Photodecolorisation of melanoidins in vinasse with illuminated TiO2-ZnO/activated carbon composite

Benton Otieno, Seth Apollo, Bobby E. Naidoo, Aoyi Ochieng

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Abstract

A hybrid photo-catalyst, TiO2-ZnO, was synthesized by immobilizing ZnO on commercial TiO2 (aeroxide P25). Activated carbon (AC) was subsequently used to support the hybrid, thus forming a TiO2-ZnO/AC composite catalyst. Fourier transform infrared (FTIR) analysis and scanning electron microscopy integrated with energy-dispersive X-ray spectroscopy (SEM-EDX) investigations revealed successful catalyst synthesis. Optical properties of the hybrid determined from photoluminescence (PL) and Ultraviolet-visible (UV-vis) spectroscopy confirmed a restrained recombination of electron-hole pairs and reduced energy band gap due to a successful heterojunction formation. The prepared catalysts were used to photodecolorise vinasse in a 12-W UVC batch photoreactor. TiO2-ZnO had improved photocatalytic activity compared with TiO2 and ZnO separately. On supporting the hybrid onto AC, both adsorption and photocatalytic activities were further enhanced with improved overall color removal of 86% from 68%. Photodecolorisation followed the pseudo-first-order reaction model with the rate constant () observed decreasing from 0.0701 to 0.0436 min−1 on increasing the initial concentration from 5,000 to 14,000 ppm. The UV process was found to be 33-fold less energy intensive for color reduction as compared to total organic carbon (TOC) reduction. Formation of nitrates during the photodecolorisation process was attributed to the mineralization of nitrogen heteroatoms in the color-causing melanoidin compounds.
Original languageEnglish
Pages (from-to)616-623
JournalJournal of Environmental Science and Health - Part A Toxic/Hazardous Substances and Environmental Engineering
Volume52
Issue number7
DOIs
Publication statusPublished - 2017

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Activated carbon
Catalysts
Composite materials
Color
Scanning electron microscopy
Ultraviolet visible spectroscopy
Organic carbon
Band structure
Heterojunctions
Energy dispersive spectroscopy
Nitrates
Rate constants
Fourier transforms
Photoluminescence
Energy gap
Optical properties
Nitrogen
Infrared radiation
Adsorption
Electrons

Cite this

@article{8f108e21ff484b42be04b448c896e5dc,
title = "Photodecolorisation of melanoidins in vinasse with illuminated TiO2-ZnO/activated carbon composite",
abstract = "A hybrid photo-catalyst, TiO2-ZnO, was synthesized by immobilizing ZnO on commercial TiO2 (aeroxide P25). Activated carbon (AC) was subsequently used to support the hybrid, thus forming a TiO2-ZnO/AC composite catalyst. Fourier transform infrared (FTIR) analysis and scanning electron microscopy integrated with energy-dispersive X-ray spectroscopy (SEM-EDX) investigations revealed successful catalyst synthesis. Optical properties of the hybrid determined from photoluminescence (PL) and Ultraviolet-visible (UV-vis) spectroscopy confirmed a restrained recombination of electron-hole pairs and reduced energy band gap due to a successful heterojunction formation. The prepared catalysts were used to photodecolorise vinasse in a 12-W UVC batch photoreactor. TiO2-ZnO had improved photocatalytic activity compared with TiO2 and ZnO separately. On supporting the hybrid onto AC, both adsorption and photocatalytic activities were further enhanced with improved overall color removal of 86{\%} from 68{\%}. Photodecolorisation followed the pseudo-first-order reaction model with the rate constant () observed decreasing from 0.0701 to 0.0436 min−1 on increasing the initial concentration from 5,000 to 14,000 ppm. The UV process was found to be 33-fold less energy intensive for color reduction as compared to total organic carbon (TOC) reduction. Formation of nitrates during the photodecolorisation process was attributed to the mineralization of nitrogen heteroatoms in the color-causing melanoidin compounds.",
author = "Benton Otieno and Seth Apollo and Naidoo, {Bobby E.} and Aoyi Ochieng",
year = "2017",
doi = "10.1080/10934529.2017.1294963",
language = "English",
volume = "52",
pages = "616--623",
journal = "Journal of Environmental Science and Health - Part A Toxic/Hazardous Substances and Environmental Engineering",
issn = "1093-4529",
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TY - JOUR

T1 - Photodecolorisation of melanoidins in vinasse with illuminated TiO2-ZnO/activated carbon composite

AU - Otieno, Benton

AU - Apollo, Seth

AU - Naidoo, Bobby E.

AU - Ochieng, Aoyi

PY - 2017

Y1 - 2017

N2 - A hybrid photo-catalyst, TiO2-ZnO, was synthesized by immobilizing ZnO on commercial TiO2 (aeroxide P25). Activated carbon (AC) was subsequently used to support the hybrid, thus forming a TiO2-ZnO/AC composite catalyst. Fourier transform infrared (FTIR) analysis and scanning electron microscopy integrated with energy-dispersive X-ray spectroscopy (SEM-EDX) investigations revealed successful catalyst synthesis. Optical properties of the hybrid determined from photoluminescence (PL) and Ultraviolet-visible (UV-vis) spectroscopy confirmed a restrained recombination of electron-hole pairs and reduced energy band gap due to a successful heterojunction formation. The prepared catalysts were used to photodecolorise vinasse in a 12-W UVC batch photoreactor. TiO2-ZnO had improved photocatalytic activity compared with TiO2 and ZnO separately. On supporting the hybrid onto AC, both adsorption and photocatalytic activities were further enhanced with improved overall color removal of 86% from 68%. Photodecolorisation followed the pseudo-first-order reaction model with the rate constant () observed decreasing from 0.0701 to 0.0436 min−1 on increasing the initial concentration from 5,000 to 14,000 ppm. The UV process was found to be 33-fold less energy intensive for color reduction as compared to total organic carbon (TOC) reduction. Formation of nitrates during the photodecolorisation process was attributed to the mineralization of nitrogen heteroatoms in the color-causing melanoidin compounds.

AB - A hybrid photo-catalyst, TiO2-ZnO, was synthesized by immobilizing ZnO on commercial TiO2 (aeroxide P25). Activated carbon (AC) was subsequently used to support the hybrid, thus forming a TiO2-ZnO/AC composite catalyst. Fourier transform infrared (FTIR) analysis and scanning electron microscopy integrated with energy-dispersive X-ray spectroscopy (SEM-EDX) investigations revealed successful catalyst synthesis. Optical properties of the hybrid determined from photoluminescence (PL) and Ultraviolet-visible (UV-vis) spectroscopy confirmed a restrained recombination of electron-hole pairs and reduced energy band gap due to a successful heterojunction formation. The prepared catalysts were used to photodecolorise vinasse in a 12-W UVC batch photoreactor. TiO2-ZnO had improved photocatalytic activity compared with TiO2 and ZnO separately. On supporting the hybrid onto AC, both adsorption and photocatalytic activities were further enhanced with improved overall color removal of 86% from 68%. Photodecolorisation followed the pseudo-first-order reaction model with the rate constant () observed decreasing from 0.0701 to 0.0436 min−1 on increasing the initial concentration from 5,000 to 14,000 ppm. The UV process was found to be 33-fold less energy intensive for color reduction as compared to total organic carbon (TOC) reduction. Formation of nitrates during the photodecolorisation process was attributed to the mineralization of nitrogen heteroatoms in the color-causing melanoidin compounds.

U2 - 10.1080/10934529.2017.1294963

DO - 10.1080/10934529.2017.1294963

M3 - Article

VL - 52

SP - 616

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JO - Journal of Environmental Science and Health - Part A Toxic/Hazardous Substances and Environmental Engineering

JF - Journal of Environmental Science and Health - Part A Toxic/Hazardous Substances and Environmental Engineering

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