Degradation of imidacloprid in water by photo-fenton and TiO2 photocatalysis at a solar pilot plant: A comparative study

The technical feasibility, mechanisms, and performance of degradation of aq ueous imidacloprid have been studied at pilot scale in two well-defined pho tocatalytic systems of special interest because natural UV light can be use d: heterogeneous photocatalysis with titanium dioxide and homogeneous photo catalysis by photo-Fenton. Equivalent pilot-scale and field conditions used for both allowed adequate comparison of the degree of mineralization and t oxicity achieved as well as the transformation products generated in route to mineralization by both systems. Ninety-five percent of mineralization (< 2.0 mg/L) was reached after 250 min of photocatalytic treatment with Fenton and 450 min with TiO2, meaning that TOC disappears 2.4 times faster with p hoto-Fenton photocatalytic treatment than with TiO2. The Daphnia Magna test for final residual TOC does not reveal any toxic behavior. Transformation products evaluated by GC-MS/AED after two SPE procedures and LC-IC were the same in both cases. The main differences between the two processes are in the amount of transformation products (TPs) generated, not in the TPs detec ted which were always the same. At the end of both processes low concentrat ion( <0.1 mg/L) of 2 pyrrolidinone (transformation product) remains in the dissolution and around I mg/L of formate in the case of photo-Fenton.