Photocatalytic Degradation of Two Selected Textile Dye Derivatives, Eosine Yellowish and p-Rosaniline, in Aqueous Suspensions of Titanium Dioxide

Abstract

Thephotocatalytic degradation of two selected textile dye derivatives, eosine yellowish (1) and p-rosaniline (2) has been investigated in aqueous suspensions of titanium dioxide under a variety of conditions. The degradation was studied by monitoring the change in substrate concentration employing UV spectroscopic technique and decrease in Total Organic Carbon (TOC) content as a function of irradiation time under a variety of conditions. The degradation of the dye was studied under different conditions such as pH, catalyst concentration, substrate concentration, different types of TiO₂ and in the presence of electron acceptor such as hydrogen peroxide (H₂O₂), potassium bromate (KBrO₃), and ammonium persulphate (NH₄)₂S₂O₈) besides molecular oxygen. The degradation rates were found to be strongly influenced by all the above parameters. The photocatalyst Degussa P25 was found to be more efficient as compared with other photocatalyst in the case of p-rosaniline, whereas UV100 was found to be better for the degradation of eosine yellowish. The xanthene dye (1) was found to degrade faster as compared to the triphenylmethane dye (2). The degradation products were analyzed by GC/MS technique and plausible mechanism for the formation of products have been proposed.

Keywords:

• Photocatalysis
• Textile dye
• Eosine yellowish
• p-rosaniline
• Titanium dioxide
• Semiconductor

Acknowledgments

Financial support by the Department of Science and Technology (DST), Govt. Of India, New Delhi and The Third World Academy of Sciences, Triesty, Italy is gratefully acknowledged. Total Organic Carbon (TOC) analyzer used for the analysis of the samples was a gift equipment from the Alexander von Humboltd Foundation, Bonn, Germany.