Formation of chlorinated by-products during photo-Fenton degradation of pyrimethanil under saline conditions. Influence on toxicity and biodegradability

This study evaluated the formation of chlorinated transformation products during photo-Fenton treatment of pyrimethanil (PYR-20 mg L-1) in two water matrices, demineralised water (DW) and water containing 5 g L-1 of NaCl (DWNacl). All experiments were carried out in compound parabolic collectors (CPC) at an initial Fe2+ concentration of 5 mg L-1 and H2O2 concentration of 150-350 mg L-1. Dissolved Organic Carbon (DOC), High-Performance Liquid Chromatography with Diode-Array Detection (HPLC-DAD), Liquid Chromatography-Time-Of-Flight Mass Spectrometry (LC-TOF-MS), toxicity and biodegradability tests were conducted to control the photocatalytic treatment. In DW, PYR was completely eliminated after 11.8 min of illumination and initial DOC was reduced 50% after 79 min of illumination with 33 mM of H2O2 consumed. On the other hand, in DWNacl water matrix, the same reduction in DOC took 110 min of illumination and H2O2 consumption of 39 mM, and total degradation of PYR was observed at 12 min of illumination. PYR transformation products (TPs) were identified by LC-TOF-MS. It was demonstrated that photo-Fenton in a DWNacl produces some chlorinated TPs in addition to the non-chlorinated TPs identified during degradation in the DW. All TPs formed were eliminated during photo-Fenton. Additionally, the presence of chlorinated TPs does not increase the toxicity of the water, and TPs formed are more biodegradable than PYR. (C) 2012 Elsevier B.V. All rights reserved.