Photodegradation of petrol station wastewater after coagulation/flocculation with tannin-based coagulant

This work investigates the combined treatment of petrol station wastewater by coupling coagulation/flocculation and heterogeneous photocatalysis processes. Coagulation/flocculation was performed using a tannin-based coagulant, Tanfloc. Commercial TiO2, ZnO and Nb2O5 were applied as photocatalysts, after calcination at 500 degrees C/5 h. In order to evaluate synergic effects, the semiconductor oxides were mixed (50 wt%) and their activities were investigated under UV and VIS radiations. High reductions of absorbance, chemical oxygen demand and elimination of toxicity to Artemia salina was achieved with TiO2-ZnO under UV radiation. Chemical oxygen demand was reduced from 1363 mg L-1 (untreated) to 362 mg L-1 after coagulation/flocculation and finally to 104 mg L-1 after photocatalytic treatment. (C) 2012 Elsevier B.V. All rights reserved.