Abstract:
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This article reports the high performance of a solid polymer
electrolyte cell, equipped with a Nafion¿ N117 membrane packed
between a 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 a 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 •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. |