Pesticide removal from water suspension by UV/TiO2 process: a parametric study

Linuron is a phenylurea herbicide which is generally used for eliminating various herbs. The advanced oxidation processes represent a promising alternative technology for the destruction of pesticides contained in wastewater. In this present work, the degradation of linuron is performed using a helical photochemical reactor. The UV lamp (HPA 18 W/S with a monochromatic radiation at 365 nm and a nominal power of 18 W) is set in axial position in the open space of the sheath. The experimental results showed that the photodegradation of linuron increased significantly compared with adsorption and photolysis. The parametric study of the pollutant oxidation showed that an increase in the initial concentration of catalyst (0.1-0.8 g/L) revealed the existence of an optimum for 0.3 g/L where the oxidation was complete after 4 h of radiation exposure. The best degradation of linuron was obtained at an optimum flowrate of 396 mL/min, where 98% of herbicide was oxidized after 4 h of UV illumination. Results showed also that the presence of hydrogen peroxide (an electron acceptor), acids or bases disadvantaged the photocatalytic process. Removal of linuron increased at low pH (3 and 5 adjusted along the photodegradation), where 93% was oxidized. Photodegradation of linuron process accords well with Langmuir-Hinshelwood pseudo-first-order kinetics.