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Artigo Acesso aberto Produção Nacional Revisado por pares
BIBTEX RIS

Sensor based on β - NiOx hybrid film/multi-walled carbon nanotubes composite electrode for groundwater salinization inspection

2017; Elsevier BV; Volume: 323; Linguagem: Inglês

10.1016/j.cej.2017.04.077

ISSN

1873-3212

Autores

Mônica Libânia Mendonça Firmino, Simone Morais, Adriana N. Correia, Pedro de Lima‐Neto, Francisco Adriano O. Carvalho, Suely S.L. Castro, Thiago M.B.F. Oliveira,

Tópico(s)

Electrochemical sensors and biosensors

Resumo

The enrichment of groundwater with different nutrients (Na+, Ca2+, Mg2+, Cl−, CO32−, among others) triggers the salinization of the aquifer and makes it inappropriate for many purposes. In this work, we developed a highly sensitive and selective electrochemical sensor, based on Ni-inorganic films electrosynthetized in situ onto multi-walled carbon nanotubes composite paste electrode (MWCNE), which allows the early detection of salinization. The working sensor (β-NiOx/MWCNE) was derivatized from nickel hexacyanoferrate modified electrode in strong alkaline medium (pH = 12), producing a hybrid film composed by β-Ni(OH)2 and β-NiO(OH). The electrochemical properties, morphology and chemical composition of the formed β-NiOx thin films were evaluated by voltammetry, scanning electron microscopy and X-ray spectroscopy. The developed β-NiOx/MWCNE sensor was highly sensitive to the presence of Na+ cation by ion-exchange, and the increase of Na+ concentration in the range 4.46 × 10−7 to 4.93 × 10−6 mol L−1 inhibited linearly the reversible electrochemical signal of the device, allowing to determine trace concentrations of this ion (LOD = 9.86 × 10−8 mol L−1) with high correlation coefficient of the data (r = 0.999) and suitable precision/reproducibility of the measurements (RSD < 9%). Using Na+ as salinization marker and β-NiOx/MWCNE as electroanalytical device, we found evidences of groundwater salinization in Grossos, a Brazil coast city, whose inhabitants have hypertension above the national average. The attained results were comparable to those obtained by the standard methods for Na+ analysis (percentage error ranging from 0.5 to 1.6%), confirming the accuracy of the proposed electroanalytical platform.

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