ORIGINAL RESEARCH
Photocatalytic Removal of Azo Dyes Using a CNT
Doped ZnO/Fe2O3 Catalyst
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1
Department of Structures and Environmental Engineering, University of Agriculture, Faisalabad, Pakistan
2
World Wide Fund Nature - Pakistan
3
Department of Farm Machinery and Power, University of Agriculture, Faisalabad, Pakistan
Submission date: 2020-09-16
Final revision date: 2020-12-07
Acceptance date: 2020-12-18
Online publication date: 2022-05-20
Publication date: 2022-09-01
Corresponding author
Chaudhry Arslan
Structures and Environmental Engineering, University of Agriculture, Faisalabad, Pakistan, Dr. Ch. Arslan, Structures and Environmental Engin, 42000, Faisalabad, Pakistan
Pol. J. Environ. Stud. 2022;31(5):4279-4289
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ABSTRACT
Textile dyes especially azo dyes are the prime pollutants in wastewater due to the presence of
complex azo bond (−N=N−). Many conventional methods such as physicochemical, mechanical and
biochemical were employed recently for removal of these organic pollutants. These methods have not
been proved to be so efficient. Photocatalysis, a latest physio-chemical methods is employed currently.
Present work investigated the synthesis of a Carbon Nano Tubes (CNT’s) doped ZnO/Fe2O3 catalyst by
microwave-assisted sol-gel method. Removal efficiency of the synthesized catalyst was observed through
removal of two azo dyes direct orange-26 and acid red-151 for different concentrations. The prepared
ternary nano-hybrid was characterized by X-ray diffractometry (XRD), scanning electron microscopy
(SEM) and Energy Dispersive Spectroscopy (EDS). The average crystalline size of the catalyst
was calculated as 8.47nm by using data from XRD analysis. SEM images revealed the formation o
f nano-flakes of catalyst. And results of EDS investigation publicized that the distribution
of all the atoms of Zn, Fe, O and C is homogeneous throughout the catalyst. Percentage removal by
synthesized catalyst for direct orange-26 and acid red-151 was determined as 58.8% and 72.7%
respectively without adding oxidant. After adding oxidant the percentage removal increases to
70.6% for direct orange-26 and 85.2% for acid red-151. The effect of pH, time and oxidant dose were
optimized by developing relationships between these variables using central composite design (CCD)
in response surface methodology (RSM). The results of RSM analysis show prepared catalyst performs
best in acidic conditions at pH of 3 and irradiation time of 2.7 hours for acid red-151 and at pH of 5
and irradiation time of 3.8 hours for direct orange-26.