Lanthanum ion doped nano TiO2 encapsulated in zeozyme and impregnated in a polystyrene film as a photocatalyst for the degradation of diuron in an aquatic ecosystem

Abstract

The occurrence of chlorinated herbicide diuron in water bodies is considered serious pollution and a major health hazard to flora, fauna and mankind. In the present investigation, we studied the photocatalytic degradation of diuron in an aquatic ecosystem using lanthanum ion doped nano TiO₂ (Lnp) encapsulated in NaY zeolite pores (1 : 10) and impregnated in polystyrene film (ZLT). The hydrophobic nature of the polystyrene support resulted in an efficient and highly recoverable heterogeneous system. Catalyst characterization was carried out by FT-IR, XRD, DRS-UV, fluorescence, BET, SEM-EDAX and XPS. BET results revealed the successful loading of lanthanum ion doped TiO₂ (Lnp) inside the NaY zeolite pores via a decrease in surface area for the zeolite encapsulated Lnp (ZLnp) as compared to NaY zeolite alone. DRS UV supported the impregnation of ZLnp in the polystyrene films; the bathochromic shift (Δλ) was 4 nm and the hypochromic shift decreased in intensity 10 fold. The photocatalytic reaction was carried out at a concentration of 20 mg L⁻¹ of diuron, with 0.01 M H₂O₂ and a catalytic amount of 500 mg L⁻¹ ZLT under unstirred conditions. Degradation of diuron by ZLT reached 40% after 2 hours. Noteworthy features are the good results under optimized conditions and that the same film models were used successfully in the presence of zebra fish (Danio rerio). The present investigation also demonstrated successful re-use of the photocatalytic film six times without any appreciable loss in catalytic activity. From the abovementioned results, it was proven that ZLT is an efficient and ecofriendly catalyst.