Desenvolvimento de sensor a base nanotubo de carbono e óxido de ferro para determinação de BTX em água subterrânea e solo de postos de combustíveis em São Luís/MA
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Data
2021-09-26
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Universidade Federal do Maranhão
Resumo
Environmental contamination by organic compounds represents serious problems for public
health and the environment, especially for groundwater and soil contamination. One of the main
problems is contamination by aromatic hydrocarbons. Among the monoaromatic hydrocarbons,
known as BTX [benzene (B), toluene (T) and xylenes (X)], B stands out for being the most
toxic among BTX, being considered highly carcinogenic, including their derivatives.
Monitoring these contaminants in groundwater and soil of great importance. The present work
proposes an electrochemical sensor based on iron oxide nanoparticles supported on carboxyl-
functionalized multi-wall carbon nanotubes (ECV/Fe2O3/MWCNT-COOH) for the
determination of B, T and X in soil and groundwater samples from gas stations. The
physicochemical properties of Fe2O3/MWCNT-COOH were characterized by Scanning
Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FT-IR) and X-ray
Diffraction (XRD). Using the square wave voltammetry (SWV) technique the
ECV/Fe2O3/MWCNT-COOH sensor was evaluated from the electroanalytical point of view for
BTX analysis. After optimizing the experimental parameters, the following best conditions
were found: electrolyte = H2SO4 0.1mol L-1
; pH = 1.0; frequency = 40 mV; amplitude = 20 mV;
potential step = 2 mV. Under these optimized conditions, the proposed sensor presented an
excellent electroanalytical performance for BTX oxidation and analysis, showing a linear
behavior between anode peak currents and analyte concentrations, in the range of 5 to 35 μmol
L
-1
for benzene, and 20.00 to 53.00 μmolL-1
for toluene and xylenes. Through the standard
deviations of the calibration curves the LD were calculated for the analytes (0.78 μmol L-1 for
benzene, 5.33 μmol L-1 for toluene and 20.38 μmol L-1 for xylenes). The precision (relative
standard deviation (RSD) of the method) was assessed by the repeatability of the analyte current
(n = 6) in the solution. Good RSD values were found (0.81% for benzene, 3.99% for toluene
and 2.82% for xylene). The application of the new method was carried out through the
enrichment in real samples. Recovery (accuracy) showed excellent statistical results in samples
of soil (B = 99.9%; T = 100%% and X = 99.8%) and groundwater (B = 100%; T = 99.7% e X
= 99.8%). No significant interferences were observed for other species (catechol and
benzoquinone) possibly present in the analysis of each of the analytes. The good results indicate that the proposed new electrochemical nanosensor is suitable for the determination of BTX in
soil and groundwater samples.
Descrição
Palavras-chave
BTX;, amostras ambientais;, postos de combustível;, nanotubos de carbono;, óxido de ferro., BTX;, environmental samples;, fuel station;, carbon nanotubes;, iron oxide.
Citação
PINHEIRO, Helilma de Andréa. Desenvolvimento de sensor a base nanotubo de carbono e óxido de ferro para determinação de BTX em água subterrânea e solo de postos de combustíveis em São Luís/MA. 2021. 121 f. Tese (Programa de Pós-Graduação em Rede - rede de Biodiversidade e Biotecnologia da Amazônia Legal/CCBS) - Universidade Federal do Maranhão, São Luís, 2021.