Synthesis of zinc oxide and zinc oxide / iron oxide catalysts and their photocatalytic activity in degrading herbicides

In this study, ZnO and ZnO/Fe2O3 catalysts were synthesized via precipitation method. The effect of Fe addition, calcination temperature and duration on the characteristics of the resulting catalyst were investigated by performing Thermogravimetric Analysis (TGA), X-ray Diffraction (XRD), Transmissi...

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Main Author:	Lee, Kian Mun
Format:	Thesis
Language:	English
Published:	2013
Subjects:	Zinc oxide Ferric oxide Herbicides
Online Access:	http://psasir.upm.edu.my/id/eprint/38859/1/FS%202013%209%20IR.pdf
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spelling	my-upm-ir.388592016-04-06T07:35:42Z Synthesis of zinc oxide and zinc oxide / iron oxide catalysts and their photocatalytic activity in degrading herbicides 2013-05 Lee, Kian Mun In this study, ZnO and ZnO/Fe2O3 catalysts were synthesized via precipitation method. The effect of Fe addition, calcination temperature and duration on the characteristics of the resulting catalyst were investigated by performing Thermogravimetric Analysis (TGA), X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), surface area measurement (BET method), Diffuse Reflectance Spectroscopy (DRS) and Inductively-coupled plasma atomic emission spectroscopy (ICP-AES). XRD analysis showed that the addition of Fe resulted in the formation of hexagonal structure of ZnO and cubic structure of γ-Fe2O3 by calcining the sample at 450 °C for one hour. The catalysts produced were spherical in shape. The increase in the calcination temperature and duration does not change the morphology and band gap energy of the resulting catalysts. However, the surface area of the catalyst decreased and hence leads to an increment in its particle size as the calcination temperature and duration increased. ICP-AES results revealed that the iron content in ZnO/γ-Fe2O3 is in good agreement with the calculated values. The efficiency of the synthesized ZnO/γ-Fe2O3 as photocatalysts was evaluated by photodegrading herbicides 2,4-dichlorophenoxyacetic acid (2,4-D), 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), phenoxyacetic acid (PAA) and 4-chlorophenoxyacetic acid (4-CPA) under the irradiation of ultraviolet (UV, λmax = 365 nm) light. Various parameters affecting the degradation performance such as catalyst dosage, initial concentration of herbicides and initial pH were examined. The removal percentage of chlorophenoxyacetic acids increased with increasing mass of ZnO/γ-Fe2O3 up to an optimum loading (0.4 g L-1 for 2,4-D and 2,4,5-T with 66.07 and 68.16 %, respectively and 0.5 g L-1 for PAA and 4-CPA with 60.90 and 74.38 %, respectively) but decreased with increasing initial concentration (from 10 - 50 mg L-1) of the herbicides. The removal of chlorophenoxyacetic acids is highest at pH 7. The photodegradation of chlorophenoxyacetic acids followed first-order kinetic scheme. The intermediates detected by UPLC for 2,4-dichlorophenoxyacetic acid (2,4-D), 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), phenoxyacetic acid (PAA) and 4-chlorophenoxyacetic acid (4-CPA) are 2,4-dichlorophenol, 2,4,5-trichlorophenol, phenol and 4-chlorophenol, respectively. Experimental design methodology was applied using response surface methodology (RSM) to optimise the degradation percentage of chlorophenoxyacetic acids. The multivariate experimental design was employed to develop a quadratic model as a functional relationship between the degradation percentage of chlorophenoxyacetic acids and catalyst dosage, initial concentration of herbicides and initial pH. The degradation percentage of 2,4-D approached 99.26 % under optimised conditions of 0.50 g ZnO/γ-Fe2O3, 10.00 mg L-1 2,4-D and at a pH of 7.49 whereas 2,4,5-T achieved 83.58 % under optimised conditions of 0.41 g ZnO/γ-Fe2O3, 10.60 mg L-1 2,4,5-T and at pH 7.11. The maximum removal percentage of PAA approached 76.43 % under optimised conditions of 0.51 g ZnO/γ-Fe2O3, 10.20 mg L-1 PAA and at pH 6.63. Further, 4-CPA showed maximum removal of 91.87 % under optimised conditions of 0.49 g ZnO/γ-Fe2O3, 10.10 mg L-1 4-CPA and at pH 7.25. In addition, the experimental data showed good agreement with the predicted results obtained from statistical analysis which indicates response surface methodology is applicable in optimising the degradation percentage of chlorophenoxyacetic acids. Zinc oxide Ferric oxide Herbicides 2013-05 Thesis http://psasir.upm.edu.my/id/eprint/38859/ http://psasir.upm.edu.my/id/eprint/38859/1/FS%202013%209%20IR.pdf application/pdf en public phd doctoral Universiti Putra Malaysia Zinc oxide Ferric oxide Herbicides
institution	Universiti Putra Malaysia
collection	PSAS Institutional Repository
language	English
topic	Zinc oxide Ferric oxide Herbicides
spellingShingle	Zinc oxide Ferric oxide Herbicides Lee, Kian Mun Synthesis of zinc oxide and zinc oxide / iron oxide catalysts and their photocatalytic activity in degrading herbicides
description	In this study, ZnO and ZnO/Fe2O3 catalysts were synthesized via precipitation method. The effect of Fe addition, calcination temperature and duration on the characteristics of the resulting catalyst were investigated by performing Thermogravimetric Analysis (TGA), X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), surface area measurement (BET method), Diffuse Reflectance Spectroscopy (DRS) and Inductively-coupled plasma atomic emission spectroscopy (ICP-AES). XRD analysis showed that the addition of Fe resulted in the formation of hexagonal structure of ZnO and cubic structure of γ-Fe2O3 by calcining the sample at 450 °C for one hour. The catalysts produced were spherical in shape. The increase in the calcination temperature and duration does not change the morphology and band gap energy of the resulting catalysts. However, the surface area of the catalyst decreased and hence leads to an increment in its particle size as the calcination temperature and duration increased. ICP-AES results revealed that the iron content in ZnO/γ-Fe2O3 is in good agreement with the calculated values. The efficiency of the synthesized ZnO/γ-Fe2O3 as photocatalysts was evaluated by photodegrading herbicides 2,4-dichlorophenoxyacetic acid (2,4-D), 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), phenoxyacetic acid (PAA) and 4-chlorophenoxyacetic acid (4-CPA) under the irradiation of ultraviolet (UV, λmax = 365 nm) light. Various parameters affecting the degradation performance such as catalyst dosage, initial concentration of herbicides and initial pH were examined. The removal percentage of chlorophenoxyacetic acids increased with increasing mass of ZnO/γ-Fe2O3 up to an optimum loading (0.4 g L-1 for 2,4-D and 2,4,5-T with 66.07 and 68.16 %, respectively and 0.5 g L-1 for PAA and 4-CPA with 60.90 and 74.38 %, respectively) but decreased with increasing initial concentration (from 10 - 50 mg L-1) of the herbicides. The removal of chlorophenoxyacetic acids is highest at pH 7. The photodegradation of chlorophenoxyacetic acids followed first-order kinetic scheme. The intermediates detected by UPLC for 2,4-dichlorophenoxyacetic acid (2,4-D), 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), phenoxyacetic acid (PAA) and 4-chlorophenoxyacetic acid (4-CPA) are 2,4-dichlorophenol, 2,4,5-trichlorophenol, phenol and 4-chlorophenol, respectively. Experimental design methodology was applied using response surface methodology (RSM) to optimise the degradation percentage of chlorophenoxyacetic acids. The multivariate experimental design was employed to develop a quadratic model as a functional relationship between the degradation percentage of chlorophenoxyacetic acids and catalyst dosage, initial concentration of herbicides and initial pH. The degradation percentage of 2,4-D approached 99.26 % under optimised conditions of 0.50 g ZnO/γ-Fe2O3, 10.00 mg L-1 2,4-D and at a pH of 7.49 whereas 2,4,5-T achieved 83.58 % under optimised conditions of 0.41 g ZnO/γ-Fe2O3, 10.60 mg L-1 2,4,5-T and at pH 7.11. The maximum removal percentage of PAA approached 76.43 % under optimised conditions of 0.51 g ZnO/γ-Fe2O3, 10.20 mg L-1 PAA and at pH 6.63. Further, 4-CPA showed maximum removal of 91.87 % under optimised conditions of 0.49 g ZnO/γ-Fe2O3, 10.10 mg L-1 4-CPA and at pH 7.25. In addition, the experimental data showed good agreement with the predicted results obtained from statistical analysis which indicates response surface methodology is applicable in optimising the degradation percentage of chlorophenoxyacetic acids.
format	Thesis
qualification_name	Doctor of Philosophy (PhD.)
qualification_level	Doctorate
author	Lee, Kian Mun
author_facet	Lee, Kian Mun
author_sort	Lee, Kian Mun
title	Synthesis of zinc oxide and zinc oxide / iron oxide catalysts and their photocatalytic activity in degrading herbicides
title_short	Synthesis of zinc oxide and zinc oxide / iron oxide catalysts and their photocatalytic activity in degrading herbicides
title_full	Synthesis of zinc oxide and zinc oxide / iron oxide catalysts and their photocatalytic activity in degrading herbicides
title_fullStr	Synthesis of zinc oxide and zinc oxide / iron oxide catalysts and their photocatalytic activity in degrading herbicides
title_full_unstemmed	Synthesis of zinc oxide and zinc oxide / iron oxide catalysts and their photocatalytic activity in degrading herbicides
title_sort	synthesis of zinc oxide and zinc oxide / iron oxide catalysts and their photocatalytic activity in degrading herbicides
granting_institution	Universiti Putra Malaysia
publishDate	2013
url	http://psasir.upm.edu.my/id/eprint/38859/1/FS%202013%209%20IR.pdf
_version_	1747811760129179648

Synthesis of zinc oxide and zinc oxide / iron oxide catalysts and their photocatalytic activity in degrading herbicides

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