Photocatalytic Removal of Azo Dyes Using a CNT Doped ZnO/Fe2O3 Catalyst
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Department of Structures and Environmental Engineering, University of Agriculture, Faisalabad, Pakistan
World Wide Fund Nature - Pakistan
Department of Farm Machinery and Power, University of Agriculture, Faisalabad, Pakistan
Chaudhry Arslan   

Structures and Environmental Engineering, University of Agriculture, Faisalabad, Pakistan, Dr. Ch. Arslan, Structures and Environmental Engin, 42000, Faisalabad, Pakistan
Submission date: 2020-09-16
Final revision date: 2020-12-07
Acceptance date: 2020-12-18
Online publication date: 2022-05-20
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.