Photocatalytic oxidation of six pesticides listed as endocrine disruptor chemicals from wastewater using two different TiO2 samples at pilot plant scale under sunlight irradiation

Abstract

The photocatalyzed degradation of a mixture of six pesticides (malathion, fenotrothion, quinalphos, vinclozoline, dimethoate and fenarimol) with endocrine disrupting activity has been studied in sewage wastewater effluent under natural sunlight at pilot plant scale. The initial level of each pesticide was 0.30 mg L−1. For this, two commercial TiO2 nanopowders (Degussa P25 and Kronos vlp 7000) were used as photocatalysts. The operational conditions (catalyst loading, effect of electron acceptor and pH) were previously optimized under laboratory conditions using a photoreactor. The results show that the use of TiO2 alongside an electron acceptor like Na2S2O8 strongly enhances the degradation rate of the studied pesticides compared with photolytic tests, especially Degussa P25. The photodegradation process followed pseudo-first order kinetics in all cases. In our experimental conditions, the necessary time necessary for 90% degradation (DT90) varied from 79 to 1270 min (6–108 min as normalized illumination time, t30W) for malathion and fenarimol, respectively for TiO2 vlp 7000 and 32–817 min (t30W = 3–69 min) for the same pesticides, in the case of TiO2 P25. The results confirm the efficacy of the treatment to remove recalcitrant pollutants from wastewater using natural sunlight as renewable source.