Photodecolorisation of melanoidins in vinasse with illuminated TiO 2 -ZnO/activated carbon composite

A hybrid photo-catalyst, TiO -ZnO, was synthesized by immobilizing ZnO on commercial TiO (aeroxide P25). Activated carbon (AC) was subsequently used to support the hybrid, thus forming a TiO -ZnO/AC composite catalyst. Fourier transform infrared (FTIR) analysis and scanning electron microscopy integ...

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Published in:Journal of environmental science and health. Part A, Toxic/hazardous substances & environmental engineering Toxic/hazardous substances & environmental engineering, 2017-06, Vol.52 (7), p.616-623
Main Authors: Otieno, Benton O, Apollo, Seth O, Naidoo, Bobby E, Ochieng, Aoyi
Format: Article
Language:English
Subjects:
Adsorption
Catalysis
Charcoal - chemistry
Food Industry
Industrial Waste - analysis
Industrial Waste - prevention & control
Light
Microscopy, Electron, Scanning
Particle Size
Polymers - analysis
Polymers - chemistry
Polymers - radiation effects
Spectrometry, X-Ray Emission
Surface Properties
Titanium - chemistry
Titanium - radiation effects
Waste Disposal, Fluid - methods
X-Ray Diffraction
X-Rays
Zinc Oxide - chemistry
Zinc Oxide - radiation effects
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Summary:A hybrid photo-catalyst, TiO -ZnO, was synthesized by immobilizing ZnO on commercial TiO (aeroxide P25). Activated carbon (AC) was subsequently used to support the hybrid, thus forming a TiO -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. TiO -ZnO had improved photocatalytic activity compared with TiO 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 ([Formula: see text]) observed decreasing from 0.0701 to 0.0436 min 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.
ISSN:1093-4529
1532-4117
DOI:10.1080/10934529.2017.1294963