reactive Red 180 when compared with other electron acceptors. About 80% of the dye is mineralized in 5 h through visible light photocatalytic degradation in the presence of TiO2 and oxone.

► Azo dye RR180 is effectively mineralized using TiO2 and PMS under visible light.
► The [catalyst]/[dye] ratio has significant effect on the photocatalytic degradation.
► Cause for the inverse relation between degradation rate and [substrate] is discussed.
► 95% decolorization of RR180 was achieved in 60 min visible light irradiation.
► Mechanism involving photo-induced charge transfer from dye to TiO2 is discussed.