Abstract
A nickel oxide (NiO) thin film was successfully prepared on Ni foil via a sol–gel method and a reduced state nickel oxide (r-NiO) thin film was obtained by etching NiO with hydrazine hydrate solution. Structure characterization through X-ray diffraction and scanning electron microscopy revealed the growth of nanostructure films on the surface of nickel foil. Cyclic voltammetry, linear sweep voltammetry and electrochemical impedance spectroscopy were used to assess the performance of the two films. Electroreduction of alkaline imidacloprid solution under potentiostatic conditions was carried out in a three-electrode system. The removal efficiencies of 80.2% (r-NiO) and 66.3% (NiO), and the current efficiencies of 67.3% (r-NiO) and 58.9% (NiO) were much higher than 41.7% (removal efficiency) and 0.003% (current efficiency) on the bare Ni electrode. This study prepared two novel thin films with composites of NiO or r-NiO, and thus provided feasible and efficient electrochemical degradation of imidacloprid. The degradation products were characterized and the possible degradation pathways were proposed.
Highlights
IntroductionImidacloprid (IMD), a systemic chloronicotinyl insecticide with remarkable water solubility, high toxicity, and good stability in water, is mainly applied to agriculture for controlling sucking insects in crops such as aphids, white ies and termites, and can cause IMD pollution in water sources and soil.[1,2]
Imidacloprid (IMD), a systemic chloronicotinyl insecticide with remarkable water solubility, high toxicity, and good stability in water, is mainly applied to agriculture for controlling sucking insects in crops such as aphids, white ies and termites, and can cause IMD pollution in water sources and soil.[1,2]To solve the pollution problem, various treatment processes have been studied
The structure characterizations of the nickel oxide (NiO) and removal efficiencies of 80.2% (r-NiO) lms were analyzed by X-ray diffraction (XRD) (Fig. 1)
Summary
Imidacloprid (IMD), a systemic chloronicotinyl insecticide with remarkable water solubility, high toxicity, and good stability in water, is mainly applied to agriculture for controlling sucking insects in crops such as aphids, white ies and termites, and can cause IMD pollution in water sources and soil.[1,2]. While electrochemical oxidation is effective for the degradation of IMD, anodes with expensive materials including TiO2/ Ti,[15,16] Ti/RuO2–TiO2, Ti/RuO2–IrO2–TiO2,17 Ti/SnO2–Sb2O3,18 or Pt and boron-doped diamond (BDD)[19] were purposely used. In these reports, electrochemical oxidation was carried out using expensive anode to resist the strong oxidative effect of hydroxyl radical. Been regarded as a promising electrode candidate due to its cost effectiveness, superior chemical and electrical stability, and transparently p-type semi-conductivity based high efficiency.[20,21] The characterization of the oxides is investigated by X-ray diffraction (XRD), scanning electron microcopy equipped with energy dispersive spectrometer (SEM-EDS) and electrochemical tests. IMD degradation products were characterized by high performance liquid chromatograph-mass spectrometer (HPLCMS) and the possible degradation pathways were proposed
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