Textile industry effluents are heavily contaminated with
dyes.
The discharge of these toxic dyes into waterbodies poses a serious
threat to aquatic flora and fauna. The ultimate entrance of these
toxins from thereon into the food chain affects the primary and secondary
consumers. Therefore, the adoption of a sustainable solution for protection
against the detrimental effects associated with adulterated water
is an immediate need of the hour. To address the severity of the issue,
the present work aims to design an electrochemical sensing platform
by modifying the glassy carbon electrode (GCE) with zinc oxide nanoparticles
and amino group-functionalized multi-walled carbon nanotubes (NH
2
-fMWCNTs) for the detection of Orange II, which is a toxic
azo dye. Zinc oxide nanoparticles facilitate electron transfer between
the transducer and the analyte. While, the positively charged NH
2
-fMWCNTs in acidic medium help in preconcentration of negatively
charged analyte molecules at the electrode/electrolyte interface.
The modification of the GCE catalyzed the oxidation of Orange II,
as evidenced by the negative shift of the oxidation potential and
enhancement in peak current intensity. Square wave voltammetry was
used to optimize various experimental conditions, such as the supporting
electrolyte, pH of the electrolyte, deposition potential, and deposition
time for the best performance of the designed sensor. Under the optimized
conditions, the detection limit and quantification of the designed
sensor were found to be 0.57 and 1.92 nM, respectively. The catalytic
degradation studies of Orange II was shown to be facilitated by titanium
dioxide, which acted as a photocatalyst. The addition of hydrogen
peroxide further promoted the extent and rate of degradation of dye.
The breakdown of Orange II was probed by the designed sensing platform
electrochemically and also by UV–visible spectroscopy. The
dye degraded up to 92% by following pseudo-first-order kinetics.