The present study
deals with sonochemically in situ synthesis of
a novel functional catalyst using hydrogen exfoliated graphene (HEG)
supported titanium dioxide (TiO2) and copper sulfate (CuSO4) doped with zinc oxide (ZnO) (abbreviated as Ti/Cu/Zn-HEG).
The synthesis of the Ti/Cu/Zn-HEG nanocomposite (NCs) catalyst was
confirmed through its characterizations by XRD, SEM-EDX, TEM, XPS,
FTIR, and BET methods. It was assessed for catalytic conversion of
a model aromatic compound para-nitrophenol (p-NP)
in an aqueous solution. The p-NP is a nitroaromatic compound that
has a toxic and mutagenic effect. Its removal from the water system
is necessary to protect the environment and living being. The newly
synthesized Ti/Cu/Zn-HEG NCs were applied for their higher stability
and catalytic activity as a potential candidate for reducing p-NP
in practice. The operating parameters, such as p-NP concentration,
catalyst dosage, and operating time were optimized for 150 ppm, 400
ppm, and 10 min through response surface methodology (RSM) in Design-Expert
software to obtain the maximum reduction p-NP up to 98.4% at its normal
pH of 7.1 against the controls (using HEG, Ti/Cu-HEG, and Zn-HEG).
Analysis of variance of the response suggested the regression equation
to be significant for the process with a major impact on catalyst
concentration and operating time. The model prediction data (from
RSM) and experimental data were corroborated well as reflected through
model’s low relative error (RE < 0.10), high regression
coefficient (R
2 > 0.97), and Willmott d-index (d
will‑index >
0.95) values.