Synthesis of N-Doped ZnO Nanocomposites for Sunlight Photocatalytic Degradation of Textile Dye Pollutants

Rowshon Kabir,Shah Md Masum,Md Abu Khalid Saifullah,Abrar Zadeed Ahmed,Md Ashraful Islam Molla

doi:10.3390/jcs4020049

Rowshon Kabir, Shah Md Masum + Show 3 more

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https://doi.org/10.3390/jcs4020049

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Abstract

Undoped and N-doped ZnO nanocomposites are produced by a simple and low-cost mechanochemical method. The characterizations of all nanocomposites are examined by X-ray diffraction (XRD), Fourier transform-infrared (FT-IR), scanning electron microscopy (SEM) and UV-Vis-NIR spectroscopy. The XRD measurements show that the crystal sizes of undoped and N-doped ZnO nanocomposites are ~29 and ~28 nm, respectively. The UV-Vis-NIR spectroscopy results illustrate that the transmittance of the 7 wt% N/ZnO in the visible and infrared region is a bit higher than the undoped ZnO. The photocatalytic activity of undoped and N-doped ZnO nanocomposites is investigated for the degradation of Methylene Blue (MB) and Rhodamine B (RhB) aqueous solution with direct sunlight irradiation. The photocatalytic degradation percentages with 7 wt% N/ZnO for 5 and 10 mg/L MB dye solution are found to be 93.70% and 98.11%, respectively, whereas 78.40% and 89.15% degradation percentages are found with undoped ZnO, after 3 h sunlight irradiation. Under the same conditions, the photocatalytic degradation value of RhB dye (10 mg/L) solution is measured to be 86.21% for 7 wt% N/ZnO and 64.75% for undoped ZnO. The N-doped ZnO nanocomposites are found to exhibit enhanced photocatalytic performance for both dyes’ degradation under sunlight irradiation in comparison with the undoped ZnO. Therefore, the photocatalytic degradation treatment of wastewater including dye pollutants with sunlight is an easy and simple technique, and cost-effective.

Highlights

Semiconductor photocatalysts have been employed to degrade organic dye pollutants because of their intrinsic properties [1]
Several studies have reported the effectiveness of zinc oxide (ZnO) for photocatalytic degradation of organic compounds such as textile dye [7]
The combustion reaction is a simple method for synthesizing N-doped ZnO which does not involve complicated, strictly controlled conditions and special equipment [21]

Summary

Introduction

Semiconductor photocatalysts have been employed to degrade organic dye pollutants because of their intrinsic properties [1]. ZnO is considered to be the first choice semiconductor photocatalyst due to its large quantum efficiency [3]. It can be applied for adsorption, solar cells, field emission devices, lithium-ion batteries, pressure transducers and photocatalysis [4,5,6]. Several studies have reported the effectiveness of ZnO for photocatalytic degradation of organic compounds such as textile dye [7]. Owing to the large energy band gap (3.3 eV), ZnO can be only activated under UV light radiation [9]. Doping with nonmetals can be considered as a feasible approach to improve its utilization of solar energy and charge separation efficiency [10,11]. Klingshirn et al have proved that N impurities act as shallow acceptors in ZnO thin films and bulk crystals [14]

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