Groundwater Treatment using a Solid Polymer Electrolyte Cell with Mesh Electrodes

This article reports the high performance of a solid polymer electrolyte cell, equipped with a Nafion (R) N117 membrane packed between a Nb/boron-doped diamond (Nb/BDD) mesh anode and a Ti/RuO2 mesh cathode, to degrade the insecticide imidacloprid spiked at 1.2-59.2 mg L-1 into low conductivity groundwater by electrochemical oxidation. The natural water matrix was first softened using valorized industrial waste in the form of zeolite as reactive sorbent. Total removal of the insecticide, always obeying pseudo-first-order kinetics, and maximum mineralization degrees of 70%-87% were achieved, with energy consumption of 26.4 +/- 1.6 kWh m(-3). Active chlorine in the bulk and center dot OH at the BDD surface were the main oxidants. Comparative studies using simulated water with analogous anions content revealed that the natural organic matter interfered in the groundwater treatment. Trials carried out in ultrapure water showed the primary conversion of the initial N and Cl atoms of imidacloprid to NO3- and Cl- ions, being the latter anion eventually transformed into ClO3- and ClO4- ions. 6-Chloro-nicotinonitrile, 6-chloro-pyridine-3-carbaldehyde, and tartaric acid were identified as oxidation products.