Xanthan
gum (XG) grafted polyaniline@zinc oxide nanocomposite (XGP@ZnO)
was synthesized by an oxidative free-radical graft copolymerization
reaction. The synthesized nanocomposite was approved by different
analytical processes such as Fourier transform infrared spectroscopy,
X-ray diffraction, scanning electron microscopy, transmission electron
microscopy, and thermogravimetric analysis. The material was further
employed for efficient remediation of aqueous solutions contaminated
by Cr(VI) and 2,4-dinitrophenol (2,4-DNP) under batch operations.
Solution pH values of 2.0 and 4.0 were found to be optimum pH for
the adsorption of Cr(VI) and 2,4,-DNP, respectively. On the basis
of higher R
2 value and lower χ2 value, equilibrium data was found to be best fitted by the
Langmuir model followed by the Redlich–Peterson model using
nonlinear regression analysis. The maximum monolayer adsorption capacity
was found to be 346.18 mg g–1 for Cr(VI) and 123.15
mg g–1 for 2,4-DNP. With a higher R
2 and low χ2 value, pseudo-second-order
model was established as the best model to describe the equilibrium
data suggesting the chemical adsorption to be the rate-determining
step. The value of ΔH° (+13.06 kJ mol–1) for Cr(VI) and (+10.28 kJ mol–1) for 2,4-DNP and negative value of ΔG°
(−1.56 to −3.00 kJ mol–1) for Cr(VI)
and (−1.75 to −2.94 kJ mol–1) for
2,4-DNP in the temperature range of 30–60 °C indicated
the overall adsorption process to be endothermic and spontaneous in
nature. The mechanism involved in the removal of Cr(VI) and 2,4-DNP
was electrostatic adsorption coupled reduction which is also evident
from EDX analysis.
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