Enhancing photocatalytic degradation of quinoline by ZnO:TiO2 mixed oxide: Optimization of operating parameters and mechanistic study

Divya Gupta; Rohit Chauhan; Navneet Kumar; Vikash Singh; Vimal Chandra Srivastava; Paritosh Mohanty; Tapas Kumar Mandal

doi:10.1016/j.jenvman.2019.110032

Enhancing photocatalytic degradation of quinoline by ZnO:TiO₂ mixed oxide: Optimization of operating parameters and mechanistic study

J Environ Manage. 2020 Mar 15:258:110032. doi: 10.1016/j.jenvman.2019.110032. Epub 2020 Jan 7.

Authors

Divya Gupta¹, Rohit Chauhan², Navneet Kumar³, Vikash Singh⁴, Vimal Chandra Srivastava⁵, Paritosh Mohanty⁶, Tapas Kumar Mandal⁷

Affiliations

¹ Department of Chemical Engineering, Indian Institute of Technology Roorkee, Roorkee, 247667, Uttarakhand, India. Electronic address: divya116gupta@gmail.com.
² Department of Chemical Engineering, Indian Institute of Technology Roorkee, Roorkee, 247667, Uttarakhand, India. Electronic address: rohitchn18@gmail.com.
³ Department of Chemical Engineering, Indian Institute of Technology Roorkee, Roorkee, 247667, Uttarakhand, India. Electronic address: navneetrsh@gmail.com.
⁴ Department of Chemical Engineering, Indian Institute of Technology Roorkee, Roorkee, 247667, Uttarakhand, India. Electronic address: vikashsgh11@gmail.com.
⁵ Department of Chemical Engineering, Indian Institute of Technology Roorkee, Roorkee, 247667, Uttarakhand, India. Electronic address: vimalcsr@yahoo.co.in.
⁶ Department of Chemistry, Indian Institute of Technology Roorkee, Roorkee, 247667, Uttarakhand, India. Electronic address: pmfcy@iitr.ac.in.
⁷ Department of Chemistry, Indian Institute of Technology Roorkee, Roorkee, 247667, Uttarakhand, India. Electronic address: tapasfcy@iitr.ac.in.

PMID: 31929067
DOI: 10.1016/j.jenvman.2019.110032

Abstract

This study focuses on the photocatalytic degradation of quinoline, a recalcitrant heterocyclic nitrogenous aromatic organic compound, using the mixed oxide ZnO-TiO₂ photo-catalyst. Photo-catalysts were synthesized by the solid-state reaction method at different calcination temperatures of 400 °C, 600 °C, and 800 °C. Different analytical methods, including Field emission scanning electron microscope, Brunauer-Emmett-Teller surface area, X-ray diffraction, UV-vis diffuse reflectance spectroscopy, Fourier-transform infrared spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy analysis were used for the catalyst characterization. The highest pore surface area of 57.9 m²g^-1 was obtained for the photo-catalyst calcined at 400 °C. The effects of calcination temperature, solution pH, initial concentration, catalyst dose as well as irradiation time were studied. At the optimum condition, i.e., calcination temperature of 400 °C, pH ≈8 and catalyst dose of 2.5 gL^-1, maximum quinoline degradation and total organic carbon (TOC) removal efficiency of ≈92% and ≈78% were obtained after 240 min for initial quinoline amount of 50 mgL^-1. The 1^st, 2^nd^, and n^th-order kinetic models were applied to analyze the quinoline degradation rate. The photocatalytic mechanism was studied by drawing energy level diagram with the help of the band-gap structures of the ZnO and TiO₂, potential of the free radicals like OH and O₂ and HOMO-LUMO energy gap of the quinoline molecule. The proposed pathways of quinoline mineralization were suggested on the basis of the identified intermediates by the gas chromatograph-mass spectrometer analysis and scavenger study.

Keywords: Energy level; Mineralization pathway; Photo-catalysis; Quinoline degradation; ZnO:TiO(2) mixed oxide.

MeSH terms

Catalysis
Oxides
Quinolines*
Titanium
X-Ray Diffraction
Zinc Oxide*

Substances

Oxides
Quinolines
Titanium
Zinc Oxide