Degradation of imidacloprid insecticide in a binary mixture with propylene glycol by conventional fenton process

Abstract Imidacloprid is one of the most widely used insecticides in agriculture. The fate of this highly recalcitrant pollutant and its by-product of incomplete degradation in water is of great concern due to the hazardous effects usually associated to pesticides. In the present manuscript, imidacloprid degradation by hydroxyl radical produced in-situ by conventional Fenton process is discussed. Furthermore, it has been studied the influence of propylene glycol, which is a usual excipient found in the commercial pesticides containing imidacloprid, on the conventional Fenton process performance. A two-stage degradation kinetics was observed: (i) a rapid initial decay on the first 5 min of treatment, followed by (ii) a slower kinetics defined by the Fenton-like reaction of Fe2+ catalyst regeneration. The influence of several variables on the abatement of imidacloprid such Fe2+ and H2O2 initial concentration or propylene glycol ratios have been evaluated. Experimental results demonstrate that complete imidacloprid abatement is attained under optimal conditions of 8.0 mM of H2O2 and 0.8 mM of Fe2+ after 120 min of treatment at acidic pH. However, increasing concentrations of propylene glycol diminishes the overall performance due to the competitive consumption of hydroxyl radicals.