Desenvolvimento de materiais para a detecção e degradação do bisfenol A e seus intermediários de reação
Abstract
In this study, tungsten oxide and copper composites were
developed for making applied anodes in fotoelectrolysis of bisphenol A (BPA)
and electrochemical sensors composed of carbon nanotubes (CNTs) and metal
nanoparticles (NPM) for the detection of BPA and its reaction intermediates
such as hydroquinone (HQ), catechol (CC) and phenol (Phe). The sensors were
obtained by casting method on a glassy carbon surface and the quantitation of
molecules of interest was carried out by pulsed techniques using the standard
addition method. Different methods of functionalization, and the influence of
CNTs sizes were investigated for the determination of BPA. CNTs samples with
20-170 nm in diameter were functionalized in HNO3 solution 5.0 mol L-1
solution and sulfonitric (3H2SO4: 1HNO3). The size and functionalization
directly affect the oxidation of BPA and smaller diameter CNTs with improved
sensitivity and showed the low limit of detection (LOD) of 8.4 × 10-8 mol L-1.
The simultaneous determination of HQ, CC, and BPA was made with CNTs
sensor modified with nickel oxide nanoparticles (NiO/MWCNT/GCE). The
deposition of NiO was made by cyclic voltammetry (CV) and were evaluated
the concentration of the nickel solution and the number of cycles. The best
results were obtained when NiO was deposited in a solution of 8.0 mmol L-1
Ni(NO3)2 and 40 cycles. The analytical curves showed an excellent linear
response and the LODs for the simultaneous determination of BPA, HQ and CC
were 2.8 × 10-8 mol L-1, 2.7 × 10-8 mol L-1 and 5.9 × 10-8 mol L-1, respectively.
Silver nanoparticles (AgNPs) were also incorporated in the films of
MWCNT/GCE by CV. The AgNPs/MWCNT/GCE sensor showed good
stability and reproducibility and has been successfully applied to the
simultaneous determination of HQ, CC, BPA and Phe in tap water samples.
Morphological characterization of the developed sensor was performed by
scanning electron microscopy (SEM) and electrochemical characterization was
made by CV and electrochemical impedance spectroscopy. Tungsten oxide films
doped with copper (WO3-Cu) obtained by the modified sol-gel method were
used in the studies photoelectrolysis BPA. The doping with Cu increased six
fold the value of the photocurrent density of the material compared to the WO3.
The characterization of the synthesized anode was made by techniques of X-ray
diffraction, SEM and energy dispersive microanalysis (EDX). The monitoring of
the decay of the concentration of BPA and the formation of intermediates
generated during the photoelectrolysis was made by electrochemical sensors
based on CNTs/NiO and UV-Vis absorption. The results of the total organic
carbon content showed 75% of BPA was degraded and it was found that it is
possible to monitor the BPA of degradation process and the formation of
reaction intermediates using sensors developed in this work.