Photocatalytic ozonation of parabens mixture using 10% N-TiO2 and the effect of water matrix

Abstract

Nitrogen-doped TiO2 was applied in photocatalytic ozonation reactions for the degradation of a mixture of five parabens under UVA radiation, being evaluated the influence of the reaction medium. The initial mixture parabens concentration considered in these experiments was 50 mg L−1. The parabens degradation rate was considerably enhanced under neutral pH, specially using a buffered solution, leading to a complete removal under 60 min and with transferred ozone dose (TOD) 36% lower compared to reaction under natural conditions. Isopropanol, known radical scavenger, impeded the complete contaminants removal, affecting the reaction route and by-products formation, but when KI was jointly added, total removal was achieved under 30 min and with a TOD of 25.9 mg L−1. Parabens depletion was also improved in the presence of Cl−, SO42− and HCO3−, commonly present in wastewaters. The use of river water (RW) and a secondary wastewater (SWW) as water matrices maintained the process efficiency with lower TOD required, and treated solutions presented lower phytotoxicity towards Lepidium sativum.